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DICTIONARY

SCIENTIFIC TERMS.

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RICHARD D. HOBLYN, A.M. Oxon.

AUTHOR OF

« A DICTIONARY OF MEDICAL TERMS,"

OF " MANUALS OF NATURAL PHILOSOPHY, OF CHEMISTRV, AND

OF THE STEAM ENGINE;"

OF " FIRST BOOKS IN SCIENCE," &C. &C.

NEW YORK: D. APPLETON AND CO.

PHILADELPHIA : G. S. APPLETON.

1850.

£- 4 -T ^ 3

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DICTIONARY

OF

SCIENTIFIC TERMS.

ABD

A'BACUS (a/3a£, a counter, a chess-
board). An ancient instrument for aid-
ing numerical calculations. The Greek
abacus consisted of an oblong frame,
having wires stretched across it, carrying
perforated ivory balls. In the Roman
abacus, the counters were slid along
grooves.

ABBREVIATION (abbrevio, to short-
en). An arithmetical term, denoting the
reduction of a fraction to lower terms, by
dividing the numerator and the denomi-
nator by any common factors which they
contain. Thus |^ divided by 5 gives
j^g; and this, again divided by 3, gives
AS. The fraction is thus reduced or ab-
breviated, and, when it can no more be
reduced, it is said to be in its lowest
terms.

ABDO'MEN (abdo, to conceal). The
posterior and principal cavity containing
the bowels and many other viscera of the
animal. The abdomen is distinct from
the thorax in the crustaceans, the spiders,
and the insects.

ABDOMINA'LES (abdomen, the belly).
An order of malacopterygious or soft-
f.nned fishes, which have their ventral
fins placed on the abdomen, behind the
pectorals. The sub-families of the order
are termed by Cuvier, cyprinoides, silu-
ro'ides, salmono'ides, clupeoides, and lu-
cioides, from the respective typ'cal genera
of the carps, the silures, the salmons, the
herrings, and the pikes.

ABDUCTOR MUSCLE (abduco, to
draw from). A muscle whose office is to
draw one part of the body from another.
Thus the rectus externum is called ab
ductor oculi, fiom the action of this
1

ABE

muscle in drawing the eye away from the
nose. See Adductor.

ABE'RRANT (aberro, to wander
from). A term applied in classification
to those species which deviate most from
the type of their natural group.

ABERRATION Of LIGHT (aberro,
to wander from). An astronomical phe-
nomenon consisting in an alteration in
the apparent position of all the stars,
owing to the velocity with which light
moves, and to the motion of the earth in
her orbit, in a direction which forms a
tangent to the light from the heavenly
bodies. In consequence of the aberra-
tion resulting from the combined opera-
tion of these two velocities, all the fixed
stars appear to us to be rather more back-
ward than they really are in the direction
of the earth's annual motion. Aberra-
tion is never so much as 21"; in other
words, the apparent place of the star
differs from its real place less than the
ninetieth part of the apparent diameter
of the sun.

1. Aberration, Spherical. A term em-
ployed in Optics to denote the deviation
of the rays of light from the true focus of a
curved lens or mirror ; in consequence of
which, instead of concentering in a single
point, they are spread over a certain sur-
face, forming a confused image of the
object. These aberrations proceed, 1, from
the form of curvature of the lens or mir-
ror, and 2, from the different refrangibility
of the rays of light. See Refrangibility.

2. Aberration, Chromatic. A term em-
ployed in Optics to denote the imperfec-
tion arising from the unequal refrangibi-
lity of the rays composing white light,

B

A BR

ABS

in consequence of which the image of the
object, viewed through a lens, will be
surrounded by prismatic colours. Sphe-
rical aberration produces distortion, chro-
matic aberration produces false colour, of
the object.

3. Aberration, circle of. The circle of
coloured light observed, in experiments
with convex lenses, between the point
where theviolet or most refrangible, and
the point where the red or least refran-
gible rays meet.

ABIETTN^E {abies, a fir-tree). A sec-
tion of the Coniferse, or Fir-tree tribe of
plants, comprising the Fir, the Pine, the
Araucaria, the Dammara, and the Cun-
ninghamia.

A'BLATIVE CASE (ab, from, fero,
latus, to take). Literally, the taking
away case ; a case belonging to the Latin
language, and known by prepositions,
expressed or understood. It is repre-
sented in the English language by the
preposition from. See Case.

ABNO'RMAL {ab, from, norma, arule).
Irregular ; that which deviates from the
usual order. The term anormal is also
employed to denote any thing that is
without rule or order. The terms are
nearly synonymous.

ABO'RTIVE {aborior, to be born before
the time). A term applied in botany to
any part of a plant which does not ac-
quire its normal development: stamens
which have no anthers, and seeds which
have no embryos, are said to be abortive.
But abortion may be constant : the ova-
rium of the Cocoa palm is three-celled ;
the fruit has only one cell, the other two
becoming constantly abortive.

ABR A'NCHIA (« priv., /3Pa7X"»» gills).
The third order of the Anellida of Cuvier,
comprising animals which have no gills,
or apparent external organs of respira-
tion, but respire by the entire surface of
the skin, or by internal cavities. They
are distinguished into the setigerous, or
worms, and the non-setigerous, or leeches.
The term Abranchia has been also ap-
plied to an order of amphibious animals,
which are not known to undergo meta-
morphosis, but breathe by lungs during
the whole period of life. The order
comprises only two genera, viz. the me-
nopoma and the amphiuma of North
America.

A'BRAZITE. A mineral found in the
cavities of volcanic rocks, with calcareous
spar, at Capo di Bove, near Rome. It
occurs in semi-globular masses, and in
octohedral crystals with a square base.
2

It is also termed zeagonite and gismon-
dine.

ABRU'PTLY PINNATE. A pinnate
leaf is thus named in botany, when its
petiole has no terminal leaflet or tendril,
as in Orobus tuberosus.

ABSCI'SSA (abscindo, to cut off). Linea
abscissa. A term employed in Conic Sec-
tions, to denote that portion of the major
axis of an ellipse which is cut off by an
ordinate. The term is equally applicable
to the parabola and to the hyperbola. See
Ordinate and Co-ordinaip.

A'BSOLUTE and RE'LATIVE. In
logic, a noun which denotes an object
considered as a whole, and without re-
ference to any thing of which it is a part,
or to any other part distinguished from
it, is called absolute. When, on the other
hand, an object is considered as a part of
a whole, viewed in reference to the
whole, or to another part of a more com-
plex object of thought, the noun express-
ing this view is called relative. Thus,
" father " and " son " are relatives, being
regarded, each as a part of the complex
object, father-and son ; whereas the
same object designated absolutely would
be termed a man, living being, &c.

ABSORPTION (absorbeo, to suck up).
A function in physiology, by which the
materials of growth are absorbed and con-
veyed to the organs of the body, and by
which the decayed and useless parts are
absorbed and removed from the system.

1. Interstitial Absorption. The func-
tion by which the particles of the tissue
which fill the meshes of the capillary net-
work are removed, as in the atrophy of
the tail of the tadpole, and of the pupil-
lary membrane in the foetus, and in the
development of cells in bones.

2. Absorption, in Chemistry. This term
denotes the passage of a gas or vapour
into a liquid or solid substance ; or that of
a liquid into the pores of a solid. Thus,
water absorbs carbonic acid gas, lime
absorbs water, &c.

ABSTRACT and CONCRETE. 1. In
logic, when a notion derived from the
view taken of any object, is expressed
with a reference to, or as taken in con-
junction with, the object which furnished
the notion, it is expressed by a concrete
term, as "foolish" or "fool;" when
without any such reference, by an abs-
tract term, as " folly." 2. In arithmetic,
when numbers are used with reference
to the things numbered, as 3 shillings, 4
acres, 5 kingdoms, they are said to be con-
crete numbers ; when used without such

Q>^

jfbMA

AC A

reference, merely to indicate a certain
number of units of the same kind, as
when we simply say 3, 4, 5, they are
called abstract numbers. The multipli-
cation table is a series of abstract num-
bers. See Abstraction.

ABSTRACTION {abstraho, to draw
off). The operation of the mind by
which we draw off, and contemplate sepa-
rately, some portion or property of an
object, as the scent of a rose, disregard-
ing all else that belongs to it. The ope-
ration, therefore, strictly speaking, may
be limited to the contemplation of a single
object. But the term is usually employed
in a wider sense: in contemplating several
objects which agree in certain points, we
abstract the circumstances of agreement,
disregarding the differences, and give to
all and each of these circumstances a
common name, expressive of this agree-
ment ; we are then, properly, said to
generalize. Abstraction, therefore, does
not necessarily imply generalization,
though generalization implies abstrac-
tion.

ABSU'RDUM, REDUCTIO AD. A
form of argument, frequently employed
in geometrical reasoning, by which, in-
stead of proving the thing asserted, the
absurdity is shown of every thing which
contradicts that assertion. For it follows
that, if every thing which contradicts a
proposition be false, the proposition itself
must be true.

ABU'NDANT NUMBER. Any num-
ber which is less than the sum of its di-
visors, as 12, which is less than the sum
of / 2, 3, 4, and 6, all of which are its
divisors, and their sum is 16. A deficient
number is that which is greater than the
sum of its divisors ; a perfect number,
that which is^equal to the sum of its di-
visors^*-£

ACALE'PHjE (ixaX^rj, a nettle). Sea-
nettles ; a class of gelatinous zoophytes,
found in the water of the ocean, and so
named from the stinging sensation which
many of them produce when touched.
To this class belong the sea-jelly, sea-
nettle, Portuguese man-of-war, &c. By
the old naturalists they were known by the
title of urticcB marines. See Malactinia.
ACA'NTH A i'dKavda, a thorn). A spine,
or prickle ot a plant. A prickly tin of a
fish. A spinous process of a vertebra.

ACANTHA'CEjE. The Justicia tribe
of Dicotyledonous plants, named from
the genus Acanthus. Herbaceous plants
or shrubs, with leaves opposite ; corolla
gamopetalous ; stamens mostly 2 ; capsule
3

ACC

2-celled, bursting elastically with 2 valves;
seeds usually hooked, exalbumiuous.

ACANTHA'LES. An alliance of Dico-
tyledonous plants. Flowers unsymme-
trical, usually didynamous. Seeds ad-
hering to hard hook like processes of the
placenta. Albumen 0. Calyx 4-5-leaved,
remarkably imbricated, as if in more
whorls than one ; often enveloped in
large bracts.

ACA'NTHOCE'PHALA {'dKavOa, a
spine, KetpaXij, the head). Hooked
worms; an order of the Entozoa, which
have an elongated cylindrical body, with
the anterior part closely covered with
small sharp spines, and the oral aper-
ture leading to a ramified alimentary
canal.

ACA'NTHOPTERY'GII (SKavfla, a
thorn, 7TT€pvytov, a fin). Spinous-finned
fishes, or fishes whose dorsal fins are bony
and prickly ; one of the three primary
grand divisions, or natural orders of
fishes, established by Cuvier. The order
comprises fifteen families.

ACA'NTICONE. A sub-species of
prismatoi'dal augite, occurring in primi-
tive beds and veins, in Norway and other
parts. It is of a pistachio-green colour,
and is known by the names pistacite and
epidote.

A'CARID^E. A family of the Arach-
nida, belonging to the order Tracheata,
and named from the typical genus acarus,
to which the mite, the tick, the water-
mite, and the flesh- worm belong. The
last of these is distinguished from the
rest by the presence of only six feet.

ACAULE'SCENT (a, priv., Kav\6t, a
stalk). Stemless ; a term applied to a
plant in which the stem is apparently
absent, and the leaves seem to rise from
the root, as in Cnicus acaulis. As, how-
ever, according to the theory of vegetable
development, a stem is assumed to exist,
the term subcaulescent would be prefer-
able.

ACCELERATION (accelero, to has-
ten). The increase of the motion of
moving bodies. Thus, a stone, falling to
the earth, moves faster and faster as it
descends ; its motion is therefore said
to be continually accelerated ; in other
words, its velocity continually increases.
1. Acceleration of the fixed stars. The
time by which the stars, in their diurnal
revolution, anticipate the mean diurnal
revolution of the sun ; which is three
minutes and fifty-six seconds. Thus, a
star, which to-day passes the meridian at
twelve o'clock, mean time, will pass the
B2

A C C

ACE

meridian to-morrow three minutes and
fifty-six seconds before twelve o'clock.

2. Acceleration of the planets. The
motion of the planets varies in different,
parts of their orbits, according as they
are at a greater or less distance from the
sun. From their aphelion to their peri-
helion their motion is accelerate, i ; from
their perihelion to their aphelion it is
retarded. The average of these motions
through the whole orbit (the space di-
vided by the time) is called the mean
motion. Hence, the acceleration of a
planet is the excess of its real diur-
nal motion over its mean diurnal mo-
tion.

3. Secular acceleration of the moon's
mean motion. An increase in the velo-
city of the moon's mean motion around
the earth. It amounts to about 11 se-
conds per century — a quantity small in
itself, but becoming considerable by its
accumulation during a succession of
ages.

A'CCENT {aecentus, from accino, to
sing in concert). A peculiar stress or
elevation of the voice, which distin-
guishes one syllable in every word which
consists of more than one syllable. The
syllable so distinguished is said to have
the acute accent, which is marked thus
(') ; ths grave ( ), which is seldom marked,
is supposed to be placed over those syl-
lables which are pronounced without the
elevation of the voice ; the circumflex
C or ") is supposed to be formed by a
combination of the acute and the grave,
and hence is usually placed over con-
tracted syllables. In modern languages
the accent, when it falls upon a short syl-
lable, has, in most cases, the same effect
as if it were long ; but in the ancient
languages, accent and quantity were dis-
tinguished from each other.

ACCENTS, MATHEMATICAL. Dif-
ferent magnitudes of the same kind, or
magnitudes placed in similar positions,
are denoted, in algebraical calculations,
by the use of the same letter distin-
guished by accents. The accented letter
a' is read a accented or a dashed; a" is
read a twice accented, or a twice dashed,
or, more commonly, a two dash. When
accents are inconveniently numerous,
Roman figures are employed : thus aiv is
used instead of a"". The accented letter
is the metaphor of algebra.

A'CCESSORY VALVES (accedo, to be
added). Small additional valves placed
near the um bones or bosses of the genus
pholas among shells, and on the edges of

the pedunculated barnacles, among an-
nulose animals.

A'CCIDENT {accido, to happen to).
This term, in its widest technical sense,
denotes any thing which can be attri-
buted to an object, and can only be con-
ceived as belonging to some substance,
in which sense it is opposed to "sub-
stance." In its more restricted and logi-
cal sense, it is a predicable, which may be
absent or present, the essence of the
species remaining the same. An acci-
dent is called separable, when it may be
separated from the individual ; insepa-
rable, when it cannot be separated from
the individual : the word " individual "
is here emphatic, because every accident
must be separable from the species, else
it would be a property.

ACCFPITRES {accipiter, a hawk).
Raptores. Rapacious birds; birds of
prey ; known by their hooked beak and
talons. They are distinguished into the
diurnal and the nocturnal ; the former
comprising the falcons, eagles, vultures,
&c. ; the latter the owls.

A'CCLIMA'TION. Naturalization to
a foreign or unusual climate ; a term ap-
plied to plants and animals.

ACCRETION (accresco, to grow to).
The addition of new parts, as in the
formation of a crystal by the position of
new parts around a central nucleus. The
organic and inorganic kingdoms are dis-
tinguished by their mode of increase;
the former increasing by intussusception
and alimentation, the latter by accretion
without alimentation.

ACCU'MBENT (accumbo, to lie down).
Lying against any thing, as the edges of
the cotyledons against the radicle in some
cruciferous plants. See Incumbent.

ACCUSATIVE CASE (accuso, to ac-
cuse). Literally, the aiming at case ; a
case belonging to the Latin language, and
denoting, originally, the object to which
any motion or action is directed ; it was,
afterwards, employed to distinguish the
object of any action or feeling. It cor-
responds with the objective case, or the
object, of the English Grammar. See
Case.

-ACEOUS. Terminations in -aceous
denote a resemblance to a substance, as
membranaceous, resembling membrane;
whereas terminations in -ous denote the
substance itself, as membranous, belong-
ing to membrane.

ACE'PHALA (a, priv., Ke<pa\t], the
head). Headless animals; a class of the
Mollusca, which have no head, but simply

ACE

ACH

a pharynx, or beginning of the oesophagus
without jaws, tongue, or mouth properly
so called, as in the oyster. According to
Cuvier, this class of molluscous animals
comprehends many genera with bivalve
shells, or acephala testacea ; and a few
which are devoid of shells, or acephala
nuda.

ACEPHALO'PHORA (a, priv., «e-
<pa\r], the head, 0<?pa>, to bear). A term
applied by Blainville to a class of mollus-
cous animals corresponding with the
acephala and the brachiopoda of Cuvier.

ACERA'CEiE. The Sycamore tribe of
Dicotyledonous plants, named from the
genus Acer. Trees, with leaves opposite ;
petals generally 5 ; stamens usually 8, in-
serted with the petals on a hypogynous
disk ; fruit dicarpellary, samaroid ; seeds
exalbuminous.

ACERA'LES. An alliance of Dicoty-
ledonous plants. Stamens definite in
number. Flowers usually un symmetri-
cal in their parts, or, if symmetrical,
more or less irregular ; in the majority,
small, and disposed in a compound inflo-
rescence.

A'CERIC ACID. A peculiar acid said
to exist in the sap of the acer, or maple
tree.

A'CEROSE {acerosus, chaffy). Sharp-
pointed ; tapering to a fine point, as the
leaves of juniper.

ACESCENT (acesco, to become sour).
A term applied to substances which be-
come sour spontaneously, as vegetable
and animal juices, or infusions.

ACETABULUM {acetum, vinegar). A
vinegar-cruet ; and hence a cup-like ca-
vity, as the suckers on the arms of the
cuttle-fish, the cavity of the hip-joint,
the socket on the trunk of insects which
receives the leg. Also, a Roman mea-
sure containing two ounces and a half.

ACE'TAL. A compound of aldehyde
with ether, formed by the action of plati-
num black on the vapour of alcohol with
the presence of oxygen. The term is
derived from acetum, vinegar, and the
first syllable of alcohol.

A'CETATE {acetum, vinegar). A salt
formed by the union of acetic acid with
an alkaline, an earthy or a metallic
base.

ACE'TIC ACID {acetum, vinegar). The
pure acid of vinegar. It occurs, ready
formed, in several products of the vege-
table kingdom, and is generated during
the spontaneous fermentation of many
vegetable and animal juices. By real
acetic acid is meant such an acid as
5

occurs in a dry acetate: it cannot exist in
an uncombined state.

ACETO'METER {acetum, vinegar,
/ierpoj/, a measure). An instrument for
ascertaining the strength of vinegars.
It consists of a globe of glass about three
inches in diameter, having a little ballast
ball drawn out beneath, and a stem above
of about three inches long, containing a
slip of paper, with a transverse line in
the middle, and surmounted with a little
cup for receiving weights or poises.

ACETONE. The new chemical name
for pyro-acetic spirit; a limpid colourless
liquid, prepared by distilling a mixture
of two parts of crystallized acetate of lead
and one part of quicklime in a salt-glaze
jar. The names of such pyrogen bodies
terminate in one, as contain one atom of
oxygen and are neutral.

ACETYL. A hypothetical radical,
pervading a series of compounds, includ-
ing acetic acid, and prepared by abstract-
ing two atoms of oxygen from ethyl.
The term is derived from acetum, vine-
gar, and vXrj, matter.

ACHjE'NIUM (a, priv., xa/vw, to open).
An indehiscent fruit ; one-celled, one-
seeded, superior, hard, and dry, with the
integuments of the seed distinct from it.
It occurs in the Labiatae and the Bora-
gin eae.

ACHATINjE. Spiral snails; a sub-
family of the Helicidce, named from the
genus Achatina : the spire of their shells
is elongated and conical.

ACHE'RNAR. A star of the first mag-
nitude in the southern constellation Eri-
danus.

ACHE'TIDjE. A group of Orthopte-
rous insects, belonging to the family Sal-
tatoria, and including the species known
as crickets. Many of them burrow in the
ground, and most of them, like the house-
cricket, are nocturnal. Few have any
power of active flight.

A'CHIRITE. Emerald malachite; a
mineral consisting of oxide of copper,
carbonate of lime, silica, and water.

ACHLAMY'DEOUS (a, priv., x^pvn,
a cloak). The general name of all those
plants from which the floral envelopes —
the calyx and the corolla — are both ab-
sent.

A'CHMIT. A mineral, supposed to be
a bisilicate of soda, combined with a
bisilicate of iron.

ACHROMATIC (a, priv., xpwixa, co-
lour). An optical term signifying colour-
less as applied to a lens, in which the
primary colours which usually accompany
B3

AC1

ACO

the transmission of the image of any ob-
ject through such a medium, are de-
stroyed. The colours which appear round
the edges of an object, when viewed
through an ordinary telescope, are pro-
duced by the different ref'rangibility of
the rays of light ; and telescopes which
are constructed so as to counteract or
prevent this aberration, are termed achro-
matic.

ACI'CULAR (acicula, a little needle).
A term applied, in crystallography, to
needle shaped crystals ; and, in botany, to
the leaves of plants which are long, stiff,
and pointed, like a needle ; or to surfaces
which are marked with fine needle-like
streaks.

A'CIDS. A class of compounds which
generally possess a sharp and sour taste,
and are often highly corrosive ; they red-
den the infusions of blue vegetable co-
lours, and combine with the alkalies,
earths, and metallic oxides, forming
compounds in which the characters of
the constituents are entirely destroyed,
and new characters produced differing in
every respect from those previously ex-
isting. See Alkalies.

1. Oxygen Acids. When the same ele-
ment forms two acid compounds with
oxygen, the name of that which contains
the greater proportion of oxygen is made
to terminate in ic, the other in ous, as in
sulphuric and sulphurous acids. A lower
degree of oxidation is expressed by pre-
fixing the Greek preposition hypo (biro,
under), as in hypo-sulphurous acid; while
another new compound, intermediate be-
tween the sulphurous and sulphuric acids,
was named hypo-sulphuric acid. On the
same principle, the highest degree of oxi-
dation is expressed by prefixing the
Greek preposition hyper {vnep, over), as
in hyper-chloric acid. This nomenclature
has been adopted for all analogous acids.

2. Hydrogen Acids. These are acid
compounds of certain substances, as
chlorine, sulphur, and cyanogen, with
hydrogen, and they are hence called hy-
dracids. In these compounds the names
of both constituents appear, as in the
terms hydrochloric, hydrosulphuric, and
hydrocyanic acid. Thenard has lately
altered these names to chlorhydric, sul-
phohydric, and cyanhydric acid, which
are better terms.

3. Sulphur acids. In this class of acids
sulphur is united with the other element
in the place of oxygen. The names of
the corresponding oxygen acids are some-
times applied to these with the prefix
6

sulpho, as sulpho-arsenious and sulpho-
arsenic acids, which resemble arsenious
and arsenic acids respectively in com-
position, but contain sulphur instead of
oxygen.

ACIDIFI'ABLE. Capable of being
converted into an acid by an acidifying
principle. Substances possessing this
property are called radicals, or acidifiable
bases.

ACIDIFYING PRINCIPLE. That
principle which is capable of converting
a substance into an acid.

ACIDPMETRY {acidum, an acid, Me-
rpov, a measure). The process of mea-
suring the strength of an acid, by satura-
ting a given weight of it with an alkaline
base : the quantity of the base required
for saturation is a measure of the strength
of the acid.

ACIDULOUS. Slightly acid; a term
frequently applied to mineral waters
which contain carbonic acid ; and, in
chemical language, to those salts in which
the base is combined with such an excess
of acid, that they distinctly exhibit acid
properties, as the super-tartrate of po-
tassa.

ACINA'CIFORM (acinaces, a scimitar,
forma, likeness). Scimitar-shaped ; plane
on the sides, with one border thick, the
other thin, as the succulent leaves of the
Mesembryanthemum acinaciforme.

A'CINI (plural of acinus, a grape-
stone). A term applied by some carpo-
logists to the minute component parts of
the raspberry : incorrectly, however ; for
these are drupes. The term is also ap-
plied to the secerning parts of glands,
when they are suspended like grains or
small berries from a slender stem.

ACLI'NIC LINE (a, priv., kXIvco, to
incline). The name given by Professor
August to an irregular curve in the
neighbourhood of the terrestrial equator,
where a needle balances itself perfectly
horizontally. It is sometimes called the
magnetic equator.

ACORA'CEiE. An order of Mono-
cotyledonous plants, named from the
genus Acorus. Rhizoma jointed ; leaves
ensiform ; flowers hermaphrodite, sur-
rounded with scales ; spathe leaf-like ;
stamens with 2-celled anthers, turned in-
wards ; ovaries distinct ; fruit finally
juiceless ; seeds albuminous.

A'COTYLE'DON (a, priv., kotvXvSwv,
a seed-lobe). A plant whose embryo
has no cotyledons, or seed-lobes. But
the acotyledonous embryo is not exactly,
as its name seems to indicate, an embryo

ACT

ACU

without cotyledons; for, in that case,
cuscuta would be acotyledonous. On the
contrary, it is an embryo which does not
germinate from two fixed invariable
points, namely, the plumule and the ra-
dicle, but indifferently from any point of
the surface, as in some Araceae, and in
all flowerless plants.

ACOU'STICS (ukovco, to hear). The
science of sound ; the laws which regu-
late the vibrations of air, or of other
media, in their relation to the organ of
hearing.

A'CRITA (a/cptTor, indistinct). A pri-
mary division of the Animal Kingdom,
composed of the lowest classes of the
radiate animals, and characterized by an
indistinct, diffused, or molecular condi-
tion of the nervous system, and by the
absence of distinct parietes to the ali-
mentary canal. To this division belong
the medusa, the polype, &c. These are
the cryptoneura of Rudolphi, the protozoa
and oozoa of others. See Nematoneura.

A'CROGEN (aKpov, extreme, yeipo/nat,
to grow). Point-grower ; the classical name
of a plant which grows only at its point,
or upper extremity, as a fern tree, and is
thus distinguished from an endogen on
the one hand, and an exogen on the other.

ACRO'LEINE (ckpor, extreme, e\aiov,
oil). A substance of a very pungent
odour given off by oils and fats when
boiling at a high temperature, and pro-
duced in large quantity by the distillation
of pure glycerin.

ACRO'NYCHAL (cUpoc, extreme, ™f,
night). A Greek term denoting the ex-
tremities, or the beginning and the end,
of the night. Hence, a star is said to be
acronychal, or to rise acronychally, when
it rises at sunset, and consequently sets
at sunrise.

A'CROSPIRE (a«poc, extreme, a-irelpa,
a spire). That part of a germinating em-
bryo which botanists call the plumula,
and which bears the cotyledons. It has
a curved form, and makes its appearance
at the extremity of the seed.
' ACTERAPMIN. A star of the third
magnitude, in the left shoulder of Ce-
pheus, marked a.

ACTINE'NCHYMA (cue™, a ray of
light, f7X"Ma> an infusion). A term ap-
plied by some botanical writers to the
stellate, or star-shaped variety of sphe-
roidal cellular tissue.

ACTPNIA [iatrhf, a ray of light). A
form of polype, in which the mouth oc-
cupies the centre of the upper surface,
and is surrounded by tentacuia, which
7

radiate from the centre, like the petals of
a flower. Hence, the genus has acquired
the names of animal flowers, sea ane-
mones, &c. From the fihrous character
which the substance of their bodies as-
sumes, they have been named by zooJo-
gists fleshy polyps.

ACTINO'CEROS (uht'iv, a ray, nepat,
a horn). A generic term, signifying the
radiated disposition of the horns or
feelers of animals.

ACTPNOLITE {dvrlv, a ray of light,
\i9ov, a stone). A green-coloured mine-
ral, forming a variety of hornblende, and
usually occurring in fascicular crystals,
which are arranged in the form of rays.
It is found chiefly in primitive districts
with a magnesian basis. There are three
varieties, — the crystallized, the asbestous,
and the glassy.

Actinolite slate. A hornblendic rock,
composed of actinolite and felspar, and
easily recognized by its light-green colour,
and the elongated form or fibrous appear-
ance of its principal constituent mineral.

ACTINO'METER(aKTii/, a ray of light,
p.eTpov, a measure). An instrument for
measuring the intensity of light. This
instrument indicates the force of sun-
shine at the Cape of Good Hope as 48°
75', while ordinary sunshine in England
is only from 25° to 30°.

ACTION. The motion which one body
produces, or endeavours to produce, in
another. Mechanical action is exerted
by percussion or by pressure ; and, in
either case, the force exerted by the act-
ing body is repelled in an equal degree
by the body on which it acts : the stroke
of the hammer on a nail, acts upon the
former equally as on the latter. In all such
cases, the counteracting force is termed
re-action; and it is a law in Physics that
" action and re-action are equal."

ACTIVITY, SPHERE OF. The space
within which the action of a body pro-
duces a sensible effect.

A'CUBENE. A star of the fourth
magnitude, in the southern claw of Can-
cer, marked a.

ACULEA'TA (aculeus, a sting). A
group of Hymenopterous insects, in which
the abdomen of the females and neuters
is armed with a sting connected with a
poison reservoir. The antennae are twelve
in number in the female, and thirteen in
the male.

ACU'LEATE {aculeus, a prickle).
Prickly ; a term applied, in botany, to a
surface covered with prickles, as the stem
of the rose.

B4

ADD

AD H

' ACU'LEUS (dim. of acus, a needle).
A prickle ; a hard conical expansion of
the bark of certain plants, as of the rose.
It is distinguished from the thorn or
spine by the nature of its tissue : the
prickle consists of cellular, the spine of
woody tissue.

ACU'MINATE {acumen, a sharp point).
Pointed ; ending in a tapering, acute point,
as the leaf of Salix alba.

ACU'TE (acutus, sharp). This term,
in Geometry, is opposed to obtuse: an
acute angle is that which is less than a
right angle, or does not subtend an angle
of 90 degrees ; an acute-angled triangle
is that which has three acute angles ; an
acute-angled cone is that whose opposite
sides form au acute angle at the vertex.
In Acoustics, the term acute is opposed
to grave, and denotes that the sound of
the voice or of a musical instrument is
raised with respect to some other
sound.

ADA'GIO. An Italian term signifying
slowly, and employed to indicate the
slowest movement in music. The de-
grees of movement are as follows : adagio,
very slow; largo, slow; andante, mode-
rate ; allegro, quick ; presto, very quick.

A'DAMANT (a, priv., 6afxa<a, to sub-
due). This term, which simply means
unconquerable, is usually applied to the
hardest metal, probably steel. By Plato
it was applied to a compound of gold and
steel. By others it has been referred to
the diamond.

ADAMA'NTINE SPAR. The crys-
tals of Corundum, so named from their
approaching to adamant in hardness. It
is a variety of crystallized alumina, nearly
resembling the sapphire in composition,
and is usually found in granite, and
sometimes in primary limestone.

ADDITION (addo, to give to. The
operation of adding, or taking together,
any numbers or magnitudes, with the
view of finding the resulting number or
magnitude, which is called their sum.
The sign of this operation is + , which is
read plus, or more : thus, a + b signifies
that the number indicated by b is to be
added to that indicated by a, and repre-
sents the sum of a and b.

A'DDITIVE and SUBTRACTIVE.
Terms sometimes applied to algebraical
quantities, in the same sense, respec-
tively, as positive and negative, and with
the advantage of greater precision of
meaning.

ADDUCTOR MUSCLE {adduco, to
draw to). A muscle whose office is to

draw one part of the body to another, as
that which closes the two parts of a
bivalve shell ; in this case, its base or
insertion is indicated by an irregular de-
pression in each valve, termed the mus-
cular impression. See Abductor.

ADE'LPHIA (a<kA06t, a brother).
Literally, a brotherhood ; a term applied
in botany to a combination of the fila-
ments of the stamens into a single mass.
Thus, if there is only one combination,
as in Mallow, the filaments are said to be
mon-adelphous ; if there are two, as in
Pea, they are di-adelphous ; if three, as in
some species of St. John's Wort, they are
tri-adelphous ; if many, as in Melaleuca,
they are called poly-adelphous. The
tube formed by the union of monadel-
phous filaments is termed, by Mirbel,
androphorum.

A'DEPT (adipiscor, to obtain). A
characteristic denomination of those al-
chemists, who were supposed to have ob-
tained the grand objects of their inquiry,
viz. the philosopher's stone and the uni-
versal remedy.

ADFE'CTED or AFFE'CTED. A
term applied in Algebra to those equations
into which the first or simple power enters
as well as the square of the unknown
quantity ; thus a2 + 4x = 45. When ap-
plied to a quantity, it denotes that the
quantity has a co-efficient, or proper sign ;
thus, in the quantity + 5x, the quantity x
is said to be affected with the co-efficient
5, and with the positive sign +. See
Quadratics.

ADHE'SION (adhcereo, to stick to).
A term denoting, in physics, the force by
which bodies, whether similar or dissi-
milar, adhere together, when their sur-
faces are brought in contact. It differs
from cohesion, which denotes the force by
which the particles of a body are held
together. Adhesion relates to masses,
cohesion to molecules : a drop of water
maintains its globular form by cohesion ;
it moistens other bodies, as lime and
sand, by adhesion ; and, on its solidifica-
tion in the form of mortar, the adhesion
becomes cohesion.

ADHE'SION, VEGETABLE (od/^reo,
to stick to). A property of vegetable
tissue, by which contiguous parts grow
together. Opposite leaves may adhere,
and become connate ; sepals may adhere
entirely, forming a gamosepalous calyx,
or partially, and constitute a labiate ca-
lyx ; petals may adhere, forming a gamo-
petalous corolla ; stamens may adhere,
and form an adelphia ; carpels may

ADU

AER

adhere, and form a syncarpous or com-
pound fruit.

ADHIL. A star of the sixth magni-
tude, on the garment of Andromeda.

A'DIPOCERE (adeps, fat, cera, wax).
The fatty and spermaceti-like substance
into which muscle is converted by long
immersion in water or spirit, or by burial
in moist earth.

ADIPOCERE MINERAL. A fatty
matter, resembling adipocere, found in
the argillaceous iron ore of Merthyr.

A'DIT (aditus, an approach). A sub-
terraneous passage, in mining operations,
beginning at the bottom of a valley, and
continued up to the vein, for the purpose
of carrying out the minerals and of draw-
ing off the water.

A'DJACENT ANGLES. The two
angles formed at the point where one
straight line falls upon another, the
former line constituting one of the sides
of each angle, and the latter line consti-
tuting the other side of each. See Angle.

A'DJECTIVE (adjicio, to add to). In
grammar, a word which, being added to a
noun, qualifies or limits its application.
Adjectives are termed attributive, when
they denote a quality ; numeral, when
they refer to number. The possessive
pronouns might be termed pronominal
adjectives ; the demonstrative and distri-
butive pronouns may also be referred to
the adjective, as they both precede and
designate nouns, but never supply their
place.

A'DJECTIVE COLOURS. Colours
which require the intervention of some
base or mordaunt, in order to enable them
to adhere to the cloth, in the manufac-
ture of dye-stuffs.

ADNATE {adnatus, grown to) Grown
to any thing, as the anther to the face of
the filament in polygonum. See Innate.

ADOLE'SCENCE (adolesco, to grow).
The period of life in which the body has
acquired its utmost development ; com-
mencing at puberty, and terminating, in
the male, about the twenty-fifth, and in
the female, in the twenty-first year.

ADO'PTER, or ADAPTER. A vessel
with two necks placed between a retort
and a receiver, and serving to measure
the length of the neck of the former.

ADULA'RIA. A sub-species of pris-
matic felspar, the finest specimens of
which are procured at Adula, on the
summit of St. Gothard. By lapidaries it
is termed moonstone, from the play of
light exhibited by the arrangement of its
crystalline structure. A variety from

Siberia is called sunstone by jewellers,
and to this variety the avanturine felspar
of Archangel appears to belong.

ADVENTITIOUS (advenio, to come
to). Accidental; casual ; abnormal; that
which comes from some unusual source.
In botany, it denotes any thing developed
out of the ordinary course, as aerial
roots, extra-axillary buds, &c.

A'DVERB (ad, to, verbum, a word).
In grammar, a word which qualifies a
verb, adjective, participle, or even an-
other adverb, and generally indicates
time, place, quantity, or manner. The
adverb is closely related to the adjective,
and seems to have been originally con-
trived to express compendiously in one
word what must otherwise have required
two or more.

jEO'LIAN HARP (JEolus, the god of
the winds). A musical instrument con-
sisting of a simple box of wood, with
four or five strings, two or three feet
long, fastened at each end. These are
tuned in unison, so that, when made to
vibrate with force, they produce the same
tones. But, when suspended in a gentle
breeze, each string, according to the
manner of force in which it receives the
blast, either sounds as a whole, or is di-
vided into several parts.

jE'OLI PILE (Moli pila, ball of iEolus).
A steam globe, or hollow sphere of copper
or brass, with a small orifice for the in-
sertion of a tube, for illustrating both the
meohanical and thermal properties of
steam.

jEPI'NUS'S THEORY. A theory by
which the phenomena of magnetism are
referred to the agency of a peculiar
fluid, having properties very similar to
those of the electric fluid in the hypo-
thesis of Franklin, but which act only
upon ferruginous bodies and nickel. The
particles of this fluid repel one another
with a force which decreases as the dis-
tance increases, and they are attracted by
the particles of iron with a force varying
according to the same law. This theory
further requires the supposition that the
particles of iron repel one another accord-
ing to the same law.

^EQUILATERAL (aqua latera ha-
bens). Having equal sides, as applied
to triangles which have all their sides
equal.

AERA'TION (aer, air). The impregna-
tion of a liquid with carbonic acid gas ;
or simply the saturation of a liquid with
air.

AERIAL ACID (aer, air). A name
B5

AER

^ETH

given by Bergman n to carbonic acid, from
an idea tbat it entered into the compo-
sition of atmospheric air.

A'ERIFORM {aer, air, forma, like-
ness). Air-like ; a term applied to gase-
ous fluids, from their resemblance to
common air. See Gas.

A'ERO-DYNA'MICS (iJjp, tepo?, air,
Suva/jus, power). The science which treats
of the motion of the air, and of the me-
chanical effects of the air in motion.

A'EROGRAPHY {atjp, atpos, the air,
7pa0o>, to describe). A description of the
nature, properties, and limits of the at-
mosphere.

A'EROLITE {drjp, aepo?, air, X«'0o?, a
stone). A meteoric stone, or mineral
mass, which falls through the air, accom-
panied with the disengagement of light,
and a noise like thunder. These masses
invariably contain iron, cobalt, or nickel,
or a combination of these three metals*
in union with various earthly substances.
They have a specific gravity of from 3.3
to 4.3, and are more or less magnetic.

AERO'METER (<i;7P, a'epop, air, Me-
rpov, a measure). An instrument con-
structed by Dr. M. Hall, for ascertaining
the changes in the temperature of tbe
atmosphere; in the barometrical pres-
sure ; in the external and internal heights
of the fluid in the pneumatic trough ;
and, when this trough contains water, for
the elevation and precipitation of aqueous
vapour.

A'ERONAUTICS {arjp, aepor, air,
vaimKoc, belonging tc ships). The art of
navigating the air, by means of a balloon.

A'EROPHYTES (arjp, afpor, the air,
Qvtov, a plant). Plants which live ex-
clusively in air, as distinguished from
hydrophytes, which live in water.

AERO'SCOPY (u»7p, depor, air, a-KOTreco,
to observe). The observation of the air.

A'EROSTAT {^p, tepor, the air,
o-racrt?, a standing). An air-balloon, or
hollow spherev composed of flexible and
air-tight materials, and filled with some
elastic fluid whose specific gravity is
much less than that of atmospheric air.
See Montgolfier.

A'EROSTA'TICS {dhp, depor, air,
o-Tao-tf, a standing). The science which
treats of the equilibrium of air and other
elastic fluids.
. A'EROSTA'TION {atjp, aepo?, the air,
o-Tdo-tp, a standing). A science depend-
ing on the statical operations of our
atmosphere, and exhibited in raising
heavy bodies into the air, by the buoyancy
of gases of small specific gravity. In
10

other words, it is the science which
teaches the equilibrium of bodies sup-
ported in air.

iERU'GO {ces, copper). Verdigris;
an impure subacetate of copper, formed
by placing plates of the metal in contact
with the vapours of vinegar.

jE'SCULA'CEjE. The Horse-Chestnut
tribe of Dicotyledonous plants, named
from the genus iEsculus. Trees or
shrubs, with leaves opposite; flowers un-
symmetrical; stamens 7 or 8, unequal,
hypogynous ; ovary 3-celled ; fruits 1-2
or 3-valved ; seeds large, with a broad
hilum, exalbuminous.

ESTHETICS {a'laOnw, perception).
That science which refers the first prin-
ciples in the arts to sensation and senti-
ment, as distinguished from mere in-
struction and utility. " Art," says Men-
zel, "is not the result of understanding
alone ; the inspiration of the artist has
been, and ever must be, the source of
that which gives aesthetic value to his
productions."

^ESTIVATION {astivus, belonging to
summer). Prcefloration. A botanical
term, denoting the manner in which the
floral envelopes are arranged with respect
to each other, before their expansion
Thus, in the Umbelliferae, the aestivation
is valvate ; in Rosa, it is quincuncinl ; in
papilionaceous flowers, it is vexillary,
&c. See Vernation.

jE'STUARY (cestuarium, a firth). An
arm of the sea in which the tide ebbs and
flows. A channel of a river contiguous
to the sea, in which the influence of the
tides is perceptible, without distinct cur-
rent.

jE'THEO'GAMOUS (d<70nf, unusual,
idnos, marriage). A term applied to
what are otherwise called cryptogamous
plants, from the notion that their mode
of reproduction is of an unusual rather
than of a hidden nature. The term would
be more correctly written aetheogamous.

jETHER (a\0hp, ether). A highly
limpid, volatile, and inflammable fluid,
produced by the action of acids on alco-
hol.

JE'THIOPS (eu0«, to burn, Ss\j/, the
eye or countenance). A designation of
various chemical compounds, derived
from their black appearance, resembling
that of the jEthiop. Thus we have
cethiops mineral, or the black sulphuret
of mercury ; cethiops per se, or the grey
oxide of mercury ; cethiops martial, an
old name of the deutoxide of iron ; and
vegetable cethiops, a species of charcoal,

AFF

AFF

prepared by burning the fucus vesiculo-
sus in the open air, and reducing it to a
black powder.

iE'THOGEN {aWmv, brilliant, yeivofxat,
to become). A compound of boron and
nitrogen, lately discovered by Mr. Bal-
main. It gives a brilliant phosphorescent
light when heated before the blowpipe.

JE'THRIOSCOPE {atOpia, serene wea-
ther, o-K07rt'o>, to examine). An instru-
ment invented by Sir John Leslie for
indicating the power of the clouds in
preventing radiation. It consists of the
differential thermometer, having one of
the balls excluded from the light, and
the other placed in a polished metallic
cup. Exposed to a clear part of the sky,
the heat radiated from it escapes rapidly,
and the temperature falls ; exposed to a
cloud, the radiated heat is restored, and
there is no reduction of temperature.

jETIO'LOGY {atria, a cause, \6yos, a
treatise). That branch of medical sci-
ence which treats of the causes of dis-
ease.

AETI'TES LAPIS (ue-ror, an eagle).
Eagle-stone; a variety of iron ore, so
called from the belief that it was found
in the nest of the eagle, where it was
supposed to prevent the eggs from be-
coming rotten.

AFFINITY, CHEMICAL (affinitas,
relationship). That kind of attraction
by which certain substances, when placed
in contact, exhibit a tendency to combine
with each other, forming compounds dif-
fering in all their essential qualities and
actions from their constituent ingre-
dients, and constituting distinct species
of matter. The actual phenomena of
combination suggest the idea of peculiar
attachments and aversions subsisting be-
tween different bodies ; and it was in this
figurative sense that the terra affinity
was first applied by Boerhaave to a pro-
perty of matter.

1. Single affinity is the property by
which two elementary bodies combine,
as when oxygen combines with lead,
forming a white oxide.

2. Single elective affinity is the property
by which a body exhibits a preference in
combining with another, rather than with
a third, a fourth, &c. Thus nitric acid
has an -affinity for magnesia ; it has also
an affinity for lime ; but, on mixing
these three substances together, only one
of the affinities is obeyed : the nitric acid
combines with the lime, leaving the
magnesia altogether unaffected.

3. Double elective affinity is the pro-

11

perty by which two compounds are de-
composed, and a double affinity exhibited.
Thus, when carbonate of soda is added
to nitrate of lime, carbonate of lime is
instantly formed and precipitated, nitrate
of soda being formed at the same time
and remaining in solution. This is a
case of complex affinity, connected with
double decomposition.

4. Reciprocal affinity is the property
by which bodies, which have no tendency
to unite, are made to combine by means
of a third, which is then called the me-
dium. Thus, on introducing a clean
plate of platinum into a mixture of oxy-
gen and hydrogen gases, the gases in
contact with the metallic surface in-
stantly unite and form water. This has
been termed disposing affinity, and the
affinity of intermedium.

5. Quiescent and divellent affinities are
terms introduced by Kirwan. The former
is that property which prevents decom-
position, by maintaining the elements of
a compound body in their existing state.
The latter favours decomposition, by
tending to arrange the particles of a
compound in a new form.

6. Elementary affinity is that which
takes place between the elements of a
body. Resulting affinity occurs only in
a compound, having no existence with
the elements of that compound.

7. Inductive or current affinity is a term
expressive of the peculiar exhibition of
chemical affinity in the simple voltaic
circle. The idea of any thing like a cir-
culation of electricity in this case appears
to be abandoned, the phenomena admit-
ting of a perfectly intelligible explanation
when referred to ordinary chemical affi-
nity exerting its influence at a dis-
tance, by an inductive or circulating
agency.

AFFIRMATIVE. A term employed
in logic to denote the essential quality of
a proposition : this quality is affirmative
when the copula asserts an agreement
between the predicate and the subject ;
negative, when it denies that agreement.
The essential quality of a proposition is
therefore determined by the copula.

1. An affirmative quantity in algebra is
a positive quantity, or a quantity to be
added, as distinguished from a negative
quantity, or a quantity to be deducted.

2. An affirmative sign, or a positive
sign, is a sign of addition, and is marked
+ , signifying plus, or more. See Alge-
braical signs.

A'FFIX {affigo, to fasten to). Suffix.
B6

AG A

AGO

In grammar, a particle added to a word,
to diversify its form, or alter its significa-
tion ; as artful, wealthy, strengthen, con-
vulsion, &c. See Prefix,

AFFLU'XUS {affluo, to flow to). Forma
specified. Names given in former times
to a supposed reciprocal influence of ter-
restrial bodies ; it was compared to the
effect of a magnet on iron, and of amber
on chaff. '

AGA'LMATOLI'TE ( aTa\Ma, an
image, Ai'0op, a stone). Bildstein, or
figure-stone. A massive mineral, of a
grey, brown, flesh-red colour, sometimes
spotted, or with blue veins. It has been
called steatite pagodite, from its being
carved by the Chinese into grotesque
figures. It is found at Naygag in Trans-
sylvania, and Glyderbach in Wales.

AGA'MIDiE {agama, the name of a
lizard). The first section, according to
Cuvier, of the Iguanian Sauria, charac-
terized by the absence of palatal teeth.
All the agamoid lizards possess the pro-
perty of changing their colour ; and from
this circumstance, perhaps, the name
(afafiai, to wonder at) is derived.

A'GAMOUS (a, priv., -yd/uor, mar-
riage). Sexless ; a term applied by some
botanists to what are more commonly
called cryptogamous plants, from the
notion that they possess no sexual cha-
racters—that they are absolutely destitute
of stamen and pistil.

A'GARIC (Agaria, a kingdom of Sar-
matia). The generic name of the Mush-
room tribe of the Fungi which grow in
decaying animal or vegetable matter.

AGARIC MINERAL. One of the
purest of the native carbonates of lime,
found in clefts of rocks, and named from
its resemblance to the agaric in texture
and colour. It has been considered as a
variety of meerschaum. The Germans
call it bergmehl, or mountain meal ; the
Italians, latte di luna, or moon-milk. It
is the argillo-murite of Kirwan, the talc
pulverulent silicifere of Haiiy.

AGA'STRICA (a, priv., Yao-rJ/p, the
stomach). Stomach-less ; a term applied
to certain animalcules, which were sup-
posed to be devoid of internal digestive
cavities.

A'GATE ('Ax«t^9, the name of a river
in Sicily). A genus of semi-pellucid
gems, consisting of a basis of chalcedony,
with variable proportions of jasper, ame-
thyst, quartz, opal, heliotrope, and cor-
nelian. The finer varieties are termed
oriental ; the most beautiful British spe-
cimens are known by the name of Scotch
12

pebbles, and sometimes, from their local-
ity, Cairngorms.

1. Ribbon agate consists of alternate
and parallel layers of chalcedony with
jasper, quartz, or amethyst. The most
beautiful specimens come from Siberia
and Saxony. It occurs in porphyry and
gneiss.

2. Brecciated agate consists of a base
of amethyst, containing fragments of
ribbon agate. It is of Saxon origin.

3. Fortification agate is found in no-
dules of various imitative shapes, im-
bedded in amygdaloid. This occurs at
Oberstein on the Rhine, and in Scotland.
On cutting it across, and polishing it,
the interior zig-zag parallel lines bear a
considerable resemblance to the plan of a
modera fortification. In the very centre,
quartii and amethyst are seen in a splin-
tery mass, surrounded by the jasper and
chalcedony.

4. Mocha stone is a translucent chal-
cedony, containing dark outlines of ar-
borization, like vegetable filaments, sup-
posed to arise from mineralized plants of
the cryptogamous class. It is found in
Arabia.

5. Moss agate is a chalcedony with va-
riously-coloured ramifications of a vege-
table form, occasionally traversed with
irregular veins of red jasper. In this
and the preceding species, aquatic con-
fervas have been discovered, lire.

A'GGREGATE {aggregatus, herded
together). 1. A term applied in physics
to a body or mass composed of smaller
bodies or masses. The smallest parts
into which an aggregate can be divided
without destroying its chemical proper-
ties, are called integrant parts. 2. Ag-
gregate animals are animals clustered
together in a common enveloping organ-
ized substance, as the polypes, the aca-
lephae, and the acephalous mollusca.
3. In botany, the term is applied to
parts which are crowded together, as the
florets of the compositae, the carpels of
ranunculaceae, &c.

AGO'MPHIA (a, priv., -yo^or, a
grinder). Toothless animals ; a term
applied by Ehrenberg to those rotifera
whose jaws are deprived of teeth.

AGO'NIC LINES (a, priv., ywi/ta, an
angle). The name given by Prof. August
to some lines existing on the surface of
the earth, on which the horizontal needle
points to the true north ; in other words,
where the magnetic meridian coincides
with the geographical. These lines of no
declination are two in number: one,

AIR

ALA

called the American agone, is in the
western hemisphere ; the other, or Asia-
tic, is in the eastern hemisphere. They
extend from south to north, but they do
not coincide with the meridians ; for they
both, especially the Asiatic, intersect the
latter lines under different angles. See
Isogonic lines.

AIR {di]p, aer). The general designa-
tion of a gas, or permanently elastic
fluid. Ethereal air, or ether, is an ima-
ginary fluid, supposed to fill all space
beyond the atmospheres of the earth and
other planets. Atmospheric air is the
gaseous fluid which surrounds the earth,
consisting, when pure, of 20 parts of
oxygen, and 80 of nitrogen, with a por-
tion of carbonic acid, varying from 3 to 8
parts in 10,000 by weight. Air which is
expanded, or rendered less dense than
usual, is said to be rarefied; that which
has been subjected to pressure, is said to
be condensed.

AIR-CELLS. A term applied to cavi-
ties in the stems and leaves of plants,
which, being filled with air, enable the
plants to float in water ; also to mem-
branous receptacles in birds, by means of
which their bodies, being permeated by
the atmospheric air, are adapted for
flight.

AIR-GUN. An instrument for pro-
jecting bullets, resembling a common
gun, with the addition of a hollow ball
or reservoir, into which air is introduced
and condensed by means of a syringe.
The effects of the apparatus depend on
the elasticity and compression of the
air.

AIR-PLANTS. Plants which grow
without having their roo's within the
earth. It was supposed that they were
nourished by the air ; but their locality
in a damp atmosphere, or in contact with
other vegetables, rather suggests the
usual mode of existence There are
two tribes of air-plants, viz., the Brome-
liacece and the Orchidacece.

AIR-PUMP. An exhausting syringe,
or pneumatic apparatus for rarefying the
atmospheric air and reducing it to any
required degree of tenuity, and at the
same time exhibiting the circumstances
which attend this change of condition as
displayed in other bodies.

AIR-TIGHT. That degree of close-
ness, in any vessel or tube, which pre-
vents the passage of air.

AIR-VESSEL. A vessel in which air
is condensed by pressure, for the pur-
pose of employing the reaction of its
13

elasticity as a moving or a regulating
power. The term has also been applied
to the spiral vessels of plants and to the
trachece of insects.

A'LA. The Latin term for a wing.
In Ornithology, it denotes the pectoral
extremity, the bones of which support
broad folds of skin, covered with feathers,
and adapted for flight. In Botany, it is
the lateral petal of a papilionaceous
corolla.

A'LABASTER (d\d0a<rrpov, a calca-
reous spar). A stone usually white, re-
sembling marble, but soft enough to be
scratched by iron. The term is said to
be derived from Alabastron, a town of
Egypt. 1. Gypseous alabaster is a natural
semi-crystalline sulphate of lime, forming
a compact gypsum of various colours,
and employed for making statues and
vases. 2. Calcareous alabaster is a car-
bnnate of lime, deposited by the dripping
of water in stalactitic caves, and fre-
quently found as a yellowish-white de-
posit in certain fountains. The oriental
alabaster is of this kind.

A'LALITE. Another name for diop'
side or mussite, a sub-species of oblique-
edged augite. It is found at Piedmont, in
the black rock at Musa, near AH, in veins,
along with epidote or pistacite, and hya-
cinth-red garnets.

ALA'NGIA'CEjE. An order of Dico-
tyledonous plants, named from Alangium,
the Malabar name of one of the genera.
Large trees, with leaves alternate ; petals
5-10 ; stamens 2-4 times as numerous as
the petals; fruit drupaceous, esculent;
seeds albuminous, fleshy, pendulous.

A'LANTINE. An amylaceous sub-
stance, procured from the root of the
Angelica Arch angelica, an umbelliferous
plant.

ALASMODO'NTIN^. A sub-family
of the Unionidce, unios, or river mussels,
named from the genus alasmodon.

ALA'TE (ala, a wing). Winged ; a
term applied to any body, as a stem or
seed of a plant, which is bordered by a
leafy or membranous expansion resem-
bling a wing.

ALAU'DIN^E (alauda, a lark). Alau-
dine birds, or larks ; a family of the
Cantatrices of Macgillivray, intimately
allied to the Wagtails on the one hand,
and to the Thrushes on the other. They
do not belong, according to this author,
to the Conirostral or Thick-billed birds,
as generally supposed ; for their bill i*
differently formed, and they never shell
or husk seeds, but swallow them entire.

AL C

ALE

A'LBIN {alius, white). An opaque
white mineral found in Bohemia. It
occurs massive in aggregate crystalline
laminae.

ALBI'NO (albus, white). A term ap-
plied hy Dr. Prichard to one of those
varieties of mankind, including all indi-
viduals or races which have white hair,
and are also distinguished by red eyes.
The term. Albino is derived from the Por-
tuguese, by whom it was applied to indi-
viduals found on the coast of Africa, who
resembled the negroes in every respect
except in colour. These negroes were also
called Leuccethiopes, a term denoting
white negroes.

A'LBITE. Soda Felspar. A silicate
of alumina, resembling felspar in its pro-
perties, with the substitution of soda for
potash. It occurs in crystals under the
'form of hemitropes. These hemitropes
are formed when two crystals are so
joined to each other, that the upper plane
of the one is applied upon the lower
plane of the other. See Cleavlandite.

ALBU'MEN {albus, white). One of
the most important proximate principles
of animal bodies, existing, in the solid
state, in several of the textures of the
body, as the cellular membrane, the
skin, &c. ; and, in the liquid state, con-
stituting the principal part of the white
of egg. Vegetable albumen closely re-
sembles animal albumen, and appears to
be an ingredient of emulsive seeds gene-
rally, and to exist in the sap of many
plants.

ALBU'RNUM {albics, white). The ex-
ternal, last formed, and whiter portion of
the wood of exogenous trees. From its
being the channel of the ascending sap,
it is commonly called sap-wood. See
Duramen.

ALCA'RGEN; ALCA'RSIN. Arseni-
cal compounds derived from acetyl. The
former is synonymous with cacodylic
acid ; the latter, with oxide of cacodyl,
and known as the liquor of Cadet.

ALCE'DINiE {alcedo, the king-fisher).
Alcedine birds, or King-fishers ; a family
of the order Jaculatrices of Macgillivray,
of the Insessores of other writers. See
Halcyonidce.

A'LCHEMY. The fanciful search after
the philosophers' stone, by which the
baser were to be transmuted into the
precious metals ; and the elixir vitce, by
which human life was to be indefinitely
prolonged. Those alchemists who were
supposed to be skilled in the art were
termed Adepts.
14

A'LCIlLE {alca, the auk). The Auk
or Penguin tribe ; a family of the Nata-
tores, or Swimming birds, which exhibit
the most remarkable adaptation of struc-
ture for aquatic habits, their short feather-
less wings being admirable representa-
tives of fins or paddles.

A'LCOATES. Crystalline compounds
formed by alcohol with several of the
salts which it dissolves. Tney corre-
spond with hydrates, but are much less
stable.

A'LCOHOL. An alchemical term, of
Arabic origin, denoting the essence of
bodies, separated by sublimation from
all impurities. It now signifies ardent
spirit of wine, as obtained by distillation
and subsequent rectification from all
liquids which have undergone vinous
fermentation. The first product of dis-
tillation is called low wine; this, on re-
distillation, becomes raw spirit, and, on
repeating the process, rectified spirit. In
its most concentrated state it is termed
absolute alcohol, and is then free from
water.

A'LCOHO'METER {alcohol, fxirpov, a
measure). An' instrument, also called
cenometer, for ascertaining the quantity
of alcohol contained in a vinous liquid.

A'LCYONITES. A general term for
the fruit-like, spongiform fossils common
in chalk formations. They are fossil
alcyonia, or zoophytes nearly allied to
sponges, the production or habitation of
polypi.

ALDE'BARAN. The Arabic name of
a star of the first magnitude, marked a
Tauri, situated in the eye of the constel-
lation Taurus. It is the bright star in
the group of the Hyades. It frequently^
suffers occultation by the moon, when the I
ascending node is in Virgo, and exhibits \
the phenomenon of projection on the I
moon's disk. — -^

A'LDEHYDE. A colourless liquid,
formed by the action of oxidating bodies
upon alcohol, by which two atoms of hy-
drogen are abstracted, and the elements
of aldehyde left. Its name is derived
from the words oZcohol dehydrogena,-
tus: it is, in fact, alcohol minus hydro-
gen.

ALDERA'MIN. A star of the third
magnitude in the northern constellation
Cepheus.

ALDHA'FERA. A star of the third
magnitude in the constellation Leo.

ALECTO'RIDES (dX&rttp) a cock).
A tribe of gallinaceous or rasorial birds,
including the curassow and others which

ALG

ALG

resemble the common fowl in the form of
the beak. See Cracidce.

ALE'MBIC. A chemical vessel, em-
ployed in distillation, and consisting of a
body, cucurbit, or matrass, which serves
as a boiler, and a head, or capital, with a
pipe and receiver.

A'LEMBROTH SALT. A compound
of bichloride of mercury and sal ammo-
niac ; the salt of wisdom of the alchemists.

A'LGiE {alga, a sea-weed). Algacece.
The Sea-weed tribe of Cellular or Crypto-
gamic plants. Leafless, flowerless plants,
without any distinct axi3 of vegetation,
growing in water. Reproductive matter,
either absent or contained in the joints
of the filaments, or deposited in peculiar
thecae formed in the substance of the
frond. Sporules without any proper in-
tegument.

1. Jointless Algce. These comprise all
the broad membrane-like sea and fresh-
water species, as well as the large and
tough tangles and dulses so common on
our coasts. The genera fucus and ulva
belong to this division of algae.

2. Jointed Algce. These are generally
termed Conferva;, and comprise the
greater number of fresh-water species,
and many of marine station. They con-
sist of thread-like jointed tubes.

3. Disjointed Algce. These are cha-
racterized by their original or final spon-
taneous separation into distinct frag-
ments, which have a common origin, but
an individual life. They constitute the
organic limits of the animal and the
vegetable kingdoms.

A'LGAROTH, POWDER OF. An
oxichloride of antimony, precipitated on
throwing a concentrated solution of the
chloride into water, and named after a
physician of Verona.

A'LGEBRA. The science which teaches
to reason about indeterminate quantities
by means of letters of the alphabet, and
certain signs and symbols, which are em-
ployed to represent both the quantities
themselves and the manner in which
they are connected with other quantities.
It is, in fact, universal arithmetic. The
term algebra is derived from some Arabic
words, signifying restoration and reduc-
tion.

ALGEBRA'IC. An expression is said
to be algebraic, as distinguished from
transcendental, when its number of terms
is finite, and when each term contains
only addition, subtraction, multiplica-
tion, and division, and extraction of
roots, the exponents of which are given.
15

Thus, all infinite series, as well as ex-
pressions containing

log. x, a*, sin. x, cos. x, &c,
though used in Algebra, in the widest
sense of the word, are properly said to be
not algebraic, but transcendental. Simi-
larly, a curve is said to be algebraic when
its equation contains no transcendental
quantities.

ALGEBRA'IC CURVE. A curve of
which the relation between the abscissa
and the ordinates is expressed by an
algebraic equation, or an equation of
which the terms contain only algebraic
quantities. This is also called a geome-
trical curve, in contradistinction to a
mechanical or transcendental curve.

ALGEBRAIC GEOMETRY. A name
given to the application of Algebra to the
solution of geometrical problems.

ALGEBRA'ICAL SIGNS. Certain
signs used in algebraical and mathe-
matical operations, to denote the relation
of numbers, magnitudes, and quantities.
The characters with which they are used
are either the arithmetical figures, as
denoting numbers, or the letters of the
alphabet, as denoting magnitudes or
quantities. The explanation of these
signs is as follows : —
= Equality, denotes that the numbers
or quantities between which it is
placed are equal to each other : as 2
and 2 = 4.
+ Addition, generally called plus, a
Latin word for more: it denotes that
the numbers, or quantities between
which it is placed, are to be added to-
gether : as 3 + 2, or 3 more 2, are
equal to 5 ; or 3 + 2=5.
— Subtraction, called minus, meaning
less : it is placed between numbers or
quantities, and denotes that the num-
ber, &c, placed after it, is to be sub-
tracted from that which is before it •
as 5 — 2= 3.
X or • , Composition, or Multiplication,
denotes that the numbers between
which it is placed are to be multiplied
by each other, or together: as 5x3,
or 5 • 3 = 15. In numbers it is best
to use x, as • is apt to be mistaken
for a decimal point. With letters it
is indifferent which is used ; and
single letters are understood to be
multiplied where there is no sign be-
tween them : as a b denotes the pro-
duct or result of the multiplication of
the two numbers represented by a
and b. Numbers multiplied together
are called factors.

ALGEBRAICAL SIGNS.

-5- Resolution, or Division, denotes that
the number before it is to be divided
by the number after it : as 15 -j- 3 = 5.
When the number after the sign is
greater than that before it, the quo-
tient, or result of the division, cannot
be expressed in a common number,
because it is less than 1, which is the
least common number. In these cases
the quotient is indicated by placing
the number to be divided above a line,
and the divisor below. Thus the quo-
tient of 3 -J- 4 is expressed by f . When
we require only to express the divi-
sion and not perform it, the fraction
♦ is sufficient : as ^ is the same as

15 +- 3. Arithmetical operations can-
not be performed with letters, and
thus the fraction is the only form in
which we can point out the dividing
of one letter by another : as ~ is the
only way in which we can express the
quotient of a-i-b.
I Ratio, denotes that the numbers or
quantities between which it is placed
have some relation or proportion to
each other. In expressing ratios that
are equal, instead of =, the usual sign
of equality, ; ; is used. Thus the
expression a \ b \\ c \ d, means
that as a is to b so is c to d; and
2 ; 4 :: 6 : 12, as 2 is to 4 so is 6
to 12. Any one relation of the mag-
nitude or value of one thing, or quality,
is called a ratio.

> Majority, denotes that the number or
quantity which is placed before it is
greater than that which follows: as
a > b, that the quantity expressed
by a is greater than that represented
by b.

< Minority is the reverse of majority,
as c K. d expresses that the quantity
c is less than that of d.

=, >• and <, are used to denote the re-
lations of ratios, or proportions, as
well as of single numbers and quan-
tities : thus a \ b = c \ d, means that
a is the same part or portion of b that
c is of d; a \ b> c \ d, means that
a is a greater part of b than c is of d ;
and a '. b < c '. d, means that a is a
less part of b than c is of d. The
same may be expressed by making
the first, or antecedent term of each
ratio, numerator of a fraction, and the
last or consequent term, denominator.

Thus "J -5-i *>J'andT<^'are
respectively the same as, a * b — c \ d,
16

a \ b > c ; d, and a * b < c \ d.
When ratios vary, the signs are con-
veniently written = , >, <.

Connexion {vinculum, or tie) drawn

over numbers or quantities, connected
by signs, or the enclosing of such be-
tween parenthetical characters, de-
notes that they are to be taken as
one, that is, as the single number or
quantity that would result after all
the operations were performed. Thus,
8+6TT, or (8+fi)+-7, denotes that
the sum of 8 and 6 is to be divided
by 7, and is the same as \f, or 2 ; but
8+6 +-7, without the sign of con-
nexion, is 8f. Again, 24 — 3 x 8, or
(24— 3)x8, is the same as 21x8, that
is, 168; but if the sign of connexion
be taken away, it becomes 24 — 24,
or 0.

* a Power. A number or letter written
over the right of another in a smaller
character is called an exponent, and
denotes that the number or letter
over which it is written is understood
to be used as a factor in multiplica-
tion as often as is expressed by the
exponent. Thus 43 is the same as
4x4x4, or 64. An expression of
this kind is called a power of the
number or quantity to which the ex-
ponent is affixed, and that number or
quantity is called the root. The per-
forming of the multiplications is
called involution; and the number of
multiplications is always one less than
the number expressed by the expo-
nent, because two factors are required
for the first multiplication, and one
additional factor for every succeeding
one. If the root consist of several
numbers or letters, they must be in-
closed in parentheses, or placed under
a vinculum.

\/ a Root. When a number or letter is
considered as a power, the root of it
is denoted by placing the sign *J
before it, and writing the exponent
over the sign, in the place of the small
letter n : thus ^/64 is the third root
of 64, that is, it is 4. If the power
consist of several numbers or let-
ters, they must be connected. Thus,
2/4+12, or ^(4 + 12), is 4; but
1^/4+12, without the connexion, is
14. For the second root, or, as it is
called, the square root, the sign is
used without the exponent : as
^/9=3. Roots are also expressed by

/jJJkMM

ALK

fractional exponents, over the right :

as a? is the same as \J a.
oo Indefinitude, denotes that the quan-
tity before which it is put, is greater

or less than any value that can be

assigned : as ^, or j.

A'LGENIB. A star of the second
magnitude, on the right side of Perseus.

A'LGOL. Medusa's Head. A variable
star in the constellation Perseus.

A'LGORAB. A star of the third mag-
nitude, in the right wing of Corvus.

A'LGORITHM. An Arabic term ex-
pressing numerical computation, and now
generally used to denote the operative
part of arithmetic or of algebra.

A'LIFORM (ala, a wing, forma, like-
ness). Wing-like; shaped like a wing.

A'LILACE. An Arabic term for the
index which traverses the centre of an
astrolabe or quadrant, carrying the sights
or telescope, and indicates on the limb of
the instrument the number of degrees
and minutes which an object is elevated
above the horizon.

A'LIQUOT PART {aliquot, some).
A number which divides a given num-
ber without leaving a remainder : thus,
2, 4, 5, and 10 are aliquot parts of 20. All
the aliquot parts of any number may be
thus found :— divide the given number
by its least divisor ; then divide the quo-
tient also by its least divisor; and so on,
always dividing the last quotient by its
least divisor, till the quotient 1 is ob-
tained ; all the divisors thus taken are
the prime aliquot parts of the given
number.

ALISMA'CEvE. The Water-Plantain
tribe of Monocotyledonous plants, named
from the genus Alisma. Floating plants,
having leaves with parallel veins ; petals
and sepals 3 ; stamens definite or indefi-
nite ; ovaries superior ; fruit dry, indehis-
cent; seeds exalbuminous ; embryo shaped
like a horse-shoe.

A'LIZARIN. A peculiar colouring
principle obtained from madder, and
named from alizari, the commercial
name for madder in the Levant.

AL'KAHEST. An Arabic term, de-
noting the pretended universal solvent
or menstruum of the old chemists.

ALKALE'SCENT. A term applied to
substances on which alkaline (ammo-
niacal) properties are beginning to be
developed.

ALKALI PRUSSIAN. Phlogisticated

alkali. A name formerly given to a fixed

alkali, when ignited with some animal

substance, and lixiviated. It is found

17

ALL

to be in a great measure saturated with
Prussic acid.

A'LKALIES (al, the Arabic definite
article, and kali, the name of a plant
from which the alkali is obtained by
burning, and an old name for potash).
A class of bodies, which possess a strong
acrid and powerfully caustic taste, and
exercise a corrosive action upon all
animal matter; they turn the infusions
of blue vegetable colours to green, and
combine with the various acids, forming
an extensive class of compounds called
salts. There are three alkalies :

1. The Vegetable, ror/x,d alkalies,

or Potash, be^ lefJm,theA

2. The Mineral, ^ asl>es of in,land

or Soda, .and marine plants

^respectively.

3. The Animal, or Ammonia, or vola-
tile alkali, being raised by distillation
from hartshorn, &c.

ALKALl'METRY {alkali, and fierpov,
a measure). The method by which the
value of the alkalies, or carbonated alka-
lies, is determined. By means of an in-
strument, called an alkalimeter, the
quantity of alkali in a given substance is
ascertained by the quantity of dilute sul-
phuric acid of a known strength which
a certain weight of them can neutralize.

A'LKALINE AIR. The term by
which Priestley first described ammonia,
or ammoniacal gas, the volatile alkali.

A'LKALINE EARTHS. A term ap-
plied to magnesia, lime, baryta, and
strontia, from their earthy character and
alkaline properties.

ALKALFNITY. The property of an
alkali, viz. that of turning vegetable
blues into green.

ALKALIZA'TION. The impregna-
tion of any substance with an alkali.

A'LKALOIDS {alkali, eido?, likeness).
Vegeto-alkalies. A general term for cer-
tain bodies containing nitrogen, which
have the properties of the basic or me-
tallic oxides, and form salts with acids.
They are produced in plants during vege-
tation.

A'LKANET. A reddish purple dye,
obtained fron the roots of the Anchusa
tinctoria.

A'LKER. A star of the third magni-
tude in the constellation Crater.

A'LLAGITE A mineral of a brown
or green colour, consisting of a carbo-
silicate of manganese.

A'LLANITE. A mineral containing
cerium, found in Greenland, and named
from Mr. Allan.

ALL

ALM

ALLANTOIC ACID {allantois, a
membrane situated between the amnion
and the chorion). A white crystallizable
acid, described by Vauquelin under the
name of amniotic acid, and said to exist
in the liquor amnii of the cow. This
fluid contains a crystalline substance
called allantoin.

ALLEGORY (dW^yopia, a descrip-
tion of one thing under the image of an-
other). In Rhetoric, a figurative repre-
sentation by which some meaning is
signified beyond what is expressed: as
in the " Fairy Queen" of Spenser, and
Swift's " Tale of a Tub."

ALLE'GRO. An Italian adjective,
signifying gay, sportive, and denoting,
in music, quick time. Allegretto is a
diminutive of allegro, and denotes a tune
rather quick and sportive, but less so
than that indicated by the term allegro.

ALLIA'CEOUS {allium, garlic). A
term applied to any thing which has the
odour of garlic. In botany, \\ denotes
plants which partake of the properties of
garlic or of the onion.

ALLIGA'TION (alligo, to bind toge-
ther or unite). A rule in arithmetic,
applied only in commerce, by which the
price of a mixture is found, when the
price of the ingredients is known. Me-
dial alligation is the method of finding
the rate or quality of a compound, from
the given rates and quantities of the in-
gredients. Alternate alligation is the
method of finding the quantities of ingre-
dients necessary to form a compound of
a given rate.

A'LLIOTH. A star of the third mag-
nitude in the tail of the Great Bear.

ALLITERATION (ad, to, litera, a
letter). In composition, the frequent
recurrence of the same letter at the com-
mencement of words, as in the line of
Churchill,

** And apt alliteration's artful aid."

A'LLOCHRO'ITE ('d\\o?, another,
Xpoa, colour). A mineral allied to the
garnet, exhibiting several changes of
colour, when melted with phosphate of
soda before the blowpipe.

A'LLOPHANE (ciWoc, different, <pai-
vofxai, to appear). A mineral of a blue,
green, or brown colour, formerly called
Riemannite, and found in a bed of iron-
shot lime-stone in Greywacke slate, in
the forest of Thuringia.

A'LLOTROPIC STATE (&XXoc, an-
other, TpoiTof, condition). A term applied
to the dissimilar condition observed in
certain elements of which the various
18

forms of carbon, as diamond, graphite,
&c, afford a well-known example. This
is one of the causes of the isomerism of
their compounds.

ALLO'XAN; ALLOXA'NTIN. Com-
pounds containing cyanogen and carbonic
oxide, and discovered in the decomposi-
tion of uric acid. Alloxan is another
name for the erythric acid of Brugna-
telli. Alloxanic acid is produced by the
metamorphosis of alloxan by caustic
alkalies.

ALLO'Y (alloyer, French, to mix one
metal with another, for the purpose of
coinage). A natural or artificial com-
pound of two or more metals, as brass,
bell-metal, bronze, &c. But the term is
not employed when mercury enters into
the compound ; it is then called an amal-
gam.

ALLU'VIUM (alluo, to wash upon).
A general designation of earth, sand,
gravel, stones, and other transported
matter, which have been washed away
and thrown down by rivers, floods, or
other causes, upon land not permanently
submerged beneath the waters of lakes
and seas.

Alluvial Deposits. These are divided
by many authors into two kinds. 1. Old
Alluvium, or Diluvium, which is gene-
rally referred to the tertiary series, and
often contains remains of animals, more
or less resembling those living at the
present day. 2. Recent Alluvium, or
deposits of the same nature, but pro-
duced by causes which are in operation
at the present day.

ALMAAC. A star of the second mag-
nitude in the northern constellation An-
dromeda

ALMACA'NTER. An Arabic term
formerly employed in astronomy to de-
note a small circle of the sphere parallel
to the horizon. Two stars which have
the same almacanter, have the same alti-
tude, and hence the term almacanter sig-
nifies a circle of altitude, just as a small
circle parallel to the equator, all whose
points have therefore the same declina-
tion, is called a circle of declination.

A'LMANAC. An Arabic term signi-
fying reckoning, and applied to a calen-
dar, wherein the days of the month, fes-
tivals, lunation, motion of the heavenly
bodies, eclipses, &c, are reckoned for
each year. See Era.

A'LMANDINE. A designation of pre-
cious or noble garnet, occurring in pri-
mitive rocks and primitive metalliferous
| beds, and used for ring-stones.

ALT

ALU

ALOE'TIC ACID. The bitter prin-
ciple of aloes ; a precipitate procured by
heating nitric acid on aloes.

ALPHABET. A term derived from
the first two letters of the Greek lan-
guage, alpha, beta, or from the cor-
responding Hebrew letters, aleph, beth;
and applied to the series of letters used
in different countries. The term corre-
sponds with our familiar expression, the
A, B, C ; and some writers have assigned
an analogous origin to the Latin name
given to the letters, viz. elementa, which
corresponds with the pronunciation of
the three liquids, /, m, n.

ALPHAORCEIN ; BETAORCEIN.
Terms applied by Dr. Kane to two sub-
stances composing the orcein of archil :
the latter is produced by oxidation of the
former, and is the orcein of chemists.

A'LPHERATZ. A star of the second
magnitude in the head of Andromeda.

ALPHO'NSINES. A series of astro-
nomical tables drawn up by order of
Alphonso X. of Castile, in the year 1252.
They contain the places of all the fixed
stars, and all the methods and tables
then in use for the computation of the
places of the planets.

ALPINE PLANTS. Plants which
grow naturally in mountainous situa-
tions, where they are covered with snow
during the winter.

ALSINA'CEjE. The Chickweed tribe
of Dicotyledonous plants. A section of
the Caryophyllaceae, in which the sepals
are disunited. See Silenacece.

A'LTAN. A star of the first magni-
tude in the northern constellation Aquila,
the eagle with Antinous.

ALTERATIVES {altero, to change).
Remedies which produce a change. Re-
medies which very gradually re-establish
the health, as a drop of water, by fre-
quently falling, hollows a stone.

ALTE'RNATE {alternatus, changed
by turns). A term applied in geometry
to the angles which are made by two lines
with a third, on opposite sides of it. In
algebra, those terms of a proportion are
said to be alternate, which are separated
from one another by another term : thus,
in the proportion

2 : 4 : : 8 : i6,

2 and 8 are alternate terms, as also are
4 and 16. 'If alternate terms be rendered
consecutive, and consecutive terms alter-
nate, the proportion is still maintained:
thus,

2 : 8 : : 4 : i6. N

This relation is referred to in the fifth
19

book of Euclid by the Latin word alter-
nando, which signifies " by alternation,"
or alternately.

1. Alternate, in Botany. That position
of leaves upon the stem, in which one
leaf is placed above or below another,
and on the opposite side. The term is
generally employed in distinction to oppo-
site, or that arrangement in which two
leaves are developed from the same plane.

2. Alternately pinnate. A term used
in botany, where the leaflets of a pinnate
leaf are placed alternate^ on the common
petiole, as in potentilla rupestris.

ALTHE'INE. A supposed new vege-
table principle, extracted from the roots
of althea officinalis, and found to be iden-
tical with asparagin.

ALTHIO'NIC ACID. An acid found
in the residue of the preparation of de-
fiant gas, by means of alcohol and sul-
phuric acid, and named from the words
alcohol and ethionic.

A'LTITUDE (altus, high). A term
applied in Astronomy to the angle of
elevation of a celestial body above the
horizon, measured in the arc of that
vertical circle which passes through the
body.

1. The apparent altitude of a star is
the angle found by immediate observa-
tion ; the real altitude is ascertained by
correcting the apparent altitude for re-
fraction, parallax, &c.

2. The altitude of the pole is the geo-
graphical latitude of the place of observa-
tion, and remains the same throughout
the twenty-four hours.

3. In Geometry, the term altitude is
synonymous with height. Thus, the alti-
tude of a triangle is measured by the
straight line drawn from the vertex per-
pendicular to the base ; that of a cone, by
the straight line drawn from the vertex
perpendicular to the plane of the base ;
that of a parallelogram, by the perpen-
dicular drawn from its base to the oppo-
site side; that of a prism, by the perpen-
dicular distance between its bases.

A'LUDEL. A pear-shaped vessel re-
sembling the alembic, and used by the
old chemists in the process of sublima-
tion.

A'LULA (dim. of ala, a wing). A
little wing.

A'LUM. Alumen. A salt consisting
of a ternary compound of alumina, or
pure argillaceous earth, potass, and sul-
phuric acid. Alum is the base of pure
Way. The indurated beds of clay em-
ployed for obtaining the alum are called

AM A

AMB

alum-stone, a siliceous subsulphate of
alumina. Alum-slate is a rock, from
which alum is prepared.

Rock alum is a variety of alum
brought from Roccha, formerly Edessa,
in Syria Roman alum is the purest
variety of alum, containing no ammonia
in its composition. Ammonia alum is a
double salt, consisting of the sulphates of
ammonia and of alumina. Soda alum is
a double salt, consisting of the sulphates
of alumina and of soda. Iron alum,
manganese alum, and chrome alum are
salts of alumina, to which the generic
term alum is applied, their specific dif-
ferences being denoted by the name of
the metallic peroxide which they respect-
ively contain.

ALU'MINA. The earthy oxide of
aluminum ; a primitive earth, constitut-
ing the plastic principle of all clays, loams,
and boles, and her.ce termed argil, or
argillaceous earth. The name alumina
is derived from alumen, or alum, the salt
from which it is generally obtained in a
pure state.

ALU'MINITE. The name by which
mineralogists designate the native hy-
drated subsulphate of alumina.

ALU'MINUM. A metallic substance
resembling platinum, constituting the
base of alumina, and obtained from its
chloride by the action of potassium.

ALUTA'CEOUS {aluta, tanned leather).
Of a pale brown colour, like that of tanned
leather.

A'LVEOLATE {alveolus, a socket or
cavity). A term applied in Botany to a
surface covered with cavities, as the
receptacle of some species of the Com-
positae.

A'MADOU. A variety of the boletus
igniarius, found on old ash and other
trees. By means of nitre it is converted
into German tinder.

AMA'LGAM (a/j.a, together, yafiea),
to unite). A compound of mercury with
other metals. A native amalgam, which
is of silver, occurs in Hungary and Swe-
den, in various forms. The amalgam
employed in electrical apparatus con-
sists of one part of tin, two of zinc,
and six of mercury, mixed with some
unctuous matter, and spread on silk or
leather.

AMALGAMATION. The process of
making an amalgam, or mixture of mer-
cury with some other metal, for the pur-
pose of separating silver and gold from
their ores. The operation is founded on
the property which mercury possesses of
20

dissolving these metals out of the mine-
rals with which they are associated.

AMARANTA'CE^E. The Amaranth
tribe of Dicotyledonous plants. Herbs
or shrubs, with leaves simple, exstipu-
late ; flowers in heads or spikes ; stamens
hypogynous ; ovary superior ; fruit a
utricle ; seeds lentiform, with farinaceous
albumen ; embryo curved round the cir-
cumference.

AMARYLLIDA'CE^E. The Narcissus
tribe of Monocotyledonous plants. Gene-
rally bulbous, sometimes fibrous-rooted,
occasionally with a lofty stem. Leaves
ensiform ; calyx and corolla equally
coloured, superior; stamens 6; anthers
bursting inwardly ; stigma 3-lobed ; albu-
men fleshy or horny.

AMA'RYTHRIN (amarus, bitter, ery-
thrin). A bitter extractive matter pro-
cured from erythrin, sometimes termed
erythrin bitter.

AMAZO'NIAN STONE. A beautiful
green felspar, occurring in rolled masses
near the Amazon river.

A'MBER. Succinum. A hard, brittle,
transparent or opaque substance, of an
orange colour, considered to be an indu-
rated vegetable juice, or concreted balsam.
By destructive distillation of this sub-
stance, a light yellow sublimate is pro-
cured, called amber camphor, or volatile
resin of amber.

A'MBERGRIS (ambre gris, grey am-
ber). A sebaceous substance supposed
to be formed in the intestines of the
physeter macrocephalus, or spermaceti
whale, and sometimes found floating in
the sea, or thrown upon the shore. The
Japanese call it whale's dung.

A'MBITUS (ambio, to encompass).
The circumference, or bounding line, of
a surface, as of a leaf.

AMBLY'GONITE. A rare mineral,
consisting of a phosphate of alumina
and lithia, and occurring in granite, in
Saxony. It appears to be a species of
spodumene.

A'MBREIN. A peculiar substance
obtained by digesting ambergris in hot
alcohol. By absorption of oxygen it is
converted into an acid called ambreic
acid.

AMBULA'CRA (ambulacrum, an al-
ley). The narrow longitudinal portions
of the shell of the echinus, or sea-urchin,
which are perforated by small orifices,
traversed by tentacular suckers, and
alternated with the broad tuberculate
spine-bearing portions.

A'MBULATORY {ambulo, to walk).

AMI

AMN

Formed for walking ; as applied to the
feet of those birds in which the toes are
placed three before and one behind.
Such birds were called by Illiger ambu-
latores.

AME'NTUM. A catkin; a form of
inflorescence, in which the flowers of a
spike are destitute of calyx and corolla,
the place of which is occupied by bracts,
and the whole inflorescence falls off in a
single piece, either after flowering or the
ripening of the fruit, as in the hazel and
the willow. Plants which have this kind
of inflorescence were formerly called
amentaceous.

AME'RICAN RACE. One of the five
principal varieties of mankind, originally
spread over the whole of the Americas,
south of the sixtieth degree of north lati-
tude. This variety is characterized by a
reddish-brown complexion, long black
lank hair, deficient beard, eyes black
and deep-set, receding brow, cheek-
bones prominent, but more arched and
rounded than in the skull of the
Mongolian, aquiline nose, small skull,
with the apex high and the back part
flat, large mouth, and tumid lips, with
fine symmetrical frames of middle
height.

AMETA'BOLA (a, priv., ne-raftoX^,
change). A term applied by zoological
writers to those genera of insects which
do not undergo metamorphoses; which
escape from the egg nearly under the
same form as they preserve through life,
and which, on reaching their perfect
state, do not acquire wings. See Meta-
bola.

A'METHYST (a, priv., ^ed'ro, to be
intoxicated). The oriental amethyst is
a rare violet-coloured gem, called corun-
dum, or adamantine spar, with the qua-
lities of the sapphire or ruby. The occi-
dental or common amethyst is merely
a coloured crystal or quartz. The name
is derived from its reputed virtue of pre-
venting intoxication.

AMIA'NTHOIDE. A flexible, fila-
mentous mineral, of an olive green
colour, found at Oisans in France.

AMIA'NTHUS (a, priv., fuaitm, to
corrupt). Mountain flax. An incom-
bustible mineral, consisting of very deli-
cate and regular silky fibres. The term
appears to have been derived from the
circumstance that soiled cloths, made
of this substance, are better cleansed by
being thrown into the fire, than by wash-
ing. See Asbestos.

A'MIATITE. Fiorite, or pearl-sinter ;
21

a volcanic production, chiefly silica, in a
stalactitical form.

A'MIDES. A series of saline com-
pounds, in which the compound of nitro-
gen and hydrogen occurs, containing an
atom less of hydrogen than ammonia.
The term amidogen has been applied to
their radical.

A'MIDIN (amidon, starch). Gelati-
nous starch ; the soluble part of starch ;
a substance intermediate between gum
and starch.

A'MILENE. A liquid hydrocarbon,
obtained by distilling hydrate of oxide of
amyl repeatedly with anhydrous phos-
phoric acid.

A'MMELIDE: A'MMELINE. Two
of the products of the decomposition of
sulpho-cyanogen. See Melam.

AMMO'NIA. Ammoniacal Gas. A
transparent, pungent gas, formed by the
union of nitrogen and hydrogen, and
named from the substance sal ammoniac,
of which it constitutes the basis. It has
also been termed alkaline air, and the
volatile alkali.

AMMONI'ACAL AMALGAM. A sub-
stance formed by the action of galvanism
on a salt of ammonia, in contact with a
globule of mercury.

AMMONI'ACO. A term prefixed to
the names of salts, in which ammonia
has been added in sufficient quantity to
combine with both the acid and the base.
A'MMONITE. An extinct and very
numerous genus of molluscous animals,
called Cephalopoda, allied to the modern
genus Nautilus, which inhabited a cham-
bered shell, curved like a coiled snake.
Species of it are found in all geological
periods of the secondary strata ; but they
have not been found in the tertiary beds.
From its resemblance to the horns of the
statues of Jupiter Ammon, it is called
cornu Ammonis; from its coiled form, it
is popularly called snake-stone.

AMMO'NIUM. A hypothetical com-
pound of nitrogen and hydrogen. It is
not an elementary body, and possibly not
even a metal. Berzelius, however, con-
sidered it the metallic base of ammonia.
AMMONIU'RET. A compound con-
taining ammonia and a salifiable base, or
other substance not acid.

A'MNIOS. In Botany, a gelatinous
substance, in which the embryo of a seed
is at first suspended. It is subsequently
absorbed, or solidified in the form of
albumen.

AMNIOTIC ACID. An acid supposed
to be found in the liquor amnii of the

AMP

AMP

cow, but actually belonging to the liquor
of the allantois.

AMO'RPHOUS (a, priv.,/iop0»/,form).
Shapeless, irregular ; a term applied to
mineral and other substances which oc-
cur in forms not easy to be defined.

AMO'KPHOZO'A (anopcpo?, shapeless,
£wov, animal). Shapeless animals ; a term
applied by Blainville to the Porifera of
other writers, including the sponges.

A'MPELIC ACID. An acid obtained
from the oils of bituminous schist. The
term ampelin denotes an oily matter pre-
pared from the same substance.

AMPE'LID^E {ampelis, the chatterer).
Chatterers; a family of the Insessores,
or perching birds, or the Cantatrices of
Macgillivray, distinguished by the enor-
mous width of their gape, which in many
extends beyond the eye, and in some is
nearly as wide as in the goatsucker.
They belong, generally, to tropical Ame-
rica ; only one, the waxwing, is found in
Europe. See Dentirostres.

A'MPELITE (ci^TreAo?, a vine). A
kind of slate, found in the fossililerous
and in the metamorphic series of rocks.
The aluminous variety is the alum slate ;
the graphic, the graphic slate.

AMPERE'S THEORY. An electro-
dynamic theory, by which the mutual
attraction or repulsion of two magnets is
referred to the mutual action of electric
currents, according to a certain funda-
mental law, in a manner resembling
the polar attraction of statical electricity,
i. e. of electricity in a state of tension.
In following out this theory, it was sup-
posed by Ampere, that around each par-
ticle of a body, which has been consti-
tuted a magnet, there is constantly cir-
culating, in a certain stated direction, a
small current of electric fluid.

A'MPHI-; A'MPHIS- (dufl, d/x^i'O.
The former of these prefixes is a Greek
preposition, signifying on both sides,
around, that which may be understood in
two ways. The latter prefix has strictly
the same meanings, but is mostly used
as an adverb.

1. Amphi-bia (plot, life). The second
class of the Vertebrata, comprising ani-
mals which commence their larva state
as fishes, and undergo various stages of
metamorphosis in advancing towards the
condition of reptiles, their most striking
peculiarity consisting in the change from
aquatic respiration by branchiae to an
atmospheric respiration by true lungs,
They are consequently designated as ani-
mals having a double life.
22

2. Amphi-bole. A silicate of lime and
magnesia, otherwise called hornblende.
The derivation of this term is, perhaps,

4upl/3o\os, equivocal, from the liability
of this mineral to be mistaken for augite,
which is similarly constituted.

3. Amphi-bolia (dfi<pl(3o\os, equivocal).
The "fallacia amphiboliae" of logicians
is seen in those amphibolous sentences
which are capable of two meanings, not
from the double sense of any of the words,
but from their admitting of a double
construction, as in the witch-prophecy of
Shakspere, "The duke yet lives that
Henry shall depose." This is what the
French call " construction louche," a
squinting construction; i. e. where some
word or words may be referred either to
the former or latter clause of the sen-
tence.

4. Amphi-bolites. Trap-rocks, the basis
of which is amphibole or hornblende, a
silicate of lime and magnesia. The deri-
vation is the same as that of amphibole.

5. Amphi-gamous (yd/jLos, nuptials). A
term applied by De Candolle to those
cellular cryptogamous plants, which have
no trace whatever of sexual organs, as
distinguished from the other cryptoga-
mous plants, which, from the unusual
character of their fructification, are called
cetheogamous.

6. Amphi-gen (jevos, a kind). A double
silicate of potash and alumina, other-
wise called leucite or Vesuvian. The
name appears to be derived from its com-
position, the oxygen of the silica being
equal to that of the bases.

7. Amphi-pneurta (irveut, to breathe).
An order of amphibious animals, includ-
ing the proteus and the siren, which re-
tain their gills during life, and acquire
lungs in addition by the partial meta-
morphosis which they undergo.

8. Amphi-poda (irovs, nodos, a foot).
A group of crustaceous animals, which
have feet for both walking and swimming.
The best known British species is the
sand-hopper, which burrows in the sand,
and which, unlike most of the group,
seldom enters the water.

9. Amphi-sarca [a «p£, <rapKor, flesh). In
botany, a compound fruit, many-celled,
many-seeded, superior, indehiscent; in-
durated or woody externally, pulpy inter-
nally, as in adansonia.

10. Amphis-btenidce (ftalvta, to walk).
Double-walkers ; a small family of Ophi-
dian reptiles, intermediate in some re-
spects between the true serpents and the

I slow-worms. They derive their name

AMY

ANA

from their power of moving either back-
wards or forwards with equal facility.
The group is restricted to the warmest
parts of South America.

11. Amphi-scians {ama, shadow). A
designation of the people who inhabit the
torrid zone, and are so called because
they have their shadows at noon turned
sometimes one way, sometimes another,
or north and south — that is, to the north,
when the sun at noon is to the south of
their zenith, and vice versa.

12. Amphi-spermium (a-7r«?p^.a, seed). A
term applied by Link to a pericarp which
is of the same figure as the seed it con-
tains.

13. Amphi-stoma (oro/ia, the mouth).
A genus of suctorial parasitic worms,
which have pores, like mouths, at both
ends of the body.

14. Amphi-tropal (tpotto?, a turn). That
which is curved round the body to which
it belongs ; a term applied to tlie embryo
of the seed, when curved round the al-
bumen, so that its two ends are presented
to the same point.

15. Amphi-tropous (tpotto?, a turn). A
term applied to the ovule of plants, when
the foraminal and chalazal ends are
transverse with respect to the hilum.

AMPLE'XICAUL {amplector, to em-
brace, caulis, a stem). Stem-embracing;
as applied to leaves which sheathe the
stem, as in many ranunculaceous plants.

A'MPLITUDE {amplus, large). A
term applied, in astronomy, to the angu-
lar distance of a celestial body, at the
time when it rises or sets, from the
east or west point of the horizon. The
amplitude is measured by the arc of the
horizon intercepted between the east or
west point, and the centre of the celes-
« tial body, at the period of its rising or
setting on any particular day. See
Horizon.

Amplitude magnetic. A term applied
to the distances of the points of rising or
setting, from the east or west, as shown
by the compass.

AMPULLA'RINTE. Apple-snails; a
sub-family of the Turbidce, named from
the genus ampullaria : these animals
have a respiratory siphon ; the shell is
globular or turbinate.

AMY'GDALE.E (duvyidXa, an al-
mond). The almond tribe of Dicotyledon-
ous plants, a sub-order of the Rosacese.
Trees or shrubs with leaves alternate ;
corolla polypetalous ; stamens perigynous ;
ovary superior, solitary, simple ; fruit
drupaceous.
23

AMY'GDALIN {duvyddXa, an almond).
A principle found in the bitter almond
and the berries of the cherry-laurel. By
the action of alkalies on amygdalin, an
acid is obtained called amygdalic acid.

AMY'GDALOID {d/jivyddXa, an al-
mond, et(3o?, likeness). One of the forms
of the Trap-rocks, in which agates and
simple minerals appear to be scattered,
like almonds in a cake. Such rocks are
termed amygdaloidal claystone, amygda-
loidal felspar, &c. Also, a compound
mineral, consisting of lithomarge, green
earth, calc spar, steatite, and sometimes
hornblende, imbedded in greenstone or
wacke.

A'MYL (anvXov, fine meal, vXt], matter
or principle). The hypothetical radical
of a series of amylaceous compounds,
generally considered as an alcohol, from
the analogy which exists between oil of
potatoes, or hydrate of oxide of amyl, and
ordinary alcohol.

A'MYLIC ACID {amylum, starch).
A volatile acid, procured by digesting
moistened starch with peroxide of man-
ganese.

AMYRIDA'CEiE. An order of fra-
grant Dicotyledonous plants, named from
the genus Amyris. Trees or shrubs, with
leaves compound, with pellucid dots ;
corolla polypetalous ; stamens hypogy-
nous ; ovary superior ; fruit sub-drupa-
ceous, samaroid, or leguminous.

ANACARDIA'CE,E. The Cashew
tribe of Dicotyledonous plants, abound-
ing in a resinous, sometimes acrid, highly
poisonous juice. Trees or shrubs with
leaves alternate; flowers usually uni-
sexual ; stamens perigynous ; ovary su-
perior ; fruit generally drupaceous.

ANACOLU'THON ( uvaKoXovOeco,
not to follow). A grammatical term,
denoting a want of sequence in the
parts of a sentence. It occurs when the
latter part of a sentence does not agree in
syntax with the former, which sometimes
happens when a parenthetical clause has
intervened, so that the author has lost
sight of the construction with which he
set out.

ANAI'MA (a priv., al/xa, blood). The
name by which Aristotle designated
those animals which have no red blood,
and which he therefore supposed to be
without blood.

ANA'LCIME. A simple mineral of
the Zeolite family, also called cubizite,
of frequent occurrence in the trap-rocks.
It is found in grouped crystals deposited
by water, in the fissures of hard lavas.

ANA

ANA

In chemical language, it is the soda sili-
cate proportionate to amphigen.

ANALE'MMA {dvaKnuna, a pedestal
for a sun-dial). A projection of the sphere
on the plane of the meridian, made by
straight lines and ellipses, the eye being
supposed at an infinite distance, and in
the east and west points of the horizon.
Also, an instrument of brass or wood, on
which the projection is made (the plane
of projection being the solstitial colure),
with a moveable horizon attached to it.

ANALE'PTICS (dvaXan^dvu, to re-
store). Restoratives ; tonic remedies for
restoring the health, when it has been
impaired by disease or other causes.

ANA'LOGOUS NOUN (dvd\oyo?t ac-
cording to rule). A logical term, applied
to a noun which has only one significa-
tion, but admits of being applied in a
modified or subordinate sense, to objects
which bear no more than an analogy or
similarity to its original signification : as
the noun sting— of an animal— of con-
science— of an epigram.

A'NALOGUE {dvdXoyos, according to
rule). A body which resembles or cor-
responds with another body : a recent
shell of the same species, as a fossil shell
is the analogue of the latter. A part or
organ in one animal which has the same
function, as another part or organ in a
different animal is an analogue of the
latter. See Homologue.

ANA'LOGY (uvdAoYoc, according to
rule). A term denoting, in common ac-
ceptation, an imperfect degree of resem-
blance between different objects. In
Geometry it signifies proportion, simili-
tude, or equality of ratios or relations.
In Zoology it indicates the relation which
animals bear to one another in conse-
quence of their resemblance in the early
period of development, or in the less pro-
portion of their organization, and must
not be confounded with affinity : thus, a
whale is analogous to a fish, from its
general resemblance and its habitation,
but it belongs to the class Mammalia,
which includes no fishes.

ANA'LYSIS (dvaXum, to resolve). A
method of instruction, which begins with
those objects which are most known ;
examines their properties and relations ;
compares them together; traces back
effects to causes ; and thus proceeds by a
path opposite to the course of nature,
until it arrives at general principles and
laws. This is the process of induction.
The synthetic method is the reverse of
the analytic, as it proceeds from general
24

to subordinate truths, from universals to
particulars, from causes to effects.

1. Geometrical Analysis is defined by
Pappus, as " the course which, setting
out from the thing sought, and which for
the moment is taken for granted, con-
ducts by a series of consequences to
something already known, or placed
among the number of principles admitted
to be true. By this method, therefore,
we ascend from a truth or a proposition
to its antecedents ; and we call it analy-
sis, or resolution, as if indicating an
inverted solution. In synthesis, on the
contrary, we set out from the proposition
which is the last in the analysis, and
proceed by arranging, according to their
nature, the antecedents which present
themselves as consequents in the ana-
lytic method, and combining them to-
gether till we arrive at the conclusion
sought."

2. Chemical Analysis. The resolution of
compounds into their elementary parts.
When merely the number and nature of
these are ascertained, it is termed quali-
tative analysis ; when their proportions
also are determined, the analysis is quan-
titative. Every distinct compound, which
exists really formed, is called a proxi-
mate or immediate principle, and the pro-
cess of procuring it is termed proximate
analysis. The reduction of the proxi-
mate principles into their simplest parts
constitutes ultimate analysis. Lee Syn-
thesis.

ANAMORPHO'SIS (dvd, again, n6p-
0axrtf, formation). A distorted repre-
sentation of an object, which is capable,
however, of assuming its proper appear-
ance, when viewed in a particular direc-
tion or through a particular medium.
The figure is also restored, in some*
cases, by causing the anamorphosis to be
reflected from specula with certain sur-
faces, as those of cones and cylinders.
The term catoptric anamorphosis is ap-
plied to a drawing which has been dis-
torted according to regular laws, in order
to produce this effect ; and also to its re-
flected image in a cylindrical or conical
mirror.

ANASTATIC PRINTING {ixv'una-
fiai, to rise up). A recently invented
process for copying from a printed page
of any size, from a line engraving, or
from any other print, founded on the re-
pulsion of dissimilar, and the mutual
attraction of similar, particles, as exhi-
bited by water, oil, and gum arabic. The
term is derived from the technical ex-

ANC

ANF

pression of setting off, applied to that
part of the process by which a slight film
of ink is communicated by the copy to a
zinc plate.

ANA'STOMOSE (ui/ci, through, arofxa,
the mouth). A term denoting that the
mouths of two vessels come into contact
and blend together, or that two vessels
unite as if such kind of union had taken
place.

A'NATASE. A pure oxide of tita-
nium, having the property of exhibiting
various colours by reflected light, from
indigo blue to reddish-brown. It occurs
in granite, gneiss, mica slate, and transi-
tion limestone.

ANA'TID^E. The Duck tribe; a
family of the Natatores, distinguished
by a thick bill, wrhich is horny only at its
extremity ; the remainder of the man-
dibles being invested with a soft skin,
which in other birds is found only at
their hinder part. Under the general
designation of ducks, geese, and swans,
all the birds of this family may be ar-
ranged.

ANATFFIDA. An order of Cirrho-
pods, named from the genus anatifa, and
characterized by the peduncle by which
the animal is attached to its shell. See
Cirrhopoda.

ANATOMICAL SYPHON. An ap-
paratus invented by Wolf, for the pur-
pose of illustrating the exertion of a very
great pressure, by means of a small quan-
tity of liquid.

ANATOMY (dva, through, tf/xvoj, to
cut). A term simply meaning dissection,
but generally applied to the whole science
of organization — the science whose object
is the examination of the organs or in-
struments of life. Animal anatomy is
• distinguished into human anatomy and
comparative anatomy, according as it
treats of the organization of the human
body, or of that of other animals.

ANA'TROPOUS (di/aTp<?7ra>, to turn
upside down). Inverted; turned entirely
over ; a term applied to the condition of
ovules in many plants, as in the apple.
The inversion is occasioned by the con-
tinued growth of only one side of the
ovule, until that portion of it which was
originally near the apex is brought down
to the hilum ; the base of the nucleus
is then at the apex of the ovule.

ANCELLA'RIN^. An aberrant sub-
family of the Volutidce, or volutes, named
from the genus ancellaria, having the
aperture wide, and the base of the pillar
alone thickened and striated.
25

ANDALU'SITE. A massive mineral,
of a red colour, first found in Andalusia
in Spain.

ANDA'NTE (andare, Ital., to go). A
term employed in Music, to denote a
medium movement between the extremes
of slow and quick. See Adagio.

ANDR^EA'CEiE. An order of Cryp-
togamous plants, named from the genus
Andrsea. Branching moss-like plants,
having a four-valved theca, without oper-
culum or peristome.

ANDRE'OLITE. A mineral first
found at Andreasberg, in the Hartz ; also
called harmotone, and, from the form of
its crystals, cross-stone.

ANDROCE'UM (u'i%>> a man, olnot, a
house). A term applied to the male ap-
paratus in plants, commonly called the
stamens — the apices of old botanists.

ANDRO'GYNOUS {wnp, a man, <ytm/,
a woman). A term applied to a herma-
phrodite, or animal which possesses the
generative organs of both sexes.

ANDRO'MEDA. A northern constel-
lation, so called by the Greeks from
Andromeda, the daughter of Cepheus.
It contains sixty-six stars.

ANDRO'PHORUM (avtjp, a man,
<}){pa>, to bear). A term applied in
Botany, by Mirbel, to the tube formed
by the union of the filaments in a mon-
adelphous combination, as in passiflora.
ANEMO'METER (ai/e/uof, the wind,
nerpov, a measure). An apparatus for
measuring the force of the wind, and in-
dicating its direction at every minute of
the day. An exterior vane is connected
with an index, which traverses a sheet of
paper in a room beneath. The index
being influenced by the movements of a
clock, and the paper being marked into
divisions for every hour of the day, an
accurate record is effected

A'NEMOSCOPE (aveixo?, the wind,
a-icoTreu}, to examine). An instrument
for determining the direction of the wind,
and so constructed that the spindle of a
weathercock is connected with the hand
of a dial on which the points of the com-
pass are marked.

ANE'NTEROUS (a, priv., evrepa,
bowels). A term applied to the infuso-
rial animalcules, which have no intestinal
canal.

ANFRA'CTUOUS {anfractus, a wind-
ing backward and forward). Spiral ; re-
sembling in direction the spire of a cork-
screw, as applied in Botany to the direc-
tion of a stem ; or folded back upon itself,
as the anther of cucumis.

C

AN G

ANG

ANGEI'OCARPOUS (dyyelov, a ves-
sel, Kdpiros, fruit). A term applied by
Mirbel, in Carpology, to those plants
which have their fruit seated in enve-
lopes not forming part of the calyx : as
the filbert, which is enveloped in a husk;
the acorn, which is seated in a cupula.

ANGEI'OSFE'RMIA {dyyelov, a ves-
sel, cnripua, seed). A term applied to
all those plants which have their seeds
enclosed in a vessel, or pericarp, as dis-
tinguished from those which have no
such protection, and are termed gymno-
spermia. Thus, the leguminosa; are
angeiospermous, the coniferae gymno-
spermous.

A'NGLE (angulus, a corner). A plane
angle, according to Euclid, is " the in-
clination of two lines to one another,
which meet together, but are not in the
same direction." The point at which
they meet is called the vertex of the
angle ; and the angle, there formed, is
greater or less, according as the lines
torming it diverge more or less from each
other.

I. In Mathematics.

1. A Right Angle is formed when one
straight line meets another straight line
perpendicularly, and it contains 90 de-
grees, or the quarter part of a circle. An
obtuse angle is that which is greater than
a right angle ; an acute angle, that which
is less than a right angle.

2. Angle, Spherical. In Trigonometry,
the angle formed by the meeting of two
lines on the surface of a sphere or globe.
Trace any two meridians on the terres-
trial globe, as those of London and Peters-
burg, from the equator northwards ;
they will meet at the north pole, and
there form a spherical angle, which,
measured on the equator, will be found
equal to 30°.

3. Angle, Solid. The angle formed by
three or more planes which meet at the
same point, as the angles of solid
bodies.

4. Angle, Re-entrant. An angle whose
vertex is turned inwards, and which is
consequently greater than two right
angles. It is, in fact, a convex angle.

5. Angle of Contingence, or Contact.
The angle made by a curved line and its
tangent to it. at the point of contact.

6. Angle, Rectilinear, Curvilinear, Mix-
tilinear. 1. The first is formed by the
inclination of two right lines to each
other, which meet together, but are not
in the same right line. 2. The second is
formed by the tangents of two curves,

26

where they meet each other. 3. The
third is formed by the meeting of a right
line and a curved line.

7. Angles, Adjacent and Contiguous.
1. When a side of one angle, being pro-
duced, forms a side of another, the two
angles are said to be adjacent. Hence,
adjacent angles are supplements to each
other, making together 180°, or two right
angles. 2. When two angles have the
same vertex, and one side common to
both, they are said to be contiguous.

8. Angles, Opposite and Alternate.
1. When two angles have their sides mu-
tually continuations of each other, they
are said to be vertical or opposite, and it
may be shown that opposite angles are
equal, because they have a common sup-
plement. 2. The angles which are made
on the opposite sides of a line cutting
two parallel lines, are called alternate.

9. Angles, Supplemental and Comple-
mental. 1. When two angles are toge-
ther equal to two right angles, they are
said to be supplemental, and one is called
the supplement of the other. 2. When two
angles are together equal to a right angle,
they are said to be complemental, and one
is said to be the complement of the other.

II. In Optics.

10. Angle of Vision. The angle con-
tained between lines coming from op-
posite parts of an object and meeting in
the eye. On the magnitude of this angle
depends the apparent magnitude of all
objects perceptible to the sight.

11. Angle of Incidence. The angle
contained between the line described
by the incident ray, and a line per-
pendicular to the surface on which the
ray strikes, raised from the point of in-
cidence. •

12. Angle of Reflection. The angle
contained between the line described by
the reflected ray, and a line perpen-
dicular to the reflecting surface, at the
point from which the ray is reflected.

13. Angle of Refraction. The angle
contained between the line described by
the refracted ray, and a line perpendicu-
lar to the refracting surface at the point
in which the ray passes through that
surface.

III. In Astronomy.

14. Angle at the Sun. The angle under
which the distance of a planet from the
ecliptic appears at the sun.

15. Angle of Longitude. The angle
formed by the circle of a star's longitude

ANG

ANI

with the meridian at the pole of the
ecliptic.

16. Angle, Horary. The angle formed
with the meridian of any place by a great
circle, which passes through a star and
the pole.

17. Angle of Commutation. The angle
at the sun, formed by two lines, one
drawn from the earth, and the other
from the place of the planet reduced to
the ecliptic, meeting in the sun's centre.

18. Angle of Elongation. The angle
formed by two lines drawn from the
earth, the one to the sun, and the other
to the planet ; or it is the difference be-
tween the sun's place and the geocentric
place of the plaaet.

19. Angle of Erection. An inequality
in the motion of the moon, by which,
at or near her quadratures, she is not
in the line drawn through the centres
of the earth and sun, as she is at the
syzygies, but makes an angle with that
line of about 2° 51'.

IV. In Mechanics.

20. Angle of Draught. A term applied
to express that direction of a drawing
power which is best adapted to overcome
friction and weight ; and this is found to
be the angle made by the line of direc-
tion with a line upon the plane 4\er
which the body is drawn, and perpendi-
cular to that line of direction

21. Angle of Direction and of Elevation.

1. In mechanics, the angle of direction
is that comprehended between the lines
of direction of two conspiring forces.

2. The angle of elevation is that which is
comprehended between the line of direc-
tion and any plane upon which the pro-
jection is made, whether horizontal or
oblique.

22. Angle of Incidence and of Reflection.
When an elastic body strikes an elastic
plane at a certain angle, this body re-
turns under the same angle, but in the
opposite direction ; the former is called
the angle of incidence, the latter the
angle of reflection.

V. In Zoology.

23. Angle, Facial. An angle com-
posed of two lines, one drawn in the
direction of the basis of the skull, from
the ear to the roots of the upper incisor
teeth, and ,the other from the latter point
to the most projecting part of the fore-
head.

24. Angle, Frontal. In Ornithology, the
angle which the culmen, or upper part of
the beak, makes with the forehead.

27

VI. In Fortification.

25. Angles in Fortification. These are
of two sorts, real and imaginary. 1. Real
angles are those which actually exist and
appear in the wor^s, as the flanked angle,
the angle of the epaule, the angle of the
flank, and the re-entering angle of the
counterscarp. 2. Imaginary or occult
angles are those which are only subser-
vient to the construction, and which ex-
ist no longer after the fortification is
drawn, as the angle of the centre, the
angle of the polygon, the flanking angle,
the salient angle of the counterscarp, &c.

ANGUI'NID^E {unguis, a snake).
Slow-worms ; a family of Ophidian rep-
tiles, which combine the characters of
the serpents and the lizards. They ap-
proach the latter in the possession of
rudimentary legs under the skin, as well
as in other points of their organization.
The slow-worm of this country, erro-
neously called blind worm, has remark-
ably brilliant eyes.

A'NGULAR MOTION. The varia-
tion in the angle described by a line, or
radius, which connects a moving body
with the centre about which it moves.
Thus, a pendulum has an angular motion
about its point of suspension, and the
planets have an angular motion about the
sun.

Angular Intervals, in Astronomy, mea-
sured by means of the transit instrument
and clock, are those arcs of the equinoc-
tial, which are intercepted between cir-
cles of declination passing through the
objects observed.

A'NHYDRITE (a, priv., vdap, water).
Sulphate of lime ; a mineral occurring in
a crystalline form without water.

A'NHYDROUS (a, priv., vdap, water).
Without water ; a term applied to crys-
tals and gases which are deprived of
water. See Hydrate.

A'NILIC ACID. An acid formed by
the action of nitric acid upon indigo, and
named from the anil, a plant growing in
America, from the leaves of which indigo
is prepared. The acid was formerly
called indigotic.

A'NILINE. An oily liquid, which
distils over when finely-pulverized indigo
is decomposed by a highly concentrated
solution of caustic potash or soda, in a
retort.

A'NIMA. The name given by Stahl
to the intelligent agent supposed to pre-
side over many paits of the animal eco-
nomy. This is the archceus of Van Hel-
mont, and has been termed the vital
C2

ANI

principle, the spirit of animation, &c. In
pure Latin, the word denotes hreath,
animal life, the air we breathe; and is
sometimes synonymous with animus, the
soul.

ANIMAL KINGDOM. The appella-
tion given to that great division of natu-
ral bodies, to which animals belong.

I. Sub-kingdom Vertebrata.

Myelencephala (Owen)
Spinicerebrata (Grant),

ANN

These were distributed by Cuvier into
four large groups, viz. Vertebrata, Mol-
lusca, Articulata, and Radiata. This
arrangement has, however, been modi-
fied, and new terms introduced by more
recent writers, as will appear in the sub-
joined table :

Class 1. Mammalia.

2. Aves.

3. Amphibia.
II. Sub-kingdom Articulata.

Homogangliata (Owen).
Diploneura (Grant).
Annulosa (Macleay).
Class 1. Cirrhopoda. i 4. Insecta.

2. Annellida. 5. Arachnida.

3. Myriapoda. | 6. Crustacea.

4. Reptilia.

5. Pisces.

II. Sub-kingdom Mollusca.

Heterogangliata (Owen).

Cycloglangiata (Grant).

Class 1. Cephalopoda, i 4. Pteropoda.

2. Gasteropoda. 5. Conchifera.

3. Brachiopoda. | 6. Tunicata.

IV. Sub-kingdom Radiata.
Cycloneura (Grant).

Nematoneura (Owen).

Class Radiaria, Lamarck.

Acrita (Macleay).

Echinoderma, Cuvier.

Class Polypi, Cuvier.

Acalepha, Cuvier.

Ciliobrachiata, Farre.

Anthozoa, Ehrenb.
Class Entozoa, Rudolphi.

Nudibrachiata, Farre.

Coelelmintha, Owen.

Class Infusoria, Cuvier.

Sterelmintha, Owen.

Rotifera, Ehrenb.

ANIMAL MAGNETISM. A supposed
agent, of a peculiar nature, discovered
by Anton Mesmer, and said to be capable
of producing, in some mysterious way,
the most powerful effects on the human
economy.

ANIMALCULES (dim. of animal).
Microscopic animals existing in rivers and
ponds, and in all animal and vegetable in-
fusions. The term was originally applied
to a vast number of creatures widely dif-
fering from one another in every parti-
cular except minuteness of size, but is
now restricted to that division of infu-
sorial animalcules, termed, from their
digestive apparatus, polygastrica.

A'NION (dviov, that which goes up).
A term applied by Mr. Faraday to the
body which passes to the positive pole,
or anode of the decomposing body, as
it is separated by electricity. See Ration.

ANISO'BRYOUS ('dviaos, unequal,
28

Polygastria, Ehrenb.
fipvw, to grow). That which grows un-
equally; a term applied by some writers
to monocotyledonous plants, which, hav-
ing only one cotyledon, grow with unequal
force on the two sides of their axis. For
the same reason, such plants have been
called anisodynamous, from dova/jiis, force.

ANISOSTE'MONOUS (fotaos, un-
equal, o-rr/juwv, a stamen). A term ap-
plied to plants in which the number of
stamens does not correspond with the
number, or any power of the number, of
the petals or of the sepals.

ANNEALING. The process of heat-
ing a metallic body, and suffering it to cool
again in a moderate temperature, in
order to restore its malleability, which it
is apt to lose tinder the operation of ham-
mering. If cooled too suddenly, it be-
comes extremely brittle. The Annealing
of Glass is conducted in the same man-
ner, and is necessary to prevent its flying

ANN

ANO

to pieces on the application of violence
or a high temperature.

ANNE'LLIDA (annellus, a little ring).
A class of animals which have their
bodies formed of a great number of small
rings, as the earth-worm. They were
distinguished, in Cuvier's arrangement,
by their red blood, and by the circulation
of their blood in a double system of com-
plicated vessels. MM. Audoin and Milne
Edwards adopt four divisions, differing
in habits and structure : —

1. Errantia. Walking or swimming
animals, rarely sedentary. Head distinct
from the body ; with antennae, eyes, and
generally jaws. These are the dorsi-
branchia of Cuvier, the nereidce of Sa-
vigny.

2. Tubicola. Sedentary animals, in-
habiting the interior of solid tubes. Head
not distinct ; without eyes, antennae, or
jaws.

3. Terricola. Animals furnished with
bristles instead of feet ; dwelling in the
earth. No distinct head, antennae, or
jaws.

4. Suctoria. Animals without feet or
bristles, but furnished at each extremity
of the body with a prehensile cavity or
sucker. No distinct head; but generally
with eyes and jaws. Chiefly parasitic.

Divisions of Dr. Grant. Dr. Grant
divides the Annellida into the following
orders, by the differences of their respi-
ratory organs : —

1. Apneumata, or those which have
no perceptible respiratory organs, as
the nais.

2. Cephalobranchia, or those which
present distinct branchiae at the ce-
phalic extremity of the body, as the
serpula.

3. Dorsibranchia, or those which
have external or internal branchiae
disposed along the back of the trunk,
as the nereis.

4. Pulmonata, or those which breathe
by pulmonary sacs, as the lumbricus.

ANNUAL REVOLUTION. The
yearly course of the earth in its orbit
round the sun. It must be distinguished
from the diurnal motion. The latter
produces only day and night ; the former
causes the different lengths of day and
night, as well as the phenomena of the
seasons.

ANNULAR ECLIPSE (annulus, a
ring). A term applied in Astronomy to
those eclipses of the sun, in which a ring
of light is visible around the dark body
of the moon.

A'NNULATE {annulus, a ring).
Ringed ; surrounded or marked by rings,
as certain vessels in plants ; also certain
animals which appear to be composed of
a succession of rings.

ANNULO'SA (annulus, a ring). A de-
signation given by Macleay to the divi-
sion of animals included in the Articu-
lata of Cuvier, the Homogangliata of
Owen, and the Diploneura of Grant.
Macleay's term relates merely to their
annulated skin.

A'NNULUS. A ring. 1. The geome-
trical term for a solid formed by the revo-
lution of a circle about a straight line
exterior to its circumference, as an axis,
and in the plane of the said circle. 2. The
term annulus is applied, in Botany, to
that part of the theca of ferns, where the
stalk is united with its side ; and to the
collar which surrounds the stipes in the
highest forms of the fungi.

A'NODE (ava, upwards, 666s, a way).
A term applied by Mr. Faraday to that
part of the surface of a decomposing
body which the electric current enters —
the part immediately touching the posi-
tive pole. See Kathode.

ANODO'NTINjE (a, priv., bdovs,
636i/Tor, a tooth). A sub-family of the
Unionidce, or River Mussels, named from
the genus Anodon, the shell of which
has no articular processes, or teeth, at the
hinge.

ANODY'NE (ai/wdi/i/o?, without pain).
That which relieves from pain. An agent
of this kind which induces sleep, is called
a hypnotic ; if it causes insensibility, it
is termed a narcotic.

ANO'MALI'STIC YEAR (dvdfiaXo?,
irregular). The interval which occurs
between two consecutive returns of the
earth to the perihelion, or its least dis-
tance from the sun. The difference be-
tween the anomalistic and the tropical or
common year is owing to the orbit of the
earth representing an ellipse, of which
the major axis has a slow motion of
11 ".8 per annum in advance. In de-
scribing this arc, the earth occupies
4' 39". 7, which, being added to the side-
real period, gives 365d. 6h. 13m. 49s.3
for the anomalistic year. See Tropical
Year.

ANO'MALY (dvcofxaXo?, irregular).
A term applied, in Astronomy, to the
angle through which the radius drawn
from a planet to the sun has moved with
the planet from the time when this was
at its least distance from the sun. The
mean anomaly is proportioned to the time
C3

A N T

ANT

of description : to derive the true ano-
maly from this, is to find the mean angu-
lar motion which would have been per-
formed had the motion in angle been
uniform instead of the motion in area,
and involves a problem of the transcen-
dental kind.

ANOMOU'RA (ai/o/uof, unlawful,
ovpd, a tail). A family of Decapods,
distinguished by the very unusual con-
formation of the tail :— instead of being
encased in a hard coat of mail, as in the
macroura, the hinder part of the body is
soft and coriaceous, possessing only a
few detached calcareous pieces, ana-
logous, it is true, to those found in the
lobster, but strangely altered in struc-
ture. They are known by the name of
soldier-crabs or hermit-crabs.

ANONA'CE.E. An order of Dicotyle-
donous plants, named from the typical
genus Anona, and characterized by a
powerful aromatic taste and smell in all
their parts. Trees or shrubs, with leaves
alternate ; petals 6, hypogynous ; ovaries
numerous ; fruit consisting of many car-
pels, distinct or concrete into a fleshy
mass.

A'NOPLOTHE'RIUM (SvoTrXoc, un-
armed, dnpiov, a wild beast). An extinct
fossil quadruped, belonging to the order
Pachydermata, resembling a pig. The
name is derived from the animal having
been remarkably deficient in the means
of defence, from the form of its teeth,
and the absence of claws, hoofs, and
horns.

ANO'RMAL (anormis, without rule).
Irregular; contrary to the usual rule;
or, more precisely, destitute of rule. See
Abnormal.

ANO'RTHITE (dv-, the negative pre-
fix, of which a, priv., is a shortened form ;
bp66?, upright). A mineral consisting of
silica, alumina, lime, magnesia, and
oxide of iron. Its name, which signifies
without right angles, distinguishes it
from felspar, two of whose cleavages are
at right angles to each other.

ANOU'RA (a priv., ovpa, a tail). An
order of Amphibious animals, comprising
the Frogs and Toads, in which the gills
and the tail disappear on their reaching
the perfect state.

A'NSjE (ansa, a handle). In Astro-
nomy, those parts of Saturn's ring which
project beyond the disk of the planet, and
appear like handles to the body of the
planet

ANTAGONIST POWERS (uvtI, op-
posite, aywi/t'tojucw, to struggle). Two
30

powers in nature, of which the action of
one antagonizes, or counteracts, that of
the other; hence a kind of balance or
equilibrium is maintained, and the de-
structive effects, which would ensue from
the unchecked operation of either, pre-
vented. Of this kind are the centrifugal
and centripetal forces in Astronomy, the
attractive and repulsive agencies in Che-
mistry, &c.

ANTA'RCTIC {dvrl, apart™?, from
apKTot, the bear). That which is oppo-
site to the Arctic.

1. The Antarctic Pole is the South
Pole, and is opposite to the Arctic or
North Pole, which points to the constel-
lations of the Great and the Little Bears.

2. The Antarctic Circle is an imaginary
circle distant 23° 27'. 5 from the Antarctic
or South Pole, and 66°. 5 from the equator,
and parallel to it.

3. The Antarctic Ocean is, properly
speaking, the ocean between the Ant-
arctic circle and the South Pole.

ANTA'RES. The Scorpion's heart; a
star of the first magnitude, marked a, in
the constellation Scorpio.

ANTECEDENT (antecedo, to go be-
fore). In Logic, that part of a conditional
proposition from which the other part, or
the consequent, results ; the connexion
between the two, expressed by the word
" if," is called the consequence. In the
proposition, "If logic is useless, it de-
serves to be neglected," both antecedent,
and consequent are false ; yet the whole
proposition is true — the consequent fol-
lows from the antecedent.

The term Antecedent, in Mathematics,
denotes the former of the two terms of a
ratio, as distinguished from the latter
term, or consequent. Thus, in the con-
tinued proportion,

2 : 4 : : 3 ; 6 ; : 4 : 8 : : 5 ; io, &c

2, 3, 4, 5, &c, are antecedents, and 4, 6,
8, 10, &c, are consequents. Antecedents
and consequents may be inverted, with-
out destroying the proportion. Thus, if

2 : 4 : : 5 : io,

it is equally true that

4 : 2 ; : io : 5.

ANTECEDE'NTIA. An astronomical
term, denoting that a celestial body moves
contrary to the order of the signs of the
Zodiac ; it is then said to move in ante-
cedentid. When it moves in the order of
the signs, it is said to move in conse-
quentid.

ANTELO'PIDjE. The Antelope tribe ;
a family of the Ruminantia, remarkable

ANT

ANT

for the activity of their movements, and
for the solidity of the core, or bony
support of their horns. The name ante-
lope is a corruption of antholops, and this
is derived from ikvOos, a flower, and
wf, the eye, — in allusion to the beautiful
eyes of the gazelle, or "antholops" of
Eustathius.

ANTE'NNjE {antenna, a yard-arm).
The articulated horns, or jointed feelers,
with which the heads of insects and
crustaceans are invariably furnished. In
the latter class they are usually four in
number, consisting each of a scape, a
pedicel of two joints, and a clavolet, which
is divided into many minute joints. The
term antennae is sometimes applied to
the analogous parts, which are not
jointed, in worms and other animals.

ANTE'RIOR. Before. This term,
applied to bivalve shells, denotes that
valve in which the ligament is not placed.

ANTHE'LION {dvii, opposite, rjXtor,
the sun). A bright spot, opposite to the
sun. The horizontal circle attendant
upon halos is usually accompanied by
parhelia, and occasionally by anthelia.

A'NTHER (dv6np6s, from bvMm, to
flourish). The part of a plant which has
hitherto been considered as the fertilizing
organ. It is the essential part of the
stamen, consisting, in most cases, of two
thecae placed at the top of the filament,
and hence called the bilocular anther.
The anther is termed,

1. Innate, when it is attached to the
filament by its base, as in sparganium.

2. Adnate, when it is attached to the
filament by its back, as in polygonum.

3. Versatile, when it is attached to the
filament by a single point of the con-
nective, from which it lightly swings, as
in grasses.

4. Antica or introrsa, when the line of
its dehiscence is towards the pistil.

5. Postica or extrorsa, when the line of
its dehiscence is towards the petals.

ANTHERI'DIA. Little anthers; a
designation of the jointed filaments
which occur in mosses, containing vibrios
lodged in mucous cells, and surround
the rudiment of the future theca. They
are also called staminidia, or little sta-
mens, though they appear to have no
analogy to the stamens of flowering
plants. '

A'NTHIARIN. A gum resin, obtained
from the Anthiaris toxicaria, the most
deadly of the Upas poi>ons, employed by
the inhabitants of the East Indian Archi-
pelago to poison their arrows.
31

ANTHOCA'RPOUS {uvdo?, a flower,
/captor, fruit). A term applied, in Bo-
tany, to multiple fruits formed by masses
of inflorescence in a state of adhesion, as
the pine-apple, the fir-cone, &c.

ANTHO'DIUM (i„0«3»ie, flowery, full
of flowers). A term sometimes applied
by botanists to the inflorescence of the
Compositae, which is more commonly
called a capitulum. In either case it is
merely a depressed spike.

ANTHO'PHORUM Cdv0os, a flower,
$e'pa), to bear). A term applied by De
Candolle to an elongated internode which
occurs below the receptacle in the Caryo-
phyllaceae, and bears on its summit the
petals and stamens.

ANTHOPHY'LLITE (fefer, a flower,
<pi>\\ov, a leaf). A massive mineral, of a
brownish colour, found at Konigsberg in
Norway. Its appearance suggests that
of the anthophyllus, or clove, which de-
rives its name from the fragrance of its
flowers and the beauty of its leaves.

ANTHOZO'A (&i/0o?, a flower, £u>ov,
an animal). A term applied by Ehren-
berg to a class of polyps, including the
actinia and allied species, commonly
called animal-flowers.

ANTHRACITE (fivflpaf, a burning
coal). A species of slaty coal found in
the transition-rock formation, and often
called stone coal, glance coal, and blind
coal. It differs from common coal, which
it frequently accompanies, in containing
no bituminous substances, and in not
yielding inflammab'e gases by distillation.
It consists, in some specimens, of 95 per
cent, of carbon. Its varieties are the
massive or conchoidal, the slaty, and the
columnar.

A'NTHRACOTHEBITJM {&v9{>a$, a
coal, 9npiov, a wild beast). The name of
an extinct quadruped, supposed to belong
to the Pachydermata, the bones of which
were first found in lignite and coal of the
tertiary strata.

ANTHRANI'LIC ACID. An acid
obtained by the action of fused potash
on indigo.

ANTHROPO'GRAPHY (3i/0pa»ropt
man, ypd^oo, to describe). A description
of mankind, with reference to their geo-
graphical distribution, the physical cha-
racter and language of their classes, their
distinction into nations and tribes, and
their religious and domestic habits. See
Ethnography.

ANTHROPO'LOGY ('dvOpunot, man,
\6io?, an account). The science or theory
of man, with reference to the physiolo-
C4

ANT

APE

gical and the mental phenomena of his
nature. The term is sometimes restricted
to the science of Anatomy.

ANTILO'GARITHM. A term de-
noting the number to the logarithm : thus,
100 is the antilogarithm of 2. because 2
is the logarithm of 100. Among the
French, the term is more generally em-
ployed in the sense of the complement of
the logarithm, viz. the remainder pro-
duced by subtracting the logarithm from
the next higher term in the series 1, 10,
100, &c.

A'NTIMONY. A brittle whitish
metal, usually found associated with
sulphur. Sometimes this sulphuret is
termed crude antimony, to distinguish it
from the pure metal, formerly called
regulus of antimony. Its name has been
fancifully derived from its fatal effects
upon some monks {anti-moine), upon
whom Valentine is said to have tested its
properties.

Argentine flowers of Antimony is a
name for the sesqui-oxide of the metal,
derived from its silvery whiteness. In
the powder of Algaroth, the physician
Algarotti has given his name to the oxy-
chloride. The glass, liver, and crocus of
antimony are oxy-sulphurets of the old
apothecaries ; the saffron is a substance
formed by dissolving the oxide of the
metal out of the glass, by means of acids.
The kermes mineral is a sulphuret, re-
sembling in colour the insect kermes ;
the golden sulphuret is a similar sub-
stance. The butter of antimony is the
sesqui-chloride, a soft solid, of the con-
sistence of butter.

A'NTIPERISTA'LTIC {Avrl, opposite,
ireoiaraXTLKo^ , clasping and compressing).
A term denoting that the vermicular con-
tractions of a muscular tube follow one
another in a direction the reverse of the
ordinary one.

ANTI'PODES (avTi, opposite, Troder,
feet). The inhabitants of our globe who
live diametrically opposite to each other,
and who may therefore be said literally
to stand feet to feet. All gravitate to the
centre of the earth; and the terms up and
down must be considered, in astronomi-
cal language, merely in relation to bodies
being further from or nearer to the
centre. The antipodes differ in longi-
tude 180°, and the one class of inhabi-
tants has the same latitude north as
the other has south.

ANTI'SCII (Jvt'i, opposite, anta,
a shadow). Those inhabitants of the
earth, whose shadows fall in opposite di-
32

rections. The inhabitants of the north
and south temperate zones are always
antiscians ; those residing within the
tropics, are antiscians during only one
season of the year. See Ascii.

ANTISE'PTIC {!xvtI, against, o^ttw,
to putrefy). A term applied to substances
which prevent putreafction in animal or
vegetable matter, as common salt.

ANTITHESIS (dVTi0e<rts, opposition).
In Rhetoric, this term denotes contrast of
ideas, whether expressed by single words
or by single clauses. Quinctilian renders
it by the Latin term contrapositum, and
the following is an illustration from
Cicero :— u quod scis, nihil prodest ; quod
nescis, multum obest."

ANTI'TROPOUS (ivti, against, Tpe™,
to turn). Straight, and having a direction
contrary to that of the body to which it
belongs ; a term applied in Botany to the
direction of the embryo compared with
that of the seed : thus, if the nucleus be
erect, the embryo may be inverted, and
it is then said to be antitropous, as in the
nettle. The radicle of the embryo is then
turned to the point most remote from the
hilum.

A'NTLIA. The Latin term for a
pump, and hence applied to the spiral
instrument of the mouth of butterflies
and allied insects, by which they pump
up the juices of plants.

A'NTLIA PNEUMATIC A. The Air-
pump ; the name of a constellation in
the southern hemisphere.

ANTCE'CI (uvTt, opposite, oIkos, a ha-
bitation). Those who live under the same
meridian, and at the same distance from
the equator, but the one party having
north, and the other south latitude. See
Ascii.

A'NTONOMA'SIA (dvri, instead of,
ovofxa, a name). A rhetorical figure, by
which a proper name is used for a cha-
racteristic appellation, as when a bene-
factor is called " a Howard," a despot " a
Turk;'' or vice versa, as when a queen
is called "Her Majesty," or Homer "the
prince of poets."

A'ORIST (uopto-Tov, indeterminate).
A term applied, in Grammar, to those
inflexions of the verb in which the time
of the action is undefined.

A'PATITE (uTrardu), to deceive). Phos-
phate of lime ; a mineral which occurs in
tin veins, and possesses phosphorescent
properties. It is named from its having
been confounded with other minerals.

A'PERTURE (apertura, a little open-
ing). The mouth of univalve shells, or

APH

A P 0

the cavity from which the head of the
animal is protruded.

APE'TALOUS (a, priv., neraXov, a
petal). A term applied to plants which
have a calyx, but no corolla or petals.
They are also called monochlamydeous,
as having a single envelope, viz. a
calyx.

A'PEX. The pointed top of a cone.
The point or nucleus of a shell; and
hence the term is applied to the bosses
of bivalves, the points or tops of limpets,
or of univalves. In Botany, the apex of
a seed is the extremity opposite to the
base; the apex of a fruit is the part
where the remains of the style are
found.

APHjE'RESIS (utto, from, alpeca, to
take). Literally, a taking away ; a gram-
matical figure by which words are shorn
of their fair proportions, as when we say
'tis for " it is ;" 'tisn't for " it is not."

APHANI'PTERA (a<pav^, obscure,
TTTepov, a wing). The Flea tribe ; an
order of insects which have only the
rudiments of wings, in the form of little
scales, attached to the second and third
segments of the body, in which there is
no proper distinction of thorax and ab-
domen. They undergo metamorphosis.

A'PHANITE (a0ai/»/f, indiscernible).
A greenstone rock containing amphibole
as its principal ingredient, and named
from the indiscernible distinction of its
parts. It is the lapis corneus trapezius
of the old mineralogists.

APHE'LION (iTro, from, riXtot, the
sun). An astronomical term, denoting
the greatest distance of a planet from the
sun. Its opposite point is the perihelion,
which is the nearest point to the sun.
These two points are, therefore, the two
extremities of the greater axis of an
orbit.

A'PHID^E (aphis, the plant-louse).
The Plant Lice ; a family of the dimerous
Homoptera, which infest plants, and are
vulgarly supposed to give rise to the phe-
nomena of blights and honey-dew.

APHLOGI'STIC {d(p\6i«TTO?, not in-
flammable). Without flame; a term ap-
plied to a lamp in which the combustion
is effected without flame.

A'PHRITE (d(pP6t, foam). Earth foam ;
a silvery-white, friable carbonate of lime,
found in calcareous veins.

A'PHRIZITE. A variety of black
tourmaline.

APHY'LLOUS (a, priv., QvXXov, a
leaf). Leafless ; a term applied to plants
which have large scales, but no true
33

leaves ; also to plants in which the true
leaves are so small as to be reduced to
scales.

APIA'CEiE (upturn, parsley). A term
recently applied to the family of Umbel-
liferous plants, as more consonant with
the plan of forming natural orders. See
Umbelliferas.

A'PICAL (apex, the top of a cone).
Belonging to the pointed end of a cone-
shaped body.

APIO'CRINITE (&mov, a pear, Kpivov,
a lily). Pear-encrinite ; a sub-genus of
fossil encrinites, in which the stem is
rounded and dilated at its upper extre-
mity into a pear-shaped figure.

APIS MUSCA. A modern southern
constellation, consisting of four stars.

APLANA'TIC (a, priv., nXdvn, error).
Free from error ; a term applied to those
optical instruments in which the spheri-
cal and the chromatic aberrations are
completely corrected. This term is more
correct than achromatic, which merely
implies correction of the chromatic ab-
erration ; whereas a good, or aplanatic,
instrument has its errors of sphericity
balanced equally with those of colour.

APLO'ME (an\6os, simple). A mine-
ral usually considered as a variety of the
garnet, from which, however, it appears
to differ in its primitive form. It crys-
tallizes in rhombic dodecahedrons, de-
rived by the simplest laws of decrement
from the cube.

APOCA'RPOUS (dno, from, Kapnos,
fruit). A term applied, in Botany, to
that condition of the carpels, in which
they are distinct from one another, or
easily separable, as in ranunculaceous
plants. See Syncarpous.

APOCY'NACEjE. An order of Dico-
tyledonous plants, named from the typical
genus Apocynum, and agreeing with
Asclepiadaceae, but of rather more sus-
picious properties. Trees or shrubs
usually milky, with leaves opposite, some-
times whorled ; corolla monopetalous,
hypogynous; stamens inserted into the
corolla ; ovaries two ; fruit a follicle,
capsule, drupe, or berry, single or double.

A'PODA (a, priv., ttoi/c, 7ro36s, a foot).
An order of Amphibious animals, com-
prising only one genus, the Ccecilia, of a
serpent-like form, and altogether desti-
tute of feet. The term is also applied to
an order of fishes which have no ventral
fins. See Malacopterygii.

APO'DOSIS (aTTodoats, a giving back).
A term employed in Rhetoric to denote
the consequent proposition, as opposed to
C5

APP

APP

protasis, which is the hypothetical or
limiting clause of a period.

A'POGEE (dTz-6, from, tf, the earth).
That point of the moon's orbit in which
she is furthest from the earth. Her
perigee is that in which she is nearest to
the earth. Formerly, when the earth
was considered as the centre of the sys-
tem, the terms apogee and perigee were
applicable to the places of all the planets,
and also of the sun, with respect to their
variable distances from the earth ; but
now they refer only to the moon. What
was then called the sun's apogee is now
the earth's aphelion ; and the perigee of
the former has become the perihelion of
the latter.

APOPHY'LLITE (<Wo0t/X\<7>, to
strip off leaves). Ichlhyophthalmite, or
fish-eye stone. A scarce mineral, having
a pearly lustre, like the species of felspar
called moonstone. It is found in the
iron mines of Uto, in Sudermania, a
province of Sweden. The term is derived
from the lamellar structure of the mine-
ral, and its exfoliation under the blow-
pipe.

APOPHYSIS (<W6, from, <pia>, to
grow). A process of a bone, and a part
of the same bone. An unequal expan-
sion sometimes found at the base of the
theca in mosses.

A'POSIOPE'SIS {inroa-iandu), to be
silent after speaking). Literally, the
becoming silent; a rhetorical figure, by
which, for emphasis or modesty, the
sentence is broken off, as in Virgil, JEn.
I. 135. The aposiopesis is expressed, in
writing, by a short horizontal line at the
point where the sense is broken off.

APOSTASIA'CEjE. An order of Di-
cotyledonous plants, named from the
genus Aposlaaia, and closely allied to the
Orchidaceae, from which they differ essen-
tially in having a 3-celled fruit, with
loculicidal dehiscence, and in the style
being altogether free from the stamens
for the principal part of its length.

APOTHE'CIA (utto, from, fHjifa a cap-
sule). Scutella, or little shields ; a term
applied, in Botany, to the reproductive
Jfc organs of lichens.

APPA'RENT {appareo, to appear). A
term applied in Astronomy to those phe-
nomena which are actually observed, as
distinguished from real or true pheno-
mena, which result from correction or
reduction. Thus, the apparent altitude
of a star requires a correction for refrac-
tion ; the apparent place of a planet
requires a reduction to that place in
34

which it would be seen from the centre
of the earth.

1 . Apparent diameter of a planet. The
angle made by two lines drawn to the
eye from the opposite points of the planet's
disk. The true diameter is the line which
joins the opposite points of the disk
itself.

2. Apparent horizon. The sensible
horizon, or the plane in which lies the
circle which actually bounds our view.
The real or rational horizon is a plane
parallel to the preceding, drawn through
the centre of the earth.

3. Apparent magnitude. The angle
under which any line appears at the eye ;
that is, the angle made by lines drawn
from its extremities to the eye.

4. Apparent motion. The velocity and
direction in which a body appears to
move, when the spectator is himself un-
consciously in motion.

APPENDI'CULATE {appendicular a
little appendage). That which has small
appendages, as applied in botany to the
calyx of Scutellaria.

APPE'NDIX (appendo, to hang to).
An appendage ; a process appended to
any part of a body, without being essen-
tial to the existence of the body, as a
thorn or gland in plants.

A'PPETENCY {appeto, to seek). The
disposition of organized beings to acquire
and appropriate substances adapted to
their support.

APPOSITION {appono, to place near).
That part of the function of nutrition,
by which the constituents of the blood
are transformed on the free surface of an
organ into a solid unorganized substance,
which is the mode of growth of the non-
vascular tissues. See Transformations.

APPREHE'NSION, SIMPLE. In lo-
gic, that act or condition of the mind, in
which it receives a notion of any object.
It is analogous to the perception of the
senses. Incomplex apprehension regards
one object, or several without any rela-
tion being perceived between them, as a
man, a card, &c Complex apprehension
regards several objects with such a rela-
tion, as a man on horseback, a pack of
cards, &c.

APPROXIMATION {ad, to, proxi-
mus, nearest). A result in experimental
philosophy, which approaches more or
less near to the truth, as the calculation
of the distance, or of the diameter, of a
celestial body. In mathematics, quan-
tities are said to be approximate, which
are nearly, but not absolutely, equal.

' " Y

A~2*^^

AQU

APPU'LSE {appello, to drive to). The
near approach of two celestial bodies to
each other in angular distance, so as to
be seen, for instance, within the field of
a telescope.

APRIO'RI. A POSTERIO'RI. Terms
expressive of two different modes of rea-
soning. By the argument a priori, a
conclusion is drawn from an antecedent
fact, whether the consequence be in the
order of time, or in the necessary rela-
tion of cause and effect. By the argu-
ment a posteriori, we reason from what
is consequent in the order of time to
what is antecedent, or from effect to
cause. An individual may fall under
suspicion of murder for two reasons : he
may have coveted the deceased's pro-
perty, or he may be found with it in his
possession ; the former is an a priori, the
latter an a posteriori argument against
him.

A'PSIDES (a^/r, a curved link of a
chain). Apses. Those points in a planet's
orbit, in which it is at its greatest or least
distance from the sun or earth. The
line joining them, and passing through
the sun's or the earth's centre, is called
the line of the apsides. This term occa-
sionally coincides with other terms.
Thus, in the orbit of the earth, or of any
primary planet, its higher apsis is also its
aphelion, its lower apsis its perihelion ; in
the moon's orbit, the higher apsis is equi-
valent to the apogee, the lower apsis to
the perigee.

A'PTERA (a, priv., irrepov, a wing).
A series of insects characterized by the
absence of wings. Some of these do not
undergo metamorphosis ; these compose
the orders thysanoura and parasita, while
those which undergo this change, form
the order syphonaptera.

A'PUS (a7roi»?, without feet). Avis In-
dica. Bird of Paradise; a constellation
in the southern hemisphere, consisting
of eleven stars. The bird of Paradise
was formerly supposed to have no feet.

A'PYROUS (a, priv., ttZp, fire). A
term applied to bodies which sustain the
action of a strong heat for a long time
without change of figure or other proper-
ties. It is synonymous with refractory.

AQUA FORTIS. An impure nitric
acid, distinguished by the terms double
and single, the latter having only half
the strength of the former. The more
concentrated acid, which ismuch stronger
than the double aqua fortis, is called by
artists spirit of nitre.

AQUA MARINE. A designation of
35

A R A

beryl, a mineral of a green colour of
various shades, also called greenish-
yellow emerald.

AQUA REG I A. Royal water ; an al-
chemical designation of nitro-muriatic
acid, from its property of dissolving gold,
the king of metals.

AQUA'RIUS. The eleventh of the
zodiacal constellations, consisting of 108
stars, the principal of which is Scheat.
It presided over the second month of
summer, and extended from the 20th of
July to the 20th of August. The inun-
dation of the Nile increases during this
month.

A'QUEOUS {aqua, water). A term
synonymous with hydrate, and employed
for expressing definite combinations with
water. It admits of prefixes, as Jin-
aqueous, when two atoms of water enter
into a compound.

A'QUEOUS ROCKS. A term applied
in geology to rocks of the second and
third classes, as composed of matter de-
posited by water. Those of the second
class are more especially named meta-
morphic, from the supposition of their
having undergone a remarkaole change
in the course of their formation. Aque-
ous rocks are likewise called stratified, as
being invariably found in strata or layers.

AQUIFOLIA'CE^. The Holly tribe
of Dicotyledonous plants, named from
the typical genus aquifolium. Trees or
shrubs, with leaves alternate or opposite,
coriaceous ; corolla 4 or 5-parted, hypo-
gynous; ovary fleshy, superior, 2-4-celled;
fruit fleshy, indehiscent, with 2 to 6 stones.

A'QUILA. The Eagle; a northern
constellation, containing (with Antinous)
seventy-one stars, the principal of which
is Altan.

AQUILARIA'CEjE. The Agallochum
tribe of Dicotyledonous plants, named
from the typical genus aquilaria. Trees
with leaves alternate ; calyx turbinate or
tubular; stamens 10 or 5; ovary supe-
rior; capsule pear-shaped, 1-celled, 2-
valved.

AQUITE'LjE {aqua, water, tela, a
web). A family of spiders, which spread
their silken filaments under water, to en-
trap aquatic insects.

A'RA. The Altar ; a southern con-
stellation, containing nine stars.

ARA'CEjE. Aroidece. The Arum tribe
of Monocotyledonous plants. Herbace-
ous plants with leaves sheathing at the
base ; flowers unisexual, arranged upon
a spadix, within a spathe ; stamens hypo-
gynous; ovary superior; fruit succulent.
C6

AR A

ARACHNI'DA (aPaXvr], a spider). A
class of the Articulata, or the Diplo-
gangliata of Grant, comprising, arti-
culated animals, generally with four
pairs of legs, without wings or meta-
morphosis, as the spiders, mites, and
scorpions. They are divided, by the dif-
ference of their respiratory organs, into

1. Tracheata, which breathe by rami-
fied tracheae, as the phalangium, in
which there are only two abdominal stig-
mata ; and

2. Pulmonata, which breathe by pul-
monary sacs opening by 2-8 transverse
abdominal stigmata, as in the scorpions
and spiders.

ARiEO'METER (iptuor, thin, /uexpoi/,
measure). An instrument, also called a
hydrometer or gravimeter, for ascertain-
ing the specific gravities of bodies, by the
depth to which it sinks in these bodies,
the amount being shown either by
weights, or by a scale attached to it.
Hence they are distinguished as weight
and scale araeometers, the former being
used chiefly for finding the specific gravity
of solids and fluids, whilst the latter
serve only for finding that of fluids, after
which, indeed, they are frequently named.

Per Cent. Araeometer. An araeometer
made for particular and mixed liquors,
in which the scale is so graduated as to
express the component parts per cent.,
either by weight or volume. It is named
after the fluid it is used to test, as spirit
of wine araeometer, beer araeometer. To
this class belongs the powder araeometer,
for ascertaining the proportion per cent,
of saltpetre in gunpowder.

ARALIA'CEiE. The Aralia tribe of
Dicotyledonous plants. Trees, shrubs, or
herbs, with, in all respects, the habit of
Umbelliferae, from which they are dis-
tinguished chiefly by their many-celled
fruit and more shrubby habit.

ARANEI'DiE {aranea, a spider). A
section of the Arachnida, including the
Spiders, which are distinguished by hav-
ing the abdomen furnished with spin-
nerets, by means of which these animals
manufacture silken filaments for the
construction of their web.

ARA'NEIFO'RMES {aranea, a spider,
forma, likeness). An order of edentulous
crustaceous animals, in which the extre-
mities are rod-like, long, and adapted for
walking.

ARA'NGOES. A species of beads
made of rough carnelian, formerly im-
ported from Bombay, for re-exportation
to Africa.
36

ARC

A'RBOR. A term fancifully applied
to certain arborescent forms assumed by
metals under particular circumstances :
thus arbor Dianas signifies silver, when
precipitated from its oxide in the metallic
form by mercury; arbor Saturni denotes
lead, when separated from its salts in a
metallic state by zinc.

ARBORE'SCENT (arbor, a tree).
Having the characters of a tree, as dis-
tinguished from those of a shrub or
herb.

ARC (arcus, a bow). A portion of a
curved line or circle. Thus the latitude
and declination are arcs of the meridian,
and the longitude is the arc of the
equator or parallel circle.

1. Arc of direction. The arc which
a planet appears to describe, when its
motion is direct or progressive.

2. Arc of retro gradation. The arc
which a planet describes whilst moving
contrary to the order of the signs, or
from east to west.

A'RCAD^E. Arch-shells ; a family of
the atrachian bivalves, named from the
typical genus area, in which the shell is
of various shapes, but the valves close
all round.

ARCA'NUM. A secret ; a secret re-
medy, as arcanum duplicatum, an old
name for sulphate of potash ; arcanum
tartari, deutoxide of mercury, &c. The
philosophers' stone was named by the
alchemists area arcanorum, a chest of
secrets.

ARCHjE'US {upxh> beginning). A hy-
pothetical intelligent agent, adopted by
Van Helmont, resembling the anima of
Stahl. See, Anima.

A'RCHIL. A violet red paste, pre-
pared from the lichen Parmelia, or Roc-
cella, and used in dyeing. The plant,
reduced to a pulp, and treated with im-
pure ammoniacal liquor, yields a rich
purple tincture, called litmus, or turn-
sole, used in chemistry as a test.

ARCHIME'DES' SCREW. An ap-
paratus employed by Archimedes for
raising water and draining land in Egypt.
It consists of a large tube, coiled round
a shaft of wood, to keep it in place and
give it support. Both ends of the tube
are open, the lower one being dipped into
the water to be raised, and the upper one
discharging it in an intermitting stream.
The shaft turns on a support at each end,
the upper support being elevated in the
air, the lower being hidden beneath the
water.

ARCHIPE'LAGO. A general term

ARG

A RG

applied to a cluster of islands, especially
to those lying between the shores of
Greece and Asia Minor. The term is
perhaps derived from A'ijetov ireXayos,
uEgceum pelagus, the iEgean sea.

A'RCTIC CIRCLE (&pkto?, a hear).
An imaginary line extending round the
North Pole, 66^ degrees from the equator,
and parallel to it. This, and the Antarc-
tic circ'e, are called the polar circles.

A'RCTIC CURRENT. A current in
the North Atlantic, which seems to ori-
ginate in the extensive masses of ice
surrounding the North Pole, runs down
along the eastern shores of Greenland,
doubles the Cape, and runs up the west-
ern coast of Greenland, crosses Davis's
Strait, follows the coast of Labrador, runs
to the east of Newfoundland, and even-
tually joins the gulf stream between 43°
and 47° of longitude.

A'RCTIC POLE (aPKTOp, a bear). A
designation of the North Pole of the
earth, from its pointing to the constella-
tions of the Great and Little Bears.

ARCTU'RUS or a BOO'TES (fyenw,
the bear, ovpa, the tail). A star of the
first magnitude in the northern constel-
lation Bootes. It is nearly in a right
line drawn through the two hinder stars
in the tail of the Bear.

A'RCUATE (arcus, a bow). Curved
or arched ; a term applied, in Botany, to
any thing bent like the arc of a circle, as
the legume of medicago falcata, the em-
bryo of certain plants, &c.

A'RDEIDjE (ardea, the heron). The
Heron tribe ; a family of the Grallatores,
or wading birds, including the herons,
cranes, and storks, in which the beak is
long, thick, and stout, usually with cut-
ting edges as well as a point.

A'REA. The Roman area was a
threshing-floor ; but the term is em-
ployed by geometricians to denote any
superficies or surface of a determinate
extent, and is applied exclusively to
plane figures.

A'REOLATE {areola, a little space).
Divided into areola? or small spaces, as
applied to surfaces.

ARFWE'DSONITE. A ferruginous
variety of hornblende, named from Arf-
wedson.

A'RGAL. Wine-stone. Crude tartar;
an acidulous concrete salt, deposited on
the interior of wine-casks, and used by
dyers as a mordant. On being purified,
it is called cream or crystals of tartar.

ARGAND LAMP. A lamp with a
hollow wick, for furnishing a rapid sup-
37

ply of air to the interior as well as to the
exterior of the flame. It is named from
its inventor, who was a native of France.

ARGILLA'CEOUS EARTH. Argilla.
White clay, or potters' earth; the earth
or clay, called by chemists alumina,
from its being obtained in its greatest
purity from alum.

ARGILLA'CEOUS ROCKS {argilla,
clay). Homogeneous soft substances,
composed chiefly of aluminous earth, or
clay. They comprise the shale or slate-
clay, bituminous shale, clay, and marl.

ARGI'LLITE {argilla, *clay). Argil-
laceous schist, or clayslate; a mineral
abundantly distributed in both primitive
and transition mountains.

ARGO NAVIS. The Ship ; a southern
constellation, containing sixty-four stars,
the principal of which is Canopus.

A'RGUMENT. In Logic, an expres-
sion in which, M from something laid
down and granted as true {the premises),
something else {the conclusion) beyond
this must be admitted to be true, as fol-
lowing necessarily from the other."

I. The term Argument, in ordinary
discourse, has several meanings. 1. It
is very often used for the premises alone,
in contradistinction to the conclusion ;
e.g., "the conclusion which this argu-
ment is intended to establish is so and
so." 2. It is sometimes employed to de-
note what is, strictly speaking, a course
or series of such arguments, as when it
is applied to an entire dissertation.
3. Sometimes it signifies a disputation,
or two trains of argument, opposed to
each other. 4. Lastly, the various forms
of stating an argument are sometimes
spoken of as different kinds of argument,
as if the same argument were not capable
of being stated in various ways. — Whately.

II. The term Argument, in astronomical
tables, denotes the angle or quantity on
which a series of numbers depends. If,
for instance, a table were formed of the
sun's declination, corresponding to every
degree, &c, of longitude, so that, the longi-
tude being known, the declination might
be found opposite to it in the table, the
longitude would then be called the argu-
ment of the declination, and the table would
be said to be entered with the argument.

ARGUME'NTUM AD HOMINEM.
A form of argument, described by logi-
cians, in which the conclusion actually
established is not the absolute and gene-
ral one in question, but relative and par-
ticular; viz., not that "such and such is
the fact," but that " this man is bound to

AR1

ARS

admit it, in conformity to his principles
of reasoning, or in consistency with his
own conduct, situation," &c.

1. The argumentum ad hominem, in
the popular but less scientific sense, " is
addressed to the peculiar circumstances,
character, avowed opinions, or past con-
duct of the individual, and therefore has
a reference to him only, and does not
bear directly and absolutely on the real
question, as the argumentum ad rem does.

2. "The argumentum ad verecundiam,
in like manner, is described as an appeal
to our reverence to some respected au-
thority, some venerable institution, &c. ;
and the argumentum ad populum, as an
appeal to the prejudices, passions, &c, of
the multitude.

3. "The argumentum ad ignorantiam
is usually enumerated with these, but is
evidently nothing more than the employ-
ment of some kind of fallacy, in the
widest sense of that word, towards such
as are likely to be deceived by it."

A'RIES. A zodiacal constellation of
rixed stars, drawn on the globe in the
figure of a ram. It is the first of the
twelve signs of the zodiac, from which a
twelfth part of the ecliptic takes its
name. It indicates the first month of
autumn, extending from the 20th of Sep-
tember to the 20th of October. It con-
sists of 66 stars.

A'RIETIS. A star of the second
magnitude, in the head of the Ram.

ARI'LLUS. A term applied, in Bo-
tany, to an expansion of the placenta, or
funiculus, about the seed : the mace of
the nutmeg, and the red covering of the
seed of the spindle-tree, are instances.

ARI'STOLOCHIA'CEjE (aP«<TTov, the
best, Xoxeia, delivery). The Birthwort
tribe of Dicotyledonous plants, so named
from the reputed emmenagogue proper-
ties of the genus Aristolochia. Herba-
ceous plants or shrubs, with leaves alter-
nate; flowers apetalous, hermaphrodite;
stamens epigynous ; ovary many-celled;
fruit dry or succulent, many-celled.

ARITHMETIC {apt0/jLo?, number).
The science which treats of numbers, of
the mode of expressing them, of the
manner of computing by them, and of
the various uses to which they are ap-
plied in the practical business of life.

1. Arithmetical Complement. That
which a number wants of the next high-
est decimal denomination. Thus, what
7 wants of 10, viz. 3; what 32 wants of
100, viz. 68; what 159 wants of 1000,
viz. 841 ; or .017 of 1, viz. .983 ; are the

arithmetical complements of these num-
bers.

2. Arithmetical Mean. That number
or fraction which is intermediate between
two other numbers, as 10 between 6 and
14; 10£ between 4 and 17. To find the
arithmetical mean, take the half sum of
the two numbers.

A'RMATURE (armatura, armour). A
term, in its general sense, denoting
armour. A natural magnet is, however,
said to have an armature, or to be armed,
when its two poles are polished and
covered over with smooth plates of iron,
which terminate in two strong projecting
ends. The magnetic power, imparted by
this means to the two iron plates, is con-
centrated in the knobs, and thus a north
and a south pole are made.

A'RMILLARY SPHERE {armilla, a
bracelet). A hollow sphere, representing
the several circles of the globe : it is so
constructed that all the surface of the
sphere is cut away, except the equator,
ecliptic, colures, &c. See Astrolabe.

A'RQUIFOUX. A lead ore, commonly
called potters' ore, from its being used by
potters as a green varnish.

A'RRAGONITE. An impure species
of carbonate of lime, found in Arragon
in Spain. It occurs in the form of fibrous
branches, which ramify from a centre,
called fios ferri, or iron-flower.

ARROW-HEADED CHARACTERS.
A term applied to certain marks stamped
on the bricks of Babylon, and cut on the
marble monuments at Persepolis. Their
character is formed from the isosceles tri-
angle or wedge, and hence they are termed
in 'Latin cuneiformes, or wedge-shaped.

A'RSENIC {apaeviKov, masculine; an
old epithet, denoting powerful properties).
A bluish-white metal, of great brilliancy,
resembling steel. The arsenic of com-
merce, commonly called white arsenic,
and known as a violent poison, is arse-
nious acid. The fuming liquor of arsenic
is the sesquichloride, a colourless volatile
fluid, which fumes strongly on exposure
to the air. Realgar, also called ruby, or
red arsenic, is the protosulphuret. Orpi-
ment, or yellow arsenic, is the sesquisul-
phuret, and constitutes the colouring
principle of the pigment called king's
yellow. Another well-known pigment,
called Scheele's mineral green, consists of
an arsenite of copper. On exposing the
metal to a moist atmosphere, a black
powder is obtained, called poudre a
mouches, or fly-powder. Lastly, a solu-
tion of arsenic in muriatic acid, heated

ART

ASC

and condensed, sublimes into a thick
liquid, formerly called butter of arsenic.

ARSE'NICAL MINERALS. A class
of minerals in which arsenic acts the
part of the electro negative element.
They occur in primitive districts, and
are usually associated with metallic sul-
phurets.

A'RSENOVI'NIC ACID. An acid pro-
duced by the action of arsenic upon alcohol.

A'RSIS and THE'SIS (ftp**, eleva-
tion; deats, depression). Technical terms
employed in ancient music and ancient
metrics. Arsis denoted an elevation of
the voice, which is now called metrical
accentuation. Thesis was a depression
of the voice, and was opposed to arsis.
In Music, the terms signified the rising
and the falling of the hand in beating
time; and hence the Latin word ictus, or
stroke, corresponded with arsis. Lastly,
per arsin expressed, in Music, a fall from
acute to grave ; per thesin, a rise from
grave to acute.

ART and SCIENCE. Art is the ap-
plication of knowledge to practical pur-
poses. Science is a knowledge of the
principles of art. If the knowledge be
merely accumulated experience, its ap-
plication is empirical art; but if it be
experience reasoned upon and brought
under general principles, it assumes a
higher character, and becomes a scientific
art.

ARTE'RIALIZA'TION. The conver-
sion of the venous into the arterial blood,
during its passage through the lungs,
by the extrication of carbonic acid, and
the absorption of oxygen from the air.

ARTE'SIAN WELL. A perpendicu-
lar perforation of the crust of the earth,
of small diameter and of great depth,
through which water rises to the surface
by an artificial jet. The term is derived
from Artesium, or Artois, where con-
siderable attention has been paid to this
means of procuring water.

ARTHRO'DIAL (ZpOpov, a joint).
Belonging to a joint, but restricted to
that form of joint in which a ball is re-
ceived into a shallow cup, commonly
called the ball-and-socket joint.

A'RTICLE {articulus, a joint). The
name given by grammarians to two
words, a or an, and the, which are pre-
fixed to ' substantives for the purpose of
showing whether they are used in a
general sense or in particular relation to
an individual. An is a corruption of one,
and a is a greater corruption of the same
adjective. The appears to be derived
39

from the Greek to, through the Gothic
sa or tha, and thence through the German
der or the Dutch de.

A'RTICULA'TA (articulus, a joint).
Articulated or jointed animals ; one of
Cuvier's four great divisions of the Ani-
mal Kingdom, in which the skeleton,
which is external, is formed of numerous
pieces or segments, jointed or articulated
together, as in the lobster, the centi-
pede, &c. This division corresponds
with the Annulosa of Macleay, the
Homogangliata of Owen, and the Diplo-
neura of Grant.

ARTOCA'RPE^E. The Artocarpus,
or Bread-fruit tribe of Dicotyledonous
plants ; a division of the Urticaceae, or
Nettle tribe, distinguished by their con-
solidated flowers and milky juice.

ASBE'STOS (a, priv., cfiewvut, to
extinguish). A mineral substance, of a
fibrous structure, from which an incom-
bustible linen is made. There are several
varieties, all more or less flexible and
fibrous, and termed common asbestos,
amianthus, mountain leather and paper,
and mountain wood.

ASCENDING SIGNS. The signs are
said to be ascending, when they are east-
ward from the meridian, and are, con-
sequently, approaching the meridian
through the effect of the diurnal rotation
of the earth.

ASCE'NSION, RIGHT (ascendo, to
rise). An astronomical term, applied to
those arcs in the heavens which corre-
spond to longitudes on the earth. Hence
the right ascension of a star denotes the
arc of the equator intercepted between
the first point of Aries and that point of
the equator which comes to the meridian
at the same instant with the star.

1. Oblique Ascension is a term nearly
out of use. It is an extension of the
right ascension to the oblique sphere, in
which one pole is above the horizon, and
the other below it. The oblique ascen-
sion of a star is the arc of the equator
intercepted between the vernal equinox
and that point of the equator which
comes to the horizon at the same time
with the star.

2. Ascensional Difference is also a term
nearly out of use. It denotes the dif-
ference between the oblique and the right
ascensions, and is chiefly used in respect
to the sun, because, when the arc which
it expresses is turned into time, it shows .
the time before or after six o'clock of
sunrise.

A'SCI (daKos, a leathern bag). The

ASC

ASP

botanical designation of the sporuliferous
tubes imbedded in the nucleus of the
shields of lichens.

ASCI'DIA (ao-Kof, a bottle). An order
of the tunicated Mollusca, named from
their resemblance in shape to a leathern
bottle. In these, the two orifices ap-
proach one another more or less closely,
and the body is either immediately fixed
to some solid mass, or attached to it by
a foot-stalk. See Salpce.

ASCIDIOI'DA {ascidia, and eZdor,
likeness). An order of the Polypi-
pherous Radia'a, named from their affi-
nity to the ascidice, a group in the lowest
class of Mollusca. They have also been
called bryozoa, from their fancied re-
semblance to mosses, and cilio-brachiata,
from the presence of cilia on their arms.

ASCI'DIUM {dcKibiov, dim. of uo-kos,
a leathern bag). The botanical term for
the pitcher of Nepenthes and other
plants, consisting in a peculiar modifica-
tion of the leaf, by which the petiole is
dilated and hollowed out at its upper
end, and the lamina is articulated with
it and closes its orifice.

A'SCII (a, not, awia, shadow). A term
applied to the inhabitants of the Torrid
Zone, because, the Sun being sometimes
exactly vertical to them at noon, they
have no shadow at all. At t^ie other
times of the year, their noon-shadow
points both northward and southward,
according to the place of the sun, when
he is not vertical to them ; and hence
, they are called Amphiscii, from dn<ph,
on both sides, and oiua, shadow,

1. Heteroscii (erepos, another, <nud,
shadow). A term applied to the inha-
bitants of the Temperate Zones, from
their having their shadows, at noon,
always on one side or other of them, either
north or south, according as they may be
situated, throughout the whole year.

2. Periscii (nepi, around, anui, shadow).
A term applied to the inhabitants of the
Frigid Zones, because at certain seasons
of the year, during many revolutions of
the earth, the sun does not set at all to
them, nor so much as touch the horizon,
and hence their shadows move completely
round them once in 24 hours ; and, in pro-
portion as they are nearer the Poles, will
be the greater continuance of the sun
above the horizon, for one, two, or, it
may be, six months together.

3. To these may be added the Bra-
chyscii {ftpaxw, short), or such as pro-
ject short shadows at noon : the Ma-
croscii (^ua^pof, long), who project long

40

shadows at noon ; and the Antiscii (uvtI,
opposite), whose shadows are in opposite
directions, from their having the sun on
opposite sides.

4. The ancients, likewise, distinguished
the inhabitants of the earth, with respect
to their longitude and latitude, into the
Perioeci {nepl and otKof, habitation), who
dwelt in the same latitude, but in opposite
longitudes; the Antoeci (ui/ri and o'Uos),
who dwelt in the same longitude, but in
opposite latitudes ; and Synoeci {avv and
otKof), who lived in the neighbourhood
of each other. The Antipodes had both
latitudes and longitudes diametrically
opposite to each other.

ASCLEPIADA'CEjE. The Asclepias
tribe of Dicotyledonous plants. Shrubs
or herbaceous plants, with leaves opposite,
alternate, or whorled ; corolla monope-
talous, hypogynous ; stamens inserted into
the base of the corolla ; ovaries two ; fruit
one or two follicles.

ASE'PTIC (a, priv., o^tto), to putrefy).
A term applied to substances which are
free from the putrefactive process.

ASPA'RAGIN. A crystalline sub-
stance, formed spontaneously in the juice
of asparagus which has been evaporated
to the consistence of syrup. It is gene-
rally procured from the root of the marsh-
mallow.

ASPA'RAMIDE. A principle dis-
covered in the juice of the asparagus,
and in the root of the marsh-mallow and
liquorice. It is the agedoite of Robiquet,
and synonymous with asparagin.

ASPA'RTIC ACID. An acid obtained
from asparagin, when boiled for some time
with hydrated oxide of lead or magnesia.

A'SPECT. An obsolete astronomical
term, applied to the various positions of
the planets with respect to one another,
as seen from the earth. Five aspects
have been reckoned : at conjunction, 6 ,
two planets have the same longitude ;
when sixty degrees apart, the aspect is
sextile, •* ; when ninety, quartile, Q ;
when 120, trine, A; when 180 degrees
apart, they are in opposition, £ .

ASPERGI'LLIFORM {aspergillus, a
brush, forma, likeness). Brush-like; di-
vided into minute ramifications, as the
stigmas of grasses, certain hairs of the
cuticle of plants, &c.

ASPHA'LTENE. A solid black sub-
stance, obtained by submitting the bitu-
men of Bechelborum, purified by ether,
to a high and prolonged temperature.

ASPHA'LTUM (a<r0a\To?, asphalt,
bitumen). A black or brown, brittle sub-

AST

ATA

stance, also called bitumen Judaicum, or
Jews' pitch, forming in lumps on the
surface of some waters, especially near
Babylon, and employed by the Egyptians
for embalming, under the name of mu-
mia mineralis.

ASPHODE'LEiE. The Asphodel or
Lily tribe of Monocotyledonous plants.
Herbaceous plants, with bulbs, occa-
sionally arborescent, with leaves not arti-
culated with the stem, parallel-veined ;
flowers hexapetaloideous ; stamens hypo-
gynous ; ovary superior ; fruit succulent
or dry and capsular.

ASSA'YING. The chemical operation
of ascertaining the quantity of any metal
in an ore or mixture. It differs from
Analysis only in degree, and is performed
in the dry way, as by heat ; in the moist
way, as by acids and other re-agents ; or
by both methods. See Cupellatiun.

ASSIMILATION (assimilo, to liken
to). The function by which organized
bodies convert aliment into their own
proper substance.

ASSOCIATE MOVEMENTS. Con-
sensual Movements. Those movements
which, contrary to our will, accompany
other, voluntary, motions. Thus, the eye
cannot be moved inwards by the action of
the rectus internus, without contraction
of the iris being produced.

ASTA'TIC (a, priv., arau, to stand).
A term applied to a magnetic needle,
when its directive property is destroyed
by the proximity of another needle of
equal magnetic intensity, fixed parallel
to it, and in a reversed position, each
needle having its north pole adjacent to
the south pole of the other. In this state
the needles, neutralizing each other, are
unaffected by the magnetism of the earth,
while they are still subject to the influence
of galvanism.

ASTE'RIA (uo-r^p, a star). A variety
of sapphire, showing a star-like opa-
lescence in the direction of the axis,
when cut round.

ASTE'RISM (ua-rJ/p, a star). A small
cluster of stars, either distant from, or
forming a part of, a constellation.

ASTEROI'DA (uoTqp, a star, eUos,
likeness). An order of the polypipherous
Radiata, named from the star-shaped
form presented by the tentacula, when
expanded^ They may be also termed
Alcyonian polypiphera, from the name of
one of the principal groups.

A'STEROIDS (do-rJjp, a star, e?3oc,
likeness). A term applied by Herschel
to the recently discovered planets, Ceres,
41

Juno, Pallas, and Vesta, and including
those celestial bodies which move in
orbits of any eccentricity round the sun,
whatever angle their orbits make with
the ecliptic, whether the motion of these
bodies be direct or retrograde, whether
they have or have not atmospheres.

ASTRI'NGENT PRINCIPLE. A
principle existing in the gall-nut and
other substances, and characterized by
the property of contracting the muscular
fibre. From the use of this principle in
tanning skins, it has been called tannin.

A'STROLABE (a<rTpo*, a star, \afx-
/3di/w, to take). Planisphere. A pro-
jection of the sphere upon the plane of
one of the great circles : it is furnished
with a graduated rim, to which sights are
added, for the purpose of taking altitudes.

ASTRO'LOGY (aarpov, a star, X6yo?,
an account). A term strictly meaning
the science of the stars, but applied to
the pretended discovery of future events
by means of the position of the heavenly
bodies.

ASTRO'NOMY {'6.<ttPov, a star, vo/jlov,
a law). The science which treats of the
motions, the distances, the size, the phy-
sical constitution, the eclipses, and all
other phenomena of the heavenly bodies.
By the term astra, the ancients under-
stood not only the stars, properly so
called, but also the sun, the moon, and
all the bodies which compose the visible
universe.

1. Descriptive astronomy demonstrates
the magnitudes, distances, and densities
of the heavenly bodies, and explains
the phenomena dependent on their mo-
tions, as the change of seasons, and the
vicissitudes of day and night.

2. Physical astronomy explains the
theory of planetary motion, and the laws
by which this motion is regulated and
sustained.

3. Practical astronomy details the de-
scription and use of astronomical in-
struments, and develops the nature and
application of astronomical calculations.

ASY'MPTOTES (uav^nnoTos, that
which does not fall with). A term ap-
plied to two lines (one of which, at least,
must be a curve), which, although con-
tinually approaching nearer and nearer,
and although indefinitely produced, never
meet each other. This properly occurs in
the hyperbola, and appears of a paradox-
ical character.

ATA'CAMITE. A native muriate of
copper, found in the desert of Atacama,
between Chili and Peru. It occurs in a

ATM

ATO

compact and in an arenaceous form ; in
the latter, it is termed copper sand.

ATHANOR. An ancient kind of fur-
nace, so constructed that the fire should
be constantly supplied with fuel in pro-
portion to the consumption.

ATHERI'CERA (u^i/p, an ear of corn,
tcppa<;, a horn). A section of Dipterous
insects, in which the antennae have only
two or three joints, the last being fur-
nished with a bristle. It includes the
Flies, strictly so called, the Bot-flies, &c.

ATHE'RMANOUS (a, priv., 0<-'pMn,
heat). A term applied to those sub-
stances which retain all the heat they
receive, as distinguished from diather-
manous bodies, which transmit all the
rays of heat through their substance.

ATMO'METER (trr/io?, vapour, fxerpov,
measure). An instrument for measuring
the quantity of exhalation from a moist
surface in a given time.

A'TMOSPHERE (aTjuor, vapour,
o-(pa7pa, a sphere). That volume of air
which surrounds the earth. Its mean
height has been estimated at from 44 to
47 miles, its volume as the twenty-ninth
of that of the globe, and its weight only
forty-three thousandths.

1. Atmospheric Pressurexs indicated by
the length of a column of mercury. A
mercurial column, 30 inches in length,
presses on a given surface with the same
force as the atmosphere in its ordinary
state ; and hence the force of a 60-inch
column is equal to the pressure of two
atmospheres ; that of 15 inches, to half an
atmosphere ; that of one inch, to l-30th of
the atmospheric pressure.

2. Atmospheres— two, three, fyc. Mul-
tiplied pressures of air arising from con-
densation, the ordinary pressure being
fifteen pounds on the square inch. Press-
ures arising from other causes, as the
weight of liquids and the force of steam,
are also frequently counted by atmo-
spheres.

3. Atmosphere, refraction of. A term
expressive of the refraction of the rays
of light, as they pass from the celestial
bodies into the atmosphere, owing to its
being denser than the ethereal or vacuous
medium which intervenes between it and
the celestial bodies. This refraction
varies with the density of the atmo-
sphere, and also with the direction in
which the rays enter. The atmosphere
gradually increases in density from the
higher to the lower strata; and, there-
fore, a ray of light will be more and more
refracted in its passage to the earth's sur-

42

face, so as to descend in a curved line.
The curve, too, varies with the direction
of the ray, that coming from the zenith
alone being a straight line.

4. Atmosphere, electrical. The dis-
tance at which an electrified body is
capable of resolving the neutral electri-
city of unelectrified bodies into its ele-
ments, when brought into proximity to
the former, is termed the electrical at-
mosphere of that body.

5. Atmosphere, magnetic. The range
within which a magnet exerts its influ-
ence in any magnetizable body within a
certain distance of itself, is termed its
circle of magnetic influence, or its mag-
netic atmosphere.

ATMOSPHERIC ENGINE. A term
applied to the single-action steam-engine,
in which only the ascent of the piston is
effected by means of steam, its descent
being mainly effected by the pressure of
the atmosphere.

A'TOLLS. Coral-islands, or lagoon-
islands, of an annular form, or consisting
of a circular strip or ring of coral sur-
rounding a central lagoon.

A'TOM (a, priv., re'/ivto, to cut). An
ultimate particle of matter, incapable of
further division. Berzelius distinguished
atoms into elementary and compound.
The latter are subdivided into, 1. Com-
pound atoms of the first order, or atoms
formed of only two elementary sub-
stances united; 2. Organic atoms, or
those composed of more than two ele-
mentary substances, and found only in
organic bodies, or bodies obtained by the
destruction of organic matter ; and,
3. Compound atoms of the second order,
or those formed by the union of two or
more compound atoms, as the salts.

ATO'MIC THEORY. A theory for
explaining the nature of matter, founded
by Leucippus. He considered the basis
of all bodies to consist of extremely fine
particles, differing in form and nature,
which he supposed to be dispersed
throughout space, and to which his
follower Epicurus first gave the name of
atoms. To these atoms he attributed a
rectilinear motion, in consequence of
which such as are homogeneous united,
whilst the lighter were dispersed through-
out space. See Dynamic Theory.

ATO'MIC WEIGHTS. An expression
connected with the theory that all bodies
consist of atoms, which are of the same
size and shape in the same body, but
which differ in weight in different bodies.
The weight of an atom of oxygen is eight

ATT

AUG

times as great as that of an atom of hy-
drogen, and half as great as that of an
atom of sulphur. On this theory are
founded three universal laws : —

1. That the parts by weight in which
bodies mutually combine, stand in a fixed
numerical relation to each other.

2. That in every chemical combination
the parts by weight of one element may be
represented by certain weights of other
substances.

3. That the weights which mutually
represent one another at once furnish the
proportion in which these equivalent sub-
stances combine.

ATRA'CHIA (a, priv., Tpaa>, to per-
forate). A tribe of bivalved Mollusca,
which are destitute of siphons for im-
bibing food. See Macrotrachia.

ATRACTE'NCHYMA ( 'drpaKTos, a
spindle, Zyxvua, an infusion). A term
applied by some botanical writers to the
fusiform, or spindle-shaped, variety of
spheroidal cellular tissue.

A'TROPOUS (a, priv., rpe'Trw, to turn).
That which is not inverted, as applied in
Botany to the erect ovule. In this case,
the parts of the ovule undergo no altera-
tion of position during their growth, and
thus the two sacs and the nucleus are
all connected at the base of the ovule.
The term is synonymous with orthotro-
pous.

ATTE'NUATE {ad, to, tenuis, thin).
Tapering ; gradually diminishing in
oreadth, and terminating in a point.

ATTENUATION (attenuo, to make
thin). The process by which a fluid
becomes of less specific gravity, as when
it undergoes fermentation, and parts
with carbonic acid.

ATTRACTION (attraho, to draw to).
A general term denoting the mutual
tendency of bodies towards one another,
and explanatory of certain physical and
chemical properties of matter.

1. Attraction of Cohesion. The ten-
dency of the particles of bodies to cohere,
and form masses. On the degree of this
force depend the three aggregate forms of
matter, which are distinguished as the
solid, the liquid, the gaseous. Cohesion
is the antagonist of affinity.

2. Attraction of Gravitation. The mu-
tual tendency of the masses of bodies
towards one another. Universal gravi-
tation relates to the mutual action of the
celestial bodies on each other and the
pravitation of our earth ; terrestrial
gravity relates to the mutual operation of
terrestrial objects, or to the effects which

43

the earth produces on all bodies more
immediately connected with it. Cohesion
operates at sensible, gravitation at insen-
sible distances.

3. Attraction of Affinity. The tendency
of the atoms of dissimilar bodies to com-
bine and form chemical compounds.
This force effects the combination and
decomposition of dissimilar bodies, with
the production of individual properties
distinct from those which they had in
their former state. See Affinity.

4. Attraction, Capillary. The power
by which a liquid ascends in the interior
of a capillary tube, or tube of small bore,
above the surface of the liquid which
surrounds it. The phenomenon occurs
in solid bodies which are capable of being
wetted.

5. Attraction, Superficial. A term
sometimes applied to that modification
of the adhesion of bodies which is caused
not merely by the mass of bodies, but
also by the number of points of contact,
or the extent of their touching surfaces.

6. Attraction, Electrical. The force
which is exhibited in the tendency of the
free positive and negative electricities to
regain their equilibrium by combination
each with its antagonist. Hence, elec-
trified bodies attract all other non-elec-
trified bodies, and all oppositely electrified
bodies, in order to saturate themselves
with the opposite electricity and regain
electrical quiescence.

7. Attraction, Electrodynamical. A
term expressive of Ampere's discovery,
that " the electricities in a state of mo-
tion, i.e. as electric currents, act attrac-
tively and repulsively on each other
according to a certain law," in a manner
resembling the polar attraction of statical
electricity, i. e. of electricity in a state of
tension.

8. Attraction, Magnetic. The property
by which bodies endowed with magnetism
attract certain metals; display towards
one another a force partly attractive,
partly repulsive ; and exhibit a tendency
to arrange their mass in a certain direc-
tion.

ATTWOOD'S MACHINE. A ma-
chine invented by Mr. Attwood for cal-
culating exactly the velocity of a falling
body from an actual measurement of its
height, and the time which it takes to
reach the ground.

AU'GITE (avyii, lustre). Pyroxene.
A simple mineral, of a dark-green or
black colour, with an internal shining
lustre, forming a constituent part of

AUT

AX1

many varieties of trap and volcanic
rocks. It is a silicate of lime and mag-
nesia. Augite rock is a particular kind
of trap rock, consisting of augite and
compact felspar, the former being pre-
dominant or in equal proportion.

AURA ELECTRICA. A gale of elec-
tricity ; a term expressive of electricity,
as received from a point, from the sensa-
tion it communicates.

AURA'NTlA'CEiE. The Orange tribe
of Dicotyledonous plants, abounding in
a volatile, fragrant, bitter, exciting oil.
Trees or shrubs with leaves alternate,
often compound, dotted with transparent
receptacles of volatile oil ; flowers poly-
petalous ; stamens hypogynous ; ovary
many-celled ; fruit pulpy, many-celled,
its rind filled with receptacles of oil.

AURE'LIA {aurum, gold). Chrysalis.
A fanciful name for the nymph or pupa
state of insect life, from the glittering
spots of golden hue with which it is
sometimes speckled.

AU'RIC ACID (aurum, gold). Auric
oxide. A name proposed by Pelletier
for the peroxide of gold, from its property
of forming salts with alkaline bases.

AURI'CULATED (auricula, a little
ear). A term applied to a few bivalves
which have a flat angulated projection on
one or both sides of the umbones or
bosses. These processes are highly de-
veloped in the pecten, and are merely
an incipient modification of the hinge
margin in byssoarca and several other
genera. The term is also applied, in
Botany, to leaves which have two
rounded lobes at the base.

AU'RIFORM (auris, the ear, forma,
likeness). Ear-shaped ; as applied to the
haliotis among the mollusca.

AURFGA. The Charioteer ; a north-
ern constellation, consisting of sixty-
six stars, the principal of which is Ca-
pella.

AURO'RA BOREA'LIS. Northern
Lights; Polar Lights, or Streamers. A
luminous meteor, generally appearing in
the northern part of the sky, and re-
sembling the Aurora, or morning twi-
light. It is usually referred to the
agency of electricity in the upper regions
of the atmosphere.

AUSTRAL. The six signs of the zo-
diac, which are south of the equinoctial,
are called Austral signs.

AUTHORITY. 1. This term is em-
ployed in its primary sense, when we
refer to any one's example, testimony, or
judgment ; in this sense it answers pretty
44

nearly to the Latin auctoritas. 2. Some-
times it is employed as equivalent to
"potestas," power; as when we speak of
the authority of a magistrate.

AUTO'MALITE. Fahlunite. A mi-
neral found in a talcose rock at Fahlun
in Sweden. Its constituent parts are
alumina, silica, and the oxides of zinc
and of iron.

AUTOMATIC MOTIONS (aironaTOf,
self-moving). Those muscular actions
which are not dependent on the mind,
and which are either persistent, or take
place periodically with a regular rhythm,
and are dependent on normal causes
seated in the nerves or the central organs
of the nervous system.

AUTUMN. The third quarter of the
year, which begins when the sun enters
Libra, that is, about the 21st or 22nd of
September, when the days and nights
are equal.

AUTUMNAL EQUINOX. The time
when the sun enters Libra, or the de-
scending point of the ecliptic, called also
the Autumnal point. The signs Libra,
Scorpio, and Sagittarius, are called au-
tumnal signs.

A'VALANCHE. A mass of snow
which, being detached from a great height
in the Alps, acquires enormous bulk
by accumulation as it descends. It is
termed, in the dialects of Switzerland,
lavange and lavanche.

AVA'NTURINE. A variety of quartz
containing mica spangles.

A'VES (avis, a bird). The fourth class
of the Vertebrata, or Encephalata, com-
prising birds; a class of oviparous ani-
mals, with warm blood, a double circula-
tion, a covering of feathers, and arms
constructed for flight.

AVICU'LIDiE. Mussels and Pearl
Oysters ; a family of the atrachian bi-
valves, named from the genus avicula ;
the animal is attached, and byssifer-
ous ; the shells are lamellar, internally
perlaceous ; the valves generally gaping.

AWN. A stiff bristle, formed by a
continuation of the midrib of a bract in
certain grasses, and commonly called the
arista or beard.

AXE-STONE. A sub-species of jade,
used by the New Zealanders for making
hatchets. It is sometimes called Ama-
zonian stone, from its being found on the
banks of the river Amazon.

AXI'LLA. The Latin term for the
arm-pit, and applied to other parts of the
animal body which form a similar angle.
In Botany, it denotes the angle made by

A X I

AZO

a leaf-stalk with the stem, the normal
position of the hud, which is hence called
axillary.

A'XINITE (af/i/n, an axe). Thumer-
stone. A mineral found at Thum in
Saxony, and named from the resemblance
of its crystals to an axe in the form and
sharpness of their edges.

A'XIOM {afimna, dignity). A self-
evident proposition, incapable of being
established by proof, and assumed as the
basis of demonstration.

A'XIS (af coy, the axle-tree of a chariot).
A term applied to an imaginary straight
line passing through the centre of a body,
and on which the body turns. The axis
of the earth is a line of this kind passing
from one pole to the other; and, if we
suppose this line to be extended in both
directions, it will become an axis of the
heavens, and will mark two points which
are also called poles, around which, or
rather their line of junction, all the fixed
stars appear to revolve.

1. Axis, rotation on. The different
points of a body may at the same time
move in different directions ; this is
called a rotatory motion. Rotation on an
axis implies, in addition to this rotatory
motion, that all the parts of the body
shall revolve around an imaginary right
line in a state of rest, called the axis.

2. Axis, free or moveable. A term
applied to an axis which is free from all
pressure, in consequence of the mass of
the body surrounding it being so equally
arranged about it, that the centrifugal
forces of its particles mutually counteract
one another. The axis of the earth is a
free or moveable axis.

3. Axis of refraction. The right line
drawn perpendicular to the surface of the
refracting medium through the point of
incidence of the refracted ray. Of crys-
tals which possess the property of double
refraction, many, like Iceland spar, have
only one axis of double refraction ; others
have two axes, which are variously in-
clined to each other, as the topaz. When
the ray of extraordinary refraction is in-
clined from the axis, the crystal is said
to have a, negative axis; when it is in-
clined towards it, more than the ordinary
ray, the crystal is said to have a positive
axis.

4. Axes of crystals. The lines which
join the points, and pass through the
middle of a crystal, are called its axes.
Most of these bodies have three such
axes at right angles to each other: that
which is most unlike the other two, is

45

called the principal axis, and the other
two secondary or subordinate axes.

5. Axis of a lens. A right line drawn
through the optical centre of the lens,
and perpendicular to both its surfaces.
At this point no refraction is produced
on perpendicular rays.

6. Axis of a spherical mirror. A right
line which passes through the geometri-
cal and the optical centres of the mirror.

7. Axis of a cone. A right line drawn
from the vertex of the cone to the centre
of its circular base.

8. Axes of an ellipse. These are called
the major and the minor axes, and they
are respectively synonymous with the
transverse and the conjugate diameters.

9. Axis of a parabola. The line which,
passing through the vertex of the para-
bola, divides the figure into two equal
and similar portions.

10. Axis of a magnet. The imaginary
line which connects the north and south
poles of a magnet.

11. Axis anticlinal. The imaginary
line lying between the strata which dip
in opposite directions on the two sides of
a hill or of a valley. In a row of houses
with steep roofs facing the south, the
slates represent inclined strata dipping
north and south, and the ridge is an east
and west anticlinal axis.

A'YMESTRY LIMESTONE. A group
of the Ludlow rocks, consisting of grey
or bluish argillaceous limestone, full of
the remains of shells and corals.

A'ZIMUTH. An Arabic term de-
noting the angular distance of a celes-
tial object from the north or south point
of the horizon, when the object is re-
ferred to the horizon by a vertical circle.
Or, it is the angle comprised between
two vertical planes, one passing through
the elevated pole, the other through the
object.

1. Azimuth circles. Great circles of
the sphere, passing through the zenith,
and intersecting the horizon at right
angles.

2. Azimnih compass. A compass used
at sea for finding the horizontal distance
of the sun or a star from the magnetic
meridian.

3. Azimuth dial. A dial of which the
style or gnomon is perpendicular to the
plane of the horizon, and so called from
its shadow marking the sun's azimuth.

A'ZOTANE. Chloride of azote. The
term is derived from Davy, who pro-
posed to designate the compounds of
chlorine by the termination ane.

B A C

BAL

A'ZOTE (a pnv., £w\h life). A gas
constituting 73 per cent, of the atmo-
sphere, and thus named from its being
incapable of supporting respiration. It
is more commonly called nitrogen, from
its being the basis of nitric acid.

AZOTIC and AZO'TOUS ACIDS.
Names given by Thenard to the nitric
and the nitrous acids, respectively, of
other chemists. The latter acid was
termed hyponitrous by Turner.

A'ZURE. A fine blue pigment, com-
monly called smalt, consisting of a glass
coloured with oxide of cobalt, and ground
to an impalpable powder.

AZURE STONE. Lapis lazuli. An
azure blue mineral, from which ultra-
marine is prepared.

A'ZURITE. Prismatic azure spar, or
Lazulite. A mineral occurring in mica
slate, and consisting of alumina, silica,
magnesia, lime, and oxide of iron.

B

B. in astronomical tables, stands for
Bissextile, or Leap year.

BA'BINGTONITE. A crystalline min-
eral, associated with cleavlandite, flesh-
coloured felspar, and green amphibole.

BA'CCA. A berry ; an inferior, inde-
hiscent, pulpy fruit, as the gooseberry.
The seeds lose their adhesion when ripe,
and lie loose in the pulp. The term is,
however, differently employed by some
botanical writers. Link applies the term
bac^a sicca to a fruit which is fleshy when
unripe, dry when ripe, and then distin-
guishable from the capsule by not being
brown.

BA'CC ATE (bacca, a berry). Berried ;
having a juicy succulent texture, as the
calyx of blitum.

BACK STAFF. An instrument in-
vented by Capt. J Davis for taking the
sun's altitude at sea. In using it the
observer was obliged to turn his back to
the sun. It is now superseded by the
quadrant and the sextant.

BACONIAN PHILOSOPHY. A sys-
tem of philosophy founded on induction,
enforced by the talent and writings of
Francis Bacon, Lord Verulam. This sys-
tem holds an intermediate place between
the merely empirical and the dogmatical
schools. " While the one," he observes,
"like ants, content themselves with
heaping up materials for immediate use,
the latter, after the manner of spiders,
spin webs out of their own brain. There
is a better and a middle way— that of the
bee, which derives, indeed, its material
from the flowers of the garden and the
field, but converts and digests it by its
own proper virtue."

BA'CUUTE (baculus, a staff). An
extinct genus of Molluscous animals,
4G

allied to the Nautilus, which inhabit a
str light-chambered shell resembling a
staff.

BAFKALITE. A light-green variety
of augite, found at the mouth of a river
which flows into lake Baikal In Siberia.

BA'LA LIMESTONE. A dark-coloured
slaty limestone, forming a subordinate
portion of the Cambrian group of rocks.
In Westmoreland it is 100 feet in thick-
ness, and both there and in Wales con-
tains organic remains.

BALiE'NID^E (<pd\aiva, bal&na,- a
whale). The Whale tribe of cetaceous
Vertebrata, in which the head constitutes
one-third, or even one- half, of the entire
length. By this disproportionate size
they are distinguished from the Delphi-
nidcB, or Dolphin tribe. By the term
balcenopUra (irrepov, a fin), De Lacepede
distinguished from the other balaenas
those whales which have an adipose fin
on their back, and are hence called fin-
ners by sailors.

BALANCE (bilanx, from bis and lanx,
i. e. a duabus lancibus, a beam with
balances). One of the simple mechani-
cal powers, consisting of a lever turning
on a pivot or fulcrum, and constructed
for the purpose of finding the weight of
different bodies. The lever, or rod, of a
balance is termed the beam, and the parts
of the beam on each side of the pivot on
which it turns are its arms. In the com-
mon balance those arms are equal, and
balance each other; and its ends, to
which the body to be weighed and its
equivalent counterpoise are hung, are
called the points of suspension.

1. Roman Balance, or Steel-yard. This
kind of lever differs from the common
balance, in having its support near one

B A L

BAR

end, instead of in the middle ; and also,
in having the weights suspended hy
hooks instead of being placed in a dish.
Here the fulcrum is between the power
and the weight. This is the principle
also of the Chinese balance.

2. Danish Balance. This kind of lever
consists of a bar of wood or iron, having
a leaden weight at one extremity, and
the goods to be weighed fixed in a hook
at the other. The bar is suspended by
a loop, which is moved backward and
forward until the equilibrium is obtained.
The weight of the goods and the leaden
weight are then to each other recipro-
cally as their respective distances from
the loop.

BALANCE ELECTROMETER. An
instrument constructed on the applica-
tion of the common balance and weights,
for the purpose of estimating the mutual
attraction of oppositely electrified sur-
faces.

BALANCE OF TORSION. A deli-
cate electrometer, invented by Coulomb,
on the principle of establishing an equi-
librium between the force of electricity
and that of the torsion, or twisting,
of a fibre of the web of the silk-worm.

BA'LANCERS. A term generally ap-
plied to the posterior pair of wings in
Dipterous insects, in which they appear
in the condition of minute clavate ap-
pendages.

BALANI'DA ( balanus, an acorn).
Acorn-barnacles ; an order of Cirrhopods,
named from the genus balanus, and cha-
racterized by their being enclosed in a
conical shell, adherent by its base to
foreign substances, and closed at its apex
by four valves.

BA'LANOPHO'RE^E. A small fa-
mily of leafless rhizanths, parasitical
upon roots, named from the genus bala-
nophora, and natives of the West Indies,
South America, &c. Their properties
are unknown.

BA'LAS RUBY. A technical term
for the bright red varieties of the spinel,
a sub-species of ruby.

BALAU'STA {(3a\av(niov, the flower
of the wild pomegranate). A term ap-
plied, in Botany, to the many-celled,
many-seeded, inferior, indehiscent fruit
of the pomegranate.

BALDWIN'S PHOSPHORUS. The
ignited nitrate of lime. This salt de-
rives its name from its property of emit-
ting a beautiful white light in the dark,
when kept in a stoppered phial, and ex-
posed for some time to the rays of the sun.
47

BALLISTIC PENDULUM (/3d\X«>,
to throw). A heavy wooden pendulum,
for measuring the velocity of cannon and
musket balls, and for determining the
resistance of the air to rapid motions.
The mechanical problem to be solved is
this : — Given, the weight of the shot, the
place at which it strikes, the weight,
form, &c, of the pendulum, and the
number of vibrations produced upon it
by the shot ; required, the velocity of the
shot.

BALLOON {ballon, French, a little
ball). A chemical instrument or re-
ceiver, of a spherical form, for condens-
ing vapours from retorts. The term
balloon signifies any spherical hollow
body, of whatever material composed, or
to whatever purpose applied : in its most
common use, it denotes a machine for
navigating the air.

BA'LSAMS. Vegetable juices, either
liquid, or becoming spontaneously con-
crete, and consisting of ethereal or
essential oils with resin and benzoic acid.
The liquid balsams are copaiva, opo-
balsam, balsam of Peru, storax, and
Tolu ; the concrete are benzoin, dragon's
blood, and red or concrete storax. Those
compounds which have no benzoic acid
are miscalled balsams, being, in fact, true
turpentines.

BALSAMA'CEiE. Balsamiflute. An
order of Dicotyledonous plants, found ia
tropical India, and characterized by their
balsamic products. The fragrant resin
storax is yielded by several species of
Liquidambar, the only genus of the
order.

BALSAM I NA'CE^E. The Balsam
tribe of Dicotyledonous plants ; a small
order of plants, closely allied to the
Geraniacece, and chiefly remarkable for
the elastic force with which the valves of
the fruit separate when ripe, and expel
the seeds.

BANDA'NA. A mode of calico print-
ing practised in India, by which white or
brightly coloured spots are produced upon
a red or dark ground.

BARBA'DOS TAR. Petroleum. A
species of bitumen, differing from naphtha
in its greater weight and impurity.

BARDIGLIO'NE. A blue variety of
anhydrite, cut and polished for orna-
mental purposes.

BARPLLA. The commercial name of
the impure carbonate of soda extracted
from the ashes of the plants salsola and
salicornia, and imported from Spain or
the Levant. Kelp, or British barilla, is

BAR

BAR

a more impure alkali, made in this coun-
try by burning various sea-weeds.

BA'RIUM (/3api)i, heavy). A peculiar
metal, the basis of the alkaline oxide or
earth barytes, named from the great
density of its compounds.

BARK OF PLANTS. The external
envelope of trees and shrubs. It was
formerly distinguisbed into an external
cortical or cellular integument, and an
internal or fibrous portion, called liber.
More recently, bark has been distin-
guished into four portions : —

1. Epidermis. The external and cel-
lular envelope, continuous with the epi-
dermis of the leaves. Tbis is never
renewed; the following parts increase
by successive additions to their in-
terior.

2. Epi-phlceum {kni, upon, <p\oio?,
bark). A cellular portion lying imme-
diately under the epidermis. Cork is the
epiphlceum of the Quercus suber.

3. Meso-phloeum (jueo-of, middle, <p\oios,
bark). A cellular portion, lying imme-
diately under the epiphlceum. This por-
t:on differs from the preceding in the
direction of its cells.

4. Endo-phlceum {evdov, within, <p\otos,
bark). The liber, part of which is cellu-
lar, part woody.

BA'ROLITE (papvs, heavy, \t'0o?, a
stone). Heavy stone ; a carbonate of
baryta.

BARO'METER (/Japop, weight, /ue-
Tpov, a measure). An instrument for
measuring the weight or pressure of the
atmosphere, by balancing a column of air
against a column of mercury ; and, by
that test, measuring heights and depths,
determining variations in the state of the
air, and foretelling changes in the wea-
ther. "When employed for determining
the degree of rarefaction attained in
the receiver of an air-pump, it is called
a barometer-gauge.

1. The cistern barometer is a Torricel-
lian tube, whose open end is immersed
in a wider cistern of mercury. The zero
point is on a level with the surface of the
mercury. This is the oldest form of the
instrument.

2. The common barometer is a Torri-
cellian tube, whose open end is turned
up and is of a spherical form. The
globe performs the office of the cistern
described in the preceding barometer :
the scale is graduated from the same
point in both these instruments.

3. De Luc's syphon barometer consists
of a glass tube bent upwards so as to

48

form two parallel legs : the longer is her-
metically sealed, and constitutes the
Torricellian tube ; the shorter is open,
and on the surface of the mercury the
pressure of the atmosphere is exerted.
The difference between the levels in the
two legs is the barometric height.

BA'ROMETZ {baronez, Russian, a
little lamb). A species of Aspidium, or
shield fern, which, from its procumbent
position and shaggy appearance, has ac-
quired the name of 'Scythian lamb,"
and the credit of possessing some of the
properties of this animal.

BA'ROSCOPE (/Sapor, weight, o-kottco),
to perceive). A perceiver of weight ; a
term sometimes applied to the barometer.
Etymologically speaking, a baroscope is
not a barometer, thotigh a barometer is a
baroscope.

BA'RRAS, or GALIPOT. The resin-
ous incrustation on the wounds made in
fir-trees.

BA'RRIER REEF. A coral produc-
tion, similar to the Atoll, or coral island.
It runs parallel with the shores of a
larger island or continent, separated,
however, from the land by a broad and
deep lagoon channel, and having the
outer side as steep as in the lagoon
islands.

BA'RTER. A rule in Arithmetic, by
which the values of commodities of dif-
ferent kinds are compared, for the pur-
pose of exchange.

BARYSTRO'NTIANITE. Stromnite.
A mineral found in veins, or rather
nests, accompanied by galena, at Strom-
ness, in Orkney. It consists of the car-
bonates of strontia and of lime, sulphate
of baryta, and oxide of iron.

BARY'TES (/3aPw, heavy). Baryta.
The protoxide of barium, an alkaline
earth, the heaviest of all the earths, and
a violent poison. The native sulphate is
called heavy spar, or cawk. The native
carbonate has been named, after Dr.
Withering, its discoverer, wilherite. A
solution of barytes in water is called
barytes water, and is used as a chemical
re-agent.

BARY'TIN. A new vegetable base,
discovered in the rhizome of Veratrum
album, and named in consequence of its
being precipitated from its solution, like
baryta. See Jervin.

BARY'TO-CALCITE. A mineral
found in Cumberland, consisting of the
carbonates of baryta and of lime, with
an outer coating of sulphate of baryta.

BA'RYTON (/3aPv?, heavy, tovov,

B AS

B AS

tone). Baritone. That compass of the
male voice which is between those of the
tenor and of the base. The term bari-
tenor, employed by Bennati, is preferable,
as it expresses what is really meant, viz.
a high base.

BA'RYTONE VERBS (/3aPv?, heavy,
T01/09, tone). That class of Greek verbs
which terminate in a>, and have either a
consonant before «, or a vowel a, e, o,
before a>. These are called barytone,
because they have the accent (acute) on
the penultima, and the last syllable neces-
sarily has the grave accent, not expressed
in writing.

BA'SALT (basal, iron, Ethiopian). One
of the most common varieties of the
Trap-rocks. It is a dark green or black
stone, composed of augite and felspar,
very compact in texture, and of con-
siderable hardness, often found in regular
pillars of three or more sides, called
basaltic columns. These occur in the
Giants' Causeway, and at Fingal's Cave
in StafFa. The rock often contains
much iron. Basaltic hornblende oc-
curs in various basaltic and floetz trap-
rocks.

BA'SANITE (paaavifa, to test, from
pdaavos, a Lydian stone). A stone by
which the purity of gold was formerly
tested; it consists of silica, lime, mag-
nesia, carbon, and iron.

BASE or BASIS (/3«<r<?, a base). A
chemical term applied to alkalies, earths,
and metallic oxides, in their relations to
the acids and salts. It is sometimes also
applied to the particular constituents of
an acid or oxide, on the supposition that
the substance combined with the oxygen,
&c. is the basis of the compound to
which it owes its particular qualities.
This notion seems unphilosophical, as
these qualities depend as much on the
state of combination as on the nature of
the constituent. — Ure.

1. In the Arts, the term base is syno-
nymous with mordaunt, and is applied to
a substance used in dyeing, which has an
affinity for both the cloth and the colour-
ing matter.

2. In Malacology, the term base is
generally used in opposition to the apex,
or pointed extremity of univalve shells.
In bivalves which adhere to other sub-
stances by one of their valves, as in
spondylus, that which adheres is termed
the basal valve ; in unattached bivalves,
the term is not correctly admissible. In
spiral shells, the last or largest whorl is
termed the basal whorl.

49

3. In Geometry, the base is the lowest
side of the perimeter of any figure. The
base of a triangle is, properly, the side
which is parallel to the horizon, though
the term may be applied to either of the
other sides. In rectangled triangles, the
base is, properly, the side opposite to the
right angle.

BASE VOICE. The lowest compass
of the human voice, usually ranging
from G or F below the base staff to D or
E above it.

BASIC WATER. A term applied in
cases in which water appears to act the
part of a base: phosphoric acid, for in-
stance, ceases to be phosphoric acid, un-
less three equivalents of water to one of
acid be present.

BASI'DI A. Small bases ; a term ap-
plied to the cells on the apex of which
the spores of fungaceous plants are
formed.

BASIGY'NIUM (/2aW, a base, -yw^
a female). Podogynium. A botanical
term applied to the long stalk upon
which the ovary, instead of being sessile,
is seated in certain plants, as in the Pas-
sion flower. It is frequently called the
thecaphore and gynophore.

BA'SILAR (basis, a base). Belonging
to the base ; in Zoology, to that of the
skull.

BA'SIN (bassin, French). A term ap-
plied, in Physical Geography, to the whole
extent of country from which the waters
of a particular river are drawn. In Geo-
logy, the term denotes those depressions
of the surface of the earth in which
waters accumulate so as to form lakes :
of this kind are the lakes of North Ame-
rica, lake Aral, the Caspian and Dead
Seas, &c.

Basins of Paris, of London. Deposits
lying in a hollow or trough, formed of
older rocks. The term basin is some-
times used, in Geology, almost synony-
mously with "formation," to express the
deposits lying in a certain cavity or de-
pression in older rocks.

BA'SSORINE. A substance extracted
from the gum resins which contain it, by
treating them successively with water,
alcohol, and ether. Its name is derived
from bassora, the gum in which it was
first discovered.

BA'SYLE (/?aW, a base, v\t), nature
or principle). A term proposed by Mr.
Graham to denote the metallic radical of
a salt. Thus, sodium is the basyle of
sulphate of soda; soda is the base, and
sulphatoxygen the salt radical, if the
D

BAY

BEL

salt be viewed as consisting of sulphat- I
oxide of sodium.

BATH, CHEMICAL. An apparatus
for modifying and regulating the heat in
various chemical processes, by inter-
posing sand or some other substance
between the fire and the vessel intended
to be heated. The water bath, formerly
called balneum mar ias, and the sand bath,
are most commonly used. Solution baths,
consisting of saturated solutions, will
produce temperatures as high as 360°.
For higher temperatures, metal baths are
employed, as of mercury, fusible metal,
&c. ; the temperature may thus be raised
to 600°.

BATH, ELECTRICAL. This is ad-
ministered by placing a person on an
insulating stool, and directing the elec-
tric current from the conductor to dif-
ferent parts of the body by means of some
pointed conductor.

BATRA'CHIA (/Sarpaxor, a frog). An
order of the class Reptilia, comprising
the frog, toad, salamander, and siren.

BATTERY, ELECTRICAL. An ar-
rangement of Leyden jars which commu-
nicate together by both their inner and
outer surfaces, and are thus rendered
capable of being charged with electricity
and discharged at the same time.

1. Battery, Galvanic. A combination
of several pairs of zinc and copper plates
soldered together, and so arranged that
the same metal shall always be on the
same side of the compound plate. A
combination of this kind is sometimes
termed a compound hydro-electric battery,
or a voltaic pile or battery.

2. Battery, Trough. In this apparatus
the zinc and copper plates are fastened
to a slip of mahogany wood, and united in
pairs by a piece of metal soldered to each.
The whole are then placed in a trough
of wood, or of Wedgewood's ware, divided
into cells, so that each pair of plates
shall enclose a partition of the trough,
each cell of the trough containing a plate
of zinc connected with the copper plate
of the succeeding cell, and a plate of
copper joined with the zinc plate of the
preceding cell.

3. Constant Battery. A term applied to
a battery in which the effect of the cur-
rent is for a long time unimpaired, owing
to the employment of concentrated nitric
acid, by means of which the platinum,
and by analogy the carbon also, become
depolarized and relatively exalted in their
electromotive functions. Of this kind
are the batteries of Grove and Bunsen.

50

BAY. A projection of the ocean into
the continent, of less expanse than that
of a sea, but communicating with the
ocean by a broader passage. See Gulf.

BAY SALT. A general name for
coarse-grained salt, but particularly ap-
plied to salt obtained by spontaneous
evaporation of sea-water in large shallow
pits or bays.

BDE'LLIUM. A name applied to two
gum-resinous substances. One of these
is the Indian bdellium, or false myrrh,
procured from the Amyris commiphora.
The other is called African bdellium,
and is obtained from the Heudolotia
African a.

BEAD-PROOF. A term denoting the
strength of spirituous liquors, as shown
by the continuance of the bubbles or
beads on the surface.

BEARING. A term denoting, in
Navigation, the situation of one place
from another with respect to the points
of the compass. Thus, if A lies in the
direction of south-west from B, then to
an observer at B, A is said to bear south-
west, or to have a south-west bearing;
while to an observer at A, the point B
will bear north-east, or have a north-east
bearing. To take bearings, is to ascer-
tain the points of the compass on which
objects lie.

BEATS. A term applied, in Music,
to the beatings or pulsations resulting
from the joint vibrations of two sounds
of the same strength and nearly the same
pitch ; that is, of two sounds differing
little, if at all, in intensity, and almost,
but not exactly, in unison : when the
unison is complete, no beats are heard.

BEGUIN'S SULPHURATED SPI-
RIT. A variety of hydrosulphate of
ammonia, commonly called hepatized
ammonia.

BE'LEMNITE (/3e\e/ivov, a dart). An
extinct genus of the Cephalopods, allied
to the sepia, and having a long, straight,
and chambered conical shell, resembling
a dart, in the interior of the body. They
have been termed lapides lyncis, from
an old idea that they came from the lynx ;
and, from their resemblance to fingers,
petrified fingers, devil's fingers, spectre
candles, &c.

BELLA'TRIX. A star of the second
magnitude, the smaller of the two bright
upper stars in Orion. It is marked y by
Bayer, and 24 by Flamstead.

BELL-METAL. An alloy of 100 parts
of copper with 20 to 25 of tin.

BELL-METAL ORE. A designation

BET

BI

of the sulphuret of tin found in Corn-
wall, from the appearance of bronze or
bell-metal which it possesses, in conse-
quence of its containing copper pyrites.

BENGALEE YEAR. This appears
to have been once identical with the
Hegira; but the solar computation having
subsequently been adopted, of which the
years exceed those of the Hegira by 11
days, it has lost nearly 11 days every
year, and is now about 9 years later, the
year 1245 of the Hegira having com-
menced in July, 1829, and the Bengalee
year 1236 having begun 13th April of the
same year. The number 593 must be
added to bring this to the Christian era.

BENZOIC ACID. Flowers of Ben-
jamin. An acid exhaled from benzoin,
dragon's blood, and other resins, by
heat.

BENZO'IN. Asa dulcis. A balsam
which exudes from incisions made in the
Styrax Benzoin, or Benjamin-tree.

BE'NZOYL. Benzoile or benzule of
several English chemical writers. The
hypothetical radical of a series of com-
pounds, including benzoic acid, from
which it derives its name, and the
essence or volatile oil of bitter almonds.

BE'RBERIN. A crystalline substance
of a fine yellow colour, derived from the
bark of the barberry root ; used as a dye
stuff.

BERG, or ICE BERG (berg, Swedish,
mountain). A mountain of ice, met with
in the Polar Seas. Flat sheets of wide-
spread ice are called fields ; and small
portions, floes, from their being found
floating.

BE'RGMEHL. Literally, Mountain
meal; an earth, so named in Sweden,
resembling fine flour, and celebrated for
its nutritious qualities. It is found to
be composed entirely of the shells of
loricated animalcules, which having accu-
mulated at the bottom of the waters in
which the living animals are found, form
a stratum of considerable thickness.

BE'RYL. A variety of the emerald; a
mineral or gem, usually of a green colour
of various shades, passing into honey-
yellow and sky-blue. When coloured
green by oxide of chromium, it forms
the true emerald, and when colourless
and transparent, aqua marina.

Chryso-b&ryl (xpuao?, gold). One of the
finest of the gems, consisting of glucina
and alumina.

BE'TELGEUSE. A star of the first
magnitude in the southern constellation
Orion.
51

BE'ZOAR (pdd-zahr, Persian, a de-
stroyer of poison). A morbid concretion
formed in the bodies of land animals.
Such are the hog-bezoar, found in the
stomach of the wild boar in India ; the
bovine bezoar, found in the gall-bladder
of the ox, common in Nepaul ; the camel-
bezoar, found in the gall-bladder of the
camel, and much prized as a yellow paint
by the Hindoos ; and the goat-bezoar,
produced from animals of the goat kind,
capra gazella. The Greek term for this
species of concretion is, cegagropila, lite-
rally, mountain-goat ball.

BI, BINUS (bis, twice). Two; a pair.
Also a prefix of certain saline compounds,
into which two proportions of acid enter
for one of base, as bi-arseniate.

1. Biarticulate. Having two articuli,
or joints, as applied to the antennae, or
to the abdomen of certain insects.

2. Biauriculate. Having two auricles
of the heart, as the mammalia, birds,
reptiles, and most bivalve mollusca.

3. Bicarbonates. Salts containing a
double proportion of carbonic acid gas.

4. Bicongregate. Bigeminate, or ar-
ranged in two pairs, as the leaflets of
mimosa unguis cati.

5. Bicrenate. Doubly crenate ; when
the crenate toothings of leaves are them-
selves crenate.

6. Bidentate. Two-toothed, as applied
to the fruit or achenia of bidens.

7. Biennial. Enduring throughout two
years and then perishing: as plants which
bear only leaves the first year ; leaves,
flowers, and fruit the second year, and
then die.

8. Bifarious. Arranged in two rows,
not necessarily opposite to each other;
in this particular, the term is differenced
from distichous.

9. Bifoliolate. "When two folioles or
leaflets are developed at the same point
at the end of the petiole, as in zygophyl-
lum fabago. The term is synonymous
with conjugate.

10. Biforines. Minute oval bodies
found in the leaves of some araceous
plants. When placed in water, they dis-
charge innumerable spicula? from each
extremity, until they become entirely
emptied.

11. Bifurcate. Twice-forked, as ap-
plied to the inflorescence of stellaria,
and synonymous with dichotomous.

12. Bijugous. In two pairs, as applied
to the leaflets of a pinnate leaf.

13. Bilabiate. Having two lips, as
applied to a calyx which has its sepals

D2

BI

BIN

cohering into two parcels, or to a corolla
which has its petals similarly disposed.

14. Bilobate. Two-lobed, as applied to
the leaves of bauhinia, &c.

15. Bilocular. Having two loculi or
cells, as applied to the anther, and to
certain capsules in plants.

16. Bimana. Two-handed; a designa-
tion of the first order of the Mammalia,
comprising the single species man, and
characterized by the presence of hands
(or feet with opposable thumbs) on the
upper extremities only.

17. Bimedial. In geometry, when two
lines commensurable only in power, as
the diagonal and the side of a square,
are joined together, the sum is irrational
with respect to either of the two lines,
and is called by Euclid a bimedial.

18. Binate. Growing in pairs ; a term
synonymous with bifoliolate.

19. Binervate. Two-nerved ; as ap-
plied to the wings of insects which are
supported by only two nerves.

20. Binocular. That which belongs or
applies to both eyes, as applied to a tele-
scope, by which the object maybe viewed
with both eyes at the same time.

21. Binomial. An algebraical quantity
consisting of two terms, as a + A, or
2a — 2>bx. The binomial theorem, first
announced by Newton, is a formula by
which any binomial may be raised to any
given power, without the ordinary pro-
cess of involution.

22. Biocellate. Having two ocelli or
eyelets, as applied to the wing of an in-
sect when marked with two eye-like
spots.

23. Bipartite. Parted in two, as ap-
plied to the segments of a leaf.

24. Bipectinate. When a part has two
margins toothed like a pecten or comb.

25. Bipeltate. When an animal or a
part has a defence like that of a double
pelta or shield.

26. Bipinnate. When the leaflets of a
pinnate leaf themselves become pinnate,
as in fumaria officinalis.

27. Bipupillate. When an eye-like
spot on the wing of a butterfly has two
pupillae or dots within it of different
colours.

28. Biquadratic. In algebra, the power
immediately succeeding the cube; that
is, the square of the square, or the fourth
power. A biquadratic equation is that
in which the unknown quantity rises to
the fourth, but not to a higher power.

29. Biradiate. Applied to a part which
has two radii or rays.

52

30. Biserial. Arranged in two series,
or rows ; a term synonymous with bifa-
rious.

31. Biserrate. Doubly sawed, as ap-
plied to the margins of leaves, when the
serrations are themselves serrate.

32. Bisetous. When a part is furnished
with two setae or bristle-like appendages.

33. Bisexual. Applied to flowers which
contain both stamen and pistil in the
same envelope ; a term synonymous with
hermaphrodite.

34. Bispinose. When an animal or
part is furnished with two spines.

35. Bisulcate. Applied to a foot which
rests upon two sulci or hoofed digits.

36. Biternate. When three secondary
petioles proceed from the common pe-
tiole, and each bears three leaflets, as in
fumaria bulbosa.

37. Bivalved. Having two valves ;
applied to the shells of certain mollusca.

BIBLIO'GRAPHY {/3t/3\iov, a book,
•ypa'^a), to write). Among the ancients
this term denoted the writing or the
transcription of books. In modern times,
it signifies the science of the knowledge
of books, with reference to their authors,
subjects, editions, and history.

BICE. A blue colour, prepared from
the lapis armenius, for painting.

BILLION. In numeration, a million of
millions, expressed by 1,000,000,000,000.
By this term the French signify only a
thousand millions.

BI'NARY COMPOUNDS. A series
of chemical compounds, formed by the
union of two elementary bodies with each
other in their combining proportions only,
or in multiples of them, and in no inter-
mediate proportions. If the constituents
of a binary compound be represented by
A and B, the latter being the oxygen or
electro-negative constituent, the most
frequent combination is A + B, then
A + 2B, A+3B, and A+5B. The com-
bination of 2A4-3B is not unfrequent;
but 2A+B, A+4B, A+7B, 2A+2B, or
2A+5B are of comparatively rare occur-
rence. The five compounds of nitrogen
and oxygen afford a good illustration of
this law of combination.

BI'NARY NOTATION. A kind of
notation, proposed by Leibnitz, in which
only two characters are used, 1 and 0, the
zero having the power of multiplying the
number it follows by two, as in the com-
mon notation it multiplies by ten. The
number one is represented by 1 ; two, by
10; three, by 11; four, by 100; five,
by 101 ; six, by 110 ; seven, by 111 ; eight,

BIT

BL A

by 1000; nine, by 1001; ten, by 1010,
&c.

BIO'GRAPHY (/3/of, life, ypaftj, writ-
ing). That department of literature
which treats of the lives of individuals.
It is thus distinguished from history,
which treats of states and nations.

BIRD'S-EYE VIEW. A mode of
prone perspective representation, by which
objects are shown, in nature or in paint-
ing, below the spectator, who can see
them only by looking down upon them.
The reverse of this is the supine per-
spective, termed di solto in su, employed
for ceiling-pieces, which the spectator
can view only by looking upwards.

BIRDS' NESTS, ESCULENT. The
nests of the Hirundo esculenta, a species
of swallow peculiar to the Indian islands,
formed of a viscid substance, not unlike
isinglass. Nothing satisfactory is known
as to the formation of these eatable
nests.

BI'SMUTH {wismuth, German). A
reddish-white metal, usually found in tin
mines. It occurs as an oxide, under the
name of bismuth ochre; as a sulphuret,
called bismuth glance; as a sulphuret
with copper, called copper bismuth ore;
and with copper and lead, called needle
ore. The subnitrate is known, in Phar-
macy, under the name of magistery of
bismuth. The sublimed oxide is known
by the name of flowers of bismuth ; the
chloride as the butter of bismuth. An
alloy of bismuth, lead, and tin, consti-
tutes Newton's fusible metal.

BISSE'XTILE, or LEAP-YEAR. A
term adopted in the Julian calendar.
Julius Caesar, having ascertained that
the solar year consisted of 365£ days,
made the civil year 365 days, and added
a sixth at the end of four years, to com-
pensate for the quarter of a day dropped.
This fourth year, which contained 366
days, was termed bissextile, from its
doubling the 24th of February, or, ac-
cording to the Roman way of reckoning,
the sextilis, or sixth of the calends of
March (bissextus dies). This arrange-
ment was denominated the Julian Style,
or the Old Style, as distinguished from
the Gregorian or New Style.

BISTRE. A brown pigment, made
from the roots of beech and other woods,
reduced to soot, and then boiled and
evaporated.

BITTER PRINCIPLE. A general
term applied to an intensely bitter sub-
stance, procured by digesting nitric acid
on silk, indigo, &c. The bitter of Welter
53

is the former name of picric or carbazotic
acid, formed by the action of nitric on
anilic or indigotic acid.

BITTERN. The mother water, or un-
crystallizable residue left after muriate
of soda has been separated from sea-water
by crystallization. It owes its bitterness
to sulphate and muriate of magnesia.
It contains bromine.

BFTTERSPAR. Rhombspar. A crys-
talline mineral, bearing the same relation
to dolomite and magnesian limestone,
that calcareous spar does to common
limestone.

BITU'MEN {wlrvna, TrtTt/f, pine). A
mineral pitch, supposed to be formed in
the earth by the decomposition of animal
and vegetable substances. In its most
fluid state it constitutes naphtha; when
of the consistence of oil, it becomes petro-
leum ; at the next stage of induration it
becomes elastic bitumen; then maltha;
and so on until it becomes a compact
mass, and is then called asphaltum.

BITU'MINOUS SHALE. An argil-
laceous shale, much impregnated with
bitumen, which gives it a dark brown or
blackish colour; its structure is slaty,
the streak brown and shining.

BPVALVE (bis, twice, valvce, folding-
doors). A shell which has two valves,
belonging to the order Dithyra.

BLACK COMPOUNDS. 1. Black
lead, or plumbago, is a carburet of iron,
found in a pure state only at Borrowdale
in Cumberland. It derives its name from
its leaden appearance, for it does not
contain a particle of lead. 2. Black dye
is a compound of oxide of iron with gallic
acid and tannin. 3. Black flux is a mix-
ture of charcoal and carbonate of potash.
4. Black chalk is a mineral found in
primitive mountains, and sometimes near
coal formations. 5. Black jack is the
technical term for blende or mock lead,
an ore of zinc. 6. Black wadd is an ore
of manganese, called the black oxide,
and used as a drying ingredient in paints.
7. Black turpeth is the protoxide of mer-
cury, commonly called the gray, ash, or
black oxide. 8. Lamp black is a species
of charcoal procured by burning resinous
substances in a furnace. 9. Spanish black
is also a charcoal made of burnt cork,
and first used by the Spaniards. 10. Black
salts, is the name given in America to
wood-ashes, after they have been lixi-
viated, and the solution evaporated, until
the mass has become black.

BLADDER GREEN. A green pig-
ment, prepared from the ripe berries of
D3

B LE

BL U

the Rhamnus catharticus, or Buck-
thorn, mixed with gum arabic and lime
water.

BLANCHING. Etiolation. The pro-
cess of whitening the leaves and stems
of plants, by excluding the light, and
thus preventing the development of their
natural properties.

BLANK VERSE. Verse without
rhyme or the consonance of final syl-
lables!

BLASTE'MA (/3\a<rTa'va>, to bud). A
Greek term applied to the rudimental
mass of an organ in the state of forma-
tion ; it is said to consist of fluid, nucle-
ated cells, and granules which spontane-
ously change into cells and into nuclei of
cells. Botanical writers apply the term
to the thallus of lichens; according to
Mirbel, the blastema comprises the ra-
dicle, plumule, and caulicle of the em-
bryo.

BLASTOCA'RPOUS (/?\ac~r6r, a shoot,
Kapnot, fruit). A term applied, in Bo-
tany, to those plants in which germina-
tion takes place within the fruit before
it fells, as in the mangrove.

BLA'STUS (fiXaaros, a shoot). A term
sometimes applied to the plumule of
grasses. With the same idea, Richard
considers the scutelliform cotyledon of
these plants to be a particular modifica-
tion of the radicle, and calls it hypo-
blastus ; the anterior occasional cotyledon
he views as a peculiar appendage, and
names it epiblastus ; the radicle is a pro-
tuberance of the caulicle, and termed
radiculoda. Finally, to embryos of this
description he gives the general designa-
tion of macropodal. Dr. Lindley observes
that in these ideas Richard was wrong,
as is now well known.

BLA'TTID^. A family of Ortho-
pterous insects, named from the genus
blatta, a familiar species of which is
known under the vernacular term cock-
roach.

BLEACHING. The chemical process
of whitening linen or woollen stuffs.
1. Linen is bleached, by the old process,
by exposure to air and moisture ; by the
new process, by means of chlorine or
solution of chloride of lime. 2. Woollen
stuffs are bleached by soap and water,
which is called the Natural Method ; or
by exposure to the vapour of sulphur,
which is commonly called bleaching by the
flower, or bleaching of Paris, because this
method is employed in that city more
than elsewhere.

BLEACHING POWDER. Chloride
54

of lime, prepared by exposing hydrate
of lime gradually to chlorine gas. This
compound is obtained in solution by
transmitting a stream of chlorine gas
through hydrate of lime suspended in
water, and the solution is tnen called
bleaching liquid, or oxymuriatic alkaline
water.

BLENDE. A term signifying a mine-
ral which contains no ore, particularly
applied to the native sulphuret of zinc,
but extended by mineralogists to other
substances, as manganese-blende, anti-
mony-blende, ruby-blende, &c.

BLETTING. A term adapted by Dr.
Lindley to denote that peculiar bruised
appearance in some fruits, called blessi
by the French, for which we have no
equivalent English expression.

BLIGHT, A popular name for various
diseases of plants. These diseases are
probably owing to arrest of the natu-
ral functions of plants by circumstances
depending on temperature and the con-
ditions of the atmosphere.

BLO'EDITE. A massive translucent
salt, found at Ischel in Upper Austria,
together with prismatic gypsum.

BLOODSTONE. Haematites. A green
agate coloured by chlorite, with nume-
rous red spots like drops of blood ; called
also heliotrope and oriental jasper.

BLOW-PIPE. A small conical tube,
bent at one end, so as to be easily intro-
duced into the flame of a candle or lamp,
for the purpose of directing a stream of
flame, by blowing through it, upon any
object which is to be heated.

Oxy-hydrogen Blow-pipe. An apparatus
for producing intense heat, by supplying
a stream of hydrogen with pure oxygen,
so that the two gases issue together in
the form of a jet from the nozzle of the
blow-pipe.

BLUE COMPOUNDS. 1. Prussian
or Berlin blue is the sesquiferricyanide
of iron ; basic Prussian blue is a com-
pound of Prussian blue and peroxide of
iron. 2. Saxon blue is a sulphate of in-
digo, or a solution of indigo in concen-
trated sulphuric acid. 3. Blue verditer is
an impure carbonate of copper ; blue cop-
per ore is the finely crystallized subcar-
bonate of copper. 4. TurnbulVs blue is
the ferricyanide of iron, precipitated on
adding red prussiate of potash to a proto-
salt of iron. 5. Blue vitriol, copperas,
or blue stone, is the sulphate of copper,
prepared by roasting and oxidating the
sulphuret of copper. 6. Blue John is a
technical name for fluor or Derbyshire

BOM

BOR

spar. 7. Blue black is another name for
ivory black.

BLUFFS. A term employed in the
United States to designate high banks
presenting a precipitous front to the sea
or a river.

BODY. A term applied in Physics to
any determinate part of matter, but of
itself utterly passive, capable of any sort
of motion, and of all figures and forms.
Body, or substance, which is the same
thing, is usually denoted by the general
term matter. Its forms are the solid, as
crystals ; and the fluid, which are elastic
and aeriform, as gases, or inelastic and
liquid, as water. In Geometry, the term
body is synonymous with solid.

BOG-EARTH. An earth composed
of light siliceous sand and about 25 per
cent, of vegetable fibre in a decomposing
state.

BOG IRON ORE. A ferruginous de-
posit, occurring at the bottom of peat
mosses and in marshy places, owing to
the presence of oxide of iron in solution
in almost all water. These ferruginous
matters sometimes form, below the soil,
a plate, or pan, which is impermeable to
the roots of trees.

BOILING POINT. That degree in
the scale of the thermometer, at which
ebullition is produced under the medium
pressure of the atmosphere. Thus, 212°
is the boiling point of water, when the
barometer stands at 30 inches ; at 31
inches, it is 21376; at 29, it is only 210*19;
in a common vacuum, it is 70°.

BOLE (/3S>\or, a mass). A friable
earthy substance, a species of the soap-
stone family. It is found in Lemnos,
and is hence termed Lemnian earth ; also
in Armenia, France, and other places.
Its colours are yellow -red, and brownish-
black, when it is called mountain soap.

BOLE'TIC ACID. An acid procured
from the expressed juice of the Boletus
pseudo-igniarius, a species of mush-
room.

BOLO'GNIAN STONE. Native sul-
phate of barytes; a phosphoric stone
found at Bologna. When heated with
charcoal, it becomes a powerful solar
phosphorus.

BOMBIC ACID (poupvf, the silk-
worm). An acid contained in a reservoir
near the apus of the silk-worm. It forms
salts with the alkalies, earths, and me-
tallic oxides, which have been called
bombiate8.
BOMBY'CIDjE (bombyx, the silk-
55

worm). A tribe of Lepidopterous insects,
named from the genus Bombyx, and
consisting of Moths allied to the common
silk-worm. The principal characteristics
of the family are the presence of merely
rudimentary maxillae, remarkably small
palpi, and bipectinated antennae.

BOMBY'LIDjE. A family of Dipterous
insects, named from the genus Bomby-
lius, and distinguished chiefly by their
long proboscis.

BONE EARTH. The residue of bones
which have been calcined, and converted
into a friable substance, consisting chiefly
of phosphate of lime.

BOOTES. A northern constellation,
containing fifty-four stars, the principal
of which is Arcturus.

BORA'CIC ACID. An acid compound
of boron and oxygen, formerly called
Romberg's sedative salt and sedative salt
of borax. It occurs native on the edges
of hot springs in Florence, &c, in small
pearly scales, and also in a massive
state. It forms salts with bases, which
are called borates, of which the only im-
portant one is borax.

BO'RACITE. A mineral consisting
of an anhydrous compound of magnesia
and boracic acid, in the extraordinary
ratio of 3 equivalents of the former to 4
of the latter. The rare mineral hydro-
boracite is said to be a compound of a
borate of lime and borate of magnesia,
in both of which the acid and the base
are in the same ratio as in boracite, with
18 equivalents of water.

BORAGINA'CEjE. The Borage tribe
of Dicotyledonous plants. Herbaceous
plants or shrubs, with leaves alternate,
covered with asperities ; corolla gamo-
petalous; stamens inserted in the corolla;
fruit, four nuts, distinct.

BORAX {baurach, Arab.)- A native
bi-borate of soda, chiefly found in an im-
pure state, and then called tinkal, or
rough borax, as a saline incrustation in
the beds of certain small lakes in an up-
per province of Thibet. When the re-
fined salt is deprived of its water of
crystallization by fusion, it forms a vi-
treous transparent substance, called glass
of borax.

BOREAL SIGNS. Those on the north
side of the equinoctial ; viz. Aries, Tau-
rus, Gemini, Cancer, Leo, and Virgo.

BORNEEN. The name given to a
compound of carbon and hydrogen found
in valeric acid, supposed to be identical
with liquid camphor.

D4

BOTANY.

BO'RON. An elementary substance,
somewhat analogous to carbon, always
found in combination with oxygen as bo-
racic acid, from which it was first ob-

tained by Davy by the action of the
voltaic battery.

BO'RURET. A compound of the ele-
ment boron with a metal.

BOTANY (/3oTai/n, a plant). The science which treats of the Vegetable King-
dom. 1. Structural Botany relates to the laws of vegetable structure, internal or
external, independently of the presence of a vital principle. 2. Physiological
Botany relates to the functions of plants and their changes in disease or health.

3. Descriptive Botany relates to the description and nomenclature of plants.

4. Systematic Botany relates to the principles upon which plants are connected with,
and distinguished from, one another.

I. SYSTEM OF LINSMEUS.

1. Classes.— Plants are distributed into twenty-four classes, founded on the num-
ber, position, and relative connexion of the sexual organs. Of these classes, the
first twenty have hermaphrodite flowers ; the following three, unisexual flowers ; the
last has no flowers. The first eleven classes are founded on the number of the
stamens ; the 12th and 13th, on their number and position; the 14th and 15th, on
their number and relative length; the 16th, 17th, and 18th, on modes of connexion
subsisting between the filaments of the stamens; the 19th, on connexion of the
anthers of the stamens; the 20th, on connexion of the stamens with the pistil ; the
•21st, 22nd, and 23rd, on modifications arising from unisexuality and hermaphroditism;
the 24th, on the absence, or obscure nature, of the sexual organs, as compared with
those of all the other classes.

2. Orders. — The classes are distributed into orders, the first thirteen classes being
divided, each, into several orders depending on the number of the styles ; the 14th,
into two orders, the seeds, in the one, being covered by a seed-vessel, those in the
other being, as Linnaeus erroneously supposed, naked; the 15th, into two orders,
the one characterized by a long seed-vessel, or siliqua, the other by a short one, or
silicula; the 16th, 17th, and 18th, into several orders founded on the number of the
stamens; the 19th, into three orders relating to the unisexual, hermaphrodite, or
neutral condition of the florets ; the 20th, 21st, and 22nd, into several orders
dependent on the number and modes of connexion of the stamens ; the 23rd into
three orders founded on unisexuality and hermaphroditism; the 24th, on general
natural affinities. This and the preceding paragraph may be studied in connexion
with the tables on the two following pages.

CLASSES OF THE LINN^EAN SYSTEM.
•Class

1. Monandria 1 S tamen in each flower.

2. Diandria 2 Stamens equal in length.

3. Triandria 3 „ „

4. Tetrakdria 4 „ „

5. Pentandria 5 ,, ,,

6. Hexandria 6 ,, ,,

7. Heptandria 7 „ ,,

8. Octandria 8 ,, „

9. Enneandria 9 ,, ,,

10. Decandria 10 „ ,,

11. DODECANDRIA 12 to 19 „

12. Icosandria 20 or more, on the calyx.

13. Polyandria 20 or more, on the receptacle.

14. Didykamia 4; 2 long, 2 short.

15. Tetradynamia .... 6; 4 long, 2 short ; flowers cruciform.

16. Monadelphia Filaments united at the base into one set.

17. Diadelphia Filaments united into two sets.

18. Polyadelphia Filaments united in to three or more sets.

19. Syngenesia Anthers united. Flowers compound.

\ 20. Gynandria Stamens inserted on the Pistil

56

BOTANY.

CLASSES OF THE LINNjEAN SYSTEM (continued).
/Class

u3 I 21. Moncecia Stamens and Pistils in separate flowers on the

& g I same plant.

^ xj y 22. Dicecta Stamens and Pistils in separate flowers on two

jfW \ separate plants.

3g j 23. Polygamia Stamens and Pistils separate in some flowers,

p I united in others, either on the same plant, or

V on tfwo or f/jree distinct plants.

24. Cryptogamia Fructification concealed.

ORDERS OF THE LINN^EAN SYSTEM.

1. The Orders of the first thirteen Classes are founded on the number of styes

1. Monogynia, 1 style. 6. Hexagynia, 6 styles.

2. Digynia, 2 styles. 7. Heptagynia, 7 styles.

3. Trigynia, 3 styles. 8. Octogynia, 8 styles.

4. Tetragynia, 4 styles. 9. Decagynia, 9 styles.

5. Pentagynia, 5 styles. 10. Polygyria, many styles.

2. The Orders of the fourteenth Class are two, founded on the presence or (sup-
posed) absence of a seed-vessel : —

1 . Gymnospermia, seeds 4, apparently naked ; or ovarium 4-lobed.

2. Angeiospermia, seeds in a distinct seed-vessed.

3. The Orders of the fifteenth class are two, founded on the comparative length
of the seed-vessel : —

1. Siliquosa, seeds in a long seed-vessel, or siliqua.

2. Siliculosa, seeds in a short seed-vessel, or silicula.

4. The Orders of the sixteenth, seventeenth, and eighteenth Classes are founded
on the number of stamens in each adelphia, or brotherhood :—

1. Triandria, 3 stamens. 3. Decandria, 10 stamens.

2. Pentandria, 5 stamens. 4. Polyandria, many stamens.

5. The Orders of the nineteenth Class are founded on the structure of the flower :—

1. JEqualis, all the florets perfect.

2. Superflua, florets of the disk perfect ; of the ray, pistilliferous only.

3. Frustranea, florets of the disk perfect ; those of the ray neuter.

6. The Orders of the twentieth Class are founded on the number of the stamens :-
1. Monandria, 1 stamen. 2. Diandria, 2 stamens, &c.

The Orders of the twenty-first and twenty-second Classes are founded on the
number, union, and situation of the stamens : —
1. Monandria, 1 stamen. 2. Diandria, 2 stamens. 3. Monadelphia, &c.

8. The Orders of the twenty-third Class are three, founded on the separation of
the sexes in the same plant, or in different plants : —

1. Moncecia, unisexual flowers accompanied by barren or fertile flowers, or
, both, all on one plant.

2. Dicecia, the same, on two different plants.

3. Tricecia, the same, on three different plants

9. The Orders of the twenty-fourth Class are Natural orders, or Families :—
• 1. Fiiices. 2. Musci. 3. Hepaticce. 4. Lichenes. 5. Fungi. 6. Alga.
57 D5

BOTANY.

II. NATURAL SYSTEM.

Class I. — Exogens, or Dicotyledonous Flowering Plants.

Leaves reticulated. Stem with bark, wood, medullary rays, and pith ; increasing in
diameter by the addition of new matter to the exterior. Flowers with a quinary, or
more rarely a quaternary, division. Seeds in a pericarp. Cotyledons two, opposite ;
or, if more, whorled, or on the same plane. Germination exorrhizous.

1. Divisions of Jussieu.— The primary divisions are founded on the separation,
the combination, and the absence of the petals, and are termed the polypetalous, the
monopetalous, and the apetalous groups; to which is added a fourth, founded on the
separation of the sexes in flowers having no petals, and termed diclinous. The first
three are divided with reference to the insertion of the stamens, which are epi-
gynous, perigynous, or hypogynous ; further, the monopetalous epigynous group is
subdivided into plants which have their stamens united and those which have them
distinct. Hence we have eleven classes : —

Class.

{Stamens epigynous 1
Stamens perigynous 2
Stamens hypogynous 3

! Corolla hypogynous 4

Monopetalous ^rolla perilous 333^-35^ J
^Corolla epigynous {Anthers distinct 7

{Stamens epigynous 8
Stamens perigynous 9
Stamens hypogynous 10

Diclinous 11

2. Divisions of De Candolle. — De Candolle reduced the eleven classes of Jussieu
to four ; the first three being founded on the separation or cohesion of the several
parts of the flower, the fourth on the suppression of the floral envelopes. Thus, in
Thalamiflorae, all the parts are present and distinct from each other; in Calyciflorae,
the stamens adhere to the calyx ; in Corolliflorae, the petals cohere with each other;
in Monochlamydeae, the corolla is suppressed, and, in the most imperfect orders, the
calyx also.

PnlvnPtalmn / Stamens hypogynous Thalami force.

roiypeiaious I Stamens perigynous Calyciflora.

Monopetalous Corollifiorce.

Apetalous Monochlamydece.

3. Divisions of Dr. Lindley. — Dr. Lindley first distributes the Class into the
Polypetalous, Monopetalous, and Incomplete sub-classes; these are next divided
into groups. The principles on which these divisions are founded are stated in the
following table : —

Table of Groups.
Sub-class I. Polypetalae. Groups.

Albumen very considerably larger than the minute embryo Albuminosce.

Albumen absent, or only forming a layer between the embryo and
the seed-coat.

Ovary inferior (often with an epigynous disk) Epigynosce.

Ovary superior.

Placentae parietal Parietosce.

Placentae in the axis.

Calyx dislocated Calycosce.

Calyx complete ; its parts being all on the same plane.
Carpels united into a solid pistil, parallel with

each other Syncarposce.

Carpels oblique, upon a gynobase Gynobaseosce.

Carpels disunited Apocarposce.

58

BOTANY.

Sub-class II. Incompletae, or Apetalae.

Calyx altogether absent Achlamydosce.

Calyx present.

Embryo curved round albumen Curvembryosce.

Embryo straight.

Stamens monadelphous Columnosa.

Stamens distinct.

Calyx tubular, often corolliform Tubiferoscc.

Calyx very imperfect Rectembryosee.

Sub-class III. Monopetalae.

Fruit consisting of but one perfect carpel Aggregosce.

Fruit of several carpels.

Ovary inferior Epigynosce.

Ovary superior.

Carpels three or more Polycarposce.

Carpels only two.

Fruit nucamentaceous Nucamentoscs.

Fruit capsular Dicarposce.

Class II. — Endogens, or Monocotyledonous Flowering Plants.

Leaves straight-veined. Stem increasing in diameter by the addition of new matter
to the centre. Flowers with a ternary division. Embryo with one cotyledon. Germi-
nation endorrhizous.

Divisions of Br. Lindley. — There are two primary divisions, one having the
organization of the flowers perfect, i. e. with a distinct calyx and corolla, and a
regular consolidated cotyledon ; the other imperfect, the calyx and corolla being
either entirely absent, or in an incomplete condition, and the cotyledon being com-
monly rolled up without consolidation, or actually flat. The former includes four
groups, the latter two, the characters of which are stated in the following table : —

Perfect Endogens.

Group I.—Epigynos^:. Anthers distinct. Flowers complete, formed upon a ter-
nary plan. Ovary inferior ; or, if superior, then the leaves either
scurfy or equitant.
Zingiberaceae. Musaceae. Haemodoraceae. Taccaceae. Bromeliaceae
Marantaceae. Amaryllidaceae. Burmanniaceae. Iridaceae. Hydro-
characeae.
Group 2. — Gynandros-s:. Stamens and style consolidated into a central column.
Flowers complete, formed upon a ternary plan. Ovary inferior, usually
once-celled, with scobiform seeds.
Orchidaceae. Vanillaceae. Apostasiaceae.
Group 3. — Hypogynos-e:. Flowers coloured, formed upon a ternary plan. Ovary
superior.
Palmaceae. Melanthaceae. Liliaceae. Butomaceae. Juncaceae.
Pontederaceae. Gilliesiaceae. Commelinaceae. Alismaceae. Phily-
draceae.
Group 4. — Retos-e. Leaves either with many ribs, the intervals between which are
irregularly netted, or with a midrib and netted sides ; foot-stalk taper,
articulated with the stem. Embryo without a lateral slit. Flowers
never arranged in a spadix. Floral envelopes complete.
Smilaceae. Dioscoreaceae. Roxburghiaceae.

Imperfect Endogens.

Group 5.— Spadicosje. Flowers herbaceous or imperfect ; the perianth sometimes
absent. Embryo with a lateral slit for the emission of the plumule.
Pandanaceae. Araceae. Typhaceae. Juncaginaceae.
Cyclauthacese. Acoraceae. Naiadaceae. Pistiaceae.
"59 D 6

BOU

BRA

Group 6.— Glumos;e. Bract scale-like, glumaceous, imbricated, in the room of a
calyx.

Graminaceae. Desvauxiaceae.
Cyperacese. Restiaceae. Xyridaceae.

Class III. — Acrogens, Cryptogamic, or Flowerless Plants.

Plants usually composed of cellular tissue only. Stem, when such exists, increasing
by extension of its point. Reproduction taking place either by spores inclosed in
thecce, or imbedded in the substance of the plant. Germination occurring at any part
of the surface of the spore.
Sub-class 1. — iETHEOGAMOus. Plants furnished with air-vessels and stomates.

Filices. Marsiliaceae. Lycopodiaceae.

Equisetaceae. Salviniaceae. Marchantiaceae. Jungermanniaceae.
Sub-class 2. — Amphigamous. Plants having neither air-vessels nor stomates.

Characeae. Andraeaceae. Fungaceae.

Musci. Lichenaceae. Algaceae.

BOTANY BAY RESIN. An aro-
matic resin which exudes from the trunk
of the Acarois resinifera of New Hol-
land.

BOTHRE'NCHYMA (/360pot, a pit,
eixvfxa, enchyma). A name recently ap-
plied in Botany to the pitted tissue or
dotted ducts of former writers, the appear-
ance of these tubes being occasioned by
the presence of little pits sunk in their
walls. It is either articulated or conti-
nuous.

BOTRY'LLARIjE (poTpvs, a bunch of
grapes). A group of the tunicated mol-
lusca, in which the individuals con-
sist of small ovoid bodies, which attach
themselves to sea-weed or other sub-
stances in regular bunches, arranged
like the rays of a star around a common
centre.

BOTRY'LLI (/SoTpv?, a bunch of
grapes). A little cluster of berry-shaped
bodies.

BOTRYOI'DAL (/36tPu?, a bunch of
grapes, ctdor, likeness). Clustered, like
a bunch of grapes.

BO'TRYOLITE (/3eTpur, a bunch of
grapes, \i0os, a stone). A mineral oc-
curring in botryo'idal masses, in a bed of
gneiss near Arendahl in Norway, and
considered by some writers as a variety
of datholite. Its basis is boron.

BOULDERS. Erratic Blocks. A
provincial term for large rounded blocks
of stone lying on the surface of the
ground, or sometimes imbedded in loose
soil, different in composition from the
rocks in their vicinity ; hence it appears
that they have been transported from a
distance.

BOURGEON; BOUTON. Terms ap-
plied by French botanists to the leaf-bud
60

and the flower-bud, respectively, of Eng-
lish writers.

BOUSTROPHE'DON (fioZs, an ox,
<rTpe<pu>, to turn). A term descriptive of
a mode of writing alternately from left to
right and from right to left, from its re-
semblance to the mode of making fur-
rows in ploughing a field. Some speci-
mens occur among the Arundelian
marbles at Oxford.

BOVEY COAL. Brown Coal. A va-
riety of coal found at Bovey Heathfield,
near Exeter. It consists of wood pene-
trated with petroleum, sometimes con-
taining pyrites, alum, and vitriol.

BO'VIDJE (bos, bovis, an ox). The
Ox tribe; a family of the Ruminantia,
in which the horns are directed upwards
and forwards, and increase by layers
during life.

BOYLE'S FUMING LIQUOR. Hy-
dro-sulphuret of ammonia, or volatile
liver of sulphur. See Fuming Liquor.

BRA'CCATE (bracca, breeches). A
term applied to the feet of birds when
concealed by long feathers descending
from the tibia.

BRACHELY'TRA {/3PaXv?, short, $\v-
rpov, a wing-case). A family of the pen-
tamerous Coleoptera, characterized by the
presence of four palpi, and by the short-
ness of the wing-cases. The staphylinus
is the only genus of the family.

BRA'CHIATE (brachium, an arm).
A term applied in Botany to branches
which diverge nearly at right angles from
the stem.

BRACHIO'PODA (foaxiw, an arm,
n-ouf, Trodop, a foot). A division of the
Mollusca, so named by Cuvier from their
having two long spiral arms placed on
each side of the mouth, which in many

BRA

BRE

species can be unrolled to a considerable
length, and protruded to some distance,
in search of aliment. See Palliobran-
chiata.

BRACHI'STOCHRONE (/?Pdx«rrcK,
shortest, xp°vo?, time). The name given
by Bernouilli to a particular curve, by
which a body arrives at a given point in
a shorter time than if it followed any other
direction.

BRA'CHIUM. The arm. The second
segment of the anterior extremity of the
lower mammalia. The brachia of insects
are the first pair of legs in the hexapods,
the direction of which is usually towards
the head.

BRACHY'PTEROUS (/3paXvv, short,
Trrepov, a wing). A term applied to birds
whose folded wings do not reach the base
of the tail.

BRACHYU'RA (/3paXv?, short, ovpa,
a tail). A family of Decapods, distin-
guished by the shortness of the tail, as
in the common crab.

BRACT {bractea, a thin leaf or plate
of any metal). A term applied to the
flower-leaf, or that leaf from whose axil
the flower-bud is developed. These are
the leaves which composse the involu-
crum of the Compositae, the glumes of
Graminaceae, the spathe of Araceae, &c.
But the term is extended to all those
modifications of leaves which are found
upon the inflorescence, and are situated
between the true leaves and the calyx of
the flower. These are termed by some
writers bracteolce, or bractlets.

BRA'NCA'S WHEEL. A machine
contrived by Giovanni Branca, in 1629,
for raising water, and other purposes.
It consists of a wheel furnished with flat
vanes around its circumference, like the
boards of a paddle-wheel. Upon these
vanes steam is propelled from a close
vessel; a rotatory motion is thus pro-
duced, and communicated to appropriate
machinery.

BRA'NCHIA {/3P,'nXta). Gills, or
respiratory organs which extract the
oxygen from air contained in water.

BRANCHIO'PODA (/3p«tx«*» giUs.
7roi/9, 7ro36r, a foot). A designation of
those Crustacea which have the branchiae
attached to numerous pairs of similar
feet. They possess mandibles and max-
illae, and are generally small, monoculous
or binoculous animals, with a large cara-
pace enveloping the whole body.

BRANCHIO'STEGI (/3pdyXla, gills,
areata, to cover). A tribe of cartila-
ginous fishes, in which the gills are free
61

and covered by a membrane, as in the
sturgeon.

BRAND or BURN. A disease in
plants by which their leaves and tender
bark are partially destroyed, as if they
had been burned.

BRASQUE. A term used by the
French metallurgists to denote the lining
of a crucible or a furnace with charcoal.

BRASS. An alloy consisting of three
parts of copper and one of zinc.

BRAZIL CURRENT. A branch of
the great Equatorial Current, separating
from the equatorial at 8° S. lat., opposite
Cape St. Augustin, running to the south-
west along the shores of Brazil to the
mouth of the Plata river, and traced to
the Straits of Magalhaens and Le Maire.
See Guiana Current.

BRAZIL WOOD. The wood of the
Ccesalpinia Braziliensis, which yields a
red colouring matter used by dyers.

BRAZILETTO. An inferior species
of Brazil wood, brought from Jamaica.
It is one of the cheapest and least es-
teemed of the red-dye woods.

BRE'CCIA. An Italian term signify-
ing an opening or breaking in any sub-
stance, applied by mineralogists to those
compound stones which consist of agglu-
tinated fragments of considerable size.
When the agglutinated parts are rounded,
the stone is called pudding-stone. Ac-
cording to the nature of their component
parts, breccias are called calcareous, sili-
cious, &c.

BREEZE, SEA and LAND. Names
given to winds of a very limited range,
experienced on the coasts of tropical
countries, and depending on local cir-
cumstances.

1. Sea breeze. From its low conduct-
ing power, the surface of the land is
more quickly heated than the sea, so
that soon after sunrise the expanded air
over the former begins to ascend, and is
replaced by the colder air from the sea,
forming the sea breeze.

2. Land breeze. After sunset, the
earth's heat, being diminished, is more
quickly dissipated by radiation than that
of the sea, , and the air over the land
becomes dense and flows outwards, dis-
placing the air over the sea, and pro-
ducing the land breeze.

BRENTl'DES. A family of Coleo-
pterous insects, named from the genus
Brentus, and belong to the section Rhyn-
cophora and sub-section Recticornes.

BRE'VIPENNES (brevis, short, penna,
a quill). Short-quilled; a designation

BRU

B UL

of Cuvier's first family of the order
Grallcc, of which the ostrich is the type.

BRE'ZILIN. The colouring matter of
Brazil wood, obtained from several spe-
cies of Ccesalpinia.

BRISTOL STONES or DIAMONDS.
Small brilliant crystals of quartz found
in the neighbourhood of Bristol.

BRITISH GUM. This is starch re-
duced to a gum-like state by great heat,
and used by calico printers.

BRITTLENESS. A quality of certain
bodies by which they admit of being
easily broken, or separated into irregular
fragments.

BRO'MAL. A colourless oily liquid,
corresponding with chloral, and formed
by adding bromine to alcohol.

BROMATO'LOGY {/3PS>na, food, X6-
Yor, a description). A description or
treatise of food.

BROMELIA'CE^. The Pine-apple
tribe of Dicotyledonous plants, named
from the genus bromelia, and chiefly in-
teresting from their capability of existing
in a hot dry air without contact with the
earth. See Air Plants.

BRO'MINE (/3P»/uo9, a stench). A
deep red-coloured fetid liquid, formerly
called muride; an ingredient of sea-
water, of several salt springs, of the
ashes of sea-weeds, and of those of the
Janthina violacca, and other animals. It
combines with oxygen, and forms bromic
acid; and with hydrogen, forming the
hydrobromic.

BRO'MURET. A combination of the
bromic acid with iodine, phosphorus,
sulphur, &c.

BRONZE. An alloy of copper, 8 or 10
per cent of tin and other metals.

BRO'NZITE. A variety of diallage,
of a metallic or bronze colour.

BROWN COAL. An imperfect kind
of coal, termed also, from its ligneous
structure, bituminous wood.

BROWN SPAR. Pearl spar or sidero-
calcite. A massive mineral, harder than
calcareous spar, but yielding to the
knife.

BRU'CIA. A substance procured from
the bark and seeds of nux vomica, and
from St. Ignatius's bean. It is said to be
a compound of strychnia and resin, and
not a peculiar alkaloid.

BRUNO'LIC ACID. One of the par-
ticular products which have been isolated
in the distillation of coal.

BRUNSWICK GREEN. An ammo-
niaco-muriate of copper, used for oil
painting.
62

BRYOZO'A (fipvov, moss, £woi/, an
animal). A term applied by Ehrenberg
to a class of highly-organized polyps,
most of the species of which incrust
other animals or bodies like moss. They
have been recently designated by Dr.
Arthur Farre, ciliobrachiate polyps. They
are among the species ranged by Cuvier
under the head of tubular polyps.

BU'CCAL {bucca, the mouth or cheeks).
Belonging to the mouth.

BUCCINI'NJE. Whelks ; a sub-family
of the Muricidce, named from the genus
buccinum, and including shells generally
recognized by the abrupt termination of
the base, which is deeply notched.

BUCE'RIDjE. The Hornbills ; a fa-
mily of the Insessores, or Perching-birds,
readily distinguished by the enormous
size of their bills, which are enlarged
into protuberances resembling horns.
See Conirostres.

BUD, LEAF, and FLOWER. I. A
leaf-bud (bourgeon) is a young plant
produced without the agency of sexes,
and consisting of rudimentary leaves
surrounding a growing vital point, which
elongates upwards in the form of stem,
and downwards in the form of root.
2. A flower-bud (bouton) consists also of
rudimentary leaves surrounding a fixed
vital point, which, when fully developed,
assumes the form of floral envelopes, or
sexual apparatus.

BUFO'ID^E {bufo, a toad). The Toad
tribe ; one of the principal divisions of
the Anoural order of Amphibious ani-
mals, which undergo a metamorphosis
similar to that of the frogs, but, unlike
these, are usually found at a distance
from water. See Rnnidce.

BULB. A scaly leaf-bud, which deve-
lopes roots from its base, and a stem from
its centre. When the outer scales are
thin, and cohere in the form of a thin
envelope, as in the onion, this is the
tunicated bulb. When the outer scales
are distinct and fleshy, as in the lily, this
is called the naked bulb. There can be no
such thing as a solid bulb. See Cormus.

BU'LBLET. Bulbille. A bulb which
separates spontaneously from the stem
of a plant, as in lilium bulbiferum.

BULBOTU'BER. A short, roundish,
underground stem, resembling a bulb.
The term was applied by Ker to the
Cormus.

BU'LLAD^E. A family of marine
mollusca, belonging to the fourth order
of Cuvier's Gasteropods, and named from
the genus bulla .

C AC

BUPRE'STIDjE. A family of Coleo-
pterous insects, named from the genus
buprestis, and belonging to the section
Pentamera and sub-section Sternoxi of
Latreille.

BURE'TTE. A French term applied
to a chemical instrument for dividing a
given portion of liquid into 100 or 1000
equal parts.

BURNING-GLASS. A glass lens
which refracts the rays of the sun into a
focus. The solar rays may also be brought
to a focus by reflection from a concave
mirror, which is then called a burning
mirror.

BURNT- EAR. A disease in corn, in
which the fructification of the plant is
destroyed, and, as it were, burned up.
By the French it is called charbon, by
the Germans brand. The disease is pro-
duced, according to De Candolle, by a
minute fungus, termed uredo carbo,
which he distinguishes from the uredo
caries, or the cause of smut.

BUTOMA'CEiE. A natural order of
Monocotyledonous plants, named from
the butomus umbellatus. They are tri-
petaloideous, with several carpels, the
entire lining of which is covered with
seeds.

BUTTERS. A term formerly applied,
in Pharmacy, to butter-like substances,
as those of antimony, of bismuth, &c,
meaning the chlorides of those metals.
Precipitated sulphur was also called
butter of sulphur. Vegetable butters is a

CAD

term also applied to the concrete oil of
certain plants, from its resemblance to
butter produced from the milk of
animals.

BUTTON. A technical term applied
to the round mass of metal found at the
bottom of the crucible after fusion, or in
the cupel in the process of assaying.

BU'TYRIC ACID {butyrum, butter).
An oily limpid liquid ; one of the volatile
acids of butter. By distillation it yields
a substance called butyrone.

BU'TYRINE {butyrum, butter). A
peculiar oleaginous matter, found in but-
ter, combined with oleine and stearine,
and a small quantity of butyric acid.

BYSSI'FERA (byssus, and fero, to
bear). A family of acephalous mollusca,
which are attached to foreign bodies by
means of a byssus.

BY'SSOLITE (/3vacof, byssus, \l0ot, a
stone). A massive filamentous mineral,
implanted like moss on certain stones, at
the foot of Mont Blanc, and also near
Oisans, on gneiss.

BY'SSUS (/3uo-«ro9, fine flax). A term
applied to the silky filaments which pro-
ject from the bivalve called Pinna, and
hence applied to the analogous parts in
other molluscous animals. In Crypto-
gamic botany, the term byssus has been
given to all those filamentous plants
which inhabit cellars and subterranean
abodes, and are now ascertained to con-
sist of fungaceous plants in an early
state of growth.

CA'CHOLONG. A variety of quartz
found on the borders of the river Cach,
in Bucharia. In the Calmuc language,
cholong is said to signify a stone.

CACODY'L (icaKtodn?, fetid). A limpid
liquid, supposed by Berzelius to be the
compound radical of a series of arsenical
compounds, and named in reference to
the repulsive odour of its oxide, alcarsin.
Cacodylic acid is obtained by the oxida-
tion of cacodyl and its oxide, and is syn-
onymous with alcargen.

CACTA'CEjE. The Indian-Fig tribe
of Dicotyledonous plants. Succulent
shrubs, usually without leaves and with
spinous buds. Sepals and petals con-
founded ; stamens indefinite ; ovary in-
ferior, 1 -celled; fruit succulent, eaten
63

under the name of Indian figs. All the
species are considered to be American.

CA'DENCE {cado, to fall). The close
of a passage in music, or the resolution
of a dissonant into a consonant chord.
Also, an extemporaneous addition made
by the performer at the end of a piece of
music.

The perfect cadence is composed of the
chord of the dominant, or of the domi-
nant seventh, followed by that of the
tonic. The imperfect cadence consists of
the chord of the tonic, followed by that
of the dominant, but rarely occurs as a
final close. The interrupted or deceptive
cadence is formed by a chord quite foreign
to that which was expected, thus evading
the close, and deceiving expectation.

C AL

C AL

The plagal cadence, sometimes called an
imperfect cadence, consists of the chord
of the subdominant, followed by that of
the tonic.

CADET, LIQUOR OF. Alcarsin.
A liquid obtained by distilling acetate of
potash and arsenious acid, and remark-
able for its insupportable odour and
spontaneous inflammability in air.

CA'DMIUM. A bluish-white metal
found in several of the ores of zinc ; so
named from cadmia fossilis, a former
name of the common ore of zinc.

CADU'CIBRA'NCHIATE {caducus,
falling, branchice, gills). A division of
Amphibious animals, which, though fur-
nished in the early period of their exist-
ence with gills and lungs, eventually lose
all traces of the former, as in the frog,
the newt, &c.

CADU'COUS {cado, to fall). A term
applied in Botany to parts which fall
early, as the calyx of the poppy, the
petals of the gum cistus, &c. Parts which
continue on the plant long are termed
persistent.

CiE'CUM {ccecus, blind). A blind tube,
or cul-de-sac; a tube which terminates
in a closed end.

CiE'SPITOSE {ccespes, a turf or sod).
Growing in tufts ; forming dense patches
or tufts, as the young stems of many
plants.

CjESU'RA {ccedo, to cut). A term de-
noting a cutting, equivalent to the Greek
roixrj, and applied by grammarians to the
place in a verse where a word ends, and
the voice pauses a little. 1. In a heroic
or hexameter, the most common caesura
is the penthemimeral, which occurs after
the fifth foot, as, " Tityre, tu patulae,"
&c. 2. The hepht/i emimeral caesura oc-
curs after the seventh half-foot, as " For-
mosam resonare doces," &c. 3. The
bucolic caesura, used by the bucolic or
pastoral poets, occurs after the fourth
dactyl, as, " Ambo florentes aetatibus,"
&c. 4. The caesura occurs also after the
third trochee, after the second dactyl, and
after the third dactyl, the last instance
being somewhat rare. See Incision.

CA'FFEIC ACID. An acid discovered
in coffee, containing the aroma of the
roasted seed. Caffein is a neutral crys-
talline substance obtained from unroasted
coffee.

CAIRNGORM. A species of quartz,
so named from a mountain of that name
in Scotland, where it was once plentiful.
It is a variety of rock crystal.

CA'LAMINE {calamus, a reed). The
64

impure carbonate of zinc; a pulveru-
lent mineral, generally of a reddish
colour.

CA'LAMITE. A light-green mineral
found in serpentine with magnetic iron
and calcareous spar, near Normark in
Sweden.

CA'LAMUS. A reed ; a term adopted
by De Candolle for all fistular simple
stems without articulations, as those of
rushes.

CA'LATHIS; CALA'THIUM {nd\a-
6ts, KaXdOtov, a basket). Terms adopted
by some continental botanists for the
capitulum or anthodium of other writers,
denoting the inflorescence of Composite.

CALC SINTER (kalk, lime, sintern,
to drop). A German name for carbonate
of lime, occurring in stalactitical forms
by the infiltration of carbonated lime-
water through the crevices of the roofs of
caverns.

CALCAIRE GROSSIER. Coarse lime-
stone; an extensive stratum, or rather,
series of strata, found in the Paris-
Basin, belonging to the Eocene tertiary
period.

CA'LCARATE {calcar, a spur).
Spurred, having a spur or spur-like ap-
pendage, as the petals of aquilegia. The
calcar is sometimes called nectarotheca,
or honey-depository, though it rarely
secretes honey.

CALCA'REOUS. The name of a class
of earths, consisting of lime and carbonic
acid, as chalk, marble, &c. 1. Calcareous
rock is another term for limestone. 2. Cal-
careous spar is crystallized carbonate of
lime ; Iceland spar is one of its purest
varieties. 3. Calcareous grit is a sub-
division of the middle oolitic forma-
tion. 4. Calcareous sandstone is another
subdivision of the same formation.

CA'LCES. Plural of calx, quicklime.
A former name for oxides, from their
earthy character, resembling lime. The
calx of tin is now called the oxide of
tin.

CALCINATION {calx, quicklime).
A term formerly applied to express the
oxidation of a metal effected by the action
of the air : the oxide thus formed was
denominated a calx, from its being earthy
like lime. The term is now generally
applied whenever any solid matter has
been subjected to heat, so as to be con-
vertible into a state of powder.

CA'LCIUM {calx, quicklime). A pe-
culiar metal discovered by Davy, of
which lime is the well-known oxide.

CALCTUFF. An alluvial formation

C AL

C AL

of carbonate of lime, probably deposited
from calcareous springs.

CA'LCULUS. The Latin term for a
pebble, used in former times for the pur-
pose of calculation. Hence it is applied
to any branch of mathematics which in-
volves calculation ; any, in fact, except
pure geometry. The several branches
are noticed under their specific names.

CA'LENDAR (/ca\<?<o, to call). Ka-
lendar. A table of the days of the year,
arranged to assist the distribution of
time, and to indicate remarkable days
connected with devotion or business.
The term is derived from the Roman
Calends, or the first day of the month,
when the pontiffs called the people to-
gether, to apprise them of the days of
festival in that month.

1. Roman Calendar. In the Roman
Calendar, as said to have been introduced
by Romulus, the year was divided into
10 months only, comprising altogether
304 days. The year of Romulus was,
therefore, of 50 days' less duration than
the lunar year, and of 61 days' less than
the solar year; and its commencement
of course did not correspond with any
fixed season. Numa Pompilius corrected
this calendar, by adding two months,
Januarius and Februarius, which he
placed before Mars,

2. Julian Calendar. In order to render
the calendar still more correct, Julius
Caesar fixed the solar year at 365 days,
6 hours, comprising, as was supposed,
the period from one vernal equinox to
another. The six hours were set aside,
and, at the end of four years, forming a
day, the fourth year was made to consist
of 366 days. The day thus added was
called intercalary. See Bissextile.

3. Gregorian Calendar. The Julian
Calendar was defective in this particular
— that the solar year, consisting of 365
days, 5 hours, and 49 minutes, and not
of 365 days, 6 hours, there was a dif-
ference, between the apparent year and
the real year, of eleven minutes. This
difference having amounted, in the year
1582, to ten entire days, Gregory XIII.
ordained that the 5th of October in that
year should be counted as the 15th, thus
cutting off ten days from that year ; and
to prevent the recurrence of this error, it
was further determined that the year
beginning a century should not be bis-
sextile, with the exception of that begin-
ning each fourth century. This is the
Gregorian or New Style, as distinguished
from the Julian or Old Style.

65

CALFBRE. A French term, signifying
the bore of a cannon, and generally ex-
pressive of the diameter of any round
substance, and, figuratively, of the mental
capacities. The calibre of round bodies
is measured by what are called Callipers,
or calliper compasses, which are formed
with curved legs, furnished with knobs
instead of points.

CA'LICO-PRINTING. The art of
dyeing cotton cloth, called calico from
Calicut in India, with one or more colours,
in certain parts, leaving the rest of the
material in its original state.

CALFPPIC PERIOD. In ancient
chronology, a correction of the Metonic
cycle of nineteen solar years, proposed
by Calippus. At the end of four of these
cycles, there is an excess of one day and
six hours over the number of lunations.
Calippus, therefore, proposed to quadruple
the Metonic period, and deduct a day
from the end of it by reducing the days
of one of the months from 30 to 29.

CALLUS, or CALLOSITY. A term
applied to the thickening of enamel upon
a shell, resembling a tumour, as in the
inner lip of the olives, and near the
hinge of some bivalves.

CALO'RIC (calor, heat). An ima-
ginary fluid, or condition diffused through
all bodies. In chemical language, caloric
is, properly, the matter producing the
sensation of heat. The words, however,
are often confounded, the term heat being
employed for both the cause and the
effect.

1. Sensible or free caloric is that which
produces the sensation of heat, or affects
the thermometer. Insensible or latent
caloric is that portion which passes into
bodies during a change of form, without
elevating their temperature ; as into ice
at 32°, as it becomes water, and termed
caloric of fluidity ; or into water at 212°,
as it passes into vapour, and termed
caloric of vaporization.

2. Specific caloric is the relative pro-
portion of caloric which any body retains
without the effects being sensible; and
the power of retention which a body pos-
sesses, is called its capacity for caloric.
The specific caloric of water is 23 times
as great as that of mercury; thus, if
equal weights of the former at 40°, and
of the latter at 160°, be mixed together,
the resulting temperature is 45°.

CALORFFIC RAYS. Those rays
proceeding from the sun or any burning
body, which impart the sensation and
other effects of heat.

CAM

CAM

CALORI'METER (calor, heat, Mt'Tpov,
measure). An apparatus for measuring
the capacity of bodies for heat by the
quantity of ice which they are capable of
melting. Rumford's water calorimeter,
consisting of a vessel filled with water
through which a spiral tube is conducted,
is employed for ascertaining the specific
heat of gases.

CALOfRIMOTOR, (calor, caloric,
moveo, to move). An apparatus, con-
structed by Dr. Hare of Philadelphia, for
evolving caloric.

CALY'BIO {kcl\v/3iov, a little hut). A
term by which Mirbel designates the
fruit called gland or nucule by other
writers. It is applied to the fruit of the
oak, of the chestnut, of the hazel.

CALYCIFLO'RiE (calyx, a flower-cup,
flos, a flower). Plants which have their
flowers furnished with both a calyx and
a corolla, the latter consisting of distinct
petals, and their stamens perigynous.

CALY'CULATE (calyculus, a little
calyx). Having an involucrum of bracts
exterior to the calyx, as in many of the
compositae.

CALY'PTRA (Ka\«'/7TT&), to veil). Lite-
rally, a veil or hood. A term applied to
a membranous covering, which envelopes
parts of certain plants, as the spore-
vessel of mosses, the stamens of euca-
lyptus, &c. Such parts are said to be ca-
lyptrate.

CALYPTR.E'ID,E. Chambered lim-
pets ; a family of gasteropods, named
from the genus Calyplrcea. Some of
these occur in a fossil state in beds of the
pliocene, miocene, and eocene periods.

CALYX (fcdAuf, a cup). The flower-
cup, or external envelope of the floral
apparatus. See Sepal.

CA'M BIUM. A viscid juice abounding
in spring between the bark and wood of
trees, and supposed to be closely con-
nected with the developement of woody
fibre.

CA'MBRIAN GROUP. A Welsh
group of rocks, constituting the upper
of the clay-slate series, and comprising
the Snowdon Rock, the Bala Limestone,
and the Plinlimmon Rocks.

CAME'LIDjE. The Camel tribe; a
family of the Ruminantia, including the
camels of the Old World, and the lamas
of the New. By some naturalists they
are referred to the horse tribe of the
Pachydermata.

CAM E'LO PARDEE. A family of the
Ruminantia, including only the giraffes,
and characterized by the shortness and

permanence of the horns, which are co-
vered by a skin.

CAME'LOPA'RDALUS. The Ca-
mel o,. aid ; a modern northern constel-
lation, consisting of fifty -eight stars.

CA'MERA OBSCURA. An instru-
ment consisting, as the term denotes, of
a darkened chamber, into which the rays
of light, from an illuminated object, are
admitted by means of a small aperture ;
these rays are received upon a white
screen, and thus the object is distinctly
seen in an inverted position. The in-
strument is constructed on the principle
that light is propagated in right lines.

Camera lucida. This term denotes a
lightened chamber, though no chamber is
employed. The contrixance is founded
on the fact, that when light is attempted
to be thrown from a denser into a rarer
medium at more than a certain angle,
depending on the two media, no light
will pass through, but all will be reflected.
The principle is the same as that of the
camera obscura, viz. that of throwing
images of external objects upon a plane
or curved surface, for the purpose of
drawing or amusement.

CAMPANULA'CEtE (campanula, a
little bell). The Campanula tribe of
Dicotyledonous plants. Herbaceous
plants or under-shrubs, yielding a milky
juice. Corolla gamopetalous, inserted
into the top of the calyx, and withering
on the fruit. Stamens inserted into the
calyx, alternate with the lobes of the
corolla. Ovary inferior, with two or
more cells. Fruit dry, crowned by the
withered calyx and corolla, and dehiscing
by apertures or valves.

CAMPA'NULATE (campanula, a little
bell). Bell-shaped ; a term applied in
Botany to the calyx and the corolla, when
shaped like a little bell.

CA'MPHINE. A spirit for burning
in lamps, said to consist of oil of turpen-
tine with a species of naphtha.

CA'MPHOGEN. A colourless liquid
procured by distilling camphor with an-
hydrous phosphoric acid.

CA'MPHORIC ACID. An acid pro-
cured by digesting camphor in nitric acid,
Campholic acid has the consistence of
camphor, but contains two parts more of
hydrogen and oxygen.

CA'MPHRONE. A light oil procured
by placing Camphor in contact with red-
hot quicklime.

CAMPYLO'TROPOUS Oaju^Xor,
curved, Tpen-w, to turn). A term applied
to the ovule of plants, when its axis, in-

CAN

CAP

stead of remaining rectilinear, is curved
down upon itself, the base of the nucleus
still continuing to be contiguous to the
hilum.

CAMWOOD. A red dye-wood, prin-
cipally obtained from Sierra Leone, and
used with alum and tartar as a mordaunt.

CANAL. A groove observed in dif-
ferent parts of certain spiral shells, be-
longing to the Zoophaga, or carnivorous
tribe, and adapted for the protrusion of
the long cylindrical siphon possessed by
these animals. This part, also, consti-
tutes the base of the shell.

Besides this there is, in many of the
mitres, strombi, and other predaceous
genera, another canal or groove, placed
in the interior of the upper part of the
aperture, the use of which has not been
ascertained.

CANALI'CULATE {canaliculus, a little
canal). Channelled ; long and concave, as
the leaves of tradescantia.

CANCE'LLATE (cancelli, lattice-
work). Latticed ; any thing which is
cross-barred, or marked by lines which
cross each other at right angles ; the cha-
racter of a leaf which has veins without
connecting parenchyma, anastomosing
and forming a kind of net-work, as in
hydrogeton fenestralis.

CA'NCER. The Crab ; the fourth of
the zodiacal constellations, consisting of
83 stars. It denotes the first month of
winter, extending from the 20th of De-
cember to the 20th of January, and bears
allusion to the retrograde motion of the
sun at the winter solstice.

CANES VENA'TICI. Asterion and
Chara, the Greyhounds ; a modern north-
ern constellation, consisting of twenty-
five stars.

CANI'CULAR PERIOD (canicula,
the dog-star). A period of forty days,
comprising, according to the old calen-
dars, twenty before and twenty after the
heliacal rising of the Canicula, Sirius, or
dog-star. The time of the heliacal rising
of the dog-star, however, varies in con-
sequence of the precession of the equi-
noxes, so that, instead of happening in
the warmest season, it has gradually ad-
vanced towards the autumn. In modern
almanacs, therefore, the period of the
rising of the star has been disregarded,
and the canicular days are reckoned as
commencing on the third of July, and
ending on the eleventh of August.

CA'NID^ (canis, a dog). The Dog
tribe ; a family of carnivorous Vertebrata,
which, like the felidae, are digitigrade,
67

but have no retractile claws, and they
are further characterized by the presence
of two flat tuberculated molar teeth be-
hind the great incisor.

CANIS MAJOR. The Greater Dog ;
a southern constellation, consisting of
thirty-one stars, the principal of which is
Sirius.

Canis Minor. The Lesser Dog ; a
southern constellation, consisting of four-
teen stars, the principal of which is
Procyon.

CANNEL COAL. A bituminous sub-
stance, which yields, on combustion, a
bright flame without smoke. The term
is probably a vulgarism for candle coal,
in allusion to its illuminating properties.
It occurs in most of the English collieries,
especially at Wigan in Lancashire.

CANNON METAL. An alloy of cop-
per, tin, and small quantities of other
metals, used for casting cannon.

CANO'PUS. A star of the first mag-
nitude, in the rudder of the southern
constellation Argo.

CANTATRICES (canto, to sing).
Songsters ; an order of Birds, so named
by Macgillivray on account of their being
pre-eminently musical, as the orioles,
thrushes, chanters, &c. They are all of
small size, with the bill slender, and
adapted for seizing insects, worms, or
soft fruits. They thus differ from the
Vagatrices, which have the bill more
elongated and stronger; and from the
Deglubitrices, in which it is short, stout,
and conical.

CANTON'S PHOSPHORUS. A sub-
stance made by exposing calcined oyster-
shells and sulphur to # red heat. On
exposure to light, it acquires the property
of shining in the dark.

CAOUTCHOUC. India Rubber. An
elastic resin or dried juice of certain trees
growing in South America and the East
Indies. Caoutchine is a liquid procured
by the distillation of caoutchouc.

CAPACITY FOR HEAT. The power
which a body possesses of retaining a
certain proportion of latent heat. See
Caloric, Specific.

CAPE (caput, a head). A headland,
or projecting portion of a coast. It some-
times terminates in an acute angle, and
is then called a point. If the projecting
portion is small or low, the affix ness is
employed in England, as in such terms
as Dungeness; and in Scotland that of
mull, as the mull of Galloway.

CAPE'LLA or a AURI'G^. The She-
Goat, a star of the first magnitude in the

CAP

CAR

body of the goat, which Auriga is repre-
sented as carrying. This is a double
star, with a small proper motion.

CAPILLAME'NTUM {capillus, a hair).
A term applied by some botanical writers
to the filament, or that part of the stamen
which supports the anther.

CAPILLARY TUBE {capillus, a hair).
A minute hair-like tube, so small as to be
less than the twentieth of an inch in
diameter inside, used for experiments in
illustrating capillary attraction. See At-
traction, Capillary.

CAPILLI'TIUM (capillus, a hair). Li-
terally, the hair of the head ; a kind of
purse or net, in which the sporules of
some fungi are retained, as in trichia.

CA'PITATE {caput, capitis, the head).
A term applied to any part of a body
which is terminated by a knob, like the
head of a pin ; or to certain hairs in
plants which terminate in a glandular
enlargement.

CAPI'TULUM (dim. of caput, a head).
A little head ; a form of inflorescence, in
which numerous flowers are placed on a
depressed axis, as in Compositae. It is
also termed anthodium, calathium, &c.

CA'PNOMOR (Ka7rv6r, smoke, /xolpa,
part). A colourless transparent liquid,
found among the products of the distilla-
tion of wood. Its name is derived from
it3 being one of the ingredients of smoke.

CAPPARIDA'CE^. The Caper tribe
of Dicotyledonous plants. Herbaceous
plants, shrubs, or trees ; leaves alternate ;
sepals 4, petals 4, cruciate ; stamens defi-
nite or indefinite ; ovary stalked ; fruit
1-celled. The flower-buds of Capparis
spinosa are the Capers of shops.

CA'PRIC and CAPRO'IC ACIDS. Vo-
latile odoriferous compounds, yielded by
butter on its conversion into soap.

CAPRICO'RNUS. The Goat; the
tenth of the zodiacal constellations, con-
sisting of fifty-one stars. The first month
of summer, extending from the 20th of
June to about the 20th of July. Capri-
corn opens and begins the year ; he is
the leader of the celestial animals, as on
earth he is the leader of the flock.

CA'PRIDiE {caper, a goat). The Goat
tribe; a family of the Ruminantia, in
which the horns are directed upwards
and backwards, and their bony core is
partly cellular. It includes only the
goats and sheep.

CAPRIFICA'TION (caprificus, the

wild fig-tree). The process of fertilizing

the fig, as practised in the Levant. At

the ripening period, branches of the wild

68

fig are placed upon the cultivated plants ;
an insect, the cynips psenes, brought with
the wild plant, pierces the fruit, and ac-
celerates its maturation.

CA'PRIFOLIA'CEJE. The Honey-
suckle tribe of Dicotyledonous plants.
Shrubs or herbaceous plants with leaves
opposite ; flowers corymbose, monopeta-
lous; stamens alternating with the lobes
of the corolla ; ovarium inferior, many-
celled ; fruit indehiscent.

CAPRI MU'LGIDjE (caprimulgus, the
goat-sucker). The Goat-suckers; a fa-
mily of the Insessores, or Perching birds,
remarkable for their nocturnal habits,
light and rapid flight, and great activity
(see Fissirostres). By Macgillivray, these
birds are placed in a group, belonging to
an order which he names Volitatrices, or
Gliders.

CA'PSTAN. A modification of the
wheel and axle, used on board of ships.
It consists of an axle placed upright,
with a head or drum, pierced with holes
for the levers. The weight is drawn by
a rope passing two or three times round
the axle, to prevent its slipping. The
capstan is, in fact, a wheel and axle, of
which the wheel turns horizontally ; when
the wheel turns vertically, the machine
is called a windlass.

CA'PSULA (dim. of capsa, a chest).
A capsule or little chest ; a term applied
in botany to a dry, superior fruit, dehis-
cent by valves, and always proceeding
from a compound ovarium. By some
writers, the term capsella is applied to
the same kind of fruit, if small and one-
seeded.

CARA'BIDjE {carabus, a beetle). A
family of the pentamerous Coleoptera,
consisting of a numerous tribe of Beetles,
characterized by the presence of six palpi,
and by the hooked termination of their
claws. They are aquatic, or terrestrial ;
most of them are carnivorous.

CA'RADOC SANDSTONE. A divi-
sion of the Lower Silurian Rocks, con-
sisting of red, purple, green, and white,
micaceous, sometimes quartzose grits,
and limestones, 2500 feet thick, contain-
ing corals and mollusca.

CARBAZO'TIC ACID. Nitro-picric
acid. An acid formed by the action of
nitric acid on indigo, and named from
the terms carbon and azote.

CARBON {carbo, a coal). A substance
well known under the form of coal, char-
coal, lamp-black, &c. In chemical lan-
guage, it denotes the pure inflammable
principle of charcoal ; in its state of ab-

CA R

CAR

solute purity, it constitutes the dia-
mond.

1. Carbon Vapour. The name of a hypo-
thetical substance, for carbon has never
been obtained in the insulated form of
vapour. When the term is used in che-
mical works, it denotes the condition of
carbon as it exists in carbonfb acid.

2. Carbon, Animal. Animal charcoal,
bone charcoal, and ivory black, are names
applied to bones calcined, or converted
into charcoal, in a close vessel.

3. Carbon, Mineral. A term applied
to charcoal, with various proportions of
earth and iron, without bitumen. It has
a silky lustre, and the fibrous texture of
wood. It occurs stratified with various
kinds of coal.

4. Carbonic Acid. A pungent and
acidulous gas, often issuing naturally
from the ground in volcanic countries,
and produced by the combustion of char-
coal ia oxygen gas. It was termed by
Black fixed air, from its having been
found to exist, in a fixed state, in lime-
stone. It is the gas produced by the
vinous fermentation.

5. Carbonates. Compounds of carbonic
acid with the salifiable bases. They are
composed either of one atom of acid and
one of the base, or of two of acid and one
of the base ; the former are called car-
bonates, the latter bi-carbonates.

6. Carboniferous. A term usually ap-
plied, in a technical sense, to an ancient
group of secondary strata. But any bed
containing coal may be termed carbonife-
rous. See Coal Formation.

7. Carbonization The union of carbon
and iron. To decarbonize cast-iron or
steel, is to drive off its carbon in the form
of carbonic acid gas.

8. Carburets. Combinations of carbon
with some metals by fusion : thus, steel
is a carburet of iron. The term has also
been applied to a peculiar compound of
sulphur and hydrogen, the carburet of
sulphur, also termed sulphuret of carbon,
and alcohol of sulphur.

9. Carburetted Hydrogen. A colour-
less inflammable gas, abundantly formed
in nature in stagnant pools, wherever
vegetables are undergoing the process of
putrefaction; it also forms the greater
part of the gas obtained from coal. This
gas was formerly called heavy inflammable
air. See defiant Gas.

CA'RBUNCLE. A precious stone of

the ruby kind, of a very rich, glowing,

. blood-red colour. Ure says it is probably

the alamandine, a variety of noble garnet.

69

CA'RCERULE {career, a prison). Die-
resilis. A term applied by Mirbel to a
species of compound fruit, which is
many-celled, superior ; the cells are dry,
indehiscent, few-seeded, and cohere by a
common style round a common axis. It
occurs in the tropaeolum, the mallow, the
lime, &c. See Coenobio.

CARDIA'CEiE. The Cockle tribe ; an
order of the conchiferous Mollusca,
named from the genus cardia; in these
the mantle is not only closed, but ex-
tended at the respiratory apertures into
tubes of greater or less length. The foot
is very strong.

CA'RDINAL (cardo, a hinge). An
epithet implying importance, being sug-
gestive of the hinge or pivot, on which
every thing else depends. Thus, it de-
notes the north, south, east, and west
points of the compass ; the zodiacal signs
Aries, Cancer, Libra, and Capricorn, &c.

CARI'NA. Literally, a keel, and
hence applied to the two lower petals of
a papilionaceous corolla, which cohere by
their lower margin in the form of a keel,
to the glumes of grasses, &c. By Link,
the combination is expressed by the term
scaphium.

CA'RINTHINE. A sub-species of the
mineral augite, found in Carinthia, in a
bed in primitive rock, associated with
quartz, Kyanite, garnet, and zoisite.

CARMIN E. A beautiful red pigment,
obtained from cochineal.

CARNE'LIAN {caro, carnis, flesh).
A variety of agate, presenting in some
cases a flesh colour; its colour is uni-
form ; it is never figured or striped, like
other varieties of agate.

CARNEOUS or CARNOSE (carnosus,
fleshy). Of a fleshy consistence, as ap-
plied to succulent leaves, &c.

CARNI'VORA {caro, carnis, flesh,
voro, to devour). A group of mammi-
ferous animals, constituting the typical
order of that great division of the class
which subsist on animal food. These
are the carnassiers of Cuvier.

CARNO'SA {carnosus, fleshy). Fleshy
animals, an order of polyps, including
the sea-anemone, &c.

CARPEL (Kapvrof, fruit). A technical
term, applied in Botany to a leaf in a
particular state of modification, consti-
tuting the pistil. The blade of the leaf
forms the ovary ; the elongated midrib,
the style ; and the apex of the midrib,
the stigma. The edge of the carpel, which
corresponds to the midrib of the leaf,
constitutes the dorsal suture; that of

CAS

CAT

the united margins, the ventral. See
Pistil.

CARPO'LOGY (KapTrof, fruit, X6709,
description). That branch of botany
which treats of the structure of fruits.

CARTESIAN DIVER. A well-known
glass figure, constructed so as to float in
a vessel of water above whose level a
small portion of air is confined in such a
manner that if this air be compressed,
the figure will immediately descend, and
rise again to the surface, when the pres-
sure ceases to be exerted.

CARTE'SIAN PHILOSOPHY. A
system of mystical and pantheistic philo-
sophy introduced by Rene des Cartes.
According to him, consciousness is the
ground of all knowledge, and constitutes
the essence of the soul; its objects or
ideas are of three kinds — acquired, com-
pounded, and innate. All physical phe-
nomena are referred to vortices, or mo-
tions of matter, excited by the Author of
all things. Des Cartes was born in 1596,
and was contemporary with Lord Bacon.

CA'RTHAMIN. A beautiful red pig-
ment, also called carthamic acid, pro-
cured from the flowers of the Carthamus
tinctorius or Bastard Saffron, and used
in silk dyeing.

CARU'NCLE (caruncula, dim. otcaro,
flesh). A little piece of flesh; a soft
wart-like eminence ; an irregular protu-
berance of the testa about the umbilicus
of certain seeds.

CARYOPHYLLA'CEiE. The Chick-
weed tribe of Dicotyledonous plants.
Herbaceous plants, with leaves opposite,
and tumid nodes; flowers polypetalous,
symmetrical ; stamens definite ; ovarium
one-celled, with a free central placenta,
fruit a one-celled capsule, by obliteration
of the dissepiments.

Caryophyllaceous Corolla. A corolla,
the petals of which have long, narrow,
and distant claws, as distinguished from
the alsinaceous corolla, in which the
petals are short and distant.

CARYO'PSIS [acipvov, a nut, 6'^«p,
likeness). A one-cetled, one-seeded, su-
perior, dry, indehiscent fruit, with the
integuments of the seed cohering insepa-
rably with the endocarp ; the character-
istic fruit of the Graminaceae.

CASE {casus, a falling). This word is
used by grammarians, in its strict sense,
to signify a certain " variation in the
writing and utterance of a noun, denoting
the relation in which it stands to some
other part of the sentence." But it is
sometimes used to denote that relation
70

itself, whether indicated by the termina-
tion, or by a preposition, or by its collo-
cation. Much confusion has arisen from
this ambiguity of the term. Whately.

CASE-HARDENING. The process of
converting the external part of iron into
a coating of steel, by cementation for a
limited time.

CA'SEIC ACID (caseus, cheese). An
acid extracted from cheese, and supposed
to contain many of the properties of this
substance. Casein or caseum is the curd
of the coagulable portion of milk, a prin-
ciple analogous to albumen. Caseous
oxide is another name for aposepedine,
a substance procured by the putrefaction
of animal matter.

CASSI'DEOUS (cassis, a helmet). Hel-
met-shaped ; a designation of the irre-
gular corolla of aconitum and other
plants, in which one petal is very large
and hooded, or helmet-shaped.

CA'SSIN^E. Helmet-shells; a sub-
family of the Muricidce, named from the
typical genus cassis, and characterized
by their large and often gigantic size.

CAST IRON. A very variable mix-
ture of reduced substances, of which the
principal is iron combined with carbon.
The fused metal is run into channels
formed in sand, and thus cast into in-
gots or pigs. White cast iron, which is
the most definite variety, consists of four
atoms of iron and one atom of carbon.

CASTOR or a GEMINORUM. A
star of the first magnitude in the head of
the Twins, being the nearer of the two to
the pole.

CA'STORIDjE (castor, the beaver).
The Beaver tribe ; a family of the Ro-
dentia, comprising the beavers, voles,
lemmings, &c, and containing many
genera which closely resemble the rats.

CAT'S EYE. A mineral, of a beautiful
appearance, brought from Ceylon. Its
colours are grey, green, brown, red, of
various shades. From a peculiar play of
light, arising from white fibres inter-
spersed, the name has been derived : the
French call the appearance chatoyant.

CA'TACLYSM (KuTaKAixr/iof, a flood).
A term applied by geologists to a deluge
or inundation.

CATALOGUE OF THE STARS. A
table of the fixed stars, arranged accord-
ing to their right ascensions, or longi-
tudes, with their declinations, or latitudes,
together with their annual variations and
magnitudes.

CATA'LYSIS (aara, downwards, \va,
to loosen). Decomposition by contact.

C A U

C A V

A body in which the catalytic force re-
sides, resolves others into new com-
pounds, merely by contact with them, or
by an action of presence, as it has been
termed, without gaining or losing any
thing itself. The body which determines
changes in another is called the catalytic
agent: yeast resolves sugar, by contact,
into carbonic acid and alcohol.

CATEGOREMA'TIC {KaTnyopnua, a
predicate). A logical designation of a
word which is capable of being employed
by itself as a term or predicate of a pro-
position. Adverbs, prepositions, &c.,and
also nouns in any other case besides the
nominative, are syncategorematic, i. e.
can only form part of a term.

CATEGO'RICAL {aarnvoptKo?, cate-
gorical, as opposed to hypothetical). A
logical term, applied to a proposition,
which affirms or denies a predicate of
a subject absolutely, and without any
hypothesis. See Proposition.

CATEGORIES {naTnyopia, a head of
predicables). Categories or predicaments
are certain general heads, employed by
logicians, to one or more of which every
term may be referred. The categories
enumerated by Aristotle are, oiia-ia,
•noaov, iroluv, wpop ri, wov, ttotc, KeioQat,
exeiv, woieiv, wderxetvi which are usually
rendered in English by substance, quan-
tity, quality, relation, place, time, situa-
tion, possession, action, suffering. They
may all be ultimately referred to the two
heads of substance and attribute, or, in
the language of some logicians, accident.

CATE'NARY {catena, a chain). The
curve described by a rope or chain which
hangs when supported at both ends. All
catenaries are similar curves.

CATKIN. The vernacular name of
a mode of inflorescence, termed by the
old writers catulus, iulus, and nucamen-
tum. See Amentum.

CATO'PTRICS {kc'itotttpov, a mirror).
That branch of the science of Optics
which treats of the reflection of light.
See Optics.

CAUCA'SIAN RACE. One of the five
principal races of mankind, to which the
nations of Europe and some of the west-
ern Asiatics belong. In this class the
head is almost round, and of the most
symmetrical shape ; the cheek-bones
without ariy projection ; the face oval ;
and the features moderately prominent.

CAU'DATE (cauda, a tail). Tail-
pointed ; excessively acuminated, so that
the point is long and weak, like the tail
of an animal.
71

CAU'DEX. The trunk of a tree. In
Botany, the stem, or ascending axis of
growth, is termed caudex ascendens ; the
root, or descending axis, caudex de-
scendens. The rhizome of Iridaceae and
epiphytous Orchidaceae is often called
caudex repens.

CAU'LICULE (cauliculus, a little
stalk). By this term some botanists dis-
tinguish the neck of the embryo in plants
from the plumule or gemmule. Mirbel
comprises, under the general term blas-
tema, the radicle, the plumule, and the
caulicule. The term cauliculi is also
applied to those small stems, which pro-
ceed from buds formed at the neck of a
plant, without the previous production
of a leaf.

CAU'LINE (caulis, a stem). Belong-
ing to the stem, as applied to leaves
which grow from the stem, as distin-
guished from radical or root leaves.

CAU'LIS. The Latin term for a stem,
but applied in botany to the ascending
caudex of herbaceous plants or shrubs.
In trees, the main stem is sometimes
called caulis arboreus, but more com-
monly the trunk. The caulis excurrens
is a stem which rises vertically from the
earth, and bears branches on its sides ;
the caulis deliquescens, a stem which at a
certain distance from the earth throws
out irregular ramifications. The stem of
grasses is called the culmus or straw ; that
of rushes, the calamus or reed. Plants
which have no distinct stem, are called
acaulescent.

CAULOCA'RPOUS (Kau\6r, a stem,
Kapno?, fruit). A term applied in bota-
nical glossology to those polycarpous
plants, whose stem endures many years,
constantly bearing flowers and fruits; as
trees and shrubs. See Rhizocarpous.

CAU'STIC CURVE (/caixm/co?, burn-
ing). In transcendental geometry, a curve
to which the rays of light, reflected or
refracted by another curve, are tangents.
It is termed caustic, owing to the accu-
mulation of heat from the collection of
the rays of light along the curve. Caustic
curves are of two kinds ; catacaustics, or
those formed by reflection, and dia-
causlics, or those formed by refraction.

CAUSTI'CITY {Kaita. Kavau), to burn).
That property of certain substances, as
the pure alkalis, concentrated acids, and
metallic salts, by which they combine so
powerfully with organized bodies as to
destroy their texture.

CA'VERNOUS TEXTURE. A term
applied, in geology, to that texture of

CEM

CEP

aggregated compound rocks, which is cha-
racterized hy the presence of numerous
small cavities, of a roundish, oval, or
other form, as in lava.

CA'VID^. The Guinea-pig tribe; a
family of the Rodentia, containing the
largest-sized animals of the order, indi-
genous in tropical America, where they
replace the hares and rabbits of cold
climates)

CAVTTA'RIA {cavitas, a cavity). In-
testinal worms, or Entozoa, which have
an intestinal canal floating in a distinct
abdominal cavity.

CAWK. A technical term applied to
opaque sulphate of baryta, or vitriolated
heavy spar.

CE'BRIONITES. A family of Coleo-
pterous insects, of the section Malaco-
derma of Latreille, named from the
genus cebrio.

CE'DRIRET. A substance 'found
among the products of the distillation
of wood.

CE'LAPRAXITE'LLIS. A modern
southern constellation, consisting of six-
teen stars.

CE'LESTINE (caelum, the sky). Sul-
phate of strontian, so named from its
frequently presenting a blue colour.

CELLARIAD^. The second family
of the Polypiaria membranacea of Blain-
ville, named from the genus cellaria, and
consisting of hydriform animals, distinct
from one another, contained in mem-
branous cellules with a bilateral opening,
and comprising the flustra, lunulites, &c.

CE'LLULAR TISSUE (cellula, a little
cell). The elastic connecting tissue of
the various parts of animal and vegetable
bodies, consisting of cellules or vesicles
of various figures, adhering together in
masses.

CELLULARES {cellula, a little cell).
Cellular plants ; those which consist, in
many cases, entirely of cells, and have
no flowers or spiral vessels. They are
also called cryptogamous and acotyledo-
nous plants. See Vasculares.

CEMENT. A preparation made of
various materials, which is applied in a
soft state, and afterwards hardens and
unites the surfaces to which it is applied.

Roman Cement. A mortar made of
lime, and puzzolano ground to fine
powder. The latter substance consists
principally of pumice, found near Poz-
zuoli.

CEMENTATION. A process by which
the properties of a body are changed, on
being surrounded with the powder of
72

other bodies, and exposed to a high
temperature, as the conversion of iron
into steel, by cementation with charcoal.
The substance so employed is called
cement powder.

CENTAURUS. The Centaur ; a south-
ern constellation, consisting of thirty-five
stars.

CENTRAL ECLIPSES. A term ap-
plied to annular eclipses, because the
centres of the sun and of the moon ap-
pear to coincide.

CENTRAL FORCES. The forces
which cause a moving body to tend
towards, or recede irom, the centre of
motion.

CENTRAL MOTION. A curvilinear
motion round that point of a body which
is called the centre of gravity, resulting
from the balance of the centripetal and
the centrifugal or tangential forces.

CENTRI'FUGAL FORCE {centrum,
a centre, fugio, to avoid). The force by
which all bodies, when set in motion
round a centre, tend to move uniformly
in a straight line, and thus to fly from the
centre, in a tangent to the circle in which
they move.

Centrifugal Evolution. Leaving the
centre ; a term applied to inflorescences,
in which the central flowers open first.

CENTRI'PETAL FORCE (centrum,
a centre, pelo, to seek). The force or
gravity by which a body tends towards
some point as a centre : in obedience to
this law all the planets are drawn to the
centre of their respective orbits, and all
bodies tend towards the centre of the
earth.

Centripetal Evolution. Approaching
the centre ; a term applied to inflores-
cences, in which the marginal flowers
open first.

CEPHALA'NTHIUM (ne<pa\n, the
head, avOo?, a flower). A head of flowers ;
a designation of the inflorescence of
Compositae, more commonly called a
capitulum or anthodium.

CE'PHALOTHO'RAX (Ke</.aA^, the
head, Owpat-, the thorax). The anterior
division of the body in spiders, scorpions,
&c, which consists of the head and chest
blended together, answering to the first
two segments of insects in a confluent
state.

CEPHALO'PODA (/ce^aX^, the head,
7roi»9, 7to56p, a foot). A group of mollus-
cous invertebrate animals, in which the
head is situated between the trunk and
the feet, or principal organs of locomo-
tion, as in the cuttle-fish.

CER

CET

CE'PHEUS. A northern constellation,
consisting of thirty-five stars, the prin-
cipal of which is Alderamin.

CERAMBY'ClDiE. A family of Co-
leopterous insects, of the section Longi-
cornis of Latreille, named from the genus
cerambyx, and chiefly characterized by
the great length of the antennae.

CE'RASIN (cerasus, the cherry). A
gummy substance, procured from the
cherry and the plum-tree, which swells
in cold water, but does not readily dis-
solve in it.

CERA'TIUM (/cepftTtoi/, a little horn).
A compound fruit, which is one-celled,
many-seeded, superior, linear, dehiscent
by two valves separating from the re-
plum, and differing from the siliqua in
the lobes of the stigma being alternate
with the placenta, instead of opposite.
It has been termed capsula siliquiformis.
It occurs in glaucium, the horned pop-
py, &c.

CE'RCjE («ep«op, a tail). The feelers
which project from the hind part of the
body in some insects.

CERCA'RLE (Kepxo?, a tail). A de-
signation of those animalcules whose
body is terminated by a tail-like ap-
pendage.

CERCO'PIDjE. A family of the tri-
merous Homoptera, remarkable for their
grotesque forms, and represented in this
country by the cuckoo-spits and the frog-
hoppers, so named from the frothy secre-
tion which covers them in their larva
and pupa states.

CE'REBRIC ACID (cerebrum, the
brain). A peculiar acid found in the sub-
stance of the brain, containing phos-
phorus.

CERES. A telescopic planet, situated
in the solar system, between Mars and
Jupiter. It revolves round the sun in
about 4J years, and is about 264,000,000
of miles distant from it. It was dis-
covered on Jan. 1st, 1801, by M. Piazzi,
whose name it sometimes bears.

CE'RIC ACID (cera, wax). An acid
produced by the action of the fixed al-
kalies on wax.

CE'RIN {cera, wax). 1. That consti-
tuent of common wax which dissolves in
alcohol. 2. A peculiar substance pro-
cured by the action of alcohol on grated
cork. 3. A variety of allanite.

CE'RITE. A rare mineral, consisting
of the siliciferous oxide of cerium.

CERPTHIN.E. The Club-shells; a
sub-family of the Strombidce, or Wing-
shells, named from the typical genus
73

Cerithium, and characterized by their
clavate form ; the spire is very long ; the
outer lip considerably dilated ; the base
either truncate, or forming a short re-
curved channel.

CE'RIUM. A white metal found in
two Swedish minerals called cerite and.
cerine, and more recently in allanite, at
Alluk, in East Greenland.

CE'RNUOUS (cernuus, hanging down
the head). Drooping; inclining from the
perpendicular towards the horizon; a
term applied to flowers.

CERTHI'ADiE {certhia, the tree-
creeper). A family of the Insessores, or
Perching birds, consisting of the Tree-
creepers, Nuthatches, &c, which re-
semble the Melliphagidae, or Honey-
suckers, in general structure. See
Tenuirostres. According to Macgillivray
these birds constitute a family of the
Reptatrices, or Creepers, characterized,
by having the three fore toes more or
less united at the base and spreading
little.

CE'RULIN (cceruleus, blue). The
name given to indigo in the modified,
state which it acquires during solution.

CE'RUSE. Carbonate of lead, occur-
ring naturally in the form of carbonate
of barytes. Under the name of white
lead, it is employed by painters to give
body to their colours.

CERVI'COBRANCHIA'TA (cervix,
the neck, fipafxta, gills). The name of
an order of Gasteropods, comprising, ac-
cording to Blainville's arrangement, the
patellae or limpets, and three other
genera. The order is subdivided into
the retifera and the branchifera ; the
former are the patellae, which he sup-
poses to respire by means of a net-work
belonging to the cavity which is above
their head.

CE'RVID^E (cervus, a stag). The
Stag tribe ; a family of the Ruminantia,
in which the antlers are periodically cast
off.

CESTOI'DEA (kco-to?, a girdle, ei<5or,
form). Tape-worms ; an order of the
Enfozoa, which have a long, depressed,
flat, tape-like, articulated form, each seg-
ment having distinct nutritive and gene-
rative organs.

CETA'CEA (cete, a whale). An order
of vertebrated mammiferous animals
inhabiting the ocean, as the whale, the
dolphin, &c. These animals resemble
fishes in shape, but they breathe air, have
warm blood, and a double circulation,
like other mammalia j the tail-fin is also
E

CH A

CH A

horizontal, and not vertical, as in true
fishes.

CETIC ACID {cete, a whale). An acid
procured from spermaceti, consisting of
margarine and fatty matter. Cetine is a
white laminated substance, constituting
pure spermaceti.

CETONIA'D,E. A family of Coleo-
pterous insects, of the section Melitophili
of Latreille, named from the genus ceto-
nia, of which the common rose beetle
affords a good example, and presenting
one of the most extensive as well as the
most brilliant of the beetle tribes.

CETUS. The Whale ; a southern con-
stellation, containing ninety-seven stars,
the principal of which is Menkar.

CETYL. The supposed radical of a
series of compounds derived from sperma-
ceti.

CEVA'DIC ACID. Sabadillic acid.
A crystalline fatty acid, obtained by
saponification of the oil of cebadilla, or
the seeds of the Asagrcea officinalis.

CEY'LANITE. A mineral found in
Ceylon, termed by Haiiy, pleonaste.

CHA'BASITE. A mineral found in
the fissures of some trap rocks, and in
the hollows of certain geodes disseminated
in the same rocks.

CHAFF OF RECEPTACLE. A term
popularly applied to the paleae, or the
membranous, colourless bracts, placed
between the florets upon the receptacle
of Composite.

CHALA'ZA (xaXa^a, a small swelling).
A small brown spot observed at the apex
of some seeds, as of the Orange, formed
by the union of certain vessels proceeding
from the hilum.

CHALCE'DONY. A silicious simple
mineral, uncrystallized, entering into the
composition of agates, and found at Chal-
cedon in Bithynia. It is of a uniform
milky white or pale yellow colour, often
with a wavy internal structure, and a
peculiar mammillary surface.

CHALCFDID.E. A family of Hymeno-
pterous insects, of the section Pupivora
of Latreille, named from the genus chal-
ets, and characterized by minuteness of
size, brilliancy of colours, and the general
absence of nervures from the wings.

CHALK. Carbonate of lime. In Geo-
logy, a rock which forms the higher
part of the cretaceous group.

CHALYBEATE WATERS. Ferru-
ginous waters. Mineral waters, whose
predominating or active principle is iron.
There are two kinds: the carbonated,
containing carbonate of the protoxide of
74

iron ; and the sulphated, containing sul-
phate of iron. Some of the latter con-
tain sulphate of alumina, and are called
aluminous sulphated chalybeate*. »

CHAMA'CEiE. Clamp-shells ; an or-
der of the conchiferous Mollusca, named
from the chama ; in these, the mantle is
closed, with the exception of three aper-
tures, two of which are for the ingress
and egress of water, and the third for the
passage of the foot, which is here usually
more powerful.

CHAMjE'LEON. A modern southern
constellation, consisting of ten stars.

CHAM^E'LEO'NIDJE. The Chame-
leon tribe ; a family of Saurian reptiles,
characterized by their extraordinary
length of tongue, and by the adaptation
of their feet and tail for climbing.

CHAMBERED. Divided internally
into chambers or compartments, as the
testaceous cephalopods, or the nautilus.

CHAMELEON MINERAL. A com-
bination of black oxide of manganese
and potash, which gives a green colour
to water, passes gradually through all the
shades of the prism, and at last becomes
colourless.

CHA'MID^E. A family of macrotra-
chian Bivalves, named from the typical
genus chama; in these animals the
length of the siphons, which charac-
terizes the tribe, is much reduced.

CHARA'CE^E. A small family of
cryptogamous plants, consisting of the
two genera chara and nitella. These are
submerged aquatic plants, interesting to
the physiologist, as displaying the special
circulation, or cyclosis, in vegetables.

CHARADRI'ADjE (charadrius, the
plover). The Plover tribe ; a family of
the Grallatores, or Wading birds, in
which the bill is of moderate size, and
the hinder toe either entirely deficient,
or not long enough to reach the ground.

CHARCOAL*. The residue of animal,
vegetable, and many mineral substances,
when heated to redness in close vessels.

CHARLES'S WAIN. Seven con-
spicuous stars in Ursa Major or the
Great Bear.

CHART {charta, paper). A geographi-
cal or nautical representation of a portion
of the earth's surface on paper, according
to a scale which regulates the relative
proportion of the parts. Geographical
charts, being of a general character, are
commonly called maps; but nautical or
marine charts are particularly devoted to
delineations of a coast and part of the
adjacent sea.

CHE

CHL

Marine charts are constructed in two
ways. 1. A plane chart represents the
meridians, as well as the latitudes, by
equidistant and parallel straight lines ;
and, consequently, the longitudes and
latitudes appear equal, differing from the
fact. 2. A Mercator's chart represents
the meridians as well as the circles of
latitude by parallel straight lines; but
the distances of the latter increase in a
determinate ratio from the equator to the
poles.

CHEILO'GNATHA (xelAor, a lip,
fvdOos, a jaw). An order of Myriapods
or Centipedes, in which the two man-
dibles and the tongue are united to form
a large lower lip.

CHEILO'PODA (xeTXop, a lip, now,
tto56?, a foot). A family of insects, of
the class Myriapoda, or Centipedes, in
which the lower lip is formed by a pair
of feet.

CHEIRO'PTER A (Xelp, a hand, nrepbv,
a wing). An order of mammiferous
quadrupeds, which have their extremities
connected together by a wing-like expan-
sion of the integuments, for the purpose
of flight, as in the bat.

CHELE' {xh^)- A claw; particularly
applied to the bifid claw of the Crustacea,
the scorpion, &c.

CHELI'CERA (x^/Xn, a claw, nepa?, a
horn). The prehensile claws of the
scorpion, which are the homologues of
antennae.

CHELIOSO'MID,E. A tribe of bi-
valved mollusca, which have a cartila-
ginous covering, analogous to that of the
chitons and the tortoises.

CHELO'NIA (xeXwi/»i, a turtle). An
order of Reptiles, which have their ribs
immoveable, comprising the tortoises,
the turtles, &c. The body of these ani-
mals is enclosed in a shell, the upper and
arched portion of which is termed the
carapace; the lower plate is called the
plastron.

CHELO'NIDjE (xeXtovn, a turtle). The
Turtles ; a family of Chelonian reptiles,
distinguished by the incompleteness of
their shelly covering, and by the pecu-
liar modification of the feet for swim-
ming.

CHEMICAL ATTRACTION. Elec-
tive attraction or affinity. These terms
denote the action by which the particles
of one class of bodies, when presented to
those of certain other classes, unite to
form new compounds, making a choice,
or election, of those with which they
unite.
75

CHEMICAL COMBINATION. An
intimate union of two or more substances,
which forms a compound differing in
one or more of its essential qualities
from those of its constituent bodies.

CHEMISTRY. A term, of Arabic
origin, signifying the knowledge of the
composition of bodies, and of the changes
of constitution produced by their mutual
action on each other.

CHENOPODIA'CE^E. The Goosefoot
tribe of Dicotyledonous plants, comprising
beet, mangel wurzel, spinach, &c. Her-
baceous plants or undershrubs, with
leaves alternate ; flowers small ; stamens
inserted into the base of the calyx ; ovary
superior ; fruit membranous.

CHERT. A silicious mineral, nearly
allied to chalcedony and flint, but less
homogeneous and simple in texture. A
gradual transition from chert to lime-
stone is not uncommon.

CHIAROSCU'RO (chiaro, light, os-
euro, dark). In painting, the judicious
arrangement and combination of light
and shade, and of bright and dark
colours.

CHIA'STOLITE. A mineral found
imbedded in clay-slate, resembling stea-
tite. Chiastolite- state, or rather clay-
slate, is a division of the Cumbrian group
of rocks; it is dark-coloured, and gene-
rally soft, containing crystals of the mine-
ral chiastolite.

CHI'LDRENITE. A mineral found
in Devonshire, consisting of a phosphate
of alumina and iron.

CHINA-CLAY. Kaolin. A variety
of clay prepared from decaying granite.

CHINA GLAZE. A preparation for
printing blue frit, made from ten parts
of glass, two parts of lead, and three or
more of blue calx.

CHINCHI'LLID,E. The chinchilla
tribe ; a small family of the Rodentia, in-
digenous in South America, and valuable
in commerce for their furry skins.

CHI/TINE (x<twv, a tunic). A prin-
ciple discovered in beetles and other in-
sects, also called entomoline, and consist-
ing of the base of their external skeleton.

CHITO'NID^E. A family of Gastero-
pods, named from the genus Chiton, and
characterized by the presence of a pro-
tecting tunic-like shell, formed of many
portions, which are often in contact and
overlap one another.

CHLORATES. The salts of chloric
acid, formerly called hyper-oxy muriates.
The principal are those of potash and
baryta.

E2

CHO

CHR

CHLORIMETRY. The process of esti-
mating the bleaching power of chloride
of lime, by the quantity of a solution
of sulphate of indigo which a known
weight of chloride can discolour or render
yellow.

CHLORINE (xXcapof, green). A green-
ish gas, obtained by the action of mu-
riatic acid on peroxide of manganese. It
was first described under the name of
dephlogisticated marine acid, and was
afterwards called oxy-muriatic acid. Its
compounds, which are not acid, are called
chlorides (or chlorurets), and are charac-
terized by the same prefixes as the oxides.
CHLORITE (xXwpor, green). A fri-
able mineral, of a green colour, allied in
characters to talc and mica. It occurs dis-
persed in rocks, or forms beds of itself.
The species are chlorite earth, common
chlorite, chlorite slate, and foliated chlo-
rite.

CHLORFTIC SAND (xXwpof, green).
Sand coloured green by an admixture of
the simple mineral chlorite.

CHLOROCARBONIC ACID GAS. An
acid termed by Davy phosgene gas, con-
sisting of chlorine and carbonic acid.

CHLO'ROPAL. A silicate of iron, a
mineral found associated with copal ; its
varieties are the conchoidal and the
earthy.

CHLO'ROPHANE (x^copof, green,
<paivu>, to shine). A variety of fluor spar,
which gives out an emerald green light
by the mere heat of the hand.

CHLOROPHCE'ITE. A green mineral
found imbedded in basalt or in black in-
durated ironstone.

CHLO'ROPHYLLE (x^wpor, green,
(pvWov, a leaf). The green colouring
matter of leaves. See Chromule.

CHLOROUS POLE. A term founded
on the theory that the particles of matter
are susceptible of polarity. Hence that
pole of a particle of zinc or of hydro-
chloric acid, which has the attraction or
affinity which is characteristic of chlo-
rine, or chlorous attraction, is called the
chlorous pole. See Zincous pole.

CHOKE DAMP. The name given by
miners to carbonic acid gas, which is apt
to be formed and to accumulate in coal-
mines.

CHO'NDROPTERY'GII (x6v3pof, car-
tilage, Tr-repuf, a fin). Cartilaginous fishes ;
one of the primary divisions of the class
Pisces, so named from their skeleton con-
taining little calcareous matter, and this
disposed, not in fibres or plates, as in Osse-
ous fishes, but in small granules. There
76

are two orders of these fishes, viz. those
with free gills, as the sturgeons, and those
with fixed gills, in which the external
edge of the gills is attached to the skin,
as the sharks, rays, and lampreys.

CHORD OF AN ARC (chorda arc&s,
the string of a bow). The straight line
which joins the two extremities of a curve
or arc. To find the chord of a given arc,
find the angle subtending the arc ; then, to
find the chord of the angle, multiply the
diameter by the sine of half the angle.

CHORD IN MUSIC. A combination
of three or more harmonious sounds.
1. The perfect chord consists of any given
note combined with a major 3rd and a
perfect 5th; this and its inversions are
called consonant chords. 2. The chord of
the seventh, or dominant seventh, con-
sists of any given note, combined with a
major 3rd, a perfect 5th, and a minor 7th ;
this and its inversions are called dis-
sonant chords.

CHOROGRAPHY (%<apa, a country,
7pa0a>, to describe). The description of
countries ; a term differing from geo-
graphy, as a part differs from the whole.
CHREMATFSTICS {XPW*Ta, wealth).
The name given by continental writers to
that branch of political economy which
relates to the wealth of nations.

CHROMA'TIC SCALE {xp&H^ co-
lour). The scale of semitones employed
in music. The term chromatic either
denotes that the musical characters were
written in colours, or suggests the variety
of shades which, figuratively, charac-
terize this scale. By chromatic music is
usually meant that in which extreme
intervals are used.

CHROMATICS (xp^/ua, colour). That
branch of optics which treats of the
colours of light, their several properties,
and the laws by which they are sepa-
rated.

CHROME ALUM. A term applied
to a crystallizable double salt, consisting
of sulphate of chromium. This salt is
isomorphous with alum, and analogous
to it in constitution, but the alumina is
replaced by oxide of chromium.

CHROME IRON. Chromate of iron ;
one of the ores containing chromium;
it occurs massive and crystallized.

CHROME YELLOW. A well-known
pigment, consisting of chromate of lead.

CHRO'MIUM (xpwMa, colour). A
metal found in a Siberian mineral, called
chromate of lead, or red lead, and named
from its remarkable tendency to form
coloured compounds. It combines with

CHR

CIN

oxygen and forms chromic acid, the sa-
line compounds of which are called chro-

CHRO'MULE {xpuna, colour). The
name of the colouring matter of plants.
It has been also termed chlorophylle ; but
as the latter term merely expresses the
greenness of leaves, it is inapplicable to
the variously coloured granules found in
vegetable tissue.

CHRONO'LOGY {xpovot, time, X6-
709, description). The arrangement of
historical events according to the order
of time. Dates are to History, what
the latitude and longitude are to Naviga-
tion, fixing the exact position of the
object to which they are applied.

CHRONO'METER (xpovor, time, fxe-
rpov, measure). A time-keeper ; an in-
strument used for determining the longi-
tude at sea, and for the purpose of mea-
suring accurately small periods of time.
It differs from a common watch in having
a detached escapement, and a compensa-
tion for heat and cold.

CHRY'SALIS (xpixtop, gold). A fan-
ciful name for the nymph or pupa state
of insect life, from the glittering spots of
golden hue with which the animal is
sometimes speckled.

CHRY'SENE. A substance found
among the products of the distillation of
wood.

CHRYSI'DIDjE. A family of Hyme-
nopterous insects, of the section Pupi-
vora, named from the genus chrysis, and
remarkable for their brilliant colours.
Some of them are termed ruby-tail flies.

CHRYSOBA'LANACEjE. The Cocoa-
plum tribe of Dicotyledonous plants,
nearly allied to Rosaceae, from which
they differ in having a style proceeding
from the very base of the ovary, and
irregular stamens and petals. The fruit
of Chrysobalanus Icaco is eaten, in the
West Indies, under the name of cocoa-
plum.

CHRY'SOBERYL. A green gem, con-
sisting of glucina and alumina, occurring,
massive and crystallized, in North Ame-
rica and Brazil. It is the cymophane of
Haiiy.

CHRY'SOLITE. A precious stone
brought from the Levant, termed peridot
by Haiiy. Ure says that chrysolite is the
topaz of the ancients, while our topaz is
their chrysolite. A variety called, from
its colour olivine, occurs in basalt in
Germany. Chusite is said to be another
variety of this gem.

CHRY'SOPRASE. A rare apple-green
77

chalcedony, found in Silesia, which owes
its colour to the presence of nickel.

CICA'DIDiE {cicada, a cricket). The
Cricket tribe; a family of the trimerous
Homoptera, characterized by their power
of producing a shrill, continuous sound,
by means of a peculiar apparatus situated
beneath the abdomen.

CICA'TRICULE {cicatrix, a scar).
A little scar ; the scar formed by the
separation of a leaf from its stem. A
stem so marked, is said to be scarred or
cicatrized.

CICHORACEiE. A division of the
Compositae, in which the florets are all
ligulate, the juice usually milky, bitter,
astringent, and narcotic, as in cichorium
or succory, endive, and some species of
lettuce.

CICINDE'LID^. A family of Coleo-
pterous insects, named from the typical
genus cicindela, and distinguished by the
presence of six palpi, and by their de-
riving their subsistence on the land.

CI'LIA {cilium, an eye-lash). A term
used to designate a peculiar sort of mov-
ing organs, resembling microscopic hairs.
The terms ciliary motion and vibratile
motion have been employed to express
the appearance produced by the moving
cilia. Any part is said to be ciliated
which is fringed Kith hairs, as the margin
of some leaves.

CILIOBRA'CHIATE {cilia, vibratile
hairs, brachium, the arm). A term ap-
plied by Dr. Arthur Farre to those polyps,
whose arms are covered with cilia, form-
ing important agents in securing prey.
These are the bryozoa of Ehrenberg, and
are ranged among the tubular polyps of
Cuvier.

CILIO'GRADA {cilia, vibratile hairs,
gradior, to advance). A group of the
Acalephce, in which the organs of motion
consist of vibratile cilia disposed upon
the surface of the body, which in their
motions and office resemble those of the
polygastric animalcules.

CIMI'CID^. A family of Hemipte-
rous insects, named from the " familiar
beast" cimex. or the bug.

CI'MOLITE. Cimolian earth. A hy-
drous silicate of alumina, found in the
island of Cimola, used for the same pur-
poses as fuller's earth.

CINCHONA'CEjE. The Cinchona
tribe of dicotyledonous plants. Trees or
shrubs with leaves opposite ; flowers in
panicles; stamens arising from the co-
rolla ; fruit inferior, either splitting into
two cocci or indehiscent.

£3

cm

cm

CINE'NCHYMA (4*fc* to move,
67xuM«> infusion). A botanical terra ap-
plied to the laticiferous tissue in plants,
distinguished by its irregular branching
and anastomozing character.

CI'NGULUM. Literally, a girdle. In
Zoology, the neck of a tooth. The term
cingula denotes the transverse series of
bony pieces connected by flexible joints,
as in the armour of the armadillo.

CI'NNABAR. Sulphuret of mercury ;
the common ore of mercury, sometimes
occurring crystallized as a beautiful ver-
milion.

CINNAMON STONE. A silicate of
lime, alumina, and oxide of iron, brought
from Ceylon, and named from its colour.

CI'NNAMYL. The hypothetical radi-
cal of the essence of cinnamon and of
cinnamic acid — an acid formed by the
oxidation of the essence of cinnamon in
air.

CINNY'RID^. The Sun-birds; a
family of the Insessores, or Perchers,
named from the genus cinnyris, closely
allied to the Trochilidae, or Humming-
birds, which they represent in the Eastern
Continent. See Tenuirostres.

CITHER (sifr, Arabic). A term sig-
nifying empty, and used as a substantive
to denote the figure 0.

CI'POLIN. A green marble with white
zones, brought from Rome.

CI'RCINATE (circino, to make a
circle). Rolled inwards, or spirally down-
wards, from the point to the base, as the
aestivation of certain plants, the deve-
lopment of the young fronds of ferns, the
inflorescence of Boraginaceous plants,
fee.

CI'RCINUS. The Compasses; a mo-
dern constellation, consisting of four
stars, not very far from the South Pole.

CIRCLE (circulus, dim. of circus, a
ring). A plane figure contained by one
line, which is called the circumference,
and such that all straight lines drawn
from a certain point within the figure to
the circumference are equal to one an-
other; this point is called the centre of
the circle, and the straight lines, radii,
or rays.

1. Circles, Arctic and Antarctic. Circles
supposed to be drawn round the Arctic
and the Antarctic pole, at the distance of
about 23^ degrees. On the terrestrial
globe these circles surround what are
called the two frozen zones, or girdles of
the earth.

2. Circle, Astronomical. A term usually
applied to an astronomical instrument, of

78

which the sole or principal use is the
measurement of angles of altitude, or
zenith distance.

3. Circles, Co-ordinate. Two circles at
right angles to each other ; or two circles,
one of which passes through the pole of
the other. By reference to two such
circles a point in the sphere is deter-
mined: e.g., on the earth, by determin-
ing the longitude and latitude; in the
starry heavens, by the right ascension
and declination; in the visible hemi-
sphere, by the azimuth and altitude.

4. Circles, Concentric. Circles which
have the same centre, the one surround-
ing the other, as with a ring. Circles
which are wholly or partially surrounded
by another, but have different centres,
are termed eccentric.

5. Circle of Declination. A circle on
which declination is measured, i. e. a
horary circle passing through the poles.
According to some writers on Astronomy,
the term denotes a parallel of any declina-
tion, or the small circle, all of whose
points have the same declination; that
is, a parallel to the equator.

6. Circles, Tropical. Circles drawn
parallel to the equator through the sol-
stices.

7. Circle of Illumination. That imagi-
nary circle which divides the enlightened
hemisphere of the earth from the dark-
ened hemisphere.

8. Circles of the Sphere. Circles whose
planes pass through the sphere, and have
their circumference upon its surface. If
the plane pass through the centre of the
sphere, it is called a great circle ; if not,
it is called a less circle. The equator and
ecliptic are great circles ; the polar circles
and the parallels of latitude or declina-
tion, are small circles.

9. Circles of Perpetual Apparition.
Small circles parallel to the equator, and
touching the horizon of any given place.

10. Circles of Perpetual Occultation.
Small circles parallel to the equator, and
touching the lower part of the horizon,
or never appearing above it.

11. Circles of Position. Great circles
of the sphere, passing through the com-
mon intersection of the meridian and
horizon, and through any degree of the
ecliptic, or centre of a star or planet.

CFRCULAR PARTS. The name given
to Napier's proposition in Trigonometry,
which generalizes the relations between
the parts of a spherical right-angled tri-
angle under two formulas.

CIRCULAR VELOCITY. The velo-

CIR

CIS

city of a revolving body, measured by an
arc of a circle.

CIRCU'MFERENCE (circum fero, to
carry round). A line which bounds a
figure, commonly applied to curvilinear
figures. The Greek synonymous term
periphery is, however, applied to recti-
linear figures.

CIRCU'MFEREN'TOR. An instru-
ment used by surveyors for taking angles.

CI'RCUMFLEX VERBS. A term ap-
plied by Greek grammarians to those
verbs which are also called pure or con-
tracted because, after contraction, the <o
receives a circumflex, as <pi\ew, <pi\a>.
See Accent.

CIRCUMPO CAR STARS. Stars which
revolve round the pole, without setting in
a given latitude. The number of these
stars increases with the latitude of the
place, or the elevation of the pole above
the horizon.

CIRCUMSCFSSILE (circum, around,
scindo, to cut). Divided around by a
transverse separation, as applied to that
mode of dehiscence of fruits which oc-
curs in hyoscyamus, in anagallis, in
lecythis, &c.

CIRRHO'PODA (mpp6s, frizzled hair,
TToi/c, 7ro36r, a foot). A class of aquatic
invertebrate animals, with numerous la-
teral articulated cirrhi, and their body
fixed in a multivalve shell. The class is
composed chiefly of the barnacles and
acorn-shells. The following orders have
been distinguished : —

1. Balanida, or those which are en-
closed in fixed, sessile, multivalve, coni-
cal shells, as the balanus.

2. Anatifida, or those which have the
enveloping shell attached by means of a
long fleshy contractile tubular peduncle,
as in the anatifa. — Grant.

CFRRHOSE (Kipp6s, frizzled hair).
Any thing which terminates in a tendril,
or filiform appendage, as the leaf of seve-
ral leguminous plants.

CFRRI (plur. of cirrus, a curl). The
curled filamentary appendages which re-
present the feet of the barnacles.

CIRRFGRADA (cirrus, a curled lock
of hair, gradior, to advance). A group
of the Acalephce, the lower surface of
some of which is furnished with nume-
rous appendages, called cirri, which are
organs of prehension, and, it is supposed,
of progression.

CFRRIPEDES (cirrus, a curl, pedes,
feet). A class of articulate animals,
having curled jointed feet. See Cirrho-
poda.

79

CIRRO-CUMULUS (cirrus, a curled
lock of hair, cumulus, a heap). The
sonder-cloud ; an intermediate modifica-
tion of clouds between the cirrus and the
cumulus. It consists of extensive beds
of numerous small well-defined orbicular
masses of cloud, or small cumuli, in close
horizontal opposition, but at the same
time lying quite asunder or separate from
each other. The prevalence of this cloud,
in summer, forebodes an increase of tem-
perature ; in winter, the breaking up of
a frost, and warm and wet weather.

CIRRO-STRATUS (cirrus, a curled
lock of hair, stratus, a bed or covering).
The wane-cloud ; an intermediate modi-
fication of clouds between the cirrus and
the stratus, distinguished by its flatness,
and great horizontal extension in pro-
portion to its perpendicular height. From
its generally changing its figure, it has
been called wane-cloud. Varieties of this
cloud occur in the mackerel-back sky of
summer evenings ; and in the cymoid
modification, which consists of small rows
of little clouds, curved in a peculiar man-
ner. The prevalence of these clouds is a
sure sign of rain or snow ; the cymoid
variety always indicates stormy weather.

CFRRUS (Lat., a lock of hair curled).
The curl-cloud ; a primary form of clouds,
characterized by its curling and flexuous
form, by the lightness of its appearance,
its fibrous texture, and the great and
perpetually changing variety of its figure.
It accompanies a variable state of the
weather, and forebodes wind and rain.
The comoid cirrus, vulgarly called mare's
tail, is the proper cirrus ; it resembles a
distended lock of white hair, or a bunch
of wool drawn out into fine pointed ends.
Modifications of this texture occur in the
linear cirrus, in which the lines of cloud
are parallel ; and in the reticular cirrus,
in which they cross each other in various
directions, presenting the appearance of
net- work.

CFSSOID (uLaraos, ivy, 6i<5o?, likeness).
Resembling ivy; a fanciful designation
of a curve line of the second order, em*
ployed by the Greeks in the celebrated
problem of finding two mean propor-
tionals between two given straight lines.

CISTA'CE^E. The Cistus or Rock-
rose tribe of Dicotyledonous plants ;
characterized by the fragrant resinous
secretion of their leaves, the beauty of
their fugitive flowers, and the produc-
tion, from some of their species, of the
green labdanum.

CISTE'LIDES. A family of Coleopte-
E4

CL A

CLE

rous insects, of the section Heteromera
and subsection Stenelytra, named from
the genus cistela.

CITRATE. A salt formed by the com-
bination of citric acid with a base.

CI'TRENE {citrus, a lemon). A pe-
culiar carburetted hydrogen, constituting
the principal part of the volatile oil of
lemons.

CITRIC ACID (citrus, a lemon). The
acid of limes, lemons, &c. By exposure
to heat, it is decomposed, with the forma-
tion of the pyro-citric and citricic acids.

CLADE'NCHYMA (/c\a5of, a branch,
^yxv/Jia, infusion). A modification of the
parenchyma of plants, characterized by
its branched form.

CLADO'CERA. An order of the bran-
chiopodous Crustacea, in which the cara-
pace is formed like a bivalve shell, and
there are five pairs of thoracic members.
A characteristic example occurs in the
daphnia pulex, or water-flea.

CLAIRVO'YANCE. Clearsightedness;
a peculiar mode of sensation, or second
sight, connected with somnambulism, and
supposed to be diffused over the whole
surface of the body, but to be especially
seated in the epigastrium and fingers'
ends.

CLARIFICATION (clarus, clear, fio,
to become). The process of clearing
liquids, by subsidence of the suspended
particles, and decantation of the super-
natant liquor; by filtration through
porous substances ; or by coagulation, or
the admixture of albumen, and the sub-
sequent action of caloric, acids, &c.

CLA'VATE {clavus, a club). Club-
shaped ; a form in which one extremity
is slender and pointed, while the other is
thick and obtuse, as in many of the zoo-
phagous mollusca; in filaments, styles,
and the vittae of umbelliferous plants.

CLAVICO'RNES (clavus, a club, cornu,
a horn). A family of the pentamerous
Coleoptera, characterized by the club-
shaped form of the extremities of the
antennae, the terminal points frequently
forming a club.

CLAW OF PETAL. The narrow part
at the base of some petals, which is ana-
logous to the foot-stalk of a leaf, as in
the pink.

CLAY. An argillaceous rock, of an
unctuous, soft, friable, and dense homo-
geneous texture, forming a tenacious
paste with water, and of various colours.
The varieties of clay are essentially sili-
cates of alumina.

1. Indurated Clay is a variety of trap
80

rocks, with a dull earthy fracture, vary-
ing in colour from greenish-grey to grey-
ish-white, or red, or brown, or even
black.

2. Kimmeridge Clay is a subdivision of
the Upper Oolite Formation, of a blue
or yellowish colour, more or less slaty or
passing into slate, sometimes so impreg-
nated with bitumen as to be used for
fuel, and containing remains of saurian
reptiles and shells.

3. Oxford Clay, or Clunch Clay, is also
a subdivision of the Middle Oolite Forma-
tion, of a dark blue colour ; some of the
beds are bituminous, and abound in sep-
taria, or masses having internal dissepi-
ments. In its lower part are beds of
Kelloway rock, calcareous grit or sand-
stone, coral rag and oolite, and calcareous
sandstone.

4. Weald Clay. The upper portion of
the Wealden Formation, composed of
beds of clay of a bluish or brownish
colour, sandstone, calcareous sandstone,
conglomerate, limestone, and iron-stone.
The mass contains scales of mica, iron-
pyrites, crystals of selenite, and traces of
lignite.

CLAY IRON-ORE. One of the ferri-
ferous rocks from which iron is procured
in great abundance. It is of an earthy
aspect, with an even or conchoidal frac-
ture, yellow streak oi powder, and dull
colours.

CLAY SLATE. By this name different
rocks have been designated. 1. A mica-
ceous rock is so named, appearing to be
mica-slate in a state of extreme division,
the scales of mica having gradually be-
come so attenuated, as to give it a homo-
geneous, glistening appearance. 2. A
more extensive series of strata of clay-
slate is found associated with grey-wack.6
and other rocks of a less crystalline tex-
ture than the primary, and occurs in the
Cumbrian and the Cambrian Groups of
rocks.

CLAYSTONE. Compact felspar, with
an earthy aspect, conchoidal uneven frac-
ture, and of various colours. It is often
porphyritic, containing crystals of felspar.
It occurs in veins, as well as in mountain
masses.

CLEAVAGE. The mechanical divi-
sion of crystals, by which the inclination
of their lamina is determined.

Certain rocks, usually called slate-
rocks, admit of being cleaved into an in-
definite number of thin laminae which
are parallel to each other, but which are
generally not parallel to the planes of the

CLI

CLO

true strata or layers of deposition. The
planes of cleavage are, therefore, distin-
guishable from those of stratification.

CLEA'VLANDITE. A mineral for-
merly ranked among felspars, but differ-
ing in this, that the 13 or 14 per cent,
of potash in felspar is replaced by about
10 per cent, of soda in the cleavland-
ite.— Ure.

CLEF. The French term for a key.
In music, it is a symbol placed at the
beginning of the staff to determine the
names of the lines and spaces, and the
character of each note. 1. The treble
clef is placed on the second line, to which
it gives the name of G. 2. The mean
clef gives the name of C to any line on
■which it is placed. It is called the so-
prano clef when placed on the first line;
the mezzo soprano, when on the second;
the alto, contratenor, or countertenor,
when on the third ; and the tenor, when
on the fourth. 3. The base clef is placed
on the fourth line, to which it gives the
name of F.

CLEPSY'DRA {K\e^viPa, from k\<? ttto),
to steal, v&up, water). A water-clock,
made somewhat like our sand-glasses,
with a narrow orifice through which the
water trickled slowly, used by the Greeks
to time speeches in the law-courts. This
instrument was commonly employed by
astronomers for the measurement of
time before the invention of clocks and
watches.

CLE'RIDjE. A family of Coleopterous
insects, of the section Malacodermi,
named from the genus Clerus.

CLIMACTE'RIC (KA^aK-rJ/p, the step
of a ladder). The progression of the life
of man. It is usually divided into pe-
riods of seven years ; the ninth period,
or 63rd year, being the grand climac-
teric.

CLI'MATE (KX*'/xa, inclination). A
term applied in its popular sense to the
state of the air, in order to express the
particular combination of temperature
and moisture, which exists in the atmo-
sphere of any given country.

In its geographical and technical appli-
cation, Climate, or Clime, denotes an
imaginary narrow belt of the globe, paral-
lel to the equator; and is so called be-
cause the difference of climates depends
on the inclination, or obliquity of the
sphere. The belts constituting the seve-
ral climates are small, depending on the
average length of the longest day : that
of each increasing by half an hour, from
the equator to the polar circles, when the
81

climates are counted by months, till they
reach the poles.

CLI'MAX UMjuaf , a ladder or stair-
case). In rhetoric, a gradual ascent from
weaker to stronger expressions, as in the
celebrated M gradatio " of Cicero, — abiit,
excessit, evasit, erupit.

CLINA'NTHIUM (kAu/o, to incline,
avOos, a flower). A term applied by some
botanical writers to the receptacle of com-
positae which is not fleshy, but is sur-
rounded by an involucrum. By other
writers, this part is called thalamus and
phoranthium.

CLINKER. Black oxide of iron, or
the oxidum ferroso-ferricum of Berzelius.
It is always formed when iron is heated to
redness in the open air, and is therefore
readily obtained at the blacksmith's
forge.

CLINKSTONE. Ahardfelspathicrock,
named from the sharp noise which it
emits when struck with the hammer;
its fracture is splintery and conchoidal,
its lustre glistening, its colours various,
often with veins of jasper.

CLINO'METER {k\Lvu>, to incline,
H^rpov, a measure). A quadrant adapted
for showing the inclination of strata in
geological operations.

CLIO'NIDjE. The Clio tribe; a fa-
mily of naked marine mollusca, the first
order of Cuvier's Pteropods.

CLOA'CA (a sewer). A receptacle
observed in the monotremata, in birds,
in reptiles, and in many fishes, which
receives the faeces and the urine, to-
gether with the semen of the male, and
the ovum of the female.

CLOCK. A well known machine for
measuring time, regulated by the uni-
form motion of a pendulum. Common
clocks are made to show mean solar
time, but those used at observatories, for
the purpose of observing the time of the
stars transiting the meridian, show side-
real time.

CLOUDS. Masses of visible aqueous
vapour, which float in the sky, or drift
through it with the wind, at different
elevations, assuming every variety of
colour and form. They have been clas-
sified by Howard under three primary
forms, and four modifications.

1. Primary Forms. These are the cir-
rus, or curl-cloud, composed of fibrous
stripes, which are parallel, flexuous, or
diverging, and extensible in all direc-
tions ; the cumulus, or stacken-cloud,
heaped together in convex or conical
masses, and increasing upwards from a
E5

CO A

COC

horizontal base ; and the stratus, or fall-
cloud, spreading horizontally in a con-
tinuous layer, and increasing from below.
The first of these forms is confined chiefly
to the higher regions of the atmosphere ;
the second occupies a lower, but still an
elevated station ; the third usually rests
upon the surface of the earth, constitut-
ing mists,

2. Modifications. Of the four modified
forms of clouds, two are intermediate,
and two are composite. 1. The inter-
mediate forms are the cirro-cumulus,
consisting of small, roundish, and well-
defined masses in close horizontal ar-
rangement; and the cirro-stratus, like-
wise in small and rounded masses, but
attenuated towards a part, or towards the
whole, of their circumference. 2. The
composite forms are the cumulo-stratus,
made up of the cirro-stratus blended with
the cumulus, the cirro-stratus being
either intermingled with the larger
masses of the cumulus, or widely en-
larging the cumulous base ; and the
cumulo-cirro-stratus, nimbus, or rain-
cloud, being a horizontal layer of aque-
ous vapour, over which clouds of the
cirrous form are spread, while other
clouds of the cumulous form enter it
laterally and from beneath.

CLOVES. A technical appellation of
the small bulbs developed at the base of
a parent bulb.

CLUPE'IDJL The Herring tribe; a
family of Malacopterygious or soft-spined
fishes, named from the genus Clupea,
and differing from the Salmonidae in the
absence of fatty matter in the dorsal
fin.

CLY'PEIFORM (clypeus, a shield,
forma, shape). Shield-shaped; a term
applied to the large prothorax in beetles.
Clypeate is a similar term, applied, in
Botany, to the scales found on the leaves
of certain plants, and synonymous with
scutate or scutiform.

COAGULA'TION {con and agere, to
bring together). A term formerly syn-
onymous with crystallization, but now
applied to the partial solidification of a
fluid body by exposure to cold, or by the
addition of some agent. Spontaneous
coagulation denotes the cohesion of the
particles of the blood, of some effused
fluids, &c. Induced coagulation denotes
the effect produced upon albumen by
heat, alcohol, acids, rennet, &c.

COAL. A combustible mineral, con-
sisting of bitumen, carbon, and earthy
matter, in various proportions. The

varieties are easily recognized, being
hard, black, brittle, and laminated. Peat,
which consists of partially decomposed
roots and stems of various plants, may
be considered as forming one extremity
of the series, which terminates in the
other with glance coal or anthracite.

COAL FORMATION. A term gene-
rally employed as synonymous with that
of coal measures or carboniferous group.
This very comprehensive group embraces
not only the coal strata, and the beds of
sandstone, limestone, and others alter-
nating with it, but the mountain lime-
stone and the old red sandstone, on which
the proper coal group may be said to
rest.

Werner's Coal Formations. The first
or oldest is called the independent forma-
tion, from the individual depositions
composing it being independent of, and
unconnected with, each other. The se-
cond occurs in the newest floetz-trap
formation ; the third in alluvial land. A
fourth would comprehend peat and other
similar substances.

COAL GAS. A gas procured from
coal, when subjected in close vessels to
a red heat, and employed for illumi-
nation.

COA'RCTATE (coarcto, to compress).
An epithet applied to the pupa of an in-
sect, which is enclosed in a case, giving
no indication of the parts contained in it.

COARSE COAL. A sub-species of
black coal, occurring in the German coal
formations. To this head is also referred
the soot coal, which occurs together with
slate-coal, in the Forth district, &c.

COATING. Loricalion. A method of
securing or repairing retorts used in dis-
tillation. Coatings are made of marly
earth, kneaded with fresh horse-dung,
slaked lime, and linseed oil, &c.

COBALT (Cobalus, the demon of
mines). A metal, found chiefly in com-
bination with arsenic, as arsenical co-
balt; or with sulphur and arsenic, as
grey cobalt ore. These ores are em-
ployed to give the blue colour of por-
celain and stone- ware.

CO'BALUS. The demon of mines,
which obstructed and destroyed the
miners. The Germans formerly used a
form of prayer for the expulsion of the
fiend. The ores of cobalt, being at first
mysterious and intractable, received their
name from this personage.

CO'CCIDiE (coccus, the cochineal in-
sect). The Scale insects ; the single
family of the monomerous Homoptera,

COH

COL

remarkable for the production of cochi-
neal and other valuable dyes.

CO'CCOLITE (ko/ckov, a kernel, Xi'0or,
a stone). A green mineral, occurring in
loosely aggregated concretions, together
with granular limestone and other sub-
stances, in beds subordinate to the trap
formation.

COCCOO'N (kokkop, a berry or kernel).
The silken case which certain insects
spin for a covering during the period of
their metamorphosis, as that of the silk-
worm when passing into the pupa state.

CO'CCUS (kokkop, a kernel). A term
applied, in Botany, to a pericarp of dry,
elastic pieces, or coccules, as in Euphor-
bia. In this plant, the cocci are three in
number, and the fruit, generally called a
regma, is therefore also termed a tricoc-
cous capsule.

COCHINE'AL. The technical name of
the coccus cacti, a homopterous insect,
brought from Mexico, and employed by
dyers. Cochinilin is a colouring matter
obtained from cochineal, and is a consti-
tuent of carmine. The term granilla is
applied to very small insects of this kind,
from their resemblance to little grains.

CO'CHLEATE (cochlea, from K6xXof,
a conch). Shell-shaped; shortly spiral,
like a snail's shell, as the legume of
medicago falcata.

COCFNIC ACID. Cocostearic acid.
The crystallizable acid of the butter of
the cocoa nut.

CO'DA (coda, Ital., a tail). In Music,
a passage of variable length at the end
of a movement which follows a length-
ened perfect cadence.

CO'DEINE (K<a8eia, a poppy head).
One of the vegetable bases of opium.

CO-EFFICIENT. A term applied, in
Algebra, to the number, negative or
positive, which is prefixed to any alge-
braical quantity, to show how often it is
to be taken. It is that factor which is a
number, as 3a, or 5a2c.

CCELELMI'NTHA (koIXo?, hollow,
eX/uti/p, a worm). Intestinal worms which
are hollow, and contain an alimentary
tube in the cavity of the body. These
are the cavitary intestinal worms of Cu-
vier, the nematoidea of Rudolphi.

CCENO'BIO (Kotvofitos, living in com-
munion with others). The term by
which Mirbel designates the fruit of the
Labiatse. It differs from the carcerule
merely in the low insertion of the style
into the ovaria, and the distinctness of
the latter.

COHE'SION (cohcereo, to stick to-
83

gether). That relation among the com-
ponent parts of a body, by which they
cohere, or are kept together. The un-
known principle by which particles co-
here is called the attraction of cohesion.
On the degree of this force depend the
aggregate forms of matter, distinguished
as the solid, the liquid, and the gaseous.

COHOBA'TION. The continuous re-
distillation of a liquid from the same
materials, or from a fresh parcel of the
same materials.

COKE. The residue of coal, when the 1 |

volatile matters have been driven off.

CO'LCOTHAR. The brown-red oxide
of iron, which remains after the distilla- y /

tion of the acid from sulphate of iron.
It is used for polishing glass, &c, under . / >'
the name of crocus, or crocus martis. c * V r r*

COLEOPHY'LLUM (KoXeop, a sheath,
<pv\\ov, a leaf). Coleoptile. In Botany,
the sheath within which the young leaves
of monocotyledons are developed. By
the term coleorrhiza (pi£a, root), Mirbel
designates the sheath at the base of the
radicle of monocotyledons.

COLEO'PTERA (KoXeoc, a sheath,
nrepov, a wing). Sheath-winged insects ;
an order of insects which have four
wings, the upper pair being crustaceous,
and forming a sheath, or shield (elytron),
to the lower pair, as in the beetle. The
order has been distinguished by Latreille,
with reference to the number of joints
in the tarsi, or divisions of the foot, into
the pentamera, heteromera, tetramera,
and trim era.

COLLECTOR, ELECTRICAL. The
upper plate or disc of a condenser, em-
ployed for collecting electricity.

COLLECTORS. A term applied, in
Botany, to those hairs with which the
style of Compositae, Campanulaceae, and
others, is often densely covered, and
which seem intended as brushes to col-
lect and clear the pollen out of the cells
of the anthers.

COLLE'NCHYMA (K6\\a, glue, e'y
xvfxa, infusion). A term applied by
Link to the cellular substance in which
the pollen of Orchidaceous and Ascle-
piadaceous plants is generated. It is
supposed to constitute the appendage of
the pollen-masses of the former of these
tribes of plants.

COLLIMA'TION, LINE OF (collimo,
for collineo, to level, or aim in a right
line). The line of sight in an astronomi-
cal or geodesical instrument. The central
line of a telescope, or that which joins
the centres of its object-glass and its eye-
E6

COL

COL

glass, is called in Astronomy its line of
collimation. The difference between the
existing and the required positions of an
instrument is called the error of collima-
tion. This error is determined, without
reversal of the instrument, by means of
a contrivance called a collimator.

CO'LLUM. The neck. This term de-
notes, in Botany, that portion of the axis
of growth where the stem and the root
diverge : by Grew it was termed coarc-
ture ; by Lamarck, vital knot.

CO'LOPHONITE. A mineral with a
resinous fracture, found in magnetic
iron-stone in Norway, identical with
the resinous garnet of Haiiy and Jame-
son.

CO'LOPHONY. Resin of turpentine ;
the residue of common turpentine, after
its essence has been removed by distilla-
tion. It is not a homogeneous product,
but has been divided into two different
resins, named by Unverdorben the sylvic
and pinic acids.

COLOURS. A general term for those
modifications of light, whether direct or
reflected from other bodies, by which the
sight is affected with distinct sensations.
The colour of a body is designated by the
particular species of light reflected from
its surface, which may therefore be called
the objective colour, or that which is per-
manent to the body.

1. Prismatic Colours. Colours pro-
duced by transmitting white light through
colourless prismatic bodies. The light
undergoes refraction, and is dispersed,
presenting the phenomenon of the solar
or prismatic spectrum. The colours ex-
hibited by opaque or non-luminous sub-
stances, when they either reflect or trans-
mit white light, are called natural
colours.

2. Primary Colours. These are red,
orange, yellow, green, blue, and violet,
being the different colours into which a
solar ray of light may be decomposed.
White is, therefore, a compound of these
colours, and black is the absence of all
colours. The primary colours are not
decomposable, but have uniform refrac-
tion ; hence they were termed by Newton,
homogeneous colours, to distinguish them
from common or white light, which he
called compound or heterogeneous.

3. Secondary Colours. According to
Brewster, there are only three primary
or fundamental colours; viz. red, yellow,
and blue; the other three, viz. orange,
green, and violet, being produced by
combination of the former, and therefore

84

properly termed secondary or compound
colours.

4. Complementary Colour. That colour
with which each of the prismatic colours
will combine, and form white light. The
complementary colour to each of the
three primaries, is the compound colour
obtained by combining the other two pri-
maries ; and, for each of the secondaries,
that primary one which does not enter
into its composition.

5. Accidental Colours. A series of
optical phenomena, commonly called
ocular spectra. If the eye be steadily
directed, for some time, to a white wafer
upon a dark ground, and be then turned
aside, a spectrum of the wafer will be
perceived, with the colours reversed : the
wafer will appear dark, the ground white.
If the wafer be red, its spectrum will be
bluish-green ; if orange, blue ; if blue,
orange-red, &c. Darwin classes the
spectra under the heads of direct and re-
verse, the former depending on the per-
manence of the impression, the latter
upon exhaustion. Accidental colours
are sometimes called subjective or phy-
siological, to distinguish them from the
permanent or objective colours.

6. Entoptic Colours. A term applied
by Seebeck to the spectra obtained by
transmitting polarized light through a
crystal cut at right angles to its axis, the
light being made to pass in the direction
of the axis. The phenomena consist of
concentric rings of various colours, re-
sembling Newton's prismatic rings, and
intercepted in the middle by a rect-
angular cross.

COLOURED RINGS. Luminous
rings produced by interference of the
rays of light, or by electro-chemical de-
composition. Of the former kind are
Newton's coloured rings, which may be
produced by pressing a watch-glass upon
a piece of plate-glass ; the rings will ap-
pear about their point of contact, of the
same colour as the incident rays, if the
light be homogeneous. Of the second
kind are NobilVs rings, which are pro-
duced when a feeble current of electricity
is directed upon a polished metallic plate,
this plate being used as an electrode,
and immersed in an electrolytic fluid;
the rings will then appear upon the
plate.

COLOURING MATTER. Colouring
principles found in vegetable substances,
and employed in dyeing. Colours are
termed substantive, when they adhere to
the cloth without the intervention of a

COL

COM

base ; adjective, when they require a base
for that purpose.

COLPE'NCHYMA (koXtto?, a loose
fold, eyxvua, infusion). A term applied
by Morren to the sinuous form of the
parenchyma of plants.

COLUBE'RIDjE {coluber, a snake).
A family of Ophidian reptiles, including
the Boa Constrictors of the New World
and the Pythons of the Old, and other
non-venomous snakes not belonging to
the other families of the order.

COLU'MB A NO'ACHI. Noah's Dove ;
a modern southern constellation, consist-
ing of ten stars, close to the hinder feet
of Canis Major.

COLUMBE'LLIN^. Dove-shells; a
sub-family of the Strombidce, or Wing-
shells, named from the typical genus
columbella ; these are small shells, with
sharp-pointed spires ; the outer lip is
thick, turned inwards, more or less
toothed on its edge, and gibbous above ;
there are also tuberculated teeth at the
base of the inner lip, but no regular
plaits.

COLU'MBID^E {columba, a dove or
pigeon). The Pigeon tribe; a group
of the Rasores, or Scratching birds,
chasacterized by the double dilatation
of the crop, and their habit of feeding
their young with food disgorged from
this receptacle. Macgillivray considers
that the Pigeons belong neither to the
Rasores nor to the Insessores, but appear
to form an order separated by well-
defined limits. See Gemitrices.

COLUMBIUM. Another name for the
metal tantalum, from its having been
brought, as it is said, from Massachusetts
in North America. By fusion of its ore,
or columbite, an acid is obtained, called
columbic acid.

COLUME'LLA (dim. of columna, a
pillar). A little pillar ; the internal sup-
port of most spiral shells, round which
the whorls are convoluted. In botany,
it denotes the axis from which the valves
of a fruit separate, on dehiscence ; the
axis which occupies the centre of the
sporangium of mosses, &c.

COLU'MNA. A column ; a term ap-
plied, in botany, to the solid body formed
by a combination of the filaments, as in
stapelia, rafflesia, &c.

COLURES (xoWpop , a truncated tail).
An old term employed in Astronomy to
designate two great circles of the sphere,
which pass, the equinoctial colure through
the equinoctial points and the poles of
the equator, the solstitial colure through
85

the solstitial points and the poles of the
ecliptic and of the equator.

COLY'MBIDuE {colymbus, a diver).
The Divers ; a small family of the Nata-
tores, or Swimming birds, characterized
by remarkably short wings, and a length-
ened, strong, straight bill.

CO'MA. Literally, hair ; and hence
applied to the assemblage of branches
which forms the head of a forest tree.
Cyma is sometimes employed, though
erroneously, to express the same thing.

COMA BERENICES. Berenice's
Hair ; a modern northern constellation,
consisting of forty-three stars, and named
after the wife of Ptolemy Euergetes.

COMBINATIONS. In Algebra, the
combinations of any number of quan-
tities are the different sets which can be
made of them, taking a certain number
together, without regard to the order in
which they are placed. Thus, the com-
binations of a, b, c, d, taken 3 together,
are abc, abd, acd, bed.

COMBINATION, CHEMICAL. The
union of the particles of different sub-
stances, by chemical attraction, in form-
ing new compounds. See Atomic Weights.

COMBINING QUANTITY. Various
terms have been proposed for expressing
the combining quantities of elementary
and compound substances, and all ob-
jectionable. Atom is not only hypotheti-
cal, but often inapplicable, as when half
atoms occur. Equivalent is only expres-
sive when comparison with a correlative
equivalent is directly implied. Proportion
means similitude of ratios. Proportional
is one of the terms of a proportion.
Combining quantity or weight is some-
times expressive ; but, besides being
unwieldy, it is not always applicable.
Dr. Donovan adds, the word dose is
universally employed to designate a de-
terminate or definite quantity of a thing
given; it has the quality of involving
nothing beyond a fact, and can often be
used with advantage.

COMBU'STIBLE. A body which, in
rapid union with other bodies, disengages
heat and light. Simple combustibles are
hydrogen, carbon, boron, sulphur, phos-
phorus, nitrogen, and the metals ; com-
pound combustibles are the hydrurets,
carburets, sulphurets, phosphorets, me-
tallic alloys, and organic products.

COMBU'STION {comburo, to burn to-
gether). The act of burning ; a pheno-
menon produced by the chemical combi-
nation of two substances, attended by the
development of heat and light ; it usually

COM

COM

takes place in the combination of oxygen,
but, in a few cases, in that of chlorine
and of sulphur. Bodies which are con-
sidered as the causes of this phenomenon
are called supporters of combustion, whilst
the radicals which combine with them
are called combustibles.

1. Combustion, Invisible. A term ap-
plied by Davy to those phenomena of
combustion which are effected without
the disengagement of light, as when
oxygen and hydrogen, confined in tubes,
are carefully exposed to a high tempe-
rature.

2. Combustion, Spontaneous. This is
said to occur in the human body ; and it
does occur when masses of vegetables, as
damp hay, or oily cotton, are heaped to-
gether. There are also cases on record
of the spontaneous ignition of charcoal,
both dry and moist.

COME'NIC ACID. A bibasic acid,
formed from the meconic acid, of which
it is a congener. It is decomposed by
heat, and another congener is produced,
viz. pyromeconic acid.

CO'MET (KOfxtiTw, from Ko/itj, hair).
Literally, a hairy star. A celestial body
which occasionally traverses our system
in a very eccentric orbit, without appear-
ing to form a part of it. Its central
point, which is more or less lustrous, is
called its nucleus. The nebulous light
surrounding the nucleus, is the chevelure
or hair. The luminous train by which
most comets are accompanied was for-
merly called beard or tail, accordingly as
it preceded or followed the comet in its
course. At present it is called tail, what-
ever be its position. Lastly, the nucleus
and the chevelure together constitute
the head of the comet.

COMETA'RIUM. A machine show-
ing the motion of a comet about the
sun ; any instrument capable of describ-
ing an elongated ellipse.

COMMA (K<5/x/Lia, that which is struck).
The smallest interval in music, being the
ninth part of a major tone.

COMMISSURAL (committo, to solder).
Belonging to a line or part by which
other parts are connected together. The
connecting line is the commissure.

COMMON MEASURE. In Arith-
metic, a number which divides two or
more other numbers without leaving a
remainder.

COMMON TERM. A logical expres-
sion for a term which is applicable in the
same sense to more than one individual
object. Common terms, therefore, are

called "predicables," that is, affirmatively
predicable, from their capability of being
affirmed of others. See Singular Term.

COMMUTATOR or GY'ROTROPE.
An apparatus included in the circuit
between the battery and the electro-
magnetic apparatus, for the purpose of
reversing the direction of the current
without the necessity of changing the
arrangement of the conductors from the
poles.

COMPASS, MARINER'S. A mag-
netic needle, balanced on a pivot, for
pointing out the true direction of north
and south. In the mariner's compass,
the circle traversed by the point of the
needle is marked off into 32 rhumbs or
points; in the azimuth compass the same
circle is divided into 360°.

COMPATIBLE TERMS. In Logic,
terms expressive of two views which
may be taken of the same object at the
same time, as to be "white and cold."
See Opposite terms.

COMPENSATION PENDULUM. A
pendulum made of different substances,
so combined that the effects of* heat
counteract each other, and the length of
the rod remains unaltered.

CO'MPLEMENT {compleo, to fill up).
A magnitude which, taken with another,
makes up a given magnitude. The com-
plement of an arc or angle is what is
required to complete a quadrant or right
angle. The arithmetical complement of
a number is the number by which it falls
short of the next higher decimal denomi-
nation. The complement of a logarithm
is the number by which a logarithm falls
short of 10. The complement of altitude
is the zenith distance ; that of latitude,
the polaoiirtance.

COMPOSITE. The Synantherous
tribe of dicotyledonous plants. Herba-
ceous plants or shrubs with leaves alter-
nate or opposite ; flowers (called florets)
unisexual or hermaphrodite, collected in
dense heads upon a common receptacle,
surrounded by an involucrum ; florets
monopetalous ; anthers syngenesious ;
ovarium one-celled ; fruit a dry, inde-
hiscent pericarp, termed achenium or
cypsela.

COMPOSITION {compono, to put
together). A technical term used by
geometers to signify one of the ways of
changing the order or magnitude of pro-
portionals, so that they continue still to
be proportionals. Thus of four propor-
tionals, the first, together with the
second, is to the s< cond, as the third,

CON

CON

together with the fourth, is to the fourth.
See Force.

COMPOSITION, FALLACY OF. A
logical fallacy, in which the middle terra
is used in one premiss collectively, in the
other distributively. The form in which
it is most usually employed, is to esta-
blish some truth, separately, concerning
each member of a certain class, and
thence to infer the same of the whole
collectively. Thus, it may be argued that,
because it is not very improbable that
a person may throw sixes in any one out
of a hundred throws, therefore it is no
more improbable that he may throw
sixes a hundred times running. Whately.

COMPOUNDS. The following terms
are employed in designating compounds :

1. Binary, ternary, quaternary. These
terms refer to the number of elements or
proximate principles— two, three, or four
— which exist in a compound. The binary
compounds of oxygen, chlorine, iodine,
bromine, and fluorine, which are not
acid, terminate in ide, as oxide, chloride,
&c. ; those of all other substances termi-
nate in uret, as hydruret of carbon, sul-
phuret of iron, &c.

2. Bis, ter, quater. These are Latin
numerals, indicating the number of aioms
of acid, which are combined with one of
the base in a compound, as fo'-sulphate of
soda, &c.

3. Dis, iris, tetrakis. These are Greek
numerals, indicating the number of atoms
of base, which are combined with one of
the acid in a compound, as de-chromate
of lead, &c. No prefix is used when the
compound consists of one atom of each
ingredient. But there are many excep-
tions to these rules : protoxide and deut-
oxide are frequently used for oxide and
bin-oxide respectively.

COMPRESSIBILITY (comprimo, to
compress). A property of masses of mat-
ter, by which their particles are capable
of being brought nearer together. Bodies
which recover their former bulk on re-
moval of the compressing cause, are
called elastic.

CO'MPTONITE. A mineral found in
drusy cavities, in ejected masses, on
Mount Vesuvius ; first brought to this
country by Lord Compton, in 1818.

CONCENTRATION. The strengthen-
ing of solutions or mixtures by evapora-
tion of their watery parts.

CONCE'NTRIC. Having the same

centre, as applied to circles which are

described about the same point, to the

striae of bivalves which run parallel to

87

the margin, &c. The concentric theory
is the theory of epicycles, as opposed to
the eccentric theory. See Epicycle.

CONCEPTA'CULUM. Literally, a
receptacle ; a term applied, in Botany, to
a species of compound fruit, which is two-
celled, many-seeded, superior, separating
into two portions, the seeds of which
detach themselves from their placenta,
and lie loose in the cavity of each cell.
This fruit occurs in Asclepias, and is also
called the double follicle.

CONCH A'CEA {Ko^Xn, a shell). A
family of conchiferous molluscs, in De
Blainville's arrangement, corresponding
with Cuvier's Cardiaceae, or the Cockle
tribe. See Cardiacece.

CONCHPFERA {concha, a shell, fero,
to carry). A class of the Mollusca, com-
prising acephalous aquatic animals, co-
vered with a bivalve or multivalve shell.
There are two orders, viz. —

1. Monomyaria, in which the shells
are narrow longitudinally, and have but
one muscular impression on the valve,
as in the spondylus.

2. Dimyaria, in which the shell is ex-
tended longitudinally, and has two mus-
cular impressions on the valve, as in the
area barbata.

CONCHOID (noyxoeiSijs, resembling
a shell). The designation of a curve,
employed by Nicomedes for finding the
two mean proportionals, and the dupli-
cation of the cube.

CONCH O'LOGY (rfy%*, a shell, A6709,
a description). The " art " of arranging
the shells of testaceous animals, without
reference to the animals which they con-
tain. See Malacology.

CONCLUSION. In Logic, the propo-
sition which is inferred from the premises
of an argument.

CO'NCORD. A term applied in Music
to two combined sounds which are uni-
versally agreeable to the ear. The 8th,
or octave, and the 5th are called perfect
concords, because as concords they are
not liable to alteration by flats or sharps ;
the 3rd and 6th are termed imperfect con-
cords, because alterable.

CONCRETE. A term denoting a qua-
lity accompanied with its particular sub-
ject, as opposed to abstract, which de-
notes the quality without its subject.
The names of Classes are abstract, those
of individuals concrete; and from con-
crete adjectives are made abstract sub-
stantives. See Abstract.

CONCRETIONARY DEPOSITS. In
Geology, a designation of those Recent or

CON

CON

Alluvial strata, which include calcareous
and other deposits from springs, stalac-
tites, travertines, bog iron -ore, and salt.

CONCURRENTS. Common years con-
sist of 52 weeks and 1 day, and Bissex-
tile years consist of 52 weeks and 2 days.
The day or two days supernumerary are
called Concurrents, because they concur
with the Solar Cycle, whose course they
follow. The first year of this cycle is
termed Concurrent 1, the second 2, the
third 3, the fourth 4, the fifth 6 (instead
of 5, because that year is bissextile), the
sixth 7, the seventh 1, the eighth 2, the
ninth 4 (instead of 3, because that year
is likewise bissextile), and thus, with the
other years, always adding one in com-
mon years, and 2 in bissextile years ; and
always recommencing with 1 after having
reckoned 7, because there are no more
than 7 Concurrents, — that being the
number of days in a week and of the
Dominical Letters.

CONDENSATION (condenso, to thick-
en). The act of diminishing the bulk of
a body, by compression, as in the conver-
sion of gases into liquids, of liquids into
solids ; or by cold, as in the conversion
of steam into water.

CONDE'NSER (condenso, to thicken).
1. A vessel in which steam is condensed,
or converted into water, by the applica-
tion of cold. 2. An apparatus used for
detecting the presence of electricity, by
collecting and condensing it before it
gains a sufficient degree of tension to
affect the electroscope. Its action de-
pends on the induction of electricity, and
on this being held in a latent state.

CONDENSING SYRINGE. A hollow
metallic cylinder, furnished with a pis-
ton, piston-rod, and receiver, for increas-
ing the density of air in a given space.

CONDITIONAL PROPOSITION. In
Logic, a proposition which asserts the
dependence of one categorical proposition
on another. A conditional syllogism is
one in which the reasoning depends on
such a proposition.

CONDUCTION (conduco, to bring
with). A term expressive of that pro-
perty by which certain bodies transmit
heat, or electricity, through their sub-
stance. The rate at which this equaliza-
tion^ effected in any body is the measure
of its conducting power ; and substances
are, accordingly, divided into good and
bad conductors with reference to this
power.

CONDUCTORS METALLIC. A term
applied to long metallic rods, whose

points are raised above buildings for the
purpose of attracting or receiving the
electric fluid, and of conducting it into
the earth, or into water, thereby to pre-
vent such buildings from being struck
by lightning.

CONDU'RRITE. An ore of copper
found in a vein in Condurrow mine, in
Cornwall.

CONDYLO'PODA (/c6i/3t/\or, a joint,
irovs, irodbs, a foot). Articulated animals
with jointed legs, as insects, crabs, and
spiders.

CONE (kwvos, a cone). A geometri-
cal solid, with a circular base, tapering
equally upwards until it terminates in a
vertex or point. A right line drawn from
the vertex to the centre of the base, is
termed the axis of the cone. When this
axis is at right angles to the base,
the solid is termed a right cone; if
otherwise, it is an oblique, or scalene
cone.

CONE, in BOTANY. The fruit of
the Coniferae, or Fir-tribe of plants, con-
sisting of a conical amentum, of which
the carpels are scale-like, spread open,
and bear naked seeds.

CONE OF RAYS The rays of light
which fall from a luminous point upon a
given surface, as upon the object-glass
of a telescope.

, CONE'NCHYMA (kSi/o?, a cone, ?-yXw-
fia, infusion). A term applied by Mor-
ren to that form of parenchyma in plants,
which is conical, as in hairs.

CONFERVA. A section of Algace-
ous plants, consisting of simple tubular
jointed species inhabiting fresh water.

CONFLA'TION (conflo, to blow to'
gether). The process of casting or melt-
ing of metals.

CO'NFLUENT (confluo, to flow toge-
ther). Growing together ; a term syno-
nymous with connate, expressive of the
cohesion of homogeneous parts.

CONFO'RMABLE. A term applied
in Geology to the planes of one set of
strata which are parallel to those of an-
other set which are in contact with them.

CONGELATION (congelo, to freeze).
The passing from a fluid to a partially or
wholly solid state, by the agency of cold.

CO'NGENER. That which is of the
same kind; a term applied to species
which belong to the same genus.

CONGLOMERATE (conglomero, to
heap together). Puddingslone. Rounded
water- worn fragments of rock or pebbles,
cemented together by another mineral
substance, which may be of a silicious,

CON

CON

calcareous, or argillaceous nature. The
term is synonymous with the Italian
word breccia.

CONIC SECTIONS. The designation
of that science which treats of the pro-
perties of certain curves which are formed
by the cutting of a cone. These curves,
or sections, are the ellipsis, the parabola,
and the hyperbola.

CONICAL PROJECTION. A me-
thod of describing a representation of a
part of a sphere upon a plane.

CO'NICINE. A vegeto-alkali exist-
ing in all parts of the conium maculatum,
or hemlock. It is also called conia and
coneine.

CONI'FERjE. The Fir or cone-bearing
tribe of Dicotyledonous plants. Trees or
shrubs with a stem abounding with re-
sin ; leaves linear, acerose, or lanceolate ;
flowers monoecious, or dioecious ; ovarium
in the cones, spread open, appearing like
a flat scale destitute of style or stigma ;
fruit a solitary naked seed or a cone;
seeds with a hard crustaceous integu-
ment.

CONI'NjE. The Cone-shells ; a sub-
family of the Strombidce, or Wing-shells,
named from the typical genus conus,
having the spire so depressed as to be
turbinated, and scarcely raised above the
body-whorl; the aperture is always
smooth ; the outer lip without any lobe,
and only slightly detached above.

CONIRO'STRES {conus, a cone, ros-
trum, a beak). A large group of the
Insessores, or Perching birds, character-
ized by a stout beak, more or less conical,
and with regular edges, including the
crows, starlings, finches, hornbills, and
crossbills. The structure of their feet
enables them to walk on the ground with
nearly the same facility as they perch
upon trees.

CO'NITE. A mineral found in the
Meissner trap-hill in Hessia, &c. The
same name has been applied to another
pulverulent mineral, found in the trap-
hills of Kilpatrick and other places.

CO'NJUGATE (conjugatus, yoked toge-
ther). A term applied, in Mathematics,
to two lines, points, &c, when considered
together in any property in such a man-
ner that they may be interchanged with-
out altering the way of enunciating the
property. '

CONJUGATION (conjugo, to yoke
together). A term, in grammar, denot-
ing all the inflexions of a verb, with re-
lation to mood, time, number, person,
voice, &c.
89

CONJUNCTION (conjungo, to join
together). A part of speech used to join
words and propositions together. It is
termed copulative, when it not only joins
the words, but indicates that the things
are to be united ; disjunctive, when it
unites the words, but indicates that the
things are to be separated.

CONJUNCTION and OPPOSITION.
When a planet, as seen from the earth,
is in the same direction as the sun, it is
said to be in conjunction with the sun.
This, however, in the case of an inferior
planet, may be either when it passes be-
tween the sun and the earth, or when it
is on the further side of the sun ; the for-
mer is the Inferior, and the latter the
Superior Conjunction. A superior planet,
never passing between the sun and the
earth, is only once in conjunction with
the sun during its revolution. In the
point of its orbit, when the earth is be-
tween it and the sun, the planet is said
to be in Opposition to the sun. The Con-
junctions and Oppositions of the moon
have the general name of Syzygies.

CONNATE (connascor, to be born to-
gether). Born with another ; congenital.
A term applied in botany to two opposite
leaves united at their bases, as in the
garden honeysuckle.

CONNE'CTIVE. That part of the
stamen in plants which connects the two
lobes or cells of the anther ; it is usually
continuous with the filament, but is fre-
quently enlarged in various ways.

CO'NOID {ku>vos, a cone, eldov, like-
ness). A geometrical solid, formed by
the motion of a parabola or of a hyper-
bola round its axis. Conoids vary in
thickness in comparison with their
height, according to the proportions of
the parabola, or hyperbola, by which they
are generated. The spheroids, some-
times included in the class of conoids,
are more usually limited to the parabo-
loid and the hyperboloid. The term
conoid is sometimes used synonymously
with spheroid, although the latter has no
resemblance to single cones, and but
little to double ones.

CO'NSEQUENT. In Logic, that part
of a conditional proposition which de-
pends on the other. By consequence is
meant the connexion between the ante-
cedent and the consequent of a con-
ditional proposition.

CO'NSONANCE {consono, to sound
together). A term applied, in Music, to
a combination of harmonious sounds. See
Chord.

CON

COP

CONSTELLATION (cum, with, stelLi,
a star). A group of stars, designated
by the name of some man or lower ani-
mal. The several stars of a constella-
tion are distinguished, in the order of
their brilliancy or apparent magnitude,
by the letters of the English and Greek
alphabets, by the ordinal numbers, &c.
Forty-eight of the constellations are of
unknown antiquity; the twelve which
occupy the zodiac are termed the twelve
signs.

CO'NTINENT (contineo, to hold toge-
ther). A space of land of vast extent,
surrounded by water. The Old Continent
includes the three divisions of Europe,
Asia, and Africa, and is so named from
its having, till the discoveries of Colum-
bus, in 1492, been the only one known to
Europeans. The New Continent includes
North and South America.

CONTINGENT. A term applied in
Logic to the matter of a proposition when
the terms of it in part agree, and in part
disagree.

CONTRACTILITY (contraho, to draw
together). The property by which a body
contracts ; by which a fibrous tissue re-
turns to its former dimensions after being
extended ; by which the muscular fibre
shortens itself on the application of a
stimulus. The last exhibition of this
property is usually called irritability.

CONTRADICTORY PROPOSI-

TIONS. Propositions which, having
the same terms, differ both in quantity
and quality. Contrary propositions are
two universals, affirmative and negative,
with the same terms.

CONTRARY TERMS. In Logic,
those terms which, coming under some
one class, are the most different of all
that belong to that class; as "wise" and
"foolish"

CONVE'CTION {conveho, to carry). A
mode of communication of heat through
fluid bodies. A portion of water or of
air being heated above, or cooled below,
the surrounding portions, expands or
contracts in magnitude, and thus be-
coming specifically lighter or heavier,
rises or sinks accordingly, carrying with
it the newly acquired temperature, what-
ever that temperature may be.

CONVERGENT; DIVERGENT. In
Algebra, an indefinite series of terms
which continually diminish, so that no
number of them, added together, will
equal a given number, is said to be con-
vergent, as 1 + | + £ + £ + &e. But,
when such a number of them can be
90

added together as will surpass any given
number, the series is called divergent, as
1 + i + h + i + &c.

CONVERSION. In Logic, a propo-
sition is said to be converted, when its
terms are transposed; i.e. when the sub-
ject is made the predicate, and the pre-
dicate the subject : when nothing more
is done, this is called simple conversion.
No conversion is employed for any logical
purpose, unless it be illative ; i. e. when
the truth of the converse is implied by
the truth of the proposition given ; e. g.,
" No virtuous man is a rebel, therefore
no rebel is a virtuous man."

In Geometry, the term conversion de-
notes a mode of changing the order or
magnitude of proportionals, so that they
continue still to be proportionals. Thus,
of four proportionals, the first is to its
excess above the second, as the third to
its excess above the fourth.

CONVOLVULA'CE^S. The Bindweed
tribe of Dicotyledonous plants. Herba-
ceous plants with leaves alternate ; flowers
regular, monopetalous ; stamens inserted
into the base of the corolla ; ovarium
superior 2-4 celled ; seeds albuminous.

CO-O'RDINATES (con, together, or-
dino, to arrange). A term applied in
Geometry to a system of lines, to which
points under consideration are referred,
and by means of which their position is
determined. In plane geometry one of
these lines is called the abscissa, the
other the ordinate.

COPAHU'VIC ACID. A name ap-
plied to the resin of copaiva, said to
possess the same composition as colo-
phony.

CO'PAL. This substance, erroneously
called gum copal, is the concrete juice of
the Hymenaea Courbaril ; it is used as a
varnish, and known by the names of
jatahy and jatchy. The copal of the
Mexicans is supposed to be procured
from a species of Icica.

COPE'PODA. An order of the ento-
mostracous Crustacea, which have the
body divided into distinct rings, but
without carapace, and the appendages to
the mouth in considerable numbers.
The animals of this order are commonly
termed monoculous, from the two eyes
being united in one mass.

COPE'RNICAN SYSTEM. A system
of Astronomy, so named from Nicholas
Copernicus, who was born a.d. 1473, at
Thorn in Prussia. He taught, as Py-
thagoras had taught before him, that the
sun occupied the centre of the universe,

COR

COR

and that the planets moved round him in
elliptical orbits proportioned to their size.
This system was established by the new
arguments and discoveries of Galileo,
Kepler, and Newton. The great prin-
ciple on which it rests is gravity, or that
force in nature by which all the planets
are attracted to the centre of their re-
spective orbits.

COPPER {Cuprum, quasi ces Cyprium ;
from the island Cyprus, where it was
first wrought). A red metal found in
the common ore called copper pyrites.
Among its compounds are red copper, or
the protoxide ; black copper, or the per-
oxide; copper glance, or the protosul-
phuret ; resin of copper, the protochloride
or white muriate ; and the white copper
of the Chinese, an alloy of copper, zinc,
nickel, and iron.

CO'PPERAS. Sulphate of iron, or
green vitriol. See Vitriol.

COPPERNICKEL. A native arseni-
uret of nickel, a copper-coloured mineral
of Westphalia,

CO'PROLITE (/coTrpor, dung, \i9os, a
stone). The petrified faecal matter of
carnivorous reptiles, resembling an ob-
long pebble or a kidney potato, and found
at Lyme Regis in Dorsetshire.

CO'PULA. In Logic, that part of a
proposition which affirms or denies the
predicate of the subject; viz., is, or is
not, expressed or implied.

COR CA'ROLI. A modern northern
constellation, consisting of three stars.

COR HYDR^E. A star of the first
magnitude in the southern constellation
Hydra.

COR LEO'NIS. Another name for
Regulus, a star of the first magnitude in
the constellation Leo.

COR SCORPIO'NIS. Another name
for Antares, a star of the first magnitude
in the zodiacal constellation Scorpio.

CORACI'IISLE {coracias, the roller).
Coraciine Birds, or Rollers ; a family of
the Excurtrices of Macgillivray, the In-
sessores of other writers, indigenous in
warm climates, and for the most part
gaudily coloured.

CORAL RAG. A subdivision of the
middle Oolitic formation, named from
its containing abundant remains of corals
of various kinds.

CORAL RED. The calcareous in-
ternal skeleton of a polypipherous ani-
mal, consisting of carbonate of lime,
coloured with oxide of iron, and ani-
mal matter.

CORALLI'DiE {corallum, coral). Co-
91

rallicolce. A family of compound polyps,
yielding the substance called coral, and
constituting the third order of the class
Polypi.

CO'RALLINE DEPOSITS. In Geo-
logy, a designation of those recent or
alluvial strata, which consist of the
marine banks, shoals, and islands, en-
tirely composed of corals.

CO'RCULUM (dim. of cor, the heart).
The embryo, or vital principle of a seed,
so named from its frequent resemblance,
in form, to a little heart. It consists of
two parts, the rostellum, or radicle, which
elongates downward to form a root ; and
the plumula, or feather, which lengthens
upward to form a stem and leaves.

CO'RDATE (cordatus, from cor, a
heart). Heart-shaped ; having two
rounded lobes at the base, as applied to
certain leaves.

CORIA'CEOUS (corium, hide). That
which has the texture of rough skin, as
the leaves of prunus laurocerasus.

CO'RMUS. The dilated base of the
stem of monocotyledonous plants, inter-
vening between the roots and the first
buds, and forming the reproductive por-
tion of the stem in acaulescent plants.
It occurs in colchicum, in crocus, &c.

CO'RNEOUS {cornu, a horn). Horny;
resembling the colour or substance of
horn, as the epidermis of some, and the
operculum of other, spiral shells ; the
albumen of many plants, &c.

CO'RNEULE. A diminitive of cornea ;
a term applied to the minute transpa-
rent segments which defend the com-
pound eyes of insects.

CORNI'CULATE {corniculum, a little
horn). Horned ; terminating in a horn-
like process, as the fruit of trapa bi-
cornis.

CORNU AMMO'NIS. An old Latin
name for the fossil shell, commonly called
ammonite, from its fancied resemblance
to the horn with which the head of Ju-
piter Ammon was sculptured. See Am-
monite.

CORNU'BIANITE. A slaty rock
abundant in the western part of Corn-
wall, in contact with granite. It is of a
dark blue or purple colour, uniform,
striped or patched, hard and laminated.

CORO'LLA (dim. of corona, a crown).
Literally, a little crown. The internal
envelope of the floral apparatus. Its
separate pieces are called petals; when
these are distinct from each other, the
corolla is termed poly-petalous ; when
they cohere, gamo-petalous, or incorrectly

COR

COT

mono-petalous. A petal, like a sepal,
may be spurred, as in violet. Compare
Calyx.

CO'ROLLARY. A corollary to a geo-
metrical proposition is a statement of
some truth, which is an obvious conse-
quence of the proposition. The term is
derived from the Latin corollarium, a
reward given to actors, champions, or
fencers,' above their due.

CORO'NA AUSTRA'LIS et BOREA'-
LIS. The Southern Crown and the
Northern Crown ; two of the old constel-
lations of Ptolemy, the former in the
southern, the latter in the northern
hemisphere.

CO'RONATED {corona, a crown).
Crowned ; a term applied to spiral shells
which have their whorls more or less
surmounted by a row of spines or tuber-
cles, as in the typical volutes, several
cones, mitres, &c.

CORPU'SCULAR THEORY {corpus-
culum, a little body). A theory for ex-
plaining the nature of light. According
to this, the sun and all other luminous
bodies have the property of emitting cor-
puscles, or exceedingly minute particles
of their substance, with prodigious velo-
city. Hence it has been also termed the
Theory of Emission. See Undulatory
Theory.

CORRO'SIVE SUBLIMATE. The
bichloride, formerly called the oxymu-
riate, of mercury.

CO'RRUGATE {cum, with, ruga, a
wrinkle). Wrinkled; folded up in every
direction, as in the aestivation of the
poppy.

CORTI'NA. A curtain ; a name given
to a portion of the velum of fungaceous
plants, which adheres to the margin of
the pileus in fragments.

CORU'NDUM. A stone found in
India and China; it crystallizes in six-
sided prisms, which, from their hardness,
are termed adamantine spar. The ame-
thyst, ruby, sapphire, and topaz, are
considered as varieties of this spar, dif-
fering from one another chiefly in colour.
These are termed Oriental gems ; but the
names are applied to stones of other
countries. Jameson distinguishes three
species of corundum, the octohedral, the
rhomboidal, and the prismatic or chryso-
beryl.

CORVI'DiE {corvus, a crow). Corvine
birds, or Crows ; a family of the Insessores,
or of the Excur trices of Macgillivray,
including the crow, the raven, the mag-
pie, the jay, and other conirostral birds.
92

CORVUS. The Crow; a southern
constellation, consisting of nine stars,
the principal of which is Algorab. It is
sometimes called Hydra et Corvus, the
Corvus resting on part of the body of
Hydra.

CO RY'D ALINE. A vegeto-alkali,
found in the root of Corydalis bulbosa
and fabacea.

CORYLA'CEiE. The Nut tribe of
Dicotyledonous plants, named from the
genus corylus, and comprising the oak,
the beech, the hazel, the hornbeam, and
the sweet chestnut. See Cupulifercc.

CO'RYMB. A form of inflorescence,
in which the lower stalks are so long
that their flowers are elevated to the
same level as that of the uppermost
flowers. The expansion of the flowers of
a corymb is centripetal. See Fascicle.

CO'RYMBOSE. That arrangement of
the ramifications of plants, in which the
lower branches or pedicles are so long as
to bring the leaves or flowers to the same
level as that of the upper ones.

CO-SECANTS, CO-SINES, CO-TAN-
GENTS. These are the secants, sines,
and tangents, of arcs which are the com-
plements of those in question. See Trigo-
nometry.

CO'SMICAL (koo-juop, the universe).
A term opposed to acronychal, and, as
such, denotes the rising or setting of a
star in the morning at the moment of
sunrise. The cosmical and acronychal
risings of a star are invisible to the naked
eye, because the light of the sun in the
horizon effaces that of the star. See
Heliacal.

COSMO'GRAPHY {kov/jlo?, the uni-
verse, ypd<p(d, to describe). A description
of the system of the universe; a term
differing from Geography, as a whole dif-
fers from its part. The term should be
distinguished from cosmogony {yovrj, ge-
neration), which relates to the origin and
creation of the world ; and from cosmo-
logy (\070p, account), which treats of the
metaphysical philosophy of the constitu-
tion of the world.

CO'TTON {kutun, Arab.). The hairy
covering of the seeds of several species
of Gossypium. The cotton-plant must
not be confounded with the cotton-tree
{Bombax), the cotton of which cannot be '
manufactured.

COTYLE'DON (koti/\m<5wi/, a cavity).
The seed-lobe of a plant. Plants have
been distinguished, with reference to the
number of their cotyledons, into di-
cotyledonous, or those which have two

CRA

CRI

cotyledons in their seeds; mono-cotyle-
donous, or those which have only one;
and a-cotyledonous, or those which have
none.

COUCH. The heap of moist barley,
about 16 inches deep, on the malt-floor.

COU'MARIN. A neutral substance,
extracted from the tonka bean, the fruit
of the Coumarouna odorata, and the
flowers of the melitot.

COU'NTERPOINT (contra punctum,
point against point). A term in Music,
synonymous with harmony, and derived
from the old method of placing the stem-
less points, or notes, against or over one
another, in compositions of two or more
parts.

COURONNE DE TASSES. Lite-
rally, a crown or circle of cups. An ap-
paratus employed in voltaic electricity,
consisting of a circle of cups containing
salt water, and connected together by
compound metallic arcs of copper and
zinc.

COU'ZERANITE. A mineral found
in limestone, in the deep defiles of Sa-
leix called des Couzerans.

CRA'CIDJE (crax, a curassow). The
Curassows ; a group of the Rasores, or
Scratching birds, the legs of which are
unarmed with spurs, and the hind toe
so much developed, as to give them con-
siderable power in perching.

CRAG. A provincial term in Norfolk
and Suffolk for certain tertiary deposits
usually composed of sand with shells,
belonging to the older pliocene period.

CRANIO'SCOPY (upaviov, the skull,
cKoireu), to investigate). An investiga-
tion of the skull. Dr. Prichard has cha-
racterized the primitive forms of the
skull according to the width of the
bregma, or space between the parietal
bones: hence —

1. The steno-bregmate (o-rei/o?, narrow),
or ^Ethiopian variety.

2. The meso-bregmate (necros, middle),
or Caucasian variety.

3. The platy-bregmate (ttAcutup, broad),
or Mongolian variety.

CRANK. A mechanical contrivance
for converting a revolving into an alter-
nate motion.

CRASS ULA'CE^. The House-leek
tribe of Dicotyledonous plants, named
from the gertus crassula. Succulent herbs
or shrubs, with showy flowers usually in
cymes, sepals from 3 to 20, petals distinct
or cohering, stamens inserted with the
petals, fruit of several follicles, opening
on their face.
93

CRA'TER (crater, a large cup or bowl).
The circular cavity at the summit of a
volcano, from which the volcanic matters
are ejected. Besides the craters of erup-
tion, more extensive craters are supposed
to have been formed by the elevation of
the ground previous to volcanic erup-
tions, and are therefore called craters of
elevation.

CRATER (in Astronomy). The Cup,
a southern constellation consisting of
thirty-one stars.

CREMOCA'RPIUM (Kpe/xau, to sus-
pend, Kap7r6r, fruit). In Botany, a com-
pound fruit, 2-5-celled, inferior ; cells
1-seeded, indehiscent, dry, perfectly close
at all times ; when ripe, separating and
hanging from a common axis. Mirbel
restricts the term to the fruit of Ura-
belliferae. See Polakenium.

CRENA'TED (crena, a notch or slit).
A term applied to shells, which present
small indentations, generally of a sharp
and regular form, frequently observed on
the outer lip of spiral shells, particularly
on many of the typical mitres. A leaf is
said to be crenelled, when its margin has
rounded toothings or teeth.

CRE'OSOTE (xpeas, flesh, cobfr, to
preserve). Kreasote. An oily, colour-
less, transparent liquid, discovered first
in pyroligneous acid, and subsequently
in the different kinds of tar. Its name
is derived from its preventing the putre-
faction of meat or fish, when dipped in it.

CREPITATION (crepito, to crackle).
The crackling noise occasioned by press-
ing cellular membrane which contains
air ; also the sound emitted by certain
salts during calcination.

C REP U'SCULARI A (crepusculum, the
twilight). The twilight-moths, or Hawk-
moths ; a tribe of Lepidopterous insects,
corresponding with the Linnaean genus
Sphinx, and named from their general
habit of flying only in twilight.

CRETA'CEOUS SYSTEM (creta,
chalk). A geological series of rocks, in
which calcareous matter forms the pre-
dominating mass, to which the flints and
other extraneous minerals are subordi-
nate. Part of it seems to have been de-
posited in a sea of considerable depth,
and all of it is marine. In a general sense,
it is distinguished into the Green Sand
and the Chalk Formations.

CRFCHTONITE. A mineral found
associated with anatase, and on rock
crystal, in Dauphiny.

CRINOI'DEA (uptvov, a lily, eldos,
like). A term applied to a tribe of

CRU

CRY

Echino-dermatous animals which resem-
ble lilies, of which the fossils called stone-
lilies and encrinites are examples. The
fossil remains called trochi and St. Cuth-
bert's beads are separated portions of the
earthy framework of encrinites.

CRITICAL PHILOSOPHY. A term
sometimes applied to the metaphysical
system of Kant from his famous work
entitled "Criticism of Pure Reason."

CROCO'NIC ACID (crocus, saffron).
An acid derived from carbonic oxide, and
named from the saffron colour of its
salts, called croconates.

CROCUS (/cpoKo?). Saffron. An old
term applied to oxides and other prepa-
rations of the metals, from their saffron
colour: thus we have crocus marlis, or
oxide of iron ; crocus metallorum, or
oxide of antimony ; crocus Veneris, or
oxide of copper.

CROP, or CRAW. A sort of prelimi-
nary stomach in some birds, formed by
an expansion of the oesophagus. Com-
pare Gizzard.

CROP OUT. A technical term, to
denote the rising up, or exposure at the
surface, of a stratum or series of strata.

CROSS-STONE. Harmotone, or py-
ramidal zeolite, found in mineral veins
and agate balls.

CROTA'LIDjE (crotalus, a rattle-
snake). A family of Ophidian reptiles,
including the Rattlesnakes and the
Vipers, and all the venomous species.
They are distinguished from the Colu-
beridae principally by the character of the
teeth.

CROTCHET. In Music, a character
constituting the fourth part of a semi-
breve ; its duration, in slow time, is
about one second.

CROTO'NIC ACID. Iatrophic acid.
A solid, volatile, and highly poisonous
acid derived from croton oil, the fat oil
of the seeds of Croton tiglium.

CRU'CIATE (crux, crucis, a cross). A
designation of the corolla of cruciferous
plants, from the resemblance of the
arrangement of the petals to the pieces
of a Maltese cross.

CRU'CIBLE. An earthern vessel in
which substances are exposed to high
temperatures. The term is derived either
from crux, a cross, which the alchemists
stamped upon the vessel ; or from crucio,
to torture, because the metals were tor-
tured in crucibles, in order to convert
them into gold.

CRUCI'FERiE (crux, crucis, a cross,
fero, to bear). The Cruciferous tribe of
94

Dicotyledonous plants. Herbaceous plants
with leaves alternate ; flowers polype-
talous ; sepals 4, deciduous, cruciate,
alternating with 4 cruciate petals ; sta-
mens 6, hypogynous, tetradynamous ;
fruit a siliqua or a silicula.

CRUST OF THE EARTH. The super-
ficial parts of our planet which are acces-
sible to observation.

CRUSTA. A term applied to the brittle
crustaceous thallus of lichens; to the
bony covering of the crab, the lobster, &c.

CRUSTA'CEA (crusta, a shell). A
class of articulated animals with an ex-
terior shell which is generally hard and
calcareous, and is cast off periodically, as
in the crab, the shrimp, the lobster, &c.

CRUX. The Cross; a southern con-
stellation, situated close to the hinder
legs and under the body of Centaurus.

CRY'OLITE (kPvos, frost, \i6os, a
stone). A mineral consisting of the
double hydrorluate of alumina and soda,
occurring in gneiss. The term is derived
from the property which this mineral
presents of fusing readily in the flame of
a candle.

CRYO'PHORUS (>cpuop, cold, 0epa>, to
bring). An instrument for exhibiting the
degree of cold produced by evaporation.
The term denotes frost-bearer, and it is
well illustrated by the Cryophorus of
Wollaston, which consists of two hollow
glass balls connected by a bent glass
tube, one of them containing water ; the
cold is transferred from one ball to the
other.

CRY'PTA (Kpvmos, concealed). Glan-
dules impresses. A term applied to the
vesicular receptacles of oil found in the
leaves of the orange and of all myrta-
ceous plants.

CRYPTOBRANCHIA'TA (kpi/ttto?,
concealed, /?p«7x<n, gills). A designa-
tion of those molluscous and articulate
animals, which have no conspicuous
gills.

CRYPTOGA'MIA (kPvht6<:, concealed,
ydfxos, nuptials). A class of plants, in-
cluding ferns, mosses, sea-weeds, &c., in
which the fructification, or organs of re-
production, are concealed. These are
also called agamous, acotyledonous, and
cellular plants. See Phanerogamia.

CRYPTO'GRAPHY (Kpvmos, secret,
7pci0oj, to write). The art of writing in
a secret manner, as in cypher. See
Cypher.

CRYPTONEU'RA (kputttop, concealed,
vevpov, a nerve). A term applied by Ru-
dolph! to those radiate animals in which

CRY

CUB

no nervous filaments or masses have been
discovered. They correspond with the
Acrita of Macleay, and the Protozoa and
Oozoa of other writers.

CRY'STAL (Kpi'/<rTa\\o5, ice). A solid
body of a limited symmetrical form, in-
cluded by plane surfaces. In organized
bodies spherical forms predominate, whilst
unorganized bodies are mostly angular.
Quartz, being often found in a crystalline
form, and being transparent like ice, was
called rock-crystal ; and hence all other
minerals of regular forms are called
crystals, whether they be clear or opaque.

1. The structure of a crystal is the
arrangement of its component parts, and
this is ascertained by splitting it in the
direction of its planes of cleavage ; the
crystal is thus obtained in its primitive
form, and, when this differs from the
figure at first presented by the body, the
latter is called the secondary form.

2. Primitive Forms. By the term
"primitive form," Haiiy designates the
nucleus of crystals ; " secondary forms"
are varieties which differ from the primi-
tive form. The primitive forms of crys-
tals are the tetrahedron, the parallelopi-
pedon, the octohedron, the hexagonal
prism, the rhombic dodecahedron, and
the dodecahedron with triangular faces.
To the parallelopipedon belong the cube
and the rhombohedron.

3. The angles at which the edges of
the planes or faces of a crystal meet, are
called plane angles ; and the point formed
by the union of three or more of these, a
solid angle. The lines which join these
points, and pass through the middle of
the crystal, are called its axes ; there are
usually three of these, a principal axis,
and two secondary or subordinate axes.

4. In the Wernerian language of crys-
tallization, the following terms are em-
ployed : — When a secondary form differs
from the cube, the octohedron, &c, only
in having several of its angles or edges
replaced by a face, this change of the
geometrical form is called a truncation.
The alteration in the principal form pro-
duced by two new faces inclined to one
another, and which replace, by a kind of
bevel, an angle or an edge, is called a
bevelment. When these new faces are to
the number of three or more, they pro-
duce what Werner termed a pointing or
acumination. When two faces unite by
an edge in the manner of a roof, they
have been called culmination. The term
replacement is occasionally used for bevel-
ment.

95

CRYSTAL ELECTRICITY. A term
sometimes applied to thermo-electric polar
tension, from its being displayed princi-
pally in crystallized substances, especially
in those which belong to the mineral
kingdom. The crystals which exhibit
this property are termed thermo-electric
crystals, as tourmaline.

CRYSTALLINE LENS. A thick com-
pact humour, in form of a flattish convex
lens, situated in the middle of the eye,
and causing that refraction of the rays of
light which is necessary to make them
meet in the retina, and form an image
thereon, whereby vision is performed.

CRYSTALLIZATION (KpvaraWos, a
crystal). The process by which the par-
ticles of liquid or gaseous bodies form
themselves into crystals, or solid bodies
of a regularly limited form.

Crystallization, Alternate. This term
is applied to a phenomenon which takes
place when several crystallizable sub-
stances, having little attraction for each
other, are present in the same solution.
That which is largest in quantity and
least soluble crystallizes first, in part;
the least soluble substance next in quan-
tity then begins to separate ; and thu3
different substances, as salts, are often
deposited in successive layers from the
same solution.

CRYSTALLOGRAPHY {KpixnaWos,
a crystal, ypaQw, to describe). The science
which investigates the relation of crys-
talline forms, and the origin and struc-
ture of crystals.

CTE'NOBRANCHIA'TA (/cretc, a
comb, /3pa7x«a> gills). A term synony-
mous with Pectinibranchiata, applied to
an order of Gasteropods which breathe
by means of pectinated gills.

CTENOI'DES (KTeif, a comb, eldos,
likeness). An order of fishes, furnished
with scales composed of layers with pec-
tinated or toothed posterior margins.

CU'BATURE. The measurement of
the contents of a solid body, or the find-
ing a cube equal to it.

CUBE (nv/3ov, a cube). A geometrical
solid, contained by six equal squares. It
is the measuring unit of solid content, as
the square is that of superficial extent,
or area.

CUBE ORE. Hexahedral Olivenite,
or Wurfelerz ; a green mineral, which
occurs crystallized in a perfect cube,
in Cornish mines, accompanied with
iron-shot quartz. It is an arseniate of
iron.
CUBIC EQUATION. An equation

CUM

CUR

which involves the cube, or third power
of the unknown quantity. Like equations
of any other degree, cubic equations are
either pure or adjected.

CUCULI'D^E [cuculus, a cuckoo). The
Cuckoo tribe ; a family of the Scansores,
or Climbing birds, characterized by the
short and slender structure of the feet,
and by their migratory habits. Mac-
gillivr'ay places them next to the goat-
suckers, from the great similarity of their
digestive organs. They are little capable
of walking, and belong to a group, of
which the habit is to perch on trees or
shrubs, whence they glide after passing
insects.

CUCU'LINjE. A family of bees which,
having no femoral plates for transporting
pollen, resort to the combs of other bees
in order to deposit their eggs— a habit
resembling that of the cuculus, or cuckoo.
CUCU'LLATE (cucullus, a hood).
Hooded ; having the apex and sides
curved inward, as the upper sepal of
aconite.

CUCURBIT A'CEjE ( cucurbita, a
gourd). The Gourd tribe of Dicotyle-
donous plants. Climbing plants with
leaves palmated, succulent ; flowers uni-
sexual, monopetalous ; stamens cohering
in three parcels ; ovarium inferior ; fruit
fleshy ; seeds flat ; testa coriaceous.

CUDBEAR. A neutral colouring mat-
ter, prepared from the Leconora tartar ea
and other lichens, and named from Sir
Cuthbert Gordon. The Germans call it
persio.

CULFCIDjE (culex, a gnat). The
Gnat tribe ; a family of Dipterous in-
sects, belonging to the section Nemocera,
distinguished by their beautifully tufted
antennae.

CULM. The peculiar stem of grasses,
sedges, &c. Also, a provincial synonym
of anthracite.

CULMINATION (culmen, the top of
any thing). The transit or passage of a
star over the meridian, or the point of its
highest altitude.

CU'MBRIAN GROUP. A group of
rocks constituting the lower series of the
Clay-slate system, upwards of 3000 feet
in thickness, and comprising the horn-
blendic clay-slate, chiastolite-slate, and
clay-slate.

CUMULO'STRATUS. The twain-
cloud; a composite modification of clouds,
known by its generally flat base, with a
superstructure resembling a bulky cumu-
lus overhanging the base in large fleecy
protuberances, or rising into the forms
96

of rocks and mountains. The Latin term
is derived from the frequent grouping of
considerable cumuli, or masses, upon a
common stratum, or base; the English
term, from the frequently visible coales-
cence of two other modifications, viz. the
cirrus and the cumulus. This cloud
may always be regarded as a stage to-
wards the production of rain or snow,
and, in this case, it always ends in the
nimbus.

CU'MULUS (Lat. aheap). The stacken-
cloud ; a primary form of clouds, known
by its irregular hemispherical or heaped
superstructure, and usually flattened
base. It is formed by the gathering
together of detached clouds, which then
appear stacked into one large and ele-
vated mass. It may be called the cloud
of day, as it usually exists only during
that period.

CUMY'L. The compound radical of a
series of compounds procured from the
seeds of the Cuminum Cyminum.

CU'NEIFORM(cwwews, a wedge, /orma,
likeness). Cuneate. Wedge-shaped ; in-
versely triangular, with rounded angles ;
a shape characteristic of certain bivalves,
analogous to the clavate form among uni-
valves.

Cuneiform Letters. A term applied
to the inscriptions found on old Baby-
lonian and Persian monuments, from
the characters being formed like a
wedge.

CUPEL (kuppel, German). A small
flat cwp-like crucible, made of bone ash,
used in the assays of the precious metals,
which are fused on a cupel with lead.

CUPELLA'TION. The process of pu-
rifying gold and silver by melting them
with lead, which becomes first oxidated,
then vitrified, and sinks into the cupel,
carrying along with it all the baser
metals, and leaving the gold or silver
upon its surface.

CU'PULA. A form of involucrum,
occurring in the oak, the beech, the
hazel ; and consisting of bracts not much
developed till after flowering, when they
cohere by their bases, and form a kind
of cup.

CUPULI'FERjE {cupula, a small cup).
The Oak tribe of Dicotyledonous plants.
Trees or shrubs with leaves alternate ;
flowers amentaceous, dioecious, apetalous;
ovarium inferior, inclosed in a cupule ;
fruit a horny or coriaceous nut.

CURCUMA PAPER. Paper stained
with a decoction of turmeric, and em-
ployed by chemists as a test of free alkali,

CUR

CUR

by the action of which it receives a brown
stain.

CU'RCUMINE. The colouring matter
of turmeric, obtained in a state of purity
by separating it from its combination
with oxide of lead.

CURD. The coagulum which sepa-
rates from milk, upon the addition of
acid, rennet, or wine.

CURRENTS, ATMOSPHERIC. Dis-
turbances of the atmospheric mass from
regular or accidental causes. 1. Regular
or periodical currents are the trade-winds,
monsoons, sea and land breezes, which
are caused by the rotatory motion of the
globe being greater than that of the air,
by the combined attraction of the sun
and moon producing tides in the atmo-
sphere, &c. 2. Irregular currents are
ordinary winds, produced by variations
of temperature or of electrical distribu-
tion, and have frequently a circular or
rotatory motion.

CURRENTS OF THE SEA. Certain
motions of the sea, which are independent
of the tides, and named drift- currents
and stream-currents.

1. Drift-currents are motions produced
on the surface of the sea by the perpetual
or the prevailing winds. Thus, in the
Atlantic Ocean, a drift-current occurs
between the tropics, where it is produced
by the trade-wind; other drift-currents
occur to the north and the south of 30°,
where they are ascribed to the effects of
the prevalent winds.

2. Stream-currents are motions pro-
duced to a great depth, perhaps to the
bottom, of the sea ; their causes are con-
sequently unknown. Amongst these
may be noticed the equatorial current,
running from the coast of Africa to that
of South America; and the gulf-stream,
flowing from North America to the shores
of Europe.

CURRENTS, SUBTERRANEAN.
Subterranean currents of water, sup-
posed to be the cause of the formation of
caverns in limestone districts by gra-
dually wearing away the rock in the
course of fissures.

CURSO'RES (cursus, a course). Cours-
ers ; an order of birds, so named from
their remarkable velocity in running.
They were included by Cuvier in the
Grallatoreg, or Waders, probably on ac-
count of the length of their legs. They
comprise the ostrich, the cassowary, the
emu, the apterix, and the dodo. These
birds exhibit the nearest approach to
the Mammalia. [Under

97

Under the term Cur sores, Walcknaer
arranges those spiders which make no
webs, but catch their prey by swift
pursuit.

CURSO'RIA {cursus, a course). A
family of Orthopterous insects, the legs
of which are all alike, and adapted for
running. They include the ear-wig, the
cockroach, and the mantis. See Sana-
toria.

CU'RTATE (curtatus, shortened). A
term sometimes applied, in Geometry or
Astronomy, to a line projected ortho-
graphically upon a plane.

Curtate Distance, in Astronomy, de-
notes a planet's distance from the sun,
reduced to the plane of the ecliptic.

CURVE {curvus, bent). A term ap-
plied to a line of which no portion, how-
ever small, is straight. A crooked line
may be either a curved line, or the junc-
tion of two or more straight lines drawn
in different directions. The principal
curves are the circle, the ellipse, the
parabola, the hyperbola, and the cycloid.

1. Curve, Algebraic and Transcendental.
1. Algebraic curves are those in which
the relation between the abscissa and the
ordinate is expressed by an algebraic
equation. 2. Transcendental curves are
those in which the relation between x
and y is not expressed by an algebraic,
but by a differential equation ; that is, by
an equation between dx and dp.

2. Curve, Evolute and Involute of. If
a thread, having one of its ends fixed, be
wound round a curve, this primary curve
is called the evolute. If the thread, thus
tightly applied upon the convexity of the
curve, be then unwound, it will describe
a secondary curve at the back of the
former, termed the involute. It will be
seen that the thread, at every point of
unwinding, is a tangent to the evolute.

3. Curve, Equation of. An algebraic
expression, pointing out the relation be-
tween the ordinate and the abscissa. In
every conic section, these two lines are at
right angles to each other ; and at what-
ever point of the axis (in the same sort
of curve) the ordinate may be drawn,
these two lines will always have the same
relation to each other.

4. Curves of Double Curvature. Curves
traced on surfaces which are not plane : a
double curvature thus arises, viz. that
belonging to the line itself, and that of
the surface on which it is traced.

5. Curve Surfaces. A curve surface
is represented algebraically by an equa-
tion containing three variables, as x, yt

F

CYC

CYC

and z. It is geometrical when its equation
is algebraic, and expressed in finite terms ;
and mechanical, when the equation is
not algebraic, but differential.

CUS P (cuspis, a point). In Geometry,
the point where two parts of a curve
meet and terminate. In Astronomy it
denotes the tip or horn of the crescent
of the moon. In an eclipse of the sun,
the borders of the sun and moon make
two cusps at their point of intersection.

CU'SPIDATE {cuspis, a spear). Spear-
shaped; tapering to a stiff point; ab-
ruptly acuminate; a term applied to
leaves.

CUTICLE (dim. of cutis, skin). In
Botany, a thin homogeneous membrane,
external to the epidermis, formed of or-
ganic mucus, and overlying every part
of plants, except the stomates and the
stigmatic tissue.

CY'ANIC ACID. A volatile, corrosive
acid, procured from cyanogen, existing
only in combination. It is converted
spontaneously into a white solid matter
called cyamelide.

CY'ANITE (nvavos, blue). Disthene.
A mineral occurring in the granite and
mica- slate of primitive mountains, and
used in India as an inferior kind of sap-
phire. Its principal colour is Berlin-
blue, which passes into grey and green.

CY'ANO- (Kvavov, blue). A Greek
term, denoting a clear bright blue colour.

CYAN'OGEN {nvavos, blue, yewda, to
generate; so called from its being an
essential ingredient in Prussian blue).
Bi-carburet of nitrogen ; a gas. It forms,
with oxygen, the cyanic, cyanous, and
fulminic acids; and with hydrogen, the
hydro-cyanic, or prussic. All its com-
pounds, which are not acid, are termed
cyanides or cyanurets.

CYANO'METER {nvavo?, blue, fxerpov,
a measure). An instrument invented by
Saussure, for comparing the different
shades of blue in order to determine the
deepness of the tint of the atmosphere.

CY'ATHIFORM (cyathus, a drinking-
cup, forma, likeness). Cup-shaped; as
applied to the form of certain corollas.

CYCADA'CEjE. A family of Gymno-
spermous plants, named from the genus
cycas, and consisting of trees, with a
cylindrical trunk, increasing by a single
terminal bud.

CYCLE {kukXov, a circle). A certain
period of time, in which the same revolu-
tions begin again ; a periodical space of
time.

1. Cycle of the Sun. A revolution of

twenty-eight years, at the expiration of
which the days of the months return
again to the same days of the week; the
sun's place to the same signs and degrees
of the ecliptic on the same months and
days, so as not to differ one day in 100
years ; and the same order of Leap-years
and of Dominical Letters returns ; hence
it is also called the Cycle of the Sunday
Letter.

2. Cycle of the Moon. A revolution of
nineteen years, after which the various
aspects of the moon are, within an hour,
the same as they were on the same days
of the month nineteen years before. This
cycle was adopted on the 16th of July,
b.c. 433, by Meton, whose name it also
bears.

3. Cycle, Paschal. The cycle of the
Sun consists of twenty-eight, and the
cycle of the Moon of nineteen years;
these cycles, multiplied by each other,
form a third, which is called the Paschal
Cycle, because it serves to ascertain when
Easter occurs. At the end of a revolu-
tion of 532 years, the two Cycles of the
Moon, the Regulars, the Keys of the
Moveable Feasts, the Cycle of the Sun,
the Concurrents, the Dominical Letters,
the Paschal Term, Easter, the Epacts,
with the New Moons, recommence as
they were 532 years before, and continue
the same number of years.

4. Cycle, Ecliptical. An unknown pe-
riod of time during which the angle be-
tween the ecliptic and the equator, con-
stituting the obliquity of the ecliptic, has
completed all its changes. The present
rate of diminution of the obliquity is
estimated at about 48 seconds of a degree
every century.

CY'CLICA (ki5k\oc, a circle). A section
of Coleopterous insects, with bodies of
a rounded or oval form. According to
Latreille, they constitute a subsection of
the section Tetramera.

CY'CLIN^E. A sub-family of the
Tellinidae, or Solid and Closed Bivalves,
named from the genus cyclas ; these
animals are generally fluviatile, and have
their shells covered by an epidermis.

CY'CLOBRANCHIA'TA {kvk\o*, a
circle, /3pa7x*a, gills). An order of Gas-
teropods, in which the branchia form a
fringe around the body of the animal,
between the edge of the body and the
foot. The order consists principally of
the limpets.

CYCLO-GANGLIATA (riicXo?, a cir-
cle, fayyXiov, a nerve-knot). A term
applied by Dr. Grant to the fourth sub-

CYL

C YP

kingdom of animals, or Mollusca, com-
prising animals distinguished by the
high development of the cerebral ganglia,
and their circular distribution around the
oesophagus. These are the Heterogan-
gliata of Owen .

CYCLO-NEURA {kvk\os, a circle, vev-
pov, a nerve). A term applied by Dr.
Grant to the first sub-kingdom of ani-
mals, or Radiata, as expressive not only
of the common circular form of the
nervous axis in this division, but also of
its rudimental state of simple filaments.

CY'CLOID (kvkXo?, a circle, eidor,
likeness). A geometrical transcendental
curve, described by a point in the circum-
ference of a circle, which rolls along a
plane until it has completed a revolu-
tion. Thus the nail on the felly of a
wheel moves in a cycloid, as the carriage
goes along, and as the wheel itself both
turns round its axle and is carried along
the ground.

When the tracing point is placed with-
out the circle, the curve has its base
shortened, and is called the curtate or
contracted cycloid. If the point is within
the circumference, the curve is called
the prolate or inflected cycloid.

CYCLO'SIS {kvkXo?, a circle). A cir-
cular movement of the globular particles
of the sap, as observed in the cells of
Chara and Nitella, and in the jointed
hairs projecting from the cuticle of
several other plants. A similar motion
has been recently found by Mr. Lister to
exist in a great number of Polypiferous
Zoophytes.

CYCLO'STOMI (KwcXor, a circle, <rr6-
fia, a mouth). An order of Chondropte-
rygious or Cartilaginous Fishes, having a
round fleshy lip, by which they adhere to
their prey, obtaining their food by suction,
as in the lamprey. The lip is supported
by a cartilaginous ring, formed by the
union of the jaw-bones. In fishes of this
order the vertebrated structure is found
in Us lowest form.

CYGNUS. The Swan ; a northern con-
stellation containing eighty-one stars, the
principal of which is Dereb Adige.

CY'LINDER {Kvhtvdpos, a cylinder).
A geometrical solid, with a circular base,
described by the revolution of a right-
angled parallelogram about one of its
sides, which remains fixed. It is a cir-
cular prism, as a cone is a circular pyra-
mid. The axis of a cylinder is the fixed
straight line about which the parallelo-
gram revolves. When the base is ellip-
tical, the solid is a cylindroid ; when the
99

sides are perpendicular to the base, it is
aright cylinder or cylindroid; in other
cases it is an oblique cylinder.

CYLINDRE'NCHYMA (kuXiv3Poc, a
cylinder, ejxvH<*i infusion). A designa-
tion given by Morren to the cylindrical
variety of the parenchyma of plants.

CYM'BIFORM (cymba, a boat, forma,
likeness). Navicular, or boat-shaped, as
applied to the glumes of certain grasses,
and synonymous with carinate.

CYME. A form of inflorescence re-
sembling an umbel and a corymb, but
with a centrifugal expansion, indicated
by the presence of a solitary flower in
the axis of the dichotomous ramifications.

CY'MOPHANE. The designation
given by Haiiy to chrysoberyl.

CY'MOSE. Resembling a cyme,, as
applied to inflorescences and leafy
branches.

CYNARA'CEiE. A division of the
Compositce, named from the genus cy-
nara, and comprising plants charac-
terized by intense bitterness, which de-
pends upon the mixture of extractive
with a gum which is sometimes yielded
in great abundance.

CYNA'RRHODON. In Botany, an
aggregate fruit, consisting of distinct
ovaries ; the pericarps are hard, inde-
hiscent, enclosed within the fleshy tube
of a calyx, as in rose, calycanthus, &c.
The term is a Greek compound for dog-rose.
CYNI'PIDjE (cynips, the gall-fly).
The Gall-flies ; a family of the entomo-
phagous Terebrantia, which, by means
of their ovipositor, form tumors on plants,
commonly termed galls, nut-galls, or gall
apples.

CYPERA'CE^E. The Sedge tribe of
Monocotyledonous plants, named from
the genus cyperus. These plants re-
semble grasses in appearance, but have a
solid and angular stem, without a dia-
phragm at the articulations ; the flowers
grow in the axil of a single bract ; and the
cotyledonar extremity of the embryo is
enclosed within the albumen. See Gra-
minacecs.

CYPHE'LLjE (icv<pe\\a, the hollows of
the ears). Pale tubercle-like spots on the
under surface of the thallus of lichens, as
in sticta.

CY'PHER or CIPHER. In common
language, to cypher is to calculate ; and
to write in cyphers is to write in secret or
unknown characters, such as were the
Arabic numerals when first introduced
into Europe.

CYPRiE'IDiE. The Cowries or Por-
F2

DAM

DAT

celain shells ; a family of carnivorous
Gasteropods, named from the typical ge-
nus cyprcea ; the shells are without any
spire, the last whorl enveloping all the
others, as in the bullas.

CYPRI'NIDjE (cyprinus, the carp).
The Carp tribe; a family of Malaco-
pterygious or soft-spined fresh-water
fishes, having the ventral fins placed be-
neath the abdomen.

C Y'PS EL A (Kvyj/e\ti, any hollow vessel).
In Botany, the compound fruit of the
Compositae. It is one-celled, one-seeded,
indehiscent, with the integuments of the
seed not cohering with the endocarp ; in
the ovarial state evincing its compound
nature by the presence of two or more
stigmata ; but nevertheless unilocular,
and having but one ovulum.

CY'PSELIN^E (cypselus, a swift).
Cypseline Birds, or Swifts ; a group of
Macgillivray's Volitatrices or Gliders,
remarkable for the extreme rapidity of
their flight and unwearied activity.

CYSTIBRA'NCHIANS (tfrrit, a blad-
der, /?pct7x<a, gills). A family of Isopo-

dous Crustaceans, comprising those
which have the branchiae lodged in vesi-
cular cavities.

CY'STICA {km™, a bladder). Cyst-
worms or hydatids ; an order of Entozoa,
which have one or more buccal orifices
leading into a terminal cyst.

CYSTFDIUM (dim. of avari?, a blad-
der). In Botany, a term employed by
Link as synonymous with utricle. By
the term cystidia are denoted the pro-
jecting cells, or supposed male organs of
agarics, &c.

CY'STULA or CISTELLA. A round
closed apothecium in lichens, filled with
sporules adhering to filaments arranged
round a common centre, as in sphaero-
phoron. The term is also applied to the
little open cups on the upper surface of
the fronds in marchantia.

CYTOBLAST (kvtov, a cavity, /3\a-
ardvoi, to sprout). A nucleus observed in
the centre of some of the bladders of the
cellular tissue of plants, and regarded
by Schleiden as a universal elementary
organ.

D

DACTYLO'LOGY (ddnTi/Xof, a finger,
Ao-yor, an account). The art of spelling
words by placing the fingers in such
positions as to signify the letters of the
alphabet. Dactylology is to alphabetic
writing what this is to speech.

DAGUERRE'OTYPE. A process by
which all images produced by the camera
obscura are retained and fixed in a few
minutes upon surfaces of silver, by the
action of light. The name is derived
from Daguerre, the inventor.

D'ALEMBERT'S PRINCIPLE. A
principle in Mechanics, which may be
thus stated: — "If several non-elastic
bodies have a tendency to motion, with
velocities, and in directions which they
are constrained to change, in consequence
of their reciprocal action on each other,
then these motions may be considered as
composed of two others ; one, which the
bodies actually take ; and the other such,
that, had the bodies been acted on by
such alone, they would have remained in
equilibrium."

DAMPS. The permanently elastic
fluids which are extricated in mines.
These are choke damp, or carbonic acid ;
100

and fire damp, consisting almost solely
of light carburetted hydrogen, exploding
on contact with a light.

DAOU'RITE. Rubellite. A variety
of red schorl found in Siberia, mixed
with white quartz.

DASY'METER (3a<w, dense, nerpov,
a measure). A measurer of density; an
instrument employed for testing the
density of the air. It is used for this
purpose instead of a barometer, and is
sometimes called a manometer.

DA'TA. Things given. A term used
in Geometry to denote certain things
or quantities, which are either actually
exhibited, or can be found out; that is,
which are either known by hypothesis, or
can be demonstrated to be known.

DA'THOLITE. A mineral found in
Norway, containing boracic acid, silica,
and lime. See Botryolite.

DATIVE CASE (dativus, from do, to
give). The giving case of nouns, known
by the signs to and for, and serving to
denote the remoter object to which the
action of the subject is directed; for
which, to the benefit or loss of which,
something is done.

DEC

DEC

DA'VITE. A fibrous sulphate of alu-
mina, found in a warm spring near Bo-
gota in Columbia.

DAY. In common language, the in-
terval of time which elapses between the
rising and the setting of the sun ; this is
called an artificial day.

1. The civil day begins at twelve
o'clock at midnight, and lasts till the
same hour of the following night. It is
counted in two portions of twelve hours
each, viz. from midnight to noon, and
from noon to the succeeding midnight.

2. The astronomical or solar day begins
at noon, and is counted up to twenty-four
hours, terminating at the succeeding
noon. This mode of reckoning the day
is employed in the Nautical Almanac,
and may lead to mistakes with persons
not familiar with this mode of computa-
tion. Thus, January 10, fifteen hours, in
astronomical time, is January 11, three
in the morning, civil time.

3. The sidereal day is the time which
elapses between that of a star being in
the meridian of a place to the moment
when it arrives at the meridian again.
This period is always the same, not being
affected by the motion of the earth in her
orbit, as the solar day is. The sidereal
day is about four minutes less than the
mean solar day.

DEBA'CLE (debacler, to unbar, to
break up as a river after a long frost).
A great rush of waters which, breaking
down all opposing barriers, carries for-
ward the broken fragments of rocks, and
spreads them in its course.

DE'CAGON (3<?/«x, ten, yavia, an
angle). A geometrical figure, having ten
sides and consequently ten angles. If
the sides and angles are all equal, the
figure is a regular decagon, and may be
inscribed in a circle.

DECAGY'NIA (deva, ten, ywrj, a wo-
man). The designation of those orders
of plants in the Linnaean system, which
are characterized by the presence of ten
pistils.

DECA'NDRIA (5<?<ca, ten, iv^p, a
man). The tenth class of plants in the
Linnaean system, characterized by the
presence of ten stamens.

DECANTA'TION. The act of pour-
ing off clear fluid from sediment, or from
suspended impurities,— a method some-
times adopted to avoid the use of filters,
which might be destroyed by an acid or
alkaline solution.

DECATODA (3e«a, ten, ttou?, ttoSop, a
foot). The highest order of the Crus-
101

tacea, which have ten ambulatory feet,
the cephalic, thoracic, and pro-abdominal
segments united, and the branchiae con-
cealed under the sides of the carapace, as
seen in the astacus fluviatilis.

DECA'RBONIZA'TION. The process
of depriving a body of its carbon ; as em-
ployed, artificially, for converting cast
iron into malleable iron ; and, in nature,
in removing the superfluous carbon of
the seed in the function of germination.

DECI'DUOUS {decido, to fall off).
Falling off; a term applied to any thing
which falls off in a certain stage of
growth, as the terminal whorls of the
pupaform land-shells, the petals and se-
pals of certain flowers, &c. The term is
synonymous with caducous, and opposed
to persistent, which denotes permanence.

DE'CIMAL (decimus, the tenth). A
fraction whose denominator is 10, or
some power of 10, as 100, 1000, &c. In-
stead, however, of writing the denomi-
nator under the numerator, as in vulgar
fractions, it is expressed by pointing off,
from the right of the numerator, as many
figures as there are cyphers in the deno-
minator ; thus, *2, "23, '127, signify
respectively & t&, TooV

DECLE'NSION {declino, to deflect).
In Grammar, the deriving of the cases
of nouns from one another ; the changes
of termination corresponding to the vari-
ous relations in which the subject is con-
ceived to stand.

DE'CLINATE (declino, to bend down-
wards). Bent downwards ; as applied to
the stamens of plants when they all bend
to one side, as in amaryllis.

DECLINATION (declino, to bend).
The distance from the equator of the
parallel described by a star ; it is counted
from 0 up to 90 degrees, and is austral
or southern, boreal or northern, in refer-
ence to the equator. Declination on the
celestial globe corresponds with latitude
on the terrestrial; and the parallels of
declination are similar to the parallels of
latitude.

1. Declination circles are small circles
of the sphere, parallel to the equator, in
which the stars perform their apparent
diurnal revolution.

2. Declination of the magnetic needle
is the angle which the horizontal needle
makes with the geographical meridian of
any given place.

DECOLLATED (decollo, to behead).
A term applied to those univalve shells
in which the apex or head is worn off in
the progress of growth.

F3

DED

DEF

DECOMPOSITION. The resolution
of a body into its component parts, either
spontaneously or by chemical agency.

DE'COMPOUND. A term applied, in
Botany, to those ramifications of plants
which are variously compounded, as to
leaves in which the petiole bears second-
ary petioles. When the secondary petioles
are divided into a third set, such leaves
are said to be supradecompound.

DE'CREMENT {decrementum, a de-
crease). A term used in Crystallography
to denote a deficiency of successive layers
of molecules in a crystal, when this de-
ficiency takes place in any regular order.
This decrement is measured by the edges
of the defect or part wanting to complete
the simple or primary form ; and the re-
lation which these edges bear to the cor-
responding edges of the primary form, is
called the law of the decrement. This is
invariably found to be a simple numerical
ratio, rarely exceeding the number six.
The planes resulting from these decre-
ments are called secondary planes, and
the forms bounded by secondary planes
are secondary forms.

Decrements in breadth are those in
■which each lamina has only the height
of a molecule, so that their whole effect,
by one, two, three, &c, courses, is in the
■way of breadth. Decrements in height
are those in which each lamina, exceed-
ing only the following one by a single
course in the direction of the breadth,
may have a height double, triple, quadru-
ple, &c, of that of a molecule: this is
expressed by saying, that the decrement
takes place by two courses, three courses,
&c. in height.

DECREPITATION (decrepo, to crac-
kle, as a candle, when almost entirely
burnt). The crackling noise which oc-
curs when certain salts part with their
water of crystallization, on the applica-
tion of heat, and fall in pieces.

DECUMBENT {decumbo, to lie down).
Lying prostrate, but rising from the
earth at the upper extremity, as applied
to the directions taken by plants.

DECU'RRENT (decurro, to run down)
Decursive. Running down ; a term ap-
plied, in Botany, to leaves which are pro-
longed down the stem, giving it a winged
appearance.

DECUSSATION (decusso, to cross like
an X). A term applied to parts which
cross each other, as leaves on a stem,
when arranged in pairs which alter-
nately cross each other.

DEDUCTIVE REASONING. The
102

process of scientific inquiry by which we
pursue laws into their remote conse-
quences, as distinguished from inductive
reasoning, by which we arrive at laws or
axioms by an accumulation of facts.

DE'FERENT CIRCLE (defero, to
carry away). In the Ptolemaic system,
a circle or orbit on which the centre of
another circle or orbit is carried round.
Thus, the earth's orbit is a deferent on
which the moon's orbit is carried. See
Epicycle.

DE'FINITE TERM. In Logic, a term
which defines, or marks out, a particular
class of beings, or a single person, as
distinguished from an indefinite term,
which does not define or mark out an
object. Thus, all animals are rational,
or not-rational ; the former is a definite,
the latter an indefinite term. Definite
terms are positive, indefinite terms are
privative or negative.

DEFINITION. A metaphorical term,
literally signifying the "laying down a
boundary," and employed, in Logic, to
denote " an expression which explains
any term, so as to separate it from every
thing else," as a boundary separates
fields.

A definition is called nominal, when it
merely explains the meaning of the term ;
real, when it explains the nature of the
thing ; essential, when it assigns the con-
stituent parts of the essence or nature ;
accidental, when it assigns the properties
and accidents of the essence ; physical,
when it lays down the real parts of the
essence which are actually separable ;
metaphysical or logical, when it lays down
the ideal parts of it, which cannot be
separated except in the mind.

DEFLAGRATION [defiagro, to be
utterly consumed by fire). The oxidation
of metals by mixing them with nitrate or
chlorate of potash, and projecting the
mixture into a red-hot crucible.

1. Deflagrating Mixtures. These are
generally made with nitre, the oxygen of
which is the active ingredient in pro-
moting their combustion.

2. Deflagrator. The name given by
Dr. Hare to a very effective battery, in
which the plates were so connected to-
gether as to admit of the whole being
immersed into the exciting liquid, or
removed from it, at the same instant.

DEFLE'CTION (defiecto, to bend off).
The distance by which a curve departs
from another curve or from a straight
line; or any effect of curvature or of
discontinuous change of direction ; also,

DEL

DEN

the bending of a ray of light from its
rectilinear course towards an opaque body
in its immediate neighbourhood. See
Diffraction.

DEGLUBITRI'CES {deglubo, to pull
off the skin or rind). Huskers ; the name
given by Macgillivray to an order of birds
which remove the shell or husk of seeds
in their bill, before swallowing them.
They are all easily recognized by their
stout conical bill, and include all our
small finch-like birds. Most of them have
a modulated song, which is, however,
much inferior to that of the Cantatrices.

DEGRADING CAUSES. A term ap-
plied, in Geology, to those causes which
refer to the dissolving and wearing away
of the elevated parts of the earth's sur-
face, and the carrying of these parts
down into lower levels. These causes
are meteoric, connected with the atmo-
sphere ; fluviatile, depending on rivers ;
and oceanic, in which the ocean is the
immediate agent.

DEGREE, MINUTE, SECOND. The
circumference of every circle, whatever
be its actual dimensions, is usually con-
sidered as consisting of 360° (degrees),
each of which is divided into 60' (minutes),
each of these again into 60" (seconds), and
so on to thirds ("'), and fourths (""), and
fifths, if necessary, each term being a six-
tieth of its predecessor. By some writers
the decimal system is preferred.

DEGREE, IN ALGEBRA. The de-
gree of an algebraical term is the number
of letters which enter into it as factors ;
thus x2y3 is absolutely of the fifth de-
gree, but of the second degree with re-
gard to x, and of the third degree with
regard to y. The degree of an equation
is the power of its highest term ; if the
index of this term be 4, the equation is
said to be of the fourth degree.

DEHISCENCE (dehisco, to gape). A
term applied, in Botany, to the sponta-
neous separation of the valves of the
fruits of certain plants, for the discharge
of the seeds ; and, in Zoology, to the
splitting open of the bag which contains
the eggs.

DEINOTHE'RIUM (deivov Bnplov, a
terrible beast). A fossil genus of gigantic
pachydermata, characterized by the down-
ward projection of enormous tusks from
the loweir jaw.

DE'LIAN PROBLEM. A celebrated
problem, proposed by the oracle at Delos,
and known to geometers as the duplica-
tion of the cube.

DELIQUESCENCE {deliquesce, to
103

melt away). The property of certain
salts of becoming liquid by their attract-
ing moisture from the atmosphere. In
Botany, a panicle is said to be deli-
quescent, when it is so much branched
that the primary axis disappears— seem-
ing, as it were, to melt away.

DELPHI'NIDiE (delphinus, a dol-
phin). The Dolphin tribe ; a family of
the cetaceous Vertebrata, distinguished
from the Balaenidae, or Whale tribe, by
the relative size of the head and body :
in the former, the head is not out of the
usual proportion ; in the latter, it is im-
moderately large.

DELPHI'NUS. The Dolphin ; one of
the old Greek constellations, consisting
of eighteen stars, and succeeding Aquila
in the heavens.

DE'LTA (3e\ra, the Greek letter A).
A term applied to the alluvial land
formed by a river at its mouth, when it
divides, before entering the sea, into
separate and diverging streams. The
term was first applied in the case of the
Nile, from the resemblance of the alluvial
land to the form of the Greek letter A,
the sea forming the base of the triangle ;
but geologists employ the term in analo-
gous cases, without reference to the pre-
cise shape.

DE'LTOID (deXroeidii?, delta-shaped,
triangular). Shaped like the Greek letter
A ; a term applied to a solid, the trans-
verse section of which has a triangular
outline.

DEMONSTRATION (demonstro, to
point out). In the old writers, this term
signified no more than the pointing out
the connexion between a conclusion and
its premises, or that of a phenomenon
with its asserted cause. It now denotes
a necessary consequence, and is synony-
mous with proof.

DEMOTIC WRITING (dnnoriMs, of
the people). A mode of writing in com-
mon use among the Egyptians, approach-
ing very nearly to the Chinese method.
It is also termed the epistolographic and
the enchorial style.

DE'NEB. An Arabic term for tail,
generally applied to the bright star (/3) in
the tail of Leo.

DENOMINATOR. An arithmetical
term, employed in fractions, to denote
the number of parts into which the unit,
or integer, is divided. The other part of
the fraction, or the numerator, denotes
how many of these parts are taken to
make up the given fraction.

DE'NSITY (densitas, closeness). A
F4

DEP

DES

term relating to the compactness of
bodies, and denoting the comparative
quantity of matter, in different bodies,
which is contained under a certain bulk.
As gravity is understood to act in propor-
tion to the relative quantity of the matter
of bodies, their specific gravities are pre-
sumed to be the measure of their densi-
ties. See Rarity.

DENTIRO'STRES {dens, a tooth,
rostrum, a beak). A group of the In-
sessores, or Perching birds, in which the
horny covering of the upper mandible is
notched or toothed towards the point, as
in the shrikes, the thrushes, the warblers,
the chatterers, and the fly-catchers.

DENUDATION {denudo, to make
bare). The carrying away, by the action
of running water, of a portion of the
solid materials of the land, by which in-
ferior rocks are laid bare.

DEONTO'LOGY (8eov, what is due,
X670?, an account). The science of duty ;
a term applied by the followers of Ben-
tham to their system of ethics.

DEOXIDA'TION. The separation of
oxygen from a body ; the reducing a body
from the state of an oxide.

DEPA'RTURE. A nautical term, de-
noting the number of miles which a ship
has sailed east or west; but more spe-
cifically defined to be " the sum of all the
successive elementary meridian distances,
when the nautical distance is assumed to
be divided into an indefinite number of
equal parts." See Nautical Distance.

DEPHLEGMA'TION. The chemical
process of concentration, by depriving
a body of water. By phlegma is meant
a watery distilled liquor, as distinguished
from a spirituous liquor.

DEPHLOGI'STICATED. That which
is deprived of its phlogiston; in modern
language, that which is oxidized. The
term is derived from the old theory of
combustion, in reference to which, oxy-
gen gas was called dephlogisticated air;
and chlorine, dephlogisticated marine
acid. See Phlogiston.

DEPRESSION, ANGLE OF. The
angle by which a line drawn from the
eye to any object dips below the horizon.

DEPRESSION, IN ALGEBRA. The
reduction of an equation to a lower de-
gree, by dividing both sides of it by a
common measure.

DEPRESSION OF THE HORIZON.
Dip of the horizon. In Nautical Astro-
nomy, the depression or dipping of the
visible horizon below the true horizontal
plane, owing to the eye of the observer
104

being placed above the level of the sur-
face of the sea.

DERBYSHIRE SPAR. Fluor-spar,
technically called blue- John ; fluate of
lime, or a combination of calcareous earth
with fluoric acid, found abundantly in
Derbyshire.

DEREB ADIGE. A star of the first
magnitude in the northern constellation
Cygnus.

DERIVATION, LAW OF. In finding
the successive differential co-efficients
of a power of x, the law is, to get the
next differential co-efficient, multiply the
last by its exponent, and reduce the ex-
ponent by a unit.

DERIVATIVE WORDS. In Gram-
mar, these are words either compounded
of two significant words in the language,
or of one significant word and a termina-
tion which modifies its meaning, as
schoolmaster, scholar. They are distin-
guished from primitive words, which have
no derivation in the language, as school.

DERMA'PTERA (depfxa, skin, Trre-
p6v, a wing). Ear-wigs; an order of
insects, having their anterior pair of
wings coriaceous, not employed in flight ;
the posterior membranous, only partially
covered by the elytra.

DERME'STIDiE (dermestes, from dep-
jua, skin, €<T0ioi, to eat). Skin-eaters ; a
family of Coleopterous insects, of the sec-
tion Necrophaga of Macleay, named from
the genus dermestes, which is well known
for its ravages on the preserved skins of
animals.

DE'RMOBRANCHIA'TA (depfta,
skin, /3p<i7X'a> gills)- A family of Gaste-
ropods, named from the genus dermato-
branchus, and comprising those mollusks,
which respire by means of external bran-
chiae or gills, having the form of mem-
branous plates, filaments, or tufts.

DE'RMOSKE'LETON (d<?PMa, skin,
aae\erov, skeleton). The hard integu-
ment which covers most invertebrate,
and some vertebrate animals.

DERO'SNE'S SALT. A crystalline
substance, obtained by treating opium
with ether, and also termed narcotine
and opiane. „

DESCENDING NODE. That point
of a planet's orbit, where it cuts the eclip-
tic, proceeding southward, marked £S.

DESCRIPTION. In Logic, an acci-
dental definition, or that which assigns
the circumstances belonging to the
essence, viz. properties and accidents.
See Definition.

DESPUMA'TION {despumo, to scum).

DEW

DI A

Literally, the throwing off of froth or
scum, and generally, the clarifying of a
fluid, or the separating its foul parts.

DESQUAMATION {desquamo, to scale
fishes, to bark trees). The falling off of
the cuticle, in the form of squamce or
scales.

DETER'MINATE PROBLEM. A
problem which admits of one solution
only, or of a limited number of solutions ;
as distinguished from an indeterminate
problem, which admits of an indefinite
number of solutions.

DETONATION (detono, to thunder
mightily). Instantaneous ignition, ac-
companied by a loud noise and a violently
disruptive force, owing to the sudden
expansion of gas.

DETRITUS {de, from, tero, to rub).
Matter worn or rubbed off from rocks,
consisting of blocks of various sizes,
gravel, sand, and clay.

DEUTO- (ikt/T€po9, second). A prefix
denoting two, or double, as rfew^-oxide,
having two degrees of oxidation ; deuto-
chloride, &c.

DEUTOXIDE (3euTepo?, second). A
term applied to a substance which is in
the second degree of oxidation. This term
is often used to denote a compound of
3 atoms of oxygen with 2 of metal, as in
deutoxide of manganese, of lead, &c.

DEVELOPMENT. In Algebra, the
process by which any mathematical ex-
pression is changed into another of equi-
valent value or meaning, and of more
expanded form.

DEVONIAN SYSTEM. A geological
system, comprising the old red sandstone,
and forming the material of the grand
and rugged mountains which fringe many
parts of our Highland coasts, and range,
on the south flank of the Grampians,
from the eastern to the western sea of
Scotland. These formations, in Devon-
shire and Cornwall, abound in shells and
corals, and present a structure which
brings them into a mineralogical com-
parison with our older slate rocks.

DEW. The moisture insensibly de-
posited from the atmosphere on the sur-
face of the earth. It occurs whenever
that surface is lower in temperature than
that of the dew-point of the atmosphere
immediately in contact with it.

DEW-POINT. That temperature of
the atmosphere at which its moisture be-
gins to be precipitated. By some, it is
called the point of saturation ; by Daniell,
the degree of " the constituent tempera-
ture of atmospheric vapour."
105

DEXIA'RLE. A family of Dipterous
insects of the section Creophilae, named
from the genus dexia, and subsisting
chiefly on the juices of flowers.

DEXTRAL {dexter, the right hand).
On the right hand, as applied to the
mouth or aperture of the great majority
of spiral shells-, when the mouth is on
the left, it is said to be sinistral or re-
versed. No generic distinctions can,
however, be founded on this character.

DEXTRIN {dexter, the right hand).
Mucilaginous starch, prepared by boil-
ing a solution of starch with a few drops
of sulphuric acid. Its name is derived
from its property of turning the plane of
the polarization of light to the right
hand.

DIA {did). A Greek preposition, de-
noting through. Words compounded
with 6ia imply extension, perversion,
transition ; also that which in English
and Latin is expressed by the prefixes
di- or dis-, as in divido, to divide ; dis-
jungo, to disjoin.

DIACAU'STIC {6ta, through, Kavart-
Kor, burning). A term applied to those
caustic curves, which are formed by re-
fraction, as distinguished from the cata-
caustic curve, which is formed by reflec-
tion. See Caustic curve.

DIACOU'STICS {dtanova, to hear
through). That branch of physics which
treats of the properties of sound refracted
in passing through media of different
densities.

DIACRITIC MARKS {dtcmptTiKos, fit
to distinguish). Marks employed, in
Palaeography, to distinguish letters which
are similar in form ; thus, in the German
running hand, the letter u is distin-
guished by the superposition of the mark
" from the letter n.

DIADE'LPHIA {6k, twice, u6e\<p6?,
a brother). The seventeenth class of
plants in the system of Linnaeus, cha-
racterized by the union of the filaments
into two parcels, or brotherhoods. See
Adelphia.

DIURESIS {diatpeu, to divide). A
division ; a grammatical figure, denoting
the division of one syllable into two, as
siliice for silvce.

DIAGO'METER, ELECTRICAL {6id-
yw, to conduct, fserpov, a measure). An
apparatus used by Rousseau for ascer-
taining the conducting power of oil, as
a means of defecting its adulteration. It
consists of one of Zamboni's dry piles,
and a feebly-magnetized needle, moving
freely on a pivot. The deviation of the
F5

DI A

DI A

needle is less in proportion to the low
conducting power of the interposed sub-
stance.

DIA'GONAL (dia, through, ytavia, an
angle). A right line drawn across a
quadrilateral figure, from one angle to
another; by some called the diameter
of the figure.

DI'AGRAM {bidypawxa, a figure or
plan). A mathematical figure of any
kind, drawn for the purpose of illustra-
tion.

DIAKE'NIUM. The term by which
Richard designates the fruit of the Urn-
belliferae, from its consisting of two ake-
nia. See Achcenium.

DIAL, or SUN-DIAL. An instrument
for determining the hour of the day by
the shadow of a point or line upon a
graduated surface.

DI'ALECT (diaAeKTor, discourse). The
language of a country, especially that of
a particular district; any variety of a
common language.

DIALECTICS (dtaXe/cTiKor, skilled in
argument). In Aristotle, this term de-
notes the logic of probabilities, as op-
posed to strict philosophical argument.
Plato employed it as synonymous with
metaphysics, or the highest philosophy.
The term simply means " the art of con-
versation," but is now generally applied
to the practical part of logic.

DIA'LLAGE' (dtaXXcryq, difference).
A variety of augite, generally of a bronze
yellow colour, possessing the most perfect
cleavage in the direction of the diagonal
of the prism, its natural joints and frac-
tures exhibiting a very different lustre
and appearance.

Diallage Rock, or Euphotide. An orna-
mental stone, consisting of felspar and
diallage, in crystals aggregated together
in the manner of granite. The diallage
in the rock is called gabbro.

DIALU'RIC ACID {8ia, through,
olpovy urine). A new acid produced, in
combination with ammonia, by the de-
composition of alloxan tin.

DIA'METER {dianerpea, to measure
through). A straight line passing through
the centre of a circle, and terminating
at both ends in the circumference.

Diameter, transverse and conjugate.
These terms are applied to the two un-
equal diameters of an ellipse, the former
to the longer, the latter to the shorter,
diameter. They are also termed the
greater and the lesser axis. These lines
are at right angles to each other. Any
other line which passes through the cen-
106

tre of an ellipse, and terminates in opp o-
site points of its circumference, is also
said to be a diameter.

DIAMOND. A brilliant gem, consist-
ing of carbon in its highest state of
purity. Rose-diamonds are usually cut
out of the octohedral crystals ; brilliants,
from those with curvilinear faces.

DIA'NDRIA (die, twice, uvtjp, a man ).
The second class of plants in the system
of Linnaeus, characterized by the presence
of two stamens.

DIAPA'SON (S«i iraawv, through all).
In Music, the interval of the octave ; the
compass of an instrument or of the
voice, a term signifying the same as con-
cert-pitch.

DIA'PHANOUS {dia, through, 0a/vw,
to show). That quality of a substance
which renders it permeable to light.
Translucent is a more common term of
the same import. Transparent expresses
more than translucent, implying not
merely the admission of light through
the substance, but the vision of external
objects. The terms semi-translucent and
semi-transparent denote feebler degrees
of these qualities.

DIAPHO'NICS (dta, through, <p<avi],
sound). The doctrine of refracted sound.
DI'ASPORE (diaanopa, dispersion).
A rare mineral, which crackles by the
heat of a candle, and is dispersed in mi-
nute fragments.

DI'ASTASE (3ta'crra(7i9, separation).
A vegetable principle, allied in its general
properties to gluten, which appears in the
germination of barley and of the seed of
plants, and converts their starch into
gum and sugar for the nutrition of the
embryo. The name is derived from its
property of separating two supposed con-
stituents of starch.

DIATHE'RMANOUS (diaBepfxaiva, to
warm through). A Greek term syno-
nymous with the Latin transcalent, and
denoting the free permeability of a sub-
stance by heat.

Diathermancy. The property possessed
by nearly all diathermanous bodies, of
admitting the passage only of certain spe-
cies of calorific rays. When the quan-
tity of heat transmitted independently of
the quality is to be denoted, the term
diathermaneity has been suggested by
Melloni, in order to preserve the same
termination as in the word diaphaneity,
indicating the analogous property in re-
lation to light.

DIATO'NIC SCALE (dia. through,
tokos', a tone). A scale of music, con-

DIC

DIF

sisting of seven intervals, viz. five tones
and two semitones.

DIBO'THRIANS (3ic, twice, j366piov,
a pit). A division of tape-worms, includ-
ing those bothriocephallans which have
only two fossae or pits on the head.

DIBRA'NCHIA'TA (6ir, twice, fady
Xta, gills). An order of Cephalopods, in
which the branchiae are two in number,
one situated on each side of the body. It
embraces all the ordinary genera, and is
subdivided into two tribes, viz. the deca-
pods, which have the eight ordinary arms
and the two longer tentacula, and the
octopods, in which the tentacula are ab-
sent. See Tetrabranchiata.

DFCERATES (dif, twice, Kt?pa?, a
horn). A family of Gasteropods which
have two tentacula on the head, in De
Blainville's arrangement. The diceras
was applied by Lamarck to a fossil genus
of bivalves.

DICHO'TOMOUS (3«Xa, doubly, Te>a>,
to divide). A term applied to stems or
branches which bifurcate, or are con-
tinually divided into pairs. Hence, to
dichotomize, is to cut into two equal and
similar parts.

DI'CHROISM (3ip, twice, xpoijiia, co-
lour). In Optics, the property by which
a crystallized body assumes two distinct
colours according to the direction in
which light is transmitted through them.

DI'CHROITE. A mineral consisting of
a silicate of alumina and magnesia.

DICLE'SIUM (3tK\ip, folding two
ways). In Botany, a collective fruit,
consisting of a pericarp indehiscent, one-
seeded, enclosed within an indurated
perianth, as in mirabilis.

DI'COTYLE'DONS(dic, twice, kotvM-
dwv, a seed-lobe). A grand division of
the vegetable kingdom, comprising all
those plants in which the embryo con-
tains two cotyledons or seed-lobes. The
dicotyledonous embryo coincides with the
exogenous development of wood, and,
hence, Dicotyledons and Exogens are con-
vertible terms.

DICTUM DE OMNI ET NULLO.
A principle established by Aristotle as
the basis of his logical system, viz. "that
whatever is predicated (i. e. affirmed or
denied) universally of any class of
things, maybe predicated, in like manner
(viz. affirmed or denied), of any thing
comprehended in that class."

DICTYO'PTERA (SUtvov, a net, me-
pov, a wing). An order of insects, com-
prising the cock-roaches, in which the
wings are four in number when they
107

exist; but they are generally of equal
size, and never folded.

DIDA'CTYLE (5i?, twice, baKrvXov, a
finger or toe). Two-fingered, or two-
toed ; as applied to various animals which
have two digits on their extremities.

DI'DYM (3/au/io?, twin). The name of
a metal recently discovered united with
oxide of cerium, and so called from its
being, as it were, the /wi»-brother of
lantanium, which was previously found
in the same body.

DIDYNA'MIA (3i?, twice, bvvayn^,
power). The fourteenth class of plants
in the system of Linnaeus, characterized
by the presence of four stamens, of which
two are long, two short. This condition
occurs in the natural order Labiatae.

DIELE'CTRIC. A body which has
the power of transmitting the electric
influences through itself, — a property
observed in the most perfect non-con-
ductors of electricity, whether solid,
liquid, or aeriform. See Induction.

DIERESFLIS {diaipeats, separation).
A general term applied by Mirbel to
those fruits which spontaneously sepa-
rate into several cocci, when ripe, as in
the mallow. The term is almost syn-
onymous with carcerule.

DI'FFERENCE. DIFFERENTIA.
In Logic, the formal or distinguishing part
of the essence of a species ; in common
discourse, it is the characteristic ; when
necessarily applicable, it is a property;
when contingently, an accident.

DIFFERENTIAL CALCULUS. The
term differential, in the higher Mathe-
matics, denotes a quantity infinitely
small, or less than any assignable magni-
tude. The object of the differential cal-
culus is to find the ratios of the differ-
ences of variable magnitudes, on the
supposition that these differences be-
come infinitely small. It agrees with
fluxions in every respect excepting its
notation and the manner of its expla-
nation.

DIFFERENTIAL COEFFICIENT.
In analysis, the ratio of the differential
of any function of a variable quantity to
the differential of the variable.

DIFFRA'CTION OF LIGHT {dif-
fringo, to break in pieces). Inflexion of
light. The turning of light from a recti-
linear course by the interposition of an
opaque body.

DIFFUSION OF HEAT. A term
expressive of the modes by which the
equilibrium of heat is effected, viz. by con-
duction, by radiation, and by convection.
F6

DIG

DICE

DIFFUSION VOLUME. A term
adopted to express the different dispo-
sition of gases to interchange particles ;
the diffusion-volume of air being 1, that
of hydrogen gas is 3*83.

Diffusion Tube. An instrument for
determining the rate of diffusion for dif-
ferent gases. It is simply a graduated
tube, closed at one end by plaster of
Paris, a substance, when moderately dry,
possessed of the requisite porosity. The
diffusion of gases, as thus conducted,
closely corresponds with the endosmosis
of liquids, which occurs under similar
circumstances.

DIGA'MMA. Double gamma. In some
parts of Greece, the old Greek 7 was a
kind of aspirate, called, from the way
of writing it (f), digamma. This aspi-
rate was carried by the Pelasgian race
into Italy, and remained in Latin as a
real consonant V, vau. It supplies the
data for resolving those cases of metrical
difficulty, where the lengthening of a
short syllable uniformly takes place be-
fore particular words.

DIGE'STER. A strong vessel of cop-
per or iron, with an air-tight lid, for
preventing the loss of heat by evapo-
ration.

DIGE'STION {digero, from diversim
gero, to carry into different parts). In
Physiology, the change of the food into
chyme, and the absorption and distribu-
tion of the more nutritious parts, or the
chyle, through the system. In Chemistry,
the continued action of a solvent upon
any substance.

DIGESTIVE SALT. A salt discovered
by Sylvius, since named muriate of
potash, and now chloride of potassium.

DI'GIT {digitus, a finger). An old
measure of a finger's breadth. In Astro-
nomy, it denotes the twelfth part of the
diameter of the sun or moon, and is used
to express the quantity of an eclipse:
thus the moon is said to be six digits
eclipsed, when half of her face is covered
by the earth's shadow. In Arithmetic,
a digit is any symbol of number from
0to9.

DI'GIT ATE {digitus, a finger). A term
applied to that kind of expansion, in
which the parts are spread out into
finger-shaped processes, as in the outer
lip of the scorpion strombi.

DIGITI'GRADA {digitus, a toe, gra-
dior, to walk). A division of the terres-
trial Carnivorous animals, which walk
upon their toes, and bound along with
considerable elasticity and swiftness, as
10b

the weasel, the civet, the hyena, and the
cat tribes. See Plantigrada.

DIGY'NIA (5ir, twice, yvvt], a woman).
The name of those orders of plants
in the system of Linnaeus, which are
characterized by the presence of two
pistils.

DILE'MMA {6i\t]nfxa, a double pro-
position ; from dk, twice, and \afi-
y8d»/a), to take). In Logic, a complex kind
of conditional syllogism, having more
than one antecedent in the major pre-
miss, and a disjunctive minor. In other
words, it is a complex conditional reasont
ing, in which either one of the antece-
dents must be admitted, or one of the
consequents must be denied.

The expression, horns of a dilemma,
relates to the taking hold of both ways :
if a person is not caught by the one
antecedent or consequent, he must be
caught by the other.

DILU'VIUM {diluo, to wash away).
Accumulations of gravel and loose mate-
rials, which are said to have been pro-
duced by the action of a diluvian wave
or deluge sweeping over the surface of
the earth.

DIME'NSION. In Algebra, a term
synonymous with degree ; thus x2y is of
three dimensions, or of the third degree.
In Geometry, length is of one dimension,
surface of two, solidity of three; hence,
geometry of three dimensions is another
term for solid geometry.

DI'MERA (<J«p, twice, /xepo?, apart).
A section of Homopterous insects, in
which the tarsi are two-jointed, as in the
Aphidae.

DIMO'RPHOUS (3ir, twice, fxoP<prj,
form). A term applied to some natural
and to some artificial productions, which
occur in two distinct forms. For ex-
ample : arragonite and carbonate of lime
are chemically the same, though belong-
ing to different primary forms ; and the
crystals of sulphate of nickel, if de-
posited from an acid solution, are square
prisms; but if from a neutral solution,
they are right rhombic prisms. This
property of assuming two incompatible
forms, is called dimorphism.

DIMYA'RIA (5i?, twice, /uv?, a mus-
cle). A general name for those bivalves
whose shells are closed by two ad-
ductor muscles distinct and widely re-
moved from each other, as in the mussel.
See Monomyaria.

DIOS'CIA (3i?, twice, o'luot, a house).
The twenty-second class of plants in
Linnaeus's system, in which the stamens

DIP

DIP

and pistils are in separate flowers, and on
separate plants.

DIOPHA'NTINE PROBLEMS. A
species of problems, in which it is re-
quired to solve certain questions, the an-
swers to which shall be whole numbers
only. They are found in a treatise on
Algebra by Diophantus, an Alexandrian
Greek, who lived in the second or third
century of the present era. In character
they closely resemble the Hindoo Algebra.

DIO'PSIDE (3<oV'«r, a view through).
A mineral which may be considered as
the type of the augite genus. Several
varieties, differing little from the above,
are called baikalite and fassaite, names
indicative of their locality.

DIO'PTASE. Emerald copper ore; a
crystallized silicate of copper, found in
Siberia and the Bannat.

DIO'PTRICS {dioirrpa, an optical in-
strument). That branch of the science
of Optics, which treats of the refraction
of light, when it passes through different
media, as air, water, glass, &c. The phe-
nomena are generally referred to the sub-
ject of refraction.

DIO'SMEjE. The Buchu tribe of
Dicotyledonous plants. Trees and shrubs
with leaves exstipulate, dotted ; flowers
axillary or terminal, polypetalous, her-
maphrodite; stamens hypogynous; ova-
rium many-celled ; fruit consisting of
several concrete capsules ; seeds twin or
solitary.

DIO'XIDE. According to the electro-
chemical theory, the elements of a com-
pound may, in relation to each other, be
considered oppositely electric; the equi-
valents of the negative element may then
be distinguished by Latin numerals, those
of the positive by Greek ; thus a bin-
oxide denotes a compound which con-
tains two equivalents of the negative
element oxygen ; whereas a rfi-oxide in-
dicates that one equivalent of oxygen is
combined with two of some positive body.
And so of 6i-chloride, di-chloride, &c.

DIP. When a geological stratum does
not lie horizontally, but is inclhud, it is
said to dip towards some point of the
compass, and the angle it makes with
the horizon is called the angle of dip or
inclination.

DIP OF MAGNETIC NEEDLE. The
angle which the magnetic needle, when
poised so as to move freely in a vertical
direction, makes with the plane of the
horizon. It is more scientifically termed
the inclination of the needle, or the mag-
netic inclination.
109

DIP OF SEA HORIZON. The ap-
parent angular depression of the visible
horizon, caused by the position of the
observer above the surface of the sea.

DI'PHYDA (dip, twice, <pv<a, to grow).
A group of the Acalephce, named from
the genus diphyes, in which each animal
seems to consist of two portions so
slightly joined together, that it is diffi-
cult to understand their connexion.

DFPLOE' (dinXon, a joining). A term
applied by Link to the parenchymatous
substance of the leaf, which lies imme-
diately beneath the two surfaces. See
Mesophyllum.

DI'PLO-GANGLIA'TA (dtw\owt dou-
ble, yay/Xiov, a nerve-knot). A desig-
nation of the Entomoida, or articulate
animals, which have *' their nervous
columns arranged in the same relative
position as the diplo-neura, with the gan-
glia increased in size, and corresponding
with the increased development of the
segments and of their lateral appen-
dages."— Grant.

DI'PLO-NEURA {dnrXovs, double,
vevpov, a nerve). A designation of the
Helminthoida, comprising the various
forms of Worms, in which the nervous
columns have their ganglionic enlarge-
ments very slightly developed, and are
marked by a greater lateral separation
from each other along the median line,
than is observed in the next sub-king-
dom."— Grant.

DIPLO'PTERA (dtvXofc, double, tttc-
pov, a wing). A group of aculeate hy-
menopterous insects, which have their
upper wings folded longitudinally, when
at rest, as in some species of wasp.

DIPLOTE'GIA {dinkoZs, double, re-
709, a covering). In Botany, a compound
fruit, differing from the capsule only in
being adherent to the calyx. It occurs
in campanula.

DIPNEUMO'NEjE (3ip, twice, 7rve6-
fivv, a lung). A section of spiders which
have only two pulmonary sacs.

DIP PEL'S OIL. An animal oil pro-
cured by the destructive distillation of
animal matter, especially of albuminous
and gelatinous substances.

DI'PTERA (3ip, twice, mepbv, a
wing). An order of insects which have
only one pair of wings fully developed,
and these are on the mesothorax. Instead
of posterior wings, there are pedunculated
appendages, called halteres or poisers.
The mouth contains a soft proboscis, of
which the common house-fly affords a
familiar instance. See Rhipiptera.

DIS

DIS

DIPTEROCA'RPEjE. The Camphor-
tree tribe of Dicotyledonous plants. Trees
abounding in resinous juice ; leaves alter-
nate; flowers polypetalous; stamens hy-
pogynous ; carpella concrete ; calyx tu-
bular ; fruit coriaceous.

DI'PTEROUS (<3Jc, twice, mepov, a
wing). Two-winged; a term applied to
certain seeds which have their margins
prolonged in the form of wings.

DIPTERY'GIANS (dit, twice, nrepi-
ftov, a fin). A family of fishes comprising
those which have only two fins.

DIPY'RE (6U, twice, irvp, fire). Leuco-
lite. A silicate of alumina and lime, found
in the western Pyrenees. This mineral
derives its name from its twofold sus-
ceptibility to the action of fire: when
heated before the blowpipe, it first be-
comes phosphorescent, and then fuses.

DIRECT AND RETROGRADE. As-
tronomical terms expressive of the direc-
tion in which the heavenly bodies move.
The direct course is from west to east ;
the retrograde, from east to west. These
motions are otherwise indicated, the
former by the term in consequential the
latter by in antecedentia.

DIRECTION, NUMBER OF. The
number of days after the 22nd of March,
including both days, upon which Easter
Sunday takes place.

DIRECTIVE FORCE. A term em-
ployed in Magnetism to denote the ten-
dency in one magnet to assume a par-
ticular position with relation to another
magnet.

DIRE'CTRIX. Linea directrix. A
term applied, in Conic Sections, to a line
drawn at right angles to the axis of a
parabola, when produced to a certain
point ; and this point is equally distant
from the vertex as the focus of the curve.

DISC {blano?, discus, a dish, or quoit).
The face of a circular plate ; a term ap-
plied to the apparently plane surface of
the heavenly bodies, from the resem-
blance of this surface to a flat round
dish. The discus of the ancients was a
circular piece of wood, stone, or metal,
used in their games.

DISCHARGER. An instrument for
discharging a jar or battery of its elec-
tricity. It consists of two bent metallic
rods, each of them terminating at one
end in a brass knob, and connected at
the other end by a joint, which is fixed
to a glass handle.

DISCO'BOLI (dtV/cop, a disk, /3d\\<o,
to throw). A family of Malacopterygious
or soft-spined fishes, in which the ventral
110

fins are formed into a disk or sucker, by
which the fish is enabled to attach itself
to rocks and other hard substances.

DI'SCOID (dtanoeidv, quoit-shaped).
Circular or disk-shaped, and much flat-
tened, as the fresh-water genus planor-
bis, and many land-shells.

DISCORD. Dissonance. In Music, a
dissonant and inharmonious combination
of sounds, unless treated according to
the rules of art.

DISCOURSE. Discursus. In Logic,
an operation of the mind commonly called
reasoning, or the act of proceeding from
one judgment, to another founded upon
that one, or the result of it.

DISCOVERY OF TRUTH. There
are two modes of discovering truth.
1. The one is by Information, and it
relates to matters of fact previously
unknown, but communicated by observa-
tion and testimony, independent of all
a priori reasoning. 2. The other is by
Instruction, and it relates to truths which
may be elicited by reasoning, and are
therefore implied in what we already
know, independent of observation or
testimony. The historian informs, the
mathematician and the moralist instruct.

DISCRETE PROPORTION (discre-
tus, separated). An arithmetical propor-
tion, in which the ratio of the antece-
dents to the consequents is different from
the ratio of the consequent of the first
pair of terms to the antecedent of the
second, as in 2 \ 3 .* : 4 ; 6. On the
other hand, a continual proportion is
that in which the ratio of every contiguous
pair of terms is the same throughout, as

in 2 : 4 : : 8 : i6.

DISCRETE QUANTITY (discretus,
separated). A quantity of which the
component parts have a separate and dis-
tinct existence : numbers, for instance,
are discrete quantities, being composed
of separate units.

DISJUNCTIVE. A logical term ap-
plied to a proposition which consists of
two or more categoricals, so stated as to
imply that some one of them must be
true ; e. g., either A is B, or C is D. A
syllogism is said to be disjunctive, the
reasoning of which turns on such a pro-
position.

DISK. A term applied, in Botany, to
certain bodies or projections, situated be-
tween the base of the stamens and the
base of the ovary, forming part with
neither. It is often incorrectly called
nectary.

DISPERSION OF LIGHT. The di

DIS

DI V

vision of a ray of white light into its vari-
ously coloured component rays, as seen
upon the spectrum, after it has under-
gone refraction by transmission through
a prism.

DISSE'PIMENT {dissepio, to sepa-
rate). Septum. A term applied, in Bo-
tany, to the partition which divides a
capsule into cells.

DISTANCES, LAW OF. A curious
law observed by Professor Bode, of Ber-
lin— that the intervals between the planet-
ary orbits go on doubling as we recede
from the sun, or nearly so. This law was
interrupted between Mars and Jupiter,
but the deficiency was afterwards strangely
supplied by the discovery of four new
planets in that very interval, revolving
in orbits tolerably well corresponding
with the law in question.

DISTHENE. Cyanite. A very hard
crystallized mineral, consisting of sub-
silicate of alumina.

DI'STICHOUS (air, twice, <rT<'x°r» a
row). Arranged in two rows, as the
florets of many grasses ; a term synony-
mous with bifarious.

DISTILLATION (distillo, to drop by
little and little). The vaporization and
subsequent condensation of liquids, by
means of a retort, alembic, or still. Dry
distillation is performed in the same
way as the humid, except that the sub-
stance is neither immersed nor dissolved
in any menstruum. It is termed sub-
limation.

Distillation, Destructive. The process
of exposing organized substances, or
their products, to distillation, until the
whole has undergone the entire effects of
the furnace.

DI'STOMA (alp, twice, cro/ia, the
mouth). Intestinal worms with two
pores,

DISTRA'CTILE (distraho, to draw
apart). In Botany, a connective which
separates into two unequal portions, the
one supporting an anther, the other with-
out an anther, as in salvia.

DISTRIBUTED. An epithet applied,
in Logic, to a term which is employed in
its full extent, so as to comprehend all
its significates— every thing to which it
is applicable.

DISTRIBUTION OF HEAT. A
term expressive of the several ways by
which the rays of heat, as they fall upon
the surface of a solid or liquid body, may
be disposed of. 1. They may be reflected,
or rebound from the surface ; 2. they
may be absorbed, or received into the
111

substance of the body ; or, 3. they may
be transmitted, or pass directly through
its substance. In the first and third
cases, the temperature of the body on
which the rays fall is entirely unaffected ;
in the second, it is increased.

DITHYRA (dif, twice, 06pa, a door).
A term applied by Aristotle to the bi-
valved mollusca, or those which have
double shells, as the oyster and the
cockle. These comprise the first order
of Cuvier's Acephala, the seventh order
of his Gasteropoda, and the fifth class of
his Mollusca. See Monothijra.

DIU'RNA (diurnus, daily). A desig-
nation of the Butterfly tribe of Lepido-
pterous insects, from their habit of ap-
pearing only by day. They are distin-
guished by the vertical position of their
wings during repose. The tribe corre-
sponds with the Linnaean genus Papilio.

DIU'RNAL MOTION {diurnus, daily).
The daily revolution of the earth upon
its axis, which produces day and night,
and causes us to imagine that the sun,
planets, and stars, move round the
earth. See Axis.

DIURNATION (diurnus, daily). A
term introduced by Dr. M. Hall, to ex-
press the state of some animals, as the
bat, during the day, as contrasted with
their activity at night. See Hybernation.

DIVA'RICATING (divarico, to spread
one from another). Spreading out nearly
at a right angle from any thing, as
branches from a stem.

DIVERGENT RAYS. Those rays,
which, proceeding from a point of the
visible object, are dispersed, and con-
tinually depart one from another, in pro-
portion as they are removed from the ob-
ject ; in which sense they are opposed to
convergent rays.

DIVERTICULUM. The Latin term
for a by-road, and hence applied to a
blind tube branching out from the course
of a longer one.

DIVISIBILITY (divido, to divide).
The property by which bodies are capable
of being separated into minute parts.
The divisibility of matter, though mathe-
matically illimitable, is closely connected
with its constitution, and must, therefore,
cease with the ultimate particles of which
all matter is supposed to consist.

DIVI'SION. In Arithmetic, the me-
thod of finding how often one number is
contained in another, i. e. how often one
number must be taken to make up an-
other. Hence Division bears the same
relation to Subtraction, as Multiplication

DOK

DOU

bears to Addition. In Algebra, the sign
-T- placed between two quantities means
that the former of those quantities is to
be divided by the latter : thus a-i-b means
that a is to be divided by b. This divi-
sion is more simply expressed by making
the former quantity the numerator, and
the latter the denominator, of a fraction,
as |", which expresses the quotient of a
and b.

DIVISION, FALLACY OF. A fallacy
in Logic, occasioned by using the middle
term in the major premiss collectively,
and in the minor distributively, the term
which is first taken collectively being
afterwards divided.

DIVISION, LOGICAL. A metapho-
rical expression to signify "the distinct
(i. e. separate) enumeration of several
things signified by one common name."
It is analogous to the real division of a
whole into its parts, and is directly oppo-
site to generalization, which is performed
by means of abstraction.

DOBEREINER'S LAMP. A method
of producing an instantaneous light, by
throwing a jet of hydrogen gas upon
recently-prepared spongy platinum ; the
metal instantly becomes red hot, and
then sets fire to the gas. The discovery
was made by Dobereiner of Jena, in 1824.

DODE'CAGON (dwde/ta, twelve, yovia,
an angle). A regular polygon of twelve
equal sides. The area of such a figure
is, in general, equal to the square of its
side multiplied by the constant number
11196.

DODECAGY'NIA (dJ>6ena, twelve,
7U1/J7, a woman). The designation of
those orders of plants in the Linnaean
system, which are characterized by the
presence of twelve styles.

DODECAHE'DRON (dwSexa, twelve,
edpa, a seat). A geometrical solid, con-
tained by twelve equal pentagons, which
are equilateral and equiangular.

DODECA'NDRIA (dcofexa, twelve,
uvijp, a man). The eleventh class of
plants in the system of Linnaeus, charac-
terized by the presence of twelve stamens.

DOG-DAYS. The period of the year
comprising forty days, twenty before and
twenty after the heliacal rising of the
dog-star. This period, being the hottest
of the year, was considered by the Greeks
as the season of fevers, plagues, and
death. See Canicular Period.

DOKIMA'STIC ART {ioiuntifa, to

prove by trial). The art of assaying

minerals and ores, in order to determine

the quantity of metal which they contain.

112

DOLA'BRIFORM (dolabra, an axe,
forma, likeness). Axe-shaped; a term
applied to the succulent leaves of a
species of Mesembryanthemum, which
are thick at one border and thin at the
other.

DO'LERITE. One of the varieties of
the Trap rocks, composed of augite and
felspar.

DO'LOMITE. A crystalline lime-
stone, containing magnesia, and named
after the French geologist Dolomieu.
The compact or brown kind is commonly
called Magnesian Limestone.

DOMI'NICAL LETTER. One of the
first seven letters of the alphabet, em-
ployed in the calendar to denote the
Sundays, or days of the Lord (i.e. Domini),
throughout the year. If the year con-
sisted of exactly 52 weeks, the dominical
letter would always be the same ; but, as
there is an excess of l£ day, the Sunday
letter falls back one letter each year, ex-
cept in leap-year, when it falls back two
letters. As every fourth year is bissextile,
and as the number of letters employed is
seven, the same order of dominical letters
will return only in four times seven, or
twenty-eight years, whereas, without that
intervention, it would return in seven.

DO'MITE. A white mineral found in
the Puy de Dome in Auvergne.

DO'RSAL (dorsum, the back). Any
thing placed on the back. In Malaco-
logy, the term is applicable to the valves
of bivalves, in which it serves to distin-
guish that part of their circumference on
which the bosses are placed, from that
which is nearest the belly, when the ani-
mal is crawling. The upper part of a
spiral shell, when the mouth is down-
ward, may be termed its back, or dorsal
surface. The term dorsad signifies to-
wards the back.

DORSIBRA'NCHIA'TA (dorsum, the
back, branchia, gills). An order of Anel-
lida, or red-blooded worms, in which the
branchial tufts are attached to the back.
These were termed by Milne Edwards
errantes, from their powers of locomo-
tion. In popular language they are
termed sea-centipedes, sea-mice, or ne-
reids.

DOUBLE STARS. A term applied
to some fixed stars which, though appa-
rently single to the naked eye, are found,
by means of the telescope, to consist of
two or more stars exceedingly near to
each other.

DOUBLER. An instrument employed
in electrical experiments, and so con-

DUC

DUR

trived that, by executing certain move-
ments, very small quantities of electricity
communicated to a part of the apparatus
may be continually doubled, until it be-
comes perceptible by an electroscope.

DRACO. The Dragon; a northern
constellation, consisting of eighty stars,
the principal of which is Rastaber.

DRAUGHT OF WATER. The
depth to which the lowest point of a ship
sinks in water ; in ships of the largest
size the draught is nearly thirty feet.

DRIFT. A term used in Navigation
to express the angle which the line of a
ship's motion makes with the nearest
meridian, when she drives with her side
to the wind, and is not governed by the
power of the helm ; and also the distance
which the ship drives on that line in a
storm.

The drift of a current is its velocity;
the direction of a current is called its set.

DROP. The smallest perceptible por-
tion of a liquid. It is of a globular form,
and thus illustrates the theory that the
molecular forces of all bodies are equally
exerted around the centre of their
masses.

DROSO'METER (3p6<rop, dew, fierpov,
a measure). An instrument for mea-
suring the quantity of dew deposited
upon the surface of a body.

DRUPE {drupes, unripe olives). In
Botany, a pulpy fruit, without a valve or
outward opening, containing a bony nut,
as the cherry.

DRY PILE. The name of a galvanic
apparatus, constructed with pairs of
metallic plates, separated by layers of
farinaceous paste mixed with common
salt. The name is inappropriate, as the
apparatus evidently owed its efficacy to
the moisture of the paste.

DRY ROT. A species of decay to
which wood is subject. The wood loses
all its cohesion, and becomes friable, and
fungi generally appear upon it ; but the
first destructive change is probably of a
chemical kind, allied to the action of fer-
mentation.

DU'ALISM (duo, two). A system of
philosophy which refers all existence to
two ultimate principles.

DU'BHE. A star of the first magni-
tude in the northern constellation Ursa
Maj r.

DUCT, IN PLANTS. A membranous
tube with conical or rounded extremities,
and its sides marked with transverse
lines, rings, or bars; unlike the spiral
vessel, it is incapable of unrolling with-
113

out breaking. The varieties are the
closed, the annular, the reticulated, and
the scalariform.

DUCTI'LITY (duco, to draw). That
property of bodies by which they admit
of being drawn out into wire. Platinum
has been drawn into threads not much
larger than those of the spider's web,
and gold wire has been found so thin,
that 550 feet of it weighed only one
grain.

DU'CTUS (duco, to lead). A duct or
tube which conveys away the secretion of
a gland.

DU'MASINE. An empyreumatic oil,
obtained by rectifying acetone derived
from the acetates.

DUMOSE (dumus, a bush or bramble).
The character of a shrub which is low
and much branched.

DUNES or DOWNS. Low hills of
blown sand which skirt the shores of
Holland, England, Spain, and other coun-
tries.

DUODECIMALS (duodecim, twelve).
An operation in Arithmetic, technically
called cross multiplication and squaring
of dimensions. Its object is to find the
contents of any surface or solid by mul-
tiplying together its linear dimensions.

DUPLICATE RATIO. The compo-
sition of a ratio with itself once; thus,
the ratio of a2 to ft2 is the duplicate of the
ratio of a to b. If there be three quan-
tities in continued proportion, the first
is to the third in the duplicate ratio of
the first to the second; thus, if a, b, c
be continual proportionals, that is, if
a '. b '. ; b '. c, then, a is to c m the du-
plicate ratio of a to b.

DUPLICATION OF THE CUBE. A
celebrated problem, proposed by the ora-
cle of Delos, viz. "to double the altar of
the God ;" this was tantamount to finding
the side of another cube of twice the solid
content. This problem, requiring the
solution of a cubic equation, was inca-
pable of solution by pure geometry, and
was, therefore, reduced by Hippocrates of
Chios to the insertion of two mean pro-
portionals between two given straight
lines.

DU'PLO- (duplum, from duo, two,
plica, a fold). A Latin prefix, signifying
two-fold, as in duplo-carburet ; also, that
the organs of any body to which the term
is prefixed are twice as numerous or large
as those of some other body.

DURA'MEN (durus, hard). The in-
terior, more deeply-coloured, and harder
portion of the trunk and branches of

EAR

E AS

trees, commonly called heartwood, as dis-
tinguished from the exterior portion,
alburnum, or sapwood.

DUTCH GOLD. An alloy of copper
and zinc, in which the zinc is in greater
proportion than it exists in brass. It is
allied to tombac and pinchbeck.

DUTCH MINERAL. Metallic copper
beaten out into very thin leaves.

DUTCH PINK. Chalk or whiting,
dyed yellow, with a decoction of birch
leaves, French berries, and alum.

DYES. Colouring matters derived from
vegetable substances. See Lakes.

DYKE or DIKE (a provincial name
for wall). A term applied to a mass of
the unstratified or igneous rocks, as
granite, trap, and lava, when it appears
as if injected into a rent in the stratified
rocks, cutting across the strata. A mass
of this kind is sometimes seen running
along the ground, and projecting, like a
wall, owing to the softer strata on both
sides of it having wasted away. A dyke
differs from a vein in being generally of
larger dimensions, and having its sides
parallel for a considerable distance ; while
a vein has generally many ramifications,
and these often become gradually reduced
to slender threads.

Dyke is also the name given to a mound

of earth, stones, &c, employed as a bar-
rier against inundation by the sea, as the
dykes of Holland.

DYNA'MICS {dvvants, force). That
branch of mechanics which relates to
the action of forces which are not in
equilibrio. It, therefore, treats of bodies
in motion. See Statics.

DYNAMIC THEORY. A theory for
explaining the nature of matter, or the
mode of its formation, invented by Kant.
He supposed that all matter existed or
was originated by two antagonist and
mutually counteracting principles, which
he called attraction and repulsion, all
the predicates of which he referred to
motion. See Atomic Theory.

DYNAMO'METER (*&«*<* force,
jueVpoi', a measure). A measurer of
power; an instrument for measuring,
with accuracy, the magnifying powers of
microscopes and telescopes, the force of
machinery, the strength of animals, &c.

DYNA'STIDjE (bwdartv, a master).
A family of beetles, comprehending the
giants of the Coleopterous order, remark-
ably powerful in excavation.

DYSO'DILE (3u<rw3»jf, fetid). A mi-
neral found near Syracuse, emitting, on
combustion, an insupportably fetid odour.

E

EAGLE STONE. Aetites lapis. A
globular clay iron stone, supposed to
have been found in the nest of the eagle.

EARTH. Terra. A planet of the
solar system, the orbit of which lies be-
tween Venus and Mars. It revolves
round the sun in 365 days, 5 hours, and
48 minutes, at the distance of 95 millions
of miles. Its diameter is 7912 miles.
Its rotation upon its axis furnishes a
uniform measure of time, called the
sidereal day.

EARTH (in Chemistry). A solid,
opaque, friable substance, without lustre,
and incombustible; it is thus distin-
guished from metals on the one hand,
and from carbon and other combustible
substances on the other. In chemical
language, the earths are termed metallic
oxides, and formerly, earths of the metals.
Four of these, viz. baryta, strontia,
lime, and magnesia, are termed, from
their properties, alkaline earths.
114

EARTH OF ALUM. A preparation
used for paints, and procured by preci-
pitating the earth from alum dissolved
in water, by adding ammonia or potass.

EARTH OF BONE. A phosphate
of lime, sometimes called bone phos-
phate, existing in bones after calcina-
tion.

EARTH-FALL. A natural pheno-
menon which occurs when portions of the
earth's surface are elevated, then cleft
asunder and depressed, the space once
occupied by solid earth becoming covered
with water.

EARTHQUAKE. A sudden motion
of the solid surface of the globe, probably
occasioned by the same causes as those
which produce volcanic eruptions.

EAST. That point of the compass
which is in a direction at right angles to
that of the north and south, and towards
the right hand of the spectator when
facing the north. It is that point of the

ECH

ECL

horizon in which the sun is seen to rise
at the time of the equinoxes.

EASTER. This holiday is directed to
be celebrated on the first Sunday after
the full moon which happens next after
the 21st of March ; this, being the four-
teenth day of the first Jewish month,
corresponds with the first day of the week
after the Passover, the anniversary of
the Resurrection of Christ. The time at
which this day must happen varies with
the year ; but the limits within which it
must fall are the 22nd of March and the
25th of April, inclusive, making a period
of thirty-five days.

EBULLITION (ebullitio, a bubbling
up). The boiling or bubbling of liquids ;
the production of vapour at the boiling
point.

EBURNI'NjE. A sub family of the
Turbinellidce, or Turnip-shells, named
from the typical genus eburna, and hav-
ing the base of the shell truncate and
notched, the pillar smooth, and the inner
lip considerably thickened and spreading.

ECCE'NTRIC {sk, out, nevrpov, the
centre). A term applied to circles and
spheres which have not the same centre,
and consequently are not parallel; in
opposition to concentric, which denotes a
common centre, and therefore paral-
lelism.

Eccentricity. The distance of the
centre of the orbit of a planet from the
centre of the sun ; that is, the distance
between the centre of the ellipsis and the
focus.

E'CDYSIS (&c3u<m, the act of strip-
ping). Moulting of the skin.

ECHTNATE (ex*™?, the sea-hedge-
hog). Bristly ; covered with stiff hairs
or prickles, like an echinus ; a term ap-
plied to bristly fruits, as that of the sweet
chestnut, &c.

ECHI'NID-ffi (exTvoc, the sea-hedge-
hog). A family of radiated animais.
comprehending those marine animals
commonly known by the name of sea-
eggs or sea-urchins, and constituting,
according to De Blainville, the second
order of the class Echinodermata. By
the term echini, geologists denote the
calcareous petrifactions of the echinus,
which occur through all the formations,
from the epoch of the transition series to
the present time.

ECHI'NODE'RMATA (*xZ*ot, the sea-
hedgehog, bepua, skin). A class of the
Radiata, comprising aquatic invertebrate
animals, which have the surface of their
skin generally covered with calcareous
115

spines, as the common sea-urchin and
the star-fish. The following orders have
been founded on differences of their
general form : —

1. Crino'ida, or those species, chiefly
fossil, which are fixed by a jointed pe-
duncle, and have long ramified articu-
lated tentacula extending from around
the abdominal cavity, as in encrinus and
pentacrinus.

2. Aster ida or Stellerida, comprising
the articulated, free, flexible, stellated
species, which are destitute of peduncle,
and with a short axis, as in asteria.

3. Echinida, in which the body is in-
flexible and covered with a solid articu-
lated shell, the exterior surface being
covered with moveable calcareous spines,
as in echinus.

4. Holothurida, in which the axis of
the body is placed horizontally, and there
is a soft, coriaceous skin, seldom pro-
tected with spines, as in holothuria. —
Grant.

E'CHO (hxu> a sound ; especially, a
returned sound). A wave of sound,
which, falling perpendicularly on a re-
flecting surface, returns in the same
direction, and arrives at the spot from
which it originated.

ECLIPSE (ftcXei^M, a defect). A
lunar eclipse is caused by the projection
of a shadow upon the (full) moon, in
consequence of the interception of the
sun's rays by the earth. A solar eclipse
is occasioned by the interception of a
part or of the whole of the sun's rays, by
the (new) moon. The eclipse is partial,
when the moon hides only a part of the
sun's disk ; total, when she covers the
whole of it; annular, when the sun,
masked by the moon, projects all round
in the form of a luminous ring ; central,
when the spectator's place is in the pro-
longation of the line joining the centres
of the sun and the moon.

ECLI'PTIC (€K\et4ns, an eclipse). The
orbit described apparently by the sun
round the earth, and in reality by the
earth round the sun. It is named from
the circumstance that all eclipses can
happen only when the moon is in the
same plane, or very near it. The lowest
and highest points of the ecliptic are the
winter and summer solstices respectively.
See Solstice.

1. Ecliptic, Obliquity of. The inclina-
tion of the ecliptic to the equator of the
earth, amounting to an angle of 23° 28'.
This inclination gives rise to the pheno-
mena of the seasons.

EPF

EL A

2. Ecliptic, Plane of. A plane sup-
posed to pass through the ecliptic, and to
he indefinitely extended. In other words,
it is the plane which contains the earth's
orbit.

3. Ecliptic Digit. The twelfth part of
the diameter of the sun or moon ; a term
employed for defining the magnitude of
an eclipse. Thus, an eclipse is said to be
of ten digits, if ten parts of the twelve
constituting the diameter are concealed.

4. Ecliptic Limits. The greatest dis-
tances at which the moon can be from
her nodes, in order that an eclipse of the
sun or moon may take place.

E'DDY (Sax. ed, water, ea, backwards).
A circular motion of the water, occurring
in rivers when the proper current meets
a counter current ; and in seas, where
two currents run in parallel, but different,
directions, as between the equatorial and
the North African current. See Whirl-
pool.

EDENTATA (edentulus, toothless).
An order of the Mammalia, agreeing in
the unimportant character of the absence
of incisive teeth. The order may be
distinguished into the edentata proper,
containing the ant-eaters, armadillos, &c,
all of which are insectivorous ; and the
tardigrada, or sloths, characterized by
the slowness of their motion.

The term Edentata has also been ap-
plied to a group of Crustaceous animals,
in which the mouth is prolonged in the
shape of a sucker. See Maxillosa.

E'DINGTONITE. A crystalline mine-
ral, found implanted upon crystallized
Thomsonite, in the Kilpatrick hills, near
Glasgow, accompanied by calcareous spar
and harmotone.

EDRI'OPHTH A'LMA (Zdpalot, sessile,
6<p$a\/jLos, the eye). A group of the
malacostracous Crustacea, which have
immoveable sessile eyes. It comprises
the orders Amphipoda, Laemodipoda, and
Isopoda. See Podophthalma.

EDULCORA'TION (dulcis, sweet).
The process of freeing a difficultly soluble
substance from one that is easily soluble
by means of distilled water. It differs
little from lixiviation, except that the
former term respects the insoluble re-
sidue, the latter the soluble portion.

EDULCORATOR. Dropping Bottle.
An instrument for supplying small quan-
tities of water to test tubes, watch-glasses,
&c, by causing water to drop from a
phial, properly prepared, by expansion of
the liquid by the warmth of the hand.

EFFERVE'SCENCE {effervesco, to
116

grow hot). The commotion produced in
liquids by the rapid escape of gas, in the
form of bubbles, as on pouring acid on
chalk.

EFFLORE'SCENCE (effloresco, to blow
as a flower). The pulverescence of crys-
tals, by the removal of their moisture, on
exposure to the air. See Deliquescence.

E'GERAN. A sub-species of pyramidal
garnet, occurring in a bed of felspar and
hornblende, at Haslan, near Eger in Bo-
hemia.

EIGHTH (in Music). The octave or
eighth note of the diatonic scale. It is a
perfect concord, and harmonizes with the
fifth and the third. It may form a part
of any chord.

EI'SENRAHM. A term applied to
a red and a brown ore— the scaly iron
ore, and the scaly magnetic ore.

ELA'IN {e\aiov, oil). The oily prin-
ciple of solid fats, so named by its dis-
coverer, Chevreul: this and stearine
constitute the fixed oils. Elaic or oleic
acid is obtained from elain by saponi-
fication with a strong solution of pot-
ash.

ELA'OLITE (ZXaiov, oil, A/0or, a
stone). A sub-species of pyramidal fel-
spar, of a blue and of a red colour. The
former is opalescent, and is termed fett-
stein by Werner, from its resinous nature.

ELAIOMETER ($\aiov, oil, perpov, a
measure). An instrument for detecting
the adulteration of olive oil.

ELAO'PTEN (e'Xcuov, oil). The liquid
portion of a volatile oil. The concrete
portion is called stearopten.

ELA'STIC CURVE. The figure as-
sumed by an elastic plate, of which one
end is fixed horizontally, while the other
end is loaded with a weight which, by its
gravity, produces the curve.

ELASTICITY {kXavw, to push or
drive back). The property or power by
which a solid or fluid body, when com-
pressed or forcibly expanded, endeavours
to reassume its former bulk.

E'LATER (eXa-r^p, a driver). A spiral
fibre, enclosed in a membranous case,
found in great numbers mixed with the
sporules, in the thecae of some crypto-
gamic plants. When fully ripe, the
membranous case usually disappears, the
spiral fibres, which are powerfully hygro-
metric, uncurl, and the sporules are dis-
persed.

ELATE'RIDjE. A family of Coleo-
pterous insects, belonging to the section
Sternoxi, and named from the genus
Elater, a species of which (noctilucus)

ELE

ELE

is known in America by the name of fire-
fly.

ELATE'RIUM (e\ai->/p<or, driving
away). A term applied by Richard to
the tricoccous capsule of Euphorbia, in
which the cells burst from the axis with
elasticity into two valves. See Regma.

ELEA'TIC PHILOSOPHY. A sys-
tem of philosophy introduced by Xeno-
phanes of Elea, or Velia of the Romans.
Its object was to deny the validity of the
testimony of sense and experience, and
to ascribe to reason exclusively the merit
of arriving at the truth, independently of
any attempt to reconcile appearance and
reality.

ELECTRICITY {r,XeKTpov, amber).
The science which investigates the attrac-
tions and repulsions, the emission of
light and explosions, which are produced,
not only by the friction of vitreous, resin-
ous, and metallic surfaces, but by the
heating, cooling, evaporation, and mu-
tual contact of a vast number of bodies.

2. Electricity, vitreous and resinous.
1. Vitreous electricity comprises the
phenomena exhibited on rubbing surfaces
of glass. This is also called plus or posi-
tive electricity, and it denotes that the
substance is overcharged. 2. Resinous
electricity relates to the phenomena dis-
played on rubbing amber or resinous sub-
stances. This is also called minus or
negative electricity, and it denotes that
the substance is undercharged.

2. Electrics and non-electrics. The
former are bodies capable of electric ex-
citement ; the latter are bodies totally
incapable of it. These terms were for-
merly supposed to be respectively syno-
nymous with non-conductors and con-
ductors ; but the distinction is quite inac-
curate, since a conductor may be also an
electric, if excited in an insulated state.

3. Electric circuit. The communica-
tion of electricity from one body to an-
other is effected by means of metallic
wires. It is said to move in a current,
from an overcharged to an undercharged
body ; this current is termed the electric
circuit. If the communication be ar-
rested by bad conductors, the circuit is
said to be broken ; it is at this point of
the circuit that bodies are placed, through
which the electrical current is to be

4. Electrical machine. An apparatus
for developing a large quantity of elec-
tricity of high tension. It consists of
1, a non-conductor, usually of glass, which
is positively excited by friction; 2, a
117

rubber, or soft, elastic substance, of low
conducting power, which is negatively
excited; and 3, two conductors, which
are hollow, insulated, metallic cylinders,
the one for receiving the positive elec-
tricity of the glass, the other, the nega-
tive electricity of the rubber ; the former
is called the positive, the latter the nega-
tive conductor.

5. Electric current. The discharge of
electricity by convection, or the transfer
of the two electrical forces in opposite
directions, defined by Faraday as "an axis
of power having contrary forces, exactly
equal in amount, in contrary directions."

6. Electrical columii. A species of
electrical pile, invented by De Luc, com-
posed of thin plates of different metals in
the usual order, with discs of writing
paper interposed between them.

ELECTRICITY, ANIMAL. Galvan-
ism. A power possessed by, and evolved
from, certain living animals, by means of
which several of the phenomena, exhi-
bited by common and by voltaic elec-
tricity, are produced. Volta proved, that
the phenomena proceeded from the con-
tact of two dissimilar metals, copper and
iron, producing such a disturbance of the
electric equilibrium, as was sufficient to
affect the most delicate of all electro-
scopes, the irritability of a newly-killed
frog, though it was insensible to every
electroscope of human construction.

ELECTRO-CHEMISTRY. A system
of chemistry based on the assumption that
the attractive force of opposite electricities
is the fundamental cause of all chemical
combination ; every compound substance,
therefore, consists of one positively and
one negatively electrified element.

ELE'CTRODE. A term in Electricity,
synonymous with pole, denoting the waij
(6d6s) by which the electric current
enters or departs. It is, therefore, the
boundary of the decomposing matter in
the direction of the electric current, the
anode being the point at which the elec-
tricity enters, or the point immediately
touching the positive pole ; the kathode,
the point at which the electricity departs,
or the point next to the negative pole.

ELECTRO-DYNAMICS. The science
which investigates the phenomena of
electricity in motion ; and this comprises
the phenomena of electro-magnetism
and magneto-electricity.

ELECTRO'LYSIS (\va>, to decom-
pose). The process of resolving a com-
pound body into its elements, or proxi-
mate principles, by the voltaic current.

ELE

ELE

Substances directly decomposable by
electricity are termed electrolytes. The
elements of an electrolyzed body are
called ions— that which passes to the
anode, anion ; that to the kathode, kation.
Thus, if water be electrolyzed, oxygen
and hydrogen are ions; the former an
anion, the latter a kation.

ELECTRO-MAGNETISM. The sci-
ence which comprehends all the pheno-
mena in which electricity develops mag-
netic influences.

ELECTRO-METALLURGY. The art
of working in metals by galvanic agency.

ELECTRO'METER (/xeTpov, a mea-
sure). An instrument for ascertaining
the intensity of electricity, or the quan-
tity and quality of electricity in an elec-
trified body.

ELECTROMOTIVE FORCE. A term
applied by Volta to the development of
electricity in voltaic combinations. The
bodies by whose mutual contact it is
developed are called electromotors.

ELECTRO-NEGATIVES and POSI-
TIVES. These terms denote that, during
decomposition, bodies exhibit a different
electric condition from that of the pole
at which they appear. The former are
those bodies which appear at the positive
pole of the battery ; the latter are those
which pass to the negative pole. Oxygen
is the most electronegative, potassium
the most electro-positive, of all known
bodies.

ELECTRO'PHORUS (0<sPw, to carry).
A carrier of electricity : an instrument
which possesses the property of main-
taining for a length of time, by its in-
ductive process, the electrical tension
which has been excited by friction in a
non-conductor.

ELE'CTROPO'LAR. A term applied
to conductors, one end or surface of
which is positive, the other negative — a
condition which they commonly exhibit
when under the influence of induction.

ELE'CTROSCOPE (o-kottpo), to ex-
amine). An instrument for indicating
electrical excitement, and the electrical
state by which it is produced ; in other
words, for exhibiting the attractive and
repulsive agencies of electricity.

ELECTRO - THERMANCY. The
branch of science which investigates the
effects produced by the electric current
upon the temperature of good conductors,
when it passes from one metal into an-
other in the same circuit. These effects
are the converse of those of thermo-elec-
tricity. I
118

ELECTRO-TINT. An application of
electrotype, in which the required sub-
ject is painted on copper with a thick
varnish or paint ; the plate is then pre-
pared in the usual way, and submitted to
the voltaic circuit ; a plate is thus ob-
tained from which prints are furnished.

ELECTROTO'NIC STATE. The pecu-
liar latent state of an induced conductor,
during the continued action of the elec-
tric current upon it, resembling that of a
conductor put in a state of tension by in-
duction.

ELECTROTYPE. The science by
which facsimile medals are executed in
copper by means of electricity. It con-
sists in preparing for a negative plate
models or moulds of objects to be co-
pied ; and in so arranging the battery, or
apparatus which generates the voltaic
current, as to release the metals in a
compact and solid form.

ELECTRO - VITAL CURRENTS.
Neuro-vital Currents. The name of two
electric currents, supposed to exist in
animals, — the one external and cuta-
neous, moving from the extremities to
the cerebro-spinal axis ; the other inter-
nal, going from the cerebro-spinal axis to
the internal organs situated beneath the
skin.

ELE'CTRUM. Argentiferous gold ; an
ore of gold, consisting of 64 parts gold,
and 36 silver, occurring together with
massive heavy spar in Siberia.

ELEMENT. A simple substance ; a
substance which has not been chemically
resolved into different substances, as
iron. The rust of iron, on the other
hand, is a compound, being resolvable
into metallic iron, oxygen, and carbonic
acid. A compound may consist of sub-
stances which are susceptible of further
decomposition : these are called proxi-
mate elements. If the decomposition be
repeated without obtaining simple sub-
stances, the constituents then found are
intermediate elements ; and those last
arrived at are known as ultimate ele-
ments.

Example .-—Saltpetre is a compound.
It consists of two compounds, potash
and nitric acid : these are proximate and
intermediate elements. Each of these is
resolvable — the former into potassium
and oxygen, the latter into nitrogen and
oxygen : these are ultimate elements.

E'LEMI. A resin which exudes from
incisions made in the bark of the Amyris
elemifera, an American tree.
ELE'NCHUS {eXeyxos, a proof). In

ELL

EMA

Logic, a syllogism by which the adversary
is forced to contradict himself. The
ignoratio elenchi, commonly called the
fallacy of irrelevant conclusion, is a
sophism which consists in proving some-
thing irrelevant, and therefore, though
it may be perfectly true, it does not de-
termine the question. The latent fallacy
is best exposed by showing that both
propositions may be equally true.

ELEVATING CAUSES. A term ap-
plied in Geology to those causes which
refer to the operation of volcanoes, earth-
quakes, and gradually elevating forces.
As degrading causes are chiefly owing to
water, so elevating causes are chiefly
owing to fire, and are, therefore, some-
times comprehended under the term
igneous agency.

ELEVATION {elevo, to lift up). In
Astronomy, the altitude or angular
height of a celestial body above the
horizon. The elevation of the pole is the
arc of the meridian intercepted between
the pole and the horizon.

ELIMINATION (elimino, to put out).
The algebraical operation of reducing a
number of equations, containing certain
letters, to a smaller number, in which
one or more of the letters shall not occur.
To eliminate a quantity is, therefore, to
cause that quantity to disappear from an
equation.

ELIQUATION (eliquo, to clarify). The
separation of a more fusible from a less
fusible substance, by applying a degree
of heat sufficient to fuse the former, but
not the latter.

ELI'SION (elisio, a cutting off). In
Grammar, the cutting off a vowel at the
end of a word, for the sake of euphony
or of metre.

ELIXIR (elikscir, Arab., an essence,
or pure mass without any dregs). A
term formerly applied to compound tinc-
tures, and, by the alchemists, to various
solutions in the art of transmutation.

ELLAGIC ACID (from the word galle,
read backward). An acid which is ob-
tained from galls, in the process for
making gallic acid.

ELLIPSE (<?XXe<i/^?, a defect). A sec-
tion of a right cone by a plane oblique to
its base, but which does not meet it. It
is named frpm its plane forming with the
base of the cone a less angle than that of
the parabola. To describe it, fix a cir-
cular thread by two points, and, keeping
it at full stretch with the point of a pen-
cil, carry the pencil all round : the two
fixed points are the foci of the ellipse,
119

and its eccentricity is its distance from
the centre to the foci.

Ellipse, axes of. By generalizing these
directions, we learn that an ellipse is a
plane figure bounded by one curved line,
of such a nature that the respective sums
of the distances of any two points in it
from the two foci, are equal. The line
which joins the foci, and terminates both
ways in the circumference, is the major
axis; the line drawn through the centre
at right angles to the major axis, and
terminating both ways in the circum-
ference, is the minor axis of the ellipse.

ELLFPSOID (e'XXetvW?, an ellipse,
e'idoi, likeness). A term generally ap-
plied to a spheroid. The ellipsoid of
revolution is the solid generated by the
revolution of an ellipse about its lesser
axis.

ELLI'PSOSTO'MATA. A family of
Gasteropods, in the arrangement of De
Blainville, including all the pectini-
branchiate gasteropods of Cuvier, except
the genus pleurocerus.

ELLI'PTIC COMPASSES. An in-
strument for describing an ellipse by
continued motion.

ELLIPTI'CITY. A term employed
in describing the figure of the earth, to
denote the deviation of the earth's form
from that of a sphere. It means the
fraction which the excess of the major
axis over the minor axis of an ellipse is
of the minor axis itself.

ELONGATION. An astronomical
term for the angular distance between
two celestial bodies, as seen from the
earth. The term is commonly applied to
bodies of the solar system, one of which
is generally the sun. Hence, we speak
of the distance of two fixed stars, but of
the elongation of Mercury from the sun.

ELUTRIATION {elutrio, to cleanse).
The chemical process of washing, by
which the lighter earthy parts are sepa-
rated from the heavier and metallic.

ELVAN COURSES. A local desig-
nation of the large beds or dykes of gra-
nite which frequently occur in the slaty
rocks.

ELYTRA (e'Xm-pov, a sheath). The
wing sheaths, or upper crustaceous mem-
branes, which form the superior wings of
Coleopterous insects. They cover the
body, and protect the true membranous
wings.

EMA'RGINATE (<?, out of, margo, the
margin). Having a notch, as if a portion
had been cut out of the margin, as the
base of most predaceous testacea, not pro-

EME

EN A

vided with a canal ; the leaf of hox, &c.
The term is opposed to immarginate.

EMBERIZIN.E (emberiza, the bunt-
ing). Emberizine birds, or Buntings ; a
family of the Deglubitrices of Macgil-
livray, which gradually pass into the
passeres, or sparrows. They have a strong,
rapid, rather undulated flight, and move
on the ground by short leaps.

EMBOITEMENT (the situation of
one box within another, from boite, a
box). A term used by Bonnet to describe
that species of generation by which
hundreds and thousands of individuals
lie one within the other, each possessing
a complete series of organized parts. See
Evolution.

EMBOLI'SMIC {en(3o\iarn6s, inter-
calation). A terra synonymous with
intercalary, generally applied to the ad-
ditional months required to fill up the
lunar cycle.

E'MBRYO {enftpvov, from ev, in, fovea,
to bud forth). Corculum. In Botany, a
fleshy body occupying the interior of the
seed, and constituting the rudiment of
the future plant. It is' distinguished
into three parts, the radicle, the coty-
ledons, and the plumule.

1. Embryo-buds. A term applied by
Dutrochet to those nodules which occur
in the bark of the beech, and some other
trees, and which are externally indicated
by small tumours of the bark. He con-
siders them to be adventitious buds
arrested in their development.

2. Embryo, Fixed. This term has
been applied by some botanists to the
leaf-bud. The function of the two or-
gans is analogous, but their origin and
structure are entirely different. The leaf-
bud consists of both vascular and cellular
tissue, the embryo of cellular tissue only ;
the leaf-bud is produced without fertili-
zation, which is essential to the embryo ;
lastly, the leaf-bud perpetuates the indi-
vidual, the embryo continues the species.

EMBRYO'TEGA (enfipvov, embryo,
T670?, a covering). A small callosity ob-
served in some seeds, at a short distance
from the hilum ; it gives way, like a lid
or covering, at the time of germination,
for the emission of the radicle of the
embryo.

E'MERALD. A gem found in Peru,
of a green colour, rather harder than
quartz, and always in crystals, which are
translucent and generally transparent.
Prismatic emerald is the euclase of Haiiy ;
rhomboidal emerald comprises the pre-
cious emerald and beryl. What if? called
120

Oriental emerald is a. green sapphire. The
emerald of Brazil is a tourmaline.

EME'RSION. An astronomical term,
denoting the re-appearance of a heavenly
body from behind another, after an eclipse
or occultation.

E'MERY. A granular variety of
corundum, found in Spain, the Greek
islands, &c, and named from Cape
Emeri, in the island of Naxos. When
triturated and attached to brown paper,
it forms emery paper, and is used for
polishing.

EMISSION, THEORY OF. Corpus-
cular theory. A theory propounded by
Newton for explaining the nature of
light. According to this, the sun, as well
as all luminous bodies, has the property
of emitting exceedingly minute particles
of its substance in right lines with
prodigious velocity. See Undulatory
Theory.

EMPI'RICAL (k/jiTreiptKos, expe-
rienced). A term applied to an act
which is purely experimental, or per-
formed without previous experience or
principle of guidance. It is remarkable
that the term empiricism, which, strictly
speaking, is the character of modern
science, should have fallen into disgrace,
and serve only to designate the practice
of ignorant pretenders in the medical
art.

EMPYREU'MA (fcffvptft*, to set on
fire). The peculiar vapour produced by
destructive distillation. Empyreumatic
oils are obtained by distilling organic
substances at high temperatures. Harts-
horn is called the empyreumatic alkali.

E'MYDJE (emys, a tortoise). Fresh-
water Turtles, or Mud-Tortoises ; a
family of Chelonian reptiles, intermediate
in form between the turtles and the land-
tortoises. They are distinguished from
the marine turtles by the distinctness of
their clawed toes, which are, however,
webbed, to enable them to swim, and to
prevent their sinking in the mud.

E'MYDO-SAURIANS(|Mu?, the water-
tortoise, aavpa, a lizard). An order of
the class Reptilia, including the tribe of
Crocodiles, which form part of the order
Sauria of Cuvier.

ENA'MEL. A peculiar preparation
of glass, used in painting on enamel, in
the imitation of precious stones, &c.
Common glass, fused with oxide of tin,
is converted into enamel.

ENA'LIOSAU'RIA (evdXios, marine,
aavpa, a lizard). An order of Reptiles,
intermediate between the Turtles and

END

ENH

Crocodiles, and comprising the fossil
genera Ichthyosaurus and Plesiosaurus,
marine animals connected with the
Chelonia by the flattening of their ex-
tremities into fin-like paddles.

ENCAU'STIC PAINTING {hyKava-
Tt/coc, belonging to burning in). A
method of painting employed by the
ancients, in which the colours were ren-
dered permanent by a process of heating
or burning. The practice is briefly,
but not sufficiently, described by Pliny,
in his " Natural History," xxx. 11.

ENCE'PHALA {ev, in, Ke<pa\tj, the
head). Those molluscous animals which
have a distinct head.

ENCEPHALA'TA {ky<e(pa\ov, the
brain). A term applied by Dr. Grant to
the Vertebrata, consisting of animals
in which the brain is enclosed in a bony
cavity.

ENCHELIDE MONAD. An animal-
cule which performs the usual function
of the green parts of plants, decomposing
carbonic acid and evolving oxygen, under
the influence of the light of the sun.

ENCHO'RIAL WRITING {kyxuptos,
belonging to a country). The common
mode of writing among the Egyptians,
resembling the Chinese method, and also
called demotic and epistolographic. It
was termed enchorial, because its cha-
racters differed from those employed in
Greece.

ENCKE'S COMET. A periodic comet
of the solar system, revolving round the
sun in about 1200 days, within the orbit
of Jupiter.

E'NCRINITES {kv, in. Kpivov, a lily).
Stone-lilies. Petrified radiated animals,
included by Cuvier among his pedicil-
lated echinoderms. The term is fre-
quently applied to the crinoidea gene-
rally, both recent and fossil.

ENDE'CAGON {Zv&eica, eleven, ymwta,
an angle). A plane geometrical figure
bounded by eleven sides. If the sides
are all equal, and the length of each be
supposed =1, the area of the figure is
9-36564.

ENDO- (hdov). A Greek adverb,
signifying in, within.

1. Endo-carp Uapndt, fruit). The in-
nermost of the three layers which collec-
tively form the pericarp of fruits; when
it is of a bony consistence, it is also
termed putamen. The stone of the drupe
is the putamen or endocarp ; by Richard,
however, it is termed the nux or nut.

2. Endo-gen {yeivofxai, to be produced).
Inside-grower; a plant which increases

121

in diameter by deposition to the centre ;
a term descriptive of the structure of the
axis of monocotyledonous plants, in
which the newest-formed fibres are al-
ways developed towards the centre of the
stem.

3. Endo-phlosum {<p\ot6s, bark). The
liber, or the innermost layer of the bark
of exogenous plants, composed partly of
cellular, partly of woody tissue.

4. Endo-phyllous {<pv\\ov, a leaf). A
term applied by Dumortier to the endo-
rrhizous embryo, in consequence of the
young leaves of monocotyledons being
evolved from a coleophyllum, or leaf-
sheath.

5. Endo-pleura (irXevpa, the side). The
innermost layer of the testa, or integu-
ment of the seed of plants, named by
Willdenow tunica interna, and by Mirbel,
tegmen and hilofere.

6. Endo-ptile (iniXov, a feather). A
term applied by Lestiboudois to the mo-
nocotyledonous embryo, in consequence
of its plumule being enclosed within the
cotyledon.

7. Endo-rrhizous (piga, a root). A
term expressive of the mode of germina-
tion in endogenous plants, in which the
radicles are emitted from within the sub-
stance of the radicular extremity of the
embryo, and are, in fact, enclosed within
a sheath of this substance, called the
coleoptile, coleophyllum, or leaf-sheath.

8. End-osmose (wo/sor, impulsion). The
property by which a rarer fluid passes
through membranous substances into a
cavity or space containing a denser fluid.
The endosmometer is an instrument con-
trived by Dutrochet for measuring the
force of this action.

9. Endo-siphonites (<ri<p<av, a tube). A
genus of extinct Cephalopods, with cham-
bered convolute discoidal shells, having
the siphon placed at the inner side of the
convolutions, as in spirula. They occur
in the slate rocks of the Cambrian sys-
tem.

10. Endosperm {critepixa, seed). That
which is within the seed : a term applied
by Richard to the albumen, or body en-
closing the embryo. By Jussieu, it was
called perisperm.

11. Endo-stome (o-Toyua, a mouth). The
foramen or orifice of the inner integu-
ment, or secundine, of the ovule, in
plants.

12. Endo-thecium {Own* a case). A
term applied by Purkinje to the fibro-
cellular lining of the anther, in plants.

ENHARMO'NIC SCALE. A scale
G

ENT

EPA

in Music, which proceeds by quarter
tones. Thus a distinction is made be-
tween C sharp and D flat, the former
being }j|ths, the latter $jths of the string
sounding C. The transition from the
one to the other of these intervals is
called an enharmonic change, and a
change of key so effected is termed an
enharmonic modulation. In the modern
scale these intervals are practically dis-
regarded.

E'NNEAGON (ewea, nine, fwvia, an
angle). A plane geometrical figure
bounded by nine sides. Assuming the
sides to be equal, and representing a
side by 1, the area of an enneagon is
6-18182.

ENNEA'NDRIA (4Wa, nine, avtjp,
man). The ninth class of plants in the
system of Linnaeus, characterized by the
presence of nine stamens.

ENS. The present participle of the
verb sum, employed as a substantive in
philosophical language for any being or
existence. In Chemistry, it denotes a
substance supposed to contain all the
qualities or virtues of the ingredients
from which it is drawn, in a small com-
pass : thus we have ens Martis, ammo-
niated iron ; ens Veneris, muriate of
ammonia and copper; ens primum, an
alchemical tincture for the transmutation
of the metals.

E'NSIFORM (ensis, a sword, forma,
likeness). Gladiate. Sword-shaped ;
lorate ; straight, flat, and pointed, as the
leaf of iris.

ENTHELMI'NTHA (irtfe, within,
eXfxivi, a worm). Intestinal worms; a
term synonymous with entozoa.

E'NTHYMEME (l^n/xa, a thought).
An argument, called by Aristotle the
rhetorical syllogism, i. e. a syllogism
drawn from probable premises, and
which, therefore, does not pretend to be
demonstrative. In Logic, however, the
term denotes an abridged form of argu-
ment or syllogism, in which one premiss
is expressed, and the other understood,
whether major or minor, as " Caesar
was a tyrant ; therefore he deserved
death."

ENTIRE. A term applied, in Botany,
to leaves which have no marginal divi-
sion, or toothings of any kind, as the
leaves of galium. Sometimes it denotes
not pinnatifid ; and also, nearly destitute
of marginal division.

E'NTOMOLINE (eVro^ov, an insect).
A peculiar chemical principle, found in
large quantities in the wings and elytra
122

of coleopterous insects, and termed chi-
tine by M. Odier.

ENTOMO'LOGY (evTo^ov, an insect,
\6fos, an account). That branch of
Zoology which treats of insects. The
Greek word evro/jia, as well a3 the Latin
term insecta, relates to the division of
the body of these animals into numerous
segments.

ENTOMO'PHAGOUS (eVroMa, in-
sects, (ptiyo, to devour). Insect-eating;
a term applied, in Zoology, to those ani-
mals which subsist on insects.

ENTOMOSTO'MATA (foropo* an
insect, o-To/ia, a mouth). The name
given by De Blainville to a family of
conchiferous mollusca, in which the
mouth is armed with a proboscis. They
constitute the second family of his first
order Siphonobranchiata, and are nearly
identical with the genus buccinum of
Linnaeus.

ENTOMO'STRACA (li/xo/xa, insects,
ocrTpaKov, a shell). Shell insects ; a sec-
tion of the Crustacea, many of which are
enclosed in an integument, like a bivalve
shell. They are distinguished into the
Entomostraca proper, and the Xipho-
sura. The orders are Copepoda and
Ostrapoda.

ENTOZO'A (evTo?, within, fSov, an
animal). Intestinal worms ; a class of
articulated animals, comprising the pa-
rasites which inhabit the internal parts
of other animals.

EN'TROCHI (hv, in, TPoXor, a wheel).
A genus of fossils, consisting of several
round joints, which, when detached from
one another, are called trochitcs. They
seem to be the petrified arms of that
singular species of the sea star-fish,
called Stella arborescens.

E'OCENE (nw9, the dawn, kcuvop, re-
cent). A designation of the lowest divi-
sion of the tertiary strata, containing an
extremely small per centage of living
species among its fossil shells, which in-
dicates the first commencement, or dawn,
of the existing state of the animate crea-
tion.

E'PACT (^raK-rop, adscititious). A
term applied, in Astronomy, to the num-
ber of days by which the solar year ex-
ceeds the lunar. The year of 365£ days,
contains twelve lunations and nearly
eleven days more ; so that, were it to
begin with the new moon, she would be
eleven days old on the first day of the
succeeding year ; the next year she
would be twenty-two days ; and on the
third new year's day she would have

EPI

EPI

passed a whole lunation, and about three
days more. The age of the moon (thus
varying) on the first day of any year is
termed the Epact.

EPI- {kiri). A Greek preposition, with
the radical signification of upon ; hut de-
noting also, in some compounds, over, all
through, besides.

1. Ep-agomince (kirayo/jievai rjjuepcu, in-
tercalated days). A term applied to the
five days which were added by the Egyp-
tians to their calendar at the end of each
year, to complete the number of 365.
At the end of every fourth year, a sixth
epagomene was added, to remedy the in-
convenience arising from the six hours
still remaining at the completion of every
year.

2. Epi-genesis (yeveais, generation). A
term applied to a theory of non-sexual
generation, in which each new germ is
an entirely new production of the parent
organism. See Evolution.

3. Ep-hemeridce {hpepa, a day). A
group of Neuropterous insects, named
from the ephemera, or day-fly, which are
aquatic in their preparatory states, and
emerge from the water to undergo their
final metamorphosis. The ephemera is
so named from its last stage of existence
being generally limited to twenty-four
hours.

4. Ep-hemeris (rj/iepa, a day). A term
applied to an astronomical table or al-
manac which assigns the place of a planet
for a number of successive days.

5. Epi-blastus (/3\ao-To?, germen, a
shoot). A term applied by Richard to a
peculiar appendage which occasionally
occurs in the monocotyledonous embryo,
in the form of an anterior cotyledon.

6. Epi-caridians (/capir, a shrimp). A
family of Tsopodous crustaceans, which
are parasitic upon shrimps.

7. E pi-carp (/<ap7r6?, fruit). The ex-
terior portion of the pericarp, commonly
termed the skin of the fruit.

8. Epi-cycle {kvk\o<:, a circle). Literally,
a circle upon a circle. The ancient
astronomers supposed that the motions
of the heavenly bodies must necessarily
be in circles : and in order to make that
doctrine tally with observation, they in-
vented, in succession, the two theories of
Epicycles^ and Eccentrics. In the former,
called also the Concentric Theory, the
earth was supposed to be placed in the
centre of a circle, on the circumference of
which the centre of another circle re-
volved; and on the circumference of this
second circle (called an Epicycle) the

123

planet was imagined to move : a suppo-
sition which accounted in some degree
for the apparent irregularities of its mo-
tion. The primary circle was called the
Deferent. In the Eccentric Theory, the
earth was also placed stationary in the
centre of the starry sphere ; but the sun
was carried round in a circle, the centre
of which was eccentric from that of the
earth.

9. Epi-cycloid (nvuKoeidrir, circular).
If a circle roll upon the circumference of
another circle instead of a straight line,
points, either on, within, or without its
circumference, if on the same plane, will
form varieties of Epicycloids.

10. Epi-dermis {deppa, skin). The ex-
ternal covering of the skin, eommonly
called cuticle, in plants and animals.
Also the outer rough coating of shells,
over which it is spread as a fibrous horny
skin, though destitute of sensation.

11. Epi-dote (3i'3&)/x<, to give). A sub-
species of prismatoidal augite, also termed
acanticone and pistacite, occurring in
primitive beds and veins. The name is
said to be derived from an enlargement
of the base of the prism in one direction,
the prefix here denoting besides.

12. Epi-gene crystals {yevos, a kind).
Substances found naturally crystallized
in a form which does not belong to them-
selves, but to some other compound of
the same base : thus, crystals of oxide of
iron are found with the form of sulphuret
or carbonate of iron. In these, it appears
that the crystals must have undergone a
chemical change, unaccompanied by
change of form.

13. Epi-geous (in, the earth). A term
applied to the situation of plants, when
they grow close upon the earth ; and to
those cotyledons which emerge from the
ground, and assume the colour of leaves.

14. Epi-gonium {yovrj, the seed). A
membranous bag which encloses the
conceptacle or capsule of Jungermannia,
and is ruptured as the latter elongates.
It is somewhat analogous to the calyptra
of Mosses, but is not carried up on the
summit of the capsule.

15. Epi-gynous {ywrj, a woman). That
condition of the stamens of a plant, in
which they adhere both to the calyx and
the ovarium, appearing to be inserted
upon the summit of the ovarium, as in
umbelliferous plants.

16. Epi-meral (/uepoc, a part or limb).
A term applied to the part of the seg-
ment of an articulate animal which is
above the joint of the limb.

G2

EPO

EQU

17. Epi-phlceum (^Xotoc , bark). A term
applied by Link to the second portion of
the bark of plants, consisting of several
layers of thin-sided tubular cells, rarely
coloured green. This is the phlceum or
peridermis of Mohl.

18. Epiphragma {(ppafna, a fence). A
term applied, in Bryology, to the mem-
brane (peristomium) which sometimes
closes up the orifice of the theca. It is
sometimes called tympanum, from the
drum-like appearance which the theca
thus presents.

19. Epi-phyllospermous (<pv\\ov, a leaf,
a-rrepua, seed). An old term for those
plants which bear their organs of repro-
duction upon the back of their fronds, as
the ferns. These are now called dorsi-
ferous, from dorsum, the back, and fero,
to bear.

20. Epi-phyllous {cpvWov, a leaf). A
term applied to any thing which is in-
serted upon the leaf of a plant.

21. Epi-phyie (Qvtov, a plant). A plant
which grows upon other plants, adhering
to their bark, and rooting among the
scanty soil found on their surface. The
term is generally restricted to those Or-
chidaceous plants which grow upon trees.
The old term was epidendrum.

22. Epi-pterous (mepov, a wing). A
term applied to a fruit or seed which is
furnished with a broad margin or wing,
when it terminates. See Pterous.

23. Epi-rrheology (emppoij, a flowing
on, \6yos, description). That branch of
science which treats of the effects of ex-
ternal agents upon living plants.

24. Epi- sperm {wnepixa, seed). The
terms episperm and perisperm are ap-
plied by Richard to the testa, or integu-
ment of a seed — the spermoderm of De
Candolle.

25. Epi-zoa {&ov, an animal). An
order of the Entozoa, which are at first
free and natant larvae, afterwards fix-
ing themselves permanently, by strong
organs of attachment, to the soft super-
ficial parts of aquatic animals.

EPI'STOLOGRA'PHIC WRITING
(kni<TTo\ri, a letter, ypdcpoo, to write). A
designation of the demotic or enchorial
mode of writing, in common use among
the Egyptians, and approaching very
nearly to the Chinese method.

E'POCH (67rox»/, a pause in the reck-
oning of time). In Chronology, a point
at which one period closes and another
begins. The epoch of a star is its place
in the heavens. In order to predict the
longitude of a planet at any epoch, some
124

preceding epoch must be taken, at which
the longitude is known. The latter is
emphatically called the epoch; and the
term longitude at the epoch has been
shortened into epoch.

EQUATION (in Astronomy). The
term applied by astronomers to their
practice of reducing all their observations,
both of right ascension and of declina-
tion, to vsome common and convenient
epoch. These corrections, or equations,
are necessary in consequence of the
elliptic figure of the moon's orbit, the
sun's attraction, and other causes.

1. By equating the observation for nuta-
tion, is meant the getting rid of a periodi-
cal cause of fluctuation, and present-
ing a result, not as it was observed, but
as it would have been observed, had
that cause of fluctuation had no exist-
ence.

2. Equation of time. In popular lan-
guage, this expression denotes the differ-
ence between the times indicated by an
accurately constructed sun-dial and a
well-regulated clock. Astronomically, it
signifies the difference, expressed in
mean solar time, between the true or
apparent right ascension of the sun and
its mean right ascension. There are only
four days in the year, when the apparent
and the mean time coincide, and the
equation of time is nothing, viz. April 15th,
June 15th, September 1st, and Decem-
ber 24th. Between April 15th and June
15th, the clock is earlier than the sun, and
the equation is subtractive ; between
June 15th and September 1st, the clock
is later than the sun, and the equation
is additive.

EQUATION (in Mathematics). An
assertion of the equality of two magni-
tudes, represented by the symbol =. It
is of two kinds, viz. an equation of con-
dition, which will be true only on the
supposition of certain conditions, as
2a + 1 = 13, which requires that a should
represent 6 ; or an identical equation,
which is true independently of all condi-
tions, i. e. whatever may be the value of
the symbols employed, as a + a = 2a.

EQUA'TION, ALGEBRA'IC. An
expression of two algebraic quantities,
when connected together by the sign of
equality. The solution of an equation is
the operation by which the values of the
unknown quantities are found in terms
of the known quantities. If the equation
contains no power of the unknown quan-
tities, but these quantities merely in
their simplest fonn, it is called a simple

EQU

EQU

equation ; if it contains the square of the
unknown quantity, it is called a quadratic
equation ; if the cube of the unknown
quantity, a cubic equation ; if the fourth
power, a biquadratic, &c.

Equation, Quadratic. This is pure or
adfected. 1. Pure quadratic equations
are those which contain only the square
of the unknown quantity, as x2 = 36.
2. Adfected quadratic equations are those
which involve hoth the square and the
simple power of the unknown quantity,
as x* + 4x = 45.

EQUATION OF PAYMENTS. An
arithmetical rule for finding the mean
time for paying the amount of several
sums which are due at different times.
Rule: — Multiply each term by its time,
and divide the sum of the products by
the whole debt ; the quotient is accounted
the mean time.

EQUATOR {aequo, to make equal).
The Great Circle on the earth's surface,
every point in which is equally distant
from the poles. It divides the earth into
two equal parts, the one being called the
Northern, the other the Southern Hemi-
sphere. See Equinoctial.

EQUATO'RIAL. An apparatus, for-
merly called a parallactic instrument,
used for all those astronomical observa-
tions which require an object to be kept
long in view. Its value consists in its
being capable, when once set upon an
object, of following the object for an inde-
finite period by a single motion, i. e. by
merely turning the whole apparatus
round on its polar axis.

EQUATO'RIAL CURRENT. Adrift-
current which traverses the Atlantic
Ocean, named from its course lying under
or near the line. It is supposed to be
formed in the Bay of Benin, whence it
proceeds westward on both sides of the
equator, as far as 22° W. long. ; it then
declines somewhat southward towards
the Brazilian coast, and separates into
two currents, called the Guiana current
and the Brazil current.

EQUIA'NGULAR {cequus angulus,
equal angle). As applied to a single
geometrical figure, the term denotes that
all its angles are equal, as in all regular
polygons; as applied to two figures of
the same kind, it denotes that the cor-
responding angles of the two figures are
equal, though, separately, they may not
be equiangular figures.

E'QUIDjE (equus, a horse). The Horse
tribe; the solidungulous family of pachy-
dermatous animals, with only one ap-
125

parent toe and a single hoof to each
foot.

EQUILATERAL {aqua latera ha-
bens). A term applied to a geometrical
figure bounded by equal sides.

EQUILIBRIUM {ceque, equally, libro,
to poise). A term expressive of the
equable diffusion of temperature which
all bodies on the earth tend to produce ;
and of the equal distribution of the elec-
tric fluid in its natural undisturbed state.
Equilibrium of forces. When two forces
counteract, or balance each other, they
are said to be in equilibrio. To produce
this state in solid bodies, it is only neces-
sary to support the centre of gravity : a
pair of scales are in equilibrio, when the
beam is in a horizontal position.

EQUIMULTIPLES. The products of
quantities multiplied by the same num-
ber. Thus six times A and six times B
are egwi-multiples of A and B; m*np
and m* nq are equi-multiples of p and q;
a league and a yard are equimultiples of
a mile and a foot.

EQUINO'CTIAL. A synonymous term
for the equator, because, when the sun
is in the plane of it, nodes cequantur, it
is equal day and night over the whole
world.

EQUINO'CTIAL POINTS. The two
points of the ecliptic where the equi-
noctial or equator crosses it; viz., in the
first point of Aries and the first of Libra.
The times of the year answering to these
points are called Vernal and Autumnal
Equinoxes, the one happening in the
spring, the other in the autumn; the
vernal being that at which the sun
crosses the equinoctial from south to
north; the autumnal, when it quits the
northern and enters the southern hemi-
sphere. See Precession.

EQUISETA'CEjE. Leafless branched
plants, with a striated fistular stem. i»-
florescence consisting of peltate scales.
Reproductive bodies in the inside of the
lobes of the scales, consisting of four
club-shaped bodies, enveloping a naked
spore.

EQUISE'TIC ACID. A peculiar acid,
existing, in combination with magnesia,
in the Equisetum fluviatile.

EQUIVALENTS, CHEMICAL {esqud,
equally, valeo, to avail). A term applied
by Wollaston to the combining propor-
tions of elementary and compound sub-
stances, as the quantities of acid and
base, in salts, required to neutralize each
other. The following are instances of
this law :—

G3

ERA

ERA

Arsenic acid. . 57*68 Lime 28

Muriatic acid 37 Magnesia... 20

Nitric acid ... 54 Potash 48

Sulphuric acid 40 Soda 32

Thus 57*68 of arsenic acid, 37 of muri-
atic, 54 of nitric, and 40 of sulphuric,
comhine with 28 of lime, forming, re-
spectively, a neutral arseniate, muriate,
nitrate, and sulphate of lime ; &c. &c.

E'QUIVALVED. A term applied to
hivalves, when the two valves are of
equal size and depth.

EQUI'VOCAL NOUN (aqud, equally,
voco, to call). In Logic, a noun which has
more than one signification, each of its
significations being equally applicable to
several objects, as bull — the animal ; the
pope's official letter ; a blunder. " Strictly
speaking, there is hardly a word in any
language which may not be regarded, as
in this sense, equivocal ; but the title is
usually applied only in any case where a
word is employed equivocally ; e. g. where
the middle term is used in different
senses in the two premises ; or where a
proposition is liable to be understood in
various senses, according to the various
meanings of one of its terms." — Whately.
EQUU'LEUS PICTO'RIS. The Paint-
er's Horse, or Easel ; a modern southern
constellation, consisting of eight stars,
situated close to the principal star of Argo.
E'QUULUS. The Horse's Head; a
northern constellation, consisting of ten
stars.

E'RA or iERA. A fixed point of time,
at which the computation of ensuing
years is commenced. The following are
the principal eras : —

1. Era of the Olympiads. The most
ancient method of computing time, first
instituted in the year b.c. 776, and con-
sisting of a revolution of four years. It
originated from the Olympic games,
which were celebrated every fifth year
at Olympia, a city of Elis in Greece.

2. Era of the Foundation of Rome.
This has been variously fixed. The
Varronian computation, which fixes it in
the year b.c 753, was adopted by the
Roman emperors, and has received the
sanction of most modern chronologists.

3. Christian Era. This commenced
Jan. 1, in the middle of the fourth year
of the 194th Olympiad, the 753rd of the
building of Rome, and the 4714th of the
Julian period. The years of this era are
described in ancient documents as the
years " of Grace," of " the Incarnation,"
of " the Nativity," of " the Circumcision,"
and "annus Trabeationis."

4. Julian Era. The era of the reform-
ation of the Roman Calendar by Julius
Caesar, who ordained that the year of
Rome 707 should consist of 15 months,
forming altogether 445 days; that the
ensuing year, 708, should consist of 365
days ; and that every fourth year should
contain 366 days, the additional day
being introduced after the 6th of the
calends of March, i.e. the 24th of Febru-
ary, which year he called bissextile, be-
cause the 6th of the calends of March
was then doubled.

5. The Indictions. The Indictions
consisted of a revolution of fifteen years,
which are separately reckoned as Indic-
tion 1, Indiction 2, &c, up to 15, when
they recommence with 1. The first In-
diction is usually referred to the year
A.D. 313. See Indictions.

6. Mundane Era of Alexandria. The
Alexandrian era of the Creation of the
World was fixed at 5502 years before
Christ. This computation was continued
until a.d. 284, or the year 5786 of the
Alexandrian era; but in the following
year, ten years were subtracted, and that
year was accordingly a. alex. 5777.

7. Mundane Era of Antioch. By this
era, the Creation of the World was fixed
at 5492 years before Christ, or ten years
later than by the era of Alexandria. As,
however, ten years were subtracted from
the Alexandrian era in a.d. 285, the two
eras thenceforward coincided.

8. Era of Constantinople. This era
refers the Creation of the World to the
5508th year before Christ, and is still
used by the Greek Church. In this era
there are two years : the civil, which be-
gins with the month of September ; and
the ecclesiastical, which commences on
the 21st of March, and sometimes on the
1st of April.

9. Era of the Seleucidce. This era,
also called the "Era of the Greeks,"
sometimes the " Era of Alexandria," and
occasionally the " Era of the Syro-
Macedonians," commenced in the year
of Rome 442, twelve years after the
death of Alexander, and 311 years and
4 months before the birth of Christ, being
the epoch of the conquest of Babylon by
Seleucus L, surnamed Nicator, or the
"Victorious. It is still used in the Levant.

10. C cesarean Era of Antioch. This
era was instituted at Antioch, in conse-
quence of the victory gained by Julius
Caesar in the plain of Pharsalia, on the
9th of August, in the year of Rome 706,
and 48 years before Christ.

ERA

ERI

11. Era of Pisa. This era, which was
sometimes used in France, especially in
the twelfth century, differed from our
common era by preceding it by one year
only.

12. Era of Spain. An era founded in
consequence of the conquest of Spain by
Augustus, in the year of Rome 715,
thirty -nine years before the birth of
Christ. The era commenced Jan. 1,
a.u.c. 716, and 38 B.C. It prevailed in
Portugal so lately as 1415, if not until
1422.

13. Era of Diocletian, or of the Mar-
tyrs. This era dates from August 29,
a.d. 281, the day when Diocletian was
proclaimed emperor at Chalcedon ; and
in consequence of his persecution of the
Christians, it is also called the " Era of
the Martyrs." It was generally used by
Christian writers until the introduction
of the Christian era in the sixth century,
and it is still used by the Ethiopians and
Copts.

14. Era of the Hegira. This era, also
called the " Era of the Turks, Arabs, and
other Mahomedans," commences on Fri-
day, July 16, a.d. 622, the day of the
flight of Mahomet from Mecca to Medina,
which is the date of the Mahomedans ;
but astronomers and some historians
assign it to the preceding day — an im-
portant fact, to be borne in mind when
perusing Arabian writers.

15. Era of Abraham. This era pre-
ceded the birth of Christ by 2015 years,
and began on the 1st of October, 2016.

16. Era of Nabonassar. The author of
this era was Nabonassar, the founder of
the kingdom of Babylon. It commenced
on Wednesday, Feb. 26, in the 3967th
year of the Julian period, i.e. b.c. 747.
It included a period of 424 Egyptian
years, from the commencement of Na-
bonassar's reign to the death of Alexan-
der the Great, and was thence brought
down to the reign of Antoninus Pius.

17. Era of Tyre. This era began 125
years before Christ, in the year of Rome
628, and in the 186th year of the era of
the Seleucidae.

18. Actiatic Era. This era is founded
on the battle of Actium, which rendered
Augustus master of the Roman empire.
The Romans commenced this era on the
1st of January, a.u.c. 724, and in the
16th of the Julian era. In Egypt, it
commenced in the same year as that of
the battle, and prevailed until the reign
of Diocletian. The Greeks of Antioch
used it as late as the ninth century.

127

19. Era of Augustus. This was later
by four years than the Actiatic era, and
began in the year of Rome 727, twenty-
seven years before the Christian era.

20. Era of the Ascension. This era is
supposed to have been used only by the
author of the Chronicle of Alexandria,
who dates the year of the Martyrdom of
St. Menas of Cotys at the period corre-
sponding with the 12th of November,
a.d. 295.

21. Era of the Armenians. This era
commenced on Tuesday, July 9th, a.d.
552, the period when the Council of
Tiben, or the Armenians, confirmed the
condemnation of the Council of Chalce-
donia, which was pronounced in a.d. 536,
and by which they completed their
schism.

22. Era of Tezdegird III., or the Per-
sian Era. This era commenced on the
accession of Yezdegird to the throne of
Persia, on the 16th of June, a.d. 632.

23. Jewish Era. This era is commonly
supposed to be not more ancient than the
fifteenth century. The Jews now date
from the creation of the world, which
they consider to have taken place 3760
years and 3 months before the commence-
ment of the Christian era.

24. Era of the Caliyug. This is the
most ancient era of India, and dates from
a period 3101 years before Christ. Other
eras are used in different parts of India,
as those of Salivahana, of Vicramaditya,
of Parasurama, &c.

25. Era of the French. The era of the
National Convention, which commenced
on the 22nd of September, 1792, being
the epoch of the foundation of the Re-
public ; but its establishment was not
decreed till the 4th " Frimaire" of the
year u. (Nov. 24, 1793.) Two days after-
wards the public acts were thus dated.
This calendar existed till the 10th " Ni-
vose," of the year xiv. (Dec. 31, 1805,)
when the Gregorian mode of computation
was restored.

E'REMACAU'SIS (^pe/xop, slow, Kav-
o-if, burning). A term applied by Liebig
to the slow combustion or oxidation of
organic matters in air, as the conversion
of wood into humus, the formation of
acetic acid from alcohol, nitrification, &c.

ERICA'CE.® (erica, a heath). The
Heath tribe of Dicotyledonous plants.
Shrubs, with leaves evergreen, rigid, en-
tire, whorled or opposite ; flowers mono-
petalous, regular ; stamens definite ; ova-
rium superior, many-seeded ; seeds apte-
rous.

G4

ER Y

ERI'DANUS. A southern constella-
tion, consisting of 84 stars, the principal
of which is Achernar.

ERINACE'AD^i. The Urchin or
Hedgehog tribe ; a family of insectivor-
ous vertebrata, which are remarkable not
only for their covering of spines, but for
the great development of the muscular
envelope of the body immediately beneath
the skin.

E'RINITE. A heautiful emerald-green
arseniate of copper, named from its being
found in the county of Limerick in Ire-
land.

ERTO'METER {epiov, wool, p.erpov, a
measure). An instrument, invented by
Dr. Young, for the purpose of measuring
the diameters of minute fibres.

E'RLAMITE. A new mineral, forming
a part of the oldest gneiss formation.

ERO'SE (erosus, gnawed off). Gnawed;
having the margin irregularly divided, as
if bitten by an animal : a term applied to
the margin of certain leaves.

ERRA'NTES (erro, to wander). A
term applied by M. Edwards to an order
of the Anellida, which are at once the
highest organized and the most locomo-
tive. These are the dorsibranchiata of
Cuvier, and are commonly known by the
names of sea-centipedes, sea-mice, or
nereids.

ERRATIC BLOCKS. A term syno-
nymous with boulders, derived from their
wide distribution over the surface of the
earth. See Boulders.

ERY'THRO- (epuflpor, red). A Greek
term employed in composition to denote
any pure red colour. It agrees with the
ruber of the Latins.

1. Erythric Acid. A red substance pro-
duced by the mutual action of the nitric
and uric acids. Dr. Prout considers it
to be not a peculiar acid, but a com-
pound of nitric and purpuric acid and
ammonia.

2. Erythrin. One of a series of sub-
stances including erythrilin, erythrin
bitter or amarythrin, telerythrin, &c,
obtained by Dr. Kane from the Roccella
tinctoria.

3. Erythro-gen (yewdco, to produce).
A green-coloured substance found in the
gall-bladder, in a case of jaundice. It
unites with nitrogen, and produces a red
compound.

4. Erythro-phylle ((pvXKov, a leaf). A
term applied by Berzelius to the red
colouring matter of leaves and fruits in
autumn.

5. Erythro-stomum (o-Toyua, a mouth).

128

EST

A terra applied by Desvaux to the
aggregate fruit, more generally termed
etcerio.

ESCA'RPMENT (escarper, to cut
steep). The abrupt face of a ridge of
high land, where subjacent strata are
observed to " crop out."

ESO'CIDiE (esox, the pike). The Pike
tribe ; a family of Malacopterygious or
soft-spined fishes, having the ventral
fins placed under the abdomen, and in-
cluding most of the voracious fresh-
water fishes, as well as several important
marine species. They are distinguished
by the position of the dorsal opposite to
the anal fin, and by the absence of fatty
matter in the former.

ESOTE'RIC (Wrep<K6f, inner). A
term applied to the disciples of Pytha-
goras, Aristotle, &c, who were scientifi-
cally taught, as distinguished from the
exoteric, who had merely popular views.
The term esoteric is sometimes applied to
a mysterious doctrine, which was taught
only to the more enlightened, and was
thus distinguished from the exoteric, or
published doctrine. In this sense *1 eso-
teric" is synonymous with acroamatic,
or that which is communicated by oral
instruction.

E'SSENCE (essentia, a being). A scho-
lastic term denoting the essential perfec-
tion of a being, i. e. its entity and attri-
butes. It sometimes signifies merely the
principal attributes of a being.

ESSENTIAL DEFINITION. In Lo-
gic, a definition which assigns, not the
properties or accidents of the thing de-
fined, but what are regarded as its essen-
tial parts, whether physical or logical.
See Definition.

ESSENTIAL OILS. Oils obtained by
distillation from odoriferous vegetable
substances. Several of the volatile or
essential oils are called essences.

ESTIVA'TION {ccstivus, belonging to
summer). Prcefloration. A botanical
term applied to several modes in which
the floral envelopes are folded up in the
un expanded or bud state. It is said
to be —

1. Involute, when the edges are rolled
inwardly spirally on each side.

2. Revolute, when the edges are rolled
backwards spirally on each side.

3. Obvolute, when the margins of one
leaf alternately overlap those of the oppo-
site leaf.

4. Convolute, when one leaf is wholly
rolled up within another leaf.

5. Supervolute, when one edge is rolled

EST

ETH

inwards, and is enveloped by the
opposite edge rolled in an opposite di-
rection.

6. Induplicate, when the margins are
bent abruptly inwards, and the external
face of these edges is applied to each
other without any twisting.

7. Conduplicate, when tbe sides are
applied parallelly to the faces of each
other.

8. Plaited, when they are folded length-
wise, like the plaits of a closed fan.

9. Replicate, when the upper part is
curved back and applied to the lower.

10. Curvative, when the margins are
slightly curved, either hackwards or for-
wards, without any sensible twisting.

11 . Wrinkled, when the parts are folded
up irregularly in every direction.

12. Imbricated, when they overlap each
other parallelly at the margins, without
any involution.

13. Equitant, when they overlap each
other parallelly and entirely, without in-
volution, as in iris.

14. Reclinate, when they are bent down
upon their stalk.

15. Circinate, when they are rolled
spirally downward.

16. Valvate, when they are applied to
each other by the margins only.

17. Quincuncial, when the pieces are
five in number, of which two are ex-
terior, two interior, and the fifth covers
the interior with one margin, and has its
other margin covered by the exterior, as
in the rose.

18. Twisted, which is the same as
contorted, except that there is no obli-
quity in the form or insertion of the
pieces.

19. Contorted, when they are twisted
in such a manner that each piece of a
whorl overlaps its neighbour by one
margin, and is overlapped by its other
neighbour by the other margin.

20. Alternative, when the pieces being
in two rows, the inner is covered by the
outer in such a way that each of the
exterior rows overlaps half of two of the
interior, as in liliaceae.

21. Vexillary, when one piece is much
larger than the others, and is folded over
them, they being arranged face to face,
as in papilionaceous flowers.

22. Cochlear, when one piece, being
larger than the others, and hollowed like
a helmet or bowl, covers all the others,
as in aconite, some species of personate
flowers, &c. — Lindley.

ESTUARIES {cestus, the tide). In-
129

lets of the land, which are entered by
tides of the sea and by rivers. They
occur in the Thames, the Severn, the
Tay, &c.

ETiE'RIO (eTaipeia, an association).
A term applied by Mirbel to an aggre-
gate fruit, the separate parts of which
are achaenia, as in ranunculus, rubus,
fee.

ETE'SIAN WIND (ei^o-toc, annual).
A northerly or north-easterly wind which
prevails very much in summer all over
Europe. See Winds.

E'THAL. A peculiar oily substance,
obtained from spermaceti ; also termed
hydrate of oxide of cetyl. The term is
formed of the first syllable of the words
ether and a/cohol, on account of its ana-
logy to these liquids in point of compo-
sition.

ETHER (a\9rjp, ether). An imaginary
fluid, supposed by some philosophers to
fill all space beyond the atmospheres of
the earth and other planets.

ETHER (in Chemistry). A very vola-
tile fluid, produced by the distillation
of alcohol with an acid. It is some-
times distinguished as sulphuric ether,
from the mode of preparing it ; but when
well rectified, the ether is the same,
whatever acid has been employed.

ETHE'REUM (alflJ/p, ether). A hypo-
thetical carburetted hydrogen, so named
by Dr. Kane, and identical with the
ethule of Berzelius. Etherine is a
peculiar carburetted hydrogen, which
has also been regarded as the basis of
ether.

ETHE'RID^. River Oysters; a fa-
mily of the atrachian bivalves, named
from the genus etheria.

ETHICS (hOiKds, belonging to morals).
The science of Morals, or those affections
of the mind which develop themselves in
action. Aristotle derives the word from
another, which signifies habit (h9iKrjv
a7r6 rod $0ovs), moral disposition being
formed upon habit.

ETHIO'NIC ACID (4i%, ether, 6elov,
sulphur). Ethero- sulphuric acid. An
acid produced by the action of the vapour
of anhydrous sulphuric acid upon abso-
lute alcohol kept cold.

ETHIOPIAN or NEGRO RACE. One
of the five principal races of mankind, in
which the head is narrow and compressed
at the sides, the forehead very convex,
the cheek-bones projecting forwards, the
nostrils wide, the jaws lengthened, the
skull in general thick and heavy, the
face narrow, projecting towards the lower
G5

EUP

EVE

part, the nose spread and almost con-
founded with the cheeks, the lips, parti-
cularly the upper one, very thick.

ETHNO'GRAPHY (gfror, a race,
7pd0w, to describe). A historical inves-
tigation into the origin, migrations, and
connexion of various peoples. In this
sense, ethnography is purely of a his-
torical character, and may be considered
as distinct from anthropography. A series
of anthropograpmes, of different epocns,
would form the true basis of ethno-
graphy.

ETHU'LE (a\9hp, ether, v\n, matter).
A hypothetical radical, existing in ether
and its compounds ; ether being the
oxide of ethule, and alcohol the hydrated
oxide of ethule.

ETIOLATION. The process of blanch-
ing plants, as celery, kale, &c, by shel-
tering them from the action of light.
The natural colour of the plants is thus
prevented from being formed.

ETYMO'LOGY (to 'drvfiov, the deriva-
tion of a word from its root, \6yos, an
account). That part of Grammar which
treats of the formation of words. Under
this general definition are included the
classification of words, the various modi-
fications they undergo to express different
meanings, and their origin and history.

EUCHLORINE (el, brilliant, x^wpop,
green). The name given by Davy to the
protoxide of chlorine, from its being con-
siderably more brilliant than simple chlo-
rine.

EU'CHRONIC ACID (eZxpoo?, of a
fine colour). An acid procured by the
decomposition of the neutral mellitate of
ammonia by heat. It forms a blue com-
pound with zinc, called euchrone.

EU'CLASE (el, well, K\d<a, to break).
Prismatic emerald; a beautiful mineral
found in Peru and Brazil.

EUDFALITE. A brownish-red mine-
ral, belonging to the tessular system of
Mohs.

EUDIO'METER (evSia, calm weather,
fxerpov, a measure). An instrument for
ascertaining the purity of the air, or,
rather, the proportion of oxygen con-
tained in a given gas.

EUKAIRITE. A new mineral found
in the copper mine of Skrickerum, and
consisting of silver, selenium, copper,
and alumina.

EUPHE'MISM (eixpnuia, the use of
words of good omen). A mild name for
a bad thing; a rhetorical figure em-
ployed to prevent giving offence to " ears
polite," and adopted, in daily use, in
130

deference to the fastidiousness which

prevails on certain points : " Strabonem

Appellat Pcetum pater ; et Pullum,

male parvus
Si cui filius est," &c.

EU'PHONY {elxpuvia, goodness of
voice). An agreeable quality of language
arising from the harmonious combination
of sounds. It consists in an uninter-
rupted flow of words, which neither im-
pedes the speaker's utterance, nor offends
the hearer's ear ; and is opposed to caco-
phony, or a harsh and disagreeable style.

EUPHORBIA'CEjE. The Euphor-
bium tribe of Dicotyledonous plants.
Trees, shrubs, and herbaceous plants,
with leaves alternate ; flowers apetalous,
unisexual ; ovarium three-celled, the cells
separating with elasticity from their com-
mon axis.

EU'PHOTIDE. A rock consisting
essentially of felspar and diallage, aggre-
gated together in the manner of granite.
The Italian artists call it gabbro.

EUPION (el, well, irtV, fat). A
colourless liquid, obtained by distillation
from the tar of animal matters, and so
named from its great limpidity.

EUPY'RION (el, easily, ™P, fire).
Any contrivance for obtaining an instan-
taneous light, as the phosphorus bottle.

EURITE, or WHITESTONE. A va-
riety of granite, in which felspar is the
predominant ingredient ; or in which all
the ingredients are blended into a finely
granular mass of a white appearance.

EVAPORATION. 1 . Spontaneous eva-
poration is the production of vapour by
some natural agency, without the direct
application of heat, as on the surface of
the earth or ocean. This is commonly
termed exhalation. 2. The chemical ope-
ration is usually performed by applying
heat to any compound substance, in order
to separate the volatile parts, which are
dissipated and lost. In this respect, eva-
poration differs from distillation, which
chiefly consists in preserving the volatile
parts.

EVE'CTION (eveho, to raise up). A term
applied to certain irregularities, con-
sisting of elongations or contractions, of
the moon's orbit. They depend upon the
varying attraction exercised by the earth
upon the moon, according as the latter is
in apogee or perigee, and as consequently
more or less under the influence of the
sun's attraction. They are periodical,
running through all their changes in
about twenty-seven days. See Angle of
Evection.

EXC

EXO

EVERGREEN. A terra applied to
plants which have persistent or perennial
leaves ; i. e. leaves which remain perfect
upon the plant beyond a single season, as
holly, common laurel, &c.

EVERLASTING FLOWERS. A po-
pular designation of certain flowers which
retain their colour for many months after
they have been gathered, owing to the
hardness of their tissue, and the small
amount of moisture which they con-
tain.

E'VOLUTE (evolutus, unrolled). A
curve from which any given curve may
be supposed to be formed by the evolu-
tion or unlapping of a thread from a sur-
face having the same curvature as the
first curve. See Curve.

EVOLUTION {evolvo, to roll out). A
term applied to a theory of non-sexual
generation, according to which the first
created embryos of each species must
contain within themselves, as it were in
miniature, all the individuals of that spe-
cies which shall ever exist ; and must
contain them so arranged, that each gene-
ration should include not only the next,
but, encased within it, all succeeding
generations. Hence this theory has also
received the name of the emboitement
theory. Compare Epigenesis.

EVOLUTION (in Algebra). The ex-
traction of roots, or the method of find-
ing a quantity, which, raised to a pro-
posed power, will produce a given quan-
tity. It is just the reverse of in-
volution ; and to perform the operation,
we must inquire what quantify multi-
plied into itself, till the number of fac-
tors amounts to the number of units in
the index of the given root, will gene-
rate the quantity whose root is to be ex-
tracted.

EXCENTRICITY (ef, out, Kevrpov,
centre). The ratio which the distance
between the centre and focus of an ellipse
or hyperbola bears to the whole semi-
axis. Half the distance between the
foci of an ellipse is called its excen-
tricity, and sometimes its ellipticity. It
is in this way that we speak of the excen-
tricity of the orbits of the planets which
are supposed to move in ellipses ; the cir-
cle which circumscribes the elliptic orbit
of a planet being called the excentric.
Hence, the excentric anomaly is the arc
of the excentric between the perihelion
of the orbit, and the straight line drawn
through the centre of the planet perpen-
dicular to the major axis. See Anomaly.

EXCHANGES, THEORY OF. A
131

theory introduced by Prevost for explain-
ing the equilibrium of temperature of
any body. It is founded on the suppo-
sition that the quantity of heat which
the body diffuses by radiation, is equal to
that which it receives by radiation from
surrounding objects, and which it either
wholly or in part absorbs.

EXCFPULUS. That part of the thallus
which forms the rim and base of the
shields of lichens.

EXCITATION OF ELECTRICITY.
The disturbance of the electric equili-
brium by friction, elevation of tempe-
rature, contact, &c. Bodies have been
distinguished into conductors and non-
conductors, according to the facility with
which the electric influence passes, or is
conducted, along their surfaces.

EXCITO-MOTORY. A designation of
that function of the nervous system,
discovered by Dr. Marshall Hall, by
which an impression is transmitted to a
centre, and reflected so as to produce con-
traction of a muscle, without sensation
or volition.

EXCU'RRENT {excurro, to run out).
A term applied to that mode of ramifica-
tion in plants, in which the axis remains
always in the centre, all the other parts
being regularly disposed around it, as in
pinus abies.

EXCURTRI'CES {excurro, to rush
hastily). Snatchers; a name given by
Macgillivray to an order of Birds, inter-
mediate between the flying and walking
tribes, and belonging to the Insessores of
other writers. They include the shrikes
and fly-catchers, the thick-bills and the
rollers.

EXHALATION. A general term for
all the effluvia or steams raised from the
surface of the earth in form of vapour.
Some distinguish exhalations from va-
pours, expressing by the former all steams
emitted from solid bodies, and by the
latter, the steams raised from water and
other fluids.

EXI'NTINE. A term applied by
Fritzsche to a third membrane situated
between the extine and the intine, in
the pollen of yew, juniper, cypress, &c.

EXO- (efa>). A Greek adverb, signify-
ing without, on the outside, &c.

1. Exo-genous (jeivo/jiai, to be pro-
duced). Outside-growing ; increasing in
diameter by deposition to the exterior : a
term applied to the structure of the axis
of dicotyledonous plants, in which the
newest-formed fibres are deposited on
the exterior of those previously formed,
G6

EXP

EXT

exhibiting, on a transverse section, a
series of concentric circles or zones.

•2. Exo-phyllous {<pu\\ov, a leaf). A
term applied by Dumortier to the exo-
rrhizous embryo, in consequence of the
cotyledons being always naked, i. e. not
evolved from a coleophyllum or leaf-
sheath.

3. Exo-ptile (tttIKov, a feather). A
term applied by Lestiboudois to the dico-
tyledonous embryo, in consequence of its
plumule being naked, i. e. not enclosed
within the substance of the cotyledons.

4. Exo-rrhizous (pi£a, a root). A term
expressive of the mode of germination
in exogenous plants, in which the radicle
appears at once on the surface of the
radicular extremity of the cotyledons,
and consequently has no coleophyllum or
sheath at its base, as occurs in the en-
dorrhizous germination.

5. Ex-osmose (wtrjuor, impulsion). The
property by which a rarer fluid passes
through membranous substances out of a
cavity into a vessel containing a denser
fluid. i

6. Exo-stome (aro/jLa, a mouth). The
foramen or orifice of the outer integu-
ment, or primine, of the ovule in plants.

7. Exo-thecium (d^nn, a case). A term
applied by Purkinje to the coat of the
anther, in plants.

EXOCHNATA (efoxor, prominent). A
designation of the long-tailed Crustacea,
as the lobster and shrimp.

EXOTE'RIC (e£<oTep<K6?, external).
A term applied to those disciples of Py-
thagoras and others, who were not yet
initiated into their highest philosophy;
as distinguished from the esoteric, who
were scientifically taught. The term
"exoteric" was also applied to those
writings which were in a more popular
form, while the " esoteric " writings were
of a more scientific and exact character.

EXPANSIBILITY (expando, to spread
out). That property of a body by which
it is capable, under certain circumstances,
of occupying more space than it usually
requires. The principal agent in the ex-
pansion of bodies is caloric.

EXPERIMENTUM CRUCIS. A cru-
cial or decisive experiment in attempting
to interpret the laws of nature ; so called,
after Bacon's manner, from the crosses, or
way-posts, used to point out roads, be-
cause they determine at once between
two or more possible conclusions.

EXPLOSION. The sudden and vio-
lent expansion of the constituent parts of
a body.
132

EXPO'NENT (expono, to explain). A
small figure, or other symbol, placed at
the right hand of an algebraical quantity,
to express its power. It is equivalent to
the number of factors, and is also called
the index of the power. Thus, in the
expression a2, the figure 2 is the index
or exponent, and denotes that the quan-
tity is the square of a.

1. Exponent of a rank. The number
or place of any term in a series : thus, in
the series 1, 3, 5, 7, 9, 11, 13, 15, &c, 7 is
the exponent of the rank of 13, this term
being the 7th in the order of the series.

2. Exponent of a geometrical ratio.
The quotient which arises from dividing
the consequent by the antecedent of the
ratio. Thus, in the ratio of 2 to 8, the
exponent is § = 4; and, in the ratio of
8 to 2, the exponent is | = £. Some ma-
thematicians, however, consider loga-
rithms as the exponents of ratios.

EXPONENTIAL. This term is va-
riously applied. The exponential calculus
is that part of Algebra which relates to
exponential quantities, or quantities raised
to powers of which the exponents are in-
determinate or variable. An exponential
curve is a curve defined by an exponential
equation, or an equation which contains
an exponential quantity. Exponential
equations are commonly resolved by
means of logarithms.

EXSERTED {exsertus, thrust out). A
term applied to the stamens of plants,
when they are longer than the corolla.

EXSICCATION {exsicco, to dry up).
A variety of evaporation, producing the
expulsion of moisture from solid bodies
by heat, and generally employed for de-
priving salts of their water of crystalliza-
tion.

EXTENSION (extendo, to stretch out).
That property of matter by which it occu-
pies space : it relates to the qualities of
length, breadth, and thickness, without
which no substance can exist ; but has
no respect to the size or shape of a body.
This property is termed, in common lan-
guage, size or volume.

EXTINE {extimus, outermost). The
outermost membrane of the pollen-grain
in plants.

EXTRA'CTION OF ROOTS. The
arithmetical or algebraical operation of
finding the root of a number or quantity ;
in other words, the finding that number
or quantity which, multiplied into itself
a certain number of times, will produce
the given number or quantity. See Evo-
lution.

FAC

FAL

EXTREME AND MEAN RATIO.
A straight line is said to be divided in
extreme and mean ratio, when the whole
is to the greater part as the greater part
to the less ; or when the rectangle con-
tained by the whole line and the smaller
segment is equal to the square of the
greater segment.

EXTRE'MES (extremus, last). In
Logic, the subject and predicate of a pro-
position are called its extremes or terms,
being, as it were, the two boundaries,
having the copula (in regular order)
placed between them. In speaking of a
syllogism, the word is often understood
to imply the extremes of the conclusion.

EXTRORSE (extrorsum, towards the
outside). Turned outwards ; turned away
from the axis to which it belongs; a

term applied, in botany, to those anthers,
whose line of dehiscence is towards the
petals. Brown uses the term posticce in
this sense.

EXU'VIiE {exuo, to put off). The
slough, or cast-off covering of certain
animals, as the skins of the serpent and
the caterpillar. This term relates, how-
ever, in geological language, not only to
the rejected envelopes of animals, but to
fossil shells and other remains which
have been left by animals in the strata of
the earth.

EXUVIATION (exuviez, a slough, the
cast-off skin of certain animals). A term
applied, in Zoology, to the process by
which the crustaceous animals throw off
their old shell, and form a new one.

F

FA'CET. A term derived from the
French, denoting a flat surface, with a
definite boundary. The English term
face has the same meaning in Geometry,
and is applied to the plane which forms
one of the surfaces of a polyhedron.

FACIAL ANGLE. This angle is mea-
sured by drawing a line from the pro-
minent centre of the forehead to the most
advanced part of the lower jaw-bone, and
observing the angle which it makes with
the horizontal line. By measurement of
this angle it has been affirmed that a
scale might be traced from "apes with
foreheads villainous low " to the African
variety of the human species, and from
that to the European.

FACTITIOUS {factito, to practise).
Made by art, as factitious cinnabar, in
distinction from the natural production.
This term is also applied to waters pre-
pared in imitation of natural waters, as
those of Brighton.

FA'CTOR. A term applied in Algebra
to each of the quantities which are mul-
tiplied into one another in order to form
( facer e) a product, i. e., to the multiplier
and the multiplicand ; thus a and a + x
are the factors of the product a {a + x),
or a2 + ax Factors are also called divi-
sors, especially in speaking of a number,
which is regarded as the product of seve-
ral others.

Factorial expression. A term some-
times applied to an expression of which
133

the factors are in arithmetical progression,
as —

(x+ 1) (* + 2) (x + 3) (x + 4).

FA'CULA (dim. of fax, a torch). A
little torch. The term faculce is applied
to certain luminous spots on the surface
of the sun ; they are of irregular form,
of variable duration, and are commonly
surrounded by a penumbra. By such
spots the diurnal revolutions of the
planets, as well as that of the sun, have
been determined.

FAHLERZE. Fahlore. A grey copper
ore, comprising the arsenical and the
antimonial varieties. In this, and in seve-
ral other double sulphurets of silver and
other metals, the sulphuret of silver and
the sub-sulphuret of copper, being iso-
morphous, replace each other in inde-
terminate proportions.

FA'HLUNITE. Automalite. A sub-
species of octohedral corundum, found in
a talcose rock, at Fahlun in Sweden.

FA'LCATE (falx, a scythe or sickle).
Sickle- shaped ; any thing plane and
curved, with parallel edges. The moon
is said to be falcate, when the enlight-
ened part appears in the form of a cres-
cent. In Zoology, a part is said to be
falcate, when it is curved with the apex
acute.

FALCO'NID.E. The Falcon tribe ; a
family of the Raptores, or Rapacious
birds, distinguished from the Vultures by
their shorter, sharper, and notched bill.

F AL

FAU

and by the sharpness and curvature of
their retractile talons. The falcons have
been divided into the noble, ox falcons
proper, capable of being trained to the
sport of falconry, and the ignoble, which
are incapable of this training. This
family includes the eagle, the hawk, the
kite, the osprey, &c.

FA'LLACY (fallacia, deceit). In
Logic, •' an unsound mode of arguing,
which appears to demand our conviction,
and to be decisive of the question in
hand, when in fairness it is not." Falla-
cies are of two kinds : —

1. Logical Fallacies, or fallacies "in
dictione," in which the fault is in the
reasoning, and in that alone, the conclu-
sion not following from the premises ; as
in the indistributed middle, illicit pro-
cess, negative premises, or affirmative
conclusion form a negative premiss, and
vice versd.

2. Non-logical fallacies, or fallacies
" extra dictionem," in which the fault is
in the matter. Of these there are two
kinds ; viz. 1st, when the premises are
such as ought not to have been assumed ;
2nd, when the conclusion is not the one
required, but irrelevant. To this head
belong the fallacies of "non causa pro
causa," " petitio principii," &c.

FALSE. This term, in its strict logi-
cal sense, denotes the quality of a pro-
position which states something not as it
is. Logicians express this quality of a
proposition by the word falsity, as being
more precise than the word falsehood,
which is opposed not merely to logical,
but also to moral truth.

FALSE CADENCE. In Music, a
cadence in which the base rises a tone or
semitone, instead of rising a fourth or
falling a fifth.

FALSE POSITION. A rule in arith-
metic, according to which, by false or
supposed numbers, taken at pleasure, the
true required number is discovered.
There are two methods : by single posi-
tion, one supposed number is used, and,
by working with this as the true one, the
real number required is found ; by double
position, two supposed numbers are used,
and if both prove false (as it generally
happens), they are subjected to further
arithmetical investigation.

FALSE'TTO. An Italian term, ap-
plied in Music to a false or artificial
voice, by which the vocal compass is ex-
tended, by contracting the aperture of
the throat, several notes above the natu-
ral voice. The Italians call the falsetto
134

voce di testa, or voice from the head ; the
natural voice, voce di petto, or voice from
the chest.

FALUNS. A French provincial name
for some tertiary strata, abounding in
shells, in Touraine, which resemble in
lithological characters the "Crag" of
Norfolk and Suffolk.

FAMILY. In classifications of Zoology,
Botany, &c, this term denotes the group
next in value and comprehensiveness
above the genus. As species constitute
a genus, so genera constitute a family, or
order.

FARI'NA (far, f arris, corn). Meal,
or vegetable flour, made from the seed
of the Winter Wheat. See Amylum.

Farinaceous. A term for all those sub-
stances which contain farina; viz. the
cerealia, legumes, &c.

FA'SCLE (fascia, a band). Stripes or
belts observed on the disc of Jupiter and
other planets. In Botany, contiguous
stems or fruits, which have grown unna-
turally together, are said to be fasciated.

FA'SCICLE (fasciculus, a little bundle).
A form of inflorescence resembling a
corymb, but having a centrifugal, instead
of a centripetal, expansion. It is a kind
of compound corymb.

FASCFCULATE (fasciculus, a little
bundle). Clustered ; as when several
bodies spring from a common point, as
the leaves of larix, the tubers of orchis,
the roots of commelina, &c.

FASTI'GIATE (fastigium, the top of
any thing). A term used in Botany to
denote that the branches of a tree are
appressed to the stem, assuming nearly
the same direction, as in populus fasti-
giata.

FA'TA MORGANA. Castles of the
Fairy Morgana. A meteorological phe-
nomenon occasionally witnessed in the
Straits of Messina, and depending on
unusual refraction. The images of men,
of buildings, and other objects are seen
from the coast, sometimes in the water,
sometimes at the surface of the water, or
in the air : there may be two images of
the same object, the one in a natural, the
other in an inverted position ; or the
images of the same object may be mul-
tiplied to a great degree.

FAULT. A technical term applied by
miners to a sudden interruption of the
continuity of strata in the same place,
accompanied by a crack or fissure, vary-
ing in width from a mere line to several
feet, which is generally filled with broken
stone, clay, and other materials. The

FEL

FER

displacement of the strata is owing to
the upheaving on the one side, or to sub-
sidence on the other side, of the fault.

FAUNA (Fauni, the rural divinities).
A term denoting the animals peculiar to
any particular country.

FAUX. The throat ; the orifice of the
tube of a gamopetalous corolla.

FAVOSE {favus, a honey-comb). Ho-
ney-combed ; excavated like a honey-
comb, as the receptacle of onopordum,
the seeds of poppy, &c.

FE'CULA (fcex, the grounds or settle-
ment of any liquor). Originally, any sub-
stance derived by spontaneous subsidence
from a liquid ; the term was afterwards
applied to starch, which was thus depo-
sited by agitating the flour of wheat in
water ; and lastly, it denoted a peculiar
vegetable principle, which, like starch, is
insoluble in cold, but completely soluble
in boiling water, with which it forms a
gelatinous solution.

FECUNDATION (fecundo, to make
fruitful). Impregnation. The effect of
the vivifying fluid upon the germ or
ovum, which is then called the embryo.

FE'LIDjE {felis, a cat). The Cat tribe ;
a family of carnivorous Vertebrata, cha-
racterized by their short powerful jaws,
retractile claws, and the peculiar adapt-
ation of their teeth for cutting. They
are, among the quadrupeds, what the
Falconidce are among Birds.

FELLOWSHIP. A rule in arithmetic,
by which profit or loss is divided between
two or more partners, in proportion to
the principal of each in joint stock. The
rule is applicable to cases in which the
investments are made for the same time,
and to cases in which the partners em-
ployed their principal at different times :
the former belong to the rule of fellow-
ship without time ; the latter, to that of
fellowship with time.

FE'LSPAR. A simple mineral which,
next to quartz, constitutes the chief ma-
terial of rocks. The white angular por-
tions of granite consist of felspar. This
mineral always contains some alkali in
its composition: in common felspar the
alkali is potash; in the variety called
Albite or Cleavlandite, it is soda. The
term glassy felspar denotes that the crys-
tals have a high degree of transparency.
Compact felspar appears to contain both
potash and soda. See Adularia.

Felspar-porphyry. A felspathic rock,
in which crystals of felspar are mixed
with hornblende, mica, or quartz.
FELSPA'THIC ROCKS. Rocks of
135

which felspar is the chief constituent,
comprising granite, gneiss, claystone,
lava, and other varieties.

FENE'STRATE (fenestra, a window).
Windowed ; a term applied to the incom-
plete dissepiment sometimes occurring
in the siliqua of cruciferous plants.

FE'RGUSONITE. A crystallized min-
eral, occurring principally as a columbate
of yttria. It has been found only in
Greenland, near Cape Farewell, imbedded
in quartz.

FE'RMENT (fermentum, quasi fervi-
mentum, from ferveo, to work). A sub-
stance which possesses the power of
commencing fermentation. It is either
naturally present, as in the grape, or is
added, as in the case of yeast.

FERMENTATION. Certain changes
of animal or vegetable substances, re
duced to the moist or liquid state by
water. There are several kinds : —

1. The Saccharine ; when the change
terminates in sugar, as that of starch.
/ The Panary ; as that of flour

„ j forming bread :— or

j The Vinous ; as that of the grape,
^ &c, forming wine; —
evolving alcohol.

3. The Acetous; when the result is
acetic acid, or vinegar.

4. The Putrefactive ; generally of ani-
mal substances, evolving ammonia.

5. The Lactic; when no alcohol is
evolved, but the liquid becomes mucila-
ginous and thick, with the production of
mannite and lactic acid.

FE'RRIC OXIDE (ferrum, iron). Per-
oxide of iron ; a mineral occurring abun-
dantly in nature, as oligistic or specular
iron, forming the celebrated Elba ore ; as
red hematite, which is cut, and forms the
burnishers of bloodstone ; and in combi-
nation with water, as brown hematite,
employed in most of the iron furnaces of
France.

1. Ferroso -ferric Oxide. The black
oxide, magnetic oxide of iron, or martial
ethiops. It occurs in the mineral king-
dom, under the name of magnetic iron-
ore, the massive form of which is called
native loadstone.

2. Ferroso-ferric Sulphate. The name
given by Berzelius to a combination of
the proto- and per-sulphates of iron.

FERRI'FEROUS ROCKS (ferrum,
iron, fero, to bear). Rocks in which iron-
ore is abundantly distributed, comprising
clay iron-ore and iron pyrites.

FERROCYA'NIC ACID. Ferrocya-
nide of Hydrogen. A compound of cyano-

FI F

gen, metallic iron, and hydrogen ; also
called ferruretted chyazic acid. It con-
tains the elements of hydro-cyanic acid,
hut differs from it totally In its properties.
Its salts, formerly called triple prussiates,
are now termed ferro-cyanides. The
beautiful pigment Prussian blue is a
ferro-cyanide of the peroxide of iron.

FERRU'GINOUS (ferrugo, quasi ferri
cemgn, rust of iron). Containing iron,
or of the nature of iron, as certain salts,
mineral waters, &c. The term ferrugo
is applied, in Botany, to a disease of
plants, commonly called rust, and occa-
sioned by the presence of minute fungi,
chiefly of the genus uredo.

FERTILIZATION (fertilis, fertile).
The function of the pollen of plants upon
the pistil, by means of which the ovules
are converted into seeds.

FETTSTEIN (German, fat stone). A
designation of a sub-species of pyramidal
felspar, from its resinous nature. The
term is synonymous with elaolite, which
means oil-stone.

FIBRE (fibra, a filament). A filament
of thread, of animal, vegetable, or mineral
composition. A fibril is a minute sub-
division of a fibrous root.

FI'BRIN (fibra, a fibre). A principle
found in vegetables as a constituent of
gluten ; and in the living blood of ani-
mals, constituting muscular fibre.

FI'BROLITE. A mineral of a pecu-
liar fibrous texture, found in the Car-
natic, and consisting of alumina, silica,
and iron.

FIBROUS (fibra, a fibre or thread).
Consisting of or resembling fibres ; as
indicating the structure of a shell when
fractured.

FI'BROUS COAL. A variety of
glance-coal, distinguished by its fibrous
concretions and silky lustre. It occurs
in the coal-fields of Great Britain.

FIELD OF VISION. A technical
expression for the space or range seen
through a telescope. It is measured by
dividing the angle under which it is seen
by the angle of vision of the naked eye
embracing the same field within its view.
The greater the magnifying power of the
instrument, the less will be the angle of
vision of the naked eye, compared with
that of an eye looking through the
glass.

FIFTH. An interval in Music, occur-
ring in the natural scale, in the fifth
place from the fundamental. The false
fifth is less than the fifth by a lesser
semitone.
136

FIG

FIFTEENTH. In Music, an interval
of two octaves. The fifteenth stop in
organs is a double octave above the dia-
pason.

FI'GURATE NUMBERS. Certain
series of numbers deduced from any pro-
gression, by taking the sum of the first
two, the first three, the first four, &c,
terms of the progression, and then ope-
rating on the series thus obtained, in
order to obtain a new series, and so on.
For example : —

A 1, 2, 3, 4, 5, 6, 7,

B 1, 3, 6, 10, 15, 21, 28,

C 1, 4, 10, 20, 35, 56, 84,

D 1, 5, 15, 35, 70, 126, 210.

1. The series A is the arithmetical
progression from which the other series
are deduced. The series B consists of
triangular or polygonal numbers of the
preceding progression, so named from
certain analogies which the numbers so
denoted have with the geometrical figures
bearing the same denominations. The
series C consists of triangular pyramidal
numbers, and is formed from the pre-
ceding series in the same way as this
from the original progression. The series
D consists of second pyramidals, and is
formed like the preceding series.

2. If the common difference of the first
progression were 2, the successive series
would consist of square numbers ; if the
common difference were 3, the series
would be pentagonal numbers ; if 4,
hexagonal numbers, and so on; the num-
bers thus obtained being capable of being
placed in the form of squares, pentagons,
hexagons, &c.

FIGURE. Figure, or form, is a pro-
perty of bodies, resulting from extension.
The volume of a body has no relation to
its figure: bodies which have the same
figures may possess very different vo-
lumes; and bodies may have the same
volume under very different figures;
thus, two masses of matter may present
the same volume, although the one be
round and the other square.

FIGURE (in Geometry). A finite
space, bounded on all sides by lines or by
planes. The term is also employed as
synonymous with diagram.

FIGURE, APPARENT. A term in
Optics, denoting the figure under which
an object presents itself to the eye. As
this depends on the situation of the
points from which the rays of light pass
to the eye, the apparent figure may be
very different from the real figure of an
object ; a straight line, for instance, may

FIR

FLA

appear as a point, a plane as a straight
line, and a solid as a simple surface.

FIGURE OF A SYLLOGISM. A
logical expression, denoting the situation
of the middle term with respect to the
extremes of the conclusion (i. e. the
major and the minor term). The figures
of reasoning are only different forms of
stating it.

FI'LAMENT (filamentum, a little
thread). The thread-like portion of the
stamen, which supports the anther.

FI'LICES (filix, a fern). The Fern
tribe of Acotyledonous plants. Leafy
plants, producing a rhizome; fronds
simple or variously divided; flowerless;
reproductive organs consisting of thecce
or semi-transparent cases appearing on
the back or margin of the fronds.

FILITE'L^ (filum, a thread, tela, a
web). A family of Spiders, remarkable
for the long threads of silk which they
spread about in the places where they
prowl in quest of prey.

FILTRATION. The process of strain-
ing a liquid through a. filter, or separating
it mechanically from the particles which
are mixed with it. Filters are usually
made of unsized or blotting paper.

FI'MBRIATED (fimbria, a fringe).
Fringed ; having the margin bordered by
filiform appendages; a term applied to
the thin, elevated, fin-like processes,
belonging to many of the murices, and
sometimes placed round the aperture of
cyclostomous land-shells.

FI'ORITE. Pearl sinter; a volcanic
production, chiefly silica, in a stalactitic
form.

FIRE-BALLS. Bolides, or fiery me-
teors ; luminous bodies, which suddenly
appear at a considerable height in the
atmosphere, and shoot through the
heavens with great velocity, sometimes
accompanied with the fall of an aerolite.

FIRE DAMP. A gas evolved in coal
mines, consisting almost entirely of light
carburetted hydrogen.

FIRE ENGINE. The fire engine is a
modification of the forcing pump. It
consists of two such pumps, the pistons
of which are moved by a lever with equal
arms, having a common fulcrum. When
one piston is descending, the other is
ascending- The machine acts precisely
like the forcing pump, only that its
power is doubled by having two pistons
instead of one.

FIRE, GREEK. An inflammable
composition employed in the wars of the
middle ages, supposed to consist princi-
137

pally of naphtha mingled with pitch and
sulphur.

FISH. The name applied to a class
of animals occupying the lowest station
of the four great divisions of the section
Vertebrata. They are distinguished,
with reference to the substance of their
skeleton, into the osseous and the carti-
laginous or chondropterygious. See
Ichthyology.

FISSI'PAROUS (fissus, cleft, pario,
to bring forth). A designation of that
mode of propagation, which takes place
by spontaneous division of the body of
the parent into two or more parts, each
part, when separated, becoming a dis-
tinct individual, as in the monad, vorti-
cella, &c. ; or by artificial division, as in
the hydra, planaria, &c. ; and in the
propagation of plants by slips.

FISSIPE'NN^E (fissus, cleft, penna,
a wing). A family of Lepidopterous in-
sects, commonly called Plumed Moths,
and characterized by the division of the
membrane of the wings into branches or
rays, of which each pair has from two to
six.

FISSIRO'STRES (fissus, cleft, ros-
trum, a bill). A group of the Insessores,
or Perching Birds, having a short, broad,
horizontally-depressed bill, so formed
that the gape of the mouth is extremely
wide. It comprises the swallows, goat-
suckers, bee-eaters, kingfishers, and
todies.

FISTULOUS (fistula, a pipe). Cylin-
drical and hollow, as the stems of grasses,
of umbelliferous plants, &c.

FIXED AIR. A name formerly given
by chemists to the air which was extri-
cated from lime, magnesia, and alkalies,
now called carbonic acid gas.

FIXED SIGNS OF THE ZODIAC.
These are Taurus, Leo, Scorpio, and
Aquarius ; they are so called because
the season is considered to be more
settled when the sun passes through
these signs, than at any other times of
the year.

FIXED STARS. Stars which do not
appear to change their relative situations,
as distinguished from planets and comets.

FI'XITY. The property by which
bodies resist the action of heat, so as not
to rise in vapour, as the fixed, in contra-
distinction to the volatile oils ; or non-
metallic elements, which can neither be
fused nor volatilized, as carbon, silicon,
and boron.

FLABE'LLIFORM (fiabellum, a fan,
forma, likeness). Fan-shaped ; plaited

FLI

FLO

likethe rays of a fan, as descriptive of
the leaves of some palms.

FLAGE'LLUM (Lat. a whip). An
appendage of the legs of the Crustacea,
resembling a whip. By the early bota-
nists the term flagella was applied to the
trailing shoots of the vine ; and the word
flagelliform, or whip-like, is employed to
characterize the long, taper, and supple
roots of certain plants.

FLAKE-WHITE. Oxide of bismuth,
so called from its occurring in the form
of small laminae or flakes. The term is
often applied to the purest white lead.

FLAME. Gaseous matter heated so
highly as to become luminous. The
flame of volatile carbonaceous combus-
tibles, as coal gas, consists of three parts
— an interior cone of vaporized combus-
tible, an intermediate sphere of partial
combustion, and an exterior sphere of
complete combustion.

FLAMELESS LAMP. A lamp in
which the combustion of inflammable
substances is carried on at a temperature
below that required for their inflamma-
tion. Thus, if a jet of the gaseous hydro-
carbons be allowed to escape into the air,
and a red-hot coil of platinum be intro-
duced into it, the wire will be maintained
at a red heat, and the gas will be con-
sumed invisibly ; but if the temperature
of the wire be raised to a white heat,
the gas will immediately burst into
flame.

FLAT. A character in Music, marked
(?, which depresses the note before which
it is placed a chromatic semitone. An
accidental flat is that which, not occur-
ring in the clef, affects only the bar in
which it is placed. A double flat de-
presses a note two semitones below its
natural state ; thus B double flat is, in
fact, A natural. A flat fifth is an inter-
val of a fifth depressed by a flat, called
by the ancients semidiapente.

FLEXIBILITY (flecto, to bend). That
property of bodies by which, on the ap-
plication of force, they change their form
and bend ; it is opposed to stiffness on
the one hand, and to brittleness on the
other.

FLE'XURE (flecto, to bend). The
bending of a line or surface. The point
of contrary flexure is that point of a
curve at which the curvature passes
from convex to concave, or vice versa,
with respect to the axis.

FLINT. Silex. A mineral, consisting
of silicious earth, nearly pure. In Geo-
logy* flint is a variety of the quartzose
138

rocks, of various colours, with a con-
choidal fracture and horny aspect. Flinty
slate, silicious schistus, or Lydian stone,
is another variety of the same rocks,
and, when polished, is used as a touch-
stone for ascertaining the comparative
purity of gold and silver.

FLINTS, LIQUOR OF. A solution
of flint or silica in potash, prepared by
fusing together hydrate of potash and
powdered flint or fine sand.

FLOATATION, STABLE. A term
applied to that position of a floating body
in which it is not capable of being upset
by the exertion of a small force, but in-
variably returns to its former position.
This is not the case when its position is
unstable, as small impulses then induce
a change of place, which commonly pro-
duces stable equilibrium.

FLOATING CURRENT. A move-
able conductor, invented by De la Rive,
for illustrating the action of electric cur-
rents on each other.

FLOATSTONE. A sub-species of the
indivisible quartz of Mohs. It occurs
incrusting flint, or in imbedded masses
in a secondary limestone at St. Ouen,
near Paris.

FLOCCI (floccus, a lock of wool).
Woolly filaments found mixed with spo-
rules in the interior of some fungaceous
plants. The same name is also applied
to the external filaments of Byssaceae.

FLOETZ ROCKS (flotz, German, a
layer or stratum). A term applied, in
Germany, to the secondary strata, because
these rocks were supposed to occur most
commonly in flat horizontal layers.

FLO'RA (flos,floris, a flower). A term
expressive of the botanical productions
of any particular country.

FLO'RETS. Flosculi. The small
flowers which compose the capitulum of
Compositae. Those of the circumference
are ligulate, or strap-shaped; those
within the circumference are tubular;
the former are called florets of the ray,
the latter florets of the disk.

FLOS-FERRI. A radiated variety of
carbonate of lime, or of calc-spar, often
found in veins of spathose *>ora-ore.

FLOWER. In botanical language, the
flower is a terminal bud comprising all
the organs which contribute to the pro-
cess of fecundation, as the calyx, the
corolla, the stamens, and the pistil ; of
these, the last two only are indis-
pensable.

FLOWERS (in Chemistry). A term
formerly used to denote such bodies as

FLU

FOC

assume a pulverulent form by sublima-
tion or crystallization : thus we have
flowers of zinc, or the oxide ; flowers of
benjamin, or benzoic acid ; flowers of
sulphur, or sublimed sulphur, &c.

FLU'CERINE. The native deutoxide
of cerium, occurring near Falun, in
Sweden.

FLU'ELLITE. A rare mineral, con-
sisting of hydrofluoric acid and alumina,
occurring at Stenna-gwyn, in Cornwall.

FLUENT or FLOWING QUANTITY.
This term denotes, in analysis, the vari-
able quantity, considered as increasing
cr diminishing. The term is now super-
seded by that of integral, and the methods
of fluxions and fluents have been laid
aside for the differential and integral
calculus.

FLUID. A fluid is a collection of
material particles, which are held to-
gether by so slight a degree of cohesion,
as to be easily moved among themselves.
1. Elastic fluids are those which are ca-
pable of being compressed into a smaller
bulk, and of recovering their dimensions
when the compressing force is removed ;
of this kind are atmospheric air and all
the gases. 2. Inelastic fluids are those
formerly supposed to be incompressible,
and among these were ranged water,
mercury, alcohol, and liquids generally.
But the term is incorrect : the phenome-
non of the transmission of sound through
water and other liquids had long ago
indicated that they were capable of being
compressed.

FLUI'DITY {fluo, to flow). The state
of bodies when their parts are very readily
moveable in all directions with respect to
each other. There is a partial fluidity,
in which the particles are condensed or
thickened into a coherent though tremu-
lous mass. Jellies are of this kind, and
may be considered as holding a middle
place between liquids and solids.

FLUOBO'RIC ACID. Fluoride of
boron. A gas produced by the decompo-
sition of fluor spar, by means of vitrified
boracic acid.

FLUOR SPAR. The technical name
for the fluoride of calcium, a salt found
crystallized in cubes of various colours.
A compact variety occurs in Derbyshire,
which is cut into ornamental vases.

FLU'ORIDES. Compounds of fluorine
with the electro-positive elements, ob-
tained by treating the fluate of mercury
or of lead with bodies more positive than
these metals.

FLU'ORINE. An elementary body
139

generally found in the mineral kingdom
in combination with calcium, or as fluor-
ide of calcium, which constitutes the
mineral fluor spar.

FLUOSI'LICIC ACID. Fluoride of
silicon. A colourless gas, produced by
the action of hydrofluoric acid on glass.

FLUX {fluo, to flow). A substance
used in Chemistry and Metallurgy, to
reduce ores or metallic compounds to the
metallic state, by promoting their fusion.
Alkaline fluxes are generally employed,
which render the earthy mixtures fusible
by converting them into glass. Black
flux is a mixture of nitre and bitartrate
of potash ; white flux is a carbonate of
potash. Other fluxes consist of argol,
charcoal, and some kinds of glass.

FLU'XIONS {fluxio, a flowing). In
the Newtonian analysis, fluxions are the
"velocities of motions." More particu-
larly defined, a fluxion is the magnitude
by which any flowing quantity would be
uniformly increased in a given portion of
time, with the generating celerity at any
proposed position, or instant, supposing
it thence to continue invariable. Hence
it appears that the fluxions of quantities
are always as the celerities by which the
quantities themselves increase in magni-
tude. The method of fluxions, derived
from that of prime and ultimate ratios,
has been entirely superseded by that of
the differential calculus.

FLY POWDER. An oxide of arsenic,
formed by the exposure of native arsenic
to the air, and employed, when mixed
with sugar and water, for destroying
flies.

FLY-WHEEL. A large heavy wheel
applied to steam engines and other ma-
chines, for the purpose of equalizing the
effect of the moving power. If the
moving power slackens, the fly-wheel
impels the machine forward; if the power
tends to impel the machine too fast, the
fly-wheel slackens it. Its object is,
therefore, to absorb, as it were, the sur-
plus force at one part of the action of the
machine, and to give it out when the
action of the machine is deficient. At
one time it is an impelling, at another a
retarding power.

FOCUS. The Latin term for a hearth
or fire-place ; hence it denotes any point
in which light, or heat, is concentrated.
In Optics, it is the point where several
rays are collected, in consequence of re-
fraction or of reflexion. In Geometry
and Conic Sections, it is applied to cer-
tain points in the ellipse, the parabola,

FOL

FOR

the hyperbola, where the radii from all
parts of these curves meet.

1. Foci of an Ellipse. Two points in
the transverse diameter of an ellipse,
equally distant from its ends, and so
situate that, if any point be taken in the
circumference of the ellipse, and lines
drawn from that point to the two foci,
the length of these lines, when joined
together, will always be the same, at
whatever part of the circumference the
point may be taken.

2. Foci of Mirrors. 1. The focus of a
concave mirror is that point of the axis
through which the reflected rays of light
pass ; the principal focus is the focus of
parallel rays. 2. In the convex mirror,
the focus lies as far behind the reflecting
surface as in the concave it lies before
it ; it is generally call* d the virtual focus,
because it is only an imaginary point,
and is not formed by the actual union of
rays in a focus. Similar terms are era-
ployed in speaking of the foci of lenses.

3. Focus, Geometrical and Refracted.
The point in which the rays of light, ac-
cording to their known laws, ought to be
concentrated, when reflected from a con-
cave mirror, or refracted through a lens,
is termed the geometrical focus ; that in
which they are actually found, is the
refracted focus. These foci are separated
from each other in proportion to the
degree of spherical aberration.

4. Focal Distance. In the concave
mirror, this is the distance between the
focus and the vertex of the mirror, and
it is always equal to half the radius of
that sphere of which the mirror forms a
segment. In the convex lens, it is the
distance of the focus from the surface of
the glass, or from the optical centre.

FO'LIATE CURVE {folium, a leaf).
A curve line of the third order, defined
by the equation xs+y3=axy. It is one
of the species of defective hyperbolas,
having one asymptote and two infinite
branches. Its name is derived from the
resemblance of its figure to that of a leaf.

FO'LIATED {folium, a leaf). Resem-
bling a leaf. The external surface of a
shell is said to be foliated, when its va-
rices or spines are divided at their mar-
gins into leaf-like segments, as in the
rose-bush murex. The substance of a bi-
valve shell is also said to be foliated,
when it consists of thin flat plates
overlapping each other.

FO'LIATED COAL [foliatus, having
the texture of leaves). A sub-species of
black coal, occurring in the coal forma-
140

I tions, and distinguished by its lamellar
concretions, splendent lustre, and easy
frangibility.

FOLIA'TION {folium, a leaf). A term
synonymous with vernation, denoting the
manner in which the young leaves of
plants are arranged in the leaf-bud. The
terms expressive of the various modes of
arrangement of leaves are the same as
those employed for the floral envelopes,
and will be found under the word Esti-
vation.

FO'LIOLE {foliolum, a little leaf). A
leaflet; a term applied, in Botany, to the
small leaves which are borne on the
several divisions of what is commonly
called a compound leaf.

FO'LLICLE (dim. of follis, a pair of
bellows). Literally, a little bag, or scrip
of leather. The term denotes, in Botany,
a one-celled, one-valved, superior fruit,
dehiscent along its face, as in paeon ia.

Double Follicle. This term is applied
by Mirbel to the conceptaculum of other
writers, and consists of a two-celled, su-
perior fruit, separating into two portions,
the seeds of which do not adhere to mar-
ginal placentas, as in the follicle, but
separate from their placentas, and lie
loose in each cell, as in asclepias.

FO'MALHAUT. A star of the first
magnitude in the southern constellation
Piscis Australis.

FORA'MEN {foro, to pierce). An
opening. A passage observed at the
apex of the ovule in plants, and com-
prising both the exostome and the en-
dostome.

FORAMINI'FERA {foramen, an open-
ing, fero, to bear). The name of a family
of microscopic shells, the chambers of
which communicate with each other by
a small opening or foramen. They are
not all cephalopods, as D'Orbigny sup-
posed, who gave them the name.

FORCE. The general designation of
any exertion which has a tendency to
move a body at rest, or to affect or stop
the progress of a body already in motion.
This is sometimes termed active force, in
contradistinction to that which merely
resists or retards the motion of a body,
but is itself, apparently, inactive. The
degree of resistance to any motion may
be measured by the active force required
to overcome that resistance, and hence
writers on Mechanics make use of the
terms resisting forces and retarding forces.
The straight line in which any force
tends to make a body move, is termed
the line of direction of the force.

FOR

FOR

1. Forces, Composition of. An expres-
sion employed in Mechanics, when two
or more forces act on a body in the same
direction, or in diametrically opposite
directions, or at some angle. In all these
cases, the force which represents the
combined effects of all the forces is called
the resultant. 1. In the first case, the
resultant is the sum of all the forces, and
the line of direction is one and un-
changed. 2. In the second case, the
body will remain at rest, if the forces are
equal; but if they are unequal, the re-
sultant is the difference of the forces, and
the direction that of the greater force.
3. In the third case, the resultant is a
mean force in an intermediate direction.
Thus any number of forces may be re-
solved into one resulting force, the effect
of which is the absolute motion ; and any
motion may be assumed to be the result
of a single force, or of a combination of
many. This is termed the composition
and resolution of forces.

2. Forces, Parallelogram of. A term
used as explanatory of the third case in
the preceding paragraph. If the lines
which each of two forces, acting singly,
would have caused a body to describe in
a given time, make any angle whatsoever
with each other, the line which the body
will describe in that time, when both the
forces act upon it at the same instant, is
the diagonal of the parallelogram under
the two first-mentioned lines.

3. Force, Accelerated. The increased
force which a body exerts, in consequence
of the acceleration of its motion. By
some writers this is termed accumulated
force. See Acceleration.

4. Forces, External and Internal. The
former are those which act upon masses
of matter at sensible distances, as attrac-
tion and repulsion. The latter, or mole-
cular forces, are those which act only
on the constituent molecules of matter,
and at insensible distances, as cohe-
sion.

5. Force, Centrifugal and Centripetal.
The tendency of the planets to move
forward in a straight line, is called the
centrifugal force, and the attraction of
the sun, by which they are drawn down-
wards, or towards a centre, is called their
centripetal force ; and it is by these two
forces that the planets are made to per-
form their constant revolutions around
the sun.

6. Forces, Polar. Those forces which
are conceived to act with equal intensity
in opposite directions at the extremities

141

of the axes of molecules, or of masses of
matter

FO'RCER. A solid piston, employed
in the construction of pumps for pro-
ducing a constant stream, or raising
water to a greater height than it can be
raised by atmospheric pressure.

FORE-STAFF. An instrument used
at sea for taking the altitudes of the
celestial bodies. It is now superseded
by more perfect instruments.

FOREST MARBLE. A portion of
the series of the Lower Oolite Formation,
consisting of a coarse laminated shelly
oolite, interposed between beds of clay,
sand, and grit.

FORFICU'LIDuE {forficula, a forked
claw). A family of orthopterous insects,
named from the genus forficula, and
constituting, according to some writers,
the order Dermaptera. They comprise
the various species of earwig.

FORM. The mode in which an object
is presented to our mind or senses : in
the former case it belongs to the catc
gories ; in the latter to figure.

FORMATION. A group of alluvial
deposits, sedimentary strata, or igneous
rocks, referred to a common origin or
period. In geological treatises, one or
more simple minerals constitute a rock ;
one or several rocks, united by certain
common characters, constitute a forma-
tion, or connected series ; and several
formations constitute a system of rocks.

FO'RMIC ACID {formica, an ant).
A peculiar acid extracted from red ants,
and procured artificially from all vege-
table substances by oxidation with acids.
Its salts are called formiates.

FORMI'CID^ (formica, an ant). The
Ant tribe; a family of Hymenopterous
insects, distinguished by their subterra-
nean habits, and the existence among
them of neuters, which perform the la-
bours of the family.

FORMULA (dim. of forma, a form).
A short general form or rule for the per-
formance of any operation. In Algebra,
the expression of a general rule for the
solution of a problem.

FORMULAE, CHEMICAL. A simple
mode of exhibiting the composition of che-
mical combinations by representing the
substances by the initial letters of their
Latin names, and adding figures or lines
to indicate the number of equivalents.
Thus K. denotes one equivalent of po-
tassium ; O5, five equivalents of oxygen ;
N or N, two equivalents of nitrogen.
For every equivalent of oxygen a dot, for

FO U

FRA

every equivalent of sulphur, a comma is
placed over the symbol ; thus C repre-
sents carbonic acid; K, sulphuret of

potassium ; K N. nitrate of potassa.

FO'RMYL. A hypothetical radical of
a series of compounds, one of which is
formic acid.

FORNAX CHEMICA. The Chemist's
Furnace ; a modern southern constella-
tion, consisting of fourteen stars, and
situated immediately below Cetus.

FORNIX. Literally, an arch ; a term
applied to an assemblage of small plates,
or lamellae, which overarch the orifice of
the tube of the flower in certain plants,
as cynoglossum.

FO'RSTERITE. A crystallized mine-
ral containing silica and magnesia, found
atVesu vius, accompanied by pleonaste and
pyroxene, and named from Mr. Forster.

FO'SSIL (fossilis, dug out of the
earth). Any thing dug out of the earth.
The term is now restricted to " organic
remains," or the petrified remains of ani-
mal and vegetable substances found im-
bedded in the strata of the earth.

FOSSIL COPAL. Highgate resin. A
mineral of a resinous odour, found in the
bed of blue clay at Highgate, near Lon-
don, and at Wocklow in Moravia.

FOSSILI'FEROUS (fossilis, dug out
of the earth, fero, to bear). A term ap-
plied to a formation or rock containing
organic remains, or fossils, while those
rocks in which no such relics are found
are called non-fossiliferous.

FOSSO'RES (fossor, a digger). Dig-
gers ; a general term for a group of acu-
leate hymenopterous insects, commonly
known as sand and wood wasps, which
dig cells in the earth or in wood, for the
deposition of their eggs and stores.

FOUNDING. The mechanical art
which comprises all the operations of
reducing ores, and of smelting and cast-
ing metals.

FOURTH. One of the harmonica!
intervals of music, containing four sounds
or terms between its extremes, and three
intervals ; or as being the fourth in order
from the fundamental sound in the na-
tural or diatonic scale. The diminished
fourth consists of a whole tone and two
semitones; the perfect fourth, of two
whole tones and a semitone ; the super-
fluous fourth, extreme sharp, or tritonus,
of three whole tones.

FOUSEL OIL. Hydrate of oxide of
cmyl. Oil of grain-spirits or potatoes ;
142

an oil produced in the fermentation of
unmalted grain and potatoes.

FOVI'LLA. A viscous liquor con-
tained in the pollen-vesicle of plants.

FRACTION (fractio, a breaking). An
arithmetical quantity which represents a
part or parts of an integer, or whole
number. A vulgar fraction is expressed
by means of two numbers placed one over
the other, with a line between them ; the
lower of these is the denominator, and
shows into how many equal parts the
integer is divided ; the upper is the nu-
merator, and shows how many of these
parts are taken to form the fraction, as |.

1. A proper fraction is one whose nu-
merator is less than the denominator, and
which is itself therefore less than the
whole in question, as f. An improper
fraction is one whose numerator is equal
to or greater than the denominator, and
which is itself therefore equal to or
greater than the whole in question, as

I, V-

2. A mixed number is one formed of a
whole number and a fraction, as 2§. A
compound fraction is a fraction of a frac-
tion, as f of f . A complex fraction is one
in which either the numerator or deno-
minator, or both, are fractions, as —

3£ 2_ 1| g of 3
1» 4§' 3f' 2i *

3. A continued fraction is one whose
denominator is continued by being itself
a mixed number, and the denominator of
the fractional part again continued as
before, and so on ; as —

1 5 1

~T "T i

2+ 3 + — p +

1 9+&c. 1

3 + — 2 + —'

4 r + &c.

4. A vanishing fraction is one in which
a supposition is made which destroys
both numerator and denominator at the
same time ; thus,

a;2 — 1

x—l
is a fraction which will assume the form

of _, when x = I.
0
FRACTURE (fractura, a breaking).
A term employed in geology to designate
the appearance of a fresh surface of a
rock, when exposed by the stroke of a
hammer or any other forcible separation
of its parts. It may be even, or form a
plane of greater or less extent ; uneven,
or formed of variously inclined planes of

FRE

FRI

small extent ; conchoidal, when one of the
separated surfaces is concave, the other
convex ; splintery, when the surface pre-
sents the appearance of thin-edged scales ;
hackley, when covered with very sharp
protruding points.

FRAGMENTARY ROCKS. Rocks
formed of fragments of other rocks, gene-
rally of sufficient size to admit of heing
distinguished into different kinds. When
the fragments are very small, they form
sandstones and tufas; when large and
rounded, they constitute conglomerates ;
when large and angular, breccice. The
fragments are commonly cemented to-
gether hy an intervening substance.

FRANGIBI'LITY. In Geology, the
degree of facility with which a rock
yields to the hammer.

FRA'NKLINITE. A mineral re-
sembling oxidulous iron, occurring in
New Jersey, together with the red oxide
of zinc.

FRAU'NHOFER'S SPECTRUM.

Fraunhofer found that, in a perfect solar
spectrum, the coloured spaces are not
continuous, but are interrupted by dark
lines parallel to the slant edge of the
prism. These lines, which are called
Fraunhofer's, are more than 500 in num-
ber, and were employed by the discoverer
for accurately measuring the refraction,
the breadths of the individual colours,
and the intensity of the light of different
luminous bodies.

FREE CHARGE. A term applied, in
experiments with the Leyden jar, or bat-
tery, to that portion of the induction
which is directed through the air to sur-
rounding conductors.

FREEZING MIXTURES. The rapid
absorption of heat which bodies exhibit
in passing from the solid to the fluid
state, explains the operation of freezing
mixtures. If nitre be dissolved in water,
the temperature of the liquid falls above
16 degrees. If snow and a third of its
weight of common salt be mixed toge-
ther, they become liquid, and the tem-
perature of the mixture may fall to 0°.
These phenomena depend upon the affi-
nity which exists between these salts and
water; in order to satisfy this affinity,
the bodies melt, and in so doing absorb
heat, which becomes latent in them,
from surrounding bodies. By this means,
considerable degrees of cold may be pro-
duced : the degree of cold depends on
the quantity of heat which passes from
a free to a latent state ; and this, again,
depends upon the quantity of the sub-
143

stance liquefied, and the rapidity of the
liquefaction.

FREEZING POINT. A fixed point
in the scale of the thermometer, at which
snow or ice melts. The length of the de-
grees depends on the system of gradu-
ation adopted ; in Fahrenheit's ther-
mometer, the freezing point is marked
32°. The space between the freezing
and the boiling point is the fundamental
distance, or length of the scale.

FRENCH WHITE. The common de-
signation of finely pulverized talc.

FRIABI'LITY' {frio, to crumble). The
property by which a substance is capable
of being crumbled and reduced to
powder.

FRICTION {frico, to rub). The act
of rubbing the surfaces of bodies upon
one another. In Mechanics, it is a hin-
derance of motion, and is termed a re-
tarding force. Friction is said to be
sliding, when the parts of one surface
move parallel with the other, as when an
axle moves in the nave of a wheel; and
rolling, when a round body turns about
the surface of some other body, so that
fresh points of both the surfaces are con-
tinually brought into contact with each
other.

Measure of Friction. The force re-
quired to abrade the elevated parts of the
moving surfaces, or to raise them from
the depressions in which they had be-
come lodged. This is usually found by
trying what part of the weight of the
moving body must be exerted to maintain
its equilibrium, or to overcome the re-
sistance arising from this source. The
fraction expressing this ratio is called the
co-efficient of the friction.

FRICTION WHEELS. A contriv-
ance for diminishing attrition by the sub-
stitution of a rolling motion. The ex-
tremities of an axle, instead of resting
in a cylindrical socket, are made to rest
on the circumference of two revolving
wheels, to which the friction is trans-
ferred, and consequently diminished in
the ratio of the radius of the friction
wheels to the radius of the axle.

FRIESLAND GREEN. Brunswick
green. Ammoniaco-mnriate of copper.
FRIGID ZONES. The two divisions,
or belts, of the surface of the earth, which
lie between the Polar Circles and the
Poles — one in each hemisphere. They
are so called from their excessive cold,
arising from the total absence of the sun
from them during a great part of the
year.

FRU

FUL

FRINGT'LLID^ (fringilla, a finch).
The Finches ; a family of the Insessores,
or Perching birds, readily known by the
strength and shortness of their conical
bills. See Conirostres.

FRINGING REEF. A Coral produc-
tion, differing from the Barrier Reef in
having a comparatively small depth of
water on the outer side, and a narrower
and shallower lagoon channel between it
and the main land.

FRITH or FIRTH (/return, a narrow
sea). A narrow and deep inlet of the
sea, especially in a rocky and elevated
coast. Such an inlet is commonly called
a sound.

FRITT. The mass produced by the
materials of glass, on calcination.

FROND (frons, a branch). A term
applied to the foliaceous part of Ferns and
other Cryptogamic plants, from their
partaking at once of the nature of a leaf
and a branch.

FRONT (frons, frontis, the forehead).
That part of a shell near which the head
of the animal protrudes. The term is
also applied to the under surface of spiral
shells, where the aperture is placed, in
contra-distinction to the back.

FRO'NTLET (frons, the front). The
margin of the head behind the bill of
birds, generally covered with stiff bris-
tles.

FROST. The water or vapour of the
atmosphere congealed by cold. Hoar-
frost is frozen dew, and indicates an in-
sensible transition from dew, in conse-
quence of reduced temperature. Frost-
smoke consists of frozen particles of
water floating in the atmosphere in the
form of crystallized spiculae ; when these
occur in large masses, they become ag-
glutinated together into flakes, and fall
to the earth in the form of snow.

FRUIT. In botanical language, the
fruit is the ovary or pistil arrived at ma-
turity ; the term is also extended to what-
ever parts are combined with the ovary
when ripe. An inferior fruit is that in
which the pericarp adheres to the calyx ;
a superior fruit is that in which no such
adhesion takes place : the apple is an in-
ferior, the orange a superior fruit.

FRUSTUM. Literally, a fragment.
A portion cut off from any solid figure.
The frustum of a cone is any part cut off
from a cone which does not contain the
vertex ; otherwise, the part cut off would
be itself a cone. The frustum differs
from fragment, which is a piece broken ,
and from segment, which is a piece cut off.
H4

FRUTEX. A shrub; a plant whose
branches are perennial, proceeding di-
rectly from the surface of the earth with-
out any supporting trunk. When very
small, the plant is termed fruticulus, or
little shrub.

FUCFVOROUS (fucus, sea-weed, voro,
to eat). A term applied to animals which
subsist upon sea-weed.

FUGUE. A musical composition, in
which the subject, or brief air, passes suc-
cessively and alternately from one part
to another, according to certain rules of
harmony and modulation.

FULCRUM. The prop, or support on
which a lever is sustained, and about
which it moves. In raising a stone, the
body on which the lever rests, is the ful-
crum.

FULGO'RIDiE (fulgora, the lantern-
fly). A family of the trimerous Homo-
ptera, characterized by the large develop-
ment of their forehead, in which the
luminosity of the lantern-fly is said to
exist.

FULGURA'TION (fulgur, lightning).
A term applied, in assaying, to the sud-
den brightening of the fused globule of
gold or silver when the last film of oxide
of lead or copper leaves its surface.

FU'LGURITE (fulgur, lightning). A
term applied to a bore or tube produced
by the passage of lightning into a sandy
soil, into which it sometimes penetrates
to a depth of twenty feet, fusing the
gravel which it penetrates.

FULFGINOUS (fuligo, soot or smoke).
A term applied to vapours which possess
the property of smoke.

FUL1GULFN.E. The Sea ducks ; a
sub-family of the Anatidce, named from
the genus fuligula : they frequent the
sea principally, but many of them are
also found in fresh-water lakes and deep
rivers.

FULLER'S EARTH. A variety of
clay, of an unctuous quality, forming a
part of the Lower Oolite Formation. It
is named from its being employed by ful-
lers to remove the grease from cloth
before the soap is applied.

FU'LMINATE (fulmen, a thunder-
bolt). A compound of the fulminic acid
with a base, detonating by heat or friction.

FU'LMINATING POWDER (fulmen,
a thunder-bolt). A general term applied to
powders which fulminate on the applica-
tion of heat or friction. Of this kind are
the fulminating gold, prepared by keep-
ing recently precipitated peroxide of gold
in strong ammonia for a day ; fulmi-

FUN

FUS

noting mercury, employed for percussion
caps, and obtained by dissolving mercury
in nitric acid, and pouring the solution
into alcohol ; fulminating silver, prepared
by leaving oxide of silver for a day in a
strong solution of ammonia.

FULMINA'TION {fulmen, a thunder-
bolt). The explosion which takes place
in chemical bodies by heat or friction.

FULMI'NIC ACID {fulmen, a thunder-
bolt). A compound of cyanogen, cor-
responding in its ultimate composition
with cyanic acid, and exploding when
heated, rubbed, or struck.

FUMA'RIC ACID. A monobasic acid,
existing in fumaria or fumitory, and pro-
duced artificially by heating malic acid.

FUMING LIQUOR (fumus, smoke).
A chemical mixture, which emits fumes
or vapour on exposure to the air. Boyle's
fuming liquor is the protosulphuret of
ammonium ; Cadet's is procured by dis-
tilling acetate of potash and arscnious
acid ; Libavius's is the anhydrous bichlo-
ride of tin.

FUNCTION (fungor, to discharge an
office). The office of an organ in the ani-
mal or vegetable economy, as of the heart
in circulation, of the leaf in respiration.
Animal functions are those which relate
to the external world, as the senses,
voluntary motions, &c. Vital functions
are those immediately necessary to life,
as those of the heart, the brain, the lungs,
which have been termed the tripod of
life.

FUNCTION (in Analysis). A term
applied to an algebraical expression in
which a certain letter or quantity is com-
pounded with other letters or quantities :
the expression is then said to be a func-
tion of that letter or quantity; thus a+x
and o2+xs are, both, functions of x ; the
circumference of a circle is the function
of the radius.

Functions, calculus of. That branch
of analysis which investigates the form
of a function, and not its value in any
particular case, nor the conditions under
which it may have a particular value.
Thus, the calculus of func tions may be
considered as similarly related to alge-
bra, as algebra is to common arithmetic.

FUNDAMENTAL BASE. The root,
or lowest note of a musical chord, found
by inverting its notes so as to set them
in thirds above this root.

FUNGACEjE. The mushroom tribe
of Cellular or Acotyledonous plants.
Plants consisting of a congeries of cel-
lules, chiefly growing upon decayed sub-
145

stances. Sporules lying either loose
among the tissue, or enclosed in mem-
branous cases called sporidia.

FU'NGATES. The saline compounds
of a peculiar acid extracted from mush-
rooms.

FUNGIC ACID. An acid procured
from several species of fungus, by ex-
pressing their juice, boiling it, forming an
extract, and treating it with alcohol.

FUNGIN. A whitish substance form-
ing the base of fungi.

FUNI'CULAR MACHINE (funiculus,
a little rope). A mechanical contrivance
by which bodies are supported by means
of force applied to an assemblage of
ropes, as in bracing the sails of ships.

FUNFCULUS (dim. of funis, a cord).
The little cord, by which the ovule of
plants is attached to the placenta, of
which, indeed, it is a prolongation.

FURNACE. A fire-place used for the
purposes of fusion, distillation, sublima-
tion, and the oxidation and deoxidation,
or reduction of metals. It is termed eva-
poratory, when employed to reduce sub-
stances into vapour by heat; reverbera-
tory, when so constructed as to prevent
the flame from rising ; and forge, when
the current of air is determined by bel-
lows.

FUSCIN (fuscus, tawny). A brownish
matter obtained from empyreumatic ani-
mal oil.

FU'SCITE (fuscus, tawny). An opaque
greyish or greenish-black mineral, found
in Norway, in rolled masses of granular
quartz.

FUSELOL. An oily liquor obtained
from alcohol, also termed oil of grain,
and, hypothetically, hydrate of amyl.

FUSIBI'LITY. The property by which
solid bodies are capable of assuming
the fluid state on the application of
heat.

FU'SIBLE METAL. An alloy of eight
parts of bismuth, five of lead, and three
of tin. This compound, sometimes called
Newton's, from the name of its disco-
verer, melts at the heat of boiling water,
and may be fused over a candle in a piece
of stiff paper, without burning the paper.
Rose's fusible alloy is a similar com-
pound.

FU'SIFORM (fusus, a spindle, forma,
likeness). Spindle-shaped, thickest in
the middle and tapering to the extremi-
ties, as the cells composing woody fibre,
the fleshy part of the long radish, &c.

FU'SIN.E. Spindle-shells; a sub-
family of the TurbinellidcBy or Turnip-
H

GAL

GAL

shells, named from the typical g?£us
fusus, and characterized by the remark-
able length, generally equal, of the canal
and of the spire.

FUSION (fusus, melted, from fundo,
to pour out). The state of melting.
Substances which admit of being fused
are termed fusible, but those which
resist the action of fire are termed
refractory. Fusion differs from lique-
faction in being applied to metals and

other substances which melt at a high
temperature.

1. Aqueous Fusion. The solution of
salts which contain water of crystalliza-
tion, on exposure to heat.

2. Dry Fusion. The liquefaction pro-
duced by heat after the water of crystalli-
zation has been expelled.

3. Igneous Fusion. The melting of
anhydrous salts by heat without under-
going any decomposition.

G

GA'BBRO. The Italian name for a
rock consisting essentially of felspar and
diallage, called by the French geologists
euphotide.

GA'DIDjE (gadus, the cod). The Cod
tribe; a family of malacopterygious, or
soft-spined, fishes, distinguished by the
softness of all their fins, and by the in-
sertion of their pointed ventrals under
the throat. They comprise the cod, the
ling, the haddock, the whiting, &c.

GA'DOLINITE. A rare mineral found
by Gadolin in Sweden, containing yttria,
oxide of cerium, &c. When heated, it
appears to burn, emits light, and becomes
yellow, but undergoes no change in
weight.

GAGE or GAUGE. A term derived
from the Anglo-Saxon, and denoting, in
Physics, any apparatus for ascertaining
dimension. The gage of the air-pump is
a barometer, connected with the machine,
for the purpose of determining the pres-
sure of the air within the receiver, and,
consequently, the degree to which the
air has been rarified.

GA'HNITE. Automalite. A native
aluminate of zinc, in which the alumina
plays the part of an acid. It is named
from its discoverer, Gahn. A similar
combination occurs in spinel, which is an
aluminate of magnesia.

GALA'CTIC ACID (yd\a, milk). Lac-
tic acid. The acid of milk, supposed to
be merely animalized acetic acid. Ga-
lactin is art ingredient in the sap of the
Galactodendron utile, or Cow-tree of
South America.

GALATHE'IDjE. A group of crus-
taceous animals, named from the genus
Galathea, and constituting, according to
Milne Edwards, a transition from the
anomourous to the macrourous Crustacea,
146

more particularly approaching the por-
cellancB.

GA'LAXY (yuXafmc kvkXos, circle of
milkiness). The Milky Way; a broad
line of light passing entirely round the
heavens, and named from its milky white-
ness. Herschel supposes the sidereal
universe to be divided into clusters or
strata of stars, and the " milky way" to
be that particular cluster or stratum in
which our sun is placed. See Nebula.

GA'LBULUS. The Latin term for the
fruit of the cypress, and employed by
Gcertner as synonymous with strobile,
from which it differs only in being round,
and having the heads of the carpels much
enlarged. The fruit of the Juniper is a
galbulus, with fleshy coalescent carpels.
Desvaux calls it arcesthide.

GA'LEA. The Latin term for a hel-
met, and hence applied, in botany, to the
upper arched lip of the corolla of several
labiate plants, as in Lamium album.

GALE'NA (yaXeb), to shine). Lead-
glance ; the native sulphuret of lead.

GA'LIPOT. A white resin derived
from the pinus maritima, consisting
almost entirely of a colourless, crystal-
lizable resin, named pimaric acid.

GA'LLIC ACID. An acid obtained
from gall-nuts, but principally by decom-
position of tannic acid. By the applica-
tion of a brisk heat to gallic acid, the
pyrogallic acid is obtained as a crystalline
sublimate ; and, on applying heat to the
same acid by means of an oil bath, the
metagallic or melangalic acid of Berze-
lius remains as a fixed residue in the
retort.

GALLFCOLjE. Gall-inhabiters ; a
family of hymenopterous insects, of the
section pupivora, which deposit their ova
in the leaf-buds of several species of

GAL

GAN

oak; the buds undergo a morbid action
enlarge into a globular form, consti-
tuting a nidus for the larva of the insects,
and eventually become the galls of com-
merce.

GALLI'NjE [gallus, a cock). Galli-
naceous birds, so named from their affi-
nity to the common cock, and consti-
tuting the fifth order of the class Aves.

GALL-INSECTS. Coccidce. A family
of homopterous insects, the females of
which are apterous, and assume, at the
period of ovi-position, a globular form
analogous to the galls produced by the
Gallicolce.

GALLS. Protuberances found on cer-
tain plants, occasioned by the puncture
of an insect. They differ in consistency,
from the hard nut-gall, to the soft and
spongy berry or apple-gall. The Aleppo
galls are extensively used in dyeing and
in the manufacture of ink. See Gal-
licolce.

GALT. A provincial name applied in
the east of England to a series of beds of
chalk marl, the geological position of
which is between the upper and the
lower Greensand.

GALVANISM. A form of electricity
named after Galvani, and usually elicited
hy the mutual action of various metals
and chemical agents upon each other.
The additional discoveries of Volta led
to the term Voltaism, or Voltaic Electri-
city ; and its effects on the muscles of
animals newly killed, suggested the term
Animal Electricity.

1. Galvanic Circle. If, between two
plates of different metals, a fluid be inter-
posed capable of exciting a chemical effect
on the one plate, while it has little or no
influence on the other ; and if a com-
munication be then formed between the
plates at some point, by means of a wire
or other conducting substance, a con-
tinued current of electricity will pass
along the conductor from one plate to the
other, so long as the chemical action is
excited. This constitutes a simple gal-
vanic circle.

2. Galvanic Pile. This arrangement
consists of a number of pairs of plates,
similar to those above described, placed
alternately with an acting fluid inter-
vening between each pair, and having
the two ends of the series connected by a
wire. The effect is thus multiplied by
each pair of plates. The end of the pile
which gives out the electric fluid is called
the positive pole, while the other end in
which the wire terminates, and which

147

receives the electric matter, is called the
negative pole of the pile.

3. Galvanic Battery, or Trough. An
apparatus for accumulating galvanism,
consisting of plates of zinc and copper
fastened together, and cemented into a
wooden or earthenware trough so as to
form a number of cells ; the trough is
then filled with diluted acid.

4. Galvano-meter (ue-rpov, a measure).
An instrument which indicates the
feeblest polarization of the magnetic
needle, or slightest current in the con-
necting wire of a voltaic circle.

5. Galvano-scope (o-KOTreco, to examine).
An instrument by means of which the
existence and direction of an electric
current may be detected. A magnetic
needle is a galvanoscope.

6. Galvano-magnetic induction machine.
A machine principally used for medical
purposes, and consisting of an induction
spiral connected with a hydro-electric
battery, which is fitted up with an appa-
ratus for establishing and breaking con-
tact with great rapidity.

GA'MMUT. An old term in Music,
now applied to the diatonic scale, and
also called the harmonical hand, in con-
sequence of Guido having arranged the
musical notes upon the figure of a hand.
The term gammut, or gammfut, was de-
rived from the Greek letter ydnp.a, ap-
plied by Guido to a note which he added
below the " supernumerary " note, with
the addition of ut, which is the same as
do in the syllabic scale.

GAMOPE'TALOUS itaneu, to marry,
TreraXov, a petal). A term applied, in
Botany, to a corolla consisting of cohering
petals, in order to avoid the inaccuracy
of the word mono-petalous.

Gamo-sepalous. A corresponding term,
denoting a calyx formed of cohering se-
pals, and therefore preferable to the more
common term mono-sepalous.

GA'NGLIONE'URA {^yXtov, a
nerve-knot, vevpov, a nerve). A term
applied by Rudolphi to the Articulate
and Molluscous divisions of the Animal
Kingdom, which are characterized by a
ganglionic disposition of the nervous
system. In the former class, the ganglia
are arranged symmetrically along the
middle line of the body, and communi-
cate by a double chord ; these are termed
homogangliata. In the latter class, the
ganglia are dispersed in an unsymmetri-
cal manner, apart from one another and
from the middle plane ; these are called
heterogangliata.

H2

GAS

GEM

GA'NGUE. A term applied to the
stones found in the cavities which form
the veins of metals, constituting the ma-
trix of the ore.

GA'NOID FISHES (7ai/ov, splendour,
et3or, likeness). A group of fossil fishes,
found in the old red sandstone, and other
rocks of that period, and named from the
brilliant lustre of their scales, which are
generally coated with polished enamel.
See Placoid Fishes.

GAPING. A term applied to a bivalve
shell, when any parts of the margins do
not meet each other.

GARNET. A simple mineral, gene-
rally of a deep red colour, crystallized;
occurring most frequently in mica slate,
but also in granite and other igneous
rocks. Common garnet is less hard, and
less transparent than Precious Garnet,
which is often perfectly diaphanous.
Resinous garnet is another name for the
mineral colophonite.

GARNET-BLENDE. Zinc-blende. A
sulphuret of zinc ; a massive mineral of
adamantine lustre, and often black.

GAS. An old Teutonic word, signifying
air or spirit ; now applied to permanent
aeriform fluids for the purpose of distin-
guishing them from common air, which
is a mixture of two kinds of gas. Gases
are distinguished from liquids by the
name of elastic fluids ; and from vapours,
by their retaining their elasticity in all
temperatures.

GASO'METER. A gas-holder ; a me-
tallic apparatus for containing a large
quantity of any gas which is insoluble
in water.

GASTERO'PODA (yavrrip, the sto-
mach, 7r63e?, feet). The third class of
the Mollusca, including the slugs and
shell-snails, and distinguished by the
structure and position of their locomo-
tive apparatus, which consists of a mus-
cular disc attached to the ventral surface
of the body, serving either as an instru-
ment for crawling, or, in rarer instances,
compressed into a muscular membrane
for swimming. They may be divided
into three orders by the forms of their
respiratory organs and of their external
covering : —

1. Nudibranchia, or those which
breathe by branchiae unprotected by an
external or internal shell.

2. Tectibranchia, or those which have
the branchiae protected by an external
or internal calcareous covering.

3. Pulmonata, or those which respire
by means of a pulmonary sac.

148

GAY-LUSSITE. A crystalline mine-
ral found abundantly in South America,
and named from the French chemist Gay
Lussac, who ascertained it to be a double
carbonate of soda and lime, with 5 equi-
valents of water.

GECKO'TIDjE. The Gecko tribe; a
natural family of Saurians, named from
the genus gecko, and characterized by the
peculiar structure of the foot, the sole of
which is converted into a sucker, enabling
the animal to crawl up walls and along
ceilings, after the manner of the flies on
which they feed.

GE'HLENITE. A mineral, allied to
Vesuvian, found together with calcareous
spar in the valley of Fassa in the Tyrol.

GE'INE {yrj'ivos, earthy). Geic acid.
Another name for humus, or vegetable
mould, produced by the decomposition of
vegetable matters.

GELATINE {gelu, frost). An animal
or vegetable substance, constituting the
principle of jelly, and distinguished from
albumen by its not becoming consistent
by heat. The purest variety of gelatine
is isinglass; the common gelatine of
commerce is glue; and the hydrate of
gelatine is jelly.

GE'LATINES. The term applied by
Mr. Kirby to the Acalephcs of Cuvier, or
the Radiaires molasses of Lamarck, from
the gelatinous consistency of their bodies.

GE'MINI. The third of the zodiacal
constellations, consisting of eighty-five
stars, the principal of which are Castor
and Pollux. It denotes the third month
of Autumn, from the 20th of November
to the 20th of December. In the Egyp-
tian zodiac this sign is represented by a
young man and a girl. In this month
seeds germinate. The Greek appellation
for this sign, 6i6v(xot, is vague.

GEMITRFCES (gemo, to moan or
coo). Cooers ; an order of Birds, com-
prising, according to Macgillivray, the
single family of Columbince, or Pigeons,
and named from their peculiar cooing
sound.

GE'MMA. A leaf-bud, or the rudi-
ment of a young branch, consisting of
scales surrounding a growing point, which
is in direct communication with the
woody and cellular tissue of the stem.
This term, as applied to zoophytes, de-
notes a young animal not enclosed in an
envelope or egg.

GEMMA, a CORONA BOREALIS.
Alphacea. A star of the second magni-
tude in the Northern Crown.

GEMMI'PAROUS {gemma, a bud,

GEN

GEO

pario, to bring forth). A designation of
that mode of propagation, which takes
place by the growth of the young, as of a
bud, from the parent, as in many of the
infusoria.

GE'MMULE (dim. of gemma, a bud).
A term synonymous with plumule, and
denoting the growing point of the em-
bryo in plants. It is also applied to the
embryo of the radiated animals at that
stage of their existence when they re-
semble ciliated monads.

GENDER. In Grammar, that acci-
dent of a noun which points out the sex
or the absence of sex.

GENERALIZATION. The act of
comprehending under a common name
several objects agreeing in some point
which we abstract from each of them,
and which that common name serves to
indicate. Each of these names is called,
in Logic, a common term, from its be-
longing to them all alike ; or a predicable,
because it may be predicated affirma-
tively of them, or of any one of them.
See Abstraction.

GENERATING FUNCTION. A term
applied by Laplace to any function of x,
considered with reference to the coeffi-
cients of its expansion in powers of x.
It is employed in solving equations of
differences, &c.

GENERATION. In Geometry a line
is said to be generated by the motion of a
point, a surface by the motion of a line,
a solid by that of a surface. Thus, a
sphere is generated by the revolution of
a semicircle about its diameter ; a circle,
by the revolution of its radius about one
of its extremities. The figure thus gene-
rated is termed the generant. From this
mode of considering quantity as gene-
rated by motion, arose the terms fluxion
and fluent in infinitesimal analysis.

GENI'CULATE (geniculum, a little
knee or joint). Knee-jointed ; bent ab-
ruptly in the middle, as the stems of
many grasses, the filament of certain
plants, &c. The term geniculum is ap-
plied to the node, or point of the stem
from which the leaves are developed.

GENITIVE CASE {gigno, to beget).
In Grammar, the getting case, known by
the sign of, and answering to the ques-
tion whose, or whereof? It denotes the
relation of property, and indicates the
subject to which a thing belongs.

GENTIANA'CEjE. The Gentian tribe
of Dicotyledonous plants. Herbaceous
plants with leaves opposite ; flowers ter-
minal, axillary; stamens alternate with
149

the segments of the corolla; ovarium
single, superior, 1 or 2-celled; fruit a
many-seeded berry.

GE'NUS. In Logic, a predicable which
is considered as the material part of the
species of which it is affirmed. A subal-
tern genus is that which is capable of
being a species in respect of a higher
genus. A genus which is not considered
as a species of any thing, is called sum-
mum (the highest) genus. "When it is
said of a magnet, that it is "a kind of
iron-ore," this is called its proximum
genus, because it is the closest (or lowest)
genus which is predicated of it: " mine-
ral" is its more remote genus. — Whately.

In Natural History, a genus denotes a
class of animals or plants which possess
some common property. The other per-
manent differences between the indivi-
duals of the same genus constitute a
species; and the accidental differences
found among the species are termed
varieties.

GEOCENTRIC (7n, earth, nevrpov,
the centre). Having the same centre as
the earth, or having the earth for its
centre. Thus the moon's orbit is geo-
centric ; but the orbits of the other
planets, and of the earth itself, are helio-
centric, having the sun as their centre of
motion. The geocentric place of a planet
is the place in which it would appear to
an eye in the centre of the earth. The
geocentric latitude of a planet is its lati-
tude as seen from the earth ; or it is the
inclination of a line connecting the planet
and the earth to the plane of the ecliptic.
The geocentric longitude of a planet is
the distance, measured on the ecliptic, in
the order of the signs, between the geo-
centric place and the first point of Aries.

GEOCO'RISA (fT,, earth, Kopts, a bug).
The Land-bugs ; a section of Hetero
pterous insects, including several families
which strongly resemble the Cimicidae,
or common bugs. See Hydrocorisa.

GEO'DES (Tea>an?, earthy). A variety
of aetites, or eagle-stone, the cavity of
which, instead of containing a nodule,
contains only loose earth, and is gene-
rally lined with crystals.

GEODE'SY (yeudaiffia, a dividing of
earth). A term literally signifying a
division of the earth, and so far synony-
mous with geometry, or land-measuring.
In a more general sense, however, it sig-
nifies that branch of practical geometry
which comprehends all the operations,
geometrical and trigonometrical, required
for determining the general figure of the
H3

GEO

GEO

earth, the figures and areas of large por-
tions of the earth's surface, and the
variations of the intensity of gravity in
different regions, by means of direct ob-
servation and measurement.

GEO'GRAPHY (7^, the earth, TPa0&>,
to describe). The science which teaches
the knowledge of the earth. This is the
strict etymological meaning of the term,
which is thus distinguished from hydro-
graphy, or the description of water, or
seas, which constitute the greater portion
of the terraqueous globe. It differs from
cosmography, as a part differs from the
whole ; from chorography and topography,
as a whole differs from a part.

1. Physical Geography, though, strictly
speaking, it denotes merely a description
of the principal features of the earth's
surface, usually includes the subjects of
climate and of temperature, the effect of
these agents on the condition of the
human race, and, generally, an account
of the animals and productions of the
globe. Hence it comprises the various
questions of Hydrography, Meteorology,
and Climate.

2. Mathematical Geography is that
branch of the general science which is
derived from the application of mathe-
matical truths to the figure and dimen-
sions of the earth, to its relations with
the celestial bodies, to the relative posi-
tions and distances of places on its sur-
face, and to their representations by
globes or maps.

3. Political Geography relates to his-
tory and statistics, and comprises all the
moral and social conditions of nations, as
inhabitants of the globe.

GEO'LOGY (TJj, the earth, \6yos, an
account). Geognosy. A description of
the structure of the earth, and of the
theories entertained respecting its forma-
tion. A short tabular view of the suc-
cessive geological periods is here given,
with particular reference to the forms of
organic life most strikingly exhibited in
each: —

I. The First or Ancient Epoch.

1. The period antecedent to the intro-
duction of life. The deposit of non-
fossiliferous rocks.

2. The period of invertebrated animals,
as the most highly organized inhabitants
of the sea. The Silurian rocks.

3. The introduction of fishes, the cha-
racteristic animals of the second fossili-
ferous period. The Devonian, or Old
Red Sandstone system of Formations.

150

4. The period marked by the presence
of vegetables and the first introduction
of reptilian animals. The Permian and
Carboniferous Systems.

II. The Middle Epoch.

5. The periods of the frog-like, bird-
like, and marine reptiles. The formation
of the New Red Sandstone, or Triassic
Series. Animals characteristic of the
Lias Formation.

6. The periods of the gigantic land
reptiles, the flying reptiles, the gigantic
crocodilians, and the first introduction of
mammalian animals. Wealden and Oolitic
Formations.

7. The periods of the Chalk and Green-
sand, during the deposit of which there
was probably a deep sea, covering a large
proportion of the existing land. Creta-
ceous Period.

III. The Modern Epoch.

8. The period of the pachydermatous
animals of the Paris basin, and of the
sub-tropical (?) fruits and animals of the
London and Hampshire basins. Older
Tertiary System.

9. The period of various large animals
of the Middle Rhine valley, succeeded
by that of the mastodon and elephants
in North America, England, Northern
Europe, and India. Middle Tertiary
System.

10. The period of the caverns and
gravel; with Carnivora, the Megaceros
and other gigantic ruminating animals,
and the elephants of Europe; and of
various gigantic animals in Asia, Ame-
rica, Australia, and New Zealand. Newer
Tertiary System.

GEO'METRY {^eui^erpia, land-mea-
suring). The etymological meaning of
this term seems to imply that the mea-
surement of land was the most important,
perhaps the only, use to which this
science was at first applied. It now em-
braces the measurement of the earth and
of the heavens ; and it forms, with Arith-
metic, the basis of all accurate conclusions
in the mixed sciences.

Geometry, Descriptive. A term em-
ployed by Monge to denote a systematized
method of geometry, by which a ground-
plan and an elevation are made to give
the form and dimensions of a building.
The projections of a point upon two
planes at right angles to each other,
called the planes of projection, being
given, the position of the point itself is
given.

GIB

GL A

GEO'RGIUM SIDUS. The name
given by Herschel to the planet dis-
covered by himself in 1781 ; it is, how-
ever, more generally known by the name
of its discoverer, or by that of Uranus.

GE'OTHERMO'METER (in, the
earth, thermometer). An instrument in-
vented by Magnus, for measuring the
degree of terrestrial heat at different
places, especially in mines and Artesian
wells. The temperature appears to rise
1° F. for every 60 or 70 feet of descent
below the surface ; hence, at a depth of a
few miles, the earth must be in a state of
incandescence.

GERANIA'CE^E. The Geranium tribe
of Dicotyledonous plants. Herbaceous
plants or shrubs, with stems tumid and
separable at the joints; stamens mona-
delphous ; fruit composed of five cocci,
each terminated by an indurated style,
consolidated round a long beak-like axis,
from which they separate with elasticity,
when ripe, by the rolling back of the
styles.

GERMAN SILVER. Packfong. A
white alloy of nickel, formed by fusing
together 100 parts of copper, 60 of zinc,
and 40 of nickel.

GE'RMEN. The term, applied by
Linnaeus to the ovary of plants, or the
hollow case forming the base of the pistil,
enclosing the ovules, and always contain-
ing one or more cells or cavities.

GERMINA'TION (germino, to bud).
A term applied by botanists to that func-
tion by which the embryo contained in
the seed is first called into life.

GEY'SER. A boiling fountain in Ice-
land, which frequently throws out its
contents to the height of more than a
hundred feet, sometimes to thrice that
elevation.

GIANTS' CAUSEWAY. A columnar
basaltic formation on the northern coast
of Antrim in Ireland, connected with a
trap district which occupies almost the
whole of the county, &c, comprehending
an area of about 800 square miles on both
sides of the valley of the Bann.

GFBBOUS (gibbus, protuberant).
Humped ; a term applied to the convex-
ity of a solid body, and used in reference
to the enlightened parts of the moon,
whilst she is moving from her first
quarter to the full, and from the full to
the last quarter. In Zoology, any part
of a shell more particularly elevated
above the surface, or unusually so in
comparison with other species, is termed
gibbous, as in strombus gibbosus.
151

GIE'SECKITE. A granular mineral
brought from Greenland by Sir C.
Giesecke.

GI'NGLYMOID (7^77X^6?, a hinge,
et'3o?, likeness). Hinge-like ; a term ap-
plied to a joint formed for motion on one
plane.

GI'RASOL. A term derived from the
Italian giro-sole, or turn-sun, and applied
to a milk-white or bluish opal, which
reflects a reddish colour when turned to
the sun. The term has been corrupted
into Jerusalem, as applied to a species of
sunflower, the helianthus tuberosus, vul-
garly said to turn its flowers to the sun.

GLA'CIAL ACID (glades, ice). The
strongest acetic acid which can be pro-
duced. It exists in a crystallized state
under 50° Fahr., and contains 79 percent,
of real acid.

GLA'CIER (glace, ice). An accu-
mulation of ice and hardened snow,
occurring in the valleys and on the slopes
of the Alps and other lofty mountains.
Saussure distinguishes two kinds of gla-
cier ; viz. those contained in the valleys
more or less deep, and which, though at
great elevations, are still commanded on
all sides by mountains higher still ; and
those not contained in the valleys, but
spread out on the slopes of the higher
peaks. See Moraine.

GLA'CIS. A term borrowed from the
language of fortification, in which it de-
notes an easy insensible slope or decliv-
ity, less steep than that of a talus.

GLAI'RINE. A term referred by some
to a gelatinous vegetable matter ; by
others to a pseud-organic substance
formed on thermal waters.

GLANCE (glanz, splendour). A de-
signation of certain minerals which have
a metallic or pseudo-metallic lustre, as
glance-coal, lead-glance, &c.

GLANCE-COAL. Anthracite. A va-
riety of coal which burns without flame
or smell. It occurs in beds in clay-slate,
greywacke, and alum-slate, but most
abundantly in secondary rocks, as in coal
and trap formations. Slaty glance-coal
is another variety, called in this country
blind coal. A third variety occurs in
basaltic columnar rows, near Cumnock
in Ayrshire.

GLAND (glans, an acorn). In Botany,
a small mass of firm cellular tissue,
which is often much harder and more
coloured than that which surrounds it.
It may be simple or compound, stalked
or sessile. Glands are termed utricular,
when they appear as elevated, distended
H4

GLA

GLO

bladders of the epidermis ; lenticular,
when they exist as brown oval spots upon
the bark; internal, when of the nature
of cysts or nuclei situated below the
cuticle; &c. The disk, or fleshy body
which surrounds the base of the ovary
in certain plants, is commonly called a
hypogynous gland.

GLANS. In Botany, a compound in-
ferior fruit, with a dry pericarp, one-
celled, but proceeding from an ovary
which contains several cells, and seated
in a persistent involucre called a cupule.
The gland is solitary in the oak ; in the
beech and the sweet chestnut there are
several, completely enclosed in the cu-
pule. The gland is termed calybio by
Mirbel, and nucula by Desvaux.

GLASS. The varieties of glass derive
their vitreous character from the silicates
of potash and soda. Green or bottle-
glass consists of the silicates of alumina,
of the oxides of iron, magnesia, and
potash or soda. Flint-glass is a silicate
of potash and lead. Window-glass is
a silicate of soda and lime. Plate-glass
used for mirrors, crown-glass, and the
beautiful Bohemian glass, are silicates of
potash and lime.

The term glass is also applied to glassy
substances, as the glass of antimony, or
the sulphuret; Muscovy glass, or mica;
tin glass, or bismuth, &c.

GLASS-GALL. Sandiver. The salt
scum which floats on the surface of fused
glass.

GLAUBER'S SALT. Native sulphate
of soda, occurring together with rock
salt and Epsom salt, on the borders of
salt lakes, and dissolved in the waters of
lakes and of the ocean, &c. Glauber's
secret sal ammoniac is a sulphate of am-
monia, a constituent of soot from coal.

GLAU'BERITE. A crystallized salt,
consisting of nearly equal parts of the
sulphates of lime and of soda, and found
imbedded in rock salt brought from
South America and from Spain.

GLAUCIC ACID (^Xauxif, blue, sea-
green). An acid procured from the teazle
and scabious plants.

GLAU'COLITE {yXavKot, blue, \i0os,
a stone). A bluish-green mineral, found
near lake Baikal in Siberia, and consist-
ing of a silicate of alumina and lime.

GLAU'CONIE (yXavKas, blue, sea-
green). A French term applied by
Brongniart to some stratified deposits
associated with chalk, which correspond
with the green sands of English geo-
logists.

152

GLI'ADINE (y\ia, glue). Vegetable
albumen ; one of the constituents of
gluten. See Zymome.

GLIMMER. A name occasionally
applied to micaceous earths.

GLIRES (glis, a dormouse). The
fourth order of the Mammalia in the
Systema Natures of Linnaeus, comprising
the porcupines, hares, beavers, mice,
squirrels, bats, &c, characterized by the
presence of two long chisel-shaped in-
cisors in each jaw. See Rodentia.

GLOBE (globus, a ball). A round or
spherical body, bounded by one uniform
convex surface, every point of which is
equally distant from a point within,
called the centre.

1. Artificial Globes are instruments
employed for conveying the first ideas of
the figure and rotation of the earth, of
latitude and longitude, and of the situa-
tion of places with respect to each other
and to the sun at the different seasons of
the year. They are formed of metal or
plaster, on the surface of which is de-
lineated a map of the earth, or of the
celestial constellations, together with the
principal circles of the sphere ; in the
former case the instrument is called a
terrestrial, in the latter a celestial globe.
These globes are also used for the pur-
pose of solving mechanically a few ele-
mentary problems of Astronomy, relative
to the difference of the hour of the day at
different places, the times of the rising
and setting of the sun, the limits of the
visibility of eclipses, &c.

2. Perennial Globe. A contrivance in
which there is a motion of the stars
about the pole of the ecliptic, and also
one about the pole of the equator, so that
all the diurnal phenomena can be repre-
sented for any epoch, however distant
from our own, past or future.

GLOBULAR CHART. A delineation
of the terrestrial surface, or of any part of
it, on a plane, according to the principles
of globular projection. See Projection.

GLOBULAR MASSES. Nodules. The
geological term for rocks of irregular
form, varying from a foot to a mile or
more, and imbedded either in a stratified
or a massive rock.

GLOBULAR SAILING. In Naviga-
tion, the sailing from one place to an-
other over an arc of a great circle, or
the shortest distance between the two
places.

GLO'BULINE. The name given by
Turpin to the amylaceous granules found
in the cells of plants. He considers

GLU

GOL

them as the elementary form of vegetable
tissue.

GLOBULUS. A little globe ; a round
deciduous shield, formed of the thallus
of lichens, and leaving a cavity when it
falls off, as in isidium.

GLO'CHIS (7\wx«r , a projecting point).
A form of hair occurring in plants, and
commonly called a barb ; it is forked at
the apex, both divisions of the fork, being
hooked, as in the nuts of myosotis lap-
pula.

GLOME'RULI (dim. of glomi, clews
of thread). The heaps of powdery bodies
which lie upon the surface of the thallus
of lichens. See Soredia.

GLOMERULUS or GLO'MUS. A
term applied, in inflorescence, to a clus-
ter of capitula enclosed in a common
involucre, as in echinops. It bears the
same relation to a capitulum as the com-
pound to the simple umbel.

GLOSSO'LOGY {yXwcaa, a tongue,
X670P, an account). The science of
scientific language ; the explanation of
the peculiar terms employed in any
science.

GLOSSOPE'TRA (yXZaaa, a tongue,
nerpa, a rock). A term applied to the
fossil teeth of fishes allied to the shark,
occurring in the upper, secondary, and
tertiary strata of England, France, &c.
They are also called odontopetre, lamio-
dontes, &c.

GLUCIC ACID {yXvKvs, sweet). An
acid formed by the action of a saturated
solution of lime or barytes on grape
sugar. The anhydrous acid is formed
from grape sugar by the loss of the ele-
ments of water.

GLUCI'NA (yXvuvs, sweet). A rare
earth, constituting nearly 14 per cent, of
the emerald or beryl. Its metallic basis
is glucinum, a metal named in allusion
to the sweet taste of the salts of its oxide
glucina.

GLUCO'SE (vXuKvf, sweet). A syn-
onymous term for starch sugar, diabetic
sugar, grape sugar, or the sugar of fruits.

GLUME {gluma, the husk of corn).
A term applied to the peculiar envelope
of the floral apparatus in grasses, which
are hence called glumacece. It is a modi-
fication of the bract.

GLUME'LLE. A diminutive of glume,
and, as such, applied by De Candolle to
each of the bracts of grasses, situated
immediately within the glumes ; they are
commonly called palece. A further di-
minutive occurs in glumellule, which the
same writer applies to the minute hypo-
153

gynous scales situated within the glu-
melles or paleae, and which are also called
squamulcB.

GLUTEN (gelo, to congeal). A viscid
substance obtained from wheaten flour.
It has been separated into gliadine, or
vegetable albumen, and zymome, or that
portion of the mass with which the acid
that is present has united. Glutine is a
principle resembling gluten, but differing
from it in not being soluble in alcohol.

GLY'CERIN (jXvkvv, sweet). The
sweet principle of oils, also called hydrate
of oxide of glyceryl, the hypothetical
radical of glycerin.

GLYTTODON (yXvirrbs, sculptured,
63oi/f, a tooth). A colossal armadillo,
occurring in the geological period of the
megatheroid animals, remarkable for
the complicated structure of its teeth.
It resembled the great land tortoise,
whose remains are found in the Sewalik
hills.

GNEISS. A term applied by the Ger-
man miners to a stratified primary rock,
composed of the same materials as gra-
nite, but having usually a larger propor-
tion of mica, and a laminated texture.
Three principal kinds of gneiss have been
distinguished — the granitic, the slaty,
and the laminar.

GNO'MON {yvcofxav, a gnomon). In
every parallelogram, any of the parallelo-
grams about a diameter, together with the
complements, is called a gnomon. The
term gnomon also designates an upright
pillar, from the shadow of which the
ancient astronomers determined the alti-
tude of the sun and of the other heavenly
bodies. The style or index of a dial is
likewise termed a gnomon.

GOBEL'S PYROPHORUS. A mix-
ture of charcoal and lead, in which the
latter is in such an extreme state of
division, as to take fire on exposure to
the air. It is formed by heating the
tartrate of lead in a close vessel or tube
to dull redness.

GO'BIOD^E {gobius, the goby). The
Goby tribe ; a family of Acanthopterygious
fishes, distinguished by the thinness and
flexibility of their dorsal spines. Many
of them are viviparous, as the blenny.

GOLD. A yellow metal, occurring
native, in a massive state, and dissemi-
nated in veins through rocks, or in grains
among the sand of rivers. Gold coin is
termed sterling, when it consists of 22
parts of gold and 2 of copper ; standard,
when it consists of 18 parts of gold and
6 of copper.

H5

GON

GR A

GOLD LEAF ELECTROMETER.
An instrument for detecting the presence
of electricity by the divergence of two
slips of gold leaf.

GOLDEN NUMBER. At the end of
every nineteen years, the new and full
moons happen at very nearly the same
times of the year. The ancients ascer-
tained this fact, and reckoned the nine-
teen years, or " cycle of the moon," as it
is called, so that it terminated the year
before the Christian era. This cycle was
marked by the Greeks with letters of
gold. Therefore, to find the golden
number, or number of the year in this
cycle, add 1 to the date ; divide by 19 ;
the quotient is the number of cycles of
the moon since the birth of Christ, and
the remainder is the golden number.
Thus, 1847 + 1 = 1848. Divide by 1 9, and
the quotient is 97 cycles, and 5 remain-
ing, which is the golden number for
1847.

GOLDEN SULPHURET. A sulphu-
ret of antimony, also termed sulphanti-
monic acid, and prepared by precipitating
antimonic acid by sulphuretted hydro-
gen. See Kermes Mineral.

GO'MPHOLITE (yonQot, a nail, X/flo?,
a stone). A term applied by Brongniart
to conglomerate rocks of the tertiary
series, called by the Swiss Nagelflue.

GONG. Tam-tam of the Chinese. A
highly sonorous species of cymbal, con-
sisting of an alloy of about 80 parts of
copper and 20 of tin.

GO'NGYLI (yoyfv\o*t round). The
granules contained in the shields of
lichens, supposed to be the spores by
which the plants are propagated. The
term gongylus is also applied to a round
hard body, which falls off from the
mother plant in some of the algaceae,
producing a new individual, as in the
fuci.

GO'NIATITES (ycovia, an angle) The
name of some spirally twisted species of
cephalopods which inhabited the seas
during the Carboniferous period, and are
characterized by the angular markings
made by the intersections of the walls of
the chambers and the outer shell.

GONIO'METER. An instrument for
measuring angles, particularly those of
crystals.

GONIO'METRY (yoi/m, an angle, Me-
Tpew, to measure). " The measurement
of angles ; a name which should be sub-
stituted for trigonometry, if it were ad-
visable to alter established designations.
The latter science, beginning with the
154

measurement of triangles, made all that
was known of the analysis of angular
magnitude its own peculiar instrument.
The various accessions which real gonio-
metry received were, therefore, consi-
dered as additions to trigonometry; so
that, at this day, under a word which
imports measurement of triangles, we
have a science which wanders as far
from the etymology of its name as geo-
metry does."— Penny Cycl.

GO'NOPHORE (76vu? , offspring, 0<?po>,
to bear). The name given by De Can-
dolle to a prolongation of the receptacle,
which elevates itself from the base of the
calyx of certain flowers, and bears the
numerous stamens peculiar to these
plants, as in Anonacea? and Magnoliaceae.

GO'NOPLA'CIANS (yuvia, an angle,
?r\a£ , a plate). A tribe of brachyurous
crustaceans, named from the genus gono-
plax, and characterized by the square or
rhomboidal form of the carapace, or
upper crustaceous plate, and by the
length of the eye-stalks. Some species
of the gonoplax are fossil.

GORGO'NIA NOBILIS. Red coral;
a substance consisting of an interior
stem of gelatinous matter and carbonate
of lime, and an external coating of mem-
brane, carbonate of lime, and colouring
matter.

GOULARD'S EXTRACT. A satu-
rated solution of subacetate of lead, ob-
tained by boiling powdered litharge in
vinegar.

GO'VERNOR. A piece of mechanism
applied to steam-engines and other ma-
chines, for the purpose of equalizing
their motion.

GRACULI'NjE {graculus, a jay). Gra-
culine birds, or Grackles ; a term adopted
by Macgillivray instead of that of
Thremmaphilince, and applied to a group
of birds, allied to the Crows on the one
hand, and the Thrushes on the other, in-
cluding the starling, the cow-bird, &c.
By several authors they are called stur-
nidcc.

GRADUATION {gradus, a degree).
The process of dividing a mathematical
or astronomical instrument into degrees,
minutes, &c, either by copying a system
of divisions already existing, or by origi-
nal division, depending on the geometri-
cal properties of the circle.

GRADUATOR. A contrivance for
accelerating spontaneous evaporation by
exposing large surfaces of liquids to a
current of air. This process of gradu-
ation is sometimes employed in salt

GRA

GR A

works, for the purpose of concentrating
the brine, by allowing a shower of it to
trickle over fagots.

GRAFTING. The horticultural ope-
ration by which a portion of one plant is
so applied to another plant that a vital
union may take place between them ;
the portion so applied, is called the scion;
the rooted plant to which it is applied, is
the stock or stem. There are various
modes of grafting, which have received
the names of whip, cleft, saddle, and
crown grajting.

Grafting by approach, or Inarching, is
a mode of grafting, by which the scion is
not separated from its parent plant, until
it has become vitally united to the stock.
GRAINER. The ley obtained by the
infusion of pigeon's dung in water, em-
ployed for imparting flexibility to skins
in the process of tanning.

GRALLATO'RES ( grallce, stilts).
Waders, or Stilt-birds ; an order of aquatic
birds frequenting marshes, and named
from their being raised on their long legs,
as on stilts. They comprise the heron,
the snipe and woodcock, the rail and
coot, and the plover.

GRAMINA'CEjE {gramen, grass).
The grass tribe of Monocotyledonous
plants. Herbaceous plants with cylin-
drical stems; leaves alternate, with a
split sheath ; flowers hermaphrodite,
sometimes monoecious, glumaceous ;
glumes alternate, unequal; stamens hy-
pogynous ; ovarium simple.

GRAMMAR (ypan^a, a letter). That
branch of science which relates to the
component parts of language, and em-
braces the subjects of orthography, ety-
mology, syntax, and prosody.

GRA'NITE (granum, a grain). An
unstratified or igneous, coarse, granular
rock, occurring generally beneath, or
associated with, the oldest of the strati-
fied rocks, and sometimes penetrating
them in the form of dikes and veins. It
commonly consists of three simple mine-
rals— quartz, felspar, and mica. Several
varieties of granite have received dis-
tinctive names, as the porphyritic, the
graphic, the schorly, the talcose, and the
hornblendic.

GRANI'VORiE (granum, a grain, voro,
to devour). An order of birds, including
the Insessores, which feed on grains.

GRANULA (dim. of granum, a grain).

Little grains, a term applied to the large

sporules continued in the centre of many

Algaceous plants.

GRA'NULATED (granulatus, grained).

153

Grained ; marked by elevated, closely-
set, regular grain-like dots ; an appear-
ance very common at the base of the
predacious spiral genera of mollusca.

GRANULATION [granum, a grain).
The division of a metallic substance into
grains or minute particles, for the pur-
pose of facilitating chemical combination ;
it is performed by pouring the metal into
water, or by agitating it in a closed vessel
until the moment of congelation, when it
falls into powder.

GRA'PHIC GRA'NITE. A modifi-
cation of granite, which derives its name
from its presenting, when polished, some
appearance of written characters. See
Granite.

GRAPHIC ORE or GOLD. An ore
of tellurium, occurring in veins in por-
phyry, in Transylvania, and consisting of
tellurium, gold, and silver.

GRAPHITE (7pa0w, to write). Plum-
bago or black-lead ; a carburet of iron,
named from its use in writing. Compact
graphite occurs at Borrowdale in Cum-
berland, in beds of variable thickness,
included in a bed of trap, which is sub-
ordinate to clay-slate. Artificial graphite
is produced by placing an excess of char-
coal in contact with fused cast iron.

GRAPSOIDIANS. A tribe of bra-
chyurous crustaceans, named from the
genus grapsus, and placed by M. Milne
Edwards, near the Gonoplacians.

GRA'PTOLITE (ipanrd?, written,
\»0oc, a stone). A fossil sertularian co-
ralline, one of the most simply organized
of the Silurian species, consisting appa-
rently of the horny skeletons of animals
resembling those found on the coral and
sea- weed of our own coast. By this term
Linnaeus designated those stones which
are marked with various forms, repre-
senting buildings, vegetable structures,
as ruin marble, moss-agate, &c.

GRAVPMETER (gravis, heavy, p.e-
rpov, a measure). An unclassical term,
adopted by M. Greyton in preference to
hydrometer or araeometer, because these
terms imply that the substance weighed
is a liquid, whereas, when solids are
weighed, the liquid is only the term of
comparison to which the unknown weight
is referred.

GRAVITA'TION (gravitas, weight).
This term has been sufficiently explained
under the head of Attraction. The laws
of gravitation, as laid down by Newton,
and universally admitted, are as follows :
— The gravitating forces of bodies are to
each other, 1, directly as their masses •
H6

GRE

GRO

and 2, inversely as the squares of their
distances. Thus, if the mass of one body
be 2, 3, 4, or 5 times greater than that of
another, its gravity is also 2, 3, 4, or 5
times greater; and with a distance of
2, 3, 4, or 5 times greater, the force of
gravity will be 4, 9, 16, or 25 times less.

GRAVITY (gravitas, heaviness). A
name given, in Physics, to the tendency
which all bodies have to the centre of
the earth. The term is often used syno-
nymously with attraction, from which,
however, it differs as a species from a
genus : we speak, for instance, of capil-
lary attraction and of magnetic attrac-
tion, but not of capillary or magnetic
gravity.

1. Gravity, specific. The density of
bodies, as ascertained by comparison with
an equal bulk of water, which is assumed
as unity, or the absolute weight. One
substance is said to have a greater specific
gravity than another, when a less portion
of its bulk is of equal weight to that other.
Thus, a cubic inch of platinum is nearly
twice as heavy as a cubic inch of silver ;
the specific gravity of the former is,
therefore, double that of the latter.

2. Gravity, centre of. That point in a
body, about which all its parts, in any
situation, balance one another. Hence
if the body could be suspended from this
point, it would remain at rest, with re-
ference to its tendency towards the earth,
in whatever respective position the sur-
rounding parts may be turned. Thus,
the centre of gravity of a globe, if of uni-
form density, is its common centre, and
that of a balanced beam is the pivot on
which it turns.

3. Gravity, line of direction of. That
line which passes through the centre of
gravity of a body in a direction to the
centre of the earth.

GRAYSTONE. A term suggested for
designating certain volcanic rocks com-
posed of felspar, augite, or hornblende,
and iron; the felspar being sometimes
replaced by leucite or melilite.

GREEK FIRE. An explosive sub-
stance, invented by the Greeks, supposed
to consist of asphaltum, nitre, and sul-
phur.

GREEN EARTH. An earthy or granu-
lar variety of chlorite, which occurs mas-
sive, dispersed in rocks, or enclosed in
some simple minerals, as rock-crystal,
and often in the globular cavities of cer-
tain rocks. It is the mountain green of
artists in water colours.

GREEN MINERAL. A carbonate of
156

copper, employed as a pigment. Scheele's
green is an arsenite of copper; Bruns-
wick green, an oxychloride of copper.

GREENSAND. A designation of beds
of sand, sandstone, and limestone, be-
longing to the Cretaceous Period. They
are so named from the abundance of
green earth or chlorite which is often
scattered through their substance.

GREENSTONE. A variety of trap,
consisting of hornblende and felspar, in
nearly equal proportions, and having a
granitic structure. The name is not very
appropriate, for, besides being sometimes
greenish, it is not uncommonly reddish
or whitish, the colour depending chiefly
on that of the felspar, which is generally
compact, or at least not highly crystalline.
This rock is called diabase by the French
geologists, who name the compact green-
stone aphanite.

GREGORIAN TELESCOPE. A re-
flecting telescope, having a hole in the
centre of the great speculum, through
which the image is thrown by the
small reflector to the eye. The dis-
tinctness of the object seen through
this telescope is somewhat diminished
by the hole in the great speculum.

GRENATITE. Staurotide. A desig-
nation of the prismatic garnet.

GREYWACKE' {grau, grey, wacke, a
provincial miner's term). A German
designation of some of the most common
fossiliferous strata, consisting of a series
of arenaceous and slaty rocks, of evidently
mechanical origin, intermixed with small
beds of limestone. The rocks are very
often of a grey colour.

GRIDIRON PENDULUM. Harri-
son's compensation pendulum, which is
constructed of different substances, so
combined that the effects of heat coun-
teract each other, and the length of the
rod remains unaltered.

GRIT. A provincial name for a coarse-
grained sandstone, employed for mill-
stones, &c. Calcareous grit, or sandstone,
is one of the subdivisions of the Middle
Oolite Formation.

GROSSIFICA'TION. A term applied
to the swelling of the ovary of plants
after fertilization.

GRO'SSULAIRE. A green crystal-
lized mineral, found imbedded with ve-
suvian, in a pale greenish-grey claystone
in Siberia.

GROTTO DEL CANE. The Dog'a
Grotto ; a cave in Italy, in which there is
a constant natural exhalation of carbonic
acid gas, which, occupying the lowest

GUL

GYM

stratum of the air, causes asphyxia in
animals introduced into it.

GROUND BASE. In Music, a base/
consisting of a very few bars, which are!
continually repeated during the wholel
movement.

GRU'IDjE {grus, a crane). A family
of wading birds, named from the genus
grus.

GRUMOUS (grumus, a clot). Knotted ;
collected into granular masses, as the
fecula in the stem of the Sago palm.

GRUS. The Crane ; a southern
constellation consisting of fourteen
stars.

GRY'LLIDjE {gryllus, a grasshopper).
The Grasshopper tribe ; a group of or-
thopterous insects, belonging to the tribe
saltatoria, and distinguished by the roof-
like position of the elytra, or wing-cases,
when these are closed.

GRYPHjE'A. A genus of bivalves,
allied to the oyster, and found abundantly
in the secondary strata of Europe from
the lias upwards to the chalk, but scarcely
known in the tertiary strata.

GRY'PHITE LIMESTONE. A de-
signation of the Lias formation, from the
numerous shells of the genus gryphcea
which it contains.

GUANO. A manure employed in
South America, consisting of urate of
ammonia and other ammoniacal salts.
It appears to consist of the excrements
of sea- fowl.

GUIA'NA CURRENT. A branch, or
rather a continuation, of the great equa-
torial current, running from Cape St.
Roque in Brazil to the Island of Trini-
dad, along the low co^st of Guiana, and
at no great distance from it, and lost in
the Caribbean sea. Its whole course ex-
tends to about 2500 nautical miles. See
Brazil Current.

GUINEA, or NORTH AFRICAN
CURRENT. A current in the North
Atlantic, which has its origin in the sea
between the southern coast of Ireland
and Cape Finisterre in Spain, and ranges
along the coast of Guinea. Near its ori-
gin, a branch, called RennelVs Current,
separates itself from the main stream,
and performs a complete rotation be-
tween Spain, France, and the Atlantic
at large.

GULF. A portion of the ocean running
up into the land between two promon-
tories, and spreading out info a capacious
bay. A bay (bow) is a projection of the
ocean into the land, but is not necessarily
a gulf, which includes the idea of a sort
157

of abyss where the waters are engulfed,
or swallowed up.

GULF STREAM. The name given
by navigators to that current of the
Atlantic, which traverses the sea between
the parallels of 36° and 44° in the northern
hemisphere. It enters the gulf of Mexico,
through the strait formed by the western
end of Cuba and the opposite peninsula,
follows the bendings of the Mexican
coast, and flows into the gulf of Florida.
~*GUM. "Vegetable mucilage; a com-

I

mon proximate principle of plants. Gum-
resins are the concrete juices of certain
plants, consisting of resin, gum, essential
oil, and extractive matter.

GUNPOWDER. An explosive mix-
ture of five parts of nitre, one of sulphur,
and one of charcoal, finely powdered, and
very accurately blended. The grains are
smoothed by friction, and are then said
to be glazed.

GUNTER'S LINE. A logarithmic
line engraved on scales, sectors, &c, for
facilitating the multiplication and divi-
sion of numbers. The numbers are
usually drawn upon two separate rules,
which slide against each other. See Scale.

GURHO'FFITE. Compact dolomite,
occurring in serpentine rocks in Lower
Austria.

GUTTA PERCHA. A substance con-
tained in the sap of a tree belonging to
the natural order Sapotacece, abounding
in the island of Singapore and in the
Malayan peninsula. It is plentiful in
Sarawak, where it is called Niato, and is
probably to be found over the whole
island of Borneo. The substance, as an
article of commerce, appears likely to
rival caoutchouc in its application to the
useful and ornamental arts.

GUTTIFERjE (gutta, a drop, fero, to
bear). The Mangosteen tribe of Dico-
tyledonous plants. Trees or shrubs, oc-
casionally parasitical, yielding resinous
juice; leaves entire, opposite; flowers
polypetalous ; stamens hypogynous ; car-
pels concrete ; ovary consisting of several
cells.

GYMNOCA'RPOUS (yvfxvor, naked,
Kap7r6?. fruit). A term applied to a class
of fruits in the arrangement of Mirbel,
in which the fruit is not disguised by the
adherence of any other organ than the
calyx. See Angeiocarpous.

GYMNODO'NTES (71/^69, naked,
b&ovs, a tooth). A family of the plecto-
gnathous fishes, including the spinous
globe-fishes, in which the jaws are co-
vered with a substance resembling ivory,

H AB

H.EM

arranged in small plates, representing
united teeth. These plates are repro-
duced as soon as destroyed by use.

GY'MNOSPERMS (jappfe, naked,
cnrtpfia, seed). A class of plants which
agree in all respects with Exogens, ex-
cept that their ovules, instead of being
enclosed in a pericarp, are exposed naked
to the fertilizing influence of the pollen,
as in the Coniferae and the Cycadaceae.
See Angeiospermia.

GYNjECE'UM {ywaiKelov, the wo-
man's part of the house). A term ap-
plied by Roper to the entire female sys-
tem of plants, with reference to the fan-
ciful language of Linnaeus. It is com-
monly called the pistil, and comprises
the ovary, the style, and the stigma. See
Androceum.

GYNA'NDRIA {yvvrj, a woman, uvrjp, a
man). The twentieth class in the Lin-
naean system of plants, in which the
stamens are situated upon the style,
above the ovary, as in passiflora.

GY'NOBASE (ywrj, a woman, fidotr,
a base). A term applied to the recep-
tacle in plants, when it is dilated and
supports a row of carpels, which have an
oblique inclination towards the axis of the
flower, as in Labiatae, Boraginaceae, &c.

GY'NOPHORE (-yut/^, a woman, <pePa>,
to bear). Thecaphore. A term applied,
in Botany, to the stalk upon which the
ovary is sometimes seated, instead of
being sessile, as in taesonia.

GYNOSTE'MIUM (ywtj, a woman,
(rrrjuuiv, a stamen). A term applied by
Richard to that condition of the filaments
in Orchidaceae, in which they are com-
bined into a solid body called the
columna.

GY'PSUM (71^0?, chalk; from yn,
earth, e^o>, to bake). Sulphate of lime;

a modification of limestone, with a granu-
lar or crystalline texture, forming beds
and irregular masses, and, when highly
burned, constituting plaster of Paris.
There are two species, according to
Jameson,— the prismatic, and the axi-
frangible.

GY'RATE (7i;po9, curved). Curved
in from apex to base, as the fronds of
ferns; a term synonymous with circi-
nate.

GYRA'TION (gyrus, a circle). The
act of turning round a centre, in the
manner of a wheel. The centre of gyra-
tion is that point in a revolving body,
into which, if all its matter could be col-
lected, it would continue to revolve with
the same energy as when its parts were
in their original places.

Gyration, circle of. A wheel in
motion may be considered as an indefi-
nite number of pendulums, each of which
has its own centre of oscillation. If the
wheel be nearly balanced, these several
points of oscillation will accommodate
themselves so as to form, in their con-
tinued motion, a set of points equally
distant from the rim. These are centres
of gyration, and in their junction they
will form a circle of gyration.

GYRO'GONITE (yvpos, curved, yo^,
seed). A term applied to the fossil seed-
vessel of plants of the genus Chara, found
in fresh-water deposits. The name was
derived from the idea that they were
shells of polythalamous cephalopods.

GYRO'MA (71/poc, curved). Gyrus.
A term sometimes used as synonymous
with the annulus of the theca of ferns.
It is also applied to the shield, or trica,
of lichens, the surface of which is covered
with sinuous concentric furrows.

H

HAA'RKIES (haar, German, hair).
A designation of capillary pyrites occur-
ing in very delicate acicular crystals.
The term is also applied by German
mineralogists to a native sulphuret of
nickel.

HABITATION. A technical term em-
ployed in botany to indicate generally the
country where a plant grows wild. It
must be distinguished from the term
station. The study of stations has been
styled the topography, that of habitations
158

the geography, of botany. Thus, the
station of a plant may be a salt-marsh,
in a temperate climate, a hill-side, the
bed of the sea, or a stagnant pool. Its
habitation may be Europe, North Ame-
rica, or New Holland between the tropics.
See Station.

HEMATITE {oJ/jLa, blood). Blood-
stone ; a native oxide of iron, so named
from its blood-red streak. The red
haematite is an anhydrous, the brown a
hydrated, peroxide.

HAL

HAR

HAIDI'NGERITE. An ore of anti-
mony, consisting of sulphuret of anti-
mony and protosulphuret of iron.

HAIL. Drop3 of rain, more or less
suddenly frozen by exposure to a tempe-
rature below 32°. They assume various
figures, being sometimes round, at other
times pyramidal, cuneated, angular, thin
and flat, and sometimes stellated with
six radii like the small crystals of snow.
Hail occurs only in summer or in warm
climates, and when the sun is above the
horizon.

HAIRS OF PLANTS. Minute fila-
mentous processes found on the cuticle
and in certain cavities of plants, consist-
ing of elongated cellular tissue, and con-
stituting, in the cotton plant, the pecu-
liar substance which envelopes the seeds,
and is manufactured into linen. The
variable qualities of hairs have given
rise to various designations, as pilosity,
villosity, pubescence, velvet, bristles,
stings, glandular hairs, hooks, barbs, &c.
Hairy surfaces are also named, with
reference to the quality and form of the
hairs, silky, arachnoid, manicate, bearded,
rough, and stellate or starry.

HA'LCYON DAYS {halcyon, the king-
fisher). Originally, the seven days which
precede and follow the winter solstice,
the period of incubation of the halcyon,
generally remarkable for calm weather.
Hence the term denotes generally days of
calmness.

HALCYO'NID.E. AlcedincB. The
King-fishers ; a family of the Insessores,
or Perching birds, remarkable for the
great length of their bill, and the extreme
shortness of their feet. They feed upon
small fishes and insects. See Fissi-
rostres.

HALIO'TID^l (a\c, the sea, oSj, the
ear). Ear-shells ; a family of the phyto-
phagous Gasteropods, named from the
genus haliotis, and known by their flat,
ear-shaped shells, having only the rudi-
ment of a spire, and without any pillar ;
hence they may be even called turbi-
nated or spiral limpets.

HALISPO'NGIA. The generic type
of a group of sponges, characterized by
the presence of siliceous spiculae, and
thus distinguished from the calcispongia,
which contains calcareous spiculae, and
from spongia, which is of a horny tubular
structure.

HALLEY'S COMET. A comet named
from Edmund Halley, who in 1682 pre-
dicted its return in 1759 : the event co-
inciding with the prediction, this comet
159

was first proved to belong to the solar
system, and to perform its revolution in
75 or 76 years.

HA'LO (a\wf, an area). A meteor in
the form of a luminous ring, of various
colours, appearing round the bodies of
the sun, moon, or stars. See Parhelion.

HA'LOGENE (a\r, salt, 7e»/vaa>, to
produce). A term employed by Berze-
lius to denote bodies which form salts
with metals, as chlorine, bromine, iodine,
fluorine, and cyanogen. The salts thus
produced are called haloids.

HALOID SALTS (&Xt, the sea, sea-
salt, eidor, likeness). Salt-like com-
pounds, consisting of a metal on the one
hand, and of chlorine, iodine, and the
radicals of the hydracids in general,
excepting sulphur, on the other. Be-
sides the simple haloid salts, Berzelius
distinguishes the three following com-
binations : —

1. Hydro-haloid Salts, or combinations
of a simple haloid salt and the hydracid
of its radical.

2. Oxy-haloid Salts, or combinations of
a metallic oxide with a haloid salt of the
same metal.

3. Double Haloid Salts, consisting,
1. of two simple haloid salts, which con-
tain different metals, but the same non-
metallic ingredient ; 2. of two haloid
salts consisting of the same metal, but in
which the other element is different ;
and, 3. of two simple haloid salts, of
which both elements are entirely dif-
ferent.

HA'MITE {'dfxt], hamus, a reaping-
hook). A genus of fossil cephalopods,
with chambered shells bent in the form
of a hook or siphon, with parallel but
unequal limbs and sinuous septa, occur-
ring in the gait, greensand, and other
cretaceous beds.

HARDNESS OF MINERALS. The
comparative hardness of minerals is
tested by reference to a scale of sub-
stances formed by Mohs. The hardness
of a mineral which neither scratches nor
is scratched by any particular substance
in this scale, is expressed by the number
prefixed to that substance. They are
1, talc; 2, rock salt; 3, calcareous spar;
4, fluor spar; 5, apatite; 6, adularia;
7, rock crystal; 8, topaz; 9, corundum;
10, diamond. The hardness of minerals
is also tested by the application of a file.

Hardness of Rocks. This character
does not require so precise a determina-
tion as in the case of simple minerals.
The extremes are the hardness of quartz

HAS

HE A

on the one hand, and soft chalk on the
other.

HARMO'NICON, CHEMICAL. An
apparatus for imparting a sonorous pro-
perty to the air. If a small flame of hy-
drogen gas be made to burn in a tube of
glass or of any other material, of from
one to three inches in width, the column
of air contained in the tube will in a
short time be heard to give forth musical
sounds. These are occasioned by the
combustion of the hydrogen in the atmo-
spheric air contained in the tube, and
thus an influx of the surrounding atmo-
sphere is produced. The sounds are
heard when the flame of the hydrogen
becomes small and steady.

HARMO'NICS (apuovla, concord).
The doctrine of harmonical combinations
in music, as they occur in the natural
series, I, 2, 3, 4, &c. Thus, the first
interval, 1 I 2, is an octave ; the second,
1 I 3, is a twelfth ; the third, 1 I 4, is a
fifteenth; the fourth, 1 ; 5, a seven-
teenth ; the fifth, 1 I 6, a nineteenth;
&c.

HA'RMONY (apfjLovla, concord). A
combination of sounds, forming a mu-
sical chord, or a succession of chords.
The harmonic triad, or common chord,
consists of a note, with its third and
perfect fifth, and is the result of the
vibration of all sonorous bodies.

HA'RMOTOME {ap/sos, a joint, to/u»j,
a section). A silicate of barytes and
alumina, containing water, found at An-
dreasberg in the Hartz : the crystals of
this mineral intersect one another length-
wise, and are easily separable. It is also
called staurolite, or cross stone.

HARPA'LlD^i A family of Coleo-
pterous insects of the section Geodephaga,
named from the genus Harpalus, dis-
tinguished by the tarsi of the two ante-
rior pairs of legs being dilated in the
male sex.

HARVEST and HUNTERS' MOON.
Twice in the year the moon rises almost
at the same hour during a week. This
occurs in September or October, and in
March or April : in the former case the
moon is termed the harvest moon, in the
latter the hunters' moon.

HA'STATE (hastatus, spear-shaped).
A term applied, in Botany, to leaves
which have three lance-shaped lobes,
one in the direction of the midrib, the
other two at the base, at right angles to
the first, as in arum maculatum.

HASTINGS SAND. The middle
group of the Wealden formation, consti-
160

tuting the uppermost part of the Oolitic
system in England, and occurring around
Hastings in Sussex. It consists of yel-
lowish grains of sand, very loosely cohe-
rent, alternating with beds of clay and
conglomerate, containing fragments of
bones and scales of fishes.

HA'TCHETINE. Mineral adipocire.
A wax-like substance occurring in the
nodules of iron-stone in South Wales,
and named after Mr. Hatchett.

HAUSMA'NNITE. A designation of
pyramidal manganese ore.

HAUSTELLA'TA {haustellium, a pro-
boscis). Haustellate insects ; a group in
which the mouth is furnished with a
haustellium, or proboscis, adapted for
suction. This division includes the
homopterous, heteropterous, lepidopte-
rous, and dipterous insects. See Mandi-
bulata.

HAUYNE. Latialite. A blue mine-
ral, occurring in basalt or lava, and
named from the mineralogist Haiiy.

HAY'TORITE. A variety of rhom-
boidal quartz, containing 0*5 per cent, of
oxide of iron.

HEADLAND. Any projection of the
land into the sea. Thus, a cape is a
headland, and is distinguished in each
case by a particular designation ; a pro-
montory is also a headland, but, in ac-
cordance with its Latin derivation, is
applied only when the projecting head is
a high point or a rock.

HEART-WHEEL. A mechanical con-
trivance employed in cotton mills for
converting a circular into an alternating
rectilinear motion. It consists of a re-
volving ellipse, on the edge of which a
moveable point or circle presses ; the
latter receives an alternating motion
from the circumference of the ellipse,
which in its revolution presses it to dif-
ferent distances from the centre of mo-
tion.

HEART-WOOD. The popular name
for the hard interior portion of the stem
and branches of exogenous trees, as dis-
tinguished from sap-wood, or the exterior
and softer portion. In botany the former
is termed duramen, the latter alburnum.

H EAT. In popular language, the sen-
sation experienced on touching a body of
a higher temperature than that of the
blood. In chemical language, it is the
cause of that sensation, or caloric, a term
by which philosophers distinguish the
matter of heat from its effect.

HEAVY SPAR. Another name for
baryta, the heaviest of all the earths.

HEL

This genus has been distinguished into
four species; viz. 1. the rhomboidal or
witherite, which is a carbonate of baryta,
occurring in lead veins ; 2. the prismatic,
or heavy spar, or sulphate of baryta,
found in primitive and transition rocks,
in secondary limestone, and in lead
mines ; 3. the di-prismatic or strontianite,
a carbonate of strontia occurring in
veins which traverse gneiss ; and 4. the
axifrangible or celestine, a sulphate of
strontia, occurring in trap-tuff and in red
sandstone.

HEDENBER'GITE. A variety of
augite, of a dark-green colour, sometimes
nearly black: it resembles those horn-
blendes in which iron prevails, and is
found in Sweden.

HE'DYPHAN. A phosphate of lime,
in which a portion of phosphoric acid is
replaced by arsenic acid.

HE'GIRA. This mode of computing
time among the Mahomedans has been
noticed under the article Era. It may
here be added, that the years of the
Hegira are divided into cycles of thirty
years, nineteen of which are termed
common years, of 354 days each, and the
other eleven are called intercalary, or
abundant, from their consisting of one
day more. To reduce the Christian era
to the Mahomedan, subtract 622 from the
current year ; multiply by 1 0307 ; cut
off four decimals, and add *46 : the sum
will be the year and decimal of the day,
Old Style.

HEIGHT. This term, in Geometry,
is synonymous with altitude, and denotes
the perpendicular let fall from the ver-
tex, or top, of any rectilinear figure, upon
the base or side subtending it. It also
represents the position of any object, in a
vertical direction above the horizon.

The measurement of heights is gene-
rally effected by observing the differences
of atmospheric pressure as indicated by
the barometer. In 1815, Capt. Smith
ascertained, trigonometrically, that the
height of Etna was 10,874 feet. In
1824, Sir J. Herschel determined, by
barometrical measurement, that the
height was 10,872^ feet. This singular
agreement of results, so differently ob-
tained, was spoken of by Herschel as "a
happy accident;" but Wollaston re-
marked that " it was one of those acci-
dents which would not have happened to
two fools."

HE'LIACAL (iiXto?, the sun). A term
applied to the rising and setting of a
star, when it rises in the morning a little
161

HEL

f before the sun, or sets in the evening a
j little after him. It is only in his heliacal
rising and setting that the planet Mer-
cury is ever visible to the naked eye. See
Cosmical.

HELIANTHOI'DA {helianlhus, the
sun-flower, eidov, likeness). An order of
the polypipherous Radiata, named from
their resemblance, when expanded, to
the sun-flower. They are also termed
actiniform polyps, from their general
resemblance to the sea-anemone.

HELFCIDjE {helix, a snail). Snails j
a family of phytophagous Gasteropods ;
these are pulmonary animals, breathing
by a lateral opening ; the shell is light,
turbinated, or spiral ; the aperture al-
ways entire, rarely closed by an opercu-
lum, and sometimes only rudimentary.

HELI'CINiE. Common Land Snails ;
a sub-family of the Helicidcc, having
perfect turbinated shells more or less
depressed; the aperture entire, but
without teeth.

HE'LICOID (e\t?, a helix, e'ibo?, like-
ness). Parabolic spiral. In Geometry,
a curve generated by the bending of the
axis of the common parabola into the
circumference of a circle, the ordinates
still retaining their places and perpendi-
cular positions with respect to the circle,
all these lines still remaining in the same
plane. The equation of this curve re-
mains the same as when it was a para-
bola.

HE'LIOCE'NTRIC (Jj\<of, the sun,
Kevrpov, a centre). Having the sun as a
centre ; a term applied to the place of a
planet, as seen from the centre of the
sun, and opposed to its geocentric place, as
seen from the centre of the earth.

1. The heliocentric longitude of a planet
is the angle at the sun's centre formed
by the projection of its radius vector on
the ecliptic, and the straight line drawn
from the centre of the sun to the first
point of Aries.

2. The heliocentric latitude of a planet
is the inclination of a line drawn between
the centres of the sun and the planet, to
the plane of the ecliptic.

HELIO'GRAPHY (JjXto?, the sun,
1pd<ph>, to write). Photography. A me-
thod of giving permanency to images ob-
tained by means of convex lenses, by the
chemical effects of light.

HELIO'METER (JjXtor, the sun, /ne-
rpov, a measure). A kind of micrometer
invented by M. Bouguer for measuring
the diameters of the heavenly bodies.

HE'LIOSCOPE {ii\io9, the sun, <tko-

HEM

HEP

Treco, to observe). A telescope invented
by Scheiner, for making observations on
the sun without injuring the eye. The
usual method is to place a disc of co-
loured glass before the eye-piece of the
instrument.

HE'LIOSTAT (JjXto?, the sun, ardan,
a placing or setting). An instrument by
which the sun-beam can be steadily di-
rected to one spot during the whole of its
diurnal period.

HE'LIOTROPE. A sub-species of
rhomboidal quartz, found in rocks belong-
ing to the secondary trap formation. It
is termed bloodstone, from the blood-red
specks which occur on its green surface,
owing to disseminated jasper.

HELIX (eXtf, a spiral). A spiral, or
winding line; a coil of wire used in
magneto-galvanic experiments.

HELO'PIDjE. A family of coleopte-
rous insects, of the section heteromera
and sub-section stenelytra, named from
the genus helops, several species of which
abound in England, living in rotten wood
and under the bark of trees.

HE'LVINE. A sub-species of dode-
cahedral garnet, found in beds subordi-
nate to gneiss, in Saxony.

HE'MATOSIN (alfxa, blood). This
and globulin are two of the most charac-
teristic constituents of the blood, both
closely related to albumen.

HEMATO'XYLIN. The colouring
matter of logwood, the wood of the
Hematoxylon campeachianum : it was
named hematin by Chevreul, who first
distinguished it.

HEMERO'BIANS (h^epa, day, plot,
life). A family of neuropterous insects,
of the section planipennes of Latreille,
named from the typical genus hemerobius,
and, like the ephemerae, of very short
existence.

HEMI- (nfxicvt, half). A Greek term
frequently employed in composition to
denote half, and synonymous with the
Latin semi : —

1. Hem-elytra (eXvrpov, a sheath). A
wing, of which one half is opaque and
firm, like an elytrum.

2. Hemi-gyrus (yupo?, a circle). A term
applied in carpology, by Desvaux, to the
fruit of Protaeaceae. It differs little from
the follicle of other writers.

3. Hemi-hedral (e&pa, a seat). A term
applied to a variety in some forms
of crystals (particularly those of which
the cube and the rhomboid are the pri-
mary), characterized by the existence of
only half the number of faces belonging

162

to any particular modification, which the
law of symmetry requires. These hemi-
hedral forms are parallel or oblique, ac-
cording to the relative position of the
existing and omitted faces. The penta-
gonal dodecahedron is an example of the
former kind, and the tetrahedron, of the
latter. As the tetrahedron contains half
the planes by which the octahedron may
be derived from the cube, it has been
sometimes called the hemi-octahedron.

4. Hemi-ptera {irrepov, a wing). An
order of insects, in which the anterior or
upper pair of wings are coriaceous in
their texture through one half of their
extent, the posterior portion being thin
and membranous, as in the notonecta, or
water-boatman.

5. Hemisphere (cnpaipa, a sphere). A
half -sphere, produced by cutting a sphere
through the centre by a right line in any
direction; thus the equator divides the
sphere of the earth into the northern and
southern, the eastern and western, the
upper and lower, hemispheres.

6. Hemi-tone (toi/os, tone). An inter-
val in ancient music, the ratio of which is

m

7. Hemi-trope {Tpeirw, to turn). A term
applied by Haiiy to twin crystals, from
their being generally conceived to result
from cutting a crystal in halves, and
turning one portion half round on the
other. The plane common to the two
portions of the crystal is called the twin
plane, and is parallel either to one of the
primary planes, or to a secondary plane
resulting from some simple law of decre-
ment. These crystals may frequently be
recognized by the existence of notches,
called re-entering angles, or by lines on
the surface, which point out the position
of the twin plane.

HE'PAR (hirap, the liver). A term
formerly applied to the combinations of
sulphur, from their liver-Uke appearance.
Thus we had hepar sulphuris, a sulphuret
of potash ; hepar antimonii, an oxysul-
phuret of antimony ; hepar calcis, a crude
bisulphuret of calcium, &c.

HEPA'TIC {faap, liver). A term
applied to various substances of a brown
or liver-like colour. Hepatic pyrites is a
variety of prismatic iron pyrites, which
becomes brown on exposure to the air.
Hepatic cinnabar is a dark-coloured,
steel-grey variety of cinnabar. Hepatic
air is another name for sulphuretted hy-
drogen gas.

HEPA'TICjE (hrtap, Uttcito?, the liver).
The Liver-wort tribe of Acotyledonous

HER

HET

plants. Cellular, flowerless plants, con-
sisting of an axis or stem, either leafy or
bordered : reproductive organs are valved
thecce of different kinds.

HE'PATITE {r,irap, liver). A variety
of heavy spar, or sulphate of barytes,
containing a minute portion of sulphur,
and emitting, when heated or rubbed, a
fetid sulphurous odour.

HE'PATULE (nnap, liver). The name
given by Kirwan to the hydrosulphuret of
other writers.

HE'PTAGON (^tttu, seven, ytavia,
angle). In Geometry, a plane figure of
seven sides. The area of a regular hep-
tagon is equal to the square of one of its
sides multiplied into the constant num-
ber 3.6339124, or seven-fourths of the
tangent of the angle at the base to ra>
dius 1.

Heptagonal Numbers. A kind of po-
lygonal numbers in which the difference
of the terms of the corresponding arith-
metical progression is 5, thus, —

Arithmetical*— 1, 6, 11, 16, 21, 26, &c.

Heptagonals— 1, 7, 18, 34, 55, 81, &c,
where the heptagonals are formed by
adding continually the terms of the arith-
meticals, above them, whose common
difference is 5.

HEPTAGY'NIA (tiri-a, seven, yv^, a
woman). The name of those orders of
plants in the system of Linnaeus, which
are characterized by the presence of seven
pistils.

HEPTA'NDRIA (fortt, seven, uvJ/p, a
man). The seventh class of the Linnaean
system of plants, characterized by the
presence of seven stamens.

HERBA'RIUM (herba, a herb). A
collection of dried specimens of plants,
formerly known by the expressive term
hortus siccus, or dried garden.

HER'CULES. Eugonasia. A northern
constellation, consisting of 113 stars.
This constellation has also been named
Hercules cum Ramo et Cerbero. Its prin-
cipal star is called Ras Algratha.

HE'RDERITE. The prismatic fluor-
haloid of Mohs ; a mineral found in
crystals imbedded in fluor, in Saxony,
and named from Herder, its discoverer.

HERMA'PHRODITE ('EPMrjc, Mer-
cury, 'A0Po3tTrj, Venus). A term ap-
plied, in> Botany, to plants in which the
stamen and the pistil are contained in
the same flower; all other flowering
plants being termed unisexual, as monoe-
cious and dioecious plants.

HERME'TIC SEAL. The closure of
the end of a glass vessel when heated to
163

the melting point. The name is derived
from the Egyptian Hermes, supposed to
have been the father of chemistry, which
has hence been called the Hermetic
art.

HERO'S FOUNTAIN. An apparatus
in which the compression of air is em-
ployed to produce a jet of water. Hero's
Ball is a similar contrivance for the same
purpose. Hero's steam-engine is a con-
trivance for producing a rotatory motion
by means of steam, and was invented
120 years before the present era.

HERPETO'LOGY {tpnerov, a reptile,
\6yos, a description). That branch of
Zoology which treats of the structure,
history, and classification of Reptiles.

HER'SCHELorU'RANUS. The most
remote, but one, of the planets, accom-
plishing its revolution round the sun in
eighty-four years. Its time of diurnal
rotation is not determined.

HE'RSCHELITE. A mineral found
in olivine, brought by Mr. Herschel from
Sicily.

HESPE'RIDIN. A crystalline sub-
stance, obtained from the skin of the
unripe orange or lemon,

HESPERI'DIUM. A many-celled,
superior, in dehiscent fruit, covered by a
spongy separable rind, as the orange.

HE'TEPOSITE. A phosphate of iron
and manganese, found at Haute Vienne.

HE'TERO- (trepof, the other, one of
two). A Greek term, in composition
generally denoting difference, and thus
distinguished from the term homo-, which
indicates resemblance : —

1. Hetero-branchiata (fipdyxia, gills).
The name given by Blainville to the
fourth order of his Acephalophora.

2. Hetero-carpien (Kapnos, fruit). A
term applied by Desvaux to that kind of
fruit which is more commonly called
inferior, from its contracting adhesions
with other organs. On the same prin-
ciple, he designated superior fruits as
auto-carpien, owing to their freedom
from such adhesions.

3. Hetero-cephalous (Ke<f>a\rj, the head).
A term applied by De Candolle to those
plants in which some of the capitula are
composed entirely of male flowers, and
others entirely of female flowers.

4. Hetero-cercal(nepKof, a tail of a beast).
A term applied to the tail of all the palae-
ozoic fishes : their back-bone runs to a
point above the tail, which is placed be-
below, like a triangular rudder. This
structure is still seen in our sharks,
sturgeons, and in the sauroids of the

HET

HEX

North American lakes (bony pike). See
Horn o-cercal.

5. Hetero-gamous (fdnos, marriage).
A term applied, in Botany, to those
capitula in which the outer flowers are
neuter or female, and the inner herma-
phrodite or male : when all the flowers
are hermaphrodite, the capitulum is
termed homo-gamous.

6. Hetero-gangliata (ydyyXiov, a nerve-
knot). A term applied by Owen to Cu-
vier's grand division Mollusca of the
animal world, the beings of this division
having a ganglionic nervous system, and
the ganglions scattered often unsymme-
trically. These are the cyclogangliata
of Grant. See Homo-gangliata.

7. Hetero-geneous {yevos, kind). A
term applied to substances the parts of
which are of different kinds, and there-
fore of different qualities.

8. Helero-mera (/uepof, a part). A sec-
tion of coleopterous insects, in which the
tarsi are differently parted, the four an-
terior being five-jointed, the two poste-
rior four-jointed. — Latreille.

9. Hetero- trior phous (nop<prj, form). Of
an irregular or unusual form ; a term
applied to the larvae of certain insects
which differ in form from the imago, and
applicable to the true larval state of all
insects.

10. Hetero-phyllous (<pv\\ov, a leaf).
A term applied to those plants in which
the leaves are not of the same kind as
regards form, &c.

11. Hetero-poda (irovs, tto56?, a foot).
A small order of Gasteropods, including
certain families in which the foot is so
much compressed, as to constitute a ver-
tical muscular lamella, which presents
merely a remnant of the ventral sucker,
so characteristic of the entire class, and
which can only be serviceable in per-
forming the office of a fin used in swim-
ming.

12. Hetero-ptera (mepov, a wing). An
order of insects in which the two pairs of
wings are of different consistence, the
anterior pair being horny or leathery,
but generally tipped with membrane.
They comprise the land and the water-
bugs.

13. Heter-organa (opyavov, an organ).
By this term, and that of hom-organa,
Schultz has divided the vegetable king-
dom into two primary cla>ses, with re-
ference to the Rotation, or general motion
of the sap: the latter class consisting
wholly or in great measure of cellular
tissue, and containing all the cellular

164

fiowerless, and some flowering, plants of
a low organization; the former all the
higher flowering plants, and the vascular
fiowerless.

14. Hetero-scii (ama, a shadow). This
and some similar terms, as amphi-scii
and peri-scii, are of old date, but still
remain in works on the use of the globes.
The first are the inhabitants of the two
temperate zones, the noon-day shadows
of each being always thrown one way,
but those of the two being always in dif-
ferent ways. The second are the inha-
bitants of the torrid zone, who have their
noon-day shadows sometimes cast north,
sometimes south. The third are the in-
habitants of the frigid zones, whose vi-
sible shadows make complete revolu-
tions.

15. Hetero-tropal (tp€7tw, to turn).
That which has its direction across the
body to which it belongs, as applied, in
Botany, to the embryo of the seed, as in
primrose.

HEU'LANDITE. A mineral formerly
ranked among the zeolites, consisting of
silica, alumina, and lime, and found in
the Faroe Isles, the trap of the Giants'
Causeway, &c.

HE'XAGON (ef, six, -yow'a, an angle).
In Geometry, a plane figure bounded by
six sides, and consequently having six
angles. The side of a regular hexagon
is equal to the radius of its circumscri-
bing circle. The area is equal to the
square of the side multiplied into the con-
stant number 2.598076 ; that is, into three
times half the tangent of 60°.

HEXAGY'NIA (ef, six, yvvrj, a wo-
man). The name of those orders of
plants in the Linnaean system, which are
characterized by the presence of six
pistils.

HEXAHEDRON (ef, six, £3pa, a
seat). A cube, or a solid geometrical
figure, having six faces. The whole sur-
face of a hexahedron is equal to 24 times
the square of the radius of the inscribed
sphere, and to 8 times the square of the
radius of the circumscribed sphere. Its
solid content is 8 times the cube of the
inscribed sphere.

HEXA'NDRIA (ef, six, i^p.aman).
The sixth class of plants in the system
of Linnaeus, characterized by the pre-
sence of six stamens.

HE'XAPOD (ef, six, nrovt, irodbs, a
foot). Six-footed ; a term applied to ani-
mals with six legs, as the true insects
Hence, the term Hexapoda has been ap-
applied by Mr. Kirby to a sub-order of

H I P

HOL

apterous insects, including those which
have no more than six legs.

HIERA'TIC WRITING (leP6c, sa-
cred). A mode of writing employed by
the priests of Egypt, consisting in an
abridged form of the hieroglyphic cha-
racters, adopted for the sake of conve-
nience and expedition, and sometimes
found attached to mummies.

HIERO'S FOUNTAIN. An appara-
tus for raising water, which acts by the
elasticity of the air, and on the same
principle as the fire engine.

HIEROGLY'PHICS {(cpfe, sacred,
y\v<p<0, to engrave). Sacred engravings;
a term applied to a mode of sculpture-
writing employed in Egypt, and consist-
ing of the images of visible objects,
chiefly used in monumental inscriptions.
Champollion distinguishes three kinds of
characters, viz. —

1. The hieroglyphic, properly so called,
in which the figure represents the object
itself, entire or in an abridged form.
These are termed figurative, and are
distinguished into figurative proper,
figurative conventional, and figurative
abridged.

2. The symbolical, in which the figure
of a visible object represents an idea ;
thus a censer represents adoration, the
hawk's eye omniscience, a circle eter-
nity. Here, the symbol indicates an abs-
tract idea, a type suggests an antitype.

3. The phonetic, in which the figure
represents neither an object nor an idea,
but a sound. Thus the letter A sug-
gests the term " eagle," being the initial
letter of ahorn, the Egyptian term for
that animal. Twenty-nine elementary
sounds were thus represented.

HIGH PRESSURE ENGINE. A
variety of the Steam Engine, in which
the water is heated till it acquires an
expansive force of from two to ten atmo-
spheres.

HIGHGATE RESIN. Fossil Copal;
found in the bed of blue clay at High-
gate, near London. It is imbedded in
the clay in detached nodules.

HI'LOFERE. A term applied by
Mirbel to the internal integument of the
seed, from the insertion of the hilum on
this part of the testa.

HI'LUM. Umbilicus. The point of
the seed by which it is attached to the
placenta. This is the base of the seed.

HINGE MARGIN. The hinge of
bivalves, composed of the ligament, the
cartilage, and the te.eth. See Dorsal.

HI'PPIDES. The Hippa tribe ; the
165

name by which Latreille designates a
tribe of the macrourous decapod crus-
taceans, comprising the genera remipes,
albunea, and hippa, animals of pecu-
liar forms, adapted for burrowing in sand.

HIPPOBO'SCIDjE (i'TTTror, a horse,
/36aKU), to feed). Forest-flies, or spider-
flies of the French ; a family of dipterous
pupiparous insects, parasitic on birds
and quadrupeds, of which the tick among
sheep is a well-known example.

HIPPOTHE'RIUM (iWos, a horse,
Otjpiov, a beast). An extinct quadruped
allied to the horse, found in sand at
Epplesheim, and belonging to the second
or miocene period of the tertiary forma-
tion.

HIPPU'RIC ACID (fmror, a horse,
olpov, urine). An acid obtained from
the urine of the horse, the cow, and other
graminivorous animals, when mixed
with muriatic acid in excess. It re-
sembles benzoic acid, but contains nitro-
gen ; the salts of the two acids are, more-
over, distinct.

HI'PPURITES. A fossil coral belong-
ing to the Ei el transition limestone, and
characteristic of the rocks of the creta-
ceous era in many parts of Europe. It
is considered to be a bivalve, and is re-
ferred by Lamarck to the group of ru-
dista.

HI'RCIN (hircus, a goat). A sub-
stance, similar to butyrine, contained in
the fat of the goat and the sheep, com-
bined with olein, and yielding, by saponi-
fication, the hircic acid.

HIRUNDI'NID^E (hirundo, a swal-
low). The Swallow tribe ; a family of
the Insessores, or Perching birds, charac-
terized by the great length of their wings
and the rapidity of their flight. (See
Fissirostres.) By Macgillivray, these
birds are placed in a group, belonging to
an order which he names Volitatrices, or
gliders.

HISI'NGERITE. A black massive
mineral, found in the cavities of calca-
reous spar.

HISTO'LOGY (Icrrof, a tissue, \670r,
a discourse). The doctrine of the tissues
which enter into the formation of an ani-
mal and its various organs.

HOAR-FROST. This is an insensible
transition from dew, being, in fact, frozen
dew, and indicative of greater cold.

HO'LMITE. A new mineral, consist-
ing of carbonate of lime, named after
Mr. Holme, who analyzed it.

HOLOTHU'RIDiE {6\o0ovPiov, a kind
of zoophyte, Arist.). A family of Echi-

HOM

HOR

noderms, commonly termed, from their
general shape and appearance, " sea-
cucumhers." See Echinodermata.

HOMBERG'S PHOSPHORUS. Ig-
nited muriate of lime. See Phosphorus.

HOMBERG'S PYROPHORUS (iriJp,
fire, <p4p<o, to hring). A mixture of alum
and brown sugar, which takes fire on
exposure to the air. A more convenient
mixture is made with three parts of lamp-
black, four of burnt alum, and eight of
carbonate of potash.

HOMBERG'S SEDATIVE SALT.
A name for boracic acid, which appears,
however, to possess no sedative property.

HO'MO- (ojuoc , one and the same). A
Greek term, in composition denoting
resemblance, and thus distinguished from
the term hetero-, which denotes differ-
ence : —

1. Homo-centric (nevrpov, a centre).
Having the same centre, or being con-
centric.

2. Homo-cereal (Kepico?, the tail of a
beast). A term applied to those fishes
which have tails with rays regularly di-
verging from the end of the backbone,
like the tail of a herring or trout. See
Hetero-cercal.

3. Homo-dromal (5p6/xor, a course). A
term recently suggested, in Botany, to
characterize the peduncles of the cyme
of monocotyledons, in which the direc-
tion of the spire is the same as that of
the central stem, and as distinguished
from the anti-dromal direction, which is
the reverse of that of the central stem.

4. Homo-gamous (^a/uop, marriage). A
term applied, in Botany, to those capi-
tula, in which all the flowers are herma-
phrodite.

5. Homo-gangliata (ydfy\tov, a nerve-
knot). A term applied by Owen to Cu-
vier's grand division Articulata of the
animal world ; the beings constituting
this division having a ganglionic nervous
system, and the ganglions symmetrically
arranged. They correspond with the an-
nulosa of Macleay, and the Diploneura
of Grant. See Heiero-gangliata.

6. Homo-geneous (7^1/0?, kind). A term
applied to substances consisting of similar
parts and properties, as distinguished
from hetero-geneous substances. Thus,
in minerals, sandstone is a homogene-
ous, granite a heterogeneous substance.

7. Homo-logous (\6yos, a ratio). Having
the same ratio or proportion. Equiangu-
lar triangles, having sides containing cor-
responding equal angles proportional, are
said to be similar, and the corresponding

166

sides are homo-logous, i. e. having the
same ratio. Similar magnitudes, occu-
pying different places in a proportion, one
being an extreme, the other a mean, are
said to be homo-logous.

8. Homo-logue (\6yos, a description).
The same organ in different animals
under every variety of form and function.

9. Homo-morphous {fxop<prj, form). Of
similar form ; a term proposed by Mr.
West wood for certain neuropterous in-
sects, which, in their larva state, are
similar in form to the perfect insect,
though wingless.

10. Homo-phonous {(pasvl], a sound or
voice). A term applied, in Music, to two
or more sounds which are exactly of the
same pitch. In language the term is
applied to words or syllables which have
the same sound, though they are ex-
pressed in writing by various combina-
tions of letters.

11. Homo-ptera (inepov, awing). An
order of insects in which the four wings
are of the same consistence, all of them
being composed of a firm membrane, as
in the lantern-fly.

12. Hom-organa (opyavov, an organ).
One of the primary classes of plants, as
divided with reference to their Rotation,
or general motion of the sap. See Heter-
organa.

13. Homo-tropal {Tpenu, to turn). Hav-
ing the same direction as the body to
which it belongs, but not being straight,
as applied, in botany, to the embryo of a
seed.

HONEY-DEW. A sweetish substance
ejected by very small homopterous in-
sects, called aphides, upon the leaves of
plants, and vulgarly supposed to be
caused by a blight, or some disease in the
plant. There is another kind of honey-
dew, observed only at particular times,
and in certain states of the atmosphere,
hanging occasionally in drops from the
points of the leaves of plants ; its cause
is not known.

HONEY-STONE. Mellite. Mellitate
of alumina ; a mineral of a honey-yellow
colour, found situated on bituminous
wood and earth coal, and usually asso-
ciated with sulphur.

HO'RARY (hora, an hour). This term,
as uSed^n astronomy, denotes the
which a Celestial body describ^s^fn one
hour, or the iJmgle whi£h«**Cnat arc sub-
tends at the eye^^tne spectator: the
horary motion jd( aNjelestial body is
therefore l£<br the twe>R£y-fourth part
of a circle;

Horary circles, on globes, are hour
lines, or circles marking the hours ; they
are drawn at the distance of 15° on the
equator from each other. They are the
same as meridians.

HO'RDEIN (hordeum , barley). A ve-
getable product found in barley, supposed
to exist only in the husk ; it is a peculiar
modification of starch.

HORI'ZON (opifa, to bound). That
which bounds any thing, particularly the
line which bounds our view of the earth
and heavens.

1. The sensible horizon is a plane tan-
gent to the globe at the point where the
observer is stationed. It is the plane of
the circle which bounds our view. When
the sun rises, he appears above the
sensible horizon ; and when he sets, he
sinks below it.

2. The rational horizon is a plane pass-
ing through the centre of the earth parallel
to the sensible horizon. It is that line
which would bound our view, if we
could see at once half the globe. It is
represented on the terrestrial globe by
the wooden circle which surrounds it.

HORN. A substance consisting of
coagulated albumen and gelatine. It
differs from bone in containing only a
trace of earth.

HORN SILVER. Luna cornea. The
chloride of silver: the term is derived
from its forming a grey semi-transparent
mass, which may be cut with a knife,
and much resembles horn.

1. Horn Lead. Plumbum corneum;
the chloride of lead, a semi-transparent
mass, resembling horn.

2. Horn Quicksilver. A natural proto-
chloride of quicksilver, having a white
horn-like appearance.

HORNBLENDE. Amphibole. A sili-
cate of lime and magnesia ; a simple
mineral, of a dark-green or black colour,
which enters largely into the composition
of several varieties of the Trap rocks.
There are three varieties, viz., common
hornblende, hornblende-slate, and basaltic
hornblende.

1. Hornblende-rock. The primitive
greenstone of many writers ; a crystalline
compound of hornblende and felspar, not
laminar nor fissile, but massive, although
generally, disposed in strata.

2. Hornblende-slate. A primary rock,
generally of a distinct slaty structure,
composed of crystals of hornblende, often
intermixed with felspar, and passing
through numerous varieties into acti-
nolite-slate.

167

3. Hornblende Schist. A term applied
by M'Culloch to a variety of mineral ag-
gregates in which hornblende abounds,
and which are mostly, but not univer-
sally, of laminated structure.

4. Hornblendic Clay-slate. A rock of
the Cumbrian group, not composed of
hornblende and felspar, like the primary
hornblende-slate, but of clay-slate, in
which are interspersed crystals of horn-
blende and actinolite.

5. Hornblendic Granite. A variety of
granite, in which hornblende is substi-
tuted for mica. Frequently, however,
both these substances are associated in
granite, and the hornblendic gradually
passes into the common granite. See
Syenite.

HORNSTONE. A siliceous mineral
substance, sometimes approaching nearly
to flint or common quartz. It has a
conchoidal fracture, and is infusible, by
which characters it is distinguished from
common felspar. It has been distin-
guished into the splintery, the conchoidal,
and woodstone.

HOROLO'GIUM. The Horologe or
Clock , a southern constellation, consist-
ing of twelve stars. It is cut by a line
passing through Canopus to the southern
part of Eridanus.

HORO'LOGY (wpa, an hour, \6fos, a
description). A description of the prin-
ciples adopted for the measurement of
time, and of the various machines em-
ployed for this purpose. These comprise
the clepsydra and other horologia of the
ancients, and the several kinds of watches
and clocks of modern times.

HO'ROSCOPE (wpa, an hour, anonta,
to consider). An astrological scheme of
the twelve signs of the zodiac at any par-
ticular hour, supposed to indicate the
future destinies of any individual by their
aspect at the moment of his birth. The
signs were called Houses, as being the
monthly abodes of the sun, and, besides,
every house was appropriated to some
planet, every planet having two. In
a more particular application the Ho-
roscope denoted the point and sign of
the Ecliptic which rose above the horizon
at the hour in question ; that point
was the Ascendant; and the planet to
which the sign was appropriated was
termed the Lord of the Ascendant, and
had its influence over the fate of the new-
born child.

HORSE-POWER. A mode of mea-
suring the performance of a steam-engine
by reference to the useful effect which

HOU

H Y A

one horse would produce during his ordi-
nary work. Various values have been
affixed to this unit of comparison ; but it
is now generally estimated as a force
which would be capable of raising a
weight of 33,000 lbs. a height of one foot
per minute, or 550 lbs. per second; and,
on a railway, as a force capable of trans-
porting ,400 tons one mile per day.

HORTUS SICCUS. Literally, a dry
garden; an emphatic appellation given
to a collection of specimens of plants,
carefully dried and preserved : a more
general term is herbarium.

HOUR. The twenty-fourth part of a
natural day, answering to fifteen degrees
of the equator.

1. Hour, Sidereal. The sidereal day
is four minutes shorter than the mean
solar day ; it is the actual revolution of
the heavens (see Day). The astronomer
always makes it begin when the vernal
equinox is on his own meridian ; he di-
vides it into twenty-four sidereal hours
(each a little shorter than the hour of the
common clock) of 60 sidereal minutes, of
60 sidereal seconds each, and he mea-
sures it by a sidereal clock, with a pen-
dulum a very little shorter than that of
the common clock. He rejects the sub-
division into two periods of 12 hours
each, and speaks of 15 o'clock, or 16
o'clock, under the phrase 15 hours or
16 hours, meaning 15 or 16 hours from
the commencement of the sidereal day,
from the time when the vernal equinox
was last on the meridian.

2. Hour of Angular Measure. The
twenty- fourth part of a revolution which
is made in twenty-four hours, and divided
in reference to the division of time. Thus,
an arc of a circle is said to be a certain
number of hours, minutes, and seconds,
of time ; meaning, that the arc in ques-
tion would be described in that number
of hours, minutes, and seconds, if the
whole circle were described in twenty-
four hours. At this rate, a revolution
being divided into 360 equal parts or
degrees, 15° make one hour, 15' one
minute of time, 15" one second of time ;
also, 1° is four minutes of time, 1' is four
seconds of time, and l"is one-fifteenth
of a second of time.

3. Hour-circle. In Astronomy, the
equator is the principal circle employed ;
it is the circle of progression and regres-
sion most commonly used. All second-
aries to the equator are called hour-
circles ; or rather, each half of a secondary
is an hour smi-circle, the two halves of

168

the same secondary belonging to different
hours ; in fact, a meridian on the earth
always answers to an hour-circle in the
heavens. Every star is on one hour-
circle, and on one only ; unless it be at
one of the poles of the equator, and then
it is on all hour-circles.

4. Hour-angle. The hour-angle of a
star is the angle which its hour-circle
makes with the meridian of the place
(represented by the brazen hour circle
when the globe is properly elevated).
This hour-angle is nothing when the star
is on the meridian, and is an hour of
angular measure for every sidereal hour
to or from the time of the transit, being
eastward before transit and westward
after it.

HUM'BOLDTITE. A rare mineral,
consisting of a boro-silicate of iron, and
found in chalcedonic geodes in trap rocks
in the Tyrol. From this must be distin-
guished Humboldtine, which is a native
oxalate of the protoxide of iron.

HU'MITE. A reddish-brown mineral
found near Naples in a rock of granular
topaz, and named from Sir Abraham
Hume.

HUMMOCK. A sheet of ice, which
presents a surface generally level, but
here and there diversified by projections,
arising from the ice having been thrown
up by some pressure or force to which it
has been subject. (See Iceberg.) Also, a
term applied by navigators to a circular
and elevated mount appearing at a dis-
tance.

HUMUS. Vegetable mould; woody
fibre in a state of decay. The various
names of ulmin, humic acid, coal of hu-
mus, and humin, are applied to modifi-
cations of humus.

Humic acid of chemists. A product
of the decomposition of humus by al-
kalies ; it does not exist in the humus of
vegetable physiologists. — Liebig.

HURAU'LITE. A new mineral found
in the Haute Vienne, consisting of a
phosphate of iron and manganese.

HURRICANE. A phenomenon sup-
posed to be of electric origin. A large
vacuum is suddenly created in the atmo-
sphere, into which vacuum the surround-
ing air rushes with immense rapidity,
sometimes from opposite points of the
compass, spreading frightful devastation
along its track.

HY'ACINTH. A sub-species of pyra-
midal zircon; a red mineral found in
volcanic sand in Ceylon, &c.

HY'ADES (uo), to rain). The name

H YD

H YD

of seven stars in the Bull's head, famous
among the poets for causing rain.

HY' ALINE {va\o*, glass). Of a glassy,
thin, and semi-transparent substance.
The pellucid substance which determines
the spontaneous fission of cells.

HY'ALITE (iJaXo?, glass). A siliceous
mineral occurring near Frankfort on the
Maine, in fissures in vesicular basalt and
basaltic greenstone, and employed by
lapidaries for ring-stones.

HYALCE'ID^l {va\os, glass). A fa-
mily of Pteropods in the systems of
Cuvier and Lamarck, named from the
genus hyaloca, which is remarkable for
the delicacy and transparency of the
shell.

HYBERNA'CULUM. Literally, a place
to winter in; a term fancifully applied
by Linnaeus to the bud of a plant, because
it protects the young and tender enclosed
parts during the winter.

HYBERNATION (hyberna, winter-
quarters). A reptile ( state of the func-
tions, which occurs in some animals in
winter, as the bat, hedge-hog, dormouse,
hamster, &c. Compare Diurnation.

HY'BRID (hybrida, a mongrel). In
Botany, a plant produced by artificial
fecundation ; i. e. by crossing two dis-
tinct species of the same genus, or two
varieties of the same species. In a few
cases, mule plants have been artificially
obtained from individuals of different
genera.

HYDATID (Mart*, a vesicle). A term
applied to several species of entozoa, or
parasitic animals, which have a distinct
independent vitality.

HYDR-, HYDRO- {Mop, water). A
Greek prefix generally denoting the pre-
sence of water in definite proportions ;
but, owing to the changes of nomencla-
ture, it sometimes denotes the presence of
hydrogen in certain chemical compounds.
In a few of the following terms it relates
to the hydra or fresh-water polyp : —

1. Hydra {vdpa, hydra). A fresh-water
polyp, common in the ponds and clear
waters of our own country, and affording
an excellent example of the structure of
the Acrita, being destitute of any percep-
tible trace of nervous substance, of mus-
cular fibre, of a vascular system, or of
reproductive apparatus.

2. Hydra (in Astronomy). The Water-
snake ; a southern constellation, consist-
ing of sixty stars.

3. Hydr-acids. Hydro-acids; a class
of acid compounds, into which hydrogen
enters as the supposed acidifying prin-

ciple, as the hydro-chloric, the hydro-
cyanic, &c. See Oxacids.

4. Hydr-argillite (apytWos, clay). Na-
tive phosphate of alumina, erroneously
supposed to consist of alumina and water.

5. Hydrates. Chemical compounds of
bases and water, still retaining the solid
form, as sulphur, soap, &c. These are
also termed hydr-oxures and hydro-oxides.
When there is more than one atom of
water, prefixes are employed, as bin-
aqueous, ter-hydrate, &c.

6. Hydr-aulics {ai>\6s, a pipe). That
branch of Natural Philosophy which in-
vestigates the laws by which fluids in
motion are regulated, and consequently,
the construction of machines in which
water is employed as a moving power, or
by which that fluid is put in motion.

7. Hydraulic Press. An apparatus
contrived or applied by Mr. Bramah, for
illustrating the hydrostatical law of the
equal pressure of liquids in all directions.
A small quantity of water is driven by
sufficient pressure into a vessel already
full, and provided with a moveable sur-
face or piston of great size. Under such
circumstances something must give way ;
the great surface of the piston accumu-
lates the pressure on it to such an extent
that nothing can resist its violence. The
apparatus is employed in compressing
bodies, in lifting weights, in raising trees
from the soil, or piles from the beds of
rivers.

8. Hydraulic Ram, or Water Ram. A
hydraulic machine for raising water by
means of its own impulse, invented by
Mr. Whitchurch, and improved by Mont-
golfier.

9. Hydr-iodic acid. A gaseous com-
pound of hydrogen and iodine, procured
by the mutual decomposition of iodide of
phosphorus and water.

10. Hydro-benz amide. A colourless
substance obtained by placing hydrate of
benzoile in a solution of ammonia.

11. Hydro-branchia (/3p«7X'a« gj^s)«
Under thi3 term Lamarck includes
the Nudibranchia, Scutibranchia, and
Tectibranchia of Cuvier, together with
certain genera, which are arranged in a
section. Se Pneumobranchia.

12. Hydro-bromic acid. A gaseous
compound of hydrogen and bromine,
obtained by the mutual decomposition
of bromide of phosphorus and water.

13. Hydro-carbon. A combustible mi-
neral substance found in the interstices
of lignite. A compound of hydrogen
and carbon : these elements combine in

I

H YD

H YD

various proportions, forming a series of
compounds commonly termed hydro-
carburets.

14. Hydro-chloric acid. An acid con-
sisting of hydrogen and chlorine, and
long known under the names of spirit of
salt, marine acid, and muriatic acid.
Some chemists term it chlorhydric acid.

15. Hydro-chloric ether. An ether
which has received the various names of
chlorhydric, marine, and muriatic ether,
and hypothetically, chloride of ethule.

16. Hydro-corisa («6p<r, a bug). The
Water-Bugs ; a section of hemipterous
insects, characterized by their aquatic
habit, and by a peculiar form of the body,
which has gained for some of them the
popular name of boat-flies. See Geocorisa.

17. Hydro-cyanic acid. An acid con-
sisting of hydrogen and cyanogen, and
commonly called prussic acid, from its
having been procured, though interme-
diately, from Prussian blue.

18. Hydro-dynamics (3tW/itr, power).
The mechanics of fluids ; or that branch
of natural philosophy which investigates
the phenomena of equilibrium and mo-
tion among fluid bodies, especially such
as are heavy and liquid. It is distin-
guished into hydrostatics, which treats of
the weight and pressure of liquids ; and
hydraulics, which treats of their motion.

19. Hydro-electric machine. A machine
constructed by Armstrong on the sup-
position that electricity is generated when
steam is exposed to friction. On the
escape of steam from certain cocks pro-
vided for that purpose, the pressure being
70 lbs. on the square inch, an effect
is obtained 7 times greater than from a
good electrical machine with a plate 3
feet in diameter.

20. Hydro-fluoric acid. A highly corro-
sive compound of fluorine and hydrogen,
obtained by the action of sulphuric acid
upon fluor-spar, or fluoride of calcium,
on the application of a moderate heat.

21. Hydro-gen (>yevvd(a, to produce). A
gas occurring most generally, and abun-
dantly, in combination with oxygen, in
the form of water. From its inflammable
nature, it was formerly called inflammable
air; and, from it having been considered
the matter of heat, it was called phlogiston.

22. Hydro graphy (ypd^w, to describe).
That branch of Geography which treats
of the water or seas, which compose a
part of the terraqueous globe. Hydro-
graphical charts or maps are projections
of some portion of the ocean, in which the
rhumbs, meridians, parallels, &c. with

170

the coasts, capes, &c. are laid down for
the use of navigation.

23. Hydr-oida (et<5or, likeness). An
order of the polypipherous Radiata, con-
sisting of animals allied in structure to
the hydra. They are also called hydri-
form polypes.

24. Hydro-logy (\6709, a description).
That branch of natural history which
treats of water, of irs various properties
and modes of existence in nature.

25. Hydro-mancy (/j-avreia, prophecy).
An ancient superstition respecting the
divining nature of certain springs and
fountains ; hence, perhaps, arose the dis-
covery of the medicinal virtues of mineral
waters.

26. Hydro-meter {nerpov, a measure).
An instrument for measuring the gravity
of liquids ; when floating in a liquid, it
rises in proportion as the density of the
liquid increases; it is graduated from
1.000 to 1.060, so as to exhibit at once the
specific gravity.

27. Hydro-metridcB. A family of he-
mipterous insects, named from the genus
hydrometra, and adapted for walking on
the surface of water.

28. Hydr-ophidce (6>tr, a snake). Water-
snakes; a family of Ophidian reptiles,
characterized by the vertical compression
of the tail and hinder part of the body,
by means of which they are enabled to
swim with facility.

29. Hydro-phane ((paivw, to appear).
A variety of opal, which is perfectly
opaque when dry, but becomes transpa-
rent when immersed in pure water. It is
also called oculus mundi.

30. Hydro-jphilidce {q>t\e(a, to love). A
family of coleopterous insects, named
from the genus hydrophilus, and charac-
terized by their aquatic habits.

31. Hydro-phyU* {<Pvt6v, a plant).
Plants which grow in water ; a name
restricted by botanists to algaceous
plants found in fresh-water.

32. Hydro-silicite. A new mineral
found in Serpentine in Siberia, consist-
ing apparently of pure silica and water.

33. Hydro-statics (water standing).
That branch of mechanics which treats
of the weight, pressure, and equilibrium
of fluids, when in a state of rest ; and of
these properties of solids, when immersed
in fluids.

34. Hydro-static balance. A balance
for weighing substances in water, in order
to ascertain their specific gravities.

35. Hydro-static bellows. An apparatus
for illustrating the hydrostatic paradox t

fah

H YL

HYP

or that property of liquids by which they
transmit pressure equally in every direc-
tion.

36. Hydro-static paradox. A term de-
noting that any quantity of fluid, how-
ever small, may be made to balance or
counterpoise any quantity, however large.

37. Hydro-sulphur -et. A compound of
sulphuretted hydrogen with a salifiable
base.

38. Hydro-thionic acid {Oelov, sulphur).
A name given in Germany to sul-
phuretted hydrogen, or the hydro-sul-
phuric acid of Gay Lussac.

39. Hydro-zoa {vdpa, hydra, and £Cbov,
an animal). Hydriform Polyps ; a term
applied by Owen to a class of Polyps,
which are organized like the hydra, or
common fresh-water polype. These cor-
respond with the Dimorphcea of Ehren-
berg, the Serlulariens of Milne Edwards,
and the Nudibrachiata of Farre.

40. Hydr-uret, or Hydroguret. A com-
pound of hydrogen with a metal.

41. Hydrus. The Water Snake ; a
modern southern constellation, consist-
ing of ten stars.

HYGRO'METER. {vypo?, moist, yue-
rpov, a measure). An instrument for
ascertaining the degree of moisture of
the atmosphere. The quantity of
moisture present in the air is inferred
from the reduction of temperature re-
quired to produce a deposition of dew
from the air ; the less the reduction of
temperature required, the greater the
amount of moisture in the air.

Hygrometric Water. That portion of
moisture which gases yield to deliques-
cent salts.

HY'GROSCOPE {lypbs, moist, <tko-
neu), to examine). An instrument for
indicating the presence of aqueous va-
pour in the atmosphere, without mea-
suring the amount. Hygroscopic sub-
stances are mostly of animal or vegetable
origin, as hair, fish-bone, animal mem-
branes, the beard of the wild oat, &c.

HYLjE'OSAURUS (fcAalo?, of the
wood, <ravpoi, a lizard). An extinct gi-
gantic land reptile, of the Wealden strata
of Kent and Sussex, forming, with the
megalosaurus and iguanodon, a natu-
ral and well-marked group of colossal
animals, connected with the middle se-
condary period.

HYLO'BATES {bXapdrnv, one who
haunts the wood). The name given by
Illiger to the long-armed Apes or Gib-
bons, which haunt the forests, and re-
semble the Orangs in form and dentition.
171

HYME'NIUM (vnrjv, a membrane).
That part of a fungaceous plant in which
the sporules immediately lie : in agaricus
it consists of parallel plates, called la-
mella, or gills.

HYMENO'PTERA {vfirjv, a mem-
brane, Trrepov, a wing). An order of
mandibulate insects, which have four
membranous, naked, and unequal wings,
and undergo complete metamorphosis, as
the wasp. They are distinguished by
Latreille into the terebrantia, in which
the abdomen of the females is furnished
with a saw or borer ; and the aculeata,
in which the abdomen of the females is
armed with a sting.

HYPER ({>7rep, over or above). A
Greek preposition, denoting a position
above, or excess. In chemical nomen-
clature, it denotes that the acids to which
it is prefixed contain more oxygen than
those to which the word per is prefixed,
as hyper-chloric acid. It corresponds
with the Latin preposition super.

HYPE'RBOLA (i/7rep/9o\^, a throwing
beyond). A section of a cone by a plane,
which, if extended, would cut the oppo-
site cone, so that the sections of both
cones will exhibit curves expanding
continually, like the parabola, but with
different properties. This conic section
is called a hyperbola, because the angle
which its plane forms with the base of the
cone is greater than that of the parabola.
Hyperbol-oid (etioc, likeness). A geo-
metrical solid, formed by the motion of a
hyperbola round its axis. It is also
termed a hyperbolic conoid.

HY'PERSTHENE. Labrador horn-
blende. A variety of augite, of a green-
ish-black colour, very similar in its
general appearances and characters to
diallage. It consists of silica, oxide of
iron, magnesia, and alumina.

Hypersthene Rock. A compound of
hypersthene and felspar, the latter being
compact, crystalline, or glassy. These
form three varieties, to which M'Cul-
lock has given the general name of
hypersthene rock.

HYPHA {v<f>r), a web). A term applied
by Willdenow to the filamentous, fleshy,
watery thallus of byssaceae.

HYP-, HYPO- (far*, under). A Greek
preposition, signifying a position under,
or deficiency. In chemical nomenclature
it denotes the presence of a smaller
quantity of acid than is found in the
compounds to which it is prefixed. It
corresponds, in all these applications, to
the Latin preposition sub : —
12

HYP

1. Hyp-allage (viraWayt], an inter-
change). A figure of speech, by which
the parts of a proposition seem to be
interchanged, or two words mutually
exchange their respective cases, as " dare
classibus austros," for dare classes aus-
tris. This figure has little place in cor-
rect prose, but is an allowable resource
for poets.

2. Hyp-anthodium. A term applied by
Link to the receptacle of plants when it
is fleshy, and not enclosed within an
involucrum, as in dorstenia and ficus.
See Anthodium.

3. Hypo-blastus (/3\ao-T09, a shoot). A
term applied by Richard to the scutelli-
form cotyledon of grasses, which he con-
siders to be a particular modification of
the radicle.

4. Hypo-crater if or m {crater a, a salver,
forma, likeness). Salver-shaped ; as ap-
plied to a calyx or corolla, of which the
tube is long and slender, and the limb
flat, as in phlox. The term is at once
unwieldy and unclassical : sub-crater/form
or hypo-crater old would be classical, but
either is unwieldy.

5. Hypo-gene Rocks (^ivojxai, to be
produced). Those rocks which are nether-
formed, or which have not assumed their
present form and structure at the sur-
face, as granite, gneiss, &c. This term,
which includes both the plutonic and
metamorphic rocks, is substituted for
primary, because some members of both
these classes, as granite and gneiss, are
posterior to many secondary or fossilife-
rous rocks.

6. Hypo-geous (yij, the earth). Sub-
terranean ; as applied to those cotyledons
which remain beneath the earth after
germination, and as opposed to epi-
geous.

7. Hypo-gynous (ywij, a woman). That
condition of the stamens of a plant in
which they contract no adhesion to the
sides of the calyx, as in ranunculus.

8. Hypo-nitrous Acid. The name given
by Turner to nitrous acid, or the azotous
of Thenard ; while hypo-nitric acid is the
nitrous acid of Turner, or the peroxide
of nitrogen.

9. Hypo-phyllum ((pvWov, a leaf). A
term applied by Link to a petiole which
has the form of a small sheath, is desti-
tute of blade, and surrounds the base of
certain small branches having the appear-
ance of leaves, as in asparagus.

10. Hypo-stasis {biroaTCHTts, strictly, a
standing under ; essence, substance). A
term expressing " that which stands

172

H YS

under (i. e. is the subject of) attributes."
It is worth observing, as a striking in-
stance of the little reliance to be placed
on etymology as a guide to the meaning
of a word, that " Hypostasis," " Sub-
stantive," and " Understanding," so
widely different in their sense, corre-
spond in their etymology.

11. Hypo-stasis (in Botany). The name
given by Dutrochet to the suspensor, or
delicate thread which descends from the
summit of the ovule into the quintine,
and bears at its extremity a globule,
which is the nascent embryo.

12. Hypo-tenuse (vTroreivu, to extend
under). That side of a right-angled tri-
angle which is opposite to the right
angle. Of the other two sides, one is
frequently termed the base, and the
other the perpendicular.

13. Hypo-thecium {$f]<n, a hollow case).
The substance which surrounds or over-
lies the perithecium of lichens, as in
cladonia.

14. Hypo-thesis (viroTidr\p.i, to suppose).
A supposition, or doctrine, founded on
theory. The term is used synonymously
with system, but, further, conveys the
uncertainty which attaches to a system.

15. Hypothetical Proposition. In Lo-
gic, a proposition which asserts, not
absolutely, but under a hypothesis, indi-
cated by a conjunction. A hypothetical
proposition, called by some writers com-
pound, is defined to be two or more cate-
gorical! united by a copula (or conjunc-
tion); and the different kinds of hypo-
thetical propositions are named from
their respective conjunctions, viz., con-
ditional, disjunctive, causal, &c. A hypo-
thetical syllogism is one of which the
reasoning depends on such a proposition.
— Whately.

16. Hypo-zoic System {£S>ov, an ani-
mal). A geological term, applied by
Phillips to those rocks of crystalline
slates which occur especially in the cen-
tral ridges of mountain chains. The
term implies that they contain no organic
remains, and that they are geologically
below all the rocks which do contain
traces of animal life. See Metamorphic.

HYSTERA'NTHOUS (Sarepov, after-
wards, avOos, a flower). A term applied,
in Botany, to those plants in which the
leaves appear after the flowers, as in
almond.

HYSTRFCIDjE (Sirrpif vel S«r0pif,
having hog's bristles; from 5?, a hog,
and 0pi£, hair). The Porcupine tribe ; a
family of the Rodentia, characterized by

ICE

ICH

the stiff and pointed quills with which
they are armed, resembling those of the
hedge- hog, though usually larger. The
term porcupine is a corruption of the

French porc-epin, or hog's-spine ; be-
sides, the general appearance and pecu-
liar grunt of the porcupine are not unlike
those of the hog.

IA'NTHINjE. Oceanic shells ; a sub-
family of the Turbidcc, named from the
genus ianthina, comprising those fragile
violet and white snails which so much
resemble the Helicidce. The animal is
of peculiar structure.

ICE, POLAR. The poles are pro-
bably surrounded by a continuous ex-
panse of ice, the borders of which have
been explored by navigators, and desig-
nated by various appellations, in reference
to the form and extent of its masses :—

1. An Ice-berg, or ice-hill, is a vast
isolated mass of ice, sometimes rising to
the height of 100, and even 200, feet
above the surface, and extending beneath
it to a much greater depth. Ice-bergs
are formed by glaciers, which, some-
times terminating a precipitous edge on
the coast, and being gradually protruded,
at length break off, and fall into the
sea.

2. A Field of Ice is a continued sheet
of ice, so large that its boundaries can-
not be seen from the mast-head of a
vessel ; it has sometimes an area of more
than 100 square yards, and rises above
the level of the sea from two to eight
feet. Ice-fields are generated in the
open sea, and are almost constantly
driving in summer, their general motion
being south-westward. They acquire
occasionally a rotatory motion, when
their circumference attains a velocity of
several miles an hour.

3. A Pack of Ice consists of pieces of
ice broken off from a field, when driven
to the southward, and exposed to the
effects of a ground swell ; these pieces
are about forty or fifty yards in diameter,
and extend so widely as not to be seen
over from the mast-head.

4. A Patch of Ice is a collection of
pieces of ice, which assume a circular
form. When the collection is of an
elongated form, it is called a stream.
Pieces of very large dimensions, but
smaller than fields, are called floes.
Small pieces broken from larger masses
by attrition, are called brash-ice.

5. A Hummock of Ice is a protube-

173

ranee raised upon any plane of ice above
the common level. A calf of ice is a
portion extending below the surface of
the water.

ICE-SPAR. A sub-species of prism-
atic felspar, of vitreous lustre, translu-
cent and transparent, found at Monte
Somma near Naples.

ICELAND-SPAR. One of the purest
varieties of calcareous spar, or crystal-
lized carbonate of lime. It is not, how-
ever, peculiar to Iceland. Of all crys-
tallized bodies, this exhibits most readily
the phenomenon of double refraction.

ICHNEUMO'NIDjE. A family of the
entomophagous Terebrantia, named from
the typical genus ichneumon, and charac-
terized by their habit of depositing their
eggs in the bodies of other insects, on
which the young feed, when hatched.

ICHTHYODO'RULITES (lx^f, a
fish, 86pv, a spear, \i6os, a stone). Fossil
spear-like projections from the back and
belly of a shark-like fish, supporting fins,
and serving probably also as weapons.
They occur in the carboniferous strata,
and seem to be identical with the bony
spine with which the Port Jackson shark
is provided.

ICHTHYO'LOGY (ix0ir, a fish, \6yot,
a description). That branch of zoology
which treats of Fishes, a class of animals
occupying the lowest station of the four
great divisions of the section Vertebrata.
They are distinguished by Cuvier, with
reference to their skeleton, into the
Osseous and the Cartilaginous.

1. Osseous Fishes are those which have
a bony skeleton, the bony matter being
disposed in fibres; the sutures of the
cranium are distinct ; the maxillary and
the intermaxillary bones are, either one
or both, present. The sections are the
Pectinibranchii, the Plectognathi, and
the Lophobranchii. The first of these
comprises the orders Acanthopterygii,
Malacopterygii, and Apodes.

2. Cartilaginous Fishes (chondropte-
rygii) are those which have a cartilagi-
nous skeleton, the bones being destitute
of fibres ; the sutures of the cranium are

13

IDE

I D 0

indistinct ; the maxillary and the inter-
maxillary bones are either wanting or
rudimentary, their place being supplied
by the palatine or vomer. The orders are
the Eleutheropomi, Plagiostomi, and Cy-
clostomi.

ICHTHYOPHTHA'LMITE (ix0w, a
fish, o(p0a\iJios, an eye). Fish-eye stone ;
a species of zeolite, with a pearly lustre,
resembling the eye of a fish. See Apo-
phyllite.

ICHTHYOSAU'RUS (ix0i/?, a fish,
cavpof, a lizard). A gigantic fossil ma-
rine reptile, intermediate in its characters
between a crocodile and a fish, occurring
in the lias formation. It differs from
any known reptile of the present day, in
the substitution of paddles for feet.

I'COSAHE'DRON (eiWt, twenty,
edpa, a seat). In Geometry, a solid figure
bounded by twenty equal and equilateral
triangles.

ICOSA'NDRIA (eiWt, twenty, avtjp,
a man). The twelfth class of plants in
the system of Linnaeus, characterized by
the presence of twenty or more stamens
inserted into the calyx.

IDEA (idea, form). In its widest accep-
tation, this term denotes an impression
of an external object upon the senses, or
of an object of thought upon the mind.
In the Platonic philosophy the Ideai, or
" Ideas," were not only e'idn, or species,
but something more, viz. the perfect
archetypes, models or patterns, of which,
respectively, all created things were the
imperfect anti-types or representations;
eldo? might therefore be used for idea,
but not Idea for eidor.

IDE'AL THEORY. A scholastic
theory, which refers all perception to the
impression on the mind of certain ideas
or images of external objects, the organs
of sense having no percipient power them-
selves, but merely transmitting the ideas
of these objects to the mind.

IDE'NTICAL {idem, the same). I. In
its primary and proper sense, this term
denotes oneness or sameness, and is ap-
plicable only to a single object. 2. In its
secondary and improper sense, it is em-
ployed to denote great similarity, as
when two guineas, struck from a wedge
of uniform fineness, are said to be " of one
and the same form and weight, and also of
one and the same substance." Yet they
are not identical, but numerically dis-
tinct. Further, in this secondary sense,
the term popularly admits of degrees :
we speak of two things being nearly iden-
tical, nearly the same, but not entirely ;
174

whereas personal identity does not admit
of degrees.— Whately.

IDEOGRA'PHIC WRITING (Idea,
an idea, ypacpio, to write). A kind of
writing by which objects or abstract ideas
are symbolically represented, as in the
figurative part of the Egyptian hierogly-
phics. It is opposed to phonetic writing,
in which the symbols employed represent
sounds.

IDEO'LOGY (idea, an idea, Xdyoc, a
description). By this term the later dis-
ciples of Condillac have designated the
science of ideas, or the history and evo-
lution of human ideas, considered as
successive modes of certain original or
transformed sensations.

IDIOSYNCRASY {'idio?, peculiar, auy-
upacrts, composition). Individual pecu-
liarities, hereditary or induced. Thus,
there are persons in whom opium does
not induce sleep ; others, in whom milk
seems to act as a poison.

I'DOCRASE (etdof, form, Kpaan, mix-
ture). A designation of Vesuvian or
Pyramidal Garnet, from the mixed forms
of other minerals which it presents. It
is an alumino-silicate of lime, with a
portion of oxide of iron.

I'DOLS {eUwXov, an image). By this
fanciful term Lord Bacon points out the
various general sources of those errors
which we are apt to commit in forming
our notions of things. These idols, or
false notions of the mind, are divided
into four classes, viz. : —

1. Idols of the Tribe ; so called because
they are common to the whole tribe or
race of mankind, being, in fact, those
general prejudices which arise from the
infirmity of human nature itself. " The
understanding of man is like a mirror
whose surface is not true, and so, mixing
its own imperfection with the nature of
things, distorts and perverts them."

2. Idols of the Cave or Den ; or " each
man's particular demon, or seducing
familiar spirit ;" or, less figuratively,
those prejudices which stamp upon each
mind its own peculiar character, and are
identified with every individual man.
Every mind is compared to " a glass,
with its surface differently cut, so as dif-
ferently to receive, reflect, and refract,
the rays of light which fall upon it.w

3. Idols of the Market-place; or pre-
judices arising from mere words and
terms in our common intercourse with
mankind ; these proceed, in short, from
the imperfection of language, and are
" the most troublesome of all." Defini-

IGU

1MB

tions themselves cannot wholly remedy
the evil; for "definitions consist of
words, and words produce words; so
that recourse must he had to particular
instances."

4. Idols of the Theatre ; or the preju-
dices and perversions of the mind arising
from fabulous and visionary theories and
romantic philosophies. They are thus
named, "because all the systems of phi-
' losophy which have been hitherto in-
vented, or received, are but so many
stage-plays which have exhibited nothing
but fictitious and theatrical worlds ; and
there may still be invented and dressed
up numberless other fables of the same
kind."

I'DRIALINE. A substance obtained
from a mineral from the quicksilver
mines at Idria in Carniola. It consists of
carbon and hydrogen.

IGASURIC ACID. The name given
by Pelletier and Caventou to a peculiar
acid, which occurs in combination with
strychnia in nux vomica, and the St. Ig-
natius's bean ; but its existence, as dif-
ferent from all other known acids, is
doubtful. It is so called from the Malay
name by which the natives in India de-
signate the faba Sancti Ignatii.

I'GNEOUS ROCKS {ignis, fire). A
term applied to all rocks, as lava, trap,
and granite, which are known or sup-
posed to have been melted by volcanic
heat.

IGNIS FATUUS. A luminous ap-
pearance or flame, frequently seen in
the night in the country, and called Jack
o' lantern, or Will with the wisp. It is
probably occasioned by the extrication
of phosphorus from rotting leaves and
other vegetable matters.

IGNITION {ignis, fire). The emission
of light from a heated body, unattended
by change of composition. Bodies begin
to become ignited, or red-hot, at about
800° Fahr. ; the highest point of ignition
consists in the emission of a perfectly
white light.

I'GREUSINE. Elaiodon. That por-
tion of volatile oils which is odoriferous,
and is coloured by treating it with nitric
acid.

IGUA'NIDJE. A family of saurian
reptiles, including some of the largest of
this tribe, both recent and fossil. They
agree with the lizards in general form,
but differ in the shortness and thickness
of their tongues. See Iguanodon.

IGUA'NODON {iguana, a recent West
Indian lizard, b6oi>s, a tooth). A gigantic
175

fossil saurian, exceeding eighty feet in
length, occurring in the Wealden forma-
tion, and known to us by the teeth and a
considerable part of the skeleton. Its
name is derived from the resemblance of
its teeth to those of the iguana.

I'LLATIVE CONVERSION. In Logic,
a mode of conversion in which the truth
of the converse follows from the truth of
the exposita, or proposition given. Con-
version can then only be illative, when
no term is distributed in the converse,
which was not distributed in the expo-
sita. Illative conversion is not a process
of reasoning ; it is only stating the same
judgment in another form. See Con-
version.

ILLUMINATION {illumino, to throw
light upon). The process of rendering a
body visible by light: every object ex-
posed to the sun is illuminated ; a lamp
illuminates a room and every object
in it.

IMAGE. The appearance of an ob-
ject made either by reflection or refrac-
tion. In all plane mirrors, the image is
of the same magnitude as the object, and
it appears as far behind the mirror as the
object is before it. In concave mirrors
the image appears larger, and in those
which are convex it appears less, than
the object.

Image, Aerial. When an object is
placed at a greater than its focal distance
from a convex lens, it produces on the
opposite side of the glass an inverted
image floating in the air; hence called
an aerial image.

IMA'GINARY QUANTITIES. In
Algebra, this term is applied to the even
roots of negative quantities, as sj — x3.
Such expressions indicate operations
which are impossible, and hence they are
also called impossible quantities. The
difference between surd and impossible
quantities is, that the former have real
values, though we cannot exactly find
them, while there cannot be a quantity,
positive or negative, an even power of
which would produce a negative quan-
tity.

IMA'GO. A term applied to the third
and perfect state of insect existence, in
which, the skin of the pupa having
burst, the animal escapes, furnished
with wings adapted for flight.

IMBIBI'TION {imbibo, to drink in).
The terms imbibition, and exudation or
transpiration, used in Physiology, are
analogous to those of aspiration and ex-
piration, and have been lately translated,
14

I MP

INC

by Dutrochet, by the two Greek words
endosmosis and exosmosis.

I'MBRICATED {imbrex, a roof-tile).
A designation of that form of aestivation,
or vernation, in which the pieces of the
bud overlap each other parallelly at the
margins, without any involution. The
term is particularly applicable to the
bracts of glumaceous plants.

IMMER'SION (immergo, to plunge
into). An astronomical term, denoting
the disappearance of any celestial body
behind another or in its shadow, as in
the eclipses of Jupiter's satellites. The
re-appearance of the body, after occupa-
tion, is termed its emersion.

I'MPACT {impingo, to impinge). By
Impact or Percussion is meant the colli-
sion of two bodies, of which one at least
is in motion. The impact is said to be
central, when the directions of the
centres of gravity of the two solid bodies
are in a right line ; eccentric, when this
is not the case ; direct or perpendicular,
when the direction of the moving body is
at right angles to the side of the body
impinged on ; oblique, when this is not
the case.

I'MPARI-PINNATE. A term ap-
plied, in Botany, to that mode of the
composition of leaves, in which they are
pinnate with an odd one, as when the
petiole of a pinnate leaf is terminated by
a single leaflet, as in mountain-ash.

IMPE'NETRABI'LITY {in, not, pene-
tro, to penetrate). That property by
which a body occupies any space, to the
exclusion of every other body. In a
popular sense, all matter is penetrable;
but, philosophically speaking, it is im-
penetrable, what is called penetration
being merely the admission of one sub-
stance into the pores of another. A nail
driven into a board or piece of lead, does
not penetrate the wood or metal; it
merely separates or displaces the particles
of these substances.

IMPERATIVE MOOD {impero, to
command). That mood of the verb
which commands an action to be per-
formed, or a state to exist.

IMPO'NDERABLES {in, priv., pon-
dus, weight). Agents which are desti-
tute of weight, as heat, light, and elec-
tricity. These are supposed to be of so
subtile a nature as to pass through all
material bodies, by which, therefore, they
cannot be either enclosed or divided.

IMPOSSIBILITY. This term is used
in three different senses : —

1. A mathematical impossibility is that
176

which involves an absurdity and self-
contradiction, as that two straight lines
should enclose a space. No limitation
of power is here implied ; it is, in reality,
nothing that is required to be done.

2. A physical impossibility is some-
thing at variance with the existing laws
of nature, and which, consequently, no
being, subject to those laws, can sur-
mount ; but we can easily conceive a
Being capable of bringing about what in *
the ordinary course of nature is impos-
sible. An occurrence of this character
we call miraculous.

3. A moral impossibility is that high
degree of improbability which leaves no
room for doubt. This implies no contra-
diction, nor any violation of the laws of
nature, but which yet we are rationally
convinced will never occur, merely from
the multitude of chances against it ; as
that unloaded dice should turn up the
same faces one hundred times succes-
sively. And yet why should they not ?
since the chances are the very same
against any given one hundred throws. —
Whately.

IMPOSSIBLE. In Logic, the matter
of a proposition is said to be impossible,
when the extremes altogether disagree.
The proposition is then equivalent to a
universal. Thus, brutes neither eat nor
drink more than nature requires ; that is,
no brutes, #c.

An impossible quantity, in Algebra, is
the same as an imaginary quantity. See
the latter term.

I'MPULSE {impulsus, a. push or stroke).
The direct action of one body upon an-
other in the production of motion. Bodies
are impelled, or driven forward, either
by percussion or by pressure — by a stroke,
as by a hammer, or by a push, as by a
spring or living power. The former is
instantaneous, the latter continuous. In
both cases the moving body flies from
the power; in the action of pulling, or
attraction, it does the reverse.

INCANDE'SCENCE {incandesco, to
become white-hot). The glowing or
shining appearance of heated bodies;
properly, the acquisition of a white
heat.

INCEPTIVE (incipio, to begin). That
which begins any thing ; a term some-
times applied to a moment or principle,
from which, as from a starting-point,
something may be extended; thus a
point or a line, in mathematics, though
possessing no magnitude, is said to be
inceptive of enlargement. But this is a

INC

IND

verbal fallacy ; for that which has no
parts, cannot be enlarged.

I'NCIDENCE (incido, to fall upon).
The direction in which one body strikes
on another. The term is used in different
senses by writers on mechanics and
writers on optics. See Angle of Incidence,
in each case.

INCINERATION {incinero, to re-
duce to ashes, from cinis, a cinder). The
reducing to ashes by burning. The com-
bustion of vegetable or animal substances
for the purpose of obtaining their ashes
or fixed residue.

TNCI'SION (incido, to cut). This term
must be distinguished from the ccesura
of metre. Incision is the coincidence of
the end of the foot with the end of the
word ; it is essential in some species of
verse, and is used also in the hexameter
under certain forms.

INCLINATION. In mathematics,
the mutual approach of two lines, or
planes, towards each other, so as to make
an angle. The inclination of the orbit
of a planet is the angle which the plane
of the planet's orbit makes with the
ecliptic, or the earth's orbit. The in-
clination, or dip of the magnetic
needle is the angle which such needle,
when supported on its centre of gra-
vity, makes with the plane of the ho-
rizon.

INCLINED PLANE. One of the
five simple mechanical powers, con-
sisting of a plain smooth surface, which
is inclined towards or from the earth. A
board, with one end on the ground, and
the other end resting on a block, becomes
an inclined plane.

INCLU'SA (includo, to enclose). An
order of the conchiferous acephalous
mollusca, in which the mantle has only
one opening for the passage of the foot ;
at the posterior end it is prolonged into
tubes of great length, which can be ex-
tended far beyond the shell, as in the
common solens or razor-shells.

INCOMBUSTIBLE CLOTH. A cloth
manufactured of the fibres of asbestos ;
on burning away the fibre, the mineral
texture remains.

INCOMME'NSURABLES. Any two
magnitudes which cannot be represented
by means' of the same unit, and cannot
consequently have any common measure,
are said to be incommensurable, as the
diagonal and the side of a square. Num-
bers are said to be incommensurable
in power, when their squares or second
powers are incommensurable, as 2 and 3,
177

the squares of which. 4 and 9, have no
common measure.

INCOMPAT1BLES, CHEMICAL. A
term applied to salts or other compounds,
which cannot exist together in solution,
without mutual decomposition, as the
salts of barytes and those which contain
sulphuric acid.

INCOMPRESSIBILITY. That pro-
perty of a substance, whether solid or
fluid, by which it resists being pressed
or squeezed into a smaller bulk. The
ultimate particles of all bodies are sup-
posed to be incompressible.

INCREMENTS, METHOD OF. A
method of analysis, more commonly
called the calculus of finite differences.
In the higher mathematics, the terms
increment and decrement are employed,
when two quantities are considered toge-
ther, one of which is greater or less than
the other ; the latter is then said to be
the former with an increment or decre-
ment.

INCU'MBENT (incumbo, to lie upon).
That which lies upon any thing ; a term
applied, in Botany, to the cotyledons of
those cruciferous plants, which are folded
with their backs upon the radicle. See
Accumbeni.

INDEFINITE. In Geometry, this
term is applied to a straight line, which
may be produced to any length in a given
direction, without affecting the conditions
of the problem. The term is sometimes
used in the sense of infinite, as when we
hear of a magnitude being indefinitely
great, an indefinitely small arc being
equal to its chord, a circle being a poly-
gon of an indefinitely great number of
sides, &c.

INDEFINITE PROPOSITION. In
Logic, a proposition which has for its
subject a common term without any sign
to indicate distribution or non-distribu-
tion. In these cases, the quantity of a
proposition is ascertained by the matter,
or the nature of the connexion between
the extremes : in necessary and in impos-
sible matter, an indefinite is understood
as a universal ; in contingent matter, as
a particular.

INDEFINITE TERM. In Logic, a
privative or negative term is called inde-
finite, in respect of its not defining or
marking out an object ; and it is opposed
to a definite or positive term, which does
define or mark out. Thus, " organized
being" is a definite, "unorganized being"
an indefinite term.

INDEHFSCENT (in, not, dehisco, to
15

IND

IND

gape). A term applied, in Botany, to
the state of those fruits in which the
pericarp, when arrived at maturity, con-
tinues perfectly closed, as in the hazel
nut. See Dehiscence.

INDE'NTED. A term applied to any
part of a body which is depressed or sunk
beneath the surrounding surface, whether
the indentations consist of lines, dots,
irregular cavities, or tooth-like depres-
sions.

INDEPENDENT COAL FORMA-
TION. By this term Werner designated
the first or oldest formation, because the
individual depositions of which it is com-
posed are independent of, and uncon-
nected with, one another. It contains
exclusively coarse coal, foliated coal,
cp.nnel coal, slate coal, a kind of pitch
coal, and slaty glance coal.

INDESTRUCTIBI'LITY. That pro-
perty of matter by virtue of which it
never ceases to exist : it may change its
form, and disappear ; but it is not anni-
hilated. In what is called destructive
distillation, the matters subjected to the
operation are evidently indestructible ;
for the products, when collected and
weighed, are found to be exactly as
heavy as the original matters.

INDETE'RMINATE. 1. In Mathe-
matics, a problem is said to be inde-
terminate, when it admits of an infi-
nite number of solutions. 2. In Algebra,
the co-etficients of an assumed form of
expansion are said to be indeterminate,
and the process by which they are then
found, is called the "method of indeter-
minate co-efficients." 3. If owe equation
contain two unknown quantities, the
number of values of these by which it
will be satisfied, is unlimited, and the
equation is said to be indeterminate.

INDEX {indico, to point out). 1. In
Algebra, a small figure placed at the right
of a quantity, to signify its power (See
Exponent). 2. The index of a logarithm,
or its characteristic, is the 5gure prefixed
to the logarithm for the purpose of indi-
cating the unit's place in the correspond-
ing number. 3. In optics, the index of
refraction is the constant ratio which ex-
ists between the sines of the angles of
incidence and refraction.

FNDIANITE. A whitish or greyish
mineral, consisting of silica, alumina,
lime, iron, and manganese, occurring in
masses in the Carnatic, where it consti-
tutes the gangue of corundum.

INDICATIVE MOOD {indico, to
point out). In Grammar, that condition
178

of the verb which declares the action or
state to exist simply and as a fact.

INDFCTION. In Chronology, a re-
volution of fifteen years, as already no-
ticed under the term Era. Its origin
has not been ascertained ; but Gibbon
observes, that the name and use of the
"Indictions" were derived from the
Roman tributes. There are four descrip-
tions of Indictions :—

1. The Indiction of Constantinople,
which was instituted by Constantine in
a. d. 312, and began on the 1st of Sep-
tember.

2. The Imperial or Cesarean Indiction,
which began on the 24th of September.

3. The Roman or Pontifical Indiction,
which commences on the 25th of Decem-
ber or 1st of January, according as either
of these days was considered as the first
of the year. This was generally used in
papal bulls, at least from the ninth to
the fourteenth century.

4. The fourth kind of Indiction, which
is to be found in the register of the par-
liaments of Paris, began in the month of
October.

INDI'FFERENCE. This term, in its
application in respect of the will and of
the judgment, is subject to an ambiguity
which may perhaps be thought hardly
worth noticing, the distinction between
unbiassed candour and impartiality on
the one side, and carelessness on the
other, being so very obvious. Yet, under
the same name, these things are con-
founded ; and, in fact, the judgment is
often, though by no means always, biassed
by the will. Our aim should be to pre-
serve the indifference of the judgment,
even where the will neither can nor should
be indifferent. — Whately.

INDFGENOUS (indigena, a native).
A term applied to animals or plants pe-
culiar to a certain country.

INDIGO. A blue pigment, obtained
from the leaves of all the species of
Indigofera, and various other plants.
White indigo, also called reduced indigo,
is procured by the action of deoxidizing
bodies upon blue indigo; in this state,
Liebig termed it indigogen.

FNDIGOLITE. An indigo-coloured
crystallized mineral, found at Utoe in
Sweden, and considered to be a variety
of tourmaline.

INDIGO'TIC ACID. Anilic Acid. An
acid formed when indigo is dissolved in
nitric acid considerably diluted. This is
the nitranilic acid of Berzelius.

INDIVI'DUAL {individuus, that can-

IND

INF

not be divided). An object which is, in
the strict and primary sense, One, and,
consequently, cannot be logically divided ;
which is a metaphorical expression to
signify "'the distinct (i . e. separate) enu-
meration of several things signified by
one common name." This operation is
directly opposite to generalization, which
is performed by means of abstraction;
for as, in that, we lay aside the differences
by which several things are distinguished,
so as to call them all by one common
name, so, in Division, we add on the dif-
ferences, so as to enumerate them by their
several particular names. Thus "mine-
ral" is said to be divided into " stones,"
" metals," &c. ; and metals again into
" gold," " iron," &c. ; and these are called
the parts, or members of the division. —
Whately.

INDIVISIBLES, METHOD OF. A
method formerly employed in Algebra,
founded on the assumption that quan-
tities are composed of infinitely small
quantities incapable of further division.
It was a kind of atomic theory, by which
lines were considered as made up of an
infinite number of points, surfaces of an
infinite number of lines, and solids of an
infinite number of surfaces. The method
has been entirely superseded by the dif-
ferential and integral calculus.

INDU'CTION {induco, to bring in, to
infer). A kind of argument which in-
fers, respecting a whole class, what has
been ascertained respecting one or more
individuals of that class. Induction, so
far as it is an argument, may, of course,
be stated syllogistically ; but so far as it
is a process of inquiry with a view to ob-
tain the premises of that argument, it is,
of course, out of the province of logic ;
and the latter is the original and strict
sense of the word. — Whately.

INDU'CTION (in Electricity). The
law by which an electrified body induces,
or tends to produce, in contiguous sub-
stances an electric state opposite to its
own.

INDU'CTIVE SCIENCE. A science
which ascends from particular facts to
general principles, and descends from
these general principles to particular ap-
plications. Induction is the opposite of
hypothesis, which consists in laying down
a theory at the outset of an inquiry, and
trusting to future experiments, or ex-
ample, for its proof.

INDUCTOMETER, DIFFEREN-
TIAL. An instrument, so named by
Faraday, consisting of three insulated
179

metallic plates, placed parallel to, and at
equal distances from, one another, each
exterior plate being connected with an
insulated gold-leaf of an electrometer.

INDUS. The Indian ; a modern south-
ern constellation, consisting of twelve
stars, situated between Sagittarius and
the South Pole.

INDU'SIAL LIMESTONE. A fresh-
water limestone, abounding in the indu-
siae of the larva of phrygania, encrusted
by hard travertin and converted into
rock.

INDU'SIUM (induo, to put on). A
term applied, in Botany, to that portion
of the epidermis of ferns which covers
the sori; also, to the peculiar form as-
sumed by the hairs of the style in certain
plants, when they are united into a cup,
enclosing the stigma, as in Goodeniaceae.

INDU'VI^ (induvice, clothes). In
Botany, this term denotes the withered
remains of leaves, which, not being arti-
culated with the stem, do not fall off, but
decay with it. A part so covered is said
to be induviate.

INE'NCHYMA. A term applied by
Morren to the fibro-cellular tissue of
plants.

INEQUALITY. 1. In Algebra, if
one quantity be greater or less than
another, or than nothing, and this be
expressed algebraically, it is called an
inequality. Thus * — a>b—x is an
inequality, of which x — a forms one
side, and b — x the other. 2. In Astro-
nomy, the term denotes any deviation in
the motion of a planet or satellite from
its uniform mean motion.

INE'RTIA (iners, inactive). That
property of matter by which it would al-
ways continue in the same state of rest
or motion in which it was put, unless
changed by some external force. The
quantity of matter of a body is deter-
mined by its quantity of inertia ; and
this is estimated by the quantity of force
required to put it in motion at a given
rate.

IN ESSE; IN POSSE. The former
of these Latin terms is applied to things
which do actually exist; the latter, to
things which do not, but may, actually
exist.

INFERENCE AND PROOF. " Rea-
soning comprehends Inferring and Prov-
ing ; which are not two different things,
but the same thing regarded in two dif-
ferent points of view : like the road from
London to York, and the road from York
to London. He who infers, proves ; and
16

INF

INN

he who proves, infers; hut the word
• infer ' fixes the mind first on the pre-
miss and then on the conclusion; the
word ' prove,' on the contrary, leads the
mind from the conclusion to the premiss.
Hence, the substantives derived from
these words respectively, are often used to
express that which, on each occasion, is
last in the mind ; Inference being often
used to signify the conclusion (i. e., pro-
position inferred), and Proof, the pre-
miss. To infer, is the business of the
philosopher ; to prove, of the advocate" —
Whately.

INFERIOR FRUIT. In Botanical
language, a fruit or ovary is termed infe-
rior, when the calyx adheres to its walls ;
when no such adhesion occurs, the fruit
or ovarium is said to be superior. So,
also, the calyx is called superior in the
former case, and inferior in the latter.
French botanists employ in the same
sense, and with much greater precision,
the terms adherent and non-adherent.

INFERIOR VALVE. That valve of
adherent bivalves by which they are
united to other substances.

I'NFERO-BRANCHIATA {inferus,
beneath, branchice, gills). An order of
Aquatic Gasteropods, in which the bran-
chiae resemble two long rows of leaflets,
placed on the two sides of the body,
under a projecting edge formed by the
mantle. Cuvier records two genera, viz.
phyllidia and diphyllidia.

INFIMA SPECIES. In Logic, the
lowest species, or that which is not sub-
divided, except into individuals. See
Species.

FNFINITE {infinitus, boundless). In
Geometry, an infinite quantity is that
which is greater than any assignable mag-
nitude ; in other words, it is an abstrac-
tion of the mind, formed by excluding
the idea of limitation. On the same
principle, an infinitely small quantity is
a quantity considered as less than any
assignable magnitude. Such a quantity
is called an infinitesimal, and the em-
ployment of such quantities as aux-
iliaries, in investigating the relations of
proposed quantities, is called the infinite-
simal analysis.

INFFNITIVE MOOD (infinitus, un-
defined). In Grammar, that condition of
the verb which expresses the state of an
action, as in progress or completed, but
without specification of person, number,
or time.

INFLAMMABLE AIR. Hydrogen
gas, named from its highly inflammable
180

nature. It was formerly called phlogis-
ton, from its having been considered the
matter of heat.

INFLE'XION (infiecto, to bend in).
In Grammar, any change made in a word
in order to modify its meaning is called
its accident or inflexion. Thus, the words
Ccesar's, legions, were, feared, are said to
be inflected forms, or, simply, inflexions
of the words Caesar, legion, was, and
fear. Inflexion must not be confounded
with termination ; it denotes any change
which takes place in a word between the
root and the termination.

INFLEXION OF WAVES. If a cir-
cular wave of a non-elastic fluid impinge
on a solid in which there is an aperture,
that part of the wave which comes against
the aperture will pass freely through,
while the other part, which strikes
against the solid, will be curved about
the edges of the aperture, so that one
semicircle will be in front of the aper-
ture, and the other beyond it. This is
the inflexion of waves. The new circular
waves formed about the aperture will in-
tersect the original wave and each other,
so that interference points and lines will
be produced. Similar phenomena occur
in waves of sound.

INFLORESCENCE ( infloresco, to
flourish). A term expressing, generally,
the arrangement of flowers upon a branch
or stem. The various forms of centri-
petal inflorescence, which have received
distinct appellations, are usually referred
to modifications of the spike and of the
raceme. The centrifugal inflorescence is
represented by the cyme.

INFORMED STARS. Stars which are
not included in any of the constellations.

INFUNDIBU'LIFORM {infundibu-
lum, a funnel, forma, likeness). Funnel-
shaped ; a term applied to an organ
which has an obconical tube and an
enlarged limb, as the corolla of tobacco.

INFUSO'RIA {infundo, to pour in).
Water animalcules ; microscopic animals
found in infusions of animal and*vege-
table matter. They are distinguished
into the Polygastrica and the Motif era.

IN'GRESS {ingressus, an entering).
The entering of the sun into any of the
twelve signs, or other parts of the zodiac.

INNATE (innatus, grown upon).
Growing upon any thing by its end ; as
applied, in Botany, to the anther when
it is attached by its base to the apex of
the filament.

INNOVATIONS. A term applied, in
Botany, to shoots \» hich have not com-

INS

I NT

pleted their growth, especially those of
mosses.

INOPE'RCULAR (in, not, operculum,
a lid). A term applied to univalve shells
which have no operculum or lid.

INOSCULATION (in, and osculum,
a little mouth). The union of vessels, or
anastomosis : the latter term, however, is
sometimes used to designate union hy
minute ramification ; the former, a direct
communication of trunks.

INSCRIBED FIGURE. In Geome-
try, a circle is said to he inscribed in a
triangle or a polygon, when it touches all
the sides of these figures. A triangle or
a polygon is said to be inscribed in a
circle, when all the angles of the former
figures touch the circumference of the
latter.

INSE'CTA (insecius, divided into seg-
ments). Insects ; a class of articulated
animals with six feet, which breathe by
tracheae, have a dorsal vessel for circu-
lation, one pair of antennae, compound
eyes, generally pass through a distinct
metamorphosis and acquire wings, and
are oviparous with the sexes distinct
Burmeister divides them as follows : —

1. Insecta ametabola. Insects which
do not undergo metamorphosis. The
larva resembles the perfect insect, but
is without wings. The pupae of such
species as have wings in their imago
state possess rudiments of those organs.
The pupa runs about and eats. To this
division belong the orders Hemiptera,
Orthoptera, and Dictyoptera.

2. Insecta metabola. Insects which
undergo metamorphosis. The larva is a
worm either with or without legs. The
pupa is quiet ; or, if it moves, it does not
eat. To this division belong the orders
Neuroptera, Diptera, Lepidoptera, and
Coleoptera.

INSECTI'VORA {insecta, insects,
voro, to devour). A group of mammi-
ferous animals, considered by Cuvier as
a family of the great carnivorous order,
and characterized by their molar teeth
being studded with sharp points, which
enables them to devour insect prey.
They comprise the mole, the hedgehog,
the shrew, &c.

INSEPARABLE ACCIDENT. A
logical accident, which cannot be sepa-
rated from the individual to which it
belongs, though it may from the species,
as for a person to be a native of London.
See Accident.

INSESSO'RES {insideo, to sit upon).
Perchers; an order of Birds, the foot
181

of which is especially formed for grasping
or perching— a peculiarity evinced by the
situation of the hinder toe, which is
invariably placed on the same level or
plane as those in front.

INSOLATION (in, and sol, the sun).
A term sometimes employed to denote
exposure to the sun for the purpose of
promoting the chemical action of one
substance upon another.

INSOLUBILITY (in, not, solvo, to
loose), A property, resulting from co-
hesion, by which a substance resists so-
lution.

INSPISSATION (in, and spissatus,
thickened). The process of making a
liquid of a thick consistence.

INSTANCES, PREROGATIVE. Un-
der this term Lord Bacon cites all those
instances, or facts, which have a chief
claim to be noticed in the attempt to in-
terpret the laws of nature. He distributes
them into three classes, viz. those which
address themselves to the understanding,
those which assist the senses, and those
which conduce to practice.

INSTINCT. The spontaneous impulse
by which animals perform certain ac-
tions. Under this term should be dis-
tinguished the instinctive faculty, which
leads the duckling, untaught, into the
water, and the chick, untaught, to avoid
the water ; and the instinctive motions,
or those involuntary actions which are
excited mediately through the nerves, as
the closing of the eye-lids, the act of
swallowing, &c.

INSULATION (insula, an island). A
metaphorical term applied to a body con-
taining a quantity of electric fluid, and
surrounded by non-conductors, so that it
is insulated, or its communication with
other bodies is cut off.

INSU'RANCE. A per-centage paid
for insuring property from fire, &c.
When the charge is settled for any kind
of property, it is reckoned per cent, upon
the whole amount of it. The annual
payment is called the premium, and the
legal document, by which the securer is
insured from loss so long as he continues
to pay the premium, is called the policy
of insurance.

I'NTEGER. Literally " whole ;»' and,
hence, applied in arithmetic to a whole
number, as distinguished from a fraction.
INTEGRAL CALCULUS. That branch
of mathematical science which investi-
gates the processes by which a function
may be found such that its differential
shall be a given quantity. It was for-

INT

INT

merly called the inverse method of flux-
ions; the function itself was called the
fluent, or flowing quantity; it is now
termed the integral or sum of the pro-
posed differential.

INTEGRAL PARTICLES (integer,
entire). The most minute particles into
which any substance, simple or com-
pound, can be divided, similar to each
other, and to the substance of which they
are parts. Thus, the smallest portion of
powdered marble is still marble ; but if,
by chemical means, the calcium, the
carbon, and the oxygen of this marble be
separated, we shall then have the ele-
mentary or constituent particles.

INTENSITY. The degree or rate of
the power or energy of any quality, as of
heat and cold. In electricity, it denotes
the degree to which a body is electrically
excited.

INTENTION, FIRST and SECOND.
In Logic, the "first intention" of a term
is a certain vague and general significa-
tion of it, as opposed to one more precise
and limited, which it bears in some par-
ticular art, science, or system, and which
is called its "second intention." Thus,
the term "bird" in its first intention
signifies any individual of the feathered
tribes ; in the language of sportsmen, or
its second intention, it is limited to the
partridge. — Whately.

I'NTERAMBULA'CRA. The imper-
forate plates which occupy the intervals
of the perforated plates, or ambulacra, in
the shells of the Echinoderms. See Am-
bulacra.

INTERCALATION. The insertion of
a supernumerary or intercalary day into
the calendar for the purpose of preserving
the account of time. See Calendar.

INTERCE'LLULAR SPACES. Spaces
existing between the cells and other
simple tissues of plants.

I'NTEREST. The consideration paid
for the use of money. The rate of in-
terest is the sum paid for the use of a
certain sum for a certain time, generally
one year. The sum originally lent is
called the principal; the principal, to-
gether with its interest for any time, is
called the amount for that time ; the prin-
cipal is also called the present value of
the amount. Interest is called simple,
when it is paid as soon as due, or when,
if deferred, interest is not charged on
interest ; when the latter charge is made,
the interest is called compound.

INTERFERENCE. A term applied,
in Optics, to certain phenomena occa-
182

sioned by the mutual action of the rays
of light on one other : according to the
distances respectively from which the
rays of light proceeding from two lumi-
nous points fall upon the same spot, the
effect is diminished or increased ; and it
is this mutual action which is called
interference.

INTERJE'CTION. A sound uttered
under the impulse of strong emotion.
Interjections are indeclinable, stand in
no close connexion with the sentences in
which they occur, and cannot be properly
considered as a distinct part of speech.

INTERMEDIATE. A term applied
to a third substance, employed for com-
bining together two other substances ;
thus, alkali is an intermediate between
oil and water, forming soap.

FNTERNODE (inter, between, nodus,
a node or knot). Merithallus. That por-
tion of the stem of a plant which occurs
between two nodes.

INTERPOLATION. This term de-
notes, simply, the insertion of something
into original matter. In Algebra and
Astronomy, it is a method adopted for
filling up the intermediate terms of a
series of numbers or observations, by
numbers which follow the same law.

INTERROGATION, FALLACY OF.
A logical fallacy, which may be referred
to the head of " Ambiguous Middle." It
consists in asking several questions which
appear to be but one ; so that whatever
one answer is given, being of course ap-
plicable to one only of the implied ques-
tions, may be interpreted as applied to
the other. The refutation is, to reply
separately to each question, i. e. to detect
the ambiguity.

INTERRUPTED. A term denoting
a disturbance of a normal arrangement.
A leaf is said to be interruptedly pinnate,
when some of the pinnae are much smaller
than the rest, or absent.

INTERSCE'NDENT. A term applied
by Leibnitz to those algebraical quan-
tities of which the exponents of their
powers are irrational ; the term denotes
their holding an intermediate place be-
tween algebraic and transcendental quan-
tities.

INTERVAL, MUSICAL. A term
applied to a certain relation between
musical notes, which depends on the
number of their vibrations. The sim-
plest or most consonant interval is that
of the octave, in which the higher note
makes twice as many vibrations as the
fundamental note from which it is de-

IN U

IOD

rived ; its ratio is that of 1 ; 2 ; 4 '. 8,
&c. Compound intervals are those which
exceed an octave, and they are named
according to the distance of the two
boundary notes.

INTERVE'NIUM (inter, between,
vena, a vein). That portion of the par-
enchyma of leaves, which lies between
two or more veins or veinlets.

INTESTI'NA. An order of worms
which inhabit the bodies of other ani-
mals. They are distinguished by Cuvier
into the Cavitaria, which have cavities
or stomachs; and the Par en chymata, or
cellular-bodied, as the tape-worm.

INTE'XINE. That coating of the
pollen-grain which is situated next to
the extine, constituting a fourth layer of
the pollen-grain in certain plants.

I'NTINE. The inner coat of the shell
of the pollen-grain in plants. See Ex-
tine.

I'NTROIT (introitus, an entering in).
A term employed in ancient chronicles,
signifying the first two or more words
which form the commencement of a
mass, which, from being appropriated to
a certain Sunday, or other festival, gave
the name of such commencement or
" introit " to those days. Thus, the term
" adorate Dominum" is the introit and
name of the third Sunday after the Epi-
phany.

INTRO'RSE (introrsus, qu. intro-
versus, inwardly). Turned inwards; as
the, anthers of plants in which the line of
dehiscence is towards the axis of the
flower. See Extrorse.

INTUITION (intueor, to look into).
That simple faculty of the mind by
which we immediately perceive the
agreement or disagreement of two ideas.
In this the mind is at no pains of proving
or examining, but perceives the truth as
the eye does the light, only by being
directed to it. Intuitive truth has ac-
cordingly been defined as that " which is
perceived immediately on a bare atten-
tion to the ideas under review."

INTUS-SUSCEPTION (intus, within,
suscipio, to receive). The inversion of a
part of a tube within a contiguous part.
When it takes place downwards, it may
be termed progressive ; when upwards,
retrograde. The term intussusception is
also applied to the process of nutrition,
or the transformation of the components
of the blood into the organized substance
of the various organs.

I'NULIN. A starch-like substance
which is spontaneously deposited from a
183

decoction of the root of the Inula Hele-
nium, or Elecampane.

INVAGINATION {in, in, vagind, a
sheath). A sheathing of one part within
another ; a term synonymous with intus-
susception.

INVARIABLE. In Mathematics, a
term synonymous with constant, and
applied to a quantity which is absolutely
invariable. It may also denote a func-
tion which is not absolutely invariable,
but which does not vary in the processes
required by a given equation.

INVE'NTION. A term frequently
confounded with discovery, which simply
means the finding out something already
existing. Invention, however, includes
conception, and relates to the mental
operation by which obj cts are selected
and arranged with reference to a parti-
cular result. The polarity of the magnet
was discovered ; its application to navi-
gation was invented : the binomial theory
was a discovery ; the method of fluxions
an invention.

INVERTEBRA'TA. A negative and
unsatisfactory term by which Lamarck
designated all those animals which are
not furnished with a vertebral column
or backbone.

INVOLU'CRUM (involvo, to wrap in).
In Botany, a whorl of bracts which sur-
round several flowers, as in composite
and umbelliferous plants. In the latter
family, the bracts which surround the
general umbel are called the universal
involucrum ; and those which surround
the umbellules, a partial involucrum, or
involucellum.

I'NVOLUTE. That kind of curve
which is described by the extremity of a
cord as it is unrolled from the arc of
another curve about which it has been
lapped, the latter being called the evolute.
The two may be described as, the curve
unrolled, and the curve from which it is
unrolled. See Curve.

INVOLUTION (in Algebra). The
process of finding the powers of quan-
tities. The examples of involution are,
therefore, only examples of multiplica-
tion where the factors are all the same.
See Evolution.

FODINE (lw5^r, or loetdrj?, violet-
coloured, from 'iov, a violet, and ei3or,
likeness). A non-metallic, crystallized,
solid substance, found in marine plants,
in the ocean, and in mineral springs ; it
becomes volatile by a slight increase of
temperature, and forms a beautiful violet
vapour.

IRO

ISO

1. Iodal (iodine and alcohol). An ole-
aginous liquid obtained by the action of
iodine upon nitric alcohol.

2. Iodic Acid. An anhydrous acid,
termed oxiodine by Davy, and produced
by the combination of iodine with oxy-
gen. It combines with metallic oxides,
and forms salts which are termed
iodates.

3. Iodides, or Iodurets. The compounds
of iodine with metals, and with the sim-
ple non-metallic substances.

4. Iodous Acid. A compound prepared
by the action of iodine on chlorate of
potash, — probably by the combination of
iodine and chlorine.

5. Chloriodic Acid. This is also called
chloride of iodine ; and is formed by the
absorption of chlorine by dry iodine.

POLITE. A variety of quartz, inter-
mediate in colour between violet-blue
and blackish-blue, occurring in primitive
rocks in Finland.

FON (iov, that which goes ; neut. part,
of elm, to go). A term introduced by
Faraday, explanatory of his views of
electrolysis. He is of opinion that the
force does not emanate from the poles of
the battery, but that it resides in the
substance undergoing decomposition, of
which one element, or ion, goes to the
positive, the other element, or ion, to the
negative, end of the battery. The ion
which goes to the anode, or positive pole,
he terms an-ion ; that which goes to the
kathode, or negative pole, kat-ion. See
Electrode.

IRIDA'CE^. The Cornflag tribe of
Monocotyledonous plants, represented by
the iris and the crocus. Smooth herba-
ceous plants, with leaves ea^mtant', flowers
hexapetalous, triandrous; stamens 3;
ovarium 3-celled, many-seeded.

IRIDE'SCENT (iris, a rainbow). The
property of shining with many colours,
like the rainbow.

IRIDINI'NjE. A sub-family of the
Unionidcs, or River Mussels, named
from the genus iridina.

IRI'DIUM {iris, a rainbow). The
most infusible of all known metals,
named from the variety of colours it dis-
plays while dissolving in hydro-chloric
acid.

IRON. The most abundant of the
true metals, occurring in the form of
oxides and clay iron-ore, and entering
into the composition of many rocks,
which frequently owe their grey colour
to it.

Cast or pig iron is the name given to
184

the metal when first extracted from its
ores. Its varieties are the white cast
iron, which is extremely hard and
brittle, and appears to consist of small
crystals ; grey or mottled cast iron, so
called from the inequality of its colour,
softer and less brittle than the preceding ;
and black cast iron, the most unequal
in its texture, and least cohesive of the
three.

IRON-PYRITES. Yellow sulphuret
of iron. An ore of iron, of a brass-yellow
or greenish-yellow colour, compact or
fibrous, emitting a sulphurous smell
when struck ; granulated, or even earthy,
when impure.

IRONSTONE. A stratum of the coal-
formation, forming thin beds, or disposed
in globular or depressed masses, alter-
nating with layers of shale. It is of a
brown or grey colour, and is principally
composed of iron combined with oxygen,
carbonic acid, and water, usually with a
little alumina, silica, and lime.

IRRA'TIONAL NUMBERS. A terra
applied, in Algebra, to those numbers or
quantities, the roots of which are incom-
mensurable by unity, and the exact value
of which can therefore never be deter-
mined ; in other words, to those num-
bers or quantities which are inexpres-
sible by an arithmetical ratio, and are
therefore " arithmetically irrational."
These numbers are generally called
surds, from the Latin surdus, deaf or
senseless.

IRREDU'CIBLE CASE. An alge-
braical term, applied to that class of
cubic equations in which Cardan's for-
mula fails in its application. The reason
of the failure arises from the imaginary
expression of the formula, and from the
fact that the cubic equations in question
have all the three roots real.

IRREGULAR BIVALVES. Those
bivalves which are not uniform in shape
throughout the species ; a deviation al-
most confined to the perforating groups.

IRREGULAR MASSES. A term
applied by MacCulloch to rocks of no
determinate form, and of any size, as
granite, greenstone, and porphyry.

FSERINE. An iron-black mineral,
containing titanium aod uranium, found
near the origin of the river Iser, dis-
seminated in granite sand, and in allu-
vial soil, together with pyrope, in Bo-
hemia.

ISO- (tVof, equal). This prefix denotes
equality, or similarity. Hence,—

1. Iso-barysm (fidpos, weight). Simi-

ISO

larity of weight, supposed to be the cause
of the identity in the size and shape of
molecules which cohere into the crystal-
line form.

2. Iso-bryous {/3pvia, to grow). That
which grows equally ; a term applied by
some writers to dicotyledonous plants,
which, having two cotyledons, grow with
equal force on the two sides of the axis.
For the same reason, such plants have
been called iso-dynamous, from dt/va/ui?,
force. See Anisobryous.

3. Iso-chromatic (xpw/ua, colour). Hav-
ing the same colours, as applied to
lenses. The light which is decomposed
by doubly refracting crystals, forms a
double series of coloured curves of dif-
ferent forms, arranged in a different order,
each curve in the one series having a
curve corresponding to it in form and
colour in the other. The two curves
which have the same tint, are called iso-
chromatic.

4. Iso-chronous (xpovor, time). That
which occurs in equal times ; as the
strokes of the pulse, the vibrations or
oscillations of pendulums of the same
length, &c. Hence, the term isochron-
ism is applied to that property of all sys-
tems which are in equilibrio, by which
the retardation or acceleration of the
oscillations is not perceptibly influenced
by any disturbing force.

5. Iso-clinic Lines (nXivat, to incline).
Lines of equal inclination or dip ; a term
applied to curves which connect those
places in the two hemispheres where the
dip of the magnetic needle is equal ; they
surround the globe, running nearly paral-
lel with the magnetic equator. These
curves coincide in position with the iso-
thermal lines. See Aclinic Line.

6. Iso-cyclous (kukAoc, a circle). A
term applied to animals which are com-
posed of a succession of equal rings, as
some of the Crustacea.

7. Iso-dynamic Lines (hvvayus, power).
Lines of equal power; a term applied by
Hansteen to lines which connect those
places where the intensity of the terres-
trial magnetism has been found to be
equal, and which resemble in form and
position the isoclinic lines, though they
approach still more nearly to the iso-
thermal lines.

8. Iso-gonic Lines (ywvia, an angle).
Lines of equal declination ; a term ap-
plied to lines connecting those places
which have an equal declination west or
east. Most of these lines are drawn
around two points near to the north and

185

ISO

south poles of our planet, called the
magnetic poles of the earth, or, more cor-
rectly, magnetic poles of convergence.

9. Iso-merism {fiepot, part). A term in
chemistry expressive of the relation ex-
isting becween bodies, which agree in
composition but differ in properties. Iso-
meric bodies have in general been found
to agree in the relative proportion of
their constituents only, and to differ
either in the aggregate number of the
atoms composing them, or in the mode
of arrangement of these atoms. Berze-
lius has employed three terms to in-
clude the different cases of these
bodies, viz. isomeric, polymeric^ and meta-
meric.

10. Iso-morphism {^opcptj, form). A
term in chemistry applied by Mitscherlich
to the relation in form which exists in
different bodies, as a general consequence
of similarity of composition. The law
at which he arrived is as follows :— The
same number of atoms combined in the
same way produce the same crystalline
form ; and crystalline form is independent
of the chemical nature of the atoms, and
determined only by their number and
relative position.

11. Iso-morphous (fxop<ptj, form). A
term applied to some groups of chemical
substances, which, having the same
crystalline form, are found to enter into
analogous combinations, which also re-
spectively present the same form ; and to
some other groups which have been ob-
served to enter into similar combinations,
having very similar crystalline charac-
ters. Of these iso-morphous bodies, the
salts of phosphoric and arsenic acids
afford remarkable examples.

12. Iso-perimetrical (irepifxeTpov, cir-
cumference). Having the same length
of perimeter, circumference, or bounding
line. Of all iso-perimetrical figures, that
is the greatest, which contains the most
sides or angles ; hence, the circle is the
most capacious of all iso-perimetrical
figures.

13. Iso-poda (wove, vrodo?, a foot). A
group of crustaceous animals, which have
seven pairs of similar unguiculate feet,
attached to seven moveable segments
behind the cephalic. A characteristic
example is found in the oniscus, or wood-
louse.

14. Iso-pyre. A new mineral found in
Cornwall, imbedded in granite; it re-
sembles obsidian, or even some varieties
of iron slag.

15. Isosceles (<rxe\of, a leg). The

JET

JUL

designation of a triangle of which two
sides, or legs, are equal.

16. Iso-stemonous ((tt^juwv, a stamen).
A term applied by De Candolle to those
plants, the stamens of which are equal in
number to the petals. See Anisostemonous.

17. Iso-thermal Lines (04p/j.n, heat).
Lines of equal temperature ; a term ap-
plied, in physical geography, to lines con-
necting all those places on the surface of
the Globe which have the same mean
temperature. Lines drawn through places
having the same summer, and the same
winter temperatures, are termed, respec-

tively, iso-theral (0<?por, summer), and
iso-cheimal (xe»Ma> winter) lines ; while
lines drawn through places having other
common temperatures, receive other ap-
propriate names.

I'STHMUS. A narrow neck of land
lying between two seas, and connecting
two masses of land greater than itself.

ITACONIC ACID. Another name
for the pyrocitric or citricic acid.

I'TTNERITE. A rare mineral, con-
sisting chiefly of silica, alumina, and
soda, together with some hydrosulphu-
ret ; named after Ittner.

JACULATRI'CES (jaculum, a dart).
The name given by Macgillivray to an
order of birds, from the peculiar form of
their bill, and their rapid flight. The
families composing the order are the
Alcedinae, the Galbulinae, and the Tro-
goninae, of which the last two have the
feet zygodactyle.

JADE. Nephrite. A mineral sub-
stance found in granite and gneiss, in
Switzerland, and divisible into the two
varieties of common nephrite and ama-
zonian stone. The name has, however,
been applied to various minerals which
resemble one another in little else than
in colour.

JA'MESONITE. A mineral consist-
ing principally of the sulphurets of anti-
mony and of lead, and named after Pro-
fessor Jameson.

JA'RGON. Jargon of diamond is a
designation of one of the varieties of
zircon.

JA'SPER. A siliceous substance of
various colours, occurring in veins in
trap rocks, in volcanic rocks, and in the
primary and secondary series.

JATROPHIC ACID. Crotonic Acid.
An acid procured by the saponification of
croton oil.

JE'FFERSONITE. A variety of py-
roxene ; a new mineral found in Frank-
linite and garnet, in New Jersey.

JE'RVINE. A vegeto-alkali, found
in the root of veratrum album.

JET, or PITCH COAL. A black vel-
vet-coloured bitumen, used for fuel, and
for making vessels, &c. In Prussia it
is called black amber, and is cut into
rosaries and necklaces. Ure says the
186

word jet is derived from the river Gaga
in Lesser Asia.

JEWELLERS' PUTTY. Ignited and
finely-levigated oxide of tin, used by
jewellers for polishing hard objects.

JOINTS. In Geology, fissures or lines
of parting in rocks, often at right angles
to the planes of stratification. The part-
ings which divide columnar basalt into
prisms, are joints.

JU'DGMENT. In Logic, an operation
of the mind, by which we compare two
ideas or notions which are the objects
of apprehension, whether complex or
incomplex, and pronounce upon their
agreement and disagreement. Judgment
is, therefore, either affirmative or nega-
tive.

JU'GUM. The Latin term for a yoke,
and hence applied to a pair of opposite
leaflets on the petiole of a pinnate leaf.
Thus a leaf with one pair is called uni-
jugal; with two pairs, bijugal, &c.

Juga in Umbelliferous Plants. The
term juga also signifies ridges, and is
hence applied to the elevated portions by
which the carpels of umbelliferous plants
are traversed; of these juga, five are
called primary, and four, alternating
with them, secondary.

JULIAN CALENDAR. The mode
of reckoning the divisions of the year,
adopted by Julius Caesar, and afterwards
corrected by Gregory XIII. It is ex-
plained under the term Bissextile. The
Russians still retain the Julian style,
and their year consequently begins twelve
days later than ours.

JULIAN PERIOD. A revolution of
7980 years, reckoned from 4713 years

K AL

KEE

before our era, and produced by the
continued multiplication of the solar
cycle, the lunar cycle, and the cycle of
indiction, viz. 19, 28, and 15. See
Cycle.

JU'LIDiE. The lowest division of the
Myriapods, so named from the julus, or
common millepede.

JUNGERMANNIA'CEiE. An order
of creeping moss-like plants, named from
the genus jungermannia, and distin-
guished from several allied orders by
the theca opening by valves, without an
operculum. In all the orders the spores
are mixed with elaters.

JUNO. A telescopic planet, situated
in the solar system between Mars and
Jupiter, and said to be 1320 miles in dia-
meter. Its distance from the sun is
about 256 millions of miles, and it com-
pletes its revolution in 4 years, 128 days.

This planet was discovered, in 1804, by
Mr. Harding of Bremen.

JUPITER. The largest of the planets,
and, next to Venus, the most brilliant.
It is 1470 times the size of the earth. It
completes its orbit round the sun in
4332*596 days. It is accompanied by four
satellites.

JURA LIMESTONE. A term applied
to the limestones belonging to the Oolitic
group, and constituting the chief part of
the mountains of the Jura, between
France and Switzerland.

JURA'SSIC SYSTEM. A term syn-
onymous in continental writers with our
Oolitic System.

JURISPRUDENCE. General juris-
prudence is the science or philosophy of
positive law, as distinguished from par-
ticular jurisprudence, or the knowledge
of the law of a particular country.

K

KAKO'XENE. A crystalline mineral,
found in iron-stone, in Bohemia.

KALEI'DOPHON (»ca\6v, beautiful,
eldor, form, <t>u>vrj, sound). An instru-
ment, invented by Mr. Wheatstone, for
exhibiting the vibrations of an elastic
rod. If a rod of this kind, fastened at
one end, be set in motion by a blow, or
bending, it will describe paths which do
not always lie in the same plane, but
return in variously-curved lines. If the
free end of the rod be surmounted with
a polished knob, the curves will be exhi-
bited in a beautiful manner to the eye.

KALEIDOSCOPE [na\6s, beautiful,
eidor, form, anoireoj, to see). A well-
known apparatus, invented by Sir D.
Brewster, by which the image of an ob-
ject is multiplied by repeated reflections
from inclined mirrors, placed opposite to
one another.

KALI. A term of Arabic origin, de-
noting a particular plant ; hence the word
al-kali, with the article, originally signi-
fied the particular residuum obtained by
lixiviating the ashes of that plant; the
term was then used for potassa.

KA'LOTYPE (»ca\6?, beautiful, two?,
an impression). The art of fixing photo-
graphic images upon surfaces of silver,
first suggested by Wedgewood, and sub-
sequently improved by Daguerre (See
Daguerreotype). Talbot employs for this
purpose a paper which is rendered pecu-
187

liarly susceptible to light, and which is
termed kalotype paper ; a negative pic-
ture is formed upon the paper in the
camera obscura, and fixed by means of
bromide of potassium.

KAOLIN. China-clay; a fine pure
clay prepared by levigation from moul-
dering granite, and employed in the
manufacture of porcelain.

KA'RPHOLITE (xdptfxK, a straw,
Xi'tfor, a stone). A yellow mineral, oc-
curring in thin prismatic concretions.

KARPHOSIDE'RITE ( K<ip<t>os, a
straw, <ribt)pos, iron). A straw-coloured
mineral, resembling iron-sinter, and oc-
curring in Labrador.

KA'RSTENITE. Another name for
anhydrite, or prismatic gypsum.

KATHODE {Kara, downwards, 6d6s,
a way). A term applied by Mr. Faraday
to that part of the surface of a decom-
posing body at which the electricity de-
parts— the part immediately touching the
negative pole. See Anode.

KA'TION (koltiov, that which goes
down). A term applied by Mr. Faraday
to the body which passes to the negative
pole, or kathode, of the decomposing
body, as it is separated by electricity.
See Anion.

KEDRIA TERRESTRIS. Barbadoes
tar ; a mineral oil. See Bitumen.

KEEL. Carina. A term applied by
botanical writers to the two lower petals

KER

KNO

of a papilionaceous corolla, which cohere
by their lower margins, so as to present
a keeled or boat-like form.

KEEPER OF A MAGNET. A piece
of soft iron, which is placed in absolute
contact with the poles of a magnet when
not in use. The keeper tends, by
induction, to maintain, and even exalt,
the power of the magnet, whose poles are
thus employed in producing the opposite
magnetism in its respective ends.

KE'LLOWAY ROCK. A term ap-
plied to beds of limestone occurring in
the lower part of the Oxford or Clunch
clay ; it is often composed of irregular
nodules, and is sometimes full of shells,
among which predominate ammonites
and large gryphaeae.

KELP. Varec. The crude soda ob-
tained from the ashes of the Futi in
Holland and on the northern coast of
France. It is used in the composition of
soap, in the manufacture of alum, and in
the formation of crown and bottle glass.
See Barilla.

KEPLER'S LAWS. The laws of
elliptic motion about the sun as a focus,
and of the equable description of areas
by lines joining the sun and planets,
were originally established by Kepler,
from a consideration of the observed mo-
tion of Mars, and were by him extended,
analogically, to all the other planets.
These laws are three : —

1. That every planet moves so that the
line drawn from it to the sun describes
about the sun areas proportional to the
times.

2. That the planets all move in elliptic
orbits, of which the sun occupies one of
the foci.

3. That the squares of the times of the
revolutions of the planets are as the
cubes of their mean distances from the
sun.

KERATO'PHYTA (i«?par, Keparo?,
horn, (pvTov, a plant). An old name for
those polyps which have a horny axis, as
distinguished from the lithophytes, or
strong polyps.

KERMES ANIMAL. Coccus Ilicis.
A hemipterous insect, found upon the
quercus ilex, and formerly used for dye-
ing scarlet : cloth so dyed was called
coccinum, and persons wearing this cloth
were termed by the Romans coccinati.
The drug was termed grana kermes, from
the resemblance of the dried insects to
grains or seeds.

KERMES MINERAL. Formerly,
Panacea Glauberiana ; a sulphuret of
188

antimony; so named, from its resem-
blance, in colour, to the insect kermes.

KEUPER. A Gennan name for a
member of the Upper New Red Sand-
stone formation. Remains of reptiles
are said to have been found in it near
Warwick.

KEY (in Music). The particular dia-
tonic scale, in which a composition begins
and ends, and which prevails more or
less in a given piece of music. There
are twelve major and twelve minor keys.

KILLAS. The technical name ap-
plied by the Cornish miners to clay-slate,
or the grauwacke slate of other countries.

KI'LLINITE. A mineral resembling
spodumene, discovered in granite veins
at Killiney, near Dublin.

KI'MMERIDGE CLAY. A thick bed
of clay, constituting a member of the
Oolitic Group, and occurring well deve-
loped at Kimmeridge, in the isle of Pur-
beck, Dorsetshire.

KING'S YELLOW. A paint, of which
the colouring principle is orpiment, or
the sesqui-sulphuret of arsenic.

KINGDOM. A term denoting any of
the principal divisions of nature ; thus
we have the organic kingdom, compre-
hending substances which organize, and
the inorganic kingdom, comprehending
substances which crystallize.

KINIC ACID. Quinic acid. An acid
found in the Cinchona barks. It forms
salts called kinates.

Kino'ile. A neutral substance pro-
duced by the calcination of a kinate by
a gentle heat.

KITE, ELECTRICAL. An appara-
tus for proving the existence of sensible
electricity in the atmosphere. A wooden
rod, of several feet in length, fastened by
its lower end to a glass tube, and sur-
mounted at the other by a pointed brass
or copper wire, forms an insulated
conductor to attract the electricity. A
second wire, attached to the first, is con-
nected with a delicate electrometer, which
exhibits the electricity conducted to it
from the atmosphere.

KNE'BELITE. A grey spotted mine-
ral, consisting of silica, iron, and manga-
nese.

KNOWLEDGE. " Knowledge implies
three things ; 1st, firm belief; 2ndly, of
what is true ; 3rdly, on sufficient grounds.
If any one, e. g. is in doubt respecting
one of Euclid's demonstrations, he cannot
be said to know the proposition proved by
it ; if, again, he is fully convinced of any
thing that is not true, he is mistaken in

LAB

LAC

supposing himself to know it ; lastly, if
two persons are each fully confident, one
that the moon is inhabited, and the other
that it is not (though one of these opi-
nions must be true), neither of them
could properly be said to know the truth,
since he cannot have sufficient proof of
it."— Whately.

KOBELL S DISCOVERY. A method
proposed by Kobell of Munich by which
pictures drawn in bistre or Indian ink
may be multiplied by the process of elec-
trotype, or gal vano- plastics.

KO'LLYRITE. A white mineral
found in porphyry, in Hungary.

KO'NIGINE. A green mineral, pro-

bably consisting of a subsulphate of

copper.

4 KOUTHOLITE {koZ<j>o?, light, \i9os,

a stone). A variety of prehnite found

near Bareges.

KRAME'RIC ACID. A peculiar sub-
stance supposed to exist in the root of
the krameria triandra.

KUNDAH Oil. An oil obtained from
the seeds of the Carapa Toulouconna,
also called tallicoonah oil.

KUPFERN1CKEL. The German name
for sulphuret of nickel, in which the
metal is generally mixed also with arse-
nic, iron, and cobalt.

LABA'RRAQUE'S SOLUTION. A
disinfecting liquid, consisting of a solu-
tion of the chlorides of lime and of soda.
It is analogous to the well-known bleach-
ing powder, chloride of lime.

LABE'LLUM (dim. of labium, a lip).
A little lip ; the botanical designation of
the lip-like, or undermost, petal of orchi-
daceous plants.

LABIA'TiE {labium, a lip). The La-
biate or Mint tribe of Dicotyledonous
plants. Herbaceous plants, with leaves
opposite ; flowers irregular, unsymmetri-
cal; stamens four, didynamous, inserted
into the corolla ; ovarium deeply 4-lobed ;
fruit 1 — 4 small nuts.

LA'BIATE {labium, a lip). A botani-
cal designation of a gamopetalous calyx
or corolla, which is separated into two
unequal divisions, resembling lips, the
one anterior, the other posterior, with
respect to the axis. Hence, the term bi-
labiate is more commonly used. This
form of the floral envelopes is character-
istic of the Mint tribe. See Labiates.

LA'BORATORY. A room properly
furnished for the performance of chemical
operations.

LA'BRADOR FELSPAR. Labrador-
ite. A species of felspar found chiefly on
the coast of Labrador, and in the transi-
tion syenite of Laurwig in Norway. It
is also called opalescent felspar, from its
often exhibiting a beautiful play of co-
lours in cut and polished specimens. It
is probably a variety of albite.

LA'BRID^E. A family of acantho-
pterygious fishes, named from the genus
189

labrus, or the wrasse. They comprise
the Parrot-fishes, so remarkable for the
convex form of the jaws.

LAB RUM. Literally, the extremity
of the lips ; also, the brim of any vessel.
In Entomology it is applied only to the
lower lip of insects.

LABYRI'NTHODON (KapvptvOot, a
labyrinth, bbov?, a tooth). The name
now given to the Cheirotherium, a sup-
posed crocodilian animal of considerable
size, to which have been referred the
singular footsteps found impressed on
several beds of marly sandstone in va-
rious parts of England and Europe,
bearing a remarkable resemblance to the
human hand. The present name is de-
rived from the complex or labyrinthine
structure of a section of the tooth, as
seen under the microscope.

LAC {laak, Arab ). A resinous sub-
stance, improperly termed a gum, depo-
sited by the insect coccus lacca, on the
leaves and branches of several trees, over
its eggs, as a present protection, and as a
future food for the maggot. Stick-lac is
the substance in its natural state, en-
crusting twigs ; seed lac is the lac sepa-
rated from the twigs, and of a granulated
form, like mustard seeds ; shell- lac is the
substance obtained after purification ;
lump-lac is the seed-lac melted and
formed into cakes. Lac-dye, lac-lake,
or cake-lac, are designations of the colour-
ing matter extracted from the stick-
lac.

LAC LUNiE. Moon-milk; a snow-
white substance, resembling chalk, and

LAC

L AK

consisting almost wholly of alumina,
saturated with carbonic acid.

LACCIC ACID. An acid obtained
from stick-lac, forming salts called lac-
cates.

LACCIN. A principle discovered in
lac, intermediate between wax and resin.

LACE'RTA. The Lizard; a modern
northern constellation, consisting of six-
teen stars. It is surrounded by Andro-
meda, Cepheus, Cygnus, and Pegasus.

LACERTI'NIDiE {lacertus, a lizard).
A family of Saurian reptiles, including
the common lizards of this country, and
most of the Saurians of active habits.
They are characterized by their small
head, thick neck, and long, slender,
forked tongue.

LACI'NIATED (lacinia, the fringe of
a garment). A term applied, in Botany,
to those leaves which are divided by
deep, taper-pointed incisions. Such
leaves are also said to be slashed, decom-
posed, or multifid. The inflexed point
of the umbelliferous petal is called the
lacinula.

LA'CQUER. A solution of shell-lac
in alcohol.

LA'CTEALS {lac, lactis, milk). Mi-
nute vessels which, in the animal eco-
nomy, absorb, or take up, the chyle, or
milk-like fluid, from the alimentary canal.
See Absorption.

LACTIC ACID {lac, lactic, milk).
An acid generated whenever milk, and
perhaps most animal fluids, become spon-
taneously sour, or when the juice of beet-
root is preserved for some months at a
high temperature. Its salts are called
lactates.

LA'CTINE {lac, milk). Saccholactin.
Sugar of milk ; obtained by evaporating
the whey of milk to crystallization, and
purifying the first product by animal
charcoal and a second crystallization.

LACTO'METER {lac, lactis, milk,
fierpov, a measure). A graduated glass
tube, for ascertaining the relative quan-
tity of cream afforded by milk. A more
correct term would be galactometer.

LACTU'CIC ACID. An acid dis-
covered in the juice of the lactuca virosa,
or wild lettuce.

LACU'NiE {lacus, a lake). A term
applied by Link to the air-cells which
occur in the tissue of plants. In lichens,
they are the small hollows or pits which
occur on the upper surface of the thallus ;
and hence the term lacunose is applied to
a body which has large deep lacunae or
depressions on the surface.
190

LACU'STRINE {lacus, a lake). Be-
longing to a lake. A lacustrine deposit
consists of alluvial matter carried down
by rivers and deposited at the bottom of
lakes.

LjEMODFPODA {Xainot, the throat,
nodes, feet). A group of crustaceous
animals, which have the anterior pair of
feet attached to the cephalic segment ;
they have no post-abdominal branchiae ;
the eyes are sessile, and the mandibles
without palpi.' A characteristic example
is found in the cyamus, commonly called
the whale-louse, from its infesting the
cetacea as a parasite.

LAGOON or LAGUNE. An extensive
sheet of shallow water, formed either by
the encroachment of the sea or rivers
upon the land, or by the separation of a
portion of the sea by the intervention of
a bank. Thus, there are fluvial and
marine lagunes.

LA'GRIID^E. A family of coleopte-
rous insects, of the section Heteromera,
named from the genus Lagria, one spe-
cies of which is indigenous in this coun-
try.

LAKE. An insoluble compound,
formed by precipitating colouring matter
with an earth or oxide. The principal
lakes are carmine, obtained from cochi-
neal, by precipitation with Roman alum ;
Florence lake, prepared, in the same pro-
cess, from the sediment of cochineal, by
precipitation with solution of tin; and
madder lake, prepared from Dutch crop
madder, by precipitation with alum.

LAKE (in Geography). An inland
body of water not connected with the
ocean or any of its branches. It is formed
by accumulation of water in a basin, or
depression of the surface, deeper than
the general slope of the water-line of
valleys. There are four distinct kinds of
lakes : —

1. Those which have no outlet, and
which do not receive any running water.
They are usually very small ; some ap-
pear to be the craters of extinct volcanoes
filled with water.

2. Those which have an outlet, but
which receive no running water. They
have been formed by springs flowing
into some large hollow ; the outlets are, in
some cases, the beginnings of very large
rivers. These lakes are usually in ele-
vated situations.

3. Those which both receive and dis-
charge streams of water, as the immense
bodies of water in North America, be-
tween Canada and the United States, the

LAM

LAN

outlet of which is the great river St.
Laurence ; lake Baikal, in Asiatic Russia,
which sends forth a large stream, which
joins the Yenesei.

4. Those which receive streams of
water, and often great rivers, but have
no visible outlet whatever, as the Caspian
Sea and lake Aral, both in the west of
Asia. These are both salt lakes, and
were, perhaps, formerly connected with
the Black Sea.

LA'MANTINE. The sea-cow; a living
species of the herbivorous Cetacea, or
Whale tribe, which inhabits the mouths
of rivers on the coasts of Africa and
South America.

LAME'LLA (dim. of lamina, a plate).
The lamellae of the agaric are those pa-
rallel plates, or gills, in which the spo-
rules lie ; collectively, they constitute
the hymenium. But the term lamellar is
applied to any part which is surmounted
by little plates, or lamellae, as the style
of many plants.

LA'MELLATED {lamella, a little
plate). A term applied to shells whose
substance is composed of lamellae, or
very thin plates, which do not present a
solid surface, as in the pearl-oyster.

LAME'LLIBRANCHIA'TA {lamella,
a little plate, branchiae, gills). A class of
bivalve conchiferous mollusca, which
respire by gills in the form of vascular
plates of membrane attached to the
mantle. The common oyster and mussel
are examples of this best known class of
acephalous mollusca.

LAMELLICO'RNES {lamella, a little
plate, cornu, a horn). A family of the
pentamerous Coleoptera, characterized by
the peculiar conformation of the an-
tennae, which terminate in a lamellated
mass. They include the scarabaei, and
the lucani or stag-beetles.

LAMELLI'FEROUS {lamella, a little
plate, fero, to bear). Having a structure
consisting of thin plates or leaves, like
paper.

LAME'LLIFORM {lamella, a little
plate, forma, shape). Shaped like a thin
plate or leaf.

LAME'LLIROSTRES {lamella, a little
plate, rostrum, a beak). The name given
by Cuvier to the great family of the Ana-
tidce, comprising the duck, the goose, the
swan, &c.

LA'MINA. The Latin term for a
plate, as of metal. In Geology, the word
laminae denotes the smaller layers of
which a stratum is composed.

LA'MINARITES. The name given
191

by Brongniart to a species of fossil fucus,
found in the secondary strata of Aix,
near La Rochelle.

LAMP-BLACK. A species of char-
coal, produced by collecting the smoke
from a lamp ; but it is generally obtained
by burning resinous substances, as the
dregs of pitch, or pieces of fir-wood, in
furnaces, and collecting the smoke in a
close-boarded chamber.

LAMPIC ACID. An acid obtained
by Sir H. Davy from the combustion of
ether. It is merely acetic acid, com-
bined with some etherous matter.

LAMPY'RIDjE {\<in7ro, to shine). A
family of Coleopterous insects, of the
section Malacodermi, named from the
genus lampyris, to which belongs the
familiar species noctiluca, or the glow-
worm, remarkable for its emission of
phosphorescent light.

LANA PHILOSOPHICA. Philoso-
phical wool, flowers of zinc, or the snowy
flakes of white oxide of zinc, which arise
and float in the air from the combustion
of that metal.

LAN'CEOLATE {lancea, a lance).
Lance-shaped ; narrowly elliptical, taper-
ing to each end, as the leaves of many
plants.

LA'NDSLIP. A portion of land which
has slipped away, owing to the disturb-
ance of an earthquake, or from being
undermined by the washing away of its
lower beds by water.

LANE'S CH ARGING- JAR, or Spark-
measurer. An apparatus for ascertaining
the intensity of an electrical charge, by
measuring* the length of the spark, and
thus at the same time determining the
power of a machine ; and also for obtain-
ing a number of successive charges of
equal intensity.

LA'NIADiE {lanins, the shrike). The
Shrikes; a family of the Insessores, or
Perching birds, or the Excurtrices of
Macgillivray, in which the bill is ab-
ruptly hooked at the end, and the notch
is sometimes so deep as to form a promi-
nent tooth on each side. See Denti-
rostres.

LANIA'RIFORM {lanio, to cut or
tear, forma, shape). Shaped like the
canine teeth of the Carnivora, which are
called laniaries from their office.

LANTA'NUM (SavBuvu, to be con-
cealed). A newly-discovered metal, so
named from its properties being con-
cealed by those of cerium, with which it
is found united. It occurs in the cerite
of Bastnas.

L AT

LAY

LAPIDIFICA'TION {lapis, a stone,
fio, to become). The process of conver-
sion into stone.

LAPI'LLI {lapillus, dim. of lapis, a
stone). Small stones ; small volcanic
cinders.

LAPIS. A generic term, signifying
all kinds of stone: thus, lapis calcareus
is limestone ; lapis infernalis is an old
term for caustic potash ; lapis calami-
naris is the impure carbonate of zinc ;
lapis comensis is potstone, an intimate
mixture of talc and asbest ; lapis lazuli
is a zinc-stone, from which ultra-marine
is prepared, &c.

LA'RBOARD. By a person standing

at the stern of a ship, and looking

towards the prow, the left-hand side is

termed the larboard, and the right-hand

> ^"side the starboard.

&JfY% * LA'RIDiE {larus, the sea-gull). The

w _^^* Gx\)\ tribe ; a family of the Natatores, or

^^^ Swimming birds, including the gull, the

petrel, the albatross, &c, in which the

powers of flight are considerable, while

those of swimming and diving are

defective.

LA'RVA (Lat., a mask). A caterpil-
lar ; the earliest state of insect existence,
so named by Linnaeus because in this
condition the perfect form of the insect
is concealed, as it were, under a mask.
The term larva is applied to the grub,
the caterpillar, and the maggot. See
Pupa.

LARVI'PAROUS {larva, and pario,
to produce). A designation of those in-
sects which produce their young in the
condition of larvae.

LA'SIONITE. A phosphate of alumina
from Amberg in Bavaria. It is a variety
of hydrargyllite.

LATE'BRICOLuE {latebra, a hiding-
place, colo, to inhabit). A family of
Spiders, which hide themselves in bur-
rows and fissures, which they line with
a web.

LATENT HEAT. That quantity of
heat which is absorbed during the con-
version of a solid into a liquid, or of a
liquid into a vapour, without raising the
temperature in the least degree. See
Caloric.

LA'TERAL {latus, lateris, the side).
Belonging to the sides of a body. Thus,
the lateral teeth of bivalves, where they
exist, are on one or both sides of the
cardinal teeth, which are always central.

LATERI'GRADA {latus, lateris, the
side, gradior, to advance). A family of
Spiders, which make no web, but run,
192

crab-like, sideways or backwards, and
occasionally throw out adhesive threads
to entrap their prey.

LATEX {lateo, to be hidden). Any
kind of liquor squeezed out. This term
denotes, in Botany, a highly elaborated
and highly organized juice, which is not
formed immediately from the fluid matter
absorbed from without. The tissue, in
which this juice is found, is termed lati-
ciferous tissue, and more recently cinen-
chyma.

LATITUDE {latitudo, breadth). The
latitude of a place on the earth's surface
is its angular distance from the equator,
measured on its own terrestrial meri-
dian ; it is reckoned in degrees, minutes,
and seconds, from 0 up to 90°, and north-
wards 05 southwards according to the
•hemisphere in which the place lies. Thus
the observatory at Greenwich is situated
in 51° 28' 40" north latitude.

1. Latitude, parallels of . Small circles
on the earth's surface parallel to the
equator. Every point in such a circle
has the same latitude. Thus, Greenwich
is said to be situated in the parallel of
51° 28' 40".

2. Latitude of a star. The distance of
a star from the ecliptic, measured on the
great circle passing through the star and
the pole of the ecliptic.

LA'TROBITE. A pink-coloured mine-
ral, allied to felspar, found in Amitok
island, near the coast of Labrador, and
named from Mr. Latrobe.

LAUMONTITE. Lomonite. A zeo-
litic substance, named from Gillet-Lau-
mont. It is also called efflorescent zeo-
lite, because some of its varieties are sub-
ject to decomposition on exposure to the
air.

LAURACEjE. The Cinnamon tribe
of Dicotyledonous plants. Leaves entire,
alternate ; flowers apetalous ; stamens
perigyn'ous ; fruit baccate or drupaceous ;
seeds without albumen.

LAURINE. An acrid and bitter prin-
ciple contained in the berry of the laurel.

LA'VA. A general term for the sub-
stances emitted from volcanoes, in a
fused or fluid state. In its ordinary con-
dition, it differs from basalt chiefly in
being porous. It admits, however, of
several varieties, which are sufficiently
characterized by the terms compact, vesi-
cular, slaggy, and spumous.

LAYERING. The process of propa-
gating young plants from a parent stock,
by laying down a branch, and then sepa-
rating it from its parent. See Malleolus.

LEA

LEG

LA'ZULITE. Lapis lazuli. A blue
mineral from Styria and the Tyrol, which
furnishes the valuable pigment known
by the name of ultra-marine. It is a
silicate of alumina, soda, and lime, and is
sometimes confounded with klaprothite,
or blue spar, which is a phosphate of
alumina.

LEAD. A white metal with a blue
tinge; the softest of all the durable
metals. White lead, or ceruse, is a white
substance produced, in the form of
flakes, by the action of the vapour of
vinegar on lead. It may be dissolved in
acetic acid, forming a crystallizable salt,
called sugar of lead, from its sweet taste.
Red lead, or minium, is the red oxide of
lead, a tasteless powder of an intensely
red colour. Black lead, or graphite, is a
misnomer, being a carburet of iron.

LEAF OF PLANTS. The leaf is an
expansion of the bark at the base of a
leaf-bud, prior to which it is developed.
It consists of a midrib, on each side of
which is a parenchymatous expansion,
composed of a double stratum of cellular
tissue, separated by vessels. A simple
leaf is that of which the lamina or blade
consists of one piece only, whatever may
be the depth of its divisions ; a compound
leaf is that of which the cellular tissue is
separated into several portions, each
forming a complete blade by itself.

LEAF-STALK. Petiole. That part
of the leaf which connects the blade with
the stem. It consists of one or more
bundles of fibro-vascular tissue sur-
rounded by cellular substance.

LEAFLET. The designation of each
of those small separate leaves, which
together compose a compound leaf.

LEAGUE. The twentieth part of a
degree of latitude, or three geographical
miles, each of which is the sixtieth part
of a degree. The French have two kinds
of league; the first consisting of 2000
toises, or 2-42 English statute miles ; the
second of 2-77 English miles, or 25
leagues to the degree ; the former is their
legal posting measure.

League, Nautical. Seamen measure
by nautical miles, 60 of which make a
degree of latitude, or a degree of longi-
tude at the equator ; and three nautical
miles make a nautical league, which is,
accordingly, 3*45 land or statute miles,
or three miles, four tenths, five hun-
dredths, which is easily remembered.

LEAP-YEAR. The name given to
every fourth year of the Julian calendar,
in which one additional day— the 29th of
193

February— is reckoned. The year is so
called, because the day of the month,
after February, leaps over a day of the
week. The reason for adding a day
every fourth year is, because the tropical
exceeds the civil year by six hours, which
excess amounts, in four years, to one
day. See Bissextile.

LEAST SQUARES, METHOD OF.
A method of finding the most probable
truth, when a number of discordant ob-
servations have been made upon a phe-
nomenon. "If three observations give
93, 94, and 98, then the mean of the three
is 95, and if this be assumed as true, it
is also assumed that the errors of the
observations were 2, 1, and 3. The sum
of the squares of these is 4+1 + 9, or 14,
and this is the least possible sum which
can be thus obtained. If, for example,
we assume any thing but 95, say 95* 1, the
assumed errors are then 2*1, l'l, and
2*9, the squares of which are 4*41, T21,
and 841, the sum of which is 1403, more
than 14."— Pen. Cycl.

LEAVEN or YEAST. A substance
which possesses the power of commenc-
ing fermentation in other substances.

LECO'NORIN. A white crystalline
substance procured from the Leconora
tartarea and other lichens, employed in
the manufacture of cudbear.

LEE. An epithet to distinguish that
half of the horizon to which the wind is
directed, from the other part where it
arises, which latter is accordingly called
to windward.

LEE'LITE. A red siliceous stone
found at Gryphytta in Westmannia, and
named from Mr. Lee of Cambridge.

LEEWARD. The lee-side of a ship is L/^C^J,
that half of a ship (divided lengthways),
which is opposite to that on which the
wind blows when it crosses her course,
and which is called the weather-side. All
objects on the lee-side are said to be to
the leeward, and those on the weather-
side to the windward of the vessel.

LEEWAY. The angle made by the line
on which the ship should run, according
to the point of the compass steered upon,
and the real line of the ship's way occa-
sioned by contrary winds, rough sea, or
the set of a current.

LEGER LINES and SPACES. In
Music, the lines and spaces which are
added to the staff, when the notes ex-
ceed the ordinary compass.

LEGU'MEN (lego, to gather). A le-
gume ; a one-celled, two-valved, superior
fruit, dehiscent by a suture along its face

LEM

LEN

and its back, and bearing seeds on each
margin of its ventral suture.

1. Legumen Lomentaceum. A lomen-
tum ; a fruit differing from a legume in
being contracted in the spaces between
each seed, and there separating into dis-
tinct pieces.

2. Legumin. A peculiar principle,
found in the fleshy cotyledons of the
seeds of papilionaceous plants.

LEGUMINO'S^E {legumen, a legume).
The Pea tribe of Dicotyledonous plants.
Herbs with leaves alternate ; stamens peri-
gynous, monadelphous, or diadelphous;
ovarium superior, solitary, simple ; fruit
leguminous ; seeds without albumen.

LEIDENFROST'S PHENOMENON.
If water in minute quantities be placed
on a red-hot plate, it will not boil, nor
evaporate quickly, but, as the metal be-
gins to cool, the liquid assumes a globular
figure, and exhibits a rotatory and oscil-
lating movement, during the continuance
of which the process of evaporation is
carried on much less rapidly than during
ebullition. When the metal has cooled
down to a still lower degree, the liquid
boils with great violence, and is dispersed
in every direction.

LEIOTRICHA'N^E. Silky chatterers ;
a sub-family of birds, in the system of
Mr. Swainson, belonging to the Ampelidce,
or Chatterers, and named from the genus
Leiothrix.

LEMMA {\r\nna, any thing taken or
received). A proposition introduced
merely for the purpose of establishing
some more important proposition. Thus,
in a treatise on mechanics, if it were
necessary to prove certain propositions
of geometry, those propositions would be
lemmas. In Logic, a lemma is an as-
sumption or premiss taken for granted.

LEMNIAN EARTH. A compound of
aluminum, found in the island of Lemnos.
It is also called sphragide (cr^payir, a seal),
and terra sigillata, from its being cut
into pieces, and stamped with a seal. It
is similar to Armenian bole.

LEMNI'SCATA {XnpviaKot, a rib-
and). In Geometry, a curve of the
fourth degree, having the form of the
figure 8, and of which the equation is
x* + y2= a\/x2—y*. It is the locus of
the point in which a tangent to an equi-
lateral hyperbola meets the perpendicu-
lar on it drawn from the centre. There
are many other curves of the same order
with a similar form, but their equations
differ from the above.

LEMNI'SCUS. The Latin term for
194

riband ; and, hence, applied to the minute
riband-shaped appendages of the genera-
tive pores in Entozoa.

LEMU'RIDjE. A family of quadru-
manous animals, named lemurs which
supply the place of monkeys in Mada-
gascar and some parts of Africa and
India.

LENGTH OF SHELLS. Spiral shells
are measured from the tip of the spire to
the base, and therefore perpendicularly.
The length of bivalves is taken horizon-
tally; thus, the solens is the longest
shell of this tribe, the length being taken
from the anterior to the posterior margin.

LENS (lens, a bean). Properly, a small
roundish glass, shaped like a lentil, or
bean. In physics, the term is applied to
any transparent medium, the essential
character of which is, that it shall refract
the rays of light, so that the divergence,
or convergence, of those rays shall be
equally produced after their passage
through the lens.

1. The usual forms and names of lenses
are the convex, which converges the rays ;
the concave, which disperses them ; the
plano-convex, having one surface plane,
and the other convex ; the double convex,
having both sides convex ; the plano-
concave, having one surface plane, and
the other concave; the double concave,
having two concave surfaces ; and the
meniscus, having one side concave, and
the other convex.

2. The point where no refraction is
produced on perpendicular rays, is called
the axis of the lens, which is a right line
passing through its centre, and perpendi-
cular to both its surfaces. In every beam
of light, the middle ray is called its
axis. Rays of light are said to fall di-
rectly upon a lens, when their axes coin-
cide with the axis of the lens ; otherwise
they are said to fall obliquely. The point
at which the rays of the sun are collected,
by passing through a lens, is called the
principal focus of that lens.

3. Lens, Coddington. A well-known
lens, consisting of a sphere of glass
divided into two portions by a deeply cut
circular groove, which is filled up with
opaque matter. The lens of the cuttle-
fish is a precisely similar instrument.

LENTICE'LL^ffi. Lenticular glands,
or brown oval spots found upon the bark
of many plants, especially willows. They
are considered by De Candolle to bear the
same relation to roots as buds bear to
young branches.

LENTI'CULAR (lenticula, a little

LEP

LEU

lens). Lens-shaped ; small, depressed,
and doubly-convex, as the seed of ama-
ranth.

LENTIL-ORE. An arseniate of cop-
per, also called the lenticular arseniate.

LE'NZINITE. A silicate of alumina,
found at Eifeld in Prussia, and distin-
guished into the opaline and the argilla-
ceous varieties.

LEO WITH COMA BERENICES.
The fifth of the zodiacal constellations,
containing 95 stars, of which Regulus is
the principal. It indicates the second
month of winter, and extends from the
20th of January to the 20th of February.
In Egypt the earth assumes its most
beautiful aspect in the month of Fe-
bruary; a part of the harvest is already
begun. The king of animals was chosen
to typify the strength and the magni-
ficence of nature at this period.

LEO MINOR. A modern northern
constellation, containing fifty-three stars.
LE'PADITES. A designation of the
reputed bivalvular opercula of am-
monites, found at Solenhofen, and also
termed trigonellites, solenites, and apty-
chus.

LE'PADOIDS. A group of Cirrho-
pods, named from the typical genus
lepas, and commonly known by the name
of barnacles. They are distinguished by
their pedunculated character from the
other group, or balanoids, which are
sessile.

LEPIDODE'NDRON {Xenk, Xeirtdot,
a scale, devdpdv, a tree). A genus of
fossil plants of the coal measures, inter-
mediate in character between the Lyco-
podiums and coniferous plants; they ap-
pear, from their great abundance, to have
contributed in large proportion to the
solid matter of coal. The name is de-
rived from the trunk of the tree being
marked along its whole length with
scales or scars.

LE'PIDOLITE (XeffJc, a scale, A/0o?,
a stone). A name for several beautiful,
variously-coloured, scaly varieties of
lithia-mica, some of which are, however,
referable to the silicates combined with
fluorides. They are found at Rozna in
Moravia, and other places.

LEPIDO'PTERA {Xewlt, Xeiridos, a
scale, 7TT€p6v, a wing). An order of in-
sects which have four membranous and
scaly wings, and undergo complete meta-
morphosis, as the butterfly, the moth, &c.
All the Caterpillars are the larvae of lepi-
dopterous insects.
LE'PIDOTE (AeTTi?, a scale). Le-
195

prous ; covered with minute peltate
scales, as the leaf of elaeagnus.

LEPI'SMAD,E. A family of wingless
insects, belonging to the order Thysa-
noura, in which the abdomen is termi-
nated by long jointed bristles, as in the
sugar-louse.

LE'PORIDjE (lepus, a hare). The
Hare tribe; a family of the Rodentia,
distinguished from all the other families
by the presence of two small incisors be-
hind the rodent teeth. The hare is a
ruminating animal, though destitute of
the complex stomach of the ruminantia.
LE'PTIDES. A sub-family of dipte-
rous insects, of the family Brachystoma,
named from the genus leptis.

LEPTOPHPNA. A sub-family of ser-
pents, belonging to the family Colubridae,
and comprising the genera leptophis and
dryinus.

LEPUS. The Hare, a southern con-
stellation, containing nineteen stars.

LERNjEIFO'RMES. An order of the
edentulous crustaceans, in which the
extremities are but little developed, and
the body presents great variety of form.

LETTERS FOR STARS. Towards
the end of the sixteenth century, Bayer
published the first charts in which the
stars were not only constellated, but dis-
tinguished in their constellations by
letters. Beginning with the Greek alpha-
bet, he put a to the star which he con-
sidered brightest, /3 to that which was
next in brightness, and so on throughout
the constellation, using the Roman letters
when the Greek were exhausted. His
successors added more letters, frequently
going through both the Greek alphabet
and the Roman, where Bayer had ex-
hausted only a part of the Greek, and
sometimes even adding another alphabet
of capital Roman letters.

LEUCIN (Aev*co9, white). A peculiar
white principle obtained from muscle.
Nitric acid converts it into a crystalliz-
able acid, called nitro-leucic.

LEU'CITE (Aei/Kop, white). Amphi-
gen. A mineral allied to felspar, found
chiefly at Vesuvius, in separate crystals
of various sizes and degrees of trans-
parency, massive, embedded in pyroxenic
and other lavas.

LEUCOL. A particular substance
produced in the distillation of coal.

LEU'TTRITE. A greyish-white mine-
ral found at Leuttra, near Jena in Sax-
ony. It appears to be a recomposed
rock, analogous to some of the sandy
varieties of domite.

K2

LEV

LIB

LEVEL. Two points on the surface
of the earth are said to be on the same
level, where they are equally distant from
the earth's centre. A level surface, there-
fore, is not a plane, but a portion of a
spherical surface; and this is the form
which a sheet of water, or any other
liquid, naturally assumes.

Horizontal and dead level. There are
various instruments used in levelling,
which are called levels. These all give a
horizontal level, that is, a tangent to the
earth's surface ; and in the case of a
drain or canal, the bottom of the exca-
vation must be carried lower than the
level indicates, otherwise the water would
not run. The declivity must be in a
circle equivalent to that of the earth's
circumference before the water could
reach it, and this would then be termed
a dead level.

LE'VER (levo, to raise). A physical
or compound lever is any inflexible rod or
solid body whatever, supported on one
point, and acted on at two other points,
by two forces tending to move it in oppo-
site directions about the point of support.
The two forces acting on the lever are
called the power and the weight, and the
point on which the lever is supported, or
about which it turns, is called the ful-
crum. The power of this instrument
depends on the proportion between the
lengths of the parts of the lever on each
side of the fulcrum.

1. Lever, one, or two-armed. 1. In the
one-armed lever, the power and the
weight are both on one side of the ful-
crum, as in the common wheel-barrow.
2. Tn the two-armed lever, the fulcrum
is between the power and the weight,
being either equidistant from the two
forces, or nearer to one of the forces than
to the other.

2. Levers are rectilinear or curvilinear,
according as their arms are straight or
curved lines. A lever is angular, when
the arms form an angle, in which case
the fulcrum is at the vertex of the
angle.

3. Lever, Universal. An instrument
constructed by combining the lever with
the wheel and axle; its object is to give
a continued rectilinear motion to a heavy
body, by means of the reciprocating
motion of the lever.

LEVIGATION (Icevigo, to polish ;
from Icevis, smooth). The process of
rubbing earths and some metallic sub-
stances with a muller upon a flat table
of hard stone. Some fluid is added to
196

assist the operation, and in this respect
it differs from trituration.

LE'VINE. A scarce zeolitic sub-
stance, occurring in the cavities of an
amygdaloid rock, at Dalsnypen in Faroe.

LEY. Lixivium. A technical term
for a solution of alkali in water.

LEYDEN JAR. An apparatus for
accumulating and condensing electricity,
constructed on the principle that the oppo-
site electricities may be held in a latent
state. It consists of a cylindrical glass-
jar coated to a certain height, inside and
outside, with tinfoil, so that every point
of both sides of the glass may be brought
into communication at the same moment.
To convey the fluid to the interior of the
jar, a brass wire runs through its lid, the
upper end terminating in a ball, and the
lower end, divided into several fine points,
touches the foil within the jar. A com-
bination of such jars is called an electri-
cal battery.

LHF/RZOLITE. A mineral consist-
ing of coccolite mixed with serpentine.

LIAS. A subdivision of the Oolitic or
Jurassic system of Geology, consisting of
a great argillaceous deposit with some
thick arenaceous bands, and many con-
cretions and beds of argillaceous lime-
stone. It is continued without interrup-
tion from the coast of Dorsetshire to the
north-east coast of Yorkshire. The term
lias is supposed to be derived from the
appearance of the bed in riband-like
layers of different colours, observed in
some parts of England.

LIBELLU'LIDiE {libellula, the dra-
gon-fly). A group of neuropterous in-
sects, which are aquatic in their prepa-
ratory states, and emerge from the water
at the period of their final metamor-
phosis.

LIBER. The inner bark of a tree,
used instead of paper by the ancients to
write upon. In botanical language, it
denotes the interior fibrous portion of the
bark, lying immediately upon the albur-
num ; the endophloeum of later writers.
See Bark.

LIBRA. The Balance; the seventh
of the zodiacal constellations, consisting
of fifty-one stars, the principal of which
is Zubenich Meli. It denotes the first
month of spring, and extends from the
20th of March to the 20th of April. This
month answers to the vernal equinox
and the equality, or balance, of the days
and nights.

LIBRA'TION {libro, to balance). A
slight swaying motion, like that of a

LIE

LIG

balance. The expression is applied by
astronomers to an apparent oscillation of
the moon, in consequence of which she
exhibits sometimes a little more, some-
times a little less, of one side or the
other.

1. Libration in Longitude. The phe-
nomenon by which the moon, during the
period of acceleration, exhibits on the
east some portion of her surface not
previously seen, whilst corresponding
parts disappear on the west. The converse
of this takes place during retardation.

2. Libration in Latitude. The pheno-
menon by which the moon, in conse-
quence of her axis of rotation being in-
clined to her orbit, and of its always
preserving its parallelism, turns each of
her poles to us alternately, and displays
to us the spots situated about it.

3. Diurnal Libration. The phenome-
non by which the moon, when on the
horizon, presents some parts the more
of one side, and a corresponding portion
the less of the other side. This is in
consequence of the spectator being re-
moved from the centre of the earth
(towards which the same hemisphere of
the moon is constantly turned) by the
length of the earth's radius.

LICHE'NES. The Lichen tribe of the
Aphyllae, or leafless plants. Aerial, leaf-
less, perennial plants, spreading over
almost all dry surfaces, of trees, stones,
&c. ; reproductive organs are sporules
lying in thecae in the medullary sub-
stance, or separated cellules of the me-
dullary layer of the thallus.

LFCHENIN. Lichen starch ; a pecu-
liar vegetable product, obtained from the
cetraria islandica, or liverwort ; it is said
to combine, like the alkalies, with acids,
but it does not form crystallizable salts
with them.

LICHTENBERG'S FIGURES. The
phenomena observed on discharging a
positive spark and a negative spark on
different parts of the same polished re-
sinous surface ; the two electricities will
be retained, in a latent state, on their re-
spective spots. If the surface be now
sprinkled with flowers of sulphur, the
powder will be attracted and retained by
the electricities; and, if the rest of the
powder be blown away, a radiant star-
like figure will be found at the positively
electrified spot, and a round clouded
speck at the spot which wa3 negatively
electrified.

LIE'VRITE. A pyroxenic mineral,
also called ilvaite and yenite, occurring in
197

particularly perfect crystals, chiefly from
Elba.

LFGAMENT (ligo, to bind). An ex-
ternal substance, by which the two valves
of acephalous testacea are united, and
which, in fact, is the true hinge. The
internal part is generally composed of
another substance, and is called the car-
tilage.

LIGHT. The agent of vision, or the
cause of those sensations and colours
which we refer to the eye, or sense of
seeing, as their source. It is distin-
guished into two kinds; viz. natural
light, proceeding from the sun and stars ;
and artificial light, proceeding from
bodies which are strongly heated, and
thus become incandescent.

1. A ray is a single line of light, as it
comes from a luminous body. A beam
of light is a body of parallel rays. A
pencil of light is a body of diverging or
converging rays. Divergent rays are
such as come from a point, and con-
tinually separate wider apart, as they
proceed. Convergent rays are those which
approach each other, so as to meet at a
common point. Luminous bodies emit
rays, or pencils of light, in every direc-
tion, so that the space through which
they are visible is filled with them at
every possible point.

2. Light barometrical. A luminous
appearance exhibited in the vacuum of
some barometers, when the mercury is
shaken in the dark— a phenomenon pro-
bably depending on electricity.

LIGHT-EQUATION. Roemer ob-
served that the eclipses of the satellites
of Jupiter, which occurred at and about
the opposition of the planet, or its nearest
point to the earth, took place too soon
for his calculation ; whereas those which
happened when the earth was in the
part of its orbit most remote from Jupi-
ter, were always too late. The cor-
rection required in consequence of the
time employed by light in traversing
the solar system, is called the light-equa-
tion.

LIGHTNING. A phenomenon usually
referred to the accumulation of sensible
electricity in the atmosphere, and its
consequent neutralization : a strong elec-
tric spark traverses a stratum of air
intervening between oppositely electrified
clouds, or between a cloud and the earth's
surface. See Conductors Metallic.

LI'GNIN (lignum, wood). The basis
of woody fibre— the most durable product
of vegetation. When heated in close
K3

LI M

LI N

vessels, it yields pyro-ligneous acid; and
a peculiar spirituous liquor is produced,
called pyro-xylic spirit.

LIGNIPE'RDOUS {lignum, wood,
perdo, to destroy). A term applied to
insects which destroy wood.

LI'GNITE (lignum, wood). A variety
of coal, of a brown, dull, compact, or
laminated appearance, often woody, burn-
ing with flame and smoke.

LI'GNONE (lignum, wood). Xylite.
A liquid which exists in commercial
pyroxylic spirit, — a product of the dis-
tillation of wood.

LI'GNUM. Wood; that portion of
arborescent plants which comprises the
alburnum and the duramen.

LI'GULA. A peculiar membranous
process at the top of the sheath in grasses,
between the sheath and the blade.

LI'GULATE FLOWERS (ligula, a
strap). Strap-shaped flowers, or those
which have a gamopetalous corolla slit on
one side, and opened flat, as in many of
the composite plants.

LI'GURITE. A silicate of alumina,
lime, and magnesia, found in a talcose
rock on the banks of the Stura in the
Apennines. It is reckoned superior to
the chrysolite as a gem, in colour, hard-
ness, and transparency.

LILIA'CEjE. The Lily tribe of Mo-
nocotyledonous plants. Bulbous, tuber-
ous, creeping, or arborescent plants;
calyx and corolla inferior, coloured, regu-
lar ; stamens 6 ; anthers opening in-
ward ; fruit 3-celled.

LILY ENCRINITE. A radiated ani-
mal occurring in the seas of the new red
sandstone, enclosed within a stony habi-
tation, said to consist of nearly thirty
thousand separate pieces, and planted
upon a stony but moveable column,
nearly cylindrical, and attached at its
base to the solid rock. See Encrinites.

LIMACI'NjE. Slugs ; a sub-family of
the Helicidce, named from the genus
Umax, and having either no shell, or one
much too small to contain the body.

LIMB. A term applied to the curved
edge of a circle, as the graduated limb of
a quadrant. In Astronomy, it denotes
the outermost border of the sun or moon ;
thus, it is usual to speak of the moon's
lower or upper limb, and even of her
eastern or western limb ; and especially,
in the case of an eclipse, when a portion
of her disc is obscured.

LI'MBILITE. A compact mineral,
found in the form of irregular grains in
the volcanic hill of Limbourg.
198

LIME. The oxide of calcium ; an al-
kaline earth, found as a carbonate in
marble, chalk, and limestone. These
substances become lime, when burned in
a white heat. Quick lime is limestone
which has been burned, and acquired
new properties. Slaked lime is the pow-
der produced by pouring water upon
quicklime ; this is a hydrate, and, when
diffused through water, yields the sub-
stance called milk or cream of lime.

LIMESTONE. A designation of the
various modifications of calcareous rocks,
consisting of carbonate of lime. The
principal kinds are the primary or crys-
talline, the secondary or compact, the
oolite, chalk, &c. Saccharine limestone
is a term applied to a few small beds oc-
curring in the inferior stratified series of
rocks, from its resemblance to refined
sugar; it is sometimes called primitive
limestone, from the period of its occur-
rence in this series.

LIMIT (limito, to bound). A bound-
ary. But the term limit is employed in
the sciences in a wider sense. There are
certain effects in Natural Philosophy, as
well as quantities in Mathematics, which
cannot be determined with accuracy;
but, in many of these cases, we may fix
a, point which that effect or quantity must
certainly exceed, and another at which
it cannot possibly arrive. These points
are the limits of the problem. Thus,

1. We cannot predict the exact height
at which the mercury will stand, at the
level of the sea, in a barometer, on any
future day; but we may assert, from
past e-perience, that it will be some-
where between twenty-eight and thirty-
one inches. So also,

2. We cannot determine exactly the
length of the circumference of a circle ;
but we are certain that it is greater than
that of any inscribed polygon, and less
than that of any circumscribed one, how-
ever numerous their sides may be.

LIMNACI'NiE. River-snails ; a sub-
family of the Helicince, named from the
genus limnea, and having only two de-
pressed or flattened tentacula, and no
operculum.

LIMNiE'ID-ffi (Xifjivt), a marsh). A
family of fresh-water testaceous mol-
lusca, consisting of the genera limncea,
physa, and planorbis. Lamarck defines
them as amphibian trachelipods, gene-
rally inoperculate, with flattened tenta-
cula, and a spirivalve shell.

LINA'CEjE. The Flax tribe of dico-
tyledonous plants. Herbaceous plants,

LIN

LIT

with leaves usually alternate ; flowers sym-
metrical, polypetalous ; stamens hypo-
gynous ; ovarium entire, many-celled;
seeds compressed and inverted.

LINE. Euclid defines a mathematical
line as that which has " length without
breadth." This, however, is a pure ab-
straction, and can be only mentally con-
ceived by the aid of another abstraction :
thus, if a mathematical point be imagined
to move in space, and to mark its course
by a trace or track, this trace or track
will be a mathematical line. Such a line
is the boundary of a surface, having
length only. A right line, or straight
line, is that which lies evenly between
its extreme points. Any line of which
no part is a right line, is called a curve.

LINEAR EQUATION. An equation
of the first degree; in other words, an
equation connected with straight lines.

LINNjE'AN SYSTEM. A method of
classifying plants, introduced by Lin-
naeus, and founded on modifications of
the sexual apparatus. See Botany.

LIPS OF SHELLS. The two sides of
the aperture of spiral shells are termed
the lips. That which joins, and gene-
rally folds over, the lower part of the
columella, is called the inner lip, while
that part of the circumference which is
opposite is the outer. The latter, of
course, is found in all shells, because it
is the termination of the last whorl ; but
the former is frequently absent, or indi-
cated merely by a thin, whitish, almost
transparent enamel.

LIQUA'TION {liquo, to melt). Eli-
quation. An old process for separating
silver from copper. During reduction,
the silver is mixed with lead, which has
little affinity for the copper, but combines
readily with the silver ; the lead is then
separated from the silver by cupellation.

LIQUEFACTION (liquefacio, to melt).
The passing of a substance from the solid
to the liquid state— one of the effects of
caloric. The term is sometimes syno-
nymous with fusion, with deliquescence,
and with solution.

LIQUID {liqueo, to melt). An ine-
lastic fluid, the particles of which move
on each other, and yield to the slightest
impression. All liquids may be arranged
into two great classes, viz. simple liquids,
as mercury, and compound liquids, as
combined gases, &c.

LI'THARGE (X/0o?, a stone, apyvpo?,
silver). A semi-crystalline protoxide of
lead, obtained in the process of sepa-
rating silver from lead ores. Litharge
199

is more or less white or red according to
the metals with which the silver is al-
loyed, the white being called litharge of
silver, the red litharge of gold.

LITHIA (XiOos, a stone). The pro-
toxide of lithium; an alkaline oxide
existing in certain minerals, and in the
waters of Carlsbad, in combination. Its
name is derived from its occurring only
in the mineral kingdom.

LITHIC ACID (,\i'0op, a stone). Uric
acid. A principle constantly present in
healthy urine, and generated by the
action of the kidneys.

LFTHIUM (\i0os, a stone). A metal
first found in the minerals petalite and
spodumene, and more recently in ambly-
gonite and lepidolite, where it exists in
combination with silica.

LITHO'DOMI {XiOoi, a stone, dep.<a,
to build). Molluscous animals which
form holes in solid rocks, in which they
lodge themselves. The holes are not
perforated mechanically, but the rock
appears to be dissolved.

LITHO'GENOUS (Ai'flor, a stone, yev-
vctco, to form). A term applied to polyps
which form coral.

LITHOGRAPHIC STONE (\i9os, a
stone, 7pa0o>, to write). A slaty com-
pact limestone, of a yellowish colour and
fine grain, used in lithography.

LITHOI'DAL (\i6os, a stone, ei3oy,
likeness). Having a structure resembling
stone.

LITHOLO'GICAL (\t'0oc, a stone, \6-
70?, an account). A term denoting the
stony structure or character of a mineral
mass. The lithological character of a
stratum is distinguished, in the language
of geology, from its zoological character.

LI'THOMARGE. Steinmarck. Stone-
marrow, a mineral which has been asso-
ciated with steatite, although most of its
varieties are silicates of alumina ; the
more remarkable of which are, that of a
reddish-yellow colour in porphyry, from
Rochlitz, and the fine purplish-blue va-
riety from Planitz, formerly called terra
miraculosa Saxonica, &c.

LITHO'PHAGI (Xiflot, a stone, <pdyia,
to eat). Molluscous animals which form
holes in solid stones. See Lithodomi.

LITHOPHA'GIDjE (\ieos, a stone,
<pdy<a, to eat). A general designation of
those conchiferous and other animals,
which perforate stones or corals, forming
therein a nidus, or shallow basin-like
lodgment for themselves.

LITHO'PHYTA (\iOos, a stone, (pvrov,
a plant). A designation of those polyps
K4

LIT

LOC

which have a stony axis, as distinguished
from the keratophyta, or horny polyps.

LITMUS. Turnsol, A blue pigment
obtained from the Lichen orcella, and
employed by chemists for detecting the
presence of an uncombined acid. Litmus
paper is prepared by digesting pow-
dered litmus in water, and painting
with it white paper which is free from
alum.

LI'TUUS. The name given to a spiral
thus described :— Let a variable cir-
cular sector always have its centre at
one fixed point, and one of its termi-
nal radii in a given direction. Let the
area of the sector always remain the
same; then the extremity of the other
terminal radius describes the lituus.
The polar equation of this spiral is
r* 0 = a.— Pen. Cycl.

LIVER-ORE. Hepatic mercurial ore.
A mixture of cinnabar with bituminous
and earthy particles, from Idria, compact
and slaty.

LIVER-PYRITES. Sulphuret of iron,
of a radiated texture ; distinct from the
fer sulphure hepatique of some French
mineralogists, which cousists of both ra-
diated and common iron-pyrites con-
verted into brown iron-stone.

LIXIVIA'TION {lixivium, a ley). The
application of water to a saline body
which consists of both soluble and inso-
luble ingredients. The solution obtained
is the lixivium, or ley, — a term used by
the older chemists to signify a solution of
an alkali in water ; what is now called
an alkaline solution, being formerly
called an alkaline lixivium or ley.

LLANDEILO FLAGS. The name of
one of the Lower Silurian Rocks, con-
sisting of a bed, 1200 feet in thickness,
of hard, dark-coloured, slaty sandstones,
frequently calcareous, sometimes slightly
micaceous, containing mollusca and tri-
lobites.

LOADSTONE. An ore of iron which
possesses the peculiar properties of at-
tracting iron, and of turning towards the
north pole, when freely suspended. M.
Haiiy observes, that the ores in which
the iron contains the least oxygen inde-
pendently of other combinations, form
natural magnets ; and he terms the load-
stones of commerce, found in different
parts of the world, oxidulated iron. The
properties of the natural loadstone may
be communicated to iron and steel, which,
when properly prepared and touched by
the loadstone, are called artificial mag-
nets. See Magnet.
200

LOAM. A soil consisting chiefly of
clay, silicious sand, and chalk, or car-
bonate of lime. The quality of a loamy
soil varies considerably with the relative
proportions of these constituents.

LOAM or BRICK CLAY. A variety
of clay of variable appearance, its colour
depending on the proportion of oxide of
iron which it contains. It lies upon the
London clay, and contains a few organic
remains, sometimes the teeth of the ele-
phant. The Hedgerley loam, found near
Windsor, is used in making lutes, &c.

LOBELIA'CEiE. The Lobelia tribe
of dicotyledonous plants. Herbaceous
plants or shrubs, with leaves alternate ;
flowers axillary or terminal; stamens
syngenesious ; ovary inferior ; fruit cap-
sular.

LO'BOITE. A magnesian idocrase
occurring in Norway.

LOCOMO'TIVE {locus, place, moveo,
to move). A term generally expressive
of motion attended by a change of place,
and thus opposed to stationary: thus, a
locomotive power, or engine, is any power
or engine employed for transport, which
travels with the load it draws.

LOCULICI'DAL {loculus, a cell, ccedo,
to cut). That mode of dehiscence of
fruits, in which the loculi, or cells, are
severed at their backs, as in lilac. The
older botanists described it as dehiscence
with the valves opposite to the dissepi-
ments.

LO'CUS. The Latin word for a place.
In geometrical analysis, it denotes a line
or surface traversed by a point which va-
ries its position according to some deter-
minate law. 1. The locus of the vertex
of an isosceles triangle described upon a
given base, is the straight line which bi-
sects the base at right angles. 2. The
locus of the vertex of a triangle which
has a given base and a given area, is a
pair of straight lines parallel to, but on
different sides of, the base. 3. The locus
of the vertex of a triangle which has a
given base and a given vertical angle,
and which lies on a given side of the
base, is an arc of a circle of which the
given base is the chord.

1. Plane and Solid Loci. "When the
locus of the variable point is a straight
line or a circle, it was called by the an-
cient geometers a plane locus ; when one
of the conic sections, a solid locus.

2. Orders of Loci. Loci are distin-
guished into orders or degrees, according
to the dimensions of the algebraic equa-
tions by which they are represented.

LOC

LOG

The loci of all equations of the second
degree are conic sections or circles.

LOCU'STA. In Botany, a spikelet, or
the partial inflorescence of certain grasses,
as the brome and the wheat. This term
is also applied to those other inflores-
cences, in which the flowers are sessile,
and arranged upon a lengthened axis,
which is permanent ; it is thus distin-
guished from the catkin, which is deci-
duous.

LOCU'STIC ACID. An acid procured
from the locusta, or grasshopper, differ-
ing little from acetic acid.

LOCU'STID^E {locusta, a locust). The
Locust tribe; a group of Orthopterous
insects, belonging to the class Saltatoria,
remarkable for their migratory habits
and devastating powers.

LODE. A technical term for a metallic
or mineral vein. Live lodes are those
which contain metallic ores ; dead lodes,
those which contain only stony matters.

LOESS, or LOSS. A German desig-
nation of a peculiar loamy deposit in the
valley of the Rhine, occurring in patches
between Cologne and Basle. The term
is sometimes applied in this country to
a peculiar yellow loam with calcareous
concretions. >

LOG and LOG-LINE. The Log, in
sea-language, is the name of a piece of
wood in the form of the sector (usually a
quadrant) of a circle of Ave or six inches
radius. It is about a quarter of an inch
thick, and so balanced by means of a plate
of lead nailed upon the circular part, as to
swim perpendicularly in the water with
about two-thirds immersed under the
surface. The Log-line is a small cord of
about one hundred fathoms in length,
one end of which is fastened (by means of
two legs) to the centre and to the arched
part of the Log, while the other is wound
round a reel in the gallery of the ship.
The Log thus poised keeps its place in
the water while the line is unwound from
the reel by the ship's sailing; and the
length of line unwound in a given time
gives the rate of the ship's course. This
is calculated by knots made on the line
at between forty and fifty feet distance,
while the time is measured by a sand-
glass of a certain number of seconds.
The length between the knots is so pro-
portioned to the time of the glass, that
the number of knots unwound shows the
number of miles which the ship is sailing
in the hour.

LO'GARITHM (\6yo?, a ratio, 3p<0-
/uor, number). Logarithms are a series
201

of numbers adapted in a certain way to
a series of natural numbers, to facilitate
the processes of numerical computation.
A simple idea of this system may be ac-
quired by taking a set of numbers, as
1, 2, 3, 4, 5, 6, having for their common
difference the first number of the series ;
and placing under them another set of
numbers, which proceed by continued
multiplication by the first number of the
series, as 2, 4, 8, 16, 32, 64. The former
set are the logarithms of the latter, which
are called natural numbers. Thus,

1, 2, 3, 4, 5, 6, &c.

2, 4, 8, 16, 32, 64, &c.

1. If now we add together any two of
the upper set, and note the number be-
neath their sum in the lower set, this
number represents the product arising
from multiplying together the numbers
of the lower set corresponding with the
numbers of the upper set which were
added together. Thus, on adding 2 to 4,
we have 6 in the upper set, beneath
which is 64 ; and this is the product of
4 and 16 in the lower set, opposite to 2
and 4 in the upper. So that, instead of
multiplying the natural numbers, we add
their logarithms together, and at once find
the product.

2. In like manner, if we subtract one
of the upper numbers from another, and
note the number beneath their difference
in the lower set, this number represents
the quotient arising from the division of
one of the lower numbers by another,
both corresponding with the upper num-
bers which were subjected to the process
of subtraction. Thus, on subtracting 4
from 6, we have 2 in the upper set, be-
neath which is 4 ; and this is the quotient
arising from the division of 64 (the num-
ber beneath 6) by 16 (the number beneath
4). So that, instead of dividing the natu-
ral numbers, we subtract their logarithms,
and at once find the quotient.

3. By the aid of logarithmic tables,
time and labour are saved to an extraor-
dinary degree. Supposing, for instance,
we had to multiply a number, consisting
of seven figures by itself, and this pro-
duct again by the original number, we
shall have to multiply seven places of
figures by an equally large number, and
then fourteen places of figures by seven
places, till at last we reach a product
of twenty-one places. But, by the aid of
logarithms, we have only to take three
times the logarithm of the original num-
ber, and that gives the logarithm of the

KS

LOG

last product of the 21 places of figures,
without any further multiplication.

4. The index or characteristic of the
logarithm of a number is one less than
the number of integral figures of the
number. Thus, if the number contain
five integral figures, the index is 4 ; if it
contain four,. the index is 3; and so on.
When the number has no integral figures,
the index of its logarithm is negative,
and is one more than the number of ci-
phers immediately after the decimal
place; that is, the number of prefixed
ciphers. Thus, if there is no cipher after
the decimal, the index is — 1 ; if there is
one prefixed cipher, the index is — 2 ; and
so on. The negative sign is placed over
the index, thus : ~T, ~2, &c.

5. The logarithm of a number to a given
base is the quantity expressing the power
to which the base must be raised to be-
come equal to the number.

6. Logarithmic Curve and Logarithmic
Spiral. " The former has for its rectan-
gular equation y = ax, and its most re-
markable property is that its subtangent
is the same at every point of the curve.
The latter has r = ca® for its polar equa-
tion, and its tangent always makes the
same angle with its radius vector ; whence
it is called the equiangular spiral." — Pen.
Cycl.

LOGIC (\oytKtj Te%vfi, the art of rea-
soning). Logic, in its most extensive
application, is the science, as well as the
art, of reasoning. So far as it institutes
an analysis of the process of the mind in
reasoning, it is strictly a science; while,
so far as it investigates the principles on
which argumentation is conducted, and
furnishes rules to secure the mind from
error in its deductions, it may be called
the art of reasoning. — Whately.

LONDON CLAY. An extensive de-
posit of a bluish clay, except near the
surface, where it has the usual appearance
of clay. It abounds in Middlesex, Essex,
Suffolk, and part of Norfolk. It occa-
sionally includes beds of sandstone, and
of a coarse argillaceous limestone, from
which Parker's Roman cement is made.
It contains also the bones of the crocodile,
the turtle, &c.

LONGICO'RNES {longus, long, cornu,
a horn). A family of the tetramerous
Coleoptera, characterized by the great
development of the antennae, which
are often longer than the body of the
animal.

LONGIPE'NNES {longus, long, penna,
a feather). A family of long-winged
202

LOO

oceanic birds, comprising the albatross,
the petrel, &c.

LONGITUDE {longitudo, length). 1.
The longitude of a heavenly body is
measured on an arc of the ecliptic, inter-
cepted between the vernal equinoctial
point and a great circle passing through
the body, and perpendicular to the
ecliptic. 2. The longitude of a place on
the earth's surface is the inclination of
its meridian to that of some fixed station
referred to as a point to reckon from.
English astronomers and geographers
use the observatory at Greenwich for this
station ; foreigners, the principal ob-
servatories of their respective nations.
The terms longitude and latitude were
employed in Geography from an idea
of the ancients that the earth was longer
from east to west than from north to
south ; the former dimension was called
its length, the latter its breadth.

1. Proposed Change of Expression. As
latitude is reckoned north or south, so
longitude is usually said to be reckoned
west or east. "It would add greatly,
however, to systematic regularity, and
tend much to avoid confusion and am-
biguity in computations, were this mode
of expression abandoned, and longitudes
reckoned invariably westward from their
origin round the whole circle from 0 to
360°. Thus, the longitude of Paris is,
in common parlance, either 2° 20' 22"
east, or 357° 39' 38" west of Greenwich.
But the latter is its proper designation."
— Herschel.

2. Longitude in Time. Longitude is
reckoned in time at the rate of 24 hours
for 360°, or 15° per hour. Thus the
longitude of Paris is 23h. 50m. 38£s.
Hence, by longitude in time is denoted
the difference in time in which two
places, situated east and west of each
other, see the same heavenly bodies : a
place 15° east of us sees the sun and
stars an hour earlier than we do ; at the
same distance west, an hour later.

LONGITU'DINAL {longitudo, length).
Lengthwise ; that which has a perpen-
dicular direction from the apex to the
base of a body, as contradistinguished
from the term "transverse," which de-
notes a direction across its breadth.

LONGITUDINAL VALLEYS. The
name given by Saussure to the great
valleys which separate the mountain-
chains, and give passage to rivers, as
that of the Danube, those of the Rhine
and the Rhone, &c.

LOOKING-GLASSES. Plain mirrors

LOP

LUN

of glass, which, being impervious to the
light, reflect the images of things placed
before them.

LO'PHIODON (\6<pos, a crest. o<3ot/?,
a tooth). A genus of extinct pachyderms,
allied to the tapir, and named from emi-
nences of the teeth. They are known
only by imperfect fragments.

LOPHOBRA'NCHII (X6</>or, a crest or
tuft, /3pa7x«*» gills). An order of Fishes,
in which the gills, instead of hanging in
regular fringes, like the teeth of a comb,
from the branchial arches, are disposed
in tufts, as in the pipe-fish, &c.

LORPCA. Literally, a coat of mail.
A kind of lute, with which vessels are
coated before they are exposed to the
fire. Hence the term lorication in che-
mistry, for coating. See Lute.

LORICA'TA {lorica, a coat of mail).
1. An order of Reptiles, including the
crocodiles, alligators, and gavials, inter-
mediate between the fresh- water tortoises,
and the true lizards, and characterized
by the plate-armour with which their
body is protected. 2. Also, a group of
polygastric animalcules, enclosed in a
shell, and thus distinguished from the
group termed nuda, in which the body is
entirely soft.

LOWER GREENSAND. The geo-
logical designation of the early deposits
of the Cretaceous Period, consisting, in
England, principally of sand, varied oc-
casionally by calcareous and muddy
bands ; but on the Continent including
many beds of limestone. See Neoco-
mian.

LO'XIKDM. The Cross-bill tribe; a
family of the Insetsores, or Perching birds,
named from the genus loxia, and charac-
terized by the strong curvature of the
mandibles, which is carried to such an
extent that the extremities pass over
each other. See Conirostres.

LOXODRO'MIC CURVE (\oS6s, ob-
lique, apogee, a course). A term applied
to a curve of a very peculiar nature,
commonly called, in Navigation, the
oblique rhumb line. It is a spiral, and
has the remarkable property of winding
round and round the pole of the earth,
constantly approaching, yet never reach-
ing it ; so that, if a ship could sail on the
same oblique course for ever, she would
approach infinitely near either to the
north or the south pole, but could never
actually reach them. See Rhumb Line.

LUCERNl'NUE. Land Volutes, or
Lamp snails ; a sub-family of the Heli-
cidce, named from the genus lucerna, and
203

having an orbicular, depressed, or flat-
tened shell, with the aperture furnished
with distinct teeth.

LUCU'LLITE. A sub-species of lime-
stone, of which there are three kinds,
the compact, the prismatic, and the fo-
liated. The name was derived from the
consul Lucullus. It is the Nero antico
of the Italians.

LUDLOW ROCKS. A portion of the
Upper Silurian rocks, 2000 feet in thick-
ness, composed of three groups : — 1. The
Lower Ludlow Rock, or Mudstone, con-
sisting of sandy, dark-coloured shales
and flags, with concretions of earthy
limestone, and containing marine mol-
lusca, corals, and fishes; 2. The Ayme-
stry Limestone, grey or bluish argillaceous
limestone, full of remains of shells and
corals; and, 3. The Upper Ludlow Rock,
thin, grey, slightly micaceous sandstones
and shales, containing shells and trilo-
bites.

LUMACHE'LLA, CARINTHIAN.
Fire marble; a variety of shell lime-
stone, much esteemed for ornamental
purposes.

LUMIE'RE CENDRE'E. The ashy
light; a term applied by the French to
the feeble lustre observable on the un-
illuminated portion of the moon, arising
from the light reflected upon her from
the earth. It is popularly called, in this
country, the old moon in the new moon's
arms.

LUNA. The Moon; the satellite of
the Earth, being the fiftieth part of the
bulk of this planet, and 230,000 miles
distant from it. She revolves round the
earth in 29 days, 12 hours, 44 minutes,
2 seconds, turning upon her own axis
precisely in the same time as she takes
to revolve round the earth.

LUNA CORNEA. Horn silver; the
chloride of silver, so named from its
horn-like appearance and consistence.
Luna was the alchemical name for
silver.

LUNAR DISTANCE. In nautical
astronomy, the distance of the moon from
the sun, a fixed star, or a planet ; by de-
termining this, the longitude of the ship
is found.

LUNATE (luna, the moon). Present-
ing the form of a crescent or half-moon,
as the muscular impressions of most
bivalves.

LUNA'TION {luna, the moon). The

interval from one new moon to another.

This is the original month, but, to avoid

confusing it with the arbitrary months

K6

LUN

MAC

of the calendar, it is generally called a
lunation.

LUNE (luna, the moon). Lunule.
The spherical surface included between
two semicircles ; or, the figure described
on a sphere or on a plane by two arcs of
circles which enclose a space.

LU'NULITES {lunula, a little moon,
XiOot, a stone). A genus of fossil cella-
riadce, consisting of animals (unknown)
contained in cellules, and arranged in
single tiers, so as to form orbicular poly-
paria.

LUPUS. The Wolf; a southern con-
stellation, consisting of twenty -four stars,
and represented in maps as a wolf trans-
fixed by the spear of the Centaur. It is
situated directly beneath Scorpius.

LUSTRE of ROCKS. This is one of
the distinguishing characters of rocks.
According to Mac Culloch, the highest de-
gree of lustre is the plumbaginous, or
that of graphite or black lead, which is
seen in some clay-slates. The other ex-
treme is that of chalk, which is dull, or
almost destitute of lustre. The principal
intermediate kinds are the silky, resin-
ous, vitreous, flinty, and waxy.

LUTE. A compound paste, made of
clay, sand, &c, for closing retorts and
receivers, in order to render them air-
tight.

LYCOPODIA'CEjE. The Club-moss
tribe of flowerless plants, characterized
by their creeping stems, the axis abound-
ing in annular ducts. Reproductive or-
gans are axillary sessile thecse, containing
either minute powdery matter, or sporules
marked at the apex with three minute
ridges.

LYCO'PODITES. A general term for
those fossil plants which correspond in
some of their characters with some of the
genera composing the Lycopodiacese.

LYDIAN STONE. Flinty slate; a
kind of quartz or flint, allied to horn-
stone, but of a greyish black colour. .

LYE or LEY. A solution of potass, or
other alkaline substance, used in the
arts. See Lixiviation.

LYMPH (lympha, water). A colour-
less liquid which moistens the surface of
cellular membrane. The lymph of plants
is the unelaborated sap, so called from
its resemblance to water.

M

MAASTRICHT ROCKS. These rocks
are considered by geologists as an upper
part of the chalk formation ; and then-
place in the scale of strata is in imme-
diate superposition above the chalk of
England, and at some small interval be-
low the calcaire grossier of the Paris
basin.

MACE. The external envelope of the
seed of the myristica moschata, affording
an interesting example of an arillus, or
expansion of the placenta.

MACERA'TION (macero, to make
soft by steeping). The steeping of ani-
mal or vegetable substances in a cold
liquid, for the purpose of softening the
parts previously to distillation, or for
that of dissolving their aromatic prin-
ciples.

MA'CHINA PNEUMA'TICA. The
Pneumatic Machine ; a modern southern
constellation, consisting of three stars.

MACHINE {machina, a frame or con-
trivance). Any instrument by which
power, motion, or velocity, is applied or
regulated. The force which puts a ma-
chine in motion is called the first or
prime mover. The point at which that
204

force is applied is the acting point; and
that at which the effect is produced is
the working point; the machine being
the medium through which the power is
transferred, and by which it is modified
so as to answer the intended purpose.
When a simple body is the medium be-
tween the acting and the working points,
it is an instrument.

MACI'GNO. The Italian term for a
hard siliceous sandstone, sometimes con-
taining calcareous grains, mica, &c.

MA'CLE. Chiastolite. A mineral found
imbedded in clay-slate, in the Pyrenees,
and consisting principally of silica and
alumina.

MACLU'REITE. Chondrodite or bru-
cite. A mineral substance consisting of
a silicate of magnesia with other matters,
occurring in New Jersey and at Pargas
in Finland, and named after Dr. Maclure.

MACQUER'S SALT. Neutral arseni-
cal salt ; super-arseniate of potass.

MACROCEPHALOUS (MaKP6p, large,
K€(pa\rj, the head). Large-headed; a
term applied by Richard to those dico-
tyledonous embryos, in which the two
cotyledons cohere, as in horse-cheatnut.

MAC

MAG

Gartner terms these embryos pseudo-
monocotyledonous,

MA'CROCOSM (/laKpo?, large, Ko<rjuo9,
the world). A term employed as synony-
mous with universe; while microcosm
has been used by some philosophers as
a designation of man.

MACRODA'CTYLES (/jLanpos, large,
ddnTv\os, a finger or toe). A tribe of the
Grallatores, or wading birds, charac-
terized by the extreme length of their
feet.

MACRO'PODAL (juaxpo?, large, ttovs,
7Tod6?, a foot). Large-footed; a term
applied by Richard to a modification of
the monocotyledonous embryo, in which
the radicle presents an unusual protu-
berance, as in wheat.

MACROPO'DIANS (nanpos, large,
irovs, Trodor, a foot). A tribe of brachyu-
rous decapod crustaceans, remarkable for
the enormous length of their feet, which
has procured for them the name of sea-
spiders.

MACROTRA'CHIA. A tribe of bi-
valved mollusca, in which the mantle of
the animal is so united and prolonged as
to form one or two long siphons or tubes,
by which the food is imbibed.

MACROU'RA (/LiaKpor, large, otpa, a
tail). A family of decapod Crustacea,
distinguished by the large size of the tail,
as in the common lobster.

MA'CULiE (macula, a spot). Dark
spots frequently seen on the disc of the
sun. They change their appearance as
the sun revolves on his axis, and appear
greater or less to an observer on the
earth, as they are turned to or from him.
One of these was estimated to be more
than six times the size of our earth.

MA'DREPORE. A genus of corals ;
but the term is generally applied to all
the corals distinguished by superficial
star-shaped cavities. In zoological lan-
guage, the madrepores are compound
polyps, the common body of which se-
cretes calcareous matter on its exterior
in arborescent masses, presenting upon
their surface multitudes of cells, in each
of which, when alive, a polyp existed.

MA'DREPORITE. Anthraconite. Co-
lumnar carbonate of lime, found in Nor-
way in transition rocks, in Greenland, &c.

MAGDEBURG HEMISPHERES. An
apparatus for exhibiting the force of the
atmospheric pressure. Two hollow me-
tallic hemispheres, whose edges fit accu-
rately, are placed on each other, and the
air is exhausted. Supposing the super-
ficial content to be 100 square inches, and
205

the height of the mercury to be 30 inches,
the pressure exerted on the hemispheres
will amount to 1475 lbs., and it will re-
quire the force of two horses to pull them
asunder.

MAGELLA'NIC CLOUDS. The name
of three nebulae in the southern hemi-
sphere, two of them about 12° or 13°
from the south pole, the third more dis-
tant. They were first recorded by the
navigator Magellan.

MAGIC LANTERN. The magic lan-
tern is a microscope, on the same prin-
ciple as the solar microscope. But in-
stead of being used to magnify natural
objects, it is commonly employed for
amusement, by the casting of shadows
of small transparent paintings, done on
glass, upon a screen placed at a proper
distance.

MAGIC SQUARE. A series of num-
bers in arithmetical progression, so ar-
ranged in a square order, that the vertical,
horizontal, and diagonal columns give
the same sum. Thus :

1

2

3

4

1

16

11

6

5

6

7

8

or

13

4

7

10

9

10

11

12

8

9

14

3

13

14

15

16

12

5

2

15

MA'GISTERY (magister, a master).
A masterly preparation, formerly applied,
in Chemistry, to all precipitates, but now
restricted to a few substances, as the
magistery, or subnitrate, of bismuth, a
brilliant white powder of pearly lustre,
composed of microscopic crystalline
grains ; the magistery of silver, the alche-
mical name of the nitrate ; &c.

MAGNE'SIA. An alkaline earth,
having a metallic base, called magnesium.
It has been found native, in the state of
a hydrate. The term magnesia was ori-
ginally applied to any substance which
had the property of attracting some prin-
ciple from the air.

MAGNESIAN LIMESTONE. An
extensive series of beds, lying imme-
diately above the Coal Measures, and so
named from the presence of a large quan-
tity of magnesia in the limestone. It
contains fossils, and among them a few
corals and shells.

MAGNE'SITE. Carbonate of mag-
nesia; a white, hard, compact mineral,
found in Moravia, in serpentine rocks.

MAGNE'SIUM. A metallic substance,
resembling silver, fusing at a red heat,
and then, on burning in air or oxygen,

MAG

MAG

producing magnesia, or oxide of magne-
sium, which is white, inodorous, and
forms an ingredient in many rocks, to
which it usually communicates a soapy
or greasy feel.

MAGNET. Magnets are suhstances
which attract certain metals; which dis-
play towards one another a force partly
attractive and partly repulsive; and,
lastly, which exhibit a tendency to ar-
range their mass in a certain direction
{see Pole). The term is probably derived
from Magnesia, owing to the native iron
ore, or loadstone, having been found in
abundance near that city.

1. Magnet, Natural and Artificial. 1.
The natural magnet, or loadstone, is a
chemical combination of the oxide and
the suboxide of iron. It occurs in the
northern parts of the world, where it
forms entire mountains. 2. Artificial
magnets are commonly of steel, to which
the magnetfy properties are communi-
cated by a particular process. They are
of various forms : if cylinders or parallel-
opipeds, they are called bar magnets ; if
curved in the middle, so as to bring the
two ends near together, they form horse-
shoe magnets ; when several bars or horse-
shoes are combined, the apparatus is
called a compound magnet, or a magnetic
battery, or, more simply, a bundle of mag-
nets. Those artificial magnets which are
constructed so as to move freely, and
which will then invariably assume a
certain definite position with respect to
the earth, are called needles.

2. Magnetic North. A term applied
to the direction of the magnetic needle,
which, though commonly said to point to
the north, usually points some degrees
from it, one way or the other. For in-
stance, all along the line which passes
through the Cape de Verd Islands, the
magnetic north is 15° west of the true
meridian ; and hence, a ship on this line,
wanting to sail any particular course,
steers 15° wrong by her compass to be
right by the meridian.

3. Magnetic Indifference, Point of.
That point of a magnet, somewhere
about midway between the two extre-
mities, where the attractive force, after
continually diminishing as we proceed
from either pole, ceases altogether.

4. Magnetic Fluid. The hypothetical
agent, to which the phenomena of mag-
netism have been referred. Some have
supposed two such fluids,— a boreal or
northern, and an austral or southern.
The former of these is also distinguished as

206

positive, the latter as negative magnetism,
neither of which, however, is found singly
combined with the particles of matter,
but always both together.

5. Magnetic Curves. The curved lines
into which iron-filings arrange them-
selves when dropped gently on a plate of
glass having a magnet beneath it. The
filings will be found to accumulate most
perceptibly about the poles of the magnet,
and to arrange themselves in curved lines
extending from one pole to the other.

6. Magnetic Induction. That property
by which each pole of a magnet excites
magnetism in any magnetizable body
within a certain distance of itself, im-
parting an opposite polarity to its own to
the contiguous end of such a body, and
similar polarity to its remote end. The
range within which the magnet exerts an
influence is termed its circle of magnetic
influence, or its magnetic atmosphere.

7. Magnetic Points of Convergence.
The name given to two points, near to
the north and south poles of our planet,
around which are drawn the isogonic
lines, or lines of equal declination. The
two points are also called the magnetic
poles of the earth.

8. Magnetic Equator. The name of an
irregular curve in the neighbourhood of
the terrestrial equator, where a needle
balances itself perfectly horizontally. It
is also called the aclinic line.

9. Magneto-electrical Rotatory Machine.
An apparatus for rendering the magneto-
electric induction currents continuous,
and for converting their alternating di-
rection into a constant one. Such a
machine may be employed as a substitute
in part for a common electrical machine,
and in part also for a voltaic pile, as it is
capable of producing electric sparks, in-
candescence and fusion of wire, intense
light at charcoal points, physiological
effects, chemical decomposition, and
magnetic action of many kinds.

MAGNET, ARSENICAL. A corro-
sive preparation of equal parts of sulphur,
white arsenic, and common antimony,
mixed by fusion.

MAGNETIC PYRI'TES. Native
black sulphuret of iron. It attracts the
magnetic needle.

MA'GNETISM. A term expressing
the peculiar property occasionally pos-
sessed by certain bodies, more especially
by iron and some of its compounds, by
which, under certain circumstances, they
mutually attract or repel one another, ac-
cording to determinate laws. See Magnet.

MAG

M AL

MAGNETO-ELECTRICITY. A term
applied to those electric phenomena which
may be produced by magnetism.

MAGNETO'METER. The term ap-
plied by Gauss to a magnetic apparatus
consisting of bars of iron from one to
four feet in length, and weighing from
1 lb. to 25 lbs. These masses are not
affected, like the needle, by variations of
temperature, nor by the presence of
other similar bodies, while at the same
time they are capable of indicating the
minutest variations in the intensity of
the earth's magnetism, by changes in the
position of the magnetometer, which can
be measured to an angle of one second.

MAGNE'TOMO'TOR. A voltaic se-
ries of two or more large plates, for pro-
ducing a great quantity of electricity of
low tension, and thus exhibiting the
phenomena of electro-magnetism.

MAGNIFYING GLASS. A convex
lens, which increases the apparent size
of objects viewed at a small distance
through it. It is also termed a burning
glass, because, when the sun's rays are
brought to a point, after passing through
a lens of this kind, they produce a strong
heat.

MA'GNITUDE (magnitudo, size). The
general term for quantity of space. In
Geometry, it denotes the space occupied
by any figure, and has relation to the
three dimensions of length, breadth, and
thickness. It may, in fact, be applied to
any thing which involves the question of
"greater or less."

1. When one magnitude is compared
with another of the same kind, the first
is called the antecedent, and the second
the consequent.

2. One magnitude is said to be a mul-
tiple of another, when it contains that
other a certain number of times exactly :
and the other magnitude, which is con-
tained in the first a certain number of
times exactly, is said to be a submultiple,
or measure, or part of the first. Hence,
also, one magnitude is said to measure
another, when it is contained in the other
a certain number of times exactly.

3. Two magnitudes are said to be equi-
multiples of two others, when they con-
tain those others the same number of
times exactly : and the other magnitudes,
which are contained in the first the same
number of times exactly, are said to be
like parts of the first two. Thus, 7 A,
7 B, are equimultiples of A, B; and
A, B, are like parts of 7 A, 7 B.

4. Two magnitudes are said to be com-

207

mensurable with one another, when a
common measure of the two may be
found, that is, a magnitude which is con-
tained in each of them a certain number
of times exactly. In like manner, any
number of magnitudes are said to be
commensurable, when there is some mag-
nitude which is contained in each of
them a certain number of times exactly.
Magnitudes which have no common
measure are said to be incommensurable.

MA'GNITUDE, APPARENT. The
name given to the angle under which an
object appears at the eye, or the angle
formed by lines drawn from the extrem-
ities of the object to the eye. The idea
which we form of the real magnitude is
not that which is necessarily conveyed
with the first gift of sight, but is gra-
dually made out by the help of expe-
rience. The sun and moon are nearly of
the same apparent size.

MA'GNITUDE OF STARS. The
magnitudes of stars are vaguely derived
from their apparent brilliancies. Very
brilliant stars, though of varying bril-
liancy, are said to be of the first magni-
tude ; stars of the next degree of bril-
liancy are said to be of the second magni-
tude; and so on. Yet there is little
perceptible difference between the boun-
dary stars of any two adjoining classes,
and hence there is no little confusion.

MA'IIDiE or MA'INS. A tribe of
brachyurous crustaceans, or Crabs, named,
from the genus maia, or sea-spider, as it
is commonly called.

MAJOR and MTNOR. These terms
are applied, in Music, to imperfect con-
cords, which differ from each other by a
semitone.

MAJOR TERM. In Logic, the Major
Term of a syllogism is the predicate of
the conclusion. The Major Premiss is
the one which contains the major term.
In hypothetical syllogisms, the hypotheti-
cal premiss is called the major. #

MA'LACHITE. Green bice. A car-
bonate of copper; a green carbonate,
occurring with a fibrous structure and
velvety appearance, and with a compact
structure in the mines of the Uralian
mountains.

MA'LACOLITE. Sahlite. A pyrox-
enic mineral, consisting of a silicate of
magnesia and lime, found in Shetland,
&c. It is a sub-species of oblique-edged
augite.

MALACO'LOGY (Ma\aic6?, soft, X67op,
a description). The science of the Mol-
lusca, termed by Aristotle malakia, com-

MAL

MAM

prehending the examination both of the
animal and of the shell. It differs from
Conchology, which is limited to the ar-
rangement of the shells, and, in this
respect, cannot claim a place amongst
the sciences.

MALACO'PTERY'GII (ixaXands, soft,
iTTepvyiov, a fin). An order of Osseous
Fishes, in which the fins are all soft or
jointed. The order is subdivided, ac-
cording to the position or absence of the
ventral fin, into —

1. M. abdominales, in which the ven-
tral fins are attached to the abdomen
behind the pectorals. These include the
greater part of the fresh-water fishes.

2. M. sub-brachiati, in which the ven-
tral fins are brought forward under the
pectorals, and the fishes, which are chiefly
marine, enjoy a considerable power of
ascending and descending in the water.

3. M. apoda, in which the ventral fins
are always wanting, and not unfrequently
the pectoral also.

MALACO'STRACA {naXanos, soft, '6a-
rpanov, a shell). A sub-class of the Crusta-
cea, in which the animals have seven tho-
racic and seven abdominal segments. The
term was given by Aristotle to the modern
Crustacea, because their shells were softer
than those of the Mollusca, or ordinary
shell-fish. The Malacostraca are divided
into two groups, according to the attach-
ment of the eyes : those with immoveable
sessile eyes form the Edriophthalma ;
those with moveable pedunculated eyes,
the Podophthalma.

MALACTI'NIA (/xaXaKot, soft). The
third class of the Radiata, consisting of
soft aquatic animals, emitting an acid
secretion from their surface, which is
capable of irritating and inflaming the
human skin, like the stinging of a nettle ;
hence the name acalephce, or nettles, has
been commonly given to this class. They
are divided, according to their modes of
locomotion, into the following orders : —

1. Ciliograda, or those which move by
vibratile cilia, as beroe.

2. Physograda, which float by means
of air-sacks, as physalia.

3. Palliograda, which move by the
muscular contractions of a superior dis-
coid mantle, as rhizostoma Cuvieri. —
Grant.

MALAY RACE. One of the five
principal divisions of mankind, in which
the summit of the head is slightly nar-
rowed, the forehead a little arched, the
upper jaw somewhat projecting, the face
less narrow, and the features more pro-
208

minent and better marked than in the
negro. This race includes the inhabi-
tants of the South Sea Islands.

MALIC ACID {^a\ov, an apple). An
acid existing in apples, but generally
prepared from the berries of the sorbus
aucuparia, or mountain ash. It forms
salts with alkaline and magnesian bases,
called malates.

MALLEABI'LITY {malleus, a ham-
mer). A property of some metals, by
which they are capable of being beaten
out into plates, or leaves, by the hammer,
as in the case of gold-leaf. This pro-
perty depends upon a high degree of
tenacity, connected with a certain degree
of softness.

MA'LLEID^l. A family of mono-
myarian conchifers, in the system of
Lamarck, named from the genus malleus,
and belonging to the ostracea of Cuvier,
the oxygones of Latreille.

MALLEOLUS. This term is Latin
for a hammer, and is applied, in the bo-
tanical process of layering, to the layer
which is separated from the parent plant,
from its lower end resembling a hammer-
head, of which the new plant represents
the handle.

MALTHA. Sea-wax. A solid, whitish,
bituminous substance, not unlike tallow,
found in Siberia and Persia. It is, pro-
bably, the bitumen candidum of Pliny.

MALTING. The process of making
malt ; it consists in the inducing of an
artificial growth or germination of barley,
by steeping in water, and then evolving
the saccharine principle by the applica-
tion of heat.

MALVACEAE. The Mallow tribe of di-
cotyledonous plants. Herbaceous plants,
trees, or shrubs, with leaves alternate;
flowers polypetalous / stamens hypogy-
nous, monadelphous ; fruit capsular or
baccate, containing seed with crumpled
cotyledons.

MAMMA'LIA {mamma, a teat). The
fifth class of Vertebrate animals, which
are provided with mammary glands for
the lactation of their young. To this it
may be added, that the visceral cavity is
separated into a thorax and an abdomen
by a muscular diaphragm, and that all
the animals of the class breathe by means
of lungs precisely similar to our own.
See Zoology.

MAMMA/LOGY. An unclassical term,
denoting the science of mammals, or
animals furnished with mammae, includ-
ing man, the quadrupeds, the quadru-
manous animals, and the whales. The

MAM

MAN

terms mastology and mastozoology have
been suggested, as being entirely of Greek
derivation. See Mammalia.

MA'MMIFERS (mamma, a breast,
fero, to bear). Mammal. A term applied
to animals which give suck to their
young, including all the warm-blooded
quadrupeds and the cetaceous animals.

MA'MMILLARY (mammilla, a little
breast). A term applied to a surface
which is studded over with prominences
which are smooth, thick, and rounded,
like a teat.

MA'MMOTH. A word of Tartar ori-
gin, denoting an extinct species of the
elephant (Elephas primigenius), of which
the fossil bones occur in various coun-
tries. The term is applied in Siberia to
animals which burrow under ground.

MAN. Under the several articles,
American, Caucasian, Ethiopian, Malay,
and Mongolian Race, the characters of
these varieties of man are briefly re-
corded. Dr. Prichard refers the differ-
ences of complexion in man to three
principal varieties, viz. : —

1. The Melanocomous, or black-haired,
which is the complexion generally preva-
lent, except in the northern parts of
Europe and Asia. The colour of the
skin varies in intensity from the black of
the African negro to the light olive of the
northern Hindoo, thence to every degree
of shade in the Persian and other Asia-
tics, to that of the swarthy Spaniard and
of black-haired Europeans in general.

2. The Leucous, albino, or white-
haired, occurring in all countries, per-
haps most frequently in hot climates.
They are characterized by the entire ab-
sence of colouring matter from the skin,
hair, and eyes ; the skin is consequently
milk-white or of a pinkish hue, the hair
silky-white or at most yellowish, the iris
rosy, and the pupil intensely red.

3. The Xanthous, or yellow-haired, in-
cluding the light-brown, auburn, yellow,
and red varieties. The complexion is
fair, becoming more or less red on expo-
sure to heat and light. The eyes are
light-coloured. This variety predomi-
nates in the temperately cold regions of
Europe and Asia. <r

MA'NAKINS. A group of small birds,
remarkable, for their rich plumage. Mr.
Swainson makes them a sub-family of
the Ampelidae, under the name of
Piprince.

MA'NATIDjE (manatus, the sea-cow,
or lamantine). A small family of aquatic
herbivorous animals, placed by Cuvier
209

among the Cetacea. By others they are
considered to differ from the whales, and
to resemble the hippopotamus, suffi-
ciently to be placed among the Pachyder-
matous animals.

MANDIBULA'TA (mandibulum, a
mandible or jaw). Mandibulate Insects ;
a group in which the mouth is furnished
with mandibles or jaws, adapted for
biting and bruising. This division in-
cludes the coleopterous, orthopterous,
neuropterous, and hymenopterous in-
sects. See Haustellata.

MA'NGANESE. A metal similar to
iron, brittle, and with difficulty fused,
occurring in the state of oxide in some
rocks, to which it generally gives a pur-
plish-red colour. The binoxide, used in
chemistry, is commonly termed native
black, or peroxide of manganese.

MANGANESE BLENDE. Kobellite.
An ore of manganese, in which sulphur
occurs in combination with the metal,
found at Nagyag in Transylvania and in
Mexico.

MA'NGANIC ACID. An acid con-
sisting of one atom of manganese and
three of oxygen. It has not hitherto
been obtained in a separate state, but
exists in the manganate of potash, com-
monly called mineral chameleon.

MA'NGANITE. An ore of manga-
nese, consisting of two prime proportions
of the deutoxide of the metal, combined
with one of water.

MANHEIM GOLD. A species of
brass, consisting of three parts of copper
and one part of zinc.

MANIPULATION (manipulus, a
handful). In chemistry and experi-
mental philosophy, this term denotes the
application of skill in conducting the
various operations of the laboratory.

MANO'METER (navot, rare, fxerpov,
a measure). Manoscope. A steam-baro-
meter, employed chiefly for measuring
the force of the steam in boilers. The
term is also applied to an instrument for
testing the rarity of the air. See Dasymeter.

MA'NTIDjE. A family of orthopte-
rous insects, named from the genus
mantis, and remarkable for their gro-
tesque forms, closely resembling that of
a plant. The mantis religiosa, or praying
insect, has received its name from the
peculiar position of the anterior pair of
legs, like the hands of a person at prayer.

MANTLE. The external soft con-
tractile skin of the Mollusca, which
covers the viscera and a great part of the
body, like a cloak.

MAN

MAR

MANU'RES. Animal, vegetable, or
mineral matters, deposited in the soil, to
accelerate vegetation and increase the
production of crops.

MAP (mappa, a napkin). A repre-
sentation, upon a plane, of some portion
of the surface of a sphere, on which are
traced the particulars intended to be ex-
pressed, whether they be continuous out-
lines or points. The projections chiefly
used in maps are the orthographic, the
stereographic, and Mercator's. See Pro-
jection.

MARBLE. A term applied to every
limestone which is finely coloured and
capable of receiving a high polish, or of
being worked into statuary; the pure
white crystalline kinds being those em-
ployed for the latter purpose. Forest
marble is a coarse laminated shelly oolite,
interposed between beds of clay, sand,
and grit.

MARCEL'S BLOWPIPE. An appa-
ratus for increasing temperature, by urg-
ing the flame of an alcohol lamp by a
blowpipe supplied with oxygen gas.

MA'RGARIC ACID (napyaplt, a
pearl). An acid obtained from human
fat and vegetable fixed oils, and also
produced by the dry distillation of ox
and mutton suet, and of stearic acid. Its
name is derived from its pearly lustre.

MA'RGARIN. Margarate of glyceryl ;
a peculiar fatty matter contained in vege-
table oils and animal fats.

MA'RGARITE. A greyish-white mine-
ral, resembling silvery mica.

MARGARFTIC ACID. One of the
fatty acids produced by the saponifica-
tion of castor oil. The other acids ob-
tained by this process are the ricinic and
the eloeodic.

MA'RGARONE. A solid white fatty
matter, crystallizing in pearly scales, ob
tained by dry distillation of margaric
acid.

MARGINELLI'NjE. Date-shells; an
aberrant sub-family of the Volutidce, or
volutes, named from the typical genus
marginella, having plaits upon the pillar,
and crenated teeth on the thickened
outer lip; the foot very large, but the
mantle not lobed nor reflected.

MARINE ACID. Spirit of salt. Mu-
riatic or hydrochloric acid, procured from
common salt by distilling it with sul-
phuric acid and water over a water-bath

MARINE CONGLOMERATES. De

posits formed by sand thrown by the sea

upon its shores, mixed with remains of

shells and corals, which are agglutinated

210

by a calcareous cement, finally acquiring
a tolerably firm consistence. Rocks of
this kind are daily forming on the shores
of Sicily, and are very abundant in the
West Indies.

MARINER'S COMPASS. An instru-
ment consisting of a small magnetic bar,
called a needle, poised on its centre of
gravity, so as to be enabled to turn
readily every way in ahorizontal direction.
After a few vibrating motions, during
which it is said to traverse, the needle
takes its direction nearly north and south,
which direction is said to be in the plane
of the magnetic meridian of the place
where the compass happens to be.

Compass variation. A term expressive
of the angle, which the magnetic meri-
dian is east or west from the geogra-
phical, or true north and south. It varies
in different places and at different times.
MARIOTTE'S LAW. Boyle and Ma-
riotte experimentally investigated the
ratio subsisting between the density of
the air, its elasticity, and the space it
occupies, when the following law was
detected : — that the density and elasticity
of atmospheric air are directly, but the
space it occupies is inversely, as the force
of compression.

MA'RKAB. A star of the second
magnitude in the northern constellation
Pegasus.

MARL. An argillaceous rock, con-
sisting of clay mixed with lime ; soft,
friable, but not forming a tenacious paste
with water; it is grey, yellow, green,
blue, or red. The variegated marls, or
keuper, are red, greenish-grey, and
bluish, and contain subordinate beds of
sandstone and dolomite, deposits of
brown coal, masses of gypsum, and salt.
These marls are covered with a white
quartz sandstone, which connects them
with the lias.

MARLSTONE. A constituent of the
lias formation, consisting of arenaceous
and calcareous layers, with nodules of
ironstone. This rock is well developed
in Yorkshire and Leicestershire.

MA'RMOLITE. A variety of serpen-
tine, found at Hoboken, in New Jersey.

MARS. • The planet which imme-
diately follows our earth in respect of
distance from the sun, from which he is
separated by 146 millions of miles. His
diameter appears to be sometimes 18",
sometimes 19". He revolves on his axis
in 24h, 31' 22", and completes his orbit
round the sun in 686d, 23h, 30' 41", 4.
MARSH'S APPARATUS. An appa-

MAR

MEA

ratus for detecting the presence of arseni-
ous acid in solution.

MARSUPIA'TA {marsupium, a pouch).
Marsupial animals; an order of Mam-
malia, having a sack or pouch under the
belly in which they carry their young, as
the kangaroo and opossum. They are
ovo-viviparous animals, being interme-
diate between the truly viviparous mam-
malia, and the oviparous birds and rep-
tiles.

MA'RTIAL. An old mythological de-
signation of several preparations of iron,
from Mars, the god of war. Hence we
have martial ethiops, or the protoxide ;
martial pyrites, or the sulphuret.

MASS (ndacronai, to knead together).
In physics, a term synonymous with
quantity : thus, the mass of a body is the
quantity of matter it contains. The mass
and density of bodies are estimated ac-
cording to their various degrees of poro-
sity. The mass represents the number
of material particles in a body : the
greater the mass, the less porous is the
substance. Density, on the contrary,
expresses the relation of the masses
when the volumes are equal: i.e. "of
two bodies that is the more dense, which
with equal bulk contains the greater mass."

MASSES, GLOBULAR. Nodules.
These terms are applied, in Geology, to
rocks of irregular form, varying from a
foot to a mile or more, and imbedded
either in a stratified or a massive rock.
Irregular masses are rocks of no deter-
minate form, and of any size, as granite,
greenstone, porphyry.

MA'SSICOT. Yellow oxide, or pro-
toxide of lead. When partially fused by
heat, it is called litharge.

MA'STODON (/icurrdf, abreast, b&ovs,
a tooth). A genus of fossil extinct qua-
drupeds, allied to the elephant, and so
called from the form of the hind teeth,
or grinders, which have their surface
covered with conical mammillary crests.

MATER ACETI. Mother of Vine-
gar; a mould- plant, belonging to the
genus mycoderma, which is developed
in vinegar, and forms thereon a thick
leather-like coat, similar to the inflam-
matory crust which covers the crassa-
mentum of blood drawn from rheumatic
patients, i

MATERIALISM. A philosophical
system which refers all existence, in-
cluding the nature of the mind or soul
itself, to a modification of matter. By
this system the brain is supposed to se-
crete thought, as the liver secretes bile.
211

MATHEMATICS {n<idr\™, learning).
The science which teaches the properties
of numbers and of figures. It is, accord-
ingly, divided into two branches, viz.
arithmetic, the science of number, and
geometry, the science of figure.

Mixed Mathematics denotes mathema-
tical reasoning upon facts in nature, and
is so named in contradistinction to pure
or abstract mathematics, which is em-
ployed in reasoning on figures and num-
bers, without reference to facts in nature.

MATRASS. A cucurbit, or vessel of
glass, porcelain, or metal, usually of a
globular shape, and open at the top, for
the chemical purposes of digestion, eva-
poration, &c. See Alembic.

MATRIX. Gangue. The earthy or
stony matter which accompanies ores, or
envelopes them in the earth.

MATTER. The general designation
of whatever occupies space, and possesses
extension and impenetrability : all bodies
are matter with fixed boundaries. The
physical and chemical properties of matter
have given rise to two branches of
science, viz. physics and chemistry.

MAXILLO'SA (maxilla, a jaw). A
group of Crustaceous animals, in which
the mouth is furnished with jaws, as dis-
tinguished from the Edentata, in which
the mouth is prolonged in the shape of
a sucker. These two groups are pre-
cisely analogous to those of the mandi-
bulata and the haustellata among insects.

MA'XIMA and MI'NIMA. These
terms, simply signifying "the greatest"
and "the least," are employed, in ana-
lysis, to signify not the absolute greatest
and least values of a variable quantity,
but the values it has when it ceases to
increase, and begins to decrease, and vice
versa". A variable quantity may, there-
fore, have many maxima and minima, as
the highest and lowest points at which
the mercury stands in a barometer at
different times.

MEAN QUANTITY. In Mathema-
tics, the mean of two or more quantities
is a quantity of intermediate value, found
by determinate rules. There are several
modes of finding a mean quantity.
Thus :—

1. The arithmetical mean of several
quantities is simply the average found by
dividing the sum of all the quantities by
their number ; and this is the mean al-
ways understood, unless another kind be
specified. Thus, if three measures of
the same length give 122, 123, and 123-4,
the average or arithmetical mean is 122*8.

ME A

MEC

2. The geometrical mean of two quan-
tities is the square root of the product of
those quantities. In Geometry, the term
is synonymous with mean proportional,
and it is a quantity, such that, if placed
between two given quantities, a series of
three continued proportionals would be
formed ; in other words, the first of the
two given quantities is to the mean pro-
portional as this is to the other given
quantity.

3. The harmonical mean is a number,
such that, the first and third terms being
given, the first is to the third as the dif-
ference of the first and second is to tbe
difference of the second and third, the
second being the harmonical mean.

MEAN SUN. Solar days are not
equal in duration ; a clock regulated by
the sun would, consequently, need fre-
quent adjustment. To avoid this, an
imaginary or mean sun is supposed to
move regularly round the equator in the
same time as that in which the true sun
moves irregularly round the ecliptic.
Such a time represents a mean solar day,
and it is the average of all the apparent
solar days in a year. See Equation of Time.

1. Mean Noon. This is an expression
connected with the above fiction of a
mean sun; and the term " mean" is here,
as above, opposed to "apparent" or
" real." Thus, apparent noon is the real
or true noon, when the true sun, the sun
which appears, is on the meridian ;
whereas mean noon takes place when the
mean sun, the average imaginary sun,
which does not appear at all, is on the
meridian.

2. Mean Moon. The still greater ab-
sence of uniformity in the actual motion
of the moon induced astronomers to em-
ploy an imaginary or mean moon, in the
same manner as the " mean sun" above
mentioned. This mean moon is made
to move uniformly in the equator, or in
the ecliptic, as required. The Kalendar
Moon is another fictitious moon, em-
ployed for regulating the finding of
Easter ; this moon is generally a day or
more distant from the mean moon.

3. Mean Time. Equal or mean time
is that which is reckoned by a clock,
supposed to indicate exactly twenty-four
hours, from twelve o'clock on one day to
twelve o'clock on the next day. Appa-
rent or real time is that which is mea-
sured by the apparent motion of the sun
in the heavens, as indicated by a meri-
dian line, or sun-dial.

4. Mean Anomaly of a Planet. Its

212

angular distance from the aphelion or
perihelion, supposing the planet to re-
volve in a circle with its mean velocity.

5. Mean Conjunction or Opposition.
The mean place of the sun when in con-
junction with, or opposition to, the mean
place of the moon in the ecliptic.

6. Mean Distance of a Planet from the
Sun. An arithmetical mean between
the planet's greatest and least distances ;
or, the semi-transverse diameter of its
orbit.

MEANS and EXTREMES. In any
proportion the first and fourth terms are
called the extremes, the second and third
the means, and the product of the former
is equal to the product of the latter. Thus,
in the proportion 15 .'20 ; '. 21 ; 28,
since the two ratios are equal, we have

15 _ 21

20 ~ 28 J
and, if we multiply each of these equals
by 20 x 28, we have 15 x 28 = 20 x 21,
or the 1st x 4th = 2nd x 3rd. See
Proportion.

MEASURE OF A NUMBER. One
number is said to be a measure or a factor
of another, when it divides it exactly,
without a remainder. Thus, 1, 2, 3, 4,
6, 12, are all measures or factors of 12.
Unity, however, is not generally named
among the divisors of a number.

1. Greatest Common Measure. Any
number which divides without remainder
each of two or more numbers, is said to
be a common measure or common factor
of those numbers ; and, of course, the
greatest number which so divides them
is their greatest common measure. Thus,
3, 5, 15, are each of them common mea-
sures of 30 and of 45, and 15 is their
greatest common measure.

2. Measure, in Geometry. A magnitude
or quantity assumed as a unit, and em-
ployed to express the relations of other
magnitudes or quantities of the same
kind. Euclid defines the measure of a
quantity to be that which, being repeated
a certain number of times, becomes equal
to the quantity measured.

MEASURES (in Geology). A term
sometimes employed as synonymous with
beds or strata.

MECHANICAL CURVE. This is now
called the transcendental curve. It is a
curve in which the relation between the
abscissa and the ordinate cannot be ex-
pressed by an algebraic equation.

MECHANICAL ORIGIN, ROCKS
OF. A term applied to rocks composed
of sand, pebbles, or fragments, to distin-

MEC

MEG

guish them from those of a uniform crys-
talline texture, which are of chemical
origin.

MECHANICAL PHILOSOPHY. The
application of mechanics to physical
science. Hence the term Mechanists
was applied to those philosophers who
referred all the phenomena of the uni-
verse to the agency of mechanical forces,
in opposition to the Dynamical school,
which insists on a living principle in
nature, antecedent to, and distinct from,
the visible phenomena of nature.

MECHANICAL POWERS. The gene-
ral designation of six simple machines,
viz., the lever, the pulley, the wheel and
axle, the inclined plane, the wedge, and
the screw. All the different compound
engines, however mixed or complex
their construction, consist only of various
combinations of these few individual
powers.

MECHANICAL SOLUTION. A term
applied to the solution of those geometri-
cal problems which require other instru-
ments (machinee) than those employed in
the constructions of pure geometry. The
latter being effected merely by straight
lines and circles, require only a rule add
compasses.

MECHA'NICS {fxnxavt), a machine).
The science which treats of the equili-
brium and motion of bodies. That part
of the subject which relates to the condi-
tions of equilibrium is called statics;
while that which investigates the motion
which a body acquires when the forces
applied to it are not in equilibrium, is
termed dynamics.

MECHLO'IC ACID. A compound of
meconia, a neutral principle existing in
opium, and chlorine, discovered in 1835
by Couerbe.

MECO'NIC ACID (n^ncav, a poppy).
A tribasic acid, obtained from poppies,
constituting the characteristic acid of
opium. Its congeners are the comenic,
which is bibasic ; and the parameconic,
which is monobasic.

MEDIUM {medius, middle). In Phy-
sics, the space or substance in which
bodies subsist or move. Newton con-
ceived a universal medium, or ether,
more subtil than air, through which the
heavenly bodies move. This idea favours
the theory of the transmission of light by
undulation.

MEDU'LLARY RAYS {medulla, pith).
A botanical term applied to the thin ver-
tical radiating plates of muriform cellular
tissue, which serve to connect the centre
213

of an exogenous stem with the circum-
ference. They are technically called the
silver grain, and they produce, on a lon-
gitudinal section of the stem, the glancy
lustre which so remarkably characterizes
the plane and the sycamore.

MEDU'LLARY SHEATH (medulla,
pith). The sheath which immediately
surrounds the medulla, or pith, of exo-
genous plants. It consists of spiral ves-
sels and woody tissue, and forms an ex-
ceedingly thin layer.

MEDU'LLIN {medulla, marrow). The
name given by Dr. John to the porous
pith of the sun-flower.

MEDUSA. A genus of the Acalephae,
or Sea-nettles ; marine radiated animals,
without shells. The name is derived
from their organs of motion being spread
out like the snaky hair of the fabulous
Medusa. On being touched, they induce
redness and a tingling sensation ; they
are also supposed to occasion, in certain
latitudes, the phosphorescent appearance
of the sea.

MEE'RSCHAUM. Ecume de mer. A
silicate of magnesia; a greasy, soapy
substance, occurring in Cornwall. In
Germany and Turkey it is manufactured
into tobacco pipes.

MEGALO'PTERANS (/ueyac, great,
nrepov, a wing). A family of Neuropte-
rous insects, characterized by their large
wings horizontally folded. — Latreille.

MEGALOSAU'RUS {neydKn cavpa,
great lizard). A fossil gigantic amphi-
bious animal of the saurian, or lizard and
crocodile tribe, found in the oolitic slate
at Stonesfield, near Woodstock, and other
localities.

MEGANY'CTERANS (yueyav, large,
vvKrepis, a bat). A tribe of Cheiropterous
animals, including the largest species of
bats, or " flying foxes."

MEGAPODI'IDjE. The name given
by Mr. Swainson to a family of the Ra-
sores, from the genus megapodius, which,
with the allied genera, is referred by
other naturalists to the Cracidae, or
Curassows.

ME'GASCOPE (fxeya9, large, ovcoTreo),
to examine). An optical instrument,
constructed on the principle of the solar
microscope, for examining bodies of large
dimensions.

MEGATHE'RIUM (Me7a 6npiov, great
beast). A fossil extinct quadruped, re-
sembling a gigantic sloth, and character-
istic of the later tertiary period on the
continent of South America. This, and
some other genera of extinct Edentata,

MEI

MEN

constitute the Megatheriidce, or mega-
theroids of Owen.

MEI'ONITE. Prismato-pyramidal fel-
spar, occurring together with ceylanite
and nepheline, in granular limestone, at
Monte Somraa, near Naples. This, and
some other felspathic substances are now
united under the general term wernerite.
MELAIN (/xeAa?, black). The colour-
ing matter of the ink of the cuttle-fish.

MELAM. A substance formed by
distilling dry hydro-sulpho-cyanate of
ammonia. On boiling melam with hy-
dro-chloric acid, a crystalline substance
is generated, called melamine.

MELANIA'N^E. Black snails ; a sub-
family of the Turbidts, named from the
genus melania, and having a spiral shell,
the spire being generally longer than the
aperture, the body-whorl small.

ME'LANIC (M<?\ar, black). A term
applied by Dr. Prichard to one of the
three varieties of mankind, derived from
the colour of the hair, and including all
individuals or races which have black
hair. See Man.

ME'LANITE. A black variety of
garnet, found in the neighbourhood of
Frascati, near Rome, and in the basalt of
Bohemia.

MELA'NTERITE. A mineralogical
name for green vitriol, or native sulphate
of iron.

MELANTHA'CEjE. The Colchicum
tribe of monocotyledonous plants. Herbs
with a rhizome, sometimes fleshy ; leaves
sheathing at the base ; flowers hexapetal-
oideous, tubular ; stamens 6 ; ovarium
3-celled ; seeds albuminous.

MELASO'MA (/ueXa?, black, awfxa, the
body). A family of the heteromerous
Coleoptera, characterized by the black or
ashy-brown colour of the body. The
wings are usually absent, and the elytra,
or wing cases, united.

MELA'SSES (M<?\<, honey). The un-
crystallizable part of the juice of the
sugar-cane, separated from the sugar
during its manufacture.

MELA'SSIC ACID (Me\c, honey). An
acid produced by the simultaneous action
of alkalies and heat upon grape sugar.

MELASTOMA'CEjE ((xeXav, black,
trrojua, mouth ; from the fruit of some of
the species staining the lips black). A
family of dicotyledonous plants, charac-
terized by their opposite leaves, with
several large veins running from the base
to the apex, resembling those of mono-
cotyledonous plants ; and the long-beaked
anthers.
214

MELIA'CEiE. The Bead-tree tribe of
dicotyledonous plants. Trees or shrubs
with leaves alternate ; flowers symmetri-
cal ; calyx imbricated ; stamens hypogy-
nous ; ovarium of several cells ; seeds
definite, apterous.

ME'LILITE. A species of garnet,
found at Capo di Bove, near Rome.

MELIPHA'GID^ (M<?\<, honey, <pd^o,
to eat). The Honey-suckers ; a family
of the Insessores or Perching birds, dis-
tinguished from all the allied families by
their notched bill. They are chiefly con-
fined to Australia. (See Tenuirostres.)
According to Macgillivray, these birds
constitute a family of the Repfatrices, or
Creepers, characterized by having the
three fore toes more or less united at the
base, and spreading little.

ME'LLITATES. Salts formed by the
combination of mellitic acid with a sali-
fiable base.

ME'LLITE. Honey-stone. Mellitate of
alumina ; a salt found in beds of brown
coal at Artern in Thuringia.

ME'LLITIC ACID {fieXi, honey). An
acid discovered in mellite, or honey-
stone, a rare mineral, consisting of the
mellitate of ammonia.

ME'LLON. A lemon-yellow substance
consisting of azote and carbon, considered
as a compound radical.

ME'LODY (iueAydm, a singing). The
combination of harmonious sounds is a
chord; an agreeable succession of notes
is a melody ; and a succession of chords
constitutes harmony.

MELOLO'NTHIDjE. A family of
Coleopterous insects, of the section la-
mellicornes, named from the melolontha
vulgaris, or common cockchafer.

MELONI'DIUM (/^Xox, an apple).
The name given by Richard to an in-
ferior compound fruit with a fleshy peri-
carp—the pomum of other writers.

MELTING POINT. That point of
the thermometer which indicates the
temperature at which a solid becomes
fluid. Thus, ice melts at 32° Fahr., sul-
phur at 218°, gold at 5237°.

ME'NACHANITE. An oxide of tita-
nium, found, accompanied with fine
quartz sand, in the bed of a rivulet
which enters the valley of Menaccan in
Cornwall.

ME'NILITE. A sub-species of indi-
visible quartz ; an opaline substance,
called also liver opal, from its brown
colour, found at Menil-Montant, near
Paris, in a bed of adhesive slate. An-
other kind, called grey menilite, occurs at

MEN

MER

Argenteuil, near Paris, imbedded in a
clayey marl.

MENFSCUS (ju>;>n, the moon). A lens
which is concave on one side and convex
on the other, its section resembling the
appearance of the new moon.

MENISPERMA'CE^ (/up*, the moon,
anepfia, seed ; so named from the cres-
cent-like form of the fruit of the typical
genus menispermum). The Cocculus tribe
of Dicotyledonous plants. Leaves alter-
nate ; flowers polypetalous, unisexual ;
stamens hypogynous; fruit a 1-seeded
drupe.

MENISPE'RMIC ACID. An acid
obtained from the berries of the meni-
spermum cocculus, where it exists in
combination with the alkaloid picro-

MENKAR, or a CETUS. A star of
the second magnitude in the head of the
southern constellation Cetus.

ME'NSTRUAL EQUATION. The
name given to an apparent monthly dis-
placement of the sun in longitude, of a
parallactic kind, owing to the real nature
of the curve described by the earth's
centre, which is not an exact ellipse, but
an undulated curve. The actual devia-
tion or excursion of the earth from the
i ellipse is, however, very small, the great-
est amount of the menstrual equation
being less than the sun's horizontal
j parallax, or than 8 6".

ME'NSTRUUM. A chemical term
synonymous with solvent, and denoting
a liquid which does not change the na-
ture of the substance to be dissolved.
Thus, pure water is employed to dissolve
gum, alcohol to dissolve resins, acids to
dissolve the bases of colchicum and
squill.

MENSURATION. The operation of
measuring; a term generally denoting
the application of arithmetic to geometry,
and the methods of finding the dimen-
sions and areas of figures, the contents
of solids,. &c.

MEPH.FTIC ACID. A designation
of carbonic acid gas, derived from Me-
phitis, the fabled Roman goddess of im-
pure exhalations. Mephitic air is another
name for nitrogen gas.

MERCA'PTAN. A compound of hy-
drogen, carbon, and sulphur, named from
its energetic action on binoxide of mer-
cury— quasi mercurium captans. It is
alcohol, of which the oxygen is replaced
by sulphur.

MERCA'TOR'S CHART. An artifi-
cial mode of representing a sphere upon
215

a plane, adopted for nautical charts. See
Projection.

ME'RCURY. The nearest planet to
the sun, from which it appears to be se-
parated only from sixteen to twenty-nine
degrees. Its direct distance from the
earth is 37,143,000 miles; its apparent
diameter is about seven minutes, nearly
two-fifths that of the earth. It turns on
its axis in 24h, 5' 3", and completes its
orbit in 87d, 23h, 25' 44", with a velocity
of 111,000 miles an hour. It sometimes
crosses the disc of the sun, so as to ap-
pear like a small dark spot passing over
the sun's face ; this is called the transit
of Mercury.

ME'RCURY (in Chemistry). A metal
which is always fluid at a temperature
above —39°. From its mobility and its
resemblance to silver, it is commonly
called quicksilver.

1. Native or Virgin Mercury. The
pure metal, found in the form of globules,
in cavities of the ores of this metal.

2. Native Amalgam. An ore consisting
of mercury combined with silver.

3. Native Cinnabar. Native vermilion,
or the bisulphuret of mercury ; the ore
which yields the mercury of commerce.

4. Corneous Mercury. Mercurial horn
ore, or the proto-chloride of mercury.

MERE'NCHYMA (MePof, a part, ??-
Xvna, an infusion). Sphcerenchyma. A
term applied by Morren to the spherical
variety of the parenchyma of plants.

MERGANI'NiE. Mergince. A sub-
family of the Anatidae, consisting of the
genus mergus, the goosander or mer-
ganser of the British.

ME'RICARP (/u<?por, a part, Kapwos,
fruit). The botanical designation of a
half of the fruit of Umbelliferous plants.
What are called seeds in these plants are,
in fact, fruits, each consisting of two
achenia, or mericarps, placed face to face,
and separating from a central axis. The
two together are called cremocarp {upe-
fxdu), to suspend), from their being
suspended from the common central
axis.

MERFDIAN (meridies, noon or mid-
day). A geographical term, denoting a
great circle of the sphere passing through
the zenith and the poles of the earth.
The line which marks the longitude of a
place is called its meridian, because,
when the sun passes this circle, it is
noon in all the places situated under it.
Modern nations generally adopt the
capitals, or observatories, of their own
countries as First Meridians; thus the

MER

MET

English reckon from London, or the
Royal Observatory at Greenwich, the
French from Paris, the Spanish from
Madrid, &c. On the celestial globe the
meridian is represented by the brass
circle perpendicular to the horizon.

1. Meridian Altitude. The altitude,
or height above the horizon, in degrees,
of any celestial object, when it crosses
the meridian of a place.

2. Meridian, Magnetic. The magnetic
meridian, as pointed out by the mariner's
ompass, differs from the geographical (or
real north and south) by the amount of
the variation of the compass. In other
words, if we conceive a vertical plane to
be drawn through the axis of a magnetic
needle when in a state of rest, we have
the magnetic meridian for the particular
place where the needle is. See Dip of
Magnetic Needle.

MERITHA'LLUS (fxepo?, a part, 9a\-
X6f, a young shoot). The term applied
by Du Petit Thouars to the internodium
of other writers, denoting that portion of
the axis of a plant which is between two
nodes.

MERO'PIDjE {merops, the bee-eater).
The Bee-eaters ; a family of the Inses-
sores, or Perching birds, belonging to the
warmer regions of the Old Continent and
its islands ; one species visits this coun-
try at irregular intervals. See Fissi-
rostres.

MERULI'DjE (merulus, a thrush).
The Thrushes ; a family of the Insessores,
or Perching birds, in which the point of
the beak is not hooked, and the lateral
tooth is not so prominent as in the
Laniadee, or Shrikes. See Dentirostres.

MESEMBRYA'CE^E. Ficoidecc. The
Fig-marigold tribe of Dicotyledonous
plants. Succulent shrubs or herbs with
showy flowers ; sepals definite, succu-
lent; petals indefinite, linear; stamens
indefinite; ovary many-celled; capsule
with a starry dehiscence.

MESITE. A liquid existing in pyro-
xylic spirit, and produced in the distilla-
tion of wood. Mesiten is a similar pro-
duct of the same process. ftfysitylene is
a light oily liquid, procured by distilling
pyro-acetic spirit [acetone) with fuming
sulphuric acid.

MESO- (jueo-oc, middle). The Greek
term for middle, or that which is situate
between others.

1. Meso-carp (/captor, fruit). The in-
termediate part of the pericarp of fruits.
When fleshy, it is termed sarcocarp. The
fibrous portion of the fruit of the cocoa
216

palm is the mesocarp; the eatable part
of the cherry or peach is the sarcocarp.

2. Meso-labe (\a(3etv, to take). A ma-
thematical instrument used by Eratos-
thenes for finding mean proportional
lines, required in the problem for the
duplication of the cube.

3. Meso-lite {\iOos, a stone). Needle-
stone ; a zeolitic substance, consisting of
a hydrated silicate of alumina, lime, and
soda, and usually referred to mesotype.

4. Meso phlceum (^Xotof , bark). That
portion of the bark of plants which lies
between the epiphlceum and the endo-
phlceum, or liber. See Bark.

5. Meso-phyllum {(pvWov, a leaf). The
cellular substance of the leaves of plants,
also called diachyma and diploe.

6. Meso-sperm {cirepixa, seed). The
middle one of the three membranes by
which seeds are sometimes enveloped.

7. Meso-type (rvwo^, form). A silicate
of soda and alumina ; a simple mineral,
white, and needle-shaped; one of the
zeolite family, frequently found in trap-
rocks. To this are referred the natrolite
of Klaproth, the needle-stone of Werner,
the mesolite, &c.

META'BOLA (nerafoXn, change). A
term applied by zoologists to those genera
of insects which undergo metamorphosis,
or pass through the larva, pupa, and
imago states of insect existence. See
Ametabola.

METACE'NTRE {iieta, a preposition
denoting change, K€vrpov, a centre). When
the position of equilibrium of a floating
body has been disturbed, if the vertical
line passing through the centre of buoy-
ancy (the line of the thrust of the fluid),
when produced upward, meets the axis
passing through the centre of gravity,
the point of intersection is called the
metacentre.

METAGA'LLIC ACID. A compound
obtained by the partial decomposition of
gallic acid, when rapidly heated to 480°.

METALLIC DEPOSITS. By this
term, geologists denote metallic matters
with which the substance of rocks is fre-
quently permeated, in the form of grains,
filaments, nodules, irregular plates or
veins, and strata or beds. In these cases
the metallic matters are supposed to be
of contemporaneous origin with the rocks
or formations containing them.

META'LLIC VEINS. Metallic ores
and mineral substances found in fissures
of rocks which are composed of very
different materials. They occur chiefly
in the primary, and in the lower and

♦

MET

middle, secondary rocks ; they vary in
width from an inch, or less, to several
yards, and sometimes extend to many
miles. These veins, unlike metallic de-
posits, were formed at periods subsequent
to the formation of the rocks in which
they occur.

MET ALLOGRAPH Y {^raWov, a
metal, 7pa0o), to describe). That branch
of science which treats of metals.

ME'TALLOID (ueTaXW, a metal,
e'ldos, likeness). A term applied, at first,
to the metals obtained from the fixed
alkalies and some of the earths. The
term is sometimes applied to the inflam-
mable non-metallic bodies, as sulphur,
phosphorus, &c.

METALLU'RGY (^xeraWoi/, a metal,
epyov, work). The separation of metals
from their ores, comprising the opera-
tions of assaying, refining, smelting, &c.

ME'TALS (/ueraXAov, a mine ; a mine-
ral; a metal). A class of elementary
bodies, most of which are characterized
by their peculiar metallic lustre, and,
generally speaking, by their great specific
gravities. They are divided into different
classes, according to their affinity for oxy-
gen, and the peculiar properties of their
various oxides. They are distinguished
as : —

1. Perfect Metals. Those which com-
bine with difficulty with oxygen, and
consequently are not easily oxidized ; as
such, they readily part with oxygen by
the simple application of heat, and are
converted into pure metals. The best
known are platinum, gold, and silver.
Mercury holds an intermediate place be-
tween these and the next class.

2. Base Met tit. Those which readily
combine with oxygen, partly by mere
contact with the atmosphere, or when
heated and fused. They are not reducible
by the application of heat only, but re-
quire the admixture of some substance,
as coal, to attract the oxygen from the
oxide. The best known are iron, copper,
lead, tin, and zinc. The metals com-
posing this and the preceding class are
termed, from their great specific gra-
vities, the heavy metals.

3. Acidifying Met'ds. Those which,
entering into combination with oxygen,
possess the property of acids, which are
hence called metallic acids. These metals
are tellurium, arsenic, chromium, mo-
lybdenum, tungsten, columbium, and
selenium.

4. Terrigenous Metals. Those whose
oxides yield the earths, properly so called.

217

MET

They resist the action of heat, and are
insoluble in water. These are aluminum,
yttrium, cerium, lantanum, thorium,
glucinum, and zirconium.

5. Katigenous Metals. Those which
oxidize most readily, their oxides consti-
tuting the alkalies. These are magne-
sium, calcium, strontium, barium, li-
thium, sodium, and potassium. As the
metals of this and of the preceding class
are some lighter and others but little
heavier than water, they are called light
metals.

METAME'RIC (jue-ra, a preposition
denoting change, juepor, a part). A term
applied to compounds in which the ulti-
mate elements are the same as in other
well-known combinations, but are con-
sidered to be arranged in a different way :
thus, oxygen, hydrogen, sulphur, and a
metal, may be considered as combined in
the form of sulphuretted hydrogen and a
metallic oxide, or of water (consisting of
oxygen and hydrogen) and a metallic
sulphuret. See Isomeric and Polymeric.

METAMO'RPHIC (nera, a preposi-
tion denoting change, m°p0»7» form). A
term applied by Mr. Lyell to the series
of crystalline slates which occurs espe-
cially in the central ridges of mountain
chains. The term denotes that their
structure has been changed, since the
time of their first formation, by plutonic
action. See Hypozoic System.

METAMORPHO'SIS (vera, a prepo-
sition denoting change, and ixopcprj, form).
Literally, a change of form. A term em-
ployed by Liebig to denote that chemical
action by which a given compound is
caused, by the presence of a peculiar
substance, to resolve itself into two or
more compounds ; as sugar, by the pre-
sence of yeast, into alcohol and carbonic
acid.

METAMORPHO'SIS (in Botany).
Morphology. These terms denote a the-
ory, according to which the several organs
of plants are referred to a typical organ,
varying in their modes of development,
not on account of any original difference
in structure, but on account of especial,
local, and predisposing causes. In the
words of Gothe, the originator of the
theory, plants "develop themselves out
of themselves progressively."

METAMORPHO'SIS (in Zoology). A
term denoing a series of changes which
insects undergo, both in their outward
form and their internal structure, before
they arrive at their perfect condition.
The successive states of existence are
L

MET

the larva, or caterpillar ; the pupa, nymph,
or chrysalis ; and the imago, or perfect
state.

Fabricius distinguishes five kinds of
metamorphosis. 1. The first class com-
prises all those insects in which the
pupae, being entirely without legs, are
absolutely motionless, as in the common
house-fly; these are called coarctate.
2. The second kind occurs in the Lepi-
doptera, and is termed obtected. It is
seen in the silk-worm, which wraps itself
in a silken ball, throws off its last skin,
and becomes a quiescent pupa. 3. The
third kind of metamorphosis is termed
incomplete, and it occurs in the hymeno-
pterous and in many coleopterous insects,
in which the larva is deprived of feet or
other external organs, or possesses these
parts in a very imperfect condition; in
the pupa, however, they are perfectly
distinct. 4. A semi-complete metamor-
phosis occurs in those insects whose
larva only differs from the imago in not
being possessed of wings. 5. Metamor-
phosis is complete, when the perfect in-
sect does not acquire wings at all, but
precisely resembles the pupa.

METAPH Y'SICS (/le-rci, beyond, 0w<rtr,
nature). A vague term, simply denoting
the science of objects beyond that which
is physical and sensible. Generally
speaking, metaphysics is a science purely
speculative, which investigates the ulti-
mate grounds of being, irrespectively of
experience. In this country it usually
denotes the philosophy of mind, as dis-
tinguished from that of matter.

ME'TAPLASM (jieraTrXa 0710c, trans-
formation). In Grammar, the assumption
of a present or nominative for the derived
tenses of verbs or cases of nouns, as
Treco) for Gireo-ov, to devdpos for devdpeai.

METEMPSYCHO'SIS (MeTejLnK'X«™,
the transferring of the soul from one body
to another). The transmigration of the
soul ; a philosophical or religious system
taught by Pythagoras, and embraced by
the Hindus, Egyptians, and other na-
tions. According to this doctrine, the
soul passes into different bodies, under-
going a series of degradations or exalta-
tions, until it becomes reunited with the
Supreme Being, with which it is iden-
tified, " as a river at its confluence with
the sea merges therein altogether."

METEO'RIC STONES ( /ue-rewpor,
floating in the air). Aerolites. Stones
or mineral masses which have fallen
through the air, accompanied with the
disengagement of light and a noise like
218

MIC

thunder. They are composed of silica,
iron, and magnesia, with small propor-
tions of alumina, lime, nickel, chrome,
and sulphur.

METEORO'LOGY (MeTea>Poc, floating
in the air, \670f, a description). Lite-
rally, the science of meteors; but the
term is applied, more extensively, to the
investigation of all the physical causes
which affect the condition of our globe ;
and particularly to the effects of light
and heat on the earth, the ocean, and
the atmosphere, and the results of these
agents in the production of climate.

ME'THYL {fxeBv, wine, i/\n, wood).
The newly-discovered radical, or basyle,
of wood spirit. Methylic ether is a co-
lourless gas, the oxide of methyl. Methol
is a liquid produced in the distillation of
wood.

METONYMY (neTwwfxia, the using
of one word for another). A rhetorical
figure, by which an idea is represented
by a related idea, as substance by quality,
precedent by subsequent, effect by cause.
Thus : "I am Sir Oracle," for, I am in-
fallible. Again: " His' silver hairs will
purchase us a good opinion."

METOPO'SCOPY (/lercoTrov, the fore-
head, irKoirea, to examine). The art of
divining by inspection of the forehead;
practised among the Romans, and in the
middle ages.

METRE. The French standard mea-
sure of length, equivalent to 39 371, or
very nearly 39| English inches. The
French measures ascend and descend in
a decimal progression. Thus,

English Inches.

A Millimetre is ... . -03937

Centimetre -39371

Decimetre 3*93710

Metre 39-371

Decametre .... 39371
Hecatometre . . . 3937-1
Chiliometre . . 39371

ME'TRONOME {nerpov, a measure,
vono?, a musical strain). A short pen-
dulum used by musicians for marking
time, which may be made to vibrate
quickly or slowly as occasion requires ;
the movements of the pendulum are
regulated by wheels and a spiral spring.

MIA'RGYRITE. A sulphur-salt, first
separated byMohs from red silver, under
the name of hemiprismatic ruby-blende.

MI'ASCITE. A columnar variety of
bitterspar, intermixed with asbestos, from
Miaska in Siberia.

MICA (mico, to shine). A simple
mineral, having a shining silvery sur-

M I C

MID

face, and capable of being split into very
thin elastic leaves or scales. It consists
principally of flint and clay, with a little
magnesia and oxide of iron. It is com-
monly called talc, but mineralogists ap-
ply this term to a different mineral. The
brilliant scales in granite are mica. The
varieties which have been examined with
reference to their optical properties and
chemical constitution, are potassa-mica,
the most common variety, which has two
axes ; magnesia-mica, which has but one
axis ; and lithia-mica, including lepidote
and several large-foliated varieties of
what was formerly called common mica.

MICA-SLATE or SCHIST. Micaceous
schistus. One of the metamorphic or
crystalline stratified rocks, of the hypo-
gene class, which is characterized by
being composed of a large proportion of
mica united with quartz. This rock is
termed laminar, when the mica occurs
in continuous laminae, alternating with
layers of quartz ; granular laminated,
when the plates of mica are formed of
scales, and those of quartz of granules or
crystals ; porphyritic, when either of the
preceding varieties contains crystals of
hornblende, felspar, or garnet.

MICA'CEOUS ROCKS. Rocks of
which mica is the chief ingredient : these
are mica- slate and clay-slate. Though
few in number, they are extensively dis-
tributed.

MI'CROCOSM {fiiKpoi, small, xdc/xof,
world). A term fancifully applied by the
ancient philosophers to man, from an
idea of his resemblance in miniature to
the macrocosm, or great world.

MICROCO'SMIC SALT. A triple salt,
consisting of the phosphates of soda and
of ammonia, employed as a flux in ex-
periments with the blow-pipe.

MICRO'METER (/m»cpof, small, m<?-
rpov, a measure). An instrument adapted
to a telescope, for the purpose of measur-
ing small distances, or the diameters of
objects which subtend very small angles,
as those of the celestial bodies.

MICRO'PYLE (M'Kpos-, small, «-v\ti, a
gate). The botanical designation of the
foramen of the ripe seed, comprising the
exostome and the endostome of the ovule,
which lead to the internal portion of the
ovule, or, the nucleus.

MFCROSCOPE (/u«Kpo?, small, ano-new,
to view). An instrument for furnishing
magnified images of objects so minute
that, when held at the distance of dis-
tinct vision, viz , from eight to ten inches
of the eye, the unassisted eye is inca-
219

pable of distinguishing their form and
component parts. This end is obtained
by enlarging the angle of vision.

1. The single microscope consists of a
convex lens, with a very short focal dis-
tance. If an object be viewed through it
at less than its focal distance, but near
to the focus, the rays transmitted through
the lens will be rendered more conver-
gent, and an eye on which they fall will
see the object under a greater angle of
vision, i. e. it will see the object magnified.

2. The compound microscope consists
of two or more convex lenses, or of
a combination of concave specula and
lenses. The former is termed a dioptric
or refracting, the latter a catoptric or
reflecting microscope. 1. In its simplest
form, the refracting microscope consists
of only two convex lenses, that nearest
to the object being called the object-glass,
the other the eye-glass. 2. In reflecting
microscopes, the place of the object-glass
is occupied by a concave speculum, which
also produces an inverted image.

3. The solar microscope is nothing more
than a magic lantern, the light of the
sun being used instead of that of a lamp.
It consists of two lenses, one of which is
called the condenser, because it is em-
ployed to concentrate the rays of the
sun, in order to illuminate more strongly
the object to be magnified. The other is
a double convex lens, of considerable
power, by which the image is formed.
To these is added a plane mirror, for
reflecting the rays of the sun on the
condenser.

4. The oxy-hydrogen microscope is an
instrument in which, instead of the light
of the sun or of a lamp, an intense light
is employed, by means of the combustion
of a piece of lime in a stream of oxy-
hydrogen gas. A cylinder of the ignited
lime, of half an inch in diameter, diffuses
a light greater than that yielded by 153
wax candles.

MI'CROSCOTIUM. The Microscope ;
a modern southern constellation, consist-
ing of ten stars.

MICROZOA'RIA (pticpa £wa, small
animals). The designation given by De
Blainville to the infusory animalcules of
the earlier writers. They are distin-
guished into the heteropoda and the
apoda, the former comprising the sec-
tions rotiferae and ciliiferae, the latter
having no external appendages.

MID- HEAVEN. An astronomical
term for that point of the ecliptic which
is on the meridian at any given moment.
L2

M ID

MIN

MIDDLE EPOCH. A geological epoch
characterized by the presence of the new
red sandstone, a formation consisting of
sand and marl, with rare local interpola-
tions of limestone. See Geology.

MIDDLE LATITUDE SAILING. A
nautical term employed in estimating the
difference of longitude by means of the
differences. of latitude and the interme-
diate departure; this departure is sup-
posed to be an arc of a parallel of
longitude at the intermediate or middle
latitude.

MIDDLE TERM. In a logical syllo-
gism, the middle term (called by the older
logicians " argumenturn") is that with
which each of the other terms, the major
and the minor, is separately compared, in
order to judge of their agreement or dis-
agreement with each other.

MPDRIB. Costa. The midrib of a
leaf is the principal vein, which forms a
continuation of the petiole and the axis
of the leaf; from this all the other veins
diverge, either from its sides or its
base.

MI'EMITE. A variety of Werner's
rhomb-spar, or magnesian limestone,
found at Miemo in Tuscany, imbedded
in gypsum. There are two kinds of
miemite, the granular and the prismatic.

MILDEW. A disease in plants, caused
by the ravages of parasitic fungi.

MILE, GEOGRAPHICAL. Every
degree of latitude contains 60 geographi-
cal miles, and these are always under-
stood to be used, unless other miles are
specified. They must not be confounded
with the British statute mile, which is
the common itinerary measure of our
country, and 69| of which are contained
in a degree of latitude. Hence a great
circle contains only 21,600 geographical
or nautical miles, whilst it contains
24,869 common or statute miles ; or, a
common mile is to a geographical mile
as 21,600 to 24,869. To express this
proportion in feet, we must say,
21,600 : 24,869 \ \ 5280ft. \ 6079089 ft.
Hence a geographical or nautical mile is
about 6079 English feet.

MILK QUARTZ. Rose quartz. A
sub-species of rhomboidal quartz, with a
milk-white or rose-red colour, found in
Bavaria in beds of quartz in granite.
It is probably silica, coloured by man-
ganese.

MILK VESSELS. Laticiferous tissue.

A peculiar tissue, consisting of branched

anastomizing tubes, lying in the bark or

near the surface of plants, and containing

220

a milky juice. They are also called vital
vessels, vessels of the latex, &c. See
Cinenchyma.

MILKY WAY. An astronomical term
applied to that great luminous band
which stretches across the sky, from
horizon to horizon, and which, when
examined through powerful telescopes,
is found to consist entirely of stars scat-
tered by millions, like glittering dust, on
the black ground of the general heavens.

MILLEPO'RID^E {mille, a thousand,
porus. a pore). A tribe of lithophytous
polyps, comprising those in which the
calcareous axis is perforated by numerous
conical pores. *

MILLSTONE GRIT. A coarse sandy
grit, unlike the old red sandstone, fre-
quently replacing or covering up the
coral limestones in many parts of Eng-
land and Ireland.

MI'NERAL. A simple mineral is a
homogeneous substance, whether simple
in an elementary point of view or not,
which presents itself in certain definite
forms, and has a texture, mode of break-
ing, and other physical properties, as
hardness and colour, by which it may be
distinguished from all other substances.
The science which treats of these sub-
stances is called mineralogy, by some
oryctognosy ; while to geology belongs,
among other subjects, the consideration
of their aggregation into rocks, which, in
a geological sense, are masses of mineral
matter, of sufficient extent to constitute
an essential portion of the solid part of
the globe.

1. Minerals are termed crystalline,
when they assume particular symmetri-
cal forms, as that of a cube or a prism ;
amorphous, when they occur in no defi-
nite form.

2. The hardness of minerals is the
resistance which they oppose to the sepa-
ration of their parts. Under this head
(p. 159) the mode of testing their hard-
ness is explained. Their fragility denotes
the comparative ease with which they
may be fractured; their friability, an
imperfect state of aggregation, rendering
them easily divisible into grains.

3. The fracture of minerals, or the
surface exposed when they are broken
by a hammer, varies considerably : it
may be even, splintery, scaly, or con-
choidal— that is, concave like a shell.

4. Minerals are transparent, when they
allow sufficient light to pass through
them to enable a body to be distinguished
when placed behind them; translucent,

MIN

MIS

when they admit light, but are not trans-
parent ; opaque, when they transmit no
light, even when reduced to a finely
laminated state. The lustre, or degree
in which the surface of minerals reflects
light, is various : it may be glimmering,
glassy, pearly, resinous, silky, metallic,
adamantine.

5. The texture of minerals is regular
or irregular ; lamellar, when it presents
the appearance of thin plates ; fibrous,
when composed, as it were, of threads or
filaments ; radiating, when the fibres
converge towards a point.

MINERAL CAOUTCHOUC. A va-
riety of bitumen, resembling caoutchouc
in elasticity and softness, and in remov-
ing pencil-marks.

MINERAL CHARCOAL. A fibrous
variety of non-bituminous mineral coal.

MINERAL GREEN. A hydrated sub-
carbonate of copper, used as a pigment.

MINERAL YELLOW. Patent yellow.
A pigment consisting of chloride and
protoxide of lead.

MINERALIZATION. The process of
converting a substance into a mineral.
A metal combined with oxygen, sulphur,
&c, loses its metallic properties, and
becomes mineralized. The latter bodies
are then termed mineralizers : thus, in
the native oxides, oxygen is called the
mineralizer; in the ores of lead and
copper, sulphur is the mineralizer, &c.

MINERA'LOGY. The science which
relates to the accurate description, and
natural classification of minerals. That
branch of the subject which relates to
the arrangement of the descriptive cha-
racters of minerals, for the purpose of
distinguishing them from one another,
is more properly an art.

MI'NIMUM (superl. of parvus, small).
The least possible quantity or effect, as
opposed to maximum, or the greatest
possible.

MI'NIUM. Red lead or vermilion ; an
oxide of lead, of an intensely red colour,
employed as a pigment. Native minium,
from Hessia, Siberia, &c, is probably
produced by the decomposition of galena.

MINOR TERM. In Logic, the minor
term of a categorical syllogism is the
subject of the conclusion. The minor
premiss is that which contains the minor
term. In hypothetical syllogisms, the
categorical premiss is called the minor.

MINUTE. The sixtieth part of a de-
gree of a circle. Minutes are denoted by
one acute accent, thus (') ; the second,
or sixtieth part of a minute, by two such
221

accents (") ; and the third by three ('").
See Hour.

MFOCENE (uetW, less, Katvo?, recent).
A division of tertiary strata, intervening
between the Eocene and Pliocene forma-
tions; so called, because a minority of
its fossil shells are referable to living
species.

MIRACH, or 0 ANDROMEDA. A
star of the second magnitude, in the
constellation Andromeda.

MIRAGE. A meteorological phenome-
non, depending partly on the vapour of
the atmosphere, and partly on the inter-
mixture of strata of air of different tem-
peratures and densities. It assumes the
appearance of a sheet of water, often
exhibiting the reflected or inverted
images of distant objects. This unusual
refraction frequently occurs when there
intervenes between the spectator and the
objects an expanse of smooth water, as
on the Oldenburg coast of the North Sea,
where it is called Kimmung ; or as at the
Straits of Messina, where it is called
Fata Morgana.

MIRROR (mirer, French, to look at).
Any polished body which is impervious
to the rays of light, and reflects them
equally, so as to exhibit the images of
objects placed before it. When formed
of metal, it is sometimes termed specu-
lum, the Latin term for a looking-glass.

1. Plane Mirror. That which has a
plane surface, as the common looking-
glass.

2. Concave Mirror. That which has a
hollow surface, which collects the rays
and reflects them to a focus in front of
the mirror, thereby enlarging the image
of the object.

3. Convex Mirror. That which has a
convex surface, which disperses the rays,
and consequently diminishes the image
of the object. These concave and convex
surfaces are formed of different curves,
according to the purposes intended, and
may be spherical, parabolic, or elliptical.
Mirrors with mixed surfaces are either
cylindrical or conical. See Burning-
glass.

MISPI'CKEL. Arsenical pyrites; an
arsenio-sulphuret, some varieties of
which, containing accidentally admixed
silver, constitute Werner's weiss-ertz.

MIST. A meteorological phenomenon,
occasioned by the vapour of the atmo-
sphere becoming visible; and this is a
consequence of the temperature of the
air being reduced below that of the
vapour.

L3

MIS

MOL

MISY. A designation of green vitriol,
or sulphate of iron, as it occurs in the
form of yellow scales, in the Hartz.

MI'TRINiE. Mitre-shells ; a sub-
family of the Volutidce, or volutes, named
from the typical genus mitra ; the spire
is always acute, generally longer than the
aperture, and the lower plaits smallest ;
the foot is small, not dilated on the sides,
and the siphon rather long.

MIXTURE and COMPOUND. In a
chemical mixture, the aggregate particles
can be separated by mechanical means,
and the proportion of the different consti-
tuents determined; in a chemical com-
pound, no mechanical power can separate
the constituent particles : a new substance
is formed, which possesses no properties
in common with the original ingredients.

MNEMO'NICS (hvwovikos, belonging
to memory). A term applied to any sys-
tem in which the memory of particular
objects is exercised by artificial means.
The principle of all such systems is, to
associate in our minds two notions, one
of which is more easily remembered than
the other, but, in consequence of the
association, is always followed by that
other. t

MOBI'LITY {mobilis, moveable). A
property of matter by which it is capable
of being put into motion by the action of
a force which is sufficient to overcome
its inertia.

MOCHA STONE. A translucent chal-
cedony, containing dark outlines of arbor-
ization, like vegetable filaments, and
named from Mocha, in Arabia, where it
is chiefly found.

MODAL. In Logic, a modal categori-
cal proposition is one which asserts that
the predicate exists in the subject in a
certain mode or manner, as "accident-
ally," " wilfully," &c.

MODERN EPOCH. In Geology, the
present period comprehends all those
deposits which owe their origin to causes
now in action, and has reference to the
phenomena which are taking place at the
surface of the earth. See Geology.

MO'DULUS. 1. In the theory of loga-
rithms, the modulus is the number by
which all the logarithms in one scale of
notation must be multiplied, in order to
adapt them to the same number of an-
other scale. Thus the modulus of con-
version between the common logarithms
and the Napierean or hyperbolic scale, is
0*43,429,448. 2. In Physics, the modulus
of elasticity is a numerical co-efficient,
which is constant for the same body, but
222

variable for different bodies ; and which
has no influence on the law of elasticity,
though it serves to measure its effects.

MO'HSITE. Crystallized titaniate of
iron, found in Dauphiny.

MOIRE'E METALLIQUE. Crystal-
lized tin-plate, obtained by pouring on
heated tin-plate a mixture of two parts
of nitric acid, and three of muriatic acid
diluted with eight parts of water. When
varnished, it is worked into ornamental
vessels.

MOLA'SSE (molle, French, soft). A
provincial name for a soft green sand-
stone, associated with marl and conglo-
merates, belonging to the Miocene Ter-
tiary Period, extensively developed in
the lower country of Switzerland.

MOLE'CULAR ATTRACTION. That
mode of attraction which operates upon
the particles, or molecules, of a body, as
distinguished from the attraction of gra-
vitation. According to the molecular
theory, all bodies are viewed as aggre-
gates of minute particles, atwms, or mole-
cules, and are formed by the attractive
and repulsive forces acting on them at
immeasurably small distances.

MOLECULE (dim. of moles, a mass).
A minute particle of a mass or body.
It differs from atom, in being always con-
sidered as a portion of some aggregate.

1. Complex organic molecule. An
association of two or more binary com-
pounds, comparatively simple in consti-
tution, often isolable substances and pos-
sessed of considerable stability.

2. Integrant molecules. The name
given by Haiiy to the last particles into
which the nucleus of a crystal can be
mechanically divided.

3. Molecules, active. Minute moving
particles, found in all vegetable matter
when rubbed in pieces and examined
under a powerful microscope.

MO'LISITE. The mineralogical name
of the crystallized titaniate of iron of
Dauphiny.

MOLLUSC A (mollis, soft). A term
employed by Cuvier to designate the
fourth grand division of the animal
world, and founded upon the unimpor-
tant circumstance that the beings to
which it is applied have soft bodies, un-
supported by any internal or tegumentary
framework of sufficient density to merit
the name of skeleton. These animals
belong to the Hetero-gangliata of Owen,
the Cyclo-gangliata of Grant. See Zoo-
logy.

MOLYBDE'NUM in6\v/3ios, lead). A

MON

MON

white metal closely allied to tungsten.
Its name was derived from the resem-
blance of its native sulphuret, or molyb-
dena-glance, to lead.

MOLY'BDIC ACID. Ochry molybde-
num. An acid obtained from the native
sulphuret of molybdenum, in the form
of a yellow powder. Its salts are termed
molybdates. The molybdate of lead, or
yellow lead ore, occurs as a massive mi-
neral, lamelliform, and crystallized in
splendid groups on compact limestone,
&c. ; chiefly from Bleiberg in Carinthia.

MOME'NTUM. A term in physics
signifying the force of percussion, or
the intensity of a moving body ; and
this is always equal to the quantity
of matter multiplied into the velocity.
Thus, a ball of four pounds' weight,
moving at the rate of eighteen feet in a
second, has double the momentum of a
ball of three pounds' weight, moving at
the rate of twelve feet per second, for
4 x 18 is double of 3 x 12.

If the momenta of two or more forces,
acting in opposite directions on a solid
body, be equal, the body will continue
at rest ; and this condition is called the
equilibrium, or statical momentum of the
forces.

MON-, MONO- (/ioi/o?, single, alone).
A Greek prefix, denoting unity.

1. Mon-adelphia (a6e\<pot, a brother).
The sixteenth class of plants in the Lin-
naean system, in which the filaments are
all united into one tube.

2. Mon-andria (ui^p, a man). The
first class of plants in the Linnaean sys-
tem, containing only one stamen.

3. Mono-carpous {Kapirot, fruit). Bear-
ing fruit only once, and dying after fruc-
tification, as wheat. This is the character
of what are commonly called annual
plants, and of a few others, which, like
the American aloe, although they may
live for many years, produce flowers and
fruit only once, and then die.

4. Mono-ceros (»cepac, a horn). The
Unicorn ; a modern southern constella-
tion, consisting of thirty one stars.

5. Mono-chlamydece (x\a/uuf, a tunic).
A sub-class of exogenous plants, in which
the flowers have only one envelope, viz.
a calyx.

6. Mono-chord (xop6i], a string). Sono-
meter. An apparatus for exhibiting the
phenomena of sonorous bodies and the
ratios of their vibrations. In its most
simple construction, it consists of a single
string of wire or catgut strained by means
of two pins across two wooden bridges, I

223 '

which are fastened into a strong board ;
the part of the board beneath the string
is graduated, so that the latter may be
readily made to vibrate in any required
number of parts.

7. Mono-chroite. Subsesquichromate
of lead ; one of the ores containing chro-
mium, occurring with chromate of lead
in the Ural.

8. Mono-chromatic (xptfyza, colour).
Having only one colour ; a term applied
to a lamp which, being fed with certain
substances, yields a flame of only one
colour; and, hence, all objects viewed by
this light are deficient in those varied
hues which they reflect when viewed by
solar light or that from ordinary com-
bustibles.

9. Mono-cotyledons (kotu\m3«v, a seed-
lobe). Plants which have only one coty-
ledon, or seed-lobe. This structure of
the embryo corresponds with the endo-
genous structure of the stem ; and hence,
monocotyledon and endogen are convert-
ible terms.

10. Mon-oecia (otKof, a house). The
twenty-first class of plants in the Lin-
nean system, in which the stamens and
pistils grow on separate flowers, but on
the same individual, as in hazel, birch,
oak, &c.

11. Mono-gram (ypdnfia, a written
letter). A mark or cipher consisting of
one letter, which is formed by the inter-
lacing of two or more letters, employed
as an abbreviation, especially on ancient
coins.

12. Mono-gynia (71/1///, a female). The
name given by Linnaeus to those orders
of plants, in which each flower contains
only one pistil.

13. Mono-lith (\i9ov, a stone). A pillar
consisting of a single stone, as the
obelisk of Luxor, the Zodiac of Den-
derah, &c.

14. Mono-mera (nepo?, a part). A sec-
tion of homopterous insects, in which the
tarsi have only one joint, as in the
Coccidce, or Scale Insects.

15. Mono-morphous (fxop<pi], form). Of
a single form; a term proposed by Mr.
Westwood for certain neuropterous in-
sects, which, in their larva state, are
similar in form to the perfect insect,
though wingless.

16. Mono-myaria (/xur, a muscle). A
general name for bivalves, whose shell
is closed by a single adductor muscle, as
in the oyster and the pecten. See Di-
myaria.

17. Mono-neura {vevpov, a nerve). A

L4

MON

MON

name given by Rudolphi to those animals
which were supposed to possess only the
ganglionic system of nerves, as the mol-
lusca and the insects.

18. Mono-petalous (7rera\ov, a leaf).
Having a single petal, as applied to the
corolla of plants. The difference, how-
ever, between a mono-petalous and a
poly-petalous corolla is, that in the former
the leaves are united, whereas in the
latter they are distinct. A more proper
term for the former is gamo-petalous,
which indicates cohesion.

19. Mono-phyllous {<pv\\ov, a leaf). A
term sometimes employed as synonymous
with monosepalous, and denoting cohe-
sion of the sepals, or a gamosepalous
calyx.

20. Mono-pleurohranchians (wAcwpa,
the side, /3pu7x*a> gills). An order of
the Paracephalophora, in which the
branchiae are more or less completely
covered by a portion of the mantle, and
situated on the right side of the body.

21. Monosepalous. Having a single
sepal, or calyx- leaf. The term gamo-
sepalous is preferable, for the reason
assigned under the term mono-petalous.

22. Mono-thalamous (0d\a/uof , a cham-
ber). A term applied to a shell which
forms a single chamber, as that of the
argon auta.

23. Mono-thyra {66pa, a door). A term
applied by Aristotle to all spiral univalve
shells. See Dithyra.

24. Mono-tremata (Tpdw, to bore a
hole). An order of Mammalia, charac-
terized by the presence of a common
cloacal outlet for the excremental and
the generative products. They are ovo-
viviparous animals, being intermediate
between the truly viviparous mammalia,
and the oviparous birds and reptiles. The
order contains only two species, the
echidna or spiny ant-eater, and the orni-
thorrhynchus or duck-billed platypus.

MONAD (/uovar, unity). The smallest
of all visible animalcules, spoken of by
Buffon and his followers as constituting
the elementary molecule of organic
beings. Ehrenberg computed that a sin-
gle drop of liquid may contain 500,000,000
monads, a number equal to that of all
the human beings on the surface of the
globe.

1. Monad of the Physiologists. An
elementary particle of an organic body.
Thus, the primary cell or germ from
which all the other cells of the brain are
produced, is termed the primary monad ;
and the secondary cells or particles, pro-
224

duced by this, are termed secondary
monads.

2. Monad of the Metaphysicians. An
active kind of principle, endued with
perception and appetite, ascribed to
each elementary particle of matter. The
mutual reaction of the mind and body
upon each other, accordingly, consists of
the action of the mental monad upon the
internal states of the monads of the body,
and vice versa.

MONGOLIAN RACE. One of the
five principal races of mankind, in which
the head is almost square, the cheek-
bones projecting outwards, the nose flat,
the face broad and flattened, with the
parts imperfectly distinguished, the in-
ternal angle of the eye depressed towards
the nose.

MO'NITOR. An animal of the sau-
rian or lizard tribe, some species of
which are found in both the fossil and
the recent state.

MONS MENELAUS. A modern
northern constellation consisting of
eleven stars.

MONSOO'NS (mooseem, Malay, a sea-
son). Periodical winds, which blow
half the year from one quarter, and the
other half from the opposite direction.
From April to October a south-west wind
prevails north of the equator, southward
of this a south-east wind ; from October
to April, a north-east wind prevails north
of the equator, and a north-west between
the equator and 10° of south latitude.
The monsoons occur in the Bay of Ben-
gal, the Arabian Sea, the Mozambique
Channel, on the coasts of Sumatra and
Java, along the coast of China, and off
the western coast of New Holland.

MONTGOLFIER. An air-balloon, or
aerostat, made of paper, with a large
opening below, where fire is applied for
the purpose of rarefying the contained
air, until it is of less specific gravity than
the atmospheric air. It is named from
its inventor.

MONTH. 1. The average sidereal
month, or complete circuit of the hea-
vens, comprises a period of 27d. 7h. 43m.
11.5s. 2. The average lunation, common
month, or interval between two conjunc-
tions with the sun, consists of 29d. 12h.
44m. 2.9s. 3. The average anomalistic
month, or revolution from perigee to
perigee, consists of 27d. 13h. 18m. 37.4s.
4. The average tropical month, or period
from the vernal equinox to the vernal
equinox again (the equinox being in re-
trograde motion), consists of 27d. 7h.

M OR

MOT

43m. 4.7s. 5. The average nodical month,
or interval of time from a node to a node
of the same kind, comprises 27d. 5h. 5m.
36.0s. The quantities of these months
are here reckoned in mean solar days.

MONTMA'RTRITE. A yellowish
massive mineral, found at Montmartre,
near Paris, consisting of the sulphate and
the carbonate of lime.

MOOD (in Grammar). A mood ex-
presses the manner in which the action
or state denoted by the verb exists, as
being certain, contingent, &c.

MOOD (in Logic). The mood of a
categorical syllogism is the designation of
its three propositions, in the order in
which they stand, according to their
quantity and quality. Only eleven moods
can be used in a legitimate syllogism.

MOON. A heavenly body which
moves round the earth in the period of a
lunar month, accompanying the earth,
as a satellite, in its orbit round the sun.
The average distance of the moon from
the earth is 237,000 miles.

MOON-CULMINATING. A term
applied, in astronomy, to those stars
which pass the meridian soon before or
after the moon. In the nautical almanac,
these stars are selected for each day, and
their right ascensions are given for their
Greenwich meridian transits.

MOONSTONE. Adularia. Naker
felspar, principally found on Mount St.
Gothard. It is the famous petuntse of the
Chinese, which constitutes the vitrifying
ingredient of their porcelain. The fine
variety from Ceylon, when cut en cabo-
chon, is called moonstone. See Sun-
stone.

MORAINE. A mass of debris accu-
mulated along the anterior edge and
lateral margins of some of the larger
glaciers, in the form of a long dyke or
parapet, called in the Tyrol trockne
muren, and in Savoy moraine. In Ice-
land, where the glaciers are called jokiil,
the moraines are called joki'Usgidrde.

MORDANT (mordeo, to bite). A sub-
stance employed in dyeing, which has an
affinity both for the colouring matter and
for the stuff to be dyed ; the combination
of the colour with the texture of the
stuff is thus aided by a kind of double
decomposition. These substances were
supposed, in the infancy of the art, to
seize the fibres by an agency analogous
to that of the teeth of animals.

MO'ROXITE. Norwegian apatite; a
phosphate of lime, of a blue-green colour,
occurring native in combination with
225

fluoride of calcium, in the form of hex-
agonal prisms.

MORO'XYLIC ACID {fxopov, the
mulberry, £v\ov, wood). Moric acid.
An acid procured from the bark of the
mulberry-tree, forming compounds with
salifiable bases, called mor oxalates.

MO'RPHIA (Morpheus, the god of
sleep). A vegetable alkali existing in
opium, of which it constitutes the nar-
cotic principle.

MORPHO'LOGY (nop<pyn, form, \6yos,
a description). The history of the mo-
difications of form which the same organ
undergoes in different animals or plants.
See Metamorphosis.

MORTAR CEMENT. A mixture of
lime and siliceous sand, the former being
in the state of hydrate or slaked lime.
Hydraulic mortar is obtained from con-
cretionary masses found in marl, and
also in the form of isolated blocks in the
bed of the Thames.

MOSAIC GOLD, (aurum musivum).
The alchemical name of the bisulphuret
of tin. It is produced in fine flakes of a
beautiful golden colour, and is used as a
pigment.

MOSASAU'RUS. The saurian of the
Meuse ; a gigantic extinct aquatic lizard,
nearly allied to the monitor, and found
in the cretaceous series, chiefly on the
banks of the Meuse.

MO'SCHIDjE (moschus, the musk
deer). The Musk Deer tribe ; a family
of the Ruminantia, differing little from
the rest of the order, except in the ab-
sence of horns.

MO'SCHUS. A quadruped resembling
the chamois or mountain goat, from
which the perfume musk is obtained.

MOTACILLI'NjE {motacilla, the wag-
tail). Motacilline birds, or Wag-tails ;
a family of the Cantatrices of Mac Gil-
livray, with slender form, rather short
neck, and oblong head; readily distin-
guished from the allied families by the
elongated tail and peculiar form of the
wings.

MOTHER OF PEARL. A term ap-
plied to shells composed of alternate
layers of coagulated albumen and carbo-
nate of lime.

MOTHER WATER. The liquid
which remains when sea water, or any
other solution containing various salts,
has been evaporated, and the crystals
removed. The mother water contains
deliquescent salts, and any existing im-
purities.

MOTION. The continued change of
L5

MOT

MOU

place of a body, or of any parts of a body ;
for, in the cases of a globe turning on its
axis, and of a wheel revolving on a pivot,
the parts of these bodies change their
places, while the bodies themselves re-
main stationary.

1. Uniform motion is that of a body
which passes over equal spaces in equal
times. It is produced by a force having
acted on a body once, and having ceased
to act, as the stroke of a bat on a cricket-
ball. Were there no opposing force, as
gravity, the motion of such a body would
be uniform.

2. Retarded motion is produced by
some force acting on a body in a direc-
tion opposed to that which first put it in
motion, and thus gradually diminishing
its velocity.

3. Accelerated motion is produced when
the force which puts a body in motion
continues to act upon it during its mo-
tion, so that its velocity is continually
increased.

4. In cases of accelerated and of re-
tarded velocity, a distinction is observed
between the initial and the final velocity
of a body : the former is exhibited by
the body when it commences its motion ;
the latter only after the lapse of a certain
time : both are measured by the space
which the body would have passed over,
in one second, with the uniform initial or
final velocity, as the case may be.

5. Reflected motion is produced when
a body is turned out of a straight line by
some force independent of gravity ; it is
the result of re-action being contrary to
action. If a ball be thrown against a
wall, it rebounds, in consequence of the
re-action of the wall against which it is
struck, and it is said to have reflected
motion.

6. Simple motion is that which results
from the operation of a single force. But
when two or more forces act in different
directions on the same body, at the same
time, the motion so produced is called
compound; and the single force which
represents the combined effects of all the
forces, is called the resultant.

7. Circular motion is the motion of a
body in a ring, or circle, and is produced
by the action of two forces. By one of
these forces the moving body tends to
fly off in a straight line, while by the
other, it is drawn towards the centre, and
thus it is made to revolve, or move round
in a circle. The force by which a body
tends to go off in a straight line is called
the centrifugal force; that which draws

226

it towards the centre, is called the cen-
tripetal force.

8. In curvilinear motion the direction
of the body is neither straight forward
nor diagonal, but through a line which is
curved. This kind of motion may be in
any direction ; but when it is produced
in part by gravity, its direction is always
towards the earth. A stream of water
from an aperture in the side of a vessel,
as it falls towards the ground, is an ex-
ample of a curved line ; and a body pass-
ing through such a line, is said to have
curvilinear motion.

9. It may happen that an object is in
motion, as well as the spectator, in which
case, the motion of the latter is trans-
ferred to the former, and the whole mo-
tion of the object, compounded of that
which it has of its own, and that which
it appears to have from the motion of the
spectator, is called the apparent or rela-
tive motion.

MOTION, CENTRE OF. That point
which remains at rest, while all the other
parts of a body move about it.

MOUNTAIN. A considerable eleva-
tion of the surface of the earth, attaining
a height of more than two thousand feet.
A chain of mountains is, strictly speak-
ing, a series of which the bases are con-
tinuous. A hill is merely a small moun-
tain, and the lowest elevations of this
kind are called hillocks or mounds. A
mountain of a conical form, with the
summit narrow, is named a cone; when
of the same form, but more massy, and
with the summit depressed and rounded,
it is a dome; these are of volcanic origin.
See Platform and Peak.

MOUNTAIN BLUE. Blue copper, or
carbonate of copper, the more remark-
able varieties of which are those from
Chessy, and from the Bannat, combined
with various substances. Mountain green
is the common copper green, also a car-
bonate.

MOUNTAIN CORK. The elastic
variety of asbestos. Mountain leather
is the tough variety. When it occurs in
very thin pieces, it is called mountain
paper. The ligniform variety is named
mountain or rock wood.

MOUNTAIN LIMESTONE. Carbo-
niferous limestone. A series of limestone
strata of marine origin, usually forming
the lowest member of the coal measures.

MOUNTAIN SOAP. A mineral sub-
stance found in the island of Skye, and
employed in crayon painting.

MOUNTAIN TALLOW. A curious

MUL

MUR

mineral with the colour and feel of tallow,
found in a bog on the borders of Loch
Fyne in Scotland, and in one of the
Swedish lakes. It differs from every
known class of bodies. In volatility and
combustibility it resembles naphtha.

MOYA. A term applied in South
America to mud poured out from vol-
canoes during eruptions.

MUCIC ACID. An acid first obtained
from sugar of milk, and hence termed
saccholactic ; but as all the gums appear
to yield it, and the principal acid in the
sugar of milk is the oxalic, it is now
called mucic.

MUCUS. One of the primary animai
fluids, perfectly distinct from gelatin.

MUDSTONE. A local name for part
of the Upper Silurian Rocks of Mr. Mur-
chison.

MUFFLE. A small earthen oven,
fixed in a furnace, and used in cupella-
tion, and other processes which require
the access of air.

MUGI'LIDjE (mugil, the mullet). The
Mullet tribe ; a family of acanthoptery-
gious fishes, including the genera mugil,
tetragonurus, and atherina. This family
is included in the cycloid order in the
system of Agassiz.

MULLER'S GLASS. Another name
for hyalite, a siliceous substance found in
fissures in vesicular basalt and basaltic
greenstone.

MULTILATERAL {multa latera ha-
bens). Having many sides; as applied
to a geometrical figure, bounded by more
than four straight lines. See Polygon.

MULTILOCULAR {multos looulos ha-
bens). Having many loculi or chambers ;
a term applied to those shells which, like
the nautilus and ammonite, are divided
into many compartments.

MULTINO'MIAL {multa nomina ha-
bens). Having many terms ; an alge-
braical expression denoting a quantity
which consists of an indefinite number of
terms, as a + b — c + x — y, &c. Such
a quantity is also termed a polynomial.

MU'LTIPLE {multiplex, manifold). A
number which includes another a cer-
tain number of times ; thus 6 is a mul-
tiple of 3 or of 2 ; 18 is a multiple of 9 or
of 6. Hence, any number of equal mag-
nitudes added together give a multiple
of any one of them ; thus 6 + 6 + 6, or
18, is a multiple of 6. See Submultiple.

Least common multiple. A common

multiple of two or more numbers is one

which contains each of them ; and, of

course, the least such number is their

227

least common multiple. Thus 6, 12, 18,
&c. are all common multiples of 2 and 3 ;
but 6 is their least common multiple ; 12,
24, 36, 48, &c. are all common multiples
of 2, 3, 4, 6, and 12 ; but 12 is their leaf*
common multiple.

MULTIPLE POINTS. In Geometry,
when two or more branches of a curve
pass through the same point, this is
called a multiple point ; and it is equally
so called, whether the branches touch or
cut one another.

MULTIPLICAND. That factor, num-
ber, or quantity in multiplication, which
is to be repeated the number of times
denoted by the other factor, or the mul-
tiplier.

MULTIPLICATION. The arithme-
tical method of finding what number
would result from adding several of the
same numbers together. In other words,
it is the process of forming a multiple :
thus, to multiply 6 by 9, is to repeat 6
nine times, and to add all the results
together. This is the first and fundamen-
tal meaning of multiplication. The num-
bers multiplied are called factors, and
the result is called the product.

MULTIPLIER. An instrument in-
vented simultaneously by Schweigger
and Poggendorf, for indicating the de-
flecting influence of an electric current,
and applied in cases in which the current
is so weak as to require its conduction
several times round the needle, thus re-
peating or multiplying the deflecting in-
fluence of the single current.

MU'LTI VALVE {multos valvas ha-
bens). Having many valves, as the
chitons among testaceous mollusca.

MURjE'NIDjE {murcena, a lamprey).
Anguillidce. The eel tribe; the single
family of Malacopterygious or soft-spined
fishes, belonging to the section Apodes,
in which the ventral fins are wanting.

MURAL CIRCLE. An instrument
for measuring the distances of stars from
the poles or the Zenith. It consists of a
circle constructed of metal, and mechani-
cally divided into equal parts, as degrees,
minutes, &c. A tube is adjusted to the
circle so as to revolve together with it on
an axis concentric with the circle. The
axis is let into a wall, and rendered ca-
pable of adjustment both in a vertical
and horizontal direction ; so that, like
the axis of the transit, it can be main-
tained in the exact direction of the east
and west points of the horizon, the plane
of the circle being consequently truly
meridional.

L6

MUR

MUS

MU'RCHISONITE. A variety of
moonstone or felspar, occurring in the
new red sandstone, in the neighbourhood
of Dawlish.

% MURE'XIDE (murex, a molluscous
animal yielding a purple dye). A beau-
tiful purple product of the decomposition
of uric acid, first described by Dr. Prout
as purpurate of ammonia. Murexan is
the purpuric acid of Prout.

MU'RI ACITE. Anhydrous sulphate of
lime, also called anhydrite and cube-spar,
occurring crystalline, fibrous, granular,
and compact. To the last of these belong
some of the Italian varieties known by
the names of bardiglio and bardiglione,
as also the singular fibrous-compact
variety familiarly called tripe-stone (pierre
des trippes), from the salt mines of Wie-

MURIATE or HYDROCHLORATE.
A salt formed by the combination of mu-
riatic or hydrochloric acid. Metallic muri-
ates which contain an excess of acid
are called oxy-muriates ; those in which
there is a deficiency of acid, are named
sub-muriates.

MURIA'TIC ACID {muria, brine).
Hydrochloric acid. An acid consisting
of chlorine and hydrogen, and contained
in great abundance in sea-water, in com-
bination with soda and magnesia. Oxy-
genated muriatic acid is another name
for chlorine.

MURICA'LCITE. Another name for
rhomb-spar, a mineral consisting of the
carbonates of lime and magnesia. It is
also called bitter-spar.

MURFCID^E. The Murexes and
Whelks ; a family of carnivorous Gaste-
ropods, having the respiratory siphon in
general very much developed, and its
corresponding canal at the base of the
shell always straight.

MURICFIOS. Murexes; a sub-family
of the Muricidae, named from the typical
genus murex, and sometimes called rock-
shells, from the roughness and irregula-
rity of their surface.

MU'RIDjE (mus, a mouse). The Rat
tribe; a family of the Rodentia, con-
taining the smallest and the most nume-
rous species of the Mammalia.

MU'RI DE {muria, brine). The name
first given to bromine, from its being an
ingredient of sea- water.

MU'RI FORM (murus, a wall, forma,
likeness). Wall-like ; a term applied to
the tissue constituting the medullary
rays in plants, from its presenting an ap-
pearance similar to that of bricks in a wall.
228

MU'SCA. The Fly; a modern northern
constellation, consisting of six stars,
situated between Crux and the South Pole.

MU'SCHELKALK {muschel, a shell,
kalk, lime). A limestone, belonging to
the Upper New Red Sandstone group.
Its position is between the Magnesian
Limestone and the Lias. This formation
has not yet been found in England, and
the German name is adopted by English
geologists.

MUSCI. The Moss tribe of Acotyle-
donous plants. Cellular, Jlowerless plants,
with leaves imbricated, entire, or ser-
rated ; reproductive organs either axil-
lary bodies containing spherical or oval
particles, emitted on the application of
water, or thecce, seated on a seta or
stalk.

MUSCICA'PID^E (muscicapa, the fly-
catcher). MyiotherincB. The Fly-catchers;
a family of the Insessores, or Perching
birds, characterized by the peculiar form
of the bill, with the strong bristles at its
base, and by the small size of the feet.
See Dentirostres.

MUSCID^ (musca, a fly). The Fly
tribe ; a family of Dipterous insects, be-
longing to the sub-section Athericera,
readily distinguished by their strong gene-
ral resemblance one to another. Their
larvae are known as maggots.

MUSCOVY GLASS. Another name
for mica, most of the commercial article
being brought from Siberia, where it is
used for window-glass.

MUSCULAR IMPRESSIONS. A
term applied to those indented marks in
acephalous bivalves, which indicate the
insertion of those muscles by which the
animal is attached to its shell. Of these
there are three principal varieties ? —

1. The lateral impressions, which de-
note that the animal has two adductor
muscles, as in unio cardium, and all the
most typical bivalves.

2. The central impression, which de-
notes the presence of only one adductor
muscle, which is generally in the middle
of the shell, as in the oyster.

3. The pallial impression, which oc-
curs in all these shells, and is indicated
by a depressed line, often sinuated, run-
ning parallel with the ventral margin.

MUSICAL SOUND. A succession of
sounds which follow one another with
such regularity as to produce the impres-
sion of a single sound.

MUSOPHA'GIDvE. The Plantain-
eaters ; a family of birds intermediate
between the Finches and the Hornbills,

MYR

M Y T

the Musophaga being the most conspi-
cuous of the group.

MUSSEL BAND. The black shale
of coal mines, containing embedded
mussel-shells.

MUSSITE. A pale green mineral
from Mussa, in Piedmont, consisting
of a variety of augite.

MUSTE'LID^E {mustela, a weasel).
The Weasel tribe; a family of carni-
vorous vertebrata, which are mostly
semi-plantigrade, a portion of the sole
touching the ground. These animals,
owing to the length of theif bodies, and
the shortness of their limbs, are enabled
to insinuate themselves into small ori-
fices, and are hence called vermiform.

MYADiE. Gaping Bivalves ; a family
of the macrotrachian bivalves ; named
from the genus mya, and having the
valves more or less gaping at one or both
extremities.

MYCE'LIA (/divan?, a mushroom). The
rudiments of fungi, or the matter from
which fungi are produced.
M YELENCE'PH ALA (/m/cAop, marrow,
hyKecpaXov, the brain). A term applied by
Owen to the grand primary division Ver-
tebrata of the animal kingdom, compris-
ing animals which possess a brain and
spinal marrow. These are the Spini-
cerebrata of Grant.

MYELONEU'RA (^veXo?, marrow,
vevpov, nerve). The name given by Ru-
dolphi to a group of animals correspond-
ing with the Articulata of Cuvier, which
have a ganglionic nervous system, form-
ing a cord considered analogous to the
spinal marrow of the Vertebrata.

MY'IOTHE'RIN^ [pmd, a fly, flrjpdw,
to chase). Fly-chasers ; a family of the
Insessores or Perching birds, or the Ex-
curtrices of Macgillivray. The terra is
synonymous with Muscicapidae.

MYRIA'PODA (/jivpior, innumerable,
Trow?, irodoc, a foot). The first class of
the Diplo-gangliata, or Entomo'ida, com-
prising animals with articulated bodies,
all the segments of the trunk being pro-
vided each with one or two pairs of
jointed ambulatory feet. They are di-
vided into the two following orders by
the differences of their jaws and feet : —

1. Ctylognatha, or those which have
solid cylindrical segments, antennae with
seven joints, two strong mandibles with-

out palpi, and very short feet terminated
by simple ungues, as in the iulus,

2. Chilopoda, or those in which the
segments are more soft and depressed,
and each furnished with a single pair of
feet ; the antennae have more than thir-
teen joints, and the mouth is furnished
with palpigerous mandibles, and with an
upper and lower lip, as in the scolopendra
morsitans.

MY'RICIN. The ingredient of wax
which remains after digestion with alco-
hol.

MYRISTICA'CE^E. The Nutmeg tribe
of dicotyledonous plants. Trees with
leaves alternate ; flowers dioecious, with
no trace of a second sex ; fruit baccate,
dehiscent, 2-valved; seed nut-like, en-
veloped in a many-parted arillus.

MY'RMELEO'NIDjE (m<''PMi?, an ant,
\ca>f, a lion). A family of Neuropterous
insects, named from the typical genus
myrmeleon, the larvae of which, from
their peculiar habits, have acquired the
name of ant-lions.

MY'RMOTHERINjE (miVmh?, an ant,
0ripdu>, to chase). Myrmotherine birds,
or Ant-catchers ; a family of the Canta-
trices of Macgillivray, distinguished from
the Thrushes chiefly by their shortened
form. The only British species is the
Cinclus or Dipper.

MYRO'NIC ACID (n^pov, an odorous
oil). A bitter acid procured from black
mustard seeds.

MYRTACEiE. The Myrtle tribe of
dicotyledonous plants. Trees or shrubs
with leaves opposite, entire, and marked
with transparent dots ; flowers polype-
talous ; stamens perigynous ; carpella
concrete; inferior ovarium with several
cells.

M YSTACI'NEjE (M«5o-raf, moustache).
A family of the Infusoria, including
those which have superficial cilia dis-
posed in groups.

MYTILA'CEjE. The Mussel tribe;
an order of the conchiferous Mollusca,
named from the mytilus, in which the
mantle remains open in front (at the end
where the mouth is situated), and closed
behind, an aperture being left for the
egress of the fluid. They have a foot
sufficiently strong for crawling, and com-
monly affix themselves by a byssus.

229

NAP

NAT

N

NA'CREOUS {nacre, pearl). A term
applied to a shell which has a pearly
lustre and reflects iridescent light.

NACR1TE. The name given by
Jameson to talcite, or the earthy talc of
Werner; a very rare mineral, occurring
in veins, with sparry ironstone and ga-
lena, in the mining district of Freyberg.

NADIR. An Arabic term denoting
that point of the sphere of the heavens
which is diametrically opposite to the
zenith, and vertically beneath the feet of
a spectator. The term evidently cor-
responds with the German nieder (down).
The zenith and the nadir are the two
poles of the horizon. See Zenith.

NADLESTEIN. Another name for
rutile, an ore of titanium.

NAGYAG ORE. Foliated tellurium,
a mineral consisting of tellurium and
lead.

NAPADES. A family of fresh-water
conchiferous mollusks, comprising the
genera unio, hyria, anodon, and iridina,
occurring abundantly in the North Ame-
rican rivers.

NAKED SEEDS. An incorrect term,
applied by Linnaean botanists to the
small seed-like fruits of the Labiatae,
Boraginaceae, and other families of plants.
Seeds entirely destitute of a pericarp
occur only in Coniferae, Cycadaceae, and
Gnetaceae.

NAKER FELDSPAR. A species of
feldspar, also called adularia, and found
principally on Mount St. Gothard, but
not in the valley of Adula, from which
the latter name is derived. The fine
variety from Ceylon, when cut en carbo-
chon, is called moonstone ; and a yellow
naker feldspar with reddish dots has ob-
tained the name of sunstone, which is
also sometimes given to the beautiful
avanturino variety of common feldspar.

NANCE'IC ACID. An acid found in
many acescent vegetable substances, and
named by Braconnot from the town of
Nancy

NAPHTHA. A highly inflammable,
thin, colourless oil, which issues from
the white, yellow, or black clays in Persia
and Media, and of which there are
springs in many countries, particularly
in volcanic districts. Black Naphtha is
230

a common name for petroleum, or rock
oil.

NAPHTHALINE. A greyish white
substance found during the rectification
of the petroleum of the coal gas works,
incrusting the pipes. Mineral or resin-
ous Caphthaline has been found native
in a layer of lignite, in the coal forma-
tion of Uznach.

NAPIER'S RODS, or BONES. A
contrivance for facilitating the mecha-
nical performance of multiplication and
division. The invention has been super-
seded by the discovery of logarithms.

NAPLES YELLOW. A pigment pre-
pared by calcining lead with antimony
and potash in a reverberatory furnace,
formerly made at Naples.

NAPO'LEON. A name given to the
constellation Orion.

NASCENT STATE (nascor, to be
born). A term applied to the state of
gases, at the moment of their generation,
before they have acquired the repulsive
power.

NASSFNjE. A sub-family of the Mu-
ricidce, named from the typical genus
nassa.

NATATO'RES (nato, to swim). An
order of Birds, easily distinguished by
their oar-like feet, adapted to swimming.
They include the duck, the gull, the
pelican, the diver, and the penguin. In
the first three, the length of the wings
adapts them for flight ; in the last two,
the wings are short, and serve only as
fins.

NATFCIDjE. The Nerits; a family
of the Phytophagous Gasteropods, in
which the spire is very small, but the
pillar is always thick ; the exposed part,
or inner lip, is often very broad; the
animal is slug-shaped.

NATICFNjE. Sea-snails ; a sub-
family of the Naticidce, named from the
genus natica, and characterized by a
globose shell ; the inner lip is smooth,
not depressed.

NATRIUM. A term formerly used
to designate sodium. Natron is native
carbonate of soda, found in mineral
seams or crusts, and hence called mineral
alkali.

NA'TROLITE. A sub-species of

N A V

NEC

prismatic zeolite or mesotype, occurring
in chalk-stone porphyry in Wurtemherg
and Bohemia, &c.

NATRON. Native carbonate of soda.
There are two kinds, the common and
the radiated. See Natrium.

NATURAL. A character in music,

marked fa, employed to make a sharp
note a semitone lower, and a flat note a
semitone higher; or, in other words, to
restore to the scale of the natural key of
C any note which had been made flat or
sharp.

NATURAL ORDERS OF PLANTS.
That arrangement of plants in which
groups are formed by the association
together of those genera, which have the
greatest resemblance one to another in
all their characters taken together. Na-
ture has pointed out this plan in several
well-marked groups, and it is the object
of botanists to extend the principle to all
the individuals of the vegetable kingdom.

NATURAL PHILOSOPHY. The
science which teaches the nature and
properties of matter, the motions of
bodies, their connexions with, and their
influence upon, one another. The sub-
ject is distinguished into the two branches
of Mechanical Philosophy and Chemistry.

NAUCUM. An old Latin term ap-
plied by botanists to the exterior coat of
the drupe ; it is soft and fleshy, and
separable from the interior, hard, and
bony coat, which is called the endocar-
pium, or stone. Gsertner applied the
term nauca to seeds which have a very
large hilum, as that of the horse-chest-
nut.

NAUTICAL DISTANCE. In navi-
gation, this term denotes the line which
makes with the meridian lines the angle
called the course. In other words, the
rhumb line intercepted between any two
places through which the rhumb line
passes, is their nautical distance.

NAUTI'LIDjE. The sixth family of
Lamarck's polythalamous cephalopods,
named from the genus nautilus. It forms
the fifth family of the Polythalamaceae
of De Blainville.

NAU'TILITES. Fossil shells, analo-
gous to the nautilus, found in various
strata, from the oldest limestones and
sandstones of the Silurian system, to
those covering the chalk.

NAVIGATION (navigo, to manage a

ship). The science which teaches the

mariner how to conduct his ship from

one port or place to any other. It con-

231

sists in the practical application of a
branch of mathematics, and of a branch
of astronomy, which owes its name to
this application.

NEACOMIAN SYSTEM. A geolo-
gical formation comprising the green
sand system, and divided into the lower
green sand — gait, or Cambridge clay — and
upper green sand. The last two are con-
sidered by some writers as a part of the
Cretaceous system.

NEBULA (dim. of nubes, a cloud). A
dusky speck in the heavens, exhibiting
a dim and cloudy light, scarcely visible
to the naked eye, and supposed to con-
sist of a cluster of stars closely connected
in the most beautiful arrangement, and
at such an inconceivable distance from
our system, that each of them is con-
jectured to be composed of several thou-
sand distinct luminous bodies. Nebulae
have been distinguished by Sir W.
Herschel into —

1. Clusters of stars, in which the stars
are clearly distinguishable ; and these,
again, into globular and irregular clusters.

2. Resolvible nebulae, or such as excite
a suspicion that they consist of stars, and
which any increase of the optical powers
of the telescope may be expected to re-
solve into distinct stars.

3. Nebula, properly so called, in which
there is no appearance whatever of stars ;
which, again, have been subdivided into
subordinate classes, according to their
brightness and size.

4. Planetary nebulce, having, as their
name imports, exactly the appearance of
planets, and, whatever be their nature,
of enormous magnitude.

5. Stellar nebula, of a round or oval
figure, increasing more or less in density
towards the central point : they differ
extremely, however, in this respect, the
condensation in some being slight and
gradual, in others great and sudden, so
as to represent a star with a slight burr
round it.

6. Nebulous stars, presenting the ap-
pearance of sharp and brilliant stars sur-
rounded by a perfectly circular disc, or
atmosphere of faint light, in some cases
dying away on all sides by insensible
gradations ; in others, almost suddenly
terminated.

NECESSARY. " This word is used
as the contrary to ' impossible ' in all its
senses, and is, of course, liable to a cor-
responding ambiguity. Thus, it is
4 mathematically necessary ' that two
sides of a triangle should be greater than

NEM

NEU

the third ; there is a ' physical necessity '
for the fall of a stone ; and a ' moral
necessity ' that beings of a certain cha-
racter should act, when left perfectly
free, conformably to that character ; i. e.
we are sure they will act so ; though, of
course, it is in their power to act other-
wise." The ambiguity consists in con-
founding the second and the third kinds
of necessity, and thu3 finding an excuse
for immoral conduct. — Whately.

NECESSARY MATTER. In Logic,
the necessary matter of a proposition
denotes the essential or invariable agree-
ment of its terms. In necessary matter,
all affirmatives are true, and negatives
false ; in impossible matter, vice versd ;
in contingent matter, all universals are
false, and particulars true.

NE'CROMITE. A white mineral
found near Baltimore, in small masses,
in limestone.

NE'CTARY. That part of a flower
which secretes nectar or honey. The
term has been vaguely applied to several
parts which have no such function.

NEEDLE-ORE. A triple sulphuret
of bismuth, lead, and copper, also called
acicular bismuth glance.

NEEDLE-STONE. A zeolitic sub-
stance of a grej ish-white colour, found in
secondary trap rocks near Old Kilpatrick
in Scotland.

NEGATION, CONVERSION BY. In
logic, a mode of illative conversion, com-
monly called by contra-position. Thus it
may be said—" Every poet is a man of
genius ; therefore, he who is not a man
of genius is not a poet ; " for it is the
same thing to affirm some attribute of
the subject, or to deny the absence of that
attribute.

NEGATIVE QUANTITY. In alge-
bra, any quantity to which the sign — is
prefixed, is called a negative quantity.
The explanation of such a quantity is a
difficult matter. It is, however, usually
defined, either as a quantity less than
nothing, or as a quantity of the same
nature as a positive quantity, but ( taken
in a contrary sense or in an opposite
direction. See Quantity.

NEGATIVE TERM. In logic, a ne-
gative term denotes that a certain view
is not and could not be formed of a par-
ticular object, as a "dumb statue," a
"lifeless carcass." Compare Privative.

NEMATOI'DEA (vrina, vtifiaTor, a

thread, ei<5or, likeness). Round worms ;

an order of the Entozoa, which have a

long, cylindrical, and often filiform,

232

naked, inarticulated body, traversed by
a straight alimentary canal open at both
ends. These are the cavitary intestinal
worms of Cuvier, the stcrelmintha of
Owen.

NE'MATONEU'RA (i^Ma, n^mtm
a thread, vevpov, a nerve). A term ap-
plied by Owen to a division of the
Radiata of Cuvier, in which the nervous
matter is distinctly aggregated into fila-
ments, and in some cases nuclei of rudi-
mentary nervous centres have been
noticed.

NEMO'CERA (tffcuu a thread, icepos,
a horn). A section of Dipterous insects,
characterized by their long filiform an-
tennae, composed of more than six joints.

NE'PHELINE (vecpeXr,, a cloud).
Sommite. Rhomboidal feldspar, occurring
at Monte Somma, near Naples, in granu-
lar limestone, and in the lava of Capo di
Bove, near Rome. In nitric acid its
transparent fragments become cloudy.

NEPHRITE (i/e0p6P, a kidney). Jade.
A mineral occurring in gneiss and gra-
nite. It comprises the common variety
and axestone. The South America va-
riety is called Amazonian stone, from
its locality. It was formerly used, as an
amulet, in nephritic complaints.

NE'PIDjE. A family of the Hydro-
corisa, or Water Bugs, resembling the
Notonectidas, or boat-flies, in structure
and in habits, but endowed with slower
powers of motion.

NEPTU'NIAN THEORY. A geolo-
gical theory of Werner, which refers the
formation of rocks and strata to an aque-
ous origin.

NEREIDiE. A common name for a
highly organized order of Annellida, taken
from the Linnsean generic name Nereis,
which is almost equivalent to the ordinal
designation Errantes of Milne Edwards.
These are the dorsibranchiata of Cuvier,
the sea-centipedes and sea-mice of popu-
lar language.

NERPTIN.E. A sub-family of the
Naticidce, or Nerits, named from the
genus neritina ; in these shells the spire
is often nearly or quite obsolete.

NE'RVURES {nervus, a sinew). The
delicate frame-work of the membranous
wings of insects.

NEURO'PTERA {vevpov, a nerve,
•mepov, a wing). An order of insects
furnished with four membranous wings,
which are naked and reticulated with
ramified trachea?. It includes the dra-
gon-flies, may-flies, ant-lions, white
ants, &c.

NIM

NOB

NEUTRAL SALTS. Formerly, salts
in which the base was perfectly saturated
with the alkali, thus possessing neither
an acid nor an alkaline character. The
term now denotes those compounds,
which are composed of one equivalent
of each of their constituents, without
reference to their taste, or to their action
on coloured tests.

NEUTRALIZATION. A term gene-
rally applied to the decomposition of the
alkaline carbonates, by the addition of
some acid more powerful than the car-
bonic acid, which is consequently ex-
pelled from the alkaline bases with effer-
vescence.

NEW RED SANDSTONE. A forma-
tion consisting chiefly of sandy and
argillaceous strata, the predominant co-
lour of which is brick-red, though it
contains portions which are of a greenish-
grey. The striped and spotted appear-
ance of this series has caused it to be
sometimes termed variegated sandstone.
This formation has been divided into the
Upper New Red, in which Muschelkalk
is included, and the Lower New Red,
of which the Magnesian Limestone is a
member.

NICKEL. A metal of a colour inter-
mediate between those of silver and of
, tin, and commonly obtained from its
sulphuret, the kupfernickel of the Ger-
mans, which is generally mixed also
with arsenic, iron, and cobalt. The sul-
phuret was formerly called capillary iron
pyrites, and afterwards considered as
native nickel, till its real composition
was determined by Arfvedson.

NIDAME'NTAL {nidus, a nest). Re-
lating to the protection of the egg and
young, especially applied to the organs
which secrete the materials of which
many animals construct their nests.

NIDITE'LiE (nidus, a nest, tela, a
web). A family of Spiders, which weave
a nest, from which issue threads to en-
trap their prey.

NIGRINE. An ore of titanium, con-
sisting of this metal and iron.

NFHIL ALBUM. A former name of
the flowers or white oxide of zinc. Lana
philosophica was an equally curious de-
signation of the same substance.

NIMBUS, or CUMULO-CIRRO-
STRATUS. The rain-cloud; a compo-
site modification of clouds, resulting
from increase of density and deepening of
shade in the cumulo-stratus, indicating
a change of structure, which is always
followed by the fall of rain. All the
233

other forms of cloud may increase so as
to obscure the sky, and dissolve without
falling in rain; but the nimbus, once
formed, is always followed by rain or
snow.

NINTH. A dissonant interval in
Music, retarding the eighth and resolv-
ible into either the sixth or the third.
The major ninth consists of six tones
and two semitones ; the minor ninth, of
five tones and three semitones.

NITRATES. Compounds of nitric
acid with the salifiable bases.

NITRE. Saltpetre, or nitrate of pot-
ash. When fused, and poured into
moulds, it is called sal prunella, or crys-
tal mineral; when mixed with charcoal,
and burnt, the residuum was formerly
called clyssus of nitre ; mixed with car-
bonate of potash and sulphur, in a warm
mortar, it forms the fulminating powder ;
mixed with sulphur and charcoal, it
forms gunpowder ; and when mixed with
sulphur and fine saw-dust, it constitutes
the powder of fusion.

NITRIC ACID. A constituent of
nitre or saltpetre, existing only in com-
bination, and named, from its corrosive
properties, aquafortis.

NITROGEN {vhpov, nitre, ^wda, to
produce ; so called from its being a gene-
rator of nitre). Azote. An elementary
principle, constituting four-fifths of the
volume of atmospheric air. It was
formerly called mephitic air, and, by
Priestley, phlogisticated air.

1. Nitrous Oxide. Formerly called by
Priestley, who discovered it, dephlogisti-
cated nitrous air; but more properly,
protoxide of nitrogen. Its common name
is laughing gas.

2. Nitric Oxide, or nitrous gas. For-
merly called nitrous air ; but, more pro-
perly, deutoxide of nitrogen. When
mixed with atmospheric air, nitrous acid
vapours are produced, of a red or orange
brown colour.

3. Nitrous Acid. Formerly called
fuming nitrous acid ; an acid of un-
certain constitution, termed hyponitrous
by Turner.

4. Peroxide of Nitrogen. A compound
forming the principal part of the nitrous
acid vapours above mentioned. This
is the nitrous acid of Turner.

NITRUM FLAM MANS. Nitrate of
ammonia, so named from its property of
exploding, and undergoing total decom-
position at the temperature of 600°.

NOBILl'S FIGURES. The name
given to an electro-chemical phenomenon,

NOD

NON

discovered by Nobili. If a feeble current
be applied to polished plates of platinum,
steel, and silver, by using them as elec-
trodes, and immersing them in an elec-
trolytic fluid, certain figures will be visi-
ble, generally in the form of concentric
circles whose centre is exactly opposite to
the point of the wire, very much resem-
bling Newton's Prismatic Rings, and so
firmly fixed, that they cannot be removed
even by washing the metal with nitric acid.

NOCTILIONI'NjE. A family of in-
sectivorous Cheiroptera, which are desti-
tute of nasal appendages, and are almost
exclusively confined to tropical coun-
tries.

NOCTU'RNA (noctumus, nightly). A
designation of the true moths, a tribe of
Lepidopterous insects, the greater part
of which fly by night.

NODAL LINES. A term employed
in speaking of the undulations of solid
bodies. Thus, in the movements of
elastic planes, complete rows of points,
called nodal lines, will be formed which
do not participate in the movements of
the planes, but are in a state of rest.
These nodal lines are produced by the
continuous succession of nodal points, in
the strings of which the plane is supposed
to consist. They run in various direc-
tions across the plane, dividing it into
numerous vibrating portions, the con-
tiguous portions invariably moving in
contrary directions. The nodal lines
form peculiar figures, called, after their
discoverer, Chladni's Sonorous Figures.

NODAL POINTS. When a tense
cord is thrown into vibration, it assumes
throughout its entire length the form of
elevations and depressions impinging on
oae another, the elevation passing into
the form of a depression, and vice versa.
The point which bounds an elevation and
a depression, continuing at rest during
the vibration, is called a nodal point.

NODE {nodus, a knot). In astronomy,
the nodes are the points where the orbit
of a planet cuts the plane of the ecliptic.
The node whence the planet rises to-
wards the north above the plane of the
ecliptic is the ascending node, that whence
it descends towards the south is the de-
scending node; the line joining the two
is called the line of the nodes. Generally,
the point in which one orbit cuts another
is called the node of the first upon the
second.

NODE {in Botany). This term signi-
fies the thickened part of a stem or
branch from which a leaf is developed.
234

The space between two nodes is termed
an internode.

NO'DULE (dim. of nodus, a node).
A little node ; a small woody body found
in the bark of the beech and some other
trees, and formed of concentric layers
of wood arranged around a central nu-
cleus. Dutrochet terms it an embryo-
bud.

NODULE (in Geologij). A rounded
irregular-shaped lump or mass, varying
in size, and embedded in a stratified or a
massive rock.

NOMENCLATURE. A general de-
signation of the terms employed in any
science or art.

NOMINAL DEFINITION. In logic,
a definition which explains only the
meaning of the term defined, and nothing
more of the nature of the thing signified
by that term than is implied by the term
itself to every one who understands the
meaning of it. See Real Definition.

NOMINALISTS and REALISTS.
Two scholastic sects of the 11th century,
the former of which affirmed, according
to the Platonic doctrine, that names or
general terms have, apart from the mere
conception of them by the understand"
ing, an actual and eternal existence, and
are the models of all created beings;
while the latter maintained, according to
the doctrine of Aristotle, that these
names were eternally united to matter,
and have no existence as unconnected
with it. See Idea.

NO'MINATIVE CASE (nomino, to
name). The naming case; the case
which precedes the verb, and designates
its subject absolutely, without relation
to any other subject. A noun in the
nominative case (casus rectus) was con-
sidered by ancient grammarians as a
line perpendicular ; and in the other
cases (casus obliqui) as gradually decli-
ning or falling from the perpendicular.
To decline a noun, is, therefore, to make
it pass through these cases or fallings,
and the representation of them is called
a declension.

NON CAUSA PRO CAUSA. A logi-
cal fallacy in which the premiss (whether
the expressed or the suppressed one) is
either proved false, or has no sufficient
claim to be received as true.

NON-CONDUCTORS. Substances
which carry off free electricity slowly
when touched by an electrified body ; or,
if their condition of electrical indiffer-
ence is disturbed at any one point, they
become electrical at that point only ; and

NOR

NOT

if their whole surface he excited, and
they are then touched by some conductor
connected with the ground, they part
with their free electricity only at the
point of contact. Their characteristic is,
that they retain free electricity for a
length of time, and that they check its
motion.

NON-ELECTRICS. It was formerly
thought that none but the non-conductors
could be electrically excited, and that no
other bodies possessed electricity ; hence
the name of electrics was given to the
former, and that of non-electrics to the
latter class of substauces.

NONAGE'SIMAL DEGREE. The
highest point of the ecliptic above the
horizon. Every point, therefore, of the
ecliptic is the nonagesimal degree in
succession.

NO'NAGON (novem, nine, -yuvia, an
angle). In Geometry, a plane figure
having nine angles and consequently
nine sides. See Enneagon, which is a
classical term, the other being barbarous.

NO'NIUS. A former designation of
the Vernier, from its having been sup-
posed that this instrument was merely
an improvement of the method of sub-
division adopted by Nunnez, a Portu-
guese. See Vernier.

NO'NTRONITE. Silicate of iron ; a
mineral occurring in small nodules in an
ore of manganese, and found in the de-
partment of Dordogne in France, in the
arrondissement of Nontron.

NOON, REAL and APPARENT. In
Astronomy, the word apparent is used
not as opposed to real, but as coinciding
with it, and opposed to mean. Thus ap-
parent noon means real or true noon,
when the true sun. the sun which
appears, is on the meridian, as opposed
to mean noon, when the mean sun, the
average fiction of astronomers, which
does not appear at all, is on the meri-
dian. See Mean Noon.

NOOTH'S APPARATUS. An appa-
ratus invented by Nooth for making a
solution of carbonic acid gas.

NORFOLK CRAG. A tertiary form-
ation resting on London clay or chalk.
It is included by a line drawn from
Cromer to Wayburn, and thence southerly
about eighteen miles towards Norwich.

NORMA. The Rule ; a constellation
situated between Scorpio and Lupus.

NORMAL (norma, a rule). From its

original meaning of a rule, as used by

builders, this term was used to signify a

perpendicular ; but it is generally em-

235

ployed to denote the perpendicular to a
curve at some particular point, at which
point the normal is also perpendicular to
a tangent.

NORMAL GROUPS {norma, a rule
or pattern). Groups of certain rocks
taken as a rule or standard.

NORTH-WEST CURRENT. A
branch of the great Equatorial Current,
which separates from the equatorial at
22° w. long., takes a north-western direc-
tion, and is eventually lost in the drift
current, to which it seems to give a
north-westerly direction, which is ob-
servable from 35° w. long, to Trinidad.

NORTHERN LIGHTS. Luminous
appearances in the horizon, less trans-
ient in their duration than the light-
ning, of frequent occurrence in the higher
latitudes, more rare in the temperate
zones, and scarcely ever seen within the
tropics. In the northern hemisphere the
illuminated part surrounds the north
pole, in the opposite hemisphere the
south pole ; hence the respective names
of borealis and australis applied to the
aurora.

NOTACA'NTHA (vwrot, the back,
anavOa, a spine). A section of Dipterous
insects, in which the upper part of the
thorax or scutellum is armed with spines.

NOTATION {noto, to mark). The
act or practice of recording any thing by
marks, as by figures or letters. 1. Ma-
thematical notation comprises symbols
of number ; symbols of quantity, which
are usually letters ; and symbols of ope-
ration, as employed in algebra. 2. Nota-
tion in Music signifies the method
whereby the pitch or tune, and the dura-
tion of musical sounds are represented,
and by which definite periods of silence,
called rests, are marked. It is to music,
what letters and punctuation are to lan-
guage.

NOTHOSAU'RUS (v60os, spurious,
aavpa, a lizard). A spurious kind of
saurian, found in the shelly limestone
occurring in the middle of the sandy beds
of the New Red Sandstone Formation.

NOTIONAL and RELATIONAL.
By these terms, Dr. Becker distinguishes
all the words of language into two classes,
notional words being those which ex-
press notions, or objects of the under-
standing, as verbs and nouns ; while
relational words are either mere termina-
tions of notional words, expressing a
relation between different objects, or sepa-
rate words expressing relation, as pre-
positions. The former class of words

NUD

NUM

belong to etymology, the latter to syn-
tax.

NOTONECTID^l (i/wto?, the back,
veto, to swim). A family of the Hydro-
corisa, or water-bugs, which swim on
their backs, and, from their peculiar
aspect, are commonly called boat-flies
and water-boatmen.

NOUN (nomen, a name). A part of
speech which denotes an object, or the
qualities of an object. When it declares
its own meaning, without the addition of
another word, it is termed substantive;
when it requires to be added {adjici) to a
substantive, which stands under {sub
stat) and supports it, and of which it
shows the nature or quality, it is termed
adjective.

NOVA'CULITE. Whet slate; a mi-
neral substance found in beds in primi-
tive and transition clay-slate.

NU'CLEATED {nucleus, a kernel).
Having a nucleus or central particle ; a
term applied to the elementary cells of
animal tissues, the most important pro-
perties of which reside in the nucleus.

NUCLEOBRANCHI'ATA. The name
given by De Blainville to the fifth order
of the second section of his second sub-
class {Paracephalophor a Monoica). M.
Rang makes them the first order of
Cuvier's class Gasteropoda, and com-
prises under it some of the Heteropoda
of Lamarck, and the family Pterotrachees
of De Ferussac.

NU'CLEUS (quasi nuculeus, dim. of
nux, a nut). The kernel of a nut. The
solid centre around which the particles
of a crystal are aggregated. The pulpy
conical mass which constitutes the cen-
tral part of the ovule in plants. In
Astronomy, the term nucleus denotes
the apparently solid part or body of a
comet, as seen through the hazy atmo-
sphere which surrounds it.

NUCULA'NIUM. A superior, inde-
hiscent, fleshy fruit, containing two or
more cells, and several seeds, as the
grape. By Desvaux it was called bacca,
or berry, from which, however, it differs
in being a superior fruit.

NU'CULE {nucula, dim. of nux, a
nut). A little nut ; a term applied by
Desvaux to the fruit of the oak, the
hazel, &c. It is more commonly called
glans.

NUDIBRANCHIA'TA {nudus, naked,
branchice, gills). An order of aquatic
Gasteropods, which breathe by branchiae
unprotected by an external or internal
6hell, These comprise a part of the
236

naked Gasteropods of Cuvier. They
have no shell.

NULLI'PORA. A family of litho-
phytous polyps, the axis of which pre-
sents no visible pores on its surface.
Some naturalists consider that these
mucoso-calcareous bodies are not of ani-
mal origin. Of the latter opinion is De
Blainville, who is opposed in this matter
to Lamarck.

NUMBER. The abstract idea of num-
ber is that of times or repetitions. New-
ton defines number as the abstract ratio
of one quantity to another quantity of
the same species; and hence there are
three kinds of numbers — integers, frac-
tions, and surds.

1. Number, Abstract and Concrete.
When numbers are used with reference
to the things numbered, they are said to
be concrete numbers. When used with-
out such reference, merely to indicate a
certain number of units of the same
kind, they are called abstract numbers.
Thus 500 is an abstract, 500 pounds a
concrete number. An abstract number
is a number of times ; a concrete, a num-
ber of things.

2. Number, Perfect and Imperfect. 1 .
A perfect number is that which is equal
to the sum of all its divisors ; in other
words, it is a number whose aliquot
parts, added together, make a sum equal
to the number itself. Thus, 6 is a per-
fect number, for its divisors or aliquot
parts are 1, 2, and 3, and the sum of
these is 6. So 28 is a perfect number,
its divisors being 1, 2, 4, 7, 14, the sum
of which is 28. 2. An imperfect number
is one, of which the divisors or aliquot
parts are not equal to the number itself.
Thus, 12 is an imperfect number; for the
sum of its divisors, 1, 2, 3, 4, 6, is 16.

3. Number, Cardinal and Ordinal.
Cardinal numbers denote number, as
one, two, three, &c. ; ordinal numbers
denote the place or number in succession,
as first, second, third, &c. This distinc-
tion leads to a deceptive mode of speak-
ing. " The real distinction is that of
numeral nouns and numeral pronouns,
to the latter of which the term ■ ordinal '
might properly be applied. That ' first,
second, third,' &c, are properly pro-
nouns is obvious, if we consider that, so
far as they go, this, that, and the other,
would supply their places. The so-called
cardinal numbers denote collections ; the
ordinal numbers point out only the places
of the several units of which a collection
is composed. Even one, when its force

NUM

NUM

is simply selective or distinctive, is a
pronoun, as in * one or another ' " (Pen.
CycL). If it be asked, in what century
the birth of a person occurs, who is born
in the year 1800, the answer is, — if born
in the year eighteen hundred (cardinal),
the birth occurs in the nineteenth cen-
tury ; if in the eighteen hundredth year
(ordinal), in the eighteenth.

4. Numbers, Natural. The general
name for the whole scale of numbers,
1, 2, 3. &c. It is subdivided into the
scale of odd numbers, 1, 3, 5, &c, and
even numbers, 2, 4, 6, &c. These, again,
are subdivided into oddly odd numbers,
3, 7, 11, &c. ; evenly odd numbers, 1, 5,
9, &c. ; oddly even numbers, 2, 6, 10, &c. ;
and evenly even numbers, 4, 8, 12, &c.

5. Number, Square, Cube, &c. When
any number is multiplied by itself any
number of times, the result is called a
power of that number. The second and
third powers are usually called the square
and the cube, which are incorrect names,
derived from certain connexions of these
powers with the square and the cube in
geometry. The division of numbers into
square numbers, 1, 4, 9, 16, &c. ; cube
numbers, 1, 8. 27, 64, &c. ; fourth powers,
1, 16, 81, 256, &c, and so on, may be
carried to any extent.

6. Number, Prime and Composite. A
prime number is one which is not divi-
sible by any number except unity and
itself, as 1, 2, 3, 5, 7, 11, 13, &c. A com-
posite number is any number which is
not prime.

7. Number, Abundant, Perfect, De-
fective. An abundant number is one, of
which the sum of all its divisors exceeds
itself: thus, 12 is an abundant number,
for 1 + 2 + 3 + 4 + 6 = 16. A perfect num-
ber is one, or which the sum of all its
divisors is equal to itself: thus, 6 is a
perfect number, for 1+2+3 = 6. A de-
fective number is one, of which the sum
of its divisors is less than itself: thus, 10
is a defective number, for 1 + 2+5=8.

8. Numbers, Figurate. A flgurate
number is any one out of any of the fol-
lowing series, the first excepted, which
is only introduced as a basis : —

12 3 4 5 6 &c.

I.

II.

III.

IV.

V.

&c.

Each number is the sum of the numbers
in the preceding row : thus 10 is the sum
237

1

3

6

10

15

21

&c.

1

4

10

20

35

56

&c.

1

. 5

15

35

70

126

&c.

1

6

21

56

126

252

&c.

1

7

28

84
&c.

210

462

&c.
&c.

of 1, 3, 6 ; 70 is the sum of 1, 4, 10, 20,
35; and 70 is the fifth number of the
third order of figurate numbers.

9. Numbers, polygonal and pyramidal.
The principle of these numbers is suffi-
ciently explained under the article Figu-
rate Numbers (p. 136). The following
are some of the polygonal numbers : —
Triangular 13 6 10 15 21, &c.
Quadrangular 14 9 16 25 36, &c.
Pentagonal 1 5 12 22 35 51, &c.
Hexagonal 1 6 15 28 45 66, &c.

Pyramidal numbers are formed by
summing the polygonal numbers; thus,
to find pentagonally pyramidal numbers,
take the pentagonal numbers :

1 5 12 22 35 51, &c.

1 6 18 40 75 125, &c.

10. Numbers, Amicable. These are
numbers, each of which is equal to the
sum of all the divisors of the other. Such
are

284 and 220

17,296 and 18,416

9,363,583 and 9,437,056.

NUMBER of DIRECTION. A num-
ber not exceeding thirty-five, which
number is the limit of Easter day, this
day always falling between the 21st of
March and the 25th of April.

NUMBERS for STARS. A mode of
denoting the stars adopted by Flamsteed,
who numbered them, not in order of
brilliancy, but in that of coming on the
meridian. Thus, 1 Orionis, 1 of Orion,
means the first which comes on the me-
ridian, of all the stars in Orion which
Flamsteed observed and recorded ; 7
Leonis, 7 of Leo, is the star of this con-
stellation which comes seventh on the
meridian. So long as a star has either
Bayer's letter (See Letters for Stars) or
Flamsteed's number, both are used indif-
ferently and perfectly understood ; nor is
it expected that there will be any con-
nexion between the letter, which refers,
or was supposed to refer, to the bright-
ness of the star, and the number, which
is derived from its position. Thus 1 Vir-
ginis happens to have w for its letter; it
is only of the sixth magnitude, though it
comes early to the meridian; but a Vir-
ginis, a splendid star, is 67 Virginis in
Flamsteed.

NUMERATION (numerus, a number\
A method of calculating numbers by
means of ten sipns, viz a cipher and
nine digits. Higher numbers are sig-
nified by placing these signs by the side
of one another, and agreeing that the
first figure on the right hand shall retain

0 BL

OB L

the value which it has when it stands
alone ; that the second on the right hand
shall mean ten times as many as it does
when it stands alone; that the third
shall mean one hundred times as many
as when it stands alone; the fourth, one
thousand times ; and so on.

NUMERATOR. In arithmetic, that
part of a fraction which denotes how
many of the aliquot parts of an integer
or unit are taken, the nature of these
parts being expressed by the denomi-
nator. Thus | denotes five, not of units,
but of sixths of a unit; six is the deno-
minator, 5 the numerator or numberer
of the parts taken.

NUMERICAL. In Algebra, this term
is applied to co-efficients which consist of
numbers, as distinguished from literal
co-efficients, which consist of letters. As
opposed to algebraical, it is applied to the
magnitude of a quantity, considered irre-
spectively of its symbol; thus — 20 is
numerically greater than — 10, though
algebraically less.

NU'MMULITES {nummus, money, \l-
$ov, a stone). An extinct genus of the
order of molluscous animals, called Ce-
phalopods, of a thin lenticular shape,
resembling a coin, internally divided into
small chambers.

NUT. A dry, bony, indehiscent, one-
celled fruit, proceeding from a pistil of
three cells, and enclosed in a cupule, as

in the hazel, the acorn, &c. The term
is sometimes applied to the fruit of
borago, lithospermum, &c, but these
fruits are more properly called akenia.
The term nux baccata is sometimes ap-
plied to the fruit of taxus, &c.

NUTA'TION (nuto, to nod). The
term applied to a small and slow gyratory
movement of the earth's axis, by which,
if subsisting alone, the pole would de-
scribe among the stars, in a period of
nineteen years, a minute ellipse, having
its longer axis equal to 18" 5, and its
shorter to 13"*74; the longer being di-
rected towards the pole of the ecliptic,
the shorter at right angles to it.

NU'TTALITE. A mineral associated
with calc-spar, from Bolton in Massa-
chusetts. It appears to be an alumino-
silicate of lime, potash, and iron.

NYCTERIBI'ID^S. The Bat-lice; a
family of dipterous pupiparous insects,
parasitic on bats, and approaching to
the spiders in form.

NYMPH. A fanciful term for the
chrysalis or pupa state of insect life, ap-
plied to the active pupae of orthopterous
and hemipterous insects.

NYSSO'NIDjE. A family of hymeno-
pterous insects belonging to the section
Fossores, named from the genus Nysson,
and characterized principally by the
absence of a notch on the inner side of
the mandibles.

O

OB-. A Latin preposition, in compo-
sition signifying inversion : thus oft-ovate
means inversely ovate ; oft-conical, in-
versely conical. It is obvious that this
term can only be employed in words
which denote that one end of a body is
wider than the other. Hence, it is super-
fluous in such a word as oft-lanceolate.

OBJECTIONS, FALLACY OF. A
fallacious mode of argument, by which
it is shown that there are objections
against some plan, theory, or system,
and thence it is inferred that it should
be rejected ; whereas that which ought
to have been proved is, that there are
more or stronger objections against the
receiving than the rejecting of it.

OBLATE. A term signifying the re-
verse of oblong, or shorter in one direc-
tion than in another, and applied to a
238

spheroid which is made by the revolution
of an ellipse about the smaller of the
two axes. Thus the earth is an oblate
spheroid, the actual difference between
the polar and the equatorial diameters
being in the proportion of 300 to 301.

OBLIQUE. A term generally em-
ployed in opposition to direct or right.
In astronomical language, the term ob-
liquity denotes the angle made by the
ecliptic with the equator. The greatest
latitude at which the sun ever appears
vertical is the obliquity of the ecliptic
(See Ascension). In stereographic pro-
jection, an oblique circle is any circle
oblique to the line of projection. Oblique
planes, in dialling, are planes which re-
cline from the zenith. Oblique projection,
in mechanics, is the projection of a body
at an oblique angle with the horizontal

OCE

line. Oblique sailing, in navigation, is
that which includes the calculation of
oblique-angled triangles. Oblique sphere,
in geography, is that in which the axis of
the earth is inclined to the horizon of
the place.

OBLONG (oblongus, of a figure inclin-
ing to long). A four-sided figure, which,
like the square, has all its angles right
angles, hut, unlike the square, has not all
its sides equal. The term rectangleis often
used for it, but is obviously objectionable.
An oblong spheroid, also called the pro-
late spheroid, is generated by the revo-
lution of an ellipse about its longer axis,
and is therefore elongated at the poles.

OBSI'DIAN. A volcanic product, or
species of lava, very like common green
bottle-glass, which is almost black in
large masses, but semi-transparent in
thin masses. Pumice-stone is obsidian
in a frothy state, produced, most pro-
bably, by water which had been contained
in, or had access to, the melted stone,
and converted into steam. Solid obsi-
dian often occurs in masses, which are
partially converted into pumice. The
name is derived from that of Obsidius,
who first found it in Ethiopia.

OBSOLETE {obsoletus, gTOwn out
of use). A term denoting a faint indi-
cation of a character. Thus, the calyx
of Conium is represented by an obsolete
margin ; slight and indistinct striae upon
a shell are termed obsolete striae. In
these cases, however, the obsolete state
is not the result of accident, but of par-
tial development.

OBTUSE. Blunt or dull ; opposed to
acute, as applied to an angle which is
greater than one right angle and less than
two ; in other words, an angle which
measures more than 90 and less than
180 degrees.

O'BVOLUTE (obvolutus, rolled over).
A form of aestivation or vernation, in
which the margins of one leaf alternately
overlap those of the leaf which is oppo-
site to it.

OCCULT SCIENCES. Hidden sci-
ences; imaginary sciences, as alchemy,
astrology, magic, &c.

OCCULTA'TION (occulto, to hide).
In astronomy, the eclipsing of a fixed
star by the interposition of the moon.

OCEAN. The one continuous fluid
which spreads over nearly seven-tenths
of the globe, all the gulfs and inland seas
being branches of this universal ocean.
Different names have, however, been
given to various parts of it : —
239

OCT

I. South-Eastern Basin.

1. Antarctic Ocean. Comprised within
the Antarctic circle ; that is, between the
parallel of 66° 32' of southern latitude
and the South Pole.

2. Southern Ocean. Bounded on the
one side by the Antarctic circle, and on
the other by a line drawn from Cape
Horn to the Cape of Good Hope, thence
to Van Dietnen's Land, and again by the
south of New Zealand to Cape Horn.

3. Indian Ocean. Lying between Africa
on the west, and the peninsula of Malaya
with the islands of Sumatra, Java, &c,
and New Holland, on the east, and
bounded by Persia and Hindostan on the
north. The Red Sea or Arabian Gulf,
the Persian Gulf, and the Bay of Bengal,
are all parts of this ocean.

4. Pacific Ocean. Divided by the equa-
tor into North and South, and inclosed
between America on the east, and New
Holland, the islands of Java and Su-
matra, and the continent of Asia, on the
west. On the north it terminates at
Behring's Straits. The seas of China,
Japan, Okhotsk, &c, form parts of this
ocean.

II. Western Basin.

1. Atlantic Ocean. Commencing in
the south from a line drawn from Cape
Horn to the Cape of Good Hope, and ter-
minated on the north by the Arctic circle.
It is divi led into the North and South by
the equator, and its branches are the
Mediterranean, the North Sea or German
Ocean, the Baltic, Baffin's Bay, Hudson's
Bay, the Gulf of Mexico, and the Carib-
bean Sea.

2. Arctic Ocean. Surrounding the
North Pole, and bounded by the Arctic
circle and the northern shores of the two
continents. The White Sea, the Sea of
Kara, and the Gulf of Obe, are parts of
it.

O'CHRE. Hydrated sesquioxide of
iron ; an argillaceous earth, impregnated
with iron of a red or yellow colour.

O'CHREA. Literally, a boot; and
hence applied, in botany, to the mem-
branous tube which sheaths the stem of
rhubarb and other plants, and consists of
two stipules, cohering by their margins.

O'CTAGON Coktu>, eight, ^tovia, an
angle). A plane geometrical figure, con-
tained by eight sides, and consequently
having eight angles. When the sides
and angles are equal, the figure is a
regular octairon.

OCTAHE'DRITE (okto>, eight, edpa,
a seat). Anatase. Pyramidal titanium

CEST

OLE

ore, from Bourg d'Oisans, whence it is
also called Oisanite.

OCTAHE'DRON (k™, eight, e&pa,
a seat). In Geometry, a solid figure con-
tained by eight equal and equilateral
triangles.

OCTANDRIA (i*™, eight, ixvtjp, a
male). The eighth class of plants in the
Linnaean system, characterized by their
flowers having eight stamens.

Octo-gynia (yvvt], a female). The name
given by Linnaeus to those orders of
plants which have eight pistils in their
flowers.

O'CTANS HADLEIE'NSIS. Hadley's
Octant ; a modern southern constellation,
consisting of forty-three stars.

OCTANT. A term applied to an in
termediate point between a quadrature
and a syzygy of the moon. See
Phases.

O'CTAVE (octavus, the eighth). In
Music, the simplest and most consonant
interval, in which the higher note makes
twice as many vibrations as the funda-
mental note from which it is derived ; its
ratio is, therefore, that of 1 J 2 * * 4 * 8,
&c. This relation serves as the principal
unit of measurement in music, its entire
range embracing at most nine entire
octaves, rising from the deepest note,
which makes 32 vibrations in a second,
to the highest, which performs 16,384
vibrations in the same time.

OCTO'PODA(oktw, eight, novs, 7ro36r,
a foot). A designation of animals which
have eight feet. The name of those
Cephalopods which have eight prehensile
organs attached to the head.

OCYPO'DIANS (wkm, swift, ttow, a
foot). A tribe of brachyurous crustace-
ans, placed by Milne Edwards between
the Pinnotherians and the Gonoplacians,
and named from the genus Ocypoda. The
family are characterized by their rapidity
in running.

O'DERIT. An opaque black sub-
stance, occurring in Sweden : it is pro-
bably black mica ; for it is capable of being
split, like mica, into thin leaves.

CSNANTHIC ETHER (cuW, wine,
avOos, flower). An oily liquid, which
gives the characteristic odour to all
wines.

(Enanthic acid. An acid found in the
foregoing compound, in combination with
ether.

CE'STRIDiE {oestrus, a gad-fly). The
Bot-flies ; a family of Dipterous insects,
belonging to the section Athericera, re-
markable for the peculiar habitation of
210

the larvae, and for the absence of any
proper mouth in the imago state.

OFFICI'NA SCULPTORIA. A mo-
dern southern constellation, consisting of
twelve stars.

OFFING. If we sail out of sight of
land, whether we stand on the deck of
the ship, or climb the mast, we see the
surface of the sea — not losing itself in
distance and mist, but terminated by a
sharp, clear, well-defined line, or offing,
as it is called, which runs all round us in
a circle, having our station for its centre.

O'FFSET. Propagulum. A short
branch of certain herbaceous plants,
which is terminated by a tuft of leaves,
and is capable of taking root when sepa-
rated from the parent plant, as in house-
leek. It differs little from the runner.

O'GAM or OGMA. An occult form
of writing among the Irish, apparently
of great antiquity. The term is a primi-
tive Celtic word, signifying the secrets of
letters.

OGYGIAN DELUGE. A great in-
undation mentioned in fabulous history,
as having taken place in the time of
Ogyges, king of Attica, whose death is
fixed in Blair's chronological tables in
the year b.c. 1764.

OHM'S LAW. An important law
which refers to all the causes which tend
to impede the action of the voltaic bat-
tery. It is, that " the intensity of an elec-
tric current, when a battery is in action,
is directly as the whole electromotive
force in operation, and inversely as the
sum of all the impediments to conduc-
tion." It may, therefore, be expressed by
a fraction, whose numerator is the elec-
tromotive force, and its denominator the
sum of the resistance of all its parts.

OI'SANITE. An ore of titanium, from
the department of Oise.

OLD RED SANDSTONE. A forma-
tion lying immediately below the Car-
boniferous group. The term Devonian
has been recently proposed for strata of
this age, because in Devonshire they are
largely developed, and contain many
organic remains.

OLEA'CEjE. The Olive tribe of dico-
tyledonous plants. Trees or shrubs
with leaves opposite ; flowers regular,
monopetalous, hermaphrodite, or dioe-
cious ; stamens two ; ovarium simple,
superior, 2-celled ; seeds pendulous.

OLEFIANT GAS {oleum, oil, fio, to
become). A compound gas consisting
of carbon vapour and hydrogen, and now
viewed as a compound of the organic

ON U

OPA

radical acetyl with hydrogen. Its name
was derived from its forming an oily
substance with chlorine.

OLEIC ACID {oleum, oil). An acid
forming the essential part of fat oils
which are not drying, as oil of almonds.

OLEO-RESINS. Native compounds
of volatile oil and resin, the proper juices
of coniferous and other plants.

O'LIGIST IRON. A subspecies of
rhomboidal iron ore, comprising the com-
mon specular, and the micaceous spe-
cular varieties.

OLIGO- (6\t7os, little, few). A term
used in Greek compounds, to denote that
the number of any thing is small, not
indefinite. It is contrasted by the pre-
fix poly- (iroXvs, many), signifying that
the number is large and not definite.
Thus we have o/i^o-spermous and poly-
spermous fruits.

OLIVE MALACHITE. Octahedral
phosphate of copper, from Lebethen in
Hungary.

OLIVE ORE. Olivenite. One of the
arseniates of copper.

OLIVILE (olea, the olive). The
name given by Pelletier to a peculiar
substance which remains after gently
evaporating the alcoholic solution of
the gum which exudes from the olive
tree.

OLI'VIN^. An aberrant sub-family
of the VolutidcB, or volutes, named from
the typical genus oliva ; these shells are
cylindrical in shape ; the aperture is
linear, and the pillar thickened and con-
fusedly plaited.

O'LIVINE {olea, the olive). An olive-
coloured silicate of lime and magnesia.
In its purer state it is denominated
chrysolite or peridot ; and when protox-
ide of iron is predominant, it has by
some been called hyalosiderite.

OMNI'VOROUS {omnis, all, voro, to
devour). A term applied to animals
which feed on all substances indifferently.
The term is synonymous with the Greek
pantophagous.

O'MPHACITE. A variety of augite,
of a pale green colour, occurring in primi-
tive rocks, with precious garnet, in Ca-
rinthia.

OMPHALO'DIUM (oMtf>a\69, the um-
bilicus). A term applied by Turpin to
the centre of the hilum of the seeds of
plants, through which the nutrient ves-
sels pass to the embryo.

ONUS PROBANDI. The burden of
proof, in Rhetoric, rests with him who
would deny any generally received
241

opinion, as that of gravitation, that of
the Copernican theory, &c.

O'NYX (ovi/?, onyx, a nail). A variety
of agate, in which the siliceous particles
are disposed in alternating horizontal
layers of opaque white, and translucent
blue, grey, or brown, resembling the
marks on the human nail.

O'OLITE {d)6v, an egg, XiOos, a stone).
A limestone ; so named from its being
composed of rounded particles, like the
roe or eggs of a fish. The term is also
applied to a large group of strata, charac-
terized by peculiar fossils, in which
limestone of this texture occurs.

1. Lower Oolite. A series of strata of
oolitic limestone, clays, and marls, re-
posing above the lias, and divisible into
the Lower or Cheltenham Oolite, Fuller's
Earth, Stonesfield Siate, Great Oolite,
Forest Marble, and Corn-brash.

2. Middle Oolite. A series of strata,
consisting of coralline and shelly oolitic
limestone, calcareous sandstone, and
clays, separated from the Lower Oolite
by a great deposit of clay, and divisible
into Oxford Clay, Calcareous Grit or
Sandstone, Coral Rag and Oolite, and
Calcareous Sandstone.

3. Upper Oolite. A series of strata
separated from the Middle Oolite by a
great deposit of clay, and divisible into
the Kimmeridge Clay, Portland Sand,
and Portland Oolite.

OOZO'A (tioi/, an egg, £5>ov, an ani-
mal). A designation given by Carus to
one of the primary divisions of the Ani-
mal Kingdom, from the resemblance of
the beings composing it to the eggs or
rudiments of more perfect forms. They
correspond wih the Acrita of Macleay,
the Cryptoneura of Rudolphi, and the
Protozoa of other writers.

OPA'CITY {opticus, dark). A quality
of bodies which renders them impervious
to the rays of light. In this respect
opaque bodies are the reverse of the
transparent; but their opacity is occa-
sioned rather by their thickness than
their absolute impermeabiliiy to light.
Gold is considered opaque ; but the rays
of a candle, or of the sun, falling on a
sheet of gold leaf laid on glass, are trans-
mitted as a faint green glimmering light.

OPAL. Opaline substances are mostly
hydrates of silica, and are named —

1. Precious or Noble Opal, which owes
its beautiful play of colours to a multi-
plicity of imperceptible fissures in its
interior. A variety of this kind has the
property of becoming transparent when
M

O PP

ORC

immersed in water, and is called hydro-
phane, oculus mundi, or changeable
opal.

2. Sun or Fire Opal, of a hyacinth-red
colour, changing to a paler hue by heat ;
found only at Zimapan in Mexico, in a
particular variety of hornstone porphyry.

3. Common Opal, a translucent white
variety of which, appearing yellow or red
when held between the eye and the light,
is called girasol.

4. Semi-opal, agreeing in its principal
characters with common opal, and pre-
senting spotted, striped, or brown de-
lineations.

5. Mother-of-pearl Opal, or Cacholong,
described as a variety of quartz, found in
the river Cach in Bucharia.

6. Jasper Opal, or ferruginous opal, of
a scarlet-red and grey colour, referred by
some authors to jasper.

7. Wood Opal, or opalized wood, con-
sisting of wood petrified by silicious
earth, and acquiring a structure similar
to simple mineral opal.

8. Liver Opal, or menilite, found at
Menil-Montant, near Paris, in a bed of
adhesive slate.

OPE'RCULUM {operio, to shut up).
A cover or lid. In Malacology, the term
operculum denotes the hard lid, either
corneous or calcareous, which closes the
mouth of many spiral shells, and is car-
ried on the posterior part of the belly of
the animal.

OPHI'DIA {o(pn, a serpent). An order
of Reptiles, comprising the Serpents,
which have no atlantal or sacral extre-
mities perceptible externally, and conse-
quently no members or appendages of
locomotion.

OPPOSITE TERMS. In logic, those
terms are said to be opposite, or incon-
sistent, which express qualities inap-
plicable to the same object at the same
time, as " black and white." Relative
terms are opposite, only when applied
with reference to the same subject : as
one may be both Master and Servant ;
but not at the same time to the same
person.

OPPOSITION. Two bodies are in
conjunction, when they are at the same
point of a circle ; and in opposition, when
they are at opposite points. For the ap-
plication of these terms in Astronomy,
see Conjunction and Opposition.

OPPOSITION, LOGICAL. Two pro-
positions are said to be opposed to each
other, when, having the same subject
and predicate, they differ, in quantity, or
242

quality, or both. The four kinds of op-
position are termed contraries, sub-
contraries, subalterns, and contradic-
tories.

O'PTICS (Stttoaicu, to see). That
branch of natural science which treats of
the properties of light and vision ; in its
proper acceptation, it relates to direct
vision, while catoptrics treats of reflected,
and dioptrics of refracted vision. Prac-
tical Optics is the application of the phy-
sical properties of light, and the mathe-
matical laws of optics to the construction
of optical instruments.

O'RBIT {orbita, a track). The course
which a star describes around the sun or
another star. The Latin word orbis is a
circle, or a globe ; and hence the paths
of the planets round the sun are termed
orbits, and the planets themselves orbs,
although the former are now understood
to be elliptical, and the latter spheroidal.
The earth's orbit is the ecliptic.

1. Orbit, Plane of. The plane of an
orbit is an imaginary surface, passing
from one extremity, or side of the orbit
to the other. If the rim of a drum-head
be considered the orbit, its plane would
be the parchment extended across it, on
which the drum is beaten.

2. Orbits, inclination of. If we sup-
pose planes to pass through the orbits of
the planets, and to be indefinitely ex-
tended, all these planes will pass through
the sun's centre; but all of them will
cut the plane of the ecliptic, though at
different angles, which are respectively
called the inclination of the orbits. The
average inclination of the moon's orbit
is about five degrees.

ORBITE'LJE (orbis, an orb, tela, a
web). A family of Spiders, which spread
abroad webs of a regular and open tex-
ture, either circular or spiral, and remain
in the middle, or on one side, in readiness
to spring upon an entangled insect.

ORCEIN. A red colouring matter
found in archil, and referred by Dr. Kane
to a mixture of two substances, which
he terms alpha-orcein and beta-orcein,
the latter being produced by oxidation of
the former.

ORCHIDA'CEiE. The Orchis tribe
of Monocotyledonous plants, in which
the stamens and the style are consoli-
dated into a central column, and the
ovary is inferior. They correspond with
the Gynandria Monandria of Linnaeus.

ORCIN. A colourless matter procured
from the lichen dealbatus, assuming a
deep violet colour when exposed to am-

ORI

ORT

monia and air, owing to the formation of
orcein.

O'RDINATE {ordino, to arrange). A
term applied, in Conic Sections, to one
half of any line drawn across an ellipse,
parallel to the minor axis. The whole
line is called a double ordinate, and the
portion of the major axis which it cuts
off is called an abscissa. These terms
are equally and similarly applicable to
the parabola and the hyperbola.

ORES. The mineral bodies from
which metals are extracted. These are
termed sulphurets, when combined with
sulphur; oxides, when combined with oxy-
gen ; and salts, when combined with acids.

ORGA'NIC REMAINS (Spyavov, an
organ). The remains of organized bodies,
both plants and animals, found in a fossil
state.

ORGANO'GRAPHY (opyavov, an
organ, ypdcpta, to describe). By this term
De Candolle designated his learned
work on the structure of plants; and
although the word simply means a "de-
scription of organs," it has been restricted
to the organs of plants, comprising an
account of their elementary tissues, and
of their compound structures.

O'RGANON {opyavov, an instrument
or machine). A philosophical term, de-
noting a method, and usually applied to
a body of rules and laws for conducting
a scientific inquiry. What is called the
Organon of Aristotle, is a collection of
the views of that philosopher on the
several subjects of the Categories, includ-
ing his Logic ; of the Interpretation or
the Nature of Propositions ; of the
former and latter Analytics ; of Topics ;
and of Sophisms. The term organon
was not given by Aristotle, but is of a
date posterior to him.

Novum Organon Scientiarum. The
name given by Bacon to his learned work
on " A New Method of studying the
Sciences." This method, which is founded
on the principle of Induction, or actual
experiment, which Bacon significantly
terms "Asking Questions of Nature,"
has earned for its author the appellations
of the Prophet of the Arts and the Father
of Experimental Philosophy. See Baco-
nian Philosophy.

ORIOLI'NiE {oriolus, the oriole).
Orioline birds, or Orioles ; a family of
the Cantatrices of Macgillivray, belonging
to the warmer regions of the Old Con-
tinent. They appear to be allied to the
Rollers, not only in the form of the bill,
but also in their short tarsi and broad toes.
243

ORI'ON. A southern constellation,
consisting of seventy-eight stars, the
principal of which is Betelgeuse.

ORNITHO'LOGY (6'pw?, a bird, \6-
709, an account). The science which
teaches the natural history and arrange-
ment of birds. See Zoology.

O'RPIMENT (auri pigmentum). A ge-
neral name for two sulphurets of arsenic,
the yellow, or prismatoidal sulphur, and
the red, ruby sulphur, or hemi-prismatic
sulphur. The former is the colouring
principle of the paint called King's yellow.

O'RRERY. A machine for repre-
senting the motions, relative magnitudes,
and distances of the bodies composing
the solar system ; said to have been
named after an earl of Orrery, for whom
the first machine of the kind was made
by Prince Eugene. Planetary machines
have received various names, sufficiently
indicative of their object, viz., planeta-
rium, tellurian, lunarian, and satellite
machine.

ORSEDEW. Manheim or Dutch Gold ;
an inferior sort of gold leaf, prepared of
copper and zinc, sometimes called leaf
brass, and principally manufactured at
Manheim.

O'RTHITE {bp66t, upright). A sili-
cate containing yttria and protoxide of
cerium, and named from its always oc-
curring in straight layers, generally in
felspar.

ORTHOCERA'TA {bP06s, straight,
Kepac, a horn). An extinct genus of
Cephalopods, which inhabited a long-
chambered conical shell, like a straight
horn.

ORTHOGO'NAL (oP0or, right, ywia,
an angle). In Geometry, this term simply
means at right angles, or perpendicular •
thus, a curve cuts a set of curves ortho-
gonally, when it cuts them all at right
angles. The term is sometimes used
synonymously with orthographic, and
relates to a particular mode of projection.
See Projection.

ORTHO'GRAPHY (bP06?, right, ypd-
<pas, to write). In its general sense, this
term denotes that part of Grammar which
teaches the nature and powers of letters,
and the correct method of spelling and
writing words. The sense of the word
has, however, been restricted by gram-
marians to the proper selection of the
letters of words, and the correct division
of words when separated by the termina-
tion of lines.

ORTHO'PTERA (bpOos, straight, me-
pbv, a wing). An order of insects, com-
M2

OST

OVA

prising the locusts, grasshoppers, crickets,
&c. ; having their anterior wings coria-
ceous and overlapping each other; the
posterior partly coriaceous, partly mem-
branous, and folded longitudinally when
at rest.

O'RTIVE AMPLITUDE (ortus, a
rising). An astronomical term, denoting
the arc of the horizon intercepted be-
tween the point where a star rises and
the east point. Hence it is also called
eastern amplitude.

ORY'CTOGNO'SY (oPi/kto?, dug up,
•yvwaiv, knowledge). Oryctology. That
branch of science which relates to fossil
organic remains. The term is sometimes
applied to that branch of mineralogy
which relates to the classification of
minerals.

OSCILLATION (oscillum, an image
hung on ropes, and swung up and
down in the air). The swinging or vi-
bratory motion by which a body, when
made to change its place, returns in a
direction opposite to that in which it
first moved. The motion of a pendulum,
or that of a string of any musical instru-
ment strained tight by the finger, belongs
to this class of motion.

Oscillation, Centre of. That point in
an oscillating pendulum, in which the
whole moving force is concentrated, and
at which, if it meet with resistance, it
will instantly stop, without vibration or
strain of its other parts. This point differs
from the centre of gyration, because the
motion of the body is produced by the
gravity of its own particles ; whereas, in
gyration, the body is put in motion by
some other force, acting at one place
only. See Percussion.

OS'MELITE (5fw> to smell). A mi-
neral occurring on calcareous spar, mixed
with datholite, and emitting at the ordi-
nary temperature of a room a distinct
clayey smell, whence its name is derived.

O'SMIUM {banh> odour). A metal
discovered in 1803, in the grains of na-
tive platinum, together with iridium,
and named from the pungent and pecu-
liar smell of its oxide.

OSSEOUS BRECCIA (osseus, bony).
The cemented mass of fragments of bones
of extinct animals found in caverns and
fissures.

OS'TIOLUM (dim. of ostium, a door).
A little door ; the orifice of the perithe-
cium of some fungaceous plants.

OSTRACEiE. The Oyster tribe; an
order of the Conchiferous Mollusca,
named from the genus ostrea, in which
244

the two halves of the mantle are sepa-
rated the whole way round, or the foot
is absent or very small; they are usually
fixed by the shell to solid bodies.

OSTRA'CILVE. Oysters; a family of
the atrachian bivalves, named from the
genus ostrea; the animal is sedentary,
generally affixed by the under valve ; the
shell is foliaceous, rarely pearly.

OSTRACO'DA (SarpaKov, a shell,
eidor, form). A family of the Entomo-
straca, comprising those which have the
shell folded so as to resemble those of
bivalves.

OSTROTODA. An order of the en-
tomostracous Crustacea, in which the
body is entirely enclosed under a large
shield having the form of a bivalve shell.
The animals of this order are commonly
termed monoculous, from the two eyes
being united into one mass.

OTO'LOPHI (oS?, Atop, the ear, \6-
0o9, a crest). A group of Batrachians,
which have the muzzle angular, and the
head furnished on each side with a crest
which extends over the parotid portion.

OUTLIER. A term applied by some
mineralogists to a portion of a stratum
which occurs at some distance, detached
from the general mass of the formation
to which it belongs.

OVAL {ovum, an egg). A curve drawn
by taking a string of any certain length,
and fixing, not one end as in drawing
the circle, but both ends to different
points, and then carrying a point outside
the string, always keeping it stretched
as far as possible. The name of this
figure is derived from its resemblance to
the transverse section of an egg. Ellipses
are ovals which are formed by the above
fixed law, but the latter is a popular term
for any curved figure, approaching to
that shape. The carpenter's oval, for
example, is made up of circular arcs,
which unite without leaving any angular
appearances at their junctures.

Ovals of Descartes. These, though not
Ellipses, are governed by a determinate
law, which constitutes them as varieties
of that curve. As in the Ellipse the two
lines drawn from the foci to any point of
the circumference vary, so that the in-
crement of one shall always be equal to
the simultaneous decrement of the
others ; so, in the Cartesian Ovals, these
increments are in an invariable ratio.
" These curves may therefore be defined
the locus (place) of the vertex of a tri-
angle, on a given base, one of whose
sides bears a given ratio to the sum or

0 vu

OX Y

difference of a given line and the other
side."

OVARIUM OF PLANTS. The hol-
low case at the hase of the pistil, enclosing
the ovules. It is said to be inferior,
when the tube of the calyx contracts ad-
hesion with its sides ; superior, when no
such adhesion exists. Hence, an infe-
rior ovary involves a superior calyx; a
superior ovary, an inferior calyx. When
an ovary adheres to the calyx merely by
its back, it is termed parietal.

OVERLYING ROCKS. Interjected
Rocks. A geological term applied to
those rocks which appear lying over, or
interspersed among, the stratified rocks.
They are probably connected with de-
posits situated beneath the fundamental,
having apparently been ejected in a
melted state, through fissures in the
strata.

OVERSHOT WHEEL. A water-wheel,
to which the water is conveyed over the
top of the wheel, and applied above the
axle ; in this case the water acts merely
by its weight, and not by the impulse of
the stream.

OVFGEROUS {ovum, an egg, gero, to
bear). A term applied to parts which
contain or support the egg.

OVI'PAROUS (ovum, an egg, pario,
to bring forth). A designation of those
animals, which produce their young in
an egg, the egg being hatched after its
exclusion from the parent, as in the
cases of birds and most reptiles.

OVIPO'SITOR {ovum, an egg, pono,
to lay down). An instrument with which
some Hymenopterous insects are fur-
nished for depositing their eggs. It is
formed by a prolongation of the last seg-
ment of the body in the females, and
possesses the power of boring a hole in
certain substances. In other insects of
this order, the ovipositor is replaced by a
sting.

OVO-VIVPPAROUS {ovum, an egg,
vivus, alive, pario, to bring forth). A
designation of those animals which bring
forth their young in the living state, the
egg having been previously hatched
within the body of the parent.

OVULE OF PLANTS. A small pulpy
body, borne by the placenta, and gra-
dually changing into a seed. It consists
of two tunics and a nucleus.

OVU'LINjE. The egg-shells ; the sub-
typical group of the Cyprceidce, or Cow-
ries, named from the genus ovula, and
resembling the cowries in general form *,
but the extremities of the aperture are
245

generally produced, and there are no
teeth to the inner lip.

OXA'LIC ACID. An acid existing, in
the form of an acid salt of potash, in
many plants, particularly in the species
of Oxalis and Rumex ; combined with
lime, it forms a part of several lichens.

OXALIDA'CEjE. The wood-sorrel
tribe of Dicotyledonous plants. Herba-
ceous plants, undershrubs, or trees, with
leaves alternate ; flowers symmetrical ;
stamens hypogynous ; fruit capsular.

O'XAMIDE. A white insoluble sub-
limate, obtained by decomposing oxalate
of ammonia by heat. The term is de-
rived from the first syllable of oxalic acid
and ammonia.

OXFORD CLAY. Clunch clay; a
great argillaceous bed interposed between
the lower and the middle oolite. It is of
a dark blue colour, some *of the beds are
bituminous, and abound in septaria, or
masses having internal dissepiments. In
its lower part are beds of limestone called
Kelloway Rock.

OXIDA'TION. The process of con-
verting metals or other substances into
oxides, by combining with them a certain
portion of oxygen. It differs from acidi-
fication, in the addition of oxygen not
being sufficient to form an acid with the
substance oxidated.

O'XIDE. A generic term, consisting
of the first syllable of oxygen with a termi-
nation indicative of combination, applied
to compound neutral bodies and bases. To
this the name of the other element is
joined, to express the specific compound.
Thus, a compound of oxygen and hydro-
gen is oxide of hydrogen ; if oxygen and
potassium, oxide of potassium ; of which
compounds the first, or water, is an in-
stance of a neutral oxide ; the second, or
potash, of a base or alkaline oxide. But
the same elementary body often com-
bines with oxygen in more than one
proportion, forming two or more oxides ;
to distinguish them, the following pre-
fixes are employed : —

1. Proto (upSi-or, first), denoting the
minimum of oxygen, as protoxide.

2. Deuto (aeurepoc, second), denoting
a second proportion, as dioxide. This
is also called bin- oxide.

3. Trito {rplrof, third), denoting a
third proportion, as tritoxi&e. This is
also called ter-oxide.

4. Per {very much), denoting the max-
imum of oxidation, as peroxide.

OXY (ofv?, acid). A prefix, denoting
in some terms, the presence of acidity;
M3

P AI

PAL

in others, the presence of oxygen ; in a
third class of terms, acuteness of sense
or function ; and, lastly, sharp-pointed-
ness.

O'XYGEN (b£i>s, acid, yevvda, to gene-
rate). The name given by Lavoisier to
an elementary body, with reference to its
property of forming acids with other ele-
mentary bodies. Oxygen is a permanent
gas, when uncombined, and forms one-
fifth part of the atmospheric air. By
Priestley it was called dephlogisticated
air ; by Scheele, empyreal air ; by Con-
dorcet, vital air.

O'XYSTOMES (6fi»r, sharp, o-To/xa, a
mouth). The name given by Milne

Edwards to the fourth and last family of
brachyurous crustaceans, comprising all
those species which most resemble the
type, especially in the conformation of
the buccal apparatus.

O'ZON (6'£a>, to smell). The name
given by Schbnbein to the odorous prin-
ciple emitted during the action of an
electrical machine. He considered it to
be a body contained both in air and in
water; that it had hitherto escaped the
observation of chemists ; and that, under
certain circumstances, it was set free by
electricity. It is probably a trit-oxide of
hydrogen.

PACHYCEPHALI'NjE (iraxwp, thick,
KecpaXr], head). The name given, in
Mr. Swainson's classification of birds, to
the Great-headed Chatterers, the second
sub-family of the Ampelidae, or Chat-
terers.

PACHYDE'RMATA {va%w, thick,
iepfxa, skin). An order of the Mammalia,
comprising thick-skinned animals, as the
elephant, the rhinoceros, &c, and certain
aquatic animals, approaching to the hip-
popotamus.

PACKFONG. The white copper of
the Chinese, said to be an alloy of copper,
nickel, and zinc. It is also called Ger-
man Silver.

PA'GINA. Literally, a page of a book ;
hence, applied to a surface of a leaf,
pagina superior being the upper, pagina
inferior the lower surface.

PA'GODITE. A species of steatite or
serpentine, which the Chinese carve into
figures.

PAGU'RIANS. A tribe of anomour-
ous crustaceans, named from the genus
pagurus, and known by the popular
names of Hermit-crabs and Soldier-crabs ;
in France they are called Bernards
l'Hermite.

PAIRS, CHEMICAL. In the un-
organized kingdom the elementary sub-
stances are generally combined by the
force of affinity, either two and two in
pairs, or the pairs themselves forming
doublepairs, and in some few cases even
the double pairs united. In the organ-
ized kingdom, on the contrary, the four
elements do not enter into binary, but at
246

least into ternary, or quaternary combi-
nations, without first forming pairs.

PALiEO'GRAPHY {iraXcubs, ancient,
ypd<p<o, to write). The study of ancient
documents, including the knowledge of
the various characters used at different
periods by the writers and sculptors of
different nations and languages, their
abbreviations, initials, &c.

PALjEONTO'LOGY(7ra\cu69, ancient,
ovra, beings, \6fos, an account). The
science which treats of fossil remains,
both animal and vegetable; of their
forms and relations, of the changes which
they have undergone, and of the causes
which have produced their immersion in
the strata.

PALjEOSAU'RUS (TraXcuo?, ancient,
aavpa, a lizard). The name of a genus
of fossil Saurians discovered in the mag-
nesian conglomerate on Durdham Down,
near Bristol, in 1834.

PALiEOTHE'RIUM (nakaib?, ancient,
Qnplov, a wild beast). A fossil extinct
quadruped, belonging to the order Pachy-
dermata, resembling a pig, or tapir, but
of great size.

PALjEOZO'IC SERIES {iraXaid £5a,
ancient animals). A name given to the
fossiliferous strata of earlier geological
date than the carboniferous system, and
the mountain limestone, with reference
to their organic contents. The term
Protozoic has been applied to these early
groups of strata; but this term, it has
been observed, seems to assert more than
is necessary, perhaps more than is known.

PALEA. Chaff. The term paleee is

PAL

PAP

applied to the minute colourless bracts
at the base of the florets of a capitulum ;
and to the floral envelope of grasses,
which immediately surrounds the sexual
organs.

Paleaceous. Chaffy ; covered with pa-
leae, or membranous scales, as the recep-
tacle of some compositas.

PALLADIUM. A new metal found
by Wollaston in the ore of platinum.

PALLAS or OLBERS. A telescopic
planet, discovered by Dr. Olbers, in 1802,
and situated in the solar system between
Mars and Jupiter. Its diameter is un-
known. It describes its orbit round the
sun in four years, seven months, and
eleven days. Its distance from the sun
is 267 millions of miles.

PA'LLIAL IMPRESSION. The mark
formed in a bivalve shell by the pallium
or mantle. It occurs usually near the
margin of the shell, and is, hence, some-
times called the marginal impression. In
the Dimyaria, this mark passes from one
impression of the muscles of attachment
to the other ; if, in its passage, it bends
inwards posteriorly, it is said to be sinu-
ated, and the part where this occurs is
the siphonal scar of Mr. Gray.

PA'LLIOBRANCHIA'TA {pallium, a
mantle, branchice, gills). A term ori-
ginally proposed by Blainville for the
Brachiopodous mollusca, notwithstanding
his belief that the spiral arms were the
organs of respiration. It has since been
proved by Owen to be strictly appropriate,
and is applied by him to the class of ace-
phalous mollusca, in which the gills are
developed from the mantle.

PALMA'CEjE. The Palm tribe of
Monocotyledonous plants. Plants with
an arborescent trunk, covered with the
sheathing bases of leaves ; leaves termi-
nal, clustered, pinnate, or flabelliform ;
flowers hexapetalo'ideous, stamens defi-
nite; ovarium superior, 3-celled ; fruit
baccate, or drupaceous, with fibrous
flesh.

PALMATE LEAF. A form of leaf,
having five lobes, with the midribs radi-
ating from a common point at the base of
the leaf, and resembling the palm of the
hand. The palmate leaf admits of the
following varieties, which occur, in bota-
nical descriptions : —

1. Palmatifid, in which the lobes are
divided as far down as half the breadth
of the leaf.

2. Palmatilobate, in which the lobes
are divided to an uncertain depth.

3. Palmatipartite, in which the lobes

247

are divided beyond the middle, and the
parenchyma is not interrupted.

4. Palmatisected, in which the lobes
are divided down to the midrib, and the
parenchyma is interrupted.

PALMI'PEDES (palma, the palm of
the hand, pes, the foot). Natatores.
Swimmers ; an order of web-footed birds,
capable of swimming in the water the
instant they are liberated from their egg-
coverings. They comprehend the divers,
pelicans, albatrosses, swans*, &c.

PA'LPI {palpo, to touch). The organs
of touch developed from the labium and
maxillae of insects, commonly called
feelers.

PALPICO'RNES {palpi, feelers, cornu,
a horn). A family of the pentamerous
Coleoptera, characterized by the presence
of antennae with club-like terminations,
which are usually shorter than one of the
pairs of palpi. They are mostly aquatic.

PANDURIFORM {pandura, the an-
cient shepherd's pipe, forma, likeness).
Fiddle-shaped ; obovate, with a deep
sinus on each side, as the leaves of rumex
pulcher.

PA'NGOLINS. A common designa-
tion of the Scaly Ant-eaters, derived
from a Javanese word signifying an ani-
mal which rolls itself into the form of a
ball. The pangolins correspond with the
genus Manis of Linnaeus.

PANICLE {panicula, the woof wound
round the quill in the shuttle). A form
of inflorescence, in which the flower-buds
of a raceme have, in elongating, developed
other flower-buds, as in the oat. When
the rachis of inflorescence separates irre-
gularly into branches, so as to lose the
form of an axis, this is called by Willde-
now a deliquescent panicle.

PANTOCHRONO'METER (war, irav-
top, all, xpovo^, time, fierpov, a measure).
An instrument which combines the use
of the compass, of the sun-dial, and of
the universal time-dial.

PAPAVERACEjE. The Poppy tribe
of Dicotyledonous plants. Herbaceous
plants with leaves divided, alternate ;
flowers polypetalous, single on long pe-
duncles ; petals 4, or some multiple of 4,
cruciate ; stamens hypogynous ; ovarium
solitary ; seeds numerous.

PAPER COAL. A bituminous shale,
which separates into thin laminae of
coal, like sheets of paper.

PAPILIONACEOUS {papilio, a but-
terfly). A form of corolla resembling a
butterfly, and found in all the leguminous
plants of Europe. Of the five petals, the
M4

PAR

PAR

uppermost is dilated, and called vexillum,
or the standard ; the two lateral are con-
tracted and parallel, and called alee, or
the wings ; the two lower are contracted,
parallel, generally coherent by their an-
terior margin, and termed carina, or the
keel.

PAPPUS (irdinros, the down of the
cheek). A botanical term for the feathery
appendage which crowns the fruit of
many composite plants, being, in fact, a
reduced calyx. A familiar instance oc-
curs in the down of the dandelion.

PARA- (napd). A Greek preposition
■with various meanings, as through, near,
about, &c. In some chemical compounds,
it denotes near to, and expresses a close
alliance between two compounds.

PARA'BOLA (napafioXri, the Conic
Section parabola, so named because its
axis is parallel to the side of the cone).
A section of a cone by a plane parallel
to one of its sides ; it is therefore an open
curve, which would spread out wider and
wider, if the cone were extended. A
simple illustration of the parabola is the
curved line described by a body thrown
forward, as of a bullet from a gun, a jet
of water from a fire-engine, &c.

Paraboloid. A geometrical solid, formed
by the revolution of a parabola round its
axis (See Conoid). The term is also
applied to two surfaces of the second de-
gree, viz. the elliptic paraboloid and the
hyperbolic paraboloid, which answer to
the curve parabola.

PARACE'NTRIC VELOCITY. An
expression denoting the rate at which a
moving body approaches a certain centre,
without reference to the rate at which it
moves in space.

PARACEPHALO'PHORA {napd, be-
side, Ke<t>a\ri, the head, 0<?po>, to carry).
The name given by De Blainville to a
class of molluscous animals, in which
the head is but little distinct from the
body, but is always provided with some
of the organs of sense. They are divided
into the sub-classes dioica, monoica, and
hermaphrodita.

PARADI'SIDjE. The Birds of Para-
dise ; a family of the Insessores, or
Perchers, characterized by the extraor-
dinary development of their feathers.
They are confined to New Guinea and
the neighbouring islands. See Tenui-
rostres.

PA'RADOX (7rapa3o?ta, marvellous-
ness). A statement which is opposed
to general belief, being, at its first enun-
ciation, apparently contradictory of some

established maxim or truth. Thus, " the
wise man alone is rich," is a paradox,
for the statement would be ridiculed by
all, except the wise.

PA'RAFFIN. Petroline. A particular
hydrocarbon produced in the distillation
of wood. Its name is derived from pa-
rum afflnis, denoting its remarkable in-
difference to other bodies in a chemical
point of view.

PARALLACTIC INSTRUMENT.
Ptolemy's Rules. An astronomical in-
strument invented by Ptolemy for deter-
mining the moon's parallax, and described
in his Almagest.

PA'RALLAX (ffapdWa&v, alterna-
ation). Parallax may be generally defined
to be the change of the apparent situ-
ation of an object arising from a change
of the real situation of the observer. In
astronomical language, the word has a
more technical meaning, and is restricted
to the difference of the apparent positions
of any celestial object when viewed from
a station on the surface of the earth,
and from its centre. The centre of the
earth is the general station to which all
astronomical observations are referred :
but, as we observe from the surface, a
reduction to the centre is needed; and
the amount of this reduction is called
parallax.

1. Parallax, diurnal and annual. By
the preceding paragraph it is plain that
the parallax of a body signifies the differ-
ence between its apparent place and its
true place, or that in which it would be
seen, if the observer were situated at the
centre to which the motion is referred.
When the point of reference is the centre
of the earth itself, the change of aspect
is called the diurnal parallax ; when it
is the centre of the earth's orbit, the
change is called the annual parallax, or
parallax of the great orb. The latter is
the angle under which the semidiameter
of the earth's orbit would be seen from a
superior planet, or from a fixed star.

2. Parallax, horizontal. The parallax
changes with the planet's distance from
the earth, and also with its altitude above
the horizon. It is nothing when the
planet is in the zenith ; and greatest, the
distance .from the earth remaining the
same, when the planet is in the horizon.
In the latter case, it is called horizontal
parallax. Thus, by saying that the
moon's horizontal parallax is 58' on a
certain day, we mean that the moon's
distance is such, that if she were in the
horizon of any place, the spectator's de-

PAR

PAR

scent to the centre of the earth would
elevate her 58' above the rational horizon
drawn through the centre.

3. Parallax, angle of. In Optics, the
angle of parallax is that angle which the
axes of the eyes, when directed towards
an object, form with it at their point of
contact. This angle becomes greater as
the object is nearer.

PARALLELE'PIPED (irapaWtiKeni-
•rredov, a body with parallel surfaces). A
hexahedron, all whose faces are paral-
lelograms, and each pair of faces which
do not actually intersect are parallel. A
prism whose bases are parallelograms is
called a parallelepiped. If the bases of
a rectangular parallelepiped be squares,
and the attitude be equal to the side
of the base, all its faces will be squares,
and such a parallelepiped is called a cube.

PARALLE'LOGRAM (napaWtiXo-
7pa.niJ.0s, bounded by parallel lines). A
quadrilateral figure, whose opposite sides
are parallel. The term, as thus defined,
is applicable to the square, the rectangle
or oblong, the rhombus or lozenge, and
the rhomboid ; but these terms are sig-
nificant of relations existing between the
angles, as well as the sides of the figures.

PARALLELS (napaWtjXos, beside
one another, side by side). In Astro-
nomy, the term Parallels denotes those
circles which every point of the earth
between its poles describes by its diurnal
rotation, and which run, as it were, side
by side of one another.

Parallels Mathematical. Parallel right
lines are such as are in the same plane,
and which, being produced continually
in both directions, would never meet.

PARA'METER {irapafxerpeu), to mea-
sure by, or with, another thing). A term-
originally applied to a constant straight
line belonging to each of the conic sec-
tions, and synonymous with latus rec-
tum; that is, the perpendicular drawn to
the axis through a focus, terminated both
ways by the curve, was the parameter of
the curve. The term was afterwards
applied, in a general sense, to the con-
stant quantity which enters into the
equation of a curve. In the language of
astronomy, what were formerly called
the parameters of the orbits, are now
generally called their elements.

PARASI'TA. The Louse tribe; an
order of " familiar " insects, which are
entirely wingless, do not undergo meta-
morphosis, but agree with the true in-
sects in having only six legs. The term
parasite, derived from irapa, and (m-or,
249

provisions, denotes, in its original sense,
a hanger-on at the tables of the great.

PARATO'NNERE. The French term
for a lightning conductor, or metallic rod,
made to project above the highest part
of a building, and continued down to the
ground ; its object being to promote the
discharge of an electric cloud, and to
conduct the lightning to the ground
without injuring the building.

PARE'NCHYMA (napeyxv^a, any
thing poured in beside). The name given
by Erasistratus to the peculiar substance
of the lungs, liver, kidneys, and spleen,
as if formed separately by the blood of
veins which run into those parts : the
word o-apf he used only of the muscular
flesh. The term is generally applied to
the soft tissue of organs, in plants and
animals, particularly to that of the
glands.

PARHE'LION {napa, near, »j\<or, the
sun). A mock sun, or meteor, of a
brilliant light, resembling the sun, and
occasionally accompanying halos. The
term parhelion denotes an image of the
sun formed by reflection from a cloud.

PARIE'TAL (paries, a wall). A term
applied to any thing which is attached to
the wall of an organ, as to the placenta
of plants, when attached to the walls of
the ovary, as in poppy, violet, &c.

PA'RINjE {parus, the tit). Parine
birds or Tits ; a family of the Cantatrices
of Macgillivray, somewhat allied to the
kinglets and the jays, although, from
their diminutive size, they seem at first
sight to have little affinity to the latter.

PARI-PINNATE. Equally pinnate,
abruptly pinnate; applied to a pinnate
leaf of which the petiole is terminated
neither by a leaflet nor a tendril.

PARO'NYMOUS WORDS {napthw-
fxos, formed from a word by a slight
change). Words which belong to one
another, as the substantive, adjective,
verb, &c. of the same root. These have
not in every case a precisely corre-
spondent meaning, and the careless or
designed application of them may lead to
the logical fallaciafigurce dictionis, which
properly belongs to the case of Ambi-
guous Middle. Thus, " Projectors are
unfit to be trusted : this man has formed
a project ; therefore he is unfit to be
trusted." Here the sophist proceeds on
the hypothesis that he who forms a, pro-
ject must be a projector: whereas the
bad sense which commonly attaches to
the latter word, is not at all implied in
the former. Whately.

M5

PEA

PEC

PART, LOGICAL. Logically, species
are called parts of the genus they come
under ; and individuals, parts of the
species. Really, the genus is a part of
the species ; and the species, of the indi-
vidual.

PA'RTICIPLE. A part of speech said
to have derived its name from its par-
taking of the nature both of the verb and
of the noun. Home Tooke calls it a u verb
adjective."

PA'RTICLE {particula, a little part).
The term applied by grammarians to
those parts of speech which are inde-
clinable, and are neither nouns nor verbs,
but express the relations, connexions,
and modifications of ideas. In this sense,
particles comprehend adverbs, conjunc-
tions, prepositions, and interjections.

PARTICULAR PROPOSITION. In
Logic, a proposition in which the predi-
cate is affirmed or denied of some part
only of the subject.

PARTITE LEAF. In Botany, a leaf
is so called when it is parted or divided
into a fixed number of segments, which
are separated nearly down to the base ; a
leaf with two such divisions is said to be
bipartite ; with three, tripartite ; with
many, pluripartite, &c.

PASSERFNuE {passer, a sparrow).
Passerine birds or sparrows ; a family of
the Deglubitrices of Macgillivray, differ-
ing little from the Emberizinaa of that
author, except in the form of the bill,
and in having the upper mandible broad
and concave, instead of being narrow
and furnished with a prominent knob.
By other writers, the Passerine birds are
included in the Fringilladae or Finches,
a family of the Insessores or Perchers.

PATENT YELLOW. A pigment con-
sisting of chloride and protoxide of lead ;
also called mineral yellow.

PAVO. The Peacock ; a modern
southern constellation, consisting of four-
teen stars, and occupying a part of the
space situated between Sagittarius and
the South Pole.

PAVO'NIDjE {pavo, the peacock).
The Peacock family, the first family of
Rasorial birds, in Mr. Swainson's ar-
rangement. The term Phasianidce is
adopted by other writers.

PEA IRON-ORE. The common name
of the pisiform variety of argillaceous or
clay iron-stone.

PEA-STONE. Pisiform limestone ; a
sub-species of limestone, occurring in
round granular concretions.

PEAK. When the summit of a moun-
250

tain rises with an acclivity more abrupt
than the rest of the mountain, it is
usually, whether conical or not, called
a peak. When very slender pointed
rocky protuberances form the summits,
they are called by the French aiguilles,
or needles, but by us generally peaks.

PEAR GAGE. An instrument in-
vented by Smeaton for measuring the
degree of the rarefaction of air, and
named from its peculiar form. It is a
modification of the air-pump gage.

PEARL. A spherical concretion
formed within the pearl oyster, consist-
ing of carbonate of lime and albumen.
Sir Everard Home considered that the
abortive ova of the animal were the nu-
clei upon which the pearls were formed.

PEARL-ASH. The name of potash
when it is calcined, and of a whitish
pearly lustre. It is employed in making
flint glass, soap, &c.

PEARL-SINTER. Fiorite. A variety
of stalagmitic quartz or quartzsinter,
found at Santa-Fiora in Tuscany, &c.

PEARL-SPAR. Another name for
brown-spar or sidero-calcite. It consists
of the carbonates of lime and magnesia,
with traces of other substances, and oc-
curs abundantly in the lead mines in
the north of England, &c.

PEARL-STONE. A sub-species of in-
divisible quartz, occurring in large beds
in clay, porphyry, and secondary trap-
rocks, in Hungary and in Spain.

PEARL-WHITE. The sub-nitrate of
bismuth, formerly called Magistery of
bismuth. From the nitric solution of
bismuth is procured a powder of a pearly
lustre, used by perfumers under the
name of pearl powder.

PEAT or TURF. A carboniferous de-
posit formed in the low parts of plains
by the gradual decomposition of succes-
sive layers of vegetables, burning with
flame and grey smoke, and emitting a
pungent and somewhat fetid odour. It
occurs wherever the soil has been Jong
soaked with water, which has no means
of complete evaporation.

PE'CHBLENDE. An ore of uranium,
in which the metal exists in the state of
sulphuret.

PE'CORA (plur. of pecus, cattle). The
fifth order of the Mammalia in the sys-
tem of Linnaeus, where they are placed
between the orders glires and bellute.

PECTIC ACID (7r»KTi9, a coagulum).
A substance obtained from the carrot
and other vegetables, so named from its
remarkable tendency to gelatinize.

PED

PEL

PECTIN {irriKrh, a coagulum). The
name given by Braconnot to a principle
which forms the basis of vegetable jelly.

PE'CTINATE (pecten, a comb). In
Botany, a term expressing a modification
of the pinnatifid leaf, in which the seg-
ments are long, close, and narrow, like
the teeth of a comb.

PE'CTINATED (pecten, a comb).
Having processes resembling in form and
arrangement the teeth of a comb, as the
spines of some species of murex.

PE'CTINIBRANCHIA'TA(p<?cten, pec-
tinis, a comb, branchice, gills). The name
of the sixth, the most highly organized
and the most numerous order of Gastero-
pods, including all the inhabitants of
spiral univalve sea-shells, and many with
shells simply conical, which have their
comb-shaped gills placed internally in a
capacious cavity, into which the water is
freely admitted.

PECTI'NIDiE. A tribe of Monomy-
arian conchifers, including the pectens,
the limae, the oysters, &c.

PECTORA'LES PEDU'NCULATI. A
family of Acanthopterygious fishes, in
which the pectoral fins are attached to
the bones by a peduncle, resembling a
wrist, enabling the fish to leap in pursuit
of its prey, as in the lophius, or fishing-
frog.

PE'DAL (pes, pedis, a foot). A foot-
key in musical instruments, or a lever
for acting on the swell of the organ or
the piano-forte. A pedal-base is a base
which remains stationary on one note,
while the other parts continue to move
and form various chords which are re-
lated to the pedal-base according to the
laws of harmony.

PED ATE. A botanical designation of
that form of the palmate leaf, in which
the two lateral lobes are themselves sub-
divided, as in helleborus niger. The
same modifications occur as in the pal-
mate leaf, with similar terms, as peda-
tifid, pedatipartite, pedatisected, and pe-
datilobate.

PEDICELLA'RLE (pedicellus, a little
stalk). The name of certain appendages
to the integument of the Echini and
other echinodermata, consisting of a
dilated end or head, usually prehensile,
supported by a slender stem or pedicel.
They have been distinguished by Valen-
tin into the gemmiform, the tridactyle,
and the snake-headed, or ophicephalous.

PEDIPA'LPI (pes, pedis, a foot, palpi,
the organs of touch in insects). A divi-
sion of the Arachnida, in which the
251

palpi are exceedingly strong, and fur-
nished at their extremity with a prehen-
sile forceps, as in the scorpion.

PEDO'METER (nedov, the ground,
/jLerpov, a measure). An instrument
for measuring the distance which a person
has performed by walking or riding. It
is of a portable size, and its operation
is effected by motion communicated to
its machinery by the traveller him-
self.

PE'DUNCLE and PE'DICEL. In
botanical language, the peduncle is that
part of the inflorescence which proceeds
immediately from the stem. If it is
divided, its principal divisions are called
branches ; and its ultimate ramifications,
which bear the flowers, are named pedi-
cels. There are modifications of the
peduncle, to which other names are ap-
plied. See Rachis and Scape.

PEDU'NCULATE (pedunculus, a foot-
stalk). That which is supported on a
peduncle, or foot-stalk, as the shell of
Terebratula, or a flower furnished with a
stalk. See Sessile.

PE'GASUS. The Flying Horse ; one
of the old northern constellations, con-
sisting of eighty-nine stars.

PE'GMATITE. A granular mixture
of quartz and felspar. It often occurs
in granite veins and passes into Graphic
Granite, from which some geologists do
not distinguish it.

PELECA'NIDjE. The Pelican tribe ;
a family of the Natatores, or Swimming
birds, characterized by having the hind
toe united by membrane to the rest.
They are, nevertheless, almost the only
birds of the order which perch upon
trees. They include the pelican, the
cormorant, the frigate-bird, the gannet,
and the boobie.

PELIO'MA. Iolite. A blue-coloured
mineral, belonging to the garnet tribe,
now commonly called dichroite, from its
exhibiting two different colours when
viewed in different positions.

PELLICLE (dim. of pellis, the skin
or hide of a beast, flayed off). A thin
skin, or film. Among chemists, it de-
notes a thin surface of crystals uniformly
spread over a saline liquor evaporated to
a certain degree.

PE'LOKONITE. An amorphous mi-
neral, of a bluish-black colour, contain-
ing phosphoric acid, iron, manganese,
and copper.

PE'LTATE (pelta, a shield). Shield-
shaped; a term applied by botanists to
leaves which are fixed to the petiole by
M6

PEN

PER

their centre, or by some point within the
margin, as in tropaeolum.

PE'NCIL {penicillus, any thing which
has its end divided like a painter's brush).
In optics, a pencil of rays is a collection
of rays which converge to, or diverge
from, a point ; in geometry, a pencil of
lines is a series of lines which meet in a
point.

PE'NDULUM. Every solid body which
is freely suspended, is called a, pendulum.
A distinction is made between the simple
or mathematical, and the compound or
physical pendulum. The former is re-
garded as an inflexible imponderable
line suspended at one end, its other end
being considered as a point possessing
weight. A pure mathematical pendulum
has no actual existence. All such as
actually exist are physical pendulums,
every material particle of which acts
as the heavy point of the simple pen-
dulum. A seconds pendulum is one
whose vibration occupies one second.

PENI'NSULA (pene, nearly, insula,
an island). A part of a continent which
runs out into the sea, and is joined to
the main land by only a small portion of
its circumference. If the projections of
land reach but a little way into the sea,
they are called capes, promontories, or
headlands.

PENNATU'LID.E {pennatula, a little
feather). A family of cortical polyps, in
which the whole animal resembles a
feather, the stem supporting lateral
branches, upon which the polyps are
arranged.

PENTA'CRINITE (TreVre, five, npivov,
a lily). A pedunculated star-fish with
five rays, for the most part fossil. The
animal is so complicated that the num-
ber of separate pieces of stone of which
its singular skeleton is made up has been
calculated to amount to not fewer than
one hundred and fifty thousand.

PE'NTAGON {irevre, five, futvla, an
angle). A plane geometrical - figure,
bounded by five sides, and consequently
having five angles. When the sides and
angles are all equal, the pentagon is
called regular, and then the square of
its side is equal to the sum of the squares
of the sides of the hexagon and decagon
inscribed in the same circle as the pen-
tagon.

PENTA-GYNIA (ti/vJj, a woman).
Having five pistils ; an ordinal cha-
racter of plants in the system of Lin-
naeus.
PENTAKE'NIUM. The name given
252

by Richard to that modification of the
polakenium, in which the fruit, so desig-
nated, has five akenia, or cells. See
Cremocarpium.

PENTA'MERA (r*rr«, five, fiepos, a
paf%). A section of Coleopterous insects,
in Which the tarsi of all the feet are five-
jointed, the fourth being of ordinary size.
Latreille.

PENTA'NDRIA (Trevre, five, Uvrjp, a
man). Having five stamens; the cha-
racteristic feature of the fifth class of
plants in the system of Linnaeus.

PENU'MBRA {pene, almost, umbra,
a shadow). A partial shadow ; an
intermediate shade between pure sha-
dow and light; a shadow which re-
ceives only a portion of the rays of
a luminous body, when that body has
a measurable diameter. It occurs in
solar and lunar eclipses, in the form of
two diverging spaces, one on each side of
the cone of umbra, or pure shadow,
caused by the interception of the sun's
rays. In a solar eclipse, so long as any
part of the sun is visible, the observer
is in the penumbra, and not in the
umbra or complete shadow.

PEPERI'NO. An Italian name for a
particular kind of volcanic rock, formed,
like tuff, by the cementing together of
volcanic sand, cinders, scoriae, &c.

PEPO. A gourd ; a three-celled fleshy
indehiscent fruit, with parietal placentae,
as the cucumber. Richard uses the term
peponida.

PE'PSIN (TreTTTO), to digest). A pecu-
liar animal principle secreted by the
stomach and present in the gastric juice.

PER. A Latin preposition, which,
when prefixed to the name of an oxide,
indicates the presence of the greatest
quantity of oxygen which can exist in
a compound, as in per-oxide.

Bi-per. This double prefix is used,
when there is more than one atom of
oxygen in the base, as well as an unequal
number of atoms of acid and base, as in
the ii^per-sulphate of mercury, where
bi indicates the presence of two atoms of
acid, and per that the mercury is in the
form of a per-oxide.

PER ACCIDENS. A term formerly
employed in philosophical language to
denote an effect which does not follow
from the nature or essence of the thing,
but from some accidental circumstance
or quality; in this sense, it is opposed
to the term per se : thus, fire burns per
se ; a red-hot iron burns per accidens.
In Logic, the term per accidens is

PER

PER

applied to that mode of conversion of a
proposition in which the quantity is
changed, or limited from universal to
particular. This might fairly be named
conversion by limitation, but is com-
monly called conversion per accident.

PERCE'PTION. The mental faculty
•by which we hold communication with
the actual world. 1. It is thus distin-
guished from conception, which relates to
that which has no reality : we perceive
the present order of things, we conceive
of the future. Thus the ancients dis-
tinguished the ai(rOt]Ta, or objects of per-
ception, from the von™, or objects of
conception. 2. Perception differs from
consciousness, in the subjects of the
former being external, those of the latter
internal : we perceive a mountain, we are
conscious of a thought. 3. It differs
from remembrance, in respect to the sub-
jects being present or past : we remember
a former object of perception, but we do
not perceive it until it is again present.
4. But the term u perception " is vaguely
applied by some writers to all operations
and states of mind, comprising the pas-
sions, and all the phenomena of memory
and of imagination.

PE'RCIDjE (perca, the perch). The
Perch tribe ; a family of Acanthopterygi-
ous, or spiny-finned fishes. In the
thoracic species, the ventral fins are
placed under the pectoral ; in the jugular,
upon the throat ; in the abdominal, on
the abdomen.

PERCU'SSION (percutio, to strike).
A forcible stroke given to a resisting ob-
ject by a moving body. There is one
point of the moving body in which the
whole force of the stroke is concentrated,
and the resistance to which would neu-
tralize the blow. This point is termed
the centre of percussion, and it always
coincides with that of oscillation ; and if
all parts of the percutient body be carried
forward with the same celerity (which is
not the case of the pendulum), the centre
of percussion is the same with the centre
of gravity. The force of percussion is mo-
mentum. See Momentum.

PERDICI'N,E {perdix, a partridge)*
Perdicine birds, or partridges; a family
of the i Rasores, or Scratching birds.
There is little essential difference be-
tween the large, long-tailed birds, called
Cocks and Pheasants, and the small,
short-tailed species, called Partridges and
Quails. Their habits also are essentially
similar.

PERE'NNIBRA'NCHIATE (peren-

253 w

nis, perpetual, branchiae, gills). A divi-
sion of Amphibious animals, which pre-
serve their branchiae through the whole
period of their lives, as the proteus, the
siren, &c.

PERFECT NUMBER. A number
which is equal to the sum of all its divi-
sors. Thus 6 is a perfect number, for its
divisors are 1, 2, and 3, and the sum of
these is 6. See Number.

PERFOLIATE. The designation of
a leaf which, by union of its margins,
encloses the stem, which thus seems to
pass through it.

PERFORATED (perforo, to pierce
through). Bored, or pierced through, as
by an awl; a term applied to the ear-
shells.

PERI-, PER- (Trep/). A Greek prepo-
sition, signifying around, about, ex-
pressing the relation of circumference to
centre, and so strictly different from ufi<pi.

1. Peri-anth (avOov, a flower). A collec-
tive term for the calyx and corolla com-
bined, the limits of which are undefined,
so that they cannot be satisfactorily dis-
tinguished from each other, as in tulip,
orchis, &c.

2. Peri-carp (tcapiros, fruit). A botani-
cal term denoting all the parts of a ripe
fruit which are on the outside of the real
integuments of the seed, except the aril.
These parts are, severally, the epicarp,
the sarcocarp, and the endocarp.

3. Peri-cladium (/cXa3or, a young
branch). A term sometimes applied to
the lower part of a petiole, when this
part sheaths the branch, as in Apiaceae.

4. Peri-chcetium (xaiTn, seta, a hair).
A term applied to the peculiar leaves
which surround the base of the seta, or
stalk of the sporangium, or seed-vessel
of mosses.

5. Peri-clinium (nXivn, a couch). The
name given by Cassini to the involucrum
of composite plants. It is to be lamented
that botanists cannot agree in employing
the same term for an organ. Besides the
above designation of the involucrum,
Linnaeus called it calyx communis,
Necker, perigynandra communis, and
Richard periphoranthium.

6. Per-enchyma. In the nomenclature
of vegetable tissues propounded by
Morren, this term is applied to the
amylaceous granules contained within
the tissue of plants.

7. Peri-gee (-yfj, the earth). That point
in a planet's orbit in which it is nearest
to the earth. Its apogee is that point in
which it is furthest from the earth.

PER

PER

8. Peri-gonium {fovrj, generation). A
term synonymous with perianthium,
and denoting the parts which surround
the organs of generation in plants,
viz. the floral envelopes.

9. Peri-gynium {^wrj, a woman). A
term which has been variously employed
by botanical writers. Link applied it to
the disk found in certain plants. With
some, it is synonymous with urceolus ;
with others, it relates to the hypogynous
setce found at the base of the ovary of
cyperaceae.

10. Peri-gynous (71^, a woman). That
condition of the stamens of a plant in
which they contract adhesion to the sides
of the calyx, as in the rose.

11. Peri-helion (#\tor, the sun). An
astronomical term, denoting the greatest
approximation of a planet to the sun. See
Aphelion.

12. Peri-meter (/lerpov, a measure).
The bounding line of any plane figure, of
whatever parts or shapes that line may
consist. The bounding line of a circle, or
perhaps of any curve which returns upon
itself, is termed the circumference or
periphery.

13. Peri-oeci (oIkos, a habitation).
Those who live under the same parallel
of latitude, whether north or south, but
on opposite meridians.

14 Peri-ostracum {ocrpaKov, a shell).
The epidermis, or membrane analogous
to scarf-skin, which covers shell.

15. Peri-phery (cpepoo, to carry). The
line which bounds a circular body; a
circumference, as that of a circle, an
ellipse, or any other curvilinear figure.

16. Peri-phyllia (<pv\\ov, a leaf.) The
term applied by Link to the minute
hypogynous scales found within the
paleae of grasses. These little organs
have disturbed the nomenclature of
botany not a little ; for while some call
them corolla, others call them squamulce,
Linnaeus nectarium, Richard glumella,
De Candolle glumellula, and De Beauvois
lodicula.

17. Peri-scii (aula, shadow). The inha-
bitants of the polar circles ; those whose
shadows make complete revolutions, in
consequence of the sun being present for
twenty-four hours together. See Hete-
roscii.

18. Peri-sperm {anepua, a seed). An-
other name for the albumen, or the sub-
stance lying between the integuments
and the embryo of the seed. By Richard,
the term is applied to the testa or sper-
moderm of other writers.

254

19. Peri-sporum (anopos, a seed, a
spore). The name given by some French
writers to the hypogynous setce found at
the base of the ovary of Cyperaceae. They
have also been termed perigynium.

20. Peri-stomians {aro/xa, the mouth).
The name given by Lamarck to a family
of Gasteropods, consisting of the genera
Valvata, Paludina, and Ampullaria.
Cuvier comprises these under his tro-
choid pectinibranchians.

21. Peri-stomium (arofxa, the mouth).
The membrane, or series of tooth-like
processes, which closes the orifice of the
theca of mosses. Strictly speaking, it
consists of two membranes, and hence
we hear of an inner and an outer
peristomium. The organ is highly hy-
grometrical.

22. Peri-thecium (9t]Kn, a theca, or
case). The case which contains the re-
productive organs of certain fungi. Peri-
dium is also a kind of covering of spori-
dia ; peridiolum is its diminutive.

23. Peri-trema (xpfj^a, a hole). The
raised margin which surrounds the
breathing holes of scorpions.

24. Peri-tropal {rpeirui, to turn). A
botanical term applied to the embryo of
the seed, when it is directed from the
axis to the horizon.

PE'RICLINE. A felspathic substance,
united by some mineralogists with ice-
spar, and found in the Tyrol, St. Go-
thard, &c.

PERI DOTE. Chrysolite. A silicate
of magnesia, constituting olivine in its
purer state.

PERIOD. The time occupied by a
planet in making a revolution round the
sun ; or the duration of its course till it
returns to the same point of its orbit.
In Arithmetic, a period is the recurring
part of a circulating decimal. For its
chronological meaning, see Cycle.

PERIO'DIC ACID. An acid consist-
ing of iodine and oxygen.

PERIO'DIC FUNCTIONS. Trigono-
metry has for its subject periodic magni-
tude, i. e. magnitude which varies in
such a manner as to go through stated
cycles of changes, each cycle being a
reiteration of the preceding one. Peri-
odic functions are those which, performed
any given number of times on a variable,
reproduce the simple variable itself.
Thus 1 — x and — x are periodic func-
tions of the second order, since

1— (1— x) = x, — (— -x)=x.

PERIODICAL STARS. Stars which
undergo a regular periodical increase

PER

PET

and diminution of lustre, involving in
one or two cases a complete extinction
and revival. One of the most remark-
able of these is the star Omicron, in the
southern constellation Cetus, first noticed
by Fabricius in 1596.

PERIODICAL WINDS. Winds which
blow half the year in one direction, and
half the year in the opposite direction.
October and April are the two months, in
which the change in the direction of
these winds usually takes place. See
Monsoon.

PERKINS'S STEAM-ENGINE. A
modification of the steam-engine, in
which there is no proper boiler, but the
water is heated to a high temperature in
a cylindrical vessel, called a generator,
thence discharged through a valve, and
immediately converted into steam, hav-
ing a pressure equal to that of about 35
atmospheres, or of about 500 lbs. on the
square inch ; the steam at this high
pressure is then admitted into a cylinder
only 18 inches long and 2 inches wide,
the piston of which would perform 200
strokes per minute, and exert a force
equal to 10 horse power.

PERLATE ACID. The name given
by Bergman to the acidulous phosphate
of soda ; the phosphate of soda had been
previously called sal mirabile perlatum.
It was named by Guyton-Morveau,
ouretic acid.

PERMANENT INK. A solution of
nitrate of silver, thickened with sap
green or cochineal.

PERMANENT WHITE. Sulphate of
baryta. At a high temperature it fuses
into an opaque white enamel, which is
used in the manufacture of fine earthen-
ware, and as a pigment.

PERMEABILITY (per, through, meo,
to pass). That property of certain bodies
by which they admit the passage of other
bodies through their substance. The
cellular tissue of plants is permeable by
fluids, though at the same time imper-
forate.

PERMIAN SYSTEM. Zechstein.
Magnesian Limestone Formation. Under
these names is designated a series of
•well-known deposits which succeed the
carboniferous rocks, and sometimes pass
into them by insensible gradations.

PERMUTATIONS. By this term is
meant the number of changes which any
quantities, a, b, c, d, &c, may undergo
with respect to their order, when taken
two and two together, three and three,
&c. &c. The number of changes which
255

may be rung upon twelve bells is
479,001,600. See Combinations.

PE'RONATE (pero, a sort of high
shoe). A term applied in botany to the
stipes of fungaceous plants, which is
thickly laid over with a woolly substance,
ending in a sort of meal.

PEROXIDE. A term applied in che-
mical nomenclature to denote the highest
degree of oxidation, of which a compound
is capable. See Per.

PERPENDICULAR. A term applied
in geometry to that straight line which,
falling upon another straight line, makes
the adjacent angles equal to each other.
Each of these angles will be a right
angle.

PERSEUS. A northern constellation
consisting of fifty-nine stars, the prin-
cipal of which is Algenib.

PERSISTENT. A term applied to
those parts of plants which do not fall at
the usual period, as the corolla of cam-
panula, the calyx of paeonia. See Cadu-
cous.

PERSONATE (persona, a mask). A
term applied to that form of the gamo-
petalous corolla, in which the limb is
unequally divided : the upper division,
or lip, being arched ; the lower prominent,
and pressed against it, so that the whole
resembles the mouth of a gaping animal,
as in antirrhinum. See Ringent.

PERSONIFICATION. A metaphor-
ical mode of speech by which inanimate
objects or abstract ideas are repre-
sented as possessed of life and action.
Every scholar has enjoyed Virgil's famous
personification of the grafted tree : —
" Miraturque uovas frondes, et non sua poma."

PERSPECTIVE. The application of
geometrical rules to the delineation of
objects on a plane surface, as connected
with the arts of design.

PERTURBATIONS (perturbo, to dis-
turb). A name applied to those inequa-
lities in the lunar and planetary motions,
which arise from the universality of at-
traction. Thus, not only does the sun
attract the earth, and the earth the moon,
but these attractions are all reciprocal ;
and not only is this the case, but each
individual planet attracts, and is attracted
by, all the rest.

PETAL (nera'Kov, a leaf). In Botany,
a flower-leaf; one of the divisions of a
corolla. In some plants, as in nymphaea,
the filament is expanded, and resembles
a petal, and is then called petaloid.

PE'TALITE. A felspathic substance,
in which lithia was first discovered by

PH A

PH A

Arfvedson. It is a silicate of lithia and
alumina.

PETIOLE. The leaf- stalk of a plant,
or that which connects the blade with
the stem. A leaf so provided is called
petiolate ; if otherwise, sessile. "When a
petiole is divided into several parts, each
part bearing a separate leaf or leaflet, it
is said to be compound, the stalks of the
leaflets being called petiolules or stalk-
lets.

PETITIO PRINCIPII. A non-logical
or material fallacy in reasoning, com-
monly called begging the question. It
takes place when a premiss, whether
true or false, is either plainly equivalent
to the conclusion, or depends on it for
its own reception, as if any one should
infer the actual occurrence of the eclipses
recorded in the Chinese annals, from an
assumption of the authenticity of those
annals. Whately.

PETRIFACTIONS. Stony matters
deposited either in the way of incrusta-
tions, or within the cavities of organized
substances. In the former case, carbo-
nate of lime flows over wood and other
organic and destructible matters, of
which it preserves the form.

PETROLE'UM (irtrpa, a rock, ZXauov,
oil). Rock oil, an inflammable liquid
bituminous substance, differing from
naphtha only in being more inspissated.
It receives its name from its oozing, like
oil, from the rock. It abounds in the
United States, where it is known under
the name of Seneca or Genessee oil.

PETRO'SILEX. A name probably
given to two different minerals, viz. com-
pact quartz and compact felspar; the
latter has also been termed fusible petro-
silex.

PETUNTSE'. A species of felspar,
constituting the vitrifying ingredient in
Chinese porcelain.

PETWORTH MARBLE. Sussex
Marble. A variously coloured limestone,
occurring in the weald clay, and com-
posed of the remains of fresh-water
shells.

PEWTER. A compound metal formed
of tin and lead, in the proportions of 80
parts of the former to 20 of the latter.

PHjENO'GAMOUS {(paiva>, to show,
ydyuof, nuptials). A term applied to
those plants in which the reproductive
organs are visible, as distinguished from
the cryptogamous, in which they are con-
cealed, or of which the function is not
understood. The term is synonymous
with phanerogamous.
256

PHENOMENA {<palvoncu, to ap-
pear). The appearances upon which a
system or hypothesis is founded. Thus
the apparent motions of the celestial
bodies are phaenomena, which have sug-
gested the systems of astronomers. A
hypothesis, on the contrary, is an assumed
cause, by which we endeavour to explain
a particular class of phaenomena.

PHANEROGAMOUS (0ai/eP6c, evi-
dent, fdfxot, nuptials). Phcenogamous.
A term applied by botanists to those
plants in which the organs of reproduction
are easily distinguished. They comprise
the exogens and endogens of the natural
arrangement. See Cryptogamous.

PHA'RMACOLITE. Arsenic bloom.
Native arseniate of lime, occurring in
white acicular crystals, in veins together
with tin-white cobalt at Andreasberg, &c.

PHA'RMACOSIDE'RITE. Arseniate
of iron, occurring crystallized, chiefly in
cubes, and hence called by Werner cube-
ore.

PHARYNGI'N^ LABYRINTHI-
FO'RMjE. A family of Acanthopterygi-
ous fishes, in which the membranes of
the pharynx are divided into small irre-
gular leaves, containing cells, which the
fish can at pleasure fill with water ; and,
by ejecting a portion of this water, it
moistens its gills, and is thus enabled to
continue its respiration out of its proper
element.

PHASES (0d<m, an appearance). A
term applied in astronomy to the monthly
changes of appearance of the moon.
When she appears with a full orb, or
with all her surface enlightened, we say
the moon is full. When a part only of
her enlightened hemisphere is towards
the earth, and that part is convex, the
moon is said to be gibbous (gibbus,
bunched out). When a half only of her
enlightened hemisphere is visible to the
earth, we speak of a half-moon. When
a very small portion of the enlightened
hemisphere is towards us, and that con-
cave, the moon is said to be horned.
Lastly, when none of her enlightened
hemisphere is towards us, we say the
moon changes, or it is new moon.

When the moon is full, she is said to
be in opposition to the sun ; when new,
she is said to be in conjunction : these
two positions are called syzygies. In the
first and the last quarter, half her illu-
minated portion is visible; these posi-
tions are called quadratures, and the in-
termediate points between them and the
syzygies are called octants.

PIIL

PHO

PHA'SIANE'LLIN^E. Pheasant snails,
a sub-family of the Trochidce, or Top
Shells, named from the genus phasi-
anella, in which the shell is spiral and
obovate, the outside polished, and the
operculum shelly.

PHASIANI'DjE. The Pheasant and
Fowl tribe of the Rasores, or Scratching
Birds, distinguished by the shortness of
the hind toe, the presence of spurs on
the legs, and the beautiful development
of the tail. They pass gradually into the
Perdicince, there being no real distinction
between them.

PHI'LLIPSITE. A zeolitic substance
belonging to that division of the har-
motome minerals, which contain potass,
as distinguished from the baryte-har-
motome species.

PHILO'LOGY (0iXo\o<y/a). This term,
in its strict etymological sense, denotes
a love of talking ; generally, it signifies
a love of literature ; in modern times it
has been restricted to the study of lan-
guage and history.

PHILOSOPHICAL CANDLE. A bot-
tle fitted with a cork, through which a
slender glass or metallic tube passes. On
introducing the materials for generating
hydrogen, and fixing the cork and tube
air-tight, a jet of hydrogen is discharged,
which may be ignited by the application
of a burning body or an electric spark.

PHILOSOPHY (<t>i\o<ro<pia). This
term denotes, simply, a love of know-
ledge. But all subjects of systematic
inquiry, ranging from that of the opera-
tions of the mind to those of the arts
and manufactures, have their philoso-
phies ; and hence, although the term
carries with it no great precision, its ap-
plication in any particular case is suffi-
ciently obvious.

PHLEGRjE'AN FIELDS (<p\ey<a, to
burn). Campi Phlegrcei, or the "Burnt
Fields." The country round Naples, so
named by the Greeks, from the traces
of igneous action every where visible.

PHLG2UM ((pXotos, bark). Peridermis.
The name given by Mohl to one of the
layers of bark, the epi-phlceum of Link.
See Bark,of Plants.

PHLOGISTON ((p*eya>, to burn). A
name given by Stahl to an imaginary
substance, which was the principle of in-
flammability. Combustible bodies were
supposed to consist of an incombustible
base, united to this phlogiston, which
escaped during combustion. This pro-
cess is now attributed to the combination
of combustible matter with oxygen,
257

which is hence called a supporter of com-
bustion.

PHLORIDZIN (tf>Xot6p, bark). A
substance discovered in the bark of the
root of the apple, pear, cherry, and plum-
tree. It has been considered as crystal-
lized salicin plus two atoms of oxygen.

PHOCENIC ACID (phoccena, a por-
poise). Delphinic acid. A volatile acid
contained in train oil or seal oil, and in
the berries of Viburnum opulus.

PHO'CIDjE (phoca, a seal). The
Seal tribe of carnivorous Vertebrata, the
Amphibia of Cuvier, distinguished by
the adaptation of their form and struc-
ture to a residence in the water, and of
their teeth for retaining a hold on the
slippery surface of fish, and crushing
them before they are swallowed.

PHCENICIN {<t>oivi$, purple). Indigo-
purple ; supposed to be a hydrate of in-
digo, with two equivalents of water.

PHC2NIX. A modern southern con-
stellation, consisting of thirteen stars.

PHO'LARITE. Hydrated silicate of
alumina ; a substance occurring in small
pearly scales in the coal formation of
Fins.

PHO'LIDjE. A family of macrotra-
chian bivalves, named from the genus
pholas ; in these the valves are often
prolonged in a shelly tube, resembling
that of the Tubulibranchiata.

PHONETIC WRITING (fuvij,
sound). A kind of hieroglyphic writing
employed by the ancient Egyptians, in
which the characters represent, not
objects, but sounds. The figures repre-
senting letters were the likenesses of
certain animals or other objects, the
names of which began with those letters.
The phonetic was thus opposed to the
ideographic writing, in which the charac-
ters represented objects, or symbolically
denoted abstract ideas. See Hiero-
glyphics.

PHO'NICS {<p(avtj, sound). A term
synonymous with acoustics, denoting the
doctrine of sound. The phenomena of
direct, reflected, and refracted sound
have given rise to the three respectively
corresponding terms of phonics, cata-
phonics, and diaphonics.

PHONOLITE (0a>i/»/, sound, \i$ov, a
stone). Clinkstone. A felspathic rock of
the trap family, usually fissile, and
named from its sonorous property, when
struck with a hammer.

PHORA'NTHIUM (0«?Po>, to bear,
avOot, a flower). The term applied by
Richard to the receptacle of composite

PHO

PHO

plants. This is the thalamus and cli-
nanthium of other writers.

PHOSGENE GAS {<pS>s, light, yewdco,
to produce). Chloro-carbonic acid gas;
a compound of chlorine and protoxide of
charcoal. It is named from the peculiar
power of the sunbeam in effecting this
combination.

PHOSPHATE. A salt formed by the
union of phosphoric acid with a sala-
fiable base.

PHO'SPHITE. A salt formed by
the union of phosphorous acid with a

PHOSPHORESCENCE (tf>wp, light,
<pepa>, to carry). The emission of light
by many bodies at a low temperature,
unaccompanied by any essential change
in their properties. The luminous ap-
pearance of common phosphorus is the
result of chemical action, for it takes
place only when this substance is in
combination with oxygen or chlorine.

1. Phosphorescence by insulation is a
property possessed by many bodies, in
consequence of which, after long ex-
posure to the sun's rays, they become
luminous in the dark on the application
of heat. Of this kind are the phosphorus
of Baldwin, or the ignited muriate of
lime ; phosphorus of Canton, consisting
of oyster-shells, calcined with sulphur;
and the Bologna stone, or the sulphate of
barytes.

2. Phosphorescence of organic remains
in a state of dissolution. This luminous
property occurs in touchwood, and in
sea-fish, on which a luminous film is
formed. The phosphorescence appears
to be owing to a low sort of combustion,
as the emission of light decreases on
rarefying the air.

3. Phosphorescence of organic bodies
during life. This occurs in the marigold
and yellow lily, a little after sunset, when
the atmosphere has been very much
heated in July and August. It is pro-
bably of an electrical nature. The lu-
minosity of the infusoria, zoophytes,
fire-flies, and glow-worms, is a subject of
much obscurity.

PHO'SPHORITE. A sub-species of
apatite, comprising the fibrous and the
compact phosphates of lime.

PHO'SPHORUS (<pw, light, 0<?po>, to
carry). A solid, semi-transparent colour-
less substance, of a waxy consistence,
undergoing slow combustion at ordinary
temperatures ; burning brilliantly in air.
Combined with lime, it is a principal
constituent of the bones of vertebrated
258

animals, and is found in some kinds of
limestone.

1. Phosphorous acid. An acid pro-
duced, in the form of a white volatile
powder, by the slow combustion of
phosphorus. Its salts are called phos-
phites.

2. Phosphoric acid. An acid obtained,
in the form of white flakes, by igniting
phosphorus under a large bell jar. Its
salts are called phosphates.

PHO'SPHURET. A compound of
phosphorus with a combustible or a
metallic oxide.

PHOSPHY'TTRITE. Phosphate of
yttria ; a very scarce mineral substance,
first found in the granite of Lindenas in
Norway, and subsequently in equally
small quantities at Ytterby in Sweden.

PHO'TICITE. A mixture of the sili-
cate and the carbo-silicate of manganese.

PHOTOGE'NIC DRAWING {<pZt,
0o)Tor, light, fewdu), to produce). A
modern discovery by which objects are
represented by the chemical action of
light on a prepared metallic tablet, upon
which the images of the objects are
thrown by a camera obscura. The dis-
covery was made by Daguerre ; and the
apparatus was hence called Daguerreo-
type ; and the process itself photogeny,
photography, or heliography.

PHOTO'GRAPHY (0Sr, <P<ot6v, light,
•ypa^a), to delineate). Heliography. The
application of the chemical effects of
light to the purpose of rendering perma-
nent the images obtained by means of
convex lenses. See Daguerreotype.

PHOTO'METER (0Sf, ^w-rof, light,
fxerpov, a measure). An instrument for
measuring the relative illuminating
powers of different sources of light. In
Rumford's photometer, the depth of the
shadow is the measure used for com-
paring the intensities of different lights ;
in Ritchie's, the brightness of the illu-
mination answers the same purpose.
When the shadows are equally deep, or
when the illuminations are equally
bright, the luminous powers of the two
sources of light will be as the squares of
the distances at which they act.

Leslie's Photometer consists of the
differential thermometer with one of the
balls blackened. The clear ball transmits
all the light that falls upon it, and there-
fore its temperature is not affected ; the
black ball, on the contrary, absorbs all
the light, and a corresponding elevation
of temperature takes place. The action of
the photometer depends, therefore, on

PHY

PHY

the heat produced by the absorption of
light.

PHRA'GMOCONE (<pPayp.a, a parti-
tion, kwvos, a cone). The chambered
cone of the shell of the Belemnite.

PHRASE (in Music). This term is
denned by Rousseau as a succession of
sounds in melody or harmony, expressing
an unbroken sense more or less complete,
and terminating in a pause, thus forming
a cadence more or less perfect. But the
notions entertained of this term are
various.

PHRENO'LOGY (*>** the mind,
Aoyos, an account). The name of a
science introduced by Gall and Spurz-
heim, by which particular characters and
propensities are indicated by the con-
formation and protuberances of the skull.

PHYCOMA'TER (ipvuos, sea-weed,
liijTnp, mother). The name given by
Fries to the gelatine in which the sporules
of byssaceous plants first vegetate.

PHYLLI'DIANS. The name given
by Lamarck to a family of Gasteropodous
molluscs, typified by the genus phyllidia,
and characterized by the position of the
branchia in a circle round the body be-
tween the foot and the mantle.

PHYLLO'DIUM {<pv\\ov, a leaf). A
term applied to the petiole of a leaf,
when it is expanded and leafy, and the
lamina abortive, as in many species of

PHYLLONY'CTERANS (<pv\\ov, a
leaf, vvKTepJf , a bat). A primary division
of the Cheiroptera, commonly termed the
"foliated bats," from the peculiar mem-
branous foliations which in these animals
serve the purpose of antennae.

PHYLLO'PODA (<pv\Xov, a leaf, noi>t ,
jrodof, a foot). An order of the bran-
chiopodous Crustacea, in which the body
is elongated, and the extremities flattened
for the purpose of swimming, as in the
branchipus.

PHYLLOSO'MA {<pv\\ov, a leaf, o-w/ia,
the body). The family of double-cuirassed
crustaceans, the forms of which are re-
markable for their rounded shape and
the transparency of their integuments.

PHYLLOSTOMI'NjE (<p6\\ov, a leaf,
o-To/ua, the mouth). A family of insec-
tivorous Cheiroptera, which have the
nasal appendage simple and fleshy, and
to which the celebrated vampyre belongs.

PHY'SALITE. Pyrophysalite. A sub-
species of prismatic topaz, found in
granite at Finbo in Sweden.

PHYSCOSTE'MON (</>ucrcza>, to swell,
crfjuav, a stamen). The name given by
259

Turpin to a fleshy body found in certain
plants between the base of the stamens
and the base of the ovary. It is com-
monly called the disk.

PHYSICAL DEFINITION. A defi-
nition which assigns the parts into
which the thing defined can be actually
divided. Thus, a plant would be defined
physically, by enumerating the root,
stalk, leaves, &c, of which it is com-
posed. Logically, it would be defined
" an organized being, destitute of sensa-
tion," the former of these expressions de-
noting the genus, the latter the difference.

PHY'SICS {(pvarti, nature). That de-
partment of science which treats of the
properties of bodies, the laws of motion,
and the general phenomena of nature.
It is commonly termed Natural Philoso-
phy and Mechanical Philosophy. Bacon
endeavours to draw a line between phy-
sics and metaphysics ;— " Physic is that
which inquires of the efficient cause and
of the matter ; metaphysic, that which
inquires of the form and end."

PHYSIO'GNOMY {<pv<rioyva>p.ovia).
The science or art of judging of a per-
son's character by his outward look.

PHYSIOLOGY {<p6<ris, nature, \d70r,
an account). The science which treats
of the properties of organic bodies, ani-
mal and vegetable ; of the phenomena
which they present ; and of the laws
which govern their actions.

PHYSO'GRADA. An order of the
Acalephce, in which the body is supported
in the water by means of one or more
bladders, capable of being filled with air
at the will of the animal, and which,
when partially empty, enable the animal
to sink on the approach of danger. These
are the hydrostatic acalephce of Cuvier.
M. de Blainville considers the Physo-
grada as one of the aberrant or false
forms of the Zoophytes, and as animals
improperly referred to them.

PHYTO'GRAPHY (<pvrbv, a plant,
7pa0o), to write). An account of the
rules observed in describing and naming
plants.

PHYTO'LOGY (<pVrov, a plant, Aoyor,
an account). That branch of science
which treats of the forms and properties
of plants.

PHYTOTHAGOUS (<pvr6v, a plant,
(pdya, to eat). Plant-eating ; a term ap-
plied to a division of cetaceous animals,
and to a tribe of plant-eating gasteropods.
See Zoophagous.

PHYTO'TOMY (<f>vc6v, a plant, refxvto,
to cut). Vegetable anatomy ; the display

PIL

PIN

of the tissues of plants by means of dis-
section.

PHYTOZO'A (<puTov, a plant, £wov, an
animal). Animal plants, or polyps ; a
class of Radiate animals, named from
their plant-like forms ; the Zoophytes of
old authors.

PHYTOZOA'RIA {<j>vr6v, a plant,
£5oi/, an animal). A term applied by
Ehrenberg to those minute aquatic ani-
mals which are more commonly termed
infusoria and microzoaria. They are
distinguished into the polygastrica and
the rotifera.

PI'CAMAR (in pice amarum). The
bitter principle of tar, and of all empy-
reumatic products.

PI'CIDiE (picus, a woodpecker). Picine
birds, or woodpeckers; a family of the
Scansores, or Climbing birds, character-
ized by their long, straight, angular
beak, the end of which is compressed
into a wedge, adapted to perforate the
bark of trees.

PICRO'LITE. A green or yellow
mineral consisting chiefly of magnesia ;
found traversing beds of magnetic iron
ore.

PICRO'SMINE (mnpos, bitter, baixrj,
odour). A mineral species, consisting of
silicate of magnesia; found in the iron
mine of Englesburg, in Bohemia.

PICROTO'XIN. The deleterious prin-
ciple of the cocculus indicus. It is ex-
tracted by means of water and alcohol,
and eventually crystallizes.

PIERRE DE TRIPES. The name
given to a sub species of prismatic gyp-
sum, or anhydrite, from its convoluted
concretions.

PIEZO'METER (™£a>, to press,
nerpov, a measure). An instrument for
ascertaining the compressibility of
liquids.

PILE. An apparatus for exhibiting
the phenomena of Galvanism, and con-
sisting, literally, of a pile or column of
metallic plates of zinc and copper and
discs of wet card, placed in succession
to one another in a regular order
throughout the series.

1. Dry Pile. This apparatus, also
called ZambonVs pile, after its inventor,
differs from the hydro electric batteries
principally in this, that the presence of
the electromotive liquid is dispensed
with, its place being occupied by some
moist substance of low conducting power,
generally paper. It agrees, therefore,
mainly with the description given above,
and the term " dry " is inappropriate.
230

2. Pile of two elements only. This
apparatus, also an invention of Zamboni,
consists of one metal and one interme-
diate conductor, either dry or moist.
These piles acquire at their poles a feeble
electrical tension, the metallic pole ex-
hibiting positive electricity in the dry
pile, and the pointed end of the metal
being positively electrified in the moist
pile.

3. Secondary piles. These, sometimes
called Rater's piles, consist of alternate
layers of homogeneous metallic plates,
between which some moist conducting
substance is interposed. When they
stand alone, no electromotive tension is
excited ; but they are capable of receiv-
ing a charge by being placed in the cir-
cuit of a powerful Voltaic battery, and of
thus acquiring, though in an inferior de-
gree, the properties of the battery itself.

4. Pile of Be Luc. An electrical
column, constructed of pieces of paper,
silvered on one side, and alternating
with thin leaves of zinc; the silvered
surfaces of the paper discs being always
in the same direction.

PILEUS. The cap ; the botanical
term for the uppermost part of an agaric,
resembling an umbrella in form.

PILI'DIUM. The orbicular hemisphe-
rical shield of lichens, the outside of
which changes to powder, as in calycium.

PILOSITY (pilosus, hairy). A term
applied to that kind of hairiness in
plants, in which the hairs are long, soft,
and erect, as in the carrot.

PPM ELITE. A green silicious earthy
substance, which accompanies chryso-
prase, and, like it, owes its colour to
oxide of nickel. It is a variety of stea-
tite, found at Kosemutz in Silesia.

PINCHBECK. An alloy of copper, or
brass, and zinc, made in imitation of
gold. It is sometimes called tombac,
similor, and petit-or.

PINIC ACID (pinus, the pine). An
acid obtained from rosin ; it may be re-
garded as an oxide of oil of turpentine.

PINION. A wheel consisting of fewer
teeth than that which it drives. The
teeth of a pinion are called leaves.

PI'NITE. A talcose substance, con-
sisting of silica, alumina, and oxide of
iron ; found in granite and in porphyry.
By Kirwan it is called micarelle.

PINNATE LEAF (pinna, a feather,
a fish's fin). That form of leaf in which
simple leaflets are placed on each side of
a common petiole. The same modifica-
tions occur as in the palmate leaf, with

PIS

PLA

similar terms, as pinnatifid, pinnatipar-
tite, pinnatisected, and pinnatilobate.
A pinnate leaf which has no terminal
leaflet or tendril, is said to be equally or
abruptly pinnate.

PFNNATIPEDS {pinna, a fin, pes, the
foot). An order of birds which have the
digits bordered by membrane.

PINNOTHE'RIANS. A tribe of the
third family of the brachyurous crusta-
ceans in the arrangement of Milne
Edwards, named from the genus pin-
notheres, and characterized by their pecu-
liar habit of being housed between the
mantle-lobes of certain conchifers, as of
mytilus, pinna, &c.

PIPE-CLAY. A plastic and tenacious
variety of clay, of a greyish- white colour,
with an earthy fracture, and a smooth
greasy feel ; found near Poole in Dorset-
shire.

PIPERA'CEiE. The Pepper tribe of
dicotyledonous plants. Shrubs or herba-
ceous plants, with leav es opposite ; flowers
achlamydeous ; stamens adhering to the
base of the ovarium, which is superior
and one-celled.

PI'PRIDjE. The name given by Mr.
Vigors to a family of the Dentirostres,
from the genus Pipra. Mr. Swainson,
rejecting this family, gives the name
Piprinae to the manakins, whicli he
makes a sub-family of the Ampelidae,
Fruit-eaters, or Chatterers.

PISCES {piscis, a fish). The first
class of the Vertebrata or Encephalata,
consisting of fishes, or oviparous ani-
mals, inhabiting the water, breathing by
means of permanent branchiae, and hav-
ing fins for progressive motion. See
Ichthyology.

PISCES (in Astronomy). The twelfth
and last of the zodiacal constellations,
consisting of 113 stars. It denoted the
third month, extending from the 20th of
August to the 20th of September. During
this period, the inundation of the Nile
spreads over the whole of Egypt, and the
fishes move about.

PISCIS AUSTRALIS. The Southern
Fish ; a constellation, consisting of
twenty-four stars, the principal of which
is Fomalhaut.

PISCIS VOLANS. The Flying-fish;
a modern southern constellation, con-
sisting of eight stars.

PI'SOLITE (7uW,apea, MOo?, stone).
A variety of carbonate of lime, possess-
ing a structure like that of an aggluti-
nation of pease. It occurs in the middle
Oolite Formation.
261

PFSTACITE. The name given by
Werner to some mineral substances, now
more generally designated by the name
of epidote, a sub-species of prismatoidal
augite.

PISTIL {pistillum, a pestle). The
name given by botanists to the female
apparatus in plants. It occupies the
centre of the flower, and is distinguished
into three parts; viz. the ovary, the
style, and the stigma.

PISTON. A short plug of metal, or
other solid substance, fitted exactly to
the cavity of the barrel or body of a pump.
It serves the purpose of exhausting the
air from the barrel, and is hence com-
monly called the sucker. There are two
kinds of pistons used in pumps, the one
with a valve, and the other without a
valve, called a, forcer or plunger.

PIT COAL. Common coal ; so called
from its being obtained by sinking pits
in the ground.

PITCH-ORE. The hydrous protoxide
of uranium, also called indivisible ura-
nium; found in primitive rocks.

PITCHSTONE. A quartzose rock, of
a uniform texture, belonging to the un-
stratified and volcanic classes, which has
an unctuous appearance like that of in-
durated pitch.

PITTACAL (tti'tto, pitch, jca\6f,
beautiful). A beautiful blue colouring
matter, discovered in the oil of tar.

PITTED TISSUE. Bothrenchyma. A
variety of the cellular tissue of plants, hav-
ing its sides marked by pits, sunk in the
substance of the composing membrane.
It was formerly designated by the term
dotted ducts, vasiform tissue, &c.

PI'TTIZITE. Pitchy iron ore; a
variety of bog iron ore found near Li-
moges in France.

PLACE'NTA. In Botany, that part
of the ovary from which the ovules arise.
It generally occupies the whole or a
portion of one angle of each cell. It is
sometimes elongated in the form of a
little cord, called the umbilical cord, as
in the hazel.

PLAGIO'STOMI (TrAcrytop, transverse,
(no/da. a mouth). An order of cartilagi-
nous Fishes, which have tneir mouth
placed transversely beneath the snout.

PLANE, or PLANE SURFACE. In
geometry, this is a surface such that the
right line, which joins every two points
which can be assumed upon it, lies en-
tirely in the surfa'-e. Hence, a plane
rectilineal figure is any portion of a plane
surface which is included by right lines,

PL A

PL A

and the figure is trilateral, quadrilateral,
multilateral, &e., according as it has
three, four, or many sides.

1. Plane, vertical. A plane which
passes through the zenith, or point which
is directly over our heads, and the centre
of the earth, is called a vertical plane,
and the circle in the heavens marked hy
such a plane, is a vertical circle, or
azimuth.

2. Plane, Tangential. A plane which
touches a curvilineal solid. It is from
such a plane that angles of incidence are
measured, whether the impinging rays
be reflected or refracted.

3. Plane, inclined. In Statics, this
term denotes a plane inclined to the hori-
zon. It is used as a mechanical power,
and the problem is to find the force
necessary to prevent a body placed upon
it from sliding down under the action of
its own weight.

4. Plane of Floatation. The surface of
a heavy fluid at rest is a horizontal plane,
and the portion of this plane which we
may imagine to be within a floating body,
is called the plane of floatation.

5. Plane of Vibration. It is assumed
that in polarized light the particles of
ether vibrate only in two opposite direc-
tions; the plane in which these excur-
sions take place is called the plane of
vibration; and, if a plane be conceived to
be situated at right angles to the plane of
vibration, and in the direction of the
ray, this will be its plane of polariza-
tion.

PLA'NET (n\avf]Tm, a wanderer). A
star which is found to change its relative
situation among the other stars. Planets
are distinguished, with reference to their
centres of revolution, into primary and
secondary. Primary planets are those
which revolve round the sun as a
centre ; secondary planets, more fre-
quently called satellites or moons, are
those which revolve round a primary
planet as a centre, and are carried with
it in its revolution round the sun.

1. The Primary Planets are divided
into superior and inferior. The superior
are those more remote from the sun than
the earth, as Mars, Jupiter, Saturn,
Herschel, and Neptune. The inferior
are those which are nearer to the sun
than the earth, as Mercury and Venus.
See Asteroids.

2. The following symbols are employed
to designate the planets in tables and on
globes. Mercury §, Venus $, the
Earth 0, Mars <£, Vesta S, Juno £,

2C2

Ceres <j>, Pallas $ , Jupiter If., Saturn r\,
Herschel or Uranus H.

3. Two planets are in conjunction
when they have the same longitude ;
they are in opposition when their longi-
tudes differ by 180°.

PLANETARY PERIOD. The period
in which a planet comes again into the
position which it occupied at first with
respect to the sun. The motions of the
planets being oscillatory, a planetary
period is not that in which a planet re-
volves round the heavens, but a repe-
tition of such periods. For instance,
when Mercury has just repeated the
circuit of the earth's visible heaven, he
is not in the same position with respect
to the sun as at the beginning. The
cycle of relative positions is not com-
pleted, for this planet, in less than thir-
teen years and three days, or two days
if there be four leap years in the period.
So, in a watch, the cycle of relative posi-
tions of the minute and the hour hand is
not repeated every hour, but in every
twelve hours.

PLANIPE'NNES. One of the sec-
tions of Insects into which Latreille
divides the order Neuroptera. There
are four families : viz., the panorpidae,
the myrmeleonidae, the hemerobiidae,
and the perlidae.

PLA'NISPHERE. An old term for
any representation of the sphere upon a
plane. It now denotes any contrivance
by which plane surfaces moving on one
another fulfil any of the uses of a ce-
lestial globe.

PLANTI'GRADA {p/anta, the sole of
the foot, gradior, to walk). A division
of the terrestrial Carnivorous animals,
which, in walking, apply the entire sole
of the foot to the ground, as far back as
the end of the os calcis ; as the bear, the
badger, &c. See Digitigrada.

PLASMA. A scarce green semitrans-
parent chalcedony, of a dark tint, sup-
posed to be coloured by chlorite.

PLASTER OF PARIS. Sulphate of
lime, or gypsum, heated in an oven till
nearly anhydrous, and then reduced to
powder. On adding water, an artificial
hydrate, or stucco, is formed, which sets
in a short time, and has the same com-
position as native gypsum.

PLASTIC CLAY (yrbdaraia, to fashion).
One of the beds of the Eocene Tertiary
Period, named from its being used in
the manufacture of pottery. The term
is applied to a series of beds, chiefly
sands, with which the clay is associated.

PLE

PLI

It skirts the London clay within the
London chalk basin, and appears also in
the Isle of Wight.

PLATEAU. A terra often exclusively
applied to an elevated plain ; it is, how-
ever, sometimes used to denote a great
extent of country considerably raised
above the rest of (he land, and having
its mountains, plains, and valleys ; as in
the minor plateau of Albania, and the
great plateau of Central Asia. See
Table Land.

PLATFORM. When a mountain ap-
pears as if its summit were cut off,
leaving a level and horizontal surface, it
forms a platform, or is said to be trun-
cated. See Mountain.

PLATINUM { plata, silver). A white
metal found in the auriferous sand of
certain rivers in America. Reduced to
a state of extreme division, it has the
appearance of sponge; and it is then
called spongy platinum, and is used as a
pyrophorus.

PLECTO'GNATHI (7r\eK-r6?, twisted,
yvdOov, a jaw). An order of Fishes, in
which the bones of the upper jaw are
united to each other and to the head.

PLEI'OCENE UXeiW, more, Katv6r,
recent). By the terms Older and Newer
Pleiocene, are denoted two divisions of
the Tertiary Period which are the most
modern, and of which the largest part of
the fossil shells are of recent species.
The newer formation is also termed
pleistocene.

PLEIOSAU'RUS (7rXe/a>v,more, aavpa,
a lizard). A species of animal, the re-
mains of which are found in some of the
clay beds of the oolites ; it seems to have
been intermediate between the plesio-
saurus and the ichthyosaurus ; the teeth,
vertebrae, bones of the extremities, &c,
being more like the corresponding parts
of the former, but the animal resembles
the latter in the absence of apparent
neck ; and from this greater analogy
with reptiles it has received its name.

PLEPSTOCENE ( ttXcIo-toc, most,
Kaii/6?, recent). The newest of the ter-
tiary strata, which contain the largest
proportion of living species of shells.

PLE'ONASTE. Ceylonite. An alu-
minate of protoxide of iron and mag-
nesia.

PLESIOSAU'RUS {nXnalov, near to,
<ravpa, a lizard). An extinct genus of
Saurian reptiles, which united to the
head of a Lizard the teeth of a Croco-
dile; a neck of enormous length, re-
sembling the body of a serpent ; a trunk
263

and tail having the proportions of an
ordinary quadruped, the ribs of a Chame-
leon, and the paddles of a Whale. They
appear to have lived in shallow seas
and estuaries, and to have breathed air
like the Ichthyosauri and our modern
Cetacea.

PLEURE'NCHYMA (wXewpo, the
side, ?7xuMa> infusion). A designation of
the woody tissue of plants, consisting of
very slender, tough, transparent, mem-
branous tubes, tapering acutely to each
end, lying in bundles, and communi-
cating with one another by invisible
pores.

PLEURONE'CTIMI ( pleuronectes,
the flounder; from irXevpa, the side,
vnKrij?, a swimmer). The Flat-fish or
Flounder tribe ; a family of Malacopte-
rygious or soft spined fishes, characterized
by extreme flattening of the body, and
by deficiency of symmetry. The term
pleuronectes, or side-finned, is calculated
to produce an erroneous ; opinion what
are usually called the belly and back of
these fishes being actually the sides,
though differing remarkably in colour.

PLEURO'PTERA (nXevpa, the side,
mepov, a wing). A tribe of quadrupeds,
generally known as Flying Lemurs,
Flying Cats, and Flying Foxes. They
are generally arranged under the order
Carnassiers, and are placed by some
zoologists in the division Cheiroptera.

PLEUROTOMA'RIiE. A sub-family
of the Trochidce, named from the pleu-
rotomaria, a fossil trochiform shell,
having a slit in the outer lip.

PLEUROTO'MINjE. The slit-shells ;
a sub-family of the Strombidcs, or Wing-
shells, named from the typical genus
pleurotoma, and characterized by a deep
lobe, or slit, at the top of the outer lip ;
the spire, in general, is very long and
the shells themselves often spindle-
shaped.

PLI'CIPENNES {plica, a fold, penna,
a wing). The third section, according to
Latreille, of the Neuropterous insects.
They constitute the genus phryganea,
and are known by the name of caddis-
worm. They form the order Trichoptera
in the system of Kirby and Spence.

PLINLIMMON ROCKS. A subordi-
nate group of the Cambrian series, con-
sisting of the greywacke of various
qualities ; it corresponds with the Grey-
wacke Range of the Lammermuir, ex-
tending from St. Abb's Head, on the east
coast of Scotland, to the Mull of Gallo-
way.

POD

POI

PLOMB GOMME. Hydrated alu-
minate of lead, found in the French de-
partment of Cote du Nord.

PLOPOCA'RPIUM. A term applied
by Desvaux to a form of fruit, consisting
of several follicles united in a single
flower, as in nigella and delphinium.

PLUMB A'GO. Carburet of iron; a
mineral, also known as graphite and
blacklead, occurring in rounded masses
deposited in beds in the primitive forma-
tions, particularly in granite, mica-schist,
and primitive limestone. Borrowdale in
Cumberland is a celebrated locality of
graphite, and affords the only specimens
which are sufficiently hard for making
pencils.

PLUMBER'S SOLDER. An alloy of
one part of tin and two of lead.

PLUMBOCA'LCITE. A mineral sub-
stance in which the oxide of lead occurs
in the form of carbonate of lime; an
isomorphism by which the protoxide of
lead is connected with the magnesian
oxides.

PLUMULE (plumula, a little feather).
Gemmule. The ascending part of the
axis of the embryo of a seed.

PLUTO'NIC ACTION. The influence
of volcanic heat and other subterranean
causes under pressure.

PLUTONIC ROCKS. A designation
of granite, porphyry, and other igneous
rocks, supposed to have been consoli-
dated from a melted state at a great
depth from the surface, aud named from
Pluto, the fabled God of the infernal
regions. The term unstratified is also
applied to this, the first class of rocks.

PLUVIO'METER (pluvius, rain,
fierpov, a measure). A rain-gauge; a
vessel for catching falling rain, in order
to determine what quantity of rain has
fallen in a given period.

PNEUMATICS {itveviia, wind). That
branch of natural philosophy which treats
of the mechanical properties of air and
other compressible fluids. The term
pneumatology was once employed for
metaphysics.

PNEUMOBRANCHIA'TA (ffveu/xa,
air, f3pdyxia> gi^s)- Under this term,
Lamarck arranges several genera of
Molluscous animals into a section, which
connects his second order Hydrobranchia
with his third order Tracheli-podes. The
genera are onchidium, parmacella, limax,
testacellus, and vitrina.

PODE'TIUM (7rcn;f, Trodor, afoot). A
little foot; the stalk-like elongation of
the thallus, which supports the fructifi-
264

cation of the Cenomyce, a plant of the
order of the Lichens.

PODOGY'NIUM (ttovp, 7rod6f, a foot,
fwrj, a female). A term applied to the
stalk upon which the ovary i3 seated in
certain plants, as the Passiflora, Tac-
sonia, &c. It is also called gynophore,
and thecaphore.

PODOPHTHA'LMIA ( Troup, ttooop,
a foot, b<p0a\u6s, the eye). A group of
the malacostracous Crustacea, which have
moveable pedunculated eyes. It contains
two orders; the Decapods and the Sto-
mapods. See Edriopthalmia.

PODOSPE'RMIUM (ttoup, 7to3oP, a
foot, o-7rep/Lia, seed). A term applied by
some writers to the funiculus or umbili-
cal cord, by which the ovule of plants is
connected with the placenta.

PODU'RIDiE. A family of wingless
insects, belonging to the order Thysa-
noura, in which the extremity is pro-
longed into a forked tail, as in the
podura.

PCECILO'PODA (7ro£Ki'\op, various,
ttoup, a foot). A designation of the low-
est forms of the Crustacea, from the an-
isopodous character of their segments,
the feet of different segments being pre-
hensile, or natatory, or branchial, or
ambulatory.

POIKILI'TIC (ttoiki'Xop, variegated).
A term sometimes applied, in geology, to
the New Red Sandstone formation, owing
to the varieties of colours which it pre-
sents.

POINT. A physical point is the
smallest magnitude perceptible by the
senses. If such a point be supposed to
be infinitely diminished, an idea is
formed of a mathematical point, of which
we may say that it has "no parts." As
a mathematical line may be conceived to
proceed from the motion of a mathema-
tical point, so a physical line may be
conceived to be generated by the motion
of a. physical point.

Point of Contrary Flexure. A point
at which a curve changes its curvature
with respect to any given external point,
being concave on one side and convex
on the other.

POINTS OF THE COMPASS. Besides
the cardinal points, North, South, East,
and West, intermediate directions are
adopted by seamen and travellers,
amounting in all to thirty-two primary
directions, each of which is called a
point of the compass, and thence the
interval between them, or the angle from
point to point, is also called a. point.

POL

POL

1. The first sixteen of these interme-
diate points are named as follows I —
Half-way between north and east, is
North-East (n.e.) ; and similarly are
explained South-east, South-west, and
North-West (s.e., s.w., n.w.). Again,
half-way between North and North-East
is North-North-East (n.n.e.); and thus
are explained East- North-East, East-
South- East, South-South-East, South-
South-West, West-South-West, West-
North-West, North-North-West (e.n.e.,

E.S.E., S.S.E., S.S.W., W.S.W., W.N.W.,

N.N.W.).

2. These sixteen are subdivided, the
new and final subdivisions being de-
scribed each by the simplest of the two
adjacent directions, and the cardinal
direction in which that last direction is
left. Thus, North-East by North means
the direction next to North-East in going
towards the north, and comes between
n.e. and n.n.e. By the same rule,
North-east by North might be called
North-North-East by East, but the former
is the more simple.

3. The angle of revolution from one
point to the next is, of course, the 32nd
part of 360°, or \\\°, and it is sometimes
customary to insert fractions of a point;
thus n.n.e Je., means a quarter of a
point eastward from n.n.e.

POLAR CIRCLES. Two circles,
North and South, Arctic and Antarctic,
described by the earth in its diurnal
rotation, and so named from their proxi-
mity to the two poles, from which they
are at the same distance as the tropics
are from the equator, viz. 23£ degrees.
These polar circles bound those portions
of the earth where it is continuous day
and night during several diurnal revolu-
tions of our planet. On the terrestrial
globe these circles surround the frozen
zones.

PO'LARISCOPE. An instrument con-
trived for the exact and convenient ob-
servation of the phenomena of polarized
light, and also for the measurement of
the angle of polarization.

POLA'RITY. A term applied, in its
most comprehensive sense, to a body
possessing certain powers which are not
general, but local, and not the same, but
opposite. It is more particularly applied
to the magnet, the attractive power of
which is not possessed in an equal de-
gree by every particle composing the
magnet, but is chiefly localized in two
points at or near its extremities ; fur-
ther, the powers residing in these points
2fi5

are not one and the same, but different
—indeed contrary in their nature, and
are distinguished by the different names
of Boreal magnetism and Austral mag-
netism. These two points are called the
poles of the magnet, and the right line
joining them is the axis.

1. Polarity, Chemical. The principle
just stated has been applied to the che-
mical phenomena of the voltaic circle.
The zinc and hydrochloric acid are
equally supposed to have a polarizable
molecule: one pole of each molecule has
the attraction, or affinity, which is cha-
racteristic of zinc, or zincous attraction,
and is called the zincous pole ; while the
other has the attraction, or affinity, which
is characteristic of chlorine, or chlorous
attraction, and is called the chlorous
pole. Polarity is not an ordinary condi-
tion of the particles of either the zinc or
the acid ; but is developed in both when
brought into contact with each other.

2. Two Polarities. A term expressive
of two antagonist energies, each of which
repels that which is similar, and attracts
that which is opposite, to itself. Thus, the
two north or two south poles of two mag-
netic needles mutually repel each other;
but the north pole of one needle, and the
south pole of another, mutually attract
each other.

3. Reversion of Terms. The earth it-
self being considered as a magnet, or as
containing within itself a powerful mag-
net, lying in a position nearly coinciding
with its axis of rotation, the south pole of
a magnetic needle would point towards
the north pole of the earth ; so that the
north end is the south pole, and the south
end the north pole of a magnetic needle.

4. Boreal and Austral Polarities. To
avoid the above confusion of terms, the
words Boreal and Austral have been
applied to the magnetism of the earth,
while the terms North and South have
been restricted to that of the needle ;
what had been called northern polarity
being now Austral polarity ; what had
been called southern, being Boreal po-
larity.

5. Chemical and Cohesive Polarities.
Two hypothetical forces, supposed by
Dr. Prout to reside in the ultimate mole-
cules of matter ; the chemical being of a
binary character, existing between mole-
cule and molecule, and chiefly between
molecules of different matter ; the cohe-
sive determining, under certain circum-
stances, the cohesion of the molecules
of the same matter.

N

POL

POL

POLARIZED LIGHT. A ray of light
is said to be polarized, when, after its
emergence from the substance, or reflec-
tion from the surface, of a body, it ac-
quires poles or sides with different pro-
perties in relation to the plane of its
incidence. Polarized light is procured —
1. by reflection from the surfaces of
transparent and of opaque bodies ; 2. by
transmission through several plates of
uncrystallized bodies ; and, 3. by trans-
mission through bodies regularly crystal-
lized, and possessing the property of
double refraction, as Iceland spar.

POLE (TToXew, to turn). The extre-
mity of the axis of a circle. The extre-
mities of the axis of the earth are termed
the poles, and are, respectively, the
north and south— the Arctic and Ant-
arctic—poles of our globe. The earth's
axis, being extended each way, becomes
an axis to the spherical concavity of the
sky, and its extremities are the north
and south poles of the heavens. See
Axis.

Pole of revolution. When a globe re-
volves about one of its diameters, each
extremity of that diameter is called a
pole of revolution. Every point of the
sphere describes either the great circle
which has the poles of revolution for its
poles, or one of the parallels of that
great circle.

POLE-STAR, or POLAR STAR. A
bright star of the second magnitude, in
the tip of the tail of the northern con-
stellation Ursa Minor, or the Little Bear ;
it is named from its proximity to the
north pole of the heavens, the only one
visible in our latitude.

PO'LEMOSCOPE (TToXejuor, war, <tko-
Trew, to view). An instrument, invented
by Hevelius, for viewing objects which
cannot be seen by direct vision. It con-
sists of a perspective glass, having a
reflector placed at an angle of 45° to its
axis, so that any object falling on the
reflector is conveyed to the eye. The
name suggests that a person might, by
means of such an instrument, observe,
from a place of concealment, what is
going on in an enemy's camp.

POLITICAL ECONOMY. That branch
of political science which relates to the
production and accumulation of wealth,
its distribution and consumption. It is,
in short, to the state what private eco-
nomy is to the single family.

POLLEN. The organic matter by
which impregnation is effected in the
vegetable kingdom. It consists of fine
266

powder, or grains, enclosed within the
anther. Each grain, when mature, and
brought into contact with the stigmatic
tissue, emits a tube, containing a fluid
termed fovilla, which is charged with
molecular matter. The pollen-masses of
Orchidaceous and Asclepiadaceous plants
consist of pollen-grains cohering into
solid waxy masses.

POLLUX. A star of the second mag-
nitude, in the zodiacal constellation Ge-
mini. The same name is also given to
the hindermost twin, or posterior part,
of the same constellation.

POLY-, POL- (ttoXu?, many). A
Greek prefix, denoting many or much.

1. Pol-akenium. A term applied by
Richard to a fruit consisting of several
akenia (see Achcenium). When there are
two cells, the fruit is a di-akenium ; when
three, a tri-akenium ; and so on.

2. Poly-adelphia (ade\06?, a brother).
The eighteenth class of plants in the
Linnaean system, in which the stamens
are associated in several parcels, or
brotherhoods, as in Hypericum.

3. Poly-andria (avrjp, a man). The
thirteenth class in the Linnaean system
of plants, comprising those which have
more than twenty stamens inserted be-
neath the ovarium.

4. Poly-basiie. A double sulphuret of
silver and other metals, in which the
sulphuret of silver and the subsulphuret
of copper, being isomorphous, replace
each other in indeterminate proportions.

5. Poly-carpous {Kapwds, fruit). A term
applied to a plant which has the power of
bearing fruit many times without perish-
ing. Poly-carpous plants are distinguished
into the caulocarpous, or those whose
stem endures many years, constantly
bearing flowers and fruits, as trees and
shrubs; and the rhizocarpous, or those
whose root endures many years, but
whose stems perish annually, as herba-
ceous plants.

6. Poly-chorion (%6ptov, any skin). A
term applied by Mirbel to the fruit of
the ranunculus, &c, more commonly
known by the term etcerio.

7. Poly-chroite (xpo<*i colour). The
extractive matter of saffron, the watery
infusion of which assumes different co-
lours when treated with different agents.

8. Poly-clinum (icKivti, a bed). A gene-
ral term applied by Cuvier to all those
forms of aggregated tunicated mollusca,
which agree more or less closely, in inter-
nal structure, with the salpae and as-
cidians.

POL

POL

9. Poly-galacete. The Milkwort tribe
of dicotyledonous plants. Shrubs or her-
baceous plants with leaves generally alter-
nate; flowers polypetalous, unsymme-
trical ; stamens hypogynous ; ovary 2-
celled ; fruit dehiscent.

10. Poly-gamia {yano?, nuptials). The
name of the twenty-third class in the
Linnaean system of plants, comprising
those which bear hermaphrodite and uni-
sexual flowers on the same individual ;
or hermaphrodites on one individual,
males on a second, and females on a
third.

11. Poly-gastrica (yaaTt^p, a stomach).
A class of Radiated animals, having nu-
merous stomachs or cceca communicating
with an internal alimentary cavity, with-
out perceptible nerves or muscles, but
moving by means of external vibratile
cilia.

12. Poly-yon {ywvia, an angle). A
rectilinear figure, bounded by more than
four sides. Polygons are called penta
gons, hexagons, heptagons, &c, accord-
ing as they are bounded by five, six,
seven, or more sides. A line joining the
vertices of any two angles which are not
adjacent is called a diagonal of the poly-
gon.

13. Poly-gon of Forces. A theorem in
mechanics, which may be thus stated: —
If any number of forces act upon a point,
and a polygon be taken, one of the sides
of which is formed by the line represent-
ing one of the forces, and the following
sides in succession by lines representing
the other forces in magnitude, and
parallel to their directions, then the line
which completes the polygon will repre-
sent the resultant of all the forces.

14. Poly-gonal {ya>via, an angle). A
term applied, in arithmetic, to certain
numbers possessing this property, that
the same number of points may be
arranged in the form of that polygonal
figure to which they belong. SeeFigurate
Number, and Number.

15. Poly-gonacece. The Buck-wheat
tribe of dicotyledonous plants, herbace-
ous plants with leaves alternate ; flowers
occasionally unisexual ; stamens definite ;
ovary superior; seed with farinaceous
albumen.

16. Poly-gynia {ywij, a woman). The
designation of those orders of plants in
the Linnaean system, in which there is
an indefinite number of stamens.

17. Poly-halite (SXp, salt). A chemical
compound of several sulphates, formerly
mistaken for anhydrous sulphate of lime ;

267

compact and fibrous, from the salt forma-
tion in Bavaria and Austria.

18. Poly-hedron (e<3pa, a seat or side).
A geometrical solid bounded by several
faces or planes. In every solid poly-
hedron, the number of faces and corners
exceeds the number of edges by two.

19. Poly-meric (fxepos, a part). A term
applied in chemistry to those bodies
which contain the same relative, but not
the same absolute number of atoms of
the same elements, and whose atomic
weights are consequently unlike. Several
carburets of hydrogen afford examples of
polymerism. See Isomerism.

20. Poly-mignite. Titaniate of iron ;
a new mineral found sometimes in the
zircon-syenite of Fredrickswarn in Nor-
way.

21. Poly-nomial. A barbarous word,
sometimes employed in algebra for mul-
tinomial, and denoting a quantity of
many terms, as the expression

a + 2 b + 3 c + nd, &c.

22. Poly-optron {oirrpov, a looking-
glass). A glass for multiplying objects.
It consists of a lens one side of which is
plane, but the other presents several
spherical concavities, each of which
becomes a plano-concave lens, and dimi-
nishes the object viewed.

23. Poly-petalous (neTaXov, a flower-
leaf). A designation of that kind of
corolla, in which the petals are separate
from one another, as distinguished from
the monopetalous or gamopetalous co-
rolla, in which the petals cohere.

24. Poly-phore {<pepa>, to bear). The
name given by Richard to the succulent
and dilated receptacle of such plants as
the strawberry and the raspberry. More
commonly, such a receptacle is suffi-
ciently described by the adjective fleshy.

25. Poly-piaria. Corals. A numerous
class of invertebrated animals, belonging
to the great division of the Radiata.

26. Poly-piphera. A class of the Ra-
diata, consisting of soft, aquatic animals
of a plant-like form, which develope small
tubular digestive sacs called polypi, the
margins of which are furnished with sen-
sitive tentacula, and the sides of the
latter with vibratile cilia.

27. Poly-podiacece. One of the prin-
cipal divisions of the natural order of
Ferns, constituting the highest form of
acrogenous plants, and exhibiting the
nearest approach to the Cycadaceous
Gymnosperms.

28. Poly pus (novs, no66t, a foot). Un-
der the common name Polypi have been

N2

POR

POR

grouped together three classes of Radi-
ated animals, on account of their external
resemblance to the many-armed cuttle-
fishes, which were so denominated by
the ancient Greek naturalists. The term
now denotes a class of Radiated animals,
furnished with numerous prehensile or-
gans radiating from around the mouth.

29. Poly-scope (o-KOTrew, to view). A
lens plane on one side, and convex on
the other, the latter being formed of seve-
ral plane surfaces, or facettes, for the
purpose of multiplying any object.

30. Poly-sepalous. A designation of
that form of calyx, in which the sepals
are separate from one another, as distin-
guished from the monosepalous or gamo-
sepa'ous calyx, in which the sepals co-
here.

31. Poly-spermous {a-nepfia, seed). Hav-
ing many seeds ; a botanical term applied
to certain fruits, which contain many
seeds, and distinguished from oligo-
spermous, or few-seeded.

32. Poly-synthetic (<rvv6e<ris, a putting
together). The name applied by Du
Ponceau to the class of languages spoken
by the Indian tribes of America, from
the manner in which words are abbre-
viated and combined to express ideas.

33. Poly-thalamaceans {0d\afxo?, a
chamber). The name given by De Blain-
ville to an order of Cephalopods, includ-
ing all those which inhabit many-cham-
bered shells.

34. Poly-zonal (£an/»i, a belt). Lite-
rally, what is composed of many zones,
or belts. The term is applied to certain
lenses, composed of pieces united in
rings, which are therefore called poly-
zonal lenses.

POMA'CEiE (pomum, an apple). The
Apple tribe of dicotyledonous plants.
Trees or shrubs with leaves alternate;
flowers polypetalous ; stamens perigyn-
ous ; fruit 1 to 5-celled.

POME (pomum, an apple). A fruit
consisting of two or more inferior carpels
united together, the pericarp being
fleshy, and formed of the floral envelope
and the ovary closely adhering.

PO'NDERABLE MATTER (pondus,
weight). A term applied to all bodies
possessing weight, as metals, gases, &c,
as distinguished from light, heat, and
electricity, which, having no appreciable
weight, are termed imponderable agents.

PORCELAIN CLAY. A species of
clay with various shades of white, con-
sisting, according to Wedgwood, of 60
parts alumina and 40 silica. It probably
268

originated in the decomposition of fel-
spar.

PORCELAIN JASPER. A variety
of jasper, produced by the action of sub-
terraneous fire on clay slate.

PORI'FERA (poms, a pore, fero, to
bear). A class of the Radiata, consisting
of soft, gelatinous animals, which have
their body traversed internally by nu-
merous anastomozing canals, commencing
from superficial minute pores, and termi-
nating in large open vents.

PO'RISM (n-opto-jua, a corollary).
Something deduced from a previous
demonstration. In the original Greek
of Euclid's Elements, the corollaries to
the propositions are called porisms ; but
this scarcely explains the nature of po-
risms, as it is manifest that they are
different from simple deductions from
the demonstrations of propositions. Prof.
Playfair defines a porism to be " A pro-
position affirming the possibility of find-
ing such conditions as will render a cer-
tain problem indeterminate or capable
of innumerable solutions." This defi-
nition represents a porism as almost the
same as an indeterminate problem. Every
indeterminate problem containing a
locus may be made to assume the form of
a porism, but not the converse. Porisms
are of a more general nature than inde-
terminate problems which involve a
locus.

PORO'SITY. That property of matter,
in consequence of which it does not com-
pletely fill the space which bodies occupy ;
and this is owing to the presence of
pores, or interstices, which occur among
the particles of bodies, even the densest.
The mass and density of bodies are esti-
mated according to their various degrees
of porosity: the greater the mass, the
less porous will be the substance ; and,
of two bodies, that is the more dense,
which with equal bulk contains the
greater mass.

POR'PHYRY (7rop0i/pa, purple). An
unstratified or igneous rock. This term
was applied, in the time of Pliny, to a
red rock, with small, angular, white
bodies, diffused through it, which are
crystallized felspar, brought from Egypt ;
and hence it has been applied to every
species of unstratified rock in which
detached crystals of felspar, or other
mineral, are diffused through a base of
other mineral composition. Thus, clay-
stone with crystals of felspar, is called
claystone porphyry.

PORTLAND LIMESTONE. Port-

POS

PO w

land Beds. A series of limestone strata,
belonging to the upper part of the Oolite
group, found chiefly in England, in the
island of Portland, on the coast of Dor-
setshire. The great supply of the build-
ing stone used in London is from these
quarries. Portland Sand is an inter-
mixture of siliceous and calcareous sand,
containing green particles. Portland
Oolite is a calcareo-siliceous, more or less
oolitic freestone, of a yellowish-white
colour, containing nodules of flint in its
upper part.

PORTU'NIDvE. Paddling Crabs; a
family of the brachyurous crustaceans,
nearly allied to the Cancerians.

POSITION. An arithmetical rule,
also called the rule of Supposition, the
Rule of False, or the Rule of Trial and
Error. It consists in assuming numbers,
and operating upon them, in order to
discover the true number. Single Posi-
tion relates to those questions in which
the results are proportional to the sup-
positions, and in which, consequently,
one assumption only is required. Double
Position embraces questions in which
the results are not proportional to the
suppositions, and in which two assump-
tions are necessary in order to find the
true answer.

POSITIVE QUANTITY. In Algebra,
this term denotes an affirmative or addi-
tive quantity. Its symbol, +, which is
read plus, signifies that the quantity to
which it is prefixed, must be added ; and,
if no symbol is prefixed, the quantity is
still understood to be positive.

POSITIVE TERMS. In Logic, those
terms which denote a certain view of an
object as being actually taken of it, are
called positive. They are thus distin-
guished from privative terms, which de-
note that this view might be taken of an
object, but is not; and from negative
terms, which denote that such a view is
not and could not be formed of the object.
" A living man" is an illustration of the
first kind of terms ; " a lifeless man," of
the second; "a lifeless carcase," of the
third.

POSSIBLE. This word, like the others
of kindred meaning, relates sometimes
to contingency, sometimes to power;
and these two senses are frequently con-
founded. In the former sense, we say,
"it is possible this patient may recover,"
not meaning, that it depends on his
choice, but that we are not sure whether
the event will not be such. In the latter
sense it is " possible" to the best man to

violate every rule of morality ; since if it
were out of his power to act so if he
chose it, there would be no moral good-
ness in the case; though we are quite
sure that such will never be his choice
( Whately). See Impossibility.

POSTERIOR MARGIN. A term ap-
plied to that side of the bosses of acepha-
lous bivalves, which contains the liga-
ment.

PO'STULATE (postulatum, a thing
demanded). A thing required to be
granted, for the purpose of reasoning.
The object of the postulates in Euclid is
to declare that the only instruments, the
use of which is permitted in Geometry,
are the rule and the compass.

POTASH. Potassa. The hydrated
protoxide of potassium, procured by the
incineration of vegetables, and named
from the circumstance that the water in
which the ashes are washed is evaporated
in iron pots.

POTA'SSIUM. Kalium. A metallic
substance, white, with a brilliant lustre,
like mercury, hard and brittle at 32°,
soft and malleable at 50°, fluid at 150°,
and volatilized below a red heat.

POTENTIAL MOOD. This mood,
according to the views of Crombie and
Greenlaw, is strictly subjunctive, and
in all those cases in which its signifi-
cation is potential, it is by ellipsis,
and not by its own proper power of ex-
pression.

POT-METAL. A mixture of copper
and about a fourth its weight of lead.

POTSTONE. Lapis Ollaris. A green-
ish-grey mineral, occurring in thick beds
in primitive slate, and fashioned into
culinary vessels in Greenland. It is a
sub-species of the rhomboidal mica of
Jameson.

POTTER'S CLAY. A variety of clay
of various colours, disintegrating on ex-
posure to the air; when mixed with
sand, it is made into bricks and tiles,
and is also used for coarse pottery.

POWER. In Mechanics, this term de-
notes any force, animate or inanimate,
which, being applied to a machine, tends
to produce or to prevent motion ; in the
former case, it is termed a moving power
or force ; in the latter, a sustaining power
or force. Power is latent force.

POWER OF NUMBERS. In Alge-
bra and Arithmetic, any given number
is said to be in its first power ; multiplied
by itself, it becomes the square, or second
power; this, again, multiplied by the
original number, becomes the cube, or
N3

PRE

PRE

third power; and, by continuing the
multiplications by the same original num-
ber, we obtain the fourth, the fifth, the
sixth, &c. powers. Thus taking the
number 2, —

21 = 2, or 1" power;
2 x 2', or 22 = 4, or 2nd power ;

22 x 2, or 23 = 8, or 3rd power ;

23 x 2, or 2* = 16, or 4th power ;

24 x 2, or 25 = 32, or 5th power;

1. When it is said that 1 is the square
of 1, there is a logical error in the use
of the terms : it ought to be thus —

1 square is the square of 1 linear ; thus
1 Q is the square of —

2. The numbers indicating the powers,
are called the exponents or indices ; and
it is evident that powers of the same
quantity are multiplied by adding their
exponents, and divided by subtracting
their exponents.

3. With this subject is connected the
term dimension. Thus, a1, a2, a3, &c.
are said to be of one, two, three, &c. di-
mensions, respectively ; and, in general,
any product is said to be of n dimensions,
if the sum of the indices of its several
literal factors is equal to n. Thus ab,
that is, a'lb* is of two dimensions ; 3 a263
is of five dimensions ; and so on.

4. A power in the denominator of a
fraction is also expressed by placing it in
the numerator, and prefixing the nega-
tive sign to its index ; thus

a— *, a~it a—3, a—*,

signify-, _, — , — , respectively.
a1 a2 a3 an

These are called the negative powers of a.

PRACTICE. An arithmetical rule,
deriving its name from its wide practical
application, and teaching how to find the
value of any number of articles, having
given the value of one ; or to find the
value of any quantity, having given the
value of a single unit.

PRjEFLORA'TION (prce, before, flo-
reo, to flower). JEslivation. A term in
Botany, denoting the manner in which
the floral envelopes of plants are ar-
ranged previously to their expansion.

PRASE {irpaaov, a leek). A mineral
substance of a leek-green colour, consist-
ing apparently of an intimate mixture of
common quartz and actonite, and found
in the island of Bute and in Borrow-
dale.

PRECESSION OF EQUINOXES.
The term applied to the slow but regular
retro gradation of the equinox along the
270

ecliptic, from east to west, or in the con-
trary direction to that in which the sun
appears to move in that circle. Thus, the
place of the equinox among the stars, at
every subsequent moment, precedes (with
reference to the diurnal motion) that
which was held the moment before. The
amount of annual retrogradation is only
50"- 10, or about a degree in seventy-two
years. The period in which the equinox
would perform a complete tour of the
ecliptic, is 25,868 years.

PRECIPITATE (prccceps, headlong).
A solid substance precipitated, or thrown
down from a solution, by adding a re-
agent. Thus we have the red precipitate
or the peroxide of mercury; the white
precipitate, or the ammoniated chloride ;
the precipitate per se, or the purple, &c.

PRECIPITATION {prceceps, head-
long). The process of throwing down
solids from solutions in which they are
contained. The substance so separated
is called a precipitate ; and the substance
employed to produce this effect, a pre-
cipitant. This process is the opposite to
that of chemical solution.

PRE'DICABLE. In Logic, a term
which can be affirmatively predicated of
several others. Predicables are also
called common terms, from their be-
longing each to several others all
alike.

PRE'DICAMENT. The predicaments
or categories of logicians are certain
general heads, or summa genera, under
which all abstract ideas, and their signs,
common words, may be arranged. The
classification of predicaments will be
found under the term Categories; it
was introduced by Archytas, and adopted
by Aristotle.

PRE'DICATE. The predicate of a
proposition is that term which is affirmed
or denied of the other. Logically, the
predicate occupies the last place in a
proposition, though, not unfrequently, it
is placed first.

PREHNITE. A zeolitic substance,
the grass-green variety of which, found
in South Africa, has been mistaken for
chrysolite, chrysoprase, and even eme-
rald. The variety which occurs in small
thin crystals is called koupholite.

PREMISS. In Logic, a proposition
employed to establish a certain conclu-
sion. The major premiss is that in
which the major term is compared with
the middle ; the minor premiss, that in
which the minor term is compared with
the middle. The two premises of a syl-

PRI

PRI

logism are sometimes called together
the antecedent.

PREPOSITION (prcepositus, placed
before). A word which connects two
words together, in such a manner as to
indicate the relation which the things or
ideas signified by them bear to each
other. The name of this part of speech
has been derived from the accidental
circumstance of its being placed imme-
diately before the object related to the
other thing named ; but the essence of
the preposition is, to signify relative po-
sition. " Every preposition," says Adam
Smith, " denotes some relation con-
sidered in concrete with the correlative
object."

PRESSURE. The application of force
to a resisting body, when that force is in
continued contact with the body on which
it is exerted. The centre of pressure is
that point at which the whole amount of
pressure may be applied with the same
effect as it has when distributed.

PRIMARY. A term applied, in the
astronomical division of the sphere, to
the great circle traced upon its surface,
half way between the poles. All the
smaller circles, which intervene between
the primary and the poles, are called
parallels.

PRIMARY LIMESTONE. A modi-
fication of limestone, with a crystalline
texture, occurring under many different
aspects, and in every member of the
series, so that no particular position can
be ascribed to it. Its colours are
various.

PRIMARY ROCKS. The lowest se-
ries of the stratified rocks, characterized
by a crystalline texture, and by the ab-
sence of organic remains. This term
has no reference to priority of formation,
but expresses the order of their occur-
rence, they being the first after granite.
These rocks were termed by Mr. Lyell
metamorphic, from the supposition that
they were deposited in a sedimentary
form, and were afterwards altered by the
action of heat.

PRIME NUMBER. Any number

which cannot be separated into factors,

X f* as 7', 11, 13, 17, &c, is called a prime

f ' f ' number. Every number which can be

so separated, as 6, 8, 9, 12, &c, is called

a composite number. When two numbers

have no common measure but unity,

they are said to be prime to each other :

thus 3 is prime to 7 ; 13 to 31 ; and so

on. A prime number is one which is

prime to every other number.

271

PRIMINE {primus, first). The first
or outermost sac of the ovule in plants.

PRIMITIVE WORDS. In grammar,
these are words not derived from any
other word in the language, as school.
See Derivative Words.

PRIMULA'CEjE. The Primrose tribe
of dicotyledonous plants, peculiarly dis-
tinguished by the stamens being oppo-
site to the lobes of the gamopetalous
corolla, and by having a superior capsule
with a free central placenta.

PRIMUM MOBILE. A term given
by the old astronomers to an imaginary
sphere, by the motion of which diurnal
motion was given to the heavens.

PRINCE'S METAL. Prince Rupert's
Metal. A species of copper alloy, in
which the proportion of zinc is greater
than in brass.

PRISM {irpiafxa, from Trpt'co, to saw).
A prism is defined, in Geometry, to be a
solid figure contained by plane figures,
of which two that are opposite are equal,
similar, and parallel to one another, and
the others parallelograms. The name is
derived from the property exhibited by
the glass prism of separating a ray of
light into its constituent parts.

Prism, Achromatic. A prism through
which objects are viewed refracted in-
deed, so that they are not seen in their
true position, but yet free from a prisma-
tic fringe about their edges. It con-
sists of two prisms fitted together, the
one being of flint, the other of crown-
glass. The vertical angle of the flint-
glass prism must be less than that of the
crown-glass, and their sizes must be in-
versely as their dispersive powers. In
English flint-glass the vertical angle of
the flint-glass prism must be § that of
the crown-glass, but in Fraunhofer's it
must be £ the size.

PRISMATIC CRYSTALS. The square
prism differs from the cube only in having
its lateral edges either longer or shorter
than the terminal. The right rhombic
prism is a right prism whose base is a
rhomb. The oblique rhombic prism differs
from the preceding in being oblique in
the direction of one of the diagonals of
the base. All other prismatic crystals,
which do not possess any of the degrees
of symmetry which characterize the
other prisms, are comprehended in the
class of doubly oblique prisms. In all
the varieties of prisms, the crystals
are supposed to rest on one of the bases
or terminal planes of the prism, the sur-
faces which bound the prism lengthwise
N4

PRO

PRO

being called lateral planes. The edges
at which these meet are lateral edges ;
and the edges at which they meet the
terminal planes are terminal edges.

PRISMATIC SPECTRUM. Solar
Spectrum. The variously-coloured ap-
pearance presented by a ray of light,
when separated into its constituent parts
by refraction through a glass prism.
The appearance consists of an oblong
image, containing seven colours, which
are simple or homogeneous, as distin-
guished from the white ray, which is
compound or heterogeneous.

PRISME'NCHYMA (npiana, a prism,
2yxwm<*. infusion). The name given by
Morren to the prismatical variety of the
parenchyma of plants.

PRIVATIVE TERMS. In Logic,
terms which denote that a certain view
might be taken of an object, though it is
not so taken, are called privative. Thus,
in the expression, "the moon is some-
times invisible," the word invisible is
used privatively, for the moon is capable
of being seen. See Negative Term.

PROBABILITIES or CHANCES. The
popular use of these terms has no very
distinct meaning. The mathematical
meaning points out a real value existing
in the circumstances. A question of
probability is termed direct, when, cer-
tain causes being given as existent, from
which a certain event may proceed, the
probability of that event happening is
required. A question of probability is
termed inverse, when, an event being
given as existent, and proceeding from
one of several causes, the probability of
one proposed cause being the true one
is required.

PROBLEM (irpoflKn/jia, any thing pro-
posed as a task). A proposition in which
something is proposed to be done ; as a
line to be drawn under some given con-
ditions, some figure to be constructed,
&c. The solution of the problem con-
sists in showing how the thing required
may be done by the aid of the rule and
the compass. The demonstration con-
sists in proving that the proceos indi-
cated in the solution really attains the
required end. A postulate is a problem,
the solution of which is assumed.

PROBOSCI'DEA. A group of pachy-
dermatous animals, containing only the
elephant and its extinct congeners, the
mammoth and the mastodon, character-
ized by their elongated nose, or pro-
boscis.

PROCYON, or a CANIS MINOR. A
272

star of the first magnitude in the con-
stellation Canis Minor.

PRODUCT. In arithmetic, a product
is the result of the multiplication of two
or more quantities. The result of the
addition of two or more quantities is
called the sum.

PRODUCTA. An extinct genus of
fossil bivalve shells, occurring only in
the older secondary rocks. It is closely
allied to the living genus Terebratula.

PROGRESSION {progredior, to ad-
vance). This term, in its general sense,
means going forward ; but its use in
algebra and arithmetic denotes that the
progress takes place in a determinate
order — that it is motion measured by
some scale.

1. Progression, Arithmetical. Quan-
tities are said to be in arithmetical pro-
gression, when they increase or decrease
by a common difference. Thus, 1, 3, 5,
7, &c, 8, 4, 0, —4, &c. ; a, a + d, a + 2d,
a + 3d, &c, are in arithmetical progres-
sion, the common differences being 2,
— 4, and d, respectively.

2. Progression, Geometrical. Quantities
are said to be in geometrical progression,
when they increase or decrease by a
common factor; in other words, when
the ratio of any two successive terms is
the same. Thus, 1, 3, 9, 27, &c, 16, 4,
1. h &c, J, HSs. — 4i —5% &c-, a, ar,
ar*, ar3, &c, are in geometrical progres-
sion, the common factors, or ratios (as
they are called), being 3, £, — f, and r,
respectively.

3. Progression, Harmonical. Quantities
are said to be in harmonical progression,
when their reciprocals are in arithmetical
progression ; in other words, when any
three successive terms are so related,
that the first is to the third as the dif-
ference between the first and the second
is to the difference between the second
and the third. Thus, since, 1, 3, 5, 7,
&c, £, — £, — |, — |, are in arithmetical
progression, their reciprocals, 1, J, £,
\, &c, 4, -—4, — §, — §, &c, are in har-
monical progression. Again, if a, b, ct
are in harmonical progression,

a \ c \\ a — b \ b — c.

PROJECTILE (projicio, to cast for-
ward). A heavy body which has been
projected in a direction not vertical. The
theory of projectiles investigates the rela-
tions between the space described, the
time of motion, and the velocity acquired
by a body when impelled by some motive
force.

PROJECTION. The representation

PRO

PRO

of the surface of a sphere on a plane,
according to the laws of perspective. In
projecting a spherical surface on a plane,
some parts must be unduly contracted
or enlarged in proportion to others. The
projections chiefly used in maps are the
orthographic, the stereographic, and
Mercator's.

1. In the Orthographic projection, every
point of the hemisphere is referred to its
diametral plane or base, by a perpendi-
cular let fall on it ; so that the represen-
tation of the hemisphere thus mapped on
its base, is such as it would appear to an
eye placed at an infinite distance from
it. In this projection, only the central
portions are represented of their true
forms, while all the exterior is more and
more distorted and crowded together as
we approach the edges of the map.
Owing to this cause, the orthographic
projection, though very good for small
portions of the globe, is of little service
for large portions.

2. The Stereographic projection is in
great measure free from this defect.
The eye is supposed to be placed at the
surface of the sphere, and to view the
concave of the opposite hemisphere
through the plane of that circle, in the
pole of which the eye is placed. Hence,
the position on this plane of any point
of the spherical surface will be indicated
by a line drawn from that point through
the plane to the eye. This is a true
perspective representation : all circles
on the sphere are represented by circles
in the projection ; every very small tri-
angle on the sphere is represented by a
similar triangle in the projection. This
and the preceding mode of projection
may be considered natural, inasmuch as
they are really perspective representa-
tions of the surface on a plane.

3. Mercator's projection is entirely
artificial, representing the sphere as it
cannot be seen from any one point, but
as it might be seen by an eye carried
successively over every part of it. In it,
the degrees of latitude, and those of
longitude, bear always to each other their
due proportion ; the equator is conceived
to be extended out into a straight line,
and the meridians are straight lines at
right angles to it. Like the stereo-
graphic projection, it gives a true repre-
sentation, as to form, of every particular
small part, but varies greatly in point of
scale in its different regions; the polar
portions in particular being extrava-
gantly enlarged, and the whole map,

273

even of a single hemisphere, not being
comprisable within any finite limits.

4. In the Gnomonic or Central projec-
tion, the eye is supposed to be placed in
the centre of the sphere, and the various
objects to be delineated are transferred
from the sphere to a plane, which is a
tangent to its surface. The entire hemi-
sphere can never be represented by this
projection, since the circumference which
terminates it is on a level with the eye,
and is therefore parallel to the plane of
projection. In this case, the parallels of
latitude will be concentric circles, and
the meridians straight lines radiating
from the centre. This method is chiefly
employed in dialling, and derives its
name from the connexion between the
methods of describing it and those for
the construction of a gnomon or dial.

5. Projection by Development. By this
expression is understood the unfolding
or spreading out of the spherical surface
on a plane. As a preparatory step, how-
ever, the sphere must be converted into
a cone or a cylinder, inasmuch as por-
tions of these forms most resemble
portions of a sphere, and the forms
themselves are susceptible of the re-
quired development.

PROLEGS. The wart-like tubercles
which represent legs on the hinder seg-
ment of caterpillars.

PROLI'FEROUS {proles, offspring,
fero, to bear). A term applied in botany
to a flower which produces another flower
from its centre, as in certain roses.

PROMERO'PIDiE. The Hoopoes; a
family of the Insessores, or Perching
birds, one species of which, the upupa
epops, occasionally visits Europe. See
Tenuirostres.

PROOF AND INFERENCE. In
addition to what has been adduced under
the article, Inference and Proof, the
learned author of the " Elements of
Logic" observes, that proving may be
defined "the assigning of a reason or
argument for the support of a given pro-
position;" and Inferring, "the deduc-
tion of a conclusion from given premises."
In the one case our conclusion is given,
and we have to seek for arguments ; in
the other, our premises are given, and we
have to seek for a conclusion. He adds,
that "proving" may be compared to the
act of putting away any article into the
proper receptacle of goods of that de-
scription ; " inferring," to that of bringing
out the article when needed.

PROPA'GO; PROPA'GULUM. The
N5

PRO

PRO

former of these terms was applied by the
older botanists to the branch laid down
in the process of layering. The latter
denotes an offset in certain plants.

PROPERTIES OF BODIES. The
physical properties are divided into the
essential, or principal ; viz. extension and
impenetrability, which are common to
all bodies, and indispensable to their ex-
istence ; and the non- essential, or acces-
sory, as compressibility, expansibility,
porosity, divisibility, elasticity, and gra-
vity.

PROPERTY. In Logic, this term
denotes a predicable which expresses
something essentially conjoined to the
essence of the species. It is thus dis-
tinguished from the logical accident,
which denotes something contingently
joined to the essence. Thus, redness is
a property of blood, but an accident of a
house.

PROPORTION. This term denotes
the portions, or parts, of one magnitude
which are contained in another. In the
language of Mathematics, the term has
been appropriated to express the equality
of ratios ; or, as it may be less minutely
explained, the case in which one magni-
tude is as many times greater or less
than another, as a third magnitude is
greater or less than a fourth. See Ratio.

PROPOSITION {propono, to propose).
A short discourse, in which a geometrical
truth is stated and considered •, it being
thereby proposed either to demonstrate
something which is asserted, in which
case the proposition is called a theorem ;
or to show the manner of doing some-
thing which is required to be done, in
which case the proposition is called a
problem.

A logical proposition is "a sentence
indicative;" in other words, a sentence
which affirms or denies. A proposition
is distinguished, with reference to its
substance, as categorical, when it ex-
presses anything absolutely, as " Caesar
deserved death ;" hypothetical, when it
expresses any thing under a hypothesis,
as, " If Caesar was a tyrant, he deserved
death." Categorical propositions are
termed pure, when they assert simply or
purely, that the subject does or does not
agree with the predicate ; and modal,
when they denote in what mode or man-
ner it agrees. Thus, " Brutus killed
Caesar," is a pure categorical proposition ;
while, " Brutus killed Caesar justly," is
modal.

PROSE'NCHYMA. A term applied
274

by Link to that form of parenchyma in
plants, in which the cells taper to each
end, and overlap each other; the term
parenchyma being restricted to that form
of the tissue, in which the cells have
truncated extremities.

PROTEIN (Trpcoxeuo), to hold the first
place). The name given by Mulder to
the precipitate obtained by adding acetic
acid to a solution of caustic potash, con-
taining fibrin, albumen or gelatine, ani-
mal or vegetable, in solution.

PRO'TEOLITE. Under this term and
that of Cornubianite, Dr. Boase describes
the rock in contact with granite, which
has been called argillaceous schist, or
clay-slate, greywacke, or killas. The
proteolite is of a lighter colour than the
cornubianite, soft, arenaceous, and slaty.
They appear to be chiefly composed of
compact felspar, with quartz, mica, and
schorl, and contain beds of that sub-
stance and of quartz.

PROTHO'RAX. The first of the
three segments which constitute the
thorax in insects.

PROTO- (ttpwtop, the first). This pre-
fix denotes, in Chemistry, the lowest de-
gree in which one body unites with an-
other, as prot-ox.ide. Per denotes the
highest degree, as per-oxide.

PRO'TOGENE. Talcose Granite. A
mixture of felspar, quartz, and talc or
chlorite. It occurs abundantly in the
Alps of Savoy, and is found in Cornwall,
where, on decomposition, it yields the
china-clay or porcelain-earth, which is
annually exported in large quantities.

PROTOZO'A (wpwrov, first, £5>ov, an
animal). A designation of one of the
primary divisions of the Animal King-
dom, from their constituting the first
step of animal organization. They cor-
respond with the Acrita of Macleay, with
the Cryptoneura of Rudolphi, and with
the Oozoa of other witers.

PROTOZO'IC SYSTEM (ttpwtov, first,
£wov, an animal). A geological term, ap-
plied to the lowest system of rocks in
which the traces of any organic structure
have been discovered. It is the system
next in ascending order to the hypozoic.

PROXIMATE PRINCIPLE. A term
applied, in analyzing any body, to the
principle which is nearest to the natural
constitution of the body, and more im-
mediately the object of sense, as distin-
guished from intermediate or ultimate
principles. Ultimate principles are the
elements of which proximate principles
are composed.

PSI

PTO

PRCXIMUM GENUS. In Logic, the
nearest or least remote genus to which a
species can be referred. See Genus.

PRUSSIAN BLUE. Berlin Blue.
The sesqui- ferrocyanide of iron ; a beau-
tiful deep blue powder, used in the
arts.

PRUSSIAS. A prussiate ; a name now
exploded, except in commerce, when it
denotes a cyanide : what is termed the
yellow prussiate of potash, is a ferro-
cyanide of potassium.

PRUSSIC ACID. A designation of
hydrocyanic acid, from its being an in-
gredient in Prussian blue.

PRYING and LIFTING. In the
common use of a lever of the first kind,
the force is gained by bearing down the
long arm of the lever, which is called
prying. In the second kind the force is
gained by carrying the long arm in a
contrary direction, or upward, and this
is called lifting.

PSEUDO-BULB. A term applied to
the enlarged aerial stem of orchidaceous
plants. It resembles a tuber.

PSEU'DO-LITE. A mineral having a
close affinity to the pseudomorphous
crystals of steatite.

PSEUDOMALACHITE. Prismatic
phosphate of copper, from Rheinbreiten-
bach, where it occurs with quartz which
sometimes passes into chalcedony.

PSEUDO-MORPHOUS {favdht, false.
/uop0»7, form). A term applied to sub-
stances which, not possessing a crystal-
line structure, are found in the form of
regular crystals. These accidental forma-
tions must be considered as merely casts
of the crystals they represent.

PSEUDO-STRATA. A term proposed
by Macculloch for those extended plates
of rocks, not divided into parallel la-
minae, and commonly called table-layers.
Some geologists make a distinction be-
tween a stratum and a bed, meaning by
the latter what is called by Macculloch a
pseudo-stratum.

PSEUDO-ZOA'RIA. A term proposed
by Blainville to include vegetables, many
of which have been ranked with the
Polypiaria. They are subdivided into
two classes, viz. Calciphyta, principally
composed of the genus Corallina, and
Nematophyta, including byssus, con-
ferva, oscillatoria, &c.

PSILOMELANE. An ore of manga-
nese containing a considerable quantity
of barytes, occurring in Devonshire,
Cornwall, in the Hartz, and most manga-
nese mines.
275

PSITTA'CIDjE (psittacus, the parrot).
The Parrot tribe; a family of birds,
generally referred to the Scansores, or
Climbers, with which, however, they
correspond in little else than the struc-
ture of the foot, and this is adapted rather
for grasping than for climbing.

PSY'CHICAL Wvxikos, pertaining to
the psyche, or soul). Relating to the
phenomena of the soul, and to analogous
phenomena in the lower animals. Psy-
chology, literally, the doctrine of the
soul, denotes a description of the intel-
lectual and moral faculties.

PSYCHRO'METER Ouxpor, cold,
fierpov, a measure). An instrument for
measuring degrees of cold. Its action is
the same as that of the hygrometer, and
depends on the combination of heat
which accompanies the evaporation of a
fluid, and the consequent deposition of
the vapour contained in the atmosphere.

PTERODA'CTYL (nrepov, a wing,
daKTvXos, a finger). Wing-fingered; the
name of an extinct genus of flying rep-
tiles, species of which have been found
in the Oolite and Muschelkalk. Some
of the finger joints are lengthened, so as
to serve as the expansors of a membran-
ous wing.

PTEROPFNjE. The single family of
the frugivorous or omnivorous Cheiro-
ptera, of which the pteropus Javanicus
may be considered the type. They
abound in warm climates, and include
some of the largest species of the order.

PTERO'PODA (tttcpov, a wing, ttovp,
a foot). The tenth class of the Mollusca,
consisting of small, soft, floating, marine
animals, which swim by the contractions
of two lateral musculocutaneous fins,
but are unable to fix themselves or creep
in the sea, from the want of feet, as the
clio, cleodora, &c.

PTERY'GIANS (wi-cpuf, a wing). A
name given by Latreille to a group of the
Mollusca, corresponding to the cepha-
lopods and pteropods of Cuvier, both of
which have locomotive organs, consisting
of wing-like expansions of the skin.

PTOLEMA'IC SYSTEM. A system
of astronomy so named from the famous
geographer Claudius Ptolemaeus, who
flourished in Egypt during the reigns of
the Roman emperors Hadrian and Anto-
ninus Pius. He taught that the earth
was at rest in the centre of the universe,
and that the heavens revolved round it,
from east to west, in twenty-four hours,
carrying all the heavenly bodies with
them. This system was believed, and
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P UM

PUR

enjoyed an undisputed celebrity, for
1400 years.

PUBE'SCENCE (pubesco, to begin to
have a beard). The down of plants, con-
sisting of soft short hairs, which partially
cover the cuticle, as in geranium molle.
Also, the soft hairy down of insects.

PUDDING-STONE. Conglomerate.
Rounded water-worn fragments of rocks
or pebbles, cemented together by another
mineral substance, which may be of a
siliceous, calcareous, or argillaceous
nature.

PULLEY. One of the mechanical
powers, consisting, in its simplest form,
of a wheel, capable of turning about its
axis, which may be either fixed or move-
able. A cord passes over a portion of
the circumference ; if the axis of the
pulley is fixed, its only effect is to change
the direction of the force exerted by the
cord ; but if it is moveable, a mechanical
advantage may be gained. Combinations
of pulleys may be made in endless
variety.

PULMOBRANCHIA'TA {pulmo, the
lungs, branchice, gills). Pulmonia. An
order of terrestrial Gasteropods, named
from the resemblance between their
mode of breathing and that of animals
possessed of proper lungs. The snail,
for instance, breaths air, which is alter-
nately drawn into and expelled from a
cavity lined with a vascular network.
Many of these animals have no shell.

PULMONA'TA (pulmo, the lungs).
An order of the Arachnida, comprising
those species which breathe by means of
pulmonary sacs. See Tracheata.

PULMONI'GRAD A (;wJ»io, the lungs,
gradior, to advance). An order of the
Acalephce, so named from the contrac-
tions and dilatations of their umbrella-
shaped disc, by means of which they
move, having some resemblance to the
motion of the lungs in respiration.

PUMICE {pumex). A light spongy
lava, chiefly felspathic, of a white ap-
pearance, produced by gases or watery
vapour gaining access to the particular
kind of glassy lava called obsidian, when
in a state of fusion. It may be called
the froth of melted volcanic glass. On
account of its fibrous and vesicular state,
it is so light as to float on water.

PUMP. A machine formed on the
model of a syringe, for raising water from
various depths to the surface of the earth.
1. In the common suction pump, the water
is pressed into the pump-barrel by the
atmosphere, and thrown out by lifting.
276

2. In the lifting pump, the piston is
situated in the lower part of the barrel,
and raises the water through the whole
distance, by forcing it upward, without
the agency of atmospheric pressure.

3. The forcing pump differs from both
these, in having its piston solid, or with-
out a valve, and also in having a side
pipe, through which the water is forced,
instead of rising in a perpendicular direc-
tion, as in the others.

Chain pump. — This kind of pump is
used on board of ships, and consists of
an endless chain moving over a wheel on
the deck, which is turned round by
winches, and over a roller in the pump-
well, having saucers or flat circular pis-
tons at certain intervals. Chain pumps,
in large ships, throw out a ton of water
per minute.

PULSE GLASS. A tube of glass,
having a bore of about two lines in dia-
meter, but at right angles at each end,
where it is expanded into two bulbs of
about l£ inch in diameter. The instru-
ment contains water or spirits of wine,
the remaining space being a vacuum : if
one bulb be grasped in the hand, the
liquid will boil violently in the other,
owing to the atmospheric pressure being
removed from the surface of the liquid.

PUPA. A term literally denoting a
baby wrapped up in swaddling bands,
and applied to the chrysalis, or nymph,
or second state of insect existence, in
which, the last skin of the larva being
thrown off, the animal appears in a dif-
ferent form, enveloped in an oblong case,
without external limbs, and almost in-
capable of the slightest motion. See
Imago.

PUPI'PAROUS {pupa, and pario, to
produce). A designation of Dipterous
insects, which bring forth their young in
the pupa state. They comprise two
families, known by the names of forest-
flies and bat-lice.

PURBECK LIMESTONE. Purbeck
Beds. Limestone strata, belonging to
the Wealden Group, which intervenes
between the Greensand and the Oolite.
It is composed of fresh-water shells
united by a calcareous cement. It is
slaty, argillaceous, of a brownish colour,
alternating with slaty marl, and some-
times containing beds of compact lime-
stone.

PURPLE OF CASSIUS. A purple-
coloured powder, precipitated when pro-
tochloride of tin is added to a dilute
solution of gold.

PYR

PYR

PURPURIC ACID. An acid obtained
from uric or lithic acid, remarkable for
its tendency to form red or purple coloured
salts with alkaline bases. Its salts are
called purpurates.

PURPURI'N^E. A sub-family of the
Muricidce, named from the typical genus
Purpura, including shells whose general
form resembles that of the whelks.

PUTA'MEN (puto, to prune). A syn-
onymous term for the endocarp, or
innermost layer of the pericarp of osseous
fruits.

PUTREFA'CTION. The spontaneous
decomposition of animal or vegetable
matters, attended with fcetor ; a species
of fermentation.

PUZZOLA'NO. A substance of vol-
canic origin, composed principally of
pumice, of which a stratum is excavated
in the neighbourhood of Pozzuoli, near
Naples. The mortar which it makes
with lime is called Roman cement.

PYCNITE (Trevor, thick). A sub-
stance formerly considered as a variety
of beryl, but now referred to topaz.

PY'RAMID. A solid figure, contained
by planes which are constituted betwixt
one plane and one point above it in
which they meet. It differs from a cone,
in having for its base a right-lined, in-
stead of a circular figure. (See Cone).
The ancients derived the term nvpa/nh
or pyramid, sometimes from nvp, fire, be-
cause of its pointed shape ; sometimes
from nvpds, as if the pyramids had been
granaries ! No doubt the word, as well
as the thing, is Egyptian.

PYRITES (ttDp, fire). A compound
of sulphur and iron, usually occurring in
yellow shining crystals like brass, and in
almost every rock, stratified and unstra-
tified. The shining metallic bodies fre-
quently seen in common roofing-slate
afford a familiar example of the mineral.
The term originally denoted a fire-stone,
a sort of stone out of which fire could be
struck ; because, under particular circum-
stances, the stone produces spontaneous
heat, and even inflammation.

PYRO- (7rup, fire). Words compounded
with this term denote some change pro-
duced by the action of fire : —

1. Pyr-acid. An acid produced by the
destructive distillation of an organic acid,
as the pt/ro-citric, produced by decompo-
sition of the citric by fire.

2. Pyr-allolite. A silicate of magnesia;
a mineral belonging to the talc family,
found in a lime-quarry in Finland. Its
name is derived from its singular pro-

277

perty of blackening before the blowpipe
at a low-red heat, and afterwards becom-
ing white at a higher temperature.

3. Pyr-argillite. A silicate of alumina
and other matters, found in granite in
Finland, emitting an argillaceous odour
when heated.

4. Pyro-chlore. A new mineral found
in Norway, in zircon-syenite. It is so
called because it becomes yellow before
the blowpipe, whereas polymignite re-
tains its black colour.

5. Pyr-eneite. A greyish-black mineral,
occurring in primitive limestone, and
consisting of silica, alumina, lime, and
iron.

6. Pyro-ligneous Acid. An acid ob-
tained by distillation from wood ; in its
strongest form it is acetic acid. Pyro-
ligneous spirit is a substance, more vola-
tile than alcohol, produced during the
distillation of wood. It is more correctly
named pyro-xylic spirit.

7. Pyro-lusite. The most abundant
ore of manganese, occurring crystallized
and massive, in Devonshire, Warwick-
shire, Thuringia, Brazil, and other
places. It is the binoxide of peroxide of
manganese.

8. Pyro-meter {fxerpov, a measure). An
instrument for measuring all degrees of
heat above those which can be indicated
by a mercurial thermometer. Wedge-
wood's pyrometer acts by the contraction
of cylinders of fine white clay. The in-
dications of Daniell's pyrometer depend
on the difference in the expansion and
contraction of a platinum bar, and a
tube of black lead ware in which it is
contained.

9. Pyro-morphite (p6pq>r\, form). Phos-
phate of lead, generally divided into
brown lead ore and green lead ore.
When heated before the blowpipe, it
fuses into a globule, which assumes a
polyhedral crystalline form as it cools.

10. Pyr-ope. Chrome garnet, gene-
rally called Bohemian garnet, occurring
in rounded grains, and also imbedded in
serpentine, &c.

11. Pyr-orthite. A silicate of oxide of
cerium, iron, &c, found imbedded in
granite or quartz, near Fahlun in Swe-
den. It resembles orthite, but is differ-
ently affected by heat.

12. Pyr-osmalite. A mineral occurring
in magnetic ironstone, giving out vapours
of chlorine before the blowpipe, and be-
coming a magnetic oxide of iron.

13. Pyr-oxene. The name given by
Haiiy to augite, a silicate of lime and

QUA

QUA

magnesia, found among volcanic rocks.
It has received various names.

14. Pyro-phorous. A tenn applied to
certain substances which, by the absorp-
tion and condensation of the aqueous
vapour and gases contained in the atmo-
sphere, become heated and ignited, as
spongy platinum, which absorbs hydro-
gen and oxygen so readily, and then
condenses them, that its entire mass
becomes red-hot, and the gas is ignited.

15. Pyro-phyllite. A green radiated
variety of talc from Siberia, composed of
distinct groups of small diverging la-
minae.

16. Pyro-physalite. A sub-species of
prismatic topaz, from Fahlun in Sweden.

17. Pyro-somata (owfxa, a body). A
family of the Tunicata, consisting of
minute animals aggregated together in
great numbers, so as to form a hollow
cylinder, which swims in the sea by the
combined contractions and dilatations of
all the individuals composing it, and is

capable of emitting in the dark a brilliant
phosphorescent light, or body of fire, as
the name denotes.

18. Pyro-techny (rexvn, art). The art
which teaches the management and ap-
plication of fire to certain operations ; a
term commonly applied to the prepara-
tion of artificial fireworks.

PYRULI'NjE. Pear-shells; a sub-
family of the Turbinellidae, or Turnip-
shells, named from the typical genus
pyrula, and characterized by the short-
ness of the spire, by the smoothness and
convexity of the pillar, and by the mode-
rate length of the canal.

PYXI'DIUM (pyxis, a box). A fruit
which dehisces by a transverse incision,
so that, when ripe, the seeds and their
placenta appear as if seated in a cup,
covered by an operculum or lid, as in
hyoscyamus, anagallis, &c.

PY'XIS NAUTICA. The Mariner's
Compass; a modern southern constella-
tion, placed in Argo.

a

QUADRANT (quadrans, a quarter).
A quadrant, in Geometry, is a quarter of
a circle. The term also denotes an in-
strument for measuring angles, consist-
ing of a quarter circle of wood or metal,
having its circular part, or limb, divided
into 90 parts, or degrees, and these sub-
divided into minutes, &c, by means of
a Nonius or a Vernier.

1. Hadley's Quadrant is properly an
octant, or eighth part of a circle, in
which the angles are taken by means of
the reflexion of light ; and when the
limb is extended to 60 degrees (the sixth
of a circle), the instrument is called a
Sextant.

2. Quadrant of Altitude. The name
given to a flexible graduated slip of brass,
which is fixed to the brazen meridian of
the globe. By this the distance from one
point of the globe to another can be ob-
tained in degrees of arc. But as other
arcs besides altitudes may be measured
with it, it is sufficiently distinguished by
calling it the flexible arc.

QUADRANT ELECTROMETER.
An instrument for estimating the degree
or intensity of electricity, invented by
Mr. Henley. The differences of electric
intensity are denoted by an index which
278

traverses a quadrant divided into ninety
equal parts, called degrees.

QUADRA'NTAL. A name formerly
given to spherical triangles, one side of
which is a quadrant.

QUADRATIC EQUATIONS. Qua-
dratic equations are divided into pure
and adfected. Pure quadratic equations
are those which contain only the square
of the unknown quantity, as x2 = 36 ;
x2 + 5 = 54 ; ax2—b = c; &c. Adfected
quadratic equations are those which in-
volve both the square and the simple
power of the unknown quantity, as x2+
4a? = 45; 3x* — 2x = 2l; ax"2 + 2bx =
c + d; &c.

QUADRA'TRIX. A name given to
a curve which may be employed in the
quadrature of other curves. Some of
these have been specified ; but, after all,
the description of these curves assumes
the point which they are intended to de-
termine.

QUADRATURE (in Astronomy). The
moon is said to be in her quadrature,
when she is in either of the middle points
of her orbit, between her conjunction
and opposition, since lines from the earth
to the moon and to the sun include a
quadrant, or 90 degrees. Her face is

QUA

then half-shown ; it is bisected, or dicho-
tomized. The places of her orbit, where
she is either in conjunction or opposition,
are her syzygies.

Quadrature in Geometry. By the qua-
drature of a curve is meant the finding
of a square equal to the content enclosed
by the curve. With regard to the famous
problem of the quadrature of the circle — !
since the whole circular area is equal to
the rectangle under the radius and a
straight line equal to half the circum-
ference, the object in squaring the circle
is to determine the ratio of the circum-
ference to the diameter, and this can only
be expressed by infinite series.

QUADRILATERAL (quatuor latera
habens). Having four sides ; as applied
to a plane geometrical figure, bounded
by four straight lines. Such a figure is
also called a quadrangle.

QUADRU'MANA ( quatuor, four, ma-
nus, a hand). Four-handed ; the desig-
nation of an order of Mammalia, includ-
ing the monkey, the lemur, &c, which
have a moveable thumb on their lower
extremities opposed to the fingers ; all
their extremities are, in fact, instru-
ments of prehension.

QUALITY OF PROPOSITIONS. In
Logic, propositions are divided according
to the quality of their expression, which
is here the essential circumstance, into
affirmative and negative; and according
to the quality of their matter, which is
accidental, into true and false.

QUANTITY (quantus, how much).
Quantity is distinguished into continued
and discrete. It is continued, when the
parts are connected together, and is then
termed magnitude, which is the object of
geometry. It is discrete, when the parts
have an unconnected and independent
existence, and then constitutes multi-
tude or number, which is the object of
arithmetic.

1. Quantity, negative. The difficulty
attending the use of a minus or negative
quantity, in algebraic operations, is re-
moved at once by viewing it, as it always
must be viewed, in reference to another
quantity, which is plus or positive. A
debt may be regarded as a negative quan-
tity, inasmuch as it is a quantity to be
subtracted in case of there being any
property (which is positive), from which
to subtract it. So also,

4 — 2 = 2;
4 — 2 x 4 — 2 = 4;

Hence, — 2 is in reality — (+ 2); it
279

QUA

is the plus or real quantity 4, — the real
quantity 2.

Thus, a — quantity = a — (+ quan-
tity).

2. Quantity fractional. It has excited
surprise that £ x \ should be ^. Let the
question be tried geometrically, and the
difficulty vanishes. It is only necessary
to consider £ as the J of a line 1 ; and
the-jk as the ^ of the square of the
same line. Thus—

\ linear.

* ^ square.

Thus, the square of \ of 1 linear is ^ of
1 square ; the square of £ linear is £
superficial ; and the square of £ linear
is fy, or £ + ^. All this would be evi-
dent if, instead of multiplication, we used
the term quadration, or (if admissible)
parallelogramization.

3. Quantity, impossible or imaginary.
If an expression occur under the form
\/ — a, this indicates an impossibility;
for it signifies the square root of a nega-
tive quantity, which has no existence,
since there is no quantity, positive or
negative, which, being multiplied by
itself, gives a negative result. An im-
possible quantity, or, in other words, the
even root of a negative quantity, may be
expressed in the form of a surd, as
s/ ~8| \J — a2, &c. ; the difference be-
tween surd and impossible quantities
being that the former have real values,
though we cannot exactly find them,
while there cannot be a quantity, posi-
tive or negative, an even power of which
would produce a negative quantity.

QUANTITY OF PROPOSITIONS.
In Logic, propositions are divided ac-
cording to their quantity, or extent: if
the predicate is said of the whole of the
subject, the proposition is universal; if
of a part of it only, the proposition is
particular; in the former, the subject is
distributed, or stands for the whole of its
significates ; in the latter, it is not dis-
tributed, and stands for a part only of its
significates.

QUANTITY and TANTITY. These
terms are employed by Mr. Mill, in his
" Elements of the Human Mind," as cor-
relative, or, as he terms them, connota-
tive ; the word quantus, how much, being

R AC

RAC

answered by tantus, so much. The com-
mon use, however, of the former word
renders the latter superfluous. The
term quantuplicity, as distinguished from
quantity, means the answer to " how
many times," as distinguished from
"how much:"

QUA-QUA-VERSAL DIP {qud-qud-
versum, on every side). The dip of geo-
logical beds to all points of the compass
around a centre, as in the case of beds
of lava round the crater of a volcano.

QUART A'TION (quartus, the fourth).
An operation by which the quantity of
one substance is made equal to a fourth
part of the quantity of another: thus, in
separating gold from silver, three parts
of silver are added to the supposed gold,
and they are then fused together, the
gold thus becoming at most one-fourth
of the mass only. They are then parted
by the action of nitric acid.

QUARTILE. A term formerly em-
ployed in Astronomy to denote an aspect
of two places when their longitudes differ
by 90 degrees, or a fourth part of the
circle.

QUARTINE {quartus, fourth). The
name of the fourth membrane or enve-
lope of the nucleus in plants, as described
by Mirbel.

QUARTZ. A German provincial term,
universally adopted in scientific lan-
guage for a simple mineral, composed of
pure silex, or earth of flints, extremely
abundant in nature, from the common
pebble to large mountain veins, and even
entire rocks. See Rock Crystal.

QUARTZITE, or QUARTZ ROCK.
An aggregate of grains of quartz, some-
times passing into compact quartz.

QUATERNARY (quaternarius, of the
number four). A term applied in che-

mistry to those compounds which con-
tain four elements, as gum, fibrin, &c.
The term is also applied to any arrange-
ment in which the prevailing number is
four, as in the floral envelopes of Cruci-
ferous plants, &c.

QUE'RCITRIN. The yellow colour-
ing matter of quercitron bark. As it
restores the colour of reddened litmus
paper, and combines with and neutralizes
bases, it has been considered an acid,
and named quercitronic acid.

QUICKLIME. The protoxide of cal-
cium, obtained by exposing carbonate of
lime to a strong red heat, so as to expel
its carbonic acid.

QUI'NARY {quinarius, of the number
five). A term applied to a system in
which the prevailing number is five, as
observed in the floral envelopes of most
dicotyledonous plants.

QUINCUNX. In Botany a form of
aestivation or vernation, in which there
are five leaves, two of which are exterior,
two interior, and the fifth covers the in-
terior with one margin, while its other
margin is covered by the exterior, as in
the rose.

QUINDE'CAGON. A geometrical
figure bounded by fifteen sides.

QUINTILE. A term formerly em-
ployed in Astronomy, to denote a dis-
tance in longitude of 72 degrees, or a
fifth part of the circle.

QUI'NTINE (quintus, fifth). The fifth
membrane or envelope of the nucleus of
plants, as described by Mirbel. This is
the vesicula amnios of Malpighi, the
" additional membrane" of Brown, and
the sac of the embryo of Brongniart.

QUOTIENT or QUOTE (quoties, how
often). The result of dividing one num-
ber by another.

R

RABDOTLOGY (pd/33or, a rod, \6yot,
a description), Rhabdology. A method
for performing the arithmetical operations
of multiplication and division, by means
of an instrument invented by Lord Na-
pier, and termed from him Napier's rods
or bones. The mode of calculation is
tedious, and is now superseded by the
use of logarithms.

RACES OF MAN. Under the terms
Caucasian, Mongolian, American, Ethio-
pian, and Malay Race, will be found the

characteristics of these divisions, accord-
ing to Blumenbach. The Races are dif-
ferent forms of one species, capable
of fruitful union, and propagated by
generation.

RA'CEME (racemus, a bunch of
grapes). A form of inflorescence, in
which all the buds of an elongated
branch are developed as flower-buds,
and at the same time produce peduncles,
as in hyacinth.

RACE'MIC ACID (racemus, a bunch

RAD

R A I

of grapes). Paratartaric Acid. An acid
obtained from the grape, similar in its
composition to tartaric acid, with which
it is consequently isomeric.

RA'CHIS (pdxi*, a ridge). This term,
which should be written rhachis, denotes,
in Botany, that form of floral axis in
which several pedicles, or flower-stalks,
are developed at short distances from
each other, as in grasses.

RA'DIANT {radius, a ray). In Geo-
metry, a radiant is a straight line pro-
ceeding from a given point, or fixed
pole, about which it is conceived to
revolve.

RA'DIANT POINT. That point from
which the rays of light diverge from a
luminous body in all directions. The
point in which convergent rays meet, is
the focus.

RADIA'RIA (radius, a ray). A term
applied by Lamarck to that class of the
Radiata of Cuvier, which contains species
with a radiated form of the entire body.
They are distinguished into the soft and
gelatinous, as the medusa ; and the hard,
spiny, and echinodermal species, as the
asterias.

RADIA'TA (radius, a ray). The de-
signation of animals, most of which are
disposed around an axis in a radiated
form, as the star-fish. They compose
one of the four great divisions of the
animal kingdom.

RADIA'TION (radius, a ray). A term
applied to the emission of light, or of
heat, from the surface of a luminous or of
a heated body, in the form of radii, or
rays. In natural philosophy, whatever
sends forth emissions in all directions, is
said to radiate ; and hence we have radi-
ation, not only of heat and of light, but
also of sound.

RADICAL (radix, a root). A term
applied generally to any substance which
is capable of combining with simple
bodies. A radical is termed simple, when
it is itself an elementary body, as chlorine
in hydrochloric acid ; or compound, when,
though itself a compound, it acts as a
simple body in its modes of combination,
as cyanogen in the cyanides. In general
terms, a radical, simple or compound,
forms an acid with hydrogen, and a salt
with a metal.

RA'DICAL SIGN (radix, a root). In
Algebra, the radical sign is the symbol
„J, and denotes the extraction of a root.
It is a modification of the letter r, the
initial letter of radix, or root. See
Boot.

281

RA'DICLE (radicula, a little root)-
The rootlet, or the rudiment of the de-
scending axis of plants, as it occurs in
the embryo.

RA'DIUS. A rod ; a spoke of a wheel.
The semi-diameter of a circle, or a right
line drawn from the centre of a circle to
the circumference.

1. Radius of Curvature. In speaking
of the concavity of other curves than the
circle, the radius of curvature at a given
point is the radius of a circle which has
the same curvature as the curve has at
that point.

2. Radius Vector. The radius vector
is a right line drawn from the centre of
force (in any curve, on which a body is
supposed to move by centripetal force)
to that point of the curve where the body
is supposed to be. It is a general radius
to the curve, and has the addition of
Vector, or carrier, because it is imagined
to carry forward the body to which it is
attached. The earth, for example,
moves in an elliptic orbit, of which the
sun (the centre of force) is in one of the
foci; and, by consequence, the radius
vector is continually increasing in length
during her course from the perihelion to
the aphelion, and decreasing in the same
proportion in the progress of her return..

RA'DIX. Literally, a root ; and,
hence, applied, in arithmetic, to the fun-
damental of any system of numeration.
Thus, 10 is the radix of the decimal sys-
tem, and of the common system of loga-
rithms.

RAIN. When the temperature of the
air is above 32°, or the freezing point, the
water separated from the air falls to the
earth in the state of rain. It is generally
thought that the precipitation of water
from the atmosphere is the effect of the
mingling together of currents of warm
and of cold air.

RAINBOW. A meteor in form of a
party-coloured arch, or semicircle, ex-
hibited only at the time when it rains.
It is always seen in that point of the
heavens which is opposite to the sun,
and is occasioned by the refraction and
reflection of his rays in the drops of fall-
ing rain. The secondary rainbow may
be explained by supposing a double re-
fraction and reflection of the sun's
beams.

RAIN GAUGE. An instrument for
ascertaining the comparative quantity of
rain which falls in different places and in
different seasons. It is sometimes called
pluviometer.

RAR

RAT

RA'LLIDvE (rallus, the rail). The
Rail tribe ; a family of the Grallatores,
or Wading birds, characterized by the
extreme length of the toes.

RAME'NTA (rado, to scrape off).
Filings, as of a metal. In Botany, the
term denotes the thin, brown, foliaceous
scales, which appear on the back of the
fronds of ferns, &c.

RAMO'SE (ramosus, branched). A
term applied to those spines upon shells
which send out others in a lateral direc-
tion.

RAMPHA'STIDjE (ramphastos, the
toucan). The Toucans ; a family of
Scansorial birds, placed by Cuvier in his
third order, Grimpeurs, between the anis
(Crotophaga) and the parrots.

RANCI'DITY. The change which
oils undergo by exposure to the air. It
depends on the combination of oxygen
with the extractive principle, which is
naturally united with the oily principle.
The result is, therefore, analogous to the
oxidation of metals.

RA'NID^E {rana, a frog). The Frog
tribe ; one of the principal divisions of
the Anoural order of Amphibious ani-
mals, which pass from the tadpole to the
perfect state, and are adapted for aquatic
life. See Bufoidce.

RANUNCULA'CEjE. The Crowfoot
tribe of Dicotyledonous plants. Herba-
ceous plants with divided leaves, opposite
or alternate ; calyx of 3-6 petals ; petals
5-15, hypogynous ; stamens hypogynous,
indefinite in number ; fruit distinct,
simple carpella, and albuminous seeds.

RA'PHIDES (pa<pk, a needle). Small
acicular crystals, found within the cells
of the parenchyma of certain plants.

RAPTO'RES {raptor, a snatcher).
Raptrices. Plunderers, or Birds of Prey;
an order of birds, characterized by the
robustness and muscularity of the whole
body, by the strength of the legs and of
the bill and talons, by their rapacious
habits, solitary disposition, great quick-
ness of sight, and powerful flight. They
are distinguished into the diurnal, con-
taining the vultures, eagles, falcons, &c,
and the nocturnal, or the owls.

RAREFA'CTION {rarus, thin, facio,
to make). The act of rendering a sub-
stance less dense ; also, the condition of
diminished density. The term is gene-
rally applied to elastic fluids, which ex-
pand on the application of heat, or in
consequence of partial exhaustion, and
thence become thinner or more rarefied.
RA'RITY (rarus, thin). A property
282

of matter opposed to density, and denoting
a thinness or subtlety of bodies : mercury
is a dense fluid, ether a rare one. The
term is generally applied to aeriform
bodies, those of dilatation and expansion
being employed in speaking of solids and
liquids.

RAS ALGRATHA. A star of the
third magnitude in the northern constel-
lation Hercules. Ras Aliagus is the
principal star in the northern constella-
tion Serpentarius.

RASO'RES (rado, to scratch). Ra-
drices. Scratchers ; an order of gallina-
ceous Birds, so named from the general
habit which these graminiferous species
present of scratching up the soil to ob-
tain their food. The only general cha-
racter of the order is derived, according
to Macgillivray, from the digestive
organs. " A very large dilatation of the
oesophagus, forming a crop, lying, when
distended, equally on both sides of the
neck, and such an enlargement of the
coeca as to render their capacity at least
half of that of the intestine, occur toge-
ther in no other birds. It is very diffi-
cult to assign general characters of any
other kind to them."

RA'STABER. A star of the third
magnitude in the northern constellation
Draco.

R A'THOFFITE. A species of garnet,
found in Sweden, accompanied by calc-
spar and hornblende.

RA'TIO. When two subjects admit
of comparison, with reference to some
quality which they possess in common,
and which may be measured, this mea-
sure is their ratio, or the rate in which
one exceeds the other. With this term
is connected that of proportion, which
denotes the portions, or parts of one mag-
nitude which are contained in another.
In the language of Mathematics, the
term ratio has been adopted to express
what is more generally understood by
the term proportion : thus, instead of
" the proportion which" one thing bears
to another, we say, " the ratio which "
one bears to the other, meaning its com-
parative magnitude ; instead of saying
that A is to B "in the proportion of
5 to 6," we say, "in the ratio of 5 to 6."

I. When the ratio is commensurable
(that is, when it is reducible to numbers),
it is equivalent to proportion ; the latter
term is, however, usually employed in
the comparison of ratios, in which case
two ratios are said to be proportionals.
Thus, 3 has to 4 a certain ratio, or pro-

RAT

portion; but the expression 3 is to 4 in
the same proportion as 6 to 8, denotes
that the ratios of 3 to 4 and 6 to 8 are
equal ; 3 bearing the same proportion
to 4, as 6 to 8, that is, being three-fourths.
Ratios, however, may be unequal. Thus
it is said that the ratio of 9 to 4 is greater
than that of 7 to 6, because ^ is greater
than £ ; it being thus that ratios are
measured.

2. Ratio, direct. When two quantities,
or magnitudes, have a certain ratio to
each other, and are, at the same time,
subject to increase or diminution; if,
while one increases, the other increases
in the same ratio, or if, while the one
diminishes, the other diminishes in the
same ratio, the proportions, or compari-
sons of ratios, remain unaltered, and
those quantities, or magnitudes, are said
to be in a direct ratio or proportion to
each other. Thus if a yard of cloth be
worth a pound, ten or any number of
yards will be worth so many pounds, and
the proportion of value continues un-
altered.

3. Ratio, inverse. But, if the quan-
tities, or magnitudes, are such, that,
when one increases, the other necessarily
diminishes ; and vice versd, when the
one diminishes, the other increases, the
ratio, or proportion, is said to be inverse.
Thus, there is, at any moment, a certain
ratio of the length of the day to that of
the night; but this is an inverse ratio,
for in proportion as the length of either
increases, that of the other must dimi-
nish.

4. Ratio, compound. A compound
ratio is made up of the product of two,
or more, simple ratios ; that is, of the
product of their first terms, which are
called antecedents, compared with the
product of their second terms, called
consequents. Thus 24 : 3 is a compound
ratio of 4 : 1 and 6:3; this, being
made up of two simple ratios, is called a
duplicate ratio. When three simple
ratios are compounded, they form a tri-
plicate ratio ; when four, a quadruplicate
ratio ; and so of other compounds.

5. Ratio, Extreme and Mean. A line
is said to be so divided, when the rect-
angle under the whole line and the lesser
segment is equal to the square of the
greater segment ; and, hence, the whole
line is to the greater segment, as that
greater segment is to the lesser. The
segments of such a division, being in-
commensurable with the whole line,
cannot be exactly given in numbers, but

RE A

the geometrical construction is easy.
See Euclid's Elements, book ii. prop. 11.

RATIONAL QUANTITY. A quan-
tity, algebraic or arithmetical, which can
be expressed without the use of the signs
of evolution, such as those of the square
root, the cube root, &c. See Irrational
Number.

RAY [radius, a beam or rod). A single
radiation, or the smallest form in which
light or caloric is emitted from bodies.
Calorific rays are those rays which excite
heat ; luminous rays, those which impart
light ; chemical rays, those which, with-
out producing heat or light, produce
chemical change, as that of darkening
the white chloride of silver. The last
are also called deoxidizing or hydro-
genating rajs, from their characteristic
effect in withdrawing oxygen from water
and other oxides.

REA'CTION. The resistance made
by all bodies to the action or impulse of
others, which endeavour to change their
state, either of motion or of rest. Action
and reaction are always equal to each
other ; that is, the effect which any force
exerts— or, what is the same, its mo-
mentum — is equal to the resistance
which the body it sets in motion offers
to it. The intensity of the moving power
is therefore estimated by the mass and
velocity of the body set in motion.

REAGENT or TEST. In Chemistry,
a substance which indicates the presence
of any body existing in a minute propor-
tion in a solution, by rendering it turbid,
by imparting a particular colour to it, or
by depositing a precipitate. Thus, a
solution of nitrate of silver is a most
powerful reagent in detecting chloride of
sodium.

REAL DEFINITION. A definition
which explains the nature of the thing
defined ; viz. either the whole nature of
it, as in Mathematics, or else something
heyond what is necessarily understood
by the term (see Nominal Definition).
In the strict sciences, the nominal and
the real definition exactly coincide ; the
meaning of the word, and the nature of
the thing, being exactly the same. This
holds good also with respect to logical
terms, most legal, and many ethical
terms.

REA'LGAR. The protosulphuret of
arsenic. It is either native, and dug out
of the earth in China; or factitious, pro-
cured by boiling orpiment, or the sesqui-
sulphuret, in subliming vessels.

RE'ALISM. The opinion of a class of

RE C

REC

philosophers, that Genus and Species are
some real Things, existing independ-
ently of our conceptions and expressions ;
and that, as in the case of Singular terms
there is some real individual correspond-
ing to each, so, in Common terms also,
there is some Thing corresponding to
each ; which is the object of our thoughts
when we employ any term. This doc-
trine, though attributed to Aristotle, is
by him expressly contradicted. See
Nominalists.

REASON. Whately has pointed out
several of the ambiguities to which this
word is liable. It is used to signify,

1, all the intellectual powers collectively;

2, those intellectual powers exclusively
in which man differs from brutes ; 3, the
faculty of carrying on the operation of
the mind, which logicians call reason-
ing; 4, the premiss or premises of an
argument, especially the minor premiss ;
and it is from Reason in this sense
that the word "Reasoning" is derived;
5, lastly, it is often used to signify a
cause, as when we say, in popular lan-
guage, that the " Reason of an eclipse
of the sun is, that the moon is inter-
posed between it and the earth." This
should be strictly called the cause.

" What adds to the confusion is, that
the Cause is often employed as a Proof of
the effect : as when we infer, from a
great fall of rain, that there is, or will
be, a flood ; which is at once the physical
effect, and the logical conclusion. The
case is just reversed, when from a flood
we infer that the rain has fallen."

REASONING IN A CIRCLE. A
fallacious mode of reasoning, in which
the truth of a proposition is asserted by
adducing the conclusion. The following
is Whately's illustration : — " To allow
every man an unbounded freedom of
speech must always be, on the whole,
advantageous to the state ; for it is highly
conducive to the interests of the com-
munity, that each individual should en-
joy liberty, perfectly unlimited, of ex-
pressing his sentiments."

RECEIVER. A glass vessel employed
in pneumatical experiments for contain-
ing the object on which an experiment
is to be exhibited by means of the air-
pump. In Chemistry, the term denotes
a vessel fitted to the neck of a retort,
alembic, &c, for the purpose of receiving
the products of distillation.

RECE'PTACLE. In Botany, the di-
lated and depressed axis of the inflores-
cence termed capitulum, constituting the
284

seat of the artichoke, &c. The receptacle
is called torus or thalamus, and in Greek
compounds has the name of clinium. To
this part may be referred the gynophore,
the polyphore, and the gynobase of bo-
tanical writers.

RECI'PROCAL (reciprocus, mutual;
flowing backward or forward). A term
employed in mathematics to denote a
fraction which is formed by inverting
another fraction ; thus % is the reciprocal
of 1 ; and L the reciprocal of 7 or ^ A
reciprocal property is that which each of
two things has with reference to the
other; thus, if A and B are what is
called conjugate diameters of a conic
section, the tangent at either extremity
of A is parallel to B, and that at either
extremity of B is parallel to A. Hence,
these lines are reciprocally connected
with each other, and are therefore called
conjugate ; for the term conjugate, which
denotes joined, generally means joined
by a reciprocal property.

RECTA'NGLE {rectum angulum ha-
bens). A geometrical term, denoting a
right-angled parallelogram, or any figure
of which all the angles are right angles.
A rectangle is said to be contained by any
two of its adjoining sides. The areas of
all figures whatever, whether bounded by
straight lines or curves, are expressed by
those of equivalent rectangles.

RECTIFICATION. In Chemistry,
the repeating of a distillation or a sub-
limation several times, in order to ren-
der the substance purer and finer.

RECTIFICATION (in Mathematics).
The finding of a right line equal in length
to an arc of a curve. The term is thus
analogous to that of quadrature, as ap-
plied to the finding of its area ; for as an
area is considered to be found when a
square equal to it has been exhibited, so
the length of an arc is known when a
straight line equal to it has been found.

RECTILI'NEAL (recta linea, a right
line). A term applied in Geometry to all
figures which are contained by right lines,
as a triangle, a square, &c.

RECURRING DECIMAL. Circula-
ting Decimal. For the exact expression
of a vulgar fraction by a decimal, the
former must either have, or be capable of
being reduced to another which has 10
or some power of 10 for its denominator.
Otherwise, the decimal will go on inter-
minably, the same figure or figures recur-
ring in the same order. These are called
recurring, repeating, or circulating deci-
mals, and the part repeated is called the

REF

REP

period or repetend. A pure circulator is
one in which the period begins imme-
diately after the point; all others are
called mixed.

RED CHALK. Red clay, or reddle ;
an argillaceous iron-stone ore.

RED FIRE. A pyrotechnical com-
pound of nitrate of strontia, sulphur,
antimony, and chlorate of potash, which
burns with a red flame.

RED LEAD. Minium. An oxide of
lead with a fine red colour, with a shade
of yellow. It is intermediate between
the protoxide and the peroxide.

RED MARL. Variegated Red Sand-
stone ; a sandstone with an argillaceous
cement, often containing beds of red or
variegated marl, and subordinate beds of
reddish oolite and dolomite, with clays
containing gypsum and salt.

RED PRECI PITATE. The red oxide
of mercury, or mercuric oxide, obtained
by the decomposition of the nitrate of
mercury by heat.

REDU'CTION. A rule in arithmetic
by which we find the quantity in one de-
nomination corresponding to a quantity
expressed in another denomination; by
which, for example, we find how many
shillings there are in a certain number of
pounds, how many pounds in a certain
number of shillings, &c. In the former
case the reduction is termed descending,
and is performed by multiplication ; in
the latter it is ascending, and is per-
formed by division.

REDU'CTION OF METALS. The
conversion of the oxides of metals into
the metallic state, by the application of
heat; the operation consists in mixing
them with some substance which will
attract the oxygen from the oxides ; coal
is the substance generally employed for
this purpose.

REEF, or CORAL REEF. A pecu-
liar kind of rock produced by the coral
animalcule, found in the ocean, of con-
siderable length, of very narrow width,
and generally only a few feet below the
surface of the water. Reefs are usually
of a circular or oval form, surrounded by
a deep sea, the interior generally pre-
senting the appearance of a shallow
lagoon. But they appear under various
forms.

REFERENCES, FALLACY OF. An
artifice sometimes employed by dishonest
writers, consisting in the merely giving
of references to authorities, which may
be conceived favourable to the writers'
views ; it is supposed that few will take
285

the trouble of examining the passages
referred to, and that the confirmation of
the writers' statements by such authori-
ties will be taken for granted.

REFINING. The operation of puri-
fying anything; particularly the assay-
ing or purifying of gold and silver, by
separating them from other bodies which
are combined with them.

REFLECTING CIRCLE. An astro-
nomical instrument destined for the
same uses as the sextant, but more com-
plete, the circle being entire, and the
divisions carried all round. It is usually
furnished with three verniers, so as to
admit of three distinct readings off", by
the average of which the error of gra-
duation and of reading is reduced.

REFLECTION (reflecto, to bend back).
In Physics, this term denotes the re-
bound of the rays of light, of heat, or of
sound, from an opposing surface. Po-
lished surfaces reflect light to the eye,
and are, therefore, more generally termed
reflectors or mirrors. Heat and sound
are reflected without relation to the eye,
and are returned from more rugged sur-
faces.

Reflecting microscopes and telescopes
are such as carry a magnified image of
the object to the eye, by means of rays
reflected from a concave speculum.

REFRA'CTION (refractus, broken
back). That property of light, by which
a ray becomes refracted, or bent back,
when passing In an oblique direction
from a rarer into a denser medium, and
vice versd. The phenomenon may be
observed on immersing one end of a rod,
in a slanting direction, in a vessel of
water : the part immersed appears as if
it were bent, or broken, at the surface
of the liquid. This is termed ordinary
refraction.

1. Refraction, double. A property of
certain transparent minerals, as Iceland
spar, by which a ray of light, after enter-
ing such a medium, becomes divided
into two portions or rays, each of which
presents an image of the object. One of
these rays follows the ordinary law of the
sines, and the other is refracted accord-
ing to a new or extraordinary law; hence
these two rays have been termed the
ordinary ray, and the extraordinary ray,
respectively.

2. Refraction, index of. A term ap-
plied to the ratio which subsists between
the sines of the angles of incidence and
of refraction, which is also in every case
a constant ratio.

REG

REG

3. Refraction, terrestrial and celestial.
In astronomical and meteorological ob-
servations it is found that every differ-
ence of level, accompanied, as it must
be, with a difference of density in the
aerial strata, must also have, correspond-
ing to it, a certain amount of refraction.
That which occurs between terrestrial
stations is termed terrestrial refraction,
to distinguish it from that total effect
which is produced only on celestial ob-
jects, or such as are beyond the atmo-
sphere, and which is called astronomical
or celestial refraction.

4. Refracting microscopes and telescopes
are such as show a magnified image of
an object, by means of rays of light re-
fracted and collected into a focus through
lenses.

REFRANGIBI'LITY {refrango, to
break back). The property by which a ray
of light admits of being refracted. The
term is employed to designate the degree
of this property which is possessed by
the several divisions of a ray of light.
It is owing to their .various refrangibi-
lities that the rays separate from each
other in passing through the prism,
thereby exhibiting the phenomenon of
the coloured spectrum.

REFRIGERATION {refrigero, to
cool). The operation of cooling a body ;
also the condition of a body which has
been cooled. A refrigeratory is a chemical
vessel filled with water, for the purpose
of condensing vapours, or for cooling any
substance as it passes through it.

REGMA (p^ftrtra), to break). Capsula
tricocca. A fruit, consisting of three or
more cells, each of which bursts from the
axis with elasticity into two valves, as
in Euphorbia. The cells of this kind of
fruit are called cocci.

REGULAR BODIES. A term ap-
plied to the five regular geometrical
solids, viz. the tetrahedron, the hexa-
hedron, the octahedron, the dodecahe-
dron, and the icosahedron; these are
bounded by like, equal, and regular
plane figures, and their solid angles are
all equal. They were described by
Plato, and are hence called Platonic
bodies.

REGULAR FIGURES. These are
equilateral and equiangular polygons.
About and within such figures circles
can be described.

RE'GULARS. In chronology, there
are two kinds of Regulars, the solar and
the lunar.

1. The Solar Regulars are fixed num-

bers attached to each month. The regu-
lar for—

April and July, is | 1

January and October

2

May

S

August

4

February, March, November

5

June |

6

September and December ...

7

The Regulars are used with the Con-
currents in ascertaining on what day of
the week the first day of each month fell.
The Regulars of the month being added
to the Concurrent of the year, the sum,
if it does not exceed 7, shows the day of
the week required, 1 representing Sun-
day, 2 Monday, and so on. If it exceed
7, that number is to be subtracted, and
the remainder shows on what day of the
week the first day of each month in that
year fell. Thus, if the day of the week
of the 1st December, 1272, be required:
Regular of December (7) + Concurrent
of a. d. 1272 (5) =12. Subtract 7, and
the remainder, 5, denotes the 5th day of
the week, or Thursday.

2. The Lunar Regulars consist also of
a fixed number assigned to each month
of the year. By adding thereto the
Epact, the age of the moon on the first
day of each month is ascertained. The
following is a table of the Lunar Regu-
lars, according to the calculations of
those who began the year in January or
March :—

1 9

1 io

May

1 11

June

1 12

July

1 13

August

1 14

September and October

1 16

November and December ...

1 18

If the lunar year commenced in the
month of September, as with the Egyp-
tians, and four months before the Julian
year, the Lunar Regulars for September
and October are 5, and for November and
December 7 ; but for all the other months,
the numbers are those in the preceding
table.

By adding the Lunar Regulars to the
Concurrent of any particular year, the
day of the week is shown on which the
first day of the Paschal moon fell. If the
sum does not exceed 7, the day following
was the first of the Paschal moon ; if the
Lunar Regulars and Concurrent exceed

REP

RET

7, that number must be subtracted, and
the remainder shows that the next day
was the first of the Paschal moon.— Sir
H. Nicolas.

RE'GULUS {rex, regis, a king). The
name given by the alchemists to the
metallic matters which were separated
from other substances by fusion, from
their expecting to find gold, the king of
metals, at the bottom of the crucible.
The term has since been applied to some
metals when extracted from their ores,
as regulus of antimony, &c.

RE'GULUS (in Astronomy). A star
of the first magnitude in the zodiacal
constellation Leo. It is also called a
Leonis, or Cor Leonis. By Ptolemy and
other Greeks it was called (ZaoiXia-Ko?,
whence is derived the Latin name Regu-
lus, the diminutive of Rex.

RELATIVE and CORRELATIVE.
The nature of relative terms has been
explained under the article Absolute and
Relative. Terms are correlative to each
other, which denote objects related to
each other, and viewed as in that rela-
tion. Thus, though a king is a ruler of
men, "king" and "man" are not cor-
relative, but king and subject are.

REPEATING CIRCLE. An astro-
nomical instrument, invented by Borda,
by which the error of graduation may be
diminished to any degree, and, prac-
tically speaking, annihilated. By this
instrument the observer is enabled to
repeat or multiply the observation, by
reading it off successively on different
parts of the graduated limb. A number
of values being thus found, the mean of
the whole is taken as the correct result.

REPETE'ND (repetendus, to be re-
peated). The part of a circulating deci-
mal which is perpetually repeated. It
is called simple, when the figures are the
same ; and compound, when they vary.

REPLUM. A leaf of a door. In Bo-
tany, the framework formed by the sepa-
ration of the two sutures of a legume
from its valves.

REPTATRI'CES {repo, to creep).
Creepers ; an order of Climbing birds,
which have the three fore toes more or
less united at the base, and spreading
little. They are thus distinguished from
the Scandrices, or Climbers, in which the
outer toe is directed outwards or back-
wards.

REPTI'LIA {repo, to creep). The
third class of Vertebrate animals, con-
sisting of reptiles, most of which are
terrestrial. They are characterized by
287

cold-bloodedness, oviparous reproduction,
the absence of metamorphosis, and the
protection of the skin by means of hard
plates or scales.

REPULSION {repello, to drive back).
That property of natural bodies, by
which, under certain circumstances, they
repel, or fly off* from, each other, It is
an effect of caloric, by which the par-
ticles of a body, into which it enters, are
removed from each other. It is the op-
posite of that form of attraction which is
termed cohesion.

Repulsion, in Electricity. The law by
which light bodies fly off from an elec-
trified surface, after contact.

RESI'DUAL. An expression which
gives the remainder of a subtraction, as
a — b. A residual phenomenon is that
part of a phenomenon which remains
when every part which is capable of ex-
planation has been removed.

RESIN. A volatile oil, rendered con-
crete by combination with oxygen.

RESISTANCE. A term applied, in
Physics, to any power by which motion,
or a tendency to motion, is impeded or
prevented. Thus, the atmosphere offers
resistance to the path of a projectile, the
water to the passage of a ship, inequality
of surface to the movement of bodies on
one another, &c.

RESOLUTION OF FORCES. This
term denotes, in physics, the finding of
several forces, their directions, and in-
tensities, which by their joint action have
moved a body, exactly as it would have
been moved by a single force of deter-
minate intensity and direction. See
Force.

RE'SONANCE (resono, to sound
again). That property of sonorous bodies
by which they acquire the same vibra-
tions as are possessed by a body emitting
a sound; they thus vibrate with it, and
strengthen the original note. A tuning-
fork emits a louder sound when its
handle is placed on a table ; the notes of
a musical box are louder when the box
is placed upon a table.

RESU'LTANT. A term applied in
physics to such a si ngle for ce as is equi-
valent to the effects of all the moving
forces in any compound motion ; in other
words, it is the force which results from
the composition of two or more forces
acting upon a body. See Forces, Com-
position of.

RETI'CULUS RHOMBOIDA'LIS. A
modern southern constellation, consist-
ing of ten stars.

RH A

RHO

RETINA'PHTHA. A compound of
carbon and hydrogen, formed by dropping
resin into a red-hot cylinder.

RE'TINITE. Retinasphalt. A sub-
stance consisting of resin, asphalt, and
earth, found at Bovey Tracey adhering to
brown coal.

RETITE'L^E (rete, a net, tela, a web).
A family of Spiders, which spin webs of
an open mesh-work and of an irregular
form, and remain in the middle or on
one side, in order to seize their prey.

RETORT. A globular vessel of glass,
or porcelain, with a long neck bended
on one side, used for distillation, or de-
composition by the application of heat.

RETROGRADE {retro, backward,
gradior, to go). A term used in Astro-
nomy, in opposition to direct. Thus, all
motion from east to west, as the apparent
motion of the heavens, is retrograde;
while the earth's diurnal motion, which
causes it, is direct.

REU'SSITE. A substance consisting
of several sulphates, and occurring in
the form of a mealy efflorescence on the
surface of the earth about Seidlitz and
Seidschutz.

REVERBERATORY FURNACE
That kind of furnace, in which the flame
is driven back, or prevented from
rising.

REVERSE SHELLS. Shells which
have the aperture opening on the left
side when placed in front of the spec-
tator.

REVERSION OF SERIES. A term
sometimes confounded, in Mathematics,
with inversion. Thus, the connexion
of the square root with the square is
described as inverse ; but if y be a given
eeries of powers of x, the determination
of a? in a series of functions of y is not
called inversion, but reversion.

REVIVIFICATION (revivisco, to be-
gin to live again). In Chemistry, this
term has been applied to the reduction of
metals. In natural history, it denotes a
phenomenon which occurs in some ani-
malcules, as the rotifer redivivus, which
lives in water, but, after remaining for
years in a dry state, with all its functions
suspended, revives in a few minutes on
being placed in water.

REVOLUTION. In pure mathema-
tics, this term denotes an angle moved
over by a line which revolves round a
point from any one position to that posi-
tion again. It is, therefore, a synonym
for four right angles.

RHAMNACE^E. The Buckthorn tribe

of Dicotyledonous plants. Trees or
shrubs with leaves alternate ; flowers ax-
illary or terminal, polypetalous ; petals
cucullate ; stamens perigynous ; ovarium
superior; seeds albuminous.

RHINOLOPHI'N,E (piv, the nose,
X6(poi, a crest). A family of the insec-
tivorous Cheiroptera, named from the
peculiar form of the anterior nasal ap-
pendage, and including the greater and
lesser horse-shoe bats of our own coun-
try.

RHIPI'PTERA (pmh, a fan, mepbv,
a wing). Fan-winged insects ; an order
of insects, which have only one pair of
wings fully developed, and these are on
the metathorax ; the other pair are rudi-
mentary. See Diptera.

RHI'ZANTHS [pifa a root, &v9ov, a
flower). A class of parasitical leafless
plants, which, with many of the pecu-
liarities of Endogens, seem to constitute
an intermediate form of organization
between them and the lower Acrogens.
They are all of a fungus-like consistence,
with few traces of a vascular system ; the
flowers are propagated by the agency of
sexes ; the seeds have no embryo, but
consist of a homogeneous sporuliferous
mass.

RHIZOCA'RPOUS {pita, a root, nap-
7r6f, fruit). A botanical term applied to
those polycarpous fruits, whose root en-
dures many years, but whose stems
perish annually, as herbaceous plants.

RHIZOME {pifrna, that which has
taken root). A root-stock, or root-like
stem, which lies prostrate on the ground,
and emits roots from its under side, as
in iris.

RHODIUM {pobov, a rose). A new
metal discovered in the ore of platinum,
and named from the red colour of one of
its solutions.

RHODIZONIC ACID (p6iov, a rose).
An acid derived from carbonic oxide, and
named from the red colour of its
salts.

RHO'DONITE. A fibrous ore of man-
ganese, consisting of silica and the prot-
oxide of manganese.

RHOMB-SPAR. A variety of man-
ganesian limestone, composed of the car-
bonates of lime and of magnesia, and
occurring imbedded in chlorite slate,
limestone, &c. It has been called bitter
spar and muricalcite.

RHOMBOID (p6/i/3of, a rhombus,
etdo?, likeness). A four-sided figure,
which has its opposite sides equal to one
another, but all its sides are not equal,

RHY

ROC

nor its angles right angles. It is, in
fact, a compressed parallelogram.

In Crystallography, the rhomboid, or
rhombohedron, as it is sometimes called,
is a figure contained within six equal
rhombs ; two only of its solid angles are
formed by the union of three equal plane
angles, and these are called the terminal
solid angles ; the other six, which are
similar to one another, are lateral solid
angles. This form would result from
elongating or compressing the cube in
the direction of a line passing through
two of its opposite solid angles ; in the
former case an acute, in the latter an
obtuse rhomboid would result.

RHOMBUS {ponfios, a rhomb). A
four-sided figure, which has all its sides
equal ; but its angles are not right
angles; it is an equilateral oblique paral-
lelogram. '? J | i r

RHUMB-LINE {rumbo, or rumo, Por-
tuguese, a course). AThe shortest line
which can join two points on the globe,
cutting all the meridians which it crosses
at the same angle ; when delineated on
the globe, it forms a curve termed the
, loxodromic curve.

RHUMBS. The thirty-two points of
the horizon, as marked on the circle of
the mariner's compass; they serve to
calculate the angle which a ship's course
makes with the magnetic needle.

RHUTE'NIUM. This, and Plura-
nium, are names of two supposed
metals, contained in the insoluble re-
sidue left after the action of nitro-
muriatic acid on the Uralian ore of
platinum.

RHY'NCHOLITHES (ptJ-yxor, a beak,
\iOos, a stone). Beak-shaped fossils ;
the extremities of the mandibles of Ce-
phalopods, allied to the nautilus.

RHYNCHO'PHORjE (p*ftpf, a muz-
zle, (pep<a, to bear). The Weevil tribe ;
a family of the tetramerous Coleoptera,
characterized by the prolongation of the
anterior part of the head into a kind of
muzzle.

RHYNCHOS A'URUS (pvyX<>f, a beak
travpa, a lizard). A fossil animal pre-
senting certain characters, which con-
nect the great class of reptiles, on one
hand with the birds, and on the other
with quadrupeds. The skull and several
bones of the extremities of this animal
were found some years ago in the Grin-
sill quarries, near Warwick.

RHYTIDO'MA (p,'m?, a wrinkle).
The name given by Mohl to the deciduous
scales of the bark of trees produced by
289

the formation of epiphloeum inside the
liber or mesophloeum.

RIGEL. A star of the first magni-
tude, on the left foot of Orion.

RIGHT (in Mathematics). A term
generally used as opposed to oblique. Its
use may, however, have arisen from an
idea of simplicity: a right line is a
straight line, and the latter has been de-
fined to be " the shortest way between
two points." A right angle is formed by
two right lines perpendicular to each
other, and contains 90° ; it is the most
simple of angles. A right cone, cylinder,
prism, pyramid, &c, are those whose
sides are perpendicular, or at right
angles, to the plane of the base.

RINGENT (ringo, to grin). A term
applied in Botany to certain corollas, the
petals of which cohere into the form of
a mouth, which gapes on pressing the
sides, as in Antirrhinum.

RINGS, FAIRY. The fanciful name
given to patches or to circles of luxuriant
grass, observed in fields ; they are sup-
posed to owe their luxuriance to the
nutritive influence of decaying fungi.

RIPPLE-MARK. A term applied by
Geologists to the undulations which oc-
cur on the surface of many rocks, re-
sembling the ridges and indentations
left on mud and sand by small waves of
water. They are most distinct on sur-
faces where a change of deposit has taken
place, as where sandstones alternate with
thin clay partings.

ROASTING. A chemical process, by
which mineral substances are divided,
some of their principles being volatilized,
and others changed, so as to prepare
them for further operations.

ROBUR CAROLINUM. Royal Oak ;
a modern southern constellation, consist-
ing of twelve stars.

ROCK. A geological term, denoting
the solid parts of the crust of the earth,
formed of a single mineral species, or
composed of two or more species. One
or several rocks united by certain com-
mon characters, constitute a formation,
or connected series ; and several forma-
tions constitute a system of rocks. Rocks
have been distinguished, according to
peculiarities in their constitution, and in
their form and arrangement, into the
Plutonic, the Aqueous, and the Vol-
canic.

1. The Plutonic Rocks are primary or
primitive in arrangement, igneous in
constitution, and unst ratified in form.

2. The Aqueous Rocks are secondary

O

ROO

ROS

and tertiary in arrangement, deposited
by water and stratified in form.

3. The Volcanic Rocks are of most
recent arrangement, composed of volcanic
matter, and unstratified in form.

Other classification. Rocks may be
arranged into four groups or classes,
dependent chiefly upon their relative po-
sition. 1. Granitic Rock, or those form-
ing the basis or foundation of the rest.
2. Stratified Rocks, divided, according to
the order of their deposition, into four
groups, viz. primary, secondary, tertiary,
and alluvial. 3. Overlying or interjected
rocks, so named because they appear lying
over, or interspersed among, the stratified
rocks. 4. Volcanic rocks, of the same
nature as the last, but produced by vol-
canoes at present or recently in 'action.
The first, third, and fourth classes are
all unstratified.

ROCK BUTTER. Alum mixed with
alumina and oxide of iron, oozing out of
rocks which contain alum.

ROCK CRYSTAL. A pure crystal-
lized variety of quartz, of which the
Scotch cairngorm is a variety. The pur-
ple-coloured rock-crystals are commonly
called amethysts, and the yellow-coloured
have the name of topazes. See Corundum.

ROCK SALT. Common culinary salt,
or chloride of sodium, occurring in vast
solid masses or beds, in different forma-
tions, extensively in the New Red Sand-
stone formation, as in Cheshire ; in this
condition it is called rock salt.

ROCK WOOD. A variety of asbestus,
of a brown colour, and with the appear-
ance of wood ; found in the Tyrol, &c.

RODE'NTIA {rodo, to gnaw). Glires.
An order of Mammalia, in which the
jaws are deficient in true incisors, their
places being supplied by the canines,
which are brought forward, and adapted
to gnawing, as in the beaver, the rat, the
hare.

ROESTONE. A variety of compact
limestone, called Bath-stone, Ketton-
stone, Portland-stone, and Oolite; it is
used for building, but is porous and apt
to moulder away.

ROMA'NZOVITE. A species of gar-
net, found in Finland.

ROOT. The square root of any num-
ber, as 16, is a number which, when mul-
tiplied by itself, produces 16. The cube
root of any number, as 27, is a number
which, when multiplied by itself twice,
produces 27. The fourth, fifth, &c. roots
are numbers which, when multiplied
three, four, &c. times, produce the ori-
290

ginal numbers. The mark „J is the
radical sign, or sign of the root, being
the first letter of the Latin term radix,
a root. Hence —

^J 16 is 4; for 4 x 4 = 16

3/ 27 is 3 ; for 3 x 3 x 3 = 27

XJ 16 is 2; for 2 x 2 x 2 x 2=16.

Root of Equation. In equations the
unknown quantities have particular
values, which are sometimes called the
" roots" of the equations, and are said to
satisfy them. Thus, if #2 = 4, we know
that x = 2 or — 2 ; and 2, — 2, are called
the roots of the equation xz = 4.

ROOT OF PLANTS. The descend-
ing part of the axis of plants, or that
portion which tends towards the cen-
tre of the earth. The main body is
called the caudex, its minute divisions
being called radicles or fibrils. When a
root is divided into many fibrils, it is
termed a fibrous root ; when truncated at
the extremity, prcemorse ; when it tapers
conically downward, it is termed fusi-
form, or tap-rooted. Uuder the general
term root, many parts have been erro-
neously enumerated, as subterranean
stems, the tuber, the cormus,&c.

ROSA'CEjE. The Rose tribe of dico-
tyledonous plants. Herbaceous plants
and shrubs with leaves alternate; flowers
polypetalous; stamens perigynous ; ovaria
superior, solitary, or several ; fruit 1-seed-
ed nuts, or acini, or follicles containing
several seeds.

ROSCHGEWACHS. The name given
by the Hungarian miners to the sulphur-
salt commonly called brittle vitreous
silver. It appears to be composed of the
same constituent elements as the dark
and the bright red ruby- silver ores, but
in different proportions.

ROSE or MILK QUARTZ. A sub-
species of indivisible quartz, of rose-red
and milk-white colours. It is probably
silica, coloured with manganese. It oc-
curs in Bavaria in beds of quartz in
granite.

ROSELITE. A new mineral of a deep
rose colour, found on amorphous greyish
quartz in Saxony. It is an arseniate of
cobalt, with lime and magnesia.

ROSTRUM. Literally, a beak; and
hence, applied in Botany to any rigid
prolongation of considerable length.
Rostellum, a diminutive of rostrum, is
also employed to denote any small beak-
shaped process.

RO'SULATE (rosa, a rose). In bota-
nical nomenclature, this term is used
to designate parts wli^h are not oppo-

ROT

RUP

posite, but which nevertheless become
apparently so by the contraction of the
joints of the stem, and lie packed closely
over one another, like the petals of a
double rose, the offsets of houseleek, &c.

ROTA MERIDIA'NA. A transit
circle erected by Rbmer at Copenhagen.
It was a divided circle set upon a hollow
double cone, at right angles to the axis
of the cones, and concentric with them,
the circle being near one end of the axis.
The divisions were read by two micro-
scope verniers, fixed in a diameter of the
circle on one of the supports of the axis.

ROTAL ACTION OF AFFINITY.
A term applied to the action of chemical
affinity, as exhibited in the voltaic cir-
cle, in which it assumes a circular direc-
tion or return upon itself. It is what
has been more commonly called induc-
tive affinity, from its analogy to magnetic
induction.

ROTATE COROLLA. A wheel-shaped
corolla, of which the tube is very short,
and the segments spreading, like the
radii of a wheel, as in borago.

ROTATION (in plants). A special
motion of the sap, observed in plants of
low organization. It consists in a spe-
cial circulation of the fluid contained in
the interior of each cell, the rotation
in one cell never interfering with that
in another cell. This phenomenon
differs from that of cyclosis, which con-
sists in the motion of the latex in the
cinenchymatous vessels. The two special
motions are said never both to occur in
the same species.

ROTATORY MOTION (rota, a
wheel). When the different points of a
body move at the same time in different
directions, this is called a rotatory mo-
tion, notation on an axis implies, in
addition to this rotatory motion, that all
the parts of the body revolve round an
imaginary right line in a state of rest,
called the axis. The wheels of any piece
of machinery have a rotatory motion
round their axes ; the diurnal and annual
motions of the earth, a rolling ball, the
wheels of a waggon as it travels, are
illustrations both of direct and of rotatory
motion.

ROTELLI'NjE. Wheel-shells; a sub-
family of the Trochidcc, named from the
genus rotella; they are perlaceous, and
nearly discoid in shape, with a thickened
mass over the inner lip.

ROTI'FERA (rota, a wheel, fero, to
carry). Infusorial animalcules, consist-
ing of minute, transparent, soft, aquatic
291

animals, with distinct muscular and
nervous systems, and having the appear-
ance of revolving wheels, produced by
the rapid motion of the cilia placed round
the mouth. They are distinguished into
the loricata, which have tne surface of
the body protected by a sheath ; and the
nuda, in which the body is soft and
naked.

ROTTEN-STONE. A massive mine-
ral, consisting of alumina, silica, and
carbonaceous matter, found near Bake-
well, &c, and employed in polishing
metals.

RUBBLE. A term applied by quarry-
men to the upper fragmentary and de-
composed portion of a mass of stone.

RU'BELLITE. Red schorl or tour-
maline, found at Rbzna in Moravia.

RUBY. A crystallized gem of various
shades of red. The spinelle ruby is
scarlet-coloured ; the balass ruby is of a
pale or rose red ; the rubicelle is yellowish
red. The oriental ruby of jewellers is
the red sapphire.

RUBY SILVER ORE. A double
sulphur-salt; distinguished into the dark
and the light red, both of the same crys-
talline form, but in the latter of which
sulphuret of arsenic takes the place of
sulphuret of antimony of the former.

RUDO'LPHINE TABLES. A set of
astronomical tables computed by Kepler,
and founded on the observations of Tycho
Brahe. They were named in honour of
Rudolph II., emperor of Bohemia, and
were the first tables ever calculated on
the hypothesis that the planets move in
elliptic orbits.

RUMINANTIA (rumino, to chew the
cud). An order of the Mammalia, con-
taining the ox, deer, sheep, &c, charac-
terized by their cloven feet, the absence of
incisors in the upper jaw, and the com-
plex arrangement of the stomachs by
which rumination is effected.

RUMINATED. A term applied to
the albumen of certain plants, in which
it is perforated in various directions by
dry cellular tissue, as in the nutmeg, and
pulmaceous plants.

RUNNER. A prostrate aerial stem,
forming at its extremity roots and a
young plant, which itself gives origin to
new runners, as in strawberry.

RU'PTURING or SOLUBILITY. In
Botany, the spontaneous contraction of a
portion of the pericarp, by which its tex-
ture is broken through, and holes formed
for the dispersion of the seeds, as in An-
tirrhinum and Campanula.
02

SAG

S AI

RUTA'CEjE. The Rue tribe of di-
cotyledonous plants. Herbaceous plants,
with leaves alternate, dotted ; flowers
symmetrical; petals alternate with the
divisions of the calyx; stamens hypo-

gynous ; ovarium entire, celled ; fruit
capsular.

RU'TILE (rutilue, red). Titan-schorl.
Native oxide of titanium.

S

SAC of the EMBRYO. The name
given by A. Brongniart to a fifth mem-
brane which sometimes occurs in the
ovule of plants. Mirbel calls this the
quintine, Malpighi the vesicula amnios,
and R. Brown the additional membrane.

SA'CCHARINE MATTER (saccha-
rum, sugar). That portion of vegetable
substances which is sweet to the taste, or
which is capable of becoming sweet
under certain circumstances, or by cer-
tain manipulations. This, when suffi-
ciently fluid, readily enters into vinous
fermentation, emits carbonic acid gas,
becomes of less specific gravity, and the
product is a vinous liquor. See Alcohol.

SA'CCHAROID (aanxap, sugar, eidop,
likeness). Saccharine. A term applied
in Geology to a stone which has the tex-
ture of sugar.

SACCHARO'METER {aaKxapov,
sugar, fxerpov, a measure). Literally,
a measurer of sugar ; an instrument em-
ployed in the operations of brewing and
of making sugar, its intention being to
indicate the density of the liquid ex-
tracted from malt and of that from the
sugar cane. It acts on the same prin-
ciple as the lactometer and the hydro-
meter, and such instruments are some-
times comprehended under the general
term arcenmeter or gravimeter.

SAFETY-LAMP. An instrument in-
vented by Davy for preventing the ex-
plosion of fire-damp in mines. It consists
of a lamp completely surrounded by a
cage of fine wire-gauze, through which
the explosive mixture cannot be fired.
So soon as the gas is inflamed within the
gauze, the miner is thereby admonished
to retire, lest the intense heat of the
flame should oxidise the metal, which
would then fall to pieces.

SAFETY-VALVE. A valve fitted to
an opening in a boiler, and loaded with a
weight sufficient to withstand the elastic
pressure of the steam until it rise to a
certain degree, when it would be forced
out, and thus prevent the boiler from
bursting.

SAGITTA. The Arrow; a northern
292

constellation, consisting of eighteen
stars.

SAGITTARIUS. The Archer; the
ninth of the Zodiacal signs, consisting of
69 stars. It denotes the third month of
spring, and extends from the 20th of
May to the 20th of June. In the Egyp-
tian zodiac the animal is figured with the
body of a quadruped and with a double
head, one of a lion, the other of an armed
man about to discharge an arrow ; it
seems to drive forward the animals which
precede it, and to check those which fol-
low; every thing indicates that it will
soon reach the goal towards which it is
tending, and that its course is on the
point cf terminating.

SAH'LITE. A variety of augite, in
which the magnesia is only in part re-
placed by protoxide of iron. Berzelius
calls it malacolite. It occurs in the sil-
ver mine of Sahla in Sweden.

SAILING, or the SAILINGS. These
terms are applied to the different ways in
which the path of a ship at sea and the
variations of its geographical positions
are represented on paper. They are also
occasionally applied to the rules by
which, in particular circumstances, a
ship's place and its motion are com-
puted.

1. Plane Sailing. This consists in re-
presenting the line of a ship's course or
way, for a given time, with the difference
between the latitudes and between the
longitudes of the two extreme points of
such course by the three sides of a right-
angled plane triangle, of which the dis-
tance actually sailed is the hypotenuse ;
the spaces on all the lines being ex-
pressed in nautical miles or equatorial
minutes of a degree, as if the earth
were a plane surface and the terres-
trial meridians and parallels of lati-
tude were straight lines respectively
parallel to each other.

2. Middle-latitude sailing. This term
and that of globular sailing have been
briefly explained in their alphabetical
positions. The latter is a general term
for several modes of sailing, in which the

SAI

SAL

rules of computation are founded on the
hypothesis that the earth is a sphere.

3. Parallel sailing. The term denotes
the course of a ship sailing in a direction
either due east or due west, so as to sail
on the circumference of a parallel of lati-
tude. The determination of the ship's
place is obtained by knowing that, on
the globe, the length of a degree of a
meridian bears the same proportion to
the length of a degree of a parallel, as
the radius to the cosine of the latitude
in which that parallel is situated.

4. Mercator's sailing. In this mode of
sailing, the earth's surface is supposed
to be projected on a plane, as on a Mer-
cator's chart (See Projection), in which
the meridians and parallels of latitude
are respectively parallel to themselves.
The ship's place is then determined by
the fact that the lengths of infinitely
small portions of the circumference of the
equator have to the lengths of corre-
sponding portions of a meridian, in any
latitude, the ratio that the radius bears
to the secant of that latitude.

5. Great-circle sailing. This consists
in determining a series of points in an
arc of a great circle between two points
on the surface of the earth, for the pur-
pose of directing a ship's course as nearly
as possible on such arc ; that is, on the
curve of shortest distance between the
place from which she sets out and that
at which she is to arrive.

6. Traverse sailing. This is a general
term for the determination of a single
course equivalent to a series of succes-
sive courses, whatever be the manner of
finding the lengths of the lines forming
the triangles.

7. Oblique sailing. This consists in de-
termining the position of a ship by ob-
serving with a compass the bearings of
two or more objects on the shore, whose
places are given on a chart, and drawing
lines from those places so as to make
angles with their meridians equal to the
observed bearings : the intersection of
the lines gives on the chart the position
of the ship. This is sometimes called the
method of cross bearings.

8. The term oblique sailing is also
applied to any problem in which (when
the triangles are not right-angled) the
distance of the ship from any object on
the shore, or of such objects from one
another, is computed by the rules of
plane trigonometry from bearings ob-
served at the ship when the latter is at
two or at a greater number of stations.

9. Current sailing. This is the method
of determining the true motion of a ship
when, besides being acted upon by the
wind, she is moving in a current.

10. Windward sailing. A term applied
to that mode of navigating a ship in
which the latter endeavours to gain a
port situated in the direction whence
the wind is blowing. The ship in this
case is made, by frequent tacking, to
sail as near as possible to the wind. —
Pen. Cycl.

SAL AMMONIAC. Salmiac. Mu-
riate of ammonia. The native salt is of
two kinds, the volcanic, and the con-
choidal ; the former consisting of sal am-
moniac and muriate of soda, and found
in volcanic districts ; the latter consist-
ing of sal ammoniac and sulphate of
ammonia, found, it is said, in beds of
clay slate. Secret sal ammoniac is sul-
phate of ammonia, and was so named by
its discoverer Glauber.

SAL PRUNELLA. Nitrate of potash,
fused and cast into cakes or balls.

SALAMA'NDRIDjE. A family of
Batrachians, comprising the salamander,
the newts, and other species of long-
tailed caducibranchiate reptiles, or those
which lose their gills before they arrive
at maturity, but retain their tails.

SALICAQEjE (salix, the willow). The
Willow tribe of Dicotyledonous plants.
Trees or shrubs with leaves alternate;
flowers achlamydeous, amentaceous ; ova-
rium superior, 1 or 2-celled ; fruit coria-
ceous ; seeds indefinite, comose.

SALICARIjE. The Loosestrife tribe
of Dicotyledonous plants. Herbs with
leaves opposite, entire; flowers polype-
talous; calyx tubular; stamens peri-
gynous; carpella concrete; and a su-
perior ovarium with several cells.

SA'LICYL. The hypothetical radical
of salicylous and salicylic acids, and
some other compounds. It was viewed
by Dumas as a higher degree of oxida-
tion of benzoyl.

SALIENT ANGLES (salio, to jump
or bound forward). The prominent angles
in a zigzag line, which alternate with
the reversed or re-entering angles. The
term is frequently used in fortification,
but seldom in geometry.

SALFFEROUS SYSTEM {sal, salt,
fero, to bear). A geological term applied
to the series of calcareous, argillaceous,
and sandy strata, which produce rock
salt or brine springs, and gypsum. The
series is also termed New Red Sand-
stone, from the prevalence of the red
OS

SAL

SAP

colour ; and Poikilitic System, from the
varied colours of its rocks.

SALIFIABLE BASE (sal, a salt, fio,
to become). A substance which forms
definite compounds with an acid, and
which, when liquid, or in a state of solu-
tion, has ah alkaline reaction. The acid,
of whatever kind, was denominated by
Lavoisier, the salifying principle.

SALMO'NID^E (salmo, the salmon).
The Salmon and Trout tribe ; a family of
Malacopterygious or soft-spined fishes,
distinguished by the fatty deposition in
the dorsal fin, from part of which the
spines often disappear.

SA'LPIANS. An order of the tuni-
cated mollusca, which float in the open
sea, and are characterized by their trans-
parent elastic outer tunic, which is elon-
gated, compressed, and open at both ex-
tremities. The order is named from a
kind of fish called salpe.

SALT. A general term in Chemistry
for a combination of binary compounds
with each other, as of sulphuric acid
with soda in Glauber's salt ; such a com-
bination is called a ternary compound,
and it is thus distinguished from binary
compounds, in which one element is
combined with another element; and
from quaternary compounds, in which
salts or double salts, such as alum, are
combined together.

1. Nomenclature of Salts. Salts are
named according to the acid they con-
tain, the termination ic of the acid being
changed into ate, and that of ous into
ite. Thus a salt of sulphuric acid is a
sulphate; of sulphurous acid, a, sulphite;
&c, and the name of the oxide indicates
the species, as the sulphate of the oxide
of silver, or simply the sulphate of sil-
ver, the oxide of the metal being always
understood.

2. A sttper-sulphate contains a greater
proportion of acid than the sulphate or
neutral sulphate ; a Ji-sulphate twice as
much, and a sesqui- sulphate once and a
half as much as the neutral sulphate;
while a awft-sulphate contains a less pro-
portion than the neutral salt ; the pre-
fixes referring in all cases to the propor-
tion of acid in the salt, or to the electro-
negative ingredient, as in the case of
oxides.

3. The excess of base in sub-salts is
sometimes indicated by Greek prefixes
expressive of quantity, as di-chromate
of lead, £r/s-acetate of lead ; but this
deviation from rule is apt to lead to con-
fusion. If a precise expression for such

294

sub-salts were required, it would be
better to say, the bibasic subchromate of
lead, the tribasic subacetate of lead.
But the names of both acid and basic
salts are less in accordance with correct
views of their constitution, than the
names of any other class of compounds.
— Graham.

SALT SPRINGS. Springs of water
containing a large quantity of common
salt. They abound in Cheshire and
Worcestershire, and culinary salt is ob-
tained from them by mere evaporation.

SALTATO'RES (salto, to leap). A
family of Spiders which make no web,
but spring upon their prey by insidious'
and agile leaps.

SALTATO'RIA (salto, to leap). A
family of Orthopterous insects, in which
the thighs of the hind legs are much
larger than the rest, by which they pos-
sess great powers of leaping. They in-
clude the crickets, grasshoppers, locusts,
&c. See Cursoria.

SALTPETRE. Sal petrce. Nitre, or
the nitrate of potash. It occurs native
as efflorescence, mixed with other ni-
trates, and as crystalline crusts.

SA'MARA. The botanical designa-
tion of a two or more-celled superior
fruit, bordered by wing-like expansions,
as in sycamore.

SAME. This term, as well as " One,"
"Identical," and their derivatives, is
ambiguous, and has led to much error in
philosophy. In its primary sense it de-
notes identity, and does not admit of
degrees; in its secondary sense it is
employed to denote great similarity, and,
in popular usage, admits of degrees, as
when we speak of two things being
nearly the same, but not entirely. To
this ambiguity Whately refers much of
the error of Realism ; of Plato's theory
of Ideas ; of the personifications and dei-
fications in poetical mythology ; &c.

SA'NDIVER. Glass gall. A saline
substance, which rises as a scum in
vessels employed in the manufacture of
glass.

SANDSTONE. Any stone which is
composed of agglutinated grains of sand,
whether calcareous, siliceous, or of any
other mineral nature. The chief ingre-
dient of sand is granular quartz or flint.

SA'NIDINE. Glassy felspar; this,
and ice-spar, are substances nearly allied
to common felspar.

SAP. The ascending limpid juice of
plants, as distinguished from the de-
scending or elaborated juice.

SAT

SAX

SAPONIFICATION {sapo, soap, fio,
to become). The conversion of any sub-
stance into soap.

SAPPHIRE. A variety of rhomboidal
corundum, constituting the ruby and the
oriental topaz.

SA'RCOCARP (<rap£, o-apKor, flesh,
Kapnot, fruit). The name given by
some botanists to the parenchyma, or
fleshy part of fruits, lying between the
epicarp or skin, and the endocarp or
stone. See Pericarp.

SA'RCODERM (trap?, crap/an, flesh,
dep/xa, skin). A term applied by De
Candolle to the substance which occurs
between the integuments of the seed,
analogous to the sarcocarp of fruits.

SARCO'PHAGA (aapt, flesh, 0ay&>,
to eat). Flesh-eating animals ; a term
synonymous with the more usual one
zoophaga, and, like this, employed in
contradistinction to that of phy top haga.

SARD, or SARDOIN. A variety of
chalcedony, of a brownish yellow colour,
said to be found in Sardinia.

SA'RDONYX. A variety of onyx, in
which the opaque white alternates with
a rich deep orange brown of considerable
translucency. The name is said to be
derived from that of Sardes, in Lydia,
whence the stone was brought. By
others it is referred to Sardo, the Greek
name of Sardinia, whence the Cartha-
ginians are said to have exported it.

SARGA'SSO. The fucus natans, or
gulf-weed, which is spread over a consi-
derable part of the surface of the Atlantic,
beginning on the east at the 30th meri-
dian, and extending on the west to the
Bahama Islands. Its northern limit may
be placed at 36° n. lat., and its southern
at 19° n. lat. The abundance of this weed
has led to the Portuguese expression of
Mar de Sargasso, or Weedy Sea.

SARME'NTUM. The name given by
some botanists to the modification of
the aerial stem called a runner.

SAROS. A Chaldean name applied,
according to some writers, to an astro-
nomical period of 18 years and 10 or 11
days, according as the 18 years have 5 or
4 leap-years. Berosus, however, speaks
of the ' saros of 3600 years. It is, pro-
bably, not a chronological period, but
only a portion of time with any arbitrary
commencement.

SA'SSOLINE. Native boracic acid,
found on the edges of hot springs near
Sasse, in the territory of Florence.

SATELLITE (safeties, a life-guard).
A secondary planet, or moon, so named
295

from its attending a primary planet, as a
prince is attended by his satellites or
life-guards. See Planet.

SATIN SPAR. A fibrous limestone
with a pearly lustre, from Cumberland.
It consists chiefly, if not entirely, of
carbonate of lime.

SATURATION (saluro, to satisfy).
In the language of Chemistry, a fluid is
said to be saturated with a substance,
when it holds as much of this substance
in solution as it can dissolve. Thus,
water is said to be saturated with com-
mon salt, when it has dissolved about
one-third of its weight of the latter : it
will not dissolve any more.

Again : when two principles, which
have united to form a new body, are in
such proportion that neither predomi-
nates, they are said to be saturated with
each other, or the affinities are said to be
satisfied. If otherwise, the predominant
principle is said to be sub-saturated, or
under-saturated^ and the other super-
saturated, or over-saturated.

SATURN. A planet 900 times larger
than the earth, revolving on its axis in
10£ hours, and performing its orbit
round the sun in twenty-nine years, five
months, and fourteen days. It is ac-
companied by eight satellites, and is
surrounded by two luminous rings.

SAU'RIANS (aavpa, a lizard). An
order of Reptiles, in which the ribs are
moveable, and there are one or two pairs
of external members. It comprehends
all the lizard tribe, which are interr
mediate between the Loricata and the
Serpents.

SAU'ROID FISHES {aavpa, a lizard,
etdor, resemblance). A tribe of fishes,
exhibiting strong saurian or reptilian
analogies, chiefly in the teeth. The ex-
isting sauroid fishes consist of seven
species only, five belonging to the genus
lepidosteus, or bony pike, and two species
of polypterus, one from the Nile, the
other from the Niger.

SAU'SSURITE. Axe-stone ; jade. A
mineral found by Saussure on the bor-
ders of the lake of Geneva, consisting
principally of silica and alumina with
oxide of iron.

SAVANNA or PRAIRIE. The name
given to the vast plain constituting the
central part of North America, from the
Frozen Ocean to the Gulf of Mexico,
watered by the Missouri and the Missis-
sippi. This immense tract of country is
estimated at 2,430,000 square miles.

SAXICA'VIDiE (saxum, a stone, cavo,
04

SCA

SCH

to hollow out). A family of the macro-
trachian bivalves, named from the genus
saxicava; the inhabitants of these shells
are perforating animals, as the name
denotes.

SAXICOLI'NiE (saxum, a stone, colo,
to inhabit). Saxicoline birds, or Stone-
chats ; a family of the Cantatrices of
Macgillivray. Being intimately allied to
the Turdinae, Alaudinae, and Sylviinae,
they present no abrupt and decided cha-
racters by which they can be easily de-
fined. Most of them are migratory.

SAXONY BLUE. An intensely deep
blue, imparted by dyeing with sulphate
of indigo.

SCAGLIO'LA {scaglia, Ital., a scale).
An artificial composition employed for
making columns, and consisting of pure
gypsum, Flanders glue, isinglass, &c.

SCALE {scala, a ladder). A line di-
vided into a marked number of small
and equal parts, applied as a measurer
of other lengths which are not so di-
vided, in order to ascertain their relative
dimensions.

Plane diagonal decimal scale. This
instrument consists of a ruler divided
into a certain number of equal parts,
and these parts, by a particular con-
trivance, are again subdivided decimally,
or into tenths and hundredths of these
parts. By this instrument we are en-
abled, though with no great degree of
accuracy, to draw lines which shall bear
to each other nearly any proportions we
may please to assign them.

SCALE OF NOTATION. A system
of notation in which each figure of a
number increases its value in a certain
proportion in proceeding from right to
left. The number, according to whose
powers the values proceed, is called the
radix of the scale. This number is con-
ventional, and there may, consequently,
be any number of different scales, each
of which has its own radix. When the
radix is 2, the scale is called binary ;
when 3, ternary; when 10, denary, or
decimal; when 12, duodenary, or duodeci-
mal ; &c.

SCALE'NE (<rna\nv6s, unequal). A
geometrical term applied to a triangle
which has three unequal sides.

SCANSO'RES (scando, to climb).
Scandrices. Climbers ; a group of birds,
so named from their great facility in
climbing the branches of trees, including
the woodpeckers, the cuckoos, the tou-
cans, and the parrots. The external toe
is turned backward, as well as that
296

which is posterior in the Rasores, so
that they have two posterior and two
anterior toes.

SCAPE. A botanical term denoting
that form of inflorescence, in which the
axis of stemless plants proceeds imme-
diately from the ground, or near it, as in
cowslip.

SCA'PHITE(<rKa0o?,aboat). A genus
of fossil cephalopods, of a boat-like form.
SCA'POLITE (o-KciTTop, a rod, XiOos, a
stone). Pyramidal felspar ; a substance
now classed under the general name
Wernerite. Scapolite is divided by Jame-
son into four sub-species, viz. radiated,
foliated, compact red, and elaolite.

SCARABjE'IDjE {scarabceus, a beetle).
A large group of beetles constituting the
principal part of the section Lamelli-
cornes. They are distinguished from
the other section, or the Lucanidcs,
chiefly by the structure of their antennae,
which are proportionately shorter.

SCA'RBROITE. Hydrated silicate of
alumina, occurring in veins in the beds
of sandstone covering the calcareous
rock near Scarborough, between septa of
oxide of iron.

SCARI'TIDjE. A family of Coleo-
pterous insects, belonging to the section
Geodephaga, and named from the genus
scarites.

SCELIDOTHE'RIUM (<nce\ir, the
thigh, QvpLov, a beast). An animal of
the megatheroid type, exhibiting a tran-
sition to the ant-eater and armadillo,
which it resembles more than the sloth
in the form and structure of the skull.

SCHAALEN BLENDE. Testaceous
blende; a sulphuret of zinc, containing
iron and lead. The most characteristic
specimens are found at Geroldseck in the
Brisgau.

SCHAALSTEIN. Tabular spar or
table spar; a silicate of lime, occurring
in primitive rocks, where it is associated
with brown garnets. This is the pris-
matic augite of Jameson.

SCHAUM EARTH. Aphrite, or
earth foam; a carbonate of lime, oc-
curring usually in a friable, but some-
times in a solid state, with a shining
lustre, between semi-metallic and pearly.
SCHEAT. A star of the third magni-
tude in the constellation Aquarius.

SCHEELE'S GREEN. Arsenite of
copper ; a green pigment.

SCHEE'LIUM. Pyramidal tungsten ;
an ore of tungsten, named from Scheele,
its discoverer. Scheelite is a tungstate
of lime; scheel-lead ore, a tungstate of

SCH

SCL

lead, formerly confounded with the mo-
lybdate of this metal.

SCHELLING'S PHILOSOPHY. A
system of philosophy, which teaches the
identity, or indifference, of the ideal and
the real. It was propounded by Schel-
ling about thirty years ago, and appears
to be directly opposed to the philosophy
of Kant.

SCHERBEN COBALT. Testaceous
cobalt. Names formerly given to native
arsenic. It occurs in reniform and bo-
tryoidal shapes at Andreasburg, &c.

SCHE'RERITE. A species of com-
bustible mineral found in a bed of brown
coal in Switzerland. It seems to be a
mineral naphthaline : its constituents
are, hydrogen, 24 ; carbon, 73.

SCHIEFER SPAR. Slate spar. A
sub-species of limestone, also called
foliated carbonate of lime.

SCHILLER SPAR. A mineral sub-
stance, constituting a variety of asbes-
tine ; it is also called metalloid diallage
or diallagite. It contains two sub-species,
viz., bronzite and common schiller spar.
The term is derived from the German
schillern, to change colours, and indi-
cates the changeable hues of the mi-
neral.

SCHIST (schistus, that which may be
split). A term often used synonymously
with slate ; but it may be very useful to
distinguish between a schistose and a
slaty structure. The hypogene or pri-
mary schists, as they are termed— as
gneiss, mica-schist, and others — cannot
be split into an indefinite number of
parallel laminae, like rocks which have a
true slaty cleavage. The uneven schist-
ose layers of mica-schist and gneiss are
probably layers of deposit which have
assumed a crystalline texture.

SCHISTOSE ROCKS. Rocks which
have the character of schist. See Schist.
SCHI'ZOPODS (<T-x'£«>. to cleave, now,
a foot). A tribe of long-tailed decapod
crustaceans, the legs of which are accom-
panied by an external articulated branch
as long as the limbs, which thus appear
double in number. The mysis, or opos-
sum shrimp, is an illustration of the
tribe.

SCHMELZSTEIN. Another name for
dipyre, under which name the characters
of this mineral are noticed.

SCHO'LIUM {oxokiov, a comment).
A remark or observation. In Geometry,
a scholium is a note or observation on a
proposition not containing any infer-
ence, or, at least, none of sufficient
297

importance to entitle it to the name of
corollary.

SCHORL (scorl, Swed., brittle). Com-
mon schorl is a sub-species of rhom-
boidal tourmaline, consisting chiefly of
silica, alumina, and oxide of iron, and
occurring imbedded in granite, gneiss,
&c. Blue schorl is a variety of Haiiyne.
Red and Titanitic schorl are name3 of
rutile, an ore of titanium. Schorl rock or
schorly granite is a rock, in which crystals
of schorl are added to the usual ingre-
dients of granite ; or when quartz and
schorl only occur, the felspar and mica
having disappeared.

SCHORLITE, or SCHORLOUS TO-
PAZ. Pycnite of Werner. A mineral
consisting of alumina, silica, and fluoric
acid, occurring at Altenberg in Saxony,
in a rock of quartz and mica in porphyry.

SCHRIFTERTZ. Graphic tellurium;
a combination of tellurium with silver
and gold.

SCIiENOIDS. A family of acan-
thopterygian fishes, nearly allied to the
Percoids, and named from the genus

SCIjENU'RUS. A genus of fossil
fishes, representing the perch and other
allied forms. Its remains are very com-
mon in the London clay of Sheppey.

SCIENCE {scientia, knowledge). This
term, in its most comprehensive sense,
only means knowledge; in its ordinary
sense it denotes knowledge reduced to a
system; that is, arranged in a regular
order, so as to be conveniently taught,
easily remembered, and readily applied.

SCINCO'IDiE. The Skink tribe, or
Serpent Lizards; a family of Saurian
reptiles, characterized by the shortness
of their feet, the roundness of their body,
and the equality of the tile-like scales
with which their body is covered.

SCITAMINEiE. The Ginger tribe of
monocotyledonous plants. Herbaceous
plants with a creeping, often -jointed,
rhizome; leaves simple, sheathing;
flowers tripetaloideous ; stamens 3, dis-
tinct; ovarium 3 celled ; fruit capsular,
3-celled, many-seeded: seeds with or
without an arillus.

SCIU'RIDiE (aiciovpos, a squirrel;
from ama, shade, and ovpa, a tail). The
Squirrel tribe ; a family of the Rodentia,
comprising the squirrels, marmots, dor-
mice, &c, characterized by long, bushy
tails, and their adaptation to a residence
in trees.

SCLERODE'RMI ( <nc\»,p6r, hard,
depua, skin). A family of Plectognathous
05

SCR

fishes, characterized hy their very hard
and granulated skins. The roughness of
the skin in some of the species has sug-
gested the common term of file-fishes.

SCLE'ROGEN (c-KXrjpop, hard, yevvdw,
to produce). The matter of lignification
which is deposited on the inner surface
of the cells of plants, contributing to
their thickness.

SCO'LIADjE. A family of fossorial
hymenopterous insects, named from the
genus scolia.

SCOLOPA'CIDjE (scolopax, the wood-
cock). The Snipe tribe ; a family of the
Grallatores, or Wading birds, charac-
terized by their long, slender, and feeble
bill.

SCOLYMI'NiE. A sub-family of the
Turbinellidce, or Turnip-shells, named
from the typical genus scolymus, and
characterized by a ponderous and rough
shell, with foliated spines or tubercles.

SCOMBE'RIDjE {scomber, the mack-
erel). The Mackerel tribe ; a family of
the Acanthopteryginus or spiny-finned
fishes, including the mackerel, tunny,
sword-fish, dory, dolphin, &c.

SCO'PIPEDS [scopce, a brush, pes, a
foot). A tribe of melliferous insects, in-
cluding those which have the tarsi of
the posterior feet furnished with a brush
of hairs.

SCORIAE (oKiapla, from o-Kcbp, excre-
ment). The scum or dross of metals ;
the refuse or useless part of any sub-
stance ; volcanic cinders ; &c.

SCO'RPIO. The Scorpion ; the eighth
of the zodiacal constellations, consisting
of forty-four stars, the principal of which
is Antares., It denotes the second month
of spring, extending from the 20th of
April to the 20th of May. The heat of
this month stimulates venomous rep-
tiles, and excites disease and pesti-
lence.

SCREW. One of the mechanical
powers. It may be considered as an in-
clined plane wrapped round a cylinder,
or as a cylinder having on its surface a
projecting thread inclined in all parts at
the same given angle to the horizon.
The cylinder fits into a block pierced
with an equal cylindrical aperture, on
the inner surface of which is cut a
groove, the exact counterpart of the
thread on the screw; hence we can
cause the screw to enter the block by
merely making it revolve about its
axis.

Endless Screw. The force of the screw
is sometimes employed to turn a wheel,

SEA

by acting on its teeth, the thread of the
screw passing between the teeth or cogs
of the wheel. In this case it is called a
perpetual or endless screw.

SCROPHULARIA'CE^E. The Fig-
wort tribe of Dicotyledonous plants.
Herbaceous plants with leaves opposite ;
flowers irregular, unsymmetrical ; sta-
mens 2 or 4, didynamous ; fruit capsular;
seeds albuminous.

SCURF OF PLANTS. A term ap-
plied in Botany to the thin, flat, mem-
branous disks, with a ragged margin,
formed of cellular tissue, springing from
the epidermis of plants. They are dis-
tinguished into scurf, properly so called,
and ramenta.

SCUTE'LLUM (dim. of scutum, a
shield). Apothecium. The botanical de-
signation of the little coloured cup or
disk, found in the substance of lichens ;
it is surrounded by a rim, and con-
tains the asci, or tubes filled with spo-
rules.

SCUTIBRANCHIA'TA {scutum, a
shield, branchice, gills). An order of
gasteropods which have pectinated gills
disposed in a special cavity, with shells
which are very wide, scarcely ever turbi-
nated, and cover the body and gills,
like a shield.

SCU'TIPEDS {scutum, a shield, pes, a
foot). The name given by Scopoli to
those birds which have the anterior part
of the leg covered with segments of un-
equal horny rings terminating on each
side in a groove.

SCUTUM SOBIESKI. Sobieski's
shield ; a modern northern constella-
tion, consisting of eight stars.

SCYLLA'RIANS. A tribe of macru-
rous decapods, established by Milne
Edwards on the genus scyllarus of Fa-
bricius, and forming one of the most re-
markable groups, distinguished at the
first glance by the singular conformation
of the external antennae. It comprises
the genera Scyllarus, Thenus, and Iba-
cus.

SEA. A portion of the ocean which
penetrates into a continent by a narrow
passage, and then spreads into a large
expanse, as the Mediterranean sea. The
term is, however, frequently employed
in a larger sense to denote the whole
volume of water which occupies the
lower portion of the surface of our globe,
or three-fourths of its entire superficies ;
in this sense it is synonymous with
ocean.
SEA WAX. Maltha; a white, solid,

SEC

SEE

waxy-looking fusible substance, found on
the Baikal lake in Siberia.

SEAMS. Thin layers which separate
two strata of greater magnitude.

SEASONS OF THE YEAR. The
four quarters of the year, commencing, —
the first, or Spring quarter, when the
sun enters Aries ; the second, or Sum-
mer, when he enters Cancer ; the third,
or Autumn, when he enters Libra; the
fourth, or Winter, when he enters Capri-
corn. The variety of the seasons de-
pends on the uniform direction of the
axis of the earth ; this is always carried
round parallel to itself, and pointing
always to the same vanishing point in
the sphere of the fixed stars.

SEBA'CIC ACID {sebum, lard). An
acid obtained from the oleic, or from any
of the fats which contain this acid. Its
salts are called sebates.

SECANT (seco, to cut). A line which
cuts another line. In trigonometry, it is
a straight line drawn from the centre of
a circle to one extremity of an arc, and
produced until it meets the tangent to
the other extremity. The secant of an
arc is a third proportional to the cosine
and the radius ; hence, if the radius be
taken as unity, the secant is the recipro-
cal of the cosine. See Trigonometry.

SECOND. The sixtieth part of a
minute, in calculations either of time or
of angular measure. See Hour.

SECOND (in Music). An interval
producing a discord, the rartio of which
is 9 J 8. There are three kinds of second,
the minor or semitone, as EF; the
major, or CD; and the extreme sharp
second, as CD ft.

SECONDARIES. Secondary circles.
In Astronomy, all those circles on the
sphere which intersect a primary circle
at right angles, passing through the axis
and the poles, are called secondaries.

SECONDARY STRATA. An exten-
sive series of the stratified rocks which
compose the crust of the globe, with cer-
tain characters in common, which distin-
guish them from another series below
them called primary, and from a third
series above them called tertiary.

SECRETION (secernn, to separate).
A general term for that function in ani-
mal and vegetable physiology, by which
certain products are secreted or separated
from the circulating fluid, — from the
blood in animals, from the sap in plants.
The same term is also applied to the
products so secreted or separated. Thus,
the liver secretes bile, and bile is called
299

the secretion of the liver; the tuber
secretes starch, and this is termed a
secretion of the tuber.

SECTOR (seco, to cut). A sector of a
circle is the figure contained by two radii
and the arc between them ; it thus differs
from a segment, which is included by an
arc and its chord. A sector with a right
angle is a fourth part of a circle, and its
arc is called a " quadrant." The term
sector is also applied to a mathematical
instrument, the purpose of which is to
facilitate the graphical determination
of proportional quantities; hence it is
termed by the French the compass of
proportion.

SECTOR, ZENITH. A peculiar mo-
dification of the altitude and azimuth
instrument. It is adapted for the very
exact observation of stars in or near the
zenith, by giving a great length to the
vertical axis, and suppressing all the
circumference of the vertical circle, ex-
cept a few degrees of its lower part, by
which a great length of radius, and a
consequent proportional enlargement of
the divisions of its arc, are obtained.

SECULAR and PERIODIC. In
Astronomy, any deviation from the mean
motion or mean orbit of a celestial body
is called an inequality, and the numeri-
cal expression of the magnitude and
period of the inequality is called an
equation. An equation of this kind is
said to be periodic, when the motions it
expresses perform their changes in a
comparatively short period of time ; secu-
lar, when the changes are so gradual as
to be insensible only after the lapse of
centuries. Thus, the lunar evection is a
periodic, the acceleration of the moon's
mean motion, a secular inequality.

SECULAR REFRIGERATION (sa:-
culum, an age). The periodical cooling
and consolidation of the globe from a
supposed original state of fluidity from
heat.

SECUNDINE. The name given by
botanists to that sac of the ovule which
reposes immediately upon the primine,
and often contracts an adhesion with it,
so that the two integuments become con-
founded. Its point is usually protruded
beyond the foramen of the primine.

SEDIMENTARY ROCKS. Rocks
which have been formed by their mate-
rials having been thrown down from a
state of suspension or solution in water.

SEED OF PLANTS. The seed of a
plant is the ovule in its matured state ;
it is then a body, enclosed in a pericarp,
06

SEM

SEP

clothed with its own integuments, and
containing the rudiment of a future
plant. It is the point of development at
which vegetation stops, and beyond which
no increase, in the same direction with
itself, can take place.

SEGMENT (seco, to cut). That part
of a circle which is contained by a
straight line and the circumference it
cuts off. 1. The angle of a segment is
that which is contained by the straight
line and the circumference. 2. An angle
in a segment is the angle contained by
two straight lines drawn from any point
in the circumference of the segment to
the extremities of the straight line which
is the base of the segment. 3. Similar
segments of a circle are those in which
the angles are equal, or which contain
equal angles.

SELA'CHII. The Shark and Ray
tribe; an order of Chondropterygious or
cartilaginous fishes, distinguished by the
peculiar conformation of the mouth, the
jaws not being united into a ring, and
the true jaw-bones not being developed.
Several of the species are viviparous.

SE'LENITE {(Te\f]vt), the moon).
Sparry gypsum. A simple mineral, con-
sisting of pure gypsum, or sulphate of
lime.

SELENIUM {<re\t]vn, the moon). A
metal discovered in the sulphur of Fah-
lun, and named from its strong analogy
to another metal, tellurium, which is
named from tellus, the earth. It com-
bines with oxygen, forming the selenious
and selenic acids.

SEMI-. A Latin prefix, derived from
semis, half, and corresponding with the
term hemi in Greek compounds.

1. Semi-amplexicaul. Half stem-em-
bracing ; as applied to the leaves of plants
which partially sheath the stem.

2. Semi-anatropous. A term denoting
the same as amphitropous, except that in
the former the ovule is parallel with the
funiculus, while in the latter it is at
right angles with it.

3. Semi-circle. Half a circle ; a figure
contained by a diameter of a circle, and
the portion of the circumference cut off
by the diameter.

4. Semi-diameter. Half a diameter, or
a right line drawn from the centre of a
circle, or sphere, to its circumference ; it
is otherwise called a radius.

5. Semi-flosculous. A term applied to
the ligulate, or strap-shaped, florets of
some of the compositae, as of dandelion ;
in this and similar plants, the limbs of

300

the cohering petals are united on one
side of the floret, giving it the appear-
ance of half a floret.

6. Semi-metals. A term formerly ap-
plied to those bodies which possess the
qualities of metals, with the exception
of malleability.

7. Semi- opal. A variety of opal, of
white, grey, and brown colours ; some-
times in spotted, striped, or clouded deli-
neations ; occurring in porphyry and
amygdaloid.

8. Semi-quadrate or semi-quartile. An
astrological term denoting an aspect of
the planets when distant from one an-
other half a right angle, or 45°. The
terms semi-quartile and semi-sextile have
similar meanings, the former denoting
the half of a fifth of the complete circle,
or 36°, the latter the half of a sixth, or
30°.

9. Semi-tone. An interval in music
whose ratio is 16 \ 15, as CC % It can-
not correctly be called half a tone, as
there are different kinds of semitones,
greater, lesser, and natural.

SENECTI'N^. Sea-snails ; a sub-
family of the Trochidce, named from the
genus senectus, resembling the garden
snail in form, but perlaceous, and fur-
nished with a thick, round, fleshy oper-
culum.

SEN'SIBLE (sentio, to perceive). A
vague term applied indifferently to a
body capable of receiving, of producing,
or of conducting sensation. It has been
suggested that the term sentient should
be applied to the first of these cases, and
sensitive to the third. In the fourth and
most ordinary acceptation of the word
sensible, it is used to express the state
of the intellectual powers.

SE'PAL. The botanical designation
of each of the leaves composing the
calyx, or external envelope of the floral
apparatus. When the leaves are distinct
from one another, the calyx is termed
poly-sepalous ; whe i they cohere, it
is called gamosepalous, or, incorrectly
though popularly, mono-sepalous. A se-
pal may be hollowed out into a conical
tube, as in larkspur, and is then said to
be spurred.

SE'PIADjE (sepia, the cuttle-fish). A
family of cephalopods, vulgarly known
as cuttle-fish , and divisible into two
groups, the octopods and the decapods.

SEPTA'RIA {septum, a division). Lu-
di Helmontii. Flattened balls of stone,
generally a kind of iron-stone, which, on
being split, are found to be separate i in

SER

SES

their interior into irregular masses.
From these septaria is manufactured the
material for building under water, known
as Parker's or Roman cement.

SEPTICI'DAL {septum, a division,
ccedo, to cut). That kind of dehiscence
of fruits, in which the septa separate
each into two laminae, as in rhododen-
dron. Formerly, botanists used to say
that in this sort of dehiscence the valves
were alternate with the dissepiments, or
that the valves had their margins turned
inwards.

SEPTI'FRAGAL {septum, a division,
frango, to break). That kind of de-
hiscence of fruits, in which the backs of
the carpels separate from the septa,
which adhere to the axis, as in convol-
vulus.

SERIES. In Mathematics, a series is a
set of terms, finite or infinite in number,
connected together by addition or sub-
traction, and formed upon some distinct
law. An arithmetical series is one in
which each term differs from the preced-
ing by the addition or subtraction of a
constant number or quantity; a geome-
trical series is one in which each term is
a multiple of the preceding by a con-
stant factor.

1. Series, infinite. A series of terms
proceeding according to some law, and
continued without limit. The sum of an
infinite series is the limit to which we
approach more nearly by adding more
terms, but which cannot be exceeded by
adding any number of terms whatever.

2. A convergent series is one which has
a sum or limit, as above defined ; a di-
vergent series is one which has no such
sum or limit. Hence, every infinite
series in Geometrical progression, in
which the common ratio is less than I,
is convergent.

3. Series, recurring. If each succeed-
ing term of a decreasing infinite series
bear an invariable relation to a certain
number of the preceding terms, the
series is called a Recurring Series, and
its sum may be found. Thus a + {a + 1)
x + (2 a + 2) a;2 + (3a + 3) a* + (5a + 5)
x* + . . . is a recurring series, the co-
efficient of each term being the sum of
the co-efficients of the two preceding
terms.

4. An exponential series is one whose
terms depend on exponential quantities ;
a logarithmic series is one whose terms
depend on logarithms ; and a circular
series, one whose terms depend on cir-
cular functions, as sines, co- sines, &c.

301

5. The general term of a series is a
function of some indeterminate quan-
tity x, which, on substituting succes-
sively the numbers 1, 2, 3, &c, for ar,
produces the terms of the series.

SERPENS. A northern constellation,
consisting of sixty-four stars. Mytho-
logically, it is the serpent carried by Ser-
pentarius, the serpent-bearer.

SERPENTARIUS. Ophiuchus. A
northern constellation, containing se-
venty-four stars, the principal of which
is Ras Aliagus.

SER'PENTINE. A rock of the pri-
mary series, closely related to diallage
rock, of irregular form and of various
colours : when opaque, it is named com-
mon serpentine ; when translucent,
noble or precious serpentine. It con-
sists of hydrate of magnesia with sub-
silicate of magnesia. The name is de-
rived from its frequent contrasts of
colour, like those of the skin of some
serpents.

SERPU'LEANS. A family of cepha-
lobranchiate annellides, inhabiting cylin-
drical and tortuous calcareous tubes;
generally parasitic on shells.

SERRICORNES {serra, a saw, cornu,
a horn). A family of the pentamerous
coleoptera, distinguished by the serrated
or toothed form of the antennae. They
have four palpi, and the body is com-
pletely covered by the elytra, or wing-
cases.

SE'RTULUM. A term applied by
some botanists to the simple umbel, the
latter term being by them restricted to
the compound form of this inflorescence.

SESQUI- (contracted from semisque,
and a half). A prefix to certain words,
denoting so much and half so much, the
whole of a thing and a half more. It is
used in chemical language when the ele-
ments of an oxide are as 1 to l£, or as
2 to 3. The sulphurets, carburets, &c,
of the same substance are similarly de-
signated. Hence, also, the word sescu-
plum (quasi sesqui-plum, from sesqui and
plica, a fold) ; thus sescuplo-carburet,
one and a half-fold carburet.

Sesqui-duplicate. A term sometimes
found in treatises on Geometry, signifying
the ratio in which the greater term is
twice and a half times the less ; as the
ratio of 10 to 4; of 15 to 6 ; &c.

SESSILE {sessilis, sitting). Destitute
of any support or peduncle, as a leaf
which has no stalk, or the shell of the
anomia. The term Sessiles has been
adopted for a division of the Cirrhopoda,

SH A

S ID

comprehending those species which are
not suspended by a pedicle.

SET OF CURRENT. The direction
of a current is called its set ; a current
which flows towards the nnw. quarter,
is said to set nnw. The velocity of a
current is called its drift.

SETA. Literally, a bristle ; hence
applied to the bristle-like stalk which
supports the theca of mosses ; and,
hence, the epithet setose denotes a sur-
face covered with short, stiff hairs, as the
leaf of bugloss, the pappus of some com-
posite plants, &c.

SEVENTH. In Music, a dissonant
interval, of which there are three kinds,
the minor or ordinary seventh, from G
to F; the diminished seventh, from C
sharp to B flat ; and the major or sharp
seventh, fro n C to B.

SE'VERITE. A hydrated silicate of
alumina, found near St. Sever in France,
in a gravelly soil, in pieces from two to
five inches in diameter.

SEXTANS. The Sextant; a modern
southern constellation, consisting of
forty-one stars, situated between Re-
gulus and Cor Hydrae.

SEXTANT. An astronomical and
nautical instrument, commonly called
Hartley's, by means of which the direct
angular distance of any two objects may
be measured, or the altitude of a single
one determined, either by measuring its
distance from the visible horizon (such
as the sea-offing, allowing for its dip), or
from its own reflection on the surface of
mercury. The principle of this instru-
ment is the optical property of reflected
rays, thus announced: — "The angle be-
tween the first and the last directions of a
ray which has suffered two reflections in
one plane, is equal to twice the inclina-
tion of the reflecting surfaces to each
other."

SEXTILE ASPECT. An astrological
term, denoting the aspect of two planets,
when they are distant from each other
the sixth part of a circle, or sixty de-
grees.

SEXUAL SYSTEM. A mode of ar-
ranging plants, invented by Linnaeus,
and founded upon the number and pecu-
liarities of the sexual organs. See
Botany.

SHADOW. If an opaque body be
enlightened on one side only, the side
which is more remote from the source of
light will continue dark, and beyond it
there will be a space not affected by the
light ; this constitutes the shadoio of the
302

I

opaque body. If any object intercept
this space, that side of it which is next
to the opaque body will be darkened by
the projection of the shadow upon it.

SHALE {schalen, German, to peel, to
split). A provincial term adopted by
geologists to denote an indurated slaty
clay, or argillaceous matter, indurated,
with a slaty structure, and a dull grey
streak, and naturally divided into laminae
parallel to the plane of deposition. When
much intermixed with carbonaceous mat-
ter, and impregnated with bitumen, it
is usually named bituminous shale.
When highly impregnated with silica,
it passes into flinty slate.

SHARP. A character in Music,
marked ft, employed to raise any note
of the natural scale, a semitone higher.
The double sharp, marked x , is used in
chromatic music for raising a note two
semitones above its natural state. Thus
C double sharp is D natural.

SHEAR-STEEL. This substance, so
called because fitted for making clothiers'
shears, scythes, &c, is prepared by lay-
ing several bars of common steel toge-
ther, and heating them in a furnace until
they acquire the welding temperature.
The bars are then beaten together with
forge-hammers, after which they are
drawn anew into bars for sale.

SHELL LIMESTONE. Muschelkalk.
A compact limestone, of a smoke-grey
colour, and in certain localities contain-
ing a great variety of fossils. The most
esteemed variety for ornamental pur-
poses is that from Carinthia, called
lumachella, or fire marble. Shell lime-
stone is distinguished from Magnesian
limestone by its never presenting the
shells of the genus Producta, which
occur in this deposit ; and from the Lias,
by the absence of the Ammonites and
Gryphaeae which characterize the latter.

SHELL MARL. A deposit of clay,
peat, and other substances mixed with
shells, which collects at the bottom of
lakes.

SHIELDS OF LICHENS. Little
coloured cups or lines, also called scu-
tella and apothecia, appearing on the
upper surface of lichens; they are sur-
rounded by a rim, and contain the asci,
or sporuliferous tubes.

SHINGLE. The loose and completely
water-worn gravel on the sea-shore.

SIDEREAL DAY (sidus, a star). The
space of time elapsing between two con-
secutive returns of a star to the same
meridian. This is equal to the time

SIL

SIL

occupied by one entire revolution of the
earth upon its axis. See Hour.

SIDEREAL YEAR (sidus, a star).
The period of time in which the earth
makes one complete revolution in its
orbit ; that is, from any given star to the
same again. See Hour.

SIDERUM. The name given by Berg-
mann to phosphuret of iron.

SI'ENITE or SY'ENITE. A compound
granular aggregated rock, composed of
felspar and hornblende, and sometimes
quartz and black mica. It is found at
Syene in Egypt, and other places.

SIGHT, FIELD OF. The field of a
telescope may be measured by directing
the instrument to some star in or very
near to the equator, care being taken
that it shall pass over the middle of the
field, and then count the number of
seconds which elapse during its passage :
four seconds of time will make an
angle of one minute for the field of
vision.

SIGNS of the ZODIAC. The ecliptic
is usually divided by astronomers and
by globe-makers into 1 2 signs of 30 de-
grees each, answering to twelve constel-
lations, with the following names and
signs ; the parts adjacent to the ecliptic
being called the zodiac: —

Aries T from 0° to 30°

Taurus 8 — 30° — 60°

Gemini II — 60° — 90°

Cancer 25 — 90° — 120°

Leo & — 120° — 150°

Virgo 1tt> — 150° — 180°

Libra :£=— 180° — 210°

Scorpio rq — 210° — 240°

Sagittarius ... $ — 240° — 270°
Capricornus ... Vf — 270° — 300°

Aquarius S» — 300° — 330°

Pisces K — 330°— 360°

Of these signs, the first six are called
northern, lying on the north side of the
equator ; and the last six are called
southern, being situated to the south of
the equator.

SILENA'CEiE. A sub-order of the
family of plants termed Caryophyllaceae,
distinguished from the other sub-order,
or Alsinacece, by the possession of a
tubular calyx and clawed petals.

SILEX. The Latin term for flint ;
the name of one of the pure earths, of
which flint is wholly composed ; in
chemical language, it is an oxide of
silicon, forming the basis of chalce-
dony, cornelian, jasper, &c. French
geologists have applied the term as a
generic name for all minerals composed
303

entirely of silex, of which there are
many different external forms.

1. Silica. Siliceous earth; the oxide
of silicon, constituting almost the whole
of silex, or flint. It combines with many
of the metallic oxides, and is hence
sometimes called silicic acid.

2. Silicate. A chemical compound of
silica and another substance, as silicate
of iron.

3. Siliceous. Of or belonging to the
earth of flint. A siliceous rock is one
composed mainly of silex.

4. Silicified. Any substance which is
petrified or mineralized by siliceous
earth.

5. Silicon or Silicium. An elementary
body very abundant in the mineral king-
dom, constituting the basis of silica. It
is a dark-brown, inflammable substance,
without metallic lustre.

SILI'CULA. A diminutive of siliqua,
and applied, in botany, to a fruit of the
same construction, but shorter and
broader than the siliqua, as in candy-
tuft.

SILIQUA. A fruit consisting of two
carpels cohering together, the placentae
of which are parietal, and separate from
the valves, presenting a kind of frame
called areplum, and connected by a mem-
branous expansion, as in the stock.

SI'LLIMANITE. A crystallized va-
riety of silicate of alumina, found at
Saybrook in Connecticut, in a vein of
quartz penetrating gneiss.

SILT. The more comminuted sand,
clay, and earth, which are transported by
running water. It is often accumulated
by currents in banks. Thus, the mouth
of a river is silted up when its entrance
into the sea is impeded by such accumu-
lations of loose materials.

SILU'RIAN SYSTEM. The name
given by Mr. Murchison to the upper
part of the lower series of secondary
rocks, from its being highly developed
in that part of Wales which was formerly
inhabited by the Silures, viz., the coun-
ties of Hereford, Radnor, Brecon, Caer-
marthen, and Pembroke. He divides it
into two portions — the Lower, comprising
the Llandeilo Flags and the Caradoc
Limestone ; and the Upper, consisting
of the Wenlock Limestone and the Lud-
low Rocks.

SILURIDiE. A family of malacoptery-
gious, or soft-spined fishes, distinguished
from all other families of the order by
the absence of true scales, having only a
naked skin, or large bony plates.

SI N

S I P

SILVAN. The name given by Werner
to the metal tellurium.

SILVER. Argentum. A white metal
occurring often in the metallic state in
mines, and in combination with ores of
lead, from which it is separated by cupel-
lation. Horn silver is the chloride, re-
sembling horn in consistence. Fulmi-
nating silver is an explosive substance,
formed of oxide of silver and ammonia.

SILVER GLANCE. Vitreous silver, or
sulphuret of silver; a mineral occurring
massive, crystallized, and in other ex-
ternal forms, among which are the lami-
nar and the capillary. The black silver
ore appears to be a pulverulent variety
of this species.

SIMARUBACEiE. The Quassia tribe
of Dicotyledonous plants. Trees or
shrubs with leaves alternate ; flowers
polypetalous ; stamens twice as many as
the petals, hypogynous ; ovarium 4- or 5-
celled ; fruit, indehiscent drupes.

SI'MIADiE (simia, an ape). A family
of Quadrumanous animals, including
the apes, monkeys, and baboons of the
Old World.

SIMILAR FIGURES. In Geometry,
figures are termed similar, when they
resemble one another in shape, without
reference to their size ; when the latter
point of resemblance exists, the figures
are said to be equal.

SI'MILOR. The designation of an
alloy of zinc and copper.

SIMOON. An Arabic* term denoting
poison, and applied to a hot wind which
occurs in most countries situated near
sandy deserts, and blows from the quar-
ter of the desert. In Turkey the wind
is called Samieli ; in Egypt, Khamsin ;
in Guinea and Senegambia, Harmat-
tan.

SIMPLE MINERAL. A term applied
to individual mineral substances, as dis-
tinguished from rocks, the latter being
usually an aggregation of simple mine-
rals. They are not simple in regard to
their nature ; for, when subjected to che-
mical analysis, they are found to consist
of a variety of different substances. Py-
rites is a simple mineral in the sense in
which we use the term, but it is a chemi-
cal compound of sulphur and iron.

SINE and COSINE. In Trigono-
metry, the sine of any arc of a circle is
the straight line drawn from one ex-
tremity of the arc perpendicular to the
radius passing through the other extre-
mity. The cosine is the sine of the com-
plement of an angle or arc, the prefix
304

co being merely the abbreviation of com-
plement, first introduced by Gunter.

SINGULAR TERM. A singular term,
in Logic, is that which stands for one
individual, and cannot, therefore, be
predicated affirmatively of any thing but
that individual. See Common Term.

A Singular Proposition is one which
has for its subject either a singular term,
or a common term limited to one indi-
vidual by a singular sign, e. g. " This."
Such a proposition is universal, when the
whole of the subject is spoken of; parti-
cular, when only a part is spoken of, e. g.
" Non omnis moriar."

SINTER (sintern, to drop). A Ger-
man name for a rock precipitated from
mineral waters. Calcareous sinter is car-
bonate of lime deposited in layers ; sili-
ceous sinter, a variety of common opal.

1. Sinter, ceraunian. A variety of
quartz consisting of siliceous tubes
found in the sands of the Senner Heath
in the county of Lippe, where, on ac-
count of their supposed origin, they are
called lightning tubes, and hence are
derived the terms fulgurite, astraphya-
lite, &c.

2. Sinter, quartz. Stalagmitic quartz,
the most remarkable varieties of which
are the siliceous concretions deposited
by the celebrated hot spring in Iceland,
the Geyser. Another variety is the pearl-
sinter from Santa-Fiora in Tuscany
(whence it has obtained the name of
fiorite), and from the island of Ischia.

SINUATED {sinus, a bay or cavity).
Having a wavy margin, produced by
alternations of projecting lobes and in-
dentations.

SIPHON (<ri<pu)v, a tube). A hydraulic
instrument used for emptying liquids
from one vessel into another, without
disturbing the mass of the liquid. It is
merely a bent tube of which one leg is
longer than the other. When this is
filled with liquid, and the shorter leg
is immersed in a vessel to be emptied,
the atmospheric pressure on the surface
of the liquid will cause it to rise in the
shorter leg, and thus a continuous stream
will be produced.

SIPHON (in Zoology). A sucker ; a
fleshy process, generally long, cylindrical,
and hollow, protruded by the carnivorous
and testaceous animals from the base or
channel of their shells. The same term
is applied to the slender shelly tube
which connects the chambers of cepha-
lopod shells, or the nautili.

SIPHONO'STOMOUS (<n>«v, a tube,

SLA

SMI

trrona, a mouth). A designation of ani-
mals with a suctorious mouth like a
tube. The term is usually applied to an
order of the edentulous Crustacea which
are so characterized, as the caligus.
Under the term Siphonobranchiata, De
Blainville describes the first order of his
first sub-class of Mollusca, Paracephalo-
phora dioica.

SIPHU'NCLE. A long tube, partly
calcareous and membranous, which passes
through all the compartments of the shells
of certain cephalopods ; the membranous
siphuncle is continued into the animal,
and terminates in a cavity contained
within its body.

SIRE'NE. An instrument, invented
by Caignard Latour, for determining the
number of musical vibrations. The notes
are produced in it by breaks in a con-
stant stream of air, these breaks occur-
ring at equal intervals of time, so that
after each break there is a new wave of
air. When the number of waves amounts
to 32 in a second, the lowest note is
emitted, and the number may be in-
creased to about 16,000 per second, when
the note degenerates into a mere whistle.

SIR'IUS. The Dog-star; a star of the
first magnitude in the southern constel-
lation Canis major.

SIRO'CCO. The name given to the
hot wind which occasionally blows in
Sicily, and which is supposed to derive
its origin from the excessively heated
deserts of Africa. See Solano.

SPTTINjE {sittia, the nuthatch). Sit-
tine birds, or Nuthatches ; a family of the
Reptatrices of Macgillivray. In the form
of the feet and claws these birds resemble
the Certhiadae, while in the structure of
the bill they somewhat resemble Wood-
peckers, and in their general aspect and
habits approach the Parinae. By other
writers, the Nuthatches are included in
the family Certhiadae, belonging to the
Insessores or Perchers.

SKO'RODITE (vKdpodov, garlic). Cu-
preous arseniate of iron ; a mineral sub-
stance which appears to be closely allied
to Bournon's martial arseniate of copper.
The name is derived from the garlicky
odour it emits when heated.

SKY. The popular name for the blue
expanse of atmospheric air. The blue
colour of the sky has been found by
Brewster to be due to light which has
suffered polarization, and which is, there-
fore, reflected light, like the white light
of clouds.

SLAG. The glassy compounds pro-
305

duced during the reduction of metallic
ores by means of fluxes.

SLATE. Clay slate. A geological term
for the well-known stone with which
houses are roofed, and which consists
mainly of clay. It agrees with mica-
slate in its fissile structure, but differs in
having its cleavage more or less trans-
verse to the line of its stratification.

SLATE-CLAY. Another name for
shale, or argillaceous matter, indurated,
with a slaty structure, and a dull grey
streak.

SLATE-SPAR. Schiefer Spar. The
name of a sub-species of limestone.

SLATE, STONESFIELD. A com-
ponent part of the Lower Oolitic Series,
consisting of slaty calcareous lime-
stone.

SLATY GNEISS. A variety of gneiss,
of which the texture is usually minute,
and the scales of mica or crystals of
hornblende form small laminae, render-
ing the rock easily fissile.

SLEET. Half-melted snow, consti-
tuting an intermediate condition between
that of snow and that of rain.

SLPCKENSIDE. The name given
by the Derbyshire miners to the compact
and specular variety of galena, or sul-
phuret of lead, from the smoothness of
its surface. It occurs lining the walls of
very narrow rents.

SLIDING RULE. An instrument
consisting of two parts, one of which
slides along the other, for the mechanical
performance of addition and subtraction,
and also of multiplication and division,
by the use of logarithmic scales, instead
of scales of equal parts.

SMALT (schalmz, Germ.). A blue-
coloured glass, obtained by heating zaffre,
or the impure oxide of cobalt, with sand
and potash, reduced to powder. It is the
blue-stone used in washing.

SMARA'GD (arfjidpafdoi). Anciently,
this term was applied to a semi-trans-
parent stone like the aqua marina, but is
now usually employed to designate the
emerald.

SMELTING. The reduction of me-
tallic ores, for" the purpose of extricating
the pure metal. With the ore and fuel a
third substance, called a flux, is usually
added, the object of which is to form a
fusible compound with the earthy matter
of the ore.

SMILA'CEjE. The Smilax tribe of
Monocotyledonous plants. Herbaceous
climbing plants ; flowers hexapetalo'ide-
ous, hermaphrodite, sometimes diced-

SOD

SOL

ous ; stamens 6 ; ovarium 3-celled ; fruit
a berry.

SMOKE. Smoke consists of the un-
consumed gaseous elements of any body,
and, consequently, arises from imperfect
combustion.

SNOW. The frozen visible vapour
composing clouds. A flake of snow ex-
hibits a beautiful display of minute crys-
tals, often possessing the greatest variety
of forms. The production of snow offers
the most simple case of the precipitation
of water from the atmosphere.

SNOW LINE. That limit of elevation
in every latitude at which the air attains
the temperature of freezing water. The
line of perpetual congelation is, of course,
the summer limit.

SNOW, RED. The colouring matter
of this substance appears to be an alga-
ceous plant, named protococcus nivalis.
Agardh's definition of Protococcus is
merely, " plants with aggregated, not
mucous globules." To this Greville
added, " globules containing granules
seated on a transparent gelatinous
mass."

SNOWDON ROCKS. One of the
subordinate divisions of the Cambrian
Group of Rocks, of many colours and
textures, varying from fragmentary to
the finest roofing-slate.

SOAP. A compound, in definite pro-
portions, of certain principles in oils,
fats, or resin, with a salifiable base.
Hard soap is made of soda and fatty or
resinous matters ; soft soap is made of
caustic potash and acid oil or fat.

SOAPSTONE. Steatite. A mineral
consisting of silicate of alumina and
magnesia, and named from its resem-
blance to mottled soap and from its unc-
tuous feel.

SO'BOLES. The botanical term for
the creeping stem, or slender stem of cer-
tain plants, which creeps horizontally
below the surface of the earth, emitting
roots and new plants at intervals, as in
triticum repens.

SODA. The protoxide of sodium ; an
alkali procured from the ashes of marine
plants ; formerly called the mineral
alkali, from its being found native,
under the name of natron, in mineral
seams or crusts.

' SODA-WATER. A solution of the
bicarbonate of soda in water, when an
additional quantity of carbonic acid has
been forcibly combined with it.

SO'DALITE. A mineral substance
consisting of a silicate of soda and alu-
306

mina, found in Greenland, in Mount
Vesuvius, and in Siberia.

SODIUM. Natrium. A white metal
with the aspect of silver, soft and mal-
leable at 32°, quite liquid at 194°, and
volatilized at a red heat. Davy obtained
this metal by the voltaic decomposition
of soda, immediately after the discovery
of potassium.

SOIL, VEGETABLE. The external
thin layer of earth in which plants grow,
composed of fragments of minerals, vege-
tables, and animals, reduced to a great
degree of tenuity.

SOL. The Sun; a globe, 1,300,000
times greater than the earth, and situated
at a mean distance of 94^ millions of
miles from the earth.

SOLANA'CE^E. The Nightshade tribe
of dicotyledonous plants. Herbaceous
plants or shrubs, with leaves alternate ;
flowers monopetalous, regular; stamens
inserted into the corolla; ovarium 2-
celled ; fruit succulent.

SOLA'NO. The name given to a hot
wind which blows in Spain and Portugal.
It is a modified sirocco.

SOLAR DAY. The interval between
two transits of the sun over the meri-
dian. It is longer than the sidereal day ;
for if the sun move slowly eastward, and
if it be on the meridian with a certain
star to-day, then to-morrow, when that
star comes on the meridian, the sun
will be a little to the eastward, or not
yet on the meridian : that is, the solar
day is not quite completed in a sidereal
day.

SOLAR PHOSPHORUS. A general
term for those substances which, after
exposure to light, exhibit phosphorescent
properties, as Canton's phosphorus, &c.

SOLAR SYSTEM. The Solar System
comprises the sun as a centre, and thirty
other bodies, which revolve round him
in regular periods and at various dis-
tances. See Planet.

SOLDER. A simple or mixed metal,
by means of which metallic bodies can
be firmly united with each other. Hard
solders are ductile, malleable, and are
usually prepared of the same metal with
that which is to be soldered, with the
addition of some other ; soft solders melt
readily, are partly brittle, and therefore
not malleable ; bismuth is much used in
the composition of soft solders, from its
capability of forming with several metals
compounds of remarkable fusibility.

SOLDERING. The process of uniting
the surfaces of metals, by the interven-

SOL

SOL

tion of a more fusible metal, which,
being melted upon each surface, serves,
partly by chemical attraction, and partly
by cohesive force, to bind them together.
See Solder.

Soldering, autogenous. This process
consists in the union of two pieces of
metal without the interposition of any
solder, by fusing them at the point of
junction by jets of flame from a gas
blow -pipe.

SOLENPNjE. The Solens; a sub-
family of the Myadae, or Gaping bi-
valves, named from the genus solen, and
having their shells always open at both
extremities.

SO'LENOID (a-a>\r]v, a channel, a cy-
lindrical box, ei3or, likeness). The name
given by Ampere to what is otherwise
called an electro-dynamical screw, or elec-
tro-dynamical cylinder. It consists of a
linear series of circular currents passing
at right angles to the axis of the spiral
conductor.

SOLFATA'RA. A volcanic vent from
which sulphur, sulphureous, watery, and
acid vapours and gases are emitted. The
name is derived from Solfaterra, the cele-
brated mountain of Naples, called by the
ancients Phlegrtei campi.

SOLID. In geometry, a solid figure is
one enclosed by, at least, four planes or
faces, and named from the number of its
faces ; thus a figure with four faces is
called a tetrahedron ; one with six, a
hexahedron; those with more than six,
polyhedrons. Solids are also named ac-
cording to the figures and positions of
their faces, as the prism, the parallelo-
piped, &c.

1. Solid dimension. Length is said to
be a quantity of one dimension, surface
of two, and solidity of three, viz. length,
breadth, and thickness. The right line,
the right surface or rectangle, and the
right solid or rectangular parallelopiped
are the implements of mensuration.

2. Solid of least resistance. A term
applied to a geometrical solid of such a
shape as will enable it to move with the
least resistance through the air, water,
or other fluid. Such a solid is a conoid.

3. Solids', regular. A regular solid is
one whose faces are equal, equilateral,
and equiangular plane figures. There
are, but cannot be more than, five regu-
lar solids ; three of these have triangular
faces, one square faces, and the remain-
ing one pentagonal faces.

4. Solid problem. A solid, as distin-
guished from a plane, problem, in geo-

307

metry, is one which cannot be con-
structed by the intersections of circles
and straight lines, but requires for its
construction the description of one or
more conic sections.

SOLID (in Physics). A term denoting
that constitution of matter in which the
attractive forces of the molecules are
greater than the repulsive, and the
molecules consequently cohere with more
or less force. In the liquid state, the
two forces are balanced ; in the gaseous
the repulsive predominates.

SOLIDIFICATION. The condition
exactly opposed to liquefaction; it is
the state assumed by liquid bodies on
parting with their free caloric. With-
out adhering strictly to this rule, we
generally use the term solidification, when
we speak of such fluids as become solid
at a temperature higher than that of
freezing water; and freezing, when we
speak of such as become solid at a point
below 32°.

SOLIDU'NGULA (sola ungula, a sin-
gle hoof). Solipeds. A group of pachy-
dermatous animals, comprising quadru-
peds with only one apparent toe, and a
single hoof to each foot, as the horse.

SOLITA'RIUS. The Hermit ; an ob-
scure cons ellation of Lemonnier, situ-
ated a little above Centaurus, near the
tail of Hydra.

SO'LSTICES {sol, the sun, sto, to
stand). The two extreme points of the
Sun's apparent course north and south
of the equator. These are the first points
of Cancer and of Capricorn, where the
sun appears to make a stand, going nei-
ther northward nor southward. The two
corresponding periods of the year are
called the Summer and the Winter sol-
stices, from the seasons in which the
apparent standings of the sun occur.

SOLUBI'LITY. A contrivance of
nature for facilitating the dispersion of
seeds in some plants. It arises from the
presence of certain transverse contrac-
tions of a 1-celled pericarp, through
which it finally separates into several
closed portions, as in ornithopus, entada,
&c.

SOLUTION {solvo, to dissolve). The
operation of dissolving a solid or aeri-
form body in a liquid. The condition of
the solid or aeriform body is called its
solution ; the liquid which effects the
change is the solvent. When the liquid
will dissolve no more of the solid, but
allows the excess to be deposited on the
bottom of the vessel, it is said to be satti-

SON

SOR

rated, and the mixed fluid is then a
saturated solution of the substance which
it contains.

1. Chemical solution. This term de-
notes that a perfect chemical union of
the solid with the liquid is produced, in
accordance with the laws of definite pro-
portions. Both the constituents of the
compound exhibit a change in their pro-
perties, and are combined in an entirely
new substance formed by their union,
which substance, on the completion of
the process, generally assumes a solid
form, that is, it becomes crystallized.

2. Mechanical solution. This is the
mere union of a solid with a liquid, in
such a manner that its aggregate form is
changed without any alteration being
effected in the chemical properties of
either the solid or its solvent. If the
latter be separated from the solution, as
by heat, the former which has been dis-
solved is obtained again with its chemi-
cal properties unaltered.

3. Moist and dry solutions. In the
former, at least one of the bodies, the
solvent, must be a liquid ; in the latter,
both of the substances are solids, and
liquefaction must be brought about by
means of heat before any combination
will take place. Bronze, for instance, is
such a solution of copper and tin.

SO'LVENT (solvo, to dissolve). A
fluid which causes the solution of a solid
or aeriform body ; chemically, a men-
struum. Some of the most powerful
solvents are the sulphuric, nitric, and
chloric acids.

SOMMERVILLITE. A new mineral
from Vesuvius, occurring in cavities with
crystallized black mica.

SO'MMITE. Nepheline. Rhomboidal
felspar, occurring, in drusy cavities, at
Monte Somma, near Naples, in granular
limestone.

SONI'FEROUS BODIES. For the
production of sound there is required,
besides the sonorous body, one that is
adapted to convey the sound, or rather
the vibrations, of the former body to the
ear : bodies of this class are called soni-
ferous bodies, and they are such as can
transmit the vibrations, imparted to
them by the sonorous bodies, in all
directions throughout their mass, and
with equal velocity.

SONO'METER. An apparatus for
illustrating the phenomena presented by
sonorous bodies, and the ratios of their
vibrations, by the transverse vibrations
of tense cords. See Monochord.
308

SONOROUS FIGURES. This sub-
ject has been already noticed under the
term Nodal Lines. To make these figures
visible, and to render them permanent,
strew some fine sand on a disc of glass
or metal ; hold the disc firmly between
two fingers, and draw a violin-bow down
on its edge, and a musical note will be
heard ; at the same instant the sand will
be in motion and gather itself to those
parts which continue at rest, i. e. to the
nodal lines. The figures may also be
seen if a small quantity of water be
poured on the plate, nay, even by the
rays of light falling on it.

SO'PHISM {aocpiana, a captious
argument, a fallacy). An argument
which appears true, but is fallacious.
Sophisms are generally traceable to the
assumption of doubtful premises, or the
assumption of a hypothetical cause.

SORBIC ACID. An acid obtained
from the berries of the Sorbus aucuparia,
or Mountain Ash. It appears that the
sorbic and pure malic acids are identical.
Sorbates are compounds of sorbic or
malic acid with the salifiable bases.

SORE'DIA (dim. of o-o>p6r, a heap).
Globuli ; glomeruli. Small heaps of
powdery bodies lying upon any part of
the surface of the thallus of lichens.
The bodies of which the soredia are
composed, are called conidia by Link,
and propagula by others.

SORI'CID^. The Shrew tribe; a
family of the insectivorous vertebrata,
consisting of a kind of carnivorous mice,
which, though they do not burrow, like
the talpidae, retire into holes during the
winter for repose, and are partially
aquatic in their habits.

SORFTES ((rtopetTnf, heaped up, from
c-wpo?, a heap). In logic, a heap of syllo-
gisms, the conclusion of each forming the
premiss of the next in order. In the
abridged , form in which this argument
occurs, the predicate of the first pro-
position is made the subject of the
next; and so on, to any length, till,
finally, the predicate of the last of the
premises is predicated (in the conclusion)
of the subject of the first : e. g. A is B,
B is C, C is D, D is E ; therefore A is E.

SORO'SIS (o-upo?, a heap). A collec-
tive fruit, consisting of a juicy spike or
raceme, having all its ovaria and floral
envelopes cohering into a single mass, as
in the mulberry, the pine-apple, the
bread-fruit, &c.

SORUS (<ro)p6?, a heap). The botani-
cal term for each cluster of sporuliferous

sou

SPE

thecae developed on the under surface of
the fronds of Ferus.

SO'THIAC PERIOD. A term em-
ployed in the calendar of the Egyptians
and the Persians. Their year is supposed
to have comprised 365 days, so that every
four years they lost a day in the solar year,
and, after a period of 1460 years, called
the Sothiac Period, or great canicular
year, the civil and the solar years recom-
menced at the same time ; or, in other
words, the canicula or dog-star would
then again rise heliacally at the be-
ginning of their year. The 365 days of
the year composed twelve months, each
of thirty days, and the five remaining
days were added under the name of
epagomencc, or supplementary days.

SOUND. A sensation produced through
the ear, by the vibrating or tremulous
motion of a sounding body. This mo-
tion is communicated to the surrounding
air, and is conveyed by this medium to
the drum of the ear, which also undergoes
a vibrating motion, and this last motion,
by throwing the auditory nerves into
action, produces the sensation of hear-
ing.

1. Sound, waves of. Every vibration of
a sonorous body produces a progressive
wave in the air, which moves in a di-
rection perpendicular to the surface of
such body. These undulations are called
waves of sound, and every right line, per-
pendicular to their surface, or to that of
the sonorous body, is called a ray of
sound. It has been supposed that a
wave of vibration, " the sigh of a drown-
ing slave,"— proceeds in constant undu-
lation through space, and a similar idea
has been applied to the radiations of
light from external objects.

2. Sound, Musical. When a number
of sounds, or vibrations, succeed one
another with such regularity as to pro-
duce the impression of a single sound,
this is called a musical sound. The
quantity of a musical sound depends on
the extent and velocity of the vibrations,
and corresponds to the strength or in-
tensity of the sound. The quality of a
sound is independent of its quantity, and
relates to the different instruments by
which it is emitted, as by the human
voice, the cord of a violin, &c. Our
appreciation of the quality of sounds has
not been satisfactorily explained.

SOUNDINGS. This term denotes, in

hydrography, the depths of water in rivers,

harbours, along shore, and even in the

open seas. The term is also applied to the

309

nature of the ground at the bottom of the
water.

SPA WATER. An acidulous chaly-
beate, containing more iron and carbonic
acid than any other mineral spring.

SPACE {spatium). A general term for
extension in all directions. From the
idea of space follows that of form, which
is the conception of the manner in which
one part of space is separated from the
rest ; and from the investigation of forms
arises geometry. In this restricted sig-
nification, space denotes area, as when
it is said that two straight lines cannot
enclose a space, that is, an area.

SPADIX. A form of inflorescence, in
which the flowers are arranged close to-
gether upon a succulent axis, which is
enveloped in a sheath, or spathe. This
mode of inflorescence is characteristic of
the natural orders Araceae and Acoraceae.

SPANGLED ROD. A glass tube, on
the surface of which are pasted spangles
of tinfoil in a spiral form and at small
intervals. An electric spark transmitted
along such a conductor appears at the
same instant at all the intervals.

SPANISH CHALK. Steatite, or
soapstone; a sub-species of rhomboidal
mica.

SPAR (spath, German). A term fre-
quently applied to stones, the broken
surfaces of which present polished shi-
ning plates, placed over one another in
horizontal layers. This is the sparry
texture, and minerals of this kind are
generally called spathose.

SPA'RID^. Sparoides. A family of
acanthopterygious fishes, named from
the genus sparus, or Gilt-head. The
palate is edentulous, but the jaws are
well furnished with teeth, and it is upon
the various modifications of the teeth
that the genera are formed.

SPARRY ANHYDRITE Cube. spar.
A sub-species of prismatic gypsum, found
in the salt-mines of Halle, &e.

SPARRY IRON. Carbonate of iron,
found abundantly in limestone. It
affords an iron well suited for conver-
sion into steel.

SPATHE' {cnrddr), any broad plate, of
wood or metal ; a flower-sheath). The
botanical term for a large bract, which
envelopes the spadix of the arum and
other plants.

SPECIES. A logical species is a pre-
dicate which is considered as expressing
the whole essence of the individuals of
which it is affirmed. A predicable which
expresses only a part, is of two kinds : it

SPE

SP IT

may express the material part, and is
then called the genus ; or the formal and
distinguishing part, and is then called
the differentia. Hence the genus and
differentia, taken together, constitute the
species ; e. g. " rational" and " animal,"
constitute "man."

1. Species in Natural History. Natu-
ralists employ the term "species" in a
technical sense, or " second intention,"
when applied to organized beings. In
this case it denotes such individuals as
are supposed to be descended from a com-
mon stock, or which might have so de-
scended ; viz. which resemble one an-
other (to use Cuvier's expression) as
much as those of the same stock do.

2. Species, in Mathematics. Euclid
employed the word ' species' in its pri-
mitive sense of appearance : when the
form of a figure is given, he speaks of
the figure as given 'in species;' thus,
" rectilineal figures are said to be given
in species, which have each of their
angles given, and the ratios of their sides
given.,r

3. The term species was employed by
Vieta in its logical sense, as opposed to
individual, in designating the algebraical
notation in those cases in which letters
were used for numbers in a general sense.
Thus he termed the logistics, or the sci-
ence of calculation, specious ; and, hence,
the language of algebra was, for some
time, called the specious notation.

SPECIFIC. A term denoting any pro-
perty which is not general, but confined
to an individual or a species.

SPECTRUM. This Latin term de-
notes an ideal form, and is applied to
certain optical phaenomena, described
under the term colours accidental ; and
to the effect of refraction on a ray of
light, explained under the word pris-
matic spectrum.

SPECULAR IRON ORE. Iron-
glance, or fer oligiste of the French. A
sub-species of rhomboidal iron ore, com-
prising two varieties, viz. the common,
occurring in beds in primitive moun-
tains, and affording an excellent malle-
able iron ; and the micaceous, found in
beds in mica slate, and yielding an iron
well suited for cast ware.

SPE'CULUM. The Latin term for a
looking-glass ; a name frequently given
to a mirror used for any scientific pur-
pose, as in a reflecting telescope. See
Mirror.

SPECULUM METAL {speculum, a
looking-glass). An alloy of about two
310

parts of copper and one of tin ; used for
making mirrors.

SPEISS. An artificial arseniuret of
nickel, containing about 54 per cent, of
nickel. It collects at the bottom of cru-
cibles in which smalt or cobalt blue is
prepared.

SPELTER. The name by which zinc
is known in commerce; but it usually
contains some lead and sulphur.

SPERMATOCYSTI'DIUM (<nrepna,
a seed, kvctk, a bladder). The name
given by Hedwig to the male organ of
mosses ; it is a pedunculated oblong sac,
containing a fluid mixea with a granular
pulp, which is discharged with some
force from the sac on the application of
water. By other writers these bodies are
called staminidia or antheridia.

SPERMATO'PHORA (airep/ua, seed,
0epw, to carry). The cylindrical capsules
or sheaths in the cephalopods which con-
vey the sperm. They are also called the
moving filaments of Needham, their dis-
coverer.

SPERMATOZO'A (vwepua, seed,
£u>ov, an animal). Zoosperms, or ani-
malcules found in the vas deferens and
the vesiculae seminales of animals, and,
it is said, in cryptogamic plants, and in
the pollen grains of the higher orders of
plants.

SPE'RMODERM (anep/jia, seed, dep-
ict, skin). The testa, primine, or exter-
nal membrane of the seed of plants. The
term is sometimes applied collectively to
all the integuments of the seed.

SPH^RE'NCHYMA («r0atpa, a
sphere, e^xv^a, any thing poured in).
Merenchyma. The name given by Mor-
ren to the spherical variety of the paren-
chyma of plants.

fcPHLEROSIDE'RITE. Sparry iron
ore. Carbonate of iron, occurring crys-
tallized, fibrous, massive, and botryoidal.

SPH^E'RULITE {ccpatpa, a sphere,
\t'0os\ a stone). A silicate of alumina,
occurring in small botryoidal and sphe-
roidal masses, imbedded in pitchstone,
in pearlstone, &c.

SPHALERO-CA'RPIUM (<r0a\eP<ir,
delusive, napnos, fruit). A botanical de-
signation of the collective fruit of the
yew, blitum, &c, described as an inde-
hiscent, one-seeded pericarp, enclosed
within a fleshy perianth. This is the
nux baccata of authors.

SPHE'CID/E Sphegides. A family
of hymenopterous insects of the section
Fossores, named from the typical genus
sphex, one species of which has been

SPH

SPI

found in England, but appears to be ex-
tremely rare.

SPHENE. Prismatic titanium ore;
a silico-titanite of lime, comprising the
common and the foliated varieties.

SPHERE {<T(patpa, sphaera). A geo-
metrical solid described by the revolution
of a semicircle about its diameter, which
remains unmoved, and constitutes the
axis of the sphere. A sphere is bounded
by a curve surface, such that every point
thereon is situated at an equal distance
from a point within the solid called the
centre. The diameter of a sphere is any
straight line which passes through the
centre, and is terminated both ways by
the superficies of the sphere.

1. The term Sphere is applied, in astro-
nomy, to the great concavity formed by
the space surrounding our globe, in
which we see the celestial bodies. It
appears to revolve upon the two poles.

2. Those places with respect to which
the poles are situated in the horizon, are
said to have a right position of the sphere ;
those whose horizon coincides with the
equator, have a parallel position of the
sphere. For all intermediate places, the
position is oblique.

3. A great circle of a sphere is that
whose plane passes through the centre of
the sphere ; it divides the sphere into
two equal parts, and has the same centre
as the sphere itself. The plane of a
small circle does not pass through the
centre of the sphere.

4. Sphere, doctrine of the. An expres-
sion generally signifying the application
of the geometrical notions of the sphere
to geography and astronomy. It com-
prises an explanation of the circum-
stances under which spherical trigono
metry is applicable to these two sciences,
and the nomenclature which is employed
to facilitate explanation.

SPHE'RICAL (<r<paipa, a sphere). Re-
lating to a sphere. A spherical angle is
an angle formed on the surface of a
sphere by the intersection of two great
circles, or circles whose planes pass
through the centre. A spherical triangle
is a triangle formed by the intersecting
arcs of three such circles.

SPHERICAL EXCESS. In trigono-
metry, this denotes the sum by which
the three angles of any triangle on the
surface of a sphere or spheroid exceeds
two right angles.

SPHERICS (a<palpa, a sphere). The
doctrine of the properties of the sphere
considered as a geometrical body, and,
311

particularly, of the different circles de-
scribed on its surface.

SPHEROID (o-^cupct, a sphere, ei3o?,
likeness). A solid body approaching to
the figure of a sphere. There are two
kinds of spheroid, the oblate, and the ob-
long or prolate, the former shaped like an
orange, the latter like a lemon ; each
may be supposed to be described by the
revolution of a semi-ellipsis round its
axis, the former by the motion of the
semi-ellipsis round its lesser axis, the
latter by the ellipsis divided longwise,
and turned round the greater axis. The
earth is an oblate spheroid, being flat-
tened at the poles. See Ellipsoid.

SPHERO'METER (aQalpa, a sphere,
fjierpov, a measure). An instrument for
the accurate measurement of the thick-
ness of small bodies, the curvature of
optical glasses, &c.

SPHE'RULA. A little -sphere; a term
applied to the globose peridium of some
fungaceous plants, having a central open-
ing through which sporidia are emitted,
mixed with a gelatinous pulp.

SPHFNGIDjE. A family of lepido-
pterous insects, belonging to the section
Crepuscularia, and named from the
genus sphinx, one species of which (atro-
pos) is the death's-head hawk-moth, of
considerable size, and not uncommon in
some parts of England.

SPHRA'GIDE (o-0pa7if, a seal). Lem-
nian earth, supposed by the Turks to
possess medicinal virtue; hence it was
dug up by them with religious ceremo-
nies, divided into spindle-shaped pieces,
and stamped with a seal.

SPICA VIRGINIS. A star of the
first magnitude in the constellation
Virgo.

SPIKE. A form of inflorescence, in
which all the buds of an elongated
branch develop as flower-buds, without
forming peduncles, as in barley. It dif-
fers from a raceme merely in having its
flowers sessile.

SPIKELET. Locusta. A small spike ;
an integral portion of the inflorescence
of wheat and other grasses.

SPINE OF PLANTS. A small coni-
cal projection, consisting of a hardened
branch, sometimes bearing leaves. It
differs from the prickle in having a con-
siderable quantity of woody tissue in its
structure, and in being as much in com-
munication with the central parts of a
stem as branches them-elves.

SPI NELL. Aluminate of magnesia;
a sub species of octohedral corundum, of

SPI

SPO

a red colour, used as a precious stone.
"When it weighs four carats (about 16
grains), it is considered of equal
value with a diamond of half the
weight.

SPINELLANE. A silicate of alu-
mina, said to be a variety of Haiiyne,
found on the shores of the lake of Laach,
in a rock composed of glassy felspar,
quartz, hornblende, &c.

SPINI-CEREBRA'TA. The name
given by Dr. Grant to those vertebrated
animals, of which the central parts are
in the form of a lengthened dorsal
nervous cord, developed anteriorly into
a brain, and protected by a vertebral
column and cranium. These are the
myelencephala of Owen.

SPI'NNARETS. The articulated tubes
with which spiders construct their webs.

SPINTHERE. A substance supposed
to be a variety of sphene. It occurs in
the department of Isere in France, in-
crusting calcareous spar crystals.

SPIRACLES (spiraculum, a breathing
hole). The breathing pores in insects.

SPIRAL (ffTrelpa, any thing rolled
round on another thing). A curve which
turns round like a circle, but, instead of
ending where it began, it continues to
revolve, receding further and further
from the centre, like the spring which
moves the wheels of a watch. It may be
briefly described as a curve which winds
round a point in successive convolu-
tions.

SPIRAL VESSELS. Trachenchyma.
Long cylindrical tubes, constituting the
vascular tissue of plants. Each tube
tapers to each end, and has an elastic
spiral fibre generated within it.

SPIRE (<T7reTpa, a coil or spiral line).
A term applied, collectively, to the con-
volutions of a spiral shell which are
placed above the lowest or body-whorl,
whatever shape it may assume. In pla-
norbis the spire is sunk ; in cyprcea it is
so small as to be seen only when the
shell is young, after which period it is
covered by the enlargement of the body-
whorl.

SPIRIT. A general term for all in-
flammable liquors obtained by distilla-
tion, now almost exclusively applied to
spirit of wine or alcohol. Ordinary spirits
contain from 50 to 52 per cent, of alcohol ;
spirits of wine, from 62 to 67 per cent. ;
rectified spirits, from 82 to 85 per cent.

Spirit, proof. By the expression that
a spirit is any number, say ten, over
proof, is meant that 100 gallons of the
312

spirit would bear the addition of ten
gallons of water to reduce it to proof
strength, or it would form 110 gallons of
proof spirit, i. e spirit of density 0918633.
The term ten, under proof, means that
ten gallons of water must be taken from
100 gallons of the spirit to raise it to
proof, or that 100 gallons of it contain
only 90 gallons of proof spirit.

SPIRIT-LEVEL. A glass tube nearly
filled with spirit of wine, and hermeti-
cally sealed at both ends. The exact
horizontal position ofjts axis is ascer-
tained by the extremities of the air-
bubble being at equal distances from the
middle point in the length of the tube.
The level is used for determining the
relative heights of ground at two or
more stations.

SPIRU'LIDjE. A family of poly-
thalamous, decapodous, dibranchiate ce-
phalopods, consisting of the single genus
spirula, and named by Professor Owen.

SPODIUM (<T7rod6?, a cinder). A
name sometimes given to the oxide of
zinc, which sublimes during calcination.

SPO'DUMENE. Triphane. Prismatic
triphane spar ; a silicate of lithia and
alumina, found in embedded crystalline
masses.

SPONDY'LIDjE. A natural family of
marine conchifers, named from the genus
spondylus, which appears to be co-exten-
sive with the family itself. The fossils
of this family are very numerous, and a
somewhat wide geological distribution.
The genus plicatula is with difficulty
distinguished from spondylus.

SPONGE (spongia). A porous sub-
stance, generally referred to the class of
poriferous animals. The sponge of com-
merce is the dry skeleton of the animal,
from which the gelatinous flesh has been
removed.

SPO'NGIOLE or SPONGELET (spon-
giola, a little sponge). The absorbing
extremity of the fibril of a root, consist-
ing of extremely lax cellular tissue and
mucus. It is not a special organ, but
merely the newly formed and forming
tender tissue. The term spongiole is
also applied to the warty excrescence
often found near the hilum of seeds, and
is then nearly synonymous with stro-
phiola.

SPORANGFUM (amopa, a spore, a-y-
7€tov, a vessel). The theca, or case,
which contains the spores of cryptogamic
plants : some writers consider this organ
to be formed by the adhesion of an ex-
ternal and internal series of organs, the

SQU

ST A

Inner series being called sporangidium,
to which the peristomium belongs. A
combination of sporangia is termed by
the German botanists a sporocarpium,
especially when they are enclosed in a
common membrane.

SPORE (ffTropa, a seed). Sporule.
The reproductive body in cryptogamic
plants, analogous to the seed of other
plants, but differing from this in its
mode of development and in its struc-
ture ; being produced apparently without
the agency of sexes, and not germinating
from any fixed point, but producing its
stem and root indifferently from any
points of its surface.

SPORI'DIA. Granules resembling
sporules, occurring in algaceous plants,
but of doubtful nature. In fungaceous
plants, the term denotes the immediate
covering of sporules. Sporidiola are the
sporules themselves.

SPRING. A piece of mechanism,
formed of a plate of steel or other elastic
substance, employed as a moving power,
or as a regulator of the motions of wheel-
work ; also for the purposes of producing
resistance, or of preventing a shock from
the collision of hard bodies. In the form
of the balance, it is employed as a means
of measuring weight or force.

SPUR. Calcar. The name given to
a petal which is lengthened at the base
into a hollow tube, as in orchis, &c.
This is sometimes called nectarotheca,
though frequently without reason.

SQUA'LIDjE. A family of chondro-
pterygious fishes, named from the genus
squalus, and including the various spe-
cies of sharks.

SQUAMA. A scale; a term applied
in botany to any kind of bract which has
a scaly appearance. A diminutive of this
is squamula, and is used to denote each
of the minute hypogynous scales or
bracts found within the outer envelopes
of grasses.

SQUA'MIPENNES {squama, a scale,
penna, a fin). A family of acanthoptery-
gious or spiny -finned fishes, in which
the soft and even the spinous parts of
their dorsal fins are covered with scales,
as well as the rest of their body. The
chaetodon may be taken as a type of the
family.

SQUARE. In Geometry, a square is
a plane four-sided figure, with all its
sides equal, and all its angles right; or it
may be described as a rectangle, which
has two adjoining sides equal. In
arithmetic and algebra, a square signi-
313

fies the number produced by multiplying
a number by itself. The reason of this
double use of the word ' square ' is ob-
vious: the square of 12 is 144, and this
is the arithmetical mode of finding the
content of a square of 12 units in length
and breadth ; but, to avoid the confusion
occasioned by this double use of the
word, it has been proposed to speak of
the square on a line in geometry, and
of the square of a number in arithmetic
and algebra. See Power of Numbers.

SQUARE MEASURES. Measures
of Superficies. In square measure the
yard is divided, as in general measure,
into feet and inches, 144 square inches
being equal to a square foot, and 9 square
feet to a square yard. For land measure,
the multiples of the yard are the pole,
the rood, and the acre; the pole being
equal to 30J square yards, the rood to
40 poles, the acre to 4 roods.

SQUARE NUMBER ; SQUARE
ROOT. A square number is the product
of a number multiplied by itself, as 25,
the square of 5. A square root is the name
of a number with reference to its square,
as 5, the square root of 25. When a num-
ber has no exact root, an approximate
root may be found by the usual process
of extraction : thus, 2 has no square root,
but 1.4142136 multiplied by itself, is
nearly 2, and is therefore the square root
of something very near 2.

SQUARROSE. A term applied, in de-
scriptive botany, to parts which are
spread out at right angles from a com-
mon axis, as the leaves of some mosses,
the involucra of some compositae, &c.
By squarrose-slashed, as applied to leaves,
is meant, slashed with minor divisions
at right angles with the other divisions.

STABLE and UNSTABLE. These
are terms employed in physics in
connexion with equilibrium and centre
of gravity. Suppose a body to be in equi-
librium under the action of any forces ;
let the body be arbitrarily displaced very
slightly from the position of equilibrium,
then if the forces be such that they tend
to bring the body back to its position of
equilibrium, the position is stable ; but if
they tend to move the body still further
from the position of equilibrium, it is
unstable. An egg will rest upon its side
in a position of stable equilibrium; if
placed on one end, it will be in a position
of unstable equilibrium.

STAFF A. A small island, lying west
of the larger trap masses of Mull, en-
tirely composed of amorphous and pil-

ST A

STA

lared basalt, the pillars being generally
arched over by trap rock which is often
prismatised in an irregular manner.

STA'LACTITE (<rra\af«>, to drop).
Substances found suspended from the
roof of mountain caverns, being formed
by the oozing of water charged with cal-
careous particles, the former of which
evaporates, leaving the latter behind,
which hang down in long rods, like
icicles. The oriental alabaster appears
to be of stalactitic origin.

STA'LAGMITE {araXay^i, a drop-
ping). The crust composed of layers of
limestone, which is formed when water
holding lime in solution drops on the
floor of a cavern : the water evaporates,
the lime remains.

STA'MEN {<tt!]h<*v, the thread of the
warp). The male organ of flowering
plants, placed immediately inside the
petals, and constituting collectively the
androceum, or male apparatus of the
flower. The stamen consists of the
filament, the anther, and the pollen, the
first of which is not essential : a stamen
may exist without a filament, but it
cannot exist without an anther and pol-
len. See Adelphia.

STAMINFDIA {staminidium, a little
stamen). A term applied to small sta-
men-like organs occurring in some crypt-
ogamous plants. These are the sperma-
tocystidia of Hedwig ; they are found in
Jungermannia and in some species of
mosses, but no analogy of function to
that of the stamen in flowering plants
must be inferred from the name.

STANDARD. Vexillum. The upper,
erect, and expanded petal of a papiliona-
ceous corolla.

STANDARD STARS. The name
given by astronomers to those stars which
are best known and best adapted for ac-
curate observation.

STANNOUS OXIDE {stannum, tin).
Protoxide of tin. Stannic oxide is the
peroxide of the same metal. By stan-
nate, is meant a salt of tin or the proto-
chloride.

STAR. A general term for all the
heavenly bodies. In Astronomy, how-
ever, there are several classes of stars :
fixed stars are those which, in the revo-
lution oT-^he sphere, seem always to
occupy the same relative position, and
to preserve the same distances one from
another; erratic stars, or planets, are
those which, besides the daily revolution,
have a motion peculiar to themselves,
which alters their relative distances from
314

the other bodies around them. See
Planet and Nebula.

Binary Stars. By this term are de-
noted sidereal systems, composed of two
stars revolving about each other in regu-
lar orbits ; the individuals are equidistant
from the eye ; or, at least, cannot differ
more in distance than the semi-diameter
of the orbit they describe about each
other, which is quite insignificant when
compared with the immense distance
between them and the earth. These
must be distinguished from the double
stars, already noticed, in which these
physically connected stars are con-
founded, perhaps, with others only opti-
cally double, or casually juxtaposed in
the heavens at different distances from
the eye. Herschel.

STARCH. Fecula; amylin. An organ-
ized substance separated from the grains,
roots, and stems of many plants. It is
contained in the cavities of the vege-
table cells, in the form of small, white,
and brilliant grains, which are not crys-
talline, but have a rounded outline with-
out any determinate form. Varieties o
this substance occur in arrow-root, ami-
din, dextrin, &c.

STATICS (o-TcrnKor, causing to stand).
That division of the science of mechanics
which relates to the condition of bodies
as influenced by forces which are in equi-
librium. Tt thus differs from the other
division, or Dynamics, which treats of
forces which produce motion.

1. The general laws of Statics and
Dynamics are applicable to fluids ; but,
owing to the peculiar difficulty attending
the consideration of this class of bodies,
they are generally treated separately, that
part of the mechanics of fluids which
relates to equilibrium being termed hy-
drostatics, while that which investigates
their motion is termed hydrodynamics.

2. Statical figure. The figure which
results from the equilibrium of forces.

STATION. A technical term em-
ployed in botanical language to denote
the peculiar nature of the locality where
each species of plants is accustomed to
grow, and it has reference to climate,
soil, humidity, light, elevation above the
sea, and other analogous circumstances.
See Habitation.

STATIONARY. This term is applied
by astronomers to the condition of a
planet, so far as visible motion is con-
cerned. The planets move sometimes
from west to east, sometimes from east
to west, but much more in the former

STE

STE

than in the latter direction, so that they
may be said to progress with occasional
retrogradations. The end of each kind
of motion and the beginning of the next
is performed with such extreme slow-
ness, that for several days together the
planet does not seem to change its place
among the stars at all, whence it is said
to be stationary, i. e. so far as we can
trace its motion.

STATISTICS. That department of
political science which relates to the
investigating and the arranging of facts
illustrative of the actual condition and
resources of a state. It is the basis
upon which the statesman and the poli-
tical economist reason, and from which
they draw conclusions.

Medical statistics consists in the ap-
plication of numbers to illustrate the
natural history of men in health and
disease.

STAU'ROLITE (o-raupos, a cross, Xi-
0oc, a stone). Staurotide. A bisilicate
of alumina and of oxide of iron, called
also granatite and cross-stone, among the
specimens of which are the fine mackled
crystals from Britany, and the modifica-
tions of the simple crystals from St.
Gothard, accompanied by prisms of dis-
thene, perfectly similar to those of the
staurolite, and sometimes longitudinally
grown together with them.

STEAM. The vapour of water raised
to a high degree of elasticity by heat.
When raised at the ordinary tempera-
ture, it is termed low-pressure steam;
when heat is applied to ordinary steam,
under a constant bulk, its elasticity
rapidly increases, and it is then termed
high-pressure steam.

STEAM ENGINE. There are two
kinds of steam engine in general use,
the low-pressure and the high-pressure
engine. See Steam.

1. The term low-pressure engine is not
in all cases correct, for many of these
engines, particularly those which com-
bine expansion with condensation, work
with a considerable load on the safety-
valve, as in the case of the Cornish
engines. But the term condensing engine
always , conveys a true impression, viz.
that the engine is provided with a con-
densing apparatus.

2. The terms high-pressure engine and
non-condensing engine are equally sig-
nificant: such engines, having no con-
densing apparatus for the production of a
vacuum, are obliged to work with steam
of higher pressure than that of the atmo-

315

sphere. The essential parts of a high-
pressure engine are only two in number,
the boiler and the cylinder; the low-
pressure engine requires the presence of
a third part, the condenser.

3. Classification of Engines. The fol-
lowing classification of the various steam
engines, according to the principles by
which they are worked, may be found
convenient as a table of reference :

I. Condensing Steam Engines.

1. Simple condensation in the cylinder.

Atmospheric engines.

2. Simple condensation in the condenser.

1. Watt's single-acting engines.

2. Watt's double-acting engines.

3. Cornish single-acting engines.

3. Condensation and expansion.

1. Expansion in one cylinder.

1. Watt's engines, single and double.

2. Cornish engines, single and double.

2. Expansion in two cylinders.

Hornblower's and Woolf s engines.

II. N on- condensing Steam Engines.

1. Simple generation of steam.

2. Generation and expansion of steam.
STE'ARIC ACID (areap, suet). An

acid procured from animal and vegetable
fats, and from the bile of many animals.
Stearine is a solid crystallizable sub-
stance, the essential part of all kinds of
suet. Stearopten is the solid portion of a
volatile oil, as distinguished from elaop-
ten, or the liquid portion.

STE'ATITE (o-reap, suet). Another
name for soapstone, derived from its
greasy feel. It may easily be cut with a
knife, and yields even to impressions of
the nail. The most remarkable varieties
are, that of a yellowish-green colour from
Greenland, and that from Gbpfersgriin
in Baireuth, with small crystals of other
mineral substances, especially quartz,
converted into, and forming part of, the
massive steatite ; a variety called chalk
of Briancon, &c.

STEEL. Carburetted iron; the aver-
age proportion of carbon is supposed to
amount to ^ part. The different tem-
pers, or degrees of hardness, of rigidity,
or of elasticity of steel are given by*
means of the different degrees of heat to I
which the metal is exposed in the opera- 1
tion. '

STE EL- YARD. The steel-yard differs
from the balance, in having its support
near one end, instead of in the middle;
and also in having the weights suspended

STE

STI

by hooks, instead of being placed in a
dish.

STEINHEILITE. Blue quartz; a
variety of iolite, from Orayervi in Fin-
land.

STELLA'TjE (stella, a star). Ga-
liacece. The Madder tribe of dicotyle-
donous plants, characterized by their
square stems, and by their verticillate
leaves without stipules, presenting a
star-like appearance.

STELLE'RIDjE (stella, a star). A
family of anenterous echinoderms, in
which the radiated form is most complete
and general, and in which the species
have consequently received the common
appellation of star-fishes, or sea-stars.
They constitute the third order of the
Actinozoaria of De Blainville.

STENELY'TRANS (<rTewk, narrow,
eXvrpov, a wing-case). A family of cole-
opterous insects, comprising those in
which the elytra become narrow at the
posterior part of the body.

STENO'GRAPHY (crrevof, contracted,
ypd<p(o, to write). Brachygraphy. The
art of short-writing, or the representa-
tion of words by means of a few simple
characters. Various modes of steno-
graphy have been successively employed ;
the best is that which employs the fewest
arbitrary signs.

STEPPES. A Russian name applied
particularly to the extensive plains which
lie on the north-west of Asia. The greater
part of what is properly called the steppes
forms a considerable portion of the coun-
try known as Independent Tartary.

STERELMI'NTHA (arepeor, solid,
tXjiuvv, an intestinal worm). Intestinal
worms which have no true abdominal
cavity, as the tape-worm. These are the
parenchymatous entozoa of Cuvier.

STEREOGRA'PHIC (trrepeor, solid,
7pa0o>, to write). The term applied to
that mode of projecting a sphere upon a
plane, in which the eye is at a point in
the sphere, and the plane of projection
is the great circle of which the eye is at
the pole, or a plane parallel to it. See
Projection.

STEREO'METER (arepeor, solid, ^-
rpov, a measure). An instrument for
determining the specific gravity of liquid,
porous, and pulverulent, as well as of
solid bodies.

STE'REOSCOPE (tr-repebt, solid, <tko-
TTfw, to see). An instrument consisting
of two plane mirrors, inclined with backs
to each other, at an angle of 90°; per-
spective drawings of an object are placed
316

at the sides of the mirrors, and at equal
distances from them in the same hori-
zontal line ; the spectator placing his head
against the edges of the two mirrors,
will see a single image of the solid repre-
sented by the drawings.

STE'REOTYPE (trrepeo?, solid, two?,
a type). The art of printing from cast
plates of type metal, instead of from
moveable types.

STERNO'XI (arepvov, sternum, 6?i»?,
sharp-pointed). A tribe of coleopterous
insects, in which the sternum is pro-
longed into a point at both extremities.

STIBIUM. The old name for the ore
of antimony. Hence we meet with the
terms stibious and stibic, for the anti-
monious and the antimonic, acids.

STIGMA (o-ti'Co), to prick). The upper,
spongy, and secreting extremity of the
style in plants. From its property of
absorbing the fecundating matter con-
tained in the pollen-grain, it has been
termed the pistillary spongelet.

STILBITE. A crystallized simple
lustrous mineral, usually white, one of
the zeolite family, frequently included in
the mass of the trap rocks. It corre-
sponds in composition with felspar, but
contains in addition 6 atoms of water.

STILPNOSIDE'RITE. A mineral
allied to meadow iron-ore, said to con-
tain phosphoric acid, occurring together
with brown iron in Saxony and Bavaria.

STING OF PLANTS. A modifica-
tion of the hair of plants, stiff and pun-
gent, giving out an acrid juice when
touched, as in nettle.

STINKSTONE. Swinestone. A va-
riety of compact lucullite (a sub-species
of limestone), emitting a fetid odour on
friction. It occurs in beds in secondary
limestone, alternating occasionally with
secondary gypsum and beds of clay.

STIPES. A term applied to the sUm
of endogenous trees, to the stalk which
supports the pileus of the mushroom,
&c.

STI'PITATE {stipes, a stalk). Stalked;
that which is furnished with a stalk, as
the pappus of some composite plants.
The term does not apply to the petiole of
a leaf, or to the peduncle of a flower.

STIPULE {stipula, the husk of straw).
A small leaf-like organ, attached to the
base of the petiole of the leaf in many
plants. In pinnate leaves there is often
a pair of stipules at the base of eacli
leaflet, as well as two at the base of the
common petiole; the subordinate pairs
are called stipels. Hence the terms sti'

STR

palate, furnished -with stipules; and
exstipulate, having no stipules.

STOLE (stolo, a shoot or scion). By
this term some botanists have designated
that kind of branch of plants, which
differs from the soboles or sucker in pro-
ceeding from the stem above the surface
of the earth, into which it afterwards
descends and takes root, as in aster
junceus. By the older botanists, a
sucker was always understood by the
word stolo, and surculus indicated a
vigorous young shoot without branches.

STOMA'PODA {aropa, a mouth, now,
wo36r, foot). A group of the Crustacea,
in which the cephalic segment is free,
and supports large pediform maxillae.
In these animals the branchiae are at-
tached to natatory post-abdominal feet.

STO'MATE (ffTo/ia, a mouth). The
botanical name for an oval space, lying
between the sides of the cells in the epi-
dermis of plants, and opening into a
cavity in the subjacent tissue.

STONESFIELD SLATE. Slaty cal-
careous limestone ; a constituent portion
of the Lower Oolite formation, abound-
ing in organic remains.

STOOL (stolo, a shoot or scion). A
term applied in Botany to the parent
plant from which young individuals
are propagated by the process of layer-
ing, as it is technically called by bo-
tanists.

STOURBRIDGE CLAY. A variety
of clay with the general properties of
potters' clay, but of a dark colour, em-
ployed in the manufacture of crucibles.
It appears to have originated from the
disintegration of shale.

STRAIGHT LINE. According to
Plato's definition, " a straight line is that
of which the middle parts hide the ex-
tremities," the eye being placed in the
continuation of the line. Archimedes
defined a straight line as " the shortest
distance between two points." Euclid
defines it as " that which lies evenly be-
tween its extreme points." These are
all very amusing definitions Jo those who
Jcnow what a straight line isT"for Tfie
rest, it may be sufficient to say that " a
straight line is a straight line."

STRAIT. A narrow channel connect-
ing two seas together, or a sea with the
ocean, as the strait of Gibraltar.

STRATIFIED ROCKS. Rocks ar-
ranged in strata or beds, supposed to
have been so deposited by water. Under
the terms Primary, Secondary, and Ter-
tiary Strata, the characters of these rocks
317

STR

are described. Other particulars willoe
found under the term Stratum.

STRATUM {stratum, a layer or bed,
from sterno, to spread out). In the lan-
guage of Geology, a stratum is a bed or
mass of matter spread out over a certain
surface by the action of water, or, in
some cases, by wind. The deposition of
successive layers of sand and gravel in
the bed of a river, or in a canal, affords a
perfect illustration both of the form and
the origin of stratification. A large por-
tion of the masses constituting the earth's
crust are thus stratified, the successive
strata of a given rock preserving a gene-
ral parallelism to one another ; but the
planes of stratification are not perfectly
parallel throughout a great extent, like
the planes of cleavage. See Rock.

1. The inclination of strata from the
horizontal position is called the dip. The
direction, or line of bearing, of strata is
called the strike, and it is indicated by a
horizontal line at right angles to the dip.
When strata protrude above the surface,
or appear uncovered, they are said to
crop out. They are said to be conform-
able, when their planes are parallel, what-
ever their dip may be; unconformable,
when a set of strata is so connected with
another, that the planes of stratification
of the one series have a different direc-
tion from those of the other series. See
Fault.

2. Strata, recent or alluvial. Under
this term are included all those deposits
which have resulted from the action of
the elements, or from the progress of
vegetation, in the course of the period
which has commenced after the depo-
sition of the tertiary strata, and has con-
tinued to the present day. They may be
arranged under the heads of alluvial de-
posits, concretionary deposits, coralline
deposits, and vegetable deposits. These
terms will be found in their respective
places.

STRATUS (Lat. a bed or covering).
The fall-cloud ; a primary foirni of cloud,
which rests upon the surface of the earth.
It varies in extent and thickness, and is
generally formed by the subsidence of
vapour in the atmosphere. This form
comprises all those fogs and mists which,
on summer evenings, fill the valleys,
remain during the night, and disappear
in the morning. Hence it has been called
the cloud of night. The stratus must be
distinguished from that variety of the
cirro-stratus which resembles it in exter-
nal characters : the former does not wet
P3

STR

im objects on which it alights ; the latter
moistens every thing it touches.

STREAM-MEASURER. An instru-
ment for measuring the velocity of a
stream of water at different depths. One
of the simplest is Pictot's tube ; it con-
sists of a tube bent nearly at a right
angle, expanding in a funnel shape;
this is placed into the direction of the
stream ; the upper part above the water
must be of glass. If the water be in a
state of rest, the level within and with-
out the tube will be equal ; but if it be
in motion, the impulse of the stream
will cause a column of the fluid to ascend
until the weight of this column become
a counterpoise to the force with which
the water is impelled.

STREAM TIN. Tinstone, or native
oxide of tin, occurring in rounded par-
ticles and masses mixed with other allu-
vial matters. The finest grain tin is pro-
cured from this ore.

STREPS I'PT ERA (arpevr6^ twisted,
irrepbv, a wing). A singular order of
Insects discovered by Mr. Kirby, in
which the anterior wings are reduced to
minute appendages twisted spirally.

STRI'ATED {stria, a streak). Marked
with very slender lines, or strice, either
indented or elevated, at parallel and
nearly equal distances. When the lines
are deeper than striae, and indented, they
are called grooves ; when still deeper
and elevated, ridges.

STRFGID.E (strix, the screech-owl).
The Owl tribe ; a family of the JRaptores,
or Rapacious birds, including all the noc-
turnal birds of prey, and characterized
by the large proportion of the head to the
body, and by the size of the eyes, which
are surrounded by a fringe of feathers,
most remarkable in the barn owl and its
allies.

STRI'GOSE (strigosus, scraggy). A
term applied to a surface covered with
sharp, appressed, rigid hairs ; a term
synonymous with hispid.

STRO'BILE (orpo/fc'Xn, a plug of lint
twisted into an oval shape like a pine-
cone). Cone. An amentiform fruit, the
carpels of which are scale-like, spread
open, and bear naked seeds ; sometimes
the scales are thin, with little cohesion,
as in the hop ; but they are often woody,
and cohere into a single tuberculated
mass, as in the pine. See Galbulus.

STROBOSCO'PIC PLATES (<rTp6/3o9,

a whirling round, arKoneu), to observe).

An apparatus invented by Stampfer of

Vienna, by which an impression is pro-

318

STR

duced on the retina of an uninterrupted
line of light by the rapid motion of a
luminous object. On the same principle
is explained the action of the thauma-
trope, and of Newton's coloured wheels.

STRO'MA. A fleshy body occurring
in fungaceous plants, to which flocci are
attached, as in isaria, &c

STRO'MBIDvE. Wing-shells ; a fa-
mily of carnivorous Gasteropods, named
from the typical genus strombus ; the
outer side or lip of the aperture is con-
siderably dilated. *

STRO'MBIN^. The true Wing-
shells ; a sub-family of the Strombidez,
having the outer lip greatly dilated, with
a lobe at the base, and often on the sum-
mit also of the outer lip ; the spire being
always more or less elevated.

STRO'NTIANITE. Carbonate of
strontia; a mineral of fibrous texture,
sometimes transparent and colourless,
but generally with a tinge of yellow or
green.

STRO'NTIUM. The metallic base of
the alkaline earth strontia, named from
Strontian, a mining village in Argyle-
shire. The earth strontia is to barytes,
what soda is to potash. Sulphate of
strontia is known as celestine, and occurs
in regular crystals of the same form as
sulphate of barytes.

STRO'PHIOL^. Carunculce. Irre-
gular protuberances sometimes occurring
about the umbilicus of seeds; in such
cases, the umbilicus is said to be stro-
phiolate or carunculate.

STRUCTURE OF ROCKS. The
structure of rocks relates to the arrange-
ment of their parts, viewed on a larger
scale than that of their texture. Struc-
ture is said to be massive, when the rock
presents no internal division into plates,
prisms, or balls, but is of a uniform tex-
ture over a great extent ; prismatic or
columnar, when a mass of a rock is inter-
nally divided by fissures into prisms of
various sizes or forms, as in basalt,
greenstone, and porphyry ; tabular, when
a rock is composed of parallel plates,
separated by regular seams ; globular,
when globular masses of large size are
imbedded in a substance of the same
nature.

STRUMA. Bourrelet. A dilatation
of the petiole of a leaf, at the extre-
mity where it is connected with the
lamina. Also, a dilatation at tne base of
the sporangium of mosses.

STRUTHIO'NID^ {struthio, the
ostrich). A natural family of terrestrial

STY

SUB

birds, comprising the ostrich, the cas-
sowary, the dodo, the emu, the apterix,
&c. In these birds the locomotive power
resides in the lower extremities, the
wings being, in the majority of cases,
merely rudimentary.

STRYCHNINE. Strychnia. An al-
kali derived from the Nux Vomica class
of plants, and particularly from the seeds
of the Strychnos nux vomica, and St. Ig-
natius's bean, the fruit of Strychnos igna-
tia. Strychnine exists in these plants in
combination with strychnic acid.

STU'CCO. Sulphate of lime ; an arti-
ficial hydrate, having the same compo-
sition as native gypsum. When made
into a paste with water, it forms a hard
coherent mass, or sets, in a minute or
two, with a slight evolution of heat.

STUFAS. Jets of steam issuing from
fissures in volcanic regions at a tempera-
ture of ten above the boiling point.

STURIO'NES {sturio, the sturgeon).
The Sturgeon tribe ; an order of carti-
laginous fishes, in which the gills hang
freely, and are covered with a gill-lid
having a single wide opening, as in the
osseous fishes. In these fishes a large
swimming-bladder exists, from which is
obtained the valuable material called
isinglass.

STU'RNIDjE (sturnus, the starling).
The Starling tribe, placed by Vigors be-
tween the Fringillidae and the Corvidae,
in his Conirostres.

STYLE {aTv\ti, a pillar). In Botany,
that elongation of the ovary which sup-
ports the stigma. It is frequently ab-
sent, and then the stigma is sessile on
the ovary. It is not more essential to a
pistil than a petiole to a leaf, a claw to a
petal, or a filament to the stamen.

STYLE, OLD and NEW. By the Old
Style is meant the method of computing
time anterior to the reformation of the
calendar by Pope Gregory XIII; and by
the New Style, that which has been in
use since. The reformation took place
in 1582, in which ten days were deducted
from the year, by calling what, according
to the old calendar, would have been the
5th of October, the 15th of October, 1582.
From thence to the end of February, 1700,
new style is ten days in advance of old
style : thus January 1 (O. S.) is January
11 (N. S.) and so on. From and after
March 1, 1700, to the end of February,
1800, new style is eleven days in advance
of old style: thus January 1 (O. S.) is
January 12 (N. S.). The new style was
applied in England in 1751.
319

STYLOSTE'GIUM (<nv\n> the style,
o-Tf7&), to cover closely). Orbiculus. The
botanical name of a peculiar appendage
of the petals found in certain plants, also
called corona. In narcissus, it forms an
undivided cup, surrounding the stamens
and style. When divided, its parts bear
various names, as horns, beak, wings,
folioles, &c.

STYRA'CEjE. The Styrax tribe of
dicotyledonous plants. Trees or shrubs
with leaves alternate ; flowers monope-
talous ; stamens of unequal length ; ovary
superior, containing cells ; fruit drupa-
ceous.

SUB-. A Latin preposition, denoting,
1. a position beneath any body ; 2. a
slight modification, corresponding to the
English term somewhat, as in sub-ovate,
somewhat ovate, sub-viridis, somewhat
green ; and 3. in chemical terms, an in-
termediate degree of oxidation, as in sub-
sulphurous acid, or that which is inter-
mediate between the sulphurous and
hyposulphurous acids.

1. Sub-altern. In Logic, Subaltern
Species and Genus is that which is both
a species of some higher genus, and a
genus in respect of the species into which
it is divided. Subaltern Opposition is
between a universal and a particular of
the same quality; of these, the univer-
sal is the subalternant, and the particular
the subalternate.

2. Sub-Apennines. Low hills which
skirt, or lie at the foot of, the great chain
of the Apennines in Italy. This term is
applied by geologists to a series of strata
of the old Pliocene period.

3. Sub-contrary. In Mathematics,
when a figure or solid is symmetrical, so
that equal lines or polygons can be drawn
on two different sides, those equal lines
or polygons may be termed sub-contrary.
The two equal sides of an isosceles tri-
angle are sub-contrary. In a right cone,
every section has its sub-contrary, ex-
cept only the circle which generates the
cone, and its parallels.

4. Sub-contrary opposition. This oc-
curs, in Logic, between two particular
propositions, the affirmative and the ne-
gative. Both are true in contingent mat-
ter, but never both false. See Opposition.

5. Sub-dominant. In Music, a kind of
governing note, being the fifth below the
key-note. In the regular ascending scale
of seven notes, it is the fourth : thus, in
the key of C, F is the sub-dominant ; the
term, however, is derived from the relation
of the note to the tonic as the fifth below.

P4

SUB

SUB

6. Sub-duplicate. In Arithmetic and
Algebra, the sub-duplicate ratio of two
numbers is the ratio of their square
roots. Thus, the sub-duplicate ratio of
the numbers 9 and 16 is the ratio of 3 to 4 ;
that of the numbers a and b is the ratio
of *Ja to )Jb.

7. Sub-medial. A term synonymous
with transitional, and applied to the
lower secondary rocks, which bear a
close resemblance to some of the primary
rocks, though differing from them in
being often fragmentary, and in contain-
ing organic remains. They occur in
England, Scotland, and Wales, where
they compose the highest ranges, exclu-
sive of the Grampians.

8. Sub-multiple. The inverse term to
multiple: thus, 18 being a multiple of 6,
6 is a sub-multiple of 18. The term sub-
multiple is equivalent to aliquot part.
It is such a part of a quantity as can be
expressed by a whole number, as a third,
a fourth, &c.

9. Sub-normal. In Geometry, the sub-
normal is that part of the axis of a curve
line which is intercepted between the
ordinate and the normal. It is a third
proportional to the sub-tangent and the
ordinate.

10. Sub-oxide. By some chemists the
oxides of the mineral kingdom are
termed sub-oxides and super- oxides ; ac-
cording to this system of nomenclature,
the former term denotes the base, the
latter the acid, and the quantities of
oxygen are found in a simple numerical
proportion.

11. Sub-resin. The name given by
Bonastre to that portion of a resin which
is soluble only in boiling alcohol, and is
thrown down again as the alcohol cools,
forming a kind of seeming crystal-
lizations. It is a sort of stearine of
resins.

12. Sub-salt. A salt which has assumed
a fixed metallic oxide in the place of
crystallization. Such compounds may,
therefore, be truly neutral in compo-
sition, the excess of oxide not stand-
ing in the relation of base to the acid.
The term 'sub-salt' originally denoted
a salt which contained an excess of base.

13. Sub-stratum. A stratum lying
under another stratum, as clay under
gravel. The term sub-soil is generally
applied to the matters which intervene
between the surface soils and the rocks
on which they rest.

14. Sub-tangent. In Geometry, the sub-
tangent is that part of the axis of a curve

320

which is intercepted between the tangent
and the ordinate.

15. Sub-tense. A line, angle, &c. which
subtends, or is opposite to, another line,
angle, &c. Thus, the cord of a segment
is the sub-tense of the arc which it cuts
off from the circle.

SU'BERIC ACID {suber, the cork
tree). An acid procured by the action of
nitric acid, with heat, upon barks, but
more particularly cork. It forms salts
called suber ates.

SUBJECT and OBJECT. These are
correlative terms employed by philoso-
phical writers, the former denoting the
mind, soul, or personality of the thinker
— the Ego, or self; the latter, expressing
any thing or every thing external to the
mind, and distinct from it— the non-Ego,
or not-self. The universe itself when
considered as a unique existence, is an
object to the thinker; and the very sub-
ject itself (the mind) can become an ob-
ject, by being psychologically considered.

Secondary meaning. These terms gra-
dually lost their primary signification.
Object became metaphorically motive,
end, final cause, &c, by a common
change in all language, of the meta-
phor into a real signification. Subject
also became synonymous with object,
and probably the logical term " subject of
predication" facilitate* this confusion.
Be this as it may, the extreme want of
precision with which the words are used,
may be seen in the very common instance
of calling any thing "a subject of in-
vestigation." Pen. Cycl.

SUBJECT of a PROPOSITION. In
Logic, that term of a proposition of
which the other is affirmed or denied.
See Predicate.

SUBJUNCTIVE MOOD. The follow-
ing is Mr. Greenlaw's rule on the use
of this mood : — " If a clause be the true
subject of a proposition, or be properly
attached to the true subject, the verb of
such clause is in the indicative mood;
but if a clause be the true predicate of a
sentence (provided it does not contain
the copula blended with the verb), or if
it be properly attached to the true predi-
cate, the verb of such clause is invari-
ably found in the subjunctive mood."
See Potential Mood.

SUBLIMATION. The process by
which volatile substances are raised by
heat, and again condensed into the solid
state ; it is, in fact, dry distillation. The
substances so obtained are called sub-
limates.

sue

SUL

SUBLIME GEOMETRY. By the
older mathematicians this term was
technically applied to the higher parts
of geometry, in which the infinitesimal
calculus, or something equivalent, was
employed.

SUBSIDIARY. A quantity or symbol
is so called when it is not essentially a
part of a problem, but is introduced to
help in the solution. The term is par-
ticularly applied to those angles, which
are introduced into trigonometrical pro-
blems, in which there is no question of
angular quantity.

SUBSTANCE. In Physics, substance
is synonymous with matter. In meta-
physics, it is that which supports, or,
literally, stands under phenomena ; it is
the fundamental fact of all existence,
though as inconceivable as a point in
mathematics.

SUBSTITUTION, CHEMICAL. A
term explanatory of certain phenomena
connected with chemical affinity. When
carbonate of soda is added to nitrate of
lime, carbonate of lime is instantly formed
and precipitated, while nitrate of soda is
formed at the same time, and remains in
solution. Here a double substitution
occurs, lime being substituted for soda
in the carbonate, and soda for lime in
the nitrate. Such reactions may, there-
fore, be truly described as double substi-
tutions as well as double decompositions.
The substitution of chlorine for hydrogen
in many organic substances has been
found to take place with remarkable uni-
formity.

SUBTRACTION. The arithmetical
operation of removing one number or
quantity from another, in order to find
their difference. The operation is pre-
cisely the reverse of addition. The quan-
tity to be diminished was formerly called
the minuend ; the quantity to be removed,
the subtrahend; and the remaining quan-
tity or difference, the remainder.

SUCCINIC ACID (succinum, amber).
An acid derived from the distillation of
amber, and found also in the resin of some
coniferous plants. Its compounds with
the salifiable bases are called succinates.

SUCKER. Surculus. A term applied
in Botany to a modification of the aerial
stem, consisting of a branch which pro-
ceeds from the neck of a plant beneath
the surface of the ground, and becomes
erect as soon as it emerges from the
earth, producing leaves and branches,
and subsequently roots. It has been
termed soboles.
321

SUCTION {sugo, to suck). The act of
sucking; a term applied to the raising
of liquids through a tube, by means of a
piston, which lifts and sustains the weight
of the atmosphere from that part of the
well which is covered with the tube,
leaving it to press on the other parts of
the surface. See Pump.

SUCTO'RIA {sugo, to suck). A class
of articulate animals, which have their
mouth adapted for sucking fluid aliment.
The following orders are founded on
differences of the general form of the
body :—

1. Cystica, or those destitute of an
anal aperture, which have one or more
buccal orifices leading into a terminal
cyst.

2. Cestoidea, or those with a long, de-
pressed, flat, articulated form, without
anal aperture.

3. Trematoda, or those with a short,
broad, depressed body, without distinct
anus, and with one or more orifices,
leading into a ramified alimentary
canal.

4. Acanthocephala, or those with an
elongated cylindrical body, with the an-
terior part closely covered with small
sharp spines; the oral aperture leading
to a ramified alimentary canal destitute
of anal opening.

5. Nematoidea, or those with a long,
cylindrical and often filiform, naked,
inarticulated body traversed by a straight
alimentary canal open at both ends, and
with distinct sexes and internal impreg-
nation.

6. Epizoa, or those of a more short
and entomoid form, with a sub-articu-
lated trunk, a biforate intestine, with
rudimentary mandibles, palpi, proboscis,
and sometimes antennae and eyes. —
Grant.

SUFFIX (suffigo, to fasten). A term
applied by some mathematicians to the
index written under letters, as in a , a3f
&c.

SUFFRUTEX. An under-shrub; a
plant which differs from the frutex, or
shrub, in its perishing annually, either
wholly or in part ; and from the herb, in
having branches of a woody texture,
which frequently exist more than one
year, as in the Tree Mignonette.

SU'ID^S (sus, suis, a sow). The Pig
tribe ; a group of pachydermatous ani-
mals, having four toes on each foot, and
three sorts of teeth in each jaw.

SULPHAMIDE. A compound ex-
actly analogous to oxamide, containing
P5

SUL

SUR

the radical sulphurous acid, combined
with amidogen. See Amides.

SULPHATES and SULPHITES. The
former of these bodies are definite com-
pounds of sulphuric, the latter of sul-
phurous, acid with the salifiable bases.

SULPHATOXYGEN. According to
the new view of compound radicals, this
body is the sulphate radical of sulphate
of soda, the oxygen of the soda being
referred to the acid ; its compounds are
termed sulphatoxide.

SULPHO-SALTS. These are merely
double sulphurets, in the constitution of
which Berzelius has traced a close ana-
logy to salts. The sulphurets of the
most electro-positive metals have been
termed sulphur bases, whilst the sulphu-
rets of arsenic, antimony, &c. have been
called sulphur acids : the combination of
these bases and acids are sulphur salts.

SULPHOVINIC ACID. (Enothionic
acid. An acid formed by the action of
sulphuric acid upon alcohol.

SULPHUR. Brimstone. An elemen-
tary substance exhaled in large quan-
tities from volcanoes, either in a pure
state or in combination with hydrogen ;
by condensing in fissures it forms sul-
phur veins, from which the greater part
of the sulphur of commerce is derived.
It exists also in combination with metals,
and is extracted in considerable quantity
from bisulphuret of iron or iron pyrites.
It is likewise a constituent of sulphuric
acid in gypsum and other native sul-
phates. Lastly, it enters into organic
structures, being associated with albu-
men, in the fluid or the solid state.

Crude Sulphur is the result of the dis-
tillation of native sulphur ; roll or stick
sulphur is sulphur which has been refined
and cast into wooden moulds ; flowers of
sulphur is the name given to sulphur
which has been sublimed, in the form
of a bright yellow powder.

SULPHURET. A combination of sul-
phur with a base. A sulphuret is some-
times distinguished by the colour of the
compound, as the black and the red sul-
phuret of mercury.

SULPHURIC ACID. An acid pro-
duced by the burning of sulphur, mixed
with nitrate of potash. It was formerly
called oil of vitriol, because it was dis-
tilled from a substance of mineral origin,
called vitriol on account of its imperfect
resemblance to green glass. This acid,
when obtained in the latter way, emits
white vapours on exposure to the air,
and is hence caMe&fuming sulphuric acid. ,
322

SULPHUROUS ACID. A gas ob-
tained by burning sulphur in dry air or
in oxygen gas. By means of nitric acid,
the sulphurous is immediately converted
into sulphuric acid.

SUN. The centre of the solar system,
and the dispenser of light and heat to
all the planets. Its distance from the
earth is computed at 95 millions of miles,
its diameter at 882,000 miles, and its
bulk is about thirteen hundred thousand
times greater than that of the earth.

SUN-STONE. A yellow variety of
adularia, or naker felspar, with reddish
dots. This name is also sometimes given
to the beautiful avanturino variety of
common felspar.

SUPERDOMINANT. The sixth of
the key, in the descending scale of Music.
The supertonic is the second above the
key-note.

SUPERFICIES. Popularly, the sur-
face of any thing. In Geometry, it de-
notes the boundary of a solid, and relates
to the two dimensions of length and
breadth. The quantity of an area is
called its superficial content, as distin-
guished from linear content or length,
and from solid content or bulk. See
Surface.

SUPERPOSITION. The process, in
Geometry, by which one magnitude may
be conceived to be placed upon another,
so as exactly to cover it, or so that every
part of each shall exactly coincide with
every part of the other. It is evident
that any magnitudes which admit of
superposition must be equal, or, rather,
this may be considered as the definition
of equality.

SU'PER-SALT. A compound of an
acid and a base, in which the acid is in
excess. See Sub-salt.

SUPPLEMENT. In Trigonometry,
the supplement of an arc is its defect
from a semicircle ; the supplement of an
angle, its defect from two right angles,
or 180°. Also, chords or arcs of a circle
or other curve which have a common ex-
tremity, and together subtend an angle
of two right angles at the centre, are
sometimes called supplemental chords or
arcs. The supplemental versed sine, or
suversed sine is the difference between
the versed sine and the diameter.

SUPRACRETACEOUS ROCKS. A
term applied by geologists to certain
rocks or strata which are situated above
the chalk. They are also termed ter-
tiary strata.
SURD. This term denotes, in Alge-

SUR

sus

bra, an irrational or incommensurable
quantity, or a quantity of which the root
cannot be exactly determined. It is not,
in fact, a complete power, and it must
therefore be expressed either by the radi-
cal sign, or by its fractional index. Thus
the square root of 2 must be expressed

either by *J2, or by 2^ ; the cube root

of 3, by a/3, or by 3* ; the n the root

of a + b, by ?J a + b, or by {a + b) % •
The etymology of the term surd is un-
known.

SURFACE. Superficies. In Geometry,
ti plane surface is such that the right
line, which joins every two points which
can be assumed upon it, lies entirely in
the surface. By Plato it was defined to
be a surface whose extremities hide all
the intermediate parts, the eye being
placed in its continuation. It has been
also defined as " the smallest surface
which can be contained between given
extremities." Every surface which is
not a plane, or composed of planes, is
called a curved surface. All plane sur-
faces are perfectly alike in their proper-
ties, but curved surfaces admit of endless
variety.

1. Surf aces of the first order are those
in which the equation is of the first de-
gree, containing only plane surfaces.
Surfaces of the second order are those in
which the equation is of the second de-
gree ; these surfaces hold the same place
among surfaces as is held by curves of
the second degree, or conic sections,
among curves ; and every section made
by a plane with any surface of the second
degree must be a curve of the second
degree. The surfaces of the second de-
gree are the ellipsoid, the single and the
double hyperboloid, the elliptic parabo-
loid, and the hyperbolic paraboloid.

2. Cylindrical surfaces are those gene-
rated by a straight line infinitely pro-
duced in both directions, which moves
so as always to be parallel to a given line,
and to have one of its points on a given
curve.

3. Conical surfaces are generated by a
straight line infinitely produced in both
directions, which always passes through
a given point or vertex, and has one
point in a given curve. The common
cylinder and the cone would be described
in this science as a right circular cylinder
and a right circular cone. The cylin-
drical surfaces themselves are only an
extreme case of the conical surfaces,

323

being what the latter become when the
vertex is removed to an infinite dis-
tance.

4. Surfaces of revolution are generated
by the rotation of a curve about an axis,
relatively to which it always retains one
position. The common cone and cylin-
der, the sphere, and others of the greatest
practical use, are contained in this
class.

5. Tubular surfaces are generated by a
circle of given radius, which moves with
its centre on a given curve, and its plane
at right angles to the tangent of that
curve. When the given curve is a circle,
the tubular surface is a common ring.

6. Ruled surfaces (the ■ surfaces re-
glees' of the French writers) are those
which are described by the motion of a
straight line, which neither remains
parallel to a given line, nor always passes
through a given point. This includes,
among many others, the whole class of
conoidal surfaces, made by a straight
line which moves parallel to a given
plane, and always passes through a
straight line perpendicular to that plane
and a given curve. The surface of a
spiral staircase, as it would be if there
were no steps, but only a gradual ascent,
is an instance.

7. Developable surfaces are those which
can be unwrapped on a plane without
any doubling of parts over one another,
or separation ; that is, without being
rumpled or torn. The only familiar in-
stances are the cylinder and the cone. —
Pen. Cycl.

8. Surface gauche. The name given by
the French geometers to a surface which
cannot be developed on a plane, the
generating straight line being constrained
to move so that no two of its consecutive
positions are in the same plane.

SURSOLID. In Arithmetic, the fifth
power of a number. Thus 32 is the sur-
solid of 2.

SU'RTURBRAND. The name given
in Iceland to brown coal or bituminous
wood ; a variety of coal which retains the
structure of wood unchanged, and re-
sembles peat in the phenomena produced
during combustion. This is called in
Devonshire Bovey coal.

SUSPENSION. A term applied to
the state of solid bodies, the particles of
which are held undissolved in water, and
may be separated from it by filtration.
The solid is then said to be suspended in
the liquid.

SUSSEX MARBLE. A variety of
P6

S YC

SYM

limestone constituting one of the fresh-
water deposits of the Wealden group, and
occurring in layers varying from a few
inches to upwards of a foot in thickness,
the layers being separated by seams of
clay or of friable limestone.

SUTURE {sutura, a seam). 1. A term
applied, in Botany, to the junction of the
valves of a simple carpel, as of the le-
gume. The junction corresponding to
the margins of the carpellary leaf, is
called the ventral suture ; that which
corresponds to the midrib of the carpel-
lary leaf, is the dorsal suture. 2. In
Malacology, the term suture is applied to
the line of junction in the whorls of
spiral shells, or to that line by which two
parts join or fit into each other. 3. In
Entomology, it is the line at which the
elytra meet and are sometimes confluent.

SYCHNOCA'RPOUS (<ruXv6s, fre-
quent, napTrbs, fruit). Polycarpous. A
term used in Botany to signify the dura-
tion of vegetable existence, and denoting
the power of bearing fruit many times
without perishing. Those plants whose
stem endures many years, constantly
bearing flowers and fruits, as trees and
shrubs, are designated as caulocarpous ;
while those whose root endures many
years, but whose stems perish annually,
as herbaceous plants, are called rhizo-
carpous.

SY'CONUS (avKov, a fig). The Bota-
nical name of an aggregate fruit, con-
sisting of a fleshy rachis, having the
form of a flattened disk, or of a hollow
receptacle, with distinct flowers and dry
pericarps, as in the fig, the dorstenia, &c.

SY'ENITE. A variety of granite con-
taining hornblende instead of mica, and
so called from its being brought from
Syene in Egypt.

SY'LLOGISM ((rvWofia/jLoi. a reckon-
ing all together ; reasoning). A demon-
strative argument, in which a conclusion
is deduced by comparison of its terms
with a middle term. It is a strictly logi-
cal form of argument, the conclusiveness
of which is manifest from the structure
of the expression alone, without any re-
gard to the meaning of the terms.
Thus-
All tyrants deserve death ;
Caesar was a tyrant ;
Therefore he deserved death.

SY'LVANITE. Native tellurium,
found in some of the Transylvanian ores.

SY'LVIADjE {sylvia, the warbler).
The Warblers ; a family of the Inses-
sores, or perching birds, or the Canta-
trices of Macgillivray, characterized by
their small size, none of them much ex-
ceeding the nightingale. Most of them
are migratory. See Dentirostres.

SYMBOLS, CHEMICAL. An abbre-
viated mode of expressing the composi-
tion of bodies. The elementary sub-
stances, instead of being written at full
length, are indicated by the first letter of
their names, a second letter being em-
ployed when more than one substance
begins with the same letter, — thus C
stands for carbon, Al for aluminium, As
for arsenic, &c. These symbolic expres-
sions, or chemical formuV,ce, are given in
the subjoined table.

TABLE OF SYMBOLS

Elements.

Sym.

Elements.

Sym.

Elements.

Sym.

Aluminium . . .

Al

Gold (Aurum) . . .

Au

Potassium (Kalium)

K

Antimony (Stibium)

Sb

Hydrogen . . . .

H

Rhodium . . . .

R

Arsenic

As

Iodine

1

Selenium . . . .

Se

Barium

Ba

Iridium

Ir

Silicium

Si

Bismuth . . . .

Bi

Iron (Ferrum) . . .

Fe

Silver (Argentum)

Ag

Boron

B

Lead (Plumbum)

Pb

Sodium (Natrium)

JSa

Bromine . . . .

Br

Lithium

L

Strontium . . . .

Sr

Cadmium . . . .

Cd

Magnesium . . .

Mg

Sulphur

S

Calcium

Ca

Manganese ....

Mn

Tellurium . . . .

Te

Carbon

C

Mercury (Hydrargy-

Thorium . . . .

Th

Cerium

Ce

rum)

Hg

Tin (Stannum) . .

Sn

Chlorine

CI

Molybdenum . . .

Mo

Titanium . . . .

Ti

Chromium . . . .

Cr

Nickel

Ni

Tungsten (Wol-

Cobalt

Co

Nitrogen ....

N

fram)

W

Columbium Tanta-

Osmium ....

Os

Vanadium . . . .

V

lum

Ta

Oxygen

O

Uranium . . . .

u

Copper (Cuprum)

Cu

Palladium . . . .

Pd

Yttrium . . . .

Y

Fluorine

F

Phosphorus . . .

P

Zinc

Zn

Glucinium . . . .

G

Platinum . . . .

PI

Zirconium . . . .

Zx

SYM

S YM

1. Each symbol represents one equiva-
lent of the elementary substance : thus H
denotes one equivalent of hydrogen. A
figure prefixed multiplies the symbol:
thus 2H, 3H, 4H, denote two, three,
and four equivalents, respectively. Two
equivalents are sometimes denoted by
placing a dash through, or under, the
symbol : thus H , or H, signifies the
same as 2 H, or two equivalents.

2. Compounds are represented by
placing the symbols of their elements
together. Thus, S F e denotes sulphuret
of iron. Or the compound may be
expressed by an algebraic formula, as
S+Fe.

3. A dot ( • ) prefixed to, or placed over,
a symbol, indicates one equivalent of
oxygen. Thus -H or H denotes one equi-
valent of oxygen and one of hydrogen,
or H + O. Each additional dot denotes
another equivalent : thus, :C, or C, de-
notes one equivalent of carbon and two

of oxygen, or carbonic acid ; : • N, or N,
denotes one of nitrogen and five of ox-
ygen, or nitric acid.

4. A figure prefixed to any symbols
multiplies all the following symbols
which are not separated from it by a +
sign. Thus 2 • H -S = 2 • H + 2 j S;
in this case, the compounds *H and • S
are both multiplied by 2. But in the fol-
lowing formula,

2 H • S + K = 2 H + 2 I S + K,
the two first compounds only are multi-
plied by 2, the third being merely added.

5. A figure placed after any symbol
multiplies that symbol, but does not effect
any other symbol in the formula. Thus,
H2 C = 2 H + C ; in this case, H is mul-
tiplied, while C is only added. In the
formula, N H3 = N + 3 H, the latter
symbol alone is multiplied.

6. In complicated combinations, brackets
are often used to contain the symbols
which are supposed to be united. Thus,
in the formula

[2HC2N + C2NFe] + 2 K,
there are two compounds ; the former is
composed of the symbols within the
brackets, the latter consists of the sym-
bols placed outside the brackets.

7. A figure prefixed to any number of
symbols enclosed within brackets, multi-
plies them all, whether there are inter-
vening signs or not. A figure prefixed
to the symbols within the brackets in the
preceding paragraph, multiplies them all,
but does not effect the symbol outside
the brackets.
325

8. The animal and vegetable acids
were expressed by Berzelius by the first
letter of their names, with a dash over
it : thus T, A, C, are the symbols for tar-
taric, acetic, and citric acids. By others,
they are represented by Italic capitals,
some succeeding letter being added when
more than one acid have the same initial
letter : thus Ty A, Ct, represent the acids
above mentioned.

9. A few exercises on symbols are here
added. To the left of the sign ( = ) are
placed the materials used ; to the right,
the products formed by their reaction.
The symbol ' & ' is used to signify a sub-
stance added to, or separated from, an-
other, while + is placed between sub-
stances chemically combined :

Materials. Products.

H&Fe m Fe&H
H&Fe& ;S = IS -Fe&H

:Hg = Hg&02
2 :Mn = :Mn2&0

5 -N2&P2 = ;;P2&10N
4-N2& SFe = :S -Fe&8N

:jN = jN&O
2::N&:N = 3 • jN

S & 02 = : S
HS & 08 = ■ H & : S

A Pb& Z = A Z&Pb
:C-Pb&HS = -H&SPb& :C
SY'MMETRY (avunerpos, commen-
surable). The etymological meaning of
this term, and the meaning with which
it was first employed, in mathematics, by
Euclid, is commensur ability : two mag-
nitudes, then, were symmetrical which
admitted of a common measure ; hence,
the term was applied to magnitudes
which coincide.

1. But Coincidence had been already
denoted by the terms equal and similar,
the former relating to size, the latter to
form. Symmetry, therefore, was even-
tually employed to express that obvious
relation of equal and similar figures,
which refers to ihe\r position merely, and
consists in their corresponding portions
being similarly placed on different sides
of the same straight line. In the letter
W there is a want of symmetry, but not
in O : to make W symmetrical, both the
inner lines should be thin, and both the
outer lines thick.

2. In Algebra, a function is said to be
symmetrical with respect to any two
letters, when it would undergo no change

S YN

S YN

if these letters were interchanged, or if
each were made to take the place of the
other.

3. In Mathematical language, the term
symmetry denotes that quantities which
in any manner have a common relation,
should have something common in the
symbols of notation ; and analogy is,
perhaps, a better word than symmetry. —
Pen. Cycl.

SYMPATHETIC INK. A solution of
chloride of cobalt. The characters made
on paper with this preparation, when dry,
will be invisible; on being held to the
fire, the writing will assume a bright
blue or green colour ; as the paper cools,
the colour will again disappear, in con-
sequence of its absorbing moisture from
the air; and the phenomenon may be re-
produced many times in succession.

SYMPATHETIC SOUNDS. A term
expressive of that natural relation of
sounds which occurs in harmonical com-
binations, and is particularly illustrated
by the sounds of the jEolian harp. The
term is also applied to sounds produced
in one instrument by sounding another
close to it; but these are dependent, not
on sympathy, but on the vibrations of the
intervening air.

SYMPIESO'METER {avu-niefa, to
compress, juerpov, a measure). An in-
strument for measuring the weight of
the atmosphere by the compression of a
column of gas.

SYN- {avv). A Greek preposition, sig-
nifying with, together. For the sake of
euphony, the final n of the preposition is
changed into m before the labials b, m,
p> ph, ps, &c, as in symmetry, sym-
pathy, &c. ; into s, I, r, before these
letters, as in syllable, &c. ; and is entirely
omitted when followed by two conso-
nants, or a double one, as in syzygy.

SYNCA'RPIUM {avv, together, Kap-
iros, fruit). The botanical designation
of an aggregate fruit, in which the ova-
ries cohere into a solid mass, with a
slender receptacle, as in magnolia, anona,
&c.

SYNCA'RPOUS {avv, together, Kapnos ,
fruit). A term applied, in Botany, to
those fruits in which the carpels cohere
together, as in poppy ; when the carpels
are distinct from one another, the fruit is
termed apocarpous, as in ranunculus.

SYNCATEGOREMA'TIC {avyKarn-
t6pr\p.a, that which is said, or can be
said, of a person or thing along with
other words). In Logic, syncategore-
matic words are such as cannot singly
326

express a term, but only a part of a
term; these are adverbs, prepositions,
&c, and also nouns in any other case
besides the nominative.

SYNCHRONOUS {avv, together, Xp<5-
vov, time). That which occurs in equal
times, as the strokes of the pulse ; a term
synonymous with isochronous.

SYNDA'CTYLES {avv, together, ddn-
tv\os, a toe). A group of birds which
have the external toe nearly as long as
the middle one, and united to it as far as
the second joint. The group contains
the bee-eaters, the king-fishers, the horn-
bills, the motmots, and the todies.

SYNGENE'SIOUS {avv, together, ye-
veats, growth). A term applied to the
anthers of plants which grow together
by their margins, as in the Compositae.
A more precise term is syn-antherous.

SYNGNA'THIANS {avv, together,
yvdOos, a jaw). A family of lophobran-
chiate fishes, in which the lengthened
jaws are united by a surrounding integu-
ment, forming a tubular mouth ; they are
named from the genus syngnathus, or the
pipe-fish. The name is also applied to an
order of myriapodous insects, comprising
the Scolopendridae and the Geophilidse.

SYNODICAL PERIOD {avvoboi, a
conjunction of paths). The simplest in-
stance of a synodical period is afforded
by the two hands of a watch : the minute
hand revolves in one hour, the hour hand
in twelve hours ; but the synodic revo-
lution of the two hands is the interval
which elapses between any time at which
they are together, and the next time at
which the same thing takes place. " This
term is applied in astronomy to the
lunar month, or the period of a revolu-
tion of the moon round the earth from
one synod, or conjunction with the sun, to
another ; thus, taking the sun's actual
revolution at 365| days, and the moon's
at 27\ days, we have

SYNTAX {avv, together, rdfo, ar-
rangement). That part of grammar,
which shows how individual words, the
materials of language (the department of
etymology), are to be arranged together,
so as to form sentences, or affirmations
containing sense.

SYNTHESIS {avvOeau, a putting to-
gether). This term denotes composition,
and expresses a process the very reverse
of analysis, or resolution. The term
Analysis is given to a species of mathe-
matical investigation, which commencing

TAB

T AC

with the assumption of that which is
sought as if it were given, a chain of rela-
tions is pursued which terminates in
what is given (or may be obtained) as if
it were sought. The term Synthesis de-
notes a process in which the series of
relations exhibited commences with what
is given, and ends with what is sought.
Consequently analysis is the instru-
ment of invention, and synthesis that of
instruction. See Analysis.

Synthesis, chemical. The formation of
any body by combination of its elements,
as opposed to analysis, or the resolution
of a body into its component parts. In
the analytic operation, a portion of water
is separated, by means of galvanism, into
the two elementary gaseous bodies,
oxygen and hydrogen; in the synthetic
operation, these two gases are again
made to combine, by means of the elec-
tric spark, and a portion of water is
again produced.

SYRINGE (<tvPi^, a pipe or tube).
The common squirt, or hand-syringe, con-
sists of a cylinder or barrel, furnished
with an accurate piston ; at the end of
the barrel is a short suction-pipe ; there
is no valve. The action of the atmo-

spheric pressure is the same as in the
suction-pump (see Pump). The water
which is raised into the barrel is driven
thence into the suction-pipe, and pro-
jected into the air by mechanical force.
The act of respiration, of suction by the
mouth, of drinking, of smoking, &c,
may all be explained by reference to the
same principle.

SY'RPHIDiE. A family of dipterous
'insects, belonging to the section Atheri-
cera, named from the genus syrphus, and
closely resembling the wasps and hum-
ming-bees.

SYSTEM (owrrijiia, a whole com-
pounded of several parts). A harmoni-
ous arrangement of bodies with respect
to one another, and of the laws by which
their motions, functions, or develop-
ments are supposed to be regulated. See
Hypothesis.

SYZYGY (av&yia, union). The name
given in common to the moon's oppo-
sition to, and her conjunction with, the
sun. The quadratures are the positions
precisely intermediate between the syzy-
gies ; at new and full moon the moon is
in her syzygies ; at half moon, in her qua-
dratures. See Phases and Quadrature.

TABA'NIDjE. The Gad-fly tribe; a
family of dipterous insects, belonging to
the section of Tanystoma, and distin-
guished by their powers of perforating
the skin and sucking the blood of vari-
ous quadrupeds, and even of man.

TABASHEER. A siliceous substance
found in the joints of the bamboo, some-
times fluid, but generally in a concreted
state. In foreign countries it is termed
bamboo milk, salt of bamboo, and bamboo
camphor. The word is derived from the
Persian scher, or the Sanscrit kschirum,
signifying milk.

TABLE-LAND. An elevated plain
rising abruptly from the general level of
the country, and being, as it were, the
broad and horizontal, or gently undulat-
ing top bf an immense mountain, as the
Nilgherry district of India. Sometimes
there are several such plains placed one
upon another, at least on one or two
sides, when they are called platforms or
terraces, as those on the eastern slope of
the Cordillera of New Mexico.

TABLE-LAYERS. This term is ap-
plied by geologists to extended plates of
327

rock, not divided into parallel laminae.
Dr. MacCullock proposes to call them
pseudo-strata. Mr. Bakewell remarks on
what he calls the stratiform structure,
that many masses of rock, not really
stratified, occur divided into parallel
planes, by seams or divisions which re-
semble those found in regular strata;
such planes have not been super-imposed
in succession, but are the result of a
crystalline arrangement of the mass.

TABULAR SPAR. Table Spar. An-
other name for prismatic augite, a mine-
ral occurring in primitive rocks, asso-
ciated with brown garnets.

TABULAR STRUCTURE. A term
expressing the geological character of a
rock which is composed of paralled plates
or tables, separated by regular seams.

TACHO'METER (rdxos, velocity, Me-
rpov, a measure). An instrument in-
vented for the purpose of indicating
minute variations in the velocity of
machines.

TACHYDRO'MIANS (tclXvs, rapid,
dponos, a course). A term applied to a
family of wading birds, of which the

T AL

TAN

genus tachydromus is the type ; also to a
family of saurian reptiles, and to a family
of dipterous insects.

TA'CHYLITE. A mineral which re-
sembles obsidian, and has also been sup-
posed to be similar to isopyre. It occurs
in small masses in basalt and wacke.

TACKING. A nautical term for an
operation with the rudder and sails, by
which, when a ship is proceeding in the
course of an acute angle with the direc-
tion of the wind on one of her bows, her
head may be turned towards the wind, so
as to enable her to sail on a course
making nearly the same angle with its
direction on the other bow.

TA'GLIA. A name, borrowed from
the Italian, for a particular combination
of pulleys. The term is applied either
to a system of fixed pulleys collected in
one common block ; or to a system of
moveable pulleys in a separate block, to
which the weight is attached. Several
taglias may be so combined that one acts
upon another; this arrangement con-
stitutes a compound taglia.

TALC. A simple mineral, laminated
like mica, and often similar in colour.
It is easily distinguished from this mine-
ral by being much softer, and, although
flexible, not elastic. It occurs as a con-
stituent of certain rocks.

TALC-SLATE. A talcose rock, con-
sisting of talc and quartz arranged in
laminae ; it is of various colours, glisten-
ing, and has an unctuous feel. It is
generally associated with steatite, asbes-
tus, actinolite, and serpentine.

TALCITE. A rare mineral, called
nacrite by Jameson, and earthy talc by
Werner. It occurs in veins, with sparry
limestone and galena, in the mining dis-
trict of Freyberg.

TALCOSE GRANITE. Protogene.
A mixture of felspar, quartz, and talc or
chlorite. It occurs in Cornwall, where,
on decomposing, it yields the China-clay
or Porcelain-earth, which is annually ex-
ported in large quantities.

TALCOSE ROCKS. These resemble
the micaceous rocks, and comprise chlo-
rite-slate, talc-slate, and serpentine.

TA'LPIDjE {talpa, a mole). The
Mole tribe ; a family of the insectivorous
vertebrata, characterized by their subter-
ranean habits.

TALUS. A term applied to a sloping
heap, formed of fragments broken off by
the action of the weather from the face
of a steep rock, and accumulated at its
base. The word talus is borrowed from
328

the language of fortification, in which It
denotes the outside of a wall of which
the thickness is diminished by degrees,
as it rises in height, to make it the
firmer.

TANGENT {tango, to touch). A
straight line which touches, but does not
cut, a curve. A straight line is said to
be a tangent to a circle, when it touches
the circumference only on one point,
' making a right angle with the radius at
the point of contact. In Mechanics, a
force, which acts upon a wheel in the
direction of such a line, is said to be tan-
gential ; and it is in this direction that
motion is communicated between wheels
and pinions, or from one wheel to an-
other.

1. Tangent of an angle or arc. Aline
drawn from that extremity of the arc
through which the diameter of the
circle passes (which extremity is called
the beginning of the arc) perpendi-
cular to that diameter, touching the cir-
cle, but not cutting it, and terminated
by the radius of the circle produced,
and passing through the other extre-
mity of the arc.

2. Tangential plane. A plane which
touches a curvilineal solid. It is from
this plane that we measure the angles of
incidence on the tangential point, whe-
ther the impinging ray be reflected or
refracted.

3. Tangential force. Another term for
centrifugal force. Thus, when two forces
act upon a body, — the centripetal attract-
ing the body towards the centre of gra-
vity, the tangential driving it in another
direction, there will result a curvilinear
motion around the central point.

TANNIC ACID. A tribasic acid oc-
curring in the bark of all the varieties of
Quercus and many other trees, and in
gall-nuts, from which it is procured in
greatest purity. What is commonly
called tannin is tannic acid mixed with
some foreign matters.

TA'NTALUM. Columbium. A metal
found in the two Swedish minerals, tan-
talite and yttrotantalite. Its name is
derived from the insolubility of its oxide
in acids, in allusion to the fable of Tan-
talus.

TANTALUM ORE. Columbite of
Hatchett. A prismatic ore of tantalum,
occurring as a coarse red granite in Fin-
land.

TA'NTALUS'S CUP. A philosophical
toy, for exhibiting the principle of the
siphon. The siphon is placed in a cup,

TAR

TAX

and its legs are concealed by the hollow
figure of a man whose chin is on a level
with the bend of the siphon, so that the
figure stands, like Tantalus in the fable,
up to the chin in water, but unable to
quench his thirst.

TANY'STOMA (ravixa, to stretch,
arofia, the mouth). A section of dip-
terous insects, which have a projecting
proboscis, with the last joint of the an-
tennae undivided. To this section be-
longs the Gad-fly tribe.

TAP-ROOTED. Fusiform. A desig-
nation of that kind of root which consists
of one fleshy elongated centre tapering
to the extremity. This is termed
pivotante by the French.

TA'PIRIRffi. The Tapir tribe; a
group of Pachydermatous animals, differ-
ing from the Suidae, or Pig tribe, in the
presence of only three toes on each hind
foot, and sometimes also in the front, and
in the absence of a central cleft of the
foot.

TAPITE'LJE (tapetum, a carpet, tela,
a web). A family of spiders, which spin
great webs of a close texture like ham-
mocks, and wait for the insects which
may be entangled therein.

TA'RDIGRADA (tardus, slow, gradus,
a step). A group of the Edentata, or
toothless animals, distinguished from the
true edentata by the peculiar shortness
of the muzzle. They are characterized
by the slowness of their motion, and con-
tain the sloths, in which Cuvier ob-
serves that " nature seems to have
amused herself with producing some-
thing imperfect and grotesque."

TARE, TRET, CLOFF, &c. These
terms, though specially of commercial
importance, are found in treatises of
arithmetic, and must therefore be briefly
noticed. 1. Tare, derived from the Italian
tarare, to abate, is the allowance made
for the box or bag in which goods are
packed. 2. Tret, probably derived from
the Italian tritare, to crumble, is an
allowance of 41bs. in 1041bs. for waste.
3. dnff, or clough, defined to be that
wherein any thing is put for carriage
sake, is an allowance of 21bs. in 3cwt.,
in order that the weight may hold good,
when the article is sold by retail. 4. Crross
weight, is that of the goods and the
package taken together. 5. Suttle, pro-
bably derived from the Italian sottile,
fine or valuable, denotes the weight
which remains, when the tare only is
allowed : it is the finer part, separated
from the coarser. 6. Net, from the Italian
329

netto, signifies the weight which remains
when all allowances are made.

TARRAS or TERRAS. A volcanic
earth, found in Germany and Sweden,
and, when pulverised, used as a cement.
It does not differ much from puzzolana,
but it is much more compact, hard,
porous, and spongy.

TARSI. The feet in insects, which
are articulated, and formed of five or a
less number of joints.

TARTAR. Bitartrate of potash; a
salt deposited on the sides of casks dur-
ing the fermentation of wine, owing to
its insolubility in alcohol. This is crude
tartar, and it is also called argol ; when
purified, it is called cream of tartar.

TARTARIC ACID. A bibasic acid,
existing in many fruits, and also as tar-
trate of lime in several roots, but pre-
pared only from the juice of the grape,
which contains tartaric acid in the form
of tartar or bitartrate of potash.

TARTARINE. The name given by
Kirwan to the vegetable alkali, or potash.

TARTRATE. A neutral compound
of the tartaric acid with a base.

TAURUS. The Bull; the name of
the second zodiacal constellation, con-
sisting of 141 stars, the principal of
which is Aldebaran. It denotes the
second month of autumn, extending
from the 20th of October to the 20th of
November, and the period of tillage in
Egypt, when other countries have done
sowing.

TAURUS PONIATOWSKI. A mo-
dern northern constellation, consisting
of seven stars, formed by a Polish astro-
nomer, the Abbe Poczobut, in the year
1778. It is situated between Aquila and
Ophiuchus.

TAU'TOCHRONE (rairo, the same,
xoovos, time). A term in Mechanics for
a curve line having this property, that a
heavy body descending along it by the
action of gravity will always reach the
lowest point in the same time, from
whatever point in the curve the body
begins to descend. This is, under cer-
tain circumstances, the property of the
cycloid.

TAU'TOLITE. A crystalline mineral,
said to consist of silicate of protoxide of
iron and silicate of magnesia, and found
in the volcanic rocks of the lake of
Laach, near Bonn, on the Rhine.

TA'XICORNS (taxus, the yew, cornu,
a horn). A family of coleopterous in-
sects, in which the antennae gradually
increase in size as they extend from

TEL

TEL

the head, or terminate in an enlarge-
ment.

TECTIBRANCHIA'TA (tectus, co-
vered, branchice, gills). An order of
aquatic Gasteropods, which have their
branchiae situated on the back or on the
side, and concealed or covered by the
mantle, as in the aplysia and the pleuro-
e branchus.

TEGMEN. Literally, a covering;
hence, applied by Mirbel to the internal
integument of the seed, the endopleura
of Decandolle ; and, by Palisot de Beau-
vois, to the glume of grasses.

TEGME'NTA (tegmentum, a covering).
In Botany, the scales of the bud. They
are termed foliaceous, when they consist
of abortive leaves; petiolaceous, when
they are formed by the persistent base of
the petiole ; stipulaceous, when they arise
from the union of stipules, which roll
together and envelope the young shoot;
and fulcraceous, when they are formed
of petioles and stipules combined.

TEI'NOSCOPE. Prism telescope. An
instrument formed by combining prisms
in a particular manner, so as to correct
the chromatic aberration of light, and to
increase or diminish the linear dimen-
sions of objects viewed through it.

TELEGRAPH (x^\e, afar off, 7p«0«,
to write). An apparatus for communi-
cating intelligence to a great distance, by
means of signals to which a conventional
meaning is attached. A telegraph is also
called a semaphore {anna, a sign, (pepa,
to bear ); the latter term is, however,
more comprehensive than the former, as
it relates to the communication of intel-
ligence, not merely by signals resembling
written characters, but also by audible
signals, by beacons, and other pyrotechnic
contrivances. See Tellograph.

TELEGRAPH, ELECTRICAL. An
apparatus for conveying thought by
means of the electric current, the sig-
nals being given by the different actions
of the current, which is carried from
station to station along insulated con-
ductors. The currents are excited either
by hydro-electric batteries, or by mag-
netic induction, and rotatory machines ;
the telegraphic signals are either the de-
flections of magnetized needles, or the
intermittent excitation of magnetism in
electro-magnets, or the physiological phe-
nomena.

TELE'NGISCOPE (tf}X«, afar off, ly
fvr, near, ano-irea, to see). A new in-
strument, combining the powers of the
telescope and of the microscope.
330

TELEOSAU'RUS (*eXeor, perfect,
aravpos, a lizard). An extinct genus of
Saurian reptiles, characterized by a com-
bination of a bi-concave structure of the
vertebrae with long narrow jaws. This
genus, and that of the steneosaurus, have
been associated together by Professor
Owen, the characters of the two genera
being mainly derived from the difference
of position in the external nostril.

TE'LESCOPE {rTiKe, afar off, c-K07rea>,
to see). An optical instrument for dis-
covering and viewing distant objects.
Astronomical telescopes are of two kinds,
refracting and reflecting ; in the former,
an image of the object viewed is formed
by a lens, termed the object-glass, which
refracts the rays from the object into one
point ; in the latter, the rays of light are
reflected by a concave speculum or mirror,
by which an image of the object viewed
is produced. The point where the image
is distinctly formed by the lens or mirror
is the focus ; and the distance of this
point from either the one or the other
is the focal length of the telescope.

1. Reflecting telescopes are of three
kinds. 1. The Gregorian has a hole
pierced in the centre of the large mirror to
receive the eye-piece ; the rays from the
object falling on the large speculum are
reflected to its focus ; there they are
received by a small concave mirror,
whose focus coincides with that of the
large one, and reflected through the aper-
ture, where they are received, and the
image magnified by the eye-glass. 2. The
Cassegrainian telescope differs from the
above only by the small mirror being
made convex instead of concave. 3. The
Newtonian telescope has no aperture in
the large speculum, but the rays it re-
flects are received on a plane speculum
near the object glass of the tube, which
is fixed at an angle of 45° with the axis,
and by it are reflected to the side of the
tube, where the rays are brought to a
focus by the eye-glass. The telescope of
Lord Rosse is constructed on this prin-
ciple.

2. Terrestrial telescope. The inver-
sion of the object is of little consequence
when the instrument is employed for
astronomical purposes, for since the forms
of the heavenly bodies are spherical, their
positions, in this respect, do not affect
their general appearance. But for ter-
restrial purposes, this is manifestly a
great defect, and therefore those con-
structed for such purposes as ship or spy
glasses, have two additional lenses, by

TEM

TEN

means of which, the images are made to
appear in the same position as the ob-
jects. These are called double telescopes.

TELESCO'PIUM. The Telescope; a
modern southern constellation, consist-
ing of nine stars. It is surrounded by
Ara, Pavo, Sagittarius, and Ophiuchus.

TELLI'NIDjE. Solid and closed bi-
valves : a family of the macrotrachian
mollusca, in which the two siphons of
the animal are of enormous length.

TELLINI'NiE. A sub-family of the
Tellinidce, named from the genus tel-
lina, in which the siphons are exces-
sively long.

TE'LLOGRAPH (T^\e, afar off, \670r,
a word, fpd<p(o, to write). This term,
contracted from telelograph, is used by
Edgeworth, who observes that while
" telegraph is a proper name for a ma-
chine which describes at a distance, tele-
lograph, or, contractedly, tellograph, is a
proper name for a machine which de-
scribes words at a distance."

TELLU'RIUM {tellus, the earth). A
rare metal of a brilliant silvery-white
lustre, found in abundance at Schemnitz,
in Hungary, combined with bismuth;
and in the silver mine of Sadovinski in
the Altai, united with silver and with
lead. With oxygen, it yields the tel-
lurous and the telluric acids.

Telluretted hydrogen. A gaseous com-
pound of tellurium and hydrogen, ana-
logous in constitution and properties to
sulphuretted hydrogen.

TEMPERAMENT (tempero, to mix
together, to temper). Crasis. A mixture
or tempering of elements ; a notion
founded on an ancient doctrine of four
qualities, supposed to temper each other :
these are, in the abstract, hot, cold, dry,
moist ; in the concrete, fire, air, earth,
water.

TEMPERAMENT, EVEN. A musi-
cal instrument is said to have an even
temperament, when it has been so tuned
that the differences between the inter-
vals are perfectly equalized. To accom-
plish this, the difference, must be so dis-
tributed among all the semitones of the
octave, that, when sounded, they do not
bear an exact ratio to any fundamental
note whatever, but the deviation is so
small a3 to be imperceptible.

TEMPERATE ZONES. The two di-
visions, or belts, of the surface of the
earth, which lie between the Tropics and
the Polar Circles— one in each hemi-
sphere. They are named from their tem-
perature being free from the excessive
331

heat of the Torrid, and from the exces-
sive cold of the Frigid Zones.

TE'MPERATURE (tempero, to mix
various things in due proportions). The
comparative degree of active heat accu-
mulated in a body, as measured by an
instrument, or by its effects on other
bodies. By the term mean annual tempe-
rature is meant the temperature obtained
by adding together the temperatures of
all the months of the year, and dividing
the sum by the number of the months ;
so that the mean annual temperature ex-
presses that height at which the thermo-
meter would stand at any place, if we
could suppose it perfectly stationary
throughout the whole year.

TEMPERING. The operation of heat-
ing iron to a certain extent, indicated by
the colour presented on the surface of
the metal.

TEMPORARY STARS. Stars which
have appeared, from time to time, in
different parts of the heavens, blazing
forth with extraordinary lustre, and, after
remaining awhile apparently immove-
able, have disappeared and left no trace.
Of this kind was the star which appeared,
a.d. 389, near a Aquilae, and, after re-
maining for three weeks as bright as
Venus, disappeared entirely.

TENA'CITY {tenax, capable of hold-
ing). The degree of force with which
the particles of bodies cohere, or are held
together ; a term particularly applied to
metals which may be drawn into wire, as
gold and silver.

TENDENCY. This word is employed
in two senses. By a ' tendency ' towards
a certain result is sometimes meant, ' the
existence of a cause which, if operating
unimpeded, would produce that result.'
In other cases, a ' tendency' towards a
certain result is understood to mean ' the
existence of such a state of things that
that result may be expected to take place.''
In the former sense, we say that the
earth has a tendency to fly off at a tan-
gent ; but in the latter, the earth has a
greater tendency to remain in its orbit
than to fly off from it. In the former
sense, it may be said that population has
a tendency to increase beyond subsist-
ence ; in the latter, that subsistence has a
tendency to increase at a greater ratio
than population. Whately.

TENDRIL. Cirrhus. A particular
form of the petiole in certain plants, as
the vine; it appears to be a contrivance
employed by nature to support plants by
the aid of others, and was included by

TER

TER

Linnaeus among the class of fulcra, or
props.

TE'NNANTITE. Sulphuret of copper,
occurring in Cornwall in copper veins
which intersect granite and clay-slate,
associated with common copper pyrites.
It is a variety of grey copper ore, and
was named in honour of Mr. Smithson
Tennant.

TENOR {teneo, to hold). That com-
pass of the voice which is hetween the
highest and the lowest; neither raised to
a treble, nor lowered to a base, but rang-
ing from C, the second space in the base,
to G, the second line in the treble. The
term alludes to the air, in part-compo-
sitions, being held by the tenor. Tenor-
clef is the C, or mean clef, placed on the
fourth line for the use of the tenor voice.

TENSION or INTENSITY. Terms
employed in electricity to denote the de-
gree to which a body is excited, as esti-
mated by the electrometer. It must be
distinguished from quantity.

TENTA'CULA (tentaculum, from
tento, to feel). Feelers ; organs by which
certain animals attach themselves to sur-
rounding objects, &c.
V TENTH. An interval in Music, con-
1 sisting of nine degrees and five spaces.

TENTHREDI'NIDjE. The Saw-flies ;
a family of the phytophagous Terebrantia,
named from the genus tenthredo, and cha-
racterized by the saw-like character and
operation of the ovipositor. By Latreille,
the family is termed Securifera, or the
hatchet-bearers.

TE'NUES {tenuis, thin). The correct
distinction of the letters called tenues, as
opposed to those which are called me-
dial*, is, perhaps, this, that in the pro-
nunciation of the tenues p, k, t, the
organs employed in articulation have only
a small portion of their surfaces brought
into contact, and that but for a short
time ; while in the articulation of b, g, d,
the surface in contact is more extensive,
and the effort less rapid.

TE'NUIRO'STRES {tenuis, slender,
rostrum, a bill). A group of the Inses-
sores, or Perching birds, characterized by
a very slender and elongated, straight or
curved, bill. They include the hum-
ming-birds, the sun-birds, the hoopoes,
the honey-suckers, and the birds of para-
dise.

TERCINE. The botanical name for
the epidermis of the nucleus of the
ovule, when it separates in the form of a
third coating or integument.

TEREBRA'NTIA {terebro, to bore).
332

A section of Hymenopterous insects,
which are furnished with an ovipositor,
by means of which they are enabled to
bore a hole in certain substances for the
deposition of their eggs. See Ovipositor.

TE'REBRATING {terebra, a perfo-
rating instrument). A term applied to
those testaceous animals which take up
their abode in other substances, as the
pholas.

TERGE'MINATE. This term is em-
ployed, in Botany, when each of two
secondary petioles bears towards its sum-
mit one pair of leaflets, and the common
petiole bears a third pair at the origin of
the two secondary petioles, as in mimosa
tergemina.

TERM, LOGICAL. A proposition
consists of two terms; that which is
spoken of is called the subject ; that which
is said of it, is the predicate ; and these
are called the terms (or extremes), be-
cause, logically, the subject is placed
first, and the predicate last. In the
middle is placed the copula, which indi-
cates the act of judgment, as by it the
predicate is affirmed or denied of the
subject.

Every syllogism has three, and only
three terms : viz. the middle term, and
the two terms (or extremes, as they are
commonly called) of the conclusion or
question. Of these, 1st, the subject of
the conclusion is called the minor term ;
2nd, its predicate, the major term ; and
3rd, the middle term (called by the older
logicians " argumentum") is that with
which each of them is separately com-
pared, in order to judge of their agree-
ment or disagreement with each other.
Whately.

TERMS, ALGEBRAICAL. In Alge-
bra, those parts of an expression, which
are connected by the sign -t- or — , are
called its terms, and the expression itself
is said to be simple or compound, accord-
ing as it contains one or more terms.
Thus a2 and — 63 are each simple quan-
tities, and a2 + ab — i2 is a compound
quantity, whose terms are a2, + ab, and
-63.

When one quantity is said to be ex-
pressed in terms of another, the expres-
sion generally means merely that the
former is to be an explicit function of
the latter. Thus, in x + y = a, we have
expressed x + y in terms of a; deduce
y = a—x, and we have y expressed in
terms of a and x.

TE'RMINAL. "Term is a word of
geometry very little used, and signifying

TER

TES

boundary or extremity ; the words ' ter-
minal value' and 'terminal form' are
sometimes used to signify the last and
most complete value or form. When a
finite expression, added to a certain num-
ber of terms of a series, makes up the
equivalent of the expression from which
the series is deduced, or stands for all
the subsequent terms of the series, this
finite expression might be called the ter-
minal expression. Thus, in Taylor's
Theorem, we have one terminal expres-
sion in D'Alembert's form, another in
that of Lagrange." Pen. Cycl.

Terminal Language. "All the use of
the terms ■ infinitely small' and ' infinitely
great' is entitled to this name : when we
say that a circle is a regular polygon with
an infinitely great number of infinitely
small sides, the language used is that of
an end arrived at, a transformation
actually made ; the circle is described as
actually consisting of straight lines ; and
the language is terminal, expressive of a
boundary actually attained. But the
meaning of this language is, or is gene-
rally held to be, false ; to obviate the
difficulty, terminal language, properly
employed, may be made the means of
abbreviation of all those truths whose
announcement contains interminable ap-
proximation." Ibid.

TERMINATE and INTERMINATE.
A terminate number is an integer, a
mixed mumber, or a vulgar fraction. As
a mixed number may be reduced to a
vulgar fraction, all terminate numbers

m
may be expressed by — , where m and n

are integers ; and when the number is an
integer, n = 1, and the number = m

Interminate Number. A number which
is not terminate, is called an interminate
number. Interminate numbers compre-
hend interminate decimals, excepting
repeaters and circulaters, which can be
reduced to vulgar fractions, and are,
therefore, terminate numbers, although,
however, in the form of decimal fractions,
they are called interminate decimals.

TERMINO'LOGY. In every treatise
of science, the preliminary part, which is
devoted to the explanation or definition
of the terms employed, is called the ter-
minology of that science.

TERMITIDiE {termes, the white ant).
A group of Neuropterous insects distin-
guished from the dragon-flies and the
day-flies by their terrestrial habits.

TERMITPNjE. A section of neuro-
pterous insects, named from the termes,
333

or white ant, and comprising also the
genera mantispa, raphidia, and psocus.
By some naturalists these genera are
considered as constituting distinct fami-
lies.

TERNARY. A term applied by Dal-
ton to any chemical substance composed
of three atoms. By ternary compounds
are now generally understood combina-
tions of binary compounds with each
other, as of sulphuric acid with soda in
Glauber's salt, and the salts generally.

TERNATE, BITERNATE, &c. In
Botanical nomenclature, these terms re-
late to the composition or arrangement
of parts upon the stem. 1. Ternate de-
notes that three leaves or other organs
are in opposition round a common axis.
2. Biternate signifies that three secondary
petioles proceed from the common pe-
tiole, and that each bears three leaflets,
as in fumitory. 3. Triternate implies
that the common petiole is divided into
three secondary petioles, each of which
is subdivided into three tertiary petioles,
each of the latter bearing three leaflets.

TERRESTRIAL MAGNETISM. A
term denoting the action of the magnetic
fluid in or about the earth ; the effects of
that action being manifested in the phe-
nomena presented by magnetized needles
or bars.

TERRI'COLA {terra, the earth, colo,
to inhabit). An order of the Annellida,
which includes the earth worms.

TERTIARY STRATA A series of
sedimentary rocks, with characters which
distinguish them from two other great
series of strata— the secpndary and the
primary — which lie beneath them.

TERTIARY SYSTEM. A compre-
hensive geological term, representing all
the regular deposits newer than the
chalk. It admits of three primary divi-
sions— eocene, miocene, and pliocene —
names which imply that, in the lowest
division, we only find the dawn of exist-
ing species ; that, in the next division,
there are more living species, but that
extinct species still predominate ; and
that, in the uppermost division, extinct
species decline, and living species pre-
dominate.

TE'SSELLATED (tessella, chequer-
work). Divided into squares or chequers,
either by a division of colours, or by the
crossing of stria?.

TEST {testis, a witness). A re-agent;
a substance which, when added to an-
other substance, tests or distinguishes its
chemical nature or composition. Test

TEU

TEX

paper consists of letter-paper dipped
several times into a filtered solution of
litmus, and dried after each immersion,
until it is of a deep purple colour.

TESTA. Literally, a shell ; and, hence,
applied by botanists to the integuments
of the seed. By Mirbel, these integu-
ments are called lorica, by Richard peri-
sperm and episperm, and by De Candolle
spermoderm. It appears to consist of two
coats, and, in succulent seeds, of an
intervening substance called sarco-
derm.

TESTA'CEA {testa, a shell). Mol-
luscous animals, having a shelly cover-
ing, as the oyster.

TESTUDI'NIDjE {testudo, a tortoise).
Land-tortoises ; a family of Chelonian
reptiles, distinguished by their highly
arched carapace, and short clubby feet.

TETRABRANCHIA'TA (Terpcic, four,
/?ptiYx<a, gills). An order of Cepha-
lopods, represented in modern times by
the Pearly Nautilus, in which there are
four branchial organs, two on each side.
See Dibranchiata.

TE'TRACHORD (tctp«p, four, x°p3»,
a chord). The Greek name for any part
of the scale of music consisting of four
notes, the highest of which is a perfect
fourth to the lowest.

TETRADYNA'MIA (rerpap, four,
bvvanis, power). The fifteenth class of
Linnaeus's system of plants, characterized
by the presence of six stamens, of which
four are long, two short, as in Stock.

TE'TRAGOX (rerpaf, four, 7ama, an
angle). A figure with four angles,
usually applied jonly to the square.

TETRAHE'DRON (rerpap, four, 23pa,
a seat). A geometrical solid contained by
four equal and equilateral triangles.

TETRA'MERA {r*rpit, four, pepo?,
a part). A section o' Coleopterous in-
sects, in which all the tarsi have four
distinct joints, the fifth being very mi-
nute, and concealed in the others. La-
treille.

TETRA'NDRTA (TeTP«p, four, Av^p,
mile). The fourth class of plants in
Linnaeus's system, characterized by the
presence of four stamens of equal length.
See Didynamia.

TETRAO'NIDjE (letrao, the grouse).
The Grouse family of the Rasores, or
Scratching Birds, characterized by their
very short hind toe and very short tail.
They differ as little from the partridges
as these from the pheasants. They vary
much in size.
TEU'THIME (teuthis, a calamary). A
334

family of Cephalopods, of which the
loligo vulgaris, or teuthis, is the type.

TEXTURE OF ROCKS. By texture
is meant the mode of aggregation of the
mineral substances of which rocks are
composed, and it relates to the arrange-
ment of their parts viewed on a smaller
scale than that of their structure. In
this respect rocks may be simple or com-
pound, that is, composed of a single mine-
ral species, or of several species. Com-
pound rocks are said to be fragmentary,
when their particles or fragments are
united by a cement; aggregated, when
their particles cohere without the inter-
vention of a cement.

1. The texture of simple rocks is said
to be, 1, compact, when the particles or
crystals are so minute as not to be dis-
tinguished by the naked eye, as in some
kinds of felspar and limestone ; 2, earthy,
when the particles are minute, and hav-
ing little cohesion, readily crumble, as in
some kinds of chalk ; 3, granular, when
the particles or crystals are distinguish-
able, and of a rounded form, as in oolite ; 4,
crystalline, when the particles are readily
distinguishable, confusedly aggregated,
and present the appearance of imperfect
crystals, as in primary limestone ;
5, scaly, when the particles are disposed
in the form of small scales, as in some
varieties of clay-slate ; 6, lamellar, when
the rock is composed of very thin la-
mellae, or plates, as in some kinds of
pitchstone; 7, laminar, when composed
of thin parallel laminae, or plates, as in
clay-slate; 8, fibrous, when composed of
very elongated slender crystals, as in
fibrous gypsum; and, 9, radiated, when
the fibres present a radiated or divergent
arrangement, as in actinolite slate.

2. The texture of aggregated compound
rocks is said to be, 1, compact, when the
particles are so minute, as to give the
rock a dense, homogeneous appearance,
as in some kinds of granite and green-
stone ; 2, earthy, as in lava ; 3, granular,
as in clay and marl ; 4, crystalline, also
called granular or granitic by geologists,
as in granite and hornblende rock;

5, slaty, as in gneiss, mica-slate, and
chlorite-slate ; this texture being crystal-
line in the compound rocks, but with the
component minerals more extended in
one direction than in another, and thus
arranged so as to form distinct laminae;

6, porphyritic, when in a basis, either
crystalline or compact, distinct crystals
are interspersed, as in various kinds of
porphyry, porphyritic granite, syenite, and

TH A

THE

green-stone; 7, amygdaloid, when in a
basis, generally compact, sometimes crys-
talline or earthy, are interspersed roundish
or oval bodies, composed of one or more
mineral substances, as in amygdaloidal
clay-stone or green-stone ; and 8, cavern-
ous, presenting numerous small cavities,
roundish, oval, or of various forms, in a
compact or granular rock.

3. The texture of fragmentary rocks is
said to be, I, brecciated, when it consists
of angular fragments, cemented together,
constituting breccia; and, 2, conglome-
rated, when it consists of rounded frag-
ments of quartz, granite, flint, or other
substances cemented together, forming
conglomerate.

THALAMIFLO'RjE (thalamus, a bed,
flos, a flower). A sub-class of Exogenous
plants, having a calyx and corolla, petals
distinct, and stamens hypogynous. Every
part of the flower springs separately
from the thalamus, without contracting
cohesion with each other, as in Ranun-
culaceae.

THA'LAMUS. Literally, a bed; and,
hence, the term is applied by botanists
to the dilated summit of the peduncle
upon which the carpels are seated ; the
term is synonymous with torus and with
receptacle. In the nomenclature of fun-
gaceous plants, it is the same as thallus,
or the bed of fibres from which many
fungi arise.

THALASSI'NIANS. A family of
those macrurous decapods which have
the four anterior feet terminated by two
fingers, and are remarkable for the ex-
treme elongation of the abdomen and the
small degree of consistence of their in-
teguments. They are named from the
genus thalassina of Latreille.

THALA'SSIOPHYTES (OaXdaviov,
belonging to the sea, <pvr6v, a plant).
Sea-plants ; a general term applied to the
vegetable productions of the ocean, of its
rocks and its shores. It is synonymous
with the term hydrophytes, and com-
prises all the plants usually designated
as marine algae, viz. fucus, ulva, &c.

THALLUS. A terra applied to the
lobed frond of lichens, and to the bed of
fibres from which many fungi arise ; it is
generally employed to denote the com-
bination of stem and leaves in the lower
cryptogamic plants. Thallodes is the
adjective used to designate any thing
arising from the thallus.

THAU'MATROPE {OaZpa, a wonder,
TpeTro), to turn). A philosophical toy, in
which two objects painted on opposite
335

sides of a card, — as a man and a horse, a
bird and a cage, — are, by a quick rota-
tory motion, made to impress the eye in
combination, so as to form one picture,
of the man on the horse's back, the bird
in the cage, &c. A mental illusion
closely analogous to this, is produced,
when by a rapid and repeated transition
from one subject to another alternately,
— by a kind of intellectual thaumatrope —
the mind is deluded into an idea of the
actual combination of things which are
really incompatible. Whately.

THE'CA {ef]Kn a capsule). A term
applied, in Botany, to the cavity of the
anther, to the sporangium of ferns, to
the urn of mosses, &c.

THECADA'CTYLES (6^**, a theca or
hollow case, SuktvAos, a toe). The name
given by Cuvier to those Geckos which
have the toes enlarged throughout their
length, and furnished below with trans-
verse scales, which are divided by a
longitudinal furrow, in which the claw
may be entirely concealed.

THE'CAPHORE (0,>rj, a capsule,
<p€pa>, to bear). The stalk upon which
the ovary of plants is sometimes seated,
as in tacsonia. The term is synonymous
with gynophore, podogynium, &c.

THECODONTS (fty**, a theca or
socket, bdoi/i, a tooth). This and some
other similar terms have been employed
to denote the leading modifications in the
mode of attachment of the teeth among
the inferior or squamate saurians. The
base of the teeth may be either ankylosed
to the summit of the alveolar ridge, or
to the bottom of an alveolar groove, and
supported by its lateral wall. These mo-
difications are indicated respectively by
the terms acrodont and pleurodont. By
a third mode of fixation, the teeth are
implanted in sockets, either loosely or
confluent with the bony walls of the
cavity : these, Professor Owen calls the-
codont lacertians.

THECO-SO'MATA (O^n, a theca or
cavity, cw/jlu, a body). The name given
by De Blainville to the first family of
Aporobranchiala, or those molluscs which
are provided with natatory appendages,
without any foot properly so called, and
with the organs of respiration but little
evident. According to Mr. J. E. Gray,
the thecosomata constitute the first order
of the class Pteropoda.

THE'COSTOMES (B^n, a cavity, <tj6-
/io, the mouth). The name given by
Latreille to those insects which have a
suctorious mouth enveloped in a sheath.

THE

THE

THELPHU'SIANS. The name given
by Milne Edwards to a tribe of brachyu-
rous crustaceans belonging to his family
Catometopes, and constituting a connect-
ing link between the Cancerians and the
Gecarcinians, or land-crabs. They are
named from the genus thelphusa, sup-
posed to be the Heracleotic crabs of
Aristotle.

THE'NARDITE. Anhydrous sul-
phate of soda, found in crystalline crusts,
at the bottom of the briny waters at the
Salines d'Espartines, near Madrid. It is
used in the preparation of carbonate of
soda.

THEO'DOLITE. An instrument for
measuring horizontal angles contained
between lines supposed to be drawn from
any point to two distant objects. In its
simplest form, the theodolite consists of
a divided circle, which is to be set parallel
with the horizon ; and a telescope which
has so much motion in a vertical plane as
to enable the observer to view any object
which he may require above or below the
horizon. The etymology of the term is
obscure.

THE'OREM (fcwpujua, that which is
looked at). In Mathematics, a theorem
is a proposition in which the truth of
some principle is asserted; the object of
the demonstration being to show how the
truth of the proposed principle may be
deduced from the axioms and definitions,
or from other truths which have been
previously and independently established.
The theorem, asks for demonstration only,
and thus differs from the problem, which
asks for discovery both of method and of
demonstration. See Problem.

THEORY {Oewpia, speculation). A
system of rules, intended to explain cer-
tain facts, with reference to some real or
hypothetical law. Thus, the theory of
the planetary motions is deduced from
the principle of gravitation ; that of
light, from the undulatory hypothesis.
A hypothesis differs from a theory, as
being an assumption conceived to afford
a support to the re d or supposed law :
thus, to refer the phenomena of gravi-
tation to the universal diffusion of ether,
is a hypothesis. The theory is, however,
unaffected by the hypothesis.

THEORY OF COUPLES. The term
couple was applied by M. Poinsot to a
pair of equal and opposite forces, not
equilibrating each other, and not capal le
of being replaced by a single force, or
resultant, — in fact, an incomposible cou-
ple. The plane of the couple is the
336

plane drawn through the parallel forces
the arm of the couple is any line drawn
perpendicular to the forces from the di-
rection of one to that of the other, the
axis of the couple is any straight line
perpendicular to its plane. If we con-
sider any axis, it will be evident that the
moment or leverage of the couple to turn
the system about that axis is represented
by the product of one of the forces and
the arm. For if, with reference to the
axis, x be the arm of one of the forces,
x ± a is that of the other, a being the
arm of the couple. Hence, if P be one
of the forces, the united leverage is
P {x ± a) — Pa; or ± Pa. This product
Pa is called the moment of the cou-
ple. Pen. Cycl.

THEORY OF EQUATIONS. The
Theory of Algebraical equations is that
branch of analysis, which relates to the
discussion of equations when presented
in their most convenient form for solu-
tion ; and its great object is to develope
the properties and to evolve the values of
the real and the imaginary roots. See
Equation, Algebraic.

THERMAL RAYS {0epnn, heat).
Luminous thermal rays are those rays of
heat which are combined with flame, as
those emitted from the sun, which pene-
trate all diathermanous substances.
Those rays, on the contrary, are said to
be opaque, which proceed from bodies
heated below the point of active com-
bustion. Hence, bodies are either per-
fectly or partially diathermanous, the
former transmitting all the thermal
colours, the latter only some of
them.

THERMAL SPECTRUM. When
Thermal rays have been transmitted
through a diathermanous prism, they
compose a thermal spectrum, in like
manner as the sun's rays form a solar
spectrum. See Spectrum.

THERMO-ELECTRICITY {Oepp.*,
heat). A term applied to the phenomena
which are exhibited by electricity as de-
veloped by heat. The condition of the
electrical equilibrium of bodies is dis-
turbed by heat, especially when the tem-
perature of a part of their mass is either
raised or lowered ; the effects being exhi-
bited by the deflexions of a magnetized
and balanced needle.

THERMO-MULTIPLIER (0c?Piur),
heat). A thermo-electric pile, employed
by Melloni for detecting changes of tem-
perature, and endowed with much greater
sensibility to the impressions of heat

THE

THE

than the most delicate mercurial, or air
thermometer.

THERMOMETER (0<=p/x»i, heat, ne-
rpov, a measure). Literally, a measurer
of heat; an instrument for comparing
the degree of active heat existing in
other bodies, by its effect in expanding
a column of mercury.

1. Fahrenheit's Thermometer. That
arrangement of the scale of the instru-
ment, in which the space between the
freezing and the boiling points of water,
under a medium pressure of the atmo-
sphere, is divided into 180 parts, or de-
grees, the freezing being marked 32°,
and the boiling 212°. This scale was
adopted by Fahrenheit, because he sup-
posed, erroneously, that 32 of those divi-
sions below the freezing point of water
(which was therefore 0 on his scale) was
the zero, or greatest degree of cold.

2. Centigrade Thermometer. This is
the thermometer of Celsius, which is
used in France, and is the most conve-
nient in practice : it consists in that ar-
rangement of the scale, in which the
freezing point is marked 0, or zero ; and
the boiling point 100.

3. Reaumur's Thermometer. In this
scale the freezing point is marked 0, or
zero, and the boiling point 80°. The
degrees are continued of the same size,
below and above these points, those
below being reckoned negative.

4. These different modes of graduation
are easily convertible: the Centigrade
scale is reduced to that of Fahrenheit
by multiplying by nine and dividing by
rive ; that of Reaumur to that of Fahren-
heit by dividing by four instead of five :
or that of Fahrenheit to either of these,
by reversing the process. Thus —

C. 100° x 9=900-s-5 = 180 -I- 32°=212°F.
R. 80° x 9 = 720^4= 180 + 32°= 2 12° F.
Or, by reversing the order —
F. 212°-32 = 180x 5 = 900-5-9= 100° C.
F. 212° -32= 180x4= 720-5-9= 80° R.

5. A Table is added, showing the cor-
respondence of the three thermometers.
Fahrenheit. Centigrade. Reaumur.

212 100* 80-

200 93-33 74-66

190 87-77 70-22

180 82-22 65-77

170 7666 61 33

160 71-11 56-88

150 65-55 52 33

140 60- 48*

130 55-55 43-55

120 48-88 3911

110 43-33 3466

337

Fahrenheit. Centigrade. Reaumur.

100 37-77 30 22

90 32 22 25-77

80 26-66 21-33

70 2111 16-88

60 15 55 12*44

50 10- 8-

40 4-44 3-55

32 0- 0-

20 - 6-66 - 5-33

10 -12-22 - 9-77

0 -17-77 -14-22

6. Thermometer, Differential. This
instrument consists of two glass bulbs,
connected by a glass tube bent in the
form of the letter U. The tube is partly
filled with a coloured liquid. On ex-
posing one bulb to heat, the expansion of
the air forces the liquid down, and causes
it to rise in the opposite part of the tube.
This instrument is not intended to indi-
cate the temperature of the atmosphere,
as the application of cold or heat to both
bulbs at the same time produces no alte-
ration in the level of the liquid ; it
merely indicates the difference of tem-
perature between the two bulbs.

7. Thermometer, Register. An instru-
ment by which the highest and lowest
temperatures which occur within a given
time, are indicated and made to register
themselves. It consists of two thermo-
meters placed with their tubes in a hori-
zontal position. The one contains spirit
of wine, the other contains mercury. In
the stem of the former a small iron wire,
placed at the surface of the mercury, acts
the part of an index, being propelled
forward as the mercury expands, and
being left at the point of greatest expan-
sion, when the mercury contracts ; it
then indicates the highest temperature
which has occurred during an observa-
tion. In the stem of the latter a small
piece of ivory is immersed in the spirit,
and by a slight inclination of the instru-
ment is brought to the surface of the
liquid. When the temperature falls, the
ivory is carried back with the spirit ; but,
when the temperature rises, the spirit
only advances, the ivory being left be-
hind, thus indicating the lowest tem-
perature which has occurred. By in-
verting the thermometer, the ivory is
brought again to the surface for a new
observation.

8. Thermometer, Magnetic. An appa-
ratus for employing the thermo-electric
current as a measurer of temperature in
cases in which other instruments are not
sufficiently delicate ; or in cases in which
Q

THO

THY

the temperatures are so very high or so
very low that our ordinary pyrometers
and thermometers cannot be relied on ;
or, lastly, in places in which other kinds
of apparatus could not be used. The
strength of the current generated by the
heat in a thermo-battery measures its
temperature ; the intensity of the cur-
rent being estimated, as in hydro-electric
batteries, by the deflection of a magnetic
needle.

THE'RMO PHONE (0eP|un. heat, <pd>vr],
sound). An apparatus, also called, from
its discoverer, Trevelyan's instrument,
for producing sounds from heated metals
when placed under certain circum-
stances. It consists of a metallic body,
generally of brass, which is first heated
and then laid on a cold block of lead, to
which it gradually imparts its heat ;
during the process of cooling, the former
bcdy contracts in a manner by regular
pulsations, and in so doing emits musical
sounds, which cease entirely when the
temperatures of the two metals are
equalized.

THERMOSCOPE (0<^/un, heat, <tko-
n€<a, to observe). The name of a parti-
cular kind of thermometer, which shows
or exhibits the changes of heat to the eye.
So, pyroscope is the name of a particular
kind of pyrometer.

THERMOSTAT (0ep/tx»j, heat, tvrnfu,
to fix). Heat-governor. A self-acting
apparatus for regulating temperature,
constructed on the principle of the un-
equal expansion of metals by heat.

THIN OUT. A term employed when
a geological stratum, in the course of its
prolongation in any direction, becomes
gradually less in thickness; the two
surfaces approach nearer and nearer,
and when, at last, they meet, the
stratum is said to thin out or disap-
pear.

THIRD. An interval in music, classed
among the imperfect concords, from its
variable nature, as it may be either major
or minor. The ratio of the major third
is 5 I 4 ; that of the minor, 6 '. 5. The
former comprises one major and one
minor tone, as CE; the latter, a major
tone and a semitone, as A C.

THO'MPSONITE. A mineral of the
zeolite family, found near Kilpatrick.

THORITE. A mineral found in
syenite, in Norway, containing about
58 per cent of thorina.

THO'RIUM. A metal obtained from
a black mineral, called thorite, from the
coast of the North Sea, and named from
338

the Scandinavian deity Thor. Thorina
is considered to be a protoxide.

THOROUGH-BASE. A technical
term expressive of the art of playing
an accompaniment on keyed instru-
ments from figures representing chords,
and placed over or under the notes of
the instrumental base staff.

THREE, RULE OF. The name given
to an arithmetical rule which teaches,
from three given quantities, to find a
fourth, bearing a certain relation to them.
The relation is, that the first quantity
shall bear the same proportion to the
second as the third to the fourth, or the
required quantity. The rule may there-
fore be briefly stated to be that by which
a fourth proportional is found to three
given quantities.

Double Rule of Three. Questions may
arise in which, instead of 3 terms given
to find a fourth, we may have 5 given to
find a sixth. The rule in such cases
might be called the Rule of Five. " Write
the given quantities in two lines, keep-
ing quantities of the same sort under
one another, and those which are con-
nected with each other in the same line.
Draw a curve through the middle of
each line and the extremities of the
other. There will be three quantities on
one curve and two on the other. Divide
the product of the three by the product
of the two, and the quotient is the an-
swer to the question." Be Morgan.

THULITE. A mineral, usually granu-
lar, found in Norway, and consisting
principally of silica, alumina, and lime.

THU'MERSTONE. A mineral found
in beds at Thum in Saxony. It is also
called axinite, from the axe-like form
and edge of its crystals.

THUNDER. This phenomenon is
supposed to be occasioned by the sudden
rushing of the air into a partial vacuum
produced by the heat of lightning. For
its prolongation, various causes have
been assigned.

THYRSUS. A form of inflorescence,
consisting of a compact panicle, the
middle branches of which are longer
than those of the apex or of the base, as
in lilac. The thyrsus has been also de-
fined as an inflorescence at first centri-
petal, afterwards centrifugal.

THYSANO'URA {0v*<tu>, obsolete ;
from 0u<o, to move rapidly, ol>pa, a tail).
The Spring-tails ; an order of insects
which jump by means of their tail. They
are wingless, and do not undergo meta-
morphosis.

TIN

TOI

TIDES. A term applied to the pe-
riodic rising and falling of the ocean,
caused chiefly by the attraction of the
moon, but partly by that of the sun.
The sea flows, or rises, as often as the
moon passes the meridian, both the arc
above, and the arc below the horizon ;
and it ebbs, or falls, as often as she passes
the horizon, both east and west. When
the moon is in the first and third quarter,
i. e.,when she is new and when she is full,
or, in other words, when she is in con-
junction or in opposition, the tides are
high and swift, and are called spring-
tides ; when she is in the second, and last
quarter, i. e., when she is a half-moon,
or in her quadratures, the tides are lower
and slower, and are called neap-tides.

TILE ORE. A sub-species of octo-
hedral red copper ore. An earthy variety
occurs massive and incrusting copper
pyrites ; the indurated variety is an inti-
mate combination of red copper ore and
brown iron ochre.

TILGATE BEDS. The name given
by Dr. Mantell to a portion of the great
series of strata in the Weald of Kent and
Sussex, interposed between the green-
sands and the Portland oolite.

TIME. A certain measure of dura-
tion, depending upon the motion of the
heavenly bodies.

1. Equal or mean time, is that which
is reckoned by a clock, supposed to indi-
cate exactly 24 hours, from 12 o'clock
on one day, to 12 o'clock on the next day.

2. Apparent time, is that which is
measured by the apparent motion of the
sun in the heavens, as indicated by a
meridian line, or sun-dial.

3. Sidereal time is that portion of a
sidereal day which has elapsed since the
transit of the first point of Aries, and
represents at any moment the right
ascension of any object which is then on
the meridian.

4. Astronomical time of day is the
time past mean noon of the day, and is
reckoned on to twenty-four hours in
mean time.

5. Civil time is mean time adapted to
the purposes of civil life. The civil day
commences at midnight, and is divided
into twelve hours marked a.m. or ante
meridian, and twelve marked p.m. or
post meridian.

TIN. Stannum. A white metal ob-
tained from the peroxide, or common
ore, called stream-tin. The purer por-
tion of the metal thus obtained, is called
grain tin, the other portion ordinary tin
339

or block tin. The metal is found asso-
ciated with sulphur and copper, consti-
tuting tin pyrites ; when combined with
oxide of iron and silex, it is called tin-
stone and wood-tin. The protoxide and
the peroxide are named, respectively,
the stannous and the stannic oxide.

TIN-FOIL. An alloy composed chiefly
of tin, with a small portion of lead, and
sold in the form of a leaf of about the
l-1000th part of an inch in thickness.

TINCAL. Crude borax, as it is im-
ported from the East Indies, in yellow
greasy crystals. When purified, it con-
stitutes the refined borax of commerce.

TFNEID^E (tinea, a moth). A
family of Lepidopterous insects, consist-
ing of small moths, which infest woollen
stuffs and furs, upon which their larvae
feed.

TIPU'LIDjE. A family of dipterous
insects, belonging to the section Nemo-
cera, and typified by the species com-
monly called Harry-long -legs.

TISSUE. A web, or web-like struc-
ture, constituting the elementary struc-
tures of animals and of plants.

TITAN-SHORL. Rutile. Native
oxide of titanium, a mineral comprising
the reticulated variety with golden var-
nish, from Moutier, near the Montblanc ;
acicular and capillary crystals of rutile
in rock crystal, from Brazil, &c.

TITANFFEROUS CERITE. A
blackish-brown mineral, found on the
Coromandel coast, and consisting of the
oxides of cerium, iron, manganese, and
titanium.

TITANITE. Sphene. Silico-titanite
of lime, comprising the varieties of
brown and yellow menakan-ore, in large
crystals ; and that from St. Gothard
denominated rayonnante en gouttiere by
Saussure, on felspar with chlorite, &c.

TITANIUM (T.Vai/o?, calx). A metal
which, in the form of titanic acid, con-
stitutes several minerals, as menachan-
ite, &c.

TOADSTONE. A provincial term
applied to certain igneous or basaltic
rocks associated with the limestone
formation of Derbyshire.

TO'DIDjE. The Todies; a family
of the Insessores, or Perching birds, in-
digenous in America, where they may be
regarded as representing the king-fishers
of the Old Continent. See Fissirostres.

TOISE. Orgya. A French measure

of length, consisting of six feet, or the

ordinary height of man. It is employed in

all the older French measures of the earth.

Q2

TOR

TR A

TOMBAC. A white alloy of copper
with arsenic, called white copper.

TOME'NTUM. A term applied, in
Botany, to the hairs of plants, when they
are entangled, and closely pressed to the
stem.

TOOTHED WHEELS. Wheels which
are made to act upon, or, as it is called,
to drive one another by having the sur-
face of each indented with teeth, and
fixing the centres at such a distance from
each other that the teeth come succes-
sively into contact. The proper form for
the tooth of such wheels is a question of
much complexity.

TOOTHINGS OF LEAVES. The pro-
jecting parts of the margin of leaves,
when the adhesion of the lobes is com-
plete, and the parenchyma which sepa-
rates the extremity only of the veins is
not extended to the extremity of the
principal veins, or beyond them. Such
leaves are said to be toothed or dentate ;
and, when the teeth or toothings are
rounded, they become crenels, and the
leaf is said to be crenelled or crenate.

TOPAZ (rondCtov). A mineral species
occurring massive in imbedded and
rounded crystals. It forms an essential
constituent of a particular mountain -
rock, which is an aggregate of topaz,
quartz, and schorl, and is called topaz-
rock. It comprises three sub-species,
common topaz, schorlite, and physalite.

TOPA'ZOLITE. A variety of pre-
cious garnet, found at Mussa, in Pied-
mont.

TOPO'GRAPHY (totto?, a place,
7pa0o), to describe). The description of
a place, as of a city, a town, a village ; a
term differing from geography, as a part
ditFers from the whole.

TORNA'DO {iornar, Span, to turn).
A sudden and violent storm of wind,
accompanied by thunder, lightning, and
rain, frequently occurring in the West
Indies, and other parts. The term also
denotes, generally, a typhoon or hurri-
cane.

TO'RRELITE. A red mineral from
New Jersey, named from Dr. Torrey, and
consisting principally of silica, iron, and
lime.

TORRICELLIAN EXPERIMENT.
The name given to the experiment by
which Torricelli, a pupil of Galileo, dis-
covered that the mercury remains in the
barometer tube at a height of nearly
30 inches above the level of the mercury
in the cistern. The tube was hence
called a Torricellian tube, and the vacuum
340

in the tube above the surface of the
mercury is the Torricellian vacuum, by
which name it is distinguished from that
obtained by the air-pump, sometimes
called the Guerickian or Boylean va-
cuum.

TORRID ZONE {torridus, burning).
That division, or belt, of the surface of
the earth, which lies on each side of the
equator, extending to the two tropics of
Cancer and Capricorn, and so called from
its excessive heat. See Ascii.

TORSION BALANCE. An instru-
ment, invented by Coulomb, for the mea-
surement of small attractive and repul-
sive forces, by the torsion or twisting of
a fine metallic wire. The electrical tor-
sion balance is made of a thin thread of
shellac, carrying at its extremity a small
gilded pith ball ; this instrument forms
a very delicate electrometer, and is also
employed for estimating exactly the in-
tensity of magnetic forces.

TORUS. A rope or cord made of
twisted grass or straw, on which the
ancients laid their skins or other furni-
ture for the convenience of sleeping;
hence the term is taken for a bed, and is
used in botany as synonymous with
thalamus or receptacle.

TO'TIPALMES (tota palma, an entire
palm). The name given by Cuvier to a
group of birds whose hind toe is united
to the others by a continuous membrane ;
they comprise the pelican, the cormorant,
the boobies, the frigate-birds, &c.

TOUCAN. A modern southern con-
stellation, consisting of nine stars.

TOUCHSTONE. A variety of flinty-
slate, frequently called Lydian stone.

TOURMALINE. Schorl. A mineral
which is hard enough to scratch glass,
and becomes electric by heat. It is of
various colours and forms ; the blue
variety being called indicolite, and the
red rubellite ; it is transparent when
viewed across the thickness of a crystal,
but perfectly opaque when turned in the
opposite direction. The ancients called
it lyncurium. It occurs in gneiss, mica-
slate, talc-slate &c.

TRACHEA'TA (rpaxela, the trachea).
An order of the Arachnida, comprising
those species which breathe by means of
tracheae. See Pulmonata.

TR ACHE'LI DES (Tpaxn^oc, the neck).
A family of the heteromerous Coleoptera,
in which the head is separated from the
thorax by a kind of neck. They are
often of brilliant colours, as the blister-
ing-fly.

TR A

TRA

TRACHE'LIPODS (rpaxnW, the
neck, now, nodos, the foot). A designa-
tion of those mollusca which have the
locomotive disc or foot attached to the
head. Under this title, which represents
the third order of Lamarck, all the uni-
valved shells are arranged.

TRACHE'NCHYMA (rpaXela, the
trachea, £yxuMa> anY thing poured in).
A designation of the vascular tissue of
plants, consisting of spiral vessels, which
resemble the trachea of insects.

TRA'CHYLITE. The name of a
mineral substance resembling obsidian.

TRA'CHYTE (TpaXv?, rough). A
variety of lava essentially composed of
glassy felspar, and frequently having
detached crystals of felspar in the base
or body of the stone, giving it the struc-
ture of porphyry. It sometimes contains
hornblende and augite ; and when these
predominate, the trachyte passes into the
varieties of trap called greenstone, ba-
salt, dolorite, &c. The term is derived
from the peculiar rough feel of the
rock.

TRACTION {tractio, drawing). In
Mechanics, the act of drawing a body
along a plane, by the power of animals
or of steam. The angle of traction is the
angle which the direction of the power
makes with a given plane. The power
excited to produce the effect is called
the force of traction. See Horse-power.

TRA'CTRlX or TRACTORY. A
curve described by a heavy point attached
to a string, the other end of which is
moved along a given straight line or
curve. It is characterized by this pro-
perty, that the tangent is always equal to
a given line.

TRADE WINDS. In a belt extend-
ing about 30° on each side of the equator,
the wind is observed to blow all the year
round from nearly the same quarter of
the heavens : to the north of the equator
it blows nearly from the n.e. quarter,
and to the south of the equator from the
s.E. quarter. These winds, from the great
assistance which they afford to commerce,
are called the n.e. and the s.e. trade
winds. ' When ships are bound from
Europe to the West Indies, or to any part
of North America, south of the parallel
of about 38°, they seek the aid of these
winds ; but when they return, they keep
away to the northward for the purpose
of avoiding them.

TRAJE'CTORY. A technical name
formerly given to a curve required to be
found by means of certain conditions ;
341

generally used for the required path of a
projectile acted on by given forces.

TRAMMELS. Elliptic compasses,
used for making figures of an elliptfe
form. In this instrument, a bar carry-
ing a pencil is guided by two pins which
move in grooves.

TRANSCENDE'NTAL (transcendo, to
go beyond a certain limit). In the phi-
losophy of Kant, the transcendental ele-
ments of knowledge are those which are
original or primary, or those which are
determined & priori in reference not only
to human cognition, but also to man's
collective activity; and which, conse-
quently, are the basis of empirical know-
ledge, or that which is determined d,
posteriori. In short, all pure knowledge
makes up the transcendental philosophy,
and on it rest the authority and possi-
bility of cognition. The term is thus
synonymous with metaphysical.

A transcendental problem, according to
the earliest meaning of the term, is one
the equation of which is infinitely high,
or contains an infinite series of powers of
an unknown quantity, so that its highest
degree transcends every degree. But
the term transcendental has undergone
many changes of meaning. The writers
in the Penny Cyclopaedia predict that
it will settle into the following : " a tran-
scendental result will be one which is
incapable of expression, except by a
definite integral, or by an infinite series
which cannot be otherwise expressed
than by a definite integral."

TRANSFORMATION. A term in
Mathematics denoting a change made in
the object of a problem or in the shape
of a formula, in order to facilitate the
solution, calculation, or use of the ori-
ginal problem or formula ; as when an
equation is transformed into another
equation, having roots which bear simply
a relation to the roots of the former. All
the operation of Algebra consists in trans-
formation, from and after the point at
which the problem to be solved is re-
duced to an equation.

TRANSIT {transeo, to pass over). In
Astronomy, this term denotes the pas-
sage of one heavenly body over the disc
of a larger one, as that of Mercury, when
he transverses the sun's disc under the
form of a black spot. When the nearer
body has the greater apparent diameter,
so as to hide the other, the passage is
termed an occultation of the latter.

TRANSIT INSTRUMENT. Instru-
ment des Passages, An instrument by
Q3

TR A

TRA

means of which the culminations of ce-
lestial objects are observed. It consists
of a telescope firmly fastened on a hori-
zontal axis directed to the east and west
points of the horizon, or at right angles
to the plane of the meridian of the place
of observation.

TRANSITION SERIES. Submedial
rocks. A geological designation of the
upper metamorphic rocks, which form a
kind of link between the primary and
the secondary rooks, partaking of the
characters of both. They are divided
into two series or systems, the Greywacke
and the Silurian.

TRANSLATION. This word is used
in Mechanics, as distinguished from Ro-
tation, in the following manner: — A
body has motion of translation when all
its points move in parallel straight
lines ; when, in fact, all its points have
the same motion. If all have not the
same motion, there is either simple
rotation, that is, about one permanent
axis ; or rotation about a varying axis ;
or else a compound of translation and
rotation. The motion of a single point
must always be called translation, rota-
tion being an inadmissible idea. — Pen.
Cycl.

In Geometry, the word translation has
a wider sense; perhaps, transference
might be a preferable term, as applied to
the motion of a figure from one part of
space to another. The case meets us at
the fourth proposition of the First Book of
Euclid's Elements, in which we have to
conceive of one figure being transferred
by some means ; for it is impossible to
imagine space removed, or any part of
space made to change place. — Ibid.

TRANSLU'CENT and TRANSPA'-
RENT. 1. Translucent bodies are those
which permit light to pass through them,
but not in sufficient quantity to render
objects distinct, as to colour, distance, or
form, when viewed through them. 2.
Transparent bodies are those which per-
mit the rays of light to pass freely
through them, as air and some of the
gases, which transmit light without
being visible themselves : glass and
water are less transparent. Translucent
bodies might be termed semi-transpa-
rent.

TRANSMUTATION. The alchemi-
cal operation of changing the imperfect
into the perfect metals. In geometry, the
changing of one figure into another of
equal area or content, as of a triangle
into a square, of a sphere into a cube.
342

TRANSPOSITION. In Algebra, the
process of removing or transposing a
term from one side of an equation to the
other, at the same time changing its
sign. Thus, the equation, a = b + c
becomes, by transposition of c, the equa-
tion a—c=b, the value of which is pre-
cisely the same as that of the preceding.
The process amounts to merely subtract-
ing c from both sides of the equation.

TRANSVE'RSAL. The name given
in Mathematics to a line, whether right
or curved, which is drawn across or in-
tersects a system of other lines, right or
curved

TRANSVERSE. The name frequently
given to one of the axes of a figure,
usually that of the greater magnitude or
which goes across the figure. Thus, the
longer axis of an ellipse or of a hyper-
bola is the transverse axis ; the equato-
rial axis of the globe is the transverse.
Properly speaking, the term is merely
relative : each axis is transverse to the
other.

TRANSVERSE MAGNET. A pecu-
liar variety of bar magnets, whose poles
are not at the ends, but at the sides :
these magnets have always some even
number of polar lines. They are made
by thrusting 2, 4, 6, &c. bar magnets
through a ring in the direction of its
diameter, and with their unlike poles
opposite to each other; a sufficient space
is left between these magnets to pass the
bar between them which it is proposed
to magnetise, so that it may touch them
as it is drawn through.

TRAP and TRAPPEAN ROCKS
(trappa, Swedish, a stair). Volcanic rocks
composed of felspar, augite, and horn-
blende. The various proportions and
state of aggregation of these simple mi-
nerals, and differences in external forms,
give rise to varieties, which have received
distinct appellations, as Basalt, Amygda-
loid, Dolorite, Greenstone, and others.
The term is meant to denote that the
rocks of this class sometimes occur in
large tabular masses, which rise one
above another, like steps or stairs.

Trap conglomerate. The name given
to conglomerates formed of fragments
of greenstone, basalt, or claystone, to-
gether with portions of stratified rocks,
more or less rounded by attrition, and
imbedded in a paste of the same nature,
or having their intervals filled up by it.
Such deposits, usually in the form of
irregular beds, are named by many geolo-
gists trap tufa. A considerable portion

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of Arthur's seat, near Edinburgh, is
composed of this rock.

TRAPE'ZIUM (tpaneCiov, a little
table). A term applied to any quadri-
lateral figure which is not a parallelo-
gram ; it is therefore inapplicable to the
square, the oblong, the rhombus, and
the rhomboid. Some writers apply the
term trapezoid to a quadrilateral, which
has only two sides parallel; and trape-
zium to a quadrilateral having two sides
parallel and the other two equal, but not
parallel. It has been proposed that trape-
zium should be the general word for
plane quadrilateral figures, parallelo
grams included ; and that trapezoid
should denote a quadrilateral figure
whose sides are not in the same plane.

TRASS. A deposit of volcanic ashes
and scoriae ejected from the Eifel volca-
noes, and accumulated in valleys and old
lakes under the influence of water. It
is equivalent, or nearly so, to the puz-
zolana of the Neapolitans.

TRAUBEN-ERTZ. The massive bo-
tryoidal variety of green lead ore, one of
the divisions of phosphate of lead or
pyromorphite.

TRAUMATE. The name given by
the French geologists to graywack6.

TRAVERSE. Traverse-sailing, or the
working of a traverse, is the method of
calculating a ship's place after she has
made two or more short courses on dif-
ferent points of the compass.

TRAVERSE TABLE. A table used
in traverse-sailing and for other pur-
poses. It is a neat trigonometrical
canon, as follows :— The angle a ship
makes with the meridian is the angle of
the course ; the distance run in that
course is the hypotenuse of a right-angled
triangle, and the side opposite to the
angle of the course is called the depar-
ture (from the meridian). The side ad-
jacent to the angle of the course is called
the difference of latitude (this being found
from it by reducing miles or leagues to
degrees). The traverse table is a table
of double entry, into which, going with
the angle of the course and the distance
run, we find in two columns the cor-
responding departure, and length of the
side, called difference of latitude. — Pen.
Cycl.

TRAVERTIN. The Italian term for
a white concretionary limestone, usually
hard and semi-crystalline, deposited from
the water of springs holding lime in solu-
tion. The term is not exactly equivalent
to tufa, which expresses the loose and
343

porous surface deposit from calcareous
springs, while travertin denotes the more
solid limestone, less frequently formed
in lakes and on hill sides. This stone
was called by the ancients Lapis Tibur-
tinus, being found in great quantity by
the river Anio, at Tibur, near Rome.
Some suppose travertin to be an abbrevia-
tion of trasteverino from transtiburtinus.

TREBLE. In Music, the highest part
in a concerted piece. It is distinguished
into the first or highest, and the second
or low treble. Half-treble, or mezzo
soprano, is a high counter-tenor.

TREMATO'DA (rphi^a, a hole). An
order of sterelminthans, a parenchy-
matous entozoa, furnished with organs
of imbibition and adhesion in the form
of suckers.

TRE'MOLITE. A sub-species of
straight-edged augite, named from Val
Tremola, where, however, it is not found.
It is distinguished into the asbestous,
the common, and the glassy varieties.

TRIAD, HARMONIC. In Music, a
combination of three sounds which is
naturally divisible into two-thirds, one
major, the other minor, constituting a
fifth in the whole. Its name is derived
from its being formed of a third and a
fifth, which, with the base or funda-
mental sound, make three different
terms.

TRIADE'LPHOUS (rpetc, three, £de\-
(pia, brotherhood). A term applied in
Botany to the filaments of plants which
are combined into three masses, or bro-
therhoods, as in some species of hype-
ricum. See Adelphia.

TRIAKE'NIUM. The botanical de-
signation of a fruit which consists of
three achaenia, or cells. See Achcenium.

TRIA'NDRIA (Tpetf, three, uvrjp, a
man). The third class of plants in the
system of Linnaeus, comprising those
which have three stamens.

TRFANGLE (tres angulos habens). A
three-sided figure, having necessarily
three corners or angles. When the lines
forming the sides are straight, the figure,
being on a plane, is called a plane tri-
angle ; when they are curved, lying on
the surface of a sphere, the figure is a
spherical triangle. A triangle is equi-
lateral, when its three sides are equal ;
isosceles, when only two sides are equal ;
scalene, when all its sides are unequal ;
right-angled, when it has a right angle ;
obtuse-angled, when it has an obtuse
angle ; acute-angled, when it has three
acute angles.

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Triangle spherical. A figure drawn
upon the superficies of a sphere, com-
prehended by three arcs of three great
circles, each of which is less than a
semicircle. In any right-angled spherical
triangle, the complement of the hypo-
tenuse, the complements of the angles,
and the two sides, are called the circular
parts of the triangle, as if they were fol-
lowing each other in a circular order,
from whatever part we begin. Thus, if
any three of these five be taken, they
either will be all contiguous or adjacent,
or one of them will not be contiguous to
either of the other two : in the first case,
the part which is between the other two
is called the middle part, and the other
two are called adjacent extremes ; in the
second case, the part which is not con-
tiguous to either of the other two is
called the middle part, and the other two
opposite extremes.

TRIANGLE, ARITHMETICAL. A
table of certain numbers disposed in the
form of a triangle. The first column
contains units only; the second, the
series of consecutive numbers ; the third,
the series of triangular numbers; the
fourth, the series of pyramidal numbers ;
and so on (See Number). The columns
maybe continued vertically to any ex-
tent—

1

1

1

1

2

1

1

3

3

1

1

4

6

4

1

1

5

10

10

5 1

1

G

15

20

15 6 1

Any number in the table is obtained by
adding the number immediately above it
in the same column, to the number in
same horizontal line in the next preced-
ing column ; further, it will be found
that the oblique diagonal rows, beginning
from the left side, are the same as the
vertical columns. One of the properties
of the table is, that numbers taken on
the horizontal lines, are the co-efiicients
of the different powers of a binomial.

TRIANGLE OF FORCES. The
"Parallelogram of Forces" (See Force)
may be stated under another form,
termed the triangle of forces ; for it is
the same thing whether we say of three
straight lines that they are the sides and
diagonal of a parallelogram, or that they
will form a triangle ; hence we may
assert, that forces will be in equilibrium
when they are proportional to the sides
344

of a triangle formed by drawing lines
parallel to their directions.

TRIANGULAR COMPASSES. Com-
passes having three legs, capable of
taking off three points at once, and used
in the construction of maps and charts.
Two of the legs open as in the common
compasses, while the third turns round
an extension of the central pin of the
other two, besides having a motion on its
own central joint.

TRIANGULAR NUMBERS. A series
of numbers formed by the successive
sums of the terms of an arithmetical pro-
gression, of which the common difference
is 1. Thus—

Arith. Progression 1, 2, 3, 4, 5, 6, &c.
Triangular Numbers 1, 3, 6, 10, 15, 21, &c.

The general formula for the series
is £ n (n + 1 ). See Number.

TRI ANGULATION. A name given
to the net-work of triangles with which
the face of a country is covered in a
trigonometrical survey.

TRIA'NGULUM. The triangle; a
northern constellation, consisting of six-
teen stars, surrounded by Perseus, An-
dromeda, Aries, and Musca. The tri-
angulum australe is a modern southern
constellation, consisting of five stars,
lying between Ara, Centaurus, and the
South Pole.

TRIA'SSIC SYSTEM. New red sand-
stone and saliferous marls. A geological
system, forming the base of the great
central plains of England, and sur-
mounted by the saliferous marls and red
arenaceous beds which pass under the
great oolitic terrace, or rather the succes-
sion of terraces which stretch across
England from the coast of Devonshire to
the north-eastern coast of Yorkshire.

TRIBA'SIC SALTS. The name given
to a class of oxygen-acid salts, which, in
the language of the old theory, contain
three atoms of base to one of acid, and
of which the tribasic phosphates are the
type.

TRICA. Gyroma. In the botanical
nomenclature of lichens, this term de-
notes a shield, the surface of which is
covered with sinuous concentric furrows.

TRICHI'DIUM (rpixtiiov, from 0P<f,
a hair). Pecten. A botanical term for
a tender, simple, or sometimes branched
hair, which supports the sporules of some
fungaceous plants, as geastrum.

TRICHO'PTERA (0Pif, rpixbs, hair,
mepov, a wing). An order of insects,
distinguished by the hairy covering of
their wings and bodies. Their larvae are

TRI

TRI

well known under the name of caddice-
worms.

TRICHO'TOMOUS {rpiXa, in three
parts, re/ui/to, to cut). A designation of
the mode of branching or of inflores-
cence, when the divisions occur in threes,
as in the stem of Marvel of Peru.

TRIDACNI'DjE. The name given by
Lamarck to a family belonging to the first
section of his monomyarian conchifers,
or mollusks furnished with bivalve shells
which have a single muscular impres-
sion. This family comprises the genera
tridacna and hippopus.

TRIFID, TRISECTED, TRIPART-
ED, &c. These and other terms are
applied by botanists to the forms of
leaves, with especial reference to the
number and the depth of their lobes, ac-
cording as they have, respectively, fis-
sures, segments, or partitions. And, on
the other hand, we may, by neglecting the
number of the lobes, simply indicate
their presence by saying that a leaf is
pinnatilobed, palmatilobed, and so on.
The lobes themselves are sometimes sub-
divided upon the same principle as the
leaf itself : thus we say that a leaf is tri-
pinnatisected, tripinnatiparted, tripin-
natifid, when the subdivisions of the lobes
are themselves lobed.

TRFGLIDjE. The Gurnard tribe of
acanthopterygious or spiny-finned fishes,
generally resembling the Percidae, but
having their head armed with spines or
hard scaly plates.

TRIGO'NIDjE (tp/ywi/o?, triangular).
A family of conchiferous mollusks, named
from the genus trigonia, the shell of
which is of a subtrigonal form.

TRIGONO'METRY {jpi^avov, a tri-
angle, jueTpea>, to measure). This term
originally denoted simply the science by
which those relations are determined
which the sides and angles of a triangle
have to each other, being called plane or
spherical trigonometry, according as the
triangle was described on a plane or a
spherical surface. By means of certain
proportions always holding good between
the three sides and the three angles of a
triangle, we are enabled, by the aid of
this branch of mathematics, when any
three of these six quantities are known
(provided that one of these known quan-
tities be a side), to find the other three.
At present, the term has a much more
extensive meaning, as the science now
embraces all the theorems expressing the
relations between angles and certain
functions of them ; it embraces the
345

consideration of alternating and pe-
riodic magnitude ; in which quantity
is imagined to go through alterations
of increase and diminution without
end.

1. Definitions of Trigonometrical Lines.

1 . The complement of an arc is its differ-
ence from a quadrant; and that of an
angle, its difference from a right angle.

2. The supplement of an arc is its defect
from a semicircle ; and that of an angle,
its defect from two right angles. 3. The
sine of an arc is a line drawn from one of
its extremities, perpendicular to the ra-
dius passing through its other extre-
mity. 4. The tangent of an arc is a line
touching it at one extremity, and limited
by the radius produced through its other
extremity. 5. The secant of an arc is
that portion of the radius produced,
which is intercepted between the extre-
mity of the tangent and the centre.
6. The versed sine of an arc is that por-
tion of the radius intercepted between
the sine and the extremity of the
arc. 7. The supplemental versed sine,
or suversed sine is the difference be-
tween the versed sine and the dia-
meter. 8. The sine, tangent, &c. of the
complement of an arc, are concisely
termed the cosine, cotangent, &c. of that
arc. These terms, for conciseness, are
usually contracted into sin., tan., sec,
vers., suvers, cos., cot., cosec, covers.,
and cosuvers.

2. Trigonometrical Functions of an
Angle. 1. The ratio which the sine ot
an angle bears to its cosine is called the
tangent of the angle. 2. The inverse of
this ratio is called the cotangent. 3. The
ratio of unity to the cosine of an angle is
denominated the secant ; and that of
unity to the sine, the cosecant. 4. The
difference between unity and the cosine
is called the versed sine. 5. The differ-
ence between unity and the sine of an
angle is called the coversed sine. These
are functions of the angle, and are quite
independent of the absolute length of the
arc subtending it, or of the radius of that
arc.

3. Signs of the trigonometrical lines.
The signs + and -, which in arithmetic
indicate addition and subtraction, are
used in geometry to point out opposition
in direction. Quantities whose signs are
+ , are called positive, and those whose
signs are — , are called negative. If a
line be measured from a given point or a
given line as its origin, it is reckoned

| positive when it lies on one side of its
Q5

TRI

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origin, and negative when on the opposite
side.

4. Trigonometrical Tables. There are
two kinds of trigonometrical tables. The
first kind contains the sines, cosines, &c.
of angles, calculated to the radius unity ;
the sines, cosines, tangents, and secants
in these tables to radius 1, are called
natural, to distinguish them from those
of the second kind, which are called arti-
ficial or logarithmic. By aid of the latter
tables, instead of multiplying natural
sines, &c, we need only add the loga-
rithmic sines, &c. ; and, instead of di-
viding a natural sine or cosine, &c. by
another, we need only subtract the loga-
rithmic sine, &c, which represents the
dividend. By these operations much
time and labour are saved.

5. Trigonometrical Canon. This is a
table, which, beginning from one second
or one minute, orderly expresses the
lengths which every sign, tangent, and
secant have, in respect of the radius,
which is supposed unity; and is con-
ceived to be divided into 10,000,000 or
more decimal parts. And so the sine,
tangent, or secant of an arc, may be had
by the help of this table ; and, contrari-
wise, a sine, tangent, or secant being
given, we may find the arc it expresses.

6. Trigonometrical Curves and Series.
The former are curves having such equa-
tions as y = sin x, y = cos x, y = a cos
x + b cos 2x, &c. The latter are infinite
series of the form a sin x + b sin 2x + c
sin 3a: + &c, and a cos x + b cos 2x + c
cos 3a; + &c.

7. Trigonometrical Survey. The appli-
cation of trigonometry to geodetic opera-
tions, for topographical purposes, and
for measurements connected with gene-
ral geography and with the figure of the
earth.

TRIGY'NIA (rpelf, three, yvvt], a
woman). The name given by Linnaeus
to those orders of plants which have
three pistils.

TRILLION. A million of billions, or a
million of million of millions.

TRFLOBITE (rpel?, three, \o/36?, a
lobe). An extinct crustacean animal, al-
most the sole representative of its class
in the periods which intervened between
the deposition of the earliest fossiliferous
strata and the end of the coal formation.
It if named from the upper surface of
its body being divided into three lobes.

TRFMERA (Tpelc, three, nepos, a
part). A section of coleopterous insects,
in which only three ordinary- sized joints
346

exist in the tarsi, the fourth being mi-
nute and indistinct. Latreille.

TRIMYA'RIANS (Tpelr, three, Muc, a
muscle). A designation of those bi-
valves which present three muscular im-
pressions on each valve.

TRFNGID^E. A group of birds, dis-
tinguished from all others by the great
length, the slenderness, and the flex-
ibility of the bill, no less than by the
delicacy of the legs and the smallness of
the hinder toe. The tringa, or sand-
piper, is the type of the group. They
belong to the family Scolopacidae.

TRINO'MIAL. An algebraical name
for an expression consisting of three
terms, as a + b + c, or ax — bx3 + bx4.

TRIPHANE. Spodumene. A silicate
of lithia and alumina, first discovered in
the island of Uton in Sudermannland,
where it is associated with red felspar
and quartz, and lately by Dr. Taylor in
the vicinity of Dublin.

TRIPHYLINE. A phosphate of iron,
manganese, and lithia.

TRIPI'NNATE ; TRITE'RNATE.
1. The former of these terms is applied
by botanical writers to a leaf in which
there are three series of pinnation, as
when the leaflets of a bipinnate leaf are
themselves pinnate. 2. The latter term
denotes a leaf in which there are three
series of ternation, as when the leaflets of
a biternate leaf are themselves ternate.

TRIPLE SALTS. A term sometimes
applied, in chemistry, to salts in which
two bases are combined with one acid, as
soda and potassa with tartaric acid in
Rochelle salt. These compounds are,
however, more commonly viewed as
double salts, Rochelle salt being consi-
dered as composed of single equivalents
of the tartrates of soda and potassa.

TRPPLICATE RATIO. The compo-
sition of a ratio with itself twice : thus
the ratio of a3 to b3 is the triplicate of
the ratio of a to b. In other words, the
triplicate of a given ratio is found by
taking the cube of each of the terms of
the ratio. Thus, when it is said that
two similar solids, whose linear dimen-
sions are as 6 to 9, are in the triplicate
ratio of 6 to 9, it is meant that the con-
tents of these solids are in the ratio of
6 x 6 x 6 to 9 x 9 x 9, or 216 to 729.

TRIPLITE. Phosphate of manga-
nese, found at Chanteloube, near Li-
moges, in the department of Haute
Vienne in France, where several other
mineral substances have lately been
found, the essential constituents of which

TRO

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are iron, manganese, and phosphoric
acid.

TRPPOLI. A powder used for polish-
ing metals and stones, first imported
from Tripoli, which, as well as a certain
kind of siliceous stone of the same name,
has been lately found to be composed of
the flinty cases of infusoria. It is found
at Bakewell, in Derbyshire, where it is
called rotten-stone.

TRITO'XIDE. An oxide containing
one atom of base combined with three
atoms of oxygen.

TRO'CHIDjE. A family of phyto-
phagous Gasteropods, which have a tur-
binate, mostly trochiform, or top-like
shell, the substance of which is almost
always perlaceous; the outer lip never
thickened ; the aperture entire, closed
by a shelly or horny operculum.

TROCHI'LIDjE (trochilus, a hum-
ming-bird). The Humming-bird tribe ;
a family of the Insessores, or Perching-
birds, characterized by the brilliancy of
their plumage, and by the humming
sound which accompanies their flight.
See Tenuirostres.

TROCHl'NiE. Troehuses, or Top-
shells ; a sub-family of the Trochidce,
named from the genus trochus ; the
shape of these shells is pyramidal, the
body-whorl flattened, and the aperture
closed by a horny operculum.

TRO'CHOID (tpoX6p, a wheel, efeo?,
likeness). A curve described by any
point in a wheel as it rolls forward on a
plane. The term is synonymous with
cycloid.

TROCHOI'DAL CURVES {rpoX6t, a
•wheel or hoop, elios, likeness). " Under
this term is included a large number of
lines which are produced by the com-
position of two circular motions, includ-
ing the straight line, the circle, the el-
lipse, a class of curves called epitro-
choids, of which one particular case is
called the epicycloid, and a class called
hypotrochoids, of which one particular
case is the hypocloid. Among these
must also be included the extreme case
in which one of the motions is rectilinear,
which gives the common trochoid, the
cycloid, and a class of spirals which in-
cludes the involute of the circle, the
spiral of Archimedes, and others." — Pen.
Cycl.

Trochoidal and Planetary Motions. In
the trochoidal motion, which is univer-
sally adopted, one circle is made to roll
like a hoop, either upon a straight line,
or upon the circumference of another
347

circle. The planetary motion resembles
that in which a planet and its satellite
move round the sun. Here a circle,
without any rolling, has its centre carried
round the circumference of another.

TROGO'NIDjE. A family of the In-
sessores, or Perching-birds, remarkable
for the beauty of their plumage, com-
prising the woodpecker, the cuckoos, the
trogons, the toucans, &c.

TRONA. The name given in Africa
to the sesqui-carbonate of soda, imported
from the coast of Barbary, where it is
collected by the natives.

TRO'PHI (rpo<pot, a nourisher). In-
strumenta cibaria. In insects, the organs
which form the mouth, consisting of an
upper and an under lip, and comprising
the mandibles, maxillae, and palpi, or
the parts employed in acquiring and pre-
paring food.

TROPHOPOLLEN. The name given
by Turpin to the septum of the anther of
plants, from which the pollen has been
incorrectly supposed to separate. By
others, this part has been termed the
receptacle of the pollen, and by Link the
raphe.

TRO'PHOSPERM (rpe^us, to nourish,
(TirepiMa., seed). The name given by
Richard to the placenta in plants, the
part from which the ovules arise. It
generally occupies the whole or a portion
of one angle of each cell.

TROPICS (Tpo7riK6f, from rpena, to
turn). Those two circles on the earth,
over which the sun seems directly to
pass, when he is at the greatest distance
from the equator northward and south-
ward (viz. 23£ degrees) ; hence, the one
is called the Northern, the other the
Southern Tropic. They correspond to
the sun's position at the solstices, and
are the limits of the torrid zone.

1. Tropic of Cancer. A designation of
the Northern Tropic, because, when the
sun appears to move vertically over this
tropic, he appears to be in the beginning
of Cancer.

2. Tropic of Capricorn. A designation
of the Southern Tropic, because, when
the sun appears to move vertically over
this tropic, he appears to be in the begin-
ning of Capricorn.

3. The term Tropic denotes a point
where a turn is made ; for the line of the
ecliptic quitting the equator in the first
point of Aries, continues to rise higher
northward from it till it reaches the first
point of Cancer, when it turns to the
southward ; and, after again cutting the

Q6

TRU

TRU

equator at the first point of Libra, con-
tinues to descend southward till it
reaches the first point of Capricorn, when
it again turns to the northward and
reaches Aries.

TROPICAL YEAR. The period of
time which intervenes between two coin-
cidences of the sun with the vernal equi-
nox. This is the common or civil year,
in which the phenomena of the seasons
are repeated, and after which they recom-
mence. It depends chiefly and directly
on the annual revolution of the earth
round the sun, but subordinately also,
and indirectly, on its rotation round its
own axis, which occasions the precession
of the equinoxes. It consists of 365d.
5h. 48m. 49s. 7 ; it is, therefore, shorter
than the sidereal year, or the period of
the actual revolution of the earth round
the sun, by 4' 39". 7. See Anomalistic
Year.

TROUGH APPARATUS. Oersted's
trough apparatus is essentially the same
as Wollaston's battery. It consists of a
trough of copper plate, in the form of a
parallelopiped, about £ an inch wide at
the bottom; in it the zinc plates are
arranged so as not to touch the copper ;
the trough serves also to hold the liquid.

TROUGH, PNEUMATIC. A vessel
made of tinned iron for collecting gases.
It has a moveable stage or bridge, above
which water is to be poured to the height
of about an inch. The bridge is perfo-
rated by a round hole, communicating
above with an inverted receiver, into
which it transmits the gas conveyed to it
by a tube beneath the surface of the
water.

TRUE PLACE. In Astronomy, the
place which a star or planet appears to
occupy in the heavens is not called its
true place, but that which it would oc-
cupy if corrections were made for paral-
lax, refraction, &c. ; that is, if the spec-
tator made his observation from the cen-
tre of the earth, and without the light
passing through a refracting medium.

TRUMPET. The speaking trumpet is
an instrument, best when made of a
parabolic form, for rendering the human
voice audible at a great distance. This
object is accomplished by the rays of
sound being reflected from the interior
of the trumpet, as the words are spoken
, at the smaller end, in such a manner that
they issue from the expanded mouth
parallel to each other, and consequently
agitate the air in the direction in which
the axis of the trumpet is held, more
348

forcibly than they would had they pro-
ceeded immediately from the mouth of
the speaker. The efficiency of this in-
strument increases with its length : a
strong man's voice, sent through a trum-
pet from 18 to 24 feet in length, may be
heard at a distance of 3 miles.

The hearing trumpet inverts the opera-
tion above described, the rays of sound
being received at the large opening, and
reflected so as to become united at the
small aperture which is inserted into the
ear.

TRUNK; STEM; &c. The former
term is applied by botanists to the main
stem of trees ; while the latter is gene-
rally used to denote the ascending axis of
herbaceous plants or shrubs, but not of
trees. The culm or straw is the stem of
grasses ; to these terms De Candolle adds
calamus, applying it to all fistular simple
stems without articulations, as those of
rushes.

TRUTH. This term, in its strict logi-
cal sense, applies to propositions and
to nothing else; and consists in the con-
formity of the declaration made to the
actual state of the case ; agreeably to
Aldrich's definition of a "true" propo-
sition— vera est, quae quod res est dicit.
It would be an advantage, observes
Whately, if the word Trueness or Verity
could be introduced and employed in
this sense, since the word Truth is so
often used to denote the " true " pro-
position itself. " What I tell you is the
Truth ; the Truth of what I say shall be
proved :" the term is here used in these
two senses.

1. Truth, in its etymological sense,
signifies that which the speaker " trows,"
or believes to be the fact. The etymology
of the word aXrj0er seems to be similar,
denoting non-concealment. In this sense
it is opposed to a lie ; and may be called
moral, as the other may logical, truth.
A witness therefore may comply with
his oath to speak the truth, though it so
happen that he is mistaken in some par-
ticular of his evidence, provided he is
fully convinced that the thing is as he
states it.

2. Truth is not unfrequently applied,
in loose and inaccurate language, to
arguments ; where the proper expression
would be "Correctness," '* conclusive-
ness," or "validity."

3. Truth, again, is often used in the
sense of Reality, r6 ov. Persons speak
of the truth or falsity of facts ; properly
speaking, they are either real or fie-

TUB

TUN

titious : it is the statement that is either
"true" or "false." The "true" cause
of any thing, is a common expression ;
meaning ** that which may with truth
he assigned as the cause." The senses
of falsehood correspond. Whately.

TRYMA. The botanical designation
of a syncarpous fruit, which is superior,
by abortion one-celled, one- seeded, with
a two-valved indehiscent endocarp, and
a coriaceous or fleshy valveless sarco-
carp, as in walnut.

TUBE. The surface of a tube is gene-
rally a cylinder, but this word may be
made use of in mathematics. When a
tube is bent, there is no distinct geome-
trical name for it, but the following defi-
nition might do very well : let a surface
be called a tube when it is formed by a
circle which moves with its centre upon
a given curve, and its plane always per-
pendicular to the tangent of that curve.
This would include the straight tube, or
common circular cylinder, and every
species of bent tube. — Pen. Cycl.

TUBE OF SAFETY. A tube open
at both ends, inserted into a receiver, the
upper end communicating with the ex-
ternal air, and the lower being immersed
in water. Its intention is to prevent
injury from too sudden condensation or
rarefaction taking place during chemical
operations ; for, if a vacuum be produced
within the vessels, the external air will
enter through the tube ; and if air be
generated, the water will yield to the
pressure, being forced up the tube.
Thus, too, the height of the water in the
tube indicates the degree of pressure
from the confined gas or gases.

TUBER. An annual thickened sub-
terranean stem, provided at the sides
with latent buds, from which new plants
are produced, as in the potato. When
very small it is called tubercle.

TUBFCOLjE (tubus, a tube, colo, to
inhabit). An order of Annellida, or red-
blooded worms, enclosed in an elongated
tube, which is formed either by the ag-
glutination of foreign matters, or by the
secretion of calcareous matter resembling
that of the shells of certain bivalves.
These are the Pinceaux de Mer of the
French.

The term Tubicola also denotes a
family of Spiders, which enclose them-
selves in a silken tube, strengthened ex-
ternally by leaves or other foreign sub-
stances.

TU'BICORNS {tubus, a tube, cornu,
a horn). A family of the Ruminantia, in
349

which the horns are composed of a horny
axis covered with a horny sheath.

TUBIPO'RIDjE {tubus, a tube, porus,
a pore). A class of polyps, enclosed in a
calcareous or coriaceous sheath or tube,
from the orifice of which the polyp is
protruded when in search of prey. These
are called vaginated-polyps.

TUBFPORITES. The name given to
the fossil species supposed to belong to
tnbipora.

TU'BIVALVES (tubus, a tube, valvcc,
folding-doors). Tubicolidce. A desig-
nation of those bivalves which are fur-
nished with a testaceous tube, as teredo.
The animals of this family are borers,
burrowing in stone, wood, and even in
thick shell ; but some, nevertheless, live
in the sand.

TU'BULATURE (tubulus, a little
tube). The mouth, or short neck, at the
upper part of a tubulated retort. The
long neck is called the beak.

TU'BULIBRANCHIA'TA (tubulus, a
little tube, branchice, gills). An order of
gasteropods, the shells of which consist
of long and irregular tubes usually fixed
to foreign bodies, but having the earliest
formed portion twisted into a few spiral
curves, as in vermetus.

TU'BULIPO'RIM:. A family of the
Polypiaria solida of Blainville, who de-
scribes them, as animals contained in
cells of a tubular figure, with a round
mouth, which are accumulated irregu-
larly, so as to form an attached solid
polyparium. The animals are known
only in the genus tubulipora

TUFA, or TUFF, VOLCANIC. A
variety of volcanic rock, of an earthy
texture, seldom very compact, composed
of agglutinated fragments of scoriae and
loose materials ejected from volcanoes.

1. Tufa, calcareous. A porous rock
deposited by calcareous waters on their
exposure to the air, and usually contain-
ing portions of plants and other organic
substances incrusted with carbonate of
lime. The more solid form of the same
deposit is called travertin, into which it
passes.

2. Tufa, trachytic. Beds and irregular
deposits of conglomerate, composed of
fragments of trachyte and other volcanic
substances, are often abundant in vol-
canic districts. When reduced to the
state of sand or powder, they form beds
of tufa, analogous to those of the trap
series.

TUNGSTEN. A Swedish term, sig*
nifying heavy stone, and applied to an

TUR

TUR

element which exists in the form of
tungstic acid in several minerals, the
most important of which are the native
tungstate of lime, also called scheelite ;
and the tungstate of manganese and
iron, also called wolfram. The tung-
state of lead, or scheel-lead ore, was
formerly confounded with the molybdate
of this metal.

TUNICA'TA {tunica, a tunic). The
first class of the mollusca, comprising
soft, aquatic, acephalous animals, having
their body enveloped in an elastic tunic,
furnished with at least two apertures.
They are distinguished into two orders,
viz. the Salparia, in which the forms are
organically united ; and the Ascidiaria,
which continue isolated by their external
tunic.

TUPAFADjE. The Bangsrings ; a
family of insectivorous vertebrate ani-
mals, consisting of the single genus
tupaia. They are confined to the Indian
Archipelago, where, contrary to the usual
habits of the insectivora, they live in
trees, which they ascend with the agility
of quadrumanous animals.

TU'RBIDjE. Marine snails ; a family
of phytophagous gasteropods, which
breathe by gills, and often exhibit the
carnivorous structure of the zoophagous
division of gasteropods. The shell is
solid, but not perlaceous, spiral ; the
aperture entire, closed by an operculum.

TURBI'NjE. Winkles; a sub-family
of the Turbidce, named from the typical
genus turbo ; these are all marine shells,
with a perfectly entire aperture.

TURBINATED (turbo, a top). A
term applied to shells which have a spi-
ral or screw-form structure, as that of
the garden-snail.

TURBINE'LLIDiE. Turnip-shells ; a
family of carnivorous gasteropods, in
which the base of the shell is straight
and lengthened, and the pillar strongly
plaited. The mantle of the animal is
never dilated, but is of ordinary dimen-
sions, and drawn back into the shell with
the animal.

TURBINELLI'NiE. A sub-family of
the Turbinellidce, or Turnip-shells,
named from the typical genus turbinella,
and characterized by the great size,
weight, and smoothness of the shell, the
great length of the canal, and the gene-
rally papillary state of the spire.

TURBI'NIDjE. A family of gas-

tropodous mollusks, named from the

genus turbo. According to Linnaeus,

the animal is a limax or slug ; the shell

350

is univalve, spiral, solid; the aperture
narrowed, orbiculate, entire. Lamarck
gives the name Turbinacea to the last
family of his herbivorous trachelipods ;
all are marine shells, appearing to be
provided with an operculum.

TURDI'NjE (turdus, a thrush). Tur-
dine birds or thrushes ; a family of the
Cantatrices of Macgillivray, which have
a moderately rapid, somewhat undulated
flight, and on the ground advance by
leaping. Most of the species are re-
markable for their superiority of song.

TURIO. The botanical term for a
scaly bud, developed from a perennial
subterranean root, as in asparagus.

TURKEY-SLATE. Whet-slate; No-
vaculite. A massive greenish-grey mi-
neral, occurring in beds in primitive and
transition clay-slate. Very fine varieties
are brought from Turkey, called hone-
stones. It is used for sharpening steel
instruments.

TURMERIC. The tuber of the cur-
cuma longa, which yields a beautiful
bright yellow colour. Turmeric paper is
unsized paper, brushed over with tincture
of turmeric, prepared by digesting one
part of bruised turmeric in six parts of
proof spirit.

TURNBULL'S BLUE. Ferricyanide
of iron. A blue precipitate which is
thrown down when red prussiate of pot-
ash is added to a protosalt of tin.

TU'RNERITE. A rare mineral, con-
taining alumina, lime, magnesia, and iron,
found only on Mount Sorel in Dauphiny.

TURNER'S YELLOW. Cassel Yel-
low; Patent Yellow. An oxichloride of
lead.

TURNSOLE. A deep purple dye ob-
tained from the crozophora tinctoria, an
euphorbiaceous plant.

TURPETH MINERAL. The name
given by chemists to the sub-sulphate of
mercury.

TURQUOIS. Calaite; Odontalite. An
opaque gem found chiefly at Nishapur, in
the province of Khorasan, in nodules or
as small veins traversing a ferrugino-
argillaceous rock, and greatly esteemed
on account of its beautiful blue colour,
which will in most cases be sufficient to
distinguish it both from the blue silicate
of copper, and from fossil bones (parti-
cularly teeth) impregnated with blue
phosphate of iron or carbonate of copper
— the occidental turquoises of lapida-
ries.

TU'RRILITE. An extinct genus of
spiral, turreted, chambered shells, allied

ul:

ULT

to the ammonites, having the siphunicle
near the dorsal margin.

TU'TENAG. The commercial name for
the zinc or spelter of China, an alloy used
in the manufacture of the gong ; also the
name of a white metallic compound,
called Chinese copper. Impure oxide of
zinc is called tutty.

TWILIGHT. A phenomenon depend-
ing on reflection of the rays of light pass-
ing through the atmosphere. Before the
sun becomes visible above the horizon,
the rays of light illuminate the atmo-
sphere, which to some extent reflects and
scatters them in all directions, and the
result is a faint light which precedes the
rising of the sun and follows its setting,
and which we call twilight. Twilight
begins and terminates when the sun is
about 18° below the horizon ; its dura-
tion varies with the latitude; in some
northern latitudes it may endure all
night. The luminous lines occasionally
seen in the air, in a sky full of partially
broken clouds, which the vulgar term
" the sun drawing water," are similarly
caused.

TYCHONIC SYSTEM. A system of
Astronomy, so named from Tycho Brahe,
a noble Dane, who was born a.d. 1546,
and who partly restored the system of

Ptolemy concerning the earth remaining at
rest, whilst the other heavenly bodies moved
round it. He taught, however, that the
moon performed a monthly revolution
round the earth; that the sun was the
centre of the orbits of Mercury, Venus,
Mars, Jupiter, and Saturn, which revolve
round him in their respective periods, as
he revolves round the earth in a solar
year; and accordingly, that these five
planets, together with the sun, are car-
ried round the earth in twenty-four hours.
TYPE METAL. An alloy of lead and
antimony, used in casting printer's types.
TYPHLOPHTHA'LMES (Tv<p\6s,
blind, b<p0a\n6s, the eye). A family of
Scincoidans, comprising those Saurians
which are completely blind, or whose
eyes are so small that they seem scarcely
to exist, except in a rudimentary state,
and entirely covered with skin, as in the
genera dibamus and typhline.

TYPHOON {tv<Pm, a whirlwind). A
hot wind which occasionally blows with
great violence in Africa, Syria, Arabia,
and Persia. It is known in Egypt by the
name of sirocco, in Arabia as the simoon,
and on the coast of Guinea as the har-
mattan. The term is frequently applied
to a tropical storm.

U

ULLMANNITE. Phosphate of man-
ganese and iron, occurring massive at
Limoges in France.

ULMA'CEiE (ulmus, the elm). The
Elm tribe of Dicotyledonous plants.
Trees and shrubs with leaves alternate ;
Jlowers apetalous ; ovarium superior ;
fruit 1 or 2-celled, indehiscent ; seeds
pendulous.

ULMIC ACID, or ULMIN {ulmus, the
elm). The name given by Dr. Thomson
to a brown substance derived from a se-
cretion of the elm and some other trees,
consistinjg of mucilaginous matter com-
bined with potash. Berzelius changed
the name for that of geic acid (7^, earth),
because, on treating soils with alkalis,
a considerable quantity of a similar com-
pound is obtained. The peculiar pro-
perties of manures, soils, and what is
called moss water, are due to the pre-
sence of this substance.

Sacchulmic acid. This substance, and
sacchulmine, are formed by boiling cane
351

sugar for a very long time in dilute sul-
phuric, hydrochloric, or nitric acid. They
were supposed to be identical with ulmic
acid and ulmin, but Liebig considered
them to be of a different nature, and gave
them their present names.

ULTIMATE ANALYSIS. In che-
mistry, the resolution of substances into
their absolute elements, as opposed to
proximate analysis, by which they are
merely resolved into secondary com-
pounds. These terms are generally used
in reference to organic bodies. Gum,
starch, &c, are proximate principles ;
carbon, hydrogen, and oxygen, ultimate
principles.

ULTIMATE RATIO. The ratio of
evanescent quantities. If two variable
quantities be supposed constantly to ap-
proach each other in value, so that their
ratio or quotient continually approaches
to unity, and at last differs from unity by
less than any assignable quantity, the
ultimate ratio of these two quantities is

UMB

UND

said to be a ratio of equality. The me-
thod of prime and ultimate ratios was in-
troduced by Newton, and the terms re-
late to the ratios of variable quantities
considered as receding from, or approach-
ing to, the ratios of the limits to which
they continually and simultaneously ap-
proach.

ULTRAMARINE. A blue pigment
of great permanence, prepared entirely,
until lately, from the lapis lazuli or lazu-
lite. It is now made of silica, alumina,
soda, and sulphur.

ULVA'CE^S {ulva, laver). A tribe of
cryptogamic plants belonging to the in-
articulate division of the order Algacece.
They comprise plants found in fresh and
salt water, with a membranous, reticu-
lated structure, and the reproductive
organs imbedded in the substance of the
plant. They are the lavers, the sea-
purse, the water-gut, &c.

UMBEL {umbella, an umbrella). A
form of inflorescence, in which all the
pedicels of the flowers proceed from a
single point, and are of equal length or
corymbose. When each pedicel bears a
single flower, as in Eryngium, the umbel
is said to be simple ; when each pedicel
divides, and bears other umbels, as in
Heracleum, the umbel is termed com-
pound. In the latter case, the assem-
blage of umbels is called the universal
umbel, each of the secondary umbels
being called the partial umbel. The
peduncles which support the partial um-
bels are called radii.

VMBELLI'FERJE {umbella, an umbel,
fero, to bear). The Umbel-bearing tribe
of Dicotyledonous plants. Herbaceous
plants, with leaves usually divided ; flowers
in umbels; calyx entire or 5-toothed;
petals 5, alternate with 5 stamens; ova-
rium didymous, with 2 styles and solitary
pendulous ovula.

UMBER. An ore of iron and manga-
nese, occurring in beds with brown jasper
in the isle of Cyprus, and used as a
brown pigment.

UMBILI'CUS (dim. of umbo, the boss
of a shield). 1. A term applied in con-
chology to the hollow axis of those spiral
shells in which the inner sides of the
whorls or volutions do not touch one an-
other. 2. In Botany, the term is syno-
nymous with hilum, and denotes the
scar where the seed is united with the
placenta. 3. The term has sometimes
been applied to the focus of an ellipse ;
but, in modern works, it signifies a point
of a surface through which all its lines of
352

curvature pass. At such a point the two
principal curvatures are equal.

UMBO. Literally, the boss of a shield ;
hence applied, in conchology, to that
point in a conchifer or bivalve shell
which constitutes the nucleus or apex
of each valve, and which is generally
situated above the hinge, and always
near it.

UMBRA. A shadow; the shadow of
the earth or of the moon in an eclipse.
See Penumbra.

VNC1JE. The name given by the old
algebraists to the coefficients of the letters
in the expansion of any power of a bino-
mial.

UNCONFORMABLE. A term applied
to a set of geological strata, when their
planes are not parallel to those of another
set which are in contact. See Conformable.
UNDE'CAGON {undecim, eleven,
ywvla, an angle). A barbarous term for
a plane figure bounded by eleven sides,
and, consequently, containing eleven
angles. Endecagon is classical.

UNDER-SHRUB. Suffrutex. The
under-shrub differs from the shrub in
perishing annually, either wholly or in
part; and from the herb, in having
branches of a woody texture, which fre-
quently exist more than one year. It is
exactly intermediate between the shrub
and the herb ; such is the mignionette in
its native country, or in the state in
which it is known as the Tree Mignio-
nette.

UNDETERMINED. This word is
applied in Mathematics to a number
which has not been determined, but is
capable of being determined ; whereas an
indeterminate number is one which can-
not be determined at all in the given
case.

UNDULATED (undula, a little wave).
Wavy ; a term nearly synonymous with
sinuated, but more particularly applied
to the colouring of shells.

UNDULA'TION {undula, a little
wave). A tremulous motion or vibration
observable in a fluid, whereby it alter-
nately rises and falls like the waves of
the sea. The constituent particles of all
bodies are usually held, by the operation
of certain internal and external forces,
in a state of equilibrium ; and, where
these particles have been to a certain ex-
tent disturbed by any cause, they return
to the state of equilibrium, by alternately
approaching the position of rest and re-
ceding from it, until, by a gradually de-
creasing recession, they attain the con-

UNG

UNI

dition of repose. These movements are
called undulations, vibrations, or oscilla-
tions.

1. Progressive undulation. In this
kind of movement, the undulation suc-
cessively traverses the different parts of
the body; those particles which have
been immediately excited by the disturb-
ing cause communicating motion to those
■which are next to them, and so on. In
this case the movement of the particles
is successive, so that the position they
assume at any particular moment during
the continuance of their motion, appears
to advance from one place to another.

2. Stationary undulation. In this kind
of movement all the particles of a body
begin their undulations simultaneously,
and complete them at the same instant.
Even when the body is divided into
several vibrating portions, each of them
ceases to move independently of the rest,
the different parts of the body being
separated by points which remain
throughout in a state of rest.

U'NDULATORY THEORY {undula,
a little wave). A theory for explaining
the nature of light. According to this,
light has no material existence, but its
phenomena are produced by the vibra-
tions, or undulations, of a subtle ethereal
fluid, diffused through all nature, and set
in motion by the presence of luminous
bodies. The phenomena of vision are
thus produced by pulsations of ether on
the retina of the eye, as those of sound
are by pulsations of air on the nerve of
hearing. See Emission.

UNEQUALLY PINNATE. Impari-
pinnate. That modification of the pin-
nate leaf, in which an odd leaflet termi-
nates the petiole.

UNGUICULA'TA (unguis, a claw).
Clawed animals ; a section of the Mam-
malia, comprising those which have the
digits armed with claws, but free for the
exercise of touch upon their under sur-
face. The feet of these animals are bifid
in the camel, multifid in the elephant,
the ape, &c.

UNGUIS. The Latin term for a nail.
In Botany,! it denotes the lower part of a
petal which tapers conspicuously towards
the base, as in the pink. The upper part
is called the limb. The petal itself is
termed unguiculate.

U'NGULA. A hoof; and, from the re-
semblance of this part of the animal to
that part of a cone which is separated from
the portion containing the vertex by an
oblique plane, such a solid is called an
353

ungula, and rules for determining its con-
tent are given in books of mensuration.

UNGULA'TA (ungula, a hoof). Hoofed
animals ; a section of the Mammalia,
comprising those species which have the
digits enclosed in hoofs, the under sur-
face not being left free for the exercise
of touch. The hoof is solidipedous in the
horse, bisulcate in the ox, the goat, &c.

U'NIFORM. Though this word means
nothing more than "of one form," it has
a signification in mathematics which
might be better rendered by " of one
value," or "of one degree," when we
speak to the mathematical proficient.
But it is a convenience, though only an
accidental one. that the word does not
imply the idea of value absolutely. Pen.
Cycl.

UNILOCULAR (unus loculus, one
cell). The designation of shells which
are not divided into chambers ; of seed-
vessels which are not separated into
cells.

UNIO'NIOffi. River Mussels or
Unios; a family of atrachian bivalves,
which unite the atrachian with the ma-
crotrachian mollusca.

UNIPE'LTATES (una pelta, one
buckler). A family of stomapodous
crustaceans, including those in which
the carapace is composed of a single
shield-like plate.

UNIPO'LAR. A term applied by Ehr-
man to substances of imperfect conduct-
ing power, which are capable of receiving
only one kind of electricity, when made
to form links in the voltaic chain.

UNIT JAR. An apparatus contrived
by Mr. Harris for charging Leyden jars
with known proportions of electricity, the
quantity of electricity employed being
proportioned to the number of charges.

UNIT OF MEASURE. A term ap-
plied in Geometry to a line by which an-
other is measured ; that is, which is ap-
plied to another line, in order to deter-
mine the number of times that the latter
contains it. The primary unit by which
angles and their corresponding arcs are
numerically expressed, is the degree or
the ninetieth part of a right angle or of a
quadrant.

UNIVALVES (unus, one, valves, fold-
ing-doors). A class of mollusks, whose
shell is composed of one piece, generally
with spiral volutions.

UNIVERSAL PROPOSITION. A
proposition whose predicate is affirmed
or denied of the whole of the subject.
Thus, in the language of logic, we have

URA

URI

universal affirmative and universal nega-
tive propositions, in which the universal
signs "all," "no," "every," are em-
ployed to indicate that the subject is
distributed.

UNIVERSE; WORLD. The former
of these terms usually relates to all
created things, and hence the theory of
the Universe comprises all that is known
or conceived of the general arrangement
of the stars, planets, &c. The term
world was formerly synonymous with the
present term universe, but is now com-
monly restricted to our own planet.

UNI'VOCAL NOUN. In Logic, a
common term is called univocal in re-
spect of those things or persons to which
it is applicable in the same signification,
as the term " man." Whately observes
that " the usual divisions of nouns into
univocal, equivocal, and analogous, and
into nouns of the first and second inten-
tion, are not, strictly speaking, divisions
of words, but divisions of the manner of
employing them ; the same word may be
employed either univocally, equivocally,
or analogously ; either in the first inten-
tion or in the second. The ordinary
logical treatises often occasion great per-
plexity to the learner, by not noticing
this circumstance, but rather leading him
to suppose the contrary."

UNLIMITED. A term sometimes
employed by mathematicians in the sense
of indefinite, in order to avoid the use of
the word infinite. It is also used to de-
scribe a problem which may admit of an
infinite number of answers.

UNSTRA'TIFIED ROCKS. Rocks
which are not disposed in beds or strata.
These are also called massive and over-
lying rocks, and comprise those usually
termed Plutonic, Igneous, Trap, &c.
Many of these are so intimately related
to granite, as scarcely to be distinguished
from it, while others as obviously pass
into lava and other products of active
volcanoes.

UPU'PID^E. The Hoopoe tribe; a
family of the Insessores, or Perching
birds, named from the upupa, or hoopoe,
the last genus of Cuvier's Tenuirostres.

U'RAMIL. A crystalline substance
obtained by treating a hot saturated solu-
tion of thionurate of ammonia with hy-
drochloric acid in excess. By decom-
posing this substance an acid is obtained,
called the uramilic.

URANGLI'MMER. An ore of ura-
mium, formerly called green mica, and
by Werner chalcolite. See Uranite.
354

U'RANITE. The yellow uranite or
uran mica, and the green uranite or
chalcolite, are phosphates of oxide of ura-
nium ; they are distinguished by the
former containing a small portion of
phosphate of lime, and the latter an
equivalent portion of phosphate of
copper.

URANIUM. A metal discovered in
1781, in the mineral called, from its black
colour, pitch-blende. It was named by
Klaproth after the new planet Uranus,
the discovery of which took place in the
same year.

U'RANOCHRE. An ore of uranium,
containing this metal in the oxidised
state.

URANO'GRAPHY (oipavos, the hea-
vens, 7pa0w, to describe). A subordinate
department of the science of astronomy,
presenting an account of the arrange-
ments which have been made by astro-
nomers for delineating the starry heavens,
and working the many mathematical pro-
blems of which they are the subject.

U'RANUS or HERSCHEL. A planet
discovered by Sir W. Herschel in 1781,
March 13. Its apparent diameter is
about 4", from which it never varies
much, owing to the smallness of our
orbit in comparison of its own. Its real
diameter is about 35,000 miles, and its
bulk 80 times that of the earth. It is
attended by satellites — two at least, pro-
bably five or six — whose orbits offer re-
markable peculiarities.

URAO. A variety of sesqui-carbonate
of soda, found in Columbia.

URATES. Compounds of uric or
lithic acid with the salifiable bases.

U'RCEOLUS (dim. of urceus, a water
pitcher). A small pitcher-like body,
formed by the two bracts which, in the
genus Carex, become confluent at their
edges, and enclose the pistil.

U'REA. Anormal cyanite of am-
monia. A substance existing in the
form of lactate of urea in human urine,
and combined with hippuric acid in that
of the cow and elephant.

U'RETHANE. The name given by
Dumas to a substance which he con-
sidered to be a combination of urea with
carbonic ether. It is also considered as
a chloroxicarbonic ether, in which the
chlorine is replaced by amidogen.

URIC ACID {olpov, urine). Lithic
acid. An acid existing in the urine of all
carnivorous animals, and forming the ba-
sis of most urinary concretions. It forms,
in combination with ammonia, the white

V AG

V AL

part of the excrement of birds ; and vast
accumulations of that urate exist in the
■guano, or decomposed excrement of
aquatic birds, by which many of the
small islands on the Coast of Peru and
Chili are covered, and which is used as a
manure.

URILE. A compound radical, sup-
posed to exist in uric acid and the pro-
ducts of its decomposition. It is a com-
pound of 2 atoms of cyanogen and 4
atoms of carbonic oxide.

URN. The peculiar theca or capsule
of mosses, containing the spores. It
is placed at the apex of a stalk or
seta, bearing on its summit a hood or
calyptra, and closed by a lid or opercu-
lum.

URODEL A. An order of Amphibious
animals, including the Salamanders,
Water-newts, &c, in which the gills dis-
appear in the perfect state, but the tail is
retained. They may be distinguished
into the Tritons, which, like the frogs,
exhibit aquatic habits even in the adult
state ; and the true Salamanders, which
are more analogous to the toads in their
appearance and habits.

URSA MAJOR. The Great Bear ; a
northern constellation, consisting of 87 I

stars, the principal of which is named
Dubhe.

Ursa Minor. The Lesser Bear ; a
northern constellation, consisting of 24
stars, the principal of which is the Pole
Star.

UR'SIDjE (ursus, a bear). The Bear
tribe of carnivorous vertebrate ani-
mals. These are the true plantigrade
carnivora. Most of them possess several
tuberculous teeth.

URTICA'CEjE (urtica, a nettle). The
Nettle tribe of Dicotyledonous plants.
Trees or shrubs with leaves alternate;
flowers apetalous, solitary, or clustered ;
ovarium superior 2-celled ; fruit, a simple
indehiscent nut.

UTRICLE (utriculus, dim. of uter, a
leathern bag). Cystidium. In Botany,
a simple fruit, 1-celled, one or few-
seeded, superior, membranous, fre-
quently dehiscent by a transverse in-
cision. It may be described as a cary-
opsis, the pericarp of which has no adhe-
sion with the integuments of the seeds.
It differs from the pyxidium in texture,
being strictly simple, that is, not pro-
ceeding from an ovarium with obliterated
dissepiments. It occurs in the ama-
ranth, in chenopodium, &c.

VA'CUUM {vacuus, empty). Literally,
an empty place, or space void of matter.
This term generally denotes the space
enclosed by a vessel from which the
atmospheric air and every other gas has
been excluded, as in the Torricellian
vacuum above the surface of the mer-
cury in the barometer tube, and the Gue-
rickian or Boylean vacuum of the air-
pump. The latter vacuum is always im-
perfect ; the vessel is, nevertheless,
called an exhausted receiver.

VAGA'NTES (vagor, to wander). A
tribe of spiders comprising those which
watch their prey from the web, and also
frequently run with agility in pursuit
of their prey.

VAGATRI'CES (vagor, to wander).
Wanderers ; an order of birds, which,
being equally well adapted for walking
and for flying, might be designated ter-
restrial. They walk with ease, leap under
excitement, or even run with consider-
able speed. They include the corvine and
the graculine bir*u
355

VAGI'NA. Literally, a sheath; and
hence applied, in Botany, to a leafy ex-
pansion surrounding the stem of some
monocotyledonous plants ; occasionally
the petiole embraces the branch from
which it springs, and in such case is
said to be sheathing, and is even called a
sheath, or vagina, as in grasses.

VA'GINATED (vagina, a sheath). A
designation of those polyps which are en-
closed in a calcareous sheath or tube,
and are also called tubiporidce.

VALERIANATES. The Valerian
tribe of Dicotyledonous plants. Herbs
with leaves opposite ; flowers corymbose,
panicled, or in heads ; stamens distinct ;
ovarium inferior 2-celled ; fruit dry,
indehiscent.

VALERIANIC ACID. Valeric acid.
An acid obtained by distillation of the
root of the Valeriana officinalis with water,
as long as it reddens litmus. Its salts
are called valerianates and valerates.

VALLEY (vallis). A space lying be-
tween opposite ridges of mountains or of

VAL

hills, its lowest part being commonly the
bed of some torrent or river, which ori-
ginates in the higher grounds. A level
space of great breadth, separating two
mountain-ranges, is not, properly speak-
ing, a valley, but a plain. The same re-
mark applies to "circular valleys," as
that of Bohemia, 200 miles in diameter,
and that of Cashmere, 90 miles in dia-
meter, which are rather plains sur-
rounded by mountains.

VALUE. Value is the only relation
with which Political Economy is con-
versant ; yet there is no subject as to the
meaning of which economists are less
agreed. Whately points out the incon-
sistencies of writers on this topic : —

1. "The popular, and far the most
convenient, use of the word, is to signify
the capacity of being given and received
in exchange. So defined it expresses a
relation. The value of any one thing
must consist in the several quantities of
all other things which can be obtained in
exchange for it, and can never remain
fixed for an instant. Most writers admit
the propriety of this definition at the
outset, but they scarcely ever adhere
to it.

2. "Adam Smith defines Value to
mean either the utility of a particular
object, or the power of purchasing other
goods which the possession of that object
conveys. The first he calls 'Value in
use,' the second ' Value in exchange.'
But he soon afterwards says, that equal
quantities of labour at all times and
places are of equal value to the labourer,
whatever may be the quantity of goods
he receives in return for them ; and that
labour never varies in its own value. It
is clear that he affixed, or thought he had
affixed, some other meaning to the word ;
as the first of these propositions is con-
tradictory, and the second false, which-
ever of his two definitions we adopt.

3. "Mr. Ricardo appears to set out by
admitting Adam Smith's definition of
Value in exchange. But in the greater
part of his ' Principles of Political Eco-
nomy,' he uses the word as synonymous
with Cost; and by this one ambiguity
has rendered his great work a long
enigma.

4. " Mr. Malthus defines Value to be
the power of purchasing. In the very
next page he distinguishes absolute from
relative value, a distinction contradictory
to his definition of the term, as expres-
sive of a relation.

5. " Mr. M'Culloch distinguishes be-

356

VAL

tween real and exchangeable, or relative,
value. And in his nomenclature, the ex-
changeable, or relative, value of a com
modity consists in its capacity of pur-
chasing ;— its real value in the quantity
of labour required for its production ct
appropriation.

6. "All these differences appear ta
arise from a confusion of cause and effect.
Having decided that commodities are
valuable in proportion to the labour they
have respectively cost, it was natural to
call that labour their Value."

VALVE {valvce, folding-doors). A close
lid affixed to a tube or an opening in
some vessel, by means of a hinge, and
which can be opened only in one direc-
tion. Hence, the more forcibly it is
pressed in the other direction, the closer
it shuts the aperture, so that it either
admits the entrance of a fluid and pre-
vents its return, or admits its escape and
prevents its re-entrance.

1. The clack-valve, or ordinary pump-
valve, is of a circular form, and consists
of a flat piece of leather rather larger
than the aperture it is intended to close.
It should open at an angle of 30°, so as
to admit of a free passage, equal to its
aperture. The double-clack, or butterfly-
valve, consists of two semicircular valves,
commonly employed for pump-buckets,
and have the advantage of allowing less
water to escape into the well or cistern
while in the act of closing the orifice.
Clack-valves consist sometimes of four
sectors of circles, the angular points of
which meet vertically over the centre of
the orifice, the sides being disposed like
those of a quadrangular pyramid.

2. The conical or spindle valve consists
of a flat circular plate of metal, having
its rim bevelled and ground so as to fit in
a conical seat or nozzle. Its form is that
of the frustum of a cone, the side of
which makes an angle of 45° with a dia-
meter of the base. It is usually employed
as the safety-valve of the boiler of a
steam-engine. The diameter of the valve-
box should be to the greater diameter of
the valve as 3 to 2 ; and the valve should
not rise less than one-fourth of its greater
diameter when quite open ; but both
these proportions must be increased if
the valve be out of the centre of the
box.

3. The button-valve or puppet-clack re-
sembles the preceding valve, in being of
a circular form, with a conical side, and
having a vertical direction ; this is ef-
fected by means of a guide-rod, which is

V AL

VAR

attached to the centre of the plate per-
pendicularly to its surface, and moves
freely up and down in a perforation in
each of two hars fixed diametrically
across, and near the top and bottom of
the orifice.

4. The spherical valve is a modification
of the conical valve : the seat or nozzle
represents a portion of a sphere; the
valve itself may also be a portion of a
sphere, or an entire sphere. It has been
recommended as a safety-valve, to pre-
vent the danger of adhering in the boilers
of steam vessels. It is also called a cup-
valve.

5. The throttle-valve has, instead of
the reciprocating motion of the valves
already noticed, a rotary motion. Its
action is that of the flood-gate of a mill ;
its purpose is to regulate the power of a
steam-engine, by increasing or diminish-
ing the area of the steam-tube of a
steam-engine, and thus to increase or
diminish the amount of steam supplied
to the cylinder. The name of this valve
suggests its use: the steam- tube is throt-
tled by it.

6. The sliding valve is one which does
not rise from, and fall into, a seat or
nozzle, but slides on and off its aperture ;
hence, it is commonly called a slide. In
modern steam-engines, the steam pas-
sages are opened and closed by the action
of a single slide, which performs the office
of four valves. To this head belong the
slides of Seaward, Murray, Murdock, &c.
The last of these, from its semi-cylin-
drical form, is commonly called the
D-slide.

7. The single cock is a kind of valve
consisting of a plug of a nearly cylindri-
cal shape, inserted into a hole of cor-
responding form and dimensions in a
tube ; the plug is perforated by a large
hole, and turned by a handle outside the
tube. The four-passaged cock is a con-
trivance, founded on the principle of the
common cock, for putting four passages
into communication with each other,
alternately by pairs ; it is used in steam-
engines for establishing communications
between the boiler, two cylinders, and the
external air. Instead of this apparatus,
two doubled-passaged cocks may be em-
ployed : the four-passaged becomes a
double-passaged cock by obliteration of
one of the passages.

VALVES (in Botany). 1. A term ap-
plied to the parts into which certain
fruits separate, exhibiting the various
forms of valvular dehiscence — the septi-
357

cidal, the loculicidal, and the septifragal ;
the axis of the fruit from which the
valves separate in cases where a distinct
axis exists, is called the columella. 2. The
term valve has been also applied collec-
tively to the three classes of bracts of
which the flower of grasses is composed.
3. It also denotes the opening in the
cells of anthers, which occurs when the
pollen is about to be discharged.

VALVES (in Zoology). The term
valves denotes the two ordinary or prin-
cipal pieces which form the covering of
the acephalous testacea, or bivalves.

VANA'DIUM (Vanadis, a Scandina-
vian deity). A rare metal discovered by
Sefstrcem in 1830, in the iron prepared
from the iron ore of Taberg, in Sweden,
and procured afterwards in larger quan-
tity from the slag of that ore. It was
subsequently discovered in a new mine-
ral, the vanadiate of lead. It occurs in
the state of vanadic acid.

VANISHING QUANTITY. In Ma-
thematics, a quantity is said to vanish,
or to become evanescent, when its arith-
metical value is nothing, or denoted by 0.
See Fraction.

VAPORIZATION. The conversion
of a liquid or of a solid budy into vapour
by the application of heat. It comprises
the phenomena of evaporation and of
ebullition. When solid bodies are vapor-
ized and subsequently condensed, the
operation is termed sublimation, and it
is employed for the purification of cer-
tain substances, and for other pur-
poses.

VAPOUR. A light, expansible, and
generally invisible gas, resembling air
completely in its mechanical properties,
while it exists, but subject to be con-
densed into the liquid or the solid form
by cold. Vaporizable bodies are termed vo-
latile ; while those which resist the heat
of the furnace without undergoing vapor-
ization, are said to he fixed in the fire.

Vapour, atmospheric. The watery
vapour existing in the atmosphere from
contact with the surface of the sea, of
lakes, of rivers, and of humid soil. Its
quantity is limited by temperature, and
when this is reduced, the watery vapour
is condensed, and becomes visible in the
form of dew, clouds, rain, &c. Vapour,
when visible, is termed vesicular, from its
appearing, in that state, in the form of
minute vesicles.

VARA'NIDiE {Faranus, the monitor).
The Monitors ; a family of Lizards,
known as the Platynote or Broad-backed

VAR

Saurians, arranged by Linnaeus under
the great genus Lacerta.

VAREC. The French name for kelp,
or incinerated sea-weed.

VARIABLE MOTION. In Mecha-
nics, a variable motion is that which is
produced by the action of a force which
varies in intensity, or which continues
to act after motion has been communi-
cated to it.

VARIABLE QUANTITY. In Ma-
thematics, a quantity is called variable,
which continually increases or decreases,
asdistinguished from a constant quantity,
which remains always the same. Thus,
the abscissas and the ordinates of an
ellipsis, or other curve line, are variable
quantities, because they vary or change
their magnitudes together. The dia-
meter of a circle and the parameter of a
conic section are constant, while their
abscissas are variable. Variable quan-
tities are usually denoted by the last
letters of the alphabet, x, y, z, while the
constant are denoted by the first a, b, c.
VARIABLE STARS. Stars which
undergo a periodical increase and dimi-
nution of their lustre. The star called
Algol, or /? Persei, is usually visible as a
star of the second magnitude, and such it
continues for the space of 2d. 14h., when
it suddenly begins to diminish in splen-
dour, and in about 3£ hours is reduced to
the fourth magnitude. It then begins
again to increase, and in 3| hours more
is restored to its usual brightness, going
through all its changes in 2d. 20h. 48m.,
or thereabouts. This remarkable law of
variation suggests the revolution round
it of some opaque body, which, when in-
terposed between us and Algol, cuts off"
a large portion of its light. Herschel.

VARIATION. An algebraical rule
for investigating the relation which vary-
ing and dependent quantities bear to
each other. When one quantity y de-
pends upon another x, in such a manner
that if x is changed in value, the value
of y is changed in the same proportion,
then y is said to vary directly as x, or,
shortly, to vary as x. Variation is merely
an abridgment of Proportion ; for one
quantity is said to " vary " as another,
not because the two increase and de-
crease together, but because as one in-
creases or decreases, the other increases
or decreases in the same proportion. The
sign used to denote variation is oc (read
varies as). Thus, ar2 + 3x oc 2x* + 6x,

-i I, whatever be the

since

2x* + 6x

358

VAR

value of x. Single and Double Rule of
Three sums are solved upon the prin-
ciples of Variation and Proportion.

1. One quantity is said to vary directly
as another, when the two quantities de-
pend wholly upon each other, and in
such a manner, that, if one be changed,
the other is changed in the same propor-
tion. If the altitude of a triangle be in-
variable, the area varies as the base.

2. One quantity is said to vary in-
versely as another, when the former can-
not be changed in any manner, but the
reciprocal of the latter is changed in the
same proportion. If the area of a triangle
be given, the base varies inversely as the
perpendicular altitude.

3. One quantity is said to vary as two
others jointly, if, when the former is
changed in any manner, the product of
the other two be changed in the same
proportion. The area of a triangle varies
as its base and perpendicular altitude
jointly.

4. One quantity is said to vary directly
as a second and inversely as a third, when
the first cannot be changed in any man-
ner, but the second multiplied by the
reciprocal of the third is changed in the
same proportion. The base of a triangle
varies as the area directly and the per-
pendicular altitude inversely.

VARIATION OF THE COMPASS.
This term, as well as the expressions,
"variation of the needle " and " declina-
tion of the needle," denotes the angle
which a vertical plane passing through
the axis of a magnetized needle makes
with the geographical meridian of a ship
or station ; and as, for the purposes of
navigation, the needle is made to traverse
horizontally, the variation becomes the
angle between the magnetic axis of the
needle and a meridian line passing par-
allel to the horizon through the centre
of the compass.

VARIATION OF CURVATURE.
The change of curvature which takes
place in passing from one point of a
curve to another. In the conic sections,
the variation of curvature at any point
is proportional to the tangent of the angle
included between the diameter and the
normal, both of these passing through
that point. The circle is the only curve
in which the curvature is uniform at
every point.

VARIATIONS, BAROMETRICAL.
The changes in the altitude of the baro-
meter at the same place are in part regu-
lar, and in part extremely irregular.

VAR

VAR

The regular variations occur almost
always at the same time of day, attain-
ing daily two minima and two maxima.
They show that an ebb and a flow take
place in the atmosphere, similar to what
is observed in the sea. These are very
small, the oscillation seldom amounting
to more than a line, and are, for the most
part, observable only in the torrid zone.
The irregular changes are much greater
in degree than the regular, and are more
frequent and observable as we approach
tbe poles ; for this reason less notice is
paid by us to the regular alterations in
the height of the mercury.

VARIATIONS, CALCULUS OF.
" When a quantity is subject to one sort
of variation only, the consideration of
that variation belongs to the simple dif-
ferential calculus; but when it is sub-
ject to two or more distinct sorts of vari-
ation, suppose that of the differential cal-
culus and another, then the mode of deal-
ing with the second sort of variation
is said to belong to the calculus of vari-
ations."

Illustration. "In Dynamics, for ex-
ample, there are two distinct species of
motion to consider : one which, at the
end of the time t, the system is about to
take during the ensuing time dt in con-
sequence of the velocities acquired by its
particles ; and another which, without
any consideration of the first, must be
impressed upon it for the examination of
the conditions which express the equi-
valence of the impressed and effective
forces. Here then is a case for the cal-
culus of variations." — Pen. Cycl.

VARIATIONS, PERIODIC and SE-
CULAR. In the language of Astronomy,
the term variation denotes a change of
inclination of the orbit of a planet occa-
sioned by a disturbing body. When these
changes are compensated by the configu-
rations of the disturbed and the disturb-
ing body with each other, and therefore
in comparatively short periods, they are
called periodic variations ; and tbe devi-
ations, thus compensated, are called in-
equalities depending on configurations.
When the compensation is operated by a
period of the node, it has nothing to do
with the configurations of the bodies, but
requires an immense period of time for
its consummation, and is, therefore, dis-
tinguished from the former by the term
secular variation.

The variation of the moon is an in-
equality of the moon's motion, depending
on the angular distance of this body from
359

the sun. It arises from that part of the
sun's disturbing force which is at right
angles to the radius vector, and which
accelerates the motion of the moon from
the quadratures to the syzygies, and re-
tards it from the syzygies to the quadra-
tures.

VARIEGATION IN PLANTS. A
general term denoting the arrangement
of two or more colours in the leaves,
petals, and other parts of plants. These
parts are said to be marbled, when a sur-
face is traversed by irregular veins of
colour, like a biock of marble ; discoidal,
when there is a single large spot of colour
in the centre of some other colour ; ocel-
lated, when a broad spot of some colour
has another spot of a different colour
within it, like a little eye; tessellated,
when the colours are disposed in small
squares, like those of a tessellated pave-
ment ; lettered, when the spots of colour
present the form and appearance of
letters. Other terms are employed of
more common use, and requiring no ex-
planation, as striped, dotted, banded, &c.

VARIETIES. In Botany, varieties of
plants are individuals subordinate to spe-
cies. The variety differs from the species
in points of structure which are de-
veloped only under particular circum-
stances, and which are not essential to
the species. The characters on which a
species is founded should be invariable
under all circumstances ; the characters
of a variety are induced by local situa-
tion, by atmospheric influence, by culti-
vation, &c. ; with all the characters of the
species, the variety may differ in a change
of colour, an increased number of petals,
&c. Varieties may be subdivided, with
reference to other non-essential points,
constituting sub-varieties. The term va-
riety is similarly employed in Zoology.

VA'RIOLITE. A porphyritic rock
consisting of an imperfectly crystallized
aggregate of felspar and quartz.

VARIX. A swollen vein ; a term em-
ployed in Malacology to denote the strong
elevated ridges which cross the whorls of
several of the predaceous genera, as mu-
rex, triton, &c. ; they mark the progres-
sive enlargement of the shell, being the
remnants of former apertures, beyond
which the animal, when grown, forms
another aperture.

VARNISH. A substance made by
dissolving resins in alcohol, or oil of tur-
pentine, or in a mixture of oil of turpen-
tine and a drying oil. There are alcoholic
or spirit varnishes, volatile-oil varnishes,

VED

VEG

and fixed-oil varnishes. Lacker, or lac-
quer, is a lac varnish consisting of a
solution of shell-lac in alcohol, and ap-
plied to articles of brass, &c.

VARNISH-TREES. A technical name
applied to trees which exude liquid
resins, naturally or in consequence of in-
cisions.

VAR'VICITE. An ore of manganese,
occurring massive at Hartshill, in War-
wickshire, and in pseudo-crystals at
Ilfeld.

VASCULAR PLANTS {vasculum, a
little vessel). A term applied to the two
great divisions of plants called Exogens
and Endogens, owing to the high de-
velopment of vascular tissue in these
plants, and in order to distinguish them
from Cellular or Cryptogamic plants,
in which the tissue is principally cel-
lular.

VASCULAR TISSUE {vasculum, a
little vessel). Trachenchyma. A tissue
in plants, consisting of simple membra-
nous tubes tapering to each end, but often
ending abruptly, either having a fibre
generated spirally in the inside, or having
their walls marked by transverse bars
arranged more or less in a spiral direc-
tion. There are two principal kinds of
vascular tissue, viz. spiral vessels or tra-
cheal, and ducts : the former present the
continuous spiral fibre, and are capable
of unrolling with elasticity ; the latter
present transverse lines, rings, or bars,
and are incapable of unrolliDg without
breaking.

VAU'QUELINITE. Chromate of lead
and copper ; one of the ores containing
chromium, occurring massive, and in
minute crystals on quartz, accompanying
the chromate of lead, in Siberia.

VECTOR (veho, to carry). The car-
rier ; a term applied, in Geometry, to a
radius, which is carried round a centre;
any given point on such a radius de-
scribes a curve (See Radius Vector). In
Astronomy, a straight line drawn from
the centre of a planet to the centre of the
sun becomes a radius vector, and the
planet appears to be carried by it in its
orbit round the sun. In a conic section,
the radius vector is a straight line drawn
from one of the foci to any point in the
curve.

VEDA {vid, Sansc to know). A term
signifying the sum of all knowledge ; or,
according to another derivation, self-ovi-
dent knowledge or revelation. The word
is, however, particularly applied to the
four principal sacred books of the Hin«
360

dus, viz. the Rt'ch, the Yajush, the
Saman, and the Atharvan'a.

VEERING (virer, French). Wearing.
A nautical term for that movement of a
ship by which, when sailing with the
wind on either bow, she is brought, by
turning her head to leeward, into a con-
trary position, so as to present the other
bow to the wind, by which means her
course is reversed.

VEGA. A star of the first magnitude
in the northern constellation Lyra.

VEGETABLE jETHIOPS. A char-
coal prepared by incinerating the fucus
vesiculosus in a covered crucible.

VEGETABLE IVORY. A substance
sometimes whiter and harder than ivory,
consisting of the seed of a genus of
plants called Phytelephas, belonging to
the natural order Pandanaceae. It is
commonly called tagua plant; and in
Peru, celebra de negro, or negro's head.
It is extensively used for the same pur-
poses as ivory, but does not retain its
colour so well.

VEGETABLE KINGDOM. In addi-
tion to what has been written under the
article Botany, a sketch is here subjoined
of the connexion subsisting between the
three great kingdoms, or divisions of na-
tural bodies. These are represented each
as starting from a common point ; and the
further any group of beings is from this
point, the more are they unlike the
others.

ORGANIC MATTER.

Vegetable Kingdom. Animal Kingdom.

Exogenae.

Gymnospermae.

Endogenae.

Rhizanthae.

Acrogenae.

Vertebrata.

Mollusca.

Articulata,

Radiata.

Acrita.

Indeterminate Substances.

Organic Elements.

Gases, Water.

Metallic Oxides.

Metals

Mineral Kingdom.

INORGANIC MATTER.

VEGETABLE SOIL. The thin ex
ternal crust of the earth in which plants
grow, composed of fragments of mine-
rals, vegetables, and animals, reduced to
a great degree of tenuity.

VEGETABLE SULPHUR. Witch-
meal. A powder procured from the theca
of the lycopodium clavatum, or common

VEI

VEL

club-moss. It is highly inflammable,
and is used for pyrotechnical purposes.

VEGETABLE WAX. A wax-like sub-
stance procured from several species of
Myrica, one species of which {gale), from
the uses to which this substance has been
devoted, has been named the Tallow-
shrub or Candleberry-tree. The wax is
found, in some cases, on the berries, in
others on the cones or catkins. Another
remarkable plant of this kind is the Ce-
roxijlon andicola, a Wax Palm of the
American Spaniards.

VEGETATION, SALINE. A kind of
crystalline film which shoots up spon-
taneously from the edges of a solution of
crystallizable matter, as salt, camphor,
&c.

VEGETO - ALKALIES. Alkaloids.
A class of bodies obtained from the vege-
table kingdom, containing nitrogen, hav-
ing the properties of the basic or metallic
oxides, and forming salts with acids. Of
this class are quinine, strychnine, vera-
trine, &c.

VEGETO-SULPHURIC ACID. An
acid procured by treating ligneous fibre
with sulphuric acid.

VEINS, MINERAL. Cracks or fis-
sures in rocks filled up by substances
different from the rock, which may be
either earthy or metallic. Veins are
sometimes many yards wide ; and they
ramify or branch off into innumerable
smaller parts, often as slender as threads,
like the veins of an animal. Inconsider-
able veins, which diverge from the prin-
cipal, are called slips; and those masses
of ore which are of considerable magni-
tude, but of no great length, are called
bellies, or stockworks.

M. Came characterizes eight succes-
sive groups of veins and slides in Corn-
wall. The oldest are tin veins (lodes),
underlying (dipping) to the north,
ranging nearly e. and w. by compass.
The second class consists of tin veins,
underlying to the south, ranging e. and w.
nearly (by compass). The third includes
east and west copper veins. The fourth
are diagonal (or contra) veins, ranging
N.w. and s.e., and yield copper. The
fifth includes cross courses, ranging n.nw.
and s.se., and rarely yielding metal, ex-
cept lead. A sixth group includes ■ cross
flukans' (clay veins), ranging nearly n.
and s. An eighth includes ' the slides,'
which are formed of soft clay, and cut
through all the others.

VEINS OF PLANTS. The ramifica-
tions of the petiole among the cellular
361

tissue of the leaf are called veins, and
the manner of their distribution is termed
venation.

1. The principal vein, or that which
forms a continuation of the petiole and the
axis of the leaf, is called the midrib or
costa ; if other veins similar to the mid-
rib pass from the base to the apex of the
leaf, such veins have been called, though
incorrectly, nerves, and a leaf with such
a distribution of veins has been called a
nerved leaf.

2. A leaf is said to be three, ox five, or
otherwise nerved, if the so-called nerves
all proceed from the base of the lamina ;
it is also said to be triple, quintuple, &c.
nerved. If the veins diverge from the
midrib towards the margin, ramifying as
they proceed, such a leaf is called a
venous or reticulated leaf.

3. Dr. Lindley adopts the following
terms :— 1. The largest veins given off
from the midrib on each side, are the
primary veins ; each of these forms a
curve, and anastomoses with the back of
the next primary; the curved portion
being called the curved vein. 2. Between
the curved vein and the margin, other
veins, proceeding from the curved veins,
with the same curved direction, and of
the same magnitude, occasionally inter-
vene : these may be distinguished as
external veins. 3. The margin itself and
these last are connected by a fine net-
work of minute veins, which may be
called marginal veinlets. 4. From the
midrib are generally produced, at right
angles with it, and alternate with the
primary veins, smaller veins, which may
be called costal veins. 5. The primary
veins are themselves connected by fine
veins, which anastomose in the area be-
tween them ; these veins, when they im-
mediately leave the primary veins, are
proper veinlets, and, where they anasto-
mose, common veinlets. 6. The area of
parenchyma, lying between two or more
veins or veinlets, is called intervenium.

VELO'CITY (velox, quick). The velo-
city of a body is the rate of its motion, or
the degree of quickness with which it is
moving. The velocity of a body is uni-
form, when it moves through equal
spaces in equal times, and it is then
measured by the space described in a
certain unit of time, as a second ; when
the velocity is variable, it is measured by
the space which would be described in
the said time if the motion were con-
tinued uniform for that time.

1. Velocity, absolute and relative. The

VEN

VEN

velocity of a body is called absolute, if we
consider its motion in space, without any
reference to that of other bodies. It is
termed relative, when compared with
that of another body which is itself in
motion. If two carriages go along the
same road in the same direction, their
relative velocities will be the difference
of their absolute velocities; if in oppo-
site directions, the same. See Motion.

2. Velocities, parallelogram of. A pro-
position very nearly analogous to the
'parallelogram of forces,' employed for
finding the resultant of two velocities.
Thus, " if two velocities, with which a
particle is simultaneously animated, be
represented in direction and magnitude
by two straight lines drawn from the
particle, the resultant velocity of the
particle will be represented in direction
and magnitude by the diagonal of the
parallelogram described upon those two
straight lines."

3. Velocity, resolution of. It follows
from the proposition just stated, that, if
a particle be moving with a velocity v in
a direction making an angle 9 with a
given line, we may conceive the particle
to be animated by two velocities, v cos 0
in the direction parallel to the given line,
and v sin $ in the direction perpendicular
to it. This is called resolving a velocity.

VELUM. Literally, a veil; hence
applied to a horizontal membrane con-
necting the margin of the pileus of a
fungus with the stipes. When it is
adnate with the surface of the pileus, it
is a. velum universale; when it extends
only from the margin of the pileus to the
stipes, it is a velum partiale.

VENATION OF LEAVES. A term
denoting the manner in which the veins
are distributed among the cellular tissue
of the leaf. Writers differ much on this
point of nomenclature : the following
arrangement is taken from Dr. Lindley's
"Introduction to Botany." Leaves are
called, —

1. Veinless, when no veins at all are
formed, except a slight approach to a
midrib, as in mosses, fuci, fee., and the
lowest tribes of foliaceous plants. Under
this head, De Candolle has his folia nul-
linervia, in which there is not even a
trace of a midrib, as in ulva ; and folia
falsinervia, in which a trace of a midrib
is perceptible.

2. Equal-veined, when the midrib is
perfectly formed, and the veins are all of
equal size, as in ferns. These are inter-
mediate between those without veins and

362

those in which "primary " veins are first
apparent. The veins are equal in power
to the "proper veinlets" of leaves of a
higher class. See Veins of plants.

3. Straight-veined, when the veins are
entirely primary, generally very much
attenuated, and arising from towards the
base of the midrib, with which they lie
nearly parallel ; they are connected by
"proper veinlets;" but there are no
"common veinlets." The leaves of
grasses and of palms and orchidaceous
plants are of this nature.

4. Curve-veined, a modification of the
last form, in which the primary veins are
also parallel, simple, and connected by
unbranched "proper veinlets;" do not
pass from near the base to the apex of
the leaf, but diverge from the midrib
along its whole length, and lose them-
selves in the margin. It is common in
Zingiberaceae. The straight-veined and
curve-veined leaves are referred by De
Candolle to modifications of the petiole.

5. Netted, when all the veins of a com-
pletely developed leaf are present, ar-
ranged as described under the article
Veins of plants, without any peculiar
combination of any class of veins.§ This
is the common form of the leaves of
dicotyledons, as of the lilac, the rose, &c.
This is the folium retinervium of De Can-
dolle.

6. Ribbed, when three or more mid-
ribs proceed from the base, to the apex of
the leaf, and are connected by branching
primary veins of the form and magni-
tude of proper veinlets, as in melastoma.
This must not be confounded with the
straight-veined leaf, from which it may in
all cases of doubt be distinguished by the
ramified veins which connect the ribs.
If a ribbed leaf has three ribs springing
from the base, it is said to be three-
ribbed; if five, five-ribbed ; and so on.
But if the ribs do not proceed exactly
from the base, but from a little above it,
the leaf is then said to be triple-ribbed, as
in helianthus.

7. Falsely ribbed, when the " curved "
and "external veins," both or either, in a
netted leaf, become confluent into a line
parallel with the margin, as in all myr-
taceous plants. This has not been before
distinguished.

8. Radiating, when several ribs radiate
from the base of a netted leaf to its cir-
cumference, as in lobed leaves. To this
head are referred the pedalinerved, palmi-
nerved, and peltinerved leaves of De Can-
dolle ; the differences of which do not

VEN

VER

arise out of any peculiarity in the vena-
tion, but from the particular form of the
leaves themselves.

9. Feather-veined, in which the pri-
mary veins of a netted leaf pass in a
right line from the midrib to the margin,
as in castanea. This has the same rela-
tion to the radiating leaf as the curve-
veined bears to the straight-veined. It
is the folium penninervium of De Can-
dolle.

10. Hidden-veined, when the veins are
hidden from view by the parenchyma
being in excess, as in hoya. Such a leaf
is often inaccurately called veinless. De
Candolle calls a leaf of this nature, in
which the veins are dispersed through a
large mass of parenchyma, as in mesem-
bryanthemum, folium vaginervium.

11. The direction which the primary
veins take when they diverge from the
midrib, can be denoted by measuring the
angle formed by the midrib and the di-
verging vein, and can be stated either
in distinct words or by applying the
following terms : — thus, if the angle
formed by the divergence is between 10°
and 20°, the vein may be said to be nearly
parallel (subparallela) ; if between 20°
and 40°, diverging ; between 40° and 60°,
spreading ; between 60° and 80°, divari-
cating; between 80° and 90c right angled ;
between 90° and 120°, oblique; beyond
120°, reflexed (retroflexa).

VENE'RIDiE. A family of macro-
trachian bivalves, named from the genus
Venus, and characterized by the mode-
rate length of the two siphons, which are
sometimes united.

VENT-PEG. The pressure of the
atmosphere, transmitted as it is in all
directions with a weight of about fifteen
pounds on the square inch, prevents the
flow of liquids from a small aperture of
a vessel, unless the pressure be admitted
to the surface of the liquid. The vent-
peg is, therefore, raised in order to ad-
mit the air to the surface of a liquid
which is to be drawn off from a closed
vessel.

VENTRAL [venter, the belly). A
term applied, in Botany, to that suture of
the legume to which the seeds are at-
tached, the opposite being called the dor-
sal suture.

VENTRICOSE (venter, the belly).
Bellying ; swelling unequally on one
side ; as the corolla of many labiate and
personate plants.

VENTRICULITES. A genus of
spongoid zoophytes found in the cre-

taceous system, having their porous
tissue penetrated by distinct ventricles
or foramina, sometimes of large dimen-
sions, and with a certain degree of regu-
larity.

VENUS. The most beautiful of all
the stars. Her mean distance from the
sun is seventy millions of miles ; her
apparent diameter varies from 30" to
184". Her rotation on her axis takes
place in 23d. 21' 19", and the period of her
revolution round the sun is 224d. 16h 49'.
When Venus is in that part of her orbit
which gives her the appearance of being
west of the sun, she rises before him,
and is then called the morning star ; and
when she appears east of the sun, she is
behind him in her course, and is then
called the evening star.

VERA'S CORD-PUMP. An endless
cord, running round two wheels, descends
below the surface of the water, which it
raises by means of the adhesion subsist-
ing between the liquid and the cord, to
which a rapid motion is imparted by the
upper wheel. On this effect of adhesion
depend writing with ink, colour drawing,
the smearing of metals, especially iron,
with oil or grease, to protect them from
rust.

VERA'TRIC ACID. An acid with
which the alkali veratria is combined in
cebadilla, the seed of the helonias offi-
cinalis.

VERB {verbum, a word). That part of
speech which expresses the action or
being of a thing, and which is usually
the principal word of a sentence. A verb
is called active-transitive, when it ex-
presses an action exerted upon some ob-
ject; active-intransitive, when its action is
not communicated to any object ; passive,
when it represents its subject or nomina-
tive as being acted upon ; neuter, when it
expresses a state of existence without
action or passion.

Verbs, auxiliary. Verbs which, though
they originally expressed motions of
action, only express relations of action
when considered as auxiliary verbs, and
are accordingly employed, in connexion
with other verbs, to give them certain
relations called by grammarians tense,
mood, and voice.

VERBAL and REAL QUESTIONS.
" Sometimes the Question turns on the
meaning and extent of the terms em-
ployed ; sometimes, on the things signi-
fied by them. If it be made to appear,
therefore, that the opposite sides of a
certain Question may be held by persons
R2

VER

VER

not differing in their opinion of the matter
in hand, then that Question may be pro-
nounced Verbal ; as depending on the
different senses in which they respec-
tively employ the terms. If, on the con-
trary, it appears that they employ the
terms in the same sense, but still differ
as to the application of one of them to
the other, tben it maybe pronounced that
the Question is Real;— that they dif-
fer as to the opinions they hold of the
things in Question." — Whately.

VERBENA'CE^E. The Verbena or
Vervain tribe of dicotyledonous plants.
Trees or shrubs, sometimes herbs, with
leaves opposite ; calyx tubular ; corolla
irregular ; stamens didynamous, occa-
sionally 2 ; fruit consisting of 2 or 4 nu-
cules in a state of adhesion; seeds ex-
albuminous.

VERD ANTIQUE. A beautiful mot-
tled green marble, an aggregate of marble
and serpentine.

VERDIC ACID. An acid obtained
from the root of the scabiosa succisa and
other plants, and named from its pro-
perty of becoming green on exposure to
the air, owing to the absorption of
oxygen.

VE'RDIGRIS (verde-gris). A sub-
acetate of copper, formed by placing
plates of the metal in contact with the
fermenting marc of the grape, or with
cloth dipped in vinegar. The green salt is
found in commerce under the improper
name of distilled verdigris. A spurious
kind is sold under the name of English
verdigris, consisting of sulphate of copper
and acetate of lead.

VE'RDITER. A blue pigment, pro-
cured by adding chalk or whiting to a
solution of copper in aquafortis.

VERJUICE (verjus, Fr.). A kind of
harsh vinegar, made of the expressed
juice of the wild apple or crab, which
has undergone the vinous fermentation.
The French give this name to unripe
grapes, and to the sour liquor obtained
from them.

VERMI'CULITE. A silicate of mag-
nesia and iron, described as composed of
micaceous-looking plates cemented toge-
ther by a whitish matter.

VERMILION. A red pigment, con-
sisting of powdered cinnabar, or the
red sulphuret of mercury. This sub-
stance, if heated till sulphur begins to
sublime from it, and then suddenly
thrown into cold water, becomes black ;
although, if allowed to cool slowly, it
remains red. Yet it is of the same com-
364

position exactly in the black and red
states.

VERNAL EQUINOX. The time
when the sun enters the first point of
Aries, or the ascending point of the
ecliptic, is the vernal equinox to those
who live in the northern hemisphere,
while the first point of Libra is the same
to those in the southern.

VERNA'TION {vernus, belonging to
the Spring). Gemmation. A botanical
term denoting the manner in which the
leaves of plants are arranged in the un-
expanded or bud state. The ideas ex-
pressing these modifications are essen-
tially the same as those applied to the
parts of the flower in the same state, to
which the term ^Estivation on Prceflora-
tion is devoted. The Vernation or iEsti-
vation of plants is said to be, —

1. Involute, when the edges of the
leaves are rolled inwards spirally on each
side, as the leaf of the apple.

2. Revolule, when the edges are rolled
backwards spirally on each side, as the
leaf of rosemary ; or, in other words,
when two conduplicate leaves clasp each
other.

3. Obvolute, when the margins of one
leaf alternately overlap those of the leaf
which is opposite to it.

4. Convolute, when one leaf is wholly
rolled up in another, as the petals of
wallflower.

5. Supervolute, when one edge is rolled
inwards, and is enveloped by the oppo-
site edge rolled in an opposite direction,
as the leaves of apricot.

6. Induplicate, when the margins are
bent abruptly inwards, and the external
face of these edges are applied to each
other without any twisting, as in the
flowers of some species of clematis.

7. Conduplicate, when the sides are
applied parallelly to the faces of each
other, as in the leaves of the cherry.

8. Plaited, when the leaves are folded
lengthwise, like the plaits of a closed fan,
as in the vine and many palms.

9. Replicate, when the upper part of
the leaf is curved back and applied to
the lower, as in aconite.

10. Curvative, when the margins are
slightly curved, either backwards or for-
wards, without any sensible twisting.

11. Wrinkled, when the parts are folded
up irregularly in every direction, as the
petals of the poppy.

12. Imbricated, when the parts overlap
one another parallelly at the margins,
without any involution.

VER

VER

13. Eguitant, where the parts overlap
each other parallelly and entirely, without
any revolution, as the leaves of iris.

14. Reclinate, when the parts are bent
down upon their stalk.

15. Circinate, when the parts are rolled
spirally downwards, as the fronds of
ferns.

16. Falvate, when the parts are applied
to each other by the margins only, as the
petals of umbelliferous plants, the valves
of a capsule, &c.

17. Quincuncial, when the parts are
five in number, of which two are exterior,
two interior, while the fifth covers the
interior with one margin, and has its
other margin covered by the exterior, as
in' the rose.

18. Contorted, when each part is
oblique in figure, and overlaps its neigh-
bour by one margin, its other margin
being, in like manner, overlapped by that
which stands next to it, as in apocy-
naceae.

19. Twisted, the same as contorted,
except that there is no obliquity in the
form or insertion of the pieces, as in the
petals of oxalis.

20. Alternative, when, the pieces being
in two rows, the inner is covered by the
outer in such a way that each of the ex-
terior rows overlaps half of two of the
interior, as in liliaceous plants.

21. Vexillary, when one piece is much
larger than the others, and is folded over
them, they being arranged face to face,
as in papilionaceous flowers. See Vex-
illum.

22. Cochlear, when one piece, being
larger than the others, and hollowed out
like a helmet or bowl, covers all the
others, as in aconite, some species of
personate plants, &c.

VERNIER. A small moveable scale,
running parallel with the fixed scale of
a quadrant or other instrument, and
having the effect of subdividing the
divisions of that instrument into more
minute parts. Its name is derived from
that of its inventor. See Nonius.

Vernier, chromatic. An instrument
invented and so named by Dr, Brewster,
and employed for measuring, by com-
parison, very minute variations of tints.

VERRU'CjE {verruca, a wart). Warts,
or sessile glands, produced upon various
parts of plants, and extremely variable
in figure. They are the cellular glands of
Mirbel. As they occur on the skin of
the seed, they are the seminal spongioles
of De Candolle.
365

VE'RSATILE (versatilis, that turns
easily). Oscillating; adhering slightly by
the middle, so that the two halves are
nearly balanced, and swing backwards
and forwards; a term applied to the
anthers of plants, when they are attached
to the filament by a single point of the
connective, as in all true grasses.

VERSED AND SUVERSED SINE.
The versed sine of an arc is that portion
of the radius intercepted between the
sine and the extremity of the arc. The
suversed, or supplemental versed, sine is
the difference between the versed sine
and the diameter.

Etymology. M The term sine (the Latin
word sinus meaning the bosom) has been
the object of much discussion. It was
at one time looked on as a barbarism
from the Arabic ; and some endeavoured
to substitute semissis inscriptce, the half
of the chord, for it. Others again thought
that it was a corruption of S. Ins., the
abbreviation of the above. Dr. Hutton
asserts that the Arabic word jeib, which
is used for the trigonometrical sine in
that language, also means the bosom in
common language ; and we have been
told that this is correct : if so, the Latin
sinus is only the literal translation of the
Arabic. The arc representing a bow
(from which it gets its name), half of the
string, which represents the sine of half
the arc, would come against the breast of
the archer. The versed sine (sinus ver-
sus, or turned sine) was called the sagitta,
or arrow." — Pen. Cycl.

VERTEBRA'TA (vertebra, a joint of
the back-bone). A large division of the
Animal Kingdom, including all those
species which are furnished with a back-
bone, or vertebral column, as the mam-
malia, birds, reptiles, and fishes. These
are the Myelencephala of Owen, the Spi-
nicerebrata of Grant.

VERTEX. Literally, the top or sum-
mit of any figure. In Astronomy, it de-
notes that point in the heavens which is
directly over our heads, called the zenith.
In Geometry, it is the apex, or upper
point, of a triangle. In conic sections, it
is the point through which the genera-
ting line of the conical surface always
passes. The vertex of a curve is the
point in which the diameter meets the
curve.

VERTICAL (vertex, the top). Per-
pendicular ; being at right angles to any
body. A vertical circle, in Astronomy,
is a great circle perpendicular to the
horizon, and passing through the zenith
R3

VES

VES

and nadir of any place. A vertical line
has the same meaning. A vertical
plane, in conies, denotes a plane passing
through the vertex, and parallel to the
plane of the section.

VERTICAL CIRCLES. This name
is applied, in Nautical Astronomy, to
great circles drawn on the hollow sphere,
passing through the zenith of any place.
That particular vertical circle which
passes through the east and west points,
is called the prime vertical; the angle
contained between a vertical circle pass-
ing through a heavenly body and the
celestial meridian opposite to a place, is
called its azimuth.

VERTICILLA'STER (verticillus, a
whorl). A botanical term applied by
HofFmansegg to the cyme when reduced
to a very few flowers. It constitutes the
normal form of inflorescence of the La-
biatae, or Mint tribe, in which two verti-
cillastri are situated opposite to each
other in the axils of opposite leaves. By
Linnaeus, the union of two such verti-
cillastri was called a verticillus, or whorl ;
and by others, with more accuracy, a
verticillus spurius, or false whorl. By
Link, this form of inflorescence is called
a thyrsula.

VERTICI'LLUS (verto, to turn). Lite-
rally, a little whern, a whorl, an axis, or
spindle. This term is applied, in Botany,
to that arrangement of leaves upon the
stem, in which more than two of them
are opposite to one another, or are on the
same plane, as in Galium. The natural
order Galiaceae has, in fact, been named
Stellatce, from the stellate or whorled
arrangement of the leaves.

"VESICLE (vesicula, dim. of vesica, a
bladder). A small, circular, inclosed
space, like that contained by a little
bladder. Hence, the term vesicular tissue
is applied to one of the elementary
tissues of plants, generally consisting of
little bladders or vesicles of various
figures, adhering together in masses.
This is also called cellular and utricular
tissue.

VESICULA AMNIOS. Vesicula col-
liquamenti. The name given by Mal-
pighi to the quintine, or fifth integument
occasionally found in the ovule of plants.
This is called by other writers, sac of the
embryo, additional membrane, &c. A
very delicate thread, called the suspensor,
descends from the summit of the ovule
into the quintine, and bears at its ex-
tremity a globule which is the nascent
embryo.
366

VESPERTILIO'NID-E. The Bat
tribe; a family of insectivorous Cheiropte-
rans, characterized by peculiarities of the
nasal appendages. In the Rhinolophince,
or Horse-shoe bats, the nasal appendages
are complicated and membranaceous ;
in the Phyllostomince, or true Leaf-nosed
bats, the appendage is simple, fleshy,
solitary or double ; in the Pteropinet, or
Simple-nosed bats, in the Noctilionince,
or Bull-dog bats, and in the Vesper-
tilionince, or True bats, there is no nasal
appendage at all.

VE'SPIMi (vespa, a wasp). The
Wasp tribe ; a family of hymenopterous
insects, distinguished from all other spe-
cies of the order by having their wings
folded, when at rest, through their entire
length.

VESSELS, MILK, AND TURPEN-
TINE. Vasa propria. These names
were given by Grew to certain cavities
in plants, formed by expansion of the
simple "intercellular spaces," and filled
with the peculiar juices of the plant, as
with milk in the poppy, with turpentine
in terebinthus, &c. These are the acci-
dental reservoirs and the ccecal reservoirs
of De Candolle. See Vittcc.

VESSELS, STRANGULATED. Vasa
moniliformia, vel vermiformia. A variety
of vessels found in plants, characterized
by a moniliform, or necklace-like, appear-
ance, occasioned by irregular compres-
sion, or strangulation, when growing in
knots or parts which are subject to an
interrupted mode of development. By
the French, these vessels are termed
vaisseaux en chapelet or etrangles. They
are considered to be young spiral vessels,
which, instead of lengthening, grow toge-
ther by their ends.

VESSELS, VITAL. Vasa opophora.
A peculiar form of vessels in plants, con-
sisting of branched anastomosing tubes,
lying in no definite position with regard
to other tissue, said to be contractile,
; though destitute of valves in their in-
terior. They occur in the milky cicho-
raceous plants, in the root of dandelion,
&c. The larger trunks were called by
Schultz vasa expansa ; the fine ramifica-
tions, vasa contracta. From their con-
taining a peculiar liquid, called latex,
they have been termed laticiferous tissue,
and, more recently, cinenchyma.

VESTA. A telescopic planet, situated
in the solar system between Mars and
Jupiter, discovered by Dr. Olbers, of
Bremen, in 1807. She describes her orbit
in three years, sixty-six days, four hours.

VIB

VIN

She is thought to be 225 millions of
miles distant from the sun.

VESU'VIAN or FDOCRASE. A
stone, generally of a reddish-brown co-
lour, similar in appearance to common
garnet. It is found crystallized among
substances thrown out by volcanoes, and,
as its name indicates, particularly by
Mount Vesuvius. The rare blue variety
is found at Sonneland, in Tellemark in
Norway. At Naples it is cut into ring-
stones.

VEXI'LLUM (dim. of velum, a veil).
A standard or small banner ; a term ap-
plied to the upper petal of a papilionace-
ous corolla, from its erect and expanded
state. For the use of the term vexillary,
see Vernation.

VIBRATING SURFACES. The phe-
nomena of the production of figures by
strewing sand on vibrating surfaces, com-
monly called acoustic figures, have been
noticed under the terms " Sonorous
Figures" and "Nodal Lines." Mr.
Wheatstone shows that all the figures of
these vibrating surfaces are the resultants
of very simple modes of oscillation, oc-
curring isochronously, and superposed
upon one another; the resultant figure
varying with the component modes of
the vibration, the number of the super-
positions, and the angles at which they
are superposed. When the vibrations of
the superposed modes are unequal in
intensity, there is formed a figure inter-
mediate between the perfect resultant
and one of its compounds : these figures
are called imperfect resultants.

VIBRATION (vibro, to quiver). Os-
cillation. A term applied to those mo-
tions of a body, by which, when its con-
stituent particles have been disturbed
from their equilibriums, they return to a
state of repose. This is effected by the
particles alternately approaching the posi-
tion of rest and receding from it, until,
after some time, the equilibrium is re-
stored. See Interval.

1. The Theory of Vibrations has been
adopted for explaining the phenomena
of light, which are supposed to depend
on the vibrations, or undulations, of a fluid
called elher, diffused through all nature,
and set in motion by the presence of
luminous bodies. See Emission.

2. Bodies of a linear form are capable
of exhibiting three kinds of vibration,
the transverse, the longitudinal, and the
rotatory. 1. If a piece of whip-cord be
strained tight and firmly held at each
end, and be then pulled in the middle

367

from its position of rest, and suddenly
let go, it undergoes a series of transverse
vibrations. 2. If the cord be held at one
end, and a weight attached to the other
end be raised, and then let go, a series
of longitudinal vibrations is produced.
3. Lastly, if the cord be twisted by
means of the weight, and the weight be
suddenly allowed to fall, the cord exhi-
bits a series of rotatory vibrations.

3. Vibrations, co-existence of. This,
and the equivalent term superposition of
vibrations, denote a principle in mecha-
nics, which seems to be only a particular
case of what might be called the co-
existence or superposition of small
changes of any kind. For instance, two
stones are dropped into water at two
different places, and at a certain time,
on a certain part of the surface ; in this
case, the resulting waves cross one an-
other. If there be a particle which is at
the same time raised on both waves,
say a tenth of an inch from one, and
three-tenths of an inch from the other,
that particle will altogether be raised four
tenths of an inch, or insensibly near to
it.— Pew. Cycl.

VIBRIO'NID^E. A tribe of animal-
cules, named from the genus vibrio, and
commonly known as microscopic eels.
One species, the vibrio tritici, is parasitic
on wheat, and it has been computed that
50,000 of them might be contained in
a single grain of wheat. , .

Vl'CIEiE {vicia, the vetch). A tribe
of leguminous plants, having a papilio-
naceous corolla, diadelphous stamens,
continuous legumes, thick farinaceous
cotyledons, not changing in germination,
and a radicle curved inward. They in-
clude the vetches, the bean, the pea, &c.

VILLOSITY (villosus, shaggy). Shag-
giness ; a term denoting that state of
hairiness in plants, in which the hairs
are very long, very soft, erect, and
straight, as in epilobium hirsutura.
When in excess, the hairs are termed
crini.

VIMEN. A long and flexible shoot of
plants. This word is, however, seldom
used, the adjective being employed in-
stead: thus, we say, rami viminei, or
caulis vimineus, and so on. See Virgate.

VI'NCULUM. Literally, a bond ; and,
hence, the term denotes, in algebra, a
line sometimes used instead of brackets,
and drawn above quantities which are
connected; thus a — b — c is the same as
a — {b — c); and a — b + c x d — e
means the same as (a — b + c) x (d — e).
R4

VIR

The line which separates the numerator
from the denominator of a fraction may
he regarded as a sort of vinculum,
corresponding, in fact, in Division to
the bracket in Multiplication. Thus,

.~ c implies that the whole quan-
tity a + b — c is to he divided by 5.

VINDEMIA'TRIX. Pravindemia-
trix. A star of the third magnitude in
the constellation Virgo ; it took its name
from the vintage.

VINE. Vilicula. A stem which trails
along the ground without rooting, or
entangles itself with other plants, to
which it adheres by means of its ten-
drils, as in the vine and the cucumber,
The term is now seldom used. De
Candolle refers this kind of stem to the
sarmentum or runner, from which, how-
ever, it essentially differs in its not root-
ing.

VINEGAR. Acetic acid. A hydrated
acid derived by the action of air upon
alcoholic liquors, as wine and beer ; but
the remarkable discovery of Dr. J. Davy,
that platinum black in contact with alco-
hol became incandescent, and gave rise
to acetic acid, first led Dobereiner to the
discovery that alcohol, by absorbing oxy-
gen, gives rise to water and acetic acid,
without disengaging carbonic acid.

Wood vinegar, or pyroligneous acid, is
prepared on a large scale by the distilla-
ti# of wood, generally that of oak cop-
pice deprived of the bark, which is used
in tanning.

VIOLA'CEjE (viola, a violet). The
Violet tribe of Dicotyledonous plants.
Herbs with leaves usually alternate;
flowers polypetalous ; petals hypogynous ;
stamens alternate with the petals ; ova-
rium 1 -celled, many-seeded.

VI'PERID^E. The Venom-snakes, in-
cluding the varieties of the vipera or
adder, the naia, the rattle-snake, the
horn-snake, &c.

VIRGATE (virga, a twig). A virgate
stem differs from a vimineous stem only
in being less flexible. See Vimen.

VIRGO. The Virgin; the sixth of
the zodiacal constellations, consisting of
110 stars, the principal of which is Spica
Virginis. It denotes the third month of
winter, extending from the 20th of
February to the 20th of March. In the
Egyptian zodiacs, famenoth, or the fruit-
• ful woman, holds an ear of corn in her
hand. The Greeks were led into the
error of calling this sign napOevov, in
consequence of the Egyptian word sig-
368

VIS

nifying 'endowed with beauty;' but it
also involves the idea of fruitfulness.

VIRGULTUM. The name sometimes
given to a young slender branch of a
tree or shrub.

VIRTUAL FOCUS. A term in Optics
denoting the point from which rays of
light, having been rendered divergent by
reflection or refraction, appear to issue.

VIRTUAL VELOCITY. The velo-
city which a body in a state of equi-
librium would actually acquire during
the first instant of its motion, in case of
the equilibrium being disturbed. If we
suppose a point at which any force acts
to be slightly displaced, and from the
new position of the point a perpendicular
to be dropped upon the direction of the
force, then the line intercepted between
the foot of this perpendicular and the
original position of the point is called the
Virtual Velocity of the force.

1 . Thus, let O be the point at which
the force P acts, and suppose it to be
slightly displaced, so as to be brought
into the position O'; from O' draw the
perpendicular O'N on OP, then ON is
the Virtual Velocity of P.

ZL

O N

-5*

2. The Principle of Virtual Velocities
is thus stated : When a system of bodies
is in equilibrium under the action of any
forces, then if the system be very slightly
displaced, the sum of each force multi-
plied by its virtual velocity will equal
zero.

VIS. Force ; a term employed by the
older writers on mechanics to denote
power or force of any kind. Thus we
have vis mortua and vis viva ; the former
relating to the pressure, the latter to the
force of a body in motion, estimated by
the distance to which the body goes ; via
motrix, vis acceleratrix, vis inertice, &c.

VIS INERTIA. Inertness, or the
principle of inactivity, by which a body
perseveres in the same state of rest or
motion, in a straight line, unless obliged
to change it by a foreign force.

VISCOUS FERMENTATION. At a
temperature between 86° and 104°, the
saccharine juices of plants containing
albumen or other azotised matter, un-
dergo a species of fermentation, which is
different from the vinous, combustible
gases being evolved with carbonic acid,
and a gummy matter formed, having the

VIS

VI V

composition of gum Arabic, which ren-
ders the liquid ropy and thick, and hence
the application of the name viscous to
this fermentation. See Fermentation.

VISION. In Optics, the sense of
sight ; this sense is produced by certain
nerves which convey to the brain intel-
ligence of figures impressed by rays of
light upon the retina of the eye. Short-
sightedness is occasioned by the con-
vergence of the rays to a point before
they fall upon the retina, and a concave
lens is employed to delay their conver-
gence. Long-sightedness is occasioned by
the non-conveyance of the rays to a point
until they have passed the retina, and a
convex lens is employed to promote their
convergence.

1. Vision recrossed. A term applied
by Captain J. Grover to a distinct tribe
of ocular phenomena, in which objects
placed between and very near the eyes,
such as the two sides of the nose, appear
on opposite sides of the sphere of vision :
the object on the right side of the nose
being seen to the left by the right eye,
and that which is on the left of the nose
being seen to the right by the left eye.
It is supposed that, besides the two ex-
ternal or cranial eyes, " man is endowed
with an internal cerebral organ, which
performs the office of a third eye, by
being the common recipient of impres-
sions propagated either from one or both
of the external eyes ; and the mind, in
her chamber of percipience. steers with
regard to external objects by the same
principle on which the mariner steers by
his compass.

2. "Thus the two cranial eyes are
analogous, in principle and situation, to
two magnetic compasses placed upon a
ship's deck ; while the third, or cerebral
eye, corresponds to another compass
in the cabin below ; and the mind, situ-
ated like the captain-mariner in his
cabin, knows, from consulting the cere-
bral eye, on what point of direction the
body is steering ; although the mind no
more perceives either any external object,
nor yet any image in the cranial eye,
than the mariner perceives (even in the
vulgar sense of the word perceiving) the
far-off land, or haven, towards which he
is surely making his way."

VISUAL (visus, sight). That which
accompanies vision : the visual angle is
the angle under which a body is seen ;
and the apparent magnitude of the same
object, when viewed at different dis-
tances, depends on the size of the visual
869

angle — that is, the angle formed at the
eye by the rays proceeding from the ex-
tremities of the object. See Theodolite.

VITA'CEJE [vitis, a vine). The Vine
tribe of Dicotyledonous plants. Climbing
shrubs with tumid joints, and leaves sti-
pulate ; flowers polypetalous, on ramose
peduncles ; stamens hypogynous ; ova-
rium 2-celled ; fruit baccate ; seeds albu-
minous.

VITAL AIR. A term applied to
oxygen gas, from its being indispensable
to the maintenance of life. It was for-
merly called dephlogisticated air, em-
pyreal air, &c.

VITE'LLUS. Literally, the yoke of an
egg; a term applied by Gcertner to a
fleshy sac occasionally interposed be-
tween the albumen and the ovule, in
plants, enveloping the latter. This sac
is usually referred to the vesicula amnios
of Malpighi.

VITRIFICATION {vitrum, glass, fio,
to become). The conversion of a sub-
stance, as silica, into glass.

VI'TRIOL (vitrum, glass). A term
originally applied to any crystalline body
possessing a certain degree of transpa-
rency, but now restricted to three sul-
phates— that of iron, called ferrous oxide,
copperas, or green vitriol ; that of copper,
or blue vitriol ; and that of zinc, or white
vitriol.

1. When Green Vitriol is expqsed to
heat in a retort, it first gives off water of
crystallization, ox phlegm of vitriol ; next
comes an acid, called spirit of vitriol;
then a stronger acid, called oil of vitriol ;
the latter part of this becomes solid, and
has been called glacial oil of vitriol.

2. The stalactitic cobalt-vitriol, from
Herrengrund in Hungary, is sulphate of
magnesia, coloured red by oxide of co-
balt.

VITTjE (vitta, a riband). A term ap-
plied, in Botany, to little clavate vessels
of oil found in the coat of the fruit of
umbelliferous plants ; when situated
in the valleculas, or depressions be-
tween the ridges of the fruit, they are
termed dorsal ; when on the face of the
fruit, commissural. They offer a special
case of the vasa propria, or receptacles
of secretion. Modifications of these
vessels are found in the leaves of the
orange and of all myrtaceous plants,
where they are called crypts, vesicular
glands, or receptacles of oil. See Vessels,
Milk, #c.

VIVE'RRIDjE (viverra, the civet).
The civets ; a group of animals placed by
R5

VOI

VOL

Cuvier between the dogs and the hyenas,
which are immediately followed by the
cats. They comprise the civets, properly
so called ; the genets ; the paradoxure ;
the mangoustes ; the suricates ; and the
mangues.

VI'VIANITE. Phosphate of iron; a
mineral occurring in variously grouped
crystals in Bodenmais in Bavaria, in
Cornwall, &c, massive and pulverulent.

VI VT PAROUS (vivus, alive, pario,
to bring forth). A term applied to ani-
mals which bring forth their young alive
and perfect, as distinguished from ovi-
parous animals, which produce their
young in the egg.

VOICE, SCALE OF. The scale of the
human voice comprises four octaves, viz.
from mi or E in the bass, to mi or E4 in
the treble clef. Of this scale, the male
voice extends from E in the bass to C3 in
the treble ; the female, from F1 to E4 in
the treble

1. Subordinate scales. There are four
scales of vocal music. The scale of the
male voice is distinguished into bass and
tenor, each containing two octaves, the
bass extending from E to F2, the tenor
from C1 to C3. Eleven notes are common
to the bass and the tenor scales. The
scale of the female voice is distinguished
into contralto and soprano, each contain-
ing two octaves, the contralto ranging
from Fi to F3, the soprano from C2 toE4.
Twelve notes are common to the tenor
and the contralto, eight to the tenor and
the soprano scales. The terms alto, con-
tralto, and counter-tenor are synony-
mous.

2. The barytone is a scale of the
male voice intermediate between the
bass and the tenor, and ranging from
A to F2. The mezzo-soprano is a scale
of the female voice intermediate between
the contralto and the soprano, and rang-
ing from A1 to A3.

3. Registers. The compass of the
soprano and of some other voices is dis-
tinguished into two registers, the natural
and the falsetto. The former is termed by
the Italians voce di petto, or chest-voice ;
the latter voce di testa, or head-voice.
The Italians combine these two registers
by a third, called mezzo f also, or middle
falsetto. The uppermost notes of the
falsetto are sometimes called flautino, or
flute register. "When the pitch of a voice
proceeds lower than the natural register,
such a voice is called basso falsetto, or
lower falsetto.

4. Song-note; Speech-note, 1. The

370

song-note is a musical sound of some
fixed pitch in the musical scale. The scales
comprising the song sounds are described
under the articles chromatic, diatonic,
and enharmonic scales. 2. The speech-
note is of two kinds, the simple and the
compound ; the former consists of a
single rising or falling of the voice, rang-
ing from a semitone to an octave ; the
latter consists of a falling and a rising, or
of a rising and a falling, combined in
various circumflexes.

VOLATILITY (volatilis, from volo,
to fly). A property of bodies, by which
they are disposed to assume the state of
vapour and fly off, on the application of
heat.

VOLCANIC BOMBS. Masses of
melted lava sometimes thrown out by
volcanoes; these, as they fall, assume
rounded forms, like bomb-shells, and are
often elongated into the shape of a pear.

VOLCANIC FOCI. The subterranean
centres of action in volcanoes, where the
heat is supposed to be in the highest
degree of energy.

VOLCANIC ROCKS. The geological
designation of the fourth or most recent
class of rocks, which are evidently com-
posed of lavas, or masses of melted rocky
matter, which have been sent upward by
volcanoes. This kind of rock is also
called igneous rock.

VO'LCANITE. Another name for
augite, from its being found among vol-
canic rocks ; but it is supposed to have
existed prior to the eruption and ejec-
tion of the lava. See Augite.

VOLCANO (Vulcanus, the fabled god
of fire). An opening in the earth's sur-
face, presenting the general appearance
of a vent of subterranean fire, from which
smoke, cinders, ashes, and sometimes
large fragments of rock, and vast quan-
tities of melted rocky matter, are con-
tinually discharged.

Mud volcanoes are so termed from
their having eruptions of mud only. The
mountain of Maccaluba in Sicily, and
some hills at the town of Taman in the
Cri nea, are distinguished by eruptions
of this kind.

Extinct volcanoes are those mountains
which bear evident marks of having at
some very distant period been outlets of
fire.

VOLITATRFCES (volito, to flutter).
Gliders ; a term applied by Mac Gillivray
to an order of birds, which have a pecu-
liarly light and bounding flight, are
incapable of walking efficiently or of

VOL

VUL

advancing to any distance on the ground
or on trees. They are divided into the
Cypselinae or Swifts, the Hirundinae or
Swallows, and the Caprimulginae or Goat-
suckers.

VO'LKONSKOITE. A mineral con-
taining oxide of chromium, and found in
thin veins and nests in Mount Jess-
mictski, in Siberia.

VOLTA-ELECTROMETER. A new
instrument for the exact measurement
of electric currents. The current to
be measured is made to pass through
water acidulated by sulphuric acid, and
the gases evolved by its decomposition
are collected and measured, thereby
giving at once an expression of the quan-
tity of electricity which has passed. The
principle on which this conclusion is
founded is this new law, " that the decom-
posing action of any current of Elec-
tricity is constant for a constant quantity
of electricity."

VOLTA-METER. An instrument for
measuring the intensity of the electric
current. It consists of a cell of decom-
position, containing dilute sulphuric
acid, and so formed as to admit of the
collection and measurement of the
evolved gases. The electrolyte which
best fulfils all the requirements, is water ;
and any arrangement in which a stream
of electricity is made to decompose it, if
furnished with the means for measuring
the quantity of gas thus generated, may
be regarded as a volta-meter.

VOLTAIC CIRCLES. If a plate of
zinc and a plate of copper be immersed
to a certain depth in a vessel containing
dilute sulphuric acid, and connected
together by direct contact, a current of
positive electricity passes uninterruptedly
from the zinc through the liquid to the
copper, and from the copper to the zinc,
in the direction of the arrows. Such
an arrangement is termed a simple
voltaic circle. When it is required to
produce more decided effects, a series
of these plates is combined, form-
ing what is called a compound voltaic
circle.

VOLTAIC ELECTRICITY. The phe-
nomena of electricity, observed hy Gal-
vani, and hence termed Galvanism and
animal electricity, were attributed by
Volta to the disturbance of the electric
equilibrium by the contact of two dissi-
milar metals. The identity of the com-
. mon and the galvanic electricities was
proved by the discovery of the voltaic
pile, and the science has from that period
371

been termed by some writers, Voltaism
or Voltaic Electricity.

VO'LTATYPE. A term synonymous
with electrotype, applied to a new art of
plating performed by electro-chemical
action.

VOLTZITE. Oxysulphuret of zinc,
occurring in the form of small hemi-
spheres, divisible into thin layers. It
occurs at Roziers in France, and, as is
said, in Cornwall.

VOLUBLE (volubilis, from volvo, to
twist). Twisting; as applied to stems
which twist or twine round other bodies,
that of the hop to the right, that of the
bindweed to the left.

VOLUME (volumen, from volvo, to
roll). The apparent space which a body
occupies is called its volume; the effec-
tive space which the same body occupies
or its real bulk of matter, is its mass;
the relation of the mass to the volume
(or the quotient of the one by the other)
is its density ; and the empty spaces, or
voids, which render the volume larger
than the mass, are its pores.

Definite Volumes. The union of gases
is always effected in simple proportions
of their volumes : a volume of one gas
combines with an equal volume, or twice
or three times the volume, of another
gas, and in no intermediate proportion ;
this is called the law of definite volumes.

VOLU'Tiaffi. The Volutes; a fa-
mily of testaceous, carnivorous gastero-
pods, named from the typical genus vo-
luta; the column of the shell is regu-
larly plaited, and the mantle much de-
veloped in the typical species.

VOLUTION (volutus, rolled). A term
synonymous in Malacology with whorl.

VOLVA {volo, to roll). The wrapper,
or involucrum-like base of the stipes
of agaric. It originally was a bag en-
veloping the whole plant, and was left at
the foot of the stipes, when the plant
elongated and burst through it.

VORTICES, HYPOTHESIS OF {vor-
tex, a whirlpool). The primary hypo-
thesis of the natural philosophy of Des-
cartes was, that the universe is a, plenum,
that is, without any vacuum or unoccu-
pied space ; and that the atoms of matter
moved in numerous vortices, which car-
ried the heavenly bodies around their
several centres of motion ; such as the
planets about the sun, and, perhaps,
similar planets around the fixed stars.

VULPECULA ET ANSER. The Fox
and the Goose ; a modern northern con-
i stellation, consisting of thirty-seven

WAR

WAT

stars, and situated immediately above
Aquila and Sagitta.

VU'LPIKIN. Vulpinic acid. An acid
substance obtained from the evernia vul-
pina of Achard, or the lichen vulpinus of
Linnaeus.

VU'LPINITE. A mineral substance
consisting of sulphate of lime and silica,
and occurring together with granular
foliated limestone at Vulpino in Italy,

where it is employed for ornamental
works under the name of marmo bar-
diglio.

VULTU'RIDjE. The Vulture tribe ;
a family of the Raptores, or rapacious
birds, characterized by their untoothed
beak, and by the moderate curvature of
their talons, as compared with the fal-
cons, and by their head and part of their
neck being destitute of feathers.

w

WACKE'. A simple trap rock nearly
allied to basalt, of which it may be con-
sidered as a soft and earthy variety.
Ure states that it never contains augite
or olivine ; sometimes it is vesicular,
presenting amygdaloidal cavities filled
with various substances.

WA DD. A technical name for plum-
bago or black lead. Black wadd is an
ore of manganese found in Derbyshire,
remarkable for its property of taking fire
when mixed with lintseed oil.

WA'GNERITE. A rare mineral,
formerly confounded with the Brazilian
topaz. It consists of the phosphoric and
the fluoric acids, magnesia, iron, and
manganese. It occurs at Salzburg in
small veins of quartz in clay-slate.

WAKE OF A SHIP. A nautical
term denoting the smooth water which is
astern of a ship under sail. It serves to
show the way the ship makes: if the
wake be right astern, she makes her way
forward; if it be to leeward a point or
two, she falls to the leeward of her
course. A ship is said to stay to the
weather of her wake, when, in her stay-
ing, she is so quick, that she does not
fall to leeward upon a tack, but that
when she is tacked, her wake is to the
leeward ; and it is a sign that she feels
her helm very well, and is quick of steer-
age.

WANING. Declining in power. The
term is applied to the moon, as decrea-
sing in her light, as she proceeds from the
full to the change.

WARM-BLOODED ANIMALS. A
term applied to two classes of vertebrate
animals, viz. the mammals and the birds.
In these there are two hearts, perfectly
distinct from each other ; and a twofold
circulation, viz. that which takes place
in the lungs, called the pulmonic, and
that which takes place through the
372

entire system, called the systemic circu-
lation.

WARP. The deposit of muddy waters,
artificially introduced into low lands. In
the operation of warping, it is only ne-
cessary to produce a stagnation of the
water for a few hours to have a copious
deposit, leaving the water clear over it.

WASH. A technical term for the
fermented liquor, of any kind, from
which spirit is intended to be distilled.

WATER. Protoxide of hydrogen; a
liquid produced by the combustion of
oxygen and hydrogen, consisting of two
volumes of the latter to one volume of
the former gas, and of eight parts of the
former to one of the latter by weight.

Water, oxygenated. Peroxide of hy-
drogen ; a liquid containing twice as
much oxygen as water, but less volatile,
having a metallic taste, and instantly
bleaching litmus and other organic co-
louring matters.

WATER OF CRYSTALLIZATION.
That portion of water which combines in
a dry state with many substances, form-
ing an essential condition of their crys-
talline character. Salts which retain this
water so feebly, that it passes off on ex-
posure to the air, leaving the salt in a
pulverulent state, are termed efflorescent;
while those which have so great an affi-
nity for it, that their crystals attract more
of it from the air, and become dissolved
in it, are called deliquescent.

WATER-CLOCK. Clepsydra. A cy-
lindrical vessel with its surface divided
by lines into portions which are to one
another as the odd numbers, 1, 3, 5, 7,
&c, taken backward. Supposing such
a vessel required six hours to empty
itself, let it be divided into 36 equal
parts ; then, beginning from the surface, ,
take eleven of those parts for the first
hour, nine for the second, seven for the

WAT

WEB

third, five for the fourth, three for the
fifth, and one for the sixth; it Mill he
found that the surface of the water will
descend regularly through each of those
divisions in an hour.

WATER-GILDING. The process of
gilding by the application of an amalgam
of gold to the surface of metals; the
mercury of the amalgam is driven off by
heat, and a thin coating of gold remains.

WATER-SPOUT. A meteorological
phenomenon of the same class probably
as the whirlwinds which raise pillars of
sand in the deserts of Africa. A column
of water is observed to descend from a
cloud, until it meets a column rising
from the sea ; the two unite, and often
move with great rapidity, until they
meet with some opposing wind, or other
cause, which destroys them.

Water-tight. That degree of

closeness of a vessel or tube, which pre-
vents the ingress or the egress of water.

WATER-WHEEL. A machine in-
vented by Segner for employing the pres-
sure of water in the production of a rota-
tory motion. It consists of a hollow cylin-
der, turning upon a vertical axis, and
kept full of water. At its base are seve-
ral pipes for the issue of the water ; the
apertures of the pipes are all in one di-
rection, tangential to the circumference
of the cylinder. The pressure produced
against the sides of the pipes produces
a motion of the cylinder in an opposite
direction. The motion ceases if the
water flow in an opposite direction from
an equal number of pipes.

WATERS, MINERAL. A term con-
ventionally applied to waters distin-
guished from all others by their peculiar
ingredients or supposed medicinal effects.

1. Chalybeate waters contain iron, most
commonly in the state of carbonate dis-
solved in carbonic acid, the proportion
rarely exceeding one grain in a pound of
water. They occur at Brighton, Chelten-
ham, Bath, &c.

2. Sulphureous waters contain sul-
phuretted hydrogen gas, in a proportion
not exceeding that of air in spring water,
and no oxygen. They are recognized by
their peculiar odour, and by their blacken-
ing silver and salts of lead. They occur
at Harrowgate, Aix-la-Chapelle, &c.

3. Saline waters contain various salts
of lime and magnesia, and generally
common salt; their density is always
considerably higher than that of pure
water. They occur at Leamington, Chel-
tenham, Seidlitz, &c. Sea-water con-

373 '

tains 3£ per cent, of saline matter, and
has a density of 1.0274.

WAVE. The simplest idea of a wave
may be obtained by observing the curve
produced by a cord when its equilibrium
has been disturbed. The portion of the
curve which rises above the original posi-
tion of the cord, is the elevation of the
wave ; that which falls below the original
position of the cord, is the depression of
the wave. These movements occur in
solid, in liquid, and in aeriform bodies.
See Undulation.

WA'VELLITE. Phosphate of alu-
mina; a mineral sibstance which was
originally mistaken for a hydrate of pure
alumina, and hence called hydrargyllite.
It occurs in Devonshire, where it was
first found by Dr. Wavell ; at Amberg in
Bavaria, where it is called lasionite; in
Greeenland, &c.

WAVY. Undulated. This term is
applied, in botanical language, to a leaf,
which has an uneven, alternately convex
and concave margin, as in holly. In
entomology, it is applied to an insect
which has the margin of its body marked
by a series of arched incisions.

WEALD CLAY. The upper portion
of the Wealden Formation, consisting of
beds of clay, sandstone, calcareous sand-
stone, conglomerate, limestone, and iron-
stone. The term weald has been given
to a valley, or tract of country, lying
between the North and the South Downs
of Kent and Sussex.

WEALDEN ROCKS {wald, German,
a wood). A series of rocks which imme-
diately cover the upper oolites without
any breach of continuity. They are
essentially of fresh-water origin, and in
this respect they bear the same relation
to our older secondary rocks which the
old carboniferous system bears to the
inferior palaeozoic groups. The lowest
part of this formation is the Purbeck
Limestone; above this is the Hastings
Sand ; the uppermost portion is the
Weald Clay.

WEATHER-GLASS. The popular
name for the barometer, the variations
of this instrument being commonly sup-
posed to indicate approaching changes in
the state of the weather. In former
times, the same appellation was given to
the thermometer.

WE'BSTERITE. Aluminite. Hy-
drous subsulphate of alumina, found in
Sussex and at Halle in Magdeburg, and
formerly mistaken for pure alumina, also
for hydrate of alumina with mechanically

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admixed sulphate of lime. This mineral
must not be confounded with another
substance also called aluminite or alum-
stone (alunite of some mineralogists) from
Tolfa, &c, which is a basic sulphate of
alumina and potassa.

WEDGE. One of the mechanical
powers, consisting of a triangular prism,
or a pair of inclined planes having a com-
mon base, made of some hard substance,
and employed to remove two objects from
one another laterally, or to cleave asunder
the parts of a body. When the edge is
introduced, the wedge is driven forward
by a violent blow, as from a hammer,
which generates an enormous force, of
momentary duration. Nails, awls, needles,
and many cutting instruments act on this
principle ; the stones of an arch are trun-
cated wedges.

WEEK, DAYS OF. The English
names of the days of the week are de-
rived from the Saxons ; and these partly
adopted the names from the more civil-
ized nations of antiquity. Tuesday,
Wednesday, Thursday, and Friday are
derived respectively, from the names of
Tiw, Woden, Thor, and Friga, deities of
the ancient Saxons ; Thor being the god
of thunder, as well as the ancient Jove ;
and Friga, the wife of Woden. Saturday,
Sunday, and Monday, are derived re-
spectively, from the Saxon Seterne's,
Sun's, and Moon's day.

WEIGHT. The comparative measure
of the gravity of bodies at the earth's
surface. In mechanics, weight is the
resistance, or the thing to be moved by
the force of the power : the stone is the
weight to be moved by the force of the
lever or bar.

WEIGHT OF THE ATMOSPHERE.
The mean weight of the atmosphere at
the surface of the sea is generally esti-
mated as equal to the weight of a column
of mercury of 30 inches in height, which
is about 15 pounds on the square inch
of surface, and is equivalent to a column
of water of nearly 34 feet in height.
Hence the surface of the globe sustains a
weight of 11,449,000,000 hundreds of
millions of pounds.

WEIGHTS AND MEASURES. The
following standards have been sanctioned
by Parliament for the purpose of ascer-
taining and establishing uniformity of
weights and measures : —

ENGLISH MEASURES AND WEIGHTS.

1. Lineal, Superfitial, and Solid mea-
sures. The length of the pendulum,
374

vibrating seconds of mean time in the
latitude of Loudon at 62° Fahr., and in
a vacuum at the level of the sea, is equal
to 39.1393 inches of the Brass " Standard
Yard of 1760," or "Imperial Standard
Yard." Hence the length of the yard to
that of the pendulum is in the proportion
of 36 inches to 39.1393 inches, or of the
number 360,000 to the number 391.393 :
so that, if the length of the pendulum
be divided into 391.393 equal parts, then
will 10,000 of these parts be the length
of an inch, according to the imperial
standard.

2. The English land-chain = 22 yards
or 66 feet, and contains 100 links ; 1 link
m 7.92 inches. The square chain = 484
square yards, and 10 square chains =
1 acre.

3. Troy and Avoirdupois weights. The
old Troy pound is the standard unit of
weight, and contains 5760 grains ; while
the avoirdupois pound, now in use, con-
tains 7000 grains. Hence, the standard
pound is to the common pound as 5760
grains to 7000 grains ; or as the number
144 to the number 175. According to the
standard, one cubic inch of distilled
water at 62° Fahr., the barometer being
at 30 inches, weighs 252.458 troy grains,
one pound = 5760 grains. (A cubic inch
of distilled water, at the maximum den-
sity, weighs 253 troy grains). Then 175
troy pounds = 144 avoirdupois pounds;
and 175 troy ounces = 192 avoidupois
ounces. A cubic foot of distilled water
at 62° Fahr. weights almost exactly
997.136969 ounces avoirdupois, and at
the maximum density, 999.2777 ounces
avoirdupois.

4. Imperial Gallon Measure. This is
the measure for all sorts of liquids, corn,
and other dry goods. Ten pounds avoir-
dupois, or 277.274 cubic inches of dis-
tilled water at 62° Fahr., the barometer
being at 30 inches, are the contents of
the New Imperial Gallon. As 252.458
grains \ 1 cubic inch ; | lOlbs. or 70,000
grains I 277.274 cubic inches, which is,
consequently, the content of the impe-
rial gallon. The proportion of the impe-
rial gallon to the wine gallon is as 6 to 5
nearly, to the ale gallon as 59 to 60 nearly,
and to the corn gallon as 33 to 32 nearly ;
its proportion to the sterling pint is as
59 to 22 nearly.

5. Heaped Measure. Eighty pounds
avoirdupois, or 2218.192 cubic inches of
distilled water at 62° Fahr., the barometer
being at 30 inches, are the contents of
the New Bushel, which is to be made

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"round, with a plain and even bottom,
being 19^ inches from outside to outside,"
and to be heaped in the form of a cone to
the height of 6 inches. This is the mea-
sure for coal, culm, lime, fish, potatoes,
fruit, &c.

6. The depth of the Imperial Bushel is
required by the Act to be 8 inches,
though this is not expressed ; because
the height of the heap or cone is 6 inches,
and this must be equal to three-fourths
of the depth. The proportion of the Im-
perial Bushel to the Linlithgow wheat
firlot is as 106 to 105 nearly, and to the
barley firlot as 92 to 133 nearly.

7. Dimensions of the Dry Measures.
" The diameter shall be at least double
the depth, and the height of the cone or
heap shall be equal to three-fourths of
the depth."

FRENCH MEASURES AND WEIGHTS.

8. MUre. The standard unit of the
itinerary and other measures of length is
the Metre. It was found that a quadrant
of a meridian lying between the North
Pole and the equator measured 5,130,470
toises, or 10,936,578 English yards ; and
the ten-millionth part of this quantity,
which was to form the standard unit,
was therefore equal to 3 pieds 11 ^&fa
lignes, or 1.093578 English yards. Upon
this, the Academie des Sciences devised
the following nomenclature in the eighth
year of the Republic :—

9. The words deci (tenth of), centi
(hundredth of), milli (thousandth of), be-
ing added to that expressing the unit,
served to denominate the subdivisions ;
and the words deca (ten), hecto (one
hundred), kilo (thousand), myria (ten
thousand), expressed the multiple of the
unit. Thus the metre contained 10 deci-
metres; the decimetre 10 centimetres;
the centimetre 10 millimetres. The de-
cametre expressed ten metres; the hec-
tometre, 100; the kilometre, 1000; and
the myriamUre, 10,000 metres. The
kilometre is considered as the minute
of the new geographical degree, and is
equivalent to 513 toises old measure, and
to 1093 yards, 1 foot, 10 inches, English.

10. Toise. The new toise was fixed at
two metres exactly, making an increase
of 2£ per cent on the * toise of Paris.'
This new toise is divided as formerly into
6 feet, each foot into 12 inches, and the
inch into 12 lines. The toise is therefore
equal to 2 metres, or 6 feet, 6.42 inches
English ; the toise quarree, to 3.7987
square metres, or 3 yards, 1 foot, 84.096
375

inches English ; the pied quarre, to
0.4220 square metres, or 3 feet, 29.344
inches English.

11. Lieue. The lieue, by which dis-
tances were reckoned in France, was not
the same in every province; of the fol-
lowing four, however, the proportions
were determined : — 1, the lieue de poste,
to regulate the charges on travellers,
equal to 2000 toises, old measure, or
3898 metres, or 4262yds. 2ft. 6in. Eng-
lish ; 2, the lieue marine, twenty in the
degree, adopted by geographers, = 2850
toises, or 5554.75 metres, or 6074yds. 2ft.
English ; 3, the lieue commune, twenty-
five in the degree, = 2280 toises, or
4443.80 metres, or 4859yds. 4in. English;
and, 4, lieue moyenne, = 2565 toises, or
5000 metres, or 5470yds. English.

12. Liquid and Dry Measures. The
litre, adopted in the place of the pinte, is
equal to 1.074 pinte, and contains 1.761
English pint. Its form is cylindrical, in
height double of its diameter. The litre
is a cubic decimetre ; the decalitre con-
tains 10 cubic decimetres; the decilitre,
1-1 0th of a cubic decimetre. The hecto-
litre contains 100 cubic decimetres; the
kilolitre, 1 cubic metre, or 1000 cubic
decimetres. The Tonneau de Bordeaux
contains 931.318 litres, or 1640 pints
English.

13. Land Measures. The unit of land
measures is a square, each side of which
is 10 metres in length, and called are.
It is subdivided into 100 parts, called
centiares, each a square metre. There is
a larger measure denominated hectare,
containing 100 ares, and answering to a
square, each side of which is 100 metres.
Before the establishment of the decimal
system, the arpent was generally used
for the measurement of land.

14. Solid Measures. The measure in
use for the sale of timber is called stere,
and is a cubic metre; the decistere is
1-1 0th of a cubic metre.

15. Dry and heaped Measures. The
boisseau usuel, such as its dimensions are
now fixed, is smaller than the former,
called boisseau de Paris, by J,; its sub-
divisions are the demi-boisseau, and the
quart de boisseau. The double boisseau
is equal to 25 litres, or 5 gallons, 2 quarts ;
the boisseau to 12 litres, 50, or 2 gallons,
3 quarts ; the demi-boisseau to six litres,
25, or 1 gallon, 3 pints ; the quart de
boisseau to 3 litres, 12, or 2 quarts,
1 pint, 2 gills. This measure serves for
the sale of corn, coals, salt, lime, &c.

16. The kilogramme represents the

WEL

WHE

weight of a cubic decimetre of water at the
temperature of four degrees above that of
melting ice. The millier is 1000 kilo-
grammes, or the weight of a tun of
sea-water ; the quintal is 100 kilo-
grammes; the hectogramme is l-10th of
a kilogramme, the decagramme 1-1 00th,
the gramme l-1000ih, the decigramme

1 -1 0,000th of a kilogramme. The unit used
in weighing is the kilogramme. It has been
fixed by, and is equal to, the specific
weight of the distilled water contained in
one cubic decimetre. It is equal to

2 livres, 5 gros, 35 grains, $fa poids de
marc, and to 21bs. 8oz. 3dwt. 6.355 grains
troy weight, and 21bs 2oz. 4 drams,
16 grains avoirdupois weight. The kilo-
gramme is divided into two livres; the
livre is subdivided into 16 ounces, the
ounce into 8 gros, and the gros into 72
grains. This new livre exceeds the old
one (poids de marc) by -j2g, so that, to
reduce kilogrammes into old measure,
we must multiply by 2, and add -^.

17. Terms employed in the \6th cen-
tury. The measures appear in most cases
to have reference to the human body.
The breadth (not the length) of four bar-
leycorns make a digit, or finger-breadth ;
four digits make apalm (measured across
the middle joints of the fingers, and the
24th part of the height of a well-propor-
tioned man); four palms are afoot, or a
6th of the height of a man ; a foot and a
a half is a cubit, measured from the elbow
to the ends of the extended fingers, the
4th of the height of a man ; ten palms, or
two feet and a half are a step (gressus) ;
two steps, or five feet, are apace (passus) ;
ten feet are a perch; a hundred and
twenty-five paces are an Italic stadium ;
eight stadia, or a thousand paces, are an
Italic mile; four Italic miles are a Ger-
man mile ; and five Italic miles are a
Swiss mile.

WEISS-ERTZ. The name given by
Werner to some varieties of arsenical
pyrites or mispickel, which contain acci-
dentally admixed silver.

WELDING. A property of certain
metals, as platinum, by which at a white
heat, an incipient fusion takes place,
which covers their surface with a kind
of varnish, so that, when brought into
contact in this state, different species may
be permanently united by forging.

WELTER'S TUBE. A safety-tube,
introduced into a Woolfe's bottle, to pre-
vent retrograde pressure. The tube is
twice curved and expanded at one part
into a bulb; water is poured into the
376

tube till the bulb is half full ; when ab-
sorption takes place, the water rises in
the bulb until none remains in the tube,
and then the air rushes in ; on the other
hand, no gas can escape, since it has to
overcome the pressure of a high column
of water in the perpendicular tube.

WENLOCK LIMESTONE and
SHALE. A component part of the Upper
Silurian Rocks, 1800 feet in thickness;
it consists of a crystalline grey or blue
limestone, abounding in corals, encrinites,
marine mollusca, and crustaceous ani-
mals of the trilobite family ; and a dark-
coloured shale, with nodules of earthy
limestone, and containing mollusca and
trilobites.

WERNERIAN THEORY. Werner
supposed that all the geological strata
were originally in solution in an aqueous
fluid, from which they were deposited or
precipitated. The first deposits were in
crystals, and constituted his primitive
rocks ; these contain no fossils. The
deposits he termed ' formations,' and he
taught that ' the exterior of the earth
consists of a series of these formations
laid over each other in a certain deter-
minate order.'

1. The next deposits he called trans-
ition formations, or secondary rocks; the
former term denoting that the earth was
passing into a fit state for animals and
vegetables. These rocks contain fossils,
or alternate with those which do so.

2. A third series was then deposited,
formed in great measure from the de-
struction of the primitive and the transi-
tion formations, and containing numerous
fossils. From their greater approach to
the horizontal position, Werner termed
them floetz.

WE'RNERITE. Under this name,
which was formerly restricted to some
varieties of common and compact scapo-
lite, are now united the meionite of Vesu-
vius, and the greater part of the scapolite
of Werner, the paranthine and also the
dipyre — substances which stand in need
of further investigation as to their che-
mical and crystallographical characters.

WHEEL AND AXLE. One of the
mechanical powers, consisting of two
cylinders, having their axes coincident,
the two cylinders forming one rigid piece,
or being cut from the same piece : the
larger is called the wheel, the smaller the
axle. The cord by which the weight is
suspended is fastened to the axle and
coiled round it; the power acts some-
times by a cord coiled round the wheel ;

WHE

WH I

sometimes by handspikes, as in the
capstan; sometimes by handles, as in
the windlass.

WHEEL-CUTTING. A term applied
to a particular branch of practical me-
chanics, which comprehends the modes
of cutting the teeth in the wheels used
by watch and clock-makers, and for other
mechanical purposes.

WHEEL, EXCENTRIC. An appa-
ratus employed in double-acting steam-
engines, for the purpose of opening and
closing the valves of the cylinder. On
the shaft or axis of the fly-wheel, or
of the paddle-wheel, is fixed a wheel
which revolves with it, but whose motion
is excentric to it — that is, the centre of
the wheel does not coincide with the
centre of the shaft or axis ; and, hence,
the centre of the wheel moves round the
axis of the shaft. The distance of the
centre of the wheel from that of the shaft
constitutes the amount of excentricity,
and this amount is equal to one half of
the range of motion of the valves which
are to be worked by this mechanism.

WHEEL, PADDLE. A wheel placed
at each extremity of the shaft of a marine
steam-engine, for the purpose of pro-
pelling the vessel by its revolution. It
may be considered as a series of levers,
arranged in a circle, and brought suc-
cessively into action ; the fulcrum is ob-
tained by the re-action of the water upon
the paddles ; the resistance to be over-
come is that of the water opposed to the
progress of the vessel, and acting on the
centre of the wheel ; the power by which
the resistance is to be overcome, is ap-
plied by the cranks of the engine upon
the shaft which connects the centres of
the wheels.

WHEEL, RATCHET. A wheel em-
ployed for preventing motion in one
direction, while it permits it in another.
To effect this object, the teeth of the
wheel are cut with their faces inclining
in one direction, and a small lever or
catch is so placed, as to enter the inden-
tation and stop the wheel if it turn back-
wards, but slides over the teeth without
obstructing them, if it move forward.
Such a wheel is generally employed to
prevent a weight raised by a machine
from descending, and to obviate other
retrograde movements.

WHEEL, SPUR, CROWN, BE-
VELLED. These are designations of
toothed wheels, and denote the position
of the teeth relatively to the axis. In
the spur wheel, the teeth are raised upon
377

the edge of the wheel, or are perpen-
dicular to the axis ; in the crovm wheel,
the teeth are parallel to the axis, or per-
pendicular to the plane of the wheel ; in
the bevelled wheel, the teeth are raised on
a surface inclined to the plane of the
wheel.

WHEEL, SUN AND PLANET. A
contrivance for converting the alternating
motion of the beam of a steam-engine
into a rotatory motion. In this appa-
ratus a toothed wheel is fixed upon the
axis to be turned, and another wheel,
gearing with it, is attached to the lower
end of the connecting rod, so that it can-
not revolve on its own axis. The result of
this arrangement is that the second, or
planet-wheel, passes completely round the
first during each up and down stroke of
the engine, and, in so doing, causes the
first, or sun-wheel, to rotate upon its axis.
This apparatus has been superseded by
the crank.

WHEEL, UNDERSHOT. A water-
wheel, in which the water strikes the
float-boards below the axle, and acts by
the impulse due to its velocity. See
Overshot wheel.

WHET SLATE. Whetstone-slate. A
variety of slate, occurring in beds in pri-
mitive and transition clay-slate. Very
fine specimens are brought from Turkey,
under the name of hone-stones.

WHINSTONE. A provincial term
applied to some of the trap rocks.

WHIRLPOOL OR EDDY. The phe-
nomenon which occurs when two oppo-
site currents of the ocean meet one an-
other, turn upon a centre, and assume a
spiral form. The most celebrated whirl-
pools are those of the Euripus, the Cha-
rybdis, and the Maelstrom.

WHIRLWIND. A spiral or whirling
motion of the wind, which occurs when
its direction is influenced by the form of
precipitous mountains, or when two
winds meet each other at an angle, and
then turn upon a centre. In the deserts
of Africa, they sometimes draw up the
sand into a moving pillar, which buries
all in its way. When they occur on the
ocean, they draw up the water, and pro-
duce water-spouts. .

WHISPERING GALLERY. A dome
or room so constructed that words uttered
in a low tone at one spot are audible at
some other spot, while persons standing
between these two points cannot hear
what is said. To produce this effect, the
room should have an oval or elliptical
form, so that words spoken in one focus

WI c

may be heard in the other. The obser-
vatory at Paris contains an apartment of
this kind.

WHITE COPPER. Chinese Copper.
A white metallic compound brought from
China; its composition is not generally
known, but some of it is said to consist
of copper and arsenic.

WHITE LEAD. Ceruse. Carbonate
of lead, occurring in nature well crystal-
lized, in the form of carbonate of barytes.
It is employed by painters, as a white
pigment, to give body to their co-
lours.

WHITE PRECIPITATE. A com-
pound formed when ammonia is added
to a solution of chloride of mercury. It
is free from oxygen, and contains nothing
but the elements of a double chloride and
amide of mercury.

WHITESTONE. Eurite. A variety
of granite, in which felspar is the chief
ingredient, the quartz, and especially the
mica, being very rare ; or in which all
the ingredients are blended into a finely
granular mass of a white appearance.
Crystals of quartz are sometimes dis-
persed through the mass, rendering it
porphyritic.

WHORL. In Malacology, this word
denotes each complete turn of the spire
of a spiral shell ; the last, which termi-
nates the aperture, is the body or basal
whorl; the rest are the spiral whorls.
For the use of this term in botany, see
Verticillus.

WHY ? As an interrogative, this word
is employed in three senses: viz. "By
what proof?" (or reason.) " From what
cause?" "For what purpose?" This
last is commonly called the "final
cause." E. g. u Why is this prisoner
guilty of the crime?" "Why does a
stone fall to the earth ? " " Why did you
go to London?" Much confusion has
arisen from not distinguishing these
different inquiries. Whately.

WICKLESS LAMP. This ingeniously
contrived lamp is, as it is commonly
called, a self-generating gas apparatus.
It iserves to manufacture oil-gas without
the inconvenience of a retort and fur-
nace. In its common form this lamp con-
sists of fc light and buoyant dish, which
is intended to support the small tube
through which the oil is intended to be
raised ; this is effected, partly by capil-
lary attraction, and partly by hydrostatic
pressure. On applying a taper to the
tube, the oil is decomposed at the ex-
tremity, and gas is generated.
378

WIN

WI'LLEMITE. A variety of silicate
of zinc, from Aix-la-Chapelle.

WINCH AND AXLE. A well-known
apparatus, constituting a small windlass,
and employed in its simplest form to
raise water from a well, or solid mate-
rials from the shaft of a mine ; in a more
complex form, it is connected with a
crane for the purpose of raising heavy
packages from the ground to the upper
part of a building. Its mechanical power
is precisely that of the wheel and axle.

WIND. A current in the atmosphere,
occasioned by inequality of temperature
of the atmosphere at different points of
the earth's surface, or in different regions
of the atmosphere of equal eievanon.
Permanent winds are those which blow
constantly between, and a few degrees
beyond, the tropics (See Trade Winds).
Those which blow at certain periods, as
the monsoons, the land and sea-breezes,
&c, are called periodical winds.

1. Etesian Winds. A term formerly
applied to those winds which blow every
summer during six weeks over the coun-
tries bordering the Mediterranean, but
now applied to other periodical winds, as
those which blow on the coast of Holland.

2. Helm Wind. A violent wind which
occasionally prevails between Brampton
in Cumberland and Brough in West-
moreland, a distance of 40 miles. Its
presence is indicated by a belt of clouds,
denominated the helm bar, which re-
mains immoveable during twenty-four
or even thirty six hours, collecting or
attracting to itself all the light clouds
which approach it. So long as this bar
continues unbroken, the wind blows with
unceasing fury, not in gusts, like other
storms, but with continued pressure.

WIND-GAGE. An instrument for
measuring the force or velocity of the
wind. Various contrivances for this
purpose have been employed. One of
these is described under the term Ane-
mometer.

WIND-GUN. This is a more formid-
able instrument than the air-gun. It
contains a magazine of bullets as well as
another of air, and when it is properly
charged, the bullets may be projected
one after another as fast as the gun can
be cocked and the pan opened. The
syringe is fixed to the butt of the gun, by
means of which it is easily charged, and
may be kept in that state for a long time.

WINDLASS. A modification of the
wheel and axle, consisting of a barrel
which turns upon two points of support

X AN

XAN

on a pivot at each extremity of its axis,
or upon a pivot at one extremity only.
The winch or crank, by which the barrel
is turned, is moved round by the hand,
and there is no difference in the principle
whether a whole wheel is turned, or a
single spoke. The winch, therefore, an-
swers to the wheel, while the rope is
taken up, and the weight raised by the
axle.

WINE. The name given by chemists
to all liquors which have become spiritu-
ous by fermentation.

WINE TEST. A reagent for detect-
ing the presence of lead in wine, by con-
verting the acid into a salt of lead. That
which is usually sold is made by dis-
solving half an ounce of sulphuret of
arsenic, and one ounce of lime, in half a
pint of distilled water, and filtering the
solution.

WINTERACEjE. The Winter's Bark
tribe of Dicotyledonous plants. Trees or
shrubs, with leaves alternate; flowers
hermaphrodite or unisexual ; stamens
hypogynous ; fruit consisting of a single
row of carpella.

WI'THAMITE. A mineral found at
Glencoe in Scotland, and regarded as a
variety of epidote.

WI'THERITE. Carbonate of baryta,
or rhomboidal baryta, found in Cumber-
land and Durham in lead veins traversing
a secondary limestone, which rests on
red sandstone.

WOLFRAM. Tungstate of iron and
manganese, occurring, massive and crys-
tallized, in Bohemia and other countries ;
also in the form of octohedral supposi-
titious crystals, derived from tungstate of
lime.

WO'LKONSKOIT. An emerald-green
mineral, containing oxide of chromium,
iron, silica, and magnesia, and found at
Perm in Russia.

WO'LLASTONITE. Table spar; a
silicate of lime, found at Mount Vesu-
vius, at Nagyag, &c.

WO'LNYNE. A variety of sulphate
of baryta found at Muzsay in Hungary. |

WOOD, ROCK. Mountain wood. A
variety of asbestus, usually massive, of a
brown colour, and having the aspect of
wood.

WOOD-OPAL. Opalized wood; one
of the varieties of opal, occurring in vari-
ous vegetable forms.

WOOD-STONE. The name given by
Werner to specimens of wood which have
been converted into hornstone, a silice-
ous substance sometimes approaching to
flint or common quartz.

WOOD-TIN. The name given by
Werner to one of his divisions of oxide of
tin or tin-stone ; a variety of which, com-
posed of radiated-fibrous small globules,
and marked with concentrically-disposed
brown and yellow colours, is called toad's
eye wood-tin.

WOODY TISSUE. Pleurenchyma.
Elongated cells, tapering to each end,
and constituting the elementary struc-
ture of wood.

WOORALY. A celebrated poison,
also called woorari, ourari, or urari, pro-
duced by the Strychnos toxifera of
Guayana.

WOOTZ. Indian steel; supposed to
be an alloy of steel with small quantities
of silicium and aluminum.

WOULFE'S APPARATUS. A series
of two or three-necked bottles, connected
together by intermediate tubes, used for
impregnating water with carbonic and
other gases.

WREDE'S EXPERIMENT. An ex-
periment instituted by Von Wrede for
measuring the velocity with which heat
is propagated. By means of a thermo-
electric calorimeter, placed in a telescope,
it was found that the temperature of the
eastern edge of the sun's image exceeded
that of the western edge, and conse-
quently the velocity of the rays of heat
was less than that of the luminous rays.
The rate of the velocity of heat radiated
from the sun is only |ths the velocity
of light, or about 163,600 miles in a
second.

Biporofi

x

XANTHIC AND CYANIC SERIES.
Botanists have divided flowers into two
great series, with reference to their co-
lours, viz. those having yellow for their
type, and which are capable of passing
379

into red or white, but never into blue;
and those of which blue is the type,
which can pass into red or white, but
never into yellow. The former series is
termed, by some writers, oxidised, and

YEA

'YEA

the latter disoxidised ; and greenness is
considered as a state of equilibrium be-
tween the two series. De Can dolle called
the first series xanthic (fav#6s, yellow),
and the second cyanic {nvavos, blue). The
two series may be thus expressed : —
Green.

. fa.

I Bl

»l

Greenish-blue

Blue

Violet-blue

Violet

Violet-red

Red.

XANTHIC ACID (Sav06?, yellow).
An acid composed of sulphur, carbon,
hydrogen, and oxygen, and named from
the yellow colour of its compounds.

XANTHIC OXIDE ($avd6t, yellow).
A species of calculus, named from the
lemon-coloured compound which it forms
by the action of nitric acid.

XANTHITE. A congeries of yellow
grains, no larger than those of sand,
easily separable from one another; found
in a limestone bed at Amity in the United
States.

XA'NTHOGEN (Sav96?, yellow, yev-
vaa>, to produce). A term applied to a
compound of sulphur and carbon, form-
ing the radical of hydroxanthic acid,
from its property of forming yellow com-
pounds with certain metals.

XA'NTHOPHYLL (fav06c, yellow,
<pu\\ov, a leaf). Anthoxantine. The
yellow colouring matter which appears in
the leaves of plants in autumn. See
Chlorophyll.

XANTHOPROTEIC ACID. An
orange-yellow powder, formed when al-
bumen, or any other protein-compound
is digested in nitric acid.

XA'NTHOUS {Savdos, yellow). A term
applied by Dr. Prichard to one of the

three varieties of mankind, derived from
the colour of the hair, and including all
individuals or races which have brown,
auburn, yellow, flaxen, or red hair.

Xl'PHIAS DORA'DO. The Sword
Fish ; a modern southern constellation,
consisting of seven stars.

XIPHOSU'RA ($i<pos, a sword, ovpa, a
tail). A division of the entomostracous
crustaceans, in which the last segment of
the body forms a long, three-edged, sharp-
pointed weapon, as in the limulus or
Molucca crab.

XI'PHYRRHYNCHS (#0o*, a sword,
pvyxos, a beak). The designation of a
family of acanthopterygious fishes, of
which the xiphias, or sword-fish, is the
type.

XY'LITE (fyXov, wood). Lignone. A
liquid existing in commercial pyroxylic
spirit. There are several other products
of the distillation of wood, named xylitic
acid, xylite-resin, xylite-naphtha, xylite-
oil, &c.

XYLO'DIUM. A term applied by
Desvaux to the nut of Anacardium.
This fruit is, however, generally referred
to the achcenium of other writers.

XYLOIDINE. The name given to
paper which has been immersed for a
moment in strong nitric acid, and then
washed in distilled water. The paper
acquires the toughness of parchment and
the combustibility of tinder.

XYLOTHAGI (fuAoi/, wood, <pdya>, to
eat). Wood-eaters ; a family of the tetra-
merous Coleoptera, which usually live on
wood, which their larvae penetrate in
every direction. By the term xylotroges
(Tpa»7&>, to gnaw) is denoted a tribe of
serricorn beetles, which perforate timber ;
and by that of xylophilans (<pt\4ia, to love)
a tribe of beetles which live on decayed
wood.

YA'NOLITE. A designation of the
axinite of Haiiy, and thumerstone of
Kirwan ; an alumino-silicate of lime and
iron.

YEAR. The period of time in which
the earth performs her revolution round
the sun, or that in which the sun appa-
rently moves from a point in the ecliptic
until he returns to the same point, is
called the solar year. This is also termed
the tropical year, and it consists of 365d.
380

5h. 48m. 49s. 7. This is the period
adopted as the standard for the measure-
ment of time, for all the purposes of civil
life; hence, it is also called the civil
year.

1. The sidereal year is measured from
the departure of the sun from any fixed
star to his return to the same star ; it is
longer than the tropical year, consisting
of 365d. 6h. 9m. 9s. 6, reckoned in mean
solar time, or 366d. 6h. 9m. 9s. 6 reckoned

ZAM

ZE A

in sidereal time. The reason of this dif-
ference is, that, as the sun's apparent
annual motion among the stars is per-
formed in a contrary direction to the
apparent diurnal motion of hoth sun and
stars, it comes to the same thing as if the
diurnal motion of the sun were so much
slower than that of the stars, or as if the
sun lagged behind them in its daily
course. When this has gone on for a
whole year, the sun will have fallen be-
hind the stars by a whole circumference
of the heavens ; or, in other words, in a
year, the sun will have made fewer diur-
nal revolutions by one than the stars.
The proportion between the mean solar
and the sidereal day is, when reduced to
a decimal fraction, that of 1.00273791 to 1.

2. The anomalistic year is the time
which elapses between the sun's leaving
his apogee and his return to it, consisting
of 365d. 6h. 13m. 49s. 3. The difference
between this and the tropical or civil
year is owing to the orbit of the earth
representing an ellipse, of which the
major axis has a slow motion of 11".8 per
annum in advance.

3. Historical and ecclesiastical year.
In England, the historical year was, for
a very long period, begun on the 1st of
January. But the civil, ecclesiastical,
and legal year began, until the end of the
thirteenth century, at Christmas. In and
after the fourteenth century, it com-
menced on the 25th of March, and so
continued until the 1st of January, 1753.
Much confusion arose from these two
modes of computing dates ; for the legis-
lature, the ecclesiastics, and the civilians,
referred every event which happened be-
tween the 1st of January and the 25th of
March to a different year from historians.

4. To avoid, so far as possible, the mis-
takes which this custom produced, it was
usual to add the date of the historical to
that of the legal year, when speaking of

any day between the 1st of January and
the 25th of March ; thus,—

8 fi.e. the civil and legal
Jan. 30, 164 -j year,

9 \i. e. the historical year ;
or, thus :

January 30, 1648-9.

YEAST. Fermentum. A substance
generated during the vinous fermenta-
tion of vegetable juices and decoctions,
rising to the surface in the form of a
frothy, flocculent, and somewhat viscid
matter. It is used for promoting fer-
mentation. See Catalysis.

■Artificial Yeast may be made by boil-
ing malt, pouring off the water, and
keeping the grains in a warm place to
ferment, repeating the process till a suf-
ficient quantity is procured.

YELLOW EARTH. A massive mine-
ral of an ochre-yellow colour, consisting
of silica, alumina, iron, and lime. It
occurs in Upper Lusatia, associated with
clay and clay-ironstone. When burnt,
it is sold by the Dutch as a pigment,
under the name of English red.

YENITE. Another name for lievrite,
a double silicate of lime and iron, found
in the Isle of Elba and in Norway. It
was named yenite by Lelievre, its disco-
verer, in honour of the battle of Jena.

YOU-STONE. Chinese jade; a zeo-
litic substance referred to prehnite.

YTTRIA. A new earth, dis overedby
Gadolin, in a mineral from Yiterby in
Sweden. Its metallic base is yttrium, of
which it is considered to be a protoxide.

YTTRO-CERITE. A mineral sub-
stance containing yttria, oxide of cerium,
and fluoric acid ; it is found at Finbo in
Sweden, imbedded in quartz, or incrust-
ing pyrophysalite.

YTTRO-TANTALITE. An ore of
tantalum, also called yttrious oxide of
tantalum, found in reniform masses at
Ytterby in Sweden.

ZAFFRE. An impure oxide of cobalt,
being the residuum of the native arseni-
uret of cobalt, after the sulphur, arsenic,
and other volatile matters of this mineral
have been expelled by calcination. The
substance brought from Saxony, and
commonly sold under this name, is a
mixture of oxide of cobalt with vitrifiable
earth.

Z AMITE. The name given to the
fossil species of zamia, the principal
381

forms of which have been found in the
lias and oolitic formations. They differ
from the other species in the exsertion
and venation of their leaves.

ZANTHOPI'CRITE. A crystalline
substance extracted from the bark of the
zanthoxylum of the Caribbee islands.

ZEA'GONITE. A Vesuvian mineral
referred to the harmotone or cross-stone,
and to the potass division of this zeolitic
substance.

ZER

ZI N

15^^

ZE'CHSTEIN. A magnesian of lime-
stone, abounding in Germany, and be-
longing to the New Red Sandstone
group.

ZE'IN. A substance procured from
the zea mays, resembling gluten, but said
to be destitute of nitrogen.

ZENITH AND NADIR. These are
astronomical terms derived from the
Arabic, and they denote two points of the
sphere of the heavens, the former verti-
cally over a spectator's head, the latter
vertically under his feet ; they are, there-
fore, the vanishing points of all lines
mathematically parallel to the direction
of a plumb-line at his station. They are
the poles of the celestial horizon, t. e.
points 90° distant from every point in it.

ZENITH DISTANCE. An astrono-
mical term, denoting the complement of
the altitude of the sun, or other heavenly
body. Vertical circles of the sphere are
great circles passing through the zenith
and the nadir, or great circles perpen-
dicular to the horizon ; on these are
measured the altitudes of objects above
the horizon — the complements to which
are their zenith distances.

ZENITH SECTOR. An astronomical
instrument, consisting of a portion of a
divided circle, employed for measuring
accurately the zenith distances of stars
which pass near the zenith. This instru-
ment is also used in trigonometrical sur-
veys for determining the difference of
latitude of two stations ; for the differ-
ence of the zenith distances of the same
star, observed at its meridional passages
at two places, gives the difference of the
astronomical latitudes of the places with-
out any regard to the star's declination.

ZE'OLITES (£?«, to boil, \i0os, a
stone). A term applied to the silicates
of lime and alumina, from their frothing,
when heated before the blow-pipe. This
is a very extensive mineral genus, con-
taining the dodecahedral species, or leu-
cite; the hexahedral, or analcime; the
rhomboidal, or chabasite; the pyramidal,
or cross-stone; the diprismatic, or lau-
monite; the prismatic, or mesotype, com-
prising the fibrous zeolite, natrolite, and
mealy zeolite ; the prismatoidal, or stil-
bite, comprehending foliated and radiated
zeolite ; and the axifrangible, or apo-
phyllite.

ZE'RO {tsaphara, Arab., empty). A
term used to denote a cipher placed be-
tween the ascending and the descending
numbers of a scale or series. The zero
of Fahrenheit's thermometer is 32° below
382

the melting point of ice; that of the cen-
tigrade scale coincides with the freezing
point of water. The absolute zero is the
imaginary point in the scale of tempera-
ture at which the whole heat is ex-
hausted ; it is the expression of absolute
cold, or privation of caloric.

ZERO POINT. The term applied by
astronomers to that point of the equi-
noctial, called the equinox, through which
they suppose the hour circle to pass, from
which all others are reckoned, and which
point is itself the zero point of all right
ascensions counted on the equinoctial.

ZETE'TICS (Cnreia, to search). The
name given by Vieta to the department
of algebra which consists in the direct
search after unknown quantities. The
term is now obsolete.

ZEUXITE. A zeolitic substance, found
in Huel-Unity Mine, near Redruth, in
Cornwall.

ZINC. A bluish-white metal, occur-
ring in the form of oxide, or red zinc;
of sulphuret, or blende; of carbonate, or
calamine; of sulphate, or white or zinc
vitriol; of silicate, or electric calamine;
and ofaluminate, or automalite or gahnite.
It has been called marcasite, Indian tin,
and spelter. When rolled into thin leaves,
it is termed sheet zinc. The mineral sub-
stance, zinc bloom, is of the same com-
position as calamine, or the carbonate of
this metal.

1. Zinc, floivers of. This is the oxide,
formed by exposing the metal to the air
at a temperature a little above its melting
point, when it flies up in the form of
white flowers. It has hence received the
fanciful names of nihil album and philo-
sophical wool. By the ancients it was
called pompholix. In Holland it was
sold as a secret remedy under the
names of luna fixata and arcanum Lude-
manni.

2. Zinc, butter of. This is the chloride
or hydrochlorate, obtained as a whitish-
grey mass, with the consistency of wax
or butter.

ZINCOID AND CHLOROID. These
terms are applied, on the electrical hypo-
thesis, to the plates of a decomposing
cell : the chlorous plate, which is in con-
nection with a zinc plate, is termed the
chloroid (like chlorine, quasi-chlorine),
and is the same as the negative pole, the
negative electrode, the cathode and the
platinode ; while the zincous plate, which
is connected with a copper plate, is called
the zincoid (like zinc, quasi-zinc), and
represents the positive pole, the positive

ZO A

ZOO

electrode, the anode, and the zincode.
See Polarity, Chemical.

ZINCO'LYSIS. A term equivalent to
electrolysis, denoting a mode of decom-
position occasioned by the inductive ac-
tion of the affinities of zinc or the positive
metal.

ZI'NCOLYTE. A term equivalent to
electrolyte, denoting a body decomposible
by electricity, the decomposition being
referred to the action of zinc or the posi-
tive metal.

ZINCOUS ELEMENT. The basic or
positive element of a binary compound.
The negative is termed the chlorous ele-
ment.

ZINCOUS POLE. A term founded
on the theory that the particles of matter
are susceptible of polarity. Hence that
pole of a particle of zinc or of hydrochloric
acid which has the attraction, or affinity,
which is characteristic of zinc, or zincous
attraction, is called the zincous pole. See
Chlorous Pole.

ZINGIBERA'CE^E. Scitamineee. The
Ginger tribe of monocotyledonous plants.
Aromatic tropical herbaceous plants, with
a creeping rhizome, and stem formed of
the cohering bases of the leaves ; inflo-
rescence either a dense spike, or a ra-
ceme, or a sort of panicle, terminal or
radical. The family are monandrous,
with a whole anther, and are thus distin-
guished from the allied family maran-
tacecc, which are monandrous, with only
half an anther ; and from the musacece,
which have five or six anthers.

ZI'NKENITE. A mineral containing
sulphur, lead, antimony, and copper. It
is nearly related to plumose antimony.

ZIRCON. A heavy, hard, sparkling,
and transparent stone, having a strong
double refraction. It is usually divided
into the two varieties of hyacinth and
jargon, the former having a yellowish-red
colour, and the latter being most esteemed
when colourless.

ZIRCO'NIA. The oxide of zirconium;
a peculiar earth, discovered in the zircon
of Ceylon, a silicate of zirconia, which
is also found in the syenitic mountains of
the south-east side of Norway. The
hyacinth is the same mineral of a red
colour.

ZIRCO'NIUM. The metallic basis of
zirconia, obtained in the form of a black
powder, resembling that of charcoal.

ZOANTHA'RIA (£Sov, an animal,
av6ot, a flower). Animal-flowers ; the
third class of zoophytes, in the arrange-
ment of De Blainville, who gives the fol-
383

lowing definition : — " Body regular,
flower-shaped, more or less elongated,
free or fixed, very contractile, furnished
with an intestinal canal (?), without dis-
tinct walls, having a single large terminal
opening surrounded by variously-shaped
tentacula, which are always tubular and
in communication with the musculo-
cavernous parenchyma of the skin."

ZOA'NTHID^E. A family of the
zoantharia of De Blainville, comprising
animals coriaceous, simple, or compound,
fixed; tentacula marginal, surrounding
the mouth.

ZO'DIAC {&diov, a little animal). The
area within which the apparent motions
of the sun, moon, and all the greater
planets are confined. It consists of a zone,
or belt, extending nine degrees on either
side of the ecliptic, and named from its
containing the figures of all the animals,
&c, which formed the twelve signs. The
names of the signs are derived from com-
parisons made by the Egyptians between
celestial and terrestrial phenomena, for
the most part purely of a local nature,
and belonging exclusively to a part of
their country. See Signs of the Zodiac.

ZODI'ACAL LIGHT. A term applied
by astronomers to a revolving ring of
finely-divided or nebulous matter, situ-
ated perhaps between the orbits of Venus
and Mars, but certainly extending beyond
that of the earth. This phenomenon
rising pyramidally illumines a portion of
the unvarying length of the tropical
nights. In the temperate zone, it is only
distinctly visible in the beginning of
spring, when it may be seen after even-
ing twilight above the Western horizon,
and at the end of Autumn, before the
commencement of morning twilight above
the Eastern horizon.

ZO'ISITE. A subspecies of prisma-
toidal augite, distinguished into the com-
mon and the friable. It was named after
its discoverer, the Baron Von Zois.

ZONE {zona, a girdle). The geogra-
phical denomination of each of the five
parallel belts into which the earth is
imagined to be divided in respect to tem-
perature. The torrid zone includes all
the space which lies between the tropics,
being nearly 47 degrees, or 23£ degrees
on each side of the equinoctial line. Two
frigid zones occupy those parts which lie
between the poles and the polar circles ;
and two divisions which lie between those
circles and the torrid zone, are called the
temperate zones.
ZO'OCARFES (ffiov, an animal, »cap-

ZOOLOGY.

7to9, fruit). The name given to certain
organized bodies which have been vari-
ously considered as animals, as plants,
and as partaking of the characters of each
of these divisions of organized beings.
They are found among the lower forms of
algce of botanists, as the diatoma, the
fragillaria, &c.

ZOO'LOGY (twov, an animal, Xo'yo?, a
description). That branch of Natural
Science which investigates the nature,
properties, and classification of the sub-
jects of the Animal Kingdom. Under
the term Animal Kingdom, a table is
given of the terms employed by different
writers in classifying these subjects.

I. Divisions of Aristotle. Aristotle's
primary divisions were derived from the
presence and the (supposed) absence of
blood in animals, which were, therefore,
termed enaima [kv, in, ai/xa, blood) or
sanguineous, including beasts, birds,
reptiles, and fishes ; and anaima (a, priv.
al/xa, blood) or ex-sanguineous, including
all the lower species. The subsequent

discovery of white blood in animals, and
the substitution of the terms " red-
blooded " and white-blooded " for the pri-
mary divisions of Aristotle, were steps in
the progress of improvement.

2. Divisions of Linnceus. In the "Sys-
tema Naturae " the natural divisions of
the Animal Kingdom are indicated by
internal structure. Thus, with a bilocular
heart with two auricles, and warm, red
blood, we have viviparous animals in the
Mammalia, oviparous in the Birds. With
a unilocular heart with one auricle, and
cold, red blood, we have, furnished with
arbitrary lungs, the Amphibia, with ex-
ternal gills, the Fishes. With a unilocu-
lar heart with one auricle, and cold,
white circulating fluid (sanies), we have,
furnished with antennae, the Insects, with
tentacula, the Worms.

3. Divisions of Cuvier. The following
table exhibits Cuvier's fourfold division
of the Animal Kingdom, together with
the classes, sub-classes, orders, and an
example of each division : —

Div. I.— VERTEBRATA.

Animals which have an internal skeleton, supported by a spine.

Class,

I. Mammalia

Animals which suckle their
young.

II. Aves ....
Birds.

III. Reptilia ,
Reptiles.

Sub-Class.
I. Osseous

IV. Pisces ...

Fishes.

Order.

1. Bimana.

2. Quadrumana.

3. Carnivora.

4. Rodentia.

5. Edentata.

6. Pachyderma.

7. Ruminantia.

8. Cetacea.

rl. Accipitres.

2. Passeres.
I 3. Scansores.
i 4. Gallinae.

5. Grallae.
[6. Palmipedes.

(1. Chelonia.
) 2. Sauria.
| 3. Ophidia.
1 4. Batrachia.

1. Acanthopterygii.

2. Malacopterygii 1
Abdominales. J

3. Malacopterygii \
Sub-brachiati. j

4. Malacopterygii 1
Apodes. J

5. Lophobranchii.

6. Plectognathi.

Cartilaginous.
Chondropterygi

s. n.

"i8:

Sturiones.

Selachii.

Cyclostomi.

Example.

Man.

Monkeys.

Hyaena.

Rabbit.

Sloth.

Elephant.

Cow.

Whale.

Eagle.

Sparrow.

Parrot.

Pheasant.

Heron.

Duck.

Tortoise.

Lizard.

Serpent.

Frog.

Perch.

Pike.
Cod.

Eel.

Hippocampus.
Sun-fish.

Sturgeon.

Shark.

Lamprey.

ZOOLOGY.

Div. II.— MOLLUSCA.

Soft, invertebral, inarticulate animals, often protected by a shell.

Class.
I. Cephalopoda .
Head-footed.

II. Pteropoda

Fin-footed.

III. Gasteropoda .,
Belly-footed.

IV. Acephala

Headless.

V. Brachiopoda

Arm-footed.

VI. ClRRHOPODA

Bristle-footed.

Order.

Example.

| (One.) Cephalopoda.

Cuttle-fish.

| (One.) Pteropoda.

Clio.

p. Pulmonibranchia.

Snail.

2. Nudibranchia.

Glaucus.

3. Inferobranchia.

Diphyllidia.

4. Tectibrancbia.

Bulla.

( 5. Heteropoda.

Carinaria.

6. Ptenobranchia.

Whelk.

7. Tubulibranchia.

Vermetus.

8. Scutibranchia.

Sea-ear.

.9. Cyclobranchia.

Chiton.

1 1. Testacea.

Oyster.

12. Nuda.

Ascidia.

J- (One.) Brachiopoda. Lingula.
\ (One.) Cirrhopoda. Barnacle.

Div. III.— ARTICULATA.

Animals with bodies covered with a case divided into rings.

Annelida *

Ring-bodied animals.

a

. Tubicola. Wormshell.

Dorsibranchia. Lobworm.
Abranchia. Earthworm.

II. Crustacea,
Cmstacequs
animals.

I. Malacostracia,(
Crustaceous-shelled. '

II. Entomostracia,
Thin-shelled.

III. Arachnida

The Spider-tribe.

IV. Insecta ...
Insects.

885

1. Decapoda.

Lobster.

2. Stomapoda.

Sea mantis.

3. Amphipoda.

Shrimp.

4. Laemodipoda.

Whale-louse

5. Isopoda.

Cymothoa.

f 6. Branchiopoda.

Monoculus.

L 7. Pcecilopoda.

King-crab.

/ 1. Pulmonata.
1 2. Trachearia.

Tarantula.

Mite.

- 1. Myriapoda.

Centipede.

2. Thysanoura.

Springtail.

3 Parasita.

Louse.

4. Suctoria.

Flea.

5. Coleoptera.

Beetle.

6. Orthoptera.

Ear-wig.

7. Hemiptera.

Bug.

8. Neuroptera.

Ant-lion.

9. Hymenoptera.

Wasp.

10. Lepidoptera.

Butterfly.

11. Rhipiptera.

Stylops.

112. Diptera.

Fly.

S

ZU M

Z YM

Div. IV.— RADIATA.

Animals disposed around an axis.

Class.

I. ECHINOBERMA

, Hard-skinned.
II. Intestina

Intestinal worms.

III. ACALEPHA

Sea nettles.

IV. Polypi

Plant-like animals.

V. Infusoria

Water animalcules.

Order.

{I. Pedicellata.
2. Apoda.
( 1. Cavitaria.
\ 2. Parenchyma.
, Simplex.

Hydrostatica.

1. Carnosa.
Gelatinosa.
Corallicola.
Rotifera.

2. Homogenea.

( L

( 3.

u

Example.
Star-fish.
Sipunculus.
Guinea-worm.
Tapeworm.
Medusa.

{Spanish man-of-
war.
Sea anemone.
Vorticella.
Coral.

Wheel insect.
Globeanimalcule.

ZOO'NIC ACID (f5ov, an animal).
This is merely the acetous acid, holding
animal matter in solution.

ZOO'NOMY (fwov, an animal, vo^oc,
a law). The science which treats of the
laws of organic life.

ZOO'PHAGOUS (twov, an animal,
<pdj(o, to eat). Animal-eating ; a term
applied to a division of the cetaceous
animals, and to a tribe of carnivorous
gasteropods — the pectinibranchiata of
Cuvier. See Phytophagous.

ZO'OPHYTES (fwoi/, an animal, cpOrov,
a plant). Animal-plants; a division of the
animal kingdom, including the corals,
sponges, and other aquatic animals allied
to them. They are so named, because,
while they are the habitation of animals,
they are fixed to the ground, and have the
forms of plants. They were considered by
Cuvier as synonymous with the radiata.
Their characters are given under the
terms Echinodermata, Entozoa, Aca-
lephae, Polypus, and Infusoria.

ZUBENELY, or p LIBRA. A star of
the second magnitude, in Libra.

ZUBENESCH, or a LIBRA. A star
of the second magnitude, in Libra.

ZUBERNICH MELI. A star of the
second magnitude in the constellation
Libra.

ZUMIC ACID (tv^n, leaven). An
acid discovered in vegetable substances
which have undergone the acetous fer-
mentation. It has been shown to re-
semble closely the lactic acid.

ZUMO'METER {&ixr\, leaven, fierpov,
a measure). Zumosimeter. An instru-

ment for measuring the degree to which
fermentation has proceeded in ferment-
ing liquors.

ZU'NDERERZ. Tinder ore; an ore
of silver, occurring in the Hartz, in
fibrous flakes resembling Under.

ZURLITE. A mineral occurring in
rectangular prisms and in botryoidal
masses, of an asparagus-green colour. It
occurs on Mount Vesuvius with calcare-
ous spar.

ZYGODA'CTYLES (£vyorf a yoke,
ddKTvXot, a finger). The name given by
Zernminck to an order of climbing birds,
including those which have the toes
arranged in pairs, two before and two
behind, as the parrot, the woodpecker,
the toucan, the cuckoo, &c. They cor-
respond with the Scansores of Cuvier.

ZYG^'NIDjE. A tribe of lepidopter-
ous insects, named from the typical
genus zygcena, and arranged by Linnaeus
with the Sphinges on account of the
resemblance of their antennas to those of
that family.

ZYGOPHYLLA'CE^. The Bean
Caper tribe of dicotyledonous plants.
Trees, shrubs, and herbaceous plants,
with leaves opposite; flowers polypetal-
ous, symmetrical ; stamens hypogynous ;
ovarium many-celled ; fruit capsular.

Z Y'MOME (#/xi> leaven). The residue
of the gluten of wheat, after it has been
treated by alcohol, and has parted with
its gliadine and water. It produces vari-
ous kinds of fermentation, according to
the nature of the substance with which it
comes in contact.

Gilbert & Rivington, Printers, St. John's Spuare, London.

WORKS BY THE SAME AUTHOR.

i.
DICTIONARY OF MEDICAL TERMS.

Fourth Edition.

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Sept. 1835.

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