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- PHILOSOPHICAL
TRANSACTIONS,

\

, OF THE ~~

ROYAL SOCIETY

OF
: LONDON.
FOR THE YEAR MDCCC.

3:

PART 1

4

LONDON,
———ae ll

PRINTED BY W. BULMER AND CO. CLEVELAND-ROW, ST. JAMES’S ;
AND SOLD BY PETER ELMSLY,
PRINTER TO THE ROYAL SOCIETY.
MDCCC.

We

ii J
Paes OS,
ADVERTISEMENT.

‘Tine Committee appointed by the Royal Society to direct the pub-
lication of the Philosophical Transactions, take- this opportunity to
acquaint the Public, that it fully appears, as well from the council-
books and journals of the Society, as from repeated declarations which
have been made in several former Transactions, that the printing of
them was always, from time to time, the single act of the respective
Secretaries, till the Forty-seventh Volume: the Society, as a Body,
never interesting themselves any further in their publication, than by
occasionally recommending the revival of them to some of their Se-
cretaries, when, from the particular circumstances of their affairs, the
Transactions had happened for any length of time to be intermitted.
And this seems principally to have been done with a view to satisfy
the Public, that their usual meetings were then continued, for the im-
provement of knowledge, and benefit of mankind, the great ends of
their first institution by the Royal Charters, and which they have ever
since steadily pursued.

But the Society being of late years greatly enlarged, and their com-
munications more numerous, it was thought advisable, that a Com-
mittee of their members should be appointed, to reconsider the papers
read before them, and select out of them such as they should judge
most proper for publication in the future Transactions; which was
accordingly done upon the 26th of March, 1752. And the grounds

A@2

L iv J
of their choice are, and will continue to be, the importance and sin-
gularity of the subjects, or the advantageous manner of treating them ;
without pretending to answer for the certainty of the facts, or pro-
piety of the reasonings, contained in the several papers so published,
which must still rest on the credit or judgment of their respective
authors.

It is likewise necessary on this occasion to remark, that it is an esta-
blished rule of the Society, to which they will always adhere, never to
give their opinion, as a Body, upon any subject, either of Nature or
Art, that comes before them. And therefore the thanks which are
frequently proposed from the Chair, to be given to the authors of such
papers asare read at their accustomed meetings, or to the persons through
whose hands they receive them, are to be considered in no other light
than as a matter of civility, in return for the respect shewn to the So-
ciety by those communications. The like also is to be said with re-
gard to the several projects, inventions, and curiosities of various
kinds, which are often exhibited to the Society ; the authors whereof,
or those who exhibit them, frequently take the liberty to report, and
even to certify in the public news-papers, that they have met with the
highest applause and approbation. And therefore it is hoped, that no
regard will hereafter be paid to such reports and public notices; which
in some instances haye been too lightly credited, to the dishonour of

the Society.

CONTENTS.

1. THe Croonian Lecture. On the Structure and Uses of ithe Mem-
brana Tympani of the Ear. By Everard Home, Hsq. &% R. S.

, page 1

If. On the Method of determining, from the real Probabilities
of Life, the Values of Contingent Reversions in which three
Lives are involved in the Survivorship. By William Morgan,
Esq. F. R.S. p. 22
III. Abstract of a Register of the Barometer, Thermometer, and
Rain, at Lyndon, in Rutland, for the Year 1798. By Thomas
Barker, Esq. p. 46
IV. On the Power of penetrating into Space by Telescopes ; with
a comparative Determination of the Extent of that Power in
natural Viston, and in Telescopes of various Sizes and Con-
structions ; illustrated by select Observations. By William
Herschel, LL.D. F. B.S. Pp. 49
V. A second Appendix to the improved Solution of a Problem in
physical Astronomy, inserted in the Philosophical Transactions
for the Year 1798, containing some further Remarks, and
improved Yormule for computing the Coefficients A and B;
by which the arithmetical Work is considerably shortened and
facilitated. By the Rev. John Hellins, B.D. F.R.S. and
Vicar of Potter’s Pury, in Northamptonshire. p. 86
VI. Account of a Peculiarity in the Distribution of the Arteries
sent to the Limbs of slow-moving Animals ; together with some

Cw

other similar Facts. In a Letter from Mr. Anthony Carlisle,

_ Surgeon, to John Symmons, Esq. F. R. S. p. 98
VII. Outlines of Experiments and Inquiries respecting Sound and
Light. By Thomas Young, M. D. F. R.S. In a Letter to
Edward Whitaker Gray, M. D. Sec. R.S. p. 106
VIII. Observations on the Effects which take place from the De-
struction of the Membrana Tympani of the Ear. By Mr. Astley
Cooper. In a Letter to Everard Home, Esq. F. R.S. by
whom some Remarks are added. p: 158
1X. Experiments and Observations on the Light which is spon-
taneously emitted, with some Degree of Permanency, from
various Bodies. By Nathaniel Hulme, M.D. F.R.S. and
A.S. p. 162
X. Account of a Series of Experiments, undertaken with the View
of decomposing the Muriatic Acid. By Mr. William Henry.
Communicated by the Right Hon. Sir Joseph Banks, Bart.

PRS. p. 188

XI. On a new fulminating Mercury. By Edward Howard, Esq.

F.R.S. p. 204,
APPENDIX.

Meteorological “fournal kept at the Apartments of the Royal
Society, by Order of the President and Council.

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THE Presipent and Councit of the Royar Society adjudged,
for the year 1799, the Medal on Sir Goprrey Coprey’s Donation,
to the Rev. Jon Heruins, B.D. F.R.S. for his improved Solution
of a Problem in physical Astronomy, &c. printed in the Philosophical
Transactions for the year 1798, and his other mathematical papers.

PHILOSOPHICAL
TRANSACTIONS.

I. The Croonian Lecture. On the Structure and Uses of the Mem-
brana Tympani of the Ear. By Everard Home, Esq. F. R. S.

Read November 7, 1799.

Tue subject of inquiry appointed by the Croonian Institution,
has been greatly elucidated at different times by ingenious mem-
bers of this learned Society. A large field, however, still re-
mains open; and, respecting future investigations, I shall have
occasion to offer a fresh proof of the aid to be derived from
comparative anatomy, in ascertaining the structure of parts
which, from their minuteness and situation in the human body,
admit with much difficulty of being explored.

The principal object of the present lecture is to communicate
a discovery of the structure of the membrana tympani; which,
in some respects, affords a new and very curious instance of
the application of muscular action, and may conduce to account
for certain phenomena in the sense of hearing, in a more satis-
factory manner than has hitherto been proposed.

The membrana tympani has always been considered as a

MDCCC, B

g Mr. Home’s Lecture

common membrane, which, by means of muscles belonging to
the malleus being stretched or relaxed, became fitted, in its
various degrees of tension, to convey the vast variety of ex-
ternal sounds to the internal organ. Its shape, situation, and
office, have procured it the name of drum of the ear; and the
muscles of the malleus having been deemed sufficient for bra-
cing and unbracing it, less attention was bestowed on the struc-
ture of the membrane itself: to which may be added, that in
the human ear, and generally in the ear of quadrupeds, the
membrane is so extremely small and thin, and in its situation
so peculiarly confined, as not to be got at for inspection but with
much difficulty.

The case is different in the elephant, where this membrane
is so very large, that the parts of which it is composed are
readily distinguished: they are even conspicuous to the naked
eye; and muscular fibres are seen passing along the membrane,
in a radiated manner, from the bony rim which surrounds it,
towards the handle of the malleus, to which the central part of
the membrane is firmly attached.

This discovery in the elephant having led to that of a simi-
lar construction in the human membrana tympani, it may not
be improper to relate the circumstances by which I became
engaged in the investigation of the organ of hearing in that
animal.

Three different opportunities have occurred of dissecting the
elephant in London, by the deaths of those which had been
presented to his Majesty, and were kept at the King’s stables
at Pimlico. One of them was given to the late Dr. HunTER;
one to his brother Mr. J. HUNTER; and the third to Sir AsHToN
“LEVER. pel

on the Membrana Tympani. g

From my being connected with Mr. Joun HunrTer’s pursuits
in comparative anatomy, I was employed throughout the whole
of these dissections, and became extremely desirous of exami-
ning the internal parts of the ear, the structure of that organ in
the human body having at a very early period particularly en-
gaged my attention ;* but neither Dr. Hunrer nor his brother
could be prevailed upon to sacrifice so large a portion of the
skull as was necessary for the purpose.

When Mr. Corse arrived from Bengal, last year, and men-
tioned his having brought over a number of skulls of elephants,
in order to show the progress of the formation of their grind-
ing teeth,-+ the desire to examine the organ of hearing in that
animal recurred to me so strongly, that I requested to have one
of the skulls for that purpose, and Mr. Corse very readily and
obligingly complied with my request.

After having examined the organ in the dried skull, the want
of the membrana tympani, and of the small bones, made the
information thus received of a very unsatisfactory nature, and
increased the desire of seemg these parts in the recent head. In
considering how this could be done, I recollected a mutilated
elephant’s head, preserved in spirits, which had been sent to

* Tn the year 1776, I injected the cochlea and semicircular canals of the human ear
with a composition of wax and rosin. This was done by placing the temporal bone in
the receiver of an air pump, the upper part of which was in the form of a funnel, ren-
dered air-tight by a cork being fitted into its neck, and surrounded with bees’ wax.
After the air had been exhausted, the hot injection, poured into the funnel, melted the
wax, and the cork was pulled out by means of a string previously attached to it; the
injection immediately rushed into the receiver, and was forced, by the pressure of the
atmosphere, into the cavities of the temporal bone.

+ On this subject, a very ingenious paper has been since published by him, in the
Philosophical Transactions for the year 1799.

Be

A Mr. Home’s Lecture

Mr. Hunter, but, from the multiplicity of his engagements,
had remained neglected in the cask at the time of his death, and
in the following year was dried, to show the proboscis, that it
might not be altogether spoiled.

Upon examining this dried head, the bones had been so much
broken, that one of the organs of hearing was altogether want-
ing: the other, however, was fortunately entire; and the mem-
brana tympani and small bones, having been little disturbed in
the drying of the parts, remained nearly in their natural situation.

The membrana tympani, and every other part of the organ,
were found to be much larger in proportion than in other qua~
drupeds, or in man; differing in this respect from the eye of
the elephant, which is unusually small, when compared with
the enormous bulk of the animal.

The membrane was found of an oval form; the short dia-
meter of the oval rather more than an inch in length; the long
diameter an inch and ths.

In the human ear, the membrana tympani is nearly circular;
the longest diameter is =8ths of an inch; the shortest Uths.

As the membrane in the elephant exceeds that of the human
ear in thickness as much as in extent, which is as the squares
of their diameters, or in the proportion of 19% to 14, it is natu-
ral to conclude that the muscular fibres which are to stretch the
one, must greatly exceed in strength those capable of producing
the same degree of tension in the other.

From this statement, the muscular structure in the human
membrana tympani will necessarily be so much less distinct
than in the elephant, as scarcely to be visible to the naked eye,
and will easily be overlooked by the most attentive observer,
who is not directed by some previous information to examine

on the Membrana Tympani. -

it under the most favourable circumstances; but, when these
are attended to, it can be perceived without the aid of glasses.

If the membrana tympani of the human ear is completely
exposed on both sides, by removing the contiguous parts, and
the cuticular covering is carefully washed off from its external
surface, then, by placing it in a clear light, the radiated direc-
tion of its fibres may be easily detected. If a common magnify-
ing glass is used, they are rendered nearly as distinct as those
of the elephant appear to the naked eye; their course is exactly
the same; and they difler in nothing but in being formed upon
a smaller scale.

When viewed in a microscope magnifying 2g times, the
muscular fibres are beautifully conspicuous, and appear uni-
formly the same throughout the whole surface, there being no
central tendons, as in the diaphragm; the muscular fibres ap-
pear only to form the internal layer of the membrane, and are
most distinctly seen when viewed on that side.

In examining this membrane in different subjects, the parts
were frequently found in a more or less morbid state. In one
instance, the membrane was found loaded with blood-vessels,
was less transparent than usual, and was united by close adhe-
sion to the point of the long process of the incus. In another
instance, there was a preternatural ossification adhering to it, at
a small distance from the end of the handle of the malleus.

As muscles in general are supplied with blood-vessels in pro-
portion to the frequency of their action, it is an object of im-
portance to determine the vascularity of the membrana tympani.
Upon this subject, my own want of information has been amply
supplied by Dr. BaiLuiz, who, in a communication upon this
subject, showed me a preparation of the membrane, in which

6 Mr. Home’s Lecture

the vessels had been most successfully injected with coloured
wax.

In this preparation, the most beautiful of the kind I ever saw,
-the vessels in their distribution resembled those of the iris, and
were nearly half as numerous: they anastomosed with one an-
other in a similar manner, and their general direction was from
the circumference to the handle of the malleus; from near this
handle, a small trunk sent off branches, in a radiated manner,
which anastomosed with those which had an opposite course.

This correspondence, in the number and distribution of blood-
vessels, between the membrana tympani and the iris, is a strong
circumstance in confirmation of that membrane being endowed
with muscular action.

In the horse, the membrana tympani is smaller than in man;
its long diameter is =8ths of an inch; the short one =Sths; and
it is almost quite flat, while in man it is concave, which makes
the difference of extent considerably exceed the difference in the
diameters. In the horse, the fibrous structure is not visible to
the naked eye; it is even indistinctly seen when viewed through
a common magnifying glass; but in a microscope it is very
visible, and in every other respect agrees in structure with the
membrane in the human ear, and in that of the elephant.

In birds, the membrana tympani is larger in proportion than —
in the quadruped, and more circular in its shape.

In the goose, it is ths of an inch in its longest diameter, and
$ths in its shortest diameter. In the turkey, =.ths by =.ths.
It is thinner in its coats in birds than in the horse, and to the
naked eye has no appearance of fibres; but, when viewed in a
microscope, there is a visible radiated structure, not very unlike
the wire marks upon common writing paper.

on the Membrana Tympani. 4

In a former Lecture upon the Structure of Muscles,* in
which a comprehensive view was taken of the subject, it was
stated, that the organization necessary for muscular contraction
could exist in an apparent membrane, and that a fasciculated
structure was only necessary when muscular action was to be
enabled to overcome resistance. The coats of the Tzenia hydati-
gena were mentioned as an instance of the first; and the human
heart as the most complex of the second. In comparing the
membranz tympani of different animals, they afford a beautiful
illustration of the truth of this position.

In birds, where from the smallness of its size the resist-
ance is very trifling, the membrane is very similar to the coat
of an hydatid, only still thinner. In the elephant, fibres form-
ing fasciculi are very distinct. The membrane of the horse,
and that of the human ear, form the intermediate gradations.

The knowledge of a muscular structure in the membrana
tympani, enables us to explain many phenomena in hearing,
which have not hitherto been accounted for in a satisfactory
manner. It is principally by means of this muscle that accu-
rate perceptions of sound are communicated to the internal or-
gan, and that the membrana tympani is enabled to vary the
state of its tension, so_as to receive them in the quick succession
in which they are conveyed to it.

In the human ear, and in that of birds, the radiated fibres of
the membrana tympani have their principal attachment to the
extremity of the handle of the malleus, which is nearly in the
centre of the membrane.

In the membrane of the elephant, which is oval, the attach-
ment to the handle of the malleus is at some distance from the

* Philosophical Transactions for the year 1795.

8 Mr. Home’s Lecture

centre. In the horse, deer, and cat, which have the membrane
still more oval than the elephant, the handle of the malleus is
situated in the long axis of the membrane, with its extremity
extending beyond the centre, reaching nearer to the circumfe-
rence; and the fibres of the radiated muscle are not only at-
tached to its end, but also laterally to nearly the whole length
of its handle.

This oval form of the membrana tympani, in those quadrupeds,
and the very extensive attachment of the fibres of the radiated
muscle to the handle of the malleus, may be the reason why
their ears are not equally fitted to hear inarticulate sounds, as
the ears of birds and of man.

Should this radiated muscle of the membrana tympani (which
is probably the smallest in the body that has a distinct action)
be thought too insignificant to have an office of so much con-
sequence assigned to it, let it be remembered, that the size of
muscles is no indication of their importance, but only of the
resistance to be overcome by their action; and that the more
delicate actions are performed universally in the body by very
small muscles, of which the iris in the eye furnishes a very con-
spicuous example.

Before the mode in which the radiated muscle adapts the
membrana tympani to different sounds can be explained, it is
necessary that the more important parts of the organ should be
enumerated, and the use commonly assigned to each of them
pointed cut.

In man and the more perfect quadrupeds, this organ consists
of the following parts: the membrana tympani, situated be--
tween the external passage and the cavity of the tympanum;
four smail bones, which form achain across the tympanum,

on the Membrana Tympani. 9

connecting the membrana tympani with another membrane
lining the foramen ovale, which opens into the vee aEIaaL a
more internal part of the organ of hearing.

The bones are, the malleus, which is united to the membrana
tympani by a portion of its handle, and to the second bone or
incus by its head. ‘The incus, which is connected to the mal-
leus by a capsular ligament, forming a regular joint, the sur-
faces of the bones being covered with cartilage, but they have
only a tremulous motion on one another. The incus is also
attached to the side of the cavity of the tympanum, where the
mastoid cells open, by a ligament on which it moves back-
wards and forwards: it is united by its long process to the
orbicular bone, which is the smallest in the body, and connects
the incus to the fourth bone or stapes, which has its base ap-
plied to the foramen ovale, or opening leading into the cavity of
the vestibulum.

The cavity of the tympanum, in which these bones are si-
tuated, communicates with the external air by means of the
Eustachian tube, so that there is always air behind the mem-
brana tympani.

The malleus has three muscles, by which it is moved; one
of them is called the tensor, from its pulling the malleus in-
wards, and tightening the membrana tympani: the other two
act in an opposite direction, and relax the membrane; the lar-
gest of these is called the obliquus, and is the antagonist of the
tensor muscle; the other is very small, and is called the laxator.

The stapes has one muscle, which. acts upon it by bringing
its basis closer to the foramen ovale.

The vestibulum, which is completely separated from the
tympanum, by the membrane that lines the foramen ovale, com-

Mpcee. A Cc

10 Mr. Home’s Lecture

municates freely with the cochlea and semicircular canals; but
these cavities are filled with a watery liquor, and have no com-
munication (as the tympanum has) with the external air.

This fact was ascertained in the horse, by the following ex-
periment, repeated several times. The organ of hearing was
separated from the skull immediately after death, and the ca-
vity of the tympanum exposed; the parts were then immersed
in water, and the stapes removed ; by which means, the mem-
brane of the foramen ovale was destroyed, but no globule of
air was seen to escape through the water.*

The following uses have generally been assigned to the parts
now mentioned. |

The membrana tympani was supposed to be adapted to re-
ceive impressions, by the combined action of the tensor and
laxator muscles varying the degree of its tension, so as to bring
it in unison with different sounds: these impressions were con-
ducted, by the chain of bones, to the vestibulum, cochlea, and
semicircular canals ; in which cavities, particularly the cochlea,
they were supposed to undergo some modification, before they
were impressed upon the nerves spread upon the linings of
these cavities.

The function of modifying impressions of sound was assign-
ed to the cochlea, partly from the delicacy of its internal struc-
ture, supposed to resemble a musical instrument, and partly
from there being no other part of the organ apparently suited
for repeating the variety of delicate sounds which pass into the
ear: the changes that couid be produced upon the membrana

* This experiment was made by Mr. CiiFr, who superintends Mr. Hunt er’s col-
lection, and who has afforded me material assistance in the different parts of this

investigation.

on the Membrana Tympani. 11

tympani by the muscles of the malleus, being considered as in-
capable of answering that purpose.

This slight sketch of the organ of hearing, and of the uses,

as they are generally understood, of the different parts, will
enable me to point out, with more clearness, what parts of the
theory appear defective, and what improvements may be made
on it. \
It is true that the membrana tympani is stretched and re-
laxed by the action of the muscles of the malleus, but not for
the purpose alleged in the commonly received theory. It is
stretched, in order to bring the radiated muscle of the membrane
itself into a state capable of acting, and of giving those diffe-
rent degrees of tension to the membrane which empower it to
correspond with the variety of external tremors: when the
membrane is relaxed, the radiated muscle cannot act with any
effect, and external tremors make less accurate impressions.

The membrana tympani, with its tensor and radiated muscles,
may be not unaptly compared to a monochord, of which the
membrana tympani is the string; the tensor muscle the screw,
giving the necessary tension to make the string perform its
proper scale of vibrations; and the radiated muscle acting upon
the membrane like the moveable bridge of the monochord, ad-
justing it to the vibrations required to be produced. The com-
bined effects of the action of these muscles give the perceptions
of grave and acute tones; and, in proportion as their original
conformation is more or less perfect, so will their actions be,
and, consequently, the perceptions of sound which they com-
municate.

This mode of subdividing the motions of the membrana
tympani between two sets of muscles, allotting a portion to

Ce

12 Mr. Home’s Lecture

each, is not peculiar to this part. A remarkable instance of it
appears in the rapid movements of the-fingers, in performing
several actions, and particularly in playing on a musical instru-
ment. In all such rapid motions, the fingers are bent to a
certain degree by the long muscles that lie upon the fore-arm,
to the tendons of which a set of smaller muscles are attached,
called lumbricales. These last are unable to produce any effect
on the fingers, till elongated in consequence of the action of
the long muscles in bending the other joints; the lumbricales
then become capable of bending the fingers a little more, and
of acting with great rapidity. It is a curious circumstance,
that a similar application of muscles should be employed to fit
the fingers to produce a quick succession of sounds, and to
enable the ear to be impressed by them.

From the explanation given of the adjustment of the mem-
brana tympani, the difference between a musical ear and one
which is too imperfect to distinguish the different notes in
music, will appear to arise entirely from the greater or less nicety
with which the muscle of the malleus renders the membrane
capable of being truly adjusted. If the tension be perfect, all
the variations produced by the action of the radiated muscle
will be equally correct, and the ear truly musical; but, if the
first adjustment is imperfect, although the actions of the ra-
diated muscle may still produce infinite variations, none of them
will be correct: the effect, in this respect, will be similar to that
produced by playing upon a musical instrument which is not in
tune. The hearing of articulate sounds requires less nicety in
the adjustment, than of inarticulate or musical ones: an ear
may therefore be able to perceive the one, although it is not
fitted to receive distinct perceptions from the other.

on the Membrana Tympan.. 13

The nicety or correctness of a musical ear being the result
of muscular action, renders it, in part, an acquirement; for,
although the original formation of these muscles in some ears
renders them more capable of arriving at this perfection in their
action, early cultivation is still necessary for that purpose; and
it is found that an ear, which upon the first trials seemed unfit
to receive accurate perceptions of sounds, shall, by early and
constant application, be rendered tolerably correct, but never
can attain excellence. There are organs of hearing in which
the parts are so nicely adjusted to one another, as to render
them capable of a degree of correctness in hearing sounds
which appears preternatural.

Children who during their infancy are much in the society
of musical performers, will be naturally induced to attend more
to inarticulate sounds than articulate ones, and by these means
acquire a correct ear, which, after listening for two or three
years to articulate sounds only, would have been attained with
more difficulty. | i

This mode of adapting the ear to different sounds, appears
to be one of the most beautiful applications of muscles in the
body; the mechanism is so simple, and the variety of effects so
great. |

Several ways in which the correctness of hearing is affected
by the wrong actions of the muscles of the tympanum, that
appeared to be inexplicable, can be readily accounted for, now
that the means by which the membrane adjusts itself are un-
derstood. ‘The following are instances of this kind.

CasE1. A gentleman thirty-three years of age, who possess-
ed a very correct ear, so as to be capable of singing in concert,
though he had never learned music, was suddenly seized with a

14 Mr. Home’s Lecture

giddiness in the head, and a slight degree of numbness in the right
side and arm. These feelings went off in a few hours, but on
the third day returned, and for several weeks he had returns of
the same sensations. It was soon discovered that he had lost
his musical ear; he could neither sing a note in tune, nor in the
smallest degree perceive harmony in the performance of others.
For some time he himself thought he had become a little deaf,
but his medical attendant was not sensible of that in conversa~
tion. Upon going into the country, he derived great benefit
from exercise and sea-bathing.

Twenty months after the first attack, he was capable of sing-
ing a Scotch air with tolerable exactness, though he could not
sing in concert. He continued to improve in his health, and
in the course of two or three years completely recovered his ear
for music.

In this case, there appeared to be some affection of the brain,
which had diminished the actions of the tensor muscles of the
membrane tympani, through the medium of the nerves which
regulate their actions; this gradually went off, and the muscles
recovered their former action.

Case 2. A young lady was seized with a frenzy which last-
ed for several years. Previous to her derangement, she was
incapable of singing in tune, from the want of an ear for
music; but in the course of her madness she frequently, to the
astonishment of her relations, sung a tune with tolerable cor-
rectness.

This case is the reverse of the former; and, as it arose from a
directly contrary affection of the brain, may be considered as the
result of an unusual degree of action in the tensor muscles, giv-
ing the membrane a more correct adjustment than it had before.

on the Membrana Tympani. 15

Case 3. An eminent music master, after catching cold, found
a confusion of sounds in his ears. Upon strict attention, he dis-
covered that the pitch of one ear was half a note lower than that
of the other; and that the perception of a simple sound did not
reach both ears at the same instant, but seemed as two distinct
sounds, following each other in quick succession, the last being
the lowest and weakest. This complaint distressed him for
a long time, but he recovered from it without any medical
aid.

In this case, the whole defect appears to have been in the
action of the radiated muscle, exerted neither with the same
quickness nor force in one ear as in the other, so that the sound
was half a note too low, as well as later in being impressed
upon the organ.

This affection of the muscle of the membrana tympani is
very similar to an affection of the straight muscles of one of
the eyes, producing double vision, which I have noticed in a
former lecture, when treating of the wrong actions of that
organ.* |

In endeavouring to explain the uses of the more internal parts
of the ear, considerable advantage may be derived from class-
ing them in two divisions; namely, those which are formed for
the purpose of receiving impressions conveyed through the me-
dium of liquid or of solid substances ; and those adapted to re-
ceive impressions made by the impulses of an elastic fluid, as
the common air. :

This can be done very correctly. Fish, which are formed to
hear in water, can have only the parts belonging to the first
division; while all the parts found in the ears of birds and

* Vide Philosophical Transactions for the year 1797.

16 Mr. Home’s Lecture

quadrupeds, that are not met with in fish, must belong to the
second,

In fish, the organ consists of a vestibulum and three semi-
circular canals, and these are met with in all fish. In some
genera there is an external opening, and substances of a hard
nature are found lying loose in the vestibulum: these, how-
ever, cannot be considered as essential parts of the organ, from
their not being common to fish in general.

Birds have the vestibulum and semicircular canals in com-
mon with fish, but they have also a membrana tympani; a
slender bone connecting that membrane with the vestibulum ;
and an Eustachian tube. In birds, the membrana tympani is
convex externally, being pushed forwards by the end of the
slender bone abovementioned.

In quadrupeds and man, besides the vestibulum and canals
met with in fish, the membrana tympani, the bone connecting
it with the vestibulum, and the Eustachian tube, found in birds,
there is a cochlea. The membrana tympani is either flat or
concave externally; the bony connection between it and the
vestibulum is made up of several bones, supplied with muscles
to move them in different directions.

The parts which compose the organ of hearing in fish, must
be intended for receiving impressions conveyed through water :
those additional parts met with in birds, and the still greater
additions which are found in the quadruped and man, must be
intended by nature for rendering more perfect the impressions
conveyed to the ear through the medium of the external air.

Fish, from the structure of the organ, can only hear sounds
which agitate the water immediately in contact with the head
of the fish; so that the impulse is conveyed, without inter-

on the Membrana Tympani. 17

ruption, from the liquid in which they live, to the organ of
hearing.

Man is capable of hearing in a similar manner to fishes, when
a communication of solid parts is kept up between the sounding
body and the bones of the skull: experiments of this kind must
have been made by many members of this learned Society.

One of the most common is, applying a watch to the fore-
head, and stopping the ears, which does not prevent the ticking
from being heard: the sound is still more distinct when the
watch is applied to the mastoid process. Here, as the sound
can neither pass through the meatus externus, nor by the Eus-
tachian tube, while the mouth is kept shut, it evidently must
be conducted through the bones of the skull.

When the sound produced by boiling water is brought to the
ear, by one end of an iron rod resting upon the side of the kettle
and the other kept in contact with the teeth, the sound is con-
ducted in the same way, although in this case it has by some
been supposed to pass through the Eustachian tube.

In this mode of hearing, the vestibulum and semicircular
canals are probably the only parts of the organ which are ne-
cessary to convey the impression to the expansion of the audi-
tory nerve.

In hearing in air, the use of the membrana tympani in man
and quadrupeds has already been explained. Its office in
birds is precisely the same; but as in birds this membrane has
no tensor muscle to vary its adjustment, but is always kept
tense by the pressure of the end of the slender bone, the scale
in birds cannot descend so low as in the human ear; and the
intervals in their scale will be more minute, in consequence of
the slightest tremor communicated by the action of the radiated

MDCCC. D

18 Mr. HomMe’s Lecture

muscle to one end of the slender bone being immediately con-
ducted to the internal organ; while in the human ear it has to
pass from one bone to another, before it arrives at the vestibu-
lum.

The cochlea has been considered by all physiologists as one
of the most intricate and curious parts of the ear, and on that
account had a most important office assigned to it. This, how-
ever, is now to be transferred to the membrana tympani; and,
upon attentive consideration of the subject, it will appear im-
possible for the cochlea to be of any use in modulating sounds,
since the ear is only intended to convey impressions received
from external bodies; hence, no impression can be communi-
cated to the cochlea, which has not-been transmitted by the
membrana tympani. But, if all the varieties of sound are re-
peated by the membrana tympani, no modulation in the cochlea
is required; and, when it is considered that the cochlea contains
water, instead of air, the effect upon every part will be found to
be simultaneous.

That the cochlea is neither absolutely necessary to fit the
organ to be impressed by sounds communicated through air,
nor to render it what is termed a musical ear, is sufficiently
proved by that part being wanting in birds, whose organ is par-
ticularly adapted to inarticulate sounds. Some birds, particularly
bulfinches, can be taught to sing various airs, although it will
be always in high notes.

If it should be found that birds Heat less accurately than
quadrupeds, it will favour the idea that the great delicacy of
structure of the cochlea, is intended to render the nerves which
are spread upon it more readily impressed by weak tremors,
than those in either the vestibulum or semicircular canals.

on the Membrana Tympani. 19

The cochlea and semicircular canals must be considered as
two of the most important parts of the ear; their peculiar forms
are no doubt adapted to some essential purposes; but, what are
the precise advantages derived from their particular shape, is at
present unknown. There is, however, much ground to believe,
that a more extensive knowledge in comparative anatomy, join-
ed with future observations, may clear up this very curious and
obscure part of the physiology of the organ of hearing.

In the elephant, the small bones, the cochlea, and semicircu-
lar canals, are larger than those in the human ear, nearly in the
same proportion with the increased size of the membrana tym-
pani. In that animal, there is a very remarkable peculiarity ;
which is, a cellular structure occupying the upper and posterior
part of the skull, inclosed between the two tables, communi-
cating by a considerable aperture with the cavity of the tympa-
num, and lined by a similar membrane: the cells commu-
nicate freely with one another at their lower extremities, but
not near the upper, forming irregular.cylinders, placed in a
converging direction, towards the cavity of the tympanum.

There is no middle bony septum, separating the cells of the
skull belonging to one ear from those which open into the
other, but a ready communication between them.

On the anterior part of the skull there is also a similar cel-
lular structure, only much smaller, which communicates with
the nose, but is entirely separate and distinct from that which
forms an appendage to the organ of hearing.

That the elephant hears better than other animals, is gene-
rally asserted by those who have had opportunities of making
observations on the subject. As this opinion has been ad-
vanced by men who had no knowledge in anatomy, and had

De

20 Mr. Home’s Lecture

no previous theory to bias their judgment, it is deserving of
credit. The organ of hearing being now found more perfect,
and formed upon a larger scale than in any other animal with
which we are acquainted, considerable weight is given to this
opinion.

Mr. Corse, who resided many years at Tiperah, in Bengal,
and paid particular attention to the manners and habits of ele-
phants, concurs in the belief of their hearing being more acute
than that of man. The following circumstances are mentioned
by him in proof of it.

A tame elephant, who was never reconciled to have a horse
moving behind him, although he expressed no uneasiness if the
horse was within his view, either before or on one side, could
distinguish the sound of a horse’s foot at a distance, some time
before any person in company heard it: this was known by his
pricking up his ears, quickening his pace, and turning his head
from side to side.

A tame female elephant, who had a young one, was occa-
sionally sent out with other elephants for food, without the
young one being allowed to follow. She was not in the habit
of pining after her young one, unless she heard its voice; but
frequently, on the road home, when no one could distinguish
any sound whatever, she pricked up her ears, and made a noise
expressive of having heard the call of her young. This having
occurred frequently, attracted Mr. Corsr’s notice, and made
him, at the time the female elephant used these expressions,
stop the party, and desire the gentlemen to listen; but they were
unable to hear any thing till they had approached nearer to the
place where the young one was kept.

The foregoing observations, the object of which has been to

os 3a

on the Membrana Tympani. 21

prove that the membrana tympani of the ear has a muscular
structure, have already exceeded the limits of a lecture, which
prevents us from going further at present into the considera-
tion of this very curious and important organ. The general
analogy between the uses of its different parts and those of the
organ of vision, and the similar variations of their actions when
under the influence of disease, furnish materials which, on
some future occasion, may be laid before this learned Society.

[2s

If. On the Method of determining, from the real Probabilities
of Life, the Values of Contingent Reversions in which three
Lives are involved in the Survivorship. By William Morgan,
Esq. BRS:

Read December 12, 1799.

ON SURVIVORSHIPS.

‘Tue several papers which I have had the honour of communi-
cating to the Royal Society, on the doctrine of contingent re-
versions, contain the greater number of those cases in which
three lives are concerned in the survivorship. With the view of
completing this subject, I have been induced to investigate the
remaining problems; and, having succeeded in the solution of
them, I hope the following will not be considered as an impro-
per addition to my former communications.

Being anxious to render this paper as concise as possible, I
have omitted to state at length the different contingencies on
which the payment of the given sum depends; trusting that,
from an attentive perusal of my former demonstrations, these
will appear to be so plainly expressed by the several fractions
in each problem, as to render a more ample description of them

unnecessary.

PROBLEM I.

To determine the value of a given sum, payable on the death

Mr. Morcan on Survivorships. 23

of A or B, should either of them be the first or second that fails,
of the three lives, A, B, and C.

Solution.

In this case, the payment of the given sum must certainly
take place on the extinction of the joint lives of A and B, inde-

pendent of C, and therefore the value of the reversion will be
S.2—1 . VV AB

*

r

The fractions expressing the contingencies on which the pay-

ment of S depends, in the ist year, are ——— x a’.b—m.c—d

+a’.b—m.d+a'.c—d.m+tb—m.c—d.a—-a=

A gh aE ° ; S aaa SSS

x abc —mc.a— a’; in the ed year = ——; xa".m—n.
abcr

SSS SS SS SE
d—e+ta”’.m—n.e+a"xd—e.n+a".ne+m—n.

aber

Pea aa Plea a a ae cu dn Ja"

SS ———— ath tment athe S
+c—d.m—na—a'+ aa! +c— aM an val bo

xmcC.a—a—nc.a—a’ +a", and so on in the other years;

hence the whole value is == xr—1.V—r.AB+ AB=
Sf"! VY — AB, as before. Q.E.D.

PROBLEM II.

To determine the value of a given sum, payable on the
decease of A or B, should either of them be the second or third
that shall fail, of the three lives, A, B, and C.

* The same symbols are uniformly retained in this, as in my last two papers on the
subject, See Phil. Trans. Vol, LXXXI. page 247.

24, Mr. Morcan on Survivorships.

Solution.

In the 1st year, the value of the reversion will be — = into

ri a Mey Sa: el ya EY Te cud. 6 ees

Zz

in the ed at it; will be = = into a”.m —n.d—e+a".m—n

eee

qs Ni 4 Ch pass f
sou oe ele n €.a et tial, hm: EO ok

od
“a

b—m.d—e.a"+c—d.m—n.a'ta.m—n.e+b—m

ii SS Sh Sea —_————. - a. Cd . man
a" .etc—d.m—in.a—ata'tcoc—d.n.iait :

Diesen AC da! WORN
+ —— ; in the gd year it will be ——— intoa’”.n—o

2

al! Sole r)

.e—fta'n—o. f+ 4+21—0.e—f.a pat

SS ae ait —_- —_ <eeee
Oe he a+a+ta +b—n.e—f.a"+cec—e.n—o.a”

2

tn—o.f.a' fa" +b—n.f.a"tco—e.n—o.a—a' tata"
—— i ae 5 inisee
i ara spy Pra e. mee le iCal

——.,, “, and so on.
These different fractions being added together, will be found

Be : <— NiaatO , Be. — S htt meee

r if

n—0.€ S b—m.d m—n.e es Nc
a Et veg oa eat agtieaenae

S
x4 44 4.8.45,
S ba’ ma" n z S bea’ mda

= " 7=y= b> Se. zabe * + ne

Pes S mca’ nda" oea” S
thy SC. sie tarry taal arse ae ere

mda nea! ofa" . S ma n.a'+ a’
x “f= pe te Ga, VM ae) Some east

7

Mr. Morcan on Survivorsbips. 25

yee Socsir et Ke ipo ea +, Ge. +
tate am Fe. ae
ae Meera Foe ae Ge. Ser a sayin Se. os a

nm.a

oO. eae md.a ne.a-+t a’ :
racy <7. T: Se. Bis rE < ay fe an ie

if

S A ar aa a + a"
r ie

zabcr

, &c. which may at last be re-

duced to S$ Gate x V+ ABC — aa + AC

27r

aa

AB——— x AK + BK — 2ABK + 4x AF — AFC +

d. d. PT — ArT

x1 + AP 4+ ———
nearly of the same fue, and both older than C, this rule will
not be sufficiently accurate. If B be the oldest of the three
lives, the annuities A, AC, and AK, should be continued only
for as many years (x) as are equal to the difference between
the age of B and that of the oldest life in the table of observa-
tions. Let those annuities be respectively denoted by A’, A’C,
and A’K’; also let @ denote the probability that C survives B,*
q the number of persons living opposite to the age of A at
the end of x years, then will the value of S, after x years, be
0q . r—1.V—A*

ag ne

ner A OB EBC ANC
be= S$ into 7.x V,4+ ABC — =t-4+— ,-° _ AaB —

But, unless A and B are very

, and the whole value of the reversion will

— 2BK +—- x AF— AFC 4 x7 AP

* By the Table, page 337, Phil, Trans. Vol. LXXVIII.
MDCCC, E

26 Mr. Morean on Survivorships.

d. PT—APT —1.V—A* |
xe aS _ x=, (A* denoting the value of

an annuity on a life x years older than A).
If C be the oldest of the three lives, let a—s, s—t, t—u,

&c. be substituted for their equals a’, a”, a’’”, Gc. and c—c’,

c—e' +c", c—c +e" +c", &c. for their equals e, f, g. Ge. |

then will the value of the reversion, by pursuing the same
Tr

steps as in the former case, be found = S into = x
Vie Arse AG Ci ee Ta.
MMe os ape receg ere Dei!

1+ NPC.

But, as these series are to be continued only during C’s life,
it is evident that the annuities A, B, AB, &c. should also be
continued only during this term; and therefore, if z be the dif-
ference between the age of C and the oldest person in the
Table, A’, B’, A'B’, &c. the values of annuities respectively on
the single and joint lives of A, B, A and B, &c. for z years,
these several symbols should be substituted above, in lieu of A,
B, AB, &c. to denote the value of the reversion during the
first z years. After the extinction of the life of C, the given
sum may be received upon either of three events; ist, if A
should have died before C, and B died after him in the z + 1,
z+ 2, &c. years; edly, if B should have died before C, and
A died after him in those years respectively; gdly, if both the
lives of A and B should die after the first x years. Let @
denote the probability that C dies after A, and x the probability

Mr. Morcan on Survivorsbips. 27

that C dies after B,* then will the value of the reversion de-
pending on these several contingencies (putting p for the num-
ber of persons living opposite the age of B at the end of xz
years, and q for the same number opposite the age of A) be

SEER p-d.r—1. V—B* qu fos V = AZ 14 ABs
= § into $2 4 et ae

AB, and the whole value of the reversion will be = S into

= i ee 4 ABC

BC+AC Bi AZSARC | ok bebe
ap AB + 26 aL za

3 +
area Game 7; m
yk os NC + ae

w.g.r—t.V—A*
a; = = x 1+ AB*.+
If the lives be all Cascite the value, according to the first rule,

BARE tay oO
eed)

s.14+PNC ine p.@. T—1. V—B*
te

ames aon en:

and, eet: to the ed aie it will be =S into x

pee Ce ee Ce ee eT CT

+ sie 1+ CTT. If these expressions be resolved into their

ccr

: S.7r_
respective series, the value in each case will be found = ———

x V — C—CC + CCC, which is known to be the true value,
from self-evident principles.
But the solution of this problem may be obtained by the

* By the Table, page 229, Phil. Trans. for the year 1794.
+ In this and the following problems, A*, B, AB*, A, B*, Gc. signify the value
of an annuity on the single or joint lives of persons z or x years older than A and B, &e.

E 2

08 Mr. MorGan on Survivorships.

assistance of the 1st problem in my last paper,* supposing,
instead of a given sum, it were required to know the value of
the reversion of a given estate. For, since the possession of
this estate is an event which must certainly take place, and the
only point to be determined is the time in which it will pro-
bably happen, it is obvious that no event can postpone the pos-
session, but the contingency of C’s being the second that fails, °
of the three lives. If, therefore, the sum of the values of an
annuity on the life of B after A, provided A should die before
C, and of an annuity on the life of A after B, provided B should
die before C, (both found by the problem just mentioned, ) be
subtracted from the whole value of the reversion after the joint
lives of A and B, the remainder will be the value required.. Let
X and Y respectively denote the annuities found by problem
ist, (Phil. Trans. Vol. LXX XIV.) then will the general rule

expressing the value of an estate be = V — AB — X + Y, and
consequently of a given sum = auth xV—AB—X4++Y,
which, when the lives are equal, may be reduced, as in the

former cases, to stot x V—C—CC+ CCC. Q. E. D.

PROBLEM III.

To determine the value of an estate, or of a given sum, after
the decease of A or B, should either of them be the first or last
that shall fail, of the three lives, A, B, and C.

Solution.

The reversion of the estate in this problem, like that in the

* Phil. Trans. for the year 1794, page 235.

Mr. Morcan on Survivorships. 29

preceding one, cannot be prevented ultimately from taking
place; and there is only the single contingency of C’s being
the first that fails, of the three lives, which can postpone the
possession of it after the extinction of the joint lives. The whole
value, therefore, of the reversion, after the joint lives of A and B,
must in this case be lessened by the sum of the values of an
annuity on A’s life after B, provided B should survive C; and
of an annuity on B’s life after A, provided A should survive C,
(both found by the 2d problem in my last Paper.*) Let these
two values be respectively denoted by W and Z, then will the
general rule expressing the value of an estate be = V — AB

— W-4 Z, and the value of a given sum = ee VEOAB
%

ozs W + Z. When the lives are all equal, the value of the
reversion, by substituting the values of W and Z, becomes =

ee Oe ee Ce pe eV Oe 2"COC ac

if
cording-as it consists of an estate, or a given sum.
But the solution of this, like that of the preceding problem,
may be obtained without having recourse to any other. In the
first year, the value of the given sum will be = S into

eh Gnd it DGB ot! a.c—d.m BEems Chas. aia!
abcr ae aber ai 2abcr aR 2zabcr a5
amd bith, HaHa.
aq abcr

into

; in the ed year it will be = ame
abcr

aber

Eno <a d=e.n a" m—n.d—e.a—a' +a"
WT a cee Sil ecg tad pS tas ans ade seg ake cal Lal
m—n.d—e.a"tm—n.e.a + ~
t+a"net+m—n.e.a—av+t+a"+ec—d.m—n. a”
e=d.m—n a’ poder ote dds
Zz

> mm *the’-od- year into

S
abcri

* Phil. Trans. for the year 1794, page 240.

30 Mr. Morcan on Survivorsbips.

Se ET aa ni e—f.o.a™ n—0.e—f.a—d +a"+a"
a—o.e—f.a"tu—o.fa' 4-4 eee
fa" of pn f aa wee a" =. poe ee
aa". Cle hn 6
an

these several fractions be expanded, they will form nineteen

i heal cae “and so on in the other years. If

different series, whose sum may be found = S int

V— ABC — Ads oACHEC 4. AR. AK kane

@.AF— AFC m d.1+APT ——7y5
2b aBCerrae. c — 1+ AP.

xe

If B be the oldest of the three lives, \et 7 denote the probability
that B dies after C,* then will the value of S, after the extinc-

tion of the life of B, be = 2 —— x =

rT

, and the whole

value of the reversion will be = S into = x ¥V — ABC —

Ee ee = sch IK BK s

2 2b

ABR to" <a et 4 AP

2br

xj Ne

_.q, A’, A’C’, &c. denoting the same eres as in the
former part of the preceding problem.

If C be the oldest of the three lives, let the symbols be changed
as in the preceding problem, and the value of the given sum

will be = S$ into =! x V— ABC — £ Ap B— 2A

« . H’B’—HBC ns ———- AC+ BC m
MC a ee

2a %

14+PC+—

x1-+NC.... After the decease of C, the

* By the Table, page 229, Phil. Trans. for the year 1794.

Mr. Morean on Survivorsbips. 31

given sum may be received, provided either of three events shall
happen; 1st, if A shall have died after C in the first z* years,
and B dies in the +1.2-+2, &c. year; edly, if B having
died after C in the first x years, A dies in the z-+1.z+4 9,
&c. year; gdly, if both A and B having survived the first z years,
the survivor of them dies in any of the following years. Let a de-
note the probability that A dies after C, and @ the probability
that B dies after C, (both found by the Table in Phil. Trans. Vol.
LXXXIV. page 2299) and let all the other symbols be the same
as in the latter part of the preceding problem, then will the

value of S, after z years, be = S into 2

prea avieaaa =

ste VOB be xt ABT A PB LE »

A’ + B* — AB*, and the whole value of the reversion at pe

‘7 Sn

+ 7S xT + pe, «VB + Pt x
V — At + B*——AL— ~ AB*.....

If the three lives be equal, the first of these rules becomes
= § into —
—— x1+ CIT — x1-+ CT; and the second =S
no VEC CCC ——+ x CK— CCK -——*

xp err +-—< ——x1i+CT; but the three last fractions in

* z being, as usual, the number oe years between the age of C and the age of the
eldest person in the table.

32 Mr. MorGAN on Survivorsbips.

each of those rules destroy one another, and therefore, in both

Sti7a
7

of them the value of the reversion is =

OCC rer OWE: DD:

x V—C+CC

PROBLEM IV.

To determine the value of a given sum, payable on the death
of A, should his life be the first or second that fails, and should
B’s life, if it fail, become extinct before the life of C.

Solution.

In this case, the payment of the given sum can only be pre-
vented by the contingency of C’s dying before A, and therefore
its value is immediately found by the solution of the ed-pro-
blem in my first Paper on this subject,* being no more than
“ the Value of a given Sum on the Death of A, should C sur-
« vive him.”

The accuracy of this solution will appear from the following
investigation. In the ist year, the given sum will become pay-
able should either of four events take place, the probabilities of

: : '.b—m.c—d 'b—m.d
which are expressed by the four fractions ———"“—" 4. 22
z2abc abc

a’md a.c—d.m ac ad

shimmer isn a he as Set eee In the ed year, it will be-

come payable provided either of six events should take place,

: a". m—n.d—e a".m—n.e a'ne
expressed by the fractions ff 4

a id= eoan b—m.d—e.a" B= mn eral a'd ave

ah 2abe a5 2abe 5 abc mr aie wale 2ac- In

the third year, the payment of the given sum will depend on the

2 * Phil, Trans. Vol. LXXWIII. page 341.

Mr. Morean on Survivorships. 33

same number of events, and the probabilities of the several con-

ot au a"t_ The value, there-

tingencies may be reduced to —— a

é 6 ac aud ae
fore, of the reversion will be = —— x —~ + —=--+ =, e.

S ad ae aug 6 :
She ert ie ems pa which two series are known

to express the value of S, on the contingency of C’s surviving A.*

Were a further proof: necessary, it might be observed, that
the value of the given sum, in this problem, is equal to the sum
of the values of the two reversions depending on the con-
tingency of A’s being the first that shall fail, of the three lives ;
and on the contingency of C’s surviving A, in case B shall be
then dead. Supposing the three lives to be equal, these values

——

will be'= == x V—3CC—2CCC 4 ==" x V= CCC

= mabe x V — CC, or the value of the reversion depending

on one life’s surviving the other. ..... Q. E. D.

PROBLEM V.

To determine the value of a given sum, payable on the death
of A, should his life be the second or third that fails, and should
B’s life, when it fails, become extinct before the life of C.

Solution.

The value of the given sum, in the ist year, will be = :
aber

ad.b—m.c—d a.b—m.d,

-+-———; in the ed year, it will be =

into

* See Phil. Trans. Vol. LXXVIII. page 342.
+ See Phil. Trans. Vol, LXXIX. page 49; and Vol. LXXXI.. page 253.
MDCCC. F

34 Mr. Morecan on Survivorsbips.

° a” .m—n.d—e a".m—n. a'.m—n-e "
aber into 3 | ia + b—n m.d—e.a
ae b= meat at . S :

tA om —-— —
b—m.e.a” | ——— ;“in the gd year = ———- into

U7 a",

Saneeemain ae mat 4 0=n. al”. (EBT i

DC Cnn ae

+_— , and so on in the other years. ‘These several

fractions being expanded, will form seven series, whose sum

: EREry 4 VAL a —_ ABC SSS

will ‘be’=4 ‘Sv into Za i) Se ee ot ee
Dap 6r Bic

ABK 4+ B.FK—AFK 4. m .PC—AP APC d xi BLT 2 aes

26 gbr 6cr

Me Pt APT B EC— AFC BEICi AO =2NR
Maul VO See ah 2b sy 3 —F =! AF a aia gon Re
x.K—AK

Z2C

When B is the oldest of the three lives, let x be the number of
years between the age of B and of the oldest person in the table;
p the number of persons living opposite the age of C; and q the
same number opposite the age of A, at the end of x years; A’,
A’C, and A’K, the values of annuities on those single and joint
lives for x years. The given sum may be received after the
first x years, on the death of A, provided C shall have died
after B in that time, or if C shall have survived the said term

of x years. Let « denote the first probability,* and —— will
denote the second; then will the value of this part of the re-

: : ~r—iI,. V—A*
version be = S.into 7 + a x ee the whole

value of the reversion will be = S . into * = x2 3a 3 A’— ABC

* Found by the Table in Phil. Trans. for the year 1794, page 229.

Mr. Morean on Survivorships. 35

Bu. AFK d.14+APT
— x Bike NBK an ae x PC—APC — =
ogy FOSAPE PSAP Og, BY ABT — Sx AK’
A'C'—AB JZ ae
trop hoo
When C is the state of the three lives, let » denote the pro-
bability that C dies after B;* let z be the difference between
the age of C and that of the oldest personin the table; A’, A’F’,
and A’B’ the values of annuities on those single and joint lives
for z years; and k the number of persons living opposite a life
z years older than A; then will the value of the reversion in

this case be = S into —— x 2V — 3A’— ABC — > x BK

| ABK + <* , AFK 4 hae aE Sa

— x BT — ABT + 6 CLs a we

AC—A'B! | gk.r—1. V—A*
a ee

If A be the oldest of the three lives, let b’, b”, b’’, Gc. be sub-

PO ARG

x

d
6¢

Sututed for b'—'m) m — 1, n — 0, Sc. and a —'s, s— it, Ge.
for a’, a”, &c. then will the value of the given sum for the 1st
a—s.db'

S a—s.c—d.B
year be a aes x Tages ot + aris 3 for the od year —
ep Be” ET, cb" —
ee i sei Sea 5 Gum Gs seb
abcr

-- a rete) -” and so on for the other years. Hence the whole
value may be found = S into — x 2V — 3A — ABC——

3¢€

* By the Table in Phil. Trans, for the year 1794, page 229.
F 2

36 Mr. Morean on Survivorships.

x AK — ABK — 4-5 4 +, HC— HBC — x AT—

“eae =
s.1+NBT s NC—NBC —— AC— AB
AB eae ear pete Seely NB pts
When the lives are eee the value, a the two first rules, will
be = = se x2V
+ —— CKK + —— — x CT — CCT — = _.ECTT:

and by the third rule it will be = S into — x2V—3 3 3C—cec
— —— x CKK 4+ —— x CT 4+ ——

aS

Cer ata

air om

a x1-+CTT. In both cases, all the fractions after the

Suen

first destroy each other, so that the general rule is = =

2V — 3C — CCC, which may be proved, from other principles,
to be the true value.

As the reversion, in this problem, consists of two parts; 1st,
of the contingency of receiving the given sum on the death of
A, provided B should be then dead and C living; and edly, of
the contingency of receiving it on the death of A, provided B
should be the first, C the second, and A the third, that fails, it
follows, that the present solution may be obtained from those
of the problem in my second Paper,* and of the 6th problem +
in my last Paper on this subject. But the computations derived
from the addition of those two problems would be too tedious
and complicated, and therefore the preceding rules are pre-
ferable. In the particular case of the equality of the lives,

the general rule becomes the same as above, (or = S x = x

* Phil. Trans. Vol. LXXIX. page 41. + Phil. Trans. for the year 1794, page 253.

Mr. Morcan on Survivorships. 37

2V—3C—CCC) and consequently affords an additional
proof of the truth of the investigation of the three problems.

PROBLEM VI.

To determine the value of a given sum, payable on the death
of A, should his life be the first or last that shall fail, of the
three lives; and should B’s life, if it fail, become extinct before
the life of C.

Solution.

The value of the given sum, in the 1st year, is — i. into
abcr

_b=m. a

AE 2 od: ; in the ed year,
m—nN .€ +
; in the gd year, ——-

aor et Pita

: ° S 6 a’.m—n.d—e y)
its value is = = aa TAtO

Tt (fe D b—m .d—e.a" fe ten
2 abcrs
alt

3 ais ae ei Th Fea = es
into ~n ariel a'tofish Lote a".n SEU NE WoT a Wes nN e—f. a!

2

bon .¢—e -
——— uae ¢-«" ,and so on in the other years. The sum of these

several fractions, after reducing them into their proper series,

pense Wiis ieee AS A ABC += 4 |

sree eit APL PL AAL 4B 1 = ABL = —

ae %

Brie. Ae HO Are:

When B is the oldest of the three lives, let x be the difference
between his age and that of the oldest person in the table; and,

2er 2bc

as the given sum may be received after the necessary extinction
of his life, either on the event of C’s having died after him in x

38 Mr. Morcan on Survivorships.

years, and A’s dying in the zr + 1, x + 2, &c. years, or on
the event of C’s having lived x years, and A’s dying in the
Flee Zee &c. years, it is obvious that the preceding rule
in this case will not express the whole value of the reversion.
Retaining the same symbols as in the first case of Prob. V. the
value, depending on the former of those two events will be

=S~x aaa , and on the latter of them it will be =
AC* Es Pq: PL ,\ ee epg rts VAG AC*.
zr. SF x AT 1 ae ee — a ee
therefore, the whole value of the reversion will be = S into
ce - AB md ——_—
-e sea APES a eae HH wash aAkil—

oe en

pq.r—t .VIACe tat VE

+ BC Ar Or z2acr?+1 area
When Cis the oldest of the three lives, let @ scar the proba-
bility that C dies after B;* and let z be the difference between
the age of C and that of the oldest person in the table; A’, A’B’,
and A’F’, the values of annuities on those single and joint lives
for z years; and q the number of persons living at the age of A
after zx years; then will the value in this case be = S sr

t=). V— A’ ABC + = — 54 4.7 PAPT —

zr

= pote DUBE es

xi AT a ee + 2nFEFC

Src @q.7—t . V—A*=
— AFC + Prem

When A is the oldest of the three lives, let the symbols be
changed in like manner as in the corresponding case in the

* Phil. Trans. for the year 1794, page 229.

Mr. Morean on Survivorships. 39

preceding problem; then will the value for the 1st year be

: FERS a Te?
into

Ah GE 5 pep ope bes ab ly

abcr

ed Boe or. re es a
on for the ed year = —-—— into z é

— St Sai .eb" | 5at.dae.b—0 4b" , Sat. dae.B
Se en a ie ees ee re Cee
66 ee - y, and so on for the gd, 4th, and remaining years.

These several fractions may be expanded into twelve different

a VA ARC

: : fs
series, whose sum may be found = §S into =

r

AC Raa 2AB x. AK a .HBC d GAIA AID a Ss
Tn vere aa, Teer ABT
x1 4+ NC + NB— NBC— —*_x 14 NBT.

If the lives be equal, the value, by the first two rules, will be
Pe NCCC CCC dd a d

SSS a So x1+ CTT — eras
7-60) =o == + —— x 2CK — CCK; and by

=S into

the third rule it will be = S into =1Y=C Fh CCU +—.
zr ZC

d

2cr

CCK — CK + ——x1 + CT—-** x TF CIT. In both

cases, all the fractions after the first destroy each other; so that

the general rule becomes = me x V—C+4 CC — CCC,

2r
which may be-proved to be the true value, from other principles.
The solution of this problem might have been derived from
that of the first problem* in my third Paper, and from that of
the 6th problem+ in my last Paper on this subject, “ by finding
“ the value on the death of A, should his life be the first that

* Phil. Trans. Vol. LXXXI. page 248.
+ Phil. Trans. for the year 1794, page 253.

40 Mr. Morcan on Survivorsbips.

“ failed; and also the value of the same sum, should B be the
‘“‘ first, C the second, and A the third, that failed:” but the
foregoing rules, in being more simple, are preferable.

In the particular case of the equality of the three lives, the
value, by these problems, will be = S into ri x V— CCC +
{Vo aC 4 aC, CCCs", ¥_ oe
as before. Q. E. D.

PROBLEM VII. -

To determine the value of a given sum, payable on the death
of A, B, and C, provided C shall die after one life in parti-
cular, (A).

Solution.
In the ist year, the value of the given sum will be =

xb—m.c—d.a’; inthe ed year, it will pee ee
aber

Se
2abcr

* m—n.d—e.a" Ty qt ey eee ee a ene eR TS
int 0 td a ee

= bem e aid! = 2 MEO epee”
é ° a —s ee
d—e.a'+ = ; in the gd year = —— into =
Fy So a ae ae aE ee ee
+b—n.e—f.a'ta"+ = +n —o.e—f.a‘ta
bene fra’ :
Seay and soon in the other years; whence the

whole value may at last be found = S into x BC— B—

TATION. BC AB
BBC “Se aor

BK — ABK -+ R, (R denoting the value of S, by the 3d problem

d APT
+o x1 +AP— OH — = x

c z2C¢

Mr. Morean on Survivorsbips. 41

in my first Paper, on the contingency of C’s dying after A).*
This general rule gives the true value of the reversion, when B
is the oldest of the three lives. But, when C is the oldest of the

three lives, the general rule will be = S into x BC— B’

—— , BC_ AB mm o———, Od TH APT
Rae epne st! elon tye a _ x

2r BCL.

BE = BG ie een fps Fa a a se, ONT. denoting the difference

between the ages of C and of the oldest person in the table; p the
number of persons living at the age of B after x years; B’, A’B’;
and A’P’, the values of annuities on those single and joint lives
for x years; and » the probability that C dies after A.

When A is the oldest of the three lives, let the symbols be
changed as in the solution of the. vlc ae waa and the

whole value of the given sum will be= —- x —— + — cola

= Z , Se. 5 - “on r. os 7 Siig r3 ? Se. + a> be ama
6. 0Ee 7 S: db' ev S

be = ber

eh. —

eb > Ff. oye" be za
Fa LE +; Ge. —

scb’ ae sue S dtb' eu. Bb!
sre SHH +, Se. x a Te

2abcr r 7
ah Se eh thf seb
Se. pe EF 73 » Be. + x T +
i ear

2ab

era

= +, Be. + x Boba he eet
ted’

ps hie v4 wise olds te. mu
Rea tear ic eazalen Se +, Be. 00.

* Phil. Trans. Vol. LXXVIII. page 347.
+ Phil. Trans. for the year 1794, table in page 229.
MDCCC.

42 Mr. Morean on ‘Survivorships.

After the extinction of A’s life, the given sum may be received
on either of three events; 1st. on the death of Bin the z+ 1,
z + 2, Bc. years, (x denoting the difference between the ages
of A and of the oldest person in the table,) C having died after
A in the first 2 years; edly, on the death of C in the eS ae
242, &c. years, B having died in the first x years; gdly, on
the extinction of both the lives of B and C after the first z
years. Let @ denote the probability that C dies after A in z
years ;* p the number of persons living opposite the age of B;
and k the same number opposite the age of C at the end of z
years ; and the value on the two first of these contingencies will

bad ODP) r—1.V—B* S.b—p.k.r—1.V—C*
be Sor pep +r born

greek letters be substituted for the corresponding ztalic letters in
the first a and the value on the third of those contingencies

Again, let

a g" —_ S pee E Bb"

will be = oe x S44 + » Be. = pate eer
(4c S oR E ieee S ‘

St a Sc. + Sie Se » Se. =~ 7 ee

2B €.3'+6" . :
ra S Sbmeraee tie &c. The 1st of these series being added to
the first series in the former part of the solution, their sum will

be = S into ae — ue eer ; the ed and 4th being

added to the 4th * 5th, their sum will be = — S 4.C2SBG;
and the 3d series being added to the gd series in that part of the
solution, their sum will be ee, so that these six series

S.7=1-C—BC
last mentioned are = — SFr af: ‘The whole Wate of

tour

¢ Phil. Trans. for the year 1794, table in page 229.
+ The solution of the latter part of the case in the 6th problem, in which B is the

Mr. Morcan on Survivorships. 43
the reversion in this’ case may therefore be found = S . into
fot V B= 90 -p 2BC + AC + ABC + SS 4

Za

x HB + HC — HBC —— x BK’ AK — ABK f o+ix

——— ae ce a aa B’C’, and B’K’, denoting the

values of annuities on those ‘joint lives for z years.
When the three lives are ih equal age, the value picked the first

two malas will b

“ox rp CF ew ee ‘CCK, in
which the last three fractions destroy each other; and by the

x V—3C + 3CC—CCC;
_ that is,.in both cases, «« half the reversion after the extinction of
“ the three lives,” which from self-evident principles is known
to be the true value.

_ The solution of this problem may also be derived from those
of the 3d problem in my first Paper,* and of the 1st problem in
my last Paper, «« by deducting the value of an estate after the.
“«‘ death of C, provided that should happen after the death of A,
“ from the value of an annuity on the life of B after C, pro-
«< vided C. should die before A.’ Thus, in the case of equal

lives, the value by the first of these problems being ——— ae sons

: >

2ccr

Sex

last rule the value will be =

and the value by the second being = ——. = concer their
V—3C+3CC—CCC
z

difference, or , 1s the number of years pur-

eldest of the three lives, has. been investigated much in the same manner with the pre-
sent case; but the operation was omitted merely for the sake of conciseness.

* Phil, Trans. Vol. LXXVIII. page-347.

+ Phil. Trans, for the year 1794, page 235,

Go

AA Mr. Morcan on Survivorships.

chase tn: and consequently the value of a given sum is
3C + 3CC — CCC, as before.. But the rules

derived yi the foregoing solution are in general more simple
than those derived from the two problems just mentioned, and
are therefore to be preferred to them.

The foregoing problems, together with those which have
been investigated in my former papers, comprehend, as far as
I can perceive, all the different cases of survivorship between
three lives. The great number of contingencies on which these
reversions depend, must necessarily render the solutions intri-
cate, and consequently the general rules complicated and la-
borious. It would not, however, be a difficult task to abridge
these rules very considerably, without destroying their accuracy
in any great degree; but this would be foreign to my purpose
in these papers, which has uniformly been confined to the inves-
tigation of the correct values of the different reversions. Nor
do I think that such an abridgement is necessary, as the opera-
tions of even the longest of the present rules, may be completed
in very nearly as short a time as the inaccurate approximations
which have hitherto been employed for the same purpose.

It may not be improper to observe, that the solutions in these
papers are not only the first which have ever been deduced, in
the case of two and three lives, from just principles and the
real probabilities of life; but that, as to many of the problems,
not even an attempt has ever been made to approximate to the

value of the reversion.

Being now possessed of correct solutions of all the cases in
which two and three lives are involved in the survivorship, we
are possessed of all that is really useful, and therefore I feel the

Mr. Morean on Survivorships. | 4S

greater satisfaction in closing my inquiries on this subject. For,
in regard to contingencies depending on four or more lives, the
cases are not only much too numerous and intricate to admit of
a solution, but they occur so seldom in practice, as to render
the entire investigation of them, were it even possible, a matter
of little or no importance.

In my last Paper, printed in the Phil. Trans. for the year 1794, page 257, last

line but one,

fer BEL s read el Pha GEC™ ‘whence the general rule in the
i 2ber®+s

: _ = BC AC B
foll b = Sinton ye Vea ABC tp 2 EL
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C 46)

INI. Abstract of a Register of the Barometer, Thermometer, and

Rain, at Lyndon, ia Rutland, for the Year 1798. By Thomas
Barker, Esq.

Read December 12, 1799.

Barometer. Thermometer.

In the House. Abroad.

.|Lowest.| Mean, |High.| Low.|Mean.|High,| Low.|Mean.

Inches. | Inches.

28,47

Inches.

1,028
28,70 1,542
28,71 0,532

28,66 1,323

28,75

1,892
29511 - 950 |.

28,91 q' 2,942

29525
28,48

1,942

2,814

28,70 33030

28,21 2,546

6
28,80 1,396

Mr. BarKer’s Register, &c. 47

The year began open and mild, and drier than it had been
at the end of last year. There was near a week’s frost about
January the 10th; again about February the 6th; and the
sharpest this winter was about the 18th, but none of them lasted
a week. It was in general an open, mild, and pleasant winter,
and drying, except one great rain and flood, February 23. The
NE winds in the middle and latter end of March delayed the
grass, but the season was in general caim. It was a fine April,
chiefly dry, though with some fine rains at times, and not
without some storms. A fruitful season, though in some mea-
sure hindered by frequent frosty mornings, for the first three
weeks of April: this brought the grain on finely ; and the low
meadows, which were so thoroughly soaked by the wet last
winter, had great crops of grass; but the late laid uplands were
thin.

I think it was upon the whole one of the finest summers I
have known; a great deal of calm, sunny, and fine weather,
and moderately hot. The wet of the winter prevented the
ground from burning till the middle of the summer: then a
wet middle of July set the grass growing again; but, as rain
was wanted, it was not complained of, though in hay-time;
for it rather hindered than damaged the hay, which was for
the most part pretty well got, though rather troublesome, and
the wet made plenty of turnips, and fine eddishes. The harvest
was in general well got, with good crops of white corn; but
the weather had been full dry for the beans and peas, which
were thin, though pretty well corned; and the harvest was
early, for it was almost finished in August’ The fine harvest
made the ground begin to burn again in September; but that -
was soon stopped, by a great and windy rain before the end of

48 Mr. BarxeEr’s Register, &e.

the month. The autumn was fine, with few frosty mornings ;
yet one or two severe nights in October, before the green-house
plants were housed, killed many of them, especially the Gera-
niums: but it was afterwards warm and wet again, and conti-
nued pretty fine, for the season, till the middle of December,
when, after some misty weather, followed by very severe frost
in the last week, it was exceedingly cold, and the thermometer
was one day down at 51, which I never saw it at but once
before; and the frost continued, though not so severe, till near
the middle of January, 1799. |

[494

1V. On the Power of penetrating into.Space by Telescopes ; with
a comparative Determination of the Extent of that Power in
natural Viston, and in Telescopes of various Sizes and Con-
structions; illustrated by select Observations. By William
Herschel, LL.D. F. B.S.

Read November 21, 1799.

T+ will not be difficult to shew that the power of penetrating
into space by telescopes is very different from magnifying
power, and that, in the construction of instruments, these two
powers ought to be considered separately.

In order te conduct our present inquiry properly, it will be

necessary to examine the nature of luminous bodies, and to —

enter into the method of vision at a distance. Therefore, to
prevent the inaccuracy that would unavoidably arise from the
use of terms in their common acceptation, I shall have recourse
to algebraic symbols, and to such definitions as may be necessary
to fix a precise meaning to some expressions which are often
used in conversation, without much regard to accuracy.

By luminous bodies I mean, in the following pages, to denote
such as throw out light, whatever may be the cause of it: even
those that are opaque, when they are in a situation to reflect
light, should be understood to be included; as objects of vision
they must throw out light, and become intitled to be called
luminous. However, those that shine by their own light may

MDCCC. H

‘
Oe

50 Dr. HERSCHEL on the Power of

be called self-luminous, when there is an occasion to distinguish
them.

The question will arise, whether luminous bodies scatter light
in all directions equally; but, till we are more intimately
acquainted with the powers which emit and reflect light, we
shall probably remain ignorant on this head. I should remark,
that what I mean to say, relates only to the physical points into
which we may conceive the surfaces of luminous bodies to be
divided; for, when we take any given luminous body in its
whole construction, such as the sun or the moon, the question
will assume another form, as will appear hereafter.

That light, flame, and luminous gases are penetrable to the
rays of light, we know from experience;* it follows therefore,
that every part of the sun’s disk cannot appear equally lumi-
nous to an observer in a given situation, on account of the
unequal depth of its luminous atmosphere in different places.+
This regards only bodies that are self-luminous. But the
greatest inequalities in the brightness of luminous bodies in
general, will undoubtedly be owing to their natural texture ;

* In order to put this to a proof, I placed four candles behind a screen, at 3 of an
inch distance from each other, so that their flames might range exactly in a line. The
first of the candles was placed at the same distance from the screen, and just opposite
a narrow slit, 3 of an inch long, and 3 broad, On the other side of the screen I fixed
up a book, at such a distance from the slit that, when the first of the candles was lighted,
the letters might not be sufficiently illuminated to become legible. Then, lighting
successively the second, third, and fourth candles, I found the letters gradually more-
illuminated, so that at last I could read them with great facility; and, by the arrange-
ment of the screen and candles, the light of the second, third, and fourth, could not
seach the book, without penetrating the flames of those that were placed before them.

+ See the Paper on the Nature and Construction of the Sun. Phil. Trans. for

1795. page 46,

penetrating into Space by Telescopes. 51

which may be extremely various, with regard to their power of
throwing out light more or less copiously. -

Brightness, I ascribe to bodies that throw out light ; and those
that throw out most are the brightest.

It will now be necessary to establish certain expressions for
brightness in different circumstances.

In the first place, let us suppose a luminous surface throwing
out light, and let the whole quantity of light thrown out by it
be called L.

Now, since every part of this surface throws out light, let us
suppose it divided into a number of luminous physical points,
denoted by N.

If the copiousness of the emission of light from every phy-
sical point of the luminous surface were equal, it might in
general be denoted by c; but, as that is most probably never
the case, I make C stand for the mean copiousness of light
thrown out from all the physical points of a luminous object.
This may be found in the following manner. Let c express the
copiousness of emitting light, of any number of physical points
that agree in this respect; and let the number of these points be
n. Let the copiousness of emission of another number of points
be c’, and their number n’. And if, in the same manner, other
degrees of copiousness be called c’, c*, &c. and their numbers be
denoted by n’, 1’, Sc. then will the sum of every set of points,
multiplied by their respective copiousness of emitting light, give
‘us the quantity of light thrown out by the whole luminous body.
That is, L==cn+c'n’ +n’, &c.; and the mean copiousness
of emitting light, of each physical point, will be expressed by
cntow+e n®, Ge. Lay
ae :

Ff 2

52 Dr. Herscuen on the Power of °

It is evident that the mean power, or copiousness of throwing
out light, of every physical point in the luminous surface, mul-
tiplied by the number of points, must give us the whole power
of throwing out light, of the luminous body. That is CN = L.

I ought now to answeran objection that may be made to this
theory. Light, as has been stated, is transparent; and, since
the light of a point behind-the surface of a flame will pass
through the surface, ought we not to take in its depth, as well
as its superficial dimensions? In answer to this, I recur to what
has been said with regard to the different powers of throwing
out light, of the points of a luminous surface. For, as light must
be finally emitted through the surface, it is but referring all
light arising from the emission of points behind the surface,
to the surface itself, and the account of emitted light will be
equally true. And this will also explain why it has been stated
as probable, that different parts of the same luminous surface
may throw out different quantities of light.

Since, therefore, the quantity of light thrown out by any lu-
minous body is truly represented by CN, and that an object is .
bright in consequence of light thrown out, we may say that
brightness is truly defined by CN. If however, there should at
any time be occasion for distinction, the brightness arising
from the great value of C, may be called the intrinsic bright-
ness ; and that arising from the great value of N, the aggregate
brightness; but the absolute brightness, in all cases, will still be
defined by CN.

Hitherto we have only considered luminous objects, and their
condition with regard to throwing out light. We proceed now
to find an expression for their appearance at any assigned dis-
tance; and here it will be proper to leave out of the account,

penetrating into Space by Telescopes. 53

every part of CN which is not applied for the purpose of vision.
L representing the whole quantity of light thrown out by CN,
we shall denote that part of it which is used in vision, either by
the eye or by the telescope, /. This will render the conclusions
that may be drawn hereafter more unexceptionable; for, the
quantity of light / being scattered over 4 small space in propor-
tion to L, it may reasonably be looked upon as more uniform
in its texture; and no scruples about its inequality will take
| place. The equation of light, in this present sense, therefore, is
CNV.

Now, since we know that the density of light decreases in’
the ratio of the squares of the distances of the luminous objects,
the expression for its quantity at the distance of the observer

BB od
D, will be —--

In natural vision, the quantity / undergoes a considerable
change, by the opening and contracting of the pupil of the eye.
If we call the aperture of the iris a, we find that in different
persons it differs considerably. Its changes are not easily to be
ascertained; but we shall not be much out in stating its varia-
tions to be chiefly between 1 and 2 tenths of an inch. Perhaps
this may be supposed under-rated; for the powers of vision, in
a room completely darkened, will exert themselves in a very
extraordinary manner. In some experiments on light, made at
Bath, in the year 1780, I have often remarked, that after staying
some time in a room fitted up for these experiments, where on
entering I could not perceive any one object, I was no longer
at a loss, in half an hour’s time, to find every thing I wanted. It
is however probable that the opening of the iris is not the only
cause of seeing better after remaining long in the dark; but

5A Dr. HerscueEx on the Power of

that the tranquillity of the retina, which is not disturbed by
foreign objects of vision, may render it fit to receive impressions
such as otherwise would have been too faint to be perceived.
This seems to be supported by telescopic vision; for it has often
happened to me, in a fine winter’s evening, when, at midnight,
and in the absence of the moon, I have taken sweeps of the hea-
vens, of four, five, or six hours duration, that the sensibility of
the eye, in consequence of the exclusion of light from surround-
ing objects, by means of a black hood which I wear upon these
occasions, has been very great; and it is evident, that the open-
ing of the iris would have been of no service in these cases, on
account of the diameter of the optic pencil, which, in the 20 feet
telescope, at the time of sweeping, was no more than ,12 inch.
The effect of this increased sensibility was such, that if a star of
the 3d magnitude came towards the field of view, I found it
necessary to withdraw the eye before its entrance, in order not
to injure the delicacy of vision acquired by long continuance in
the dark. The transit of large stars, unless where none of the
6th or 7th magnitude could be had, have generally been declined
in my sweeps, even with the 20 feet telescope. And I remem-
ber, that after a considerable sweep with the 40 feet instrument,
the appearance of Sirius announced itself, at a great distance,
like the dawn of the morning, and came on by degrees, increas-
ing in brightness, till this brilliant star at last entered the field
of view of the telescope, with all the splendour of the rising sun,
and forced me to take the eye from that beautiful sight. Such
striking effects are a sufficient proof of the great sensibility of
the eye, acquired by keeping it from the light.

On taking notice, in the beginning of sweeps, of the time that
passed, I found that the eye, coming from the light, required

penetrating into Space by Telescopes. 55

near 20’, before it could be sufficiently reposed to admit a view
of very delicate objects in the telescope; and that the observa-
tion of a transit of a star of the 2d or 3d magnitude, would
disorder the eye again, so as to require nearly the same time
for the re-establishment of its tranquillity.

The difficulty of ascertaining the greatest opening of the eye,
arises from the impossibility of measuring it at the time of its
extreme dilatation, which can only happen when every thing is
completely dark; but, if the variation of a is not easily to be
ascertained, we have, on the other hand, no difficulty to deter-
mine the quantity of light admitted through a telescope, which
must depend upon the diameter of the object-glass, or mirror ;
for, its aperture 4 may at all times be had by measurement.
av
Di
accurate for the quantity of light admitted by the eye; and that
Atl
De
remembered, that the aperture of the eye is also concerned in
viewing with telescopes ; and that, consequently, whenever the
pencil of light transmitted to the eye by optical instruments
exceeds the aperture of the pupil, much light must be lost. In
that case, the expression 4*/ will fail; and therefore, in gene-

It follows, therefore, that the expression will always be

will be sufficiently so for the telescope. For it must be

ral, if m be the magnifying power, = ought not to exceed a.

As I have defined the brightness of an object to the eye of

a

-' it will be

a

D
necessary to answer some objections that may be made to this
theory. Optical writers have proved, that an object is equally
bright at all distances. It may, therefore, be maintained against
~ me, that since a wall illuminated by the sun will appear equally

an observer at a distance, to be expressed by

56 Dr. HERSCHEL on the Power of

bright, at whatsoever distance the observer be placed that views
it, the sun also, at the distance of Saturn, or still farther from us,
must be as bright as it isin its present situation. Nay, it may be
urged, that in a telescope, the different distance of stars can be of
no accoynt with regard to their brightness, and that we must
consequently be able to see stars which are many thousands of
times farther than Sirius from us; in short, that a star must be
infinitely distant not to be seen any longer.

Now, objections such as these, which seem to be the imme-
diate consequence of what has been demonstrated by mathema-
ticians, and which yet apparently contradict what I assert in this
paper, deserve to be thoroughly answered.

It may be remembered, that I have distinguished brightness
into three different sorts.* Two of these, which have been dis-
criminated by intrinsic and absolute brightness, are, in common
language, left without distinction. In order to shew that they
are so, I might bring a variety of examples from common con-
versation; but, taking this for granted, it may be shewn that
all the objections I have brought against my theory have their
foundation in this ambiguity.

The demonstrations of opticians, with regard to what I call
intrinsic brightness, will not oppose what I affirm of absolute
brightness ; and I shall have nothing farther to do than to shew
that what mathematicians have said, must be understood to
refer entirely to the intrinsic brightness, or illumination of the
picture of objects on the retina of the eye: from which it will
clearly follow, that their doctrine and mine are perfectly recon-
cileable ; and that they can be at variance only when the am-
biguity of the word brightness is overlooked, and objections,

* See page 52.

penetrating into Space by Telescopes. 57

such as I have made, are raised, where the word brightness is
used as absolute, when we should have kept it to the only meaning
it can bear in the mathematicians’ theorem.

The first objection I have mentioned is, that the sun, to an
observer on Saturn, must be as bright as it is here on earth.
Now by this cannot be meant, that an inhabitant standing on
the planet Saturn, and looking at the sun, should absolutely
receive as much light from it as one on earth receives when he
sees it; for this would be contrary to the well known decrease
of light at various distances. The objection, therefore, can only
go to assert, that the picture of the sun, on the retina of the
Saturnian observer, is as intensely illuminated as that on the
retina of the terrestrial astronomer. ‘To this I perfectly agree.
But let those who would go farther, and say that therefore the
sun is absolutely as bright to the one as to the other, remember
that the sun on Saturn appears to be a hundred times less
than on the earth; and that consequently, though it may there
be intrinsically as bright, it must here be absolutely* an hundred
times brighter.

The next objection I have to consider, relates to the fixed
stars. What has been shewn in the preceding paragraph, with
regard to the sun, is so intirely applicable to the stars, that it
will be very easy to place this point also in its proper light. As
I have assented to the demonstration of opticians with regard to
the brightness of the sun, when seen at the distance of Saturn,
provided the meaning of this word be kept to the intrinsic illu-
mination of the picture on the retina of an observer, I can
have no hesitation to allow that the same will hold good with
a star placed at any assignable distance. But I must repeat, that

* See the definition of absolute brightness, page 52.
MDCCC. I

58 Dr. Herscuex on the Power of

the light we can receive from stars is truly expressed by Xi

and that therefore their absolute brightness must vary in the
inverse ratio of the squares of their distances. Hence I am
authorised to conclude, and observation abundantly confirms it,
that stars cannot be seen by the naked eye, when they are more
than seven or eight times farther from us than Sirius; and that.
they become, comparatively speaking, very soon invisible with
our best instruments. It will be shewn hereafter, that the visi-
bility of stars depends on the penetrating power. of telescopes,
which, I must repeat, falls indeed very short of shewing stars
that are many thousands of times farther from us than Sirius ;
much less can we ever hope to see stars that are all but infi-
nitely distant.

If now it be admitted that the expressions we have laid down
are such as agree with well known facts, we may proceed to
vision at a distance ; and first with respect to the naked eye.

Here the power of penetrating into space, is not only con-
fined by nature, but is moreover occasionally limited by the
failure in brightness of luminous objects. Let us see whether
astronomical observations, assisted by mathematical reasoning,
can give us some idea of the general extent of natural vision.
Among the reflecting luminous objects, our penetrating powers
are sufficiently ascertained. From the moon we may step to
Venus, to Mercury, to Mars, to J upiter, to Saturn, and last of
all to the Georgian planet. An object seen by reflected light at
a greater distance than this, it has never been allowed us to
perceive; and it is indeed much to be admired, that we should

penetrating into Space by Telescopes. 59

see borrowed illumination to the amazing distance of more than
18 hundred millions of miles; especially when that light, in
coming from the sun to the planet, has to pass through an equal
space, before it can be reflected, whereby it must be so en-
feebled as to be above 368 times less intense on that planet
than it is with us, and when probably not more than one-third
part of that light can be thrown back from its disk.*

Theerange of natural vision with self-luminous objects, is
incomparably more extended, but less accurately to be ascer-
tained. From ovr brightest luminary, the sun, we pass imme-
diately to very distant objects; for, Sirius, Arcturus, and the
rest of the stars of the first magnitude, are probably those that
come next; and what their distance may be, it is well known,
can only be calculated imperfectly from the doctrine of paral-
laxes, which places the nearest of them at least 4125930 times
farther from us than the sun.

In order to take a second step forwards, we must enter into
some preliminary considerations, which cannot but be attended
with considerable uncertainty. The general supposition, that
stars, at least those which seem to be promiscuously scattered,
are probably one with another of a certain magnitude, being
admitted, it has already been shewn in a former Paper, + that
after a certain number of stars of the first magnitude have
been arranged about the sun, a farther distant set will come in
for the second place. ‘The situation of these may be taken to
be, one with another, at about double the distance of the former

from us.

* According to Mr. Boucvenr, the surface of the moon absorbs about two-thirds
of the light it receives from the sun. See Traite d’Optique, page 122.
+ Phil. Trans. for the year 1796, page 166, 167, 168.
| Ig

60 Dr. Herscuer on the Power of

By directing our view to them, and thus penetrating one step
farther into space, these stars of the second magnitude furnish us
with an experiment that shews what phaznomena will take place,
when we receive the illumination of two very remote objects,
equally bright in themselves, whereof one is at double the dis-
tance of the other. The expression for the brightness of such
objects, at all distances, and with any aperture of the iris,

al

D?
of reducing this to an experimental investigation will be as

; and a ‘method

according to our foregoing notation, will be

follows.

Let us admit that‘az Cygni, 6 Tauri, and others, are stars of
the second magnitude, such as are here to be considered. We
know, that in looking at them and the former, the aperture of
the iris will probably undergo no change; since the difference
in brightness, between Sirius, Arcturus, « Cygni, and @ Tauri,
does not seem to affect the eye so as to require any alte-
ration in the dimensions of the iris; a, therefore becomes a
given quantity, and may be left out. Admitting also, that the
latter of these stars are probably at double the distance of the
former, we have D* in one case four times that of the other;
and the two expressions for the brightness of the stars, will be /
for those of the first magnitude, and 4/ for those of the second.

The quantities being thus prepared, what I mean to suggest
by an experiment is, that since sensations, by their nature, will
not admit of being halved or quartered, we come thus to know
by inspection what phenomenon will be produced by the fourth
part of the light of a star of the first magnitude. In this sense,
I think we must take it for granted, that a certain idea of bright-
ness, attached to the stars which are generally denominated to

penetrating into Space by Telescopes. 61

be of the second magnitude, may be added to our experimental
knowledge; for, by this means, we are informed what we are
to understand by the expressions cs, = — We
cannot wonder at the immense difference between the bright-
-ness of the.sun and that of Sirius; since the two first expres-
sions, when properly resolved, give us a ratio of brightness of
more than 170 thousand millions to one; whereas the two
latter, as has been shewn, give only a ratio of four to one.

What has been said will carry us, with very little addition, to
the end of our unassisted power of vision to penetrate into space.
We can have no other guide to lead us a third step than the
same beforementioned hypothesis; in consequence of which,
however, it must be acknowledged to be sufficiently probable,
that the stars of the third magnitude may be placed about three
times as far from us as those of the first. It has been seen, by
my remarks on the comparative brightness of the stars, that I
place no reliance on the classification of them into magnitudes;-+
but, in the present instance, where the question is not to ascer-
tain the precise brightness of any one star, it is quite sufficient
to know that the number of the stars of the first three different
magnitudes, or different brightnesses, answers, ina general way,
sufficiently well to a supposed equally distant arrangement of a
first, second, and third set of stars about the sun. Our third
step forwards into space, may therefore very properly be said to
fall on the pole-star, on y Cygni, ¢ Bootis, and all those of the
same order.

* The names of the objects ©, Sirius, @ Tauri, are here used to express their dis-
tance from us.

+ Phil, Trans. for the year 1796, page 168, 169.

62 Dr. HerscuEx on the Power of

As the difference, between these and the stars of the preceding
order, is much less striking than that between the stars of the
first and second magnitude, we also find that the expressions

a*l aad ; 3 .
Phan? and aoe ae not in the high ratio of 4 to 1, but only

as 9 to 4, or 22 to 1. |

Without tracing the brightness of the stars through any
farther steps, I shall only remark, that the diminution of the
ratios of brightness of the stars of the 4th, 5th, 6th, and 7th
magnitude, seems to answer to their mathematical expressions,
as well as, from the first steps we have taken, can possibly be
imagined. The calculated ratio, for instance, of the brightness
of a star of the 6th magnitude, to that of one of the 7th, is but
little more than 12. to 1; but still we find by experience, that
the eye can very conveniently perceive it. At the same time,
the faintness of the stars of the 7th magnitude, which require
the finest nights, and the best common eyes to be perceived,
gives us little room to believe that we can penetrate much
farther into space, with objects of no greater brightness than
stars.

But, since it may be justly observed, that in the foregoing
estimation of the proportional distance of the stars, a consider-
able uncertainty must remain, we ought to make a proper
allowance for it; and, in order to see to what extent this should
go, we must make use of the experimental sensations of the
ratios of brightness we have now acquired, in going step by
step forward: for, numerical ratios of brightness, and sensa=
tions of them, as has been noticed before, are very different
things. And since, from the foregoing considerations, it may be
concluded, that as far as the 6th, 7th, or 8th magnitude, there

penetrating into Space by Telescopes. 63

ought to be a visible: general difference between stars of one
order and that of the next following, I think, from the faintness
of the stars of the 7th magnitude, we are authorized to conclude,
that no star, eight, nine, or at most ten times as far from us as
Sirius, can possibly be perceived by the natural eye.

The boundaries of vision, however, are not confined to single
stars. Where the light of these falls short, the united lustre of
sidereal systems will still be perceived. In clear nights, for
instance, we may see a whitish patch in the sword-handle of
Perseus,* which contains small stars of various sizes, as may be
ascertained by a telescope of a moderate power of penetrating
into space. We easily see the united lustre of them, though the
light of no one of the single stars could have affected the unas-
sisted eye.

Considerably beyond the distance of the former must be the
cluster discovered by Mr. MesstzEr, in 1764; north following
H Geminorum. It contains stars much smaller than those of
the former cluster ; and a telescope should have a considerable
penetrating power, to ascertain their brightness properly, such
as my common 1o-feet reflector. The night should be clear,
in order to see it well with the naked eye, and it will then
appear in the shape of a small nebula.

Still farther from us must be the nebula between 4 and &
Herculis, discovered by Dr. HALLEy, in 1714. The stars of it
are so small that it has been called a Nebula;-f and has been
regarded as such, till my instruments of high penetrating

* See the catalogue of a second thousand of new nebulz and clusters of stars, VI.
33» 34- Phil. Trans. Vol. LXXIX. page 251.

+ In the Connoissance des Temps for 1783, No. 13, it is described as a nebula
without stars,

64,” Dr. HERscueL on the Power of

powers were applied to it. It requires a very clear night, and
the absence of the moon, to see it with the natural eye.

Perhaps, among the farthest objects that can make an im-
pression on the eye, when not assisted by telescopes, may be
reckoned the nebula in the girdle of Andromeda, discovered by
Simon Marius, in 1612. It is however not difficult to per-
ceive it, in a clear night, on account of its great extent,

rom the powers of penetrating into space by natural vision,
we proceed now to that of telescopes.
It has been shewn, that brightness, or light, is to the naked

eye truly represented by a; in a telescope, therefore, the
light admitted will be expressed by = Hence it would fol-

low, that the artificial power of penetrating into space should be
to the natural one as 4 to a. But this proportion must be cor-
rected by the practical deficiency in light reflected by mirrors,
or transmitted through glasses; and it will in a great measure
depend on the circumstances of the workmanship, materials,
and construction of the telescope, how much loss of light there
will be sustained.

In order to come to some determination on this subject, I
made many experiments with plain mirrors, polished like my
large ones, and of the same composition of metal. The method
I pursued was that proposed by Mr. Boucurer, in his Traité
d’Optique, page 16, fig. 3.; but I brought the mirror, during
the trial, as close to the line connecting the two objects as pos-
sible, in order to render the reflected rays nearly perpendicular.

The result was, that out of 100 thousand incident rays,

penetrating into Space by Telescopes. 65

67262 were returned ; and therefore, if a double reflection takes
place, only 45242 will be returned.

Before this light can reach the eye, it will suffer some loss in
passing through the eye glass; and the amount of this I ascer-
tained, by taking a highly polished plain glass, of nearly the
usual thickness of optical glasses of small focal lengths. Then,
by the method of the same author, page 21, fig. 5. 1 found, that
out of 100 thousand incident rays, 94825 were transmitted
through the glass. Hence, if two lenses be used, 89918; and,
with three lenses, 85265 rays will be transmitted to the eye.

Then, by compounding, we shall have, in a telescope of my
construction with one reflection, 63796 rays, out of 100 thou-
sand, come to the eye. In the Newronran form, with a single
eye lens, 42901; and, with a double eye glass 40681 will re-
main for vision.

There must always remain a considerable uncertainty in the
quantities here assigned; as a newly polished mirror, or one in
high preservation, will give more light than another that has
not those advantages. The quality of metal also will make some
difference; but, if it should appear by experiments, that the
metals or glasses in use will yield more or less light than here
assigned, it is to be understood that the corrections must be
made accordingly.

We proceed now to find a proper expression for the power
of penetrating into space, that we may be enabled to compare
its effects, in different telescopes, with that of the natural eye.

Since then the brightness of luminous objects is inversely as
the squares of the distances, it follows, that the penetrating
power must be as the square roots of the light received by the
eye.

MDCCC. K

66 Dr. HERSCHEL on the Power of

In natural vision, therefore, this power is truly expressed by
/a 1; and, since we have now also obtained a proper correc-
tion x, we must apply it to the incident light with telescopes.

In the Newronian and other constructions where two
specula are used, there will also be some loss of light on account
of the interposition of the small speculum; therefore, putting 6

for its diameter, we have 4* — b* for the real incident light.
This being corrected as above, will give the general expression
Val x 4° —b' for the same power in telescopes. But here we
are to take notice, that in refractors, and in telescopes with one
reflection, b will be = 0, and therefore is to be left out.
Then, if we put natural light J = 1, and divide by a, we
a

have the general form for the penetrating power of

all sorts of telescopes, compared to that of the natural eye as a
standard, according to any supposed aperture of the iris, and
proportion of light returned by reflection, or transmitted by
refraction.

In the following investigation we shall suppose a = 2 tenths
of an inch, as being perhaps nearly the general opening of the
iris, in star-light nights, when the eye has been some moderate
time in the dark. The value of the corrections for loss of light
will stand as has been given before.

We may now proceed to determine the powers of the instru-
ments that have been used in my astronomical observations ;
but, as this subject will be best explained by a report of the

penetrating into Space by Telescopes. 67

observations themselves, I shall select a series of them for that
purpose, and relate them in the order which will be most illus-
trating.

First, with regard to the eye, it is certain that its power, like
all our other faculties, is limited by nature, and is regulated by
the permanent brightness of objects; as has been shewn already,
when its extent with reflected light was compared to its exer-
tion on self-luminous objects. It is further limited on borrowed
light, by the occasional state of illumination; for, when that
becomes defective at any time, the power of the eye will then
be contracted into a narrower compass; an instance of which is
the following.

In the year 1776, when I had erected a telescope of 20 feet
focal length, of the NewrontrAn construction, one of its effects
by trial was, that when towards evening, on account of dark-
ness, the natural eye could not penetrate far into space, the
telescope possessed that power sufficiently to shew, by the dial
of a distant church steeple, what o’clock it was, notwithstanding
the naked eye could no longer see the steeple itself. Here I only
speak of the penetrating power; for, though it might require
magnifying power to see the figures on the dial, it could
require none to see the steeple. Now the aperture of the tele-
scope being 12 inches, and the construction of the NEWToNnIAN
form, its penetrating power, when calculated according to the

given formula, will be LEE == 98,99. A, b, and a,

being all expressed in tenths of an inch.*

* I have given the figures, in all the following equations of the calculated pene-
trating powers, in order to shew the constructions of my instruments to those who may
wish to be acquainted with them.

K 2

68 Dr. HERSCHEL on the Power of

From the result of this computation it appears, that the cir-
cumstance of seeing so well, in the dusk of the evening, may
be easily accounted for, by a power of this telescope to penetrate
39 times farther into space than the natural eye could reach,
with objects so faintly illuminated.

This observation completely refutes an objection to telescopic
vision, that may be drawn from what has also been demon-
strated by optical writers; namely, that no telescope can shew
an object brighter than it is to the naked eye. For, in order to
reconcile this optical theory with experience, I have only to say,
that the objection is intirely founded on the same ambiguity
of the word brightness that has before been detected. It is
perfectly true, that the inérinsic illumination of the picture on
the retina, which is made by a telescope, cannot exceed that of
natural vision; but the absolute brightness of the magnified
picture by which telescopic vision is performed, must exceed
that of the picture in natural vision, in the same ratio in which
the area of the magnified picture exceeds that of the natural
one; supposing the intrinsic brightness of both pictures to be
the same. In our present instance, the steeple and clock-dial
were rendered visible by the increased absolute brightness of
the object, which in natural vision was 15 hundred times inferior
to what it was in the telescope. And this establishes beyond a
doubt, that telescopic vision is performed by the absolute bright-
ness of objects; for, in the present case, I find by computation,
that the itrinsic brightness, so far from being equal in the tele-
scope to that of natural vision, was inferior to it in the ratio of
three to seven. ;

The distinction between magnifying power, and a power of
penetrating into space, could not but be felt long ago, though

penetrating into Space by Telescopes. 69

*

its theory has not been inquired into. ‘This undoubtedly gave
rise to the invention of those very useful short telescopes called
night-glasses. When the darkness of the evening curtails the
natural penetrating power, they come in very seasonably, to
the relief of mariners that are on the look out for objects which
it is their interest to discover. Night-glasses, such as they are
now generally made, will have a power of penetrating six or
seven times farther into space than the natural eye. For, by
the construction of the double eye-glass, these telescopes will
magnify 7 or 8 times; and the object glass being 2+ inches in

diameter, the breadth of the optic pencil will be 93 or 34 tenths
ofan inch. As this cannot enter the eye, on a supposition of
an opening of the iris of 2 tenths, we are obliged to increase the
value of a, in order to make the telescope have its proper effect.
Now, whether nature will admit of such an enlargement becomes
an object of experiment; but, at all events, a cannot be assumed

less than ae Then, if x be taken as has been determined for

of A ASR AGS VO
three refractions, we shall have ——=——-— = 6,46 or 7,39.

Soon after the discovery of the Georgian planet, a very cele-
brated observer of the heavens, who has added considerably to
our number of telescopic comets and nebulz, expressed his wish,
in a letter to me, to know by what method I had been led to
suspect this object not to be a star, like others of the same
appearance. I have no doubt but that the instrument through
which this astronomer generally looked out for comets, had a
penetrating power much more than sufficient to shew the new
planet, since even the natural eye will reach it. But here we
have an instance of the great difference in the effect of the two
sorts of powers of telescopes ; for, on account of the smallness

70 Dr. HeRscuex on the Power of

of the planet, a different sort of power, namely, that of magni-
fying, was required ; and, about the time of its discovery, I had
been remarkably attentive to an improvement of this power, as
I happened to be then much in want of it for my very close
double stars.*

On examining the nebulz which had been discovered by
many celebrated authors, and comparing my observations with
the account of them in the Connoissance des Temps for 1783, I
found that most of those which I could not resolve into stars
with instruments of a small penetrating power, were easily
resolved with telescopes of a higher power of this sort; and,
that the effect was not owing to the magnifying power I used
upon these occasions, will fully appear from the observations ;
for, when the closeness of the stars was such as to require a
considerable degree of magnifying as well as penetrating power,
it always appeared plainly, that the instrument which had the
highest penetrating power resolved them best, provided it had
as much of the other power as was required for the purpose.

Sept. 20, 1783, I viewed the nebula between FLAMSTEED’s
ggth and 105th Piscium, discovered by Mr. Mecuan, in 1780,

«It is not visible in the finder of my 7-feet telescope; but
“ that of my 20-feet shews it.”

Oct. 28, 1784, I viewed the same object with the 7-feet tele-
scope. ;

«Tt is extremely faint. With a magnifying power of 120, it
«‘ seems to be a collection of very small stars: I see many of
se"themiet

* Magnifying powers of 460, 625, 932, 1159, 1504, 2010, 2398, 3168, 4294,
5489, 6450, 6652, were used upon « Bootis, y Leonis, « Lyre, &c. See Cat. of double
stars, Phil, Trans. Vol, LXXII. page 115, and 147; and Vol. LXXV. page 48.

penetrating into Space by Telescopes. 71

At the time of these observations, my 7-feet telescope had
only a common finder, with an aperture of the object glass of
about 3 of an inch in diameter, and a single eye-lens; there-

/

: . 1899 x75 Miele
fore its penetrating power was —=~>— = 9,56. The finder

of the 2o-feet instrument, being achromatic, had an object
glass 1,17 inch in diameter; its penetrating power, therefore,
V 85x17
72

was ——-———— = 4,50.

Now, that one of them shewed the nebula and not the other,
can only be ascribed to space-penetrating power, as both instru-
ments were equal in magnifying power, and that so low as not
to require an achromatic object glass to render the image sufhi-
ciently distinct.

The 7-feet reflector evidently reached the stars of the nebula ;
but its penetrating and magnifying powers are very consi-
derable, as will be shewn presently.

July 30, 1783, I viewed the nebula south preceding FLam-
STEED'S 24, Aquarii, discovered by Mr. Maratpl, in 1746.

« In the small sweeper,* this nebula appears like a telescopic
‘comet.11

Oct. 27, 1794, The same nebula with a 7-feet reflector.

* The small sweeper is a NEwTontan reflector, of 2 feet focal length 3 and, with
an aperture of 4,2 inches, has only a magnifying power of 24, and a field of view 2° 12'.
Its distinctness is so perfect, that it will shew letters at a moderate distance, with a
magnifying power of 2000; and its movements are so convenient, that the eye remains
at rest while the instrument makes a sweep from the horizon to the zenith.

A large one of the same construction has an aperture of 9,2 inches, with a focal
length of 5 feet 3 inches. It is also charged low enough for the eye to take in the
whole optic pencil; and its penetrating power, with a double eye glass, is

J 041 XQ27—217

- = Zor

72 Dr. Herscuzy on the Power of

“ I can see that it is a cluster of stars, many of them being
“¢ visible.”
If we compare the penetrating power of the two instruments,

we find that we have in the first Mobs senile = 12,84; and

A / 5 627 seme 12% .
in the latter #3 *~3 =" — 90,25, However, the magnify-

ing power was partly concerned in this instance; for, in the
sweeper it was not sufficient to separate the stars properly.
March 4, 1783. With a 7-feet reflector, I viewed the nebula
near the 5th Serpentis, discovered by Mr. Messier, in 1764,
‘It has several stars in it; they are however so small that I
“ can but just perceive some, and suspect others.”
May 31,1783. The same nebula with a 10-feet reflector;

° ; g a 162
penetrating power nals = 28,67.

« With a magnifying power of 250, it is all resolved into
“ stars: they are very close, and the appearance is beautiful.
«« With 600, perfectly resolved. There is a considerable star not
“far from the middle; another not far from one side, but out
“of the cluster; another pretty bright one; and a great number
“< of small ones.”

Here we have a case where the penetrating power of 20 fell
short, when gg resolved the nebula completely. This object
requires also great magnifying power to shew the stars of it
well; -but that power had before been tried, in the 7-feet, as far
as 4,60, without success, and could only give an indication of its
being composed of stars; whereas the lower magnifying power
of 250, with a greater penetrating power, in the 10-feet instru-
ment, resolved the whole nebula into stars.

penetrating into Space by Telescopes. 73

May 3, 1783. I viewed the nebula between y and ¢ Ophiuchi,
discovered by Mr. Messier, in 1764,

« With a 10-feet reflector, and a magnifymg power of 250,
« I see several stars in it, and make no doubt a higher power,
« and more light, will resolve it all into stars.: This seems to be
“a good nebula for the purpose of establishing the connection
“« between nebulz and clusters of stars in general.”

June 18, 1784. The same nebula viewed with a large New-

: cr 88*—217
TONIAN 20-feet reflector; penetrating power WAU aaT

= 61,18; and a magnifying power of 157.

<«¢ A very large and very bright cluster of excessively com-
‘* pressed stars. The stars are but just visible, and are of une-
“qual magnitudes: the large stars are red; and the cluster is
« a miniature of that near FLAMsTEED’s 42d Come Berenices.
cose tz" 6/396" s), BL): 108 18".

Here, a penetrating power of 29, witha magnifying power of
250, would barely shew a few stars ; when, in the other instru-
ment, a power 61 of the first sort, and only 157 of the latter,
shewed them. completely well.

July 4, 1783. I viewed the nebula between FLAMSTEED’s 295
and 26 Sagittarii, discovered by ABRAHAM IHLE, in 1665.

« With a small 20-feet NEWTONIAN telescope, power 200,
‘it is all resolved into stars, that are very small and close.
«« There must be some hundreds of them. With 350, I see the
*¢ stars very plainly; but the nebula is too low in this latitude
*‘ for such a power.”’

July 12, 1784. I viewed the same nebula with a large 20-feet
NEwTONIAN reflector; power 157.

‘«« A most beautiful extensive cluster of stars, of various mag-
*« nitudes, very compressed in the middle, and about 8’ in

MDCCC. L

7 Ay Dr. HERSCHEL on the Power of

‘¢ diameter, besides the scattered ones, which do more than fill
“the extent of the field of view:* the large stars are red; the
«« small ones are pale red. RA 184 29’ 39”; PD 114° 7’.”

The penetrating power of the first instrument was gg, that
of the latter 61; but, from the observations, it is plain how
much superior the effect of the latter was to that of the former,
notwithstanding the magnifying power was so much in favour
of the instrument with the small penetrating power.

July 30, 1783. With a small 20-feet Newronian reflector, I
viewed the nebula in the hand of Serpentarius, discovered by
Mr. MEssIER, in 1764.

‘* With a power of 200, I see it consists of stars. ‘They are
better visible with 300. With 600, they are too obscure to be
«« distinguished, though the appearance of stars is still preserved.
«This seems to be one of the most difficult objects to be
‘resolved. With me, there is not a doubt remaining; but
*«‘ another person, in order to form a judgment, ought previously
“to go through all the several gradations of nebule which I
«« have resolved into stars.”

May 25, 1791. I viewed the same nebula with a 20-feet
reflector of my construction, having a penetrating power of

v.64 fax soe =/7 5.00.

« With a magnifying power of 157, it appears extremely
« bright, round, and easily resolvable. With goo, I can see the
‘‘ stars. It resembles the cluster of stars taken at 16 493’ 40”,+

* This field, by the passage of an equatorial star, was 15’ 3”.

+ The object referred to is No. 10. of the Connoissance des Temps for 1783, called
“« Nebuleuse sans etoiles.”” My description of it is, «« A very beautiful, and extremely
«« compressed, cluster of stars: the most compressed part about 3 or 4 in diameter.
« RA 16% 46’ 2”; PD 93° 46.”

penetrating into Space by Telescopes. 1651

** which probably would put on the same appearance as this,
« if it were at a distance half as far again as it is. RA 17* 26°
vo"; (PD9g 10"

Here we may compare two observations; one taken with the
penetrating power of 39, the other with 75; and, although the
former instrument had far the advantage in magnifying power,
the latter certainly gave a more complete view of the object.

The 20-feet reflector having been changed from the NEw-
TONIAN form to my present one, I had a very striking instance
of the great advantage of the increased penetrating power, in
the discovery of the Georgian satellites. ‘The improvement, by
laying aside the small mirror, was from 61 to 75; and, whereas
the former was not sufficient to reach these faint objects, the
latter shewed them perfectly well.

March 14, 1798. I viewed the Georgian planet with a new

64% 240)"
ES = 95,853

and, having just before also viewed it with my_2o-feet instru-
ment, I found, that with an equal magnifying power of goo, the
25-feet telescope had considerably the advantage of the former.
Feb. 24, 1786. I viewed the nebula near FLAMSTEED’s 5th
Serpentis, which has been mentioned before, with my g0-feet
reflector; magnifying power 157.
« The most beautiful extremely compressed cluster of small
“ stars; the greatest part of them gathered together into one
‘« brilliant nucleus, evidently consisting of stars, surrounded
‘with many detached gathering stars of the same size and
‘colour. RA 15.7’ 19”; PD 87° 8’.”
May 27, 1791. I viewed the same object with my 40-feet:
Le

25-feet reflector. Its penetrating power is

"6 Dr. HERSCHEL on the Power of
telescope; penetrating power ps =1 91,69; magnify-

ing power 370. sa

“ A beautiful cluster of stars.. I counted about 200 of them.
« The middle of it is so compressed that it is impossible to dis-
“ tinguish the stars.” io

Here it appears, that the superior penetrating power of the 40-
feet telescope enabled me even to count the stars of this nebula.
It is also to be noticed, that the object did not strike me as
uncommonly beautiful ; because, with much more than double
the penetrating, and also more than double the magnifying
power, the stars could not appear so compressed and small as
in the 20-feet instrument : this, very naturally, must give it
more the resemblance of a coarser cluster of stars, such as I had
been in the habit of seeing frequently.

The 40-feet telescope was originally mtended to have been
of the NEwTonIan construction; but, in the year 1787, when
I was experimentally assured of the vast importance of a power
to penetrate into space, I laid aside the work of the small mirror,
which was then in hand, and completed the instrument in its
present form. :

“ Oct. 10,1791. I saw the 4th satellite and. the ring of
« Saturn, in the 40-feet speculum, without an eye glass.”

The magnifying power on that occasion could not exceed 60
or 70; but the great penetrating power made full amends for
the lowness of the former; notwithstanding the greatest part
of it must have been lost for want of a greater opening of the
iris, which could not take in the whole pencil of rays, for this
could not be less than 7 or 8 tenths of an inch.

penetrating into Space by Telescopes. 77

Among other instances of the superior effects of penetration into
space, I should mention the discovery of an additional 6th satel-
lite of Saturn, on the 28th of August, 1789; and of a 7th, on the
11th of September, in the same year; which were first pointed
out by this instrument. It is true that both satellites are within
the reach of the 20-feet telescope; but it should be remembered,
that when an object is once discovered by a superior power, an
inferior one will suffice to see it afterwards. I need not add, that
neither the 7 nor 10-feet telescopes will reach them; their
powers, 20 and 29, are not sufficient to penetrate to such distant
objects, when the brightness of them is not more than that
of these satellites, It is also evident, that the failure in these
latter instruments, arises not from want of magnifying power:
as either of them has much more than sufficient for the purpose.

Nov. 5, 1791. I viewed Saturn with the 20 and 40-feet
telescopes.

“ 20-feet. The 5th satellite of Saturn is very small. The 1st,
“od, 3d, 4th, 5th, and the new 6th satellite, are in their cal-
“ culated places.”

“ 4o-feet. I see the new 6th satellite much better with this
‘¢ instrument than with the go-feet. The 5th is also much larger
“‘ here than in the 20-feet; in which it was nearly the same size
“as a small fixed star, but here it is considerably larger than
‘¢ that star.”

Here the superior penetrating power of the 40-feet telescope
shewed itself on the 6th satellite of Saturn, which is a very faint
object; as it had also a considerable advantage in magnifying
power, the disk of the 5th satellite appeared larger than in the
20-feet. But the small star, which may be said to be beyond

78 Dr. Herscuer on the Power of

the reach of magnifying power, could only profit by the supe-
riority of the other power.

Nov. 21, 1791. 40-feet reflector; power 370.

“ The black division upon the ring is as dark as the heavens
“ about Saturn, and of the same colour.”

“ The shadow of the body of Saturn is visible upon the ring,
“on the following side; its colour is very different from that
“‘ of the dark division. The 5th satellite is less than the gd; it
“is even less than the ed.”

20-feet reflector; power goo.

“ The gd satellite seems to be smaller than it was the last night
“but one. The 4th satellite seems to be larger than it was the
“19th. This telescope shews the satellites not nearly so well
“as the 40-feet.”’

Here, the magnifying power being nearly alike, the superi-
ority of the 40-feet telescope must be ascribed to its penetrating

power.

The different nature of the two powers above mentioned being
thus evidently established, I must now remark, that, in some
respects, they even interfere with each other; a few instances of
which I shall give.

August 24, 1783. I viewed the nebula north preceding
FLAMSTEED’s 1 Trianguli, discovered by Mr. MEssIER, in 1764.

« 7-feet reflector; power 57. There is a suspicion that the
«‘ nebula consists of exceedingly small stars. With this low

penetrating into Space by Telescopes. 79

*« power it has a nebulous appearance; and it vanishes when I
* put on the higher magnifying powers of 278 and 460.”

Oct. 28, 1794. I viewed the same nebula with a 7-feet
reflector.

“It is large, but very faint. With 120, it seems to be com-
‘“< posed of stars, and I think I see several of them; but it will
“ bear no magnifying power.”

In this experiment, magnifying power was evidently injurious
to penetrating power. Ido not account for this upon the principle
that by magnifying we make an object less bright; for, when
opticians have also demonstrated that brightness is diminished
by magnifying, it must again be understood as relating only to
the zntrinsic brightness of the magnified picture; its absolute
brightness, which is the only one that concerns us at present,
must always remain the same.* ‘The real explanation of the
fact, I take to be, that while the light collected is employed in
magnifying the object, it cannot be exerted in giving penetrating
power.

* This may be proved thus. The mean intrinsic brightness, or rather illumination,
of a point of the picture on the retina, will be all the light tbat falls on the picture;

divided by the number of its points; or C = Ww Now, since with a greater magni-
fying power m, the number of points N increases as the squares of the power, the

expression for the intrinsic brightness —, will decrease in the same ratio; and it will

N

F Z
consequently be in general N a m7”, and vo Caw —; that is, by compounding

a
CN « = =/=1:; or absolute brightness a given quantity. M. Boucuer has
carefully distinguished intrinsic and absolute brightness, when he speaks of the quan-

tity of light reflected from a wall, at different distances. Traite' d’Optique, page 39,
and 40.

80 Dr. HERscuEL on the Power of

June 18, 1799. I viewed the planet Venus with a 10-feet
reflector.

“Its light is so vivid that it does not require, nor will it bear,
“a penetrating power of 29, neither with a low nor with a
“ high magnifying power.”

This is not owing to the least imperfection in the mirror,
which is truly parabolical, and shews, with all its aperture open,
and a magnifying power of 600, the double star y Leonis in
the greatest perfection.

« It shewed Venus, perfectly well defined, with a penetrating
** power as low as 14, and a magnifying power of 400, or 600.”

Here, penetrating power was injurious to magnifying power;
and that it necessarily must be so, when carried to a high pitch,
is evident; for, by enlarging the aperture of the telescope, we
increase the evil that attends magnifying, which is, that we
cannot magnify the object without magnifying the medium.
Now, since the air is very seldom of so homogeneous a dispo-
sition as to admit to be magnified highly, it follows that we
must meet with impurities and obstructions, in proportion to
its quantity. But the contents of the columns of air through
which we look at the heavens by telescopes, being of equal
lengths, must be as their bases, that is, as the squares of the
apertures of the telescopes; and this is in a much higher ratio
than that of the increase of the power of penetrating into space.
From my long experience in these matters, I am led to appre-
hend, that the highest power of magnifying may possibly not
exceed the reach of a 20 or 25-feet telescope; or may even lie in
a less compass than either. However, in beautiful nights, when
the outside of our telescopes is dropping with moisture dis-
charged from the atmosphere, there are now and then favourable

penetrating into Space by Telescopes. 81

hours, in which it is hardly possible to put a limit to magni-
fying power. But such valuable opportunities are extremely
scarce; and, with large instruments, it will always be lost labour
to observe at other times.

As I have hinted at the natural limits of magnifying power,
[ shall venture also to extend my surmises to those of pene-
trating power. There seems to be room for a considerable
increase in this branch of the telescope; and, as the penetrating
power of my 40-feet reflector already goes to 191,69, there can
hardly be any doubt but that it might be carried to’s00, and
probably not much farther. The natural limit seems to be an
equation between the faintest star that can be made visible, by
any means, and the united brilliancy of star-light. For, as the
light of the heavens, in clear nights, is already very considerable
in my large telescope, it must in the end be so increased, by
enlarging the penetrating power, as to become a balance to
the light of all objects that are so remote as not to exceed in
brightness the general light of the heavens. Now, if P be put

Pa?
for penetrating power, we have Ai — == 4 == Tomreet) 52

inches for an aperture of a reflector, on my construction, that
would have such a power of 500.

But, to return to our subject; from what has been said before,
we may conclude, that objects are viewed in their greatest per-
fection, when, in penetrating space, the magnifying power is
so low as only to be sufficient to shew the object well; and
when, in magnifying objects, by way of examining them mi-
nutely, the space-penetrating power is no higher that what will
suffice for the purpose; for, in the use of either power, the inju-
dicious overcharge of the other, will prove hurtful to perfect
vision.

MDCCC. M

82 Dr. HERScHEL on the Power of
Se ee OO RC

It is remarkable that, from very different principles, I have
formerly determined the length of the visual ray of my 20-feet
telescope upon the stars of the milky way, so as to agree nearly
with the calculations that have been given.* The extent of
what I then figuratively called my sounding line, and what now
appears to answer to the power of penetrating into space, was
shewn to be not less than 415, 461, and 497 times the distance
of Sirius from the sun. We now have calculated that my tele-
scope, in the NewTonian form, at the time when the paper on
the Construction of the Heavens was written, possessed a power
of penetration, which exceeded that of natural vision 61,18 times;
and, as we have also shewn, that stars at 8, 9, or at most 10
_times the distance of Sirius, must become invisible to the eye,

we may Safely conclude, that no single star, above 489, 551, or
at most 612 times as far as Sirius, can any longer be seen in
this telescope. Now, the greatest length of the former visual
ray, 497, agrees nearly with the lowest of these present numbers,
489 ; and the higher ones are all in favour of the former com-
putation ; for that ray, though taken from what was perhaps
not far from its greatest extent, might possibly have reached to
some distance beyond the apparent bounds of the milky way:
but, if there had been any considerable difference in these deter-
minations, we should remember that some of the data by which
I have now calculated are only assumed. For instance, if the
opening of the iris, when we look at a star of the 7th magnitude,
should be only one-tenth of an inch and a half, instead of two,
then a, in our formula, will be = 1,5; which, when resolved,

® Phil. Trans. Vol. LXXV. page 247, 248.

penetrating into Space by Telescopes. 83

will give a penetrating power of 81,58; and therefore, on this
supposition, our telescope would easily have shewn stars 571
times as far from us as Sirius; and only those at 653, 734, or
816 times the same distance, would have been beyond its reach.
My reason for fixing upon two-tenths, rather than a lower quan-
tity, was, that I might not run a risk of over-rating the powers
of my instruments. I have it however in contemplation, to
determine this quantity experimentally, and perceive already,
that the difficulties which attend this subject may be overcome.

{t now only remains to shew, how far the penetrating power,
ig2, of my large reflector, will really reach into space. Then,
since this number has been calculated to be in proportion to the
standard of natural vision, it follows, that if we admit a star of
the 7th magnitude to be visible to the unassisted eye, this tele-
scope will shew stars of the one thousand three hundred and
forty-second magnitude.

But, as we did not stop at the single stars above mentioned,
when the penetration of the natural eye was to be ascertained,
so we must now also call the united lustre of sidereal systems
to our aid in stretching forwards into space. Suppose therefore,
a cluster of 5000 stars to be at one of those immense distances
to which only a 4c-feet reflector can reach, and our formula
will give us the means of calculating what that may be. For,
putting S for the number of stars in the cluster, and D for its

/ zc As
a

distance, we have = D;* which, on computation.

* D = 11765475948678678679 miles.
M e

84 Dr. HERscuEL on the Power of

comes out to be above 113 millions of millions of millions of
miles! A number which exceeds the distance of the nearest
fixed star, at least three hundred thousand times.

From the above considerations it follows, that the range for
observing, with a telescope such as my 40-feet reflector, is
indeed very extensive. We have the inside of a sphere to exa-
mine, the radius of which is the immense distance just now
assigned to be within the reach of the penetration of our instru-
ments, and of which all the celestial objects visible to the eye,
put together, form as it were but the kernel, while all the im-
mensity of its thick shell is reserved for the telescope.

It follows, in the next place, that much time must be required
for going through so extensive a range. The method of exa-
mining the heavens, by sweeping over space, instead of looking
merely at places that are known to contain objects, is the only
one that can be useful for discoveries.

In order therefore to calculate how long a time it must take
to sweep the heavens, as far as they are within the reach of my
40-feet telescope, charged with a magnifying power of 1000,
I have had recourse to my journals, to find how many favour-
able hours we may annually hope for in this climate. It is to
be noticed, that the nights must be very clear; the moon
absent; no twilight; no haziness; no violent wind; and no
sudden change of temperature; then also, short intervals for
filling up broken sweeps will occasion delays; and, under all
these circumstances, it appears that a year which will afford go,
or at most 100 hours, is to be called very productive.

penetrating into, Space by Telescopes, 85

In the equator, with my 20-feet telescope, I have swept over
zones of two degrees, with a power of 157; but, an allowance
of 10 minutes in polar distance must be made, for lapping the
sweeps over one another where they join.

As the breadth of the zones may be increased towards the
poles, the northern hemisphere may be swept in about 4,0 zones :
to these we must add ig southern zones; then, 59 zones,
which, on account of the sweeps lapping over one another about
5 of time in right ascension, we must reckon of 25 hours each,
will give 1475 hours. And, allowing 100 hours per year, we
find that, with the 20-feet telescope, the heavens may be swept
in about 14 years and 3.

Now, the time of sweeping with different magnifying powers
will be as the squares of the powers; and, putting p and ¢ for

the power and time in the 20-feet telescope, and P = 1000 for

the power in. the 40, we shall have p*: ¢:: P’: s = = 59840.

Then,. making the same allowance of 100 hours per year, it
appears that it will require not less than 598 years, to look with
the 40-feet reflector, charged with the abovementioned power,
only one single moment into each part of space; and, even
then, so much of the southern hemisphere will remain unex-
plored, as will take up 213 years more to examine.

Slough, near Windsor,
June 20, 1799.

[ 86 J

V. A second Appendix to the improved Solution of a Problem in
physical Astronomy, inserted in the Philosophical Transactions
for the Year 1798, containing some further Remarks, and
improved Formule for computing the Coefficients A and B;
by which the arithmetical Work is considerably shortened and
facilitated. By the Rev. John Hellins, B.D. F.R.S. and
Vicar of Potter’s Pury, 7x Northamptonshire.

Read December 12, 1799.

a. Ir was shewn, in Art. g- of the first Appendix, that the

1+/(1—cc)
c

common logarithm of the fraction » when ¢ is ex-

pressed in numbers, might be taken out from Taytor’s excel-
lent tables, and converted into an hyperbolic logarithm by
means of table XXXVII. of Dopson’s Calculator; which

method of obtaining the H. L. iy) is undoubtedly easier

and shorter than the more obvious one of first computing the
numerical value of that fraction, and then taking out the hyper-
bolic logarithm corresponding to it from a table. But yet, that
method of obtaining the value of a, easy as it is, requires, first,
a search in the table for the angle of which ¢ is the sine, and
generally a proportion for the fractional parts of a second;
then, a division of the degrees, minutes, and seconds contained
in that angle, by 2; and, thirdly, another search for the loga-
rithmic tangent of half the angle, and another proportion to
find the fractional parts of a second. I was therefore desirous

Mr. Heuuins’s Second Appendix, &c. 87

of finding some easier and shorter method of performing the
whole business, without the use of any trigonometrical tables,
in which time is required, not only in searching for logarithms,
but also in making proportions for the fractional parts of a
second; and, after some consideration, I discovered that which
I am now to explain.

This method, then, together with some further observations
which I have made for facilitating and abridging the work of
computing the values of A and B, will make up the contents
of this Paper.

2. The jy ieee ee , which was denoted. by «, both in

the solution of the problem and in. the Appendix, is = H. 1.

4
iS be deg: Oa —— * &c. andif, for the sake of distine=

tion, the eau letter a Be put for H. L. = -~, we shall have «=a
— z a 8. (of which series, the first three terms are suffi-
cient me our eck purpose) ; and this value of « being written
a ce ° 3 3°55 . °
for it in the expression a (1 pi 6c oh which occurs in
the first theorem in Art. 12. of the first Appendix, we shall
3 35 cc 3 \. :
have (1 + see + a5 ct x [a on ee ct ; that is, by: ac--
tual multiplication,

ce BiG SeSh Ge
Geri, ga Art. 2: of
* Since H. L. ——— eyo =a + Ea + — Sree » Be. (See Art. 250
= 4 6
ee rierendee thet Lee Pi ee ae ET
2 2.2 2 4.4 2.4.6.6

&e. and consequently H. L, ~ x Ve will be = H.L.

{|

1+ (1c)
Cc oi]

c*
» Se.
c 4 4.8

88 Mr. Heruins’s Second Appendix to the improved

14+ 4¢¢ 422

ir
beens py i\ sel Tach Aa
4 4.8
Shae Pe She |
a+ acc ri teae ;
8 8.8 3 ; 3:5 4
fale a+ = ace +44 ae
Teme me ee
4 16
ou Se gt
4.8 J

Now the terms — 4 cc and — 3. ct may very easily be added
to the terms fcc and gc’, 7.e. to 0°1036802 cc and 0:0687064,c’,
which will then become — 0°1463198 ¢c, and — 01187936 c*;
and, by denoting the coefficients of these new terms by the
Roman letters — f and — g respectively, the first theorem in
the Art. before mentioned, or the value of A, is-

Zz

+e— fcc — ge
3 ‘
+a-+- acc + 33 act,

iJ ce

a (a+b) 3 a

« . -§.21 .
g. The expression « fe SEE ots cll which occurs

4.12 Abtiz giz
in the value of A’, in Art. 12. of the first Appendix, is =
3 3-5 3-5-21 A4
par A.12 GC sr AL12.32 :
a—-—c— + c
4 8
3 3-5 365-21 a
~. AGC
ThE 2 aererer 3 3-5 35 21.
a+ acc +- a
3 3.5 4 4.12 4.12.32
ee eC Gi i
16 12.16 3 19 a
— + c— ~ Cc
9 I 8.16
4
mh Sane
miteaae P 3 19 4 :
Here again the terms — cc and — 7% c* may very easily

be added to the terms zcc and kc‘, i.e. to o10551502cc and

a

Solution of a Problem in physical Astronomy. 89

0°0408309 ct, and we shall have the two new terms —
0'1323498 cc and — 01076091 c*. Let the coefficients of these
two new terms be denoted by the Roman letters — i and — k
respectively, and the second theorem in Art. 12 of the first
Appendix Bee.

[3s + —— + b—ipomn ket
I
am (a+b) % “oO ss a2

le 45 aoe We.
_ 4. The product of a (2 res 4+ = which is found in.
the third theorem of the Art. before referred to, is =

e+—ctsc

a

ct

4.12. ABs

a—.—co— —— c*
4.8
ga-+ 75 acc + 73a
b. ae gilt f2at pace + ac
=a me, 68) I Sil ot
2 | —ZCC — FC.
— 4
Here likewise, the terms — tcc and — ;4-c* may be added

to 0'3465736cc and 01793226c*, which are = /cc and mc‘
respectively; the coefficients of which being denoted by the

Roman letters | and m, the third theorem in the Art. before
referred to becomes

eis 5 5 p — lec —mc*
i i aa +2a+lacc + act
2 2.16 7

5. These new forms to which the theorems are now brought,
it is evident, are no less convenient, and on examination they
will be found no less accurate, than the original ones ; and, that
the common logarithm of -, (and consequently the hyperbolic

logarithm of it,) is much more easily and expeditiously obtained
MDCCC. N

go Mr. HeLuns’s Second Appendix to the improved

1+ (106)
Cc

than the common logarithm of , even with the use of

Tay.tor’s excellent tables, is too obvious to need a description ;
and therefore it follows, that a computation by these new for-
mule will be easier and shorter than by those in the first
Appendix.

6. But there are still some expedients by which the compu-
tations of A, B, &c. may be further facilitated and abridged.

It is pretty evident, to any one who contemplates the coeffi-
cients of the are terms in the first three theorems, that

the terms a+ 3acc + 3 3 ac‘, in the first theorem, being once

found, the logarithmic terms of the second and third theorems
may most easily be derived from them; in consequence of
which, the se part of the time of writing down the loga-
rithms of +5, 34, 4, and 3%,
logarithms of acc and ac*, and of searching in the tables for

of twice writing down the

the numbers corresponding to py ae, and ae 32 aC, in the

second theorem, and for those which correspond to tacc, and

OOy
2.16

which I am next to explain.

ac*, in the third theorem, is saved. These are the expedients

7. The three terms a, 3acc, and 32 = ac’, hich are found in

the first theorem, are evidently to “ eo terms 3a, ain ace,

5.21 ° 5
and meee which are found in the second theorem, in the
ratio of 1 to 3, 1 to £, and 1 to Z respectively ; or as 1 to1—4,

1 to 1—4, and 1 to 1—4; by which mixed numbers, the

6?
logarithmic terms in the second theorem may more easily be,
derived from those in the first theorem, than by the fractions,

as will appear further on.

Solution of a Problem in physical Astronomy. gi

8. It is no less evident, that the three logarithmic terms a,
dace, and 33 ac‘, mentioned in the preceding Art. are to the

three logarithmic terms 2a, Lacc, and —. zac’, which occur in

the third theorem, in the ratio of 1 to 2, 1 to + 4, and 1 to &
respectively; or asi1toi-+1,1to1+4,and1toi+4; by
which mixed numbers, as was observed in the preceding Art.
the logarithmic terms in the third theorem may be more easily
derived from those in the first theorem, than by the fractions.
g. The first of the logarithmic terms in the first theorem has
already been denoted by the Roman letter a; now let the

second and third, wz. acc, and ac’, be denoted by the
Homan letters b and c pe ee and let the sum of these
three terms, viz. a+ 2acc 4+ +3 act, now denoted by a+b+c,

be put = 5S; then, by Art. 4: logarithmic terms in the
second theorem will be (1 — $)a, (1 —Z)b, and (1 —£)c;

and the sum of these terms will be a+ b+ c—— _— ——
a b c , : 3 f
=S§S ee Gt ae where S is given, it being = the three

logarithmic terms in the first theorem, with which the compu-
tation ought to begin; and the 4, 4, and = of these terms respec-
tively, are very easily computed without the use of logarithms,
as will hereafter appear. by an example.

And the logarithmic terms in the third theorem will likewise
be denoted by 2a, (1-++4)b, and (1+ 4)c respectively; the
sum of which is==a-+b4c+a+tb+4c=Spa+—+<,
where S, as well as a, b, and c, being given, the fractional parts
are very easily computed without the use of logarithins.

10. Having now described these short and easy methods of
Ne

92 Mr. Hetutns’s Second Appendix to the improved

computing the values of a, b, and c, and of deriving the other
logarithmic terms from them, and having introduced a new
and more compendious notation of several of the,terms in each
of the first three theorems, it will be proper next to exhibit those
theorems in this improved state, and, after that, to give an
example or two of computing by them.

He she og es ;
x (a+b) +

aa Leal 3acc(=b) + 32 act (=c).
sie tig $b ice — ket

a b Cc

pees Gea

; I
eA SaiaE S|

p — lec —me*
2a

3. B=5 an crm} ghee

( p—lcec—me*

Or, putting A to denote the product of —— aati - x | 4s4 af toe
this theorem will be more concisely and commodiously ex-
pressed thus; B= + (Aa— A).

4. B= = (A’a—A). N.B.S=a+b-+c.

11. We might now proceed to an example of computing by
these theorems; but it will be very convenient first to set down
the constant numbers and constant logarithms which are to be
used in these computations.

The constant numbers, taken from Art. 12 of the first
Appendix, and Art. 2, 3, and 4 of this Appendix, are the fol-
lowing :

€ = 0°193154,72, b = 0'0823,604, p = 1°3862,944,

f = 0'1463,198, i = 0'1323,498, 1 = 0'1534,264,

g = 0'1187,936, k = 0'1076,091, Mm =='01831,7 74,

Solution of a Problem in physical Astronomy. 93

And the constant logarithms to be used in these calculations
are the following, which are respectively set down to as many
places of figures as are requisite.

L.g=o 3010,300, L. 3 = 1'5740,3, pe a 1796,
L.3= — 18 8239,087, LS 0.1249,4, LL. So 0'4.971,4,99;
Lf = 1'1653,0, Tyd = 1°1217,2, a — 1°1859,1,
L.= = 1°910, ie * = T7910, L. + = 1939.

By comparing this Art. with Art. 13 of the first Appendix,
it will appear, that thé number of logarithms used in the new
formule is very considerably less than the number used in those
from which they were derived; and still fewer will suffice, since
the term == which occurs in the second theorem, is most easily
derived from —, * the first term in the first theorem, the loga~
rithms of =, <3 and cc, being there ready calculated; so that

L. £ needs not be used in the computation.

12. Let us now compute A and B by the first and third of
these new formule, when Venus and the earth are the two
planets.

* See Art. 11 of the first Appendix,

94

First, for the value of A.
Numbers. Logarithms.

Here a = 1'5236,71 \ 0°1828,913
Ar. co. 1'84,00,841

2°894.9,305
0°4,72.5,855

and 6 = 1°44,51,60
a— b =0'0785,11
at b = 2-9688,31

a—b =

Wp oe = ~ 2°4,223,4,50
- - 1°8786,8 50
fog ~ 1/3) 587 O55
+c ~ - 2°999

Sum of these two logarithms 5-920 -

The sum of these four terms is

Mr. Hexuins’s Second Appendix to the improved

Numbers.*

7562841 = —
0119315 =e

7582156 == +e

— 0'00387 = — fcc

— 000008 = — gc*
—0'00395 = — fcc — ge
75,01 761.

Having now found the value of the four terms = +e —fee

—gc*, we must next find the value of the three logarithmic

terms a + 3 acc + 3S act, or atb-+-+c=S, which may

quickly and easily be done as follows,
The common logarithm of 2 is

Half the common logarithm of cc is

The common logarithm of = is

0°3010,300

1°2111,725

1:0898,575; and this lo

garithm, reduced to an hyperbolic logarithm, by Table XXXVII.

* See Art. 14 of the first Appendix, paragraph the third.

4

Solution of a Problem in physical Astronomy. 95

of Dopson’s Calculator, gives - - 250949 —=4.
a 0°39959
3¢¢ 399638
Sum of these two logarithms 2:39597 002489 = 2acc =b
2CC 2°218
Sum of these two logarithms 4614 0'0004,1 == a Sact= Cc
The sum of these three termsis = - 2:53479 = S; to which

add the sum of the four terms above found 75°81761, and we have

78°35240 =all the terms.
1°8940,523
a(a+b)* 1:2060,282

The diff. of these two 18a |
0°6880,241 4°87555 = A.
ii 3

rithms is =

13. We are next to compute the value of B; which compu-

_ tation will be much facilitated by the use of numbers already

found in the computation of the value of A. The arithmetical
work may stand as follows.

96

1°38630 = p
lec 360806 — 0'00406 =—lcec
C6 2°361
5969 — 0'00009 = — mc*
1382 15 = the sum of these three terms.
253479 = 8
2°5094,9 =a
b
0'00830 se
0°00008 =
0'8085,357 6°4.3481 = thesum of all the terms.
w(a+b)¥ 07334,427
Dif. of these two log’. 0:0750,930 —-1:188 74. = A
A 0'6880,241
a 0°1828,913
Sum of these two log’. 0°8709,154 7.4,2874,—= Aa
0'7951,846 6:240co = Aa—A
+ Ona, 14d |
= (Aa— A) 0:9362,987 863579 = B.

Mr. HEuins’s Second Appendix to the improved

14. We have now the values sought, vz. A = 48756, and

B = 8.6357; which values, computed by the new formula,
agree with those which were given in the first Appendix,
which is one proof of the accuracy of the new forms to which
the theorems are brought. And, that the calculations of these

. numbers are considerably facilitated and abridged by the use of

HL. 2“ __ 35 instead of H.L. +¥0=, and by the

Solution of a Problem in physical Astronomy. 97

easy method of deriving the logarithmic terms in the second
and third theorems from those in the first, will quickly appear
to any one who shall make trial, by a calculation both by the
original formule and by those which are given in this paper,
or who shall compare the computations of A and B in the first
Appendix, with the computations here exhibited.

MDCCC. O

C 98 J

VI. Account of a Peculiarity in the Distribution of the Arteries
sent to the Limbs of slow-moving Animals ; together with some
other similar Facts. In a Letter from Mr. Anthony Carlisle,
Surgeon, to John Symmons, Esq. F. R. S.

Read Jan. 9, 1800.

DEAR SIR,

‘Tur Maucauco you have been so obliging as to give me for
the purpose of dissection, has proved a subject of considerable
interest. This animal, the Lemur tardigradus of LINNzZvs, was
injected, with a view to exhibit the course of the arteries; and
they present a very unusual deviation from the ordinary arrange-
ment of this class of blood-vessels in animals generally. Before
I had leisure to inquire further into this peculiarity, I presented
a drawing of the appearances to my friend Dr. Suaw, of the
British Museum, for the purpose of being made public in his
work of natural history, now in the press. Since that time, I
have, through Dr. Suaw’s assistance, been enabled to investi-
gate this subject somewhat farther; and, if you consider the
following account in any degree worthy the attention of the
Royal Society, I shall receive an additional honour by its pro-~
ceeding through your hands.

The Lemur tardigradus, in its injected state, accompanies this
paper; and, for the kind of preparation, the vessels are filled
with more than ordinary success. The arteries alone are injected ;
and the peculiarity of their arrangement is to be observed in
the axillary arteries, and in the iliacs. These vessels, at their
entrance into the upper and lower limbs, are suddenly divided

Mr. CaRLIsLE on a ralliartly, &c. 99

into a number of equal-sized cylinders, which occasionally
anastomose with each other. They are exclusively distributed
on the muscles; whilst the arteries sent to all the parts of the
body, excepting the limbs, divide in the usual arborescent form;
and, even those arteries of the limbs which are employed upon
substances not muscular, branch off like the common blood-
vessels. I counted twenty-three of these cylinders, parallel to
each other, about the middle of the upper arm; and seventeen
in the inguinal fasciculus.*

This fact appeared at first too solitary for the foundation of
any physiological reasoning; but, having since had an oppor-
tunity of prosecuting the inquiry, among animals of similar
habits and character, I have been encouraged to hope that the
result may eventually assist in the elucidation of muscular
motion. The Bradypus tridactylus, or great American Sloth, has
a similar distribution of the arteries of its limbs to that already
described in the Lemur tardigradus; which will be better under-
stood by the annexed figures. See Plate II. figs. 1 and 2; and
the explanations. The communications of these vessels with
each other are’ more frequent than in the Lemur tardigradus,
and their number is considerably greater. I counted forty-two
separate cylinders upon the superficies of the brachial fasci-
culus; and, from the bulk of the fasciculus, I estimate that
there were twenty, or more, concealed in the middle. The
lower extremity has its arteries less divided, and they are of
larger diameter. I observed only thirty-four branches in the
middle of the thigh; and the first series of ramifications were
larger than the subsequent ones. May not this have some
relation to the greater distance of the lower limb from the

* See Plate I. and its references, page 103.

O2

100 Mr. CaruisLE on a Peculiarity

heart? The extremely slow movements of the Bradypus tridac-
tylus are sufficiently known among natural historians.

The Bradypus didactylus has its arterial system distributed in
some degree like the tridactylus ; but the brachial artery in the
upper limb is much less subdivided, as will appear by the repre-
sentation in Plate II. fig. 3; and, in the lower limb, the arteries of
the plexus afterwards divide a few times in the arborescent form.
It may be worthy of remark, that this correspondence of ar-
rangement, in the arteries of the lesser Sloth, bears a striking
analogy with the structure and habits of the large American
Sloth; the movements of the Bradypus didactylus being univer-
sally represented quicker than those of the Bradypus tridactylus.

The Lemur Loris was next examined, and its arterial system
was found to resemble those already described ; but, as the ani-
mal had been preserved in very strong spirit, the vessels were so
corrugated as not to admit of injection. The two Bradypi were
injected with quicksilver. The natural history of the Lemur Loris
appears not to be very well ascertained; but it is a slow-
moving animal, and has been confounded with the species called
tardigradus, although doubtless a much more agile creature.
See Plate Il. figs. 5, and 6. ;

In all the quadrupeds before mentioned, the other blood-
vessels, as well as the nerves, presented the common appear-
ances. ‘The size of the heads, and the interior capacity of the
skulls, both in the Bradypus tridactylus and the Lemur tardigradus,
seemed smaller in proportion than is usual among animals, so
that the quantity of brain must be less than ordinary.

The effect of this peculiar disposition of the arteries, in the
limbs of these slow-moving quadrupeds, will be that of retard-
ing the velocity of the blood. It is well known, and has been

in the Arteries of slow-moving Animals. 104

explained by various writers, that the blood moves quicker in
the arteries near the heart, than in the remote branches; and
also, that fluids move more rapidly through tubes which branch
off suddenly from large trunks, than if they had been propelled
for a considerable distance through small-sized cylinders ;
besides which, the frequent communications in the cylinders of
the Bradypus tridactylus must produce eddies, which will retard
the progress of the fluid. From these and a variety of other
facts, which it is not necessary to specify, it will appear, that one
effect upon the animal economy, connected with this arrange-
ment of vessels, must be, that of diminishing the velocity of the
blood passing into the muscles of the limbs. It may be difficult
to determine, whether the slow movement of the blood sent to
‘these muscles be a subordinate convenience to other primary
causes of their slow contraction, or whether it be of itself the
immediate and principal cause. The facts at present ascertained,
relative to muscular motion, do not authorize me to treat de-
cidedly of the share which the vascular system holds in the
operation of muscular contraction. Certain it is, that a larger
proportion of arteries is sent to the muscles of quadrupeds, than
to the ordinary substances; and the extreme redness of these
organs shews that their capillaries are of large diameter. A
greater degree of redness is also observable in those muscles
(of the same animal) which are most frequently called into
action. The habits of life among the tardigrade animals, give
occasion for the long continued contraction of some muscles in
their limbs: these creatures are represented clinging to the
boughs of trees, and remaining thus, without locomotion, for
several hours. The powers which require so long a time to
determine the contraction of a series of muscles, are probably

102 Mr. CaRuisLE on a Peculiarity

no less slow in restoring the parts to their former condition ;
or, if the restoration is to be effected by antagonist muscles
under the same circumstances, then, the flexion and extension of
every part of the limbs will correspond, as to time.

I have not met with any arrangement of blood-vessels ana-
logous to those described, except in the carotid artery of the
Lion. May not this peculiarity be subservient to the long conti-
nued exertion of the muscles of his jaws, whilst holding a
powerful animal, such as a Horse or Buffalo, and thus enable
him to retain his prey, until it is wearied out by ineffectual
struggles? I believe also, that those animals which chew the
cud, have a plexus of arteries in the neck, analogous to the rete
mirabile: but this fact has not yet been verified in all the rumi-
nating quadrupeds; and the effect of these arrangements seems
rather to operate as sluices to the arteries of the masticating
muscles, than directly as the means of retarding the velocity of
their fluids. It is however necessary to examine these subjects
more accurately.*

As I have instituted a series of experiments and inquiries,
with the hope of elucidating this subject, it would be improper
to trouble you, or the Royal.Society, with any physiological
reasonings until these are completed. )

I have the honour to. be, &c.

Soho Square, ANT. CARLISLE.
October 28th, 1799.

* There is a rete mirabile in the genus Bos, and in some of the Cervi which I
have seen; but of these and the other Pecora a fuller description will be given in a

future paper.

s

2

in the Arteries of slow-moving Animals. 103

P.S.. The Maucauco which you lately possessed, was suffi-
ciently quick in the movements of its head to snap a person’s
finger, when touched incautiously; and the motion of its jaw,
when chewing, was not slower than in other animals. A
Maucauco of the same species, kept among the wild beasts in the
Tower of London, was very apt to bite those who, calculating
the movements of its head by those of its limbs, approached
within the length of its neck: the chewing of this animal was
similar to that of a Cat. These external habits of motion, com-
pared with those of the limbs, coincide very much with the
internal structure here described.

REFERENCES TO THE FIGURES.

Plate I.

The figure represents a dried preparation of the Lemur tar-
digradus, exhibiting the appearances of the arterial system.

a, the carotid arteries.

b, the axillary artery, dividing into the plexus described.

c, the iliac arteries, dividing into the cylindrical ramifications.

The other parts of the arterial system are represented
according to the natural and ordinary disposition.

Plate II.

Fig. 1, shews the axilla of the Bradypus tridactylus, dissected
to expose the vessels.

a, the sterno mastoideus muscle, passing under the skin of
the neck.

6, part of the axillary plexus of nerves; the median pro-
ceeding along the arm, with the large blood-vessels, and giving
off two branches of communication with the ulnar nerve.

a

104 Mr. CaRusLe on a Peculiarity

c, the subclavian vein.

d, the first bone of the sternum, attached to its second bone,
and to the first and second ribs.

e, the subclavian artery, passing into the axilla behind the
large veins, and dividing itself into a great number of equal-
sized cylinders, which cling together, frequently anastomose, and
take the ordinary route of the main trunks of arteries in the
upper limbs of quadrupeds.

Fig. 2, the brim of the pelvis and groin of the Bradypus tri-
dactylus, with the vessels exposed.

a, the aorta, where it divides into the two great iliac branches;
the iliac artery on the right side being continued, to shew the
division into the anastomosing cylinders which are sent to the
muscles.

6, part of the iliacus internus muscle.

¢, part of the bony margin of the pelvis leading down to
the pubes.

Fig. 3, the upper limb of the Bradypus didactylus.

a, a portion of skin on the top of the shoulder.

b, the axillary artery, divided more in the ordinary way than
in the former animal. This creature had been preserved in
ardent spirit containing camphor; and the dissection could not
be prosecuted so satisfactorily as to expose every small branch.

¢, part of the axillary plexus of nerves.

Fig. 4, the iliac vessels of the Bradypus didactylus.

a, the tendon of the psoas muscle.

b, the iliac artery, proceeding into the thigh, where its divi-
sions are more discernible than in the upper limb. The cylin-
dric tubes were however much fewer than in the Bradypus
iridactylus. X counted only eight tubes in the inguinal fasciculus

ee

Lhites Tratig MD CCC. Late Lpaes. ~*

wer

Calis

Philos, ans. MD CCC Male ps4

|

Ns

eee fy

x

T*Bafir

Lhilos Trans. MD CCC Hate Inver
1

De del, ai

in the Arteries of slow-moving Animals. 105

of this Sloth, whereas in the same part of the tridactylus there
were at least forty.

c, part of the rim of the pelvis.

Fig. 5, the upper limb of the Lemur Loris.

a, the head of the os brachii.

b, the axillary artery, proceeding along the arm, and dividing
into seven or eight cylinders.

Fig. 6, the inguinal arteries of the Lemur Loris.

a, the iliac artery, dividing as it passes the groin into five or
six cylinders.
6, the bony margin of the pelvis.

The figures are of the size of the different natural objects.

MDCCC, |e

[106 j

VII. Outlines of Experiments and Inquiries respecting Sound and
Light. By Thomas Young, M. D. F. R.S. Ina Letter to
Edward Whitaker Gray, M. D. Sec. R.S.

Read January 16, 1800.

DEAR SIR,

Ir has long been my intention to lay before the Royal Society
a few observations on the subject of sound; and I have endea-
voured to collect as much information, and to make as many
experiments, connected with this inquiry, as circumstances
enabled me to do; but, the further I have proceeded, the more
widely the prospect of what lay before me has been extended ;
‘and, as I find that the investigation, in all its magnitude, will
occupy the leisure hours of some years, or perhaps of a life, I
am determined, in the mean time, lest any unforeseen circum~
stances should prevent my continuing the pursuit, to submit to
the Society some conclusions which I have already formed from
the results of various experiments. Their subjects are, I. The
measurement of the quantity of air discharged through an aper-
ture. II. The determination of the direction and velocity of a
stream of air proceeding from an orifice. III. Ocular evidence
of the nature of sound. IV. The velocity of sound. V. Sonorous
cavities. VI. The degree of divergence of sound. VII. The
decay of sound. VIII. The harmonic sounds of pipes. IX. The
vibrations of different elastic fluids. X. The analogy between
light and sound. XI. The coalescence of musical sounds. XII.

'
.
~

Dr. Youne’s Experiments and Inquiries, &c. 107

The frequency of vibrations constituting a given note. XIII.
The vibrations of chords. XIV. The vibrations of rods and
plates. XV. The human voice. XVI. The temperament of
musical intervals.

I. Of the Quantity of Air discharged through an Aperture.

A piece of bladder was tied over the end of the tube of a large
glass funnel, and punctured with a hot needle. The funnel was
inverted in a vessel of water; and a gage, with a graduated glass
tube, was so placed as to measure the pressure occasioned by
the different levels of the surfaces of the water. As the air
escaped through the puncture, it was supplied by a phial of
known dimensions, at equal intervals of time; and, according to
the frequency of this supply, the average height of the gage
was such as is expressed in the first Table. It appears, that the
quantity of air discharged by a given aperture, was nearly in
the subduplicate ratio of the pressure; and that the ratio of the
expenditures by different apertures, with the same pressure, lay
between the ratio of their diameters and that of their areas.
The second, third, and fourth Tables show the result of similar
experiments, made with some variations in the apparatus. It
may be inferred, from comparing the experiments on a tube
with those on a simple perforation, that the expenditure is
increased, as in water, by the application of a short pipe.

108 Dr. Younc’s Experiments and Inquiries
Table 1.

A is the area, in square inches, of an
A B | C | aperture nearly circular. B, the pressure
in inches. C, the number of cubic inches

00018) 25 | 3.9 |) ;
,00018] .58 | 11.7 discharged in one minute.

.00018}1. 15.6 ,
001 | .o45| 7.8 All numbers throughout this paper,
001 | .2 | 15.6 | where the contrary is not expressed, are
(0010) 77°" 1 Bt:8
004, | .35 | 46.8

to be understood of inches, linear, square,
or cubic.

Table 11.

A is the area of the section of a tube

about two inches long. B, the pressure.
.o7| 1. | 2000.} C, the quantity of air discharged in a mi-
.o7| 2. | 2900.! nute, by estimation.

A | B C

Table 111.
A B C |} D _ A is the area of the section of a
0064, | 1.15 | .2 (46.8 tube. B, its length. C, the pressure.
eeey 10. 4d; \46-8 | D, the discharge in a minute.

0064 |13.5 | -35 191-2
00641135 | -7 |46.8) -

Table iv.

A is the area of an oval aperture, formed
A | By} C by flattening a glass tube at the end: its dia~
meters were .025 and .152. _B, the pressure.

C, the discharge.

003] 28. 46.8

hie

respecting Sound and Light. 109

II. Of the Direction and Velocity of a Stream of Air.

An apparatus was contrived for measuring, by means of a
water-gage communicating with a reservoir of air, the pressure
by which a current was forced from the reservoir through a
cylindrical tube; and the gage was so sensible, that, a regular
blast being supplied from the lungs, it showed the slight varia-
tion produced by every pulsation of the heart. The current of
air issuing from the tube was directed downwards, upon a white
plate, on which a scale of equal parts was engraved, and which
was thinly covered with a coloured liquid; the breadth of the
surface of the plate laid bare was observed at different distances
from the tube, and with different degrees of pressure, care being
taken that the liquid should be so shallow as to yield to the
slightest impression of air. The results are collected in Tables
v. and vi. and are exhibited to the eye in Plate III. Figs. 1—12.
In order to measure with greater certainty and precision, the
velocity of every part of the current, a second cavity, fur-
nished with a gage, was provided, and pieces perforated with
apertures of different sizes were adapted to its orifice: the axis
of the current was directed as accurately as possible to the
centres of these apertures, and the result.of the experiments,
with various pressures and distances, are inserted in Tables vir.
vil. and 1x. The velocity of a stream being, both according
to the commonly received opinion and to the experiments
already related, nearly in the subduplicate ratio of the pressure
occasioning it, it was inferred, that an equal pressure would be
required to stop its progress, and that the velocity of the cur-
rent, where it struck against the aperture, must be in the sub-
duplicate ratio of the pressure marked by the gage. The ordi-

110 Dr. Youne’s Experiments and Inquiries

nates of the curves in Figs. 13—2 3, were therefore taken recipro-
cally in the subduplicate ratio of the pressure marked by the
second gage to that indicated by the first, at the various. dis-
tances represented by the abscisses. Lach figure represents a
different degree of pressure in the first cavity. The curve
nearest the axis, is deduced from observations in which the
aperture opposed to the tube was not greater than that of the
tube itself; and shows what would be the diameter of the cur-
rent, if the velocities of every one of its particles in the same
circular section, including those of the contiguous air, which
must have acquired as much motion as the current has lost,
were equal among themselves. As the central particles must
be supposed to be less impeded in their motion than the super-
ficial ones, of course, the smaller the aperture opposed to the
centre of the current, the greater the velocity ought to come
out, and the ordinate of the curve the smaller; but, where the
aperture was not greater than that of the tube, the difference of
the velocities at the same distance was scarcely perceptible.
When the aperture was larger than that of the tube, if the dis-
tance was very small, of course, the average velocity came out
much smaller than that which was inferred from a smaller
aperture; but, where the ordinate of the internal curve became
nearly equal to this aperture, there was but little difference be-
tween the velocities indicated with different apertures. Indeed,
in some cases, a larger aperture seemed to indicate a greater
velocity: this might have arisen in some degree from the
smaller aperture not having been exactly in the centre of the
current; but there is greater reason to suppose, that it was occa-
sioned by some resistance derived from the air returning between
the sides of the aperture and the current entering it. Where

respecting Sound and Lighi. 114

this took place, the external curves, which are so constructed
as that their ordinates are reciprocally in the subduplicate ratio
of the pressure observed in the second cavity, with apertures
equal in semidiameter to their initial ordinate, approach, for a.
short distance, nearer to the axis than the internal curve: after
this, they continue their course very near to this curve. Hence
it appears, that no observable part of the motion diverged
beyond the limits of the solid which would be formed by the
revolution of the internal curve, which is seldom inclined to
the axis in an angle so great as ten degrees. A similar conclu-
sion may be made, from observing the flame of a candle sub-
jected to the action of a blowpipe: there is no divergency
beyond the narrow limits of the current; the flame, on the con-
trary, is every where forced by the ambient air towards the
current, to supply the place-of that which it has carried away
by its friction. The lateral communication of motion, very
ingeniously and accurately observed in water by Professor VEN-
TURI, is exactly similar to the motion here shown to take place
in air; and these experiments fully justify him in rejecting the
tenacity of water as its cause: no doubt it arises from the rela-
tive situation of the particles of the fluid, in the line of the cur-
rent, to that of the particles in the contiguous strata, which is
such as naturally to lead to a communication of motion nearly
in a parallel direction ; and this may properly be termed friction.
The lateral pressure which urges the flame of a candle towards
the stream of air from a blowpipe, is probably exactly similar
to that pressure which causes the inflection of a current of air
near an obstacle. Mark the dimple which a slender stream of
air makes on the surface of water; bring a convex body into
contact with the side of the stream, and the place of the dimple

112 Dr. Youne’s Experiments and Inquiries

will immediately show that the current is inflected towards the
body; and, if the body be at liberty to move in every direction,
it will be urged towards the current, in the same manner as,
in VENTURI’s experiments, a fluid was forced up a tube inserted
into the side of a pipe through which water was flowing. A
similar interposition of an obstacle in the course of the wind, is
probably often the cause of smoky chimneys. One circumstance
was observed in these experiments, which it is extremely diffi-
cult to explain, and which yet leads to very important conse-
quences: it may be made distinctly perceptible to the eye, by
forcing a current of smoke very gently through a fine tube.
When the velocity is as small as possible, the stream proceeds
for many inches without any observable dilatation; it then im-
mediately diverges at a considerable angle into a cone, Plate IV.
Fig. 24; and, at the point of divergency, there is an audible and
even visible vibration. The blowpipe also affords a method of
observing this phenomenon: as far as can be judged from the
motion of the flame, the current seems to make something like a
revolution in the surface of the cone, but this motion is too rapid
to be distinctly discerned. When the pressure is increased, the
apex of the cone approaches nearer to the orifice of the tube, Figs.
25,26; but no degree of pressure seems materially to alter its
divergency. The distance of the apex from the orifice, is not
proportional to the diameter of the current ; it rather appears to
be the greater the smaller the current, and is much better defined
in a small current than in a large one. Its distance in one ex-
periment is expressed in Table x, from observations on the sur-
face of a liquid; in other experiments, its respective distances
were sometimes considerably less with the same degrees of pres-
sure. It maybe inferred, from the numbers of Tables vii and vir,

respecting Sound and Light. 113

that in several instances a greater height of the first gage pro-
duced a less height of the second: this arose from the nearer
approach of the apex of the cone to the orifice of the tube,
the stream losing a greater portion of its velocity by this diver-
gence than it gained by the increase of pressure. At first sight,
the form of the current bears some resemblance to the vena
contracta of a jet of water: but Venturr has observed, that in.
water an increase of pressure increases, instead of diminishing,
the distance of the contracted section from the orifice. Is it not
possible, that the facility with which some spiders are said to
project their fine threads to a great distance, may depend upon.
the small degree of velocity with which they are thrown out, so
that, like a minute current, meeting with little interruption
from the neighbouring air, they easily continue their course for

a considerable time?
Table v.

The diameter of the tube .o7.
A is the distance of the liquid from
the orifice. B, the pressure. C,
the diameter of the surface of the
liquid displaced.

MDCCC. Q

114 Dr. Youne’s Experiments and Inquiries

Table vx. Table vit.

Diameter of

the tube, .1. {
Diameter of the tube .06.

A, B, and 5 :
C, as in A is the distance of the op-
Table v posite aperture, from the orifice

of the tube. B, the diameter of
the aperture. C, the pressure,
indicated by the first gage. D,
the height of the second gage.

A
B
Cc
el
2
“Bulk:
Al >
S|.
6
7,
8

wm N

I

1.
i,
2.
4.
8.
g:
4.

I

| ee | ee | ee | ce | | ce | ce | a | mee | ef a | me | ee | ee

2 ee ee es

Tf 305) .05

Ze We I

5] 2 +22
Ter WAc3e gol at
Zig eiS 21h 30,eyua-2
Oe wlhiteye {wan ae:
Asay ate a) «4

i 32 tay Olde)

6. eh Vale:
Ts V0 ea
8. 2.1 8
9- 23 oN td
O. 2:0. Ee

~

Diameter of the tube .1. A, B, C, and D, as in Table vir.

respecting Sound and Light. 115

Table 1x. Table x.

Diameter | a | BR A is the pres-

of the tube |———|——| sure. B, the dis-

bei o tance of the a-

‘ 3 e e

ASB; C; ie Vile |P& of the cone

and D, asin {1.8 | x. |from the orifice

Table vir. {2° *5 of a tube .1 in

+ °| diameter:

Il. Ocular Evidence of the Nature of Sound.

A tube about the tenth of an inch in diameter, with a lateral
orifice half an inch from its end, filed rather deeper than the
axis of the tube, Fig. 27, was inserted at the apex of a conical
cavity contaiming about twenty cubic inches of air, and luted
perfectly tight: by blowing through the tube, a sound nearly
in unison with the tenor C was produced. By gradually
increasing the capacity of the cavity as far as several gallons,
with the same mouth-piece, the sound, although faint, became
more and more grave, till it was no longer a musical note.
Even before this period a kind of trembling was distinguishable;
and this, as the cavity was still further increased, was changed
into a succession of distinct pufis, like the sound produced by
an explosion of air from the lips; as slow, in some instances, as
4, or 3inasecond. These were undoubtedly the single vibra-
tions, which, when repeated with sufficient frequency, impress
on the auditory nerve the sensation of a continued sound. On
forcing a current of smoke through the tube, the vibratory
motion of the stream, as it passed out at the lateral orifice, was
evident to the eye; although, from various circumstances, the
quantity and direction of its motion could not be subjected to

Q2

116 Dr. Youne’s Experiments and Inquiries

exact mensuration. ‘This species of sonorous cavity seems
susceptible of but few harmonic sounds. It was observed, that
a faint blast produced a much greater frequency of vibrations
than that which was appropriate to the cavity : a circumstance
similar to this obtains also in large organ pipes; but, several
minute observations of this kind, although they might assist in
forming a theory of the origin of vibrations, or in confirming
such a theory drawn from other sources, yet, as they are not
alone sufficient to afford any general conclusions, are omitted
at present, for the sake of brevity.

IV. Of the Velocity of Sound.

It has been demonstrated, by M. DE La GRANGE and others,
that any impression whatever communicated to one particle of
an elastic fluid, will be transmitted through that fluid with an
uniform velocity, depending on the constitution of the fluid,
without reference to any supposed laws of the continuation of
that impression. Their theorem for ascertaining this velocity is
the same as Newton has deduced from the hypothesis of a par-
ticular law of continuation: but it must be confessed, that the
result differs somewhat too widely from experiment, to give
us full confidence in the perfection of the theory. Corrected by
the experiments of various observers, the velocity of any impres-
sion transmitted by the common air, may, at an average, be
reckoned 11930 feet in a second.

V. Of sonorous Cavities.

M. De La GRANGE has also demonstrated, that all impres-
sions are reflected by an obstacle terminating an elastic fluid,
with the same velocity with which they arrived at that obstacle.

respecting Sound and Light. 117

When the walls of a passage, or of an unfurnished room, are
smooth and perfectly parallely any explosion, or a stamping
with the foot, communicates an impression to the air, which is
reflected from one wall to the other, and from the second again
towards the ear, nearly in the same direction with the primitive
impulse: this takes place as frequently in a second, as double
the breadth of the passage is contained in 1130 feet; and the
ear receives a perception of a musical sound, thus determined in
its pitch by the breadth of the passage. On making the expe-
riment, the result will be found accurately to agree with this
explanation. If the sound is predetermined, and the frequency
of vibrations such as that each pulse, when doubly reflected,
may coincide with the subsequent pulse proceeding directly
from the sounding body, the intensity of the sound will be
much increased by the reflection ; and also, in a less degree, if
the reflected pulse coincides with the next but one, the next but
two, or more, of the direct pulses. The appropriate notes of a
room may readily be discovered by singing the scale in it; and
they will be found to depend on the proportion of its length or
breadth to 1190 feet. The sound of the stopped diapason pipes
of an organ is produced in a manner somewhat similar to the
note from an explosion in a passage; and that of its reed pipes
to the resonance of the voice in a room: the length of the pipe
in one case determining the sound, in the other, increasing its
strength. The frequency of the vibrations does not at all imme-
diately depend on the diameter of the pipe. It must be con-
fessed, that much remains to be done in explaining the precise
manner in which the vibration of the air in an organ pipe is
generated. M. Danis, BeRNoUuLLt has solved several difficult

118 Dr. Youne’s Experiments and Inquiries

problems relating to the subject ; yet some of his assumptions
are not only gratuitous, but contrary to matter of fact.

VI. Of the Divergence of Sound.

It has been generally asserted, chiefly on the authority of
Newton, that if any sound be admitted through an aperture
into a chamber, it will diverge from that aperture equally in all
directions. The chief arguments in favour of this opinion are
deduced from considering the phenomena of the pressure of
fluids, and the moticn of waves excited in a pool of water. But
the inference seems to be too hastily drawn: there is a very
material difference between impulse and pressure; and, in the
case of waves of water, the moving force at each point is the
power of gravity, which, acting primarily in a perpendicular
direction, is only secondarily converted into a horizontal force,
in the direction of the progress of the waves, being at each step
disposed to spread equally in every direction: but the impulse
transmitted by an elastic fluid, acts primarily in the direction of
its progress. It is well known, that if a person calls to another
with a speaking trumpet, he points it towards the place where
his hearer stands: and I am assured by a very respectable
Member of the Royal Society, that the report of a cannon
appears many times louder to a person towards whom it is
fired, than to one placed im a contrary direction. It must have
occurred to every one’s observation, that a sound such as that
of a mill, or a fall of water, has appeared much louder after
turning a corner, when the house or other obstacle no longer
intervened; and it has been already remarked by EuLeEr, on this
head, that we are not acquainted with any substance perfectly

respecting Sound and Light. 119

impervious to sound. Indeed, as M. Lampert has very truly
asserted, the whole. theory of the speaking trumpet, supported
as it is by practical experience, would fall to the ground, if it
were demonstrable that sound spreads equally in every direc-
tion. In windy weather it may often be observed, that the
sound of a distant bell varies almost instantaneously in its
strength, so as to appear at least twice as remote at one time as
at another; an observation which has also occurred to another
gentleman, who is uncommonly accurate in examining the
phenomena of nature. Now, if sound diverged equally in all
directions, the variation produced by the wind could never
exceed one-tenth of the apparent distance: but, on the suppo-
sition of a motion nearly rectilinear, it may easily happen that a
slight change in the direction of the wind, may convey the
sound, either directly or after reflection, in very different de-
grees of strength, to the same spot. From the experiments on
the motion of a current of air, already related, it would be
expected that a sound, admitted at a considerable distance from
its origin through an aperture, would proceed, with an almost
imperceptible increase of divergence, in the same direction ; for,
the actual velocity of the particles of air, in the strongest sound,
is incomparably less than that of the slowest of the currents in
the experiments related, where the beginning of the conical
divergence took place at the greatest distance. Dr. MATTHEW
Younc has objected, not without reason, to M. Huss, that the
existence of a condensation will cause a divergence in sound:
but a much greater degree of condensation must have existed
in the currents described than in any sound. There is indeed
one difference between a stream of air and a sound; that, in
sound, the motions of different particles of air are not synchro-

120 Dr. Younc’s Experiments and Inquiries

nous: but it is not demonstrable that this circumstance would
affect the divergency of the motion, except at the instant of its
commencement, and perhaps not even then in a material
degree; for, in general, the motion is communicated with a
very gradual increase of intensity. The subject, however,
deserves a more particular investigation; and, in order to obtain
a more solid foundation for the argument, it is proposed, as
soon as circumstances permit, to institute a course of experi-
ments for ascertaining, as accurately as possible, the different
strength of a sound once projected in a given direction, at dif-
ferent distances from the axis of its motion.

VII. Of the Decay of Sound.

Various opinions have been entertained respecting the decay
of sound. M. De 1a GranceE has published a calculation, by
which its force is shown to decay nearly in the simple ratio of
the distances; and M. Dantet BERNOULLI’s equations for the
sounds of conical pipes lead to a similar. conclusion. The same
inference would follow from a completion of the reasoning of
Dr. Hetsuam, Dr. MattTuEew Younc, and Professor VENTURI.
It has been very elegantly demonstrated by Macraurin, and
may also be proved in a much more simple manner, that when
motion is communicated through a series of elastic bodies
increasing in magnitude, if the number of bodies be supposed
infinitely great, and their difference infinitely small, the motion
of the last will be to that of the’first in the subduplicate ratio of
their respective magnitudes ; and since, in the case of concentric
spherical laminze of air, the bulk increases in the duplicate ratio
‘of the distance, the motion will in this case be directly, and the
velocity inversely, as the distance. But, however true this may

respecting Sound and Light. 121

be of the first impulse, it will appear, by pursuing the calcula-
tion a little further, that every one of the elastic bodies, except
the last, receives an impulse in a retrograde direction, which
ultimately impedes the effect of the succeeding impulse, as much
as a similar cause promoted that of the preceding one: and
thus, as sound must be conceived to consist of an infinite
number of impulses, the motion of the last lamina will be pre-
cisely equal to that of the first; and, as far as this mode of
reasoning goes, sound must decay in the duplicate ratio of the
distance. Hence it appears, that the proposal for adopting the
logarithmic curve for the form of the speaking trumpet, was
’ founded on fallacious reasoning. The calculation of M. De va
GRANGE is left for future examination; and it is intended, in the
mean time, to attempt to ascertain the decay of sound as nearly
as possible by experiment: should the result favour the con-
clusions from that calculation, it would establish a marked
difference between the propagation of sound and of light.

VIII. Of the harmonic Sounds of Pipes.

In order to ascertain the velocity with which organ pipes of
different lengths require to be supplied with air, according to
the various appropriate sounds which they produce, a set of
experiments was made, with the same mouth-piece, on pipes
of the same bore, and of different lengths, both stopped and
open. The general result was, that a similar blast produced as
nearly the same sound as the length of the pipes would permit;
or at least that the exceptions, though very numerous, lay
equally on each side of this conclusion. The particular results
are expressed in Table x1. and in Plate IV. Fig. 28. They ex-
plain how a note may be made much louder on a wind instrument

MDCCC. R

122 Dr. Youne’s Experiments and Inquiries

by aswell, than it can possibly be by a sudden impression of the
blast. It is proposed, at a future time, to ascertain by experiment,
the actual compression of the air within the pipe under different.
circumstances: from some very slight trials, it seemed to be
nearly in the ratio of the frequency of vibrations of each
harmonic.

respecting Sound and Light. | 123
Table x1.

STOPPED.

0.3 | 1.8
1.2] 1.7 |10.0

A, is the length of the pipe from the lateral orifice to the end. C, the pressure at
which the sound began. B, its termination, by lessening the pressure; D, by increasing
it. E, the note answering to the first sound of each pipe, according to the German
method of notation. F, the number showing the place of each note in the regular
series Of harmonics. The diameter of the pipe was .35; the air duct of the mouth-
piece measured, where smallest, .25 by .035; the lateral orifice .25 by .125. The ap-
paratus was not calculated to apply a pressure of above 22 inches. Where no number
stands under C, a sudden blast was bac to produce the note.

2

124, Dr. Youne’s Experiments and Inquiries

IX. Of the Vibrations of different elastic Fluids.

All the methods of finding the velocity of sound, agree in
determining it to be, in fluids of a given elasticity, reciprocally
in the subduplicate ratio of the density: hence, in pure hydro-
gen gas it should be 13 = 9.6 times as great as in common
air; and the pitch of a pipe should be a minor fourteenth higher
in this fluid than in the common air. It is therefore probable that.
the hydrogen gas used in Professor CHLApN?’s late experiments,
was not quite pure. It must be observed, that in an accurate
experiment of this nature, the pressure causing the blast ought

‘to be carefully ascertained. There can be no doubt but that, in
the observations of the French Academicians on the velocity
of sound, which appear to have been conducted with all possible
attention, the dampness and coldness of the night air must have
considerably increased its density: hence, the velocity was found
to be only 1109 feet in a second; while DERHAm’s experiments,
which have an equal appearance of accuracy, make it amount to
1142. Perhaps the average may, as has been already mentioned,
be safely estimated at 1130. It may here be remarked, that the
well known elevation of the pitch of wind instruments, in the
course of playing, sometimes amounting to half a note, is not,
as is commonly supposed, owing to any expansion of the
instrument, for this should produce a contrary effect, but to
the increased warmth of the air in the tube. Dr. Smit has
made a similar observation, on the pitch of an organ in summer
and winter, which he found to differ more than twice as much
as thie English and French experiments on the velocity of sound.
Brancont found the velocity of sound, at Bologna, to differ at
iiflerent times, in the ratio of 152 to 157.

respecting Sound and Light. 125

X. Of the Analogy between Light and Sound.

Ever since the publication of Sir Isaac Newrton’s incom-
parable writings, his doctrines of the emanation of particles of
light from lucid substances, and of the formal pre-existence
of coloured rays in white light, have been almost universally
admitted in this country, and but little opposed in others.
LEONARD EULER indeed, in several of his works, has advanced
some powerful objections against them, but not sufficiently
powerful to justify the dogmatical reprobation with which he
treats them; and he has left that system of an ethereal vibra-
tion, which after HuyceENs and some others he adopted, equally
liable to be attacked on many weak sides. Without pretending
to decide positively on the controversy, it is conceived that some
considerations may be brought forwards, which may tend to
diminish the weight of objections to a theory similar to the
Huycenian. There are also one or two difficulties in the New-
TONIAN system, which have been little observed. ‘The first is,
the uniform velocity with which light is supposed to be pro-
jected from all lummous bodies, in consequence of heat, or
otherwise. How happens it that, whether the projecting force
is the slightest transmission of electricity, the friction of two
pebbles, the lowest degree of visible ignition, the white heat of
_ a wind furnace, or the intense heat of the sun itself, these won-
derful corpuscles are always propelled with one uniform velo-
city? For, if they differed in velocity, that difference ought to
produce a different refraction. But a still more insuperable
difficulty seems to occur, in the partial reflection from every
refracting surface. Why, of the same kind of rays, in every cir-
cumstance precisely similar, some should always be reflected,

126 Dr. Youne’s Experiments and Inquiries

and others transmitted, appears in this system to be wholly
inexplicable. That a medium resembling, in many properties,
that which has been denominated ether, does really exist, is
undeniably proved by the phzenomena of electricity ; and the ar-
guments against the existence of such an ether throughout the
universe, have been pretty sufficiently answered by Euter.
The rapid transmission of the electrical shock, shows that the
electric medium is possessed of an elasticity as great as is neces-
sary to be supposed for the propagation of light. Whether the
electric ether is to be considered as the same with the luminous
ether, if such a fluid exists, may perhaps at some future time be
discovered by experiment; hitherto I have not been able to
observe that the refractive power of a fluid undergoes any
change by electricity. The uniformity of the motion of light in
the same medium, which is a difficulty in the NEwron1an
theory, favours the admission of the HuyGEn1ay; as all impres-
sions are known to be transmitted through an elastic fluid with
the same velocity. It has been already shown, that souhd, in
all probability, has very little tendency to diverge: in a medium
so highly elastic as the luminous ether must be supposed to be,
the tendency to diverge may be considered as infinitely small,
and the grand objection to the system of vibration will be
removed. It is not absolutely certain, that the white line visible
in all directions on the edge of a knife, in the experiments of
NewtTon and of Mr. Jorpan, was not partly occasioned by the
tendency of light to diverge. EuLER’s hypothesis, of the trans-
mission of light by an agitation of the particles of the refract-
ing media themselves, is liable to strong objections; according
to this supposition, the refraction of the rays of light, on entering
the atmosphere from the pure ether which he describes, ought

_ respecting Sound and Light. 127

to be a million times greater than it is. For explaining the
phaenomena of partial and total reflection, refraction, and inflec-
tion, nothing more is necessary than to suppose all refracting
media to retain, by their attraction, a greater or less quantity
of the luminous ether, so as to make its density greater than
that which it possesses in a vacuum, without increasing its elasti-
city; and that light is a propagation of an impulse communi-
cated to this ether by luminous bodies: whether this impulse is
produced by a partial emanation of the ether, or by vibrations
of the particles of the body, and whether these vibrations are,
as EuLER supposed, of various and irregular magnitudes, or
whether they are uniform, and comparatively large, remains to
be hereafter determined. Now, as the direction of an impulse
transmitted through a fluid, depends on that of the particles in
synchronous motion, to which it is always perpendicular, what-
ever alters the direction of the pulse, will inflect the ray of
light. If'a smaller elastic body strike against a larger one, it is
well known that the smaller is reflected more or less powerfully,
according to the difference of their magnitudes: thus, there is
always a reflection when the rays of light pass from a rarer to
a denser stratum of ether; and frequently an echo when a sound
strikes against a cloud. A greater body striking a smaller one,
propels it, without losing all its motion: thus, the particles of a
denser stratum of ether, do not impart the whole of their motion
to a rarer, but, in their effort to proceed, they are recalled by the
attraction of the refracting substance with equal force; and thus
a reflection is always secondarily produced, when the rays of
light pass from a denser to a rarer stratum. Let AB, Plate V.
Fig. 29, be a ray of light falling on the reflecting surface FG;
ed the direction of the vibration, pulse, impression, or conden-

128 Dr. Youne’s Experiments and Inquiries

sation. When d comes to H, the impression will be, éither
wholly or partly, reflected with the same velocity as it arrived,
and EH will be equal to DH; the angle EIH to DIH or CIF;
and the angle of reflection to that of incidence. Let FG, Fig.
30, be a refracting surface. The portion of the pulse LE, which
is travelling through the refracting medium, will move with a
greater or less velocity in the subduplicate ratio of the densities,
and HE will be to KI in that ratio. But HE is, to the radius
IH, the sine of the angle of refraction; and KI that of the angle
of incidence. ‘This explanation of refraction is nearly the same
as that of Euter. ‘The total reflection of a ray of light by a
refracting surface, is explicable in the same manner as its simple
refraction; HE, Fig. 31, being so much longer than KI, that the
ray first becomes parallel to FG, and then, having to return
through an equal diversity of media, is reflected in an equal
angle. When a ray of light passes near an inflecting body,
surrounded, as all bodies are supposed to be, with an atmo-
sphere of ether denser than the ether of the ambient air, the
part of the ray nearest the body is retarded, and of course the

whole ray inflected towards the body, Fig. 32. The repulsion of |
inflected rays has been very ably controverted by Mr. Jorpan,
the ingenious author of a late publication on the Inflection of
Light. It has already been conjectured by Evier, that the
colours of light consist in the different frequency of the vibra-
tions of the luminous ether: it does not appear that he has sup-
ported this opinion by any argument; but it is strongly con-
firmed, by the analogy between the colours of a thin plate and
the sounds of a series of organ pipes. The phanomena of the
colours of thin plates require, in the NEwron1rAn system, a
very complicated supposition, of an ether, anticipating by its

respecting Sound and Light. 129

motion the velocity of the corpuscles of light, and thus pro-
ducing the fits of transmission and reflection; and even this
supposition does not much assist the explanation. It appears,
from the accurate analysis of the phenomena which Newton
has given, and which has by no means been superseded by
any later observations, that the same colour recurs whenever
the thickness answers to the terms of an arithmetical progres-
sion. Now this is precisely similar to the production of the
same sound, by means of an uniform blast, from organ-pipes
which are different multiples of the same length. Supposing
white light to be a continued impulse or stream of luminous
ether, it may be conceived to act on the plates as a blast of air does
on the organ-pipes, and to produce vibrations regulated in fre-
quency by the length of the lines which are terminated by the
two refracting surfaces. It may be objected that, to complete
the analogy, there should be tubes, to answer to the organ-
pipes: but the tube of an organ-pipe is only necessary to pre-
vent the divergence of the impression, and in light there is little
or no tendency to diverge; and indeed, in the case of a resonant ,
passage, the air is not prevented from becoming sonorous by the
liberty of lateral motion. It would seem, that the determination
of a portion of the track of a ray of light through any homo-
geneous stratum of ether, is sufficient to establish a length as a
basis for colorific vibrations. In inflections, the length of the
track of a ray of light through the inflecting atmosphere may
determine its vibrations: but, in this case, as it is probable that
there is a reflection from every part of the surface of the sur-
rounding atmosphere, contributing to the appearance of the
white line in every direction, in the experiments already men-
tioned, so it is possible that there may be some second reflection
MDCCC. S

130 Dr. Younc’s Experiments and Inquiries

at the immediate surface of the body itself, and that, by mutual
reflections between these two surfaces, something like the
anguiform motion suspected by NewTon may really take place;
and then the analogy to the colours of thin plates will be still
stronger. A mixture of vibrations, of all possible frequencies,
may easily destroy the peculiar nature of each, and concur in a
general effect of white light. The greatest difficulty in this sys-
tem is, to explain the different degree of refraction of differently
coloured light, and the separation of white light in refraction :
yet, considering how imperfect the theory of elastic fluids still
remains, it cannot be expected that every circumstance should
at once be clearly elucidated. It may hereafter be considered
how far the excellent experiments of Count RumForp, which
tend very greatly to weaken the evidence of the modern doc-
trine of heat, may be more or less favourable to one or the other
system of light and colours. It does not appear that any com-
parative experiments have been made on the inflection of light
by substances possessed of different refractive powers; un-
doubtedly some very interesting conclusions might be expected
from the inquiry.

XI. Of the Coalescence of musical Sounds.

It is surprising that so great a mathematician as Dr. SMITH
could have entertained for a moment, an idea that the vibrations
constituting different sounds should be able to cross each other
in all directions, without affecting the same individual particles
of air by their joint forces: undoubtedly they cross, without
disturbing each other’s progress; but this can be no otherwise
effected than by each particle’s partaking of both motions. — If
this assertion stood in need of any proof, it might be amply

respecting Sound and Light. 131

furnished by the phenomena of beats, and of the grave har-
monics observed by Romieu and Tartin1; which M. De La
GRrancE has already considered in the same point of view. In
the first place, to simplify the statement, let us suppose, what
probably never precisely happens, that the particles of air, in
transmitting the pulses, proceed and return with uniform mo-
tions; and, in order to represent their position to the eye, let
the uniform progress of time be represented by the increase of
the absciss, and the distance of the particle from its original
position, by the ordinate, Fig. 3338. Then, by supposing
any two or more vibrations in the same direction to be com-
bined, the joint motion will be represented by the sum or dif-
ference of the ordinates. When two sounds are of equal strength,
and nearly of the same pitch, as in Fig. 36, the joint vibration
is alternately very weak and very strong, producing the effect
denominated a beat, Plate VI. Fig. 43, B and C; which is slower
and more marked, as the sounds approach nearer to each other in
frequency of vibrations ; and, of these beats there may happen
to be several orders, according to the periodical approximations
of the numbers expressing the proportions of the vibrations.
The strength of the joint sound is double that of the simple
sound only at the middle of the beat, but not throughout its
duration; and it may be inferred, that the strength of sound in
a concert will not be in exact proportion to the number of
instruments composing it. Could any method be devised for
ascertaining this by experiment, it would assist in the comparison
of sound with light. In Plate V. Fig. 33, let P and Q be the middle
points of the progress or regress of a particle in two successive
compound vibrations; then, CP being = PD, KR = RN, GQ
= QH, and MS = SO, twice their distance, 2RS = 2RN +
Se

132 Dr. Younc’s Experiments and Inquiries

2NM + 2MS=KN + NM+NM + MO= KM + NO, is
equal to the sum of the distances of the corresponding parts of
the simple vibrations. For instance, if the two sounds be as
80: 81, the joint vibration will be as 80.5; the arithmetical
mean between the periods of the single vibrations. The greater
the difference in the pitch of two sounds, the more rapid the
beats, till at last, like the distinct puffs of air in the expe-
riments already related, they communicate the idea of a conti-
nued sound; and this is the fundamental harmonic described
by Tartini. For instance, in Plate V. Fig. 34—37, the vibra-
tions of sounds related as 1:2, 4:5, 9:10, and 5: 8, are
represented ; where the beats, if the sounds be not taken too
grave, constitute a distinct sound, which corresponds with the
time elapsing between two successive coincidences, or near
approaches to coincidence: for, that such a tempered interval
still produces a harmonic, appears from Plate V. Fig. 38. But,
besides this primary harmonic, a secondary note is sometimes
heard, where the intermediate compound vibrations occur at a
certain interval, though interruptedly ; for instance, in the coa-
lescence of two sounds related to each other as 7 : 8, 5: 7, or
4: §, there is a recurrence of a similar state of the joint motion,
nearly at the interval of ,, 4, or 3 of the whole period: hence,
in the concord of a major third, the fourth below the key note
is heard as distinctly as the double octave, as is seen in some
degree in Plate V. Fig. 35; AB being nearly two-thirds of CD.
The same sound is sometimes produced by taking the minor
sixth below the key note; probably because this sixth, like every
other note, is almost always attended by an octave, as a harmo-
nic. If the angles of all the figures resulting from the motion
thus assumed be rounded off, they will approach more nearly

respecting Sound and Light. 133

to a representation of the actual circumstances; but, as the laws
by which the motion of the particles of air is regulated, differ
according to the different origin and nature of the sound, it is
impossible to adapt a demonstration to them all = if, however,
the particles be supposed to follow the law of the harmonic
curve, derived from uniform circular motion, the compound
vibration will be the harmonic instead of the arithmetical mean;
and the secondary sound of the interrupted vibrations will be
more accurately formed, and more strongly marked, Plate VI.
Figs. 41, 42: the demonstration is deducible from the pro-
perties of the circle. It is remarkable, that the law by which the
motion of the particles is governed, is capable of some singular
alterations by a combination of vibrations. By adding toa given
sound other similar sounds, related to it in frequency as the
series of odd numbers, and in strength inversely in the same
ratios, the right lines indicating an uniform motion may be con-
verted very nearly into figures of sines, and the figures of sines
into right lines, as in Plate V. Figs. 39, 40.

XII. Of the Frequency of Vibrations constituting a given
Note. )

The number of vibrations performed by a given sound in a
second, has been variously ascertained; first, by SavveEuR, by a
very ingenious inference from the beats of two sounds; and
since, by the same observer and several others, by calculation
from the weight and tension of a chord. It was thought worth
while, as a confirmation, to make an experiment suggested,
but coarsely conducted, by MERsENNUuS, on a chord 200 inches
in length, stretched so loosely as to have its single vibrations
visible ; and, by holding a quill nearly in contact with the chord,

134 Dr. Youne’s Experiments and Inquiries

they were made audible, and were found, in one experiment, to
recur 8.3 times in a second. By lightly pressing the chord at
one-eighth of its length from the end, and at other shorter ali-
quot distances, the fundamental note was found to be one-sixth
of a tone higher than the respective octave of a tuning-fork
marked C: hence, the fork was a comma and a half above the
pitch assumed by Sauveur, of an imaginary C, consisting of
one vibration in a second.

XIN. Of the Vibrations of Chords.

By a singular oversight in the demonstration of Dr. Brook
T'ayor, adopted as it has been by a number of later authors,
it is asserted, that if a chord be once inflected into any other
form than that of the harmonic curve, it will, since those parts
which are without this figure are impelled towards it by an
excess of force, and those within it by a deficiency, in a very
short time arrive at or very near the form of this precise curve.
It would be easy to prove, if this reasoning were allowed, that
the form of the curve can be no other than that of the axis,
since the tending force is continually impelling the chord to-
wards this line. The case is very similar to that of the NEw-
TONIAN proposition respecting sound. It may be proved, that
every impulse is communicated along a tended chord with an
uniform velocity; and this velocity is the same which is inferred
from Dr. TayLor’s theorem; just as that of sound, determined
by other methods, coincides with the NEwronian result. But,
although several late mathematicians have given admirable
solutions of all possible cases of the problem, yet it has still.
been supposed, that the distinctions were too minute to be actu-
ally observed; especially, as it might have been added, since

respecting Sound and Light. 135

the inflexibility of a wire would dispose it, according to the doc-
trine of elastic rods, to assume the form of the harmonic curve.
The theorem of EULER and DE LA GRANGE, in the case where
the chord is supposed to be at first at rest, is in effect this: con-
tinue the figure each way, alternately on different sides of the
axis, and in contrary positions; then, from any point of the curve,
take an absciss each way, in the same proportion to the length
of the chord as any given portion of time bears to the time of
one semivibration, and the half sum of the ordinates will be the
distance of that point of the chord from the axis, at the expira-
tion of the time given. If the initial figure of the chord be com-
posed of two right lines, as generally happens in musical
instruments and experiments, its successive forms will be such
as are represented in Plate VI. Figs. 47, 48: and this result is
fully confirmed by experiment. Take one of the lowest strings
of a square piano forte, round which a fine silvered wire is wound
in a spiral form; contract the light of a window, so that, when
the eye is placed in a proper position, the image of the light may
appear small, bright, and well defined, on each of the convolu-
tions of the wire. Let the chord be now made to vibrate, and
the luminous point will delineate its path, like a burning coal
whirled round, and will present to the eye a line of light, which,
by the assistance of a microscope, may be very accurately ob-
served. According to the different ways by which the wire is
put in motion, the form of this path is no less diversified and
amusing, than the multifarious forms of the quiescent lines of
vibrating plates, discovered by Professor CHLADNI; and is indeed
in one respect even more interesting, as it appears to be more
within the reach of mathematical calculation to determine it;
although hitherto, excepting some slight observations of Busse

136 Dr. Youne’s Experiments and Inquiries

and CHLApnI, principally on the motion of rods, nothing has
been attempted on the subject. For the present purpose, the
motion of the chord may be simplified, by tying a long fine
thread to any part of it, and fixing this thread in a direction
perpendicular to that of the chord, without drawing it so
tight as to increase the tension: by these means, the vibra-
tions are confined nearly to one plane, which scarcely ever
happens when the chord vibrates at liberty. If the chord be
now inflected in the middle, it will be found, by comparison
with an object which marked its quiescent position, to make
equal excursions on each side of the axis; and the figure which
it apparently occupies will be terminated by two lines, the more
luminous as they are nearer the ends, Plate VI. Fig. 49. But,
if the chord be inflected near one of its extremities, Fig. 50, it
will proceed but a very small distance on the opposite side of
the axis, and will there form a very bright line, indicating its
longer continuance in that place; yet it will return on the
former side nearly to the point from whence it was let go, but
will be there very faintly visible, on account of its short delay.
In the middle of the chord, the excursions on each side the axis
are always equal; and, beyond the middle, the same circum-
stances take place as in the half where it was inflected, but on
the opposite side of the axis; and this appearance continues
unaltered in its proportions, as long as the chord vibrates at all:
fully confirming the non-existence of the harmonic curve, and
the accuracy of the construction of EuLEr and DE LA GRANGE.
At the same time, as M. BERNovuLLt has justly observed, since
every figure may be infinitely approximated, by considering its
ordinates as composed of the ordinates of an infinite number of
trochoids of different magnitudes, it may be demonstrated, that

respecting Sound and Light. 137

all these constituent curves would revert to their initial state, in
the same time that a similar chord bent into a trochoidal curve
would perform a single vibration ; and this is in some respects
a convenient and compendious method of considering the pro-
blem. But, when a chord vibrates freely, it never remains long
in motion, without a very evident departure from the plane of
the vibration; and, whether from the original obliquity of the
impulse, or from an interference with the reflected vibrations of
the air, or from the inequability of its own weight or flexibility,
or from the immediate resistance of the particles of air in con-
tact with it, it is thrown into a very evident rotatory motion,
more or less simple and uniform according to circumstances.
‘Some specimens of the figures of the orbits of chords are
exhibited in Plate VI. Fig. 44. At the middle of the chord, its
orbit has always two equal halves, but seldom at any other
point. The curves of Fig. 46, are described by combining
together various circular motions, supposed to be performed in
aliquot parts of the primitive orbit: and some of them approach
nearly to the figures actually observed. When the chord is of
unequal thickness, or when it is loosely tended and forcibly
inflected, the apsides and double points of the orbits have a very
evident rotatory motion. The compound rotations seem to
demonstrate to the eye the existence of secondary vibrations,
and to account for the acute harmonic sounds which generally
attend the fundamental sound. There is one fact respecting
these secondary notes, which seems intirely to have escaped
observation. Ifa chord be inflected at one-half, one-third, or
any other aliquot part of its length, and then suddenly left at
liberty, the harmonic note which would be produced by divid-

ing the chord at that point is intirely lost, and is not to be dise
MDCCCc. T

138 Dr. Youne’s Experiments and Inquiries

tinguished during any part of the continuance of the sound.
This demonstrates, that the secondary notes do not depend
upon any interference of the vibrations of the air with each
other, nor upon any sympathetic agitation of auditory fibres,
nor upon any effect of reflected sound upon the chord, but
merely upon its initial figure and motion. If it were supposed
that the chord, when inflected into right lines, resolved itself
necessarily into a number of secondary vibrations, according to
some curves which, when properly combined, would approxi-
mate to the figure given, the supposition would indeed in some
respects correspond with the phenomenon related; as the coef-
ficients of all the curves supposed to end at the angle of inflec-
tion would vanish. But, whether we trace the constituent curves
of such a figure through the various stages of their vibrations,
or whether we follow the more compendious method of EuLER
to the same purpose, the figures resulting from this series of
vibrations are in fact so simple, that it seems inconceivable how
the ear should deduce the complicated idea of a number of
heterogeneous vibrations, from a motion of the particles of air
which must be extremely regular, and almost uniform; an uni-
formity which, when proper precautions are taken, is not con-
tradicted by examining the motion of the chord with the assist
ance of a powerful magnifier. This difficulty occurred very
strongly to Euter ; and De La GRANGE even suspects some
fallacy in the experiment, and that a musical ear judges from
previous association. But, besides that these sounds are disco-
verable to an ear destitute of such associations, and, when the
sound is produced by two strings in imperfect unison, may be
verified by counting the number of their beats, the experi+
ment already related is an undeniable proof that no fallacy

respecting Sound and Light. 139

of this kind exists. It must be confessed, that nothing fully
satisfactory has yet occurred to account for the phenomena;
but it is highly probable that the slight increase of tension pro-
duced by flexure, which is omitted in the calculations, and the
unavoidable inequality of thickness or flexibility of different
parts of the same chord, may, by disturbing the isochronism of
the subordinate vibrations, cause all that variety of sounds
which is so inexplicable without them. For, when the slightest
difference is introduced in the periods, there is no difficulty in
conceiving how the sounds may be distinguished; and indeed,
in some cases, a nice ear will discover a slight imperfection in
the tune of harmonic notes: it is also often observed, in tuning
an instrument, that some of the single chords produce beating
sounds, which undoubtedly arise from their want of perfect
uniformity. It may be perceived that any particular harmonic
is loudest, when the chord is inflected at about one-third of the
corresponding aliquot part from one of the extremities of that
part. An observation of Dr. Watts seems to have passed
unnoticed by later writers on harmonics. If the string of a violin
be struck in the middle, or at any other aliquot part, it will
give either no sound atall, or a very obscure one. This is true,
not of inflection, but of the motion communicated by a bow;
and may be explained from the circumstance of the successive
impulses, reflected from the fixed points at each end, destroy-
ing each other: an explanation nearly analogous to some
observations of Dr. MattHEw Younc on the motion of chords.
When the bow is applied not exactly at the aliquot point, but
very near it, the corresponding harmonic is extremely loud;
and the fundamental note, especially in the lowest harmonics,
scarcely audible: the chord assumes the appearance, at the
Te

14,0 Dr. Youne’s Experiments and Inquiries

aliquot points, of as many lucid lines as correspond to the)
number of the harmonic, more nearly approaching to each
other as the bow approaches more nearly to the point, Plate VI.
Fig. 51. According to the various modes of applying the bow,
an immense variety of figures of the orbits are produced,
Fig. 45, more than enough to account for all the difference
of tone in different performers. In observations of this kind, a
series of harmonics is frequently heard in drawing the bow
across the same part of the chord: these are produced by the:
bow ; they are however not proportionate to the whole length
of the bow, but depend on the capability of the portion of the
bowstring, intercepted between its end and the chord, of per-
forming its vibrations in times which are aliquot parts of the
vibration of the chord: hence it would seem, that the bow takes
effect on the chord but at one instant during each fundamental
vibration. In these experiments, the bow was strung with the
second string of a violin: and, in the preparatory application
of resin, the longitudinal sound of CHLapNI was sometimes
heard; but it was observed to differ at least a note in different
parts of the string.

XIV. Of the Vibrations of Rods and Plates.

Some experiments were made, with the assistance of a most
excellent practical musician, on the various notes produced by
a glass tube, an iron rod, and a wooden ruler; and, in a case
where the tube was as much at liberty as possible, all the har-
monics corresponding to the numbers from 1 to 1g, were dis-
-tinctly observed; several of them at the same time, and others
by means of different blows. This result seems to differ from
the calculations of Eurer and Count Riccats, confirmed as

—s

respecting Sound and Light. 141

they are by the repeated experiments of Professor CHLADNI; it
is not therefore brought forward as sufficiently controverting
those calculations, but as showing the necessity of a revision of
the experiments. Scarcely any note could ever be heard when
a rod was loosely held at its extremity; nor when it was held
in the middle, and struck one-seventh of the length from one
end. The very ingenious method of Professor CHLADNI, of
observing the vibrations of plates by strewing fine sand over
them, and discovering the quiescent lines by the figures into
which it is thrown, has hitherto been little known in this
country: his treatise on the phenomena is so complete, that no
other experiments of the kind were thought necessary. Glass
vessels of various descriptions, whether made to sound by per-
cussion or friction, were found to be almost intirely free from
harmonic notes; and this observation coincides with the expe-
riments of CHLADNI.

XV. Of the human Voice.

The human voice, which was the object originally proposed to
be illustrated by these researches, is of so complicated a nature,
and so imperfectly understood, that it can be on this occasion but
superficially considered. No person, unless we except M. FrEr-
REIN, has published any thing very important on the subject of
the formation of the voice, before or since DoparT; his reason-
ing has fully shown the analogy between the voice and the voir
humame and regal organ-pipes: but his comparison with the
whistle is unfortunate; nor is he more happy in his account of the
falsetto. A kind of experimental analysis of the voice may be
thus exhibited. By drawing in the breath, and at the same time
properly contracting the larynx, a slow vibration of the ligaments
of the glottis may be produced, making a distinct clicking sound:

142 Dr. Youne’s Experiments and Inquiries

upon increasing the tension, and the velocity of the breath, this
clicking is lost, and the sound becomes continuous, but of an
extremely grave pitch: it may, by a good ear, be distinguished
two octaves below the lowest A of a common bass voice, con-
sisting in that case of about 26 vibrations in a second. The
same sound may be raised nearly to the pitch of the common
voice; but itis never smooth and clear, except perhaps in some
of those persons called ventriloquists. When the pitch is raised
still higher, the upper orifice of the larynx, formed by the
summits of the arytenoid cartilages and the epiglottis, seems to
succeed to the office of the ligaments of the glottis, and to pro-
duce a retrograde falsetto, which is capable of a very great
degree of acuteness. The same difference probably takes place
between the natural voice and the common falsetto: the rimula
glottidis being too long to admit of a sufficient degree of tension
for very acute sounds, the upper orifice of the larynx supplies
its place; hence, taking a note within the compass of either
voice, it may be held, with the same expanse of air, two or three
times as long in a falsetto as in a natural voice; hence, too,
the difficulty of passing smoothly from the one voice to the
other. It has been remarked, that the larynx is always elevated
when the sound is acute: but this elevation is only necessary in
rapid transitions, as ina shake; and then probably because, by
the contraction of the capacity of the trachea, an increase of the
pressure of the breath can be more rapidly effected this way,
than by the action of the abdominal muscles alone. The reflec-
tion of the sound thus produced from the various parts of the
cavity of the mouth and nostrils, mixing at various intervals
with the portions of the vibrations directly proceeding from the
larynx, must, according to the temporary form of the parts,
variously affect the laws of the motion of the air in each vibra-

respecting Sound and Light. 143

tion, or, according to EuLer’s expression, the equation of
the curve conceived to correspond with this motion, and thus
produce the various characters of the vowels and semi-vowels.
The principal sounding board seems to be the bony palate:
the nose, except in nasal letters, affords but little resonance; for
the nasal passage may be closed, by applying the finger to the
soft palate, without much altering the sound of vowels not
nasal. A good ear may distinctly ebserve, especially in a loud
bass voice, besides the fundamental note, at least four harmonic
sounds, in the order of the natural numbers; and, the more
reedy the tone of the voice, the more easily they are heard.
Faint as they are, their origin is by no means easy to be ex-
plained. This observation is precisely confirmed, in a late dis-
sertation of M. Knrcur, published in the musical newspaper of
Leipsic. Perhaps, by a close attention to the harmonics entering
mto the constitution of various sounds, more may be done in
their analysis than could otherwise be expected.

XVI. Of the Temperament of musical Intervals.

It would have been extremely convenient for practical musi-
cians, and would have saved many warm controversies. among;
theoretical ones, if three times the ratio of 4, to 5, or four times
that of 5 to 6, had been equal to the ratio of 1 tog. As it hap-
pens to be otherwise, it has been much disputed in what inter-
vals the imperfection should be placed. The ArisToxENIANs
and PyTHAGOREANS were in some sense the beginners of the
controversy. SAuVEuR has given very comprehensive tables of
a great number of systems of temperament; and his own now
ranks among the many that are rejected. Dr. Situ has written
a large and obscure volume, which, for every purpose but for

144, Dr. Youne’s Experiments and Inquiries

the use of an impracticable instrument, leaves the whole subject
precisely where it found it. KrrnBERGER, Marpura, and other
German writers, have disputed with great bitterness, almost
every one for a particular method of tuning. It is not with
any confidence of success, that one’ more attempt is made,
which rests its chief claim to preference, on the similarity of its
theory to the actual practice of the best instrument-makers.
However we estimate the degree of imperfection of two tem-
pered concords of the same nature, it will appear, that the
manner of dividing the temperament between them does not
materially alter its aggregate sum; for instance, the imperfection
of a comma in a major-third, occasions it to beat very nearly
twice as fast as that of halfa comma. If indeed the imperfection
were great, it might affect an interval so materially as to destroy
its character; as, in some methods of temperament, a minor
third diminished by two commas approaches more nearly to the
ratio 6: 7, than to 5: 6; but, with this limitation, the sum of
harmony is nearly equal in all systems. Hence, if every one of
the twelve major and minor thirds occurred equally often in |
the compositions which are to be performed on an instrument,
it would be of no great consequence, to the sum of the imper-
fections, among which of the thirds they were divided: and,
even in this case, the opinion of the best practical authors is,
that the difference of character produced by a difference of pro-
portions in various keys, would be of considerable advantage in
the general effect of modulation. But, when it is considered, that
upon an average of all the music ever composed, some parti-
cular keys occur at least twice as often as others, there seems
to be a very strong additional reason for making the harmony
the most perfect in those keys which are the most frequently

respecting Sound and Light. 145

used; since the aggregate sum of all the imperfections which
occur in playing, must by this means be diminished in the greatest
possible degree, and the diversity of character at the same time
preserved. Indeed, in practice, this method, under different
modifications, has been almost universal; for, although many
have pretended to an equal temperament, yet the methods which
they have employed to attain it have been evidently defective.
It appears to me, that every purpose may be answered, by
making C:E too sharp by a quarter of a comma, which
will not offend the nicest ear; E: G*, and A’: C, equal;
F*: A* too sharp by a comma; and the major thirds of all the
intermediate keys more or less perfect, as they approach more
or less to C in the order of modulation... The fifths are perfect
enough in every system. The results of this method are shown
in Table x11. In practice, nearly the same effect may be very
simply produced, by tuning from C to F, B’, E’, G*, C*, F*
six perfect fourths; and C, G, D, A, E, B, F*, six equally im-
perfect fifths, Plate VI. Fig. 52. If the unavoidable imperfections
of the fourths be such as to incline them to sharpness, the
temperament will approach more nearly to equality, which is
preferable to an inaccuracy on the other side. An easy method
of comparing different systems of temperament is exhibited in.
Plate VII. Fig. 53, which may easily be extended to all the sys-
tems that have ever been invented, :

MDCCC, U

146 Dr. Youne’s Experiments and Inquiries

Table xi.

B Cc

iC + .0013487| 1 A, E — .0023603
2G, F .0019006/ 2 D, B .0029122
3D; B 0024525| 3G, F* — .0034641
Tipovis od 0034641) 4.C,C* .004475
5E, A’ 0044756] 5 F,G* — .0049353
6 B,C* — .0049353| 6 B’, E’ .0053950
yillie 0053950

1 EF’, G*, 'C*, F* ~ '—"c000000
2 F, B’, E, B .0004,597
3 C,G, D, A .0011562

A, shows the division of a monochord corresponding to
each note, in the system proposed. B, the logarithm of the
temperament of each of the major thirds. C, of the minor
thirds. D, of the fifths ; C and D being both negative.

Thus, Sir, I have endeavoured to advance a few steps only,
in the investigation of some very obscure but interesting sub-
jects. As far as I know, most of these observations are new;
but, if they should be found to have been already made by any
other person, their repetition in a connected chain of inference
may still be excusable. Iam persuaded also, that at least some
of the positions maintained are incontrovertibly consistent with
truth and nature; but, should further experiments tend to con-
fute any opinions that I have suggested, I shall relinquish them
with as much readiness as 1 have long since abandoned the

—— a

respecting Sound and Light. 147

hypothesis which I once took the liberty of submitting to the
Royal Society, on the functions of the crystalline lens.

Lam, &c.

Emanuel College, Cambridge, THOMAS: YOUNG.
8th July, 1799.

EXPLANATION OF THE FIGURES.
(See Plates IIT. IV. V. VI. and VII.)
Plate III.

Figs. 1—6. The section of a stream of air from a tube .07
inch in diameter, as ascertained by measuring the breadth
of the impression on the surface of a liquid. The pressure im-
pelling the current, was in Fig. 1, 1 inch. Fig. 2, 2. Fig. 3,
@.. Fig. Agde oFig.55-7> Fig. 6, 10,

Figs. 7—12. A similar section, where the tube was .1 in dia-
meter, compared with the section as inferred from the experi-
ments with two gages, which is represented by a dotted line.
From this comparison it appears, that where the velocity of
the current was small, its central parts only displaced the
liquid; and that, where it was great, it displaced, on meeting
with resistance, a surface somewhat greater than its own sec=
tion. The pressure was in Fig. 7, 1. Fig. 8, 2. Fig.9, 3. Fig.
topde re ia, Zorkigy 12710:

Figs. 13—20. A, the half section of a stream of air from a
tube .1 in diameter, as inferred from experiments with two
water gages. The pressure was in Fig. 19, .1. Fig. 14, .2. Fig.
t5, -5. Fig. 16,1. Fig. 17,3. Fig. 18, 5. Fig. 19, 7. Fig. 20,
10. The fine lines, marked B, show the result of the observa-

Ue

148 Dr. Youne’s Experiments and Inquiries

tions with an aperture .15 in diameter opposed to the stream;
C with .g; and D with .5.

_ Figs. 21—23. A, the half section of a current from a tube .3
in diameter, with a pressure of .5, of 1, and of 3. B shows the
course of a portion next the axis of the current, equal in dia-
meter to those represented by the last figures.

Plate IV.

Fig. 24. The appearance of a stream of smoke forced very
gently from a fine tube. Fig. 25 and 26, the same appearance
when the pressure is gradually increased.

Fig. 27. See Section IIT.

Fig. 28. The perpendicular lines over each division of the
horizontal line show, by their length and distance from that
line, the extent of pressure capable of producing, from the re-
spective pipes, the harmonic notes indicated by the figures placed
opposite the beginning of each, according to the scale of 22
inches parallel to them. The larger numbers, opposite the middle
of each of these lines, show the number of vibrations of the cor-
responding sound in a second.

Plate V.

Figs. 29—33. See Section X.

Fig. 34. The combination of two equal sounds constituting the
interval of an octave, supposing the progress and regress of
the particles of air equable. Figs. 95, 36, 37, a similar repre-
sentation of a major third, major tone, and minor sixth.

Fig. 38. A fourth, tempered about two commas.

Fig. 39. A vibration of a similar nature, combined with subor-
dinate vibrations of the same kind in the ratios of 3, 5, and 7.

respecting Scund and Light. 149

Fig. 40. A vibration represented by a curve of which the
ordinates are the sines of circular arcs increasing uniformly,
corresponding with the motion of a cycloidal pendulum, com-
bined with similar subordinate vibrations in the ratios of 3, 5,
and 7.

Plate VI.

Figs. 41 and 42. Two different positions of a major third,
composed of similar vibrations, as represented by figures of
sines.

Fig. 43. A contracted representation of a series of vibrations.
A, a simple uniform sound. B, the beating of two equal sounds
nearly in unison, as derived from rectilinear figures. C, the
beats.of two equal sounds, derived from figures of sines. D, a
musical consonance, making by its frequent beats a fundamental
harmonic. E, the imperfect beats of two unequal sounds.

Fig. 44. Various forms of the orbit of a musical chord, when
inflected, and when struck.

Fig. 4.5. Forms of the orbit, when the sound is produced by
means of a bow.

Fig. 46. Epitrochoidal curves, formed by combining a simple
rotation or vibration with other subordinate rotations or vibra-
tions.

Figs. 47 and 48. The successive forms of a tended chord,
when inflected and let go, according to the construction of
De ta GranceE and EvuLer.

Fig. 49. The appearance of a vibrating chord which had been
inflected in the middle, the strongest lines representing the
most luminous parts.

Fig. 50. The appearance of a vibrating chord, when inflected
at any other point than the middle.

150 Dr. Youne’s Experiments and Inquiries, &c.

Fig. 51. The appearance of a chord, when put in motion by
a bow applied nearly at one third of the length from its end.
Fig. 52. The method of tuning recommended for common use,

Plate VII.

Fig. 53. A comparative view of different systems of tem-
perament. The whole circumference represents an octave. The
inner circle L is divided into 30103 parts, corresponding with
the logarithmical parts of an octave. The next circle R shows
the magnitude of the simplest musical and other ratios. Q is di-
vided into twelve equal parts, representing the semitones of the
equal temperament described by Zar ino, differing but little
from the system of ArIsToxENuS, and warmly recommended by
Marpurc and other late writers. Y exhibits the system pro-
posed in this paper as the most desirable; and P the practical
method nearly approaching to it, which corresponds with the
eleventh method in Marpure’s enumeration, except that, by
beginning with C instead of B, the practical effect of the tem-
perament is precisely inverted. K is the system of KIRNBERGER
and SuLzer; which is derived from one perfect third, ten per-
fect and two equally imperfect fifths. M is the system of mean
tones, the sistema participato of the old Italian writers, still fre-
quently used in tuning organs, approved also by Dr. Smiru for
common use. S shows the result of all the calculations in Dr.
Smitu’s harmonics, the system proposed for his changeable
harpsichord, but neither in that nor any other form capable of
practical application.

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[151 J

VIII. Observations on the Effects which take place from the De-
struction of the Membrana Tympani of the Ear. By Mr. Astley
Cooper. In a Letier to Everard Home, Esq. F. R.S. by
whom some Remarks are added.

Read February 6, 1800.

DEAR SIR,

A\z the time you were engaged in the investigation of the
structure and uses of the membrana tympani, you mentioned
a wish to ascertain the effect a rupture of that membrane would
have upon hearing. I now send you some observations on that
subject, which, if you think them of sufficient importance, you
will do me the honour of presenting to the Royal Society.

Lam, &c.

ASTLEY COOPER.

ANATOMISTs have endeavoured to ascertain, by experiments
on quadrupeds, the loss of power which the organ of hearing
would sustain by perforating the membrana tympani: dogs
have been made the subject of these trials; but the results have
been neither clear nor satisfactory, and they accord but little
with the phenomena I am about to relate.

Mr. CHEsELDEN had conceived the design of making the
human organ itself the subject of direct experiment; and a con-

152 Mr. CoopeEr’s Observations on the

demned criminal was pardoned, on condition of his submitting
to it; but, a popular outcry being raised, it was thought proper
to relinquish the idea.

Though denied the aid of experiment, we are not without the
means of obtaining knowledge upon such subjects; since the
changes produced by disease, frequently furnish a clue which is
equally satisfactory.

It often happens, that some parts of an organ are destroyed

by disease, whilst others are left in their natural state; and.

hence, by the powers retained by such organ, after a partial
destruction, we are enabled to judge of the functions performed
by those parts, when the whole was in health.

Guided by this principle, I have made the human ear the
subject of observation, and have endeavoured to ascertain the
degree of loss it sustains in its powers by the want of the mem-
brana tympani; a membrane which has been generally consi-
dered, from its situation in the meatus, and its connection with
the adjacent parts by a beautiful and delicate structure, as essen-
tially necessary to the sense of hearing; but which, as appears
by the following observations, may be lost, with little prejudice
to the functions of the organ.

Mr. P——, a medical student at St. pom s Hospital, of
the age of twenty years, applied to me, in the winter of 1797,
while he was attending a course of anatomical lectures, request-
ing my opinion upon the nature of a complaint in his ear,
which had long rendered him slightly deaf.

Upon inquiring into the nature of the symptoms which had
preceded, and of those which now accompanied the disease, he
informed me, that he had been subject from his infancy to pains
in the head, and was attacked, at the age of ten years, with an in-

es

Destruction of the Membrana Tympani. 153

flammation and suppuration in the left ear, which continued dis-
charging matter for several weeks: in the space of about twelve
months after the first attack, symptoms of a similar kind took
place in the right ear, from which also matter issued for a con-
siderable time. The discharge in each instance was thin, and
extremely offensive to the smell; and, in the matter, bones or
pieces of bones were observable. The immediate consequence
of these attacks was a total deafness, which continued for three
months; the hearing then began to return, and, in about ten:
months from the last attack, was restored to the state in which
it at present remains.

Having thus described the disease and its symptoms, he gave
me the following satisfactory proof of each membrana tympani
being imperfect. Having filled his mouth. with air, he closed the
nostrils, and contracted his cheeks : the air, thus compressed,
was heard to rush through the meatus auditorius, with a whistling
noise, and the hair hanging from the temples. became agitated
by the current of air which issued from the ear. To determine
this with greater precision, I called for a lighted candle, which
was applied in turn to each ear, and the flame was agitated in a
similar manner. Struck with the novelty of these phenomena, I
wished to have many witnesses of them, and therefore requested
him, at the conclusion of the lecture upon the organ of hearing,
to exhibit them to his fellow students, with which request he
was so obliging as to comply. :

It was evident from these experiments, that the membrana
tympani of each ear was incomplete, and that the air issued
from the mouth, by the Eustachian tube, through an opening in
that membrane, and escaped by the external meatus.

To determine the degree in which the membrana tympani

MDCCC. Xx

154 Mr. Cooper’s Observations on the

had been injured, I passed a probe into each ear, and found that
the membrane on the left side was entirely destroyed ; since
the probe struck against the petrous portion of the temporal
bone, at the interior part of the tympanum, not by passing
through a small opening; for, after an attentive examination, the
space usually occupied by the membrana tympani was found
to be an aperture, without one trace of membrane remaining.

On the right side also, a probe could be passed into the cavity
of the tympanum; but here, by conducting it along the sides of
the meatus, some remains of the circumference of the mem-
brane could be discovered, with a circular opening in its centre,
about the fourth of an inch in diameter.

From such a destruction of this membrane, partial indeed in
one ear, but complete in the other, it might be expected that a
total annihilation of the powers of the organ would have fol-
lowed: but the deafness was inconsiderable. This gentleman,
if his attention were exerted, was capable, when in company, of
hearing whatever was said in the usual tone of conversation ;
and it is worthy of remark, that he could hear with the left ear
better than with the right, though in the left no traces of the
membrana tympani could be perceived.

When attending the anatomical lectures also, he could hear,
even at the most distant part of the theatre, every word that was
delivered ; though, to avoid the regular and constant exertion
which it required, he preferred placing himself near the lec-
turer.

I found, however, that when a note was struck upon the
piano forte, he could hear it only at two thirds of the distance
at which I could hear it myself; and he informed me, that in
a voyage he had made to the East Indies, while others, when

Destruction of the Membrana Tympani. 155

ships were hailed at sea, could catch words with accuracy, his
organ of hearing received only an indistinct impression. But the
most extraordinary circumstance in Mr. P—’s case is, that the
ear was nicely susceptible of musical tones; for he played well
on the flute, and had frequently borne a part in a concert. 1 speak
this, not from his own authority only, but also from that of
his father, who is an excellent judge of music, and plays well
on the violin: he told me, that his son, besides playing on the
flute, sung with much taste, and perfectly in tune. :

The slight degree of deafness of which Mr. P— complained,
was always greatly increased by his catching cold: an effect
which seems to have arisen from the meatus being closed by an
accumulation of the natural secretion of the ear; for it fre-
quently happened to him, after he had been some time deaf
from cold, that a large piece of hardened wax, during a fit of
coughing, was forced from the ear, by the air rushing from the
mouth through the Eustachian tube, and his hearing was in-
stantly restored.

From bathing likewise he suffered considerable inconvenience,
unless his ears were guarded against the water, by cotton being
previously forced into the meatus. When this precaution was
neglected, the water, as he plunged in, by rushing into the inte-
rior parts of the ears, occasioned violent pain, and brought ona
deafness, which continued until the cause was removed, that is,
until the water was discharged: but he had acquired the habit
of removing it, by forcing air from the mouth through the ear.

In a healthy ear, when the meatus auditorius is stopped by
the finger, or is otherwise closed, a noise similar to that of a dis-
tant roaring of the sea is produced: this arises from the air in
the meatus being compressed upon the membrana tympani. In

X 2

156 Mr. Coorer’s Observations on the

the case here described, no such sensation was produced : for, in
My. P’s ear, the air, meeting with no impediment, could suffer
no compression ; since it found a passage, through the open
membrane, to the mouth, by means of the Eustachian tube.

Mr. P— was liable to the sensation commonly called the
teeth being on edge, in the same degree as it exists in others;
and it was produced by similar acute sounds, as by the filing of
a saw, the rubbing of silk, &c. Its occurring in him seems to
disprove the idea which has been entertained of its cause; for
it has been thought, that the close connection of the nerve
called the corda tympani with the membrana tympani, exposed
it to be affected by the motions of the malleus; and that, as it
passes to nerves connected with the teeth, they would suffer
from the vibratory state of the nerve, produced by the agitations
of the membrane. But, in this case, as the membrane was en-
tirely destroyed on that side on which the sensation was pro-
duced, some other explanation must be resorted to; and I see
no reason why this effect should not be referred to that part of
the auditory nerve which lines the labyrinth of the ear, which,
being impressed by acute and disagreeable sounds, would con-
vey the impression to the portio dura of the same nerve, and
to the teeth with which that nerve is connected.

The external ear, though two distinct muscles are inserted
into it, is capable, in its natural state, of little motion; however,
when an organ becomes imperfect, every agent which can be
employed to increase its powers is called into action; and, in
the case here described, the external ear had acquired a distinct
motion upward and backward, which was observable whenever
Mr. P— listened to any thing which he did not distinctly hear.
This power over the muscles was so great, that when desired

Destruction of the Membrana Tympant. 157

to raise the ear, or to draw it backwards, he was capable of
moving it in either direction.

This case is not the only one of this description which has
come under my observation; for another gentleman, Mr. A—,
applied to me under a similar complaint, (but in one ear only,)
proceeding from suppuration, and producing the same effects.
This gentleman has the same power of forcing air through the
imperfect ear; suffers equally from bathing, if the meatus audi-
torius be unprotected; and feels, even from exposure to a stream
of cold air, very considerable pain. The only difference I could
observe was, that in Mr. A’s case, the defect of hearing in the
diseased organ was somewhat greater than in the former; for
though, when his sound ear was closed, he could hear what was
said in a common tone of voice, yet he could not distinguish
the notes of a piano forte at the same distance: a difference
which might have in part arisen from the confused noise which
is always produced by closing the sound ear; or because, as he
heard well on one side, the imperfect ear had remained unem-
ployed, and consequently had been enfeebled by disuse.

From these observations it seems evidently to follow, that
the loss of the membrana tympani in both ears, far from pro-
ducing total deafness, occasions only a slight diminution of the
powers of hearing.

Anatomists who have destroyed this membrane in dogs, have
asserted, that at first the effect on the sense of hearing was
trivial; but that, after the lapse of a few months, a total deafness
ensued. Baron Hatter also has said, that if the membrane of
the tympanum be broken, the person becomes at first hard of
hearing, and afterwards perfectly deaf. But, in these instances,
the destruction must have extended further than the membrana

158 _ Mr. Coorer’s Observations, &c.

tympani; and the labyrinth must have suffered from the removal
of the stapes, and from the consequent discharge of water con-
tained in the cavities of the internal ear; for it has been very
constantly observed, that when all the small bones of the ear
have been discharged, a total deafness has ensued.

It is probable, that in instances in which the membrana tym-
pani is destroyed, the functions of this membrane have been
carried on by the membranes of the fenestra ovalis and fenestra
rotunda: for, as they are placed over the water of the laby-
rinth, they will, when agitated by the impressions of sound,
convey their vibrations to that fluid in a similar manner, though.
in somewhat an inferior degree, to those which are conveyed by
means of the membrana tympani and the small bones which
are attached to it; and thus, in the organ of hearing, each part
is admirably adapted, not only to the purpose for which it is
designed, but also asa provision against accident or disease; so
that, whenever any particular part is destroyed, another is sub-
stituted for it, and the organ, from this depringhen suffers but
little injury in its functions.

It seems that the principal use of the membrana tympani is,
to modify the impressions of sound, and to proportion them to
the powers and expectation of the organ. Mr. P— had lost this
power for a considerable period after the destruction of the
membrane; but, in process of time,.as the external ear acquired
the additional motions I have described, sounds were rendered
stronger or weaker by them. When, therefore, he was addressed
in a whisper, the ear was seen immediately to move; but, when
the tone of voice was louder, it then remained attogeviey mo-
tionless.

Mr. Home's additional Remarks, &c. 159

Some additional Remarks, on the Mode of Hearing in Cases where
the Membrana Tympani bas been destroyed. By EvERARD
Home, Esq. 2

After having communicated to this learned Society, the very
curious facts contained in Mr. CoopEr’s paper, which prove that
the organ of hearing is capable of receiving all the different im-
pressions of sound, when the membrana tympani has been
destroyed, it may not be improper to explain, from the obser-
vations contained in a former paper on this subject, in what
manner this may take place. ©

It is there stated, that any vibrations communicated directly
to the bones of the skull, are as accurately impressed upon
the organ, as through the medium of the membrana tympani.
The office of that membrane is therefore to afford an extended
surface, capable of receiving impressions from the external air,
and of communicating them to the small bones of the ear;
which a membrane would be incapable of doing, unless it had a
power of varying its tension, to adapt it to different vibrations.

In the above cases, in which this membrane, the malleus, and
the incus, had been destroyed, it would appear that the stapes
was acted upon by the air received into the cavity of the tym-
panum, and communicated the impressions immediately to the
internal organ. This not happening for some months after the
membrane was destroyed, probably arose from the inflamma-
tion of the tympanum confining the stapes, and rendering its
vibrations imperfect.

160 Mr. Home’s additional Remarks, &c.

That sounds can be communicated with accuracy by the bones
of the skull, to the internal organ, when received from solid or
liquid substances, has long been well understood.

That the membrana tympani is incapable of perfectly an-
swering this purpose, when sounds are propagated through air,
hasebeen a generally received opinion ; to refute which, was the
object of my former paper. ‘That, in cases in which the mem-
brana tympani has been destroyed, the air is capable of acting
with sufficient force upon the stapes to communicate vibrations
to it, and to produce on the internal organ the necessary effect
for perfect hearing, is completely ascertained by Mr. Cooper’s
observations.

(eu

1X. Experiments and Observations on the Light which is spon-
taneously emitted, with some Degree of Permanency, from
various Bodies. By Nathaniel Hulme, M.D. F. R.S. and 4.5.

Read February 13, 1800.

INTRODUCTION.

"Tue discoveries which have been made with respect to light,
as it proceeds immediately from the sun, are many and im-
portant; but the observations on that species of light which is
spontaneously emitted from various bodies, are not only few in
number, but in general very imperfect. The author is therefore
desirous of drawing the future attention of the philosopher more
particularly to this subject, and of communicating his own ex-
periments and observations upon it, to this learned Society.

By the spontaneous emission of this light, the author wishes to
distinguish it from all kinds of artificial phosphorus; which, as
he apprehends, differ essentially, in some of their properties,
from that light of which he means to treat. And, by its adhesion
to bodies with some degree of permanency, he distinguishes it
from that transient sort of light which is observable in electri-
city, in meteors, and in other lucid emanations. The light whicl
is the subject of this paper, he shall therefore beg leave to dis-
criminate by the name of spontaneous light.

The substances from which such light is emitted, are princi-
pally the following. '

Marine animals, both in a living state,and when deprived of life.
MDCCC, 26

162 Dr. Hutme’s Experiments and Observations

As instances of the first may be mentioned, the shell-fish called
Pholas, the Medusa phosphorea, and various other Mollusca.

When deprived of life, marine fishes in general seem to
abound with this kind of light. The honourable Mr. BoyLe
commonly obtained light, for his use, from the whiting, as
appears from many parts of his works: the author of these
experiments and observations procured his fish light chiefly from
the herring and the mackerel.

The flesh of quadrupeds has also been observed to emit light.
Instances of this are mentioned by Fasricius ab Aquapendente ;
by T. Bartuotin; by Mr. BoyzE; and by Dr. Beatz; for
which, see T. BARTHOLIN, de Luce Animalium, p. 183; Boy.E’s
Works, Vol. III. p. 304; Phil. Trans. Vol. XI. p. 599.

In the class of insects are many which emit light very copi-
ously, particularly several species of Fulgora or Lantern-fly,
and of Lampyris or Glow-worm; also the Scolopendra electrica;
and a species of crab, called Cancer fulgens.

Rotten wood is well known to emit light spontaneously. Peat
earth also has the same property. Of the effects of the latter, a
remarkable instance is related in PLot’s Natural History of Staf-.
fordshire, p. 115.

The place where the following experiments were made, was
a dark wine-vault, which, for distinction’s sake, the author calls
the Jaboratory. The heat of this laboratory varied, throughout
the year, from about 40 degrees of temperature to 64°. The
thermometer made use of was that of FAHRENHEIT.

The weight is always to be supposed that called Troy weight.
The liquid measure employed, was that used for wine in this
country: the ‘ounce containing 8 drams Avoirdupois; and the
pint, 16 ounces,

on the Light emitted from various Bodies, 163

The water used in general for the experiments, was pure
spring water, drawn up from under ground by means of a
pump; and it was always employed cold, unless otherwise ex-
pressed.

SECTION I.

The Quantity of Light emitted by putrescent Animal Substances,
is not in Proportion to the Degree of Putrefaction in such
Substances, as is commonly supposed; but, on the contrary, the
greater the Putrescence, the less 1s the Quantity of Light emitted.

EXPERIMENTS.

Exper.1. Two very fresh herrings were bought in the
morning, and hung up in the laboratory; on examining them
in the evening, they were beginning to be luminous.

_ Exper.2. Three herrings, which were quite fresh, after being
scaled and gutted, were hung up by a string in the laboratory.
The next evening they were become exceedingly luminous in
every part, and much lucid matter had exuded, as it were, upon
their surface, which was easily scraped off by the blunt edge of a
knife; it also adhered to the fingers, or other parts of the body,
when touched; but, as they grew more putrescent, the quantity
of light diminished, and at last was extinguished.

Exper. 3. A single herring, that was perfectly sweet, was
hung up in the laboratory. On the second night, it was co-
vered with light; on the third, not so lucid; on the fourth, less
so; and so on, in proportion to the degree of putrescence.

Exper. 4. Two herrings, somewhat stale, were hung up in
the morning, and at 8 P. M. one of them was pretty lumi-
nous, but the other less so. On the next evening, the former

Y 2

164 Dr. Hutme’s Experiments and Observations

was but slightly luminous, and the latter was dark ; on the suc-
ceeding evening, they were both dark.

Exper. 5. Two mackerels were brought from the market at
1 P. M. which, to the sight and smell, were perfectly sweet and
good. Being then carried into the dark laboratory, and examined,
the one was found to be a little luminous, and the other pretty
much so, especially about its belly.

Exper. 6. A fine fresh mackerel, with a bright eye, was pur-
chased about noon, and placed as usual in the laboratory, the
temperature of which, at that time, was about 54°. At 11 P. M.
this beautiful fish was luminous about the head and upper
parts; and the inside of the mouth, which was wide open, shone

with most brilliant light. The next evening, the whole body of »

the fish was very luminous: on the third night, it was less so;
and on the fourth the light was nearly extinguished.

Exper. 7. \n the forenoon, about ten o'clock, a couple of fine-
looking mackerels were hung up in the laboratory, at the tem-
perature of 56°, and at 10 P. M. they began to shine ih various
parts, the light seeming to proceed from within outwards. On

the second night, they put on a luminous appearance all over

their surface: on the third, the light was not so vivid; and on
the fifth it was almost extinct.

N.B. In experiments of this kind, for the production of light,
the fishes should always be gutted, the roes taken out, and the
scales, if any, carefully removed. As the roes are likewise very
productive of light, they should be preserved.

OBSERVATIONS.

Obs. 1. These experiments clearly prove, that light begins to
be emitted by marine fishes, before any signs of putrefaction

on the Light emitted from various Bodies. 165

appear: they likewise demonstrate, that as soon as a great
degree of putrescence has taken place, the luminous property
of the fishes is destroyed, and the light extinguished.

Obs. 2. In the instance of light proceeding spontaneously
from animal flesh, recorded by AQUAPENDENTE, the flesh emitted
light before any sensible putrescence had taken place, the meat
being hung up in the larder for use. In that also mentioned
by BaRTHOLIN, in 1641, the flesh must have been fresh and
sweet, for it was not intended to be dressed until the next
day. Mr. Boyte, in his report of light issuing from flesh, ex-
pressly says, that neither he, nor any of those who were
about him, could perceive in it any offensive smell, whence to
infer any putrefaction; the meat being judged very fresh, and
well conditioned, and fit to be dressed. And, lastly, Dr.
BEALE, in his account of a luminous neck of veal, says, that
when it was dressed, on February the e7th, some of the
neighbours, who saw it shining, were invited to eat of it, and
all esteemed it as good as they had ever tasted; that a part of
it was kept for February 28th and goth, in which time it lost
nothing of its sweetness. |

Obs. 3. Whenever I wish to obtain a plentiful supply of light.
from fishes, for the purpose of experiments, I always endeavour
to-procure the freshest that can be had: long experience and
frequent disappointments have taught me to adopt such a pre-
caution.

SECTION IL.

The Light bere treated of is a constituent Principle of some
Bodies, particularly of Marine Fishes, and may. be separated
from them, by a peculiar Process ; may be retained, and rendered

166 Dr. Hutme’s Experiments and Observations

permanent for some Time. It seems to be incorporated with their
whole Substance, and to make a Part thereof, in the same
Manner as any other constituent Principle.

EXPERIMENTS.

The Flesh of Herring.*

Exper. 1. A fresh herring was split, or divided longitusialalad
by a knife, into two parts. Then, about four drams of it, being
cut across, were put into a solution, composed of two drams of
Epsom salt or vitriolated magnesia, and two ounces of cold
spring water drawn up by the pump. The liquid was contained
in a wide-mouthed three-ounce phial, which was placed in the
laboratory. Upon carefully examining the liquid, on the second
evening after the process was begun, I could plainly perceive a
lucid ring (for the phial was round) floating at the top of the
liquid, the part below it being dark; but, on shaking the phial,
the whole at once became beautifully luminous, and continued
in that state. On the third evening, the light had again risen to
the top; but the lucid ring appeared less vivid, and, on shaking
the phial as before, the liquid was not so luminous as on the
preceding night.

Exper.2. The same experiment was repeated. On the second
night, the liquid, being agitated, was very luminous; on the third,
not so lucid; and on the fourth the light was extinguished.

Exper. 3. With sea salt or muriated natron half a dram, and
two ounces of water. On the second night, the liquid, when
agitated, was dark; on the third, lucid; on the fourth, very lumi-
nous ; on the fifth, it began to lose light; on the sixth, it con-

¢ The quantity used in each experiment was about four drams.

on the Light emitted from various Bodies. 167

tinued to decrease; and on the seventh it was quite gone. Nei-
ther the liquid, nor the herring, had contracted any putrid smell.
Exper. 4. With sea water two ounces. On the second night,
dark: on the third, fourth, and fifth, luminous; on the sixth,
nearly extinct; and on the seventh, totally. The piece of her-
ring, when taken out and examined, was remarkably sweet.

Roe of Herring.*

Exper. 5. With Epsom salt two drams, and water two
ounces. On the second night, the liquid was pretty luminous ;
on the third and fourth, still luminous; and on the fifth its light
was extinct.

Exper. 6. With GiavuseEr’s salt or vitriolated natron two
drams, to two ounces of water. On the second night, when the
phial was shaken, as usual in all these experiments, the liquid
was pretty luminous; on the third, less so; and on the fourth
the light was scarcely visible.

Exper. 7. With sea water two ounces. On the second night,
dark; on the third, the liquid was moderately luminous; on
the fourth and fifth, it had extracted much light; and on the
seventh it was still shming. After this process, both the roe
and the sea water remained perfectly sweet.

The Flesh of Mackerel.

Exper. 8. With Epsom salt two drams, and water two
ounces. On the second night, the liquid was finely illuminated;
on the third, a similar appearance; on the fourth, a diminution
of light; on the fifth, it continued lucid in a small degree; and
on the sixth the light was extinguished.

* The quantity used in each experiment was about four drams.

168 Dr. Hutme’s Experiments and Observations

Roe of Mackerel.

Exper. 9. With Epsom salt two drams, and water two
ounces. On the second night, the liquid, when agitated, was
exceedingly bright; on the third, the same; and on the fourth
and fifth, still lucid.

The Tadpole.

Exper. 10. it occurred to my mind, in the year 1797, to try
what effect a saline menstruum would have upon the tadpole.
Accordingly, I procured some tadpoles on the 10th of June, and
put six of them into a solution of two drams of GLAuBER’s salt
in two ounces of water. On the 11th, in the evening, the men-
struum was dark; on the 12th, after shaking the phial, I was
agreeably surprised to find it impregnated with light; on the
1gth, the light was so abundant as to float on the top of the
menstruum; on the 14th, the same phenomenon appeared; on
the 15th and 16th, it was still present; on the 17th, the lucid-
ness began to diminish; on the 18th, it was faint; and on the
1gth it had vanished.

Exper. 11. On the 11th of June, six other tadpoles were
dropped into a solution of ene dram of common salt in three
ounces of water. On the 1eth and 13th, the menstruum was
dark ; on the 14th, it had extracted from the tadpoles a very
beautiful bright light; on the 15th, the menstruum was exceed-
ingly luminous; on the 16th and 17th, nearly the same: the
light then gradually faded, so that on the 21st it was merely
visible; and on the ged it disappeared.

Exper. 12. On the 21st of June, the above two experiments
were repeated; when the tadpoles remained in the menstruums

on the Light emitted from vartous Bodies. 169

till the 27th, but no light was emitted. What was the cause of
this failure in these two last experiments ? Was it the ten days’
increased growth of the animal, which was taken from the
same pond, that made the difference ?

Exper. 13. The above experiments were repeated, when the
tadpole had just put on the state of a frog, but without produ-
cing any lucid appearance. ;

Dhe Light is incorperated with the whole Substance of Marine
Fishes.

Exper. 14. A fine fresh herring, being gutted, was. divided
iongitudinally into two parts, both of which were hung up, by
pieces of string, in the laboratory. On the ed night, they were
very lucid on the skinny side, but not on the fleshy or inward
part; on the gd, the fleshy or central parts of the fish, were
thickly covered with a rich azure light; on the 4th, they con-
tinued exceedingly luminous; and on the sth and 6th they
were still lucid. It is surprismg to think what a profusion of,
light was emitted from the interior substance of this single fish.

Exper. 15. A similar experiment was made witha mackerel,
and with similar effects.. These two experiments were frequently
repeated. :

Exper. 16. But the soft-roe, of both the herring and the
mackerel, abounds more with light than even the flesh. When
it is in its most luminous state, which generally happens about
the gd or 4th night, it will sometimes shine so very splendidly,
as to appear like a complete body of light. It is remarkable
that the hard-roe, in general, does not emit so much light as
the soft-roe. When the roes were used, they were laid upon
plates, and deposited in the laboratory.

MDCCC. Z

170 Dr. Hutme’s Experiments and Observations

OBSERVATIONS.

Obs. 1. The above experiments clearly prove, as I apprehend,
that this light is a constituent principle of marine fishes: and that
it is separated, by the menstruum employed on this occasion, in
the same way that the principles of any other body are sepa-
rated, by the menstruum fitted to decompose it. They like-
wise show, that it is not partially but wholly incorporated
with every part of their substance, and makes a part thereof, in
the same manner as any other constituent principle.

Obs. 2. Light is probably the first constituent principle that
escapes, after the death of marine fishes. The experiments of
the first Section teach us that it appears soon after death, even
in fishes which, to the eye, seem quite fresh and sweet ; or, at
least, long before any sensible putrescence takes place. And
we have seen that the flesh and roes, infused in the saline men-
struums, continued to emit light for several days, without un-
dergoing any apparent putrefactive change.

Obs. 3. The experiments likewise render it probable, that no
offensive putrefaction takes place in the sea, after the death of
such myriads of animals as must needs daily perish in the vast
ocean, (quite contrary to what happens on land;) and that the
flesh of marine fishes remains pretty sweet for some time, and
may become wholesome food for many kinds of those which still
remain alive. An eminent instance this, of the wisdom of the
Creator, in the construction of the aqueous part of the world,
which comprehends, by far, the greatest portion of the terra-
queous globe, and is the most replete with animal life !

on the Light emitted from various Bodies. 171

SECTION III.

Some Bodies or Substances have a Power of extinguishing spon~
taneous Light, when it is applied to them.

EXPERIMENTS.

The luminous matter proceeding from the herring and the mac-
kerel, was quickly extinguished when mixed with the following
substances: 1. Water alone. 2. Water impregnated with quick-
lime. 3. Water impregnated with carbonic acid gas. 4. Water
impregnated with hepatic gas. 5. Fermented liquors. 6. Ardent
spirits. 7. Mineral acids, both in a concentrated and diluted
state. 8. Vegetable acids. 9. Fixed and volatile alkalis, when
dissolved in water. 10. Neutral salts: viz. saturated solutions of
Epsom salt, of common salt, and of sal ammoniac. 11. Infusions
of chamomile flowers, of long pepper, and of camphor, made
with boiling-hot water, but not used till quite cool. 12. Pure
honey, if used alone.

SECTION IV.

Other Bodies or Substances have a Power of preserving sponta-
neous Light for some Time, when it is applied to them.

EXPERIMENTS.

Exper. 1. Some luminous matter scraped from the herring,
was mixed with a solution of two drams of Epsom salt in
two ounces of cold pump water: after shaking very well for
some time the phial which contained them, the whole liquid
became richly impregnated with light, and continued shining
above twenty-four hours. This experiment was frequently re-
peated, and with the same effect.

Z2

172 Dr. Hutme’s Experiments and Observations

Exper.2. Two drams of GLavuBEr’s salt and two ounces of
water being mixed with herring light, the solution was thereby
quickly made very lucent, and remained so till the succeeding
evening.

Exper. 3. Mackerel-light, being mixed with two drams of
Rochelle salt or tartarized natron and two ounces of water,
caused the fluid to be very luminous.

Exper. 4. ‘Two drams of soda phosphorata and two ounces
of water, mixed with herring-light, formed a very lucent fluid,
which retained the light for a long time.

Exper. 5. WHerring-light, with one dram of saltpetre or
nitrated kali and two ounces of water, made the solution pretty
luminous. :

Exper. 6. Half a dram of common salt dissolved in two
ounces of water, with the addition of mackerel-light, composed
a very shining mixture, which retained its splendour for the space
of a day or two. The same effect was produced by herring-
light.

Exper. 7. Two ounces of sea water, being agitated with the
light of a mackerel, soon obtained a brilliant illumination. The
sea water preserved its luminousness for several days. The ex-
periment was successfully repeated.

Exper. 8. Two drams of pure honey, that had not been cla-
rified, or exposed to heat, were dissolved in two ounces of water;
and, after the admission of some mackerel-light, and shaking the
phial, the solution was fully impregnated with light, which was
visible the next evening. ;

Exper. 9. Two drams of purified or refined sugar being dis-
solved in two ounces of water, and mixed with the shining
matter of a herring, the fluid acquired a great degree of lucid-

on the Light emitted from various Bodies. 173
ness. The same effect took place when the experiment was
made with soft brown sugar.

N. B. It is almost needless to mention, that the degree of
illumination in these liquids must depend upon the quantity of
lucific matter applied; but, in general, as much as can be
scraped off by the blunt point of a moderately-sized knife, at
a few times, will be sufficient, being assisted by a strong agi-
tation of the containing phial. |

OBSERVATION.

These experiments enable us to take light and diffuse it
through water, so as to render the whole liquid most brilliantly
luminous, or, in other words, to impregnate water with light.
By these means, the light is so extended in its surface, and
combined in such a manner, as to become exceedingly conve-
nient and useful for various other experiments.

SECTION V.

When spontaneous Light’ is extinguished by some Bodies or Sub-
stances, it is not lost, but may be again revived in tts former
Splendour, and that by the most simple Means.

EXPERIMENTS.

Exper. 1. On the 1st of June, 1795, the following expe-

riments were made, to know what was the best proportion of
Epsom salt to water, in order to produce the most luminous
liquid. Some shining matter was taken from a mackerel, and
mixed with a solution of seven drams of the salt in one ounce of
water ; and its light was immediately extinguished. The same
effect ensued, but in a less degree, with a solution of six, and

174, Dr. Huime’s Experiments and Observations

one of five drams. In a solution of two drams, in the satae
quantity of water, the liquid was luminous; but much _more-
so when only one dram of salt was used. Observing the ex-_
tinction of light to take place, as above, in the more saturated

solutions, while the diluted solutions were luminous, it occurred

to me to endeavour to discover what became of the extinguished

light, in the former case, and whether it might not be revived
by dilution. For this purpose, I took the solution of seven drams

of salt in one ounce of water, in which the lucid matter from
a mackerel had been extinguished, and diluted it with six

ounces of cold pump water ; when, to my great astonishment,

light in a moment burst out of darkness, and the whole liquid

became beautifully luminous! This revived light remained above

48 hours, that is, as long as other light in general does, which

has never been extinguished. Hence, it had lost nothing of its

vivid luminous powers by its extinction.

Exper. 2. The last experiment was then reversed. A solu-
tion of one dram of Epsom salt in one ounce of water, was
brilliantly illuminated with mackerel iight. Then, six drams of
the salt were put into this luminous liquid; and, after shaking
the phial very well for a little time, to promote the solution of
the salt, the light was totally extinguished. But the same light
was again recovered, by the addition of six ounces of water.

In this manner, the light may be frequently extinguished, and
as often revived. In one instance, the same light, by a repe-
tition of this method, was made to undergo ten extinctions. -

Exper. 3. A good quantity of herring-light, being mixed
with a solution of four drams of common salt in two ounces of
‘water, was immediately extinguished. Then, fourteen ounces
of cold pump water were added thereto, and the whole liquid

on the Light emitted from various Bodies. 175

was at once finely illuminated. On the next evening it ap-
peared still very lucid; and likewise on the succeeding night.

Exper. 4. The experiment was reversed. Half a dram of the
salt, being dissolved in two ounces of water, had herring-light
mixed therewith, so as to be made very luminous. On the addi-
tion of two drams more of the salt, the lucidness was instantly
destroyed: but the light was again recovered, by pouring eight
ounces of cold water upon the extinguished luminous fluid.
The revived light was very vivid the next evening.

Exper. 5. Two ounces of sea water were illuminated with
mackerel-light, and then extinguished by adding two drams of
common salt. The light was again restored, by diluting the so-
lution with eight ounces of cold spring water.

N.B. If the illuminated liquid be uncommonly brilliant, it
may sometimes require more salt to extinguish the light com-
pletely, than is here specified; in that case, the measure of
water for dilution, must be always calculated in exact propor-
tion to the weight of salt employed.

SECTION VI.
Spontaneous Light is rendered more vivid by Motion.

EXPERIMENTS.

Exper. 1. A quantity of illuminated liquid was poured into a
broad vessel, which was placed in the laboratory. The next
evening, on examination, it appeared to be quite dark. Buta
finger, or rod, being drawn through it, was followed by a lumi-
nous line.

Exper. 2. A phial, containing a pretty large portion of liquid
impregnated with light, having been at rest a number of hours,

176 Dr. Hutme’s Experiments and Observations

the liquid seemed to have lost its luminous quality, except a
little glimmer floating at the top. It was then gently moved,
and the light diffused itself gradually through the whole liquid:
on agitation, the lucidness was much increased; and, the brisker
the motion, the more vivid was the illumination.

SECTION VII.

Spontaneous Light is not accompanied with any Degree of sensible
Feat, to be discovered by a Thermometer.

EXPERIMENTS.

Exper. 1. A luminous herring, and another that was quite
fresh and not luminous, were placed for a considerable time in the
same degree of temperature. A thermometer was then applied
to each of them, but no difference of heat could be discovered.

Exper. 2. The soft roe of a herring, in an exceedingly lucid
state, and a thermometer, were kept together for some time in
the laboratory. The roe was then put upon the bulb of the
thermometer, without affecting it.

Exper. 3. A mackerel, which shone with very brilliant light,
was also put to the test of a thermometer, but the instrument
remained stationary. |

Exper. 4. The bulb of a thermometer was surrounded by
many small pieces of shining wood, uncommonly luminous,
which were kept in that situation for some time; but the light
made no alteration upon the thermometer.

Exper. 5. Uluminated liquids, and spring water, being kept
together in the laboratory, always preserved the same degree of
temperature,

4

-on the Light emitted from various Bodies. 177

SECTION VIII.
The Effects of Cold on spontaneous Light.

EXPERIMENTS.

The Light of Fishes.

Exper. 1. Five small gallipots, containing three pieces of soft-
roe of herring, and two of the herring itself, all very luminous,
were placed in a frigorific mixture, composed of snow and sea-
salt; and, in about an hour and a half, the light was quite extinct,
and the bodies totally frozen. The gallipots were then removed
into a vessel of cold water, that their contents might be gradu-
ally thawed; which being done, they all recovered their pristine
luminous state. ‘The pieces were afterwards observed to shine
during three succeeding nights.

Exper..2. A small phial, containing three or four drams of
liquid impregnated with light, was placed in a frigorific mixture.
As the liquid froze, its lucidness gradually diminished; and, when
it was quite congealed, the light perfectly disappeared. The
phial was then taken out, and put into cold water, at about 49°
temperature, that the ice might be gradually liquefied; and,
when that was accomplished, the whole fluid became as lumi-
nous as before.

The Light of shining Wood.

Exper. 3. A fragment of shining wood was put into a small
wide-mouthed phial, which was plunged into a frigorific mix-
ture. As the cold affected the wood, the light gradually faded,

MDCCC. A a

178 Dr. Hutme’s Experiments and Observations

and at last was totally imperceptible. The phial was then taker
out, and placed in water at about 62°; by this change of
temperature, the frozen wood gradually thawed, and then re-
gained its former lustre.

The Light of Glow-worms.

Exper. 4. A small phial, containing a luminous dead glow-
worm, was exposed to the cold of the frigorific mixture; as
the coldness penetrated the phial, the light diminished, and at
length was totally extinct. But, by placing the phial in water
at about 62°, the glowing property of the insect soon returned.
In this experiment, the glow-worm was evidently congealed ;
for it adhered to the side of the glass, and was covered with a
hoar-frost. This experiment was frequently repeated, and with

the same result.

OBSERVATION.

By these experiments we learn, that cold extinguishes spon-
taneous light in a temporary manner, but not durably, as the
substances of the third Section do; because the light revived
again in its full splendour, as soon as it was exposed to a mo-
derate degree of temperature.

on the Light emitied from various Bodies. 179

SECTION IX.
The Effects of Heat on spontaneous Light.

EXPERIMENTS.

The Light of Fishes.

Exper. 1. One side of a luminous herring was held before the
fire, for a short space of time, but so as to receive its heat very
strongly. It was then conveyed into the laboratory ; when
that side which had been exposed to the fire was found quite
dark, but the other continued still luminous. The fish was
preserved till the next evening, but the extinguished light did
not re-appear,

Exper. 2. A whole herring, finely shining, was thrown into
a quantity of boiling-hot water, and the light was immediately
extinguished: after keeping it there for some time, it was taken
out, but the light did not revive.

The Light of shining Wood.

Exper. 3. A piece of shining wood, its light being very faint,
was put into tepid water at about 90 degrees of temperature,
and it became in a short time much more lucid. Another piece,
at 96°, was rendered beautifully luminous.

Exper. 4. A pretty thick piece of shining wood was put into
a gallipot, and sunk under water by means of a weight, toge-
ther with a thermometer, at the temperature of 64°. Boiling-hot
water was then added by spoonfuls; and the light, at first, was
rendered much more vivid, but soon after began to decrease,
and was apparently extinct at about 110°, I say apparently, be-

Aa 2

180 Dr. Hutme’s Experiments and Observations

cause on the next evening the light had somewhat revived;
which shows, that the heat of 110° was not sufficient to ex-
tinguish totally all the light inherent in this piece of wood.

Exper. 5. Finding that 110 degrees of heat did not
wholly extinguish the light of shining wood, a good many
fragments, of different sizes, were then submitted to the power
of boiling water, and detained therein for some time, in order
that the heat might penetrate them thoroughly. The effect was,
that the light became quickly extinct, and did not, as before, re-
appear on the following evening.

The Light of Glow-worms.

Exper. 6. A dead shining glow-worm was put upon two
ounces of water, contained in a wide-mouthed phial, at the tem-
perature of 58°. The phial was then sunk, about two or three
inches deep, in boiling-hot water; and, as the heat communicated
itself to the contents of the phial, the light of the glow-worm
became much more vivid. |

Exper. 7. Another lucid dead glow-worm was put into warm,
water, at 114°, to see if that degree of heat would extinguish the
light; but, on the contrary, its glowing property was aug-
mented. All the water was then poured off, yet the insect con-
tinued to shine for some length of time.

Exper. 8. The effect of that heat which is obtained from dry
solid bodies by friction, was next tried upon the light of the
glow-worm. Two living glow-worms were put into a one-
ounce phial, with a glass stopple; and, though they were per-
fectly dark at the time, yet, if the phial was briskly rubbed with
a silken or linen handkerchief, till it became pretty warm, it
seldom failed to make them display their light very finely.

on the Light emitted from various Bodies. 181

This experiment was very frequently repeated. It had the same
illuminating effect upon the light of a dead glow-worm.

Exper.g. The complete influence of 212 degrees of heat was
now applied to the light of a glow-worm, by pouring upon
one when dead, but in a luminous state, some boiling water.
Its light was instantly extinguished thereby, and did not revive.
The experiment was repeated, and with the same result.

Any of the saline Solutions mentioned in the fourth Section, being
impregnated with luminous Matter, and left some Time at rest,
are rendered more lucid by a moderate Degree of Heat.

Exper.1o. A quantity of illuminated solution was deposited
in the laboratory. The next evening, when it was examined,
it appeared in a manner quite dark; but, by putting the phial
which contained it into hot water, the light revived, and was
soon rendered exceedingly vivid.

Exper. 11. About a pint of solution impregnated with light,
had become obscure; by time and rest, as is the nature of this
mixture. Such a quantity of boiling-hot water was then added
to it, as only to give it a small degree of warmth, and it quickly
caused it to appear luminous.

Exper. 12. Uluminated liquid, to the quantity of four ounces,
was placed in the iaboratory until the next evening, when it
had become almost dark. One spoonful of boiling-hot water
being put into it, the light re-appeared; and, by means of two
more, it was rendered considerably lucid.

Their Light 1s extinguished by a great Degree of Heat.
Exper. 13. Some boiling water being poured upon three or
four ounces of illuminated liquid, in an earthen vessel, the light
was immediately extinguished; and, though afterwards kept a

182 Dr. Hutme’s Experiments and Observations

considerable time for inspection, and often agitated, to stir up the
hidden light, yet no remains of any shining property could be
perceived. This experiment was frequently repeated, and always
with the same result.

Exper. 14. Four ounces of very luminous liquid, together
with a thermometer, were put into a small earthen vessel, glazed
white, the better to reflect light. Boiling-hot water was then
added, by spoonfuls at a time, and by slow degrees. The first
few spoonfuls made it considerably more lucid; and then, by
adding more, the light began to fade, and at length was gradually
extinguished. This effect took place, in one instance, when the
liquid was heated to 96°; in another, to 98°; and in a third,
to 100°. Hence, this species of light, when thus united with
water, seems to begin to be extinguished at from 96 to 100
degrees of heat. This is a very elegant and pleasing method, of
knowing how much heat is required to extinguish the light;
because it measures it exactly, provided the hot water be added
in small quantities, and by slow degrees, as above directed.
To prevent the possibility of any light reviving after an ex-
periment of this kind, would require a much greater heat than
that of 100°. The intention of the present experiments was_
only to show, that all light may be apparently extinguished, at
so low a degree of temperature as from 96° to 100°.

Exper.15. A phial of an ounce and a half was filled with
some very luminous liquid, but not corked. It was then sus-
pended by a string, in a quart of boiling-hot water contained in
a white earthen mug, and the light was wholly extinguished
in about three or four minutes. After this, the phial was kept in
the water some time longer, was then taken out to cool, and well
shaken, but the light did not revive. It was examined the next
day, and agitated again, but no luminous appearance could be

on the Light emitted from various Bodies. 183

discovered; a proof that all the light had been totally extin-
guished by the power of heat.

If much Heat be applied to the Bottom of a Tube filled with illu-
minated Liquid, which has been some Time at rest, the Light
will descend in luminous Streams, from the Top of the Tube
to the Bottom, and be gradually extinguished.

Exper. 16. A glass cylindrical tube, closed at one end, being
9 inches long, with a bore of 154 inch, when used, was put into
a gallipot 31 inches deep, and 31 wide, which held about 12
ounces of boiling water, and was placed in another larger
vessel, to receive the overflowing water upon the immersion of
the tube. The tube being filled over night with some very lumi-
nous liquid, was placed in the laboratory until the next evening.
The light had then ascended plentifully to the top of the fluid,
(the rest being dark, ) and, taking the circular shape of the tube,
formed a very lucid rmg. The vessels with the boiling-hot water
were then carried into the dark laboratory; and the tube being
gently and carefully placed (without shaking) in the gallipot,
the light was, generally in about half a minute, seen plainly to
descend in streams from the top to the bottom, illuminating the
whole fluid in its descent in a beautiful manner, and then was
gradually extinguished. ‘The extinction of the light began at
the top of the tube, and ended at the bottom.

Exper. 17. The experiment was also made with a tube 19
inches high, + an inch in bore, having several curvatures, and
sealed hermetically at its lower end. Both the extremities were
made straight for a few inches; the one to be immersed in the
water, and the other to prevent the liquid running out. The
luminous ring being formed as above mentioned, the tube was

184, Dr. Hutme’s Experiments and Observations

put into the gallipot of boiling-hot water; and, in a short time,
the light began to descend from the top, and came waving
down, in a pleasing manner, to the bottom of the tube in the
hot water, and then was by degrees extinguished. The whole
length of the tube, including the curvatures, was 26 inches.

The most eligible solutions for this curious experiment, are
those made with Epsom salt, GLAUBER’s salt, sea-salt, and sal
ammoniac: if either of the two former be used, the proper
proportion is, one dram of salt to each ounce of water; if either _
of the two latter, 15 grains to each ounce of water will be suf-
ficient.

N. B. The experimentalist, before he views the descent of
the light in the tube, should always remain in the dark for
some little time, in order to get rid of all extraneous light ad-
hering to the organs of vision, and to accommodate the eye to

darkness.

SECTION X.

The Effects of the human Body, and of the animal Fluids, upon
spontaneous Light.

The living Body.

Exper. 1. On touching the luminous matter of fishes, the
light adhered to the fingers and different parts of the hands;
remained very lucid for some little time, and then gradually dis-
appeared. But the same kind of matter being applied to pieces
of woo:!, stone, and the like, of the same temperature as the
laboratory, continued luminous on these substances for many
hours.

on the Light emitted from various Bodies. 185

Exper.2. A piece of red blotting-paper, about one inch
square, and four times doubled, was finely illuminated by
matter from a herring, and applied to the upper part of the
inside of the thigh. After the expiration of 15 or 20 minutes, it
was taken off; and, on examination, the light was quite extin-
guished. The experiment was repeated several times, and with
the same effect. Another piece of the like paper was illumi-
nated at the same time, and placed in the laboratory; where it
retained its light above 48 hours,

Exper. 3. A piece of shining wood was placed upon the palm
of the hand, and inclosed therein for some time; on inspection,
it was found to be more lucid than before. Many trials of
this kind were made, with the like success.

Exper. 4. A dead glow-worm, being but slightly luminous,
was breathed upon several times; and its light increased hoth
in magnitude and brightness. The experiment was frequently
repeated, with the same result.

Animal Fluids.

Blood.

Exper. 5. A person having received a contusion, but other-
wise in health, was bled. The next day, some herring-light was
mixed with about two ounces of the crassamentum or red coa-
gulated part of the blood, by stirring them well together with
a knife: it caused it to be slightly luminous, but the light was
not of long duration. Nearly the same result followed the mix-
ture of lucid matter with the recent crassamentum of persons

@. . . ;
labouring under inflammatory diseases, as the pleurisy and
rheumatism.

MDCCC. Bb

186 Dr. Hutme’s Experiments and Observations

Exper. 6. But, when mixed with crassamentum that hadbeen
kept for some time, and become black and somewhat offensive
to the smell, the light seemed to be more quickly extinguished.

Exper. '7._ A singular phenomenon happened several times,
on mixing fish-light with putrescent bloody serum. It would
not incorporate, but was ejected in globules, like quicksilver
when rubbed with any unctuous substance, and afterwards
adhered to the side of the vessel in which the mixture was made,
in the form of a lucid ring.

Exper.8. The luminous matter of a herring was mixed
with about two ounces of pure serum, from the healthy subject
of the 5th experiment: it soon became finely illuminated, and
retained its shining appearance for a long time, whenever it
was stirred or agitated. |

Exper. 9. The recent serum, drawn from patients afflicted
with inflammatory complaints, was illuminated pretty much in
the same manner as in the 8th experiment; and often retained
light above 48 hours.

Urine.

Exper. 10. Mackerel-light being mixed, by strong agitation,
with some fresh urine from a healthy person, a glimpse of light
was retained at first, and then was gradually extinguished. But
stale and pungent urine, being incorporated with luminous
matter, had a still greater extinguishing effect.

Bile.

Exper.11. Some bile, taken from a person who died of a
suppression of urine, had herring-light mixed with it, which
soon became extinct. Another trial was made, with a different
bile, and with the same result.

on the Light emitted from various Bodies. 187

Milk.

Exper. 12. Human milk not being easily obtained, some
mackerel-light was incorporated, by agitation, with two ounces
of fresh cow’s milk, which was thereby rendered finely lumi-
nous, and continued shining above 24, hours. Fresh cream also
retained some light; though it was not so visible as with milk,
owing probably to its thickness. But, when either milk or
cream turn sour, they contract a very extinguishing property.
A quart-of milk was kept five days, in a moderately cool place,
in the month of June; by that time, it was changed into a
mixture somewhat resembling curds and whey, that is, into a
soft smooth coagulated part, and a very thin one, both which
were acidulous. Some fine mackerel-light was mixed with two

ounces of each of them, in separate phials, and they extinguished
it immediately.

Bb 2

£ 188 J

X. Account of a Series of Experiments, undertaken with the View
of decomposing the Muriatic Acid. By Mr. William Henry.
Communicated by the Right Hon. Sir Joseph Banks, Bart.
P.R.S.

Read February 27, 1800.

Moora chemistry, notwithstanding its rapid advancement

during the few last years, still presents to its cultivators several |

interesting objects, both of analytic and synthetic inquiry.
Among the former, the decomposition of the muriatic and of
certain other acids, holds a distinguished place; for our curio-
sity respecting the nature of these bodies, is strongly excited,
by the influence which the discovery would have on the general
doctrines of chemical science, as well as on the explanation of
individual facts. The theory of the formation of acids, for ex-
ample, one of the most important parts of the new system of
chemistry, must. be regarded as incomplete, and liable to sub-
version, till the individual acids now alluded to have been
resolved into their constituent principles. To the best of my
knowledge, however, we are not in possession of a single fact
that gives the smallest insight into the constitution of the
muriatic acid; and the attempts to effect its analysis, can only
therefore be directed by the analogy of the decomposition of

other bodies, which, from similarity of character, are arranged

in the same class.
One of the first objects, in the analysis of a compound body,

~

Mr. Henry’s Account of Experiments, &c. 189

should be its complete separation from all other substances,
which, by their presence, may tend to introduce uncertainty
into the results of the processes that are employed. But it is
seldom that a simplicity so desirable can be attained in the ob-
jects of chemical research; for, agreeably to a known law of
affinity, the last portions of any substance are separated with
peculiar difficulty; the force of attraction appearing to increase,
as we recede from the point of saturation. In a liquid state, the
muriatic acid is a totally unfit subject for analytic experiment;
for, in the strongest form under which it can be procured, it still
contains a large proportion of water. This watery portion, be-
sides the complexity which it introduces into the results of
experiments, prevents any combustible substance that may be
applied, from acting on the truly acid part; because that class
of bodies, having less difficulty in attracting oxygen from the
water than from the acid, will necessarily take it from the
former source. The state of gas, therefore, is the only one in
which the muriatic acid can become a proper object of analysis.

In the series of experiments on this gas, which I am now
about to describe, 1 employed the electric fluid, as an agent
much preferable to artificial heat. This mode of operating
enables us to confine accurately the gases submitted to experi-
ment; the phznomena that occur during the process, may be
distinctly observed; and the comparison of the products, with
the original gases, may be instituted with great exactness.
The action of the electric fluid itself, as a decomponent, is ex-
tremely powerful; for it is capable of separating from each other,
the constituent parts of water, of the nitric and sulphuric acids,
of the volatile alkali, of nitrous gas, and of several other
bodies, whose components are strongly united. I began, there-

199 Mr. HEnRy’s Account of Experiments

fore, with examining attentively the effects of the electric fluid

on the muriatic acid gas, without admixture.*

SECTION I.
On the Effects of Electricity on Muriatic Acid Gas.

\

When strong electrical shocks were passed through a portion
of muriatic acid gas, confined in a glass tube over mercury, the
following appearances took place. The bulk of the gas, after 20
or 30 shocks, was considerably diminished; and a white deposit
appeared on the inner surface of the tube, which considerably
obscured its transparency. In some instances, both the con-
traction and deposit were much more remarkable than in others.
The gas which issued from muriate of soda, soon after the affu-
sion of sulphuric acid, and while the charge was yet warm,
exhibited these appearances in an eminent degree. Of this gas,
307 measures were reduced, by 20 shocks, to 227, or were con-
tracted nearly one-fourth. Gas from the same materials, after
they had continued working for some hours, was diminished, by
similar treatment, only about a twelfth. These effects, therefore,
it seemed probable, depended in some measure on the presence

of moisture; and I accordingly found, that muriatic acid gas,

after more than a week’s exposure to muriate of lime, brought
into contact with it immediately after cooling from a state of

* The gases submitted to the action of electricity, in the following experiments,
were confined in straight glass tubes of various diameters, armed at the sealed end with
a conductor of gold, or of platina, but generally of the latter metal. ‘The shocks were
as strong as could be given without breaking the tubes, which, notwithstanding every
precaution, were often shattered by the force of the explosion. Each measure of gas

is equal to the bulk occupied by a grain of mercury. “/>

; are ah

:
f
7
;

for decomposing the Muriaitc Acid. 191

fusion, was scarcely diminished at all; and that the deposit,
though it still occurred, was less copious in quantity. This
deposit was not, like corrosive sublimate, soluble in water; but
had every property of the less saturated salt, calomel.

The mercury by which the muriatic acid was confined, was
therefore evidently oxidated; and, to the combination of a part
of the gas with the oxide thus produced, the diminution of bulk
was doubtless to be ascribed. But it was uncertain from whence
this oxygen was derived. It might either result from the de-
composition of the acid gas, or of the water chemically com-
bined with it. The following experiments were therefore made,
to determine this point.

Experiment 1. Through 1457 measures of muriatic acid gas, ()° 2/

goo electrical shocks were passed. There remained, after the
admission of water, 100 measures of permanent gas, (or not
quite 7 from each hundred of the original gas,) which, on trial,
appeared to be purely hydrogenous.

Exper. 2. Of the gas, dried by muriate of lime, 176 measures
received 120 shocks. ‘The residue of hydrogenous gas amounted
to 11 measures, or rather more than 6 per cent.

These experiments, and other similar ones, made on compa-
rative portions of muriatic acid gas, in its recent state, and after
exposure to muriate of lime, convinced me that it was impos-
sible, by this method, wholly to deprive the muriatic gas of
water. ‘The recent gas, however, when electrified in smaller
quantity than in experiment 1, gave a larger proportion of hy-
drogenous gas ; which shews, that some portion of its moisture
was removed, by exposure to muriate of lime. In order, if pos-
. Sible, to procure the gas perfectly dry, another mode of preparing
it was resorted to. Alum and common salt were first well

192 Mr. Henry’s Account of Experiments

calcined, separately, to expel their water of crystallization, and,
being then mixed, were distilled together in an earthen retort.
The gas proceeding from these materials, was received over
dry mercury; but, though only the last portion that came over
was reserved for experiment, it still, after the usual electriza-
tion, afforded a product of hydrogenous gas.

In the course of the preceding experiments, I observed that
the diminution of the muriatic acid gas stopped always at a cer-
tain point, beyond which it could not be carried by continuing
the shocks. Gas also, which had been thus treated, when trans-
ferred to another tube, and again electrified, did not exhibit any
further deposit. It became interesting, therefore, to know, whe-
ther the production of hydrogenous gas had a similar limitation ;
because, the decision of this question would go far towards ascer-
taining its source. If the evolved hydrogenous gas arose from
the decomposition of the acid, it might be expected to be pro-
duced, as long as any acid remained undecomposed. But, if
water were the origin of this gas, it would cease to be evolved,
when the whole of the water contained in the gas had been
resolved into its constituent principles.

Experiments 3 and 4. Into two separate tubes, I passed known
quantities of muriatic acid gas. Through the one portion, 200
discharges were taken; and through the other, 400. On com-
paring the quantities of hydrogenous gas produced, it proved to
bear exactly the same proportion, in each tube, to the gas origi-
nally submitted to experiment. Hence it may be inferred, that
the hydrogenous gas, evolved by electrifying the muriatic acid,
has its origin, not from the acid, but from the water which is
intimately attached to it. The agency of the electric fluid ap-
pears also, from the following experiments, to be exerted, not

jor decomposing the Muriatic Acid, 193

only in disuniting the elements of water, but in promoting the
union of the evolved oxygen with muriatic acid.

Exper. 5. A mixture of common air and muriatic acid gas,
in the proportion of 143 of the former to 116 of the latter, was
rapidly diminished by electrical shocks; 30 of which reduced
the whole to 111.* The remainder consisted of muriatic acid
and azotic gases, with a small proportion of oxygenous gas. The
deposit formed on the tube was of the same kind as before, but
much more abundant.

Exper.6. ‘The same appearances were occasioned, much more
remarkably, by electrifying muriatic acid with oxygenous gas ;
and the contraction continued, till the mercury rose so as
to touch the extremity of the platina conductor. At each ex-
plosion, a dense white cloud was seen in the tube, which soon
settled on its inner surface, and was of exactly the same che-
mical composition as the one already described. Nitrous gas
and muriatic gas, when electrified together, underwent a similar
change. |

In order to ascertain whether the mercury by which the
gases were confined, in the above experiments, had any influ-
ence on their results, they were repeated in an instrument
made, purposely for the occasion, by Mr. CurHsertson, of
London. It consisted of a glass tube, ground at each end, with
the view of receiving two stoppers, each perforated with platina
wire, which projected into the cavity of the tube. When the
stoppers were in their places, the extremities of the wires were

* This experiment suggests an additional reason, to that already given, for the
greater diminution of the first, than of the subsequent portions of muriatic acid gas;
for the former may be presumed to have been much more adulterated than the latter,
with the atmospherical air of the vessels.

MDCCC. Ce

194 Mr. Henry’s Account of Experiments

at the distance of about half an inch; and, by properly disposing
the apparatus, electrical shocks might be passed, through any
gas or mixture of gases, with the contact only of glass and
platina.

Exper. 7. In this tube I electrified the muriatic acid gas, and
then admitted to it an infusion of litmus. The sudden destruc-
tion of its colour evinced the formation of oxygenated muriatic
acid. Not the smallest deposit appeared on the tube.

Experiments 8 and g. The same phznomenon took place,
when an infusion of litmus was brought into contact with a
mixture of common air and muriatic acid, and of oxygenous gas
and muriatic acid, after electrization in this instrument; oxyge-
nated muriatic acid being produced in both cases.

The above facts prove, that the combination of oxygen with
muriatic acid, in these experiments, is not occasioned by a pre-
disposing affinity in the mercury to combine with oxygenated
muriatic acid; but that the electric fluid serves actually as an
intermedium, in combining the muriatic acid with oxygen.

-From the relation of these experiments it appears, that not
the smallest progress had been made by them, towards the de-
composition of the muriatic acid. I resolved, therefore, to
attempt its analysis, in a similar manner, with the aid of com-
bustible gases.

f

SECTION II.
Effects of electrifying the Muriatic Acid Gas with inflammable
Substances.

In a memoir read before the Royal Society, and inserted in
their Transactions for 1797, I have shewn, that when electrical

for decomposing the Muriatic Acid. 195

shocks are passed repeatedly through a confined portion of car-
bonated hydrogenous gas, the water held in solution by the
gas, is decomposed by the carbon, which forms a constituent
part of it; that carbonic acid is formed; and an addition made,
of hydrogenous gas. Hence, the bulk of the carbonated hydro-
gen gas is considerably enlarged by this process ; which shews,
by its results, that the affinity of carbon for oxygen, is rendered
‘much more powerful and efficient by the electric fluid. I have
since found, that other oxygenated substances are decomposed,
by electrifying them with carbonated hydrogen gas. Nitrous
gas, for example, is speedily destroyed by this process, and
carbonic acid and azotic gases are obtained.

Every attempt to decompose the muriatic acid, must be
founded on the presumption-that it is an oxygenated substance;
and those bodies promise to be the most successful agents, that
possess a strong affinity for oxygen. Now, of all known bodies,
charcoal most strongly attracts oxygen ; and I have, therefore,
repeatedly attempted the destruction of this acid, by passing it
over red-hot charcoal. But, in a series of experiments, which I
made some time since, with this view, in conjunction with Mr.
Rupp, we soon found reason to be dissatisfied with the difficulty
and uncertainty of this process. An immense production of
hydrogenous gas took place; but it was not easy to determine
whether it had its origin from real acid, or from water. Our
experiments, however, though insufficient to furnish decisive
proof, induced us to believe that it had the latter origin.

It next occurred to me, that the comparative affinities of the
muriatic radical, whatever it may be, and of charcoal, for oxygen,
would be elegantly and satisfactorily ascertained, by electrifying
together the carbonated hydrogen and muriatic gases. If the

Ci e.2

196 Mr. Henry’s Account of Experiments

muriatic acid be capable of decomposition by carbon, it might
be expected to be destroyed by this process; and the exact
quantity of acid decomposed, and the nature and quantity of
the products, would thus be easily determined. I electrified,
therefore, the muriatic acid and carbonated hydrogen gases,
with the most scrupulous attention to the phenomena and re-
sults. That the electric fluid might not be misapplied, in decom-
posing the water of the carbonated hydrogen gas, it was kept
more than:a week, before use, over quick lime, introduced to it

while yet hot. .

Exper. 10. Of this carbonated hydrogenous gas, 186 mea-
sures were expanded, by 130 shocks, to 211; that is, the gas was
increased about + its bulk.

Exper. 11. Of the same gas, 84, measures were mixed with
116 of muriatic acid gas, dried by muriate of lime. By 120
shocks, the mixture was a little dilated. After the admission of
a drop or two of water, there remained 91 measures; 7. e. the
addition of permanent gas was 7 measures, or about as much as
might have been expected from the muriatic gas alone. —

Exper. 12. Eighty-three measures of dry carbonated hydro-
genous gas, with 89 of muriatic acid gas, received 200 shocks.
The permanent residue, after the admission of water, was 101
measures: the addition, therefore, amounted to 18. Of the
added 18, 6 may be accounted for by the decomposition of the
water of the muriatic gas, and 10 by that of the carbonated
hydrogenous gas. There remain, therefore, only 2 measures
that can be supposed to be produced from the muriatic acid gas;
a quantity too small to afford grounds for supposing them to
arise from decomposed acid.

for decomposing the Muriatic Acid. 197

Exper. 13. Dry carbonated hydrogenous gas 132 measures,

mixed with dry muriatic gas - 108
24,0
by 200 shocks, expanded to - 268

Part of this gas was then transferred to another tube, and the
proportion of permanent gas ascertained. ‘Through the remain-
der, 150 additional shocks were passed, before the amount of
the gas thus evolved was determined. In both, it bore exactly
the same proportion to the original gas; which shews, that by
continuing the electrization, no further effects were produced.

A great variety of similar experiments convinced me, that by
electrifying together the carbonated hydrogenous and mu-
riatic gases, not the smallest progress was made towards the
decomposition of the latter. All that was thus effected, consisted
in the decomposition of the water of the two gases, by the car-
bon of the combustible gas; and, when this was completely
accomplished, no further effect ensued from continuing the
electrization. The generation of carbonic acid was proved, by
the following experiment. _ :

_ Exper. 14. To a mixture of carbonated hydrogen and mu-
riatic gases, after having received above 100 shocks, a drop of
water was admitted, which absorbed the muriatic acid. The
liquid was then taken up by blotting-paper ; and the residuary
gas, being transferred into another tube, was brought into
contact with a solution of pure barytic earth. The precipitation
of this solution, evinced the presence of carbonic acid.

It was desirable, however, that the effects should be ascer=
tained, of electrifying together pure muriatic acid and pure. car-
bonated hydrogenous gas, both perfectly free from water. Now,

198 Mr. Henry’s Account of Experiments

from the experiments related in the first Section, it appears
highly probable, that a complete purification from moisture is
produced, in both gases, by the action of the electric fluid; all
the water they before contained being thus decomposed. In the
following experiments, therefore, the two gases were separately
electrified, before they were submitted to this process conjointly.

Exper. 15.''To a portion of muriatic acid, diminished by the
action of electricity from 144 to 121 measures, 27 measures of
carbonated hydrogenous gas, expanded as far as possible, were
added, and 200 shocks passed through the mixture. The addi-
tion of permanent gas amounted to 14, measures; 10 of which
may be traced to the muriatic acid, and were evolved by its
separate electrization. The remaining 4, measures, which remain
to be accounted for, are too small a quantity to be ascribed to
the decomposition of the acid.

Exper. 16. To a quantity of carbonated hydrogenous gas,
which had received 400 shocks, and occupied the space of 212
“measures, I added 299 of muriatic acid, through which 200
shocks had previously been passed. The electrization of the
mixture was next continued, till 800 discharges had taken place.
On examining the mixture of gases, during this operation, no
change whatever took place; and, after its close, no more
muriatic acid had disappeared, than would have been deficient
after the first electrization ; nor was there any further produc-
tion of permanent gas.

Exper. 17. The same result was obtained, by electrifying
together 280 measures of carbonated hydrogenous gas, pre-
viously expanded by 600 shocks, and 114, of muriatic acid, after
400 shocks. ‘The additional discharge, through this mixture,

~

|
|
.

for decomposing the Muriatic Acid. 199

of 1000 shocks, did not evince the smallest progress towards
the decomposition of the muriatic acid.

Exper. 18. In the naturally moist state of these gases, it
follows, from the 14th experiment, that carbonic acid is pro-
duced by electrifying them in conjunction. It appeared to me
of some importance to ascertain whether, after a previous
decomposition of their moisture, carbonic acid would continue
to be generated. But the electrified carbonated hydrogenous gas:
itself contains carbonic acid, which, unless removed, would
render the result of the experiment undecisive. This was accom
plished by passing up, to a portion of electrified gas, a bubble
“or two of dry ammoniacal gas, which, uniting with the carbonic
acid, would condense any portion of it that might be present.
The remainder was transferred into another tube; and, to this
carbonated hydrogenous gas, perfectly deprived both of moisture
and carbonic acid, muriatic acid gas, previously electrified, was
added, and electrical shocks were passed through the mixture. A
drop of water was then admitted; and the residuary gas, after
having been dried, was transferred into another tube. On
passing up barytic water, not the smallest trace of carbonic acid
could be discovered. |

From the preceding experiments, the following conclusions
may be deduced.

1. The muriatic acid gas, in the driest state in which it can
be procured, still contains a portion of water. From a calcula-
tion founded on the experiments described in the first section,
the grounds of which are too obvious to require being stated, it
follows, that 100 cubical inches of muriatic gas, after exposure
to muriate of lime, still hold in combination 1.4 grain of water.

2. When electrical shocks are passed through this gas, the

200 Mr. Henry’s Account of Experiments

watery portion is decomposed. The hydrogen of the water,
uniting with the electric matter, constitutes hydrogenous gas,
and the oxygen unites with the muriatic acid; which last, acting
on the mercury, composes muriate of mercury.

3. The electric fluid serves as an intermedium, in combining
oxygen with muriatic acid.

4. The really acid portion of muriatic gas does not sustain
any decomposition by the action of electricity.

5. When electric shocks are passed through a mixture of
carbonated hydrogen and muriatic acid gases, the water held
in solutien by these gases, is decomposed by the carbon of the
compound inflammable gas; and carbonic acid and hydrogenous
gases are the result.

6. When all the water of the two gases has been decomposed,
no effect ensues from continuing the electrization; or, if the
water of each gas has been previously destroyed, by electrifying
them separately, no further effect ensues from electrifying them
conjointly.

7. Since therefore carbon, though placed under the most
favourable circumstances for abstracting from the muriatic acid,
and combining with, its oxygen, evinces no such tendency, it
may be inferred, that if the muriatic acid be an oxygenated
substance, its radical has a stronger affinity for oxygen than

charcoal possesses.

Though the first impressions excited in my mind by the total
failure of the above experiments, in accomplishing one of the
greatest objects of modern chemistry, have induced me for some
time to withhold them from the society, I am satisfied by reflec-
tion, that this communication is not without expediency. The
means employed in attempting the analysis of the muriatic acid,

ewe >

»

for decomposing the Muriatic Acid. 201

were such as, after mature deliberation, appeared to me most to
promise success; and the experiments were attended with a
degree of labour, which can only be estimated by those who
have been engaged in similar pursuits; not one third of those
which were really made having been described, in the foregoing

account of them. It may spare therefore to others, a fruitless

application of time and trouble, to be made acquainted with
what I have done; and the collateral facts, which have pre-
sented themselves in the inquiry, are perhaps not without
curiosity or value.

From the result of these experiments, I apprehend, all hope
must be relinquished, of effecting the decomposition of the

‘muriatic acid, in the way of single elective affinity. They

furnish also a strong probability, that the basis-of the muriatic
acid is some unknown body; for, no combustible substance
with which we are acquainted, can retain oxygen, when sub-
mitted, in contact with charcoal, to the action of electricity, or
of a high temperature. The analysis of this acid must, in future,
be attempted with the aid of complicated affinities. Thus, in
the masterly experiment of Mr. TENNANT, phosphorus, which
attracts oxygen less strongly than charcoal, by the intermedia-
tion of lime decomposes the carbonic acid. Yet, led by the
analogy of this fact, its discoverer found that a similar artifice
did not succeed in decomposing the muriatic acid. «© As vital
« air,” he observes, “ is attracted by a compound of phosphorus

© and calcareous earth, more powerfully than by charcoal, I was

* desirous of trying their efficacy upon those acids which may

*¢ from analogy be supposed to contain vital air, but which are
SY pp

“ not affected by the application of charcoal. With this intention,
«I made phosphorus pass through.a compound of marine acid
MDCCC, Dd

209 Mr. Henry's Account of Experiments

‘‘ and calcareous earth, and also of fluor acid and calcareous —
“earth, but without producing in either of them any alteration;
«Since the strong attraction which these acids have for calca=
reous earth tends to prevent their decomposition, it might be
“ thought, that in this manner they were not more disposed to
“part with vital air than by the attraction of charcoal: but
“this, however, does not appear to be the fact. I have found,
“that phosphorus cannot be obtained by passing marine acid
“ through a compound of bones and charcoal when red-hot:
«The attraction, therefore, of phosphorus and lime for vital
“ air, exceeds the attraction of charcoal, by a greater force than
“ that arising from the attraction of marine acid for lime.” *

By means similar to those employed in attempting the
analysis of the muriatic acid, I tried to effect that of the fluoric
acid. When electrified alone, in a glass tube coated internally
with wax, it sustained a diminution of bulk, and there remained:
a portion of hydrogenous gas. But, neither in this mode, nor by
submitting it, mixed with carbonated hydrogenous gas, to the
action of electricity, was any progress made towards its analysis.
These experiments, however, render it probable, that the fluoric.
acid, like the muriatic, is susceptible of still farther oxygenation,
in which state it becomes capable of acting on mercury. The
carbonic acid, on the contrary, appears not to admit of. different:
degrees. of oxygenation. When the electric shock has been
repeatedly passed through a portion of this acid gas, its bulk is.
enlarged, and a permanent gas is produced, which is evidently,

* Phil. Trans. Vol. LXXXI. p, 184.

for decomposing the Muriatic Acid. 203

a mixture of oxygenous and hydrogenous gases; for, when an
electrical spark is passed through the gas that remains after
the absorption of the carbonic acid by caustic alkali, it imme-
diately explodes. These results even take place on electrifying
carbonic acid from marble, previously calcined in a low red
heat, to expel its water, and then distilled in an earthen retort.*

* Messieurs Lanpriani and Van Marumo (Annales de Chimie, Tom. II. p.270.)
obtained only hydrogenous gas, by electrifying the carbonic acid gas. But the con-
ductor of their apparatus was an iron one; which metal would combine with the
oxygen of the water, and prevent it from appearing in a gaseous state. In Dy, experi-
ments, the conductors were of platina.

Dde

XI. On a new fulminating Mercury. By Edward Howard, Ey.
Fi Boe,

TQ"

Read March 13, 1800.

SECTION I,

gE mercurial preparations which fulminate, when mixed with
sulphur, and gradually exposed to a gentle heat, are well known
to chemists: they were discovered, and have been fully de-
scribed, by Mr. BayEn.*

MM. BrucnaTELLi and Van Mons have likewise produced
fulminations by concussion, as well with nitrate of mercury and
phosphorus, as with phosphorus and most other nitrates.-+
Cinnabar likewise is amongst the substances which, according
to MM. Fourcroy and VauQvuELin, detonate by concussion
with oxymuriate of potash.{ |

Mr. AmeEiLon had, according to Mr. BERTHOLLET, observed, |
that the precipitate obtained from nitrate of mercury by oxalic
acid, fuses with a hissing noise.§

/

|
4

* Opuscules Chimique de Bayen, Tom. I. p. 346, and note in p. 344.

+ Annales de Chimie, Tom. XXVII. p. 74 and 79.

t Ibid. Tom. XXI. p. 238.

§ This fact has been misrepresented, in the introduction to a work intitled The
chemical Principles of the metallic Arts, by W. Ricuarpson, surgeon, F.A.S. Sc.
(page lvii.) The author, speaking of the acid of sorrel, says, «‘ KLaAProtu of Berlin
‘* precipitated a nitrous solution of mercury with acid of wood-sorrel, neutralized with

Mr. E. Howarp ona new fulminating Meteury. 205

SECTION II,

But mercury, and most if not all its oxides, may, by, treat-
ment with nitric acid and alcohol, be converted into a whitish
crystallized powder, possessing all the inflammable properties
of gunpowder, as well as many peculiar to itself.

-I was led to this discovery, by a late assertion, that hydrogen
is the basis of the muriatic acid: it induced me to attempt to
combine different substances with hydrogen and oxygen. With
this view, I mixed such substances with alcohol and nitric acid,
as 1 thought might (by predisposing affinity ) favour, as well as
attract, an acid combination, of the hydrogen of the one, and
the oxygen of the other. The pure red oxide of mercury ap-
peared not unfit for this purpose; it was therefore intermixed
with alcohol, and upon both, nitric acid was affused. The acid’
did not act upon the alcohol so immediately as when these
fluids are alone mixed together, but first gradually dissolved
the oxide : however, after some minutes had elapsed, a smell
of ether was perceptible, and a white dense smoke, much

«< vegetable alkali, The white precipitate, well washed and dried, produced a fulmi-
* nating noise, not inferior to that of fulminating gold. Acid of sugar, perfectly neu-
“*tralized by vegetable alkali, produced the same precipitate, which, on exposure to
*¢-heat, exhibited the same fulminating power.” I must confess; I have not been able to
*< produce any such fulmination. Mr.Ricuarpsow has moreover given this supposed
discovery to Mr. Kraproru 3; whereas, Mr. BeErTHOLLETs when quoting the fact to
which I suppose Mr. Rrcwarpson intended to allude, observes, ‘« Qu’on avoit déja.
<« donné le nom d’argent: fulminant au précipité. du nitrate d’argent par l’acide oxa-
« lique, dans lequel M. Krarrorn avoit découvert la propriété de fuser avec vivacité
« lorsqu’on Vexpose a.la chaleur. M. AmeILon avoit. aussi, depuis longtems, fait.
“« connoitre que I’acide oxalique communiquoit cette propriété au. mercure, quoique
“moins fortement qu’a Vargent ; mais cet effet (he continues) est fort éloigné de.
<« celui qu’on désigne par la fulmination.”” Annales de Chimie, Tom. I. pi 57?

206 Mr. E. Howarp on anew fulminating Mercury.

resembling that from the Jiquor fumans of Lisavius, was
emitted with ebullition. The mixture then threw down a dark-
coloured precipitate, which by degrées became nearly white.

This precipitate I separated by filtration; and, observing it to be’

crystallized in small acicular crystals, of a saline taste, and also
finding a part of the mercury volatilized in the white fumes, I

must acknowledge I was not altogether without hopes that.

muriatic acid had been formed, and united to the mercurial
oxide. I therefore, for obvious reasons, poured sulphuric acid
upon the dried crystalline mass, when a violent effervescence
ensued, and, to my great astonishment, an explosion took place.

The singularity of this explosion induced me to repeat the
process several times; and, finding that I always obtained the
same kind of powder, I prepared a quantity of it, and was led
to make the series of experiments which I shall have the
honour to relate in this paper.

SECTION III.

I first attempted to make the mercurial powder fulminate
by concussion; and for that purpose laid about a grain of it
upon a cold anvil, and struck it with a hammer, likewise cold :
it detonated slightly, not being, as I suppose, struck with a flat

blow; for, upon using g or 4 grains, a very stunning disagree-

able noise was produced, and the faces both of the hammer and
the anvil were much indented. eS
Half a grain or a grain, if quite dry, is as much as ought to
be used on such an occasion.
The shock of an electrical battery, sent through 5 or 6 grains,
of the powder, produces a very similar effect : it seems indeed,.

Mr. E. Howarp on a new fulminating Mercury. 207

that a strong electrical shock, generally acts on fulminating
substances like the blow of a hammer. Messrs. Fourcroy and
VAvQuELin found this to be the case with all their mixtures of
oxymuriate of potash.*

To ascertain at what temperature the mercurial powder
explodes, 2 or 3 grains of it were floated on oil, in a capsule of
leaf tin; the bulb of a FauRENHEIT’s thermometer was made
just to touch the surface of the oil, which was then gradually
heated till the powder exploded, as the mercury of the thermo-
_meter reached the 368th degree.

SECTION IV.

Desirous of comparing the strength of the mercurial com-
pound with that of gunpowder, I made the following experi-
ment, in the presence of my friend Mr. ABERNETHY.

Finding that the powder could be fired by flint and steel,
without a disagreeable noise, a common gunpowder proof,
capable of containing eleven grains of fine gunpowder, was
filled with it, and fired in the usual way : the report was sharp,
but not loud. The person who held the instrument in his hand
felt no recoil; but the explosion laid open the upper part of the
barrel, nearly from the touch-hole to the muzzle, and struck
off the hand of the register, the surface of which was evenly
indented, to the depth of 0,1 of an inch, as if it had received the
impression of a punch.

The instrument used in this experiment being familiarly
known, it is therefore scarcely necessary to describe it; suffice
it to say, that it was of brass, mounted with a spring register,

® Annales de Chimie, Tom, XXI. p. 239.

208 Mr. E. Howarp on a new fulminating Mercury.

the moveable hand of which closed up the muzzle, to receive
and graduate the violence of the explosion. The barrel was
half an inch in caliber, and nearly half an inch thick, except
where a spring of the lock impaired half its thickness.

_SECTION V. © teal

A gun belonging to Mr. Karr, an ingenious artist of Camden-

town, was next charged with 17 grains of the mercurial powder,
and a leaden bullet. A block of wood was placed at about eight
yards from the muzzle, to receive the ball, and the gun was

fired by a fuse. No recoil seemed to have taken place; as the

barrel was not moved from its position, although it was in no
ways confined. The report was feeble: the bullet, Mr. Kerr
conceived, from the impression made upon the wood, had been
projected with about half the force it would have been by an
ordinary charge, or 68 grains, of the best gunpowder. We
therefore recharged the gun with 34 grains of the mercurial
powder; and, as the great strength of the piece removed any
apprehension of danger, Mr. Kerr fired it from his shoulder,
aiming at the same block of wood. The report was like the
first in section rv. sharp, but not louder than might have been
expected from a charge of gunpowder. Fortunately, Mr. Krrr
was not hurt, but the gun was burst in an extraordinary mannet.
The breech was what is called a patent one, of the best forged
iron, consisting of a chamber 0,4 of an inch thick all round,
and 0,4, of an inch in caliber; it was torn open and flawed in
many directions, and the gold touch-hole driven out. ” The
barrel, into which the breech was screwed, was 0,5 of an inch

thick; it was split by a single crack three inches long, but this.

Mr. E. Howarp on a new fulminaing Mercury. 209

did not appear to me to be the immediate effect of the explosion.
I think the screw of the breech, being suddenly enlarged, acted
as a wedge upon the barrel. The ball missed the block of wood,
and struck against a wall, which had already been the receptacle
of so many bullets, that we could not satisfy ourselves about
the impression made by this last.

SECTION VI.

As it was pretty plain that no gun could confine a quantity
of the mercurial powder sufficient to project a bullet, with a
greater force than an ordinary charge of gunpowder, I deter-
mined to try its comparative strength in another way.

I procured two blocks of wood, very nearly of the same size
and strength, and bored them with the same instrument to the
same depth. The one was charged with half an ounce of the best
Dartford gunpowder, and the other with half an ounce of the
mercurial powder; both were alike buried in sand, and fired by
a train communicating with the powders by a small touch-hole.
The block containing the gunpowder was simply split into three
pieces: that charged with the mercurial powder was burst in
every direction, and the parts immediately contiguous to the
powder were absolutely pounded, yet the whole hung together,
whereas the block split by the gunpowder had its parts fairly
separated. The sand surrounding the gunpowder was undoubt-
edly most disturbed: in short, the mercurial powder appeared
to have acted with the greatest energy, but only within certain
limits.

MDCCC. Ee

210 Mr. EF. Howarp on a new fulminating Mercury.

SECTION VII.

The effects of the mercurial powder, in the last experiments,
made me believe that it might be confined, during its explosion,
in the centre of a hollow glass globe. Having therefore pro-
vided such a vessel, 7 inches in diameter, and nearly half an
inch thick, mounted with brass caps, and a stop cock, (see Plate
VIII.) I placed 10 grains of the mercurial powder on very thin
paper, laid an iron wire 149th of an inch thick across the
paper, through the midst of the powder, and, closing the paper,
tied it fast at both extremities, with silk, to the wire. As the
inclosed powder was now attaclted to the middle of the wire,
each end of which was connected with the brass caps, the
packet of powder became, by this disposition, fixed in the centre
of the globe. Such a charge of an electrical battery was then
sent along the wire, as a preliminary experiment* had shewn
me would, by making the wire red-hot, inflame the powder.
The glass globe withstood the explosion, and of course retained
whatever gases were generated: its interior was thinly coated
with quicksilver in a very divided state. A bent glass tube was
now screwed to the stop-cock of the brass cap, which being
introduced under a glass Jar standing in the mercurial bath, the
stop-cock was opened. Three cubical inches of air rushed out,
and a fourth was set at liberty when the apparatus was removed
to the water-tub. The explosion being repeated, and the air all
received over water, the quantity did not vary. To avoid an
error from change of temperature, the glass globe was, both
before and after the explosion, immersed in water of the same

® With Mr. CuTHBERTSON’S electrometer.

Mr. E. Howarn on a new fulminating Mercury. 211

temperature. It appears therefore, that the ten grains of powder,
produced four cubical inches only of air.

To continue the comparison between the mercurial powder
and gunpowder, 10 grains of the best Dartford gunpowder were
in a similar manner set fire to in the glass globe: it remained
entire. The whole of the powder did not explode, for some
complete grains were to be observed adhering to the interior
surface of the glass. Little need be said of the nature of the
gases generated during the combustion of gunpowder: they
must have been, carbonic acid gas, sulphureous acid gas, nitro-
gen gas, and (according to LavoisieR*) perhaps hydrogen gas.
As to the quantity of these gases, it is obvious that it could
not be ascertained; because the two first were, at least in part,
speedily absorbed by the alkali of the nitre, left pure after the
decomposition of its nitric acid. —

SECTION VIII.

From the experiments related in the 4th and 5th sections, in
which the gunpowder proof and the gun were burst, it might
be inferred, that the astonishing force of the mercurial powder
is to be attributed to the rapidity of its combustion ; and, a train
of several inches in length being consumed in a single flash, it
is evident that its combustion must be rapid. From the expe-
riments of the 6th and 7th sections, it is sufficiently plain that
this force is restrained to a narrow limit; both because the block
of wood charged with the mercurial powder was more shattered

* See Lavoisier, Traite elementaire, p. 527.

Eee

212 Mr. FE. Howarp on a new fulminating Mercury.

than that charged with the gunpowder, whilst the sand sur-
rounding it was least disturbed; and likewise because the glass
globe withstood the explosion of 10 grains of the powder fixed
in its centre: a charge I have twice found sufficient to destroy
old pistol barrels, which were not injured by being fired when
full of the best gunpowder. It also appears, from the last expe-
riment, that 10 grains of the powder, produced by ignition four
cubical inches only of air; and it is not to be supposed that
the generation, however rapid, of four cubical inches of air, will
alone account for the described force; neither can it be accounted
for by the formation of a little water, which, as will hereafter
be shewn, happens at the same moment: the quantity formed
from 10 grains must be so trifling, that I cannot ascribe much
force to the expansion of its vapour. ‘The sudden vaporization
of a part of the mercury, seems to me a principal cause of this
immense yet limited force; because its limitation may then be
explained, as it is well known that mercury easily parts with
caloric, and requires a temperature of 600 degrees of FAHRENHEIT,
to be maintained in the vaporous state. That the mercury is
really converted into vapour, by ignition of the powder, may be
inferred from the thin coat of divided quicksilver, which, after
the explosion in the glass globe, covered its interior surface;
and likewise from the quicksilver with which a tallow candle,
or a piece of gold, may be evenly coated, by being held at a
small distance from the inflamed powder. These facts certainly
render it more than probable, although they do not demonstrate,
that the mercury is volatilized; because it is not unlikely that
many mercurial particles are mechanically impelled against the
surface of the glass, the gold, and the tallow.

Mr. EF. Howarp on a new fulminating Mercury. 213

As to the force of dilated mercury, Mr. Baumer’ relates a
remarkable instance of it, as follows.

« Un alchymiste se présenta 4 Mr. Grorrroy, et l’assura
qu'il avoit trouvé le moyen de fixer le mercure par une opéra-
‘tion fort simple. I] fit construire six boites rondes en fer fort
* épais, qui entroient les unes dans les autres ; la derniere étoit
“ assujettie par deux cercles de fer qui se croisoient en angles
« droits. On avoit mis quelques livres de mercure dans la capa-
“cité de la premiére: on mit cet appareil dans un fourneau
*‘ assez rempli de charbon pour faire rougir a blanc les boites
“ de fer; mais, lorsque la chaleur eut pénétré suffisamment le .
“¢ mercure, les boites creverent, avec une telle explosion qu’il se
“fit un bruit épouvantable: des morceaux de boites furent
*« Jancés avec tant de rapidité, qu’il y en eut qui passerent au
“ travers de deux planchers; d’autres firent sur la muraille des
“‘ effets semblables a ceux des éclats de bombes.’’*

Had the alchemist proposed to fix water by the same appa-
ratus, the nest of boxes must, I suppose, have likewise been rup-
tured; yet it does not follow that the explosion would have
been so tremendous: indeed it is probable that it would not,
for if (as Mr. Kirwan remarked to me) substances which have
the greatest specific gravity, have likewise the greatest attraction
of cohesion, the supposition that the vapour of mercury exceeds
in expansive force the vapour of water, would agree with a
position of Sir Isaac Newron, that those particles recede from
one another with the greatest force, and are most difficultly brought
together, which upon contact cobere most strongly.+-

* Chymie expérimentale et raisonnée, Tom. II. p. 393, Paris, 8°, 1773.
+ Newron’s Optics, p. 372, 4th Ed, Lond. 1730,

214 Mr. E. Howarp on a new fulminating Mercury.

SECTION IX.

Before I attempt to investigate the constituent principles of
this powder, it will be proper to describe the process and mani-
pulations which, from frequent trials, seem to me best calculated
to produce it.

100 grains, or a greater proportional quantity, of quicksilver
(not exceeding 500 grains*) are to be dissolved, with heat, in a
measured ounce and a half of nitric acid.{- This solution being _
poured cold upon two measured ounces of alcohol,t previously
introduced into any convenient glass vessel, a moderate heat
is to be applied until an effervescence is excited. A white
fume then begins to undulate on the surface of the liquor; and
the powder will be gradually precipitated, upon the cessation
of action and re-action. ‘The precipitate is to be immediately
collected on a filter, well washed with distilled water, and
carefully dried in a heat not much exceeding that of a water
bath. The immediate edulcoration of the powder is material,
because it is liable to the re-action of the nitric acid; and, whilst
any of that acid adheres to it, it is very subject to the influence
of light. Let it also be cautiously remembered, that the mer-
curial solution is to be poured upon the alcohol.

I have recommended quicksilver to be used in preference to
an oxide, because it seems to answer equally, and is less expen-

* The reason of this limitation is not on account of any danger attending the pro-
cess; but because the quantities of nitric acid and alcohol required for more than 500
grains, would excite a degree of heat detrimental to the preparation.

+ Of the specific gravity of about 1,3.

{ Of the specific gravity of about ,849.

Mr. E. Howarp on a new fulminating Mercury. 215

sive; otherwise, not only the pure red oxide, but the red nitrous
oxide, and turpeth, may be substituted; neither does it seem
essential to attend to the precise specific gravity of the acid, or
the alcohol. The rectified spirit of wine and the nitrous acid of
commerce, never failed, with me, to produce a fulminating
mercury. It is indeed true, that the powder prepared without
attention, is produced in different quantities, varies in colour,
and probably in strength. From analogy, I am disposed to
think the whitest is the strongest; for it is well known, that black
precipitates of mercury approach the nearest to the metallic
state. The variation in quantity is remarkable; the smallest
quantity I ever obtained from 100 grains of quicksilver being
120 grains, and the largest 192 grains. Much depends on very
minute circumstances. ‘The greatest product seems to be ob-
tained, when a vessel is used which condenses and causes most
ether to return into the mother liquor; besides which, care is to
be had in applying the requisite heat, that a speedy, and not a
violent action be effected. 100 grains of an oxide are not so
productive as 100 grains of quicksilver.

As to the colour, it seems to incline to black, when the action
of the acid on the alcohol is most violent, and vice versa.

SECTION X.

I need not observe, that the gases which were generated
during the combustion of the powder in the glass globe, were
necessarily mixed with atmospheric air; the facility wi h which
the electric fluid passes through a vacuum, made such a mixture
unavoidable.

The cubical inch of gas received over water was not readily

216 Mr. E. Howarp on a new fulminating Mercury.

absorbed by it: and, as it soon extinguished a taper, without
becoming red, or being itself inflamed, barytes water was let up
to the three cubical inches received over mercury, when a car-
bonate of barytes was immediately precipitated.

The residue of several explosions, after the carbonic acid
had been separated, was found, by the test of nitrous gas, to
contain nitrogen or azotic gas; which does not proceed from
any decomposition of atmospheric air, because the powder may
be made to explode under the -exhausted receiver of an air-
pump. It is therefore manifest, that the gases generated during
the combustion of the fulminating mercury, consist of carbonic
acid and nitrogen gases.

SECTION XI.

The principal re-agents which decompose the mercurial
powder, are the nitric, the sulphuric, and the muriatic acids.
The nitric changes the whole into nitrous gas, carbonic acid
gas, acetous acid, and nitrate of mercury. I resolved it into
these different principles, by distilling it pneumatically with
nitric acid: this acid, upon the application of heat, soon dis-
solved the powder, and extricated a quantity of gas, which was
found, by well known tests, to be nitrous gas mixed with car-
bonic acid gas. The distillation was carried on until gas no
longer came over. The liquor of the retort was then mixed
with the liquor collected in the receiver, and the whole satu-
rated with potash; which precipitated the mercury in a yellow-
ish-brown powder, nearly as it would have done from a solution
of nitrate of mercury. This precipitate was separated by a filter,

Mr, E. Howarp on anew fulminating Mercury. 217

and. the filtrated liquor evaporated to a dry salt, which was
washed. with alcohol. A portion of the salt being refused by this
_ menstruum, it was separated by filtration, and recognized, by all
its properties, to be nitrate of potash. The alcoholic liquor was
_ likewise evaporated to a dry salt, which, upon the affusion of a
| little concentrate sulphuric acid, emitted acetous acid, contami-
nated with a feeble smell of nitrous acid, owing to the solubility
of a small portion of the nitre in the alcohol.

SECTION XII.

The sulphuric acid acts upon the powder in a remarkable
manner, as already has been noticed. A very concentrate acid
produces an explosion nearly at the instant of contact, on
account, I presume, of the sudden and copious disengagement
of caloric from a portion of the powder which is decomposed by
the acid. An acid somewhat less concentrate likewise extricates
a considerable quantity of caloric, with a good deal of gas; but,
as it effects a complete decomposition, it causes no explosion.
An acid diluted with an equal quantity of water, by the aid of a
little heat, separates the gas so much less rapidly, that it may
with safety be collected in a pneumatic apparatus. But, what-
ever be the density of the acid, (provided no explosion be pro-
duced, ) there remains in the sulphuric liquor, after the separation
of the gas, a white uninflammable and uncrystallized powder,
mixed with some minute globules of quicksilver.

To estimate the quantity, and observe the nature, of saree un-
inflammable substance, I treated 100 grains of the fulminating
mercury with sulphuric acid a little diluted. The gas being
separated, I decanted off the liquor as it became clear, and freed
the insoluble powder from acid, by edulcoration with distilled

MDCCC. Rf

218 Mr. E. Howarp on a new fulminating Mercury.

water; after which, I dried it,and found it weighed only 84 grains;

consequently had lost 16 grains of its original weight. Suspect-
ing, from the operation of the nitric acid in the former experi-

ment, that these 84, grains (with the exception of the quicksilver
globules) were oxalate of mercury, I digested them in nitrate of
lime, and found my suspicion just. ‘The mercury of the oxalate
united to the nitric acid, and the oxalic acid to the lime. A new
insoluble compound was formed; it weighed, when washed and
dry, 48,5 grains. Carbonate of potash separated the lime, and
formed oxalate of potash, capable of precipitating lime-water,
and muriate of lime; although it had been depurated from
excess of alkali, and from carbonic acid, by a previous addition
of acetous acid. That the mercury of the oxalate in the 84
grains, had united to the nitric acid of the nitrate of lime, was
proved by dropping muriatic acid into the liquor from which
the substance demonstrated to be oxalate of lime had been sepa-
rated; for a copious precipitation of calomel instantly ensued.
The sulphuric liquor, decanted from the oxalate of mercury,
was now added to that with which it was edulcorated, and the
whole saturated with carbonate of potash. As effervescence
ceased, a cloudiness and precipitation followed ; and the preci-
pitate, being collected, washed, and dried, weighed 3,4, grains:
it appeared to be a carbonate of mercury. Upon evaporating a
portion of the saturated sulphuric liquor, I found nothing but
sulphate of potash; nor had it any metallic taste. There then
remains, without allowing for the weight of the carbonic acid

united to the 3,4, grains,a deficit from the 100 grains of mercurial _

powder, of 12,6 grains, which I ascribe to the gas separated by
the action of the sulphuric acid. To ascertain the quantity, and
examine the nature, of the gas so separated, I introduced into a

+%

Mr. E. Howarp on a new fulminating Mercury. 219

very small tubulated retort, 50 grains of the mercurial powder,
and poured upon it 3 drams, by measure, of sulphuric acid,
diluted with an equal quantity of water, and extricated the gas
with the assistance of a gentle heat. I first received it over
quicksilver, the surface of which, during the operation, partially
covered itself with a little black powder.* .

The gas, by different trials, amounted from 28 to g1 cubical
inches; it at first appeared to be nothing but carbonic acid, as
it precipitated barytes water, and extinguished a taper, without
being itself inflamed, or becoming red. But, upon letting up to
it liquid caustic ammoniac, there was a residue of from 5 to 7
inches of a peculiar inflammable gas, which burnt with a green-
ish blue flame. When I made use of the water-tub, I obtained,
‘from the same materials, from 25-to 27 inches only of gas,
although the average quantity of the peculiar inflammable gas
was likewise from 5 to 7 inches; therefore, the difference of the
aggregate product, over the two fluids, must have arisen from
the absorption, by the water, of a part of the carbonic acid in its
nascent state. The variation of the quantity of the inflammable
gas, when powder from the same parcel is used, seems to de-
pend upon the acid being a little more or less dilute.

With respect to the nature of the peculiar inflammable gas,
it is plain to me, from the reasons I shall immediately adduce,
that it is no other than the gas (in a pure state) into which
the nitrous etherized gas can be resolved, by treatment with
dilute sulphuric acid.

The Dutch chemists have shewn,- that the nitrous etherized
gas can be resolved into nitrous gas, by exposure to concentrate

* I cannot account for this appearance,

+ Fournal de Physique, p.250, October, 1794.
Ff eo

220 Mr. E. Howarp on a new fulminating Mercury.

sulphuric acid, and that, by using a dilute instead of a concen-
trate acid, a gas is obtained which enlarges the flame of a
burning taper, so much like the gaseous oxide of azote, that
they mistook it for that substance, until they discovered that it
was permanent over water, refused to detonate with hydrogen,
and that the fallacious appearance was owing to a mixture of
nitrous gas with an inflammable gas.

The inflammable gas separated from the powder answers to
_ the description of the gas which at first deceived the Dutch
chemists; ist, in being permanent over water; edly, refusing
to detonate with hydrogen; and, gdly, having the appearance
of the gaseous oxide of azote, when mixed with nitrous gas.

_The gas separable by the same acid, from nitrous etherized
gas, and from the mercurial powder, have therefore the same
properties. Every chemist would thence conclude, that the
nitrous etherized gas is a constituent part of the powder, had
the inflammable and nitrous gas, instead of the inflammable and
carbonic acid gas, been the mixed product extricated from it
by dilute sulphuric acid.

It however appears to me, that nitrous gas was really pro-
duced by the action of the dilute sulphuric acid; and that,
when produced, it united to an excess of oxygen aise in the
oxalate of mercury.

To explain how this change might happen, I must premise, |
that my experiments have shewn me, that oxalate of mercury
can exist in two, if not in three states.

ist, By the discovery of Mr. AmeiLon already quoted, the
precipitate obtained by oxalic acid, from nitrate of mercury, fuses
with a hissing noise. This precipitate is an oxalate of mercury,
seemingly with excess of oxygen. Mercury dissolved in sul-

fe ¢ Ue

Mr. E. Howarp on a new fulminating Mercury. 221

phuric acid and precipitated by oxalic acid, and also the pure red
oxide of mercury digested with oxalic acid, give oxalates in the
same state.

edly. Acetate of mercury precipitated by oxalic acid, although
a true oxalate is formed, has no kind of inflammability. I con-
sider it as an oxalate with less oxygen than those abovemen-
tioned. .

gdly. A solution of nitrate of mercury boiled with dulcified -
spirit of nitre, gives an oxalate more inflammable than any other:
perhaps it contains most oxygen.

The oxalate of mercury remaining from the powder in the
sulphuric liquor, is not only always in the same state as that
precipitated from acetate of mercury, entirely devoid of inflam-
mability, but contains globules of quicksilver; consequently, it
must have parted with even more than its excess of oxygen ;
and, if nitrous gas was present, it would of course seize at least
a portion of that oxygen. It is true, that globules of quicksilver
may seem incompatible with nitrous acid ; but the quantity of
the one may not correspond with that of the other, or the dilu-
tion of the acid may destroy its action.

As to the presence of the carbonic acid, it must have arisen
either from a complete* decomposition of a part of the oxalate;
or, admitting the nitrous etherized gas to be a constituent prin-
ciple of the powder, from a portion of the oxygen, not taken up
by the nitrous gas, being united with the carbon of the etherized.

gas.
SECTION XIII.
The muriatic acid digested with the mercurial powder, dis-

* Inflammable oxalate of mercury, made to fuse in a retort connected with the
quicksilyer tub, gives out carbonic acid SAS.

292 Mr. EK. Howarp on a new fulminating Mercury.

solves a portion of it, without extricating any notable quantity
of gas, The dissolution evaporated to a dry salt, tastes like cor-
rosive sublimate; and the portion which the acid does not take
up, is left in the state of an uninflammable oxalate.

SECTION XIV.

‘These effects all tend to establish the existence of the nitrous
etherized gas, as a constituent part of the powder; and likewise
corroborate the explanation I have ventured to give, of the
action of the sulphuric acid. Moreover, a measured ounce and
a half of nitrous acid, holding 100 grains of mercury in solu-
tion, and 2 measured ounces of alcohol, yield go cubical inches
only of gas: whereas, without the intervention of mercury, they
yield 210 inches. Upon the whole, I trust it will be thought
reasonable to conclude, that the mercurial powder is composed
of the nitrous etherized gas, and of oxalate of mercury with
excess of oxygen. |

ist. Because the nitric acid converts the mercurial powder
entirely into nitrous gas, carbonic acid gas, acetous acid, and.
nitrate of mercury.

edly. Because the dilute sulphuric acid resolves it into an un-
inflammable oxalate of mercury, and separates from it a gas
- resembling that into which the same acid resolves the nitrous
etherized gas.

gdly. Because an uninflammable oxalate is likewise left, after
the muriatic acid has converted a part of it into sublimate.

4thly. Because it cannot be formed by boiling nitrate of
mercury in dulcified spirit of nitre; although a very inflam-
mable oxalate is by this means produced.

5thly. Because the difference of the product of gas, from the

Mr. E. Howarp on a new fulminating Mercury. 229

same measures of alcohol and nitrous acid, with and without
mercury in solution, is not trifling ; and,

6thly. Because nitrogen gas was generated during its com-
bustion in the glass globe.

Should my conclusions be thought warranted by the reasons
I have adduced, the theory of the combustion of the mercurial
powder will be obvious to every chemist. The hydrogen of the
oxalic acid, and of the etherized gas, is' first united to the oxy-
gen of the oxalate, forming water;* the carbon is saturated with
oxygen, forming carbonic acid gas; and a part, if not the
whole of the nitrogen of the etherized gas, is separated in the
state of nitrogen gas ; both which last gases, it may be recol-
lected, were after the explosion present’ in the glass globe. The
mercury is revived, and, I presume, thrown into’ vapour ; as
may well be imagined, from the immense quantity of caloric
extricated, by adding concentrate sulphuric acid to the mercurial
powder.

I will not venture to state with accuracy, in what proportions:
its constituent principles are combined. The affinities I have:
brought into play are complicated, and the constitution of the
substances I‘ have to deal with not fully known. But, to make
round numbers, | will resume the statement, that 100 grains:
of the mercurial powder lost 16 grains of its original weight,
by treatment with dilute sulphuric acid: 84 grains of mercurial
oxalate, mixed with a few minute globules of quicksilver, re-
mained undissolved in the acid. The sulphuric liquor was satu--
rated with carbonate of potash, and yielded 3,4 grains of car--
bonate of mercury: If 1,4 grain should be thought a proper

* Drops of water were observed on the internal surface of the globe, the day after:
several explosions had been produced in its centre.

224 Mr. E Howarp on a a new w fulminating Pay:
flee or the 2 weight of pon acid i in | the ED ora :
to the

make that deduction, and add the r remaining 2
grains of mercurial oxalate and quicksilver I {shall then ve,
of oxalate and mercury = - ~ - 86 ‘grains
~ and a deficit, to be ascribed to ‘the nitrous: r | if
‘etherized gas and excess of oxygen - 3 - 14

It may perhaps be proper to proceed still further, and recur
to the 48,5 grains, separated by nitrate of lime from the 84
grains of mercurial oxalate and globules of quicksilver, in the
11th section. These 48,5 grains were proved to be chiefly oxa-
late of lime; but they likewise contained a minute inseparable
quantity of mercury, almost in the state of quicksilver, formerly
part of the 84 grains from which they were separated. Had the
48,5 grains been pure calcareous oxalate, the quantity of pure
oxalic acid in them would, according to BERGMANN,* be 23,98
grains. Hence, by omitting the 2 grains of mercury in the 3,4
grains of carbonate, 100 grains of the mercurial powder might
have been said to contain, of pure oxalic acid 23,28 grains; of
mercury 69,72 grains; and of nitrous etherized gas and excess
of oxygen 14 grains. But, as the 48,5 grains were not pure oxa-
late, inasmuch as they contained the mercury they received from
the 84 grains, from which they were generated by the nitrate
of lime, some allowance must be made for the mercury succes-
sively intermixed with the 84 grains and the 48,5 grains. —

In order to make corresponding numbers, and allow for
unavoidable errors, I shall estimate the quantity of that mercury
to have amounted to 2 grains, which I must of course deduct

a) 2 Dae
* Bencmawnn, de Acido Sacchari. Opuscula, Tom. I. §.6. ps 248. Leipzig, 1788.

7) I

Mr. E. Howarn on a new fulminating Mercury, 295

from the 23,28 grains of oxalic acid. I shall then have the fol-
lowing statement : : 7 ¥ up
That 100 grains of the fulminating mercury ought to contain,
of pure oxalic acid . = - - - 91,28 grains,
of mercury formerly united to the oxalic acid 60,72 -
of mercury dissolved in the sulphuric liquor ¢.
and of mercury left in the sulphuric liquor
after the separation of the gases - - 2

st Total of mercury ‘ as - 64,79
_ OF nitrous etherized gas and excess of oxygen 14,

100.

Since 100 grains of the powder seem to contain 64,72 grains of
mercury, it will be immediately inquired, what becomes of 100
grains of quicksilver, when treated as directed, in the descrip-
tion of the process for preparing the fulminating mercury.

It has been stated (in section g.) that 100 grains of quick~
silver produce, under different circumstances, from 120 to 132
grains of mercurial powder; and, if 100 grains of this powder
contain 64,72 grains, 120 grains, or 132 grains must, by parity of
reasoning, contain 78,06 grains, or 85,4/7 grains; therefore,
13,34 grains, or 20,75 grains, more of the 100 grains are imme-’
diately accounted for; because 64,72 grains ++ 13,34, grains =
78,06, and 64,72 grains + 20,75 grains = 85,47 grains. The
remaining deficiency of 21,94, grains, or 14,53 grains, which, with
the 78,06 grains, or 85,47 grains, would complete the original
100, of quicksilver, remains partly in the liquor from which the
powder is separated, and is partly volatilized in the white dense
fumes, which in the beginning of: this paper I compared to the
liquor fumans of Lisavius. The mercury cannot, in either

MDCCC. Gg

226. Mr. E. Howarp on a new fulminating: Mercury.

instance, be obtained in a ‘form immediately indicative of its —

quantity ; and a series of experiments to ascertain the quan=
tities in which many different substances’ can combine with
mercury, is not my present object. After observing, that the

mercury left in the residuary liquor can be precipitated in a very

subtle dark powder; by carbonate of potash, I shall’ content
myself with examining the nature of the white fumes.

SECTION XV.

It is clear that these white fumes contain mercury: they
may be wholly condensed in a range of Wou.rr’s apparatus,
charged with a solution of muriate of ammoniac. When the
operation is over, a white powder is seen floating with ether
on the saline liquor, which, if the bottles are agitated, is
entirely dissolved. After the mixture has-been boiled, or for
some time exposed to the atmosphere, it yields to caustic ammo-
niac a precipitate, in, all respects similar to that which is sepa-
rated by caustic ammoniac from corrosive sublimate.

I would infer from these facts, that the white dense fumes
consist of mercury, or perhaps oxide of mercury, united to the
nitrous etherized gas; and that, when the muriate of ammoniac
containing them is exposed to the atmosphere, or is boiled, the
gas separates from the mercury; and the excess of nitrous acid,
which always comes over with nitrous ether, decomposes the
ammoniacal muriate, and forms corrosive mercurial muriate or
sublimate. This theory is corroborated, by comparing the quan-
tity of gas estimated to be contained in the fulminating mercury,
with the quantities of gas yielded from alcohol and nitrous acid,

with and without mercury in solution; not to mention that

more ether, as well as more gas, is produced without the inter-

see

Mr. E. Howarp 02 a new fulminating Mercury. 227

vention of mercury; and that, according to the Dutch chemists,
the product of ether, is always in the inverse ratio to the pro-
duct of nitrous etherized gas. Should a further proof be thought
necessary, of the existence of the nitrous etherized gas in the
fulminating mercury, as well as in the white dense fumes, it
may be added, that if a mixture of alcohol and nitrous acid
holding mercury in solution, be so dilute, and exposed to a
temperature so low, that neither ether nor nitrous etherized gas
are produced, the fulminating mercury, or the white fumes, will
never be generated: for, under such circumstances, the mer-
cury is precipitated chiefly in the state of an inflammable oxalate.
Further, when we consider.the different substances formed by
an union of nitrous acid and alcohol, we are so far acquainted
with all, except the ether and the nitrous etherized gas, as to
create a presumption, that no others are capable of volatilizing
mercury, at the very low temperature in which the white fumes
exist, since during some minutes they are permanent over water
of 40° FAHRENHEIT.

SECTION XVI.

Hitherto, as much only has been said of the gas which is
separated from the mercurial powder by dilute sulphuric acid, .
as was necessary to identify it with that into which the same
acid can resolve the nitrous etherized gas; I have further to
speak of its peculiarity.*

* It must be first noticed, that it is never pure when obtained from the nitrous
etherized gas; nor am I aware how it is to be purified, unless the nitrous gas could be
taken from it, without being converted into nitrous acid; for, by that acid, it would
probably be itself converted into nitrous gas.

Gge

J

228 Mr. E. Howarp on a new fulminating Mercury.

The characteristic properties of the inflammable Bas, seem

‘to me to be the following :

ist. It does not diminish in volume, either with oxygen or

‘nitrous gas.

edly. It will not explode with oxygen by the sides shock,
in a close vessel.

gdly. It burns like ede etek but with a bluish om
flame. And,

athly. It is permanent over water. (Section 12.) on

It is of course either not formed, or is convertible into nitrous
gas, by the concentrate nitric and muriatic acids; because,
by those acids, no inflammable gas was extricated from the
powder. is

Should this inflammable gas prove not to bed a hydrocar-
bonate, I shall be disposed to conclude, that it has nitrogen for
its basis; indeed, I am at this moment inclined to that opi-
nion, because I find that Dr. PriestLry, during his experiments
on his dephlogisticated nitrous air, once produced a gas which
seems to have resembled this inflammable gas, both in the mode
of burning, and in the colour of the flame.

After the termination of the common: solution of iron in
spirit of nitre, he used heat, and got, says he,* “ such a kind
“of air as I had brought nitrous air to be, by exposing it to
‘iron, or liver of sulphur; for, on the first trial, a candle
* burned in it with a much enlarged flame. At another time,
“the application of a candle to air produced in this manner,
“‘ was attended with a real though not a loud explosion; and,
“ immediately after this, a greenish coloured flame descended.
« from the top to the bottom of the vessel in which the air was

* PrizstLey on Air, Vol. II. p. 58. Birmingham. 1790.

Mr. E. Howarp on a new fulminating Mercury. 229

‘« contained. In the next produce of air, from the same process,
« the flame descended blue and very rapid, from the top to the
« bottom of the vessel.”

These greenish and blue coloured flames, descending from
the top to the bottom of the vessel, are precisely descriptive of
the inflammable gas separated from the powder. If it can be
produced with certainty by the repetition of Dr. PrizsTLEy’s
experiments, or should it by any means be got pure from the
nitrous etherized gas, my curiosity will excite me to make it
the object of future research; otherwise, | must confess, I shall
feel more disposed. to prosecute other chemical subjects : for,
having reason to think that the density of the acid made a varia-
tion in the product of this gas, and having never found that any
acid, however dense, produced an immediate explosion, I ence
poured 6 drams of concentrate acid upon 50 grains of the
powder. An explosion, nearly at the instant of contact, was
effected: I was wounded severely, and most of my apparatus
‘destroyed. A quantity moreover of the gas I had previously
prepared, was lost by the inadvertency of a person who went
into my laboratory, whilst I was confined by the consequences
of this discouraging accident. But, should any one be desirous
of giving the gas a further examination, I again repeat, that as
far as I am enabled to judge, it may with safety be prepared,
by pouring 3 drams of sulphuric acid diluted with the same
quantity of water, upon 50 grains of the powder, and then
applying the flame of a candle until gas begins to be extricated.
The only attempt I have made to decompose it, was by ex-
posing it to copper and ammoniac; which, during several weeks,
did not effect the least alteration,

230 Mr. E. Howarp on a new fulminating Mercury.

SECTION XVII,

I will now conclude, by observing, that the fulminating mer-
cury seems to be characterised by the following properties.

It takes fire at the temperature of 368 FAHRENHEIT; explodes
by friction,* by flint and steel, and by being thrown into ‘con-
centrate sulphuric acid. It is equally inflammable under the
exhausted receiver of an air-pump, as surrounded by atmo-
spheric air; and it detonates loudly, both by the blow of a
hammer, and by a strong electrical shock.

Notwithstanding the composition of fulminating silver, and
of fulminating gold, differ essentially from that of fulminating
mercury, all three have some similar qualities. In tremendous
effects, silver undoubtedly stands first, and gold perhaps the
last. The effects of the mercurial powder and of gunpowder,
admit of little comparison. The one exerts, within certain limits,
an almost inconceivable force: its agents seem to be gas and:
caloric, very suddenly set at liberty, and both mercury and water
thrown into vapour. The other displays a more extended but
inferior power: gas and caloric are, comparatively speaking,
liberated by degrees; and water, according to Count Rumrorp,
is thrown into vapour.

Hence it seems, that the fulminating mercury, from the limi-
tation of its sphere of action, can seldom if ever be applied to
mining; and, from the immensity of its initial force, cannot be

* Consequently it should not be inclosed in a bottle with a glass stopper.

+ See Philosophical Transactions, for the year 1797, p. 222.

The hard black substance mentioned by the Count, as remaining after the com-
bustion of gunpowder, must, I believe, have been an alkaline sulphuret, mixed chiefly
with sulphite and carbonate of potash. ‘The conjecture that it is white when first
formed, is certainly just, as my experiment with the glass globe evinced.

Mr. BE. Howarn on anew fulminating Mercury. 291

used-in fire-arms, unless’in cases where it becomes an object to
destroy them ; perhaps, where it is the practice to spike cannon,
it may be of service, because, I apprehend, it may be used in
such a manner as to burst cannon, without dispersing any |
splinters. | ,

The inflammation of fulminating mercury by concussion,
offers nothing more novel or remarkable, than the inflammation,
by concussion, of many other substances. The theory of such
inflammations has been long since exposed by the celebrated
Mr. BerTHOLLET, and confirmed by Messieurs Fourcroy and
VAUQUELIN: yet, I must confess, I am at a loss to understand,
why a small quantity of mercurial powder made to detonate
by the hammer, or the electric shock, should produce a report
so much louder than when it is inflamed by a match, or by
flint and steel. It might at first be imagined, that the loudness
of the report could be accounted for, by supposing the instant
of the inflammation, and that of the powder’s confinement be-
tween the hammer and anvil, to be precisely the same; but,
when the electrical shock is sent through or over a few grains
of the powder, merely laid on ivory, and a loud report is the
consequence, I can form no idea of what causes such a report.

- The operation by which the powder is prepared, is perhaps
one of the most beautiful and surprising in chemistry; and it
is not a little interesting to consider the affinities which are
brought into play. The superabundant nitrous acid of the mer- -
_ curial solution, must first act on the alcohol, and generate ether,
nitrous etherized gas, and oxalic acid. The mercury unites to
the two last in their nascent state, and relinquishes fresh nitrous
acid, to act upon any unaltered alcohol. The oxalic acid, al-
though a predisposing affinity seems exerted in favour of its
quantity, is evidently not formed fast enough to retain all the

232 =©Mr. E. Howarp on a new fulminating Mercury.

mercury; otherwise, no white fumes, during a considerable
period.of the aperationy but eae mercury is. would
be produced.
Should any doubt still be entertained of the existence of the affi-
nities which have been called predisposing or conspiring, a proof
that such affinities really exist, will I think be afforded, by com-
paring the quantity of oxalic acid which can be generated from
given measures of nitrous acid and alcohol, with the interven-
tion of mercury, and the intervention of other metals. For
instance, when two measured ounces-of alcohol are treated with
a solution of 100 grains of ‘nickel in a measured ounce and a
half of nitrous acid, little or no precipitate is produced; yet, by
the addition of oxalic acid to the residuary liquor, a quantity of
oxalate of nickel, after some repose, is deposited. Copper affords
another illustration: 100 grains of copper, dissolved in a mea-
sured ounce and a half of nitrous acid, and treated with alcohol,
yielded me about 18 grains only of oxalate; although cupreous
oxalate was plentifully generated, by dropping oxalic acid into
the residuary liquor. About 21 grains of pure oxalic acid seem
to be produced, from the same materials, when 100 grains of
mercury are interposed. (See section 14.) Besides, according to
the Dutch paper, more than once referred to, acetous acid is the
principal residue after the preparation of nitrous ether. How can
we explain the formation of a greater quantity of oxalic’ acid,
from the same materials, with the intervention of 100 grains of
mercury, than with the intervention of 100 grains of copper,
otherwise than by the notion of conspiring affinities, so analo~
gous to what we see in other phenomena of nature? }
I have attempted, without success, to communicate ful=
minating properties, by means of alcohol, to gold, platina,
antimony, tin, copper, iron, lead, zinc, nickel, bismuth,-cobalt,,

Mr. . HowARd on a new fulminating Mercury. 239

arsenic, and manganese; but I have not yet sufficiently varied
my experiments, to enable me to speak with absolute certainty.
Silver, when 20 grains of it were treated with nearly the same
proportions of nitrous acidand alcohol as 100 grains of mercury,
yielded, at the end of the operation, about g grains of a gray
precipitate, which fulminated with extreme violence. Mr,
CrurcksHanx had the goodness to repeat the experiment: he
dissolved 40 grains of silver in 2 ounces of the strongest nitrous
acid dilutéd with an equal quantity of water, and obtained (by
means of 2 ounces of alcohol) 60 grains of a very white powder,
which fulminated like the gray precipitate above described. It
probably combines with the same principles as the mercury, and
of course differs from Mr. Bertuotxet’s fulminating silver,
alluded to in page 230. I observe, that a white precipitate is
always produced in the first instance, and that it may be pre-
served, by adding’ water, as soon as it is formed; otherwise, when
the mother liquor is abundant, it often becomes gray, and is
re-dissolved.

P.S. Since the’ preceding pages were written, I have been
permitted, by the Right Honourable Lord Howe, Lieutenant
General of the Ordnance, to make the following trials of the
mercurial powder, at Woolwich, in conjunction with Colonel
BLoMEFIELp, and Mr. CruicKsHAnk. *

Experiment 1. From the manner in which the screw of the gun-
breech, mentioned in Section v. had acted on the barrel, it was
imagined, that by bursting an iron case, exactly fitted to the
bore of a cannon, its suddén enlargement might make many
flaws, and split the piece, without dispersing any splinters. In

* Itis with pleasure I take this opportunity of acknowledging the civil attention I
received from the different officers.

MDCCC. — Hh

234 Mr. ¥. Howarp on a new fulminating Mercury.

conformity to this opinion, a cast iron case was constructed,
with a cylindrical chamber, of equal length and diameter, calcu-
lated to hold 34th ounces troy of the mercurial powder. The
case, being firmly screwed together, was charged through its
vent-hole, and introduced into a twelve-pounder carronade, the
bore of which it exactly fitted. The powder was then enflamed,
with proper precautions. The gun remained entire, but the case
divided: the portion forming the upper surface of the chamber,
was expelled in one mass; that adjoining the breech, which con~
stituted the rest of the chamber, was cracked in every direction,
and in part crumbled; yet it was so wedged into some inden-
tations which the explosion had made in the sides of the piece,
that the fragments were not removed without great labour.
Exp. 2. Another cast iron case was prepared, of the same size
as the former, with a chamber also cylindrical, but wrought in a
transverse direction, and of a greater length than diameter; the
thickness of metal at each extremity not being more than a
quarter of an inch. This case was filled with nearly 5 ounces
troy of the mercurial powder, and placed in the same carronade.
Three twelve-pound shot were next introduced, and brought into
close contact with the upper surface of the case, as well as with
each other. The gun a second time withstood the explosion :
the case was divided across the middle of the chamber, into two
equal parts; that adjoining the breech was, as in. the former

experiment, much flawed, and left immoyeable; that nearest to ~

the muzzle was also much flawed, but driven out with the shot.
All the three shot were broken ; the two lower being divided inta
_ several pieces, and the upper one cracked through the centre. _

The report was so feeble, in both experiments, that an in-
attentive person, I am confident, would not have heard it at the
distance of two hundred yards.

Mr. E. Howarp on a new fulminating Mercury. 235

Exp. 3. It was found so difficult to extract the fragments of the
case remaining in the carronade, after the last experiment, that a
channel was drilled through them, to the vent-hole of the piece.
It was then charged with 6 ounces troy of the mercurial powder,
made up as a cartridge, which did not occupy above one half of
the diameter of the bore. A wad was placed over the powder,
dry sand superadded, to fill all vacuities, and the gun filled to
the muzzle with two twelve-pound shot. A block of wood was
set at a small distance, to receive the impression of the shot,
and the powder was inflamed as usual. The carronade still
resisted. One of the shot was split into two pieces; and the
block of wood was driven to a considerable distance, but not
penetrated by the shot above the depth of one inch. The
report was somewhat louder than the former ones. In all
three instances, a considerable recoil evidently took place. I
presume, therefore, that in the first experiment related in the
fifth Section, there must have been a recoil, though too trifling
‘to be observed; and, in the instances where the gun and the
proof were burst, it was not so much to be expected.

Exp. 4,. Finding that the carronade, from the great compara-
tive size of its bore to that of its length, required a larger quantity
- of mercurial powder to burst it than we were provided with, we
charged a half-pounder swivel with an ounce and an half avoir-
dupois of the mercurial powder, (the service charge of gunpowder
being g ounces,) and a half-pound shot between two wads.
The piece was destroyed from the trunnions to the breech, and
its fragments thrown thirty or forty yards. The ball penetrated
five inches into a block of wood, standing at about a yard from
the muzzle of the gun; the part of the swivel not broken, was
scarce, if at all, moved from its original position.

#xp. 5. One ounce avoirdupois of the mercurial powder,

Hh g

236 Mr. E. Howarp on a new fulminating Mercury.

enclosed in paper, was placed in the centre of a shell 4,4, inches
in diameter, and the vacant space filled with dry sand.

The shell burst by the explosion of the powder, and the
fragments were thrown to a considerable distance. The charge
of gunpowder employed to burst shells of this diameter, is §
ounces avoirdupois.

Ezp.6. A sea grenade, 3,5 inches diameter, charged like the
shell in the last experiment, was burst into numerous fragments,
by + of an ounce avoirdupois of the mercurial powder. The
fragments were projected with but little force, and only to the
distance of eight or ten yards. The charge of gunpowder re-
quired for grenades of this size, is 3 ounces.

Exp. 7. A sea grenade, of the same diameter as the last
mentioned, and charged in the like manner, with 2 of an ounce
avoirdupois, or 574 grains, of the mercurial nd olen was split into
two equal pieces, which were not thrown ten inches asunder. |

The report in the four last experiments was very sharp, but
not loud in proportion.

It seems, from the manner in which the swivel was burst, in
the fourth experiment, that a smaller charge would have been
sufficient for the purpose. We may therefore infer, both from
this instance and from the second experiment made with the
gun,in Section v, that any piece of ordnance might be destroyed,
by employing a quantity of the mercurial powder equal in weight
to one half of the service charge of gunpowder ; and, from the
seventh and last experiment, we may also conclude, that it
would be possible so to proportion the charge of mercurial
powder to the size of different cannons, as to burst them without
dispersing any splinters, But the great danger attending the use
of fulminating mercury, on account of the facility with which it ex-
plodes, will probably prevent its being employed for that purpose.

Mr. E. Howarp on a new fulminating Mercury. 237

In addition to the other singular properties of the fulminating

mercury, it may be observed, that two ounces inflamed in the
open air, seem to produce a report much louder than when the
same quantity is exploded in a gun capable of resisting its
action. Mr. CruicksHANK, who made some of the powder, by
my process, remarked that it would not inflame gunpowder.
‘In consequence of which, we spread a mixture of coarse and
fine grained gunpowder upon a parcel of the mercurial powder ;
and, after the inflammation of the latter, we collected most, if
‘not all, of the grains of gunpowder. Can this extraordinary fact
be explained by the rapidity of the combustion of fulminating
mercury? or is it to be supposed, (as gunpowder will not
explode at the temperature at which mercury is thrown into
vapour, ) that sufficient caloric is not extricated during this
combustion ?

From the late opportunity I: have had of conversing with
Mr. CruicxsHank, I find that he has made many accurate
experiments on gunpowder; and he has permitted me to state,
“ that the matter which remains after the explosion of gun-
¢ powder, consists of potash united with a small proportion of
-“ carbonic acid, sulphate of potash, a very small quantity of
¢ sulphuret of potash, and unconsumed charcoal. That 100
“« grains of good gunpowder yield about 53 grains of this resi-
“ duum, of which three are charcoal. That it is extremely
« deliquescent, and, when exposed to the air, soon absorbs
** moisture sufficient to dissolve a part of the alkali; in conse-
«© quence of which, the charcoal becomes exposed, and. the
“ whole assumes a black or very dark colour.” Mr. Cruicx-
SHANK likewise informs me, that after the combustion of good
gunpowder under mercury, no water is ever perceptible.

238 Mr. E. Howarp on a new fulminating Mercury.

REFERENCES TO THE FIGURES OF THE GLASS GLOBE, Be.
MENTIONED IN SECTION VII.

(See Plate VIII.)

A, a ball or globe of glass, nearly half an inch thick, and
seven inches in diameter. It has two necks, on which are
cemented the brass caps B, C, each being perforated with a
female screw, to receive the male ones D, E: through the former.
a small hole is drilled; the latter is furnished with a perforated
stud or shank G. By means of a leather collar H, the neck C
can be air-tightly closed. When a portion of the powder is to
be exploded, it must be placed on a piece of paper, and a small
wire laid across the paper, through the midst of the powder:
the paper being then closed, is to be tied at each end to the
wire, with a silken thread, as shewn at I. One end of this wire
is to be fastened to the end of the shank G, and the screw D
inserted to half its length into the brass cap B; the other end
of the wire, a, by means of the needle K, is to be drawn through
the hole F. The screw E being now fixed in its place, and the
wire drawn tight, it is to be secured, by pushing the irregular
wooden plug L into the aperture of the screw D, taking care
to leave a passage for air. The stop-cock M, the section of
which is shewn at N, is now to be screwed on to the part D,
which is made air-tight by the leather collar 6. The glass tube
O is bent, that it may more conveniently be introduced under
the receiver of a pneumatic apparatus. -P, shews the manner
of connecting the glass tube with the stop-cock.

fee) |

Thilos. rars. M D CCS 4 tale VIILy. 238

ube —"

=

~ 2

Philos. Trans MDC CC HtateNMLp. 238.

METEOROLOGICAL JOURNAL,

KEPT AT THE APARTMENTS

OF THE

ROYAL SOCIETY,

BY. ORDER OF THE

PRESIDENT AND COUNCIL.

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On A A

1799

Six’s
Therm.
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Heat.

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METEOROLOGICAL JOURNAL

for January, 1799.

|
Therm.| Therm.} Barom. |Hy-{ Rain.

without.} within.

ter
Inches.

39234
303 34
39243
39543
30540
30538
30535
30935
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30,28
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30,14
29,96
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39,31 ;

30532
30,26
30,22
39,14
30,16
30,23
30325
30,21
30,21
30525
39,29
39535
30232
30,22
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me-

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Winds.

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Cloudy.

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Cloudy.
Cloudy.
Cloudy.
Cloudy.
Fine.
Cloudy.
Cloudy.
Foggy.
Cloudy.
Fine.
Foggy.
Cloudy.
Cloudy.
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Cloudy.

Foggy.

Cloudy.

Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Fair.

Fine.

[3 J

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t

METEOROLOGICAL JOURNAL

for January, 1799.
ele Time. wher: mets Barom. as Rain, Winds.
n7ggihctt ase = Tee Te alae a
Heat. |H. M. ° 6) Inches, Inches.| Points. | Str.
oO
Jan. 17) 32] & jo | 31 50 | 30,19] 71 E 1 |Cloudy,
; Saye FO 34: 51 | 30,15 | 68 E t |Fair.
18] go | 8 jo 33 2 | 29,97 | 70 ESE | 1 |Cloudy.
AG |. 2 jo 43 53 | 29:93 | 78 S { |Cloudy.
g| 41 8 Oo 42 51 30,01 | 88 S 2 Cloudy.
a 43 : o| 43 53. | 30,0a | 80 SSE | 2 |Cloudy.
3 On| Az 5O 4.) 29,931 73 SSE | 2 |Fair.
44 f Oo] 44 52) ele @sa2e|) © SSE | 2 |Cloudy.
21) 42 Oo} 43 50 | 29,62 | 86 SSE | 2 |Cloudy.
Ago Zi 40° like 5 53. | 29,62 | 85 SSE | 2 |Cloudy.
22), gia 8 10} 39 50 | 29,82] 80} 0,169| S 2 |Cloudy.
ASN JOO 45 SM ZOsae 7a S 2 |Fair.
23|,4 407 |B jo 4r RE t| 29525578] 6,077 S 1 |Cloudy.
AGEN Zi Ode 44 54 | 29.25 | 74 S 2 |Cloudy.
24\ (am | 8 jo 4) gs 51 | 29,52 | 76] 0,082 | SSW} 1 |Fair.
Age 2 10 |e 44 55 | 29355 | 67 SSW | 1 |Fair.
25) sSeetthy S: OMpe.3 7 52 | 29,704 75 SSW | 1 |Cloudy,
AZ ALA AOMY 354.2 54 | 29,65 | 75 NE | ¢ |Cloudy.
26| 3450.8 jowW (36 52 | 29,831 76 SW | 1 |Cloudy.
Ax NS JOMEE As 54 | 29,90 | 65 WNW} ¥ |Cloudy.
271, eigipe 88 JO 1 40 52 | 29,58] 78] 0,161} SSE | 1 |Cloudy.
FON a jOMecico 54 | 29.41 | 85 SSW | 1 |Rain. ©
28) 320 Jom v3.2 53 | 29,48 | 80] 0,305 | ESE | 1 |Snow. :
9g) 2 jolt) 29 54 | 29,64 | 61 NW | t |Fair.
29| 25 8 of} 26 52°41 20575175 W 1 |Cloudy.
ZA. 2 Jo. 34 54 | 29,68 | 65 S 1 |Fine.
Z0| 29S jo Ni 29 5° | 29,37 | 77 NE | 1 {Snow.
Zura joel 3h 52 | 29,461 73 NE | 1 |Fine.
31 a St fom 232 48 | 29,5572 E 1 |Cloudy,
2 2 Ou e2s 48 | 29,26 | 80 E 2 |Snow.

C4

METEOROLOGICAL JOURNAL

for February, 1799.

Six’s Therm. | Therm. | Barom. |Hy-| Rain. Winds.
Therm. | Time, }without.| within. gro-
least and me-
1799 greatest nama ter Weathes
Heat. {H. M. ° 6 Inches. Inches. | Points. | Str.

ns | i | cs ee

°

Feb. 1/2647) (0 1" g0 48 | 29,24] 92 E 1 |Snow.
332) 0 az 50 | 29,22 |91 E | 1 |Snow.

ZV LiZONa (OW W29 48 | 29,09 | go NE | 1 |Cloudy
Binge 2; HO 13 t so. | 29,11 | 82 NE | 1 |Snow.
Size iiss 1Orilwa2z 46 | 29,48 173 W | 1 |Fine.
ZO. SOU |e 27 49 | 29,53 | 68 WNW| 2 |Fair.

4) 18) a7 10 | eee 46 | 29,57 |74 NE | t |Cloudy

ZOWnliz. loll yes 48 | 29,56175 NE | 1 |Cloudy.

5} 19 |7 ©] 25 | 45 | 29:591|77 NE | 3 |Cloudy.
30) WZ) 01-420 47 | 29357174 E 1 |Cloudy

6] 125 al ato 4 aa 44 | 29,65 |70 E 1 |Cloudy
23 aia oAlie28 46 | 29,70 |69 ENE | 2 |Cloudy

7 eh Wefan Onl 2.5 44 | 29,87/71 NE | 1 {Cloudy
2S eZ O Wy 27 44 | 29,92 | 69 NE { 1 |Cloudy

SH 2g Ma 70 ON e2 43 | 30,09 | 68 NE | 1 |Cloudy

27 i 2 Cul e26 45 | 30,14 | 68 E 1 |Cloudy,.

9| 42377. Jul a0 42 | 29,84 | 84 ESE | 2 |Snow.
4001-2, *O ilie-Z0 47 | 29,88 | 84 SSW | 1 |Fair.
10/432 Pil 7 vO {ikea 45 | 30,26 | 86 SSW | 1 |Fair.

AZ 2, OAS 48 | 30,26 | 82 SSW | 1 |Cloudy.

UH ee7 Og, (OMe eso 46 | 29,18 | 84] 0,953] S 2 |Cloudy
AI 2 0 39 49 | 28,88] 78 SSE | 2 |Rain.
12120, M7, FOul) a0 45 | 29,70|68] 0,115 | NE | 2 |Fine.
area 2 AOulraesy: 49 | 29,93 | 67 NNE | 2 |Fine.

13) esOM es OL 32 46 | 29,82 | 82] 0,020 | SSW | 2 |Snow.
Al gb 2 Ol £0 49 | 29,80| 78 W | 1 {Cloudy

TA OZ2ua 7. Ob gz 47 | 29:99 177 W {1 |Fair.
44,312 Of -44 50 | 29,88 | 66 SSW } 1 |Fair.

V6) (AGO 47, 10 43 50 | 29,48 | 87] 0,088 |} WSW| 1 |Cloudy
GOW 270) co 54 | 29,45 | 67 SSW | 2 |Cloudy

r6)) 38 i) 7 [ol 140 51 | 29,07} 78] 0,380} SW | 1 |Cloudy
AicioM zy FOWL Aad: 530295121 70 WSW I 1 jRain.

ad

METEOROLOGICAL JOURNAL

for February, 1799.

Six’s Therm. | Therm.] Barom. |Hy-} Rain, Winds.
< without.| within. gro-

see Weather.
Inches. Inches. } Points. | Str.

Cloudy.
Fair.
Rain.
Rain.
Cloudy.
Rain.
Cloudy,
Cloudy.
Rain.
Fair.
Cloudy.
Cloudy.
Fair.
Fair.
Cloudy.
Fair,
Fair.
Fine.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.

I
Zz
I
1
2
2
I
I
2
2
2
2
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eco0o0000aae0oecco0a0C0C0OcC0Oea0ae000e0 Go

Ee 2

METEOROLOGICAL JOURNAL

for March, 1799.

Six’s Time. | Therm. | Therm.| Barom. |Hy-

Therm. without.} within. gro-

least and me-

1799 | greatest ter
Heat. |H. M. iS ° Inches.

nea See

Mar.1] 47 | 7 ©} 47 | 58 | 30,03} 79

S6ngqt2 SO" Hie6 61 | 29,90 | 66

2) AZNB EG eed 2 SD | | 29708 M75

50 2/0 50 62 | 30,05 | 53

3| NZOKIA7 SO | ae 58 | 30,21 | 68

AQUI 2 NO G40 60 | 30,20] 55

4) B27 FO | “33 56 | 30,19 | 74

48 Z FO 148 59 | 30.14 | 63

5) BS TO 12 30 6 ho 5G ht Be mate t

41 2 VO Ni atr 58 | 30,21 | 62

6} 35 17 0] 35 | 55 | 30.23/65

B72 SO 37 1) 56.) Besa TO4

7|- 2330 AN7 10183-4153) Beszeni67

371 2101377 | 54 | 50:19 68

8) gat 7 6 Onl ug4 53, hy 3o2 07073

38 | 2 9} 37 | 54 | 29:99} 7°

9} -29%ie7 S Ove ssa 51) e902 4

Be ae TOs 5A | | 2OSOH SH Z

FO) gael hort 51 ZOmasiet

Az ta? POW maa 54 | 30,16 | 64

Il wigowale? 1 ON toe 50 | 30,05 | 76

Gomi? FO) BO 52 Vy BOCA 7.3

12/36 |7 0} 36 | 51 | 30:04] 77

48 | 2 0} 47 54 | 30:07 | 70

13} 33 17 ©} 33 | 51 | 29,84] 70

44 [2 O!| 44 | 54 | 29,55 | 66

A) G32 Ge «Orn 33 5041 20251 | 74

36 | 2 of 36 | 52 | 29554173

BO 34s dog O34 DO 20274) | 72

AO Pie Que. 40 52 | 29,77 | 60

I 33 7 OMS 50 | 29,80 | 68

42, | 2 ol 42 | §2 | 29,87157

Rain,

Inches.

Winds.

Points.

Str.

pl aa, TO LST a Ti Hi Pa tS YO fe Yet yy rr Om

Weather.

Cloudy.
Fair.
Fair.
Fine.
Fair.
Fine.
Fair.
Fine.
Cloudy.
Fair.
Cloudy.
Cloudy.
Snow.
Cloudy.
Cloudy.
Cloudy.
Snow.
Snow.
Cloudy.
Fair.
Cloudy.
Cloudy.
Cloudy.
Pair.
Cloudy.
Cloudy.
Snow.
Cloudy.
Cloudy,
Cloudy.
Cloudy.
Cloudy.

Co 3

METEOROLOGICAL JOURNAL

for March, 1799.

Six’s Time, | Therm.| Therm.]| Barom. ly. Rain.

Winds.
Therm. without.} within. gro-
least and ; mes Weather
1799 greatest io os a ae (ae :
Heat. |H. M.| 06 ° Inches. Inches. } Points. { Str.
S a
Mar-17| 35.-.|7. © |u1 36 50 | 29,78 | 62 S 1 |Cloudy.
AZ WZ Olly v4z 51 | 29,72) 58 S 1 |Cloudy.
18) 3 7a Ws 49 | 29,67 | 63 SSE | 1 |Cloudy.
AG We 2x. © 1445 52 | 29,69 | 61 S 1 |Cloudy.
19) 2a ln. ©] A gt 50 | 29,81 | 75 W | 1 |Fair.
45 2. O-| 45 54 | 29,66 | 56 S 1 |Cloudy.
20} 33 007. © | 38 50 | 29,31} 74| 0,023| E 1 |Cloudy,
AZ Ne 2 2 O by widlZ 54 | 29,38 |.76 ESE | 1 |Cloudy.
ZB) Tae 7 oO) |) 4833 49 | 29,68|75 NE | 1 |Cloudy.
AG. 12. 0 by 46 52 | 29,70| 70 ENE | 1 |Cloudy.
22) 936 its'7 © 1536 51 | 29,72} 76 NE | 1 |Rain.
AL Glj2 . 0 |e val 53\ | 29572,|:70 ENE | 1 |Cloudy.
23) 328. of. 7'. 0 kyag8 52 | 29,70] * | 0,062} NE | 1 |Cloudy.
A5 Nz Ot 46 54 | 29,68 S 1 | Fair.
PA AO. 7 O | 43 52 | 29,62 0,028} E 1 |Cloudy.
B41 2, O bod 55 | 29555 SE | 2 |Fair.
25) 460. °h 7. © |,» 46 54 | 29,45 ESE | 2 |Cloudy.
Ona. On| 5 56 | 29,59 W | 1 |Fair.
26), 30) 7 oO | 5.48 54 | 29,74 0,018 | SSE | 2 |Fair.
AS oe « O41 43 55 | 29,60 $ 2 |Rain.
27) 897 Wi tO Ryo 54) | 2osg 1 0,031 | SW | 2 |Fair.
SL ah © 1npa5O 56 | 29,49 WSW | 1 |Fair.
28) S24 aay A ONe 63's 547) ass SW | 1 |Cloudy.
49 -| 2, © fie 49 57. | 29,66 WSW | 1 |Fair.
29) 34 17 O| 34 | 54 | 29,95 SW | 1 | Fair.
AS <i 2 Oulnn 48 56 | 29,97 E 1 | Fair.
ZO) SS let On aS) 51 | 30,00 E 2 |Cloudy.
2A alee Oo 34. 54 | 29,94 E 2 | Fair.
31)" 28 oie wes | 28 5° | 20,77 ENE | 2 |Cloudy.
34. th Ze Ont 3a: 52. | 29,73 ENE | 2 | Fair.

*. The whalebone of the hygrometer slipped out of its place.

L3J

‘ “ ~

METEOROLOGICAL JOURNAL

for April, 1799.

Time. |Therm.} Therm. | Barom. |Hy-]| Rain. Winds.
without.] within.

ae Weather.

H. M. by is Inches. Inches, | Points. { Str.

VA anew tule Yo) 48 | 29,77 NE | 2 |Fair.
200 | @37 54 | 29,83 NE | 2 |Fine.
ZrO ogo 47 | "203Q2 NE | z {Cloudy.
Zio | 38 51 | 29,97 NE ‘| 2 | Fair.
ZOO sean 48 | 29,85 E 2 |Cloudy.
2E Ohad 49 | 29,82 E 2 | Fair.

74 Ov eat 48 | 29,78 E | 2 |Fair.

2't Orne gu: 52 | 29,70 ESE | 2 | Fine.

7k OA Soy tl 29320 0,312| E z |Rain.

2% O19 453 54 | 29.24 SSE | 2 |Cloudy.
7 uO Ae 53. | 29,40 0,068| NE | 1 |Cloudy.
208" Bak 54 | 29,48 NE | 1 |Cloudy.
BLO 1636 52 | 29,76 NE | 1 |Cloudy.
ZrO | Oaa 53 | 29.79 NE | 1 |Cloudy.
7 0 138 50 | 29,66 E | 1 |Cloudy.
Ze-O er 54 | 29,55 SSE | 1 |Cloudy.
7 Of 43 52). | 20555 0,167 S 2 |Fine.
Zh iQ: bere. 57 | 29554 S 2 |Cloudy.
7 Of 46 53. | 28,86 0,100 S| 2) Rains) (tcumine
20.1% 49 gs | 28:75 S 2 |Rain. ag
TOI) ae 53. | 29:27 0,062 | SW | 2 |Fair.

Zt ORG. 56 | 29,27 SSW | z |Cloudy.
7 (Of 42: 54 | 29,36 0,039 | SSW | 1 |Clondy.
ZO} * 56 56 | 29555 NE | 1 |Cloudy.
7 sO. hae 55 | 30,01 0,036} NE j 1 |Cloudy.
ZO) | CO 56 | 30,12 NE | 1 |Fair.

7h 0} 926 54. | 30,23 NE | 1 |Fine.

22 'O |e AF 54 | 30.11 NE | 1 |Cloudy,
7 Show than 53% 129555 E 2 |Cloudy.
2° Ol? 156 57 | 29,42 E 2 | Fine.

7 O48 551 129,21 0,075} E 1 | Cloudy,
2204 55 57 29,26 SW 1 | Fair.

L’9 4

METEOROLOGICAL JOURNAL

for April, 1799.

Six’s | Time, | Therm.]Therm.| Barom.|Hy-| Rain. Winds.
ee without.| within, gro-
and! i -
179 Sear le marnE ter: al
Heat. | H. M. a ° Inches. Inches. | Points. | Str.
°
RDI U7 ae ee Ot AT 55 | 29515 0,073 | SSE | 1 (Cloudy.
Ge Or he eA. 58 | 29,22 S 2 \Cloudy.
KSb 92g clip a tOot VAT 55 | 29,02 0,076 | SSW | 2 |Fair.
15 iinet Zam 2) aia 58 | 29,00 SW | 2 [Fair.
19)" 39) he 10! [9.4.3 55 | 28395 0,185 | ESE | 1 |Rain.
50 12° 8 1 Zo 57. | 29,08 W } 1 {Cloudy
20)" Aerie 1.0: tara 55 | 29538 0,170 | NNE| 2 |Cloudy.
50 |-2 © | 50 56 | 29,52 NW | 2z jCloudy
Pil > ito ih FeO G3 55 | 29575 0,018 | NE | 2 |Cloudy
Bee Ot 50 58 | 29,82 NE | 2 |Cloudy
22) 3g. 7 © | 242 55 | 29579 S 1 |Cloudy.
a a O | SOs 57 | 29,66 S z |Rain.
23) ao 7 --O. fo246 55 | 29-41 0,086 | ENE | 1 |Rain.
zane sO) fot 57 | 29,51 ENE |} 1 |Cloudy.
ZAM leg Ol al 55 | 29387 0,028 |} NE | 1 |Cloudy
4s 2 @ | 48 56 | 29,92 NE | 1 [Cloudy
Zo) agen ee meetin ge 54 | 30,06 NE | 1 {Cloudy
ao 2 ol |) Ap 56 | 30,03 NE | 1 {Cloudy
26) Azer GL Ae 55 | 29,78 0,176 | NE | 1 {Cloudy
47 Ne OAT 57. \ 29,96 NE | 1 {Cloudy
271 30) eg Or, AI 55 | 29,98 NE } 1 |Cloudy.
BB les eS tin 53 bl) 57 1.1 29309 NE | 1 |Cloudy
28) 48" “V7 Gao 55 | 29,90 NW | 1 |Cloudy.
eal eae OA 57 | 29,89 NW | 1 {Cloudy
291 4217) Gah Az 55 | 29,96 NE | 1 |Cloudy.
49) 20.Gul 47 56 | 29,96 NE | 1 |Cloudy.
20] 41 47 OG 2 55 4 30,04 NE } 1 |Cloudy.
43 “C25 ob 48 56 | 30,02 NE | 1 [Cloudy

* E tos

METEOROLOGICAL JOURNAL

for May, 1799.

Six’s | Time. | Therm. | Therm. | Barom. Hy-| Rain. Winds.

Therm. without. within. | gro-
1799 | greatest i oes ee bin
Heat. |H. M. i 4 Inches, Inches. | Points. | Str.
May i] 37.417), 0 fo) 54 | 29, S 1 |Cloudy.
C7 liz. © a 56 mas WSW | 1 | Fair.
2) "543 Ble. (© aheayig 54 | 29,61 0,191 | NE | 1 {Rain.
47 2. O |us47 56 | 29,61 E 1 | Cloudy.
31. 30) M7, O Weare 65. | 20574 NE | 1 |Cloudy.
52 li, Ovlnaeki2 RoW 2oeaal NE | 1 |Cloudy.
A) 39) 407 Ont «Aa 55 | 29,85, ENE | 1 |Fair.
5A wz, CO wane 56 | 29,83 NE | 1 {Cloudy.
Bl 44 hy. O ile aa 56 | 29,73 NE | 2 |Cloudy.
SA 2 Oly ea 57 | 29,69 E 2. |Fair. ,
6-48 7) © \igikO 56 | 29,63 0,052 | . EB 1 | Cloudy.
62.2. O63 59 | 29,63 E 1 | Fair.
i 4a NFO slowAdAt. 57 | |- 20552 03137 |, NE, |» | Rain,
OF IN2) Oy, OL 60 | 29,48 E 1 | Fair.
BL 48 7, Oba 58 | 29,50 0,061] NE | 1 | Cloudy.
5O) 2 OL ngs 60 | 29,51 NE | 1 | Cloudy.
9] 5! 7 OtlguG2 59 | 29,58 0,053 | SW | 1 | Cloudy.
SO N2 Otago 60 | 29,58 SSW | 1 |Cloudy.
FO] 47. A 7 © ist Ao 59 | 29.58 0,020 | SSW | 1 | Rain.
7 lee . Onl se. 59 | 29555 WSW | 1 | Cloudy.
EI) 4A 0 Al AO 59 | 29355 SW: | 1 Fair.
GO aiez,. Onl aod 60 | 29,51 SE | 1 | Rain.
12) 45g Ons 58 | 29,61 0,023 NE | 1 | Fair.
OT he) Ob kgs 59 | 29.67 NE | 1 |Rain.
13) 48" 17" © |, 48 60 | 2971 0,054 | SSE | 1 | Cloudy.
Lf ay A? Jatoba PS 60 | 29,68 SSE | 1 | Fair.
VAL AG 7 Or lee Ad 59 | 2971 0,089 | NE | 1 | Cloudy.
Ba le On Raced 60 | 29,77 NE | 1 | Cloudy.
Te AGO Wa (Obie ea 57.) | 20597 NE | 2 | Cloudy.
51 27 Onl amined 58 | 30,02 NE | 2 |Cloudy.
oj ine feieant ty mola] 8 7 Ke) 57 | 130234. NE | 2 |Fine.
So Wael 56 58 1 30,38 NE |.2 |Fair.

’

C1

ee a,
METEOROLOGICAL JOURNAL

for May, 1799.

Six’s | Time. | Therm. | Therm. | Barom, |Hy-| Rain. Winds.
Therm. without.| within, gro-
feastand| TiC= Weather.
1799 greatest ter ; |
Heat. |H. M. o > Inches Inches.| Points. | Str. |
- becca
Mayi7] 41 |7 0 6 is 30,3 S 1 (Fair.
61.9 | 2 “6 - 33 sae SW | 1 |Hazy.
18) “a708) 7) “oll 49 Bye iN 20,08 0,053 | SSW | 1 |Cloudy.
66 6) 66 60 | 29,71 ay I pane
I Tenn t7a <O Se azo; 0,117 1 |Cloudy.
e ae Zao) a 26 we SW | 1 |Cloudy.
20] Sma Toul vor 58 | 29,33 0,575 | NE | 1 jRain.
SZ Ae 2: fod ¥en 69 | 29,64 N | 2 |Cloudy,
2 TA cme Ou) Ao 59 | 29,88 0,245|. W | 2 |Hazy.
Gwtie ze: O14) 5s 60 | 29,76 SSW | 2 |Cloudy.
22h, ATE Z% 0) “Go 59 | 29,97 WNW} 2z |Fine.
GArbZ. '0}} “64: 61. i! 30507 WNW) z |Fair.
23 Samu OF 'O-L "57 60 | 29,94 W | 2 |Cloudy,
Gon 2 10/1" Gg 61 | 29,95 W | 2 |Fair.
ZA| 45087. Onl 40 60 | 29,94 0,016; W_ | 2 |Cloudy.
60 2 96) 60 60 | 30,05 NW | 2 |Fair.
25 Asai ze Caleag 59) 1 40532 WNW 1 |Fair.
Ossie zs Oe Or 61 | 30526 W | 1 |Fine.
26) Ane Ae (OU GE 60 | 30,17 W | 2 |Fair.
66 |2 o| 66 61 | 30,10 W | 2 |Cloudy.
27| 48.0170) 51 | 6o, | 305nGiI™ NE | 1 |Fine.
CAs ete 2) Ont 264. 61 | 30,20 N | 1 |Fair.
28) AGRI? : “Onliarss 60 | 30,27 ENE | 1 |Hazy.
fo. Eon ein(o) 61 | 30527 E 1 |Fine.
29| -45aeI7 2 Oo 53 60 | 30,10 E 1 |Fine.
FOI ZO) 570 62 | 29,96 E 1 |Fine.
Z0| 5 ISO ans 61 | 29,81 SSW j| 1 |Cloudy.
60 y4, 46) 58 61 29,80 NW | 1 [Rain.
Z| .48 9|-7 ON G2 60 |} 30,03 0,072} NW | 1 |Cloudy.
GOm) Zo 61 | 30,07 WNW} 1 |Cloudy.

METEOROLOGICAL JOURNAL

for June, 1799.

Six’s | Time. |Therm.| Therm.| Barom, |Hy-| Rain, Winds.

lenge without.| within. gro-
east an me-
1799 | greatest ae Weather,
Heat. |H. M. 3 RB Inches. Inches. | Points. | Str.
°
June's} 48.7 10%!) 52 60 | 29,99 SW | z |Fair.
Go, ali2. 0) “58 61 | 29,88 S 2 |Raio.
2) / 40a 011| Sago 60 | 29,76 0,028 | § 1 |Cloudy.
61 2 0)! W590 60 | 29,68 SW | 2 |Fair.
3) = §Oui C70) wig 60 | 29555 0,055 | S_ | 2 |Cloudy.
61 2 0| 61 60 | 29,54 SW | 2 |Fair.
4) SO 101) aga 60 | 29,18 0,056 | SW | 2 |Rain.
GOA?) RO. ASS 59 | 29,30 SW |} 2 |Fair.
I. 4Oy A kF 0 49 58 | 29,68 SW | 2 |Fair.
62,2. 4,0 )) Wer 60 | 29,87 NW | 1 |Fair.
6) (48047 10 1M ipa 59 | 30,19 SW | 1 |Cloudy.
67 2 0} 67 60 | 30,22 SW | 1 |Pair.
Ales tl Gato heir 60 | 30,38 SW | 1 |Cloudy.
75 slv2i.20 4 35 62 | 30,41 SSW | 1 |Cloudy.
8) SS udh7, 0 {| On 62 | 30,41 E 1 |Fine.
7% ghee! Ou angi 64 | 30.35 E I |Fine.
9. $5 lez. Or 64 | 30,20 ENE | 1 [|Fine.
Th AG2 -O}) 74. 65 | 30542 NE | 1 {Fine.
40. 57.457) Oj OX 65 | 30,05 NE | 1 [Fair.
RF ARZ) OL 79 67 | 30,03 NE | 1 |Fine.
It] 490M 7,, O71 15a 65 | ||| 4O,21 NE | 2 /Fine.
BOinie2 © || eo 65 | 30,21 NE | 2 |Fine.
¥2| 45,0107, ©7450 63 -\| 30326 NE | 2 |Cloudy.
64 citi 2, ©} 64 64 | 30,15 NE | 1 |Fine.
13) 62.117), Oi gO 64 | 29,94 NW | 1 |Cloudy.
64 |2 0o| 61 64 | 29,82 NW | 2 |Cloudy,
FAL V5 ilt7). © ivasO 63 | 29,86 NE | 1 |Cloudy.
65.- W2 0 M64: 63 | 29,90 NE | 1 |Cloudy.
151 AG iAi('7), OUT VEO 62 | 30,02 NE | 1 |Fair.
60:12) oily Go 62 | 30,05 NE | 1 |Cloudy.
16). 43) 71 Ol] 50 61 | 30,15 NE | 1 {Cloudy.
SO fr 2y-ol 59 61 | 30,17 NE | 1 |Cloudy.

1% J

METEOROLOGICAL JOURNAL

for June, 1799.

Six’s | Time. Therm, | Therm, | Barom. |Hy-} Rain. Winds.

ee without.| within. gro-
€ast an = i
r, 1799 | greatest 7 ai a Weather,
Heat. |H. M.| 0 ° Inches, | Inches. | Points. | Str.
°
uner7) 46117 6.4... 50 60 | 30,17 NE jix
61 2) oun. Gt 6z | 30,15 NE | 1
ESI) Aza |e OM 5 60 | 30,21 NE | 1
64 4:2, ©} 64 62 | 30,20 NE }1
19] 40RK7. "0 753 61 | 30523 | ONE jix
67 2 )0.)) 007 62 | 30,23 NE | 1
ZO| AZ. N%) Olt 51 62 | 30,25 NE | 1
62° 4\e2) 0} 62 62) “WWa0s22 NE | 1
Zil FOVHE A: “Ook 953 62 | 30,20 NE | 1
65 ez) 0 | 705 64 | 30,20 NE: | 1
22) Ras OL BA 62 | 39,20 NE | 1
71 2\"O 71 63 | 30,11 NE | 1
zat (pate?) 0.) 60 63 | 29,90 SE) Gr
FE We2) © | 72 63 | 29,81 SW |i
ZA 47 sien © || So 62 | 30,00 0,033)| NE \iz
Gyoeiinz, 'o | 67 63 | 30,00 NE | 1
2h} - 465157) 0 | | 51 62 | 30,15 NE | 1
Goo iz, © | 63 62 | 30,10 E I
26) 54 Sie OF kA 62 | 29,98 o3o25) Wo ot
61 2; O48 So 62 | 29:95 S I
27, 56.7! O48 56 62 | 30,01 | W |i
66712, © | "66 62 | 30,05 NE | 1
28) Sele ge) Ol So 63 | 30,18 NW | 1
G7 2162) Op * Ge 63 | 30;24 NW /1
zo} S5inZ) OFF 56 63 | 30,24 roy NE j1
4 G7imui2) ©} (67 64 | 30,21 ia NE | 1
309 49 | 7 9} 53 | 63 | 30514 SW il i
97 tz OF 77 64 | 30,04 SSW | 1

La al

a Te
METEOROLOGICAL JOURNAL

for January, 1799.

Six’s | Time, |Therm.| Therm.| Barom. |Hy-
Therm. without.| within. gro-
least and me-
17 greatest

Heat. | H. M. o ° Inches,

710 | 166 64 | 29,90
201 72 64 | 29,86
7 9) 59 |. 64 | 29,83
ZO) |) yz 65 | 29,86
7 0} 59 | 65 | 29,97
Zi Olli a7iz 66 | 29,97
7 0} 57 | 65 | 30,05
2 0] 73 | 67 | 30,04
We © .462 66 | 30,10
ZecOillh a7. 67 | 30,12
7 Ke) 61 67 30,18
Zi 01h 77 677 305m
7) O.\ 163 67 } 30,10
2 0} 74 | 67 | 30,07
71.0 |) 160 68 | 30,03
2) 07} 77, 68 | 29,98
7 0} 63 | 68 | 29,94
Zio} 65 67 | 29,92
fig ONG SSR 1 17m || 30501
25.0" FO 68 | 29,98
7 9} 59 | 67 | 29,89
ZO | Fo 67 | 29,77
7 O| 62 | 67 | 29,54
Ze 10) 473 68 | 29,52
7 Of 56 | 66 | 29,77
7h 0) 69 68 29573
7 Of} 54 | 65 | 29,94
2 so) 70 66 | 29,98
aOR SS 65 | 29,58
21910 4\ 101g 65 | 29,61
7 0} 55 | 64 | 29,88
2 Vo

ter.
Inches.

——| ——>_——

Rain.

Points.

SW

0,120 S

0,110
SW
0,093 | WNW
WNW
S
W
NE
N

Winds,

Str.

m™ NNN NN NN wD me eee meee eet

Weather.

Cloudy.

Cloudy.

Rain.
Fair.

Cloudy.

Fair.

[35-4

METEOROLOGICAL JOURNAL
for July, 1799.

Time. | Therm. | Therm. | Barom. |Hy- i Winds.
without.| within.
1799 | createst ora iter: " Weather.
Heat. H. M. } ; . {| Points. | Str,
July 17 7) SW | 1 |Fair,
2 Oo) S Ze Pair.
18! a 16 ESE | 2 |Rain.
| 5 6) a SE 1 |Cloudy,
19) i aa) SW | 1 |{Cloudy.
2 O NW | 1 |Cloudy.
VO) W 1. | Cloudy.
z 0 W 1 | Fair.
7 SW | 1 |Cloudy.
Zio SW | 1 |Fair.
7 () SW | 1 |Fair.
2% SE 1 |Cloudy.
1); a) SW | 1 |Cloudy.
2 0 SW | 1 {Cloudy.
7; © S i |Rain,
2, 0 S 2 |Cloudy.
7: © S i | Fair.
ZO NW | t |Cloudy.
7 1X9) WSW | 1 Cloudy.
2 0 ENE} 1 |Fair.
7% 2 E 2 |Cloudy.
z oa E 2 Cloudy.
7+ © E 1 |Rain,
| 2 0 NE | 1 |Cloudy.
7+ © NW | 1 |Fair.
2 0 N 1 |Cloudy.
7i- © WNW] 1 |Cloudy.
2 0 NW | 1 {Cloudy.
7 © SSW | 1 {Cloudy.
z 0 S 2 |Fair.

[ane

METEOROLOGICAL JOURNAL

for August, 1799.

Six’s Ss Barom. |Hy-| Rain. Winds.
A area Time. |without.| within. gro-
1799 | greatest = eae Weather.
Heat. © o Inches. Inches. | Points. | Str.
oS ’
AUS. 1s 57H 71 Oo Pesss 6 29,78 | 63 SW | 1 |Cloudy.
; TZiwwes Oo 272 os Falta AS SSW | 1 |Fair.
2) 1G Sua May tO: ihe 7 64 | 29,97 | 65 S 1 |Cloudy.
FON 2) 0 |):68 64 | 29,91 | 49 S 2 |Cloudy,
3} BsOurig 6 © Igor 64 | 29,63|73|0,180} S 1 |Cloudy.
Fash 21, 0 | 16g 66 | 29,61 | 47 S 2 |Fair.
4) 254007 10: Pains 65 | 29,73 | 63 SW | 2 |Fine.
G22. © Nee 65 | 29,71 | 47 SSW | 2 |Fair.
Bh SPW 4D [957 64 | 29,36|70| 0,120] SE | z jRain.
69.12 © }) 68 65 | 29538 | 52 SW | z |Cloudy.
6) 54.17 1'0 1256 64 | 29,76 | 64 SSW | 1 |Cloudy.
63), '1e2 5 © | A160 64 | 29,76 | 63 SE j 1 |Rain.
9). 60 Pe 10: '\) 62 65 | 29,68) 78]0,275| S 1 |Cloudy.
CSV 2 Oo. Why 65 | 29,88 | 62 . | WSW| 1 |Cloudy.
StS Seay yO LangO 64 | 30,06 | 73 E 1 |Cloudy.
Oh 2 yO.) Gigs 64 | 29,93 | 68 E 1 |Rain.
Ql S5cnhe7 10 Pas7 63 | 29,761 73) 0,310} S 1 |Cloudy.
63.21 © P59 64 | 29,68| 74 NE | 1 |Rain.
VO) S207 ; ORS 64 | 29,93 | 70| 0,625 | SW | 1 |Fine.
TO. 2 1 O\seeGo 64 | 29,94 | 48 SSW | 2 |Cloudy.
LH BSS ain tO (ass 64 |} 29,90 | 67 SSW |} 2 |Fine,
FO UAN2 <O"} (70 64 | 29,83 | 48 SSW | 1 |Cloudy.
12] SO 7 £0. lesa 63 | 29,92 |70| 0,072 | SW |} 1 |Fine.
68 |2 of 68 64 | 29,94] 54 SW | 1 |Cloudy.
13), 4OgeN 7.1.0 Wa 63 | 30,05 | 68 SW | 1 |Fine.
Fie 110. Nie 64 | 30,04 | 45 S I |Fine.
TAY 25% 0407 ; OUlengs 64 | 30,00 | 61 E 1 |Hazy.
71 2 0 70. 64 | 29,85] 51 SE | 2 |Cloudy,
15] 160) 157.0 864 65 | 29,41 | 60 ey any 2 |Fine.
68 {2 O]| 66 65 | 29,50| 52 SSW } 2 |Cloudy.
16/952 407) Olin se 64 | 29,68 | 63 SW | 1 |Cloudy.
Gaines On fin, OF 64 | 29,74) 51 S 1 |Cloudy.

Six’s
Therm,
least and

EZ 9S Pere tcss

Aug.17
18
ng
20
21

22

23).

24

Heat.

Time.

YNA KHON AN XN NYY SON KON NN YN NN ON NN DYN NY NWV

ooo0o0o0o0o0oeoe0o0o0co0ao0o000 00000 00 0000 CO Oo:

ay

E

METEOROLOGICAL JOURNAL

for August, 1799.

Inches.

Therm. | Therm.| Barom. | Hy-
without.| within,

gro-
me-
ter.

Rain.

Inches.

0,062

0,103

0,086

0,120

Winds.

Points. | Str.

um | | | ee | | |

Weather.

Rain.
Fair.
Fair.
Fair.
Cloudy.
Fair.
Fine.
Fair.
Hazy.
Hazy.
Cloudy.
Cloudy.
Fair.
Cloudy.
Cloudy.
Fine.
Fine.
Fair.
Cloudy.
Fair. y
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Fine.
Fair.
Cloudy.
Cloudy.
Cloudy.
Cloudy.

METEOROLOGICAL JOURNAL

for September, 1799.

Six’s Therm. | Therm. | Barom. |Hy-]| Rain. Winds.
Therm. | Time. |without.| within. gro-
least and

par ————_-— Weather.
Inches. "| Inches. | Points. | Str.

‘
a | or | ee |

179 greatest
Heat. [H. M. °

Fin Wn g2 62 | 30,04 153 WNW| 1 |Fine.
6340/2 «9 | 7163 63 | 30,17 | 46 W | 1 {Fine.
2) AaaAlay's.@ | a5% 61 | 30,30] 63 SW | 1 |Fine
66 12 of} 66 62 | 30,32 145 SW | 1 [Fair
3) 4Oriia7 2 @ [go 61 | 30,32 | 64 SW | 1 |Fine
672 «oO HEE 63 | 30:27|50 SW | 1 |Fine
A 4H 1.9 |\ 49 62 | 30,32 | 68 SW {1 |Fine
682. 0 | 768 65 | 30,30 | 48 SSW | 1 |Fine.
5} 50 17-0] 54 | 63 | 30535 | 65 NE } 1 |Hazy,
gasiive; © |W 7X 65 | 30,35 | 57 .E 1 |Fine.
6} 56 17 O| 59 | 64 | 30:40} 73 1 |Cloudy
66 |2 o| 66 67 } 30,38158 E 2 |Fine.
a Sande co P56 65 | 30,321|71 E 1 |Fine
63 |2 of 63 67. “\ 305257153 E 1 |Fine.
$8} .49 17 Off 52 65 | 30,20 | 66 E 1 |Fine
63 |2 0 3 65 | 3014148 E_ | 2 |Fine.
9] 47 17 Of} 50 65 | 30,00} 71 ENE | 1 |Hazy
69 }2 0 9 66 | 29,98 | 47 ENE | 1 |Hazy.
101 AGelb7 1:0 [48 64 | 30,07 | 67 SE | 1 |Hazy.
65122 0 | *O4 64 | 30,06 | Go ENE | 1 {Cloudy
I} 60 1.7 0-] 953 64 | 29,98 | 68 NE | 1 |Cloudy
G2)0"L2, 0 162 63 | 29,87] 59 NE | 1 {Cloudy
121 SOF, o Phs7 63 | 29,49|76] 0,115] E | 1 jRain.
64 12 of 64 64 | 29,45 170 E 1 |Cloudy
13] Sig 7 1 O Wr 5s 63 | 29,64} 72] 0,690] W | 1 |Cloudy
63 |2 of 62 64 | 29,66 | 56 WNW 1 {Cloudy
41 48 17 Of} 53 | 62 | 29,62]73} 0,050} W | 1 |Cloudy
61 |2 oO] 61 63 | 29,71 | 61 N_ | 1 |Cloudy.
15} 48 [7 ©] So 62 | 29,89|70 W | 1 {Cloudy
61 [2 Of 61 62 | 29,87 | 69 SW | 1 |Cloudy.
161 46 17 Of 49 60 | 29,89]67}| 0,093} W | 1 [Cloudy
61 [2 of 61 62 129,90 | 53 SW [1 {Fair.

Six’s
Therm.
least and

1799 | greatest

Sep. 17
18
a9
20
21
22
23
ae
ae
26
mit!
28
29
30

Heat.

RN AN KN NON SN KON KN KON ANN QN NN AN NON YON

Time.

H. M.

ooo0o0ooa0caaoadcoo0o0oaadaaaaaaeoOaaaOaa00 Oo

C19 J

METEOROLOGICAL JOURNAL

for September,

Therm. | Therm.
without.} within.

oO co)
56 61
62 62
51 61
65 62
55 | O25
62 62
55; 1. OF
61
ep 60
62 62
bot) 1, OF
65 62
55 | 61
57 a
fe)
bs 60
54 | 60
64 62
54 | 60
62 61
52 60
59 | 62
§2 60
51 60
46 60
50 62
48 60
57 | 93

Barom. |Hy-

Inches,

29,78
29,65
29,64
29266
29,36
29,28
29535
29,38
29,6
25.64
29,12
29304
29,20
29,50
29,82
29,84
29,98
29;

ae 6
29,61
2953
2975
29,58
29513
29346
29513
29,32
2943

1799:

Rain.

Inches.

0,260
0,128
0,055
0,046
0,088

0,248

0,210

0,478
0, 363

Winds.

Points.

ee

Weather.

Rain.

Cloudy. [fae wind
Fair. last night,
Rain.

Rain,

Fair.

Rain.

Fair.

Fair.

[ 20 J |

ne et TE a Le amy ann nee nea coeur eaaniennen nena nn a ;

METEOROLOGICAL JOURNAL

for October, 1799.

Six’s | Time. | Therm. | Therm.] Barom., |Hy-] Rain, Winds.
eS? sa without.| within. gro-
1799 greatest —— = —_ Weather.
Heat. |}H. M. 5 5 Inches, Inches, | Points. | Str.

fe}
46 V7 oO) | 47 61 | 29,50{72| 0,080} S | 1 |Fair.
bieveae AO} | Gane 62 | 29,56] 54 N | 1 |Fair.
39 7. O |e 60 | 29,78 | 69 SW | 1 |Fine.

G7 ae, Ol Ga 62 |} 29,78 154 SW | 1 |Fair.
48 Zo 48 60 | 29,78 | 68 SW | 1 |Fair.

Go" 1-2 “0 | 44.60 62°F ih20s72 153 SW | 1 |Cloudy.
AG 7 Ol weed 60 | 29,50|56| 0,122 | SW | 2 |Fair.
BGT yz) Ol ake 61 | 29,50 | 56 SW | 2 |Fair.
4a nO lds 60 | 29,92 |65| 0,093 | SW | 1 |Pair.
SO me?) JO] ak 60 | 30,00 | 56 W | |Cloudy.
BE WZ O53 60 | 29,86 | 83} 0.173 | SSW | 1 [Rain.
60 2 oO 60 62 | 29,90] 75 SW | 1 |Cloudy.
BO gO! yas 6z | 29,91 | 74 W | 2 |Cloudy.
O36 dee?) Ons 63° | zor0K 172 SSW | 1 |Cloudy.
GO WaT O: heasi7 62 | 29,48 | 78 | 0,128 S 2 |Cloudy.
Goudie? "0" | aAso 63 | 29,40 | 62 SSW | 2 |Fair.

AQ™ a7 O ano 61 | 29,54|66|0,060 | W | 1 (Cloudy.
Sos ees Olas S 63 | |'29,72 58 WNW 1 {Cloudy.
43. 107) ©. 243 60 | 29,94 |67]|0,028 | W 1 |Fine.
ree2 Oj akc 62 | 29,98 | 53 SW | 1 |Fair.
Ae 17 OS lwuwAh 60 | 30,08 | 73 SSW | 1 Fine.
58" 1e2 Ol Aho 63 | 30,11 | 57 SSW | 1 |Cloudy.
487 (7 0 | 49 60 | 29,88] 71 E 1 Cloudy.
Gon 2’ 0 | B50 627 520,72) 75 SE | 1 |Rain.
GO ng OC! | 50 OT 4,29,70 | 75 165332) lo 1 |Cloudy.*
Se bee, (Olean 7: 63 | 29,73 | 6: S 1 |Fair.
AST? 10 mas 61 | 29,71 | 71 | 0,060 | SS 1 |Fine.
Ba lee: Olah, 62 | 29,84) 54 W jt {Fair.
AEC? 10 12-42 60 | 30,02 | 67 S 1 |Fine.
Gera: Oi mes 5 62 | 30,00) 58 S 1 |Fair.

45 17 0} 45 | 60 | 29,98! 73 S_ | 1 |Foggy.
RA 2h OSA. 61 129,95 | 60 SW | 1 jCloudy.

ce]

METEOROLOGICAL JOURNAL

for October, 1799.

Six’s | Time. | Therm. | Therm.| Barom, |Hy-| Rain, Winds.

Ra without,| within, gro-
east and) me-
1799 greatest ie Sa Weather.
Heat. |H. M. a ° Inches, Inches.} Points. | Str.
°
Oetrr7)) 44,..\\7. Oe aa 59 | 29,90) 71] 05153} W {1 jRain.
5O cl 24 O te Az 60 | 29,89 | 67 N 1 |Rain.
18) 4A 2. @ hag 58 | 2y,89]73|0028} N | 1 |Cloudy
G22 Grins 62 | 29,83 159 S 1 |Fair.
19} 48. 97. O 1% 49 58 | 29,65 |76|0,135| E 2 |Rain.
50 20) 50 60 | 29,68 | 70 SE 1° |Rain.
20; 44ers Oo | 245 58 | 29,77 |74| 0,268) NE | 1 {Cloudy
SOE? uO: || eo 59 | 29,82 | 67 S 1 |Cloudy
23) “432,197 « O fe 46 57 | 2955 |74| 0,098} E 2 |Rain.
AQ 2. O14 “49 59 | 29,49 | 68 W | 2 |Cloudy
22F LOW Fy. ON AO 57 | 29,64|75| 0,286] S 1 |Rain.
Rone). © Wik 52 | 29,62] 70 S 1 {Cloudy
23) Agen 7, O PAT 57. | 29,65 |75| 0,125 | SE 1, {Rain.
Rees Op kss 60 | 29,64 | 67 SE 1 {Cloudy
244 44 17 Of} 45 | 58 | 29.44/73 NE | 2 |Cloudy
49 |2 Of} 48 59 | 29,38|73 NE | 2 |Cloudy
25] 3a 7, © Wigs 57 2oo7 Fl W 1 12)Bine.
5Ouclh 2, Gape so 58 | 29,74 | 66 N_ | 1 [Cloudy
26f 40. 7. © tego 565 | 30,10] 70 Ni) || tifa.
AQ NZ, © WeAO 58 | 30,23 | 61 NE | 1 |Fair.
27, 35 |7 O} 35 | 55 | 3937)72 E_ | 1 |Foggy.
44 12 O07} 44 57 | 30533 (62 ESE | 1 |Fine.
PAE Ce GP ae: 39 55 | 30,31 | 70 SW | 1 |Hazy.
E25 2 8 ter 52 57. | 30.30} 70 SW | 1 {Cloudy
29) Agi 7. Cie: 47 56) 30322 | 77 SE | 1 |Cloudy
Calta te OFF ST 59 | 30,08 | 60 SE. | 1 |Fine.
30} “43. 7. Ok eas 56 | 29,7117 E 1. |Cloudy
55a 2my Cole 56 58 | 29,60 | 75 SE | 1 |Cloudy
31| 49: 57) Sie 49 57 | 29.46 |88] 0,110] SSE | 1 [Fair.
572 ez, Cnty 56 59 | 29,3470 SE | 1 |Cloudy,

[ 22

: :

————— | | | | | | ee | OOO |

Six’s
Therm.

least and

greatest

Heat.

Time.

NN VN XQN YN YON AON XN NN YN NN ON HON YN NN NON NN

(oom Ol © © © © © © © © © © © © © © © © © © © © © © © OM OOM @ i OO EEO)

METEOROLOGICAL JOURNAL

for November, 1799.

Therm.| Therm.]| Barom. |Hy-

without.| within,

Inches.

gro-
me-
ter.

Rain.

Inches,

0,250

Winds.

Points.

AM

2G 8
A ea

ag

mi NN NN Nm me ee mt NON ON ND eR ee RN eM NN

Weather,

Much wind)
Cloak, [ last night,
Cloudy.
Cloudy.
Rain.
Cloudy.
Fine,
Rain.
Cloudy.
Rain.
Rain.
Cloudy.
Fair.
Cloudy.
Rain.
Cloudy.
Fair.
Fair.
Fine.
Cloudy.
Rain.
Cloudy,
Cloudy.
Cloudy.
Fair.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Rain.
Fair.

i. 23 J

METEOROLOGICAL JOURNAL
for November, 1799.

Six’s | Time. Therm. Therm. slg Rain. Winds,

| Therm. without.] within. gro-
least and me-
7 greatest bend Tea Weather.
Heat. | H. MJ 6 ° Inches. Inches. | Points. | Str.
Nov. 17 35 7° 8 | 738 56 | 30,281 78 E | 1 | Foggy
ARS TO sag. 57 | 30531 | 76 NE | 1 |Cloudy.
BS) age? Fal aT 54 30,201 72 NE | 1 | Cloudy.
Gp ME 2? | 947 56 | 30,26 | 65 E 1 | Cloudy.
19), 44 17 ©O| 44 55 | 30:26 | 68 E t | Cloudy
ABE? ¢ & | has 55 | 30,29 | 63 E 1 | Cloudy
zol “Ao ig * al. | iA 55 | 30538 | 74. NE | 1 | Fine.
WF 2 1 vey 58 | 30,40 | 66 E 1 | Fine.
Ziel) Seed!) |, 35 55 | 30,38 | 74 NE | 1 |Hazy.
4! Ze OC} war 55 | 30537 | 73 NE | 1 | Foggy.
22h Fo ten PO 1238 54 | 30,36/78 NE | 1 {Rain.
Ag rz oO | An 56 | 30,32/73 NE | 1 {Cloudy
23) 42 17 O| 42 | 54 | 30,29) 73 NE | 1 |Cloudy
43) 1° Sob 43 56 | 30,26 | 68 NE | 1 {Cloudy
ZA 3g ea FO ess 53 | 30,08 | 70 NE | 2 |Cloudy
49 12 Gi) -39 55 f2Q,071170 E 1 | Cloudy
25) 39 |7 Of} 49 | 53 | 29.88/73 BE | 1 | Foggy.
4G 2 Oh a6 54. | 29,90 |75 NE | 1 {Cloudy
26]. 44. 7 Ol 44 54 | 3012 | 80 E 1 | Cloudy
ae wz Fat | 46 55 | 30.14.]76 NE | 1 |Clondy.
27, 43 17 ©] 43 | 54 | 30,15 176 E | 1 |Fair.
47 at Pat hh Ay 57 | 30,18 | 68 E 1 | Fine.
28) 40° 17) SO) ag 54 | 30.25 173 E 1 | Cloudy.
AE 2S Poke a4 56 | 30,23 |70 E 1 | Cloudy.
20) (gare a 45 53 |p 30.071 76 WwW 1 | Fair.
Ao) P2) | Gr go 53. | 30:07 | 76 SW | 1 |Fair.
40 39° Ie Fa 43 53 | 29,91 | 83 S I | Foggy.
4g? [> 2 Gbe*49 56 | 29,82 | 80 S I

Cloudy.

least and
greatest
Heat.

1799

__- —

Dec. 1) .ag

N CON CON CON CON CON CON CON CON CON CON CON CON CON CON CON C1

QUOLOLO .Ol1O 40 20-0: .O 10 ORO GO JOLOSONO LOROZO 2030 -O30 (00: 0.10 10 1050

C24 J

METEOROLOGICAL JOURNAL

Therm. | Therm. } Barom.
without.| within.

gro-
me-
Lene

Inches,

29.56 | 31
29.43 | 83
29,19 | 85
29,21 | 81
29533 | 81
2934 | 73
29342 | 77
2947 | 73
29,60 | 77
29,7 ONwh7
29,98 | 78
30,04 | 77
30,05 | 78
29,98 | 76
29,80. 75
29>73.\\h9
29,70 | 75
29574| 75
29,95 | 78
29:99 | 71
29599 | 73

-| 29299 | 70

30307 | 73
30,09 | 70
30,13 | 72
30,10 | 70
30,00 | 70
2995 | 89
29,86 | 73
29,79 | 69
29,66 | 70
29,65 | 67

for December, 1799.

Hy- ‘Rain.

Inches.

0,215

0,018

0,018
0,050

0,048

Winds.

Points. | Str.

2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
2
2

Weather.

Cloudy.
Rain.
Rain.
Cloudy.
Cloudy.
Fair.
Cloudy,
Cloudy.
Foggy.
Rain.
Cloudy.
Rain.
Rain,
Rain.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Fair.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.

C25]

METEOROLOGICAL JOURNAL
for December, 1799.

» | Therm. | Therm. | Barom. |Hy-| Rain. Winds.
without.| within.
Weather.

Inches, me Inches. | Points; | Str.

29,62
heh
29,58
29,65
30,10
30,20
30,32 |
30,30
30227
30,22
30318 |
30215
30,12
30,16
30307
29,98
29394
29293 |
29,91

| 29,96
30,16
30,28
30534
30,28
30,09
soa
30,22
30,28
30,51
30954

Cloudy.
Cloudy.
Snow..
Snow.
Fair.
Fair.
Snow.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Fair.
Fine.
Cloudy.
Cloudy.
Cloudy.
Cloudy.
Snow..
Fair.
Fair.
Cloudy.
Fair.
Fine.
Snow.
Fair.
-{Cloudy,
Cloudy.
Fair.
Fine..

8
2
8
2
8
2
8
2
e
7)

8
z
8
Z
8

2
8
2
8
-4
8
2
8
2
8
2
8
2
8
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PHILOSOPHIGAL

TRANSACTIONS,

OF THE

ROYAL SOGIETY

OF

LONDON.

FOR THE YEAR MDCCCG.

PART II.

LONDON,

PRINTED BY W. BULMER AND CO. GLEVELAND-ROW, ST. JAMES 'S }
AND SOLD BY PETER ELMSLY,
PRINTER TO THE ROYAL SOCIETY»
MDCCC.

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CONTENTS.

XII. On double Images caused by atmospherical Refraction. By
William Hyde Wollaston, M. D. F. R.S. - Pp. 239
XIII. Investigation of the Powers of the prismatic Colours to heat
and illuminate Objects ; with Remarks, that prove the different
Refrangibility of radiant Heat. To which is added, an Inquiry
into the Method of viewing the Sun advantageously, with
Telescopes of large Apertures and high magnifying Powers.

By William Herschel, LL. D. F.R.S. - P- 255
XIV. Experiments on the Refrangibility of the invisible Rays of the
Sun. By William Herschel, LL. D. F. R.S. - p. 284:

XV. Experiments on the solar, and on the terrestrial Rays that
occasion Heat; with a comparative View of the Laws to which
Light and Heat, or rather the Rays which occasion them, are
subject, in order to determine whether they are the same, or
different. By William Herschel, LL. D. F.R.S. p. 293

XVI. Chemical Experiments on Zoopbytes; with some Observa-
tions on the component Parts of Membrane. By Charles
Hatchett, Esq. F. R. S. - = - P. 327

XVII. On the Electricity excited by the mere Contact of con-
ducting Substances of different kinds. In a Letter from Mr.
Alexander Volta, F. R. S. Professor of Natural Philosophy

CONTENTS.

Bart. K. B. P.R.S. : i han
XVIII. Some Observations on the Head of the Onin
paradoxus. By Everard Home, Esq. F.R.S. - |

i) 7 , . #
are ot
aes
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AN
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a 240. 1
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ovr” L lodeaiott fay es |
Leno nile iy .

pO yg “ oy ae
‘ hy i a ae

PHILOSOPHICAL

TRANSACTIONS.

XII. On double Images caused by atmospberical Refraction. By
William Hyde Wollaston, M. D. F. R.S.

Read March 6, 1800.

Iw some of the last volumes of the Philosophical Transactions,
there have been related many instances of strong atmospherical
refraction, by which, objects seen near the horizon have appeared
inverted, and the horizon itself either elevated or depressed.

Mr. Hupparr first took notice of a distinct image, inverted
beneath the object itself; and, in the Philosophical Transactions
for 1797, has described several such appearances, accompanied
with an optical explanation, wherein he shews, that the lowest
strata of the air were at the time endued with a weaker refrac-
tive power, than others at a small elevation.

In the volume for 1799, Mr. Vince has given an instance
(Tab. I. Fig. 1.) where erect, as well as inverted images were
visible above, instead of beneath, the objects themselves; and,
by tracing the progress of the rays of light, in a manner similar.

to Mr. Huppart’s, concludes that these phenomena arose.
MDCCC, li

24,0 Dr. Wottaston on double Images

from “ unusual variations” of increasing ‘ik in the lower
strata of the atmosphere. ’

In the volume for 1795, Mr. Datsy mentions having seen
“ the top of a hill appear detached, for the sky was seen under
it.” In this case, as well as in the preceding, it is probable
that inversion took place, and that the lower half of the portion
detached was an inverted image of the upper, as the sky could

~ not be seen beneath it, but by an inverted course of the rays.

4

Since the causes of these peculiarities of terrestrial refraction
have not received so full an explanation as might be wished, I
have endeavoured,

ist. To investigate theoretically the successive variations of
increasing or decreasing density to which fluids in general are
liable, and the laws of the refractions occasioned by them.

edly. To illustrate and confirm the truth of this theory, by
experiments with fluids of known density.

And lastly, to ascertain, by trial upon the air itself, the
causes and extent of those variations of its refractive density, on
which the inversions of objects, and other pheenomena observed,
appear to depend.

The general laws may be comprised in three propositions.

Prop. 1. If the density of any medium varies by parallel
indefinitely thin strata, any rays of light moving through it zz
ihe direction of the strata, will be made to deviate during their
passage, and their deviations will be in proportion to the incre-
ments of density where they pass.

For each ray will be bent towards the denser strata, by a
refracting force proportioned to the difference of the densities:

above and below the line of its passage; and, as their velocities
are the same, and therefore the times of action of the forces

- -
-_—o SS ee

caused by atmospherical Refraction. 241

equal, the deviations will be as the refracting forces, 7. e. as the
increments of density.

Prop. 11. When two fluids of unequal density are brought
into contact, and unite by mutual penetration; if the densities
at different heights be expressed by ordinates, the curve which
terminates these ordinates will have a point of contrary flexure.

For the straight lines da, rn, (Plate IX.) Fig. 1. which ter-
minate the ordinates rz, dy, of uniform density, will be parallel,
and, if not united by contrary curvature, some straight line of
union, as 20, must be supposed. But, from whatever cause the
first line ao is inferred, by the same cause other intermediate
lines mp, tq, &c. will be produced, and curves defm, misr,
will be ultimately formed, having a point of contrary flexure
at m.

The form of the curve does not appear to admit of accurate
investigation, nor is it of importance to the subsequent reason=_
ing, if wholly unknown. We may, however, form some judg-
ment of its nature; for, whether the densities depend on
different specific gravities of different fluids, or on unequal
temperatures of different portions of the same fluid, the curves
will be nearly alike.

In each of these cases, to whatever small distance pc, Fig. 2,
the mutual attraction is sufficient to occasion intimate union of
the fluids, the density mu of the mixture will be an arithmetic
mean; and, for the same reason, at any intermediate smaller
distances, there will be a' series of arithmetic means ef, gb, &c.
interposed, and the line ao, uniting the ordinates, will be straight.

By progressive effect of this attraction, and successive inter-
polations, in Fig. 1, curves defm, rstm, will be formed, of which
the straight lines mp, tq, &c. are tangents.

lie

242 Dr. Wottasron on double Images

The attracting distances np, og, &c. are subtangents ; and,
if it be admitted that these are every where equal, the curves
so produced are logarithmic, and the increment of the ordinate
greatest at m, where they meet.

Prop. ut. If parallel rays pass through a medium varying
according to the preceding proposition, those above the point
of contrary flexure will be made to diverge, and those below
the same point will converge, after their passage through it.

For, since the deviation of each ray depends on the increment
of density where it passes, and since the increment of density
is greatest at the point of contrary flexure, any rays, as ab,
Fig. 3, passing near to that point, will be refracted more to-

wards the denser medium than those at cd, which move ina

higher stratum, and will diverge from them, but will be refracted
towards and meet those at ef, which pass nearer to the denser
medium, where the increments of density are also less.

Cor. Hence, adjacent portions of the converging rays will
form a focus, beyond which they will diverge again; and the
varied medium will produce effects similar to those caused by a

medium of uniform density * having a surface similar to the.

curve of densities, since convergence or divergence will be pro=
duced, according as the curve of densities is convex or concave;
epnsequentiag by tracing backwards, to the extremities: of an’

* In the ie medium, be and bm, Fig. 4, the cone pone increments of the
abscissa and ordinate, are to each other as radius to the tangent of the angle c. ‘There-
fore, the tangent of deviation, which is as the increment of the ordinate, varies as the

tangent of the angle c. (Siti Ld : aay

So also, in the ui iform medium, since the sines of refraction and incidence are in a
given ratio, their differences will bear a given ratio to either of them; and, ee the
angles are small, the tangent of deviation will vary as the tangent of incidence, or as
the tangent of the angle c, which is equal to it. ietie off

‘caused by icc dataa Refraction. 243

object, the progress of the’ sidual rays, (or axes of the pencils
received ‘by the eye,) it will be manifest that,

Any object seen through the inclined concave part rm, Fig. 5.
would appear elevated, erect, and somewhat diminished.

An object seen through md, where it is convex and inclined,
would be elevated; and, if situated beyond the focus of visual
rays from the eye, it would appear inverted. The magnitude
would depend on the relative distances of the eye and object.

~ Below the point d, where the curve terminates, vision would
be direct, so that an object might be situated so as to be seen in
all three ways at the same time, direct at O, inverted at I, and
erect again at A.

I consider the foregoing propositions as applicable to all cases
of varying density, whether occasioned by mutual solution of
different fluids, or partial rarefaction'of the same fluid; and, by
trial of various fluids, however different in’ density, or even in
viscidity, I find thatthe refractions observe a law agreeable to
_ the theory, as will appear. by the following experiments:

» \Experiment1: Into a square phial containing a small -quan-
tity of clear syrup, I put about an equal quantity of water, in
sucha way that it floated on the surface of the syrup, without
mixing. For a short time, the stratum of union was so thin
that nothing could be distinctly seen through it. But soon, by
mutual: penetration of the water and the Symp. nei effects
mepenrcnice at A, Fig: 6, were produced.

»Through-the syrup, ‘a word written on a card placed behind
was seen erect, and in its place; through the adjacent variable
medium, an inverted; image was visible above the true place;
and also, above that, a peace image of the same object a
erect. aby

2 Ac Dr. Woutaston on double Images

When these appearances are first discernible, the variations
of density are so great, that the object to be looked at may be
in contact with the phial; but, when the variations of density
become more gradual, and thereby the focus more distant, any
object so near is only elongated, and requires to be removed an
inch or two, to be seen inverted.

Exper. 2. Over the surface of the water, in the same phial,
I next put about the same measure of rectified spirit of wine.

At the stratum where the water and spirit united, the appear=
ances were the same; but, since the refractive power of spirit
exceeds that of water, the true place of the object was seen up=
permost; the inverted and erect images are below. Fig. 6, B.

When an oblique line der is viewed through any variable
medium so made, it appears bent into different forms, according
to its situation with respect to focal distance.

If it be at the distance of the principal focus, one point of it
is dilated into a vertical line, as /m. Fig. 7, A.

If beyond that focus, the portion /m is inclined backwards,
being an inverted image of d/; and mn is another image of the
same portion seen erect. Fig. 7, B.

On this account, it becomes a convenient object for ascertain-
ing the state of any medium under examination.

In these experiments, the appearances continue many hours,
even with spirit of wine; with syrup, two or three days; with

acid of vitriol, four or five; with a solution of gum arabic, much

longer; but, although their disposition to unite is so different,
the appearances produced are nevertheless the same in all.

The refraction is greatest nearly in the plain of original con-
tact of the fluids, diminishing from thence both upwards and

downwards. The exact rate of diminution above or below this:

———o7 rl rh Oh

1
:

caused by atmospherical Refraction. 245

point, I had no means of measuring, with the accuracy that
would be requisite for determining the nature of the curves of
density formed according to the first proposition.

But the truth of the second proposition appeared capable of
confirmation by experiment; for the deviation of a ray is there
said to depend on the increment of density, and time of the
rays passage, jointly ; accordingly, the deviation caused by a
given increment should be in proportion to the extent of the
medium. |

In order to try what effect a greater extent of medium would
produce,

Exper. 3. I made a rectangular glass vessel, of which the
sides were in the ratio of 10 to 30,6; and, having put into it
some clear syrup, with water on its surface, I measured the
greatest refractions through it in both directions, and found them
in the ratio of 10 to about 29. :

In another vessel, of which the sides were as to to 40,4, the ©
refractions were, on an average, as 1 to 4,

Being now fully satisfied of the effect of different fluids, I made
the following experiment, whereby it appears, that the variations
of density occasioned by difference of temperature between ad-
jacent strata of the same fluid, follow a similar law.

Exper. 4. Having put some cold water into a square vessel;
I covered its surface with a piece of writing paper perforated
with a few small holes, and then filled the vessel cautiously
with boiling water. The paper nearly prevented any mixture
of the hot and cold water; but, by floating gradually up, left
them to communicate their heat by contact alone.

While they were in this state, I examined the appearance of
remote objects through the varied medium, and found, that

246 Dr. Wotuaston on double Images.

when’my: eye was removed four or five feet from the vessel, the
effects were the same as in the preceding experiments with dif
ferent fluids; above any object viewed through the cold water,
I could distinguish two images of it, the one inverted, the other
erect, as usual; but these appearances did not continue more
than five or six minutes.

Having thus established, by donate siiaeeilin vckaibe
that the contiguity of two fluids of unequal density is capable
of occasioning all the appearances that have been observed, I
shall proceed to shew by what means the:air may be made to
exhibit similar pheenomena.

_ Exper. §. I heated a common poker: red-hot, and held, it so
as to look along the side of it, at a paper 10 or 12.feet distant.
The rarefaction occasioned by it caused a perceptible refraction,
to the distance of about 3 of an inch from the side of the poker.
A letter seen more distant from it appeared as usual; within
_ that distance there was a faint image of it reversed; and still
nearer to the poker was a second image direct, and as distinct .
as the object itself, but somewhat smaller, as in Fig. 8, in
which a section of the atmosphere surrounding the poker is
represented. At the bottom and sides it is nearly circular;
but upwards the circular form is lost in undulations, occasioned
by the rapid ascent of the rarefied air.

oP he greatest deviation produced in this case saCeiell sans

4a degree.

ae 6. By a red-hot bar of iron, 30 inches long, the bli
tions. were much greater, the extreme deviations amounting to
full 14 degree. |

The refractions observed in these experiments may, at first
view, be thought greater than could be caused by difference of

caused by atmospberical Refraction. 247

temperature alone, being in one instance more than double the
gréatest horizontal refraction of the heavenly bodies; in which
case, as the rays enter from a vacuum, the greatest possible
effect of the atmosphere might be expected. But it must be
remembered, that when a star appears in the horizon, its rays
intersect the superior strata of the atmosphere at an inclination
of several degrees, and that they pass but once through the
variations from rarity to density; but, on the contrary, that in
the experiments with red-hot iron, the rays may pass actually
in the direction of the strata, and that they are refracted, not
only by their entrance from the denser into the rarer medium,
but the effect is doubled, since the refraction caused by their
emergence is equal to that produced by their incidence.

Although a stratum of air, heated by these means to so great
a degree, affords an erect, as well as an inverted, image of
objects seen through it, the more moderate warmth communi-
cated to it from bodies heated by the action of the sun upon
them, seems insufficient to produce both images;. but the in-
verted image may generally be seen, when the sun shines upon
a brick wall, or other darker-coloured surface.

While the eye of the observer is placed nearly in a line with
the wall, if another person, at go or 40 yards distance, extends
any object towards the wall, an image frail to it will appear
to come ‘out to meet it.

It would be difficult to ascertain with accuracy the degree of
rarefaction capable of shewing this appearance, but it may be
of some use to future observers, to mention the different degtaey
of heat which I observed.

In one instance, a thermometer in contact with the “ee
‘stood at 96°: but, at 2 of an inch distance, 82°.

MDCCC. Kk

948 Dr. Woxtaston on double Images

One morning, when the sun shone bright, I examined the
temperatures and refraction produced at the surface of a deal
bar painted green, about 8 feet long. ie

A small thermometer in contact with the bar, rose to’ 96°;
at 4 of an inch distance, it stood at 79°. Neat

The refraction at the same time exceeded 20 minutes.

To explain why red-hot iron occasions two images, while
Solar heat produces but one, I imagine that the intense heat in
the former case rarefies the air for some small distance uni-
formly, and thereby affords the same series of variations as
between other fluids of uniform density ; but that, in the latter,
the heat is conveyed off as fast as it is generated; so that, as
there is no extent of medium uniformly rare, the densities cor=
responding to the concave portior. rm, Fig. 5. of the curve
before described do not take place, but the phenomena occa
sioned by the convex part md are alone produced.

It must be remarked, that the vertical position of the surface
contributes greatly to increase the effect ; for, since the heated
air rises in the direction of the surface, its ascent has in this
case no tendency to blend it with the adjacent denser strata, and
hence very different degrees of density take place in the thick-
ness of 1 of an inch; so that, as the increments of density are
great, ae refractions will be proportionally so; but, where the
heated surface is horizontal, the ascent of the rarefied air into
the superincumbent denser strata renders the variations far more
gradual; consequently, a heated surface of far greater oxtint
must be requisite, to produce equal refraction.

However, over extensive plains, when the sun shines, some
degree of inversion is very frequently to be seen; but the
inverted images: are rarely well defined, unless over a very even

caused by atmospherical Refraction. 249

“surface. One of the best situations for this purpose, is over a
level open road, with a gentle breeze blowing across it. A cur-
rent of air brings a cool stratum more closely in contact with
the heated surface; and, since refraction depends on the incre-
ment or difference of density in a given small space, a very
moderate breeze will thereby render inversion more perceptible;
but a strong wind will reduce the temperature of the surface,

-and may make the heated stratum too thin for any object to be
seen through it from a distance.

In one instance, when I saw a refraction of about 9 minutes,
at the distance of £ of a mile, a thermometer in the sand was
191°; at 4 inches above, 82°; and, at 1 foot above, 76°.

Over water, the evenness of the surface is favourable to the

production of such appearances; but, since the action of the
sun is weak on a body so transparent, a far greater extent of
surface is requisite to produce any perceptible inversion.

Being at Bognor one bright morning, when the sea was calm,
I had an opportunity of observing the appearance of Selsea
Bill, about 6 miles distant. The whole extent of coast, when
viewed with a pocket telescope magnifying about 16 times,
appeared inverted from one end to the other; and the lower
part of a brick house upon the shore, was seen as distinct as the
house itself. I judged the quantity of refraction, in this case, to
‘be about 2 minutes of a degree.

This state of atmosphere appears to be not very uncommon;
for, at Shanklin Chine, in the Isle of Wight, a few days
preceding, similar appearances were visible in several directions,
but I neglected to make any estimate of the quantity of re-
fraction. . |

In the instance of the inverted vessel seen by Mr. Hupparr,

Kk e

250 Dr. Woitaston on double Images

(Phil. Trans. for 1797, Tab. I. Fig. 3.) at the distance of 8
miles, the refraction seems to have been about 9’.

All the appearances described by him, I am imalingd to, cee
arose from difference of temperature alone. He offers a con-
jecture, that evaporation might occasion the lower strata of the
atmosphere to have a weaker refractive power; but, from the
following experiments, it seems to have a contrary effect.

Exper. 7. 1 took a plate of glass, and, while I looked along
the surface, I poured upon it a small quantity of ether. _

A line upon the opposite wall, appeared instantaneously ele-
vated many minutes, and at times above 4 a degree.

This fluid being the most volatile, a most soluble in the
atmosphere, of any known liquid, produces the greatest effect ;
since the cold, during evaporation, conspires with the ether dis-
solved in the air, to increase the refractive power. ‘S

Rectified spirit of wine also produces, from the same cause,a
very considerable effect.

Exper.8. By moistening a board, 5 feet in length, with alcohol,
and observing the elevation of an object viewed over its surface,
I found the refraction to be about 13’. |

Exper.g. I next made a similar experiment with water itself,
Of this, the effect was barely visible, when tried in the same
way; but, by means of a surface of 10 feet, and by viewing a
luminous point at a greater distance, the refraction became evi-
dent, and the object elevated above g minutes.

In the course of these experiments, I tried whether confining
the saturated atmosphere, by boards on each side, would vary
the effect, and found the refraction in all cases much lessened ;

and, when water was used, it became imperceptible ; but, as
soon as the boards were removed, and a free current allowed to

caused by atmospherical Refraction. 251

pass across, the full effect was again produced. The reason of
this difference appears to be, that the quicker evaporation in-
creases the degree of cold, and the current brings greater dif-
ferences of density contiguous. |

This state of rapid evaporation will fully account for the
phenomenon witnessed by Mr. Latuam, who has described
(in the Phil. Trans. for 1796, p. 357) an extraordinary eleva-
tion of the opposite coast of France, so as to be seen from the
beach at Hastings, and other parts of Sussex.

_ There is a fact of the same kind stated by DE ta LanpgE,
(Astron. Tom. II.) who says that the mountains of Corsica
(though at the distance of more than 100 miles) are occa-
sionally visible from Genoa. f

It is probably owing to the same cause, that other objects:
have been sometimes seen, at such distances. that we should
expect them to be intercepted by the curvature of the earth;
for it is evident, that whensoever the evaporation over each mile
of surface occasions a refraction of about 1 minute, the rays
receive a curvature equal to that of the ocean, so that its sur-_
face will appear flat, and the spherical form of the earth will
not obstruct horizontal vision of objects at any distance.

It still remained to explain the phenomena seen by Mr.
Vince, as I had not hitherto made.an atmosphere capable of
exhibiting images inverted, as well as elevated, by increased
density. For, in the refractions. produced in the 7th, 8th, and
gth experiments, by evaporation at an exposed surface, I
observed the effect was always greatest in contact with the
evaporating surface; any lower point a, Fig.9, appeared brought
nearer to a higher point c, by the pencil of rays from a being
more refracted at b, than the pencil from c was refracted at d.
Therefore, any rays passing from the eye at e, as a point, through

252 Dr. Wotaston on double Images

b and d, would be made to diverge to a and c; consequently,
visual rays could not, under these circumstances, intersect each
other, and no objects could appear inverted.

But, whenever the lowest strata of the air become saturated
with moisture, the variations between the saturated stratum and
the incumbent atmosphere of the common density, will follow
a law similar to what is found at the confines of other fluids of
unequal density; hence, inversion will become visible, as there
will be a point below which the increment of density will de-
crease, and where the refractions will consequently > less,
although through a denser medium.

Exper. 10. To produce these appearances, I procured a trough
of thin deal, 5 feet long, 1 inch.wide, with sides 94 inches high,
and closed the extremities of it with glass. A section of it is
given in Fig. io. ,

When the bottom was wetted with ether, the greatest refrac-
tion was, at intervals, more than 3 of an inch from the bottom of
the trough; and, beneath this height, I saw a second image in-
verted, when my eye was removed to 14 or 15 feet distance,
and the object at about 70 feet. The focus seemed at the same
time to be about g feet distant. antl

There was not depth enough of uniformly saturated atmo-
sphere for the object itself to be seen through it, but its true
place, compared with that of the images, is represented at a.

Exper. 11. When I made use of rectified spirit in the same
apparatus, I had also sufficient proof that the laws of evapora-
tion would admit of such appearances being produced; for the
same object now appeared curved downwards, as in Fig. 11,
so that rays nearer to the bottom were manifestly less refracted
than such as passed at some distance above. A degree of con-
vergency must therefore have been produced, although the dis-

caused by atmospherical Refraction. 253

tance at which the rays would meet, was beyond that of my
eye, and circumstances would not admit of my removing beyond
35 feet.

The evaporation of water could not be expected to produce
any sensible effect of this kind, in so short a space; but, ina view
of some miles extent, there can be no doubt, from the foregoing
experiments, that evaporation from the surface of the sea, in
such a state of the atmosphere as would allow the lower strata
to be saturated, is capable of occasioning all the phenomena
which have been described, and probably was the cause of those
which Mr. VINcE observed.

Since heat alone tends to depress objects, and evaporation
produces apparent elevation, it is probable, that in the instance
of refraction related by Mr. Da.sy, (Phil. Trans. for 1795,
p. 587), the heat of the sun was the principal agent, and that the
moisture rather tended to counteract than assist its. action.

Simple inversion may generally be seen, when the sun shines
upon a dry even road of Lori mile extent; but, when the ground
has been wet, I have very rarely seen it, and have even failed
of discerning it, when the heat has been sufficient to raise a
steam from the ground. }

The following experiment shews that it is not to be expected
but by very great extent of surface.

Exper. 12. I placed a dark-coloured board in the sunshine,
and, having examined the refraction along its surface, I made a
wet line along it, with a sponge dipped in boiling water. Not-
withstanding this additional heat, the refraction, in the direction
of the wet line, was far less than over the rest of the board, al-
though I took care to observe the effect, before the surface could
be cooled again by evaporation.

I should therefore expect the depression of the horizon at sea,

a4 Dr. Wo aston on double Images, &c.

where the refraction occasioned by heat must always be coun-—
teracted by evaporation, never to exceed a few minutes; and
that any one in a situation commanding a view of the sea, by.

attention to the various degrees of the dip of the horizon under

different circumstances, might soon form some estimate of the’

proper allowance to be made, for brightness of the sun at the
time of an astronomical observation, or for difference of tem-
perature between the sea and air.

Having now examined the several peculiarities of refraction
which I proposed for consideration, I shall, in few words, reca-"

pitulate the purport of the foregoing pages.

According to the theory here given, there appear to be two.
opposite states of the atmosphere, either of which may occasion’
objects to be seen doubled or tripled, since both increase and’

“decrease of its density, when partial, produce similar effects.

It has been explained,

ist. Why air heated by the moderate warmth of the sun’s
rays, occasions objects to appear doubled and inverted.

edly. Why rarefaction, by a higher degree of heat, gives an
additional image, which is not inverted.

gdly. In what state of evaporation the increase of the air’s

density brings distant objects into view by unusual elevation.
4thly. Under what circumstances eyaperaaan may also pro-
duce an inverted image less elevated.
And it is probable, that the same reasoning will afford a ready

explanation to other varieties of terrestrial refraction, that may

have been, or may hereafter be observed,

LThilos, Frans MD C Cc uC, Vale [IX

===

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‘

Gn,

\

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WOH
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\

Lhilos Trans MD CC CHate IX p. 254.

|

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_——

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C255 7

XIIL. Investigation of the Powers of the prismatic Colours to heat
and illuminate Objects ; with Remarks, that prove the different
Refrangibility of radiant Heat. To which is added, an Inquiry
into the Method of viewing the Sun advantageously, with
Telescopes of large Apertures and high magnifying Powers.
By William Herschel, LL. D. F. B.S.

e: Read March 27, 1800.

Ir is sometimes of great use in natural philosophy, to doubt of
things that are commonly taken for granted; especially as the
means of resolving any doubt, when once it is entertained, are
often within our reach. We may therefore say, that any experi-
ment which leads us to investigate the truth of what was before
admitted upon trust, hay become of great utility to natural
knowledge. Thus, for instance, when we see the effect of the
condensation of the sun’s rays in the focus of a burning lens, it
seems to be natural to suppose, that every one of the united
rays contributes its proportional share to the intensity of the
heat which is produced; and we should probably think it
highly absurd, if it were asserted that many of them had but
little concern in the combustion, or vitrification, which follows,
when an object is put into that focus. It will therefore not be
amiss to mention what gave rise to a surmise, that the power of
heating and illuminating objects, might not be equally distri~
buted among the variously coloured rays.

In a variety of experiments I have occasionally made, relating

MDCCC. ype eat

256 Dr. Herscnet’s Investigation of the Powers

to the method of viewing the sun, with large telescopes, to the
best advantage, I used various combinations of differently-
coloured darkening glasses. What appeared remarkable was,
that when I used some of them, I felt a sensation of heat,
though I had but little light; while others gave me much light,
‘with scarce any sensation of heat, Now, as in these different
combinations the sun’s image was also differently coloured, it
occurred to me, that the prismatic rays might have the power of
heating bodies very unequally distributed among them ; and, as
I judged it right in this respect to entertain a doubt, it appeared
equally proper to admit the same with regard to light. If cer-
tain colours should be more apt to occasion heat, others might,
on the contrary, be more fit for vision, by possessing a superior
illuminating power. At all events, it would be proper to recur
to experiments for a decision.

Experiments on the beating Power of coloured Rays.

I fixed a piece of pasteboard, AB, (Plate X.) in a frame, mounted
upon a stand, CD, and moveable upon two centres. In the
pasteboard, I cut an opening, mz, a little larger than the ball of
a thermometer, and of a sufficient length to let the whole extent
of one of the prismatic colours pass through. I then placed
three thermometers upon small inclined planes, EF: their
balls were blacked with Japan ink. That of No. 1 was rather
too large for great sensibility. No. 2 and g were two excellent
thermometers, which my highly esteemed friend Dr. Witson,
late Professor of Astronomy at Glasgow, had lent me for the
purpose: their balls being very small, made them of exquisite

of the prismatic Colours to heat and illuminate Objects. 257

sensibility. The scales of all were properly disengaged from
the balls.

I now placed the stand, with the framed pasteboard and the
thermometers, upon a small plain board, GH; that I might be
at liberty to move the whole apparatus together, without de-
ranging the relative situation of the different parts.

This being done, I set a prism, moveable on its axis, into the
upper part of an open window, at right angles to the solar ray,
and turned it about till its refracted coloured spectrum became
stationary, upon a table placed at a proper distance from the
window. ,

The board containing the apparatus was now put on the
‘table, and set in such a manner as to let the rays of one colour
pass through the opening in the pasteboard. The moveable
frame was then adjusted to be perpendicular to the rays coming
from the prism; and the inclined planes carrying the three
thermometers, with their balls arranged in a line, were set so
near the opening, that any one of them might easily be ad-
vanced far enough to receive the irradiation of the colour which
passed through the opening, while the rest remained close by,
under the shade of the pasteboard.

By repeated trials, I found that Dr. Wison’s No, 2 and
mine, always agreed in shewing the temperature of the place
where I examined them, when the change was not very sud-
den; but that mine would require ten minutes to take a change,
which the other would shew in five. No. g never differed
much from No. 2.

ist Experiment. Having arranged the three thermometers in
the place prepared for the experiment, I waited till they were
Stationary. Then, advancing No. 1 to the red rays, and leaving

Ll 2

258 — Dr. Herscuet’s Investigation of the Powers

the other two close by, in the shade, I marked down what bas
shewed, at different times.

No. 1. No. 2. No. 8.
aoe RE SRS ee
AB = 6 STORY Sige Cie Sg RE
MOy <1 -alCanscnt agen 6 19 1 On ae
i Salaam abla Maud + aiintedsbich is NV 2
Sor ssa? TeniOhey BARES ah Bea as

This, in about 8 or 10 minutes, gave 63 degrees, for the
rising produced in my thermometer, by the red rays, compared .
to the two standard thermometers.

od Experiment. As soon as my thermometer was restored to
the temperature of the room, which I hastened, by applying it
to a large piece of metal that had been kept in the same place,
I exposed it again to the red rays, and registered its march,
along with No. 2 as a standard, which was as follows.

No. 1. No. 2.
45 = SDRC ERG Si
45) te gee, DONS eae

SiKMia- ort ariiwork Gh ae
LOGS B ES OF & S0 ae,
51 = Meet

Hence, in 10 minutes, the red rays made the thenmometet
rise 7 degrees. |

gd Experiment. Proceeding in the same manner as before
in the green rays I had,

.

3

of the prismatic Colours to heat and illuminate Objects. 259

No. 1. No. 2.
43 a m sy 43
Bie i= re 43

Bok nen Wain i RS
BR rr earns, i Mee
BOE Seva ac very) SO

- Therefore, in ten minutes, the green rays occasioned a rise of
33 degrees.

_ 4th Experiment. 1now exposed my thermometer to the violet

rays, and compared it with No, 2.

EINO, 1. No. 2.
RA ole migra yA
BA oer gg mie Ade
Act he Sirah mapa erie 3
Bore soe 48

Here we have a rising of 2 degrees, in ten minutes, for the
violet rays.

5th Experiment. 1 now exposed Dr. Wi1son’s thermometer
No. 2 to the red rays, and compared its progress with No. g.

No. 2. No. 3.
Se ad
Be ue aan Gan sity Ae
2 ae HE
BE a tied ig enides

Here the thermometer, exposed to red, rose in five minutes 23
degrees. | Bey SRT

~ 6th Experiment, In red rays again.

260 Dr. Herscuer’s Investigation of the Powers %
| No. 2, No. g.
AGE; ic Sokigcan sake ee
| a ae

Boe, |, Ty isis Se
47 “ . Tes ane , ,
And here the thermometer, exposed to red, rose in five
minutes 4, degrees.
7th Experiment. In green rays. | |
No. 2. No.3.
Bae i a leg
A Ne a oa Adee
Alig Fe ade
This made the thermometer rise, in the green rays, 14
degree. =
8th Experiment. Again in green rays.

No. 2. No. 3.
Sry SCY boriaye ron BS
Adee, oT) Loutiioo Hla aaa |
LaMar pers) 2:

Here the rising, by the green rays, was 2 degrees.

From these experiments, we are authorised to draw the fol-
lowing results. In the red rays, my thermometer gave 63
degrees in the ist, and 7 degrees in the ed, for the rising as
the quicksilver: a mean of both is 62. In the gd experiment,
we had 33 degrees, for the rising occasioned by the green rays ;
from which we obtain the proportion of 55 to 26, for the power
of heating in red to that in green. The 4th experiment gave |

of the prismatic Colours to heat and illuminate Objects. 261

2 degrees for the violet rays; and therefore we have the rising
of the quicksilver in red to that in violet, as 55 to 16.

A sufficient proof of the accuracy of this determination we
have, in the result of the four Jast experiments. The rising for
red rays in the 5th, is 23; and in the 6th, 4 degrees: a meari
of both is 33. In the wth experiment, we have 14, and in the
8th, 2 degrees, for the rising in green: a mean of these is 14.
Therefore, we have the proportion of the rising in red to that
in green, as 27 to 11, or as 55 to 22,4.

“We may take a mean of the result of both chedenisceers;
which will be 55 to 24,2, or more than 22 to 1, in red to green ;
and about 3+ to 1, in red to violet.

It appears remarkable, that the most sensible thermometer
should give the least alteration, from the exposure to the coloured
rays. But since, in these circumstances, there are two causes
constantly acting different ways; the one to raise the thermo-
meter, the other to bring it down to the temperature of the
room, I suppose, that on account of the smallness of the ball in’
Dr. Witson’s No. 1, which is but little more than + of an inch,

‘the cooling causes must have a stronger effect on the mercury
it contains than they can have on mine, the ball of which is
half an inch.

More accuracy may hereafter be obtained, by attending to
the circumstances of blacking the balls of the thermometers,
and their exposure to a more steady and powerful light of the
sun, at greater altitudes than it can be had at present; but
the experiments which have been related, are quite sufficient
for my present purpose; which only goes to prove, that the
heating power.of the prismatic colours, is very far from being

262 Dr. HerscuEu’s Investigation of the Powers

equally divided, and that the red rays are chiefly eminent in
that ie i fo

Experiments on the illuminating Power of coloured Rays.

In the following examination of the illuminating power of
differently-coloured rays, I had two ends in view. The first
was, with regard to the illumination itself; and the next, with
respect to the aptness of the rays for giving distinct vision; and,
though there did not seem to be any particular reason why
these two should not go together, I judged it right to attend to
both. .

The microscope offered itself as the most convenient instru-
ment for this investigation; and I thought it expedient to view
only opaque objects, as these would give me an opportunity to
use a direct prismatic ray, without running the risk of any bias
that might be given to it, in its transmission through the colours
ing particles of transparent objects.

ist Experiment. 1 placed an object that Hane very minute
parts, under a double microscope; and, having set a prism in the
window, so as to make the coloured image of the sun stationary
upon the table where the microscope was placed, I caused the
differently-coloured rays to fall successively on the object, by
advancing the microscope into their light. The magnifying
power was 27 times. |

In changing the illumination, by admitting a different colour,
it always becomes necessary to re-adjust the instrument. Its
well known, that the different refrangibility of the rays will

of the prismatic Colours to heat and illuminate Objects. 263

sensibly affect the focal length of object-glasses ; but, in com-
pound yision, such as in a microscope, where a very small lens
is made to cast a lengthened secondary focus, this difference
becomes still more considerable.

By an attentive and repeated inspection, I found that my
object was very well seen in red; better in orange, and still
better in yellow; full as well in green; but to less advantage
in blue; indifferently well in indigo, and with more imper-

fection in violet.

This trial was made upon one of the microscopic objects
which are generally prepared for transparent vision; but, as I
used it in the opaque way, I thought that others might be
chosen which would answer the purpose better; and, in order
to give some variety to my experiments, and to see the effect
differently coloured substances might have on the rays of light,
I provided the following materials to be viewed. Red paper;
green paper; a piece of brass; a nail; a guinea; black paper.
Having also found that a higher power might be used, with
sufficient convenience for the rays of light to come from the
prism to the object, I made the miscroscope magnify 42 times.

The appearance of the nail in the microscope, is so beautiful,
that it deserves to be noticed; and the more so, as it is accom-
panied with circumstances that are very favourable for an inves-
tigation, such as that which is under our present consideration.
I had chosen it on account of its solidity and blackness, as
being most likely to give an impartial result, of the modifications
arising from an illumination by differently-coloured rays; but,
on viewing it, I was struck with the sight of a bright constella-
tion of thousands of luminous points, scattered over its whole
extent, as far as the field of the microscope could take it in.

MDCCC. M m ;

264 Dr, HerscueE.’s Investigation of the Powers

Their light was that of the illuminating colour, but differed
considerably in brightness; some of the points being dim and
faint, while others were luminous and brilliant. The brightest
of them also, admitted of a little variation in their colour, or
rather in the intensity of the same colour; for, in the centre of
some of the most brilliant of these lucid appearances, their light
had more vivacity, and seemed to deviate from the illuminating
tint towards whiteness, while on and near the circumference, it
appeared to take a deeper hue.

An object so well divided by nature, into very minute and
differently-arranged points, on which the attention might be
fixed, in order to ascertain whether they would be equally
distinct in all colours, and whether their number would be
increased or diminished by different degrees of illumination, was
exactly what I wanted; nor could I think it less remarkable,
that all the other objects I had fixed upon, besides many more
which have been examined, such as copper, tin, silver, &c.
presented themselves nearly with the same appearance. In the
brass, which had been turned in a lathe, the luminous points were
arranged in furrows; and in tin they were remarkably beautiful.
The result of the examination of my objects was as follows.

ad Experiment. Red paper. )

In the red rays, I view a bright point near an accidental
black spot in the paper, which serves me as a mark; and I
notice the space between the point and the spot: it contains
several faint points. |

In the orange rays, I see better. The bright point, I now
perceive, is double.

In the yellow rays, I see the object still better.

In the green rays, full as well as before.

Oe

of the prismatic Colours to beat and illuminate Objects. 265

In the blue rays, very well.

In the indigo rays, not quite so well as in the blue.

In the violet rays, very imperfectly.

gd Experiment. Green paper.

Red. I fix my attention on many faint points, in a space
between two bright double points.

Orange. I see those faint points better,

Yellow. Still better.

Green. As well as before. I see remarkably well.

Blue. Less bright, but very distinct, -

Indigo. Not well. — |

Violet. Bad. :

4th Experiment. A piece of very clean turned brass.

R. I remark several faint luminous points between two bright
ones. The colour of the brass makes the red rays appear like
. orange. ;

O. I see better, but the orange colour is likewise different
from what it ought to be; however, this is not, at present, the
object of my investigation, —_-

Y. I see still better.

G. 1 see full as well as before.

B. I do not see so well now.

I. I cannot see well.

_ V. Bad.

5th Experiment. A nail.

R. I remark two bright points, and some faint ones.

O. Brighter than before; and more points visible. Very
distinct.

YY. Much brighter than before; and more points and lines
visible. Very distinct.

Mme

266 Dr. HerscHe’s Investigation of ihe Powers.

G. Full as bright ; and as many points visible. Very distinct.

B. Much less bright. Very distinct. .

I. Still less bright. Very distinct.

V. Much less bright again. Very distinct.

6th Experiment. 1 viewed a guinea, at 9 feet 6 inches from
the prism; and adjusted the place of the object in the several
rays, by the shadow of the guinea. If this be not done, decep- :
tions will take place.

R. Four remarkable points. Very distinct.

O. Better illuminated. Very distinct.

Y. Still better illuminated. Very distinct. The points all
over the field of view are coloured; some green; some red ;
some yellow; and some white, encircled with black about them.

Between yellow and green is the maximum of illumination.
Extremely distinct.

G. As well illuminated as the yellow. Very distinct.

B. Much inferior in illumination. Very distinct.

I. Badly illuminated. Distinct. | a

V. Very badly illuminated. I can hardly see the object at all. q

7th Experiment. The nail again, at 8 feet from the prism.

R. I attended to two bright points, with faint ones between
them. Almost all the points in the field of view are red. ‘Very q
distinct.

O. I see all the points better: they are red, green, yellow,
and whitish, with black about them. Very distinct.

Y. I see better. More bright points, and more faint ones:
the points are of various colours. Very distinct. )

G. I see as well. The points are mostly green, and piesa
green, inclining to white. Very distinct.

B. Much worse illuminated. Very distinct.

of the prismatic Colours to heat and illuminate Olyects. 267

I. Badly illuminated. Very distinct.

V. There is hardly any illumination.

8ib Experiment. The nail again, at 9 feet 6 inches from the
prism, by way of having the rays better separated.

R. Badly illuminated. The bright points are very distinct.

O. Much better illuminated. The bright points very distinct.

Y. Still better illuminated._ All points extremely distinct.

G. As well illuminated, and equally distinct.

B. Badly illuminated. The bright points are distinct; but the
others are not so. !

I. Very badly illuminated. I do not see distinctly; but I
believe it to be for want of light.

V. So badly illuminated that I cannot see the object; or at
least but barely perceive that it exists.

gih Experiment. Black paper, at 8 feet from the prism.

R. The object is hardly visible. I can only see a few faint
points.

O. I see several bright points, and many faint ones.

Y. Numberless bright and small faint points.

Between ‘yellow and green, is the maximum of illumination.

G. The same as the yellow.

B. Very indifferently illuminated; but not so bad as in the
red rays.

I. I cannot see the object.

V. Totally invisible. | .

From these observations, which agree uncommonly well, with
respect to the illuminating power assigned to each colour, we
may conclude, that the red-making rays are very far from hav-
ing it in any eminent degree. The orange possess more of it
than the red; and the yellow rays illuminate objects still more

268 Dr. HERscHEL’s Investigation of the Powers

perfectly. The maximum of illumination lies in the brightest
yellow, or palest green. The green itself is nearly equally
bright with the yellow ; but, from the full deep green, the illu-

minating power decreases very sensibly. That of the blue is —

nearly upon a par with that of the red; the indigo has much
less than the blue; and thé violet is very deficient.

With regard to the principle of distinctness, there appears to
be no deficiency in any one of the colours. In the violet rays,
for instance, some of the experiments mention that I saw

badly; but this is to be understood only with respect to the

number of small objects that could be perceived ; for, although I
saw fewer of the points, those which remained visible were always
as distinct as, in so feeble an illumination, could be expected. It

must indeed be evident, that by removing the great obstacle to —

distinct vision, which is, the different refrangibility of the rays
of light, a microscope will be capable of a much higher degree
of distinctness than it can be under the usual circumstances. A
celebrated optical writer has formerly remarked, that a fly, illu-
minated by red rays, appeared uncommonly distinct, and that
all its minute parts might be seen in great perfection ; and, from
the experiments which have been related, it appears that every
other colour is possessed of the same advantage.

I am well aware that the results I have drawn from the Be.
going experiments, both with regard to the heating and illumi-

hating -pewers of differently-coloured rays, must be affected by —

some little inaccuracies. The prism, under the circumstances
in which I have used it, could not effect a complete separation
of the colours, on account of the apparent diameter of the sun,
and the considerable breadth of the prism itself, through which
the rays were transmitted.

‘

of the prismatic Colours to heat and illuminate Objects. 269

Perhaps an arrangement like that in Fig. 16, of the New-

TONIAN experiments, might be employed ; if instruments of suf-
ficient sensibility, such as air thermometers, can be procured,
that may be affected by the enfeebled illumination of rays that
have undergone four transmissions, and eight refractions ; and
especially when their incipient quantity has been so greatly
reduced, in their limited passage through a small hole at the first
incidence.
- But it appeared most expedient for me, at present, to neglect
all further refinements, which may be attempted hereafter at
leisure. It may even be presumed that, had there not. been
some small admixture of the red rays in the other colours, the
result would have been still more decisive, with regard to the
power of heating vested in the red rays. And it is likewise evi-
dent, that at least the red light of the prismatic spectrum, was
much less adulterated than any of the other colours; their re-
fractions tending all to throw them from the red. That. the
same rays which occasion the greatest heat, have not the power
of illumination in any strong degree, stands on as good a foun-
dation. For, since here also they have undergone the fairest
trial, as being most free from other colours, it is equally proved
that they illuminate objects but imperfectly. There is some
probability that a ray, purified in the NEwronraANn manner above
quoted, especially in a well darkened room, may remain bright
enough to serve the purpose of microscopic illumination, in which
case, more precision can easily be obtained.

The greatest cause for a mixture of colours, however, which
is, the breadth of the prism, I saw might easily be removed ;
therefore, on account of the coloured points, which have been
mentioned in the 6th and 7th experiments, I was willing to try

270 Dr. HERScHEL’s Investigation of the Powers

whether they proceeded from this mixture; and therefore co-
vered the prism in front with a piece of pasteboard, having a
slit in it of about ;% of an inch broad.

10th Experiment. The nail, at g feet 2 inches from the prism.

R. I fix my attention on two shining, red points; they are
pretty bright.

O. I see many more points. The object is better illuminated
than in the red. The points are surrounded by black; but are
orange-coloured.

Y. The points now are yellow, and white surrounded by
black. The object is better illuminated than in orange.

The maximum of illumination is in the brightest yellow, or
palest green.

G. The points are green and white, as before surrounded by
black. Better illuminated than in orange. |

B. The illumination is nearly equal to red,

I. Very indifferently illuminated.

V. Very badly illuminated.

The phenomena of the differently-coloured points being now
completely resolved, since they were plainly owing to the former
admixture of colours, and the illuminating power remaining
ascertained as before, I attempted also to repeat the experiments
upon the thermometer, with the prism covered in the same
manner; but I found the effect of the coloured rays too much
enfeebled to give a decisive result. :

I might now proceed to my next subject ; but it may be par-
donable if I digress fora moment, and remark, that the foregoing
researches ought to lead us on to others. May not the chemical
properties of the prismatic colours be as different as those which
relate to light and heat ? Adequate methods for an investigation

of the prismatic Colours to heat and illuminate Objects. 971

of them may easily be found; and we cannot too minutely
enter into an analysis of light, which is the most subtle of all
the active principles that are concerned in the mechanism of
the operations of nature. A better acquaintance with it may
enable us to account for various facts that fall under our daily
observation, but which have hitherto remained unexplained. If
the power of heating, as we now see, be chiefly lodged in the
red-making rays, it accounts for the comfortable warmth that
is thrown out from a fire, when it is in the state of a red glow;
and for the heat which is given by charcoal, coke, and balls of
small-coal mixed up with clay, used in hot-houses; all which,
it is well known, throw out red light. It also explains the
reason why the yellow, green, blue, and purple flames of burn-
ing spirits mixed with salt, occasion so little heat that a hand
is not: materially injured, when passed through their corusca-
tions. If the chemical properties of colours also, when ascer-
tained, should be such that an acid principle, for instance, which
has been ascribed to light in general, on account of its changing
the complexion of various substances exposed to it, may reside
only in one of the colours, while others may prove to be dif-
ferently invested, it will follow, that bodies may be variously
' affected by light, according as they imbibe and retain, or transmit
and reflect, the different colours of which it is composed.

Radiant Heat is of different Refrangibility.

_ I must now remark, that my foregoing experiments ascertain
beyond a doubt, that radiant heat, as well as light, whether

they be the same or different agents, is not only refrangible,.
MDCCC. Nn

272 Dr. HerscueEx’s Investigation of the Powers

but is also subject to the laws of the dispersion arising from its
different refrangibility ; and, as this subject is new, I may be
perinitted to dwell a few moments upon it. The prism refracts
radiant heat, so as to separate that which is less efficacious, from
that which is more so. The whole quantity of radiant heat
contained in a sun-beam, if this different refrangibility did not
exist, must inevitably fall uniformly on a space equal to the area
of the prism; and, if radiant heat were not refrangible at all, it
would fall upon an equal space, in the place where the shadow
of the prism, when covered, may be seen. But, neither of these
events taking place, it is evident that radiant heat is subject to
the laws of refraction, and also to those of the different refran-
gibility of light. May not this lead us to surmise, that radiant
heat consists of particles of light of a certain range of momenta,
and which range may extend a little farther, on each side of
refrangibility, than that of light? We have shewn, that in a
gradual exposure of the thermometer to the rays of the prismatic
spectrum, beginning from the violet, we come to the maximum
of light, long before we come to that of heat, which lies at the
other extreme. By several experiments, which time will not
allow me now to report, it appears that the maximum of illumi-
nation has little more than half the heat of the full red rays ;
and, from other experiments, I likewise conclude, that the full
red falls still short of the maximum of heat; which perhaps
lies even a little beyond visible refraction. In this case, radiant
heat will at least partly, if not chiefly, consist, if I may be per-
mitted the expression, of invisible light; that is to say, of rays
coming from the sun, that have such a momentum as to be
unfit for vision. And, admitting, as is highly probable, that the
organs of sight are only adapted to receive impressions from

of the prismatic Colours to heat and illuminate Objects. 274

particles of a certain momentum, it explains why the maximum
of illumination should be in the middle of the refrangible rays;
as those which have greater or less momenta, are likely to
became equally unfit for impressions of sight. Whereas, in
radiant heat, there may be no such limitation to the momentum
of its particles. From the powerful effects of a burning lens,
however, we gather the information, that the momentum of
terrestrial radiant heat is not likely to exceed that of the sun;
and that, consequently, the refrangibility of calorific rays
cannot extend much beyond that of co/ourific light. Hence we
may also infer, that the invisible heat of red-hot iron, gradually
cooled till it ceases to shine, has the momentum of the invisible
rays which, in the solar spectrum viewed by day-light, go to
the confines of red; and this will afford an easy solution of the
reflection of invisible heat by concave mirrors.

Application of the Result tof ihe hte tie ‘Observations, to the
Method of viewing the Sun advantageously, with Telescopes of
_ large Apertures and high magnifying Powers.

Some time before the late transit of Mercury over the disk
of the sun, I prepared my 7-feet telescope, in order to see it to
the best advantage. As I wished to keep the whole aperture of
the mirror open, I soon cracked every one of the darkening slips
of wedged glasses, which are generally used with achromatic
telescopes:- none of them could withstand the accumulated
heat in the focus of pencils, where these glasses are generally
placed. Being thus left without resource, I made use of red
glasses ; but was by no means satisfied with their performance.

Nne

274, Dr. HERscuEL’s Investigation of the Powers

My not being better prepared, as it happened, was of no conse-
quence; the weather proving totally unfavourable for viewing
the sun at the time of the transit. However, as I was fully
aware of the necessity of providing an apparatus for this pur-
pose, since no method that was in use could be applied to my
telescopes, I took the first opportunity of beginning my trials.

The instrument I wished to adapt for solar inspection, was a
NewroniN reflector, with 9 inches aperture ; and my aim was,
to use the whole of it open.

I began witha red glass; and, not finding it to stop light
enough, took two of them together. These intercepted full as
much light as was necessary; but I soon found that the eye
could not bear the irritation, from a sensation of heat, which it
appeared these glasses did not stop.

I now took two green glasses; but found that they did not
intercept light enough. I therefore smoked one of them; and it
appeared that, notwithstanding they now still transmitted con-
siderably more light than the red glasses, they remedied the
former inconvenience of an irritation arising from heat. - Re-
peating these trials several times,rI constantly found the same

result; and, the sun in the first case being of a deep red colour,

I surmised that the red-making rays, transmitted through red
glasses, were more efficacious in raising a sensation of heat,
than those which passed through green, and which caused the
sun to look greenish. In consequence of this surmise, I under-
took the investigations which have been delivered under the
two first heads. F

As soon as I was convinced that the red light of the sun
ought to be intercepted, on account of the heat it occasions, and
that it might also be safely set aside, since it was now proved

—_— ae.

——

.

of the prismatic Colours to beat and illuminate Objects. 275

_ that pale green light excels in illumination, the method which
ought to be pursued in the construction of a darkening appa-
ratus was sufficiently pointed out ; and nothing remained but
to find such materials as would give us the colour of the sun,
viewed in a telescope, of a pale green light, sufficiently tem-
pered for the eye to bear its lustre. .

To determine what glasses would most effectually stop the
red rays, | procured some of all sepine, and tried them in the
following manner.

I placed a prism in the upper part of a mse and received
its coloured spectrum upon a sheet of white paper. Then I
intercepted the colours, just before they came to the paper,
successively, by the glasses, and found the result as follows.

A deep red glass intercepted all the rays.

A paler red did the same.

_ From this, we ought not to conclude that red glasses will
Stop the red rays; but rather, that none of the sun’s light, after
its dispersion by the prism, remains intense enough to pass
through red glasses, in sufficient quantity to be perceptible,
when it comes to the paper. By looking through them directly
at the sun, or even at day objects, it is sufficiently evident that
they transmit chiefly red rays.

An orange glass transmitted nearly all the red, the orange,
and the yellow. It intercepted some of the green; much of the
blue; and yery little of the indigo and. violet.

A yellow glass intercepted hardly any light, of any one of
the colours.

A dark green glass intercepted nearly all the red, and partly
also the orange and yellow. It transmitted the green ; inter-
cepted much of the blue; but none of the indigo and violet, .

276 Dr. Herscuer’s Investigation of the Powers

A darker green glass intercepted nearly all the red; much
of the orange; and a little of the yellow. It transmitted the
green; stopped some of the blue; but transmitted the pee =
and violet. |

A blue glass intercepted much of the red and orange; some
of the yellow; hardly any. of the ete none of the blue,
indigo, or violet.

A purple glass transmitted some of the red; a very little of
the orange and yellow: it also transmitted a little of the green
and blue; but more of the indigo and violet.

From these experiments we see, that dark green glasses are
most efficacious for intercepting red light, and will therefore
answer one of the intended purposes; but since, in viewing the
sun, we have also its splendour to contend with, I Piotr to
the following additional trials.

White glass, lightly smoked, apparently intercepted an equal
share of all the colours; and, when the smoke was laid on
thicker, it permitted nene of them to pass.

Hard pitch, melted between two white glasses, intercepted
much light; and, when put on sufficiently thick, transmitted
none.

Many differently-coloured fluids, that were also tried, I found
were not sufficiently pure to be used, when dense ae to
stop light. |

Now, red glasses, and the two taste Tinea resources of
smoke, and pitch, any one of which, it has been seen, will stop
as much light as may be required, had still a remaining trial to
undergo, relating to distinctness; but this I was convinced
could only be decided by actual observations of the sun. |

As an easy way of smoking glasses uniformly is of some

of the prismatic Colours to beat and illuminate Olyects. 2977

consequence to distinct vision, it may be of service here to give
the proper directions, how to proceed in the operation.

With a pair of warm pliers, take hold of the glass, and place
it over a candle, at a sufficient distance not to contract smoke.
When it is heated, but no more than still to permit a finger to
touch the edges of it, bring down the glass, at the side of the
flame, as low as the wick will permit, which must not be
touched. Then, with a quick vibratory motion, agitate it in the
flame from side to side; at the same time advancing and retiring
it gently all the while. By this method, you may proceed to
Jay on smoke to any required darkness. It ought to be viewed
from time to time, not only to see whether it be sufficiently
dark, but whether any inequality may be perceived; for, if that
should happen, it will not be proper to go on. )
_ The smoke of sealing-wax is bad: that of pitch is worse. A
wax candle gives a good smoke; but that of a tallow candle is
better. As good as any I have hitherto met with, is the smoke
of spermaceti oil. In using a. lamp, you may also have the
advantage of an even flame extended to any length.

Telescopic Experiments.

No. 1. By way of putting my theory to the trial, I used two
red glasses, and found that the heat which passed through them
could not be suffered a moment; but I was now also convinced
that distinctness of vision is capitally injured, by the colouring
matter of these glasses.’

No. 2. I smoked a white glass, till it stopped light enough to —

278 Dr. Herscuer’s Investigation of the Powers

permit the eye to bear the sun. This destroyed all distinctness >
and also permitted some heat to come to the eye, by tranamnilis
ting chiefly red rays.

No. 3. I applied two white glasses, with pitch between themj

to the telescope; and found that it made the sun appear of a
scarlet colour. They transmitted some heat; and distinctness
was greatly injured.
_ No. 4. I used a very dark green glass, to stop heat; anf
behind it, or towards the eye, I placed a red glass, to stop light.
The first glimpse I had of the sun, was accompanied with a
sensation of heat; distinctness also was materially injured.

No. 5. I used a dark green and a pale red; but, the sun not
being sufficiently darkened, I smoked the red glass, and, pute
ting a small partition between the two, placed the smoke
towards the green glass. This took off the exuberance of light;
but did not remedy the inconvenience arising from heat.

No. 6. I used two pale green glasses; smoking that next to
the eye, and placing it as in No. 5, so that the smoke might be
inclosed between the two. This acted incomparably well; but,
in a very short time, the heat which passed the first glass,
(though not the second, for I felt no sensation of it in the eye,)
disordered the smoke, by drawing it up into little blisters or

stars, which let through light; and this composition, therefore, -

soon became useless.

No. 7. I used two dark green glasses, one of them smoked, ©

as in No. 5. These also acted well; but became useless, for the
reason assigned in No. 6, though somewhat less smoke had
been required than in the former composition. I felt no heat.
No. 8. I used one pale green, with a dark green smoked
glass upon it, as in No. 5. It bore an aperture of 4, inches very

a

of the prismatic Colours to heat and illuminate Olyects. 279

well, and the smoke was not disordered; but, when all the tube
was open, the pale green glass cracked in a few minutes.

~No.g. Placing now a dark green before a smoked green, I
saw the sun remarkably well. In this experiment, I had made
a difference in the arrangement of the apparatus. The cracking
of the glasses, I supposed, might be owing to their receiving
heat in the middle, while the outside remained cold; which
would occasion a partial dilatation. I therefore cut them into
pieces about a quarter of an inch square, and set three of them
_in aslider, so that I could move them behind the smoked glass,
without disturbing it. After looking about three or four minutes
through one of them, I moved the slider to the second, and then
to the third. This kept the glasses sufficiently cool; but the
disturbance of the alterations proved hurtful to vision, which
requires repose ; and, if perchance I stopped a little longer than
the proper time, the glass cracked, with a very disagreeable
explosion, that endangered the eye. |

No. 10. Two dark green glasses, both smoked, that a thinner
coat might be on each; but the smoke still contracted blisters,
though less dense than before.

No. 11. To get rid of smoke intirely, I used two dark green
glasses, two very dark green, two pale blue, and one pale green
glass, together. Distinctness was wanting; nor was light suffi-
ciently intercepted.

No. 12. A dark green and a pale blue Aa smoked. The
green glass cracked. |

No. 1g. A pale blue and a dark green glass, smoked. The
blue glass cracked. The eye felt no sensation of heat. ,

No. 14. Two pale blue glasses, one smoked. The first glass
cracked.

MDCCC, Oo

280 Dr. HerscuEL’s Investigation of the Powers

‘It was now sufficiently evident, that no glass which stops’
heat, and therefore receives it, could be preserved from cracking,
when exposed to the focus of pencils. This induced me to try
an application of the darkening apparatus to another part of the
telescope. .

The place where the rays are least condensed, without inter-
fering with the reflections of the mirrors, is immediately close
to the small one. I therefore screwed an apparatus to the spe-"
culum arm, into which any glass might be placed.

No. 15. A dark green glass close to the small speculum, and
smoked pale green in the focus of pencils, as before. I saw
remarkably well.

No. 16. The dark green as before; but, that more light might’
be admitted, a white smoked glass near the eye. Better than
No. 15; but the green glass cracked. 19

No. 17. A very dark green and white smoked glass, as
before. Very distinct, but the green glass cracked in about six
or seven minutes.

No. 18. A dark blue glass, as in No. 15, and white smoked.
This was distinct; and no heat: came to the eee The sun
appeared ruddy.

No. ig. A dark blue and a yellow glass, close together, as in
No. 15, and a white smoked one, as before. This was not
distinct. _

No. 20. A purple glass, as in No. 15, with a white smoked
one. This gave the sun of a deep orange colour, approaching
to scarlet. It was not distinct. ;

No. 21. An orange glass, as in No. 15, with a white aces
one. The colour of the sun was too red.

No, 22. A white smoked glass, as in No. 15, without any

of the prismatic Colours to heat and illuminate Olyects. 281

other at the eye. This gave the sun of a beautiful orange colour;
but distinctness was totaily destroyed.

No. 23. The heat near the small. speculum being still too
powerful for the glasses, I had a bluish dark green glass made
of a proper diameter to be inclosed between the two eye-glasses

of a double eye-piece, All glass I knew would stop some heat;

and was therefore in hopes that the interposition of this eye-
glass would temper the rays, so as in some measure to protect
the coloured glass. In the usual place near the eye, I put two
white glasses, with a thin coat of pitch between them. These
glasses, when looked through by the natural eye, give the sun
of a red colour; I therefore entertained no great hopes of
their application to the telescope. They darkened the sun not
sufficiently ; and, when the pitch was thickened, distinctness
was wanting.

No. 24. The same glass between the eye-glasses, and a dark
green smoked glass at the eye. Very distinct. This arrangement
is preferable to that of No. 15; after some considerable time,
however, this glass also cracked.

No. 25. I placed a very dark green glass behind the second
eye-glass, that it might be sheltered by both glasses, which in
my double eye-piece are close together, and of an equal focal
length. Here, as the rays are not much concentrated, the
coloured glass receives them on a large surface, and stops light
and heat, in the proportion of the squares of its diameter now
used, to that on which the rays would have fallen, had it been

placed in the focus of pencils. And, for the same reason, I now
also placed a dark green smoked glass close upon the former,
_ with the smoked side towards the eye, that the smoke might
Oo 2

289 Dr. HerscueEw’s Investigation of the Powers

likewise be protected against heat, by a passage of the rays
through two surfaces of coloured glass.

This position had moreover the advantage of leaving the
telescope, with its mirrors and glasses, completely to perform
its operation, before the application of the darkening apparatus ;
and thus to prevent the injury which must be occasioned, by
the interposition of the heterogeneous colouring matter of the
_ glasses and of the smoke.

No. 26. I placed a deep blue glass with a bluish green
smoked one upon it, as in No. 25, and found the sun of a whiter
colour than with the former composition. There was no disa-
greeable sensation of heat; though a little warmth might be
felt.

No. 27. I used two black glasses, placed as in No. 25. Here ~

there was no occasion for smoke; but the sun appeared of a
bright scarlet colour, and an intolerable sensation of heat took
place immediately. I rather suspect that these are very deep red
glasses, though their outward appearance is black.

In order to have a more sure criterion of heat, I applied Dr.
‘Witson’s thermometer, No. 2, to the end of the eye-piece,
where the eye is generally placed. With No. 25, it rose from
34, to 37 degrees, With No. 26, it rose from 35 to 46; and,
with No. 27, it rose, very quickly, from 36 to 95 degrees. I am
pretty sure it would have mounted up still higher; but, the scale
extending only to 100, I was not willing to run the risk of
breaking the thermometer by a longer exposure.

It remains now only to be added, that with No. 25 and 26 I
have seen uncommonly well; and that, in a long series of very
interesting observations upon the sun, which will soon be

Shiles Truns MDC CC LateXp 282

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of the prismatic Colours to heat and illuminate Oljects. 283

communicated, the glasses have met with no accident. How-
ever, when the sun is at a considerable altitude, it will be
advisable to lessen the aperture a little, in telescopes that have
so much light as my 10-feet reflector; or, which will give us
more distinctness, to view the sun earlier in the morning, and
later in the afternoon; for, the light intercepted by the atmo-
sphere in lower altitudes, will reduce its brilliancy much more
uniformly than we can soften it, by laying on more smoke upon
our darkening glasses. Now, as few instruments in common
use are so large as that to which this method of darkening has
been adapted, we may hope that it will be of general utility in
solar observations.

Slough, near Windsor,
March 8, 1800.

[ 284

XIV. Experiments on the Refrangibility of the invisible Rays of the
Sun. By William Herschel, LL. D. F. R.S.

Read April 24, 1800.

[x that section of my former paper which treats of radiant heat,
it was hinted, though from imperfect experiments, that the range
of its refrangibility is probably more extensive than that of the
prismatic colours ; but, having lately had some favourable sun-
shine, and obtained a sufficient confirmation of the same, it will
be proper to add the following experiments to those which have
been given.

I provided a small stand, with four short legs, and covered it
with white paper.* On this I drew five lines, parallel to one end
of the stand, at half an inch distance from each other, but so
that the first of the lines might only be 2 of an inch from the
edge. These lines I intersected at right angles with three others;
the ed and 3d whereof were, respectively, at 24 and at 4 inches
from the first. f

The same thermometers that have before been marked
No. 1, 2, and 3, mounted upon their small inclined planes, were
then placed so as to have the centres of the shadow of their
balls thrown on the intersection of these lines. Now, setting
my little stand upon a table, I caused the prismatic spectrum to
fall with its extreme colour upon the edge of the paper, so that
none might advance beyond the first line. In this arrangement,

* See Plate XI.

hte

Dr. Herscuer’s Experiments, &c. 285

all the spectrum, except the vanishing last quarter of an inch,
which served as a direction, passed down by the edge of the
stand, and could not interfere with the experiments. I had also
now used the precaution of darkening the window in which the
prism was placed, by fixing up a thick dark green curtain, to
keep out as much light as convenient.

The thermometers being perfectly settled at the temperature
of the room, I placed the stand so that part of the red colour,
refracted by the prism, fell on the edge of the paper, before the
thermometer No. 1, and about half way, or 14 inch, towards
the second: it consequently did not come before that, or the
gd thermometer, both which were to be my standards. During
the experiment, I kept the last termination of visible red
carefully to the first line, as a limit assigned to it, by gently
moving the stand when required ; and found the thermometers,
which were all placed on the second line, affected as follows.

No. 1. No. 2. No. 3.
45 - AS Fi a 4A
49 = i 45 ry 7 Ad
Be ORG TG eM aso rale) tS td
er? DS NNO A ago sil euiT 3 ABs

Here the thermometer No. 1 rose 61 degrees, in 10 minutes,
when its centre was placed + inch beyond visible light.

In order to have a confirmation of this fact, I cooled the
thermometer No. 1, and placed No. 2 in the room of it: I also
put No. 3 in the>place of No.2, and No. 1 in that of No. 33
and, having exposed them as before, arranged. on the second
line, I had the following result.

286 Dr. HERscHeEL’s Experiments on the Refrangibility

No. 2. No. 3. No. 1.
44 = Tivol” borg MoS ool ib-e7 ee Bae
47 70 G0 Sigg strsicT tonthh sate
1 Ce Bem ne
A620) can) 4 Sade hedge nla

Here the thermometer No. 2 rose 23 degrees, in 12 minutes;
and being, as has been noticed before, much more sensible than.
No. 1, it came to the temperature of its situation in a short time; ,
but I left it exposed longer, on purpose to be perfectly assured
of the result. Its shewing but 23 degrees advance, when No. 1
shewed 65, has also been accounted for before. ;

It being now evident that there was a refraction of rays coming
from the sun, which, though not fit for vision, were yet highly
invested with a power of occasioning heat, I proceeded to ex-
amine its extent as follows.

The thermometers were arranged on the third line, instead
of the second; and the stand was, as before, immersed up to the
first, in the coloured margin of the vanishing red rays. The

result was thus. :

No. 1. No. 2. No. 3
Merde: eMehn Cul:
50 ~ eo a0] yea re
SiS ey SO 9 a ei
524s ci cis to uni Geihaem es eas

- Here the thermometer No. 1 rose 5+ degrees, in 1 3 minutes,
at 1 inch behind the visible light of the red rays.

I placed now the thermometers on the 4th line, instead of
the gd; and, proceeding as before, I had the following result.

of the invisible Rays of the Sun. 287

No. 1. No. 2. No. 3.
eee ABE OR gwoltel co AGS
ee ae ym mS ae

Therefore, the thermometer No. 1 rose 3; degree, in 10
minutes, at 14 inch beyond the visible light of the red rays. ©

I might now have gone on to the sth line ;_ but, so fine a day,
with regard to clearness of sky and perfect calmness, was not
to be expected often, at this time of the year; I therefore
hastened to make a trial of the other extreme of the prismatic
spectrum. ‘This was attended with some difficulty,°as the illu-
mination of the violet rays is so feeble, that a precise termination
of it cannot be perceived. However, as well as could be judged,
I placed the thermometers one inch beyond the reach of the
violet rays, and found the result as follows.

No. 1. No. 2. No. g.
BOG HNO ai pie hos cepBatrnru ls or acta
ia? ieee a1 =i port: eid voir RG
48 prcedrpria hivaigaghte ris lit ond a
Mae 1 Oye to Nied sthapsd! Oo) -) on ni) AY
48 B ts beninesa mii ott olla

Here the several indications of the thermometers, two of
which, No, 1 and 2, were used as variable, while the 3d was
kept as the standard, were read off during a time that lasted
12 minutes ; but they afford, as may be seen by inspection, no
ground for ascribing any of their small changes to other causes
than the accidental disturbance which will arise from the motion
of the air, ina room where some employment is carried on. -

I exposed the thermometer now to the line of the very first
perceptible violet light; but so that No. 1 and 2 might again

MDCCC, rp

288 Dr. HERScHEL’s Experiments on the Refrangibility

be in the illumination, while No. g remained a standard. The
result proved as follows.

No. 1. No.2, No. 3.
48 SOE Os
AG *= 781 a
ABZ Ca FASE! le OU aay
te ce

Here the thermometer No. 1 rose 1 degree, in 15 minutes;
and No. 2 rose + degree, in the same time.

From these last experiments, I was now sufficiently persuaded,
that no rays which might fall beyond the violet, could have
any perceptible power, either of illuminating or of heating; and
that both these powers continued together throughout the pris-
matic spectrum, and ended where the faintest violet vanishes.

A very material point remained still to be determined, which
was, the situation of the maximum of the heating power.

As I knew already that it did not lie on the violet side of the
red, I began at the full red colour, and exposed my thermometers,
arranged on a line, so as to have the ball of No. 1 in the midst
of its rays, while the other two ue at the side, unaffected
by them.

No. 1. No. 2. No. 3.
ABS 8 ee 048, 9 a
Bop oe = ta Oe Loe a
555 = OAS Oe Cees

Here the thermometer No. 1 rose 7 degrees, in 10 minutes, by
an exposure to the full red coloured rays.
I drew back the stand, till the centre of the ball of No. 1 was

:
|

of the invisible Rays of the Sun. 289

just at the vanishing of the red colour, so that half its ball was
within, and half without, the visible rays of the sun.

No. 1. No. 2. No. 3.
ee a ee me aS
ot deer 7.
ee. ea AR?

Here the thermometer No. 1 rose 8 degrees, in 10 minutes.

By way of not losing time, in order to connect these last
observations the better together, I did not bring back the ther-
mometer No. 1 to the temperature of the room, being already
well acquainted with its rate of shewing, compared to that of
. No. 2, but went on to the next experiment, by withdrawing the
stand, till the whole ball of No. 1 was completely out of the sun’s
visible rays, yet so as to bring the termination of the line of the
red colour as near the outside of the ball as could be, without
touching it.

IG cai. t 1a No. 3.
Hla BMT A sletiess AB war btoe grind Ba
Bea GIs batiswn 402 aasio dt oid 9
BO Cae Feast Ted (AOR, oli Th iso To AOE
yo pte croy'd Sidi yr BO ‘oer oiby 4a

Here the thermometer No. 1 rose, in 10 minutes, another
degree higher than in its former situation it could be brought
-up to; and was now g degrees above the standard. The ball
of this thermometer, as has been noticed, is exactly half an inch
in diameter; and its centre therefore was + inch beyond the
visible illumination, to which no part of it was exposed.

_It would not have been proper to compare these last obser-
vations with those taken at an earlier period this morning, in
Ppe

290 Dr. HERscuEL’s Experimenis on the Refrangibility

order to obtain a true maximum, as the sun was now more
powerful than it had been at that time; for which reason, I
caused the line of termination of visible light, now to fall again

just 4 inch from the centre of the ball; and had the following

result.

No. 1. No. 2. No. 3.
free. ea
7x 71 9 nvo8? vinstsagedebeee
585-0 Tiliviv? 4 oP Unions heme eae
Soe Sayed BOR rere galas

And here the thermometer No. 1 rose, in 16 minutes, 83
degrees, when its centre was + inch out of the visible rays of
the sun. Now, as before we had a rising of g degrees, and
here 83, the difference is almost too trifling to suppose, that
this latter situation of the thermometer was much beyond the
maximum of the heating power; while, at the same time, the
experiment sufficiently indicates, that the place inquired after
need not be looked for at a greater distance.

It will now be easy to draw the result of these observations
into.a very narrow compass.

The first four experiments prove, that there are rays coming
from the sun, which are less refrangible than any of those that
affect the sight. They are invested with a high power of heating
bodies, but with none of illuminating objects; and this explains
the reason why they have hitherto escaped unnoticed.

My present intention is, not to assign the angle of the least
refrangibility belonging to these rays, for which purpose more
accurate, repeated, and extended experiments are required. But,
. at the distance of 52 inches from the prism, there was still a

considerable heating power exerted by our invisible rays, one

“
|
q

of the invisible Rays of the Sun. 291

inch and a half beyond the red ones, measured upon their pro-
jection on a horizontal plane. I have no doubt but that their
efficacy may be traced still somewhat farther.

The 5th and 6th experiments shew, that the power of heating
is extended to the utmost limits of the visible violet rays, but
not beyond them; and that it is gradually impaired, as the rays
grow more refrangible.

The four last experiments prove, that the maximum of the
heating power is vested among the invisible rays; and is pro-
bably not less than half an inch beyond the last visible ones,
when projected in the manner before mentioned. The same
experiments also shew, that the sun’s invisible rays, in their less
refrangible state, and considerably beyond the maximum, still
exert a heating power fully equal to that of red-coloured light;
and that, consequently, if we may infer the quantity of the effi-
cient from the effect produced, the invisible rays of the sun
probably’ far exceed the visible ones in number.

To conclude, if we call /ight, those rays which illuminate
objects, and radiant beat, those which heat bodies, it may be
inquired, whether light be essentially different from radiant
heat? In answer to which I would suggest, that we are not
allowed, by the rules of philosophizing, to admit two different
causes to explain certain effects, if they may be accounted for
by one. A beam of radiant heat, emanating from the sun,
consists of rays that are differently refrangible. The range of
their extent, when dispersed by a prism, begins at violet-
coloured light, where they are most refracted, and have the
least efficacy. We have traced these calorific rays throughout
the whole extent of the prismatic spectrum; and found their
power increasing, while their refrangibility was lessened, as far

292 Dr. Herscue.’s Experiments, &c.

as to the confines of red-coloured light. But their diminishing
refrangibility, and increasing power, did not stop here; for we
have pursued them a considerable way beyond the prismatic
spectrum, into an invisible state, still exerting their increasing
energy, with a decrease of refrangibility up to the maximum of
their power; and have also traced them to that state where,
though still less refracted, their energy, on account, we may
suppose, of their now failing density, decreased pretty fast;
after which, the invisible thermometrical spectrum, if 1 may so
call it, soon vanished.

If this be a true account of solar heat, for the support of

which I appeal to my experiments, it remains only for us to |

admit, that such of the rays of the sun as have the refrangibility
of those which are contained in the prismatic spectrum, by the
construction of the organs of sight, are admitted, under the
appearance of light and colours; and that the rest, being stopped
in the coats and humours of the eye, act upon them, as they
are known to do upon all the other ike of our body, by occa-
sioning a sensation of =

Slough, n near nb gtctrs
March 17, 1800.

EXPLANATION OF PLATE XIL
IN WHICH IS GIVEN A VIEW OF THE APPARATUS.
~ AB. The small stand.
- 4, 2, 3. The thermometers upon it.
CD. The prismat the window. ~

% E. The spectrum thrown upon the table, so as to bring the
last quarter of an inch. of the red colour upon the stand.

Thilos. lians. MDCCC. tate X\_ p 2g2.

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C 293 J

XV. Experiments on the solar, and on the terrestrial Rays that
occasion Heat; with a comparative View of the Laws to which
Light and Heat, or rather the Rays which occasion them, are
subject, in order to determine whether they are the same, or
different. By William Herschel, LL. D. F. R.S.

Part I.

Read May 15, 1800.

Tus word heat, in its most common acceptation, denotes a
certain sensation, which is. well known to every person. The
cause of this sensation, to avoid ambiguity, ought to have been
distinguished by a name different from that which is used to
point out its effect. Warious authors indeed, who have treated
on the subject of heat, have occasionally added certain terms to.
distinguish their conceptions, such as, latent, absolute, specific,
sensible heat; while others have adopted the new expressions
of caloric, and the matter of heat. None of these descriptive
appellations however would have completely answered my
purpose. I might, as in the preceding papers, have used the name
radiant heat, which has been introduced by a celebrated author,
and which certainly is not very different from the expressions
Ihave now adopted ; but, by calling the subject of my researches,
the rays that occasion heat, I cannot be misunderstood as mean-
ing that these rays themselves are heat; nor doI in any respect
engage myself to shew in what manner they produce heat.
From what has been said it follows, that any objections that
may be alleged, from the supposed agency of heat in other

294 Dr. HEeRscHeL’s Experiments on the solar, and

circumstances than in its state of radiance, or heat-making
rays, cannot be admitted against my experiments. For, not-
withstanding I may be inclined to believe that all phenomena ~
in which heat is concerned, such as the expansion of bodies,
fluidity, congelation, fermentation, friction, @c. as well as heat
in its various states of being latent, specific, absolute, or sensible,
may be explained on the principle of heat-making rays, and
vibrations occasioned by them in the parts of bodies; yet this is
not intended, at present, to be any part of what I shall endea-
vour to establish.

I must also remark, that in using the word rays, I do not
mean to oppose, much less to countenance, the opinion of those
philosophers who still believe that light itself comes to us from
the sun, not by rays, but by the supposed vibrations of an elastic
ether, every where diffused throughout space; I only claim the
same privilege for the rays that occasion heat, which they are
willing to allow to those that illuminate objects. For, in what
manner soever this radiance may be effected, it will be fully
proved hereafter, that the evidence, either for rays, or for
vibrations which occasion heat, stands on the same foundation
on which the radiance of the illuminating principle, light, is
built.

In order to enter on our subject with some regularity, it will
be necessary to distinguish heat into six different kinds, three
whereof are solar, and three terrestrial; but, as the divisions of
terrestrial heat strictly resemble those of solar, it will not be
necessary to treat of them separately; our subject, therefore, may
be reduced to the three following general heads. —

We shall begin with the heat of luminous bodies in general,
such as, in the first place, we have it directly from the sun;

on the terrestrial Rays that occasion Heat. 295

and as, in the second, we may obtain it from terrestrial flames,
such as torches, candles, lamps, blue-lights, @c.
Our next division comprehends the heat of coloured radiants.
This we obtain, in the first place, from the sun, by separating
its rays in a prism; and, in the second, by having recourse to
culinary fires, openly exposed.

The third division relates to heat obtained from radiants,

where neither light nor colour in the rays can be perceived.
This, as I have shewn, is to be had, in the first place, directly
from the sun, by means of a prism applied to its rays; and, in
the second, we may have it from fires inclosed in stoves, and
_ from red-hot iron cooled till it can no longer be seen in the
dark. ‘ .

Besides the arrangement in the order of my experiments
which would arise from this division, we have another subject to
consider. For, since the chief design of this paper is to give a
comparative view of the operations that may be performed on
the rays that occasion heat, and of those which we already
know to have been effected on the rays that occasion light, it
will be necessary to take a short review of the latter. I shall
merely select such facts as not only are perfectly well known,
but especially such as will answer the intention of my compa-
rative view, and arrange them in the following order.

1. Light, both solar and terrestrial, is a sensation occasioned
by rays emanating from luminous bodies, which have a power
of illuminating objects ; and, according to circumstances, of
making them appear of various colours.

2. These rays are subject to the laws of reflection.

g. They are likewise subject to the laws of refraction.

4. They are of different refrangibility.

MDCCC. Qqg

296 Dr. HERSCHEL’s Experiments on the Solar, and

5. They are liable to be stopped, in certain PPA when
transmitted through diaphanous bodies.

6. They are liable to be scattered on rough surfaces.

7. They have hitherto been supposed to have a ihe of
heating bodies ; but this remains to be examined.

The similar propositions relating to heat, which are intended
to be proved in this paper, will stand as follows.

1. Heat, both solar and terrestrial, is a sensation occasioned
by rays emanating from candent substances, which have a
power of heating bodies. :

2. These rays are subject to the laws of reflection.

g. They are likewise subject to the laws of refraction.

4. They are of different refrangibility.

5. They are liable to be stopped, in certain proportions, when
transmitted through diaphanous bodies.

6. They are liable to be scattered on rough surfaces.

7. They may be supposed, when in a certain state of energy,
to have a power of illuminating objects ; but this remains to be
examined.

Before I can go on, I have to mention, that the number of
experiments which will be required to make good all these
points, exceeds the usual length of my papers; on which account,
I shall divide the present one into two parts. Proceeding there-
fore now to an investigation of the three first heads that have
been proposed, I reserve the three next, and a discussion which
will be brought on by the seventh article, for the second part.

ist. Experiment. Reflection of tbe Heat of the Sun,

I exposed the thermometer which in a former paper has been
denoted by No. g, to the eye-end of a ten-feet NEwTon1an

*
Se lr

on the terrestrial Rays that occasion Heat. 297

telescope, which carried a Camera-eye-piece,* but no eye-glass.
When, by proper adjustment, the focus came to the ball of the
thermometer, it rose from 52 degrees to 110; so that rays which
came from the sun, underwent three regular reflections; one,
on a concave mirror, and the other two, on two plain ones,
Now these rays, whether they were those of light or not, for
that our experiment cannot ascertain, had a power of occasioning
heat, which was manifested in raising the thermometer 58
degrees. ms

ad. Experiment. Reflection of the Heat of a Candle.

At the distance of 29 inches from a candle, I planted a small
steel-mirror, of 37, inches diameter, and about 23 inches focal
length.{ In the secondary focus of it, I placed the ball of the
thermometer which in my paper has been marked No. 2; and |
very near it, but out of the reach of reflection, the thermometer
No. 3. Having covered the mirror till both were come to the
temperature of their stations, I began as follows.

No. 2. No. 3.

In the Focus, Standarde
or 54 54
| 55 54
2 56 54
3 57 54
4 57x 54
5 57% 54

Here, in five minutes, the thermometer No. 2 received 32
degrees of heat from the candle, by reflected rays. I now

® See Phil. Trans. Vol. LXXII, p. 176.
+ See Plate XII. Fig. 1.

& Qq2

298 Dr. Hersonen’s Experiments on the Solar, and

covered the mirror, but left all the rest of the soir un=-
touched. /

No. 2. No. 3

In the Focus. Standard.
o Vie «54
st 55% 54
55 54
6 5A 54

Here, in six minutes, the thermometer lost the 32 degrees of
heat again, which it had gained before. I uncovered the mirror
once more.
o’ 54 54

it 56 54,
32 57 54
5 RTs 54

And, in five minutes, the 3 degrees of heat were regained.
In consequence of which, we are assured that certain rays came
from the candle, subject to the laws of reflection, which, though
they might not be the rays of light, for that our experiment does
not determine, were evidently invested with a power of heating
the thermometer placed in the focus of the mirror,

3d-Experiment. Reflection of the Heat that accompanies the Solar
| prismatic Colours.

In the spectrum of the sun, given by a prism, I placed my
small steel mirror, with a thermometer in its focus.* It was
covered by a piece of pasteboard, which, through a proper
opening, admitted all the visible colours to fall on its polished
surface, but excluded every other ray of heat that might be,
either on the violet or on the red side, beyond the spectrum.

* See Plate XII. Fig. 2.

on the terrestrial Rays that occasion Heat. 299

Then, placing the apparatus so as to have the thermometer in
the red rays, but keeping the mirror covered up till the thermo-
meter became settled, 1 found it stationary at 58°. Uncovering
the mirror, I had as follows.

No. 2.
Oo’ 58
20 93

Here, in two minutes, the thermometer rose 35 degrees, by
reflected heat. I covered the mirror again, and, in a few minutes,
‘the thermometer, exposed to the direct prismatic red, came
down to 58° again. And thus the prismatic colours, if they are
not themselves the heat-making rays, are at least accompanied
by such as have a power of occasioning heat, and are liable to
be regularly reflected.

4th Experiment. Reflection of the Heat of a red-bot Poker.

I placed the small steel mirror at 12 inches from a red-hot
poker, set with its heated end upwards, in a perpendicular
position, and so elevated as to throw its rays on the mirror.*
The thermometer No. 2 was placed in its secondary focus, and
had a small pasteboard screen, to guard its ball from the direct
heat of the poker.

No. 2.
OF 54
; iz 93
I covered the mirror.
3 65

Here, in 15 minute, the thermometer rose 383 degrees, by
reflected rays; and, when the mirror was covered up, it fell in
the next 14 minute, 28 degrees. On which account, we cannot

* See Plate XII. Fig. 1.

300 Dr. HERscHEL’s Experiments on the Solar, and

but allow, that certain rays, whether it be those that shine or not,
issue from an ignited poker, which are subject to the regular
laws of reflection, and have a power of heating bodies.

5th Experiment. Reflection of the Heat of a Coal Fire by a plain
Mirror.

I placed a small speculum, such as I use with my 7-feet re-
flectors, upon a stand, and so as to make an angle of 45 degrees
with the front of it.* This was afterwards to face the fire in my .
parlour chimney, and would make the same angle with the bars
of the grate. At a distance of 34 inches from the speculum, on
the reflecting side of it, was placed the thermometer No. 1; and

close by it, but out of the reach of the reflected rays, the ther-
-mometer No. 4.. The whole was guarded in front, against the
influence of the fire, by an oaken board 12 inch thick, which
had a circular opening of 14 inch diameter, opposite the
situation of the plain mirror, in order to permit the fire to shine
upon it. The thermometers were divided from the mirror by a
wooden partition, which also had an opening in it, that the re-
flected rays might come from the mirror to No. 1, while No. 4
remained screened from their influence. On exposing this
apparatus to the fire, I had the following result.

No. 1. No. 4,
o’ GO. Go Ya
1 62 “ eGOgn
2 64, 6o
3 66 60
A 66 60
5 67 605

* See Plate XII. Fig. 3.

on the terrestrial Rays that occasion Heat. gor

Here, in five minutes, the heat reflected from the plain mirror
raised the thermometer No. 1, 7 degrees ; while the change in
the temperature of the screened place, indicated by No. 4,
amounted only to half a degree: which shews, that an open
fire sends out rays that are subject to the laws of reflection, and
occasion heat.

Gib Experiment. Reflection of Fire-heat by a Prism.

Every thing remaining arranged as in the 5th experiment, I
removed the small plain mirror, and placed in its stead a prism,
which had one of its angles of go degrees, and the other two
of 45° each.* It was put so as to have one of the sides facing
the fire, while the other was turned towards the thermometer :
the hypotenuse, consequently, made an angle of 45 degrees
with the bars of the grate. The apparatus, after having been
cooled some time, was exposed:to the fire, and the following
result was taken.

Novae Bis Nog,

oO! 625 623.
1 63 623
2 64 63

4 647 63

5 65 63%
8 65% 637
10 663. 633
11 67 642

Here, in eleven minutes, the rays reflected by the prism raised
the thermometer 44 degrees; but, the temperature of the place
having undergone an alteration of 13 degrees, we can only

* See Plate XII. Fig. 3.

302 Dr. Herscuex’s Experiments on the Solar, and

place 23 to the account of reflection. The apparatus becoming
now very hot, it would not have been fair to have continued
the experiment for a longer time; but the effect already pro-
duced was fully sufficient to shew, that even a prism, which
stops a great many heat-making rays, still reflects enough of
them to prove, that an open fire not only sends them out, but
that they are subject to every law of reflection.

7th Experiment. Reflection of invisible Solar Heat.

On a board of about 4, feet 6 inches long, I placed at one end,
a small plain mirror, and at the other, two thermometers*. The
distance of No 1, from the face of the mirror, was 3 feet 9%
inches; and No. 2 was put at the side of it, facing the same
way, but out of the reach of the rays that were to be reflected
by the mirror. The colours of the prism were thrown on a ~
sheet of paper having parallel lines drawn upon it, at half an
inch from each other. The mirror was stationed upon the paper;
and was adjusted in such a manner as to present its-polished
surface, in an angle of 4,5 degrees, to the incident coloured rays,
by which means, they would be reflected towards the ball of
the thermometer ‘No. 1. In this arrangement, the whole appa-
ratus might be withdrawn from the colours to any required
distance, by attending to the last visible red colour, as it shewed
itself on the lines of the paper. When the thermometers were
properly settled to the temperature of their situation, during
which time the mirror had been covered, the apparatus was
drawn gently away from the colours, so far as to cause the
mirror, which was now open, to receive only the invisible rays
of heat which lie beyond the confines of red. The result was
as follows,

* See Plate XII. Fig. 4.

ide

7

10

60
‘60

on the terrestrial Rays that occasion Heat.

Here, in ten minutes, the thermometer No. i
degrees of heat, reflected to it, in the strictest optical manner,
by the plain mirror of a NEwronian telescope. The great
regularity with which these invisible rays obeyed the law of
reflection, was such, that Dr. Witson’s sensible thermometer
No. 2, which had been chosen on purpose for a standard, and
was within an inch of the other thermometer, remained all the
time without the least indication of any change of temperature
that might have arisen from straggling rays, had there been any
such. I now took away the mirror, but left every thing else in
the situation it was. The effect of this was thus.

10

No. 1.

60
58
7
56

No. 2.

56
56
56
50

393

received four

Here, in ten minutes, the thermometer No. 1 lost again the
4, degrees it had acquired, while No. @ still remained unaltered;
and this becomes therefore a most decisive experiment, in proof
of the existence of invisible rays, of their being subject to the

laws of reflection, and of their power of occasioning heat.

MDCCC,

Rr

304 Dr. Herscue.’s Experiments on the solar, and

8th Experiment. Reflection, and Condensation, of the invisible
solar Rays.

I made an apparatus for placing the small steel mirror at any
required angle;* and, having exposed it to the prismatic spec-
trum, so as to receive it perpendicularly, I caused the colours to fall
on one half of the mirror, which, being covered by a semicircular
piece of pasteboard, would stop all visible rays, so that none of
them could reach the polished surface. On the pasteboard were
drawn several lines, parallel to the diameter, and at the distance
of one-tenth of an inch from each other; that, by withdrawing
the apparatus, I might have it at option to remove the last
visible red to any required distance from the reflecting surface.
In the focus of the mirror was placed the thermometer No. 2.
I covered now also the other half of the mirror, till the thermo-
meter had assumed the temperature of its situation, Then,
withdrawing the apparatus out of the visible spectrum, till the
last tinge of red was one-tenth of an inch removed from the
edge of the pasteboard, and the whole of the coloured image
thus thrown on the semicircular cover, I opened the other half
of the mirror, for the admission of invisible rays. The result
was as follows. |

No. 2.
In the Focus of invisible Heat.
o’ 61
1 ; 80

Here, in one minute, the thermometer rose 19 degrees. I
covered the mirror.

2! 72
3 67
4 64

* See Plate XII. Fig. 2.

on the terrestrial Rays that occasion Heat. 305

Here, in three minutes, the thermometer et 16 degrees, I
opened the mirror again.

No. 2.
In the Focus of inyisible Heat.
!
a 83
6 83

_ Here, in two minutes, the thermometer rose 24 degrees. I
covered the mirror once more.
ve 69

And, in one minute, the thermometer fell 19 degrees. Now,
by this alternate rising and falling of the thermometer, three
points are clearly ascertained. The first is, that there are invisible
rays of the sun. The second, that these rays are not only re-
flexible, in the manner which has been proved in the foregoing
_ experiment, but that, by the strict laws of reflection, they are
capable of being condensed. And, in the third place, that by
condensation, their heating power is proportionally increased ;
for, under the circumstances of the experiment, we find that it
extended so far as to be able to raise the thermometer, in two
minutes, no less than 24, degrees.

gth Experiment. Reflection of invisible culinary Heat.

‘I planted my little steel mirror upon a small board ;* and at a
proper distance opposite to it I erected a slip of deal, + inch
thick, and 1 inch broad, in a horizontal direction, so as “to be
of an equal height, in the middle of its thickness, with the
centre of the mirror. Against the side, facing the mirror, were
fixed the two thermometers No. 2 and No. g, with their balls-
within half an inch of each other, and the scales turned the
opposite way. A little of the wood was cut out of the slip, to ~

* See Plate XIII. Fig. 1.
Rr 2

306 = Dr. Herscnex’s Experiments on the solar, and

make room for the balls to be freely exposed. That of No. 2
was in the axis of the mirror; and the ball of No. g was screened
from the reflected rays, by a small piece of pasteboard tied to
the scale. The small ivory scales of the thermometers, with the
slip of wood at their back, which however was feather-edged
towards the stove, intercepted some heat’; but it will be seen
presently that there was enough to spare. When my stove was
of a good heat, I brought the apparatus to a place ready pre-
pared for it. it
No. 2. No. 3-.

‘ In the Focus. Screened.
o’ 52 52
1 91 58

Here we find that, in one minute, the invisible culinary heat
raised the thermometer No. 2, 39 degrees; while No. 3, from
change of temperature, rose only one, notwithstanding its
exposure to the stove was in every respect equal to that of
No. g, except so far as relates to the rays returned by the
mirror; and therefore, the radiant nature of these invisible rays,
their power of heating bodies, and their being subject to the
laws of reflection, are equally established by this experiment.

10th Experiment. Reflection of the invisible Rays of Heat of a
Poker, cooled from being red-hot till it could no longer be
seen in a dark Place.. |

The great abundance of heat in my last experiment, would
not allow of its being carried on without injury to the thermo--
meter, the scale of which is not extensive; I therefore placed a
poker, when of a proper black heat, at 12 inches from the steel _
mirror,* and received the effect of its condensed rays upon the

* See Plate XII. Fig. 1.

on the terrestrial Rays that occasion Heat, 307

thermometer No. g, placed in the focus. Then, alternately
covering and uncovering the mirror, one. minute at a time, the
effect was as follows..

No. 2..
The mirror covered. o! 61
Opens - - 1 68
Covered - 2 61.
- Open - - 3 64.
Covered Sint Gioguedtt | 59.
~ Open - - 5 61+
‘Covered. - @ 58.

Here, in six minutes, we have a-repeated result of alternate
elevations and depressions. of. the thermometer, all of which
confirm the reflexibility, the radiant nature, and the heating
power, of the invisible rays that came from the poker.

From these experiments it is now sufficiently evident, that
in every supposed case of solar and terrestrial heat, we have
traced out rays that are subject to the regular laws of reflection,
and are invested with a power of heating bodies; and this inde--
pendent of light. For though, in four cases out.of six, we had
illuminating as well as heating rays, it is to be noticed that our’
proof goes only to the power of occasioning heat, which has
been strictly ascertained by the thermometer. If it should be
said, that the power of illuminating objects, of these same rays,
is as strictly proved. by the same experiments, I must remark,
that from the cases of invisible rays brought forward in the four
last experiments, it is evident that the conclusion, that rays
must have illuminating power, because they have a power of
occasioning: heat, is erroneous; and, as this must be admitted,
we have a right to ask for some proof of the assertion, that rays

308 = Dr. Herscuex’s Experiments on the solar, and

which occasion heat can ever become visible. But, as we shall
have an opportunity to say more of this hereafter, I proceed
now to investigate the refraction of heat-making rays.

11th Experiment. Refraction of solar Heat.

With a new ten-feet NEwToNIAN telescope, the mirror of
which is 24 inches in diameter of polished surface, I received
the rays of the sun; and, making them pass through a day-
piece with four lenses, I caused them to fall on the ball of the
thermometer No. 3, placed in their focus. Those who are

acquainted with the lines in which the principal rays and pencils —

move through a set of glasses, will easily conceive how artfully,
in our present instance, heat was sent from one place to another.
Heat crossing heat, through many intersecting courses, without
jostling together, and each parcel arriving at last safely to its
destined place. As soon as the rays were brought to the ther-
mometer, it rose almost instantly from 60 degrees to 190; and,
being afraid of cracking the glasses, I turned away the telescope.
Here the rays, which occasioned no less than 70 degrees of
heat, had undergone eight regular successive refractions; so that
their being subject to its laws cannot be doubted.

12th Experiment. Refraction of the Heat of a Candle.

I placed a lens of about 1,4 inch focus, and 1,1 diameter,
mounted upon a small support, at a distance of 2,8 inches from
a candle ;* and the thermometer No. 2, behind the lens, at an
equal distance of about 2,8 inches; but which ought to be very
carefully adjusted to the secondary focus of the candle. Not far
from the lens, towards the candle, was a pasteboard screen,
with an aperture of nearly the same size as the lens. The sup-

* Sce Plate XII. Fig. 2. : ios

ce
on the terrestrial Rays that occasion Heat. — 309
port of the lens had an eccentric pivot, on which it might be
turned away from its place, and returned to the same situation
again, at pleasure. This arrangement being made, the thermo-
meter was for a few moments exposed to the rays of the candle,
_ till it had assumed the temperature of its situation. Then the
lens was turned on its pivot, so as to intercept the direct rays,
which passed through the opening in the pasteboard screen,
and to refract them to the focus, in which the thermometer was
situated.

No. 2.
o’ 535
1 555
2 55%
3 56

Here, in three minutes, the thermometer received 23 degrees
of heat, by the refraction of the lens. The lens was now turned
away.

roy ih oG

1 5Ag
2 54g
3 53%

Here, in three minutes, the thermometer lost 24 degrees of
heat. ‘The lens was now returned to its situation.

of ORS
1 54g
Soh on ui noeee
Bir 50

And, in three minutes, the thermometer regained the 21
degrees of heat. A greater effect may be obtained by a different

310 Dr. Herscnen’s Experiments on the ime and
Sth

arrangement of the distances. Thus, if the bios be pldact at 33
inches from a wax-candle, and the thermometer situated, as be-
fore, in the secondary focus, we shall be able to draw from 5to8
degrees of heat, according to the burning of the candle, and the
accuracy of the adjustment of the thermometer to the focus.
The experiment we have related shews evidently, that rays
invested with a power of heating bodies, issue from a candle,
and are subject to laws of refraction, nearly the same with
those ee light.

13th Experiment. Refraction of the Heat that accompanies the
coloured part of the prismatic Spectrum.

I covered a burning lens of Mr. Dotitonp’s, which is nearly
g inches in diameter, and very highly polished, with a piece of »
pasteboard, in which there was an opening of a sufficient size
to admit all the coloured part of the prismatic spectrum.* In
the focus of the glass was placed the thermometer No. 3; and,
when every thing was arranged properly, I covered the lens for
five minutes, that the thermometer might assume the tempera-
ture of its situation. The result was as follows.

No. 3
The lens covered ~~ 0” ' 64
Open Figen 1) 176

Here, in one minute, the thermometer received 112 degrees
of heat, which came with the coloured part of the solar spectrum,
and were refracted to a focus; so that, if the coloured rays
themselves are not of a heat-making nature, they are at least
accompanied with rays that have a power of heating bodies, and

| * See Plate XIV..

on the terrestrial Rays that occasion Heat. «git

are subject.to certain laws of refraction, which cannot differ
much from those affecting light.

14th Experiment. Refraction of the Heat of a Chimney-Fire.

I placed Mr. Dottonn’s lens before the clear fire of a large
grate.* Its distance from the bars of the grate was three feet;
and, in the secondary focus of it was placed the thermometer
No. 1. No. 4 was stationed, by way of standard, at 24 inches
from the former, and at an equal distance from the fire,
Before the thermometers was a slip of mahogany, which had
three holes in it, =& of an inch in diameter each. Behind the
centre of the ist hole, 3 of an inch from the back, was placed
the thermometer No.1; and, between the ed and gd hole,
guarded from the direct rays of the fire by the partition, at the
same distance from the back, was put No. 4. Things being
thus arranged, the situation of the apparatus which carried the
thermometers, and that where the lens was fixed, were marked.
Then the thermometers, having been taken away to be cooled,
were restored to their places again, and their progress marked
as follows.

No. 1. No. 4.
Burning Lense Screened.
of 58 58
14 65 6o
3 68 - 61
5 70 614
7 713 614
9 715 613

Here, in nine minutes, the rays coming from the fire, through
the burning glass, gave 93 degrees of heat more to the ther~
* See Plate XV.

MDCCC. Ss

312 Dr. Herscuex’s Experiments on the solar, and

mometer No. 1, than No. 4, from change of temperature, had.
received behind the screen. Now, to determine whether this.
was owing merely to a transmission of heat through the glass,
or to a condensation of the rays, by the refraction of the burning
lens, I took away the lens, as soon as the last observation of
the thermometers was written down, and continued to take
down their progress as follows.

No. 1. No. 4.
9'F 7 bot 30 Caer oue 2
rs 701 612
12. ror 613
= 694 613
145 69% 613

Here the direct rays of the fire, we see, could not keep up
the thermometer No. 1; which lost 24 degrees of heat, not-
withstanding the lens intercepted no longer any of them. I
now restored the burning glass, and continued.

15° 69+ 612 sai
16 692 6i¢ :
17 fips 613
20 7 EE 612
25 Gi 613

Here again, the lens acted as a condenser of heat, and gave
12 degrees of it to the thermometer No. 1. I now once more
took away the lens, and continued the experiment.

25/5 71 613
31 68 613

This again confirms the same, by a loss of 3 degrees of heat.

I restored the lens once more, and had as follows.

a ia

on the terrestrial Rays that occasion Heat. 313

No. 1. No. 4.
xi Burning Lens. Screened.
git 68 612
35 695 613

And here the thermometer received 14 degree of heat again;
so that, in the course of 35 minutes, the thermometer No. 1
was alternately raised and depressed five times, by rays which
came from the chimney fire, and were subject to laws of refrac-
tion, not sensibly different from those which affect light.

15th Experiment. Refraction of the Heat of red-hot Iron.

I caused a lump of iron to be forged into a cylinder of 24
inches diameter, and 24 inches long.* This, being made red-
hot, was stuck upon an iron handle fixed on a stand, so as to
present one of its circular faces to a lens placed at 2,8 inches
distance; its focus being 1,4 inch, and diameter 1,1. Before
the lens, at some distance, was placed a screen of wood, with a
hole of an inch diameter in it, by way of limiting the object,
that its image in the focus might not be larger than necessary.
The screen also served to keep the heat from the thermometers.
No. 2 was situated in the secondary focus of the lens; and
No. 3 was placed within 3, of an inch of it, and at the same
distance from the lens as No. 2. By this arrangement, both
thermometers were equally within the reach of transmitted
heat ; or, if there was any difference, it could only be in favour
of No. 3, as being behind a part of the lens which, on account
of its thinness, would stop less heat than the middle. Now, as
the experiment gives a result which differs from what would
have arisen from the situation of the thermometers, on a sup-
position of transmitted heat, we can only ascribe it to a conden-

* See Plate XV1. Fig. 1.
9S 2

314 Dr. Herscury’s Experiments on the solar, and

sation of it by the refraction of the lens; and, in this case, the
thermometer No. 3, by its situation, must have been partly
within the reach of the heat-image formed in the focus. During
the experiment, the thermometers were alternately screened
two minutes from the effects of the lens, and exposed to it for
the same length of time; and the result was as follows.

No, 2 No. 3.
In the Focus. Near the Focus.
Screened oy 56 56
Open 2 62 6o
Screened 4 59 58
Open 6 61 59
Screened 8 58 57%
Open 10 595 583

Here, in the first and second minutes, No. 2 gained two
degrees of heat more than No. g. In the third and fourth, it
lost one more than No. g. In the fifth and sixth, it gained one
more. In the seventh and eighth, it lost 14 more; and in the
ninth and tenth, it gained 3 more than the other thermometer.
This plainly indicates its being acted upon by refracted heat.
Lest there should remain a doubt upon the subject, I now
removed the lens, and, putting a plain glass in the room of it, I
repeated the experiment, with all the rest of the apparatus in its
former situation.

Screened 0! 574 563
Open 2 624 612
Screened 4 Got 60
Open! 6 61 Got
Screened 8 60 59z |

Open 10 604 Bot

— se

——— ee ee!

f

on the terrestrial Rays that occasion Heat. 815

Here we find, that both thermometers received heat and
parted with it always in equal quantities, which confirms the
experiment that has been given. And thus it is evident, that
there are rays issuing from red-hot iron, which are subject to
Jaws of refraction, nearly equal to those which affect light; and
that these rays are invested with a power of causing heat in
bodies.

16th Experiment. Refraction of Fire-beat, by an Instrument
. resembling a Telescope.

It occurred to me, that I might use a concave mirror, to
condense the heat of the fire in the grate of my chimney, and,
reflecting it sideways by a plain mirror, I might afterwards
bring it to a secondary focus by a double convex lens; and
that, by this construction, I should have an instrument much
like a Newtonian telescope.* The thermometer would figura-~
tively become the observer of heat, by being applied to the
place where, in the real telescope of the same construction, the
eye is situated to receive light. Having put together the different
parts, in such a way as I supposed would answer the end, I
tried the effect by a candle, in order to ascertain the proper
distance of the object-mirror from the bars of the chimney-grate.
The front of the apparatus was guarded by an iron plate, with
a thick lining of wood; and the two thermometers which I |
used, were parted from the mirrors and lens by a partition,
which screened them from the heat that was to be admitted
through a proper opening in the front plate, to come at the
object-mirror. In the partition was likewise an opening, of a
sufficient diameter to permit the rays to come from the eye-glass
to their focus, on the ball of the thermometer No. 1; while

* See Plate XVI, Fig. z.

316 Dr. HeErscueEx’s Experiments on the solar, and

No. 4 was placed by the side of it, at less than half an inch
distance. In the experiment, the object-mirror was alternately
covered by a piece of pasteboard, and opened again. The ther=
mometers were read off every minute; but, to shorten my
account, I only give the last minute of every change.

No. 1. No. 4.
In the Focus. Near the Focuse
The mirror covered 0! 17s 77s
The mirror open 8 84 76
Covered - - 16 864 79%
Open - iat 89% 81
Covered -~ 2% 893 Sol
Open 58 aR ONn 57 915 833
Covered - 47 84 ‘ies

Here, in the first eight minutes, the thermometer exposed to
the effects of the fire-instrument, gained 2 degrees of heat more
than the other. In the next 8 minutes, the mirror being covered,
it gained 1 degree less than the other. The mirror being now
opened again, it gained, in 5 minutes, 23 degrees more than the
other. When covered 6 minutes, it gained qt degree less than
No. 4. In the next 10 minutes, when open, it gained + degree
more ; and, in the last 10 minutes, when the fire began to fail,
and the mirror was again covered, it lost 1 degree more than
the other thermometer. All which can only be accounted for
by the heat which came to the thermometer through the fire-
instrument; and, as this experiment confirms what has been
said before of the refraction of culinary heat, so it also adds to
what has already been proved of its reflection. For, in this fire-
instrument, the rays which occasion heat could undergo no less
than two reflections and two refractions.

ae ee

\ apie

‘e,) ,
re a

i:

\) , a .
+ poe ¥ -

=

on the terrestrial Rays that occasion Heat. 317

17th Experiment. Refraction of the invisible Rays of solar Heat.

I covered one half of Mr. DoLLonp’s burning lens with paste-
board, and threw the prismatic spectrum upon that cover; *
then, keeping the last visible red colour one-tenth of an inch
from the margin of the pasteboard, I let the invisible rays be-
yond the spectrum fall on the lens. In the focus of the red
rays, or a very little beyond it, I had placed the ball of the ther-

mometer No. 1; and, as near to it as convenient, the small one
No. 2. Now, that the invisible solar rays which occasion heat
were accurately refracted to a focus, may be seen by the follow-
ing account of the thermometers.

No. 1. No. 2.
In the Focus. * Near the Focus.
0’ 57 Ari
1 BOD iv 57

_ Here, in one minute, these rays gave 45 degrees of heat to
the thermometer No. 1, which received them in the fons, while
the other, No. 2, suffered no change.

It is rani Mi that notwithstanding I kept the red colour
of the spectrum 54 of an inch upon the pasteboard, a little of
that colour ae still be seen on the ball of the thermometer.
This occasioned a surmise, that possibly the invisible rays of the
sun might become visible, if they were properly condensed; I
therefore put this to the trial, as follows.

18th Experiment. Trial to render the invisible Rays of the Sun
| visible by Condensation.
Leaving the arrangement of my apparatus as in the last
experiment, I withdrew the lens, till the last visible red colour
__™ See Plate XIV.

318 Dr. Herscuet’s Experiments on tbe solar, and

was two-tenths of an inch from the margin of the semicircular
pasteboard cover; then, taking the thermometers, I had as

“

follows.

No. 2. No. 3.
or 57 57
1 78 57

Here, there was no longer the least tinge of any colour, or
vestige of light, to be seen on the ball of the thermometer; so:
that, in one minute, it received 21 degrees of heat, from rays
that neither were visible before, nor could be rendered so by
condensation.

To account for the colour which may be seen in the focus,
when the last visible red colour is less than two-tenths of an
inch from the margin of the pasteboard which intercepts the
prismatic spectrum, we may suppose, that the imperfect refrac-
tion of a burning lens, which from its great diameter cannot
bring rays to a geometrical focus, will bring some scattered ones
to it, which ought not to come there. We may also admit, that
the termination of a prismatic spectrum cannot be accurately
ascertained, by looking at it in a room not sufficiently dark to
make very faint tinges of colour visible. And, to this must be
added, that the incipient red rays must actually be scattered
over a considerable space, near the confines of the spectrum, on
account of the breadth of the prism, the whole of which cannot
bring its rays of any one colour properly together; nor can it
separate the invisible rays intirely from the visible ones. For,
as the red rays will be but faintly scattered in the beginning of
the visible spectrum, so, on the other hand, will the invisible
rays, separated by the parts of the prism that come next in
succession, be mixed with the former red ones. Sir Isaac

teeta

on the terrestrial Rays that occasion Heat. 319

Newton has taken notice of some imperfect tinges or haziness,
on each side of the prismatic spectrum, and mentions that he
did not take them into his measures.*

19th Experiment. Refraction of invisible culinary Heat.

There are some difficulties in this experiment; but they arise
not so much from the nature of this kind of heat, as from our
method of obtaining it in a detached state. A red-hot lump of
iron, when cooled so far as to be no longer visible, has but a feeble
stock of heat remaining, and loses it very fast. A contrivance
to renew and keep this heat might certainly be made, and I
should indeed have attempted to carry some method or other of
this kind into execution, had not the following trials appeared
to me sufficiently conclusive to render it unnecessary. Admit-
ting, as has been proved in the 15th experiment, that the
alternate rising and falling of a thermometer placed in the focus
of a lens, when the ball of it is successively exposed to, or.
screened from, its effects, is owing to the refraction of the lens,
and cannot be ascribed to a mere alternate transmission and
stoppage of heat, I proceeded as follows. My lens, 1,4 focus,
and 1,1 diameter, being placed 2,8 inches from the face of the

heated cylinder of iron, the thermometer No. 2, in its focus, was,

alternately guarded by a small pasteboard screen put before it,
and exposed to the effects of condensed heat by removing it.

No. 2.
55 Very red-hot.

~

. Screened °

~ Open 2 632 Red-hot.

Screened 4 58 Still red-hot.

- Open 6 Got Still red.

-® Newron’s Optics, page 23, line 13. + See Plate XVI, Fig. 3.-.

MDCCC. - Tt

320 Dr. HERscHEL’s Experiments on the solar, and

No. 2.
Screened 8 574 A little red.
Open 10 594 Doubtful.
Screened 12 574 Not visible in my room darkened.
Open 14, 58t
Screened 16 574
Open 18 584
Screened 20 57
Open 22 58
Screened 24, 574
Open 26 58
Screened 28 574

Now, the beginning of this experiment being exactly like
that of the 15th, with the thermometer No. g left out, the
arguments that have before proved the refraction of heat in one
state, will now hold good for the whole. For here we have a
regular alternate rising and falling of the thermometer, from a
bright red heat of the cylinder, down to its weakest state of
black heat; where the effect of the rays, condensed by the lens,
exceeded but half a degree the loss of those that were stopped
by it.

20th Experiment. Confirmation of the 19th.

In order to have some additional proof, besides the uniform
and uninterrupted operation of the lens in the foregoing experi-
ment, I repeated the same, with an assistant thermometer,
No. 3, placed first of all at 3 of an inch from No. 2, and more
towards the lens, but so as to be out of the converging pencil
of its rays, and also to allow room for the little screen between
the two thermometers, that No. 3 might not be covered by it.

on the terrestrial Rays that occasion Heat. 321

No. 2. No. 3.
In the Focus. Advanced sideways.

Always open.
Screened of! 6ot 63
Open 1 633. 64
Screened 2 622 64,
Open 3 64, 644
Screened 4 693 642
Open 5 64g 64e
Screened 6 644 642
Open 7 643 64
Screened 8 644 64,

Here No. 3, being out of the reach of refraction, gradually
acquired its maximum of heat, in consequence of an uniform
exposure to the influence of the hot cylinder; after which, it
began to decline. No. 2, on the contrary, came to its maxi-
mum by alternate great elevations, and small depressions ; and
afterwards lost its heat by great depressions, and small eleva-
tions. After the first eight minutes, I changed the place of the
assistant thermometer, by putting it into a still more decisive
situation ; for it was now placed by the side of that in the focus,
so as to participate of the alternate screening, and also to
receive a small share of one side of the invisible heat-image,
which, though unseen, we know must be formed in the focus
of the lens. Here, if our reasoning be right, the assistant ther-
mometer should be affected by alternate risings and fallings;
but they should not be so considerable as those of the lens.

No. 2. No. 3.
In the Focus. In the Edge of it.
Both open 8’ 642 64
Both open 9} 693 633

Tt¢

322 Dr. HERSCHEL’s Experiments on the solar, and

No. 2. No. 3.
In the Focus. In the Edge of it.
Open - 11 6424 64,
Screened 122 63 63t
Open 14 635 631 ,
Screened 16 625 63
Open 18 633 633

Here the changes of the thermometer No. 2 were — 3 4 £
—ii+3—1+1:; and those of No. 3 were—i+44—4
+21—i4+4. All which so clearly confirm the effect of the
refraction of the lens, that it must now be evident that there are
rays issuing from hot iron, which, though ina state of total in-
visibility, have a power of occasioning heat, and obey certain laws
of refraction, very nearly the same with those that affect light. —

As we have now traced the rays which occasion heat, both
solar and terrestrial, through all the varieties that were men-
tioned in the beginning of this paper, and have shewn that, in
every state, they are subject to the laws of reflection and of
refraction, it will be easy to perceive that I have made good a
proof of the three first of my propositions. For, the same
experiments which have convinced us that, according to our
second and third articles, heat is both reflexible and refrangible,
establish also its radiant nature, and thus equally prove the first
of them. ae

END OF THE FIRST PART.

Slough, near Windsor.
April 26, 1800.

on the terrestrial Rays that occasion. Heat. 923,

EXPLANATION OF THE FIGURES.
See Piates XII. XII. XIV. XV. anp XVI.

Plate XII. Fig. 1.

Shews the piranizemiont of the apparatus used in the ed
experiment. :

A, is the small mirror with its adjusting Screws m, 1.

No. 2, is the thermometer in the focus of the mirror.

No. 3, The assistant thermometer.

B, A small screen for the thermometer oe 2.

C, The candle. |

D, The poker which, in the 4th and 10th experiments, is to
be placed in the situation of the candle; the rest of the appa-
ratus being brought nearer to it.

Plate XII. Fig. 2.

Shews ine apparatus used i in the gd and 8th experiments.
' A, The mirror.

No. 2, The thermometer.

BCD, A desk adjustable to different altitudes.

E, The prism receiving the sun’s rays through an opening
in the window shutter F.

Plate XII. Fig. g.

AB, is the front of the apparatus, which, in the sth experi-
ment, is exposed to the fire of the chimney.
C, is the opening in the front plate AB, for the admission of
heat.
D, is the small mirror which reflects the rays of heat.

324, Dr. Herscue1’s Experiments on the solar, and

E, is the hole through which the heat passes to the ther-
mometers.

No. 1 and No. 4, are the thermometers.

F, is a prism, which, in the 6th experiment, is to be placed
in the room of the mirror D.

Plate XII. Fig. 4.

A, is the board that holds the apparatus used in the 4th
experiment.

B, The prism.

C, The spectrum, thrown partly on the paper with parallel
lines, and partly on one of the small tables which support the
board. ;

D, The mirror which reflects the rays of heat sideways.

No. 1, The thermometer which receives the reflected rays. _

No. 2, The standard thermometer.

Plate XIII. Fig. 1.

AB, is the front which, in the gth experiment, is put close to
the flat side of a heated iron stove.

C, is the mirror.

D, The feather-edged slip of deal, on two pins.

No. 2, The thermometer which receives the rays condensed
in the focus of the mirror.

No. 3, The standard thermometer.

E, A small screen tied to No. 3, to guard it from reflected
heat. ae)
_ Plate XIII. Fig. 2.

A, The lens in the apparatus used for the 12th experiment.
No. 2, The thermometer placed in its focus.

on the terrestrial Rays that occasion Heat. 325

B, The screen with an aperture for admitting the rays of
heat.- ;

C, The eccentric pivot for turning away the lens.

D, The candle.

uw | Plate XIV.

A, The burning lens, covered; with the prismatic spectrum
thrown upon an opening, left for it, in the pasteboard cover of
the 13th experiment.

No. 3, The thermometer placed in its focus.

B, The prism.

C, Semicircular cover, used in the 17th and 18th experiments,
instead of the one with a square hole.

Plate XV.

A, The burning lens of the 14th experiment.

B, The fire in the chimney.

No. 1, The thermometer in the focus of the lens.

No. 4, The standard thermometer.

C, The hole through which the rays of heat pass to No. 1.

D and E, Two holes, between which the ball of the thermo-
meter No. 4 is screened from the direct rays of the fire; while
free access is given to the heat which may affect the tempera-
ture of the place.

Plate XVI. Fig. 1.

A, The iron cylinder, stuck upon its handle, as it is used in
the 15th and i1gth experiments. oe

B, The lens.

C, The screen with an opening in it.

No.2, The thermometer in the focus of the lens.

~

326 Dr. HERsScuEL’s Experiments, &c.

No. 3, The standard thermometer.
D, The little moveable pasteboard screen.

Plate XVI. Fig. 2.

AB, The front, plated with iron, that it may bear to be
exposed close to the bars of a chimney fire.
~ CC, The concave mirror. |

D, The plain mirror.

E, The lens.

No. 1, The thermometer in the focus of the lens.

No. 4, The standard thermometer.

F, A circular opening in the front plate AB, for admitting
the rays of heat to fall on the concave mirror C.

m, The first focus of the rays, from which they go on
diverging, to the small mirror, and to the lens; which brings
them to a second focus, on the ball of the thermometer No. 1.

NE :

|

———

(tate XU, pst

XI p46

ps MDC CC. Lah

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Philos Trans MWC CC. Late Xp seb

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C 327 J

XVI. Chemical Experiments on Zoophytes; with some Observa-
tions on the component Parts of Membrane. By Charles
Hatchett, Esq. F. R.S.

Read June 12, 1800.

Tue experiments and observations on shell and bone, which
I had the honour last year to lay before this learned Society,
were made in consequence of my having discovered, some little
time before, that the enamel of teeth did not consist principally
of carbonate of lime, as was generally believed, but was of a
nature similar to bone;’ with this difference, that the phosphate
of lime was not deposited in and upon a cartilaginous or mem-
branaceous substance, but was only blended with a certain
portion of animal gluten.* By the experiments subsequently
made on various shells, crustaceous substances, and bones, it
was proved, :

1st. That the porcellaneous shells resemble the enamel of
teeth in the mode of formation, but that the hardening substance
is carbonate of lime.

edly. That shells composed of nacre or mother of pearl, or
approaching to the nature of that substance, and also pearls,

* See experiments mentioned in Observations on the teeth of graminivorous qua-
drupeds, &c. by Everarp Home, Esq. F.R.S, Phil. Trans. for 1799, p. 243.

MDCCC., Uu

328 Mr. Hatcuetr’s Experiments on Zoophytes,

resemble bone in a considerable degree, as they consist of a
gelatinous, cartilaginous, or membranaceous substance, forming
a series of gradations, from a tender and scarcely perceptible
jelly to membranes completely organized, in and upon which
carbonate of lime is secreted and deposited, after the manner
that phosphate of lime is in the bones; and therefore, as the
porcellaneous shells resemble the enamel of teeth, so the shells
formed of mother of pearl, &c. in like manner resemble bone;
the distinguishing chemical character of the shells being car-
bonate of lime, and that of enamel and bones being phosphate
of lime, ‘

gdly. It was proved, that the crust which covers certain
marine animals, such as crabs, lobsters, crayfish, and prawns,
consists of a strong cartilage, hardened by a mixture of carbo-
nate and phosphate of lime; and that thus these crustaceous
bodies occupy a middle place between shell and bone, although
they incline principally to the nature of shell. And,

4thly. It was proved, that a certain portion of carbonate of
lime enters the composition of bones in general; the proportion
of it however being, to the phosphate of lime, vice versd to that
observed in the crustaceous marine substances.

Upon the view, therefore, of these facts, it is evident, that
there is a great similarity in the construction of shell and bone;
and that there is even an approximation in the nature of their
composition, by the intermediate crustaceous substances.

These remarks, with the experiments by which they are.
supported, form the principal features of that paper, which the
Royal Society honoured with a place in the last volume of
the Philosophical Transactions. At that time, it was not my

and Observations on the component Parts of Membrane. 329

intention immediately to pursue the subject; but I changed this
resolution, after a conversation with my friend Dr. Gray, Sec.
R.S. who suggested, that many marine substances still remained
to be examined in a similar manner ; and that a series of expe-
riments on Zoophytes (hitherto but little known in respect to
their component parts) would be very interesting, and might
probably lead to some improvement in their classification.

I was therefore induced to make the experiments contained
in the following pages; and, as the mode adopted was very
similar to that which was formerly pursued, it appears super
fluous here to repeat the description.

It will be proper, however, to observe, that argill is not un-
frequently lodged, as an extraneous substance, in the interstices
of many of the Madrepores, and such like bodies; and, as argill
is precipitated by pure ammoniac, it became necessary not to
rely merely on the ammoniac, as a test of phosphate of lime.

_ Whenever, therefore, any precipitate was produced by ammo-
niac, it was dissolved again in acetous acid, and this solution
was examined by the addition of acetite of lead.

§ 1. EXPERIMENTS ON ZOOPHYTES.

Madrepora virginea.*

_ This Madrepore, when immersed in very dilute nitric acid,
effervesced much, and was soon dissolved.
The solution was perfectly transparent and colourless, with

* The different species are named according to Gmeuin’s edition of Linn.£us’s
Systema Nature.

Uue

830 Mr, Hatcuett’s Experiments on Zoopbytes,

but a small appearance of gelatinous or membranaceous particles.
Pure ammoniac was then added, but did not cause any altera-
tion ; and the whole of what had been dissolved, was afterwards
completely precipitated by carbonate of ammoniac, and proved
to be carbonate of lime.

Madrepora muricata.

When treated like the former, it afforded some loose particles
of a gelatinous substance: these were separated by a filter, and
the solution was supersaturated with pure ammoniac, without
effect ; but, upon adding carbonate of ammoniac, the dissolved
part was precipitated, in the state of carbonate of lime.

Madrepora labyrinthica.

This, being examined in the manner abovementioned, proved
to be composed of carbonate of lime, and of a loose gelatinous:
substance, similar to that afforded by Madrepora muricata.

Madrepora ramea.

When this Madrepore was first immersed in very dilute nitric
acid, a considerable effervescence was produced; and, after a
few hours, a pale brown fibrous membrane remained, which in
some measure exhibited the original figure of the Madrepore.
The clear solution being poured into another vessel, only
afforded a large ar of carbonate of lime.

adetces fascicularis. pital

When this was put into very dilute nitric acid, a scieiaeisioke
effervescence arose ; and, after some hours, a tender membrane
t

and Observations on the component Parts of Membrane. 33%

was left, which retained the original shape. Pure ammoniac
did not disturb the transparency of this solution; but a copious
precipitate of carbonate of lime was obtained, by the addition of
carbonate of ammoniac.

These experiments, on only a few of the Madrepores, suffi-
ciently prove how similar they are, in composition, to shell; for
both consist of the same materials, subject to the like modifi-
cations.

Millepora caerulea.

This produced much effervescence, when immersed in very
dilute nitric acid. The blue colour disappeared, as the calca-
reous part was dissolved, and was. not afterwards restored by
ammoniac.

Some loose detached portions of a gelatinous substance
floated in the solution, which were separated by a filter. The
transparency of the solution was not disturbed by pure ammo-
niac; but a copious precipitate of carbonate of lime was produced
by carbonate of potash.

Millepora alcicornis.

This Millepore, when treated with very dilute nitric acid,
produced a great effervescence ; and, after a few hours, a tender
gelatinous substance remained, which did not retain the figure
of the Millepore.

Pure ammoniac had not any effect; but carbonate of ammoniac
precipitated a large quantity of carbonate of lime.

Millepora polymorpha.

This produced an effervescence, when put into dilute nitric

332 Mr. Hatcuetr’s Experiments on Zoophytes,

acid; and, after some hours, a substance remained, which com-
pletely retained the original figure of the Millepore,

The substance which thus remained, was composed of a
strong white opaque membrane, which formed the external
part; the interior of this, was filled with a transparent gela-
tinous substance. Ammoniac produced a very slight precipitate,
which, being dissolved in acetous acid, was proved to be phos-
phate of lime, by solution of acetite of lead. Carbonate of soda
afterwards precipitated a large quantity of carbonate of lime.

Millepora cellulosa.

This Millepore effervesced much with dilute ease bined and,
when this had ceased, a finely perforated membrane remained,
in structure and appearance like the original substance.

Ammoniac did not produce any effect ; but a large quantity
of carbonate of lime was obtained by carbonate of soda.

Millepora fascialis. |
This resembled the former in every particular; and left a
membrane perfectly like the Millepore.

Millepora truncata.

When treated with dilute nitric acid, it efferdestisl Sar like
the former; and, after a few hours, a semi-transparent membra-
naceous substance remained, which exhibited — the
shape and structure of the original Millepore.

Ammoniac did not disturb the transparency of the solutions .
but the whole of the dissolved portion was precipitated, in the
state of carbonate of lime, by carbonate of ammoniac.

The remark lately made on the Madrepores may here also

and Observations on the component Parts of Membrane. 9333

be repeated, as the composition of the Millepores appears to be
the same, with the single exception of Millepora polymorpha,
which afforded some slight traces of phosphate of lime. But
time and future experiments will shew whether this was an acci-
dental ‘circumstance, or whether the Millepora polymorpha is
thus distinctly characterised.

It is likewise necessary to add, that when these various
Madrepores and Millepores were exposed to red heat, in a
crucible, they emitted smoke, with the smell of burned horn or
_ feathers, became tinged with a paler or deeper gray colour, and
(when dissolved in acids} deposited more or less animal coal, in
proportion to the quantity of the gelatinous or membranaceous
substance detected by the experiments lately described,*

Tubipora musica.

Of the Ti ip ati I had only an opportunity to examine this
species.

_ Like the former substances, it was immersed in an acid, and
on this occasion I employed the acetous acid. A great effer-
vescence was produced, and the red colour was destroyed, in
proportion as the calcareous part was dissolved. When the
solution was completely effected, some loose particles. of a
tender membrane floated in the liquor, and were separated by a
filter. |

Pure ammoniac, added to the solution, produced a precipitate 3.
which proved to be argill, accidentally lodged in the interstices
of the Tubipore.

* The order in which these experiments are placed, is not that according to which:
they were made ; but it has been adopted, because it shews. more evidently the gradae
tions of the membranaceous sveiuiitie

894 Mr. Hatcuett’s Experiments on Zoopbytes, —

To the filtrated liquor, carbonate of potash was added, and
age a large quantity of carbonate: of lime. | 5

Flustra foliacea. ; Saee

When this was immersed in very dilute nitric acid, an effer-)
vescence of short duration took place; and, when this had —
ceased, the Flustra appeared like a finely reticulated membrane,
which retained the original shape. A

Pure ammoniac being added to the filtrated solution, pro=-
duced a slight precipitate; which, being dissolved in acetous acid,
was proved, by acetite of lead, to be phosphate of lime.

Solution of carbonate of ammoniac was then added to the
liquor from which the phosphate of lime had been separated,
and produced a copious precipitate of carbonate of lime.

When the Flustra foliacea was exposed toa low red heat, in a
crucible, it emitted a smell like burned horn, but retained ‘its
shape, by reason of the carbonate of lime with which it was
coated. The Flustra thus burned, when dissolved in dilute nitric
acid, deposited some animal coal; but, in other respects, the
present solution resembled the former nitric solution of this
substance when in a recent state.

The Flustra foliacea, when long digested with none distilled
water, communicated to it a pale brownish tinge. Infusion of
oak bark being then poured into the liquor, did not produce any
visible effect, even after 24, hours had elapsed ; but nitro-muriate
of tin formed a white cloud, in the space of a few minutes.

Corallina Opuntia.
This being put into very dilute nitric acid, produced (like ne
Flustra foliacea) an effervescence of short duration.

and Observations on the component Parts of Membrane. 335

The coralline then remained in a membranaceous state, and
retained the original figure. To the filtrated solution some pure
ammoniac was added, but it scarcely produced any visible effect.

Carbonate of ammoniac precipitated a large quantity of car-
bonate of lime.

Some of the Corallina Opuntia was then exposed to a low red
heat, in a crucible; it emitted a smell of burned horn, and in
great measure retained its shape, evidently from the calcareous
coating. | i

The burned coralline, being dissolved in dilute nitric acid,
_ deposited some animal coal.

The clear solution afforded, by pure ammoniac, a very slight
precipitate of phosphate of lime; after which, the carbonate of
lime was precipitated as before.

This coralline, when treated with boiling water, like the Flustra
_ foliacea, did not discolour it; neither was the water changed by
infusion of oak bark; but nitro-muriate of tin produced a faint
ee cloud.

Sf bon 38s Isis ochracea.

When this Jsts was immersed in dilute nitric acid, a consi-
derable effervescence was produced; and, in proportion as the
calcareous substance was dissolved, the’red colouring matter
was deposited, in the state of a fine red powder.*

When the effervescence had ceased, (which was after about —
three hours, ) a yellowish membrane remained, which completely
retained the original figure of oes Isis. °°

a This colouring substance was not paiccalved. nor - changed, when nitric or muriatic
acids were poured upon it. It appears, therefore; to be very ; different fi from the tinging
matter of the Tubipora musica, or that of the'Gérgonia ‘nobilis.

~ MDCCC. X x

336 Mr. Hatcuetr’s Experiments on Zoophytes,

The solution, being filtrated, was saturated with pure ammo-
niac, by which, a slight precipitate of phosphate of lime was
separated, A large quantity of carbonate of lime was afterwards
precipitated, by solution of carbonate of potash.

Part of a branch of this Isis was put into a crucible heated to
a low red heat. A great quantity of smoke was emitted, which
had the smell of burned horn; and, after a few minutes, the
branch separated at the knotty joints, into as many pieces as
there were joints in the branch. These joints had all the
characters of coral; but the whole of the membrane which had
invested them, as well as the knotted protuberances by which
they had been connected, were destroyed, by being converted
into coal. From this circumstance, I was desirous to examine
the internal structure of the membranaceous part, out of which
these joints of coral had been dissolved by acids.

I took, therefore, the membranaceous substance which re-
mained after the first experiment, and which (as I have already
observed) retained the complete figure of the Isis.

This substance being opened longitudinally, exhibited a series
of cavities, corresponding in form with the coralline joints, and
so situated, that each of these cavities extended from one bulb
or knot nearly to the next, throughout the whole of the branch,

The coralline joints, when viewed separately, appeared
smaller in the middle than at the ends, which were terminated
by obtuse cones.

In the branch, these joints were so vhasind that the extre-
mities or cones were opposed point to point; but were prevented
from immediate contact, by a gristly substance, which filled, and
indeed principally formed in the branch, the knot or bulb of

eS OS eee ee eee eee DC

and Observations on the component Parts of Membrane. 337

each joint, and was interposed between the cones of the coralline
substance, like the common cartilages of the articulations.

From this construction it appears, that this Isis is capable of
great flexibility when in a recent state; for the gristly part of the
bulbs is then most probably much softer, and more elastic, than
it appears to be in the dried specimens which are found in
collections,*

The gristly substance which forms the bulbs, and the coralline
joints, are kept together, and are covered, by a thin skin or
membrane, which is continued over the whole, like a tube. The
joints are not, therefore, devoid of a coating, as seems to be
implied by the definition of Linnzus.

| Isis Hippuris.

Part of a branch of this Jsis was immersed in very dilute
nitric acid, and a considerable effervescence immediately took
place. When this effervescence had ceased, there appeared little
or no change in the original form of the Iss; but the coralline
joints were now become a soft, compact, white, and opaque
‘membranaceous substance; while the dark brown intermediate
parts retained also their form, and in other characters resembled
those of horn.

The solution was mnlguaee: and transparent. When saturated
with pure ammoniac, it was not affected; but carbonate of pot-
ash produced a copious precipitate of carbonate of lime.

Another part of this [sts was exposed to a low red heat, ina

* It must here be observed, that the articulated structure abovementioned, is not to
be found in those parts which form the main stem, with its larger branches; the
joints in those parts being consolidated, so as to constitute a ica and rigid trunk,
upon which the whole fabric is supported.

Xx 2

338 Mr. Hatcuetr’s Experiments on Zoophytes,

crucible. ‘The dark brown horny parts swelled, and puffed up,
with much smoke, and a smell like that of burned horn.

The coralline joints also emitted the same ae and smell,
and became dark gray.

When put into dilute nitric acid, a solution was made, with
effervescence, during which, there was a copious deposition of
animal coal.

From this solution, nothing but carbonate of —_ was ob- ©

tained by the usual precipitants.

A tube of membrane invests the curious structure of the Isis
ochracea ; but no such tube or outer coat exists in the Isis Hip-
puris ; for the coralline joints (like some of the Madrepores,
Millepores, &c./ consist of a membranaceous substance, hardened
by carbonate of lime, and the only difference appears to be,
that in the Madrepores and Millepores, the membranaceous part
is less compact and abundant; but, even the striz of the coral-

dine joints remain visible, and unchanged, in the membrane of"

this Iszs.

The brown horny part forms also a marked characteristic
in this Js7s, and seems to approach it to certain of the Gor-
gonia.

This horny part does not however pervade the whole of the
branch; for, where the coralline jomts commence, this horny
substance immediately terminates, internally as’ well as exter-
nally, and is not to be discovered but between or in the separa-
tion of these joints.

Gorgonia nohite

I next proceeded to examine the Gorgonia sea i or red coral;
and, of this, I separately subjected to experiment different pieces,

and Observations on the component Parts of Membrane. 339

some of which were polished, and deprived of their external,
pale red, mealy coat, whilst others were in their original state.

_A piece of the unpolished red coral being put into dilute
nitric acid, an effervescence immediately took place; and, after
some hours, the whole of the calcareous substance was com-
pletely dissolved.

The external coat retained the original figure, and appeared
like a pale yellow tubulated membrane, the interior of which
was filled with a transparent gelatinous substance. From the
‘solution I only obtained a large quantity of carbonate of lime.

The next experiment was made in a manner exactly similar
to the former; but a piece of the polished or. uncoated red coral
was now taken.

The effects produced by the diluted acid were the same as
before ; but, in the solution, some loose portions of a transparent
yellow gelatinous substance were now only to be seen. _

The filtrated solution was treated as in the former experiment,
and afforded a considerable quantity of carbonate of lime.

As it was possible that the action of the nitric acid (although
much diluted) might be too powerful, I was induced to try
the effects of acetous acid, in which I immersed a piece of the
red coral in its natural state. It was gradually dissolved, with
a slow effervescence, and left an external tubulated membrane,
retaining the original form, and filled with a drangpeient gela-
tinous substance, as in the first experiment. ,

_ The solution, when filtrated, afforded carbonate of lime.

A piece of the polished or uncoated red coral was treated with
acetous acid, in a similar manner.

It was slowly dissolved, and left a transparent gelatinous

34,0 Mr. Hatcuerr’s Experiments on Zoophytes, —

substance, like that which has already been mentioned, Senta.
that it was not in detached portions.

This solution, like the former, only yielded ear B6rith of lime.

It may here be observed, that in each of the above related
experiments, the red colour of the coral was gradually destroyed,
as the solution of the calcareous substance advanced, and could
not afterwards by any means be restored ; nor could any colour-
ing principle whatever be detected by the re-agents usually
employed.

A piece of red coral, in its natural or uncoated state, was
exposed to a low red heat, ina crucible, during about ten minutes,
at which time a faint smell of burned horn was to be perceived.
When the coral was taken out of the crucible, it had completely
lost the red colour, and was become pale gray. It dissolved in
dilute nitric acid, with effervescence, and some animal coal was
separated.

To the filtrated solution pure ammoniac was added, and pro-
duced a very slight precipitate, which was collected, and was
afterwards dissolved in acetous acid. From this solution, by
the addition of acetite of lead, some phosphate of lead was
obtained.

The carbonate of lime was afterwards pein in the
usual manner.

As the very small portion of phosphate of lime discovered in
the preceding experiment, (and which had escaped the action of
the acids then employed,) might be only contained in the
coating or epidermis, a piece of the polished or uncoated coral
was treated in a similar manner; but, upon examining the solu-
tion, it afforded a small portion of phosphate, with a large

ie eg

Ee

and Observations on the component Parts of Membrane. 341

quantity of carbonate of lime; so that the result of this experi-
ment did not differ from that of the former.

From the preceding experiments it appears, that the Gorgonia
nobilis or red coral, consists of two parts; one of which is the
stem, formed of a gelatinous substance, hardened by carbonate of
lime, and coloured by some unknown modification of animal
matter; the other is a membranaceous tube, which, like a
cuticle or cortex, coats the stem abovementioned, and (when
deprived of its hardening substance) possesses all the characters
of membrane. But, although carbonate of lime could only be
discovered, when this Gorgonia was simply immersed in acids, yet
it has been proved by these experiments, that a small portion of
phosphate of lime is also present, but so enveloped by the mem-
branaceous and gelatinous parts, as not to be dissolved by the
acid menstrua, till these substances have been decomposed by
fire.

This is not an unusual circumstance, when a very small por-
tion of a substance is enveloped by large quantities of other
matter; for, BEncmann, in his supplement to ScHEELE’s Essay
on the Calculus Vesica, observes, that the presence of calcareous
earth in certain calculi, could not be discovered in the usual
manner, but by operations made expressly for the purpose.*

I do not pretend to determine whether the very small por-
tion of phosphate of lime in the Gorgonia nobilis is an essential
ingredient or not; but the mode of construction evidently proves
how much this Gorgonia differs from the Madrepores and Mil-
lepores, as well as from the Gorgonig about to be mentioned.

* ScuEELE’s Essays, translated by Dr. Benpors. Page 208

342 Mr. Hatcuetts Experiments on Zoopbytes,

Gorgonia ceratophyta.

When this was immersed in dilute nitric acid, an effervescence

was produced ; after which, the cortical part appeared like a thin.

yellowish membrane investing the stem, which was become
transparent, and similar to cartilage.

Ammoniac precipitated from the solution a large quantity of
phosphate of lime; and lixivium of potash separated some car-
bonate of lime. ) |

A quantity of the cortex (which had been separated from the

stem by beating it between folded writing paper) was steeped
in the dilute acid. This solution afterwards, with ammoniac,
scarcely afforded a vestige of phosphate of lime; but, when lixi-
vium of carbonate of potash was added, a considerable quantity
of carbonate of lime was obtained.

The stem, on the contrary, when thus treated, afforded much
phosphate of lime, and very little of the carbonate. When
burned ina crucible, it smoked, and emitted a smell like burned

horn, but the figure was not destroyed ; and, when afterwards |

dissolved in the acid, it yielded the same products as before,

Gorgonia Flabellum.
When this Gorgonia was steeped in dilute nitric acid, it pro-
duced an effervescence of short duration. The cortical part
then appeared like a thin yellowish membrane, which covered
the stem. rie, ER
- The latter was transparent, and resembled softened horn of
a reddish brown colour.
’ The solution afforded a large quantity of phosphate of lime,

and Observations on the component Parts of Membrane. 343

by the addition of ammoniac; after which, lixivium of potash
formed a less copious precipitate of carbonate of lime.

Some parts of the cortex were separated, by beating the Gor-
gonia between folded writing paper, and were immersed in the
acid. | |
This solution was scarcely rendered turbid by ammoniac; but
afforded a considerable portion of carbonate of lime by potash.

The stem from which the above cortical part had been sepa-
rated, was next examined by the dilute acid, in which, when
steeped during three days, it became soft, elastic, and in some
measure cartilaginous.

The acid was saturated with pure ammoniac, and then
changed to a deep yellow or orange colour: a large quantity of
phosphate of lime was at the same time separated ; and but very
little carbonate of lime was afterwards precipitated by potash.

The recent stem in great measure retained its shape, when put
into a red-hot crucible; but that which had been steeped in the
acid, curled up, and soon became a shapeless mass of coal,
which, by a longer continuation of the red heat, was completely
dissipated. . | |

This difference appears to have been caused by the phosphate
of lime, which was present in the recent stem, but was dissolved
and separated in the latter case by the acid.* ,

These experiments prove, that the Gorgonia Flabellum, like
the Gorgonia ceratopbyta, consists of a horny stem, containing
a certain portion of phosphate of lime; and that this stem is
invested with a membrane, hardened principally by carbonate of

* These different effects are to be observed, when bone, and when the cartilage or
membrane which remains after bone has been long steeped in acids, are subjected
to a red heat.

MDCCC. pias

B44 Mr. Hatcuett’s Experiments on Zoophytes,

lime, which serves to cover and defend it, in the manner. of a
shell.* oe ts bono)

_ Gorgonia ee

The ae part of this Gorgonia was separated tea the
stem, and was first subjected to experiment.

Some portions of this cortex were immersed in dilute, nitric
acid; and, after an effervescence which continued several hours,
a soft yellowish membranaceous substance remained, retaining
the original figure. to

The liquor, when decanted, was pale yellow, which pe
was much deepened by the addition of ammoniac; at the same
time, a small quantity of phosphate of lime was deposited.

A considerable portion of carbonate of lime was afterwards
precipitated by carbonate of potash. :

Some pieces of the cortex were boiled with distilled water
during about six hours ; and, to the filtrated liquor, infusion of
oak bark was added, by which, a large quantity of gelatin was
precipitated.

The same pieces were afterwards boiled with lixivium of
caustic potash, which effected a perfect solution, and formed the
animal soap of CHAPTAL; at the same time, the calcareous matter
subsided to the bottom of the matrass.

The cortical part of this Gorgonza, when put into a red-hot
crucible, emitted much smoke, with a smell like horn that is

2 It may here be proper to observe, that the membranaceous part of all these subs
stances, such as the Madrepores, Millepores, Flustra, Se. &c. was dissolved, when
these bodies were boiled with lixivium of caustic potash ; and animal soap was formed.

The same may also be said of shells; and Mr. Vaw Mons has noticed this effect on
those of the oyster. See Annales de Chimie, Tome XXXI, p. 123.

and Observations on the component Parts of Membrane. 345

burned ; after this, it fell into pieces, which, being dissolved in
nitric acid, afforded a small portion of phosphate of lime, and a
large quantity of carbonate of lime.

When the stem of this Gorgonia was ‘steeped during 14 or
15 days in dilute nitric acid, it tinged it with pale yellow. The
stem, after this, appeared more transparent and flexible, so as
to approach the characters of cartilage.

The yellow liquor was changed to a deep yellow or orange
colour by the addition of ammoniac; but did not yield any pre-
cipitate, even when carbonate of potash was added.

Part of a stem was cut into small pieces, and was boiled for
several hours with distilled water.

When filtrated, the water had acquired a very pale yellow
tinge; and, upon the addition of infusion of oak bark, yielded a
slight precipitate of gelatin. —

Lixivium of caustic potash was then poured upon the same
pieces ; and, being boiled, a thick dark-coloured viscid substance
was formed, which possessed all the characters of Cuaprat’s
animal soap.

_ When the stem of this Gorgonia was exposed to a red heat
in a retort, or crucible, it curled up, and smelled like burned
horn; after which, a spongy coal remained, of difficult inci-
neration. ;

_ By a’ long continuation of the heat, a residuum was left, so
small as scarcely to be collected, which, being dissolved in dilute
nitric acid, afforded, by the addition of ammoniac, a slight pre-
cipitate of phosphate of lime. |

Another species of Gorgonia, which much resembled the
suberosa, (excepting that the cortical part was much larger
in proportion to the stem,) was next subjected to examination,

? Yye:

346 Mr. Hatcuetr’s Experiments on Zoopbytes,

and proved to be of a similar composition with those already
mentioned.

‘ Gorgonia pectinata.

The cortical part of this Gorgonia effervesced with dilute
nitric acid, and left a soft yellowish white membrane.

Ammoniac precipitated a small quantity of phosphate of lime;
after which, a copious* precipitate of carbonate of lime was
obtained by potash. bole:

The stem, in its habits, resembled those which have been
described.

Gorgonia setosa.

An effervescence was produced upon the immersion of this
Gorgonia in dilute nitric acid; and, after some hours, the cortical
part appeared like a thin yellowish membrane, which coated the
horny stem. ri

The acid solution, upon the addition of ammoniac, yielded a
slight precipitate of phosphate of lime; and a large quantity of
carbonate of lime was afterwards obtained by potash. |

When the cortex was separately steeped in the acid, and the
solution examined in the way so often mentioned, only car-
bonate of lime was obtained.*

On the contrary, the stem (whether recent or burned) af-
forded a small portion of phosphate of lime, but scarcely any
trace of carbonate. The stem which had been long steeped in
the acid, became soft and Set gd 2 like a cartilaginous or
tendinous substance.

* When the yess part had been long digested in boiling distilled water, a

brownish solution was formed, which was but little affected by infusion of oak bark;

but nitro-muriate of tin produced a precipitate.

and Observations on the component Parts of Membrane. 9347

The ,Gorgonie which have been enumerated, much resemble
each other in the composition of their cortices, as well as in the
nature-of their stems.

In the cortex, the predominant hardening substance is car-
bonate of lime; but, in the stem, phosphate of lime is the chief
and almost the only earthy substance that is present.

The following Gorgonie (although in like manner invested
by a cortex) are different, as they do not afford any phosphate
of lime.

Gorgonia Umbraculum,

Gorgonia verrucosa,

and three other species not described, so much resemble each
other in their chemical characters, that it would be superfluous
to give a separate account of them.

The cortical parts of these Gorgonie were separately immersed
in dilute nitric acid. An effervescence immediately took place,
and, after some time, they were found in the state of soft,
pulpy, yellowish white membranaceous bodies, retaining nearly
their original size and form.

The acid solutions did not afford any phosphate of lime
_when ammoniac was added; but a large portion of carbonate
of lime was precipitated by solution of potash.

The stems of these Gorgonie, when immersed during 14,
days or more in the dilute acid, were very little affected, ex-
cepting, that they became softer and transparent, so as to
_ approach the characters of cartilage or softened horn.*

* The stems of the various Gorgonie, which had been thus softened by tong
immersion in. dilute nitric acid, became of a deep reddish orange colour, inclining to

348 Mr. Harcuert’s Experiments on Zoopbytes,

The acid in which they had separately been steeped, did not
afford any precipitate by the addition of the alkalies; and the
only change was in the colour, which becartte pris yellow when
ammioniac was added.

1 ri dud jeenth Wo 4

The Gorgonie now to be mentioned, ‘differ from the former,
as they are not coated with a fleshy or pulpy cortical substance.
They are here placed immediately before the Antipathes, on
account of their great similarity in chemical sepa a as Birk
as in external appearance. tte

Gorgonia Antipathes»

Some pieces of this Gorgonia were immersed in dilute nitric
acid during three weeks, at the end of which ‘time they were
much softened, and appeared to’ be composed of a pale brown,
opaque, membranaceous substance, which formed concentrical
coats, of a ligneous aspect. eis tas

‘The acid in which these pieces had bean eee was become
pale yellow, and changed to orange colour when ammoniac
was added; but not the smallest precipitate could be thus
obtained; nor was any alteration caused by the spin of
lixivium of potash.

When distilled water was boiled with the Gorgonia Antipathes
during about six hours, it became slightly tinged with yellow ;
and, some infusion of oak bark being added, a ome chi of
gelatin was precipitated. nt .gmaige

The pieces of this substance which had been thus iti
were afterwards boiled with lixivium of caustic pte a eae

brown, when subsequently eens in pure ammoniac ; and, in the course of a few
hours, they were completely dissolved.

and Observations on the component Parts of Membrane. 349

the whole was dissolved, and a very dark coloured animal soap
was formed. ,

_ When this neato was expobel to a red heat, it emitted
much smoke, with a smell of burned horn: it soon lost its
shape, puffed up, and formed a spongy coal, which, by a long
continued heat, left a few particles of a white substance, con-
sisting chiefly of muriate of soda.

Another species of Gorgonia was next examined, the stem of
which is from one quarter to nearly half of an inch in diameter
in the thickest parts; of a black colour, and a high polish, like
black sealing wax: it has probably been considered as a variety
of Gorgonia Antipatbes.

This, by immersion during 28 days in dilute nitric acid,
gradually became semi-transparent, and of a bright brownish
yellow. In this softened state, it was steeped two days in water,
and was then opened longitudinally. By this, the whole struc-
ture became apparent, and consisted of thin coats or tubes of a
beautiful transparent membrane, which, beginning from a cen-
tral point, progressively became larger, according to the order
by which they receded from the centre.

‘These membranes were so delicate, that the fibro ous texture
could scarcely be discerned. =348)

The acid in which this species had lan wens was tinged
with very pale yellow. Ammoniac being added, changed it toa
deep yellow or orange colour; but the transparency of the
liquor was not disturbed by this, or any of the other precipi-
tants which had been employed in the former experiments.

-When this Gorgonia was exposed to a red heat, it crackled,
and emitted a thick smoke, with the smell of burned horn. The
shape was soon destroyed, and a compact coal remained.

350 Mr. Hatcuett’s Experiments on Zoophytes,

By continuing the red heat, a very small portion of white
matter was obtained, which, as far as the quantity would allow,
was proved to be muriate of soda, with some carbonate of the
same.

The last species of Gorgonia which I shall here mention, is
one which so much resembles the Gorgonia Antipathes as not
easily to be distinguished from it, and, like the preceding, has
probably been confounded with it; but, upon closely comparing
them, the Gorgonia now treated of is found to be more flat in
the stem, on the thin sides or edges of which, a number of short
spines or protuberances are placed very near each other. That
it is very different from the Gorgonia Antipas, will be proved
by the subsequent experiments.

Some pieces of this Gorgonia were cols to the action of
dilute nitric acid for nearly four weeks.

The structure then became very apparent, and consisted of
strong fibres, which were placed nearly in a parallel direction,
from one extremity of the branch to the other, and, being
closely arranged side by side, formed concentric coats of a pale
brown opaque substance; but these coats were by no means so
distinct as those observed in the Gorgonie formerly mentioned,
although, like them, the fibrous substance possessed the cha~
racters of membrane.

The dilute acid in which these pieces eo been steeped, was
become pale yellow, which changed to orange colour when
ammoniac was added; at the same time, so large a quantity of
phosphate of lime was precipitated, that the liquor became thick
and viscid. :

The phosphate was separated by a filter; and lixivium of
potash was added to the clear liquor, without producing any effect.

and Observations on the component Parts of Membrane. 35%

This Gorgonia was digested in boiling distilled water during
18 hours, and tinged it with pale yellow, |

Infusion of oak bark was then poured into the liquor, and
precipitated a small portion of gelatin.

The pieces employed in the above experiment were next
boiled with lixivium of caustic potash, and formed a dark-
coloured animal soap; at the same time, the phosphate of lime
was separated, and was gradually deposited at the bottom of the
matrass.

Part of a large branch of this Gorgonia was exposed to a low
red: heat.

It immediately emitted a thick smoke, with the smell of
burned horn; and, after a long continued heat, the phosphate of
lime was left, so as to retain the original figure, like bone which
has been burned; but, in the present instance, the particles of
the mass cohered but feebly.

When this residuum was dissolved, and the phosphate sepa-
rated in the usual manner, a slight cloud of carbonate of lime
was produced by potash.

Antipathes Ulex.

When this had been immersed 14 days in dilute nitric acid,
it became transparent, and so much softened, that from a horny
substance it now nearly resembled cartilage. The acid in
which it had been steeped, changed to a very deep yellow or
orange colour when ammoniac was added; but no precipitate
could be obtained by this, or by potash.

A portion of this Antipathes was digested with boiling distilled
water, from which some gelatin was precipitated afterwards by
infusion of oak bark.

MDCCC, ZZ

352 Mr. Hartcuett’s Experiments on Zoophytes,

The Antipatbes being then boiled with lixivium of caustic
potash, was completely dissolved, and formed the animal soap
of Mr. Cuaprat,

Antipathes myriopbylla.

_ This was subjected to experiments like those above neti
and, as the effects were the same, it is not necessary that —
cular mention should here be made of them.

As the specimens of these Antipatbes were small, I was not
able to make any additional experiments; but what has been
said sufficiently proves how much they resemble the horny
stems of the Gorgonze.

-

Sponges.

Many species of Sponge were examined, but, as little or no
essential difference was found in the results, I shall include all
of them in what is now to be related.

The following species, with many others not described, were
subjected to experiment.

Spongia cancellata.
Spongia oculata.

Spongia infundibuliformis.
Spongia palmata.

Spongia officinalis.

When the Sponges had been immersed in nitric acid d (diluted
with three measures of distilled water) during 14, or 16 days, the

acid became pale yellow, and was changed to an | orange colour |
by the addition of pure ammoniac.

The Sponges which had been thus steeped in the dilute acid,

1

and Observations on the component Parts of Membrane. 353

became (like the Gorgoniz) more or less transparent, and were
considerably softened. In this state, if they were touched with
ammoniac, the part thus touched became of a deep orange
colour, inclining to a brownish red; and, when much softened
by the acid, (if afterwards immersed in ammoniac,) they were
completely dissolved, and formed a deep orange-coloured
solution.*

When digested with boiling distilled water, the Sponges
afforded a portion of animal jelly or gelatin, which was praia
tated by infusion of oak bark.

The fine and more flexible Sponges yielded gelatin in Beside
abundance, and more easily, than those which were coarse and
rigid. The gelatin was gradually and progressively imparted
to the water, and seems (even in the same Sponge) to be a
constituent principle, of different degrees of solubility ; and it
must be noticed, that in proportion as the Sponges (particularly
those which were soft and flexible) were deprived of this sub-
stance, in the like proportion they became less flexible and more
rigid, so that the remaining part, when dry, crumbled between
the fingers ; or, when moist, was torn easily, like wetted paper.

As the. above properties prove that Sponges only differ from the
horny stems of the Gorgonia, and from the Antipathes, by being
‘ of a finer and more closely woven texture,-{- so this sein
will be corroborated by the following remarks.

- When exposed to heat, they yielded the same products, che

* The same effects were observed when the horny stems of the Gorgonie, Anti-
pathes, Sc. (which had been long steeped in dilute nitric acid,) were immersed in
pure or caustic ammoniac. j

+ This is particularly to be observed by comparing the coarse sponges (such

as Spongia cancellata) with the finely reticulated parts of certain Gorgonie, especially
those of Gorgonia Flabellum, when divested of the external membrane,

2.7. 9

B54 Mr. Hatcuetr’s Experiments on Zoophytes,

same smell, and afforded a similar coal, which by incineration
left a very small residuum, consisting chiefly of muriate of soda,
occasionally mixed with some carbonate of lime, which was also

often discovered when the recent Sponges were immersed in

acids; but this, as well as the muriate of soda, is I believe
merely extraneous, and arises from small shells, parts of Ma-
drepores, and such like bodies, which are often visibly lodged in
the interstices of the Sponges.

Lastly, the Sponges, when boiled with lixivium of caustic
potash, were completely dissolved, and, like the horny stems of
the Gorgonig, formed animal soap, more especially when the
part which is apparently insoluble in water, and which remains
after the gelatin has been separated, was thus treated.

Alcyonium asbestinum.

- This, after being immersed during several hours in dilute
nitric acid, remained unchanged in figure; a feeble effervescence
was at first produced, and the reddish purple colour was de-
stroyed.

The external part became pale yellow, and was a soft opaque
pulpy substance, within which was a stem, yery similar in tex-
ture, but less soft, and which still appeared of a pale red
colour.

When pure ammoniac was added to the filtrated solution, no
apparent effect was produced ; but carbonate of potash precipi-
tated a large quantity of carbonate of lime.

When a piece of this Alcyonium was exposed to a low red
heat, it soon took fire, and emitted a smell like burned horn;
after which, it retained its figure, and became white. Being dis-
solved in dilute nitric acid, some animal coal was deposited;

:
4

and Observations on the component Parts of Membrane. 95%

_ ‘and, upon the addition of ammoniac, a small portion of phosphate
of lime was obtained, which being separated, the carbonate was
precipitated as before.

' Some pieces of this Alcyonium were digested with boiling
distilled water during six hours; the liquor was then decanted,
and infusion of oak bark being added, a quantity of gelatin was
precipitated.

On the pieces of the Aleyontum from which the water had
been decanted, some lixivium of caustic potash was poured; and,
being boiled, the whole of the membranaceous or pulpy part
was dissolved, and a substance exactly similar to Cuapra.’s
animal soap was formed, while the calcareous part subsided to
the bottom of the vessel.

Alcyonium Ficus.

When the effervescence produced by pouring dilute nitric
acid on this Alcyonium had ceased, it was found unchanged in
shape, and like a strong thick membranaceous substance of a
fibrous texture.

Pure ammoniac, added to the acid liquor, precipitated a small
quantity of phosphate of lime; after which, a copious precipitate
of carbonate of lime was obtained by potash.

Alcyonium arboreum.

This Alcyonium, being steeped in the dilute nitric acid, effer-
vesced, and was acted upon like Alcyonium asbestinum.

The calcareous part was soon dissolved ; but the form of the
Alcyonium remained unchanged, and still appeared like a pale
yellow porous substance, enveloped by a skin or epidermis.

' Ammoniac did not disturb the transparency of the solution;
but carbonate of lime was obtained by solution of potash,

356 Mr. HatcuEtt’s Experiments on Zoophytes, -

When exposed to a low red heat, it resembled Alcyonium
asbestinum; and a solution being subsequently made, afforded
some phosphate of lime, with a large portion of carbonate.

As this phosphate had not been discovered in the first expe-
riment, and therefore appeared to have been*defended from the
action of the acid by the membranaceous part, that experiment
was repeated, with this difference, that the acid was made to boil.

A complete solution of the whole was thus made, which, like
that of the burned Alcyonium, yielded phosphate of lime; and
at the same time the liquor became of an orange colour, as soon
as the ammoniac was added. .

Some pieces of this Alcyonium were digested vith boiling
distilled water, and tinged it with a pale yellow colour. . Infu-
sion of oak bark being then added, a hens quantity of gelatin
was precipitated.

' The same pieces were boiled with lixivium of caustic potash,
and, when dissolved, formed animal soap. )

The calcareous part was separated during the boiling, and
subsided in the form of a fine powder.

From the examination of the few species of Alcyonium which
have been mentioned, it appears, that as the Sponges resemble
the horny stems of Gorgonia, so these, in external and chemical
characters, resemble the fleshy or cortical substance which
invests some of those bodies; and that they chiefly differ from
the Gorgonie, by being destitute of the horny stem, which in
the latter seems to supply the place of bone.

§ II. OBSERVATIONS ON THE FOREGOING
EXPERIMENTS.
The simplicity and uniformity of the experiments fie de-
scribed, will not, I flatter myself, render the facts less worthy of

and Observations on the component Parts of Membrane. 357

attention ; and I must again repeat, that the minutiz of analysis
_ did not form part of my present plan, which was only to sketch
an outline, comprehending the most prominent chemical cha-
racteristics of certain bodies appertaining to the animal king-
dom, which hitherto had been but little or not at all examined ;
so that this outline (although defective) might serve as a chain
of connection, and as a basis, upon which a more perfect super-
structure may in future be gradually raised; and it appeared
evident, that this would be most easily and speedily executed,
by following a systematical and comparative plan. For this
reason, a great part of my attention was directed towards ascer-
taining, in these animal substances, the presence and general
proportions of carbonate and phosphate of lime; these being
the materials essentially employed by nature to communicate
rigidity and hardness to certain parts of animals, such as shell
and bone; and, although some other substances, as magnesia,
silex, iron, with some alkaline and neutral salts, might be occa-
sionally present in small proportions, (and indeed were at times
detected,) yet, as these appear to have but little influence on the
general characters of the bodies which were examined, I did not,
for the present, think proper to take particular notice of them.

The next object was, to examine the nature of the substance
in and upon which the hardening or ossifying principles were
secreted and deposited ; and it seemed to me that the best mode
to do this, was to compare and examine this substance in the
various states in which it appeared, when deprived of the harden-
ing or ossifying matter.

From what was said in the paper on shell and bone, con-
cerning the substance which remained after the carbonate of
lime in shells, and after the phosphate of lime in bones, had been

358 Mr. Hatcuett’s Experiments on Zoopbytes,

dissolved and separated by weak acids, it is evident that the sub-
stance which thus remains, is as various in relative quantity, as
it is in those qualities which apparently are produced by the
degrees of natural inspissation, and by the progressive effects of
organization.

In the porcellaneous shells, such as Cyprea, &c. this substance
was proved to be much less in quantity than in those which
were afterwards mentioned; and, although of a quality which
(like a cement or gluten ) served to bind and connect the particles
of carbonate of lime firmly together, so small was the degree of
natural inspissation, and so little advanced was the degree of
organization, that when the carbonate of lime was dissolved,
even by very feeble acids, little or no vestige of jelly, mem-
brane, or cartilage, could be perceived; nor indeed could any
be detected, but by the small portion of animal coal which was
formed, when these shells had been expe for a short time to
a low red heat. .

But, proceeding from shells of this description to others tend-
ing to the nature of nacre or mother of pearl, (such as some of
the Patelle,) a substance was left untouched by the acids, which
had the appearance of a yellowish transparent jelly.* So that
the substance which served merely as a gluten in the porcel-
laneous shells, was not only more abundant in these Patella,
but, being more inspissated, was become immediately visible

and palpable.

In the common oyster, these qualities were more strongly
marked; and, in the river muscle, and in the shells composed

* The term jelly is here employed only to denote the degree of consistency of this
‘substance, which in its nature is very different from the varieties of animal jelly called
gelatin.

and Observations on the component Parts of Membrane. 359

of the true nacre or mother of pearl, this substance was found
not only to constitute a large part of the shell, but even to be
more dense, so as no longer to appear gelatinous; and, in addition
to these, strong and visible marks of organization were stamped
on every part, and a perfect membranaceous body remained,
composed of fibres arranged parallel to each other, according to
the configuration of the shells. )

From these facts, proved by the examination of only a very
few (comparatively speaking) of the known shells, it appears
that the hardening principle, or carbonate of lime, together
with a substance varying from a very attenuated gluten to a
tough jelly, and from this to a perfectly organized membrane,
concur to form the matter of shell; and, from the result of the
experiments, and from all circumstances, there is every reason
to believe, that the substance with which, or upon which, the
carbonate of lime is mixed or deposited, is of a similar nature,
and differs only in relative quantity and density, arising from
progressive changes (peculiar to the various species of shells).
produced by certain degrees of natural inspissation, and by an.
organization more or less perfect.

The experiments made on teeth, and on the bones of various
animals, elucidated and confirmed the observations made on the
nature of shell; for,

ist. The enamel of teeth (in relation to the other bony sub-
stances) was proved to be as the porcellaneous shells are to
those formed of mother of pearl; the cementing substance of
the enamel being a gluten, in the same state, and apparently of
a similar nature, with that of the porcellaneous shells. And,

2dly. In certain bones, particularly those of fish, (such as
some of the bones of the skate,) the substance which remained

MDCCC, 3A

360 Mr. Hatcuetr’s Experiments on Zoophytes,

after the solution of the phosphate: of lime, was of a gelatinous

‘consistency, and exhibited but very imperfect traces of organi-
zation; by the others, however, a completely formed membrane
or cartilage was left, retaining the figure of the original bone.

When therefore the component parts of shell and bone are
considered, it appears that the essential characteristics are, ear- ~
bonate of lime for the one, and phosphate of lime for the other;
and that their bases consist of the modifications of-a glutinous,
gelatinous, or membranaceous substance.

I experienced much gratification in tracing the progressive
and connected changes in the composition of the various shells
and bones ; and a considerable increase of pleasure arose, in pro-
portion as the observations made on those bodies were corrobo-
rated, and the chain of connection extended, by the develope-
ment of the facts resulting from the experiments on Zoophytes,
which form the principal subject of this paper.

It will now be proper to review these experiments, and, to
examine how far they agree with those madeon shell and bone,
and how far they tend to prove, that these substances ‘are all of
a nature closely connected.

The experiments on the Madrepores afforded the following
results.

Madrepora virginea, when examined by acids, left but very
little of any gelatinous substance or membrane. /

Madrepora muricata, and Madrepora labyrinthica, coaaad
loose portions of a transparent gelatinous substance.

Madrepora ramea, and Madrepora fascicularis, when deprived
of the carbonate of lime by acids, remained in ‘the state of com-
pletely organized membranaceous bodies, which exhibited the
original figure of the respective Madrepores ; and the proportion

and Observations onthe component Parts of Membrane. 9361

of coal afforded by these last, was more abundant than what
was obtained from those which were first mentioned.

To these succeeded the experiments on the Millepores ; from
which it appeared, that

Millepora cerulea, afforded. loose detached portions of a gela~
tinous substance.

Millepora alcicornis yielded the same, but in a more coherent
State,

Millepora polymorpha Roane i ahotineeds in shape, and con-
sisted of a strong, white, opaque membrane, illed with a trans-
parent jelly.

Lastly, Millepora cellulosa, Millepora fascialis, and Millepora
truncata, afforded membranaceous bodies, ina complete state of
organization ; and all these Millepores, when exposed to a low

red heat, yielded various quantities of coal, according to the
greater or less alandance of the gelatinous or membranaceous
substance.

The universal and only hardening principle of these Madre-
pores and Millepores, was proved to be carbonate of lime, with
the single exception of Millepora polymorpha, which also appears
to be differently constructed from the other Millepore. With this
single exception, carbonate of lime seems to be'the only harden-
ing substance in these bodies; and, when every circumstance
is considered, an exact similarity is to be found between the
substance forming the various shells, and that which forms the
Madrepore and Millepore ; and the nature of these bodies is
so completely the same, that the changes or gradations of the
one are to be found in the other. For the chemical characters
which distinguish the porcellaneous. shells, are in a great mea-
sure approached by those of Madrepora virginea; and those

3A2

362 Mr. Hatcuetr’s Experiments on Zoopbytes,

which were noticed in the Patel/z, correspond precisely ‘with
the Madrepores and Millepores which afford a gelatinous sub-
stance; and lastly, the characters of the membranaceous part,
exhibited by the shells formed of nacre or mother of pearl, are
in like manner to be found among some of the Madrepores
and Millepores, such as Madrepora ramea, Millepora fascialis,
Millepora truncata; for these, like the Turbo olearius and Ha-
liotis Iris, are composed of a fibrous membrane, hardened by
carbonate of lime.

It appears therefore, that the Madrepores and Millepores, like
the various shells, are formed of a gelatinous or membrana-
ceous substance, hardened by carbonate of lime; and the only
difference is in the mode according to which these materials
have been employed.

The experiments on Tubipora musica proved, that in compo-
sition it resembled the foregoing substances. But a slight diffe-
rence was observed, in respect to the hardening substance of
Flustra foliacea and Corallina Opuntia; for a small portion of
phosphate was found mixed with the carbonate of lime; but the
membranaceous part of these bodies resembled that of certain
Madrepores and Millepores, particularly Millepora fascialis.

Two species of Isis were next examined, namely, Isis ochracea
and Isis Hippuris: both of these were proved to be formed of
regularly organised membranaceous, cartilaginous, and horny
substances, hardened, in the last mentioned species, merely by
carbonate of lime; but, in the Isis ochracea, with the addition of a
very small portion of phosphate of lime.

The subsequent experiments were made on various species of
Gorgonia, and first on Gorgonia nobilis, which was formerly
regarded as an Isis. PPL? Li | Son

and Observations. on the component Parts of Membrane. 363

The hardening substance of this was found to be carbonate of
lime, with a small portion of phosphate; but the matter form-
ing the membranaceous part was (like that of Millepora poly-
morpha) in two states; that of the interior being gelatinous; and
that of the external part being a membrane completely formed,
so as to cover the stem, in the manner of a tube.

The results of the experiments on certain Gorgoniz, such as
ceratophyta, Flabellum, suberosa, pectinata, and setosa, were not a
little remarkable ; for, when the two parts which compose these
Gorgonie (namely, the horny stem, and the cortical substance by
which it is coated, ) were separately examined, it was proved,

ist. That the stems of these Gorgonie consist of a substance
analogous to horn ; and that, by long maceration in diluted nitric
acid, this horny substance becomes soft and transparent, so as
to resemble a cartilaginous or tendinous body; moreover, the
stems of these Gorgonie afford a quantity of phosphate of Hes
but scarcely any trace of carbonate.

edly. That the cortical part, on the contrary, consists princi-
pally of carbonate of lime, with very little or none of the phos-
phate; and the carbonate of lime is deposited in and upon a soft,
flexible, membranaceous substance, which seems much to ap-
proach the nature of cuticle.

Some other Gorgonie, which were subsequently examined,
and which much resembled the former in construction, did not
yield any phosphate of lime ; pags in every other particular they
proved to be similar.

The Gorgonta Antipathes was found to be entirely formed of
a fibrous membrane; and the black shining polished Gorgonia
afforded, by maceration, a most beautiful specimen of mem-
branes concentrically arranged.

364, Mr. Hatcuert’s Experiments on, Zoophytes,

Lastly, the Gorgonia which I have described. as: very’ much
resembling the Gorgonia Antipathes, proved to be similar to that
species, as to the membranaceous part ; but so large a portion of
phosphate of lime was mixed with it, as: almost to approach it
to the nature of stag’s or buck’s horn; _ there is, therefore, great
reason to consider it as a different species.

The Antipatbes, which were next examined, were found to
be little if at all different from the horny stems of the Gorgonia.
And the various Sponges, which were afterwards subjected to
experiment, were proved to be completely formed: by the same
membranaceous or horny substance, which became varied by
the modifications of a more delicate construction, rather is by
any essential’ difference in composition. .

This. series of experiments terminated; with-an examination.
of a few species. of Alcyonium, namely, asbestinum, Ficus, and
arboreum ; all of which were found to be:composed of a soft,
flexible, membranaceous substance, very similar to the cortical
part of some of the Gorgoniz, (such as. Gorgonia suberosa,) and
in like manner slightly hardened by carbonate, mixed witli a
small portion of phosphate of lime.

From what has been said, there is reason to conclude, that
the varieties of bone, shell, coral, and the numerous tribe of
Zoophytes with- which the last are connected, only differ in
composition by the nature and quantity of the hardening or
ossifying’ principle, and by the state of the substance with
which it is mixed, or connected. For the gluten or jelly which
cements the particles of carbonate or phosphate of lime, and
the membrane, cartilage, or horny substance, which serves as a
basis, in and upon which the ossifying matter is secreted and.
deposited, seem to be only modifications of the same substance;

and Observations on. the component Parts of Membrane. 365

which ‘progressively. graduates, from a viscid liquid or gluten,
into that eelatinous ‘substance which has so often been noticed,
and which again, by increased inspissation, and by the various
and more or less perfect degrees of organic arrangement, forms
the varieties of membrane, cartilage, and horn.
I shall now attempt to prove what:I have here asserted, or
at least assign the reasons which induce me to adopt this opi-
nion; but, in so doing, I am compelled, from the close connec-
tion of the subject, to anticipate the general result of part of a
series of experiments, made with a view to investigate the nature
and composition of membrane. é f
To enter into. a minute detail of these experiments, would far
exceed the limits of a paper like the present; I shall therefore
only mention, in a concise manner, the results of those which
the subject immediately requires to be’ brought forward.*
The method which first presents itself in such an investiga-
tion, is, the comparative analysis of the different substances, —
“so that ‘their relative proportions of carbon, hydrogen, and
azote, should be precisely determined; but, when it is recol-
lected, how long a time would be requisite for making such
an immense series of analyses, and how much animal sub-
“stances are subject to be modified by: situation in the body, by
age, and by the degree of health of animals, and also that the
~ nature of these, and even that of the unorganised bodies, does not
always merely depend on the proportion of the constituent prin-
ciples, but likewise on the degree and mode of combination to
which these principles are subjected; I say that when all this,
* These are the experiments to which I alluded in my former paper, and which I

began at the request of my friend Mr. Home, soon after the experiments on the enamel
of teeth, &c.

366 Mr. Hatcuett’s Experiments on Zoophytes, -

and the plan of the present paper, is considered, I flatter myself
that I shall not be censured as hasty or negligent, if at this
time I prefer a comparison of the chemical properties of the
bodies in question, with those of other substances, which (al-
though not elementary) may be regarded as primary animal
compounds; and, when the subject is viewed in its full extent,
the mode which I have adopted will, perhaps, be deemed that
which is the most satisfactory.

§. III. OBSERVATIONS ON THE COMPONENT.
PARTS OF MEMBRANE.

In relating the preceding experiments, I have had frequent
occasion to remark, that a quantity of that animal jelly which is
more or less soluble in water, and which is distinguished by
the name of gelatin, was obtained from many of the marine
bodies, such as the Sponges, the Gorgonte, and others; but, in
the experiments made expressly to investigate the composition
of membrane, it still more frequently occurred; and although
in many cases, either from the small quantity of the body
under examination, or from the very small portion of gelatin
thus obtained, I was obliged to content myself with ascertain-
ing the presence of it, by the test of the tanning principle, and
by nitro-muriate of tin; * yet, in other experiments, when the.
solutions of gelatin were gradually reduced by evaporation, I

* Nitro-muriate of tin has been proposed as a test for the tanning principle; and
the experiments contained in this paper prove, that it may also be employed with
much utility, to ascertain the presence of gelatin, and of certain modifications of

albumen.

and Observations on the component Parts of Membrane. 367

had opportunities of frequently observing the various degrees
of viscidity and tenacity which characterize mucilage, size,*
and glue.

The difference in the viscidity and tenacity of the varieties
of these substances, is evidently an inherent quality, and not
caused by the degree of mere inspissation: if this was the case,
mucilage, size, and glue, when dry, would be of an equal quality,
which is, however, contrary to daily experience; for the varieties
of glue are not of equal tenacity. And it is well known, that
glue made from certain parts of animals, such as the skin, is
more tenacious, and of a better quality, than that which is
made in some places from feet and sinews.

Moreover, when even the same part is employed, which has
been taken from two animals of the same species, an evident
difference is found, according to the comparative age of the
animals; for the best and strongest glue is always obtained
from the more aged animals, in whom the fibre is found to be
the most coarse and strong. But a longer continued boiling
appears requisite in order to extract it; and the more viscid glues
are obtained, from the substances which afford them, with greater
difficulty than those of a less viscid quality, which may more
properly be called size: this difference is to be observed, when
muscle is boiled with repeated and frequent changes of water.

Gelatin thus obtained, whether in the state of mucilage, size,
or glue, when completely dried, is affected by water accord-
ing to its degree of viscidity: for, when cold water is poured

* The term size is employed, throughout this paper, to denote that modification of
gelatin which appears to be intermediate, between mucilage and the most viscid and
tenacious gelatinous substances or glues. The weaker kinds of glue may therefore
come under this denomination.

MDCCC. | 3B

368 Mr. Hatcuett’s Experiments on Zoophytes,

on dry mucilage, it dissolves it in a short time; but, if cold water
is poured on those varieties of gelatin which, when dissolved in
a proper quantity of boiling water, would, by cooling, form jellies
more or less stiff, it acts on them in different degrees, not so
much by forming a complete solution, as by causing them to
swell and become soft; so that, when a cake of glue has been
steeped three or four days in cold water, if it swells much
without being dissolved, and, when taken out, recovers its
original figure and hardness by drying, such = is considered
to be of the best quality. —

I shall soon have occasion’ to notice, in another place, the
effects of acids and of alkalies on gelatin; it will therefore here
be sufficient to observe, that as it is soluble in acids, so, if dry
mucilage, dry size,* and dry glue, are steeped in nitric acid
diluted with three or four parts of water, they will be progres-
sively dissolved, according to the degree of viscidity by which
they are separately distinguished.

When the solutions of these substances in water were ex-
amined by the tanning principle, and by nitro-muriate of tin,
I have found that animal mucilage is more immediately affected
by the latter than by the former ; while the solutions of size and
of glue are equally acted upon by both. And, when gold dis-
solved in nitro-muriatic acid was added to the solutions of
mucilage, size, and glue, the gold was reduced to the metallic
state in a few hours, not only on the surface, where it formed
a shining metallic pellicle, but also on the sides of the glass,
which were thinly coated with a deep yellow sediment, which,
like leaf gold, appeared of a fine pale green, when held between
the eye and the light. /

* Gelatin obtained from eel-skin, evaporated to’ dryness.

and Observations on the component Parts of Membrane. 369

The animal mucilage which I chiefly employed in these
experiments, was obtained from the Corallina officinalis,as I found
it to be pure, and not partly modified into gelatin or animal
jelly.* But Mr. Bouvier asserts, that he obtained the latter
substance ; +} and this appears to me very probable; for mucilage
may predominate in this coralline at one period, and gelatin
or jelly at another, just as is found to be the case with other
animal substances; for it is known, that in young animals
mucilage is abundant, and becomes diminished as these increase
in growth and age. Hence there is every reason to conclude,
that the substance which in the very young animals was at first
mucilaginous, becomes progressively more viscid, and assumes
the characters of gelatin; which, as animals increase in age, is
known to become more and more viscid, as has been already
mentioned in the foregoing pages. I am inclined, therefore, to
consider mucilage as’ the most attenuated, and as the lowest in
order, among the modifications of gelatin.

As the qualities of gelatin are so various, so the properties of
the substances in which it is present as a component part, are
much influenced by it; and when, for example, the skins of
different animals were compared, I have always found that the
most flexible skins afforded gelatin more easily, and of a less
viscid quality, than those which were less flexible, and of a
more horny consistency.

* By this I mean, that the mucilage had not acquired the degree of viscidity
requisite to form a gelatinous substance. ‘The expression which I have employed, is
not therefore to be understood as alluding to any essential difference in composition,
but only to denote some variation in the degree of consistency ; for the whole may be
comprehended under the term gelatin, of which, mucilage may be regarded as one
extreme, and the strongest and most viscid glue as the other.

¢ Annales de Chimie. Tom. VIII. p. 311.

3Be

370 Mr. Harenerr’s Experiments on Zoophytes,

The skin of the eel possesses great flexibility; and it affords
gelatin very readily, and in a large proportion. The skin of
the shark also, which is commonly used by cabinet makers
to polish their work, was in like manner, for the greater part,
soon dissolved, and formed a jelly, like the former. The
epidermis or cuticle of these skins, (which is very thin and
tender,) although not soluble, was reduced into small particles
by violent ebullition; and the spiculze on the shark’s skin were
also separated.

The skins of the hare, rabbit, calf, ox, and rhinoceros, were
examined in a similar manner, and with the like results; but
the gelatin obtained from the hide of the rhinoceros, (as far as
the smallness of the piece of skin would allow me to determine, )
appeared to be the strongest and most viscid. In every one of |
‘these experiments, the true skin or cutis was principally
affected, it being completely soluble (as Messrs. Cuaptat and
SEGUIN have well observed) by long boiling; but that of the
rhinoceros far exceeded the others in difficult solubility. The
cutis of these skins, when first boiled, swelled and appeared
horny; it was then gradually dissolved; but in the cutis of the
rhinoceros a few small filaments remained, which at length
contracted and adhered to the cuticle.

The cuticle of the different skins was softened, but not dis-
solved; and, as the cutis seems to be essentially formed of
gelatin,* so the cuticle appears to contain it, although but ina
small proportion : it is, however, necessary to its flexibility ; for
when, after long boiling, the cuticle of these skins was dried,

* The cartilages of the articulations are also completely soluble when long boiled
with water; but this by no means happens when other cartilages are thus treated.

and Observations on the component Parts of Membrane. 371

it became a brittle substance, which was easily reduced to a
powder.

Hair was much less affected than either of the abovementioned
substances; and this, with others in some measure similar, I
shall now more particularly notice.

The substances to which I allude, are hair, feather, horn,
horny scale, hoof, nail, and the horn-like crust which covers
some insects and other animals, such as the scorpion and the
tortoise. These I shall now mention, in as concise a manner as
the subject will allow.

When hair of various qualities, and taken from different
animals, was long digested or boiled with distilled water, it
imparted to the water a small. portion of gelatin, which was
precipitated by the tanning principle, and by nitro-muriate of
tin; and, when the hair had been thus deprived of gelatin, and
was subsequently dried in the air, the original flexibility and
elasticity of it was found to be much diminished, so that it
easily gave way, and was broken.

This effect, Mr. AcHarp has also noticed;* and I am in-
duced to believe (from various experiments which I have made
on these substances ) that the hair which loses its curl in moist
weather, and which is the softest and most flexible, is that
which most readily yields gelatin; and, on. the contrary, the
hair which is very strong and elastic, is that which affords it
with the greatest difficulty, and in the smallest proportion.

These remarks have moreover been corroborated, by the

* << La perte de la partie gélatineuse étant aux cheveux leur souplesse, i] s’ensuit
“« que c’est aux parties gélatineuses qui entrent dans la composition des cheveux qu’ils.
*« doivent leur pliant et leur élasticité.”,— Examen chimique des Chevex. Sc,
Memoires de Acad. de Berlin, Tom, XXXVI. p. 12.

372 Mr. Hatcuett’s Experiments on Zoophytes,

assertion of a considerable hair merchant in this metropolis, *
_ who, during a long experience of upwards of forty years, has
always found, that hair of the first named quality cannot be
boiled an equal time with those last mentioned, without suffer-
ing material injury in strength and flexibility.

Feather, digested in boiling distilled water, during ten or
twelve days, did not afford any trace of gelatin by the test of
the tanning principle; but nitro-muriate of tin produced a faint
white cloud.

The same was observed when quill was thus examined.

- Shavings and pieces of the horns of different animals were
next subjected to experiment, and all afforded small quantities
of gelatin, which was precipitated by the tanning principle, and
by nitro-muriate of tin; and it was generally observed, that the
more flexible horns yielded the largest quantity of gelatin, with
the greatest ease ; and, (like the substances already mentioned, )
when deprived of it, and suffered to dry spontaneously in the
air, they became more rigid, and were easily broken.

The horns which I mean, are those of the ox, ram, goat, and
chamois, which, in my former paper I considered, as I do now,
to be perfectly distinct from the nature of stag’s or buck’s horn;
for this last is as different from the former in chemical compo-
sition, as it is in construction: like bone, it affords much phos-
phate of lime, and, like bone, it affords a large quantity of gela-
tin ; and it is not a little remarkable, that phosphate of lime is
generally accompanied by gelatin, as in stag’s horn, bone,
ivory, &c. on the contrary, when carbonate of lime is the hard-
ening substance, as in shells, madrepores and millepores, no
gelatin can be discovered; for I have frequently digested these

“ Joun Coxiuick, Esq. of St. Martin’s Lane.

and Observations on the component Parts of Membrane. 373

substances many days in boiling distilled water, (after having
reduced them to a coarse powder, that they might present a
larger surface,) but I never could, by any test, discover the
slightest vestige of gelatin, The horns therefore which were
first mentioned, are very different from the composition of stag’s
horn, and yield gradually, and with great difficulty, only a
small quantity of gelatin. |

Horny scale was next examined ; but I shall first here request
permission to make a digression in respect to the scales of fish,
which I had not examined when my paper on shell and bone
was read.

As the scales of fish, when viewed by a microscope, and
according to the observations of Mr. LEEUWENHOEK, appear
to be formed of different membranaceous laminz, and as they
exhibit the colour and lustre of mother of pearl, it might be
expected, that they should prove to be of a similar nature with
the substance of stratified shells, or, in other terms, that they.
should consist of membrane and carbonate of lime.

But, when scales perfectly clean, and separated from the
skin of different fish, (such as the salmon and carp,) had been
immersed during four or five hours in diluted nitric acid, till
they became transparent, and perfectly membranaceous; the
acid liquor, being then saturated with pure ammoniac, afforded
a copious precipitate, which was proved to be phosphate of
lime.

The spiculz of the shark’s skin, formerly mentioned, were
found to be of a similar composition; and we may therefore re-
gard the spiculz and scales of fish as true bony substances, in
which the membranaceous part is more predominant than in
common bone.

37h Mr. Harcuett’s Experiments on Zoophytes,

I fully ascertained, that the phosphate of lime was afforded
by these substances only; for, when the different skins from
which these scales and spiculz had been taken, were separately
examined in the like manner, no phosphate of lime was obtained.

In addition to this I must observe, that the silver or pearly
hue of pearl, mother of pearl, and of fish-scales, is only assisted
and modified by the relative degrees of opacity produced, in
mother of pearl and in pearl, by the interposition of the par-
ticles of carbonate of lime, and in the scales by phosphate of
lime; for this peculiar lustre principally resides in the mem-
branaceous part, and remains with it when the acetous or

~muriatic acids are employed as menstrua,-but is comple
destroyed by the nitric acid.

The horny scales of serpents, uberis and such like animals,
differ from the foregoing ; as all of those which I have examined,
consist merely of the membranaceous or horny substance, in a
more or less indurated state, and appear to be devoid of phos-
phate of lime, as an ossifying matter.

Horny scales in general, (and the scales of the Manis penta-
dactyla may be mentioned as an example, ) afford but very slight
traces of gelatin after being long boiled in distilled water; and
this small portion of gelatin can only be discovered by the tan-
ning principle, and by nitro-muriate of tin, unless a very large
quantity of the scales has been employed.

Human nail digested in boiling distilled water during several
days, was only softened ; and, like quill, afforded a slight cloud,
by the addition of nitro-muriate of tin.

Shavings of ox’s hoof, when long digested as abovementioned, |
afforded a liquor which, in like manner, was only made ee
turbid by nitro-muriate of tin.

and Observations.on the component Parts of Membrane. 375

- Nail and hoof, when long boiled, became of a much darker
colour. [Bi}-

~The basi Thee crust hit covers certain insects and other
oobi ae was subsequently examined; the experiments were prin-
cipally made on the plates which covered the body of a large
African scorpion, and on the common tortoise-shell of the shops.

» The plates taken from the scorpion were not apparently
affected, although digested for a nie time in peuins distilled
water.

. The tanning Wiech eee no alteration, rihoh added to
the water; but a faint white cloud appeared, upon the addition
of nitro-muriate of tin.

Tortoise-shell, in thin slips and shavings, was “digested i ina
similar manner during three weeks; but it was. only slightly
softened; and the water, which had acquired a brownish colour,
was but little affected, even by nitro-muriate of tin, which
however formed a white cloud.* “oy

From some previous circumstances, shisha need not here be
mentioned, I was lastly induced to make some similar experi-
ments on albumen; and, as that of the blood is mixed with
gelatin, and with the substance called fibrin by the chemists,
which in chemical properties appears to be the same as muscu-
lar fibre, and as it is with some difficulty that the albumen can |
-be exactly separated from these substances, I preferred the 3
albumen of eggs, as being pure and unmixed; and, in order
that it might be brought into a state in some measure similar
to the bodies lately examined, (by which I mean simple inspis-
sation,) I dried it, after coagulation, in a vessel which was

* The crust which covers insects like the scorpion, appears in every respect to be
similar to tortoiseeshell. 3

MDCCC. gC

376 Mr. Hatcuett’s Experiments on Zoophytes,

heated to 212° of FanRENuEIT, till it became perfectly hard,
brittle, yellow, and semi-transparent, like horn.

The albumen, in this state, was digested during eight days in
boiling distilled water, which was occasionally renewed, in pfo-
portion to the evaporation. :

In a few hours after the commencement of the digestion, the
transparent horny pieces of albumen were softened, and became
white and opaque, exactly like albumen recently coagulated ;
but, after this, no farther change was observed.

At the end of eight days, the water in which the albumen had
been digested was examined, and was found exactly to resemble
that afforded by quill, nail, and tortoise-shell; for the trans-
parency of it was not. disturbed by the tanning principle,
although nitro-muriate of tin produced a faint white cloud.*

As far, therefore, as could be ascertained, by long digestion
in boiling distilled water,.and by the effects of the re-agents,
albumen was proved to be very similar to tortoise-shell, and
many of the other substances previously noticed ; but the close
resemblance, or rather indeed identity, of albumen with. those
bodies, will be placed in a stronger light, by the enumeration
and comparison of their other chemical properties.

As I have, in the former part of this paper, had occasion to
mention the gelatin obtained from the Sponges and Gorgonia,
it is not necessary here to repeat those remarks, neither is it re-
quisite that I should enter into any minute account concerning

* When infusion of oak-batk is added to recent liquid albumen, it Sbibinediaae ;
forms a precipitate ; and nitro-muriate of tin does not produce any effect till some
hours have elapsed. But after coagulation the reverse takes place; for the water in
which coagulated albumen has been long boiled, becomes turbid by the addition of
nitro-muriate of tin; and is not in any manner affected by infusion of oak-bark.

and Observations on the component Parts of Membrane. 377

the experiments made on bladder, and some other membranes.
It may therefore suffice here to observe, that all these bodies
afforded more or less gelatin ; that, when this was separated, the
remaining substance ceased to be tough, or elastic, and was easily
torn, like wetted paper; and that, when dry, the sponges, and
such membranes as bladder and cuticle, became very brittle, and
were shrivelled and curled up, like withered leaves of plants.

But, before I speak of the nature of the substance which thus
remained, it will be proper, concisely to notice the effects of
acids. on the bodies which afford gelatin; and, as the most re-

markable effects were produced by nitric acid, I shall to that
- confine the present observations.

The specific gravity of the nitric acid which I employed in
the whole of my experiments, was 1,38; and this acid was diluted
with 2, 3, or 4, measures of distilled water, according to the
quality of the substance under examination, and the intended
time of immersion. But, as an acid too powerful would have
frustrated my intentions, I commonly added the acid, by de-
grees, and at long intervals, to the water in which the substance
was immersed; during which time, if any nitrous gas was dis-
charged, more water was added, as this gas was a certain sign ©
that the acid was not sufficiently diluted.

_ Substances like the Corallina officinalis, which contain a large
quantity of animal mucilage, or of the least viscid jelly, soon
impart it to boiling water.

In like manner, when such substances were steeped in nitric
acid diluted with about three measures of water, the mucilage
was in a few hours completely dissolved, while the membrana-
ceous part remained untouched.

Pure isinglass dissolved in the diluted nitric acid, formed a

3C 2

378 Mr. Hatcuert’s Experiments on Zoopbytes,

pale yellow liquor, which by evaporation became of a deeper
colour, and, when nearly dry, was suddenly reduced to a spongy’
coal. This change was.rapid; and: was attended with a! consi—
derable effervescence, and a copious discharge of nitrous’ gas,:
not unfrequently accompanied by sparks, and sometimes flame ;)
arising undoubtedly from nitrate of ammoniac, which was formed»
towards the end of the evaporation.

The acid solutions of mucilage, isinglass, and pure glue, were
changed to a deeper yellow, when saturated by the absorbent:
earths, by the alkalies, and especially by pure ammoniac. In:
such cases, little or no precipitate was obtained from pure gela-
tinous substances ; but some faint traces of phosphoric acid were
discovered in these solutions.

The effects of the dilute nitric acid on the other various;
substances which have been mentioned, resembled those now
described, and kept pace exactly with those of boiling water;
for, when they were immersed in equal quantities of the dilute
acid during a given time, the solution of the gelatin took place
according to the order observed 1 in those substances, when water
was employed. i.e dir rami

As an instance of this, two pideds mm £ skin; wae taken fort
an ox, were subjected to'experiment, as follows:

One of the pieces was boiled in water; till the whole of the
cutis was dissolved; after which, the cuticle: remained, although,
very feeble in texture, while the hair did not seem to have suf-
fered any material alteration. i |

The other piece was steeped in nitric acid diluted with about
four measures of distilled water. At the end of five days the cutis
was dissolved, and the cuticle was become of a loose and feeble
texture; but the hair had not suffered any apparent change,

and Observations on the component Parts of Membrane. 379

excepting that of being slightly tinged with yellow. In both
cases, therefore, the effects of boiling water and of acid were
similar, and were evidently most powerful. on. those pants which
were the most gelatinous.

As water dissolves mucilage more speedily than size, and this
last more readily than strong viscid glue, so are the effects of
very dilute nitric acid on the same substances; and, when
equal quantities of dried mucilage, of eel-skin glue, and of the
strongest glue, were dissolved in equal quantities of the dilute
acid, the colour of the solutions was more intense, and the
change produced by ammoniac was more visible, according to
the order of solubility and of tenacity.

It is well known how readily gelatin is dissolved by the
caustic fixed alkalies: when, therefore, the varieties of jelly or
glue were added to boiling lixivium of caustic potash, they were
soon dissolved; and, if added to saturation, a ier pvenisia’s viscid
substance was formed.

‘I did not observe that any ammoniac was produced, neither
was any coal deposited, after long boiling the solution in which —
there was an excess of alkali. ’

The viscid matter thus obtained, did not possess the properties
of animal soap; for it neither formed a permanent lather, when
mixed and shaken with water; nor, when saturated with acids,
did it afford any precipitate; contrary to what happens, when
animal soap is thus treated. But, if the gelatinous substance was
not pure; if, for example, any parts of membrane, which are not
soluble in water, were present, then, in proportion to the quantity
of this substance, the alkaline solution exhibited more or less of
the saponaceous characters ; but these I never observed ras
pure gelatin was employed.

380 Mr. Hatcuett’s Experiments on Zoopbytes,

Gelatin, according to its quantity and quality, has a powerful
influence on some of the physical and chemical properties of
the bodies in which it is present; by these properties, I mean
flexibility, elasticity, and putrescibility. |

So much has been said already, in various parts of this paper,
tending to prove how much the degrees of flexibility and elas-
ticity, in various animal substances, depend on their gelatinous
part, that little need be added; and, when it is considered, that
bodies such as muscular fibre, membrane, sponge, hair, and
cuticle, being deprived of gelatin, and dried in the air, become
rigid and brittle, no doubt can be entertained but that this
arises from the loss of the gelatinous substance; and, as an
additional proof, when bodies such as nail, feather, quill, and
tortoise-shell (which contain little or no gelatin) are long
boiled, and then dried in the air, like the former, they are
found to have suffered scarcely any alteration in their respec-
tive degrees of flexibility and elasticity.

As to putrefaction, it is obvious to every one, that certain parts
of animals are much more susceptible of it than others; and
that, when the carcase of an animal begins to putrefy, the most
humid and flexible parts are always first affected.

Thus, the viscera, muscles, and cutis, soon suffer a change ;
while hair, feather, scale, horn, hoof, and nail, remain unchanged,
ages after the former have been decomposed; and this is evi-
dently caused by the gelatin and moisture, which are combined
in the former, and not in the latter, at least in any notable
quantity. I have already mentioned the progressive and com=
parative effects. of boiling water, and of dilute nitric acid, on the
skin of the ox; and I have shewed, that while the cutis was,
completely dissolved, the hair remained untouched. These effects

and Observations on the component Parts of Membrane. 381

are to be observed, in the same exact order, when a similar
piece of skin is exposed to putrefaction; for this commences in,
and chiefly affects, the cutis, while the hair is separated, un-
changed in its quality. I do not, therefore, hesitate to assert,
that the degree of putrescibility in the various parts of animals,
depends principally on the presence, and on the quantity and
quality, of gelatin; and the skin of the rhinoceros found
on the banks of the Vilui, near Yakutsk, was preserved, in all
probability, partly by the nature of the climate and soil, and
partly by the superior horny quality which it possessed over
other skins; for it may be much questioned, whether the hide
of an ox or horse, in the same situation, would have escaped
putrefaction for so long a period.*

From the preceding observations it appears, that gelatin is a
component part of many animal substances.

That it differs in quality, from a very attenuated jelly or
-mucilage, to that viscid substance called glue; the varieties of
which also differ in solubility and tenacity.

That it is present in various proportions; so that certain
bodies, such as the cutis, and the cartilages of the joints, are
formed by it; while others, like nail, quill, and tortoise-shell,
can scarcely be said to contain it. (%

And that, by its presence, in various states and proportions,
it may be regarded (including inherent moisture and organic

* The more viscid gelatinous substances do not appear to be so immediately sus.
ceptible of putrefaction as those of the opposite quality ; for, when solutions, in water,
of animal mucilage, cel-skin glue, and strong glue, were during a certain time exe
posed under equal circumstances, I found the mucilage to be the first, and the glue the
last, which shewed symptoms of putrefaction.

382 Mr. Hatcuett’s Experiments on Zoophytes,

arrangement) as the principal cause of those degrees of flexi-
bility, of elasticity, and of putrescibility, so various in the
different parts of animals.*

But, when gelatin has been separated from the different
substances, either by repeated boiling with water, or by being
steeped in dilute acids, a more insoluble substance remains,

of a very different nature, which I shall now proceed to
examine.

When a bone or piece of ivory has, by long wasnt

* As gelatin, according to its proportion and quality, appears to produce consider-
able effects on the parts of animals in which it is present 5 and, as the gelatin in animal
bodies is, in all probability, liable to be changed and modified by morbid causes, it is
much to be wished, that gentlemen of the medical profession would ascertain, by expe-
riments, how far the tonic properties of barks depend on the tanning principle.

Mr. Biccain has proved, (Phil. Trans. for 1799. p. 259) that willow bark, and
especially that of the Huntingdon or Leicester willow, contains the tanning matter in
a considerable quantity ; and that the latter, in this respect, even equals, or rather ex-
ceeds, that of oak.

My friend, the Rev. THomas Racxerrt, Rector of Spetisbury and Charlton, in
Dorsetshire, has employed, in these parishes, the bark of the common willow with
great success, as a'tonic and febrifuge. Moreover, Mr. WestTrinc, of Norvkoping,
has observed, (Annales de Chimie. 'Tom. XXXII. p. 179.) that those species of Cin-
chona which contain the tanning principle in the greatest quantity, are the most
efficacious in fevers ; and that the Cincbona floribunda, which contains scarcely any
tanning matter, is destitute of the abovementioned beneficial effects. Mr. WesTRinc
therefore, with great apparent reason, believes, that the relative effects produced by
the different species of Cinchona, when employed in medicine, are in proportion to
their tanning power, or the quantity of tanning principle contained in them.

If any one should be induced to make experiments on the tonic effects of the
tanning principle, it is to be hoped that some attention would also be paid to the

medicinal properties of nitro-muriate of tin, of which, at present, I believe little or
nothing is known.

and Observations'on the component Parts of Membrane. 983

water, ‘been deprived’ of a great part of its gelatin, and is
afterwards steépéd in a dilute acid, the ossifying substance is
dissolved) ahd’the cartilage remains, retaining the figure of the
original bone; or, if a similar bone or piece of ivory, which has
not been boiled, is steeped in a dilute acid, (especially nitric
acid,)’ the ossifying substance is dissolved, and, at the same
time, but more slowly, the gelatin is separated, and causes the
liquor to become yellow, when the phosphate of lime is preci-
were by ammoniac.

The cartilaginous body which remains, after the gelatin has
been thus separated, is not easily soluble in diiute acids, for
(according to its texture) many weeks, and even months, may
elapse, before a small part is taken up; but, in concentrated
nitric acid, or in boiling dilute acid, it is rapidly dissoived, as I
shall soon have occasion to mention.

This substance, when dry, is semi-transparent, like horn,
and more or less brittle.

It is the predominant and essential part, in the tissue or
web of membrane, cartilage, sponge, the horny stems of Gor-
goni@, horn, hair, feather, quill, hoof, nail, horny scale, crust,
and tortoise-shell ; and, although of similar chemical properties,
yet in consistency it varies, from a tender jelly-like substance,
to a completely formed membrane, or to an elastic, brittle, and
hard body, like tortoise-shell.* :

* These bodies, especially tortoise-shell, appear to be formed (as far as organic
arrangement is concerned) in the way of stratum super stratum. | This structure is
peculiarly to be discovered after long maceration in diluted nitric acid; for then,
tortoise-shell appears to be composed (like the black polished Gorgonia) of membra-
naceous laminz ; and the varieties of horn differ only by a tendency to the fibrous
organization.

MDCCC. 3D

384. Mr. Harcuett’s Experiments on Zoophytes,

Experiments were made separately, on each of the bodies
above enumerated; but, as I did not find any essential. dif-
ference in the results, I shall include the whole unser the
following observations. oar. m0)

1. When distilled, a small portion of water, ‘some carbonate _
of ammoniac, a’ foetid empyreumatic oil, carbonated iad ie
gas, carbonic acid gas, and prussic acid, were obtained.

2. A spongy coal, of a gray metallic lustre, remained : oie
by incineration, afforded a very small residuum, which was not
always similar in quantity, even in’ portions of the same sub-
stance; for, 500 grains of tortoise-shell, taken from different
samples, afforded from + of a grain to 3 grains of residuum,
which consisted of phosphate of lime, and phosphate of soda ;
sometimes also a little carbonate of lime was ‘present; but I do
not believe these to be essential ingredients.

3. When boiled many days in distilled water, the substance
was softened; and the water became slightly turbid with nitro-
muriate of tin; but no effect was produced by the tanning
principle.

4. Muriatic and aalpkaee acids had little effect, unless
heated; and the same was the case with: nitric acid much
diluted, or in the state proper to extract and separate gelatin;
but, if the immersion in the dilute acid was continued during
some weeks, the acid gradually acquired a yellow tinge, and,
when saturated with ammoniac, became of a deeper colour,
without having its transparency disturbed.

5. The substance which had thus been long steeped in the
acid, was much softened, was become more transparent, and,
from being horny, was now more like a cartilaginous sub-
stance: when taken out of the acid, if it was immediately

and Observations on the component Parts of Membrane. 385

Steeped in pure ammoniac, it changed to a deep orange colour,
inclining to blood red; it was gradually and silently dissolved,
without any residuum, and a deep orange or yellowish brown
coloured liquor was formed.

6. Or, when taken out of the acid, if it was first well washed
in distilled water, and then boiled, it was also dissolved, and
formed a pale yellowish solution: this, by evaporation and
cooling, became a jelly, which was again soluble in boiling
water; and was precipitated, like gelatin, by the tanning prin-
ciple, and, more slowly, by nitro-muriate of tin.

_7. If the nitric acid in which the substance was immersed
Was not sufficiently diluted, or if heat was applied, the whole
_ was rapidly dissolved, with a considerable effervescence, and
discharge of nitrous gas. _ |

8. This solution was yellow, like the Btoaiaee the colour
being intense, in proportion to the quantity dissolved; and it -
was also changed to a deep orange or yellowish brown by the
addition of ammoniac, without depositing any precipitate, un~
less a large quantity had been dissolved.

g. The nitric solutions of this substance, when ev dsonbted,
afforded much the same appearances as those of gelatin, but
the coal which remained was less spongy.

10. This substance (whether of sponge, horn, quill, hair, nail,
or tortoise-shell, &c.) was strongly distinguished from gelatin,
by the effects produced when boiled with caustic fixed alkali;
for animal soaps were formed, exactly similar in every property
excepting colour, and the whole of the original substance was
completely dissolved.

11, During the process, a considerable quantity of ammoniac

3D2

386 Mr. Hatcuett’s Experiments on Zoophytes,

was discharged; and, if the alkali was in woe: some wre |
was deposited: .

12. When the animal soap was dissolved, diluted ert dis-
tilled water, and filtrated, if an acid (such as the acetous, or
muriatic ) was added, a copious precipitate was obtained, ee
was re-dissolved by an excess of acid. |

13. This precipitate, being collected upon a filter, nrpceelind at
first like a yellow or brownish viscid substance, which, when
_ dry, was like a thick coat of varnish, or dried white of egg, and
in like manner was brittle, and broke with a glossy fracture.

14. It bummed like quill or tortoise-shell, leaving a spongy
coal; and, when distilled, afforded products like those pug
from the bodies abovementioned..

15. It was not readily soluble in dilute acids; and was acted
upon by nitric acid and ammoniac like the substances from
which it had been obtained; the properties also of its solutions
in nitric acid and ammoniac were similar.

16. With caustic lixivium of potash it ries combined, lahd
‘again formed animal soap.

17. It was not quite so insoluble in boiling water as quill or

tortoise-shell; and the water in which it had been boiled was
not only made turbid by nitro-muriate of tin, but yielded a
precipitate when infusion of oak-bark was added, after the
manner of gelatin.
' These experiments proved, that this precipitate was the same ~
as the original substance from which it had been obtained; and
that the only change it had suffered, was that of ania rendered
rather more soluble in boiling water.

The whole series of sel agi tap on the various bodies lately

and Observations on the component Parts of Membrane. 387

enumerated, convinced me moreover, by the similarity of re-
sults, that’ they essentially consisted of one and the same
substance, modified in texture by the degrees of organic arrange-
ment, and by the occasional piescace, and different proportion
and quality, of gelatin.

But the difference in Shensical properties shewed, that this
last mentioned: substance’(I mean gelatin) was quite distinct
from that: which is now under examination; and, from the
resemblance of certain effects observed when quill and tortoise-
shell. were, compared with inspissated albumen, by being long
digested in boiling water, I was induced to make a series of
comparative: experiments upon albumen, similar in every respect
to those, which have been sa soviet Besealed, of mail she fol-
nme are the results. . cf

i. By distillation, the caermrar ous cerca albus:
meriy.2 afforded products exactly similar to.those obtained from
tortoise- bell, and the. nee rane ahve have just oa
examined: i rtryd) ae bios orvir mruondo ya .O

2. A spongy aia Aa sont very yediffioult i incineration. as
towards the end of the: process it appeared vitrified, and:glazed
with a melted saline coat; which. was; ‘however; ss ee Se
by water. inotuitequa rerio o11t, ai, borditeroos eoornsted:

The residuum was. again bSipclict tora’. hate ‘continued. red
heat, and’ again treated with water, till, at length,.a°few scarcely
visible particles remained; which, as far as such:a ‘small quantity
would permit to be ascertained, proved to be phosphate of lime:

»s The: portion dissolved: by ‘water: (which:was: by muclp the
most ‘considerable ) “consisted principally of Cite dot os nixed
vot a small quantity of phosphate of soda. ga

»°g.0When steeped in dilute nitric acid, it was not soon affected ;

388 Mr. HatcuEtr’s Experiments on: Zoophytes; ...

but, after about four weeks, the acid began to be tinged with
yellow, which gradually became deeper in the course of three
months; the albumen, however, although less transparent, was
but little diminished. hy
The yellow acid solution, when satunited with ammoniac,.
changed to a deep orange colour, and remained transparent.
__ 4 The albumen which had been thus steeped in the dilute
nitric acid, was immediately immersed in ammoniac; which
changed it to a deep orange colour, inclining to a blood red,
and gradually dissolved it, without any apparent residuum.

This solution was of a deep yellowish brown.

§. If the albumen, instead of being immersed in ammoniac,
was washed, and then boiled with distilled water, it was dis-
solved, and formed a pale yellow liquor, which, by evaporation,
formed a gelatinous mass; this, being dissolved again in boiling
water, was (like gelatin) precipitated by the tanning principle,
and more slowly by nitro-muriate of tin.

6. By concentrated nitric acid, or by the dilute acid when
heated, albumen was speedily dissolved, with much efferves-
cence, and:a copious discharge of nitrous gas,

7. This solution was like that of tortoise-shell, and the other
Benes mentioned in the former experiments. |

8. When evaporated, it afforded ‘similar results. —

g. Albumen, like tortoise-shell, quill, and: nail, -was: dis-
solved by boiling naiyinann of caustic pekesly and formed: pena
soap. | | | 0. OF Ua ise
10. In like manner ralso; a tgaelidckabi aditine of ammoniac
was discharged ; and, if the alkali was in ae some coal was
‘deposited. | | W

31, The animal soap obtained Ghing ‘sthantens when dissolved

and Observations on the component Parts of Membrane. 389

in water, yielded a ‘precipitate, by the addition of acetous or
muriatic acid; and the, prenipitate. was s re-dissolved, when the
acid was,added to.excess.

12. This precipitate, when elect on a filter, appeared
more saponaceous, and’ less viscid, than that obtained from the
substances, lately examined.* When gently heated, sonie oil
flowed from its ;after -which, a brownish viscid substance re-
mained, similar in its properties to that which was obtained from
the animal soap: made by tortoise-shell, and the other bodies.--

13. It may not be improper-here to repeat, that inspissated
albumen, long boiled with distilled water, was not’ apparently
diminished; but the water. (like that in which tortoise-shell,
quill, or nail, has been boiled) had acquired the property of
becoming white and turbid; when nitro-muriate of tin was
added, although it was not: changed by the tanning principle.

To this also} may be added, that the water in which tortoises.
shell, nail, and albumen, had been boiled, became in some
measure putrid inja few days, and emitted an offensive smell.

Tam not inclined, however, to;regard this as a proof that any.
gelatin had been separated from these bodies by means of boil-
ing water, bust rather eee allen, tortoise-shell, Se.

* This precipitate, ven obtained. from. different substances, such-as hair, wool,
and muscular fibre, appeared i in some cases ee and in others less viscid, although
similar in every other property. .

It will be proper also here to observe, that the saponaceous solutions were always
filtrated, before the addition of the acids.

+ Tbe yolk of eggs, when boiled with caustic lixivium of potash, fren a pale
olive-coloured concrete animal soap, which, when dissolved in water, and saturated
with muriatic acid, is precipitated in the state of mere fat.

~Yolk of egg, by incineration, ae a small portion of phosphate of soda and
of lime,

390, . Mr. Haronsrr’sExperiments'on Zoophytesy >”

are substances really ‘soluble; although ‘in ‘so slight a degree
as to-approach insolubility; and that thus the prevalent opinion’
has arisen concerning the SAA of) Bi sres albumen’
in boiling: water. :

Neither is the putrefaction. of re water in’which the bodies’
abovementioned have been boiled, a. proof that any other than:
their real substance has been dissolved; for this putrefaction
appears to depend on its attenuated and diluted state, more’
than on any other cause. .' Tortoise-shell, nail, quill, and similar
bodies, certainly are not liable to putrefaction ; neither is albu-
men, when in the inspissated semi-transparent state.

This last substance also, when merely coagulated, does not

easily putrefy; for I kept it, when it was soft, white, and
coagulated, in water, during the whole of the month of last
April, without finding that it became really putrid : towards the
latter part of the time, it had rather a disagreeable smell; still,
however, it was far from being absolutely putrid.

But albumen which has not been coagulated, or which has.
been diluted and shaken with a quantity of cold water, begins
in a very few days to be putrid;- liquid albumen, therefore,
enters easily into putrefaction, although it is the reverse with
that which is dense and solid: and, from a comparison of the
preceding experiments upon tortoise-shell, quill, nail, Gc. with
those made on albumen, I am induced to believe, that the
former bodies are essentially composed of albumen, modified
by the various effects of organization, and reduced to a state’
of density far exceeding that which is produced by simple
inspissation.

And, although the bodies, which of late have been particu-
larly mentioned, appear to consist principally of albumen, with

and Observations on the component Parts of Membrane. 391

sometimes the addition of gelatin in different proportions, yet,
as in certain‘membranes and such like substances, portions of
muscular fibre were at times found joined or interwoven; and
as muscle, ligament, and’ tendon, seem to glide almost imper-
ceptibly into each other, I was almost unavoidably induced to
make some experiments on muscular fibre.

The muscular fibre on which the greater part of these expe-
riments was made, was that of beef; and, in order to separate
the liquid albuminous part or lymph as much as possible, a
quantity of lean muscle of ox beef, cut into small thin pieces,
was macerated during 15 days in cold water, and was subjected
to pressure each day, when the water was changed. The weather
was very cold; and the maceration was continued to the end of
the 15th day, without any sign of putrescency.

The shreds of muscle (amounting to about 3 pounds) were
then boiled with about 6 quarts of water, during 5 hours; and,
the water being changed, the same was repeated every day,
during the course of three weeks; at the end of which time, the
water afforded only slight signs of gelatin, when infusion of
oak-bark, or nitro-muriate of tin, was added. After this, the
fibrous part was well pressed, and was dried by the heat of a
water bath.

Some of the muscular fibre thus prepared, was steeped in
nitric acid diluted with three measures of water, during 15 days.
The acid acquired a yellow tinge, and possessed all the pro-
perties of the nitric solutions of albur-en.

The fibre which had been thus steeped in the acid, was
(when washed) dissolved by boiling water, and by evaporation
became a gelatinous mass; which, being again dissolved in
boiling water, was precipitated by infusion of oak-bark, and,

MDCCC. 3E

399 Mr. Hatcuetr’s Experiments on Zoopbytes,

more slowly, by nitro-muriate of tin, like the albuminous sub-
stances, when treated in a similar mariner.

When the fibre which had been steeped in the acid was
immersed in ammoniac, it was not completely dissolved, like
albumen, but afforded a residuum, which will soon be noticed.
The greater part was, however, thus dissolved; and formed a
deep orange or yellowish brown solution, similar in properties
to that of albumen.

When boiled with lixivium of caustic potash, this muscular
fibre was completely dissolved ; ammoniac was discharged, and
animal soap was formed; which, being diluted with water, and
saturated with muriatic acid, yielded a precipitate, similar in
every property to that which had been obtained from the animal
soaps formerly mentioned, excepting, that it sooner became
hard and glossy, when exposed to the air.*

Muscular fibre, when prepared as already mentioned, so as
(by long maceration, and subsequent boiling, with frequent
change of water) to be very nearly deprived of the whole of its
gelatinous part, is not easily brought into the putrid state. A
small quantity was kept moistened with water, during the
whole of last April; in the course of which time, it acquired a
musty but not a putrid smell; neither were the fibres reduced

* In respect to ceconomical purposes, it may be proper here to observe, that all
animal substances whatever, (exclusive of carbonate and phosphate of lime,) may be
converted into two substances of much utility, namely, glue, (under which term I
include all the varieties mentioned in this paper,) and soap; with the additional

advantage, that those parts which would be rejected in making the one, are the most .

proper to prepare the other.

The offensive smell of CoarTat’s soap is considered as an objection; but this may
be removed, by exposing the soap for some time, in flat vessels, to the air; after which,
it may be reduced to the proper degree of consistency, by a second boiling.

ee

and Observations on the component Parts of Membrane. 398

toa pulpy mass.* I am inclined therefore to suspect, that strong
and completely formed muscular fibre, considered as a distinct
substance, is not of easy putrescibility ; and that the readiness
with which muscle in general enters into putrefaction, is prin-
cipally owing to the gelatin, which is combined and mixed with
it, in a large proportion, as a component part, and which, with
the natural quantity of moisture, is requisite to give the fibre a
proper degree of toughness and flexibility.
_ The residuum afforded by muscular fibre which had been
long steeped in dilute nitric acid, and afterwards immersed in
ammoniac, consisted principally of fat, mixed with a small por-
tion of the fibre which had not been sufficiently acted upon by
the acid; and little or no earthy matter was thus obtained.
But, when the prepared muscular fibre was dissolved in boil-
ing nitric acid, a complete solution, resembling that of albumen,
in its general properties, was formed; and some fat floated, in
drops, at the top of the liquor.
Ammoniac was then added, so as to super-saturate the
acid, and produced the same effects as on the nitric solutions
of albumen, excepting, that a copious white precipitate was
obtained. | )
This precipitate, while moist, was agitated with a quantity of
acetous acid, which dissolved, and separated, a small portion
of phosphate of lime; but the remainder, and by much the
greatest part of this precipitate, was scarcely attacked, even
when the acid was boiled. | |
When exposed to a red heat, it became dark gray, and then

* A portion of this muscular fibre was kept under water during two months ; it
did not however become putrid, nor was it converted into that fatty substance which
is obtained from recent muscle, under similar circumstances.

gE 2

394, Mr. Harcuett’s Experiments on Zoophytes,

nearly white; after which, it was in the state of carbonate of
lime. |

Another part was dissolved in nitric acid, and lime was preci-
pitated by carbonate of soda. The slight excess of the latter was
then saturated by acetous acid; and the whole was boiled, to
expel the carbonic acid; after which, the liquor, from its effects
on solutions of lime, barytes, &c. evidently contained oxalic acid
in solution: the precipitate was therefore oxalate of lime, mixed
with a very small quantity of phosphate of lime. }

200 grains of the dry muscular fibre, dissolved and boiled
with nitric acid, afforded 17 grains of this precipitate.

Although it is known that the gelatinous liquor obtained
from muscle by boiling water, contains phosphate of soda, and
of lime, yet I did not imagine that the greater part of the latter
could be so completely separated.

I therefore, in some measure, repeated the os ietocal on the
muscle of veal; and (as I expected) found phosphate of soda,
and of lime, in the liquor. But, when the muscle was after-
wards dissolved in boiling nitric acid, and the solution was
saturated with ammoniac, I was surprized to find that, although
the same change in colour was produced as in all the former
experiments, the liquor remained transparent; and, even after
several days, only a few scattered particles appeared at the
bottom of the vessel. |

Another experiment was made, on the recent muscle of mut-
ton; but this was immediately dissolved in nitric acid, without
being previously boiled in water. The fat being separated, the
solution was, as before, saturated with ammoniac } and, as usual,

became of a deep orange colour, or yellowish brown: in a few ~

hours also, a small quantity of a white precipitate subsided.

:
.
.

and Observations on the component Parts of Membrane. 395

. This precipitate, however, was completely and readily soluble

in acetous acid; and in every respect proved to be phosphate
of lime.

Before I proceed, it will be proper to observe, that the liquor
from which the above precipitate was separated, as well as those
afforded by the muscie of veal, by the prepared muscle of beef,
by the solutions of tortoise-shell and of albumen, in boiling
nitric acid, subsequently saturated by ammoniac, all contained
a considerable portion of uncombined oxalic acid, which was
separated by acetite of lime, and of lead. But I did not find
oxalic acid in the solutions formed by immersing these bodies,
for a long time, in cold and dilute nitric acid; neither did I find
oxalic acid in solutions made by dissolving these substances
in boiling muriatic acid. It is evident, therefore, that the oxalic
acid observed in the above experiments, was a product of the
operations, and not an educt of the substances.

We may conclude, from the experiments on the muscular
substances which have been lately mentioned, that they con-
tain lime, in various proportions, and in two different states,
viz. carbonate and phosphate; and that the greater part
of the latter is gradually separated, in conjunction with the
gelatin, by means of boiling water. I would not however
have it understood, that phosphate of lime is an essential
ingredient in gelatinous substances; for, on the contrary,
isinglass, which is a perfectly gelatinous body, affords but a
mere visible trace of it. The muscular fibre of beef appears to
have been nearly deprived of its phosphate of lime, by the long
continued and repeated boiling in water to which it had been
subjected ; but still so large a quantity of lime remained, that
when oxalic acid was formed by the action of the boiling

f

396 Mr. Hatcuetr’s Experiments on Zoophytes,

nitric acid, it combined with the lime, and formed an oxalate,
which amounted to 17 grains, from 200 grains of the dry
muscular fibre, dissolved in nitric acid, and precipitated by
ammoniac.

I do not know what quantity of phosphate of lime was
separated with the gelatin, as I was then only intent on prepa-
ring the fibrous part of the muscle; but, from the quantity of
lime which remained, and which afterwards combined with the
oxalic acid, it is evident, that in the muscle of beef there is a con-
siderable portion of earthy matter; and as, by the experiment
on the muscle of veal, scarcely any precipitate was obtained
after it had been boiled, and as but a small portion of phos-
phate of lime was present in the gelatinous liquid, it appears
that, in this muscle, the whole of the small portion of lime
which it contained was in the state of phosphate; and this being
nearly separated, there did not remain any part of uncombined
lime, or carbonate of lime, which, by uniting with the oxalic
acid, (subsequently produced,) would form an oxalate; and as
lime, in the states of phosphate and carbonate, is so much more
abundant in the muscle of beef than in that of veal, we may
infer, that the earthy matter is more abundant in the coarse and
rigid fibre of adult and aged animals, than in the tender fibre
of those which are young; and this seems to be corroborated,
by the tendency to morbid ossification, so frequently observed
in aged individuals of the human species.

Gelatin, albumen, and muscular fibre, not only differ very
much from each other by the relative quantity of their saline
or earthy residua, but also by the proportion of one of their
essential and elementary principles, namely, carbon. 500 grains
of isinglass, made perfectly dry by distillation, yielded 56 grains

and Observations on the component Parts of Membrane. 397

of coal, from which, 1,50 grains of earthy residuum, obtained
by incineration, being deducted, the proportion of coal appears
to have been 54,50 grains.

500 grains of dry albumen, afforded 74,50 grains; and, as
the saline residuum amounted to 11,25 grains, the quantity of
mere coal was 63,95 grains.

500 grains of tortoise-shell, yielded 80 grains of coal; from
which, 3 grains of earthy matter being deducted, 77 grains
remain, for the proportion of coal.

And 500 grains of the dry prepared muscular fibre of beef,
when distilled, left 108 grains of coal, which, by incineration,
afforded 25,60 grains of earthy residuum ; the coal may there-,
fore be estimated at 82,40 grains.

There appears much reason therefore to believe, that the
gelatinous substances and muscular fibre, differ from simple
and unorganized albumen, by a diminution of the carbonic prin-
ciple in the one, and by an excess of it in the other; and as,
in vegetables, the fibrous part is that which contains the largest
proportion of carbon, so, in respect to the other animal sub-
stances, muscular fibre appears to contain the greatest quantity
of it.

The nature of the residua obtained by the incineration of the
substances lately mentioned, also deserves to be noticed.

Only 1,50 grain was obtained from 500 grains of isinglass ;
and, as far as the quantity would allow, was proved to be
phosphate of soda, mixed with a very minute proportion of
phosphate of lime.

The g grains afforded by tortoise-shell, consisted of phos-
phate of soda and of lime, with some traces of iron: it is
probable, that the latter was accidentally present.

998 Mr. Hatcuett’s Experiments on Zoopbytes,

The prepared muscular fibre of beef yielded 25,60 grains ; the
greatest part of which was carbonate of lime, mixed with some
pure lime, and a small portion of phosphate: there can be no.
doubt but that the latter would have been more abundant, had
it not been for the repeated boilings to which the muscular
fibre had been subjected.

The recent muscles of veal and mutton were with great dif-
ficulty reduced to ashes; for, towards the end of the process,
the ashes and remaining coal became coated and glazed with
saline matter, which appeared to be soda, partly in the state of
phosphate; and it is not a little remarkable, that the 11,25
grains obtained from albumen, consisted principally of soda,
in a caustic state, (by reason of the long continued heat, ) mixed
with a small quantity of phosphate of soda, and a very minute
portion of phosphate of lime. )

Pure albumen, therefore, which has not been subjected to
the effects of organization, appears to contain a considerable
portion of saline matter, and very little of any earthy sub-
stance; but the contrary seems to happen, in bodies which
(although evidently derived from albumen) have suffered various
changes by the action of the vital principle; which may be
considered as the cause of organization, by which these bodies
are differently modified, according to the nature of the parts of
animals which, singly or conjointly, they are employed to form.
In these bodies, the quantity of the saline substances appears
to be diminished, while that of the earthy matter is increased,
especially in the coarser kinds of muscular fibre.

Upon a comparison of the chemical properties of the sub-
stance which remains, after the separation of gelatin from the —
great variety of animal substances which have been so often

and Observations on ihe component Parts of Membrane. 399

mentioned in the course of this paper, and which need not
therefore now be repeated, there can scarcely be any doubt but
that it is one and the same substance, 1 in different states of den-
sity and texture.

For the similarity of its nature was proved by,

ist. The effects of fire, and the products obtained by distil-
lation.

_ edly. Its very difficult solubility by long digestion in boil-
ing water.

gdly. The effects produced by re-agents, on the water in
which bodies like inspissated albumen or tortoise-shell had been
boiled. 7
4thly. The effects of acids, (particularly nitric acid,) of am-
moniac, and of caustic lixivium of potash.

5thly. The animal soap which was formed; and the pre-
cipitate obtained from it, by the addition of acetous or muriatic
acid.* And,

6thly. The difficulty noses the putrefaction of the sub-
stance in question, when pure and dense.

‘The similarity in all these properties, appears to me a full
proof, that it is the same substance which constitutes the prin-
cipal part of membrane, sponge, horn, hair, &c. and even of
muscular fibre.

Moreover, upon comparing the properties of this substance
with those of pure albumen in a state of inspissation, so evident
a resemblance in every respect is discovered, that few I believe
will hesitate to pronounce albumen to be the original substance
from which tortoise-shell, hair, horn, muscular fibre, &c. have
been derived and formed.

* This appears to be a strong marked character of the albuminous substances.

MDCCC. 3F

400 ~ Mr.Hatcnerr’s Experiments on Zoopbytes, .

There is also much reason to believe that gelatin, although it it

appears so different in many respects from albumen, is Re
formed from it.*

It may be recollected, that in a former part of this paper
mention was made, that tortoise-shell, horn, muscular fibre, and
inspissated albumen, after long immersion in very dilute nitric
acid, and after being well washed, were soluble in boiling water;
and that a substance was formed, which (by becoming liquefied
when heated, by being soluble in boiling water, by being preci-_
pitated by the tanning principle and by nitro-muriate of tin, and
lastly, by forming a gelatinous mass when the aqueous solution

* In addition to the chemical properties by which gelatin and albumen are dis-
tinguished, particularly the different effects observed when these two substances were
treated with nitric acid, I shall mention some others, not less remarkable, which are
produced by the muriatic acid.

When any of the varieties of gelatin, such as glue, isinglass, &%c. are immersed in
cold muriatic acid, they are dissolved in a few hours; and the solutions thus formed
suffer no apparent change, even in the course of several months. In like manner,
gelatin may be separated and dissolved from bodies which contain it, such as sponge,
bladder, skin, and muscle; but the part which remains undissolved, and which, with
the other substances formerly mentioned, I regard as formed of albumen more or less
organized, is very differently affected; for, when coagulated albumen, the undissolved
part of bladder, muscular fibre, feather, quill, tortoise-shell, wool, and hair, were
separately steeped in muriatic acid, they gradually became of a dark colour, and the
acid was tinged with the same. The colour afforded by albumen was deep blue,
inclining to purple; that of bladder was brownish purple; feather, quill, tortoise-shell,
and muscular fibre, afforded a beautiful deep blue; and wool and hair, like bladder,
produced a brownish purple. The change began to take place in the coagulated
albumen in about eight or ten days; but wool and hair were the last which were affected.
In about three months, the different liquids were become very dark, although scarcely
any perceptible quantity of the immersed substances appeared to be dissolved. Nitric
acid, in a small proportion, changed these blue and brownish purple liquors to deep
yellow ; and ammoniac, being then added, changed them to orange colour, and pro-
duced all those effects which were observed, when the nitric solutions of these
substances were thus treated.

and Observations on the component Parts of Membrane. 401

was sufficiently evaporated and cooled,) approached and re-
‘sembled gelatin.

It would be perhaps too hasty to assert, that gelatin was thus
absolutely formed; but, if a substance so very similar to it
could be thus produced, we may with some reason conclude,
that the real gelatin, with its various modifications, is formed
from albumen, by the more efficacious and delicate operations of
nature.

In attempting to prove that albumen or the coagulating lymph
is the original animal substance, I have hitherto only stated
chemical facts; but, when the phenomena attending incubation
are considered; when the experiments made by eminent physio-
logists, such as Hauer, Maitre Jean; and Matricui, are
viewed; when the oviparous foetus is seen to be progressively
formed in and from the albumen of the egg, so that, upon the
bursting of the shell which separated it from external matter,
the young animal comes forth complete in all its parts; when
such strong facts as these are corroborated by those afforded
by chemistry, it can scarcely be doubted that albumen is the
primary animal substance, from which the others are derived ;
and there is much cause to believe that the formation of gelatin,
and of the animal fibre especially, begins with the process of
sanguification in the foetus. _

As the three principal and essential component parts of the
blood, viz. albumen, gelatin, and fibre,* appear therefore to

__ ® The whole of the blood, which by anatomists is divided into serum, red globules,
and coagulating lymph, when chemically examined, is found to consist of albumen,
gelatin, and fibre. The serum which remains liquid after the coagulation of the blood,
is composed of albumen, gelatin, some saline matter, and much water.

The clot or crassamentum also affords, by repeated washing, a large proportion of

3F 2

402 Mr, Hatcnett’s Experiments on Zoophytes, &c.

compose the various parts of animals, in such a manner that
one (being predominant) influences the nature of that part of
the animal which it is principally employed to form; and as
albumen, gelatin, and fibre, by relative proportion, by the de- —
grees of density, by the effects of organization which singly or
conjointly they have experienced, by the texture of the animal
substance which they, as materials and thus modified, have
concurred to produce, and by the proportion of natural or
inherent moisture peculiar to each part of different animals,
present an immense series of complicated causes, so are the —
effects found to be no less numerous and diversified, by the
infinite variety in texture, flexibility, elasticity, and the many
other properties peculiar to the various parts which compose ie
bodies of animals.

albumen and gelatin; after which, a substance remains, in appearance very analogous
to muscular fibre, excepting that it is in a more attenuated state. This substance
(called fibrin by chemists) may be regarded as that part of the blood which has
undergone the most complete animalization ; and from which the muscular fibre and
other organs of the body are formed. —

C 403 7}

XVEH. On the Electricity excited by the mere Contact of conduct-
ing Substances of different kinds. In a Letier from Mr.
Alexander Volta, F. R. S: Professor of Natural Philosophy in
the University of Pavia, to the Rt. Hon, Sir salle Banks,
Bart, K. B. P. RLS.

Read June 26, 1800.

A Céme en Milanois, ce zome Mars, 1800.
Avprss v un long silence, dont je ne chercherai pas a m’excuser,
jai le rd oe de vous communiquer, Monsieur, et par votre
moyen a la Société Royale, quelques resultats frappants aux-
quels je suis arrivé, en poursuivant mes expériences sur I’élec-
tricité excitée par le simple contact mutuel des métaux de diffé-.
rente espéce, et méme par celui des autres conducteurs, aussi
différents entr’eux, soit liquides, soit contenant quelque humeur,
a laquelle ils doivent proprement leur pouvoir conducteur. Le
principal de ces resultats, et qui comprend a-peu-prés tous les
autres, est la construction d’un appareil qui ressemble pour les
effets, c’est-a-dire, pour les commotions qu’il est capable de faire
éprouver dans les bras; &¢. aux bouteilles de Leyde, et: mieux
encore aux batteries électriques foiblement chargées, qui agiroient
cependant sans cesse, ou dont la charge, aprés chaque explosion,
se rétabliroit d’elle-méme ; qui jouiroit, en un mot, d’une charge
indéfectible, d’une action sur le fluide électrique, ou impulsion,
perpétuelle; mais qui d’ailleurs en. différe essentiellement, et

404 Mr. Vouta on the Electricity excited by the Contact

par cette action continuelle qui lui est propre, et parcequ’au lieu
de consister, commes les bouteilles et batteries électriques ordi-
naires, en une ou plusieurs lames isolantes, en couches minces
de ces corps censés étre les seuls électriques, armées de conduc-
teurs ou corps ainsi dit non-électriques, ce nouvel appareil est
formé uniquement de plusieurs de ces derniers corps, choisis
méme entre les meilleurs conducteurs, et par la les plus éloignés,
suivant ce qu’on a tofjours cru, de la nature électrique. Oui,
Pappareil dont je vous parle, et qui vous étonnera sans doute,
n’est que l’assemblage d’un nombre de bons conducteurs de
différente espéce, arrangés d’une certaine maniére. 30, 40, 60
piéces, ou d’avantage, de cuivre, ou mieux d’argent, appliquées
chacune a une piéce d’étain, ou, ce qui est beaucoup mieux, de
zinc, et un nombre égal de couches d’eau, ou de quelque autre
humeur qui soit meilleur conducteur que l’eau simple, comme
l’eau salée, la lessive, &c. ou des morceaux de carton, de peau,
&c. bien imbibés de ces humeurs; de telles couches interposées
a chaque couple ou combinaison des deux métaux différents, une
telle suite alternative, et totyours dans le méme ordre, de ces
trois espéces de conducteurs, voila tout ce qui constitue mon
nouvel instrument ; qui imite, comme j’ai dit, les effets des bou-
teilies de Leyde, ou des batteries électriques, em donnant les
mémes commotions que celles-ci; qui, a la vérité, reste beaucoup
au-dessous de l’activité des dites batteries chargées 4 un haut
point, quant a la force et au bruit des explosions, a l’étincelle,
a la distance a laquelle peut s’opérer la décharge, &c. egalant
seulement les effets d’une batterie chargée a un, degré trés-
foible, d’une batterie pourtant ayant une capacité immense;
mais qui d’ailleurs surpasse infiniment la vertu et le pouvoir de
ces mémes batteries, en ce qu’il n’a pas besoin, comme elles,

of conducting Substances of different kinds. 405

d’étre chargé d’avance, au moyen d’une électricité étrangére; et
en ce qu’il est capable de donner la commotion, toutes les fois —
qu’on le touche convenablement, quelques fréquents que soient
ces attouchements. ie

Cet appareil, semblable dans le fond, comme je ferai voir, et
méme tel que je viens de le construire, pour la forme, a l’organe
électrique naturel de la torpille, de l’anguille tremblante, &c. bien,
plus qu’a la bouteille de Leyde, et aux batteries électriques con-
nues, je voudrois l’appeller Organe électrique artificiel, Kt au vrai
n’est-il pas, comme celui-la, composé uniquement de corps con-
ducteurs ? n’est-il pas au surplus actif par lui-méme, sans au-
cune charge précédente, sans le sécours d’une électricité quel-
conque excitée par aucun des moyens connus jusqu ici ; agissant
sans cesse, et sans relache; capable enfin de donner a tout
moment des commotions plus ou moins fortes, selon les circon-
stances, des commotions qui redoublent a chaque attouchement,.
et qui, repétées ainsi avec fréquence, ou continuées pour un cer-
tain tems, produisent ce méme engourdissement des membres:
que fait éprouver la torpille, &c.? -

Je vais vous donner ici une description plus. détaillée de cet
appareil, et de quelques autres analogues, aussi bien que des
expériences relatives les plus remarquables.

_ Je me fournis de quelques douzaines de petites plaques rondes
_ ou disques, de cuivre, de laiton, ou mieux d’argent, d’un pouce
de diamétre, plus ou moins, (par exemple, de monnoyes,) et d’un
nombre égal de plaques d’étain, ou, ce qui est beaucoup mieux, de
zinc, de la méme figure et grandeur, a-peu-preés ; je dis a-peu-
pres, parcequ’une précision n’est point requise, et, en général,
la grandeur, aussi bien que la figure, des piéces métalliques, est
arbitraire: on doit avoir égard seulement qu’on puisse les

406 Mr. Voxta on the Electricity excited by the Contact

arranger commodément les unes sur les autres, en forme de co-
lonne. Je prépare en outre, un nombre assez grand de rouelles
de carton, de peau, ou de quelque autre matiére spongieuse,
capable d’imbiber et de retenir beaucoup de l’eau, ou de l’hu-
meur dont il faudra, pour le succés des expériences, qu’elles
soient bien trempées. Ces tranches ou rouelles, que j’appellerai
disques mouillés, je les fais un peu plus petites que les disques
ou plateaux métalliques, afin qu’interposées a ceux, de la ma-
niére que je dirai tantdt, ils n’en débordent pas. —

Ayant sous ma main toutes ces piéces, en bon état, c’est-a-
dire, les disques métalliques bien propres et secs, et les autres
non-meétalliques bien imbibés d’eau simple, ou, ce qui est beau-
coup mieux, d’eau salée, et essuyés ensuite légérement, pour
que l’humeur n’en dégoutte pas, je n’ai plus qu’a les arranger
comme il convient ; et cet arrangement est simple et facile.

Je pose donc horizontalement sur une table ou base quel-
conque, un des plateaux métalliques, par exemple, un d’argent,
et sur ce premier j’en adapte un second de zinc; sur ce second
je couche un des disques mouillés ; puis un autre plateau d’ar-
gent, suivi immédiatement d’un autre de zinc, auquel je fais
succéder encore un disque mouillé. Je continue ainsi, de la
méme facon, accouplant un plateau d’argent avec un de zinc,
et totjours dans le méme sens, c’est-a-dire, totijours l’argent
dessous et le zinc dessus, ou vice versd, selon que j’ai commencé,
et interposant a chacun de ces couples, un disque mouillé ; je
continue, dis-je, a former, de plusieurs de ces étages, une colonne
aussi haute qu’elle peut se soutenir.sans s’écrouler. |

Or, si elle parvient a contenir environ 20 de ces étages ou
couples de métaux, elle sera déja capable, non seulement de
faire donner des ‘signes a l’électrometre de CAVALLO, aidé du.

of conducting Substances of different kinds. 40F

condensateur, au-dela de 10 ou 15 dégrés, de charger ce con-
-densateur par ‘un simple attouchement, au point de lui faire
donner une étincelle, &c. mais aussi de frapper les doigts avec
lesquels on vient toucher ses deux extremités, (la téte et le pied
d'une telle colonne, ) d’un ou de plusieurs petits coups, et plus ou
moins fréquents, selon qu’on réitére ces contacts; chacun des-
quels coups ressemble parfaitement a cette légére commotion
que fait éprouver une bouteille de Leyde foiblement chargée, ou
une batterie chargée beaucoup plus foiblement encore, ou enfin
une torpille extrémement languissante, qui imite encore mieux
les effets de mon appareil, par la) suite des coups répétés qu’elle
peut donner sans cesse. )

Pour obtenir de telles légéres commotions de cet appareil que
je viens de décrire, et qui est encore trop petit pour de grands
effets, il est. nécessaire que les doigts avec lesquels on veut
toucher ses deux extremités en méme tems, soient humectés
d’eau, au point que la peau, qui autrement n’est pas un assez bon
conducteur, se trouve bien trempée.. Encore, pour réussir plus
surement, et recevoir des commotions considérablement plus
fortes, faut-il faire communiquer, par le moyen d’une lame suf-
fisamment large, ou d’un gros fil métallique, le pied de la
colonne, c’est-a-dire, le plateau du fond, avec l’eau d’un bassin
ou coupe assez grande, dans laquelle on tiendra plongé un doigt,
deux, trois, ou toute la main, tandis qu’on ira’ toucher la téte
ou extrémité supérieure, (le dernier ou un des derniers plateaux
de cette colonne, ) avec I’extrémité nette d’une lame aussi métal-
lique, empoignée par lautre main, qui doit étre bien humide,
et embrasser une large surface de cette lame,et la serrer forte-
ment. En procédant de cette maniére, je puis déja obtenir

un petit picotement, ou légére commotion, dans une ou deux
MDCCC. 3G

408 Mr. Vouta on the Electricity excited by the Contact

articulations d’un doigt plongé dans l’eau du bassin, en touchant,
avec la lame empoiginée dans: l’autre main, la quatriéme, ou
méme la troisiéme paire de plateaux; touchant ensuite la
cinquiéme, la sixiéme, et de proche en proche les autres, jusqu’
au dernier plateau, qui fait la téte de la colonne, il est curieux

d’éprouver comment les: commotions augmentent graduellement -

en force. Or, cette force est telle, que je parviens 4 recevoir d’une

telle colonne, formée de 20 paires de plateaux, (pas davantage,)

des commotions qui prennent tout le doigt, et l’affectent méme
assez douloureusement, s’il est plongé seul dans ]’eau, du bassin ;
qui s’étendent (sans douleur) jusqu’au poignet, et méme jusqu’
au coude, si la main est plongée en grande partie, ou entiére-
ment, et se font sentir encore au poignet de l’autre main.

Je suppose totjours qu’on ait pratiqué toutes. les: attentions
nécessaires dans la construction de la colonne, que chacune des
paires ou couples de métaux, resultant d’une plaque d’argent

appliquée 4 une de zinc, se trouve en communication avec la |

couple suivante, par une couche suffisante d’humeur, qui soit de
lieau salée, plutét que del’eau pure, ou par un disque de carton;
de peau, ou autre chose semblable, bien imbibée decette eausalée;
lequel disque ne soit pas trop petit, et dont les surfaces soient
bien collées aux surfaces des plateaux métalliques, entre lesquels
il se trouve interposé. Cette application. exacte et étendue des
disques. mouillés, est trés-importante; au lieu que les plateaux
métalliques de chaque paire, peuvent ne se'toucher entr’eux qu’en
peu de points; pourvu seulement que leur contact soit immédiat:

Tout cela fait-voir (pour le dire ici en passant) que si le con-
tact des métaux entr’eux en quelques points seulement suffit
(étant tous d’excellents conducteurs) pour donner libre passage

a'un courant électrique médiocrement fort, il n’en est pas de

:
q
:
;

of conducting Substances of different kinds. 409

méme pour les liquides, ou pour les corps imbibés d’humeur, qui
sont des conducteurs beaucoup moins parfaits, et qui, par consé-
quent, ont besoin d’un ample contact avec les conducteurs mé-
talliques, et plus encore entr’eux, pour que le fluide électrique
puisse passer avec assez de facilité, et pour qu’il ne soit pas trop
retardé dans son cours, sur-tout lorsqu’il est mu avec trés-peu
de force, comme dans notre cas. |

Au reste, les effets de mon appareil (les commotions qu’on
éprouve) sont considérablement plus sensibles, 4 mesure que la
température de lair ambient, ou celle de l’eau, ou des disques
mouillés qui entrent dans la composition de la colonne, et de
l’eau méme du bassin, est plus chaude; la chaleur rendant l’eaw:
plus conductrice. Mais, ce quila rend beaucoup meilleure encore,
ce sont presque tous les sels, et notamment le sel commun. Voila
une des raisons, sinon la seule, pourquoi il est si avantageux que
Yeau du bassin, et sur-tout celle interposée 4 chaque paire de
plateaux métalliques, Peau dont’ sont imbibés les disques de car- |
ton, &c. soit’ de l’eau salée, comme j’ai déja fait remarquer.

Mais tous ces moyens, et toutes ces attentions, enfin, n’ont
qu’un avantage limité, et ne feront jamais. qu’on puisse obtenir
des commotions bien fortes, tant que l’appareil ne consistera
qu’en une seule colonne formée de 20 paires seulement de
plateaux, quoiqu’ils soient des deux meilleurs métaux pour ces:
expériences, scavoir, d’argent et de zinc; car, s’ils étoient d’ar-
gent et de plomb, ou d’étain, ou de cuivre et d’étain, on n’obtien-
droit pas la moitié de l’effet, 4 moins qu’un nombre beaucoup
plus grand ne suppléat a la moindre force de chaque paire. Or
donc, ce qui augmente réellement la puissance électrique de
cet appareil, et la peut porter au degré d’égaler, et de surpasser
encore, celle de la torpille et de Yanguille tremblante, c’est le

3Ge 3

410 Mr.Vouta on the Electricity excited by the Contact

nombre des plateaux, arrangés de la maniére, et avec les
attentions, que j’ai expliqué. Si, aux 20 paires décrites ci-dessus,
on en ajoute 20 ou go autres, disposées dans le méme ordre, les
commotions que pourra donner la colonne ainsi prolongée, (je
dirai tantot comment on peut la soutenir, pour qu'elle ne s’é-
croule pas, ou, ce qui est mieux, la partager en deux ou plusieurs
colonnes, ) seront déja beaucoup plus fortes, et s’étendront dans
les deux bras jusqu’a I’épaule, sur-tout dans celui dont la main
est plongée dans l’eau; laquelle main, avec le bras entier, en res-
tera plus ou moins engourdie, si, en réitérant les attouchements
avec fréquence, on fait succéder ces commotions I’une a l’autre

rapidement, et sans relache. Cela, en plongeant toute, ou:
presque toute, la main dans l’eau du bassin; mais, si on ne

plonge qu’un doigt seul, en tout ou en partie, les commotions
concentrées presque dans lui seul, en seront d’autant plus dou-
loureuses, et si cuisantes qu’elles deviendront insupportables. |
On. s’attend bien que cette colonne, formée de 40 ou 50
couples demétaux, qui donne des commotions plus que médiocres
aux deux bras d’une personne, pourra en donner encore de sen-

sibles a plusieurs, qui, se tenant par leurs mains, (suffisamment

humides,) forment une chaine non interrompue.
‘Revenant a la construction mecanique de mon appareil, qui
est susceptible de plusieurs variations, je vais décrire ici, non pas

toutes celles que j’ai imaginées et exécutées, soit en grand, soit -

en petit, mais quelques unes seulement, qui sont ou plus cu-
rieuses, ou plus utiles; qui présentent quelqu’ avantage réel,
comme d’étre d’une exécution plus facile, ou plus expéditive,
’étre plus immanquables dans leurs effets,.ou plus long-tems
conservables en bon état. . re
Et pour commencer par une, qui, réunissant 4-peu-preés tous

:
:

oa

of conducting Substances of different kinds. 411

ces avantages, différe le plus, quant a sa figure, de /’appareil a
colonne décrit ci-dessus, mais qui a le desavantage d’étre une
machine beaucoup plus volumineuse ; je vous présente ce nouvel
appareil, que j’appellerai a@ couronne de tasses, dans la figure ci-
jointe. (Pl. XVII. Fig. 1.) |

On dispose donc une rangée de plusieurs tasses ou coupes,
de quelque matiére que ce soit, exceptés les métaux, de tasses
de bois, d’ecaille, de terre, ou mieux de cristal, (des petits verres
a boire ou gobelets, sont les plus a-propos,) 4 demi pleines
d’eau pure, ou mieux d’eau salée, ou de lessive; et on les fait
communiquer toutes, on en forme une espéce de chaine, par le
moyen d’autant d’arcs metalliques, dont un bras A a, ou seule-
ment l’extrémité A, qui plonge dans un des gobelets, est de
culvre rouge, ou jaune, ou mieux de cuivre argenté, et l’autre Z,
qui plonge dans le gobelet suivant, est d’étain, ou mieux de
zinc. J’observerai ici, en passant, que la lessive et les autres
liqueurs alcalines sont préférables, lorsqu’ un des métaux qui
doivent plonger,-est.l’étain ; l’eau salée est préférable, lorsque
cest le zinc. Les deux métaux dont chaque arc se compose,
sont soudés ensemble, dans quelque endroit que ce soit, au-des-
sus de la partie qui plonge dans le liquide, et qui doit le toucher
par une surface suffisamment large: il est pour cela convenable,
que cette partie soit une lame d’un pouce quarré, ou trés-peu
moins; le reste de l’arc peut étre plus étroit tant qu’on veut, et
méme un simple fil métallique. Il peut aussi étre d’un troisiéme
meétal, différent des deux qui plongent dans le liquide des gobe-
lets; puisque l’action sur le fluide électrique, qui résulte de tous
les contacts de plusieurs métaux qui se succédent immédiate-
ment, la force avec laquelle ce fluide se trouve poussé a la fin,
est la méme absolument, ou a-peu-prés, que celle qu’il auroit.

412 Mr. Voura on the Electricity. excited by the Contact -

recu par le contact immediat du premier métal avec le dernier,
sans aucun des métaux intermédiaires, comme j’ai verifié par des
experiences directes, dont j’aurai occasion de parler ailleurs.
Or donc, une suite de go, 40, 60, de ces gobelets, enchainés
de cette maniére, et rangés, soit dans une ligne droite, soit dans
une courbe, ou repliée de toutes les maniéres, forme tout ce
nouvel appareil ; qui dans le fond, et en substance, est le méme
que l’autre a colonne, décrit plus haut; lessentiel, qui consiste
dans la communication immediate des métaux différents qui
forment chaque couple, et médiate d’une couple avec lautre,
savoir, par l’interméde d’un conducteur humide, ayant lieu pour
l’un, aussi bien que pour Il’autre de ces appareils. |
Quant a la maniére de mettre celui a gobelets a épreuve, et
quant aux différentes expériences auxquelles il peut servir, je
nai pas besoin d’en dire beaucoup, aprés ce que jai fait observer,
et expliqué amplement, au sujet de l’autre a colonne. On com-
prendra aisément, que pour avoir la commotion, il suffit de.
plonger une main dans un des gobelets, et un doigt de l'autre
main dans un autre gobelet, assez eloigné de celui-la; que
cette commotion sera d’autant plus forte que ces deux vases
seront plus éloignés l’un de autre, c’est-a-dire, qu’il y en aura
un plus grand nombre d’intermédiaires ; que, par conséquent, on.
aura la plus forte, en touchant le premier et le dernier de la
chaine. On comprendra aussi comment, et pourquoi, les expé-
riences réussiront beaucoup mieux, en empoignant, et serrant,
dans une main bien humectée, une lame métallique aSS€Z large,
(afin que la communication soit ici assez parfaite, et se fasse par
un grand nombre de points,) et touchant avec cette lame l’eau
du gobelet, ou plutdt l’are métallique designé, tandis que I’autre
main se trouve plongée dans Yautre gobelet éloigné, ou touche,

of conducting Substances of different kinds. 413
avec une lame empdigniée dé méme, l’are de celui-ci. Enfin on
comprendra, ét on pourra méme prévoir le succés d’une grande

_variété d’expériences, qu’on peut exécuter avec cet appareil a
couronne de tasses, plus facilement, et d’une maniéré plus evi-
dente et parlante, pour ainsi dire, aux yeux, qu’avec l’autre
appareil a colonne. Je me dispenserai donc de décrire un grand
nombre de ces expériencés faciles 4 deviner, et j’en rapporterai
seulement quelques unes, qui ne sont pas moins instructives
qu’amusantes. .

Soient trois vingtaines de ces tasses ou gobelets, rangés et
enchaihés |’un a l’autre par les arcs métalliques, mais de facon
que; pour la premiére vingtaine, ces arcs soient tournés dans le
méme sens, par exemple, le bras d’argent tourné a gauche, et le
bras de zinc a droite; et pour la seconde vingtaine, en sens con-
traire, c’est-a-dire, le zinc 4 gauche, et l’argent a droite; enfin,
pour la troisiéme vingtaine, de nouveau, l’argent 4 gauche, comme
pour la premiére. Ces choses ainsi disposées, plongez un doigt
dans l’eau du premier gobelet, et touchez, avec la lame em-
poignée par l’autre main, de la manieére préscrite, le premier arc
métallique, (celui qui joint le premier gobelet au second,) puis
autre arc qui embrasse le second et le troisiéme gobelet, et suc-
cessivement les autres‘ arcs, jusqu’a les parcourir tous. Si l’eau
est bien salée et tiéde, et la peau des mains assez humectée et

‘ramollie, vous:‘commencerez déja 4 éprouver une petite commo-
tion dans le doigt, lorsque vous serez parvenu a toucher le 4e
ou le 5e arc; (je l’ai éprouvée quelquefois assez distinctement
par le contact du ge;) et, en passant successivement au 6e, 7e, &c.
les secousses augmenteront graduellement de force, jusqu’au g0e
arc, c’est-a-dire, jusqu’au dernier de ceux tournés dans le méme
sens: mais, en passant outre, au 21¢, 22e, 23e, ou 1er, ad, 3e,

414, Mr. Vouta on the Electricity excited by the Contact

de la seconde vingtaine, dans laquelle ils sont tous tournés en sens
contraire, les secousses deviendront 4 chaque pas moins fortes,
si bien, qu’au 36e, ou g7e, elles seront imperceptibles, et abso-
lument nulles au 40e; passé lequel, (et commencant la troisieme

a

vingtaine, opposée a la seconde, et analogue a la premiére,) les —

secousses seront encore imperceptibles, jusqu’au 4.4e ou 4,5€ arc ;

mais elles recommenceront a dévenir sensibles, et a augmenter

graduellement, a mesure que vous avancerez, jusqu’au 6oe, ou
elles seront arrivées 4 la méme force du 20e arc.

Or, si les go arcs du milieu étoient tournés dans le méme sens
que les 20 précedents et les 20 suivants, si tous les 60 conspi-
roient a pousser le fluide électrique dans la méme direction, on
comprend de combien l’effet seroit plus grand a la fin, et la
commotion plus forte; et en général on comprend comment,
et Jusqu’ 4 quel point, elle doit étre affoiblie, dans tous les cas

ou un nombre plus ou moins grand de ces forces, par la position —

des métaux a l’opposite, se contrarient.

Si la chaine est interrompue quelque part, soit que l’eau
manque dans une des tasses, soit qu’un des arcs métalliques ait
été enlevé, ou qu'il soit séparé en deux pieces, vous n’aurez

aucune commotion en plongeant un doigt dans |’eau du premier, |

et un autre dans l|’eau du dernier vase; mais vous l’aurez, forte
ou foible, selon les circonstances, (laissant ces doigts plongés, )
au moment qu’on rétablira la communication rompue, au mo-

ment qu'une autre personne plongera dans les deux tasses ot

manque l’arc, deux de ses doigts, (qui seront aussi frappés

d’une légére commotion, ) ou mieux, qu’elle y plongera ce méme

arc qu'on avoit dté, ou un autre quelconque; et, dans le cas de
Yarc separé en deux piéces, au moment qu’on ramenera celles-

:

ci au contact mutuel; (de dogualles maniere la commotion. sera

ah

of conducting Substances of different kinds. ALS

plus forte qu’autrement;) enfin, dans le cas de la tasse vuide, au
moment qu’en y versant de l’eau, elle abordera aux deux bras
meétalliques enfoncés dans cette tasse, et qui se trouvoient 4

Lorsque la chaine ou couronne de tasses est assez longue, et
en état de pouvoir donner une forte commotion, on |’éprouvera,
quoique beaucoup plus foible, quand méme on tiendroit plongés
les deux doigts, ou les deux mains, dans un seul bassin d’eau
assez grand, dans lequel aboutissent le premier et le dernier arc
métallique, pourvu que l’une ou l’autre de ces mains enfoncées,
ou mieux toutes les deux, on les tienne respectivement en con-
tact de ces mémes arcs, ou assez pres du contact; on éprouvera,
dis-je, une commotion, aumoment que (la chaine se trouvant in-
terrompue quelque part) la communication sera rétablie, et le
cercle completé, d’une des maniéres qu’on vient de dire. Or, on
pourroit étre surpris, que dans ce cercle, le courant électrique,
ayant son passage libre a travers une masse d’eau non interrom-
pue, dans cette eau qui remplit le bassin, quitte ce bon conduc-
teur, pour se jetter, et poursuivre son cours, a travers le corps de
la personne qui tient ses mains plongées dans cette méme eau,
en faisant ainsi un plus long trajet. Mais la surprise cessera, si
on reflechit, que les substances animales vivantes et chaudes, et
sur-tout leurs humeurs, sont en général des meilleurs conduc-
teurs que l’eau. Le corps done de la personne qui plonge
les mains dans l'eau, offrant un passage plus facile que cette
eau au torrent électrique, celui-cr doit le préférer, quoiqu’un
peu plus long. Au reste, comme le fluide électrique, lorsqu’il
doit traverser en quantité, des conducteurs qui ne sont pas par-
faits, et nommément des conducteurs humides, aime a s’é-

tendre dans un canal plus large, ou a se partager en plusieurs,
MDCCC. ec es |

416 Mr. Vota on the Electricity excited by the Contact

et A prendre méme des détours, trouvant en cela moins de résis-
tance qu’a suivre un seul canal, quoique plus court; ce n’est
dans notre cas qu’une partie du torrent électrique, qui, s’ecartant
de l'eau, prend cette nouvelle route de la personne, et la par-
court d’un bras a l’autre: une autre partie, plus ou moins grande,
passe a travers l’eau du bassin. Voila la raison pourquoi la
secousse qu’on éprouve, est beaucoup plus foible que lorsque le
courant électrique n’est point partage, lorsque la personne fait
seule la communication d’un arc a l’autre, &c.

D’aprés ces expériences, on peut croire, que lorsque la edicts
veut donner une secousse aux bras de l’homme, ou aux animaux
qui la touchent, ou qui s’approchent de son corps sous l’eau, (la-
quelle secousse est pareillement beaucoup plus foible que celle
que le poisson peut donner hors de |’eau,) elle n’a qu’a rapprocher
quelques unes des parties de son organe électrique, la ot, par
quelque intervalle, la communication manque; qu’a éter ces
interruptions entre l’une et l’autre des colonnes dont est formé le
dit organe, ou entre ces membranes, en forme de disques minces,
qui gissent les unes sur les autres, du fond jusqu’au som-
met de chaque colonne; elle n’a, dis-je, qu’a Oter ces inter-
ruptions dans un ou plusieurs endroits, et y faire naitre le
contact convenable, soit en comprimant ces mémes colonnes,
soit en faisant couler entre les pellicules ou diaphragmes sou-
lévés, quelqu’humeur, &c. Voila quelle peut étre, et, comme
jimagine, quelle est réellement, toute la tache de la torpille,
en donnant la commotion; car tout le reste, je veux dire l’in-
citation et mouvement donné au fluide électrique, n’est qu’un
effet nécessaire de son organe singulier, formé, comme on voit,
d’une suite trés-nombreuse de conducteurs, que j’ai tout le
fondement de croire assez différents entr’eux pour étre aussi

of conducting Substances of different kinds. Al]

moteurs du fluide électrique, dans leurs contacts mutuels, et de
les supposer arrangés de la maniére convenable pour pousser
ce fluide avec une force suffisante, de haut en bas, ou de bas en
haut, et determiner un courant capable de produire la commo-
tion, &c. sitét, et chaque fois, que tous les contacts et communi-
cations nécessaires ont lieu.

Mais laissons maintenant la mes et son organe électrique
naturel, et revenons a Vorgane électrique artificiel de mon inven-
tion, et particuli¢rement a celui qui imite le premier, méme par
la forme, (car celui a gobelets s’en éloigne a cet égard,) re-

venons 4 mon premier appareil a colonne. J’aurois quelque
chose encore a dire par rapport a la construction du dit appareil:

a gobelets ou a couronne de tasses, par exemple, qu’il est bon que
la premiere et la derniére tasse soient assez grandes pour pouvoir

y plonger, a l’occasion, toute la main, &c.; mais mh seroit trop

dng d’entrer dans tous ces détails.
Quant a l’appareil a colonne, j’ai cherché les moyens de
Vallonger beaucoup, en multipliant. les plateaux métalliques

sans qu’elle s’écroulat ; de rendre cet instrument commode et

portatif, et, sur-tout, durable ; et jai trouvé, entr’autres, les sui-
vants, que je vous mets. sous les yeux, par les en cl-jointes.
(Pl. XVII. Fig. 2, 3, 4.)

- Dans la Fig. ade, mm mm, sont des montants ou baguettes,
au nombre, de trois, quatre, ou plus, qui s’élévent du pied de la
colonne, et renferment, comme dans un cage, les plateaux ou
disques posés les uns sur les autres, en tel nombre, et.jusqu’a la

_ hauteur qu’on veut, et les empéchent ainsi de tomber. Les ~

baguettes peuvent étre de verre, de bois, ou de métal; seule-

ment, dans ce dernier cas, il faut empécher qu’elles touchent im-

médiatement les plateaux; ce qu’on peut faire, ou en couvrant
3Ha

418 Mr. Vouta on the Electricity excited by the Contact

chacune de ces baguettes métalliques avec un tube déverre, ouen

interposant entre celles-ci et la colonne, quelques bandes de toile

cirée, de papier huilé, ou méme de papier simple, ou tout autre.
corps enfin, qui soit ou cobibent, ou mauvais conducteur : le bois,

ou le papier, le sont assez pour notre cas, pourvu seulement

qu’ils ne soient pas extrémement humides, ou mouillés.

Mais le meilleur expédient, lorsqu’on veut former l’appareil
d’un nombre trés-grand de plateaux, au-dela, par exemple,
de 60, 80, 100, est de partager la colonne en deux ou plusieurs,
comme on voit dans les Figures 3 et 4; (Pl. XVII.) ott les piéces
ont toutes leurs positions et communications respectives, comme:
si c’étoit une seule colonne. On peut en effet regarder la Fig.
4e, aussi bien que la ge, comme une colonne repliée.

Dans toutes ces figures, les plateaux métalliques différents
sont designés par les lettres A et Z; (qui sont les initielles d’ar-
gent et de zinc; ) et les disques mouilles (de carton, de peau, &c.)
interposés a chaque couple de ces métaux, par une couche noire.
Les lignes ponctuées marquent l’union d’un métal avec I’autre, |
~ dans chaque couple, leur contact mutuel par un nombre quel-»
conque de points; ce qui est indifférent, ou qu’ils sont soudés
ensemble, ce qui est bien a plus d'un égard. cc, cc, cc, sont
des plaques meétalliques, qui font communiquer une colonne,
ou section de colonne, a l’autre; et 6,6, b,b, b, sont, les bassins
d’eaux, en communication avec les pieds ou extrémités des
colonnes.

Un appareil ainsi monté est assez commode, pas volumineux,
et on pourroit le rendre encore plus facilement et plus stre-
ment portatif, a ’aide de quelques étuis ou canons, dans lesquels.—
on enfermeroit et garderoit chaque colonne. C’est dommage’
seulement qu’il ne.dure pas long-tems en bon état; les disques

of conducting Substances of different kinds. 419

_ mouillés se desséchant, dans un ou deux jours, au point qu’il faut
les humecter de nouveau; ce qu’on peut faire pourtant, sans dé-
monter tout]’appareil,en plongeant les colonnes toutes faites dans
l’eau, et (les ayant retirées quelques tems aprés) les essuyant a
l’extérieur avec un linge, ou autrement, le mieux qu’on peut.

La meilleure maniére d’en faire un instrument aussi durable
qu’on peut le souhaiter, seroit d’enfermer et retenir l’eau inter-
posée a ‘chaque couple de métaux, et de fixer ces mémes pla-
teaux 4 leurs places, en enveloppant de cire ou de poix toute la
colonne; mais la chose est un peu difficile pour I’exécution, et
exige beaucoup de patience. J’y ai pourtant réussi; et j’ai formé,
de cette maniére, deux cilindres de 20 couples métalliques, qui
me servent encore assez bien, aprés quelques semaines, et ser-
viront, j’espére, aprés des mois.

On ala commodité de pouvoir employer ces cilindres aux
expériences, non seulement debout, mais inclinés, ou cou-
chés, comme on veut, et méme plongés dans l’eau, la téte
seulement dehors: ils pourroient encore donner la commotion
plongés entiérement, s’ils contenoient un nombre plus grand de
plateaux, ou si plusieurs de ces cilindres étoient joints ensemble,
et qu'il y eit quelqu’interruption, qu’on pit dter a volonté, &c,
avec quoi, ces cilindres imiteroient assez bien languille trem-
blante; pour mieux ressembler a laquelle, méme dans |’exté-
rieur, ils pourroient étre joints ensemble par des fils métalliques
pliables, ou des ressorts 4 boudin, et étre couverts dans toute la
longueur d’une peau, et se terminer en une téte et en une queue,
bien configurées, &c.

Les effets sensibles 4 nos organes que produit un appareil
formé de 40 ou 50 paires de plateaux, (et méme un moins grand,
_ si Yun des métaux étant argent ou cuivre, l’autre est zinc, ) ne

420 Mr. Votra on the Electricity excited by the Contact

se reduisent pas simplement aux commotions: le courant de
fluide électrique, mu et sollicité par un tel nombre et espéces de
conducteurs différents, argent, zinc, et eau, alternativement dis-
posés de la manieére décrite, n’excite pas seulement des contrac-
tions et spasmes dans les muscles, des convulsions plus ou moins
violentes dans les membres qu’il traverse dans son cours, mais -
il irrite aussi les organes du gotit, de la vue, de l’ouie, et du tact,
proprement dit, et y produit des sensations propres a chacun.

Et, premiérement, quant au sens du tact; si, au moyen d’un
ample contact de la main (bien humectée) avec une lame métal-
lique, ou mieux, en plongeant la main profondément dans ]’eau
du bassin, j’établis d’un cété une bonne communication avec
une des extrémités de mon appareil électro-moteur, (il faut
donner de nouveaux noms a des instruments nouveaux, non
seulement par la forme, mais aussi par les effets, ou par le prin-
cipe d’ot ils dependent, ) et de l’autre cété j’applique le front, la
paupiére, le bout du nez, aussi humectés, ou quelque autre partie
du corps ot: la peau soit assez délicate; j’applique, dis-je, avec
un peu de pression, quelqu’une de ces parties delicates, bien hu-
mectées, contre la pointe d’un fil métallique, qui va communiquer
convenablement a l’autre extrémité du dit appareil, je sens, au
moment que s’accomplit ainsi le cercle conducteur, a l’endroit
touché de la peau, et un peu au-dela, un coup et une piqure,
qui passent vite, et se repétent autant de fois qu’on interrompt.
et rétablit ce cercle; de sorte que, si ces alternatives sont fré-
quentes, elles me causent un trémoussement, et un picotement
fort désagréable. Mais, si toutes les communications continuent
sans ces alternatives, sans la moindre interruption du cercle, je
ne ressens plus rien pour quelques moments ; passés lesquels,
commence a la partie appliquée au bout du fil métallique, une

of conducting Substances of different kinds. 421

autre sensation, qui est une douleur aigue, (sans secousse,)
limitée précisément aux points du contact, une cuisson, non
seulement continuée, mais qui va totjours en augmentant, au
point de devenir en peu de tems imaepeoniaite, et qui ne cesse
qu’en interrompant le cercle.
Quelle preuve plus évidente de la continuation du courant
_ électrique, pour tout le tems. que les communications des con-
ducteurs qui forme le cercle continuent ? et que seulement en
interrompant celui-ci, un tel courant est suspendu? Cette cir-
' culation sans fin du fluide électrique, (ce mouvement perpetuel, )
peut: paroitre paradoxe, peut n’étre pas explicable; mais elle n’en
est pas moins vraie et réelle, et on la touche, pour ainsi dire, des
mains. Une autre preuve evidente peut aussi se tirer, de ce que,
dans ces sortes d’expériences, on éprouve souvent, au moment
qu’on interrompt brusquement le cercle, un coup, une piqure,
une commotion, suivant les circonstances, tout comme au mo-
ment qu’on le complete. avec la seule différence, que ces sen-
sations, causées par une espéce de reflux du fluide électrique, ou
par le secousse qui nait de la suspension soudaine de son cou-
rant, sont plus foibles. Mais je n’ai pas besoin, et ce n’est pas
ici le lieu, d’alléguer les preuves d’une telle circulation sans fin
du fiuide électrique, dans un cercle de conducteurs ot il y en
a qui, pour étre de différente espéce, font par leur contact mu-
tuel, l’office d’excitateurs ou moteurs: cette proposition, que
jai avancée dés mes premieres recherches et découvertes au
sujet du GaALVANISME, et totijours soutenue, en l’appuyant de
nouveaux faits et expériences, n’aura plus, j’espére, de contra-
dicteurs.
Revenant a la sensation de douleur qu’on éprouve dans les
expériences décrites ci-dessus, je dois ajouter, que si cette dou-

42% Mr. Voura on the Electricity excited by the Contact

leur est assez forte et piquante dans les parties que la peau
recouvre, elle Pest beaucoup plus ow la peaua été enlévé, dans
les blessures, par exemple, et les plaies recentes. Si par hazard
il y a une petite incision, ou écorchure, au doigt que je plonge
dans l’eau communiquante avec une des extrémités de l’appareil
électro-moteur, }’y ressens une douleur si vive et si cuisante, lors-

qu’en établissant la communication convenable avec l’autre extré- _

mité j’en completele cercle, que je dois bientét medeésister de l’ex-
périence, c’est-a-dire, retirer le doigt, ou interrompre de quelque
autre maniére ce cercle. Je dirai de plus, que je ne puis pas
méme resister au-dela de quelques secondes, lorsque la partie
de l’appareil que je mets en jeu, ou l'appareil entier, ne va qu’a
20 couples métalliques, ou environ.

Une chose que je dois encore faire remarquer, c’est, que toutes
ces sensations de picotement et de douleur sont plus fortes et
plus aigues, les autres choses égales, lorsque la partie du corps
qui doit les ressentir se trouve du cété de I’électricité négative,
c’est-a-dire, placée de manieére, dans le cercle conducteur, que
le fluide électrique parcourant ce cercle, ne soit pas dirigé contre
cette partie sensible, qu’il ne s’avance pas vers elle et y entre de
dehors en dedans, mais bien que sa direction soit de dedans en
dehors, en un mot, qu'il en sorte : par rapport a quoi, il faut con-
noitre, des deux métaux qui entrent par couples dans l’appareil
construit, quel est celui qui donne a l’autre, Or, j’avois déja
determiné cela pour tous les métaux, par d’autres expériences,
publiées il y a long-tems, a la suite de mes prenviers mémoires au
sujet du GALVANISME. Je ne dirai donc ici autre chose, sinon

que tout est pleinement confirmé, par les expériences également.

et encore plus démonstratives et éclatantes, qui m’occupent a
présent. . Sephiee)

——

of conducting Substances of different kinds. 428

Par rapport au sens du gotitt, ’avois déja découvert, et publié
dans ces premiers mémoires, ot! je me vis obligé de combattre
la prétendue électricité animale de Gatvant, et de la déclarer
une électricité extrinséque, mue par le contact mutuel des mé-
taux de différente espéce; j’avois, dis-je, découvert, en consé-
quence de ce pouvoir que j’attribuois aux métaux, que deux
piéces de ces métaux différents, et singuli¢rement une d’argent
et une de zinc, appliquées convenablement, excitoient, sur le bout
de la langue, de sensations de saveur trés-marquées; que la
saveur etoit decidément acide, si, le bout de la langue étant
tourné vers le zinc, le courant électrique alloit contre lui, et
entroit ; et qu’une autre saveur, moins forte, mais plus désagré-
able, acre, et tirante a lalcalin, se faisoit sentir, si (la position
des métaux étant renversée) le courant électrique sortoit du
bout de la langue; que ces sensations, au surplus, continuoient,
et recevoient méme des accroissements, pendant plusieurs se-
condes, si le contact mutuel des deux métaux se soutenoit, et le
cercle conducteur n’étoit nulle part interrompu. Or, quand j’ai
dit ici, que les mémes phénomeénes arrivent ponctuellement, lors-
qu’on met a l’épreuve, au lieu d’une seule couple de ces piéces
métalliques, un assemblage de plusieurs, arrangés comme il
faut; et que les dites sensations de saveur, soit acide, soit alca-
line, augmentent, mais peu, avec le nombre de ces couples, j’ai
presque tout dit. Il me reste seulement a ajouter, que si l’ap-
pareil qu’on met en jeu pour ces expériences sur la langue, est
formé d’un nombre assez grand de couples métalliques de cette
espéce, si, par exemple, il en contient 30, 40, ou davantage, la
langue n’éprouve pas uniquement la sensation de saveur qu’on
vient de dire, mais, en outre, celle d’un coup, qui la frappe 4 |’in-
stant qu'on complete le cercle, et qui lui cause une piqire plus

MDCCCc, 3I

424 Mr. Vouta on the Electricity excited by the Contact

ou moins douloureuse, mais passagere, suivie, quelques moments
apres, de la sensation durable de saveur. Ce coup produit
méme une convulsion, ou trémoussement, d’une partie, ou de
toute la langue, lorsque l’appareil, formé d’un plus grand
nombre encore de couples des dits métaux, est plus actif, et
que, moyennant de bonnes communications conductrices, le
courant électrique qu'il excite peut passer partout, avec assez de
liberté.

Je reviens souvent, et j’insiste, sur cette derniére condition,
parcequ’elle est essentielle, pour toutes les expériences ot il
s’agit d’obtenir des effets bien sensibles sur notre corps, soit des
commotions dans les membres, soit des sensations dans les
organes des sens. II faut donc, que les conducteurs non-mé-
talliques qui entrent dans le cercle, soient des bons conduc-
teurs autant que possible, bien imbibés (s’ils ne sont pas des
liquides eux-mémes) d’eau, ou de quelque autre fluide plus
conducteur que l’eau pure; et il faut, outre -cela, que les sur-
faces bien humides, par lesquelles ils communiquent avec les
conducteurs métalliques, et sur-tout entr’eux, soient assez larges.
La communication doit seulement étre retrecie, ou réduite a un
petit nombre de points de contact, la ot: l’on veut concentrer
Vaction électrique sur une partie des plus sensibles du corps,
sur quelques nerf des sens, &c. comme je l’ai déja fait remar-
quer, a propos des expériences sur le tact, savoir, des expériences.
par lesquelles on excite des douleurs aigues dans diflérentes par-
ties. Ainsi donc, la meilleure maniére que j’ai trouvée, de
produire sur la langue toutes les sensations décrites, est, d’ap-
pliquer son bout contre l’extrémité pointue (qui ne le soit pas
pourtant trop) d’une verge métallique, que je fais commu-
niquer convenablement, comme dans les autres expériences, a

of conducting Substances of different kinds. 425

une des extrémités de mon appareil, et d’établir un bonne com=
munication de la main, ou, ce qui est mieux, des deux mains en-
semble, avec l’autre extrémité. Cette application du bout de la
langue au bout de la verge métallique, peut, au reste, ou exister
déja, lorsqu’on va faire l’autre communication pour completer
le cercle, (lorsqu’on va plonger la main dans l’eau du bassin, )
ou se faire aprés l’établissement de cette communication, pen-
dant que la main se trouve plongée; et, dans ce dernier cas, je
crois sentir la piqtire et la secousse dans la langue, un tant-soit-
peu avant le véritable contact. Oui, il me paroit totjours, particu-
liérement si j’avance peu-a-peu le bout de la langue, que lors-
quil est arrivé a une trés-petite distance du métal, le fluide
électrique, (je voudrois presque dire l’étincelle, ) franchissant cet
intervalle, s’élance pour le frapper. |

A Pégard du sens de la vue, quej’avois aussi découvert pouvoir
étre aflecté par le foible courant du fluide électrique, procédant
du contact mutuel de deux métaux differents, en général, et en
particulier d’une piéce d’argent avec une de zinc, je devois m’at-
tendre, que la sensation de lumiere excitée par mon nouvel ap-
pareil, seroit plus forte, a mesure qu'il contiendroit un plus grand
nombre de piéces de ces métaux; chaque couple desquels, arran-
gées comme il faut, ajoute un dégré de force au dit courant élec-
trique, comme toutes les autres expériences le montrent, et
notamment celles avec |’électrometre, aidé du condensateur,
que j’ai seulement indiquées, et que je décrirai ailleurs. Mais je
fus surpris de trouver, qu’avec 10, 20, go couples, et davantage,
' Péclair produit ne paroissoit ni plus long et étendu, ni beaucoup
plus vif, qu’avec une seule couple. II est vrai, cependant, que
cette sensation de lumiére foible et passagére, est excitée par
un tel appareil plus aisément, et de plusieurs maniéres. En

gle

426 Mr. Vo.ta on the Electricity excited by the Contact

effet, pour réussir avec une seule couple, il n’y a, a-peu-prés,
que les manieéres suivantes; savoir, ou qu’une des piéces métal-
liques soit appliquée au bulbe méme de l’ceil, ou a la paupiére,
bien humectée, et qu’on la fasse toucher a l’autre métal appliqué
a l’autre ceil, ou tenu dans la bouche, ce qui donne le plus bel
éclair; ou, qu’on empoigne cette second piéce métallique,
avec la main bien humectée, et qu’on la porte au contact de la
premiere ; ou enfin, qu’on applique ces deux lames 4 certaines
parties de l’intérieur de la bouche, en les faisant aussi commu-
niquer entr’elles. Mais, avec un appareil de 20, go couples,
&c. on produit le méme éclair, en appliquant au bout d’une
lame ou verge métallique, qui soit en communication avec une
des extremités de cet appareil, tandis que d’une main on com-
munique convenablement avec l’autre extremité; en appliquant,
dis-je, ou faisant toucher a cette lame, non seulement Il’ceil, ou
quelque partie que se soit de la bouche, mais le front, le nez,
les joues, les levres, le menton, et jusqu’a la gorge; en un mot,
toutes les parties et points du visage, qu’on doit seulement avoir
bien humectés, avant de les porter au contact de la lame métal-
lique. Au reste, la forme, comme la force, de cette lumiére
passagére qu’on appercoit, varie un peu, en variant les endroits
de la face sur lesquels on porte l’action du courant électrique ;
si c’est sur le front, par exemple, cette lumiére est médiocre-
ment vive, et paroit comme un cercle lumineux, sous laquelle
figure elle se présente aussi dans plusieurs autres essais.

Mais la plus curieuse de toutes ces expériences, est de tenir
la lame métallique serrée entre les levres, et en contact du bout
de la langue; puisque, lorsqu’on vient ensuite completer le
cercle, de la maniére convenable, on excite a la fois, si l'appareil
est suffisamment grand, en bon ordre, et le courant électrique

.

_-«

of conducting Substances of different kinds. 427

assez fort et en bon train, une sensation de lumiére dans les
yeux, une convulsion dans les levres, et méme dans la langue,
une piqtire douloureuse sur son bout, suivie enfin de la sensation
de saveur.

Je n’ai plus qu’a dire un mot sur l’ouie. Ce sens, quej’avois
inutilement cherché a exciter avec deux seules lames métal-
liques, quoique les plus actives entre tous les moteurs d’électri-
cité, savoir, une d’argent, ou d’or, et l’autre de zinc, je suis enfin
parvenu a l’affecter avec mon nouvel appareil, composé de go
ou 40 couples de ces métaux. J’ai introduit, bien avant dans
les deux oreilles, deux espéces de sondes ou verges métalliques,
avec les bouts arrondis; et je les ai fait communiquer immédiate-
ment aux deux extrémités de l’apparei]l. Au moment que le
cercle a été ainsi compleété, j’ai recu une secousse dans la téte ;
et, quelques moments aprés, (les communications continuant
sans aucune interruption, ) j’ai commencé a sentir un son, ou
plutét un bruit, dans les oreilles, que je ne saurois bien définir ;
c’étoit une espéce de craquement 4 secousse, ou petillement,
comme si quelque pate ou matiére tenace bouillonnoit. Ce bruit

- continua sans relache, et sans augmentation, tout le tems que

le cercle fut complet, &c. ‘La sensation désagréable, et que je
craignis dangereuse, de la secousse dans le cerveau, a fait que
je n’ai pas repété plusieurs fois cette expérience.

Reste le sens de l’odorat, que jai tenté jusqu’ici inutilement,
avec mon appareil. Le fluide électrique, qui, mis en courant
dans un cercle complet de conducteurs, produit dans les mem-
bres et parties des corps vivants qui se trouvent comprises dans
ce cercle, des effets correspondants 4 leur excitabilité; qui, sti-
mulant particuliérement les organes ou nerfs du tact, du goiit,
de la vué, et de l’ouie, y excite quelques sensations propres A

428 Mr. Vora on the Electricity excited by the Contact

chacun de ces sens, comme nous avons trouvé, ne produit, dans
lintérieur du nez, qu’un picotement plus ou moins douloureux,
et des commotions plus ou moins étendues, selon que le dit cou-
rant est plus ou moins fort. Et d’ot vient donc, qu'il n’y excite
aucune sensation d’odeur, quoiqu’il arrive, comme il paroit, a
stimuler les nerfs de ce sens? On ne peut pas dire, que le
fluide électrique, par lui-méme, ne soit pas propre a produire
des sensations odorantes; puisque, lorsqu’il se repand dans lair,
en forme d’aigrettes, &c. dans les expériences ordinaires des
machines électriques, il porte au nez une odeur trés-marquée,
ressemblante a celle du phosphore. Je dirai donc, avec plus de
ressemblance, et sur un fondement d’analogie avec les autres
matiéres odoriférantes, qu'il faut justement qu'il se repande
dans l’air, pour exciter l’odorat; qu’il a besoin, comme les autres
effluves, du vehicule de l’air, pour affecter ce sens de la maniére
propre a y faire naitre les sensations d’odeur. Or, dans les ex-
périences dont il est question, c’est-a-dire, du courant électrique
dans un cercle de conducteurs tous contigus, et sans la moindre
interruption, cela ne peut absolument avoir lieu.

Tous les faits que j'ai rapporté dans ce long écrit, touchant
V’action que le fluide électrique, incité et mu par mon appareil,
exerce sur les différentes parties de notre corps, que son courant
envahit et traverse; action qui, au surplus, n’est pas momen-
tanée, mais soutenue et durable pour tout le tems que, les
communications n’étant point interrompues, ce courant suit son
train; action, enfin, dont les effets varient suivant la différente
excitabilité de ces parties, comme on a vu; tous ces faits, déja
assez nombreux, et d’autres qu’on pourra encore: découvrir, en |

-multipliant et variant les expériences de ce genre, vont ouvrir
un champ assez vaste de reflexions, et des vués, non seulement

_ of conducting Substances of different kinds. 429

curieuses, mais intéressantes particuliérement la médecine, Il y
en aura pour occuper l’anatomiste, le physiologiste, et le prac-
ticien.

On scait, par ’anatomie qui en a été faite, que l’organe élec-
trique de la torpille, et de l’'anguille tremblante, consiste en plu-
sieurs colonnes membraneuses, remplies d’un bout a l’autre
d’un grand nombres de lames ou pellicules, en forme de disques
trés-minces, couchées les unes sur les autres, ou soutenues a
de trés-petits intervalles, dans lesquels coule, comme il paroit,
quelque humeur. Or, on ne peut pas supposer, qu’aucune de
ces lames soit isolante, comme le verre, les resines, la soye, &c.
et moins encore, qu’elles puissent, ou s’électriser par frottement,
ou étre disposées et chargées a la maniere de petits tableaux
FRANKLINIENS, ou de petits électrophores; ni méme, qu’elles
soient d’assez mauvais conducteurs pour faire l’office d’un bon
et durable condensateur, comme |’a imaginé Mr. NicHo.son.
L’hypothése de ce savant et laborieux. physicien, par laquelle
il fait de chaque paire de ces pellicules, qu'il voudroit comparer
a des feuilles de talc, autant de petits e/ectrophores ou conden-
sateurs, est, a la vérité, trés-ingenieuse; c'est peut-étre ce qu’on
a imaginé de mieux pour l’explication des phénoménes de la
torpille, en se tenant aux principes et loix connues jusqu’ici en
électricité. Mais, outre que le mécanisme par lequel devroit
s‘opérer, pour chaque coup que ce poisson voudroit donner, la
séparation respective des plateaux, de tous ou d’un grand
nombre de ces électrophores ou condensateurs; devroient, dis-
je, s’opérer toutes ces séparations a la fois, et s’établir, d’un cdté,
‘une communication entr’ eux de tous les plateaux électrisés en
plus, et, de l'autre cété, une communication de tous ceux éer-
trisés en moins, comme le veut Mr. NicHoLson; outre que ce

430 Mr. Vouta on the Electricity excited by the Contact

mécanisme trés-compliqué paroit trop difficile, et peu naturel;
outre que Ja supposition d’une charge électrique, originairement
imprimée, et si durable, dans ces pellicules faisant l’office d’élec-
trophores, est tout-a-fait gratuite; une telle hypothése tombe
entiérement, vu que ces pellicules de l’organe de la torpille ne
sont, et ne peuvent étre, aucunement isolantes, ou susceptibles
d’une véritable charge électrique, et moins encore capables de
_la retenir. Toute substance animale, tant qu'elle est fraiche, en-
tourée d’humeurs, et plus ou moins succulente elle-méme, est un
assez bon conducteur : je dis plus; bien loin d’étre aussi cobibente
que les resines, ou le talc, aux feuilles duquel Mr. NicHoLson
cherche a comparer les- pellicules dont il est question, il n’y a
point, comme je me suis assuré, de substance animale vivante,
ou fraiche, qui ne soit meilleur déféerente que l’eau, excepté seule-
ment la graisse, et quelques humeurs huileuses. Mais, ni ces
humeurs, ni la graisse, sur-tout a demi fluide, ou fluide entiere-’
ment, comme elle se trouve dans les animaux vivants, peut
recevoir une charge électrique, 4 la maniére des lames isolantes,
et la retenir; d’ailleurs, on ne trouve pas, que les pellicules et les
humeurs de l’organe de la torpille soient graisseuses ou hui-
leuses. Ainsi donc, cet organe, formé uniquement de substances
‘ conductrices, ne peut étre rapporté, ni a |’électrophore ou con-
densateur, ni a la bouteille de Leyde, ni 4 une machine quel-
conque excitable, soit par frottement, soit par. quelque autre
moyen capable d’électriser des corps isolants, qu’on a toujours
crus, avant mes découvertes, les seuls originairement électriques.

A quelle €lectricité donc, a quel instrument, doit-il étre com-
paré, cet organe de la torpille, de l’anguille tremblante, &c.? a
celui que je viens de construire, d’aprés le nouveau principe
d’électricité que j’ai découvert il y a quelques années, et que

7

Lhitlos. rans. MDCCC. Plat XN f/ 40. is
, Siz y A. |
HH} Hi! IIHi] pp

TD
ml

Lites Trans MV CCC Mate XVW p90 -

of conducting Substances of different kinds. 431

mes expériences successives, sur-tout celles qui m’occupent
maintenant, ont si bien confirmé, savoir, que les conducteurs
sont aussi, dans certains cas, moteurs d’électricité, dans le cas du
contact mutuel de ceux de différente espéce, &c. a cet appa-
reil, que j'ai nommé Organe électrique arizficiel, et qui, étant dans
le fond le méme que l’organe naturel de la torpille, le ressemble
encore pour la forme, comme j’ai déja avancé. H

MDCCC. | 3K

C 432 J

XVIII. Some Observations on the Head of the Ornithorhynchus
paradoxus. By Everard Home, Esq. F. R. S.

Read July g, 1800.

Tue specimens of this. extraordinary animal which have been
sent to Europe, have been deprived of the internal parts, and
the skins are mostly dried, and but badly preserved. Such im-
perfect specimens have raised the curiosity of the naturalist, and
excited the ardor of the anatomist, without satisfying’ their
enquiries.

It was natural, under these circumstances, to reserve any ob-
servations which had been made upon this newly discovered
quadruped, till the entire animal should be brought home pre-
served in spirit, and enable us to examine the structure of its
different organs; but, finding that Professor BLuMENBACH has
been led to believe that it was an animal without teeth, an
opinion which must have arisen from the imperfect state of the
specimen he examined, it appeared highly proper to do away
the mistake, and lay before this learned Society, such obser-
vations respecting the head of this extraordinary animal, as I
‘have been enabled to make.

My opportunities of examining the Ornithorbynchus were pro-
cured through Sir JoserpH Banks; who permitted me to have
drawings made from the skin of one of a very large size, and
which, from having been preserved in spirit, was more perfect
than any of the dried specimens.

Any general description of the beak of this animal, which is
its most conspicuous peculiarity, becomes unnecessary, as the

Mr. HomMeE’s Observations, &c. 433

accompanying drawings will give a sufficiently correct idea of
the outward appearances, to answer the present purpose.

It was not permitted to examine the head anatomically; but a
smaller dried specimen, received from Sir Josepn Banxs, fur-
nished me with the following observations.

The beak of the Ornithorbynchus, whenit iscursorily examined,
appears so strongly to resemble that of the duck, as to lead to
the belief of its being calculated for exactly the same purposes ;
it will however be found to differ mastery from it, ina variety
of circumstances.

The beak is found, upon examination, not to be the animal’s
mouth, but a part added to the mouth, and projecting beyond it.

The cavity of the mouth is situated as in other quadrupeds,
and has two grinding teeth on each side, both in the upper and
lower jaw; but, instead of incisor teeth, the nasal and palate
bones are continued forwards, lengthening the anterior nostrils,
and forming the upper part of the beak; and the two portions
of the lower jaw, instead of terminating at the symphisis, where
they join, become two thin plates, and are continued forwards,
forming the under portion of the beak.

This structure differs materially from the bill of the duck,
and indeed from the bills of all birds, since in them, the cavi-
ties of the nostrils do not extend beyond the root of the bill;
and, in their lower portions, which correspond to the under jaw
of quadrupeds, the edges are hard, to answer the purpose of
teeth, and the middle space is hollow, to receive the tongue.
But, in this animal, the two thin plates of bone are in the centre;
and the parts which surround them are composed of skin and
membrane, in which a muscular structure probably is inclosed.

_ The teeth have no fangs which sink into the jaw, as in most
quadrupeds, but are imbedded in the gum; and have only lateral
gKe

434 Mr. Home’s Observations on the

alveolar processes, from the outer and inner edges of the jaw,
to secure them in their places, but no transverse ones between
the two teeth.

The tongue is extremely short, not half an inch long; and
the moveable portion not more than a quarter of an inch; the
papillze on its surface are long, and of a conical form. When
the tongue is drawn in, it can be brought intirely into the
mouth ; and, when extended, can be projected about a quarter
of an inch into the beak.

The organ of smell, in this animal, differs, in some particulars,
from that of quadrupeds in general, as well as of birds. The ex-
ternal openings of this organ are placed nearly at the end of the
beak, there being only the lip beyond them; while the turbinated
bones are in the same relative situation to the other parts of the
skuil as in quadrupeds; by which means, there are two cavities
the whole length of the beak, superadded to the organ of smell.

The turbinated bones in each nostril are two in number, and
are distinct from each other. That next the beak is the longest,
has a more variegated surface than in. the duck, and has the
long axis in the direction of the nostril; the posterior one is
short, projects farther into the nostril, and the ridges are in a
transverse direction.

The posterior nostrils do not open directly under the turbi-
nated bones, as in the duck, but about an inch farther back, and
are extremely small; the cavities of the nose, in this animal,
are therefore uncommonly extensive; they reach from the end
of the beak nearly to the occiput.

The beak itself is formed by the projecting bones already men-
tioned, covered with a smooth black skin, which extends some
way beyond the bones, both in front and laterally, forming a
moveable lip. This lip is so strong, that, when dried or hardened

Head of the Ornithorhynchus paradoxus. 435

in spirit, it seems to be rigid; but, when moistened, is very
pliant, and, as has been already mentioned, has probably a
muscular structure. The under portion of the beak has a lip
equally broad with the upper: this has a serrated edge ; but the
serre are confined to the soft part, not extending to the mem-
brane covering the bone, and are not met with in the upper one.
The extent of the lips beyond the bones, is distinctly marked in
the drawings.

There is a very curious transverse fold of the external black
smooth skin, by which the beak is covered, projecting all round,
exactly at that part where the beak has its origin. Its apparent
use seems to be to prevent the beak being pushed further into
the soft mud, in which its prey may lie concealed, than up to this
- part, which is so broad that it must completely stop its progress.

The nerves that supply the beak, in their general course,
size, and number, seem very closely to correspond with those
of the bill of the duck.

- The cavity of the skull bears a greater general resemblance
to that of the duck than of quadrupeds: there is a very un-
common peculiarity in it, which is, that there is a bony falx of
some breadth, but no bony tentorium. This is met with in no
quadruped that I know of: it is found in a small degree in some
birds, as the spoon-bill, and the parrot; but not at all so as to
resemble the falx in this animal.

The orifice of the eye lids is uncommonly small, for the size
of the animal; but the eye itself was not in a state to be
examined. —

The external opening of the ear was so small as not readily
to be perceived: it is simply an orifice; but the meatus en-
larges considerably beyond the size of the opening, and passes
some way under the skin, before it reaches the organ, which in

nostrils are so placed, to enable it

496 Mr. Home’s Observations, &c.

this specimen had been destroyed. In the duck, the orifice
leading to the ear is very large, when compared with the open-
ing in this animal.

When we consider the petaliecie in the structure of the
nose of this animal, which lives in water, it is natural to con-
clude the organ is fitted to smell ins ‘water, and the external
to discover its prey by the
smell; for that purpose, the animal n apply its nose, with great
ease, to the small recesses in which its prey may be concealed.

The structure of the beak is not such as enables it to take a
firm hold; but, when the margin lips are brought together,
the animal will have a considerable co. of suction, and in
that way may draw its prey into its S

EXPLANATION OF THE FIGURES.

Pirate XVIII. ;
Fig. 1. A view of the beak, to show the situation of the
openings of the external nostrils, marked aa.
Fig. 2. Another view of the beak, exposing the under portion.
Fig. 3. A lateral view, to show the opening of the lips, and
the situation of the eye and ear. a. Theeye. 06. The ear.

PLATE XIX.

Fi ig. 1. A view, of the upper jaw and palate, to shew the teeth
in their situation.

Fig. 2, A similar view of the ander} jaw.

Fig. 3. The bones which form the beak delineated, and the
soft surrounding parts only marked in outline.

Fig. 4. A similar view of the bones forming the lower
portion of the beak.

oe peck n>

Lhilos. trans MCC C, Male XN Wp 426
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Litlos Trans MCC C, Hale XN Wp 436

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Barefe.

PHILOSOPHICAL

TRANSACTIONS,

OF THE.

Az

ROYAL SOCIETY

OF

LONDON.

FOR THE YEAR MDCCC.

PART II.

LONDON,

PRINTED BY W. BULMER AND CO. CLEVELAND-ROW, ST. JAMES'S ;
AND SOLD BY PETER ELMSLY,
PRINTER TO THE ROYAL SOCIETY,
MDCCC.

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CONTENTS.

XIX. ExpeRIMeENTs on the solar, and on the terrestrial Rays
that occasion Heat; with a comparative View of the Laws to
which Light and Heat, or rather the Rays which occasion them,
are subject, in order to determine whether they are the same,
or different. Part 11. By William Herschel, LL. D. F. R.S.

page 437

XX. An Account of the Trigonometrical Survey, carried on in the
Years 1797, 1798, and 1799, by Order of Marquis Cornwallis,
Master-General of the Ordnance. By Captain William Mudge,
of the Royal Aritllery, F. R. S. Communicated by bis Grace
the Duke of Richmond, F. R. S. P. 539

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PHILOSOPHICAL

TRANSACTIONS.

XIX. Experiments on tbe solar, and on the terrestrial Rays that
occasion Heat ; with a comparative View of the Laws to which

_ Light and Heat, or rather the Rays which occasion them, are
subject, in order to determine whether they are the same, or

different. By William Herschel, LL. D. F, R. S.

Parry 11*

Read November 6, 1800.

Ix the first part of this Paper it has been shewn, that heat
derived immediately from the sun, or from candent terrestrial
substances, is occasioned by rays emanating from them; and
that such heat-making rays are subject to the laws of reflection,
and of refraction. The similarity between light and heat, in these
points, is so great, that it did not appear necessary to notice
some small difference between them, relating to the refraction
of rays to a certain focus, which will be mentioned hereafter.
But the next three articles of this Paper will require, that while
we shew the similarity between light and heat, we should at

* For the First Part of this Paper, see page 293.
MDCCC. 3L )

*

438 Dr. Herscue.’s Experiments on the solar, and

the same time point out some striking and substantial diffe--
rences, which will occur in our experiments on the rays which

occasion them, and on which hereafter we may proceed to
argue, when the question reserved for the conclusion of this
Paper, whether light and heat be occasioned by the same or by
different rays, comes to be discussed.

ARTICLE iv.— Different Refrangibility of the Rays of Heat.

We might have included this articlesin the first part of this
Paper, as a corollary of the former three; since rays that have
been separated by the prism, and have still remained subject to
the laws of reflection and refraction, as has been shewn, could
not be otherwise than of different refrangibility; but we have
something to say on this subject, which will be found much more
- circumstantial and conclusive than what might have been drawn
as a consequence from our former experiments. However, to
begin with what has already been shewn, we find that two
degrees of heat were obtained from that part of the spectrum
which contains the violet rays, while the full red colour, on the
opposite side, gave no less than seven degrees ;* and these facts
ascertain the different refrangibility of the rays which occasion
heat, as clearly as that of light is ascertained by the dispersion
and variety of the colours. For, whether the rays which occa-
sion heat be the same with those which occasion the colours,
which is a case that our foregoing experiments have not ascer-
tained, the arguments for their diffetent refrangibility rests on
the same foundation, namely, their being dispersed by the
prism; and that of the rays of light being admitted, the different

* See 2d and 4th experiments, pages 258 and 259.

on the terrestrial Rays that occasion Heat. 439

refrangibility of the rays of heat follows of course. So far then,
a great resemblance again takes place. ;

I must now point out a very material difference, which is, that
the rays of heat are of a much more extensive refrangibility
than those of light. In order to make this appear, I shall de-
lineate a spectrum of light, by assuming a line of a certain
length; and, dividing it into seven parts, according to the di-
mensions assigned to the seven colours by Sir Isaac NEwTon,
in the fourth figure of the second part of his Qptics, I shall
represent the illuminating power of which each colour is pos-
sessed, by an ordinate drawn to that line. And here, as the
absolute length of the ordinates is arbitrary, provided they
be proportional to each other, I shall assume the length of that
which is to express the maximum, equal to 22 of the whole line.

Thus, let GQ * represent the line that contains the arrange-
ment of the colours, from the red to the violet. Then, erecting
on the confines of the yellow and green the line LR = 21 of
- GQ, it will represent the power of illumination of the rays in
that place. For, by experiments already delivered, we have
shewn that the maximum of illumination is in the brightest
yellow or palest green rays.-{ From the same experiments we
collect, that the illuminations of yellow and green are equal to
each other, and not much inferior to the maximum ; this gives
us the ordinates K and M. Then, by the rest of the same ex-
periments, we obtain also the ordinates H, I, N, O, P, with
_ sufficient accuracy for the purpose here intended. All these
being applied to the middle of the spaces which belong to their
respective colours, we have the figure GRQG, representing
what may be called the spectrum of illumination.

* See Plate XX. + See page 262,
gle

4,40 Dr. HERScHEL’s Experiments on the solar, and

We are now, in the same manner, to find a figure to express
the heating power of the refracted prismatic rays, or what may
be called the spectrum of heat. In order to determine the
length of our base, I examined the extent of the invisible rays,
and found, that at a distance of two inches beyond visible red,
my thermometer, in a few minutes, acquired 14 degree of heat.
The extent of the coloured spectrum at that time, or the line
which answers to GQ in my figure, measured 2,997 inches. If
two inches had been the whole of the extent of the invisible
part, it might be stated to be in proportion to the visible one
as 2 to 3; but we are to make some allowance for a small space
required beyond the last ordinate, that the curve of the heating
power drawn through it may reach the base; and indeed, at 22
inches beyond visible red, I could still find $ degree of heat. It
appears therefore sufficiently safe, to admit the base of the spec-
trum of heat AQ, to be to that of the spectrum of light GQ, as
52 to 3; or, conforming to the Newrontan figure before men-
tioned, the base of which is 9,9 inches, as 573 to 33. Now, if
we assume for the maximum of heat, an ordinate of an equal
length with that which was fixed upon for the maximum of
light, it will give us a method of comparing the two spectra
together. Accordingly, I have drawn the several ordinates
B, C, D, E, F, G, H, I, K,L, M,N, O,P, of such lengths as,
from experiments made on purpose, it appeared they should be,
in order to express the heat indicated by the thermometer, when
placed on the base, at the several stations pointed out by the
letters. > eye]

A mere inspection of the two figures, which have been drawn
as lying upon one another, will enable us now to see how very
differently the prism disperses the heat-making rays, and those

on the terrestrial Rays that occasion Heat. 4A

which occasion illumination, over the areas ASQA, and GRQG,
of our two spectra! These rays -neither agree in their mean
refrangibility, nor in the situation of their maxima. At R, where
we have most light, there is but little heat; and at S, where we
_ have most heat, we find no light at all!

21st Experiment. The Sines of Refraction of the beat-making
Rays, are in a constant Ratio to the Sines of Incidence.

I used a prism with a refracting angle of 61 degrees; and,
placing the thermometer No. 4 half an inch, and No. 1 one
inch, beyond the last visible red colour, I kept No. 2 by the side
of the spectrum, as a standard for temperature.

At = inch. At 1 inch, Standard.
No. Ae No. 1. ‘No. g.
EB benleliiy nr fcr ont 94 suk om 6:4. os 03H
Bebo @ Fai ciruiarina Sy noteniat ss : 8%
5 eile gd ite = init matty Oe
By! nO ies Syren won Wort Fu'a wit ain O34

Here, in eight minutes, the thermometer at half an inch from
visible colour, rose 5£ degrees; and, at one inch from the same,
the other thermometer rose 34; while the temperature, as ap-
pears by No. 2, remained without change.

I now took a prism with an angle of forty-five degrees, and,
placing the thermometers as before, I had as follows:

55 5 i 55 3 be 55
Sa ae LSA: kiToeed Tob Dae
Cries ieromiowit, 38 4): Fenris 2} us8S
Se ee hdnaigh ili BEF vin ous yo tga gS
Here we likewise had, in 10 minutes, a rise of 7 degrees in the

442 Dr. Herscuet’s Experiments on the solar, and

thermometer No. 4, and of g3 in No. 1; while No. 2 remained
stationary.

I tried now all the three angles of a prism of whitish glass:
they were of 63, 62, and 55 degrees; and I found invisible
rays of heat to accompany all the visible spectra given by these
angles.

I tried a prism of crown glass, having an pone of go degrees ;
and found invisible heat rays as before.

I tried a prism of flint glass, with so small an angle as 19
degrees, and again found invisible heat rays.

I made a hollow prism, by cementing together three slips of
glass of an equal length, but unequal breadth, so as to give me
different refracting angles: they were of 51°, 62° go’, and 66°
30’. Then, filling it with water, and receiving the spectrum,
when exposed to the sun, as usual, on the table, I placed the
thermometer No. 1 at ,4 inch behind the visible red colour,
and No. 5 in the situation of the standard. The refracting angle
of the prism was 62° 30’; and, in five minutes, the thermometer
received 13 degrees of heat from the invisible rays. On trying
the other angles, I likewise found invisible heat rays, in their
usual situation beyond the red colour.

Now, setting aside a minute inquiry into the degrees of heat
occasioned by these invisible rays, I shall here only consider
them as an additional part, annexed to the different quantities
of heat which are found to go along with the visible spectrum;
in the same manner as if, in the spectrum of light, another colour
had been added beyond the red. Then, as from the foregomg
experiments it appears, that a change of the refracting medium,
and of the angle by which the refractions were made, occasioned
no alteration in the relative situation of the additional part AG,

on the terrestrial Rays that occasion Heat. 443

with respect to GQ; and, as the part GQ is already known to
follow the law of refraction we have mentioned, it is equally
evident, that the additional heat of AG must follow the same
law. We do not enter into the dispersive power of different
’ mediums with respect to heat, since that would lead us farther
than the present state of our investigation could authorise us to
go; the following experiment however will shew that, as with
light so with heat, such dispersive power must be admitted.

aed Experiment. Correction of the different Refrangibility of
Heat, by contrary Refraction in different Mediums.
_ I took three prisms; one of crown glass, having an angle of
25 degrees ; another of flint glass, with an angle of 24; and a
third of crown glass, with an angle of 10 degrees. These being
put together, as they are placed when experiments of achromatic
refractions are to be made, I found that they gave a spectrum
nearly without colour. The composition seemed tq be rather a
little over adjusted; there being a very faint tinge of red on
the most refracted side, and of violet on the least refracted
margin. I examined both extremes by two thermometers ;
keeping No. 3 as a standard, while No. 2 was applied for the
discovery of invisible rays; but I found no heat on either side.
After this, I placed No. 2 in the middle of the colourless illu-
mination; and in a little time it rose two degrees, while No. 3
still remained unaltered at some small distance from the spec-
trum. This quantity was full as much as I could expect, con-
sidering the heat that must have been intercepted by three
prisms. Thus then it appears, that the different refrangibility
of heat, as well as that of light, admits of prismatic correction.
And we may add, that this experiment also tends to the estab-

444 Dr. HerscueEx’s Experiments on the solar, and

lishment of the contents of the preceding one; for the refran-

gibility of heat rays could not be thus corrected, were the sines

of refraction not in a constant ratio to those of incidence. .

23d Experiment. In Burning-glasses, the Focus of the Rays of
Heat is different from the Focus of the Rays of Light.

I placed my burning lens, with its aperture reduced to three
inches, in order to lessen the aberration arising from the sphe-
rical figure, in the united rays of the sun; and, being now
apprised of the different refrangibility of the rays of heat, and
knowing also that the least refrangible of them are the most

efficacious, I examined the focus of light, by throwing hair- —

powder, with a puff, into the air. This pointed out the mean

focus of the illuminating rays, situated in that part of the pencil

which opticians have shewn to be the smallest space into which
they can be collected. That this may be called the focus of light,
our experiments, which have proved the maximum of illumi-
nation to be situated between the yellow and green, and there-

fore among the mean refrangible rays of light, have fully estab-
lished. The mean focus being thus pointed out by the reflection’
of light on the floating particles of powder, I held a stick of

sealing wax 1”,6, or four beats of my chronometer, in the con-

tracted pencil, half an inch nearer to the lens than the focus.»

In this time, no impression was made upon the wax. I applied
it now half an inch farther from the lens than that focus; and,
in 8-tenths of a second, or two beats of the same chronometer,

it was considerably scorched. Exposing the sealing wax also -
to the focus of light, the effect was equally strong in the same —
time ; from which we may safely conclude, notwithstanding the
little accuracy that can be expected, for want of a more proper -

on the terrestrial Rays that occasion Heat. 4A5

apparatus, from so coarse an experiment, that the focus of heat,
n this case, was certainly farther removed from the lens than
the focus of light, and probably not less than 4 of an inch; the
heat, at half an inch beyond the focus of light, being still equal
to that in the focus.

ARTICLE v.—Transmission of heat-making Rays.

We enter now on the subject of the transmission: of heat
through diaphanous bodies. Our experiments have hitherto
been conducted by the prism, the lens, and the mirror; these
may indeed be looked upon as our principal tools, and, as such,
will stand foremost in all our operations ; but the scantiness of
this stock cannot allow us to bring our work to perfection.
Nor is it merely the want of tools, but rather the natural
imperfection of those we have, that hinders our rapid progress.
The prism which we use for separating the combined rays of
the sun, refracts, reflects, transmits, and scatters them at the
same time; and the laws by which it acts, in every one. of these
operations, ought to be investigated. Even the cause of the
most obvious of its effects, the separation of the colours of light,
is not well understood; for, in two prisms of different glass,
when the angles are such as to give the same mean refraction,
the dispersive power is known to differ. Their transmissions
have been still less ascertained; and I need not add, that the
internal and external reflexions, and the scattering of rays on
every one of the surfaces, are all of such a nature as must
throw some obscurity on every result of experiments made
with prisms. A lens partakes of all the inconveniencies of the
prism; to which its own defects of spherical aberrations must

MDCCC. — 3M

44,6 Dr. HERScHEL’s Experiments on the solar, and

be added. And a mirror, besides its natural incapacity of sepa~
rating the rays of light from the different sorts of heat, scatters
them very profusely. But, if we have been scantily provided
with materials to act upon rays, it has partly been our own
fault: every diaphanous body may become a new tool, in the
hands of a diligent inquirer.

My apparatus for transmitting the rays of the sun is of the
following construction.* Ina box, 12 inches long, and 8 inches
broad, are fixed two thermometers. The sides of the box are
2+ inches: deep. That part of the box where the balls of the
thermometers are, is covered by a board, in which are two
holes of 3 inch diameter, one over each of the balls of the
thermometers; and the bottom of the box, under the cover, is
cut away, so as to leave these balls freely exposed. There is a
partition between the two thermometers, in that part of the box
which is covered, to prevent the communication of secondary
scatterings of heat. Just under the opening of the transmitting
holes, on the outside of the cover, is fixed a slip of wood, on
which may rest any glass or other object, of which the trans-
mitting capacity is to be ascertained. A thin wooden cover is
provided,-f that it may be laid over the transmitting holes, occa-
sionally, to exclude the rays of the sun; and, on the middle of
the slip of wood, under the holes, a pin is to be stuck perpen-
dicularly, that. its shadow may point out the situation of the
box with respect to the sun. The box, thus prepared, is to be
fastened upon two short boards, joined together by a pair of
hinges. A long slip of mahogany is screwed to the lowest of
these boards, and lies in the hollow part of a long spring,
fastened against the side of the upper one. The pressure of the

* See Plate XXI. Fig. 1. + See Fig. 2.

on the terrestrial Rays that occasion Heat. 447

spring must be sufficiently strong to keep the boards at any
angle; and the slip of mahogany long enough to permit an
elevation of about 85 degrees.

In order to see whether all be properly adjusted, expose the
apparatus to the sun, and lift up the board which carries the
box, till the directing pin throws the shadow of its head on the
place where the point is fastened. Then hold a sheet of paper
under the box, and, if the thermometers have been: properly
placed, the shadow of their balls will be in the centre of the
rays passing through the transmitting holes to the paper.

A screen of a considerable size,* with a parallelogrammic
opening, should be placed at a good distance, to keep the sun’s
rays from every part of the apparatus, except that which is
under the cover; and no more sun should be admitted into the
room, than what will be completely received on the screen, inter-
posed between the window and the apparatus.

As one of the thermometers is to indicate a certain quantity
of heat coming to it by the direct ray, while the other is to
shew how much of it is stopped by the glass laid over the trans-
mitting hole, it becomes of the utmost consequence to have two
thermometers of equal sensibility. The difficulty of getting

* See Plate XXII. Fig. 1.

+ The theory of the sensibility of thermometers, as far as it depends on the size of
the balls, may be considered thus, Let D, d, S, s, T, ¢ be the diameters, the points
on which the sun acts, and the points on which the temperature acts, of a large and a
small thermometer having spherical balls; and let x: y be the intensity of the action
of the sun, to the intensity of the action of the temperature, on equal points of the
surface of both thermometers. Then we haves: S::d*: D?,andt: T :: 4d* ; 4D’.
The action of the sun therefore will be expressed by d? z, D* x; and that of the tem-
perature by 4d*y, 4D* y; and the united action of both by —4y x a>, x—4y x D*;
which are to each other, as d?; D*, Now, the total effect being as the squares of the

g3Ma

448 Dr: Herscuex’s Experiments on the solar, and

such is much greater than can be imagined: a perfect equality
in the size and thickness of the balls is, however, the most
essential circumstance. When two are procured, they should be
tried in quick and in slow exposures. These terms may be
explained by referring to fire heat; for here the thermometers
may be exposed so as to acquire, for instance, 30 degrees of
heat in a very short time; which may then be called a quick
exposure: or they may be placed so as to make it require a
good while to raise them so many degrees; on which account
the exposure may be called slow. It is true, that we have it not
in our power to render the sun’s rays more or less efficacious,
and therefore cannot have a quick or slow exposure at our com-
mand; but a great difference will be found in the heat of
a rising, or of a meridian sun: not to mention a variety of
other causes, that influence the transmission of heat through the
atmosphere. Now, when thermometers are tried in various
exposures, they should traverse their scales together with con-
stant equality ; otherwise no dependance can be placed on the
results drawn from experiments made with them, in cases
where only a few minutes can be allowed for the action of the
cause whose influence we are to investigate.

The balls must not be blacked; for, as we have already to
encounter the transmitting capacity of the glass of which these
balls are made, it will not be safe to add to this the transmitting
disposition of one or more coats of blacking, which can never
diameters, while z : y remain in their incipient ratio, and the contents of the thermo-
meters being as the cubes, the sensible effect produced on the particles of mercury,
must be as 5 : = se - : a that is, inversely as the diameters. The small thermo-

meter therefore will set off with a sensibility greater than that of the large one, in the
same ratio, '

on: the terrestrial Rays that occasion Heat. 449

be brought to an equality, and are always liable to change,
especially in very quick exposures.

Transmission of Solar Heat through colourless Substances.
24th Experiment.

I laid a piece of clear transparent glass, with a bluish-white
cast, upon one of the holes of the transmitting machine: the
faces of this glass are parallel, and highly polished. Then, put-
ting the cover over both holes, I placed the machine in the
situation where the experiment was to be made, and let it remain
there a sufficient time, that the thermometers might assume a
settled temperature. For this purpose, an assistant thermometer,
which should always remain in the nearest convenient place to
the apparatus, will be of use, to point out the time when the
experiment may be begun ; for this ought not to be done, till
the thermometers to be used agree with the standard. In order
not to lose time after an experiment, the apparatus may be
taken into a cool room, or current of air, till the thermometers
it contains are rather lower than the standard; after which,
being brought to the required situation, they will soon be fit
for action.

All these precautions having been taken, I began the experi-
ment by first writing down the degrees of the thermometers ;
then, opening the cover at the time that a clock or watch shew-
ing seconds came toa full minute, I continued to write down the
state of the thermometers for not less than five minutes. The
result was as follows.

950 Dr. HerscuE,’s Experiments on the solar, and

No. Be No. 1. ; of tehauertd cot
Sun, ? Bluish-white glass — ¥ a2 Vinee
oy 67 67
1 683 + ine OBE,
2 7oL 691
8 a 79
4 723 79% )
5 73 Wit... 6: 42750.

Here the sun communicated, in 5 minutes, 6 degrees of heat
to the thermometer No. 5, which was openly exposed to: its
action; while, in the same time, No. 1 received only 42 degrees
by rays transmitted through the bluish-white glass: then, as
6:4£::1:,750. This shews plainly, that only 3 of the inci-
dent heat were transmitted, and therefore that 2 of it was.
intercepted by the glass.

I shall here, as well as in the following experiments, point
out the difference between heat and light, in order, as has been
mentioned before, to lead to an elucidation of our last discus-
sion. To effect this, therefore, I have ascertained, with all the
accuracy the subject will admit of, the quantity of light trans-
mitted through such glasses as I have used; but, as it would
here interrupt the order of our subject, I have joined, at the
end of this Paper, a table, with a short account of the method
that has been used in making it, wherein the quantity of
light transmitted is set down; and to: this table I shall now
refer. |

To render this comparative view more clear, we may sup-
pose always 1000 rays of heat to come from the object: then,
750 being transmitted, it follows, that the bluish-white glass
used in our experiment stops 250 of them; and, by the table at |

on the terrestrial Rays that occasion Heat. ‘451

the’end of this Paper, it stops 86 rays of light; the number of
them coming from the object also being put equal to 1000. °
It should be remarked, that when I compare the interception
of solar heat with that of the light of a candle, it must not be
understood that I take terrestrial to be the same as solar light ;
but, not having at present an opportunity of providing a similar
table for the latter, Iam obliged to use the former, on a suppo-
sition, that the Sti ‘stopped by glasses may not be very
different.

a i 25th Experiment.

I took a piece of flint glass, about 24 ansible of an a thick,
and fastened it over one ox the holes of the transmitting appa-
ratus. rei
No # . No. iat

Sim. 1) “Ot vie? ot Wise glass,
MOOR trove: od 189d
TRO leh (fe
72309. ° 72% iy ei
oT MEE ORME Tuy 73
75% 74 +++ Sz? 5 =,909

Here the heat-making rays gave, in 5: minutes, 51 degrees to
’ the thermometer No.5 ; and, by transmission through the flint
glass, 5 degrees to No; 1. Then, proceeding as before, we have,

53 = 9095 which shews that 91 rays of heat were stopped.

In the table before referred to, we find that this glass stops 34
Faye or light.” 9" 8" gO

Before I proceed, it ‘will be necessary t to adopt a method of
reducing the detail of my experiments into a narrower com~

Ab Dr. HERscueEt’s Experiments on the solar, and

pass. It will be sufficient to say, that they have all been made
on the same plan. as the two which have been given. The
observations_were always continued for at least five minutes;
and, by examining the ratios of the numbers given by the ther-
mometers in all that time, it may be seen that, setting aside little _
irregularities, there ‘is a greater stoppage at first than towards
the end ; but, as it would not be safe to take a shorter exposure
than five minutes, on account of the small quantity of heat
transmitted by some glasses, I have fixed upon that interval as
sufficiently accurate for giving a true comparative view. The
experiments therefore may now stand abridged as follows.

26th Experiment.

I took a piece of highly polished crown glass, of a greenish
colour, and, cutting it-into several parts, examined the transmit-
ting power of one of them, reserving the other pieces for some
other experiments that will be mentioned hereafter.

Sun. Greenish crown glass.
o! 665 664
5 73, Wii... 63: 5=,741

This glass therefore stops 259 rays of heat, and 20g of light.

o7th Experiment.

I cut likewise a piece of coach glass into several parts, and
tried one of them, reserving also the other pieces for future
experiments.

Sun. Coach glass.
°’ 682 682 de
a 755 The ++ 7+ Fz = 786

It stops 214 rays of heat, and 168 of light.

- on the terrestrial Rays that occasion Heat. 453

28th Experiment.

I examined a piece of Iceland crystal, of nearly two-tenths of
an inch in thickness.

Sun, Iceland crystal.

of 67 67 :
5 72%. 712... 55:44 = 5750

It stops 244, rays of heat, and 150 of light.

29th Experiment.

Sun, Talc.
o! 675 675
5 79 3 712...44:97==,861

It stops 139 rays of heat, and go of light.

goth Experiment.

Sun. An easily calcinable talc.
0! 5O 50
5 548 — (§35...48 29% =,816

It stops 184 rays of heat, and 288 of light.

Transmission of solar Heat through Glasses of the prismatic
Colours.

gist Experiment.

Sun. Very dark red glass.
;
S 73 73
5 79% 74% rege etn

This glass stops 800 rays of heat, and 9999, out of ten thou~
sand, rays of light; which amounts nearly to a total separation
of light from heat.

MDCCC, . 3N

454 Dr. Herscuen’s Experiments on the solar,and

g2d Experiment.

Sun. Dark-red glass.
o! 682 682
5 723 70 +++ Ag? 1g == 5394

This red glass stops only 606 rays of heat! and above 4999,
out of five thousand, rays of light.

33d Experiment.

Sun. Orange glass.
o a 673
5 743 703 +. OF 2 25 = 396

This orange-coloured glass stops 604, rays of heat, which is
nearly as much as is stopped by the last red one; but it stops
only 779 rays of light.

34th Experiment.

Sun. Yellow glass.
70% 704
74% 73+ - + 34223 = 667

It stops 333 rays of heat, and 319 of light.

g5tb Experiment.

Sun. Pale-green glass.
On 707 70x
3 43 ——
5 744 71g: ++ Bas taegae

It stops 633 rays of heat, and only 535 of light.

36th Experiment.
, Sun Dark-green glass.
o’ 675 675
5 Ae 68i,,.62:5:1=5,151

on the terrestrial Rays that occasion Heat. ASS

This glass stops 849 rays of heat, and g4g of light. This
accounts for its great use as a darkening glass for telescopes.

37th Experiment,

Sune Bluish-green glass.
t 3 :
e 695 695
5 762 Ri o7 112 a= 292

It stops 768 rays of heat, and 769 of light.

38th Experiment.

Sun. Pale-blue glass.
ti 3 3
9) 7°z 705
3 a 5
5 704 Flaite Ol 2A 1S

The pale blue glass stops not less than 812 rays of heat, and
only 684 of light. .
39th Experiment.

Sun, Dark-blue glass.
Oo’ 71 71
5 76% 74z > ++ 5g 85 = 638

The dark-blue glass stops only 362 rays of heat, and 801 of
- light. | |
40th Experiment.

Sun, Indigo glass.
o! 612 612
5 7 a 64,...61:2F = ‘967

This glass stops 633 rays of heat, and 9997, out of ten thou-
sand, rays of light.

3Ne

456 Dr. HERscuEx’s Experiments on the solar, and

41st Experiment.

Sun. Pale-indigo glass,
o! 762 62 :
5 672 642... 5%: 23 = 468
It stops 532 rays of heat, and g78 of light.
42d Experiment.
Sun, Purple glass.
o! 613 613
673 OAc... sO 5 2— = emi
It stops 583 rays of heat, and 999 of light.
49d Experiment.
Sun. Violet glass.
Gor Got
681 654...-55:39=,511

It stops 489 rays of heat, and 955 of light.

Transmission of Solar Heat through Liquids.

I took a small tube, 14 inch in diameter,* and fixed a stop
with a hole 2 inch wide at each end, on which a glass might.
be fastened, so as to confine liquids. The inner distance, or
depth of the liquid, when confined, is three inches. Placing now
the empty tube, with its two end glasses fixed, upon the trans-

mitting apparatus, | had as follows:

44th Experiment.

Sun. Empty tube, and two glasses.
ol Une 53 53 ae
5 59 55z ++ 6: 25 = 458

* See Plate XXII, Fig. 2,

on the terrestrial Rays that occasion Heat. AS7
These glasses, with the intermediate air, stop 542 rays of
heat, and 204 of light.

45th Experiment.

I filled the tube with well-water, and placed it on the trans-
mitting apparatus.

Sun. Well-water.
COU 524 525
5 585 55 --- OF: 23 = 442

Here two glasses, with water between them, stopped 558
rays of heat. The same glasses, and water, stop only 211 rays
of light. If we were to deduct the effect of the empty machine,
there would remain, for the water to stop, only 16 rays of heat,
and 7 of light; but it cannot be safe to make this conclusion, as
we are not sufficiently acquainted with the action of surfaces
between the different mediums on the rays of heat and light ;
I shall therefore only notice the effect of the compound.

46ib Experiment.

I filled now the tube with sea-water, taken from the head of
the pier at Ramsgate, at high tide.

Sun. Sea-water.
54a 54a
60 BO oo fe ea 1G

The compound stops 682 rays of heat, and 288 of light.

47th Experiment.

Sun. Spirit of wine.
o’ Mh sare 51g
5 572 54... 05: 23 = ,388

. The compound stops 612 rays of heat, and 224 of light.

458 Dr. wie gi 8 Experiments on tbe solar, and

48th Experiment. | : r lo saodT
Sun. Gin, ‘ Log bis 3 {
oO! 52 52
5 oe 53h --- 5a: 15 = 261

- This compound stops 739 rays of heat, and 626 of light. -

49th Experiment.

Sun. Brandy.
Q"2 : 3 56 e300) igs
5 6oL 5OZ 0. 4b == 4206 |!

This stops 794 rays of heat, and 996 rays of light. —

Other liquids have also been tried; but the experiments hav-
ing been attended with circumstances that demand a further
investigation, they cannot now be given.

Transmission of Sip Feat through scattering Substances.

50th Experiment.

I rubbed one of the pieces of crown glass, mentioned in the
26th experiment, on fine emery laid on a plain brass tool, to
make the surface of-it rough, which, it is well known, will
occasion the transmitted light to be scattered in all directions.
Supposing that it would have the same effect on heat, I tried
the transmitting capacity of the glass, by exposing it with the
rough side towards the sun, over one of the transmitting holes
of the apparatus.

Sun. Crown glass; one side rubbed on emery.
o! 67 07
5 74 70% +. +73 Ba = 2530

The glass so prepared stops 464 scattered rays of heat, and 854,
of light. Now, as the same glass, in its polished state, trans-

' on the terrestrial Rays that occasion Heat. 459

mitted-259 rays of heat, and 203 of light, the alteration pro-
duced in the texture of its surface acts very differently upon
these two principles; occasioning an additional stoppage of
only 205 rays of heat, but of 651 rays of light.

5ist Experiment.
One of the pieces of coach glass, mentioned in the 27th
experiment, was prepared in the same manner.

Sun. Coach glass; one side rubbed on emery,
the rough side exposed.
’ I . I
e 667, 667, |
i I I ° —
5 732 Cot, eo 3429

It stops 571 scattered rays of heat, and 885 of light; so that |
the fine scratches on its surface, made by the operation of
emery, have again acted very differently upon the rays of heat,
and of light, occasioning an additional stoppage of 375 of the
former, but of no less than 717 of the latter.

52d Experiment.
I took another of the pieces of crown glass, mentioned in the
26th experiment, and rubbed both sides on emery.

- Sun. Crown glass; both sides rubbed on emery.
o 693 695 | hi
; : ae I -_o—_—
sats 755 71z---6:2= 338

The glass thus prepared, stops 667 scattered rays of heat,
and 932 of light. :

53d Experiment.
Another piece of coach.glass, one of those that were men-
tioned in the 27th experiment, was. prepared in the same
manner,

}
‘

460 Dr. HERscue.’s Experiments on the solar, and

Sun, Coach glass; both sides rubbed on emery.
5 5 :
e 695 695
5 75% 7it...64: 15 = ,265

It stops 735 scattered rays of heat, and 946 of light.

54th Experiment.

I placed now the coach glass, one side of which had been
rubbed on emery, upon the transmitting hole, and over it the
crown glass prepared in the same manner, both with the
rough side towards the sun; but two slips of card were placed
between the glasses, to keep them from touching each other.

eats Crown glass. | One side of each rubbed
un.

Coach glass. on emery.
o! 67 67 : ;
5 73%. 69... 6%: 2 = ,go2

These glasses stop 698 scattered rays of heat, and 969 of
light. | |

55th Experiment,

I placed now the coach glass, with both sides rubbed on
emery, on the transmitting hole, and over it the crown glass
prepared in the same manner, with two slips of card. between
them, to prevent a contact.

Coach glass. Li sides of each rubbed on

Sun. | Crown glass. emery,

0’ 69% 695
S 75a 702... 6£: 1 =,200
These glasses stop 800 scattered rays of heat, and 979 of
light.
19 56th Experiment.
I used now all the four glasses; placing them as follows,
and putting slips of card between them, to prevent a contact, —

on the terrestrial Rays that occasion Heat. 461

s Coach glass; ditto.
wre Crown glass; rough on both sides.

Crown glass; the rough side to the sun,
{ Coach glass; ditto.

U

0 2 kai 572
ee Got 582... 523 = 5146
These four glasses stop no more than 854 apie rays of
heat, and ggg of light.

57th Experiment.

I used now a piece of glass of an olive colour, burnt into the
glass, in the manner that glasses are prepared for church
windows, which transmits only scattered light.

Sun. Olive-coloured glass,
ago 69 | 69
5 Ui ae OL. 72 1b = 161

This glass ee 8 39 scattered rays oF fem and 984, of fight

58th Experiment.

Sun, Calcined tale.
U 3 A a 3
Sento eyclunen he 513g pestis
5 55% Pay ae ies

This substance stops 867 scattered rays of heat, and so much |
light that the sun cannot be perceived through it.*

59tb Experiment.

3 "TUSunt)s White paper |“
oy 63 63. |
5 68 5 gts toGgSe. dong 2 ==, Wg Or
This substance. ei B59 scattered rays of heat, and 994 of
light. bilont 2. t Iauas ot i

: ® ‘See the 17 5th Experiment.
MDCCC. 31 ig Ov:

462 Dr, HErscue.’s Experiments on the solar, and

,

Goth en

Sun. Linen.
o! 63 63
ipa 69 et. ek meiedenml

White linen stops 916 scattered rays of i aky aia 95% sae
light.
61st Experiment.

Sun, White persian.
oft FEO § 70
ott 76% ais : 1y = 4240

This thin silk stops 760 scattered rays of hae and 916 of
light. :
62d Experiment.

_ Sun. Black muslin.
64 | O45
70 66h... 54:14 = ,286

This substance stops 714 scattered rays of heat, and 737 of
light.

Transmission of terrestrial Flame-heat through various Substances.

My apparatus rm the ‘purpose of transmitting fldme cheat i is
as follows.* ‘A box 22 inches long, 51 broad, and:13 deep, has |
a hole in the centre 1,4 inch in diameter, through which a wax
candle, thick enough entirely to, fill it, is to be put at the bot-
tom; the box being properly elevated for the purpose. There
must be two lateral holes in the bottom, 2 inches long, and 12
broad; .one on each.side’of the candle, to supply it with a cur-
rent of air, as otherwise it will not give a ica sid ee
is ae. sees aie At the distance pi 13, inch from ‘the

—

* See gins XXIII. 7 Is

on the terrestrial Rays that occasion Heat. 463

a hole in each, 3 inch in diameter, through which the heat of the
candle passes to the,two thermometers, which are: tp be placed
‘in opposite directions, one on each side, of the table. Care must
tbe taken to place them exactly at the same distance from the
‘centre of the flame, as otherwise they will not receive equal
quantities of heat. The scales, and their supports, also, must be
so kept out of the way of heat coming from the candle, that they
may not scatter it back on the balls, but suffer all that is not
intercepted by, them to. pass freely forwards in the box, and
downwards, through openings cut inthe bottom. ° Before the
transmitting holes,.between the two wooden screens, must be
‘two covers of the same material; close to the openings ; * and it
-will be necessary to join these covers at the side, by a common
handle, that they. may be removed, together, without disturbing
any part of the apparatus, when the experiment is to begin.

~ J¥Fhe:glasses are to! be put before the thermometer, close to
‘the. transmitting ‘hole, by placing them on a small support
below, while the-upper part is held close to the screen by a
light plummet, suspended by»a)thread. which is fastened on.one
side, and passes over the glass, toa hook on the other side.

In making experiments, many attentions are necessary, such
as, keeping the candle. exactly to a certain height, that the
brightest part of the flame may be just in the centre of the two
transmitting holes : that the wick may be always straight, and
not, by bending, ‘approach nearer to’ one thermometer. than
to the other: that the wax-cup of the candle be kept clean,
and never suffered to runsever, &c)

Before, and now.and,then between, the observations also, the
thermometers must be tried a few degrees, that it may be seen
. =F TR Zou * See Fig. Zu

Ago@-erish Io evar $0 eqola I

464 Dr. HERscHEL’s Experiments on the solar, and

whether they act equally ; and the candle, during the time they
cool down to the temperature, must be put out by an extin-
-guisher, large enough to rest on the bottom of the box, without
touching any part of the wax. Many other precautions I need
not mention, as they will soon be discovered by any one who
may repeat such experiments.

~
63d Experiment.
Candle. Bluish-white glasse
oy 59% 59z
re 623 6oz...3: 14: ==,3975

From this experiment we find, that while the rays of the
candle gave 9 degrees of heat to the thermometer openly ex-
posed to their action, the other thermometer, which received
the same rays through the medium of the interposed glass, rose
only 14 degrees. Hence we calculate, that this glass stops 625
rays of flame-heat, out of every thousand that fall on it. It
stops only 86 rays of candle-light; but this, having been re-
ferred to before, will not in future be repeated.

/ 64th Experiment.
Candle. ‘Flint glass. 3 .
o" poe 59% Bet: I
5 623 Got ...93:14= ,409

It stops 591 rays of flame-heat, and light as before.

65th Experiment.

. Candle. Crown glass.
o! 59% 59% ore ToE
5 625 60d yn Re eee bB64

It stops 696 rays of flame-heat.

on the terrestrial Rays that occasion Heat. 465

66th Experiment.

Candle. Coach glass.
Oo’ 60 603
5 63 | 62...3: 15 == ,542

It stops 458 rays of flame-heat.

67th Experiment.

‘Candle. Iceland crystal.
tes? 3 3
° 58% 58%
I 3 Sia ee
5 6oL 602 ...3%:13 = ,484

It stops 516 rays of flame-heat.

68th Experiment.

Candle. Calcinable talc.
, 7 7
° 585 585
z 3 Oph) Voy eases 7
5 612 603...9: 12 = ,625

This substance stops only 375 rays of flame-heat.

69th Experiment.

Candle. Very dark red glass,
’ 3 3
Oo 602 603
I a ee ss
5 63+ '612...95:1 = ,364

This glass stops 636 rays of flame-heat.

7oth Experiment.

Candle. Dark red glass.
? 3 3
1) : 60% 603.
‘ I we 3! i—_
14 633 612...93:12 = ,474

It stops 526 rays of flame-heat.

466 Dr, Henscue’s Experiments on the solar, and

vist Experiment,

Candle, ‘ Orange glass.
, I I
Oo 6olL 6o0i
3 5 nt eres
5 632 615... 35: 14 = 440

It stops 560 rays of flame-heat,

vad Experiment,

Candle. Yellow glass,
, 5 5
O 603 602

5 633 617...3: 15a
It stops 589 rays of flame-heat. ’

79d Experiment.
Candle. Paleegreen glass.
of ~ 60% 602
5 637 694...3:15 = ,500

It stops 500 rays of flame-heat.

74th Experiment.

Candle. Dark-green glass.
o! “9614 614
5 64 612...97: 2 = ,261
It stops 739 rays of flame-heat. |
wath Experiment.
Candle. Bluish-green glass.
of - 614 | 615.
‘ae 64, — 96aL... 97: 1 = 4948

It stops 652 rays of flame-heat.

on the terrestrial Rays that occasion Heat. 467

“6th Experiment.
Candle. Pale-blue glass.
o! 614 614
i 642 623...2%

It stops 609 rays of flame-heat.

77th Experiment.

‘lt stops 520 rays of flame-heat. ©

> 15 = ,391

: Candle. Dark-blue glass.
of 612 613 ;
5 S45 Go3...95:1= ,981
It stops 619 rays of flame-heat. ‘
78th Experiment.
; Candle. Indigo glass.
of 612 3 Bre
epee 653 63...31:14 = ,921
It stops 679 rays of flame-heat.
79th Experiment.
Candle. . Pale indigo glass.
°. 625 625
289 Lr ; oH 643 635 -. 25319 = 1429
It stops 571 rays of flame-heat.
80th Experiment.
y Hodis: Candle. > ‘Purple-glass. ,
25r.: ie... Say 633...» 337315 = 480

468 — Dr. HERSCHEL’s Experiments on the solar, and

‘

81st Experiment.

Candle. Violet glass.
or a 595 «598
af; - 633 HOLS ... 82: 131 ,500
It stops 500 rays of flame-heat.. | aguse we
82d apchiviens
Candle. Crown glass; one side rubbed on
ETSMIery,5) the rough side exposed.
ey 60 6o |
7 3.2 aes
5 633 60g... 33: F = 2259

This glass, so prepared, stops 741 scattered rays of flame-
heat.

83d Experiment.
Candle. Coach glass; one side rubbed on ~
"emery ; the rough side exposed.
Oo’ 59% 59% :
+ 1B
5 63% Gof... 34:15 = 338

It stops 667 scattered rays of flame-heat.

84th Experiment.

Candle. Crown glass; both sides rubbed on emery.
patie : a
° 594 594
5 63 WG 5+ Bee Ae es

It stops 615 scattered rays of flame-heat.

S5th Experiment.

2 Candle. ~*~ __ Coach glass; both sides ae on emery.
’

S) - 595 ~ (59%

i 63 Gof... 37: 1 = .320

It stops 680 scattered rays of flame-heat. == =

— 2 a

the terrestrial Rays that occasion Heat. 469

86th Experiment.

Crown glass. | One side of each rubbed
Candle. Coach glass. on emery.
’ 7
° 55g 555
3 ike Fue
- 59 562 ....391: 2 = ,280

These glasses stop 720 scattered rays of flame-heat.

87th Experiment.

eecah Crown glass. | Both sides of each rubbed
pares Coach glass. on emery.
2 it
508 508
i SLAPN EO ee
594 Ohi gg» tg\— 305

These glasses stop 667 rays of flame-heat.

88th Experiment.
Crown glass; the rough side to the candle.
Coach glass; ditto.
Candle. Crown lass 3 rough on both sides ;
Coach glass; ditto.

Shs 56S 562
5 59¢ 574 +++ 29% | = 5190
These four glasses stop 870 scattered rays of flame-heat.

8oqth Experiment.

Candle. Olive-colour, burnt in glass,
o! 60 60
5 63 603...3:5 = ,208

This glass stops 792 scattered rays of flame-heat-

goth Experiment.

Candle, White paper.
‘
© 578 87%
5 603 SUL... O.: * == 1206

This substance stops 792 scattered rays of flame-heat
MDCCC, | ‘ie P

4/70 Dr. HerscueE.’s Experiments on the solar, and

gist Experiment,

Candle. Linen.
o 573 S78
Be 64 585... 93315 ==,310

It stops 6go scattered rays of flame-heat.

ged Experiment.

Candle. White persian.
Oo" 578 57
5 - 601 583... 92:12 = ,407
It stops 593 scattered rays of flame-heat.
93d Experiment.
Candle. Black muslin.
0! 574 Oe
5 602 59... 22 3 15 == 405

It stops 565 scattered rays of flame-heat.

Transmission of the solar Heat which ts of an equal Refrangibility
with red prismatic Rays.

The apparatus which I have used for transmitting prismatic
rays, is of the same construction as that which has already been
described under the. head of direct solar transmissions; * but
here the holes in the top of the box are only two inches from
each other, and no more than $ths in diameter. On the face of
the box are drawn two parallel lines, also 3ths of an inch distant
from each other, and inclosing the transmitting holes: they
serve as a direction whereby to keep any required colour to fall
equally on both holes. The distance at which the box is to be

* See Plate XXI. + See Plate XXII. Fig. 3.

on the terrestrial Rays that occasion Heat. 471

placed from the prism, must be such as will allow the rays to
diverge sufficiently for the required colour to fill the transmit-
ting holes ; and the balls of the thermometers placed under them
ought to be less than these holes, that the projected rays may
pass around them, and shew their proper adjustment. The dia-
meters of mine, used for this purpose, are 21 tenths of an inch.

g4th Experiment.

I placed my apparatus at five feet from the prism, and so as
to cause the red-making rays to fall between the parallel lines,
in order to find what heat-making rays would come to the ther-
mometer along with them.

Red rays. . __. Bluish-white glass.

Therm. A, ; Therm. B.
or saseyts TBpt «758
5 77s W762... 2: 14'S 695

From this experiment it appears, that when a thousand red-
making rays fall on each transmitting hole, 975 of them, if they
also be the heat-making rays, are stopped by the bluish-white
glass which covers one of these holes; or, what requires no
other proof than the experiment itself; that 375 rays of heat,
of the same aor area with the red’ ea are ee ee by
this glass.

- 95th Experiment.

Red rays. Flint glass.
75% ; Ree ois
ies 76Z,..12:15 = 857

This glass stops only 143 rays of heat~ which are of the same
refrangibility with the red rays.

3Pe

472 Dr. HERSCHEL’s Experiments on the solar, and

96th Experiment.

Red rays. Crown glass.
0 75% 756 yuo
5 78 7750+ 2% 15 = ,706

This glass stops 294, rays of the same sort of heat.

97th Experiment.

Red rays. Coach glass.
4
° 545 53%
5 55% 54% ...14:1 = ,800

It stops 200 rays of the same sort of heat.

98th Experiment.

Red rays. Iceland crystal,
o 705 15
is 78 m7t...12: 14 = 800

' This substance stops 200 rays of the same sort of heat.

ggth Experiment.

Red rays. - Calcinable talc.
’ 3 I
ve 514 b1¢
5 53% 522....12:15 = ,867

It stops 133 rays of the same sort of heat.

100th Experiment.

Red rays. Dark-red glass.
o! 767 765
5 783 77k 1G tt 308

This glass stops 692 rays of the same sort of heat.

on the terrestrial Rays that occasion Heat. 473

1o1ist Experiment.

Red rays. Orange glass.
o 75 Phe),
5 Ty Tie... 2; 1 == ,500

It stops 500 rays of the same sort of heat.

102d Experiment.

Red rays. Yellow glass.
158 75
762 755. -.14:2 = 583
It stops 417 rays of the same sort of heat.
103d Experiment.
_ Red rays. - Pale-green glass.
oO’ Aa 748
5 763 75 ++. iF Al2
It stops 588 rays of the same sort of heat.
104th Experiment.
Red rays. Dark-green glass.
o 683 682
5 7s 6o¢...13:3 = ,214
It stops 786 rays of the same sort of heat.
105th Experiment.
Red rays. Bluish-green glass.
o! 69 682
5 any for 692...13:2== ,538

It stops 462 rays of the same sort of heat.

474 Dr. Herscuen’s Experiments on the solar, and

106th Experiment.

Red rays. Pale-blue glass.
' s rot
e 69% 692
5 704 692...14:2 = ,300

It stops 700 rays of the same sort of heat.

107th Experiment.

Red rays, Dark-blue glass.
o! 67 672
5 — 682 682.,..14:12 = ,929

This glass stops only 71 rays of the same sort of heat.

108th Experiment.

Red rayss Indigo glass.
’ I
fe) 682 68i
5 : TOL 691...2:14 = ,633

It stops 367 rays of the same sort of heat.

109th Experiment.

Red rays. Pale-indigo glass.
nO; 69 682

i este! BON 2 2 ee ae
It stops 313 rays of the same sort of heat. ie

110th Experiment.

Red rays. Purple glass.
o! | 665 56

5 2 TOS 57k... 92: 1b = 4556
It stops 44.4 rays of the same sort of heat, |

on the terrestrial Rays that occasion Heat. ATS

111th Experiment.

Red rays, Violet glass.
ot 578 57
5 59+ 581...12:14 = 600

It stops 400 rays of the same sort of heat.

112%b Experiment.

Red rays. Crown glass; one side rubbed on emery,
rough side exposed.
' : A 3
0 49% 49 |
5 ional. 502...22:13=> 611

* This glass, so prepared, stops 389 scattered rays of the same
sort of heat.
113th Experiment.

Red rays. Coach glass; one side rubbed on emery,
rough side exposed.
! 3 7
O 538 525
I 3 Bue Zee
5 55% 534 +-+14 + ¢ = 2500

It stops 500 scattered rays of the same sort of heat.

114th Experiment.

Red rays. Crown glass; both sides rubbed on emery.
’ 5
. 58 49s
5 523 Gla, «,.'25 2 15 = 529

It stops 471 scattered rays of the same sort of heat.

115th Experiment.

Red rays. Coach glass; both sides rubbed on emery,
, I
0 54 534
5 55z 54... 15:i= ,167

It stops 839 scattered rays of the same sort of heat.

476 Dr. HerscueEn’s Experiments on the solar, and

116tb Experiment.

Red rays. Calcined talc. -
, I I
© d1¢ 5°F
5 533 Sig +++ 297g = 263

This substance stops 737 scattered rays of the same sort of
heat.

Transmission of Fire-Heat through various Substances.

When the same fire is to give an equal heat to two thermo-
meters, at some short distance from each other, it becomes
highly necessary that there should be a place of considerable
dimensions in its centre, where it may burn with an equal glow,
and without flame or smoke. To obtain this, I used a grate

19 inches broad, and 82 high, having only three bars, which.
divide the fire into three large openings. In the centre of the |

middle one of these, when the grate is well filled with large
coals or coke, we may, with proper management, keep up the
required equality of radiance.

The apparatus I have used is of the following construction.*
A screen of wood, g feet 6 inches high, and g feet broad, lined
towards the fire with plates of iron, has two holes, 2 of an inch
in diameter, and at the distance of 21 inches from each other,
one on each side of the middle of the screen, and of a height
that will answer to the centre of the fire. 22 inches under
the centre of the holes is a shelf, about 22 inches long and 4

broad, on which are placed two thermometers, in opposite direc-_

tions, fixed on proper stands, to bring the balls, quite disen-
gaged from the scales, directly 2 inches behind the transmitting

* See Plate XXIV.

;
= a

‘on the terrestrial Rays that occasion Heat. M77"

holes. A small thin wooden partition is run up between the
thermometers, to prevent the heat transmitted through one hole
from coming to the thermometer belonging to the other.

The screen is fixed upon a light frame, which fits exactly into
the opening of the front of the marble chimney-piece ; and the
ends of the frame are of a length which, when the screen is
placed before the fire, will just bring the transmitting holes to
be 64 inches from the front bars of the grate.

A large wooden cover, also plated with iron, shuts up the
transmitting holes on the side next to the fire; but may be
drawn up by a string on the outside, so as to open oa when
required. ;

Two assistant thermometers are placed on proper stands, to
bring their balls to the same distance from the screen as those
which receive the heat of the fire; but removed sideways as far
as necessary, to put them out of the reach of any rays that pass
obliquely through the transmitting holes. They are to indicate
any change of temperature that may take place during the time
of the experiment: for, notwithstanding the largeness of the
screen, some heat will find its way round and over it; and this
acting as a general cause, its effect must be allowed for.

117th Experiment.

‘Having tried the apparatus sufficiently to find that:the ther-
mometers exposed to the transmitting holes would generally
receive 20 or more degrees of heat, without differing more than
sometimes 4 or at most. t of a degree, I now placed the bluish-
white glass of the o4th experiment upon a support prepared for
the purpose, so as closely to cover one of the transmitting holes.
A smail spring, moveable on its centre, is always turned against

MDCCC. 39

478 Dr. HErscuE.’s Experiments on the solar, and

the upper part of the transmitting pean to hs them in lee
situation. | | |

Fire. Bluish-white glass, :
o! 66 eats , ;
5 86 71.1290: 5 = 250

This glass stops 750 rays of fire-heat. By looking through it,
at the same place in the fire, after the screen was removed, in.
order to cool the apparatus for the next experiment, I found that
this glass can hardly be said to stop any of the light of the fire.

118¢h Experiment.

Fire. Flint glass.
ee 67 Biba ora
5 87 72 i VO toh Reg 2eL

It stops 750 rays of fire-heat.

119th Experiment.

Fire. Crown glass.
o’ 67 67
5 863 72F + 19S: Fy = 278

It stops 722 rays of fire-heat.

120th Experiment. att

Fire. Coach glass.
ees 863 73 +++ 19%: 53 = 286

| It stops 714, rays of fire-heat.

121ist Experiment.

Fire. Iceland crystal.
O° 68 68.) |
5 995 7B G++ + 297% = 944

This substance stops 756 rays of fire-heat,

on the terrestrial Rays that occasion Heat. 479

129d Experiment.

I took now the piece of talc used in the goth experiment,
and, placing it over the transmitting hole, I had the following
result. But, as the unexpected event of a calcination, which took
place, was attended with circumstances that ought to be noticed,
I shall, instead of the usual abridgment of the experiments, give
this at full length. .

Fire. Talc.
Therm. D. Therm. C.
0’ 65 Mes
1 79, Sia Ae TG. = OSG
2 SMR 683....12 : 3% = ,281
Bae 69x... 154: 44 = ,290
Ay, 83 Fe neh beste te TEs beam yas
e Geb Sa Lee 20, 2 Boa OB

_ This substance stops 719 rays of fire-heat.
* 1 am now to point out the singularity of this experiment;
which consists, as we may see by the above register of it, in the
apparently regular continuance of its power of transmitting heat,
while its capacity of transmitting light was totally destroyed.
For, when I placed this piece of talc over the hole in the screen,
it was extremely transparent, as this substance is generally
known to be; and yet, when. the experiment was over, it ap-~
peared of a beautiful white colour; and its power of transmitting
light was so totally destroyed, that even the sun in the meridian
could not be perceived through it. Now, had the power of trans-
mitting heat through this substance been really uniform during
all the five minutes, it would have been quite a new phenome-
‘non; as all my experiments are attended with a regular increase

3Q2

_ 480 Dr. HerscuE’s Experiments on the solar, and

of it; but since, by calcination, the talc lost much of its trans-
mitting power, we may easily account for this unexpected
regularity. ) rai Moot]

123d Experiment. — 1? grtiSekey ims
Fire, Very dark red glass. j ge’ Sides:
66 66
894 75 +++ 23529 = .387

This glass stops 619 rays of fire-heat.

124th Experiment.

Fire. Dark-red glass.
oO’ 67 67
ip 923 78...2953:11 = ,427

This glass, which stops g99,8 rays of candle-light, stops only
573 rays of fire-heat; whereas my piece of thick flint glass,
which stops no more than g1 rays of that light, stops no less
than 750 of fire-heat. It does not appear, by looking through
these glasses, that there is a difference in their disposition to
transmit candle-light or fire-light. : Hine

125th Experiment.

Fire. Orange glass.
Oo! 66 66

5 Pe? Bo FAS) An VES Be7
It stops 643 rays of fire-heat. .

126th Experiment.
Fire. Yellow glass. + IG911
o! 617 | 614 . unin AY ils
5 83 683...21:7£.cor.—14°.202: 61 = ,315

on the terrestrial Rays that occasion Heat. 4814

This experiment being made early in the morning, before
the temperature of the room was come to its usual height, the
assistant thermometers shewed a gradual rising of 14 degree in
the 5 minutes: they are in general very steady. The glass
stops 685 rays of fire-heat.

107th Experiment.

Fire. Pale-green glass.
o’ 65% 654 |
5 85 7i3....194:6 = ,g12

It stops 688 rays of fire-heat.

1282b Experiment.

Fire. . Dark-green glass,
o 68 68
3 3 \3 + pd °
5 - 883 73% ...20%: 54 COr.— 4) = 255

It stops 74,5 rays of fire-heat.

129th Experiment.

Fire. Bluish-green glass.
of 68+ 68L
5 87 7Ag...1823 53 = ,904

It stops 696 rays of fire-heat:

130th Experiment.

Fire. Pale-blue glass.
of 682 ais
5 867 734 °-° 174° 55 = 1324 |

It stops 676 rays of fire-heat.

bie Dr. Hesoury’s Experi
Clot partieerom od ri Webi shies iis
ott Srhats it PUPS Gat 3 ay? gist E. See
ri ooTgonhy gt to wert hy. bicep so ares i
vale oll ov baie -viov Leveyegaih ois yotkdes eons L

5 84E 78.4 17 PO. COn mea

idsinaieions rays of frecheat. 1b orearyad) bo sank i

L. OF@s
sgoditeepavitaent, ai
Fire. Indigo glass. om y ‘O:
Oo Si > — 6gt qt -- 695 5 ; o as ae %
5 852... 73 get -aOeog seit |

It stops 721 rays of fire-heat. |

¥ wt ey yt dake ae wi {Age ose a

aes Experinent. od

dns ees Pale indigo glass. 80 z ‘o
mol k = 00 OEE HOE. 9 Bye cee agg Se
5 ae Boe ai ta rye: GE con 45

It stops 655 rays of fire-heat. rh eat beet gt ois
CHR sk Oe f [ Biviastirs oe
ie Experiment. |

LS Bine. Purple glass, 4 coe qe a Saas

r f ) ‘glee i} »

Ai ” etd ‘ LO " he
oy) Gg: $61. Boea 7 eae > 3) ye ee

5 B31 4 ral oa one
It stops 679 rays of Sperbetty yet, berg) ice de ae

135th Experiment, er

Lok
: Fire. —sCViolet glass. Vi ¢€ 28 eis
evs i po af 662 + SRE a! 661 's 198° f

5 861 74k 1. ./20 07
It stops 615 rays of fire-heat, —

'
H aw ss VAotes se

on the terrestrial Rays that occasion Heat. 483:

136th Experiment.

Fire. , Crown glass; one side rubbed on emery.
o! 673 673
5 895 793), 901 : GL = 277
This glass, so prepared, stops 729 scattered rays of fire-heat.
137th Experiment
Fire, Coach glass ; one side rubbed on emery.
o! 68 3 674
5 O7E 72t 4195 : Ag = 5242

It stops 758 scattered rays of fire-heat.

138th Experiment.

Fire. - Crown glass; both sides rubbed on emery,
o! 681 68
ie | oe 924 TQ 29") > f= ,209

It stops 791 scattered rays of fire-heat.

139th Experiment.

Fire. Coach glass; both sides rubbed on emery.
of 67 67 ea
5 88 7oL... 21: 34.cor, — 2° = ,146

It stops 854, scattered rays of fire-heat.

140th Experiment.

Eire Crown glass. } One side of each rubbed on
i Coach glass. } emery.
oy 66 66
5 86 692....20: 92. cor, —1°== ,151

These glasses stop 849 scattered rays of fire-heat.

14gast Experiment.

! _ § Crown glass. sides of each

WYSE aH iE ire. , phi {Coach gi} ener se
fou ge 663 \ y cy :
5 Vela Te eget a el

_ These pill stop es scattered ‘rays ‘of fire-heat.

142d Experiment.
Fire. ~~ The four glasses of the two preceding experiments pat
penis aD 4 a tg
Oo! 66 BE oe oe

res

a) Ri 4 4
These four glasses stop 902 ae ra ys Wee feat

isd Teapareaay |, \? Nien

‘Fire. Olive colour, burnt Baower Gi onmne | oo " 2
oO! 3 632 tat 633 we are aitiheag 6 4
(gO SOob Bgl ined nee Bt Abie e sigh

This oe vi sete scattered rays of dvo-leab ag Howes i 4 7
14 sitet be:
boat doithy ow) set Weis

te oi vat Experiment, robb WwW cron el
iii] Piney, PAPE Tighe 4 bi t Ys3 ylddianv
x 661 665 hae Q a
5 83h} > 68 2p age —

This substance stops 912 pee one fir
turned a little yellow by the exposure. ©
145th Experiment.
mire JO Bye Linemery ry) 4
o! 633 . 633
B45 ‘2 nGqan

on the terrestrial Rays that occasion Heat. 48.5

146th Experiment.

Fire. White persian.
of 652 65%
5 — Sit 683 ...153: 93 =,171

This substance stops 829 scattered rays of fire-heat.

147th Experiment.

Fire, Black muslin.
oO! 66 66
t if I. I 1.0 + om
5 Sot 7oL... 164: 44 . cor. + 2° = ,294

This substance stops 706 scattered rays of fire-heat.

Transmission of the invisible Rays of solar Heat.

The same apparatus which I have used for the transmission —
of coloured prismatic rays,* will also do for the invisible part
of the heat spectrum: it is only required to add two or three
more parallel lines, one-tenth of an inch from each other, be-
low the two which inclose the transmitting holes, in order to
use them for directing the invisible rays of heat, by the position
of the visible rays of light, to fall on the place required for coming
to the thermometers.

148th Experiment.
) Invisible rays. Bluish-white glass.
0 48 47
5 49% Abe. ++ 14515 = 929
This glass stops only 71 invisible rays of heat.

“# See Plate XXII. Fig. 3.
MDCCC. gR

486 Dr. HeERscueEn’s Experiments on the solar, and

149th Experiment. ! "9

Invisible rays. Flint glass.
fi:
S 50% 495
5 52 i §lg. We: 1 = 1,006

_ This glass stops no invisible rays of heat.

150th Experiment.

Invisible rays. _ Crown glass.
, I 3
e Sipe AOE akg
5 512 502...13:15 = 818

It stops 182 invisible rays of heat. oT

151st Experiment.

Invisible rays. Coach glass.
I Tis
b42 53¢ |
SA T+ 3 ——
55% 54 eee ix ie — 9857

It stops 149 invisible rays of heat.

152d Experiment.

Invisible rays. ~~ Calcinable talc.
’ 3 3
ie) d1g Wee 505
~o 7 vi Ds pee
5 525 $1g---15:14 =.,750

This substance stops 250 invisible rays of heat.

153d Experiment.
Invisible rays. _ _ Dark-red glass.
/
O adh eal APA 25) |
5 485 ADR ++ 121 = 1,000.

This glass stops no invisible rays of heat. This accounts
for the strong sensation of heat felt by the eye, in looking at

; myoOrscr tT
4 DIIIULM

on the terrestrial Rays that occasion Heat. 487

the sun through a telescope, when red darkening glasses are

used. — |
154tb Experiment.
Invisible rays. Orange glass.
ST eh Sh 2, OS! oR |
5 53° 52.2 1g a= 727

It stops 279 invisible rays of heat.

155th Experiment.
: Invisible rays. Yellow glass.
Pr gn: eas
° Dag jt aah
Beer 53 Hote he Uk == 5800

It stops 200 invisible rays of heat.

(156th Experiment.

_ Invisible rays. Pale-green glass.
ee ek Baz ces
5 525 f1g...122 = 625
It stops 375 invisible rays of heat.
157th Experiment.
Invisible rays. Dark-green glass.
erie it Bae 512 3
5 525 52...1:5=,§00
It stops 500 invisible rays of heat.
(158th Experiment.
Invisible rays. Bluish-green glass.

iam 58 525

Swe 54g |

It stops 800 invisible rays of heat.
3g3Re2

488 Dr. HERscuHeE.’s Experiments on the solar, and

159th Experiment. ae been

Invisible rays. _ Pale-blue glass.
o 51g 51g
, I ° —
5 53% §15....15 33 = 417

It stops 589 invisible rays of heat.

160th Experiment.

Invisible rays. Dark-blue glass.
’ 7 5
i) Oey iy, dle
5.4; 525 52e ++ ZF = 833

It stops 167 invisible rays of heat.

161st Experiment.

Invisible rays. Indigo glass.
, 7 I
o 525 524
1 ary —
5 548 53 +--+ 12: e500

It stops 500 invisible rays of heat.

162d Experiment.

Invisible rays. Pale-indigo glass.
of 523 525
rey 533 §22...1:4==,750

It stops 250 invisible rays of heat.
163d Experiment. |

Invisible rays. Purple glass.
o! 515 50%
& 52% 513...13:1== 4,727

It stops 273 invisible rays of heat.

on the terrestrial Rays that occasion Heat. 489

164th Experiment.

Invisible rays, Violet glass.
t 3
° 53 525
I o 3 es
5 f 54g 53¢+--1:5=,5750

It stops 250 invisible rays of heat.

165th Experiment.

Invisible rays. Crown glass; one side rubbed on emery,

rough side exposed.

I if 3
° 49% 487

3 I phate bo pees

5 504 494 ---14¢: 5 = 400
This glass, so prepared, stops 600 scattered invisible rays of
heat. |

166th Experiment.

Invisible rays. Coach glass ; one side rubbed on emery,
rough side exposed.

o' 54 538
5 55 54-..15:2 = ,500
It stops 500 scattered invisible rays of heat.

167th Experiment.

Invisible rays. Crown glass; both sides rubbed on emery.

o! 50 ‘ 49g
5 51g AQ ---1

y=
> = 4,00
It stops 600 scattered invisible rays of heat.

AIM

168th Experiment.

Invisible rays. Coach glass; both sides rubbed on emery.

54g «4g
5 «55s 543... 5:5 = ,286
It stops 714, scattered invisible rays of heat.

oO’

49° Dr. HerscueEx’s Experiments on the solar, and

169th Experiment.

Invisible rays. ~ Calcined talc.
r 7
© 51g 505 :
5 53 Sir. sldee ye ie

This substance stops 889 scattered invisible rays of heat.

Transmission of invisible terrestrial Heat.

This is perhaps the most extensive and most interesting of
all the articles we have to investigate. Dark heat is with us
the most common of all; and its passage from one body into
another, is what it highly concerns us‘to trace out. The slightest
change of temperature denotes the motion of invisible heat ; and
if we could be fully informed about the method of its trans-
mission, much light would be thrown on what now still remains
a mysterious subject. It must be remembered, that in the fol-
lowing experiments, I only mean to point out the transmission
-of such dark heat as I have before proved to consist of rays,
without inquiring whether there be-any other than such existing.

My apparatus for these experiments is as follows.* A box
12 inches long, 53 broad, and g deep, has a partition through-
out its whole length, which divides it into two parts. At one
end of each division is a hole 3 3 inch in diameter; and each di-
vision contains.a idennaece with its ball exposed to the hole,
and at one inch distance from the outside of the box. Four
inches of the box, next to the holes, are covered; the rest is
open. In the front of it is a narrow slip of wood, on which
may rest any glass to:be tried; and it is held close to the wood
at the top, by a small spring applied against it. Two screws
are planted upon the front, one on .each sides rire may be

* See Plate XXV. Figy1 :

on the terrestrial Rays that occasion Heat. 491

drawn out or screwed in, by way of accurately adjusting the
distance of the thermometer from the line of action.

In order to procure invisible terrestrial heat, I have tried
many different ways, but a stove is the most commodious of
them. Iron isa substance that transmits invisible heat very
readily ; while, at the same time, it will most effectually inter-
cept every visible ray of the fire by which it is heated, provided
that be not carried to any great excess. I therefore made use
of an iron stove,* having four flat sides, and being constructed
so as to exclude all appearance of light. I had it placed close
to a wall, that the pipe which conveys away smoke might not
scatter heat into the room.

The thermometer box, when experiments are to be made, is
to be put into an arrangement of twelve bricks, placed on a
stand, with casters: -+ these bricks, when the stand is rolled
close to the stove, which must not be done till an experiment
is to begin, form an inclosure, just fitting round the sides, bot-
tom, and covered part of the top of the thermometer box, and
completely guard it against the heat of the stove. The box is
then shoved into the brick opening, close to the iron side of the
stove, where the two front screws, coming into contact with
the iron plate, give the thermometers their proper’ distance ;
which, in the following experiments, has been such as. to bring
the most advanced part of the balls to one inch and four-tenths
from the hot iron.

It will be necessary to remark, that on calculating the trans-
missions for the fifth minute, I found that it would not be
doing justice to the stopping power of the glasses, to take so.
long a time; for, notwithstanding the use of brickwork, and ne

* See Plate XXV. Fig. 2, + See Fig. 3.

492 Dr. HERscuHEL’s Experiments on the solar, and

precaution I had taken, of having two sets of it, that one might
be cooling while the other was employed, and though neither
of them was ever very hot, yet I found that so much heat came
to the box, that when it was taken out of the bricks, in order to
be cooled, the thermometers continued still to rise, at an ave-
rage, about two degrees higher than they were. I have therefore
now taken the third minute, as a much safer way to come at
the truth. |
170th Experiment.

Stove. Bluish-white glass.
' 3
fe) 56 Dai
3 ; . —a
3 59% 50g -- - 353 14 = 5800

This glass stops 700 invisible rays of heat.

171st Experiment.

Stove. Flint glass.
o! 53% 532
3 558 54g +++ 152 5 = 467—

It stops 539 invisible rays of heat.

172d Experiment.
Stove. Crown glass. _
QO’ 50f 504
3 53% S1G 6 251 F217
It stops 783 invisible rays of heat.

173d Experiment.

Stove. Coach glass.
] I ; I 7
fe) 5°97 5°>
3 : 52t lf... 223 = 4875

It stops 625 invisible rays of heat,

_ on the terrestrial Rays that occasion Heat. 493

174th Experiment.

Stove. Iceland crystal.
0" 47 405
tity Sac 485+. - 75! 251274

This substance stops 726 invisible rays of heat.

175th Experiment.

Stoves Calcinable tale,
oF, Rep 1a 51z
I I Oe Go
3 ie 54g. O51 23 = 404

At the end of five minutes, when the box was taken out of
the bricks, the talc was perfectly turned into a scattering sub-
stance: as such, it stops 596 scattered invisible rays of heat.
The sun cannot be seen through it; but this I find is chiefly
owing to its scattering disposition. It stops however 997 scat-
tered rays of light. |

176th Experiment.

Stove. Dark red glass.

oO’ 58 58

3 64,2 Got ...63:25=,970
This glass stops 690 invisible rays of heat.

177th Experiment.
Stove. Orange glass.
or 552 554
3 BEN 57k +++ 5¢1 25,476

It stops 524, invisible rays of heat.

MDCCC, 35

‘Stove. - Yellow glass. Phy.
o’ vey 573 7k

" 3 vA 613 a eke
It stops 469 invisible rays of heat. NA aD

179th Experiment. =
_ Stove. __ Pale-green glass.
o! pe 112 Sn
EHS 38 564 e" os i .. Ado: 12 ee 48 38 ;
Tt oe 632 invisible rays of heat. NS vets i

: Ke Aird satis
180tb cysts ii ova, es) Sse
‘Stove. Darkegreen glass. =>) 4
a 4852.10 4985 |
8 58% er eee
It stops 700 invisible rays of heat. | Bae

181st Experiment. 1 ya
‘ Stove. _ Bluish-green glass. oo 7
O10) seat TE ath aay meeea ae
3 555 ee
It stops 556 eee rays oft heats "01°." VEN
182d En HB 9
Stove. - “Pale-blue ek

pageaiy int e ‘Bie
87s es O58
It.stops 548 invisible sok of heat.

_ on the terrestrial Rays that occasion Heat. 495

183d Experiment.

Stove, Dark-blue glass,
885 58
5 55e 535 +°°

It stops 632 invisible rays of heat.

184th Experiment.

Stove. Indigo plass.
e. 54ce 54
3 59 555 + °

‘It stops 659 invisible rays of heat.

185th Experiment.

Stove, Pale indigo glass,
/; ;
° 537 535
3
3 59% 55G ++:

_ It stops 700 inyisible rays of heat.

186) Experiment.

Stove. Purple glass.
y 3 I
- semen 4 ple
: 3
8 563 523 -

It stops 730 invisible rays of heat.

187th Experiment.

* Stove. ; Violet glass.
7 I
12) 51 Ws
3 Sys oo°°:

It stops 684, invisible rays of heat.
A 382

vee

Texoma
1g = 5341

: 1f = .g00

a eS ~~

496 Dr. Herscue.’s Experiments on the solar, and

188th Experiment.

Stove. _ Crown glass; one side rubbed on emery.
Ul I I
0 494 * 494
3 . I
3 54 505 +++ 5: 1y = ,225

This glass, so prepared, stops 775 invisible rays of scattered
heat. |
189th Experiment.

Stove. Coach glass ; one side rubbed on emery,
o! 50 50
I 7 Ze 7, —
3 574 51g +++ 7ei le = 259

It stops 741 invisible rays of scattered heat.

190th Experiment.

Stove. Crown glass; both sides rubbed on emery.
oO’ 52 52
3 58 590. Os dome HOY,

It stops 833 invisible rays of scattered heat.

191st Experiment.

Stove. Coach glass; both sides rubbed on emery.

of 52 52 ity) 4 |
I 3 Ile — a
Be 55¢ 523... 9722 => ,291

It stops 769 invisible rays of scattered heat.

192d Experiment.

Stove. Olive colour, burnt in glass.
Bie NA I ; I
) blz blz
3 57 582 -++ 5712 = 804

It stops 636 invisible rays of scattered heat.

on the terrestrial Rays that occasion Heat. 497

193d Experiment.
Stove. White paper.
o! 52 52

8 57% Sdq +++ 5322
This substance stops only 535 invisible rays of scattered
heat.

194th Experiment.

Stove. Linen,
or 53% 53%
3 57% 55a ++ de? 2s = 5543

It stops 457 invisible rays of scattered heat.

ARTICLE vi.—Scattering of Solar Heat.

We are now come to a branch of our-inquiry which, from its
novelty, would deserve a fuller investigation than we can at
present enter into. The scattering of heat, is a reflection of it
on the rough surfaces of bodies: it is therefore a principle of
general influence, since all bodies, even the most polished, are
sufficiently rough to scatter heat in all directions. In order, there-
fore, to compare the effect of rough surfaces on heat with their
effect on light, I have made a number of experiments, from
which the following are selected, for the purpose of our intended
comparative view.

The apparatus I have used for scattering solar heat, is like
that which served for transmissions;* but here the holes
through which the sun’s rays enter,{ are very exactly 14 inch
in diameter each; and are chamferred away on the under side;-

* See Plate XXI, Fig. 1. + See Plate XXII. Fig. 4.

-“

498 Dr, Herscue's Experiments on the solar, and

that no re-scattering may take place in the thickness of the
covering board: the distance of the centre of the holes is 4
inches. A little more than an inch below, and under the centre
of the holes, are the balls of the small thermometers A and B,
well shaded from the direct rays of the sun, by small slips of
wood, of the shape of the ball, and of that part of the stem which
is exposed.

Under each thermometer is a small tablet,* on which the an
jects intended for scattering the sun’s rays are to be placed.
The tablets are contrived so as to bring the objects perpendi~
cularly under the openings, and under the centre of the balls
of the thermometers, at the distance of exactly one inch from
them. Every thing being thus alike on both sides of the box,
it is evident, from the equality of the holes, that an equal num~
ber of solar rays will fall on each object, and will by them be
scattered back on the thermometers, at equal angles, and equal
distances.

The first five experiments that follow, were made with an
apparatus somewhat different from the one here described ; and,
though the result of them may not be so accurate as if they had
been made with the present one, I must give them as they are,
since time will not allow of a repetition.

195th Experiment.

Sun. Message card scattering,
o Bn a 64,
‘| 3 4 3 ° 3 —= a
5 692 663 2 $7? 2 = 5413

Here an object of a white colour, 3,6 inches long, and 2,6
broad, scattered, in § minutes, 413 rays of heat back upon one
* See Plate XXII. Fig. 5.

on the terrestrial Rays that occasion Heat. 499

thermometer, while the other received a thousand, directly from
the sun. Now, in order the better to compare the proportion of
light and heat scattered by different objects, we shall put these
4,13 rays equal to 1000; or, which is nearly the same, multiply
them by 2,421. Then, since the message card also scatters
1000 rays of light, as will be found ina table at the end of the
transmission table, our present object may be made a standard
for a comparison with the four following ones.

196th Experiment.

Sun. Pink-coloured paper scattering. ©
Tou 64, 64,
5 70 663....6:93 = 498

Here a piece of pink-coloured paper, of the same ‘dimensions
with the card of the last experiment, and placed ‘in :the same
situation, scattered, as we find by the same mode of multipli-
cation, 1060 rays of heat ; and, by our table, it scatters 51 3 of
light.

197th Experiment.

Sun. Pale-green paper scattering,
U LE BSS I
. O45 O45
7 i 3 > I —
ie 692 664... 52: 21 = ,370

This piece of paper scatters 896 rays of heat, and 549 of
light.

198th Experiment.

Sun. Dark-green paper scattering,
, Sis ai
x 643 - 65%
5 OOS 673, 127 = 4513

This paper scatters 1242 rays of heat, ne bea 308 of
light.

Z

500 Dr. Herscuen’s Experiments on the solar, and

199th Experiment. i me groxy

Sun. Black paper scattering. »
65% 3 66 .
703 68...45:2 = ,410

This paper scatters 993 rays of heat, and 490 of light.

From these experiments it seems to be evident, that in scat-
tering heat, the colour of the object is out of the question ; or,
at least, that it is no otherwise concerned than as far as it may
influence the texture of the surface of bodies. For here we find
that pale-green, which is brighter, or scatters more light, than
dark-green, yet scatters less heat. Even black, so generally
known to scatter but little light, scatters much heat. But, in -
order to put this surmise to a fairer trial, I made the following
experiments with my new machine.

200th Experiment.

I covered one of the tablets with white paper, and the other
with black. The quantity of sunshine admitted through the
two openings, of 14 inch in diameter each, being equal, I found
the heat scattered on both thermometers to be as follows.

White paper. Black paper scattering.
oO (cn 72 .
5 753 75 +++ 35°83 = 774
I turned now the tablets, and had,
b Black paper. White paper scattering,
o’ : 13% 724
5 aD 75g +++ 23+ 3% = 760

These results, agreeing sufficiently well together, shew that
if we make white paper our standard, and suppose it to scatter

- on the terrestrial Rays that occasion Heat. 5O1

1000 rays of heat, and 1000 of light, then will black paper scat-
ter 767 rays of heat, and 420 of light.

201st Experiment.

White paper. Black muslin scattering.
of 3 3
- 134 734
3 e I =
5 77% 77 -++ 4235 = 813

This scatters 813 rays of heat; and, when it is suspended so
that the rays which pass through it may not be reflected, it
scatters only 64 rays of light. |

202d Experiment.

As my intention at present was to find a black substance that
should scatter more heat than a white one, I thought it would
be the readiest way to examine the white and black objects
separately, that of all the white ones I might afterwards take

_ that which scattered least, and compare it with the black one
which scattered most.

White paper. White linen scattering.
, 7
° 746 75
6) (i ee
5 79 79% +++ 4g * 4g == 1,000

These objects scatter heat equally, and very nearly also light;
for our table gives for linen 1008. :

203d Experiment.
White paper. White cotton scattering,
7 =
° 742 745
5 783 78L...92: 97 = 1,000

These objects scatter heat equally. .White cotton scatters
1054, rays of light.
MDCCC. 3T

502 Dr. Herscuen’s Experiments on the solar, and

ins Jowbto paiaaiie
204th Experiment. +o) ane
' White paper. White muslin scattering,
es 73% 73% ; tt
5 ‘ub Rela 705 + Bz = 875”
White muslin scatters 875 rays of heat, and 827 of light.
205th Experiment. .
White paper. White persian scattering,
> co Og ee 14
dah 775 ss 7BE« + 8318E = 1,074

White persian-scatters 1074, rays of heat; and, when sus-
pended like the black muslin in the 201st experiment, it scat-
ters 671 rays of light, |

206th Experiment.

White paper. | White knit worsted ; rough side outwards.
’ 3 é,
Ss 51 514
5 3 5. —

White worsted scatters 1231 rays of heat, and 620 of light.

207th Experiment.

White paper, White chamois leather; the smooth side
exposed. ' Mt ks
5 5 :
74 746 ie i
~ 983 79». + 922 Ae = 110g

White chamois leather scatters 1167 rays of heat, and 1228
of light.
, 208th Experiment.
Black paper. . Black velvet scattering. —
Vig (orm 4 88 he &
79% 80...35:4¢==4,179

on the terrestrial Rays that occasion Heat. ~- 503

Making now black paper the standard, and supposing it to
scatter 1000 rays of heat, and the same of light, then black vel-
vet scatters 1179 rays of heat, and only 17 of light. This last
number we obtain, by dividing the tabular number 7, for black
velvet, by ,42, which is the proportion of black paper to white.

209th Experiment.

Black paper. Black muslin scattering,
’ I
© 75% 754
, I 1D 7 —
5 73 (Gu 3708" Span +o

Black muslin scatters 1192 rays of heat, and 4g of light.

210th Experiment.

Black paper. Black satin scattering.
U I ‘ I
fe) 7 6£ 765
5 79 802...293: 3% = 1,409

Black satin scatters 1409 rays of heat, and 24g of light.

211th Experiment.

Having now ascertained, that of all the white and black sub-
stances I had tried, white muslin scatters the least, and: black
satin the most heat, I placed the former on one tablet, while the
latter was put on the other.

White muslin. . Black satin scattering.
3 : ( 3
or 76% 78%
5 80 Sot... 3%: 3% = 1,069

Here the black object scattered more heat than the white
one; but, in order to try again the equality of the tablets and
apparatus, I placed the objects under the opposite thermome-
ters, and had as follows.

3T2

504, Dr. HERSCHEL’s Experiments on the solar, and

Black satin. White muslin scattering.
or 78 ; 78 .
5 802 ! Sol... 25: 295 == 1,050

So that, notwithstanding some little difference in the appa-
ratus, or other unavoidable circumstances, the black object
gave again the greatest scattering of heat; and consequently, as
no colour can be more opposite than black and white, colour
can have no concern in the laws that-relate to the scattering of
heat. |

212th Experiment.

I wished now to try some experiments of the scattering power
of metals, and had some plates of iron, brass, and copper, two
inches square, set flat, and smooth-filed, by round strokes.

Iron.’ Copper scattering.

of 74 734

5 785 776 +++ 42 * 4g = 0917
213th Experiment. —
Tin foil. Gold-leaf paper scattering.

o! 74 74

5 774 793 +++ 35+ 53 = 1,500

But the tin foil was considerably tarnished.

214th Experiment.

Finding the form of the last experiments inconvenient, for
want of a standard, I had recourse again to white paper.

: White paper. Tin foil scattering. —
o! 50% 513) ody hoor
3 Pf i e ae ——
5 Li B88 5AG ++ Ga 25 = 885

This substance scatters 885 rays of heat, and 8483 of
light.

on the terrestrial Rays that occasion Heat. 505

215th Experiment.

White paper. Tron.
eh 51g 537
5 54g 55x + +9: 24 = 4750

Some time having elapsed between the former observation
and the present one, this plate of iron was not now so bright
as before, and seems to have suffered more than brass or copper
from having been laid by: it scatters now only 750 rays of

heat, and 10014 of light.

216th Experiment.

White paper. Brass.
f I
of 50 51z
tN rs es
Sie eit 538 55% +++ 8g * 4g = 1,320

It scatters 1920 rays of heat, and no less than 43858 of
light.
| 217th Experiment.

White paper, _ Copper.
49% 51g
53 555 +++ 3574 = 1,280

It: scatters 1280 rays of heat, and 13128 a light.

218th Experiment.

White paper. Gold-leaf paper.
Sdea 558
563 50...15: 5 =.357
I changed the tablets to see what difference there might be.
Gold paper. White paper.
55% 555

505 573% ...4:15 = 4500

506 Dr. Henscue.’s Experiments on the solar, and

A mean between the two gives ,429. Gold paper, therefore,
scatters only 429 rays of heat, and no less than 124371 rays
of light.

219th Experiment.

Black velvet. Gold paper scattering.
ro 52 ! 51%
5 53% 525-6 151 GS 558
I turned the tablets, in order to ascertain the difference.
Gold paper. Black velvet.
Oo’ 51 51%
5 514 53.-.%: 12 = 600

From a mean of both it appears, that when black velvet
scatters 1000 rays of heat, and only 7 rays of light, gold paper,
on the contrary, scatters no more than 578 rays of heat, but
124971 of light. :

Art. vil.— Whether Light and Heat be occastoned by the same,
or by different Rays,

Before we enter into a discussion of this question, it appears
to me that we are authorised, by the experiments which have
been delivered in this Paper, to make certain conclusions, that
will entirely alter the form of our inquiry. Thus, from the 18th
experiment it appears, that 21 degrees of solar heat were given
in one minute to a thermometer, by rays which had no power
of illuminating objects, and which could: not be rendered visible,
notwithstanding they were brought together in the focus of a
burning lens, The same has also been proved of terrestrial
heat, in the 9th experiment; where, in one minute, 39 degrees

of it were given to a thermometer, by rays totally invisible, even —

when condensed by a concave mirror. » Hence it is established,

on the terrestrial Rays that occasion Heat. . 507

by incontrovertible facts, that there are rays of heat, both solar
and terrestrial, not endowed with a power of rendering objects
visible.

It has also been proved, by the whole tenour of our prismatic
experiments, that this invisible heat is continued, from the be-
ginning of the least refrangible rays towards the most refran-
gible ones, in a series of uninterrupted gradation, from a gentle
beginning to a certain maximum ; and that it afterwards declines,
as uniformly, toa vanishing state. These phenomena have been
ascertained by an instrument, which, figuratively speaking, we
may call blind, and which, therefore, could give us no infor-
mation about light; yet, by its faithful report, the thermometer,
which is the instrument alluded to, can leave no doubt about
the existence of the different degrees of heat in the prismatic
spectrum.

This consideration, as his been observed, must alter the form
of our proposed inquiry; for the question being thus at least
partly decided, since it is ascertained that we have rays of heat
which give no light, it can only become a subject of inquiry,
whether some of these heat-making rays may not have a power
of rendering objects visible, superadded to their now already
established power of heating bodies.

This being the case, it is evident that the onus probandi ought
to lie with those who are willing to establish such an hypo-
thesis; for it does not appear that nature is in the habit of using
one and the same mechanism with any two of our senses;
withess the vibrations of air that make sound; the effluvia that
occasion smells ; the particles that produce taste; the resistance
or repulsive powers that affect the touch: all these are evi-
dently suited to their respective organs of sense. Are we then

508 Dr. Herscue’s Experiments on the solar, and

here, on the contrary, to suppose that the same mechanism
should be the cause of such different sensations, as the delicate
perceptions of vision, and the very grossest of all affections,
which are common to the coarsest parts of our bodiegs when
exposed to heat ?

But, let us see what light may now be obtained from the
several articles that have been discussed in this Paper. It has
been shewn, that the effect of heat and of illumination may be
represented by the two united spectra, which we have given.*
Now, when these are compared, it appears that those who
would have the rays of heat also to do the office of light, must
be obliged to maintain the following arbitrary and revolting
positions; namely, that a set of rays conveying heat, should
all at once, in a certain part of the spectrum, begin to give a
small degree of light; that this newly acquired power of illu-
mination should increase, while the power of heating is on the
decline; that when the illuminating principle is come to a
maximum, it should, in its turn, also decline very rapidly, and
vanish at the same time with the power of heating. How can
effects that are so opposite be ascribed to the same cause? first
of all, heat without light; next to this, decreasing heat, but
increasing light; then again, decreasing heat and decreasing
light. What modification can we suppose to be superadded to
the heat-making power, that will produce such inconsistent
results ? |

We must not omit to mention another difference between
light and heat, which may be gathered from the same article
of the refrangibility of heat-making trays. It is, that though
light and heat are both refrangible, the ratio of the sines of

* See page 439, and Plate XX. .

' on the terrestrial Rays that occasion Heat. | 509

incidence and refraction of the mean rays is not the same in
both. Heat is evidently less refrangible than light; whether
we take a mean refrangible ray of each, or, which I believe to
be the better-way of proceeding, whether we take the maximum
of heat and light separately. This appears, not only from the
view we have taken of the two spectra already mentioned, but
more evidently from the 23d experiment, by which we find, that
heat cannot be collected by a lens, to the same focus where light
is gathered together. |

_ Our fifth article, in which an account has been given of the
proportions of heat and light stopped by glasses and other sub-
stances, will afford us now an ample field for pointing out a
striking difference between these two principles. From the
24th to the goth experiment, we have the ene intercepted
ey colourless substances as eae

Tas_e I.

Bluish-white glass stops 250 rays of heat, and 86 of light.

White flint elass - - Qi a ie at Digg tat aha
Greenish crown glass - 259 = - - 203 = -.
Coach glass - - 214, 2 = Ge ats =
Iceland crystal - - 244 - . = eon te tt
Talc - = - 139 = - go -- KS
Calcinable talc - - 184 - = ESBS He

Now, by casting an eye on the above table, it will be seen
immediately, that no kind of regularity takes place among the
proportions of rays of one sort and of another, which are
stopped in their passage. Heat and light seem to be entirely
unconnected. The bluish-white and flint glasses, for instance,
stop nearly three times as much heat as light; whereas, the

MDCCC. 3U

510 Dr. Herscuen’s Experiments on the solar, and

greenish crown glass stops only about one-fourth more of the
former than of the latter; but, as coloured glasses take in a
much greater range, I will now also give a tabular result of the
experiments that have been given relating to them.

TasB_e II.
Very dark red glass stops 800 rays of heat, and 9992. of light.
Dark-red - - 606 - - - g993%,- -
Orange - - - 604, - = 779 = =
Yellow - - - 333 - - - 819 - -
Pale-green ~ - 6293 - — Kak eae
Dark-green - 1, > BApe ct cpees bn Rea a
Bluish-green - - 768 = ate “69 = =
Pale-blue_ - = - 812 - - - 684 at ee
Dark-blue ~ = 362 - -: SOL, vets
Indigo ase = 6930
Pale-indigo - = - 532 ~ -- -978 - -
Purple - =e BOR = - 993 - -
Violet - - - 489 - - - 955 - -

From this table, I shall also point out a few of the most
remarkable results. A yellow glass, for instance, stops only
333 rays of heat, but stops 819 of light: on the contrary, a
pale blue stops 812 rays of heat, and but 684 of light. Again,
a dark blue glass stops only 362 rays of heat, but intercepts
801 of light; anda dark red glass stops no more than 606
rays of heat, and yet intercepts nearly all the light; scarcely one
ray out of 5000 being able to make its way through it.

Before I proceed to a more critical examination of these -
results, it will be necessary to add also a table of the same kind,
collected from the experiments with liquids.

on the terrestrial Rays that occasion Heat. 5ii

Tasze III.
Empty tube and 2 glasses stop 542 rays of heat, and 204, of light.
Spring waters - el RES, ies ‘ Ey eae
Sea water = att Se) ni GSs f 4 ma
Spintof wines! Uo a e-P61e 2p - - 294 - -
Gin - - - - 739 A = 626 - =
Brandy - - - 794 = - - 996 - -

To which may be joined, a table containing the stoppages
occasioned by scattering substances.

Tas_e IV. a
Rough crown glass stops 464 rays of heat, and 854 of light.
Rough coach glass - 571 - - = 879 - =
The ist doubly rough - 667 ~~ - - 932 - -
The ed doubly rough - 735 - 2 biel VGA reli un
The @ first together - 698 4 = = HOBO cies eicen
The 2 next together - 800 - - mi OZO cet yoem
The 4 first together - 854 - ~ = ATS pret ie
Olive colour, burnt in - 839 a = seis cm oa
Calcined tale - - 867 - -= - g96 - -
White paper - - (850 = z ae ar
White linen - - gi6 - < BN Se ie
White persian - - 760 - - - 916 - -

Black muslin - - 714 - = - 794 = =

We shall now enter more particularly into the subject of
these four tables, that we may, if possible, find a criterion
by which to judge whether heat and light can be occasioned

3U2

512 Dr. HerscuE.’s Experiments on the solar, and

by the same rays or not. Now this I think will be obtained, if
we can make it appear that stopping one sort of rays does not
necessarily bring on a stoppage of the other sort ; for, if it can
be shewn that heat and light are in this respect independent of
each other, it will follow that they must be occasioned by diffe-
rent rays; and I shall make all possible objections to the ar-
guments I mean to draw from these tables, in order to shew
that no hypothesis will evade the force of our conclusions.

It has been noticed, that bluish-white and flint glasses stop
nearly three times as much heat as light; whereas, crown glass
stops only about one-fourth more of the former than of the
latter. Now, in answer to this, it may be alleged, “ that the
“ingredients of which the.former glasses are made, dispose
«them probably to stop the invisible rays of heat, and that
“ consequently a great interception of it may take place, with-
out bringing on a necessity of stopping much light; and that,
«©on the other hand, the different texture of crown glass may
“‘ stop one sort of heat as well as the other, so that nearly an
* equality in this respect may be produced.”

When a hypothesis is made in order to explain any pheno-
menon of nature, we ought to examine how it will agree with
other facts ; and, in this case, we are already furnished with ex-
periments, which are decidedly against the supposition that has
been brought forward. For, the 148th and 149th experiments
shew that the bluish-white and flint glasses transmit all, or nearly
all, the invisible rays of solar heat; whereas crown glass, by
the 150th experiment, stops a considerable number of them.
But, to assist the objecting argument, let it be alleged, as has
been proved by the g4th experiment, that our bluish-white
glass stops a considerable portion of the heat that goes with the:

on the terrestrial Rays that occasion Heat. 51g

red rays; then, if the 86 rays of light which this glass stops,
are supposed to be all of that sort, the heat which will be
stopped in consequence, will, according to the experiment we
have mentioned, amount to 86 multiplied by ,975, that is, 32
rays of heat; but, since 250 have been stopped, there: will
remain 218 to be accounted for,

In this calculation, a manifest concession has been made,
which ought to be explained. When I mention 86 red-coloured
or red-making rays, I mean so many of them as will make up
86-thousandths of the whole effect of light; for the quantity
of heat and light transmitted, or stopped, in all the experiments
that have been given, has been reduced to what proportion it
bears to unity; and, having afterwards represented the joint
effect of every ray of heat and light by 1000, each mean ray
of heat must be the thousandth part of that effect; but, a mean
ray of light, although it be likewise the thousandth part of the
whole effect of light, will not be so of heat, because the whole
effect of the latter is partly owing to rays that have been proved
to be invisible. On this account, the 86 mean rays of red light, _
stopped by our bluish-white glass, cannot even amount to a
stoppage of g2 rays of heat, which we have allowed. ©

As I have made the concession on one hand, I must explain
an advantage that may be claimed on the other; which is, that
mean rays and promiscuous ones have already, in a former
Paper, been proved to differ considerably, and that it remains
therefore unknown how many red-making rays we may sup-—
pose to be stopped, in order to make up 86 mean rays of light,
In answer to this, however, I must observe, that the number of
promiscuous rays of light and of heat must always be inversely
as their power of occasioning those sensations; so that if, for

514 Dr. Herscuer’s Experiments on the solar, and

instance, a red ray is supposed to be twice as heating as a green
one, there will only go half the number of them to make up a

certain effect of heat; and, on the other hand, if a green ray '

should have a double power of illuminating, there will be no
more than half the number of them necessary to occasion a
certain effect of light. But, by my former experiments,* a red
ray, though much inferior to a green one, is probably fully equal
in illumination to a mean ray of all the colours united together.
Now, as red rays have also been proved to be accompanied by
the greatest heat, and as our bluish-white glass stops hardly
any invisible heat rays, we have certainly gone the full length
of fair concessions, by allowing all the light stopped by this
glass to be of that sort; and thus it seems to be evident, that
the heat which lies under the colours, if I may use this expres-
sion, may be stopped, without stopping the colours themselves.

It will not be necessary to lay much stress on this single ©

experiment; our second table affords us sufficient ground on
which to rest more forcible arguments. A dark-red glass, for
instance, was found to stop 6o6 rays of heat, and ggg,8 of light.
This, even at the very first view, seems to amount to a total
separation of the two principles; but let us discuss the phzeno-
menon with precision. .

As only one ray in 5000 can make its way through this
glass, it is evident, that if the rays of light be also those of heat,
there can hardly come any heat through it but what must be
occasioned by rays that are invisible, It will therefore become
a question to be examined, how many of this sort we can ad-
mit, if we proceed on a supposition that heat consists of light,
as far as that will go. Now this, we find, has already been

* See page 270, 1oth experiment. ,

—- = =

on the terrestrial Rays that occasion Heat. 515

ascertained, in a great measure, by our 1gth, 17th, and 18th
experiments. In the 13th, one hundred and twenty degrees of
heat were given to a thermometer, in one minute, by the rays
which accompany the coloured part of the spectrum. In the
17th experiment, on the contrary, we find only 45 degrees of
heat communicated to the same thermometer, in the same time,
by the invisible rays of the same spectrum. If we would be
more scrupulous, the 18th experiment limits the heat from rays
totally invisible even to 21 degrees; but, in order to make
every possible allowance, let the proportion be the most favour-
able one of 120 to 45, which, reduced to mean rays of heat,
will give 727 of them visible, and 279 invisible, to make up
our thousand.

To return to the experiment: if the total number of rays of
heat ascribed to light should accordingly be rated at 727, it is
evident, from the stoppage of light of this glass, that 726 rays
of heat at least must also be intercepted; and, in consequence
of the 153d experiment, which shews that our glass opposes no
obstruction to any of the invisible rays, we shall require no more.
But, by our present experiment, this glass stops only 606 rays
of heat; so that 120 of them will remain unaccounted for.
Now, the moment we give up the hypothesis that heat is occa-
sioned by the rays of light, the difficulty becomes fully resolved
by our iooth experiment, which shews that full three-tenths of
the rays that have the refrangibility of the red are actually
transmitted.

In order, however, to make a second attempt to overcome this
difficulty, without giving up the hypothesis, it may be supposed,
“ that perhaps the lens which has been used in the 1th, 17th, and
“18th experiments might stop a greater number of invisible

516 Dr. Herscue.’s Experiments on the solar; and

“ than visible rays, and that its report therefore ought not'tobe
« depended upon.”” Now, although it does not appear from the
148th experiment that such a supposition can have much foun-
dation, yet, since those experiments were not made with a view
to ascertain the proportion of heat contained in each part of the
prismatic spectrum, we cannot lay so much stress upon them
as the accuracy which is required in this case renders necessary.
Let it therefore, contrary to our 100th experiment, be admitted,
in order to explain the phenomenon of the red glass, which
stops so much light and so little heat, that all the heat which
it intercepts consists entirely of the rays which are visible, and
that every one of the invisible rays of heat is transmitted:
Then will 999,8 intercepted rays of light be equal to Go6 rays
of heat; and the remaining 394, will be the number of rays
we are now to place to the account of the invisible heat which is
transmitted.

Having thus also got rid of this difficulty, we are next to
examine how other facts, collected in the same table, will agree
with our new concession. A violet-coloured glass, for instance,
stops 955 rays of light; these, at the rate of 999,8, or say 1000,
to 606, must occasion a deficiency of 579 rays of heat. But,
by our table, this glass stops only 489 of them; and there will
thus be go rays of heat left unaccounted for. To enhance
the difficulty, this glass, by our 164th experiment, stops also +
of the supposed 394, invisible rays, which will amount to an
additional sum of 98. And our 111th experiment shews, that
actually a great number of these rays, that otherwise cannot be
accounted for, come from the store of heat, the cals of which
are of the refrangibility of red light.

A dark-blue glass stops 801 rays of light ; sda if light and!

on the terrestrial Rays that occasion Heat. 517

heat were occasioned by the same rays, would produce a stop-
page of 485 rays of heat; but we find that our glass stops no
more than 362, so that 123 rays cannot be accounted for by
this hypothesis. To this we should add 66 invisible rays, (that
is, 394, x ,167,) which, according to our 160th experiment, this
glass also intercepts. But the 107th experiment, if we reject
the hypothesis, immediately explains the difficulty; for-here
we plainly see, that only 71 rays of heat of the refrangibility
of red light are stopped, whatever may be the stoppage of that
light itself. .

_ A yellow glass stops 819 rays of light: these will occasion
a stoppage of 496 rays of heat; but this glass intercepts only
333, and therefore 163 rays of heat must also remain unac-
counted for. And, turning to the 155th experiment, we find
that 79 rays, or + of the 394 allowed to be invisible ones, are
also to be added to that number.

If in the results of our second table we have had an excess
of heat, which the last hypothesis would not account for, we
shall, on the contrary, meet with a considerable deficiency,
when we come to consider those of the third table.

For instance, our tube filled with well-water, including the
glasses at the end, intercepted 211 rays of light. These, at the
rate of 606 to the thousand, would produce only a stoppage of
128 rays of heat; but here we find no less than 558 of them
intercepted. To evade the pressure of these consequences, it
may be said, ‘ that as before every invisible ray was supposed to
** have been transmitted through glasses, so they may now be all
“intercepted by liquids.” And, granting this also to be possible,
though by no means probable, for the great extent of these
researches has not allowed sufficient time for many experiments

MDCCC, 3X

518 Dr. HERSCHEL’s Experiments on the solar, and

to be made that have been planned for execution; yet, even
then, 128 visible and 394, invisible rays to be intercepted, will
only make up 5223 so that a deficiency of 36 must still remain.

In sea-water, the balance will stand thus: 288 rays of light

give 175 rays of heat; these and ggq invisible rays make up -

569; but the rays actually intercepted were ote, which argues
a deficiency of no less than 11g rays. —

But if I have for a moment admitted the entire stoppage of
the invisible rays of heat in liquids, the same indulgence can-
not be granted for the empty tube, as we know it does neither take
place in glasses, nor in air. Therefore we must calculate thus:
this compound of glass and air stops 204, rays of light; these
can amount only to 124 rays of heat; but it is found to stop
542 of them, so that 418 remain to be accounted for. Now,
we certainly can not suppose more than 100 of them to owe
their deficiency to the store of invisible heat; so that 318 will
still remain unaccounted for.

And thus, from the second table, we liad given instances
where the assumed hypothesis of visible and invisible heat, in
certain proportions, would require a greater stoppage than our
experiments will admit; ana now, on the contrary, it appears,
that interceptions calculated according to the same hypothesis,
should be less than the results in the third table give them.
From which we conclude, that every other proportion fixed
upon, would always be erroneous, either in excess or in defect.

Equal contradictions may be shewn to attend all endeavours

to account for the results contained in our fourth table, by ad- »

mitting any visible heat at all, let the quantity be what it will.
To make the proof of this general, let 1000 be the total heat,
and assume <x for that part of it which we would suppose to be

on the terrestrial Rays that occasion Heat. 519

occasioned by visible rays; then will 1000 — x be the remainder,
which must be ascribed to rays that cannot be seen. Now, by
our table, we find that crown glass, of which one side has been
rubbed on emery, stops 854, rays of light. These alone, if not a
particle of invisible heat were stopped, would be equal to 854 xr
visible rays of heat, that must be intercepted by the glass. When
the other side of this glass has also been rubbed on emery, it will
stop 932 rays of light, which will give ,932 2, for the quantity
of heat to be intercepted, on the same supposition, that all invi-
sible rays of heat are transmitted. But, by our fourth table, we
have the actual-stoppage of heat of these glasses; which will
therefore give us the two following equations; ,854.7 = 464,
and ,932 x = 667. Then, taking the first from the last, and
reducing the remaining equation, we obtain x = ae for the
visible part of the total heat. But a or 2602, being only a
part, comes out greater than 1000, which is the whole; and

this being absurd, it follows that visible rays of heat cannot be

admitted, in any proportion whatsoever. This will equally hold

good with any additional stoppage of invisible heat, provided it
_be equal in both glasses ; and, of this equality, the 165th and

167th experiments can leave us no room to doubt. :

But it is high time that we should now take into consideration _

a more direct proof, which may be drawn from our prismatic

experiments. The results of them are here brought into a table,
_ as follows. |

520 Dr. HERSCHEL’s Experiments on the solar, and

TaBLeE V.
Spa of prismatic Heat of the Refrangibility of the Red Rais:
and of the Invisible Rays.

d Red rays. Invisible rays.
Bluish-white glass stops - 375 - - 71
Flint glass ~ - - 143 - - 000
Crown glass - - - 294 - “ 182
Coach glass mem - 200 - - 143
Iceland crystal - - 200 - -
Calcinable talc - - - 198 - - 250
Dark-red glass - =4 FeOgeu Hane - 000
Orange - = - = 500 - ~ 273
Yellow - - - - 417 - - 200
Pale-green - - - 588 - - 375
Dark-green—- - - 786 - - 500
Bluish-green Sn esky 462 - 800
Pale-blue - - =. ZOO - - 750
Dark-blue - - - 71. = - 167
Indigo - - - 367 - - 222
Pale-indigo - - - 313 - - 250
Purples) 5). (rai Ui pak Bad Pe eee
Violet - - 4,00 - - 250
Crown glass, one side rough 389 - - + 600
Coach glass, ditto - - 500 - - 500
Crown glass, both sides rough 4,71 - - 600
Coach glass, ditto - - 8393 - mt oo) Walid,
Calcined tale” - ~ - 797 - ~ 889

As a necessary introduction to the decisive experiment I am
going to analyse, I must remark, that it has been shewn in a
former Paper, that the prism separates invisible heat from the'co-
loured spectrum, by throwing that which is less refrangible than
light to one side. But it has also been proved, that heat of the
same variety in refrangibility as the different colours, is likewise
contained in every part of the coloured spectrum. The question
which we are discussing at present, may therefore at once be re-

on the terrestrial Rays that occasion Heat. 521

duced to this single point. Is the heat which has the refrangibility
of the red rays occasioned by the light of these rays? For, should
that be the case, as there will then be only one set of rays, one fate
only can attend them, in being either transmitted or stopped,
according to the power of the glass applied to them. We are
now to appeal to. our prismatic experiment upon the subject,
which is to decide the question. First, with regard to light, I
must anticipate a series of highly interesting observations I have
made, but which, though they certainly claim, cannot find room
in this Paper. These have given me the means of acting sepa-
rately upon either of the extremes, or on the middle of the pris-
matic spectrum; and by them I am assured that red glass does
not stop red rays. Indeed the appearance of objects seen through
such coloured glasses, till I can give those observations, will be
a sufficient proof to every one that they transmit red light in
abundance. Next, with regard to the rays of heat, the case is
just the reverse; for, by our preceding table, the red glass stops
no less than 692, out of a thousand, of such rays as are of the
refrangibility of red light. The incipient stoppage, moreover, or
that in two minutes, of which something will be said hereafter,
amounts even to 750 rays.

Now, if it should be suspected, “ that on account of the great
« breadth of prism, some invisible heat may be thrown upon the
« spot where the red colour falls,” Ido not only agree to it, but
am certain it cannot be otherwise: but this again, will give addi-
tional weight to our present argument ; for, by the 153d experi-
ment, as our last table shews, it has already been ascertained, that
all such heat will be transmitted through a red glass; so that,
were it not for some of this admixture, the stoppage might be still
greater. |

29 Dr. HerscHeE’s Experiments on the solar, and
Si

Here then we have a direct and simple proof, in the case of
the red glass, that the rays of light are transmitted, while those
of heat are stopped, and that thus they have nothing in common
but a certain equal degree of refrangibility, which, by the power
of the glass, must occasion them to be thrown together into
the place which is pointed out to us by the visibility of the rays
of light.

The manifest use of the union of these rays, arising from
their equal refrangibility, will be explained at a future opportu-
nity, when I may perhaps throw out several hints that have
already occurred to me, where the contents of this Paper may
be applied to the useful purposes of life.

There still remains a general argument, that heat and light
are occasioned by different rays, which ought not to be omitted.
This, on account of the contracted state in which the experi-
ments have been given, cannot appear from my Paper; but, by
an inspection of them at full length, it is proved, that the stop-
page of solar heat, setting aside little irregularities, to which all
observations are liable, has constantly been greater in-the first,
second, or third minute, than in the fourth or fifth; or, more
accurately, nearer the beginning of the five minutes, than about
the end of them. Now this does not happen in the transmission
of light, which, as far as we know, is instantaneous; at least a
failure in the brightness of an object, when first we look at it
through a glass, amounting to one, two, or even three minutes,
could not possibly have escaped our observation. This seems
to suggest to us, that the law by which heat is transmitted, is
different from that which directs the passage of light ; and, in.
that case, it must become an irrefragable argument of the diffe-
rence of the rays which occasion them.

on the terrestrial Rays that occasion Heat. 523

The surmise of a difference in the law of the transmission of
heat and of light, is considerably supported by an argument drawn
from circumstances of a very different nature. In the scattered
transmissions arising from rough surfaces, we find, that when
crown glass, for instance, has one of its sides rubbed on emery,
it will stop 205 rays of heat more than while that surface re~
mained polished; but the effect of the roughness produced by
emery scratches, is far more considerable on the rays of light;
the additional stoppage of them amounting to no less than 651.

A confirmation of the same effect we have in coach glass;
which, having also one side rubbed on emery, stops only 357
rays of heat more than it did before, while there is an additional
stoppage of rays of light, amounting to no less than 717. Now,
since the interior construction of these glasses, before and after
having been rubbed on emery, remains the same, these remark-
able effects can only be ascribed to the roughness of their sur-
faces. Hence, we may conclude, that as the same cause, when
it acts upon the rays of heat and light, produces effects so very
different, it can only be accounted for by admitting the rays
themselves to be of a different nature, and therefore subject to
a different law in being scattered. It has already been shewn,
that the rays of heat are, upon an average, less refrangible than
those of light ; and now it appears that they are also, if I may
introduce a convenient term, less scatterable. :

We ought now also to take a short review of the phenomena
attending the transmission of terrestrial heat. The results of the
experiments which have been given, are drawn into one view in
the following table.

524 Dr. Herscuen’s Experiments on the solar, and

Tase VI.

: _ Rays of flame. — Fire. “Invisible heat.
Bluish-white glass stops - 625 - 750 = 700
Flint glass - - - . §91 .= 75° - 533.
Crown glass - - - 636 - .. 990.» ae
Coach glass - - wo Ab Oba: aren mA Ei a 625
Iceland crystal = - B10. = es - 726
Talc - - - =, 375 = | ane 615
Very dark red glass - 636 - 613 - —
Dark-red - - a Eo 2 Oe - 630
Orange =) =) § = 2 “560 oS) 648) S20 Seg
Yellow - - - 583 - 685 - 5931
Pale-green - - =i foots tao O88 me 632
Dark-green - - =| (:789> on iinF45 @oom ee¥eQon
Bluish-green - - 652 - 6096 mye 4 ee
Pale-blue -- = =. 4009, =) G76ee) — 548

_Dark-blue — - - = (619 pmo TOs, i). caine
Indigo - = - - O70. 720 a ee
Pale-indigo -- = 2 F7L | OSG a ae
Purple - - - 520° = SO7gT = 730
Violet - - - - §00 - 615 - 684
Crown glass, one side rough 741° = = 793° =" Wie
Coach glass, ditto - - 667 - 758 - 741
Crown glass, both sidesrough 615 - 791 - 833
Coach glass, both - - 680 - 854 - 769 ~
The two last but two, together 720 - 849 - -—.
The two last together Ti 0O% oe ¢ OOe - —
The four last together e B70, =, GOO lai
Olive-colour, burnt in glass 792 - 849 - 636
White paper - - = 792 = * O12 reas
Whitelinn - - = 690 = g10 = 457
White persian - = 593 - 829 = ee

Black muslin - - = 565 - GOO = oom

on the terrestrial Rays that occasion Heat. 525

Let us now examine what information we may draw from
the facts which are recorded in this table. The first that must
occur is, that a candle which emits light, is also a copious source
of invisible heat. If this should seem to require a proof, I give
it as follows.

That the candle emits heat along with light, the thermometer
has ascertained; and, that a considerable share of this at least
must be invisible, follows from comparing together the quantity
of light and heat which are stopped by different glasses. The
bluish-white one, for instance, stops 86 rays of light, and 625 of
heat. Hence, if only visible rays of heat came from the candle,
a glass stopping more light, as for instance the dark-red glass,
which stops 999,8, ought to stop all heat whatsoever; but the
fact is, that it even stops one hundred rays less than the former.

This instance alone shews plainly, that the existence of invi-
sible terrestrial heat in the flame of a candle, is proved; while,
on the contrary, heat derived from rays that are visible, remains
yet to be established, by those who would maintain that there
are any such. But, for the sake of argument, let us endeavour
to explain how visible rays of heat may be reconciled with the
contents of our 6th table.

“ Now although we must allow,” it may be said, “ that there
“ is a certain quantity of candle-heat which cannot be seen, we
« are however at liberty to assign any ratio that this may bear to
« its visible heat-rays. Let us therefore begin with the bluish-
« white glass, and make the most favourable supposition we can,
“ in order to explain its pheenomena. Visible or invisible, it stops
* 625 rays of heat, and also 86 of light. Now, as in the last
* column of the table we have likewise the proportional quantity
“ of invisible heat it intercepts, which is 700 out of a thousand,

MDCCC. ore,

526 Dr. Herscuen’s Experiments on the solar, and

“we may surmise that the 914 rays of light, together with the
*¢ 300 of the invisible rays which are transmitted, make up the 375
“ rays of heat which pass through the glass. Hence, by algebra,
‘* we have the number of invisible heat-rays 878, and the number
*¢ of the visible ones 122. Then, to try how this will answer, if
* 1000 rays of light give 122 of heat, 86 will give 10; and, if
« out of a thousand invisible rays 700 be stopped, 878 will give
‘* 615 to be intercepted. The sum of these will be 625, which is
«‘ exactly the number pointed out by our table.” Now this being
a fair solution of one instance, let us see how it will agree with
some others.

Before I proceed, however, I cannot help conga that
the supporters of visible heat-rays must feel themselves already
considerably confined, as our present argument will ei allow
‘them more than 122 of such rays out of a thousand.

Now, if the assumption that terrestrial heat is owing to a
mixture of visible and invisible rays, in the proportion of i22
of the former to 878 of the latter, be well founded, it ought to
explain every other phenomenon collected in our table.

The purple-coloured glass stops 993 rays of light, which,
according to our present hypothesis, should stop 121 rays of
heat: it also stops 7g0 invisible rays, which will give’641 rays
of intercepted heat ; therefore this glass should stop 762 rays of
heat, out of every thousand that come from a candle; but, from
our table, we find that it stops no more than 520, so that “ade |
rays cannot be accounted for. ip Qi

The glass with an olive colour burnt into it, stops 984 rays
of light, or 120 of heat, and 6937 invisible rays, or 559 of heat.
The sum is 679 which that glass should stop; but it stops ac-
tually 792; so that, as in the foregoing instance we had’a defi-

n
’

on the terresirial Rays that occasion Heat. 527

ciency of 242 rays, we now have an excess of 113; which plainly
shews, that no hypothesis of any other proportion between the
visible and invisible rays of heat can answer to both cases; and
that consequently, not only the present, but every other assump-
tion of this kind, must be given up as erroneous.

I shall not enlarge on these arguments, as I take them to be
sufficiently clear to decide the question we have had under con-
sideration. I also forbear going into an examination of what our
sixth article, which treats of scattered heat, might afford, in ad-
dition to the former arguments. It may just be remarked, that
_the 211th experiment points out a black object, which scatters
more heat than a white one; while the case, as to light, is well
known to be the reverse. The 219th experiment also shews,
that the scattering of heat of gold paper is considerably inferior
to that of black velvet; whereas a contrary difference, of a very
great extent, is pointed out between these two substances; for
black velvet scatters only 7 rays of light, while the scattering
of gold paper amounts to more than 124000. Iam well aware
that this difference will perhaps admit of a solution on other
principles than those which relate merely to the laws of scat-
tering, and confess that many experiments are still wanting to
complete this article, which cannot now be given; but, as this
Paper is already of an unusual length, I ought rather to apolo-
gize for having given so much, than for not giving more.

3 Y

to

528 Dr. HERSCHEL’s Experiments on the solar, and ,

Table of the transmission of terrestrial scattered Light through
various Substances ; with a short Account of the Method by
which the Results contained in this Table have been obtained.

The transmissions here delivered are called terrestrial and
scattered, to distinguish them from others, which are direct and
solar; and, in the use I have made of them in the foregoing
Paper, it has been supposed that light-making rays, whether
direct and solar, or scattered and terrestrial, are transmitted in
the same manner; or that the difference, if there be any, may
not be considerable enough to affect my arguments materially.
In this I have only followed the example of an eminent optical
writer, who does not so much as hint at a possibility that there
may be a difference. Before I describe my apparatus, I ought
to mention that it is intirely founded on the principles of the
author now alluded to,* and that no other difficulty occurs in
the execution of his plan, than how to guard properly against
the scatterings of the lamp: for the light which this will throw
on every object, must not be permitted to come to the vanes;
since these scatterings cannot remain equal on both vanes, when
one of them is moveable. In the following construction, the
greatest ditficulties have been removed; and a desirable consist-
ency in the results of the experiments, when often repeated,
has now been obtained.

A board about fourteen feet long, and six inches broad,+- has
two slips of deal, an inch square, fastened upon the two sides :
these make a groove, for two short pieces to slide in, backwards
and forwards. The two sliding pieces{ carry each a small

* See Traité d’Optique, page 16, Fig. 5 ; Ouvrage posthume de M. BouGcugr.
t See Plate XXVI. Fig. 1. t See Fig. 2 and 3.

on the terrestrial Rays that occasion Heat. 529

board or vane; one towards the right, the other towards the
left; but so as to meet in the middle, and apparently to make

. but one when placed side by side. The vanes are covered with
a piece of fair white paper, which is to reflect, or rather to scatter
light in every direction. To one end of the board is fixed a circular
piece of wood, with an opening in it, which is afterwards to be
shut up by a small moveable piece,* intended for placing the
transmitting objects upon. This moveable piece contains two
holes, at the.distance of 14 inch from centre to centre, and
2 inch in diameter each. Against the circular wooden screen,
and close over the opening in it, is placed a lantern containing
a lamp. Its construction is such as to admit a current of air
to feed the flame from below, by means of a false bottom, and
to let it out by a covered roof; and the whole of the light, by
the usual contrivance of dark lanterns, is thus kept within, so
as to leave the room in perfect darkness. In the front, that is
‘towards the vanes, the lantern has a sliding door of tin-plate,
in which there is a parallelogrammic hole, covered with a spout
five inches long, of the same shape. Two or three such doors,
with different spouts and openings, will be required to be put
in, according to the experiments to be made; but the first will
do for most of them.

A narrow arm is fastened to the long board, which advances
about three feet beyond the screen, and carries a circular piece
of pasteboard, that has an adjustable hole in the centre, through
which the observer is to look when the experiments are to be

_ made. At the farther end of the long board is a pulley, over
which a string, fastened to the back of the slider that carries
one of the vanes, is made to pass. This string returns under the

* See Plate XXVI, Fig. 4, $ See Fig. 5.

530 Dr. HerscueE’s Experiments on the solar, and

bottom of the long board, towards the other end, where, close to
the observer, another pulley is fixed; and, after going also over
this pulley, it returns at the top of the board, to the front of the
same vane, to which the other end of it is fastened at the back.
‘By pulling the string either way, the observer may bring tire
the moveable vane, or draw it back, at pleasure. |

At the side of the long board is a scale of tens of inches, num-
bered from the place of the flame of the lamp, 0, 10, 20} 30, 40,
and so on to i6o. A pair of compasses being applied from the
last ten towards the vane, ascertains its distance from the flame,
to as great an accuracy as may be required» : |

When the transmitting power of a glass is to be tried, it must
be placed over one of the holes of the small moveable piece,
which then is fastened with a button, upon the opening left for
it in the circular wooden screen. Then, looking through the
hole of the pasteboard at the two vanes, and bringing that which
is seen through the glass near enough to give an image equally
bright with that which is seen through the open hole, the obser=
vation will be completed. Having measured the odd inches by
a pair of compasses, or immediately by a scale, we deduce, as
usual, the transmitting power, by taking double the logarithm of
the distance of the farthest vane from the lamp, from double
the logarithm of the distance of the nearest vane. The remain-
ing logarithm is that of the transmitting power, as compared to
the light coming directly to the eye from the other vane.

I have now only to remark, that the use of this instrument
requires some practice, especially when coloured glasses are to
be examined ; it will, however, be found, that the difference of
the colour of the two objects, when their light is brought to an
equality, may be overcome by a little abstraction, which is

the terrestrial Rays that occasion Heat. — 531

required for the purpose; for, by attending only to brightness,
it has often happened to me, that both objects appeared at last
of the same colour; which proved to be some mean between
the two appearances considered separately.

Some glasses stop so much light, that it will be advisable to
take them by the assistance of an intermediate one. Thus, in-
stead of comparing the open vane directly to a red glass, I
settle first the ratio of the violet one to that vane; then, taking
the ratio of the red to the violet, and compounding these two
ratios, the result will be more accurate. The reason for this
will be easily comprehended, when the construction of the appa-
ratus is considered. For a red glass, immediately compared to
the open vane, would require its object to be brought extremely
near the lamp, while the other must remain at a very great
distance. This would occasion a considerable difference in the
angles, both of incidence and of reflection, between the rays
falling on one vane, and on the other. But, by dividing the
observation into two operations, we avoid the errors that might
be occasioned by the former arrangement.

In the following table, the first column contains the names of
the different substances through which light has been trans-
mitted. The second column shews the transmission of light,
expressed in decimal fractions ; or the proportion which it bears
to the whole incident light considered as unity. An arithme-
tical complement to this fraction, or what it wants to unity,
will therefore give us the proportion of light which is stopped
by each of the substances contained in the first column; and
that quantity multiplied by 1000 is placed in the third column.

532 Dr. Herscue.’s Experiments on the solar, and

Tasxe VII.

Substances without colour. Transmission. Stoppage..
Bluish-white glass - - 1914 - 86»
Flint glass - e. re ,966 i 34
Crown glass = = sate ZOE - 203
Coach glass - - - 3832 - 168
Iceland crystal - - - ,850 - 150
Talc ~ - ~ - 910.- = go
Easily calcinable talc - ~ 4 s7ae - , 288

_ Glasses of the prismatic colours.

Very dark red glass - - 30001335 - 999;9
Dark-red glass - - - ,000188 - 999,38
Orange glass - - - 3221 - 779
Yellow glass - - - ,081 - 319
Pale-green glass - - = ,465 - 535
Dark-green glass - - 0511 - 949
Bluish-green glass - - - 4231 - 769
Pale-blue glass - - - ,g16 - 684,
Dark-blue glass gibt - 5199 - . 801
Indigo glass - - - ,000281 - 999,7
Pale-indigo glass = ~ 0218 = 978
Purple glass - - 5 ,00675 - 993
Violet glass = - = 04,52 - 955
Liquids.
Empty tube and two glasses - 796 - 204
Well-water and ditto - - 5789 - 211

Sea-water - = - riz = 288

on the terrestrial Rays that occasion Heat, 533

Liquids. Transmission. Stoppage.
Spirit of wine and two glasses ~ 1776 - 22h
Gin - +. T a 374 at 626
Brandy — - - - 00381 - 996
Scattering Transmissions.
eel glass, one side rubbed onemery ,146 - 854
Coach glass, ditto - = bag - 885
Crown glass, both sides rubbed on emery ,0685 - 932
Coach glass, ditto - = 0542 - 946
The two first, together - 03158 - 969°
The two next, together —- = 0208 979
The four first, together ay!) SOOREO | 995
Olive colour, burnt in glass - - ,0160 - 984,
Calcined talc - - ~ 3003845 = 997
White paper a - ,00556 - 994 ~
_Limen _ = - - 30483 ~ 952 ~
White Persian — - - 0841 ~ g16
Bock musing, 2 -. < yom 3263 —~Ci«*si‘ 73/7

Table of the proportional terrestrial Light scattered by various |
Substances.

The same apparatus which has been used to gain the results
of the preceding table, has also been employed for the follow-
ing one, with no other difference than that while the vane with
the white paper remained on one side, the other vane was suc+
cessively covered by the objects whose power of scattering light
was to be ascertained, and both vanes were viewed directly
through the two open holes in the screen; the eye being sta-
tioned in the same place as before.

MDCCC, 32

5394 Dr. Henscurr’s Experiments on the solar; and

It will be found, that this table contains the scattering 0 of
more objects than: have been referred to in the preceding paper ;
but, as I made these experiments in a certain order, I thought
it would be acceptable to give the table at full length. basa

The first column gives the names of the objects; and the
second contains the number of rays of light scattered by them,
when compared to a standard of white paper, which is rk
ee to scatter one thousand.

Tas_eE VIII. | oso

White paper scatters - - 1000 rays of light.
Message card - a By 160g00.0W) ait
White linen - Si ke Logepgetit 200l.aiek
White cotton 2 ze re 1654, iO
White chamois leather, smooth side - 12928 - =~
White worsted = = = 620 12164 Sah
White Persian, suspended = - ~ 6m .- SoBee
- White Persian, on whitish-brown paper, - 719 - -
White Persian, on white Persian - § 19 /\ieuit sae | L
White muslin = ns = $27. lee -—
Red papers > = = = ee
Deep pink-coloured papers - - 513. Cir <
Pale pink-coloured-paper - = 1 SES Ale. Sim
Orange paper - Ls = -Gig - -
Yellow paper ee ce a) LOR EL SN
Pale-green paper — - = - 549 - “i
Dark-green paper’ = 6 810900 90) godas aame
Pale-blue paper = =| he “ GOH EROS Ot. ae
Dark-blue paper ~ J OC OO

Indigo paper, with a strong gloss - Tig See T Bee

on the terrestrial Rays that occasion Heat. 535
Dark-violet paper scatters =—S = = 45 rays of light.
Brown paper = ~ 101 - ~
Black paper, with a strong gloss - 420 = -
Black satin - - - 102 = -
Black muslin, suspended - - 64° - -
Black muslin, upon black muslin =" 18 = -
Black worsted © - 3 - tor wet Byolorione
Black velvet - - - 7 = -
Tin-fol = - = - - 8483 - =
Tron = - - 10014 = -
Copper = - - 13128 = - -
Brass ~ - - - 43858 -— -
Gold-leaf paper - =) 124371 - =

I cannot help remarking, that in making these last experi-
-ments, I found that:black paper could not be distinguished from
white; and that, on bringing it a little nearer to the light than
it should be to make them perfectly equal, any of my friends
who happened to be present, would mistake the black for the
white. '

EXPLANATION OF THE PLATES.

Plate XX, represents the spectrum of heat A, 8, Q, A; and
of light G, R, Q, G. If a prism be placed in a window, so as
to throw the colours of light upon a table, and Plate XX be
laid under the colours, so that they may respectively fall upon
the places where their names are inserted, then may these co-
lours be made to fit into their proper spaces, by lowering or
raising the prism, at pleasure. When the colours occupy their
proper situations, the line A Q will express the space over

Cw Ae)

536 Dr. Herscue.’s Experiments on the solar, and

which the prism, by-their different refrangibility, scatters the
rays of heat; and the ordinates to A Q will nearly express the
proportional elevations, which a set of equi-changeable thermo-
meters would experience, when placed in the different situa-
tions of these ordinates.

Plate XXI. Fig. 1. A, B, is the box which holds the two
thermometers, No. 1 and No. 5. C is the board which contains
the transmitting holes, the slip of wood for supporting the
glasses, and the perpendicular pin for adjusting the angle.
D, E, are the boards joined together by hinges. F is a slip of
mahogany screwed to E. G is the spring to confine the
slip F ; which will keep the board D up to any angle less
than go degrees.

Fig. 2, is the cover for shutting the transmitting sleet

Plate XXII. Fig. 1, is the screen, which may be elevated,
by the usual contrivance of springs at the back, to any required
height, so as to permit the rays of the sun to pass through the
opening in the middle, and to fall upon the perigee: holes
of the box A, B, in Plate XXI. ;

Fig. 2, is a second upper part of the box A, B, in Plate XXL.
The first upper part being screwed off, this is to be put on in-
stead of it, when experiments with liquids are to be made. It
contains, as before, the two transmitting holes, the slip of wood,
and the pin; and it has moreover a small bracket fastened un-
der one of the holes, on which the tube containing the liquid to
be tried may be laid.

Fig. 3, is a third upper part to the box A, B, of Plate XXI. It
contains two small holes, for transmitting prismatic rays to the
two thermometers A and B, which must now be put into the
ox, instead of No. 1 and No. 5. The parallel lines a, b, inclos-

on the terrestrial Rays that occasion Heat. 537

ing the holes, will direct any coloured rays to the thermometers ;
and, by drawing the red rays down to the lower parallels c or d,
invisible rays may be brought to enter the transmitting holes.

Fig. 4, isa fourth upper part to the box A,B, Plate XXI. It
contains two large holes, for admitting the rays of the sun to fall
upon the objects on Fig. 5.

Fig. 5, represents two tablets, a,b, united; they may be covered
with any objects that are to be examined; for instance, a with
white paper, and b with black velvet. These tablets, by a pro-
per contrivance, are brought under the holes of figure 4, where
a button fastens them at the required distance.

Plate XXIII. Fig. 1. A, B, is the box which holds the thermo-
meters. C, D, are the screens, with the transmitting holes in them,
opposite the flame of EF, the candle. F, is a small weight, stretch-
ing a string across the glass, or other object, placed upright
against the transmitting hole of the screen D. It may be carried
round the screen C, if required, and hold a glass against the
hole in it.

Fig. 2, is the double cover: in plane it on, it must be passed
ever the candle downwards, against the two transmitting holes.

Plate XXIV, represents a large screen, with the shelf A, B,
carrying four thermometers, No. 1 and No. § opposite the
transmitting holes, and the other two as represented. When
the fire is properly prepared, lift the screen, by taking hold a
little above A and B, and set it close to the fire, so that C, D,
may touch the bottom of the grate; then take hold of the ring
E, and pull the string far enough out to hang that ring on the
hook F: this will open the transmission holes, when the expe-
riment is to begin.

Plate XXV. Fig. 1, is the box containing the thensaameters.

538: Dr. Hersongn’s Experiments on the solar, and

The bricks are piled up, as represented in Fig. 3. The stove,
Fig. 2, being prepared, bring the stand, and brick-work, Fig. 3,
close to it; and-set also the two spare bricks, which lie on the
stand, upon the front of the stove, that no heat may pass from
the top of it to the brick inclosuré ; then put the box, Fig. 1,
into the brick-work, close up to the stove, and begin the expe-
riment. The ash-hole should also be covered with a brick.

Plate XXVI. Fig. 1, represents the Photometer. The hole
at A, is for the observer to look through, that he may have a
fixed station. The vanes F and G are moveable. By pulling
the string at H, G will be brought nearer the lamp placed at
K; and, by drawing the same string at I, it will be removed
towards the vane F; which latter may be fixed at any distance
most convenient for the experiment. —

Fig. 2 and 3, shew the mechanism of the adjustable vane 2,
and moveable one 3. There are, however, hooks on fig. 2, which
will occasionally receive the strings from the hooks on fig. 3,
when a motion of the left vane, instead of the right, is required.

Fig. 4, contains two limiting holes B,C; over one of which,
C, a glass may be laid. This piece is to be buttoned on the rab-
bet of the screen, at D E, fig. 1. When liquids are to be tried,
the second piece of fig. 4, which contains a bracket for support-
ing the transmitting tube, is to be fastened on D E, fig. 1, instead
of the former plate.

Fig. 5, gives a view of the lamp and its sliding door, with the
spout L, which, when the lamp is placed at K, fig. 1, conveys
the light to the vanes F and G, without permitting it to be
scattered on the long board.

:
;
.

Vale XX pp G6.

Shilos, Trans, MDC CC.

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: , cE 539 J

XX. An Account of the Trigonometrical Survey, carried on tn the
| Years 1797, 1798, and 1799, by Order of Marquis Cornwallis,
Master-General of the Ordnance. By Captain William Mudge,
of the Royal Artillery, F.R.S. Communicated by bis Grace
* the Duke of Richmond, F. R. S.

Read July 3, 1800.

INTRODUCTION.

Havine interspersed in the following Paper, with as much
attention to brevity as the subject admits, every intelligence
relating to the Trigonometrical Survey, I think it unnecessary
to swell the bulk of the communication, by giving a long pre-
fatory account of its progress since the year 1796.

The contents of the work now meeting the public eye, are
important and numerous: I have divided it into sections. The
first contains the calculations of the sides of the principal and
secondary triangles extended over the country in 1797, 1798,
and 1799; together with an account of the measurement of a
new base line on Sedgemoor, and a short historical narrative of
each year’s operation. The second section contains the computed
latitudes and longitudes of those places, on the western coast,
intersected in 1795 and 1796, and also such others, since de-
termined, as lie conveniently situated to the newly-observed
meridians. This section also contains the directions of those
meridians ; one on Black Down, in Dorsetshire; another on But-
terton Hill, in Devonshire; and another on St. Agnes Beacon,

540 The Account of a

in Cornwall. Among the contents are likewise to be numbered
the bearings, distances, &c. of the stations and intersected objects,
from the parallels and meridians. ,

The third and last section contains the triangles which have
been carried over Essex, the western part of Kent, and portions
of the counties joining the former, Suffolk and Hertfordshire.
It is with satisfaction I am enabled to state, that Mr. GARDNER,
the chief Draftsman, with his assistants, has almost completed
the Survey of this extensive tract, which, no doubt, like the map
of Kent, will be given to the public: the materials for these
different surveys are ample, and will be found in this section,
which concludes with the altitudes of the stations and mean
refractions.

Before I had advanced far in my work, I entertained ideas of
condensing all the data in my possession, and distributing them
in it; but, when I found my paper would, in that case, be too
large for the Philosophical Transactions, I desisted, contenting
myself with presenting little more than a moiety: it is,even now,
of inconvenient magnitude, but I could not, with propriety, still
farther abridge it, for I have, in several instances, rejected im- |
portant matter. I shall, therefore, take an early opportunity of
compiling a fourth account, in which will be given the latitudes
and longitudes of those places, in Essex, Kent, &c. found in the
last section.

It is right I should observe that, knowing from experience,
how liable surveyors are to mistake the names of places, and
also, how utterly impracticable it is to detect errors, till the
interiors of the great triangles have been filled up, I have been

cautious to give only the distances of such objects as could not
be easily anistaken, Ido not mean to insinuate that, among

Trigonometrical Survey. 54a

the great number now published, instances may not be found
of misnomers, or even wrong bearings; but I rely with great
confidence on their general accuracy, and particularly on those
constituting the surveys of Essex and the northern shore of the
Thames, as the whole of them have been verified by Mr.GARDNER.
Indeed this is to be understood as holding good throughout the
last section, in which are 375 triangles. In our former accounts
of thissurvey; we were particularly guarded in not intermixing
their contents with distances determined from numerous doubtful
intersections; and experience has hitherto not detected above
three or four errors arising from wrong bearings or misnomers.
Previously, indeed, to the compilation of them, a great part of
the objects in Sussex, Hampshire, and the Isle of Wight, were
verified by Mr. GARDNER, in process of an extensive survey, car-
ried on by the order, and performed for the service, of the Board
of Ordnance. This gentleman’will also have it in his power to
detect any errors, if such exist, in the names of places to the
westward; as the Master General has been pleased to issue his
directions for the survey of Devonshire, and as much of Somer-
setshire and Cornwall as will square the work.

I have mentioned, in the body of the account, that the Presi-
dent and Council of the Royal Society, were pleased to accede
to the request made by the Honorable Board of Ordnance, to en-
trust to my care, the circular instrument used by the late Major
General Roy, in his well known operation. It has already been
found highly useful, and will shortly prove to be still more so,
as one theodolite will be employed in carrying the above orders
of Marquis CornwALLis into effect, while the other is used
in carrying a meridional line through the country ; an under-
taking begun, and partly executed.

MDCCC. 4, A

542 The Account of a

Before I close this Introduction, I am to announce, that Mr.
Isaac Datsy, no longer able to endure the fatigues incident to
the service, has retired from it; and it would be a matter of
injustice, if I were not toacknowledge the extent of his services,
his unremitted labour, and attention. But, whilst I lament the
loss of a man so perfectly calculated to assist me in this arduous
undertaking, I derive every consolation from a knowledge, found-

ed on experience, of the talents and abilities of Mr. Simon Woot-
cot, his successor.

SECTION FIRST.

1. Particulars relating to the Operations of the Year 1797.

The principal object proposed to be accomplished this year,
was the determination of the directions of meridians at proper
stations, in order to afford the necessary data for computing the
latitudes and longitudes of places intersected in the surveys of
1795 and 11796.

From errors which are the result of computations made on
the supposition of the earth’s surface being a plane, it is expe-
dient that new directions of meridians should be observed, when
the operations are extended, in eastern or western directions, over.
_ spaces. of sixty miles from fixed meridians. The distance from
Dover to the Land’s End being upwards of 300 miles, it becomes
necessary, on this principle, that four directions of meridians
should be observed; which, with that of Greenwich, amounts to
five, dividing this space into six nearly equal parts.

Whatever be the stations farther to the westward, which offer

Trigonometrical Survey. 543

themselves as fit places for these observations, Dunnose in the
Isle of Wight presents itself as highly eligible, not only because
it is removed the necessary distance from the meridian of
Greenwich, but also because it commands a most extensive
view of the western coast: therefore, as the direction of the me-
ridian was observed on this station in 1793, (see Philosophical
Transactions for 1795, Pp. 517.) it became necessary to fix on
three places only.

In the selection of these stations, it was our wish to have
found such as should lie nearly in the same parallel, each inter-
mediate one being visible from those east and west of it; by which
means, the differences of latitude between their respective paral-
lels would be accurately determined.

When the party was at Dunnose, in the year 1793, a hill at a
very considerable distance, in a direction very nearly west, was
seen just rising out of the horizon. It then occurred to us that
this spot would, at some future period, be a very proper one for
a station whereon a new direction of the meridian might be ob-
served. Experience, in the Survey of 1795, led us to believe
this hill was actually Black Down in Dorsetshire; therefore it was
determined that our operations should commence at that station,
and the event verified the truth of our suppositions.

The party took the field early in April, as observations on the
Pole Star, for the purpose in question, are made with superior
advantage at this season of the year, because the star comes to
its greatest elongations from the meridian at those times, when
the sun produces little tremor in the air, by which means, the
staff to which the Pole Star is referred, in good weather, is easily
perceived.

_As the high land in the vicinity of Teignmouth, in Devonshire,
4A2

BAA : The Account of a

cuts off all view of the southern extremity of ee from
Black Down, the necessary alternative was, the firing of lights
on some remote station, communicating with Butterton. Rippin
Tor was quickly discovered to be the most proper spot ; and that
eminence would, in every point of view, be a most eligible one
for a new direction of the meridian, if the hills in the middle of
the moor were not considerably higher. It was, therefore,
chosen only. with a view of being subservient to the purpose of
finding the latitude of Butterton.

In making observations on the Pole Star, the same precautions |
were taken to ensure accuracy, as were observed at Dunnose and
Beachy Head in the year 1793; (see Phil. Trans. for 1795, p
460.) I shall, therefore, not enumerate them, but content
myself with observing, that no pains were spared in this per-—
formance. .

From Black Down, the party removed to Butterton ; at which
place but few observations were made, the weather being either
tempestuous or hazy, during the greatest part of the time we
were at that station: they were, however, made under favour-
able circumstances, in other respects, and are syle eas likely
to afford accurate results. |

As in the case of Rippin Tor, with respect to Black Down, so
Hensbarrow, in Cornwall, was selected as the spot for connect-
ing St. Agnes Beacon with the station on Butterton; for these
latter are not visible from each other, the high land ‘about St.
Austle, onthe northern part of which is situated Hens or Hengist
barrow, being higher and intermediate. The staff to which the
lights and star were referred, was placed on a hill: called Hem-
merdon Ball, a secondary station in the series of 1795.

On the ist of May, the party proceeded to St. Agnes Beacon; at

Trigonometrical Survey. BAS

which place the observations were completed on the 8th. The
staff for connecting the observations made on the Pole Star with
those made on the lights fired at Hensbarrow, was placed near
Peranzabulo; which spot is laid down in the plan, Pl. XXVII.

After these directions of meridians were determined, we pro-
ceeded with the survey, and from St. Agnes Beacon repaired to
Trevose Head, a promontory on the northern coast of Cornwall.
The ascent from the sea to the station on this headland being
very gradual and unobstructed, we took the opportunity of find-
ing its altitude by means of the transit instrument. The levelling
was begun on the goth of May, and finished the following day ;
from which operation, it was found that the height of the station
above low water-mark was 274,92 feet; which is, probably, within
six inches of the truth. This base of altitude, will afford the
means of computing the heights of the stations in the north
of Devon, and also of verifying those in the western part of
Cornwall. (See Phil. Trans. for 1797, p. 471.) |

In giving an account of this and similar articles, it is my
intention merely to set forth the order in which the different
parts of the survey have been performed. It would be prolix,
and perhaps, unnecessary, to assign the reasons for the choice
of each station. In the present instance, however, it may
not be improper to observe, that a station called Black
Down, near Lydford, was selected for the purpose of carrying
distances into the north of Devon, by means of the side formed
by that station and Carraton Hill. The difficulty of running
up the series of triangles from the west, (and it might have been
also added, towards the north, ) is mentioned in the account of
1797. A tract of country exists in Cornwall, possessing the same
characteristic features with Dartmoor, and has thrown in our

546 The Account of a

way equal embarrassments. The station called Carraton Hill, is
situated on its southern extremity, from which no part of the
north of Cornwall can be seen : it, therefore, became expedient
to erect a staff on the top of the rugged hill Brown Willy, (a
spot not accessible to the instrument, ) and afterwards to content
ourselves with surveying round it. ‘This resolution became the
more necessary, as by means of it, the triangles in the west of
Devon will be hereafter connected with those in the north of
Cornwall, in a shorter and more direct way than from the sides
in the more southern country. In order, therefore, to observe
the staff erected on this station, the instrument was taken a se-
cond time to Bodmin Down. The station named Cadon Barrow,
near Camelford, and those on St. Stephen’s Down, near Laun-
ceston, were also visited ; at which time it was judged expedient
to discontinue the operations in Devonshire.

In proceeding along the southern coast, in the years 1795 and
1796, with a single chain of triangles, we acted in conformity with
our instructions. It was, in many points of view, the most eli-
gible modeof proceeding; and particularly in that which regarded
an early determination of the latitudes and longitudes of the
great head-lands in the channel, and also of the Scilly Isles.

When the operations above spoken of were completed, and
those instructions carried into full execution, (ample materials
being provided for ascertaining the situations of every remarkable
point on the English side of the channel,) the want of a spot
in the southern part of Cornwall, for the measurement of a base,
was felt and regretted; we were, therefore, unwilling to .
introduce errors, if any should exist, from the sides in Cornwall,
into the north of Devon: our operations were consequently
discontinued.

T rigonometrical Survey. 547

From Devonshire we proceeded to the eastward, for the pur-
pose of carrying on a second series of triangles. These were
necessarily intended to originate from the side which connects
the station on Beacon Hill, near Amesbury, with that on Win-
green Hill, near Shaftesbury.

In the month of July, the observations were completed at
the station on the Mendip Hills, after which the instrument was
taken to Bradley Knoll; Dundry Beacon, near Bristol; Lans-
down and Farley Down; the station on Lansdown being chosen
rather for a secondary than a principal place of observation.

From Bradley Knoll, to which place the instrument was

carried from Farley Down, we proceeded to Westbury Down,
and from thence to Beacon Hill, near Amesbury; because it was
necessary that a new point on the range near Marlborough,
commonly named St. Ann’s Hills, should be observed. The
station formerly chosen at the eastern extremity of this range,
and observed in 1794, (see Phil. Trans. 1795, p. 4’71.) was this
year found to be useless, as the high land, on the same range,
‘prevented it from being seen at Lansdown : two others were,
therefore, selected to the westward of the former, and observed
from Beacon Hill; one for the purpose of connecting with Lans-
down, and a stationnear Symmond’s Hall,in Gloucestershire; and
the other with Inkpin Beacon. The particular circumstances of
this range, both as to situation and height, have thrown great im-
pediments in the way of the survey, and are the means of cutting
off, in a considerable degree, the connection between the southern
triangles and those which have been since carried on in the
midland of the kingdom. From Amesbury the party proceeded
to Inkpin Beacon, near Hungerford, where the operations
terminated.

548 The Account of a

The stations chosen and observed this year, but not visited
with theinstrument, were Monymoor, near Penhow; the moun-
tain Twymbawlin, near Newport; and Scilly Point, in Glamor-
ganshire. These stations in South Wales will connect with three
in Somersetshire, also selected this season; one on Bleak Down,
which is situated on the western extremity of the Mendip range ;
a second on Brent Beacon; and a third on the Quantock Hills.

Subsequent to the operations on Salisbury Plain, enquiries
had been often made after a spot on which a third base might
be measured. Experience had almost convinced us that, if Sedge-
moor were excepted, the southern part of England did not con-
tain one of sufficient extent for a base of three miles. Aware,
therefore, of the imperfect state in which our work must rest,
without a fresh base, Mr. Datsy and myself passed over into
South Wales, and examined the extensive level between the new
Passage House and Cardigan. After, however, a very diligent
search, we could not find any spot, four miles in length, suffici-
ently unobstructed. The advantages which the situation itself
holds out, are so great, that we should not have scrupled to dis-
pense with a desideratum, heretofore required, of the base being
one continued line. So much, however, is this flat cut up with
rbynes and ditches, that we were not able to find any point
from which two right lines might be measured, and so inclined
to each other as to afford, by means of an including angle, a third
side of five miles in length: necessity, therefore, compelled us
to think of measuring a base on Sedgemoor, which we immedi-
ately examined. That which relates to this situation, will be found
in an ensuing article: it is now only necessary to observe, that
we concluded the operations of 1797, after the practicability of
measuring a base upon it had been decided in the affirmative.

Trigonometrical Survey. 549

Biv

ART. 11. Angles taken in the Year 1797.

At Black Down.

Between eto ey Mean.

Dunnose and Abbotsbury staff = . - 164 26 33975 hs 552 5
LB, 37
Rippin Tor and Abbotsbury staff - | - - 3 8 51,75 } 5255
52575 J?
Pilsden and Abbotsbury staff = - - - 45 16 15 14, but 13

<

a LY, ; 13 preferred.
Pole star and Abbotsbury staff, April 17, morning - 104 19 26,75

18, morning == 104 19 19,25
1g, morning : 104 19 33
Ig, afternoon - 98 42 47
20, morning = 104 19 25,25
20, afternoons « 98 42 35,5
a ;
: At Butierton.
Hemmerdon Balland Rippin Tor - ~~ - By AO: panei G ale i
8,5 } 775
Hemmerdon Ball and Hensbarrow — = a ie ¥g2" 257%
: : 6,25 } 4:5

Pole star and staff on Hemmerdon Ball, May 6, afternoon = 91 29 13,75

7,morning e 97 4 14
7, afternoon - gi 29 12

- On St. Agnes Beacon.

Hensbarrow and Trevose Head - - - 47 10 0,75
Hensbarrow and Peranzabulo staff - - - 31 50 55,5 156, but
) 5 . 56,25 J 55.5 pref.
Pole star and Peranzabulo staff, May 20, afternoon ~ © 44 © 45,75
s 21, afternoon - 44 © 44,75
22, morning - 3826 185
22, afternoon - 44 O 33.25
23, morning ° 38 269
At Trevose Head. |
St. Agnes Beacon and Hensbarrow - - 65 43 43575
47 47
* 50

MDCCC. | 4B

55O The Account of a

Between avd Mabie Mean
Sebi. ua eee ‘ , . rik Jas
Hensbarrow and Bodmin Down . 34 17 3 }ases
Bodmin D d Cadon Barro - - - 233.43 \rejec-
in Down and Cadon Ww le heeos
51575 } et
52575 J
At Hensbarrow. .
St. Agnes Beacon and Trevose Head ie Sheen - 67 6 13,251.
g n 1332 5 f 13725
Bodmin Down and Trevose Head = 1 z 77 20 17575 Vig.
19:26 ds ey
At Bodmin Down.
Hensbarrow and Trevose Head - - - 68 21 57,25 }s8 25
| 59:55
Trevose Head and Cadon Barrow - - - 71 55 26,75 hey
27
Carraton Hill and staff on Brown Willy aie) ~ 52 3 595
4 1:25 7,75 *
455
Carraton Hill and picket on Brown Willy - - $1.36, Ald jie
\ Il
Cadon Barrow and staff on Brown Willy : = & 30 58 13 hi 3
: 13 ‘
Cadon Barrow and picket on Brown Willy e - 31 26 0,25)
1525 p 1575
3225 '
On Cadon Barrow.
Trevose Head and direction post on Bodmin Down =i 68 7 53.75
54
54525 54.25 4
5475
Direction post on Bodmin Down and staff on Brown Willy = 41 12 3755
39 39225
wth ‘ sit
Direction post on Bodmin Down and picket on Brown Willy - 40 40 34 } :
36375 355 5
Tresparrot Down and staff on Brown Willy - - 100 20 §2,25
55 54975
; : i" 57
Tresparrot Down and picket on Brown Willy - =.) TO "59h } ;
I

At St. Stepben’s Down.
Staff on Brown Willy and Warbstow —- - - 41 18 24,25 it ;
255 J°

Trigonometrical Survey. 55

Between Ce, r) Mean.
Warbstow Beacon and Brendon Moor - A So 99. 41. 1805 M)
J. etere 18,75 [18,75
cee e 19
Brendon Moor and Broadbury Down - - - 99 +0 40,75 } a
; 3
Broadbury Down and Black Down - - - 45 34 36D
84 one hazses
Black Down and Carraton Hill - - - 91 18 12,25 175
- 1355 5
Carraton Hill and Kit Hill ~ | : - $37 = UE5G
Black Down and Kit Hill - - - - 54 16 13
: 3 At Maker.
Carraton Hill and Black Down : - - > 53 4 28 }e .
, 39,5 9» 5
. At Carraton Hill. ‘
Black Down and Maker Heights = 4g = - TAG B25 if
esi 22,75 [775
Trevose Head and Bodmin Down = take = 77 2017575 \ V9
19325 oa
At Black Down.
Maker Heights and Carraton Hill = alan ho ° 52.501, fo7s }
! , 11575 975
Carraton Hill and St. Stephen’s Down - : < 39 44 37,25 }
| 3 40.75 J%9
St. Stephen’s Down and Broadbury Down - - 66 49 57.5 } 58
58,25
Carraton Hill and Kit Hill - - - e 13 12 58
On the Mendip Hills,
Dundon Beacon and Bleak Down - - 85 15 59,25
5975
16 1,5 25
: . 4:5
Bleak Down and Brent Knoll - - - * 29 11 35,75
8
S ; ee 39325
41575
Bleak Down and Dundry Beacon - = 33 39 305
30,5 395

552 mY) ‘The Account of a

Between }
Dundry Beacon and Lansdown tsi Sub caling
Lansdown and Farley Down - entin fo ne
Farley Down and Westbury Down - -
Westbury Down and Bradley Knoll - .
| Farley Down and Dundry Beacon on -
Farley Down and Bradley Knoll - -
At Dundry I Beacon.
Tickenham Down and Grey Hill - S
Tickenham Down and Kingsweston = = °
Kingsweston and Grey Hill - ° 2 a2 ng 2g Oe
: 27575 25575
Bleak Down and Grey Hill ° - - 120 0,23
- USGS wit 240 p25
28 ,
Lansdown and station on the Mendip Hills 2 DS N83 gg Gag ae .
19575
Farley Down and Mendip Hills - _ PLS 6p gama & Pa: sf
23. Jc.
Mendip and Bleak Down - - - 54 94.24 7 2 s 5
; tig A5RY Sudo
At Lansdown.
Kingsweston and Dundry - - va ANN 36 38 29 ©
On Farley Down. a
St. Ann’s Hill and Westbury Down . - - 3) 44 10,75" i x
i ) : é WP aca ode 11,75 :
bE 525 ;
oF x 13575 ‘ * a
Westbury Down and Bradley Knoll - - 37 5 ges75 ac”
; iarewy are fy bbudlequt 2 f Rohl.
aM oe
34.25

Trigonometrical Survey.

‘ Between

Westbury Down and Mendip Hills

Bradley Knoll and Mendip Hills

Mendip Hills and Dundry Beacon

On Bradley Knoll,

Mendip Hills and Westbury Down

Westbury Down and Beacon Hill

St. Ann’s Hill and Westbury Down

Westbury Down and Milk Hill
Beacon Hill and Wingreen
Beacon Hill and Bull Barrow
Wingreen and Bull Barrow
Bull Barrow and Ash Beacon

Ash Beacon and Mendip Hills

101 23

553
r; Mean,

51575 } rp

23
23575 peas

15,25 \rejec-
21,5 Jted.

2575 235

56,5

5775
oO
1,75

29525
39,5 29375

44,

45925 45
46,

is

53,25 }s ie
38,25
31
3395 |
34

51525

52575 i 5?
3.25 }
3.75 J 39

59

3295

by 71 34 54975
55225 J>9
Mendip Hills and Farley Down - - 63 © 21,5D
At Bull Barrow.
Ash Beacon and Mintern - - - 51 26 41
41575 fs
43
Bradley Knoll and Wingreen - : 42 55 32.75
At Pilsden Hill.
Mintern and Ash Beacon - - - cee at | 2

3 3225 J

[ ° . ;
; te ri aA
554 The Account of a
At Mintern. noowaedh
Between % ‘ | {pial a Lge ‘ vay ries?
Pilsden and Ash Bescon - - pes # 35 on
Ash Beacon and Bull Barrow - - 14,22
27 ihredhh a 23.
; ; a eh
On Westbury Down. bi
r of
Beacon Hill and Bradley Knoll ees 9 ae 114 12 18,25 7
SUE we: 18,5 78,5 —
: + a iia
Bradley Knoll and Mendip Hills ~ - . “4048 4) qo
1575 ¢ 1475
Mendip Hills and Farley D 7 beg vied
endip Hills and Farley Down - - - : z 50
Ip y % e R . 3 a ar |sues
Farley Down and St. Ann’s Hill - - 38 50 "x" ") 4 r
Hill pe
St. Ann’s Hill and Beacon Hi - - - pag ee
Beacon Hill and Milk Hill - - - 48 7 a8 }335
‘ : yi ?
Beacon Hill ( Amesbury.)
Bradley Knoll and Westbury Down - - 23 4 15
Inkpin Down and Milk Hill - - f Wes 66 14 58
Inkpin Down and St. Ann’s Hill - - = FO 51 $755 } Yee
37:75 AS
Westbury Down and Milk Hill e - SST AN Me wee Meee
Westbury Down and St. Ann’s Hill - - 48 34: Ota Abed
ry. 49 34 9925 Pp 7975
On Inkpin Down. ©
White Horse Hill and Highclere amr : 333 27 57225 } 57.5
ae id
Highclere and Beacon Hill - ° ace 106 16 52,25 }
| 5425 J 99775
Beacon Hill and Hewish: - -- -

51 53 nea ‘
—— 3325 733925
35 bs
Wie TS

‘ » 4
moma Reape

Trigonometrical Survey. | 555

ArT. 1. Particulars relating to the Operations of the Year 1798.

The object first attained this year, consisted in a trigonome-
trical survey of the counties adjacent to the northern and
southern shores of the Thames.

In the last communication it will be seen, that the survey of
Kent had been carried on from the sea-coast, till it reached the
range which runs eastward from Wrotham through Holling-
bourn, and there terminated. The country to the northward
could not be surveyed, because the view from General Roy’s
station at Wrotham is almost entirely cut off, in that direction.
In order, therefore, to obtain a base for the purpose, when the
party arrived at Wrotham, a new station was chosen, to the
eastward of the former one, and the distance between them
accurately measured; by which means, together with the included
angle at the old station, and the distance of it from Severndroog
Tower, on Shooter’s Hill, a new distance was found, which be-
came a base for the survey proposed.

The chief draftsmen and surveyors belonging to the Drawing-
room in the Tower, attended our operations in this county, and
also those afterwards carried on in Essex. It was, indeed, for
their immediate service, that we renewed the survey in this
quarter, as the Master-General had given directions to prepare
ample materials for completing the map which meets the public
eye with this article.

The stations in Kent, besides that of Wrotham, were
Gravesend, Gad’s Hill, and the Isle of Sheppey; those in Essex
were Hadleigh, South End, and Prittlewell. Observations made >
from these places afforded data for the proposed survey: after
they were completed, the small circular instrument supplied the

556 The Account of a

place of the great one, and was used, with good effect, in cattys
ing on the subsequent operations in this quarter.

In our Paper published in the Philosophical Transactions for
1795, an observation is made, of the necessity then existing for
the measurement of a base on Salisbury Plain, in consequence of
resolutions taken to inclose Sedgemoor: an act for which pur-
pose was passed a few years ago, and partly carried into execu-
tion in 1797. At this time, however, King’s Sedgemoor was only
set out into parochial allotments, as exhibited in Plate XXVIII.
accompanying this Account. The ditches, represented by lines on
this plan, were generally ten feet broad, and five feet deep ; but the
principal and secondary drains were much wider, the first being
thirty, and the last twenty-five, feet in breadth. The subdivisions
on the Moor, or the individual allotments of it, were not traced
out in the Somerton quarter, at this time, the task being deferred
till the latter part of the following year. The measurement,
therefore, of this base, in an early part of the season, became
necessary, because fewer obstacles were then expected to present
themselves.

As it appeared that many instances would probably occur, in
which a chain of 50 feet in length would be useful, if not abso-
lutely necessary, one was provided by Mr. Ramspen, in the
winter; its. make and form being precisely similar to those of
the larger chains, used in the measurement of our former bases.
Such a chain did, indeed, prove highly serviceable in the subse-
quent operation; as the handles of the 100-feet chain would
very often have had their places in ditches, or been so situated —
on their banks, as to leave imperfect means of correctly placing
the register heads under the handles.

‘The apparatus for the measurement, consisting of the sects

Trigonometrical Survey. 557

belonging to the Royal Society, pickets, iron heads, and a new
set of coffers, were sent to Somerton, after Mr. Garpyer had
been furnished with the means of proceeding with the survey
before spoken of. )

The measurement was begun in July, and finished in August;
in the course of which, very little interruption arose from any
inclemency of weather. It is unnecessary to enter minutely into
a description of the difficulties which arose from the frequent
intervention of ditches ; let it suffice to observe, that, possessed
of the 50-feet chain, these were rendered less material than they
would otherwise have been.

When we arrived at that point which ends with the 114th
chain, an offset was taken, and 41 g chains measured, in a direc-
tion perfectly parallel to that of the base, at the extremity of
which we returned into the base itself, and continued the mea-
surement. This interruption proceeded from an accidental and
unforeseen circumstance ; a great ditch having been excavated
in a direction coincident with that of the base, while the mea-
surement was going on at the upper end of it. This, however,
cannot be the means of introducing any sensible inaccuracy ;
for, to proceed in this matter correctly, when it became neces-
sary to take an offset, a silver wire was let fall from the register
head, having a plummet, under the point of which a small dot
was made, on a stake driven firmly into the ground. The great
theodolite was then placed over the stake, and the instrument
accurately adjusted over the dot. A diaphragm, whose aperture
was + an inch, was then put over the objéct-glass of the transit
telescope, which was afterwards directed towards the staff at
Lugshorn Corner, and then moved round, till it exactly made a
right angle with the base. The telescope being sufficiently

MDCCC, 4C

558 The Account of a

depressed, a peg’ was driven into the ground, with its centre
nearly under the cross wires; after which, a pin was moved on
the surface of the peg, as directed by a person looking through
the telescope, till it came to that point at which it bisected the
angle formed by the cross wires. The measurement was then
carried on, in this new direction, a space of 19 chains, at the end
of which, the same operations were repeated, and the old direc-
tion pursued. It does not seem probable, that an error amounting
to more than 4, of an inch, can have resulted from this pro-
cedure.

King’s Sedgemoor being sufficiently level, the base was
measured horizontally; an advantageous circumstance; but,
from the soft texture of the soil, the pickets could not be driven
into the ground so firmly as to be without some small degree
of motion, in case a person stood close to them. ‘Therefore,
those who attended the handles of the chains, either used long
stools, or placed themselves so as to divide the pressurewarising
from the weights of their bodies equally on each side of the pickets.
The disturbances to which the register-heads were liable, did
not discover themselves till a mile of the base had been mea-
sured; and, although it became probable that small errors only
had resulted from the want of those precautions we afterwards
followed, yet we considered what we had done as erroneous,
and recommenced the measurement, with the advantage of
experience. At present, I shall content myself with observing,
that due attention was paid to all necessary minutiz in this
measurement, and refer those who are desirous of being more
particularly informed, to the Philosophical Transactions for
1795, as the mode of proceeding on the present occasion was
perfectly similar to that on Hounslow Heath.

Trigonometrical Survey. 559

After the conclusion of this operation, we proceeded to select
such stations in the neighbourhood of the base, as might afford
means of connecting it with the triangles carried on in the prece-
ding year, The two chosen for this purpose, were Dundon Beacon,
and a spot near the village of Moor Lynch; both nearer to their
respective ends of the base than we wished to have found them ;
yet, as small rods of only an inch in diameter were placed on
those stations, when they were observed from Dundon Beacon
and Moor Lynch, and the same erected at the ends of the base,
when they were observed from those stations, it becomes pro-
bable that very trifling errors resulted from this proceeding.

The station at Ash Beacon was visited subsequent to these
just spoken of, and afterwards that on the Mendip Hills, for the
purpose of taking the angle between Moor Lynch and Dundon
Beacon. ‘The operations of 1798 then terminated with a dili-
gent search after some spot in Cornwall, for a base of only two
or three miles in length: this search, however, was fruitless, as
in fact we had reason to imagine it would prove to be; but we
were not willing to relinquish the hope, that a piece of ground
might be discovered proper for so confined a purpose. The
contrary, however, being the case, the party returned to London
in October.

art. iv. Angles taken in the Year 1798.
At Wrotham. Station of 1787.

Between me AR Mean.
New Station and staff on Severndroog Tower - 94 19 30 e

Station of 1798.

Severndroog Tower and Gravesend - : 62. 54 36,5
38,5 738
3995
4C 2

560 The Account of a

At Gravesend.
Between Lilac Le ehele bat eee Mean.
Severndroog Tower and Wroth - a ee 21 Phigic
g rotham 39 zt ja
Severndroog Tower and Langdon Hill . orl 95 53 56 "
| . 5925 759
re 54; MahS io
Langdon Hill and Hadleigh ~ - = 54-35 14955 1)
5255 53
54.
5795
Halstow and Hadleigh - - - 30 24 17
; 19:75 719
20,5
Halstow and Gad’s Hill © - : 31 38 19,75
22,25 f7"
Severndroog Tower and Hadleigh ° - 130 25 *
‘ 5155 }sexrs
Isle of Sheppey.
Gad’s Hill and Halstow ek - - 18.18 1,5 7
3 3
: 395
Halstow and Hadleigh - “ < 31 28 23
24:5 p24,25
; =
Langdon Hill and Hadleigh - - 16 26 30
Langdon Hill and Rayleigh ae - - 27 4 46

At Halstow.

Gad’s Hill and Gravesend - ie ie 24 18 21,25

; 21,25 f71975-
Gravesend and Hadleigh _ - - 107 49. ae 5} 5525
Hadleigh and Sheppey - - - 99 18 ‘ } 6
Gravesend and centre of Rayleigh Tower - - III 20 1 if
Sheppey and Rayleigh Tower — - - Thea 95 46 57,

At Hadleigh.

Sheppey and South End - - ges 38 43 29
Sheppey and Halstow = - - - 49 13 3395
Gravesend and Halstow en mie - pit 46 ge 82h

Langdon Hill and Gravesend - - 43 11 5%

Trigonometrical Survey.

Between

Gravesend and Severndroog Tower ° -
‘Langdon Hill and Sheppey - = =

At South End.
Sheppey and Hadleigh epg e “ es
Ai Langdon Hill. -

Gravesend and Severndroog - - -
Centre of Rayleigh Tower and Gravesend -
Station on Rayleigh Tower and centre of the same Tower
Station on Rayleigh Tower and Danbury Spire -
Severndroog Tower and Frierning - -
Frierning Tower and Station on Rayleigh Tower -
Frierning and Danbury Spire - - -
Severndroog Tower and Brentwood Spire - °

119 20

At Triptree Heath. 1st Station.

Tillingham Tower and Station on Rayleigh Tower -
Tillingham and Danbury Spire - - -
Station on Rayleigh Tower and Langdon Hill -

Station on Rayleigh Tower and Frierning Tower -

At Lugshorn Corner.

Greylock’s Foss and Dundon Beacon - =

Greylock’s Foss and Moor Lynch - é =

Moor Lynch and Dundon Beacon : . &

At Greylock’s Foss.
Moor Lynch and Lugshorn Corner - = -

Lugshorn Corner and Dundon Beacon - =

Dundon Beacon and Moor Lynch X ~ Z

100 28

eS
8 29
30

105 40

30575
31525 }s y

58,5
59. p59
59375

33275

58,25
59575 } 59
5957

ari 2

: bo
055 225

362 ~The Account of a.

oxen
| Near Moor Lynch Windmill. cee
Between [ pe Paar is
Greylock’s Foss and Dundon Beacon “ ° - 59 55.12,55 ° =" 4
Greylock’s Foss and Lugshorn Corner - - - 51 58 2,25 } 3025
425 f°?
Lugshorn Corner and Dundon Beacon -- - - Hine 184s 1OnTP bod bean ®
: 10,25 hie 5
Dundon Beacon and Mendip Hills - oe 54 38 50 }s0
50
Mendip Hills and Ash Beacon - - - 7 oe | ;
2355 2205
' 23°75 J
Ash Beacon and Pilsden Hill - ~ 58 4 57 Vupel a§ 0 ,
3075 ¢ 395
455
Dundon Beacon and Pilsden Hill = - - 56 43 36,25
36,5 36:75
. 37225 diets a% ¢
Pilsden and Quantock Hills ~ - - 87 15 6 } ra
. : 7 . 25
Quantock Hills and Brent Knoll ~ * - 71 38 57575
| 7%) 58,5 (58,25
58,5
Brent Knoll and Bleak Down - - - 46 1 32,75.
¢ tbe 35975
Bleak Down and Mendip Hills - Ee Nai = 43 41 43,5
45 - ,
45525 Jose
46,75
Brent Knoll and Mendip Hills - - - 89 43 19,5
2055 Jans
24
On Dundon Beacon. |
Lugshorn Corner and Moor Lynch - - =\) AL. 78) 7 rgeyeee
14,5 [ °#5
Lugshorn Corner and Greylock’s Foss - a0 oy OS Ab eee Lae
; 2955
Greylock’s Foss and Moor Lynch - - - 8 1 51,25
y ync 10 5075 sa,05
Moor Lynch and Bleak Down - = ~ i as ao

. i q - ’ y
10,25 } 1o:25
‘Or 22.54,

Moor Lynch and Mendip Hills - ie eRe ed
: 5275 ses

" op? ‘
{inti goed x wiht

ce

Trigonomeirical Survey.

At Ash Beacon.

Between
Moor Lynch and Mendip Hills - i=

Mendip Hills and Bradley Knoll - .

Bradley Knoll and Bull Barrow 2 “

Bull Barrow and Pilsden ~ c 2s «

Mintern Hill and Pilsden = = ns ut

Pilsden and Quantock Hills - - at

Quantock Hills and Mendip Hills - -

On the Mendip Hills.
Bradley Knoll and Ash Beacon - Ps -

Ash Beacon and Moor Lynch - ies «

Dundon Beacon and Moor Lynch - -

563

mie ais Means

56 29 50 F
52525 7515
52525 J

50 8 45,25

t75 L455
93 38 ne i

se

83 40 ae haus

3525 J 39
49 21 35575

39075 38:25

39575 J
59 34 40,5 r

42,25 Jans
72 57 49:75

58 16 20
PMS eee
24,25

69 26 46,5

48,25
evra
23 58 16,5

17575 fi!

ArT. Vv. Particulars relating to the Operations of the Year 1799.

I have shewn in the preceding articles, that sufficient mate-
rials are now in my possession, for calculating the latitudes and
longitudes of those places whose bearings and distances from
given stations are found in the Account of 1797. I have also
pointed out the direction which the survey has subsequently
taken ; and given a short account of the measurement of a new
base in Somersetshire.. The operations of 1799 now remain to

be spoken of.

564, The Account of a

In very early stages of the work, I had frequent opportunities »

of observing, that eminent advantages would accrue to the ser-
vice, were the survey prosecuted on a more extensive scale.
The consideration of a grand instrument being laid up in the
apartments of the Royal Society, suggested the propriety of ob-
taining it; therefore, when my appointment to my present situa-
tion gave me the means of effecting former ideas, I lost no time
in applying to the President and Council, for the loan of their
large theodolite, the excellence of which had been incontestibly
demonstrated by the late Major General Roy. The distinguished
services which the Royal Society have rendered this branch of
the public service, leave it almost unnecessary for me to observe
how readily they granted my request. The instrument was,
accordingly, put into the hands of Mr. RamspEn, early in the

month of January, for the purpose of being examined, and also |

of having new microscopes fixed to it; the former ones being
much inferior, in construction, to those attached to the instru-
ment belonging to Government.

To carry on so extensive a survey as that which is now the
subject of this Paper, much consideration is necessary. I have
endeavoured to give it the best effect, both as to design, and
celerity of execution. What degree of success has attended my
endeavours, the public, in possession of this Paper, can readily

determine. In the present stage of the survey, I have been.

sufficiently impressed with just ideas, as to the importance of
the task, and responsibility of my situation. The difficulties
which start up, in prosecuting a survey of this kind, become more
numerous as it becomes more extensive. In the earliest part
of it, when few objects only were in view, speedy execution
followed the design; but, circumstances now require every

Trigonometrical Survey. 565

exertion, as the triangles are branched out into several parts of
the kingdom.

- Were the length of a degree of the meridian, in these latitudes,
accurately known, the most eligible method of carrying on the
survey would be, that of working between any two determined
parallels of latitude, till the space between them was completed.
Yet this mode would manifestly be subject to some slight inno-
vations, from the necessity of measuring bases in certain stages
of the work : it would beright, however, to adopt the principle
for general practice. Under this idea, it would have been proper
to have commenced the operations of this year in Somersetshire,
and to have carried on the triangles from the neighbourhood of
the new base into the north of Devon.

It is mentioned in one of the former Accounts, that a zenith
sector was formerly bespoken of Mr. RamspeEn, by his Grace the
Duke of Ricumonp, for the purpose of aiding the design of
measuring the length of a degree of latitude in this country.
The pressure of other business caused Mr. RamspEn to lay
aside this instrument, after he had considerably advanced in
its construction. The real necessity, however, for our being sup-
plied with an instrument of this description being made known
to him, he resolved to take it in hand again, and complete it.
Relying on the strength of his assurances to this effect, I deter-
mined to relinquish the intention of proceeding to the westward ;
and resolved to commence this year’s operations, with running
up a series of triangles along the meridian of Blenheim. As it is’
probable my next communication will contain the result of this
interesting part of the survey, I shall now confine myself to
such particulars as relate to the subject under consideration.

- Ina former article, I have observed, that the chief Draftsman,

MDCCc. 4, D

566 The Account of a

Mr. Garpner, has been furnished with materials for surveying
the northern shore of the Thames, and the north of Kent: these
proved ample, as the map, thence compiled, will sufficiently de-
monstrate. As the Master-General issued directions, at this
time, to survey Essex, and parts of the adjoining counties, in the
same manner, and for the same purpose, as Kent has been, I was
obliged to suspend, for a short time, my intention of proceeding
with the measurement of a meridional degree, and to devise
the best means for carrying his Lordship’s instructions into
execution.

For this purpose, therefore, before any stations were chosen
in Essex, the county was very minutely examined; when it ap-
peared, that insuperable difficulties would occur, if the survey
were prosecuted with the large theodolite only. The range
commencing at Havering Bower, and running to Gallywide
Common, cuts off a regular communication between the stations
subsequently chosen in the southern and northern parts of
Essex. The difficulty resulting from this circumstance, was
made still greater, from the want of success in our endeavours
to find one spot on this range, proper for a station. The eastern
part was, in some degree, found more favourable ; but it was dis-
covered that, even here, the small instrument must frequently be
used as a substitute for the large one. Under these disadvan-
tages, the survey commenced in March; the large theodolite
being taken to a station on Hampstead Heath.

The base chosen for carrying on the distances towards the
north, was that constituted by Severndroog Tower on Shooter's
Hill and the new station on Hampstead Heath ; which distance,
although it has not, perhaps, been obtained so correctly as many
others, yet is determined with sufficient accuracy for the matter

Trigonometrical Survey. 567

in hand. When the observations were made on Severndroog
Tower, in the year 1787, the angle between Hanger Hill Tower
and the cross on the dome of St, Paul’s was taken: this was now
made use of, in order to get the angle between Hanger Hill
Tower and Hampstead Heath ; because the former station could —
not be discovered, on account of the wind blowing the thick and
darkened atmosphere of London between the stations, when the
instrument this year was carried to Shooter’s Hill.

For the purpose of connecting the eastern and western tri-
angles with each other, a station was chosen on Southweald
Tower, accessible only to the small instrument. Brentwood
Spire was also found to be conveniently situated for carrying on
the distances: this will be readily perceived by the plan. Lang-
don Hill was also selected; which, with the former station at
Gravesend, were to become the means of connecting the tri-
angles. A station on Epping Forest was judged necessary :
but no spot could be found fit for general purposes, the view
towards the north being confined. One was, however, fixed on,
ealled Highbeech, from which a high building near Berkham-
stead was found to be visible, by means of which, the distances
in the north of Essex could be verified, as the station on the
top of it would connect with Bushy Heath, near Watford, and a
point on the elevated range near Dunstable.

From Hampstead, the instrument and portable scaffold were
carried to Langdon Hill, and from thence to Triptree Heath,
near Malden; from whence the party repaired to Highbeech,
leaving the remainder of the county to be surveyed with the
small circular instrument; which seems to have been done with
considerable accuracy.

_ After the necessary observations were made at Highbeech, I
4 De

568 The Account of a

proceeded to Shotover Hill, in Oxfordshire; and, before May
elapsed, had reconnoitred the country. As the distance between
Inkpin Hill and Highclere, appeared to be shorter than was ne-
cessary for a base on which the northern triangles were to rest,
it became certain, that their sides would depend on the base on
Hounslow Heath. The only means by which the series now pro-
posed to be carried westwards, (for the double purpose of forward-
ing the survey, and also of finding a portion of the meridional
arc, ) could be properly connected with the triangles in the neigh-
bourhood of Salisbury Plain, was the side just spoken of ; for the
high land in the vicinity of Calne, intercepted the view of the

stations on the Marlborough range, from White Horse Hill. In ~

order, however, to make a connection, although imperfect, an
intermediate station was chosen on this high intercepting land.

When the ground about Nettlebed was formerly examined
by us, it appeared difficult to carry on the triangles from Bagshot
Heath towards the northward; because no spot could be found
near the former, from which the Chiltern range could be seen.
I now, therefore, departed from the usual practice of choosing
stations on the ground, and selected Pen Church Tower; by
means of which, I found a connection might be made between
the triangles carried round the Chiltern range, from White
Horse Hill and Nuffield, with'those in Hertfordshire,

At Shotover Hill the party separated, each having its instru-
ment. I shall close this article, without entering minutely into
the reasons which operated with me for the choice of all the

stations selected this year. I shall content myself with enumera-

ting the namesof the stations visited and observed, and mentioning
that Shotover Hill and Cumner Hill, in Oxfordshire, were select-
ed principally with a view of ascertaining the situations of the

Trigonometrical Survey. 569

observatories at Oxford and Blenheim. The namesof the stations
were, Nuffield, White Horse Hill, and Scutchamfly, in Berkshire.
Shotover Hill, Cumner Hill, Whiteham Hill, Crouch Hill, and
Epwell Hill, all in Oxfordshire. ‘Those in Gloucestershire were,
Pen, Cleave, Broadway Beacon, and the Malvern Hills. The
Lecky Hills, in Worcestershire. Corley and Nuneaton, in War-
wickshire. Bardon Hill, Naseby Field and Barrow Hill, in
Leicestershire. Arbury Hill, and Souldrop, in Northamptonshire.
Quainton, Brill, Wendover, and Bow Brickhill, in Buckingham-
shire. Woburn Park, and Lidlington, in Bedfordshire. Kins-
worth, Lillyhoe, Berkhamstead, Tharfield, and Bushy Heath,
in Hertfordshire. From the last mentioned station, the party
returned to London, in October.

Art. vi. Angles taken in the Year 1799.

On Hampstead Heath,

Between . sai Al Mean.
Hanger Hill Tower and Stanmore = KO 52) 15575 }iSies
: 7 7
Highbeech and Shooter’s Hill a = Wo) GN 2 gan
7 3455 i =
Highbeech and St. Paul’s, London - - gh FE725 Uo
; 22,75.

Severndroog Tower on Shooter’s Hill, and Hanger Hill Tower 117 22 13 }

At Langdon Hill.

Gravesend and Severndroog Tower - - 53 47 25
Centre of Rayleigh Steeple and Gravesend - - 122.2 46
Station on Rayleigh Steeple and centre of the same - Q (o'27
Station ‘on Rayleigh Steeple and Danbury Spire - 43 18

Severndroog ‘lower and Frierning Steeple - - 05 25.0
Frierning Steeple and Station on Rayleigh Steeple - 88 14 I9
Frierning Steeple and Danbury Spire - - 45 26 17

Severndroog Tower and Brentwood Spire = - 66 26 39

570 The Account of a

At Tripiree Heath.

Between $ | jjleasan :
Tillingham Steeple and Station on Rayleigh Steeple - 68 28 58 ‘6
Tillingham Steeple and Danbury Spire - - 100 28 21
Station on Rayleigh Tower and Langdon Hill - 21 25 14
Station on Rayleigh Tower and Frierning Steeple a a oe
At Highbeech.
Severndroog Tower and Brentwood Spire - - 71.16 43 } 44 )
eae 7
Severndroog Tower and Southweald - eS €% 37 27 has
7 29
Severndroog Tower and Hampstead “ - 58 28 18 jus |
‘ - 18
Cross on the Dome of St. Paul’s and Hampstead - - 83 111
Berkhamstead Gazebo and Hampstead - = 438 29 57 8
39 0 5°55 |
At Shotover Hill. |
Nufiield and White Horse Hill 3 : 81 53 27575 Log 9 |
| 29575) ae
Scutchamfly Barrow and White Horse Hill e - 26 8." 7,75
7275 ¢8
8,25 .
White Horse Hill and Whiteham Hill - - 48 5-31.25
) 32575 732375
33975
Wendover and Scutchamfly Barrow = ree 117 30 55 } 56
57225
On Whitebam Hill. i
Shotover Hill and White Horse Hill - - 114 54 34575 } 34
| 34075 J #75
Shotover Hill and Cumner Hill - - = 55 52 3495 has
3595
Staff over the Quadrant at Blenheim and White Horse Hill 131 25 34,5 } 36,5
3895 .7

On Cumner Hill.

Whiteham Hill and Shotover Hill : - - 99 29 47 } 4855
4955 :
Shotover Hill and Atlas on the Top of the } - 29 23 34 }

' Observatory at Oxford 34 34

Trigonometrical Survey.

On White Horse Hill.

. Between
Nuffield and Shotover Hill ia: - -
Nuffield and Brill : “te Pind sie
Scutchamfly Barrow and Shotover Hill - -
Whiteham Hill and Staff on Blenheim Observatory -
Brill and Stow on the Wold = - =
Station near Calne and Inkpin - = _-
Highclere and Inkpin - - -
Highclere and Nuffield - - - -
| | At Nuffield.
Bagshot Heath and Highclere thie -
Highclere and White Horse Hill - <
White Horse Hill and Shotover Hill - =
White Horse Hill and Brill - mihi: = -
On Scutchamfly Barrow.
White Horse Hill and Shotover Hill - -
Shotover Hill and Wendover ° - - =
At Stow on the Wold.
Cleave and Broadway Beacon - - “

o
‘

95: 34
38 48

{Ii 47
10 30

64 45
67 10
TZ

63°17

53 33
62 32

86 4

54.44

571

4 Mean
22325 | 4
23,75 [72
11,5
15525 a
50

4355 } ;
on ¢
44075 J 49°73
28,5

3235 fos
11,25

eee alae)
me
53g fro
16,5

17375
18,75

5495

5495

37 55975

57

572 The Account of a

Between
Broadway Beacon and Epwell > -

Epwell and Brill - - = -

White Horse Hill and Cleave ° -

At Broadway Beacon.

Epwell and Stow - 2 -

Stow and Cleave 2 “ 5

Cleave and Malvern Hills o S “2

Malvern and Lecky Hills * 2 2

At Epwell.

Stow and Broadway Beacon ° a =

Stow and Brill ~ = = u

Brill and Arbury Hill - - =

Arbury Hill and Corley = - =

At Corley.

Bardon Hill and Nuneaton Common = .

Nuneaton and Arbury Hill - - s

© og as Mean.

72 38 485 ) ,
49 74995
5055

60 56 6
05 bs } 635

109 40 36,25

36375
37°75

69 10 3075 |
3155 31575
32,75 |

78 53 6
8 775
995

60 28 12,5
17,75 p16
18

L
53 53 19% bios

38 10 43,25
4355
44 P44
44525 |
44,5 J

86 29 13
1305 ¢1395
13575

85 o 16,5
2055

54 55 1735
19 718,75
20,25

18,5

49 54 cd,
53 51975
110 20 52

$255
oe ike
53

Trigonometrical Survey. 573

Between Cp Mage Mean
Arbury Hill and Epwell - - - 35 17 34575

3575
36,25
39575
geen
; 39.25 J
Epwell and Broadway Beacon - - - Za? ae l
49975

“

39575

Nuneaton and Lecky Hills - - - - 153) 25 0S 5

Nuneaton and Station near Birmingham - * 49 54 5275 } 52

At Arbury Hill.
Quainton and Brill - ° - 16 12 37525 |

; Basal
40,5 p40

Brill and Epwell - - - - Go s5)420) iy

‘Near Brill on the Hill.
White Horse Hill and Stow - - - 50 14 44 t

4455
44575
Nuffield and White Horse Hill - = tho Suna Sm a iz 395

Stow and Epwell - - - - 32 34 we
435

Epwell and Arbury Hill - - F 34 23 56 }ss 5

:; 58575
Arbury Hill and Bow Brickhill = - - 68 20 7,75

Bow Brickhill and Wendover - - = 57 25 ‘\ 5
2 ty
Wendover and Shotover Hill - - - 108 5 22 f.
2505°- J 71

Quainton and Wendover - + - SI 34433925 }33

3275
Near Wendover.
Scutchamfly Barrow and Shotover Hill —- - 28 212,95

MDCcc, 4, E

574

Between Mee ’
Brill and Quainton = PBR eta - -
Brill aa Bow Brickhill = - Sa Tis ig a
Brill and pee Hill - tonhael Galle edored.
Bow Brickhill and Stanmore > oie Kaen
Pen Tower and Stanmore aa - OO See
a orstuomh
Near Quainton. ee
Bow Brickhill and Wendover - _ events: 23.
i
Wendover and Brill - esa Neh “
| At Bow Brickhill,
Brill and Arbury Hill =n oe Oa
: . Sbih: Mud ta oe
B ill d ; ~ . — ir -_ * uf
rill an Wendover | ute, bolt 73.34
Wendover and Kinsworth cel wT Sie huasl Taye Rie ne ai
rol die A AS!
Kinsworth and Quainton sé = - ae
Kinsworth and Lillyhoe —« : ase ae
ate e} ake
Kinsworth and Lidlington 2 a ee tia eo See
Trusler Hill and Lillyhoe . - mit -
; Som tes TS
Trusler Hill and Arbury Hill 5 5 a
At Kinsworth,« |
Brill and Bow Brickhill _ . = are
A eB ei ae ~ fea wai
Quarta and ag Brickhill ye oh? oP at:
. ‘ : mY VL

Pt | OE qowes ote bis

Trigonometrical Survey.

Between F
Bow Brickhill and Lillyhoe -

Lillyhoe and Tharfield Tower me a

Tharfield and Station on Gazebo at Berkhamstead -

Stanmore and Berkhamstead a =

Bow Brickhill and Stanmore S = #
Near Lillyboe.

Bow Brickhill and Kinsworth ~ 4

Lidliigton and Bow Brickhill ° . “

Bow Brickhill and Trusler Hill is 4

Station on the Ground near Tharfield Tower and Kinsworth

At Lidlington.

Kinsworth and Bow Brickhill - - i

At Crouch Hill.
Brill and Epwell © - - °

At Stanmore.

Wendover and Kinsworth - Sy
Pen Tower and Wendover - « 5
Bagshot and Pen Tower - = -
Bagshot Heath and Hanger Hill Tower - -

4,E2

575
AP ae ey Mean
82 50 26 | A
30 3935
35 J
12 12 39,75
ve haours
50 2 5555
50 be s,2s
3 055
1

41 15 5655
57975 j 57325

173 37 43 }
i” a

54 58 52,5
5255
53275

23 59 s hax
5 §2 1155
66 ;
1 ae paGves

68 16 19 ]
22575 (22,25
25525

145 23 25575
27 } 26,25

37 41 an)
Eas Gale

23. 4 4755 |
4755
47975 (4855
49,25
49,25 J

49 32 2955

59 55 54525
53.75 } 54

576 The Account of a

Between ; of)" oMiegn.
Hampstead Heath and Hanger Hill Tower , - ©) (45) 255%) ae
5155
51,5 Joos
A 52575
On Bushy Heath.
Wendover and Kinsworth - - is 38 22 «5 } f= a
8,5 275
On Bagshot Heath. Station of 1794.
Highclere and Nuffield - - - 55 32 2555
25,75 °26
26575
Nuffield and Pen Tower - - - 48 47 11
12,75 61295
12,75
Pen Tower and St. Ann’s Hill - - - 70. 30 37525 } .
39 }svas
40

ART. 7. Situations of the Stations.

Trevose Head. The station on this point of land, which is
about four miles from Padstow, in Cornwall, is situated on the
southern part of it, and is about forty feet from the declivity.
The ground seems a little higher than any other part of the Head.

Cadon Barrow. The station is on the centre of the Barrow;
which is a very remarkable one, and well known about the
country. It is about two miles from Tintagel, being in a field
lying south of the road leading from that town to Camelford.

Brown Willy. The staff is erected on the highest part of this
mountain, which is about nine miles southward of Camelford.

St. Stephen’s Down. The station is about 150 feet from the
eastern part of the building erected on this Down. It lies south-
west from the corner of it, and about twenty feet from the road.

Mendip. The station is in a field on the top of the down, beng
about two miles north of Shepton Mallet. The field is next to
the road leading from that place to Bristol, and lies west of it:
it is also north of the road which goes from Wells to Frome.

Trigonometrical Survey. 577

This road crosses the former at right angles. The station is
20 feet north of the southern hedge, and about 200. from the
eastern one. ‘The ground round the station is rather higher
than any other part of the field.
_ Dundry. The station is on the down, close to, but west of,
the town so called. The down is full of holes and pits, from
which stones have been taken for the purposes of building. The
‘station, however, may easily be found, as it is situated on a rising .
which has the appearance of having been a barrow.
- Lansdown. This place is well known, and near Bath. The
station is on the highest part of the broken ground called Crom-
WELL’s Camp, which is near Mr. GranviILLE’s monument.
Farley Down. The station on this Down is 5 feet north of
the stone wall, and about 150 feet eastward of the plantation.
Bradley Knoll. This is a remarkable hill, very near Maiden
Bradley. The highest part of the hill is towards the west, on
which there is a small ring, exhibiting an appearance of a ruined
plantation. The station is a few feet to the northward of this
ring. laresbyct he
_ Westbury Down. There are no objects on. this Down, of any
kind ; therefore, the station cannot be found from measurements.
It is, however, just above the White horse cut out in the side of
the hill. tow! eel atta |

Ash Beacon. This eminence is about four miles north of Sher-
borne :,on the top of it there is a small plantation, round which
is a circular wall. ‘The station is 85 feet east of it.

Dundon Beacon. Thisisan insulated hill, at the eastern extre-
mity of King’s Sedgemoor ; upon it are the remains of a barrow,
probably the site of the ancient beacon. ‘The station is about 4,
feet eastward of the small cavity in the centre of it.

578 The Account of a.

Lugshorn Corner, the eastern extremity of King’s Sedgemoor.
There is a small rivulet, which separates the moor from the cul-
tivated ground on the Somerton side, and, close to a particular
part of it, is a passage called Somerton Gate. About a quarter of
a mile eastward of this entrance, and in the second field, north
of the stream, is the station called Lugshorn Corner, one of the
ends of the base. The spot is 5 feet from the ditch, and 19
from the gateway. There were but three fields in this part of
the moor, at the time the base was measured.

Greylock’s Foss. This is towards the western extremity of the
moor: a causeway leads from Middlezoy to Greinton, over it.
In the second field from the bridge, near the latter, is the other
extremity of the base. The station is about 10 feet from the
ditch, running parallel to the Foss, and is in the angle formed
by the ditch contiguous to the road and the second sya north
of the drain.

Nuffield. The station is in the field ae to the church:
it is in the south-west comer of it, 14 feet from the stile, and
10 feet from the hedge.

Scutchamfly. A very remarkable Barrow, on the Berkshire
downs, situated near Little Hendred. The station is on the
south-west part of it, and can easily be found.

White Horse Hill. This is a well known eminence in Berk-
shire. The station is on the eastern side of the Saxon work,
and on the top of the small parapet surrounding the ditch. —

Shotover Hill, near Oxford. The station is 150 feet from the
hedge eastward of it, and 60 feet from that southward of it; but,
when the traces of our former operations are obliterated,” it will
be difficult to recover this station. | qf

Stow on the Wold, The station bearing this name, isina

Trigonometrical Survey. 579

field 2 miles eastward of the town: it lies on the north side of
the road leading from Stow to Burford, and may be easily dis-
tinguished, being that particular field which affords the most
commanding view. The station is 32 feet west of the corner
‘ of the hedge which forms a right angle with another abruptly
running out: it is also 279 feet from the ridge which divides
the field. © Dm,

Broadway Beacon.- This is a very high and remarkable spot,
near the village of Broadway, in Gloucestershire. The station
is about 20 feet south-east of the foundation of a building pro-
posed to be erected by the Earl of Coventry.

Corley, a village in Warwickshire. The station is in the
second field eastward of the church, being 180 feet from the
eastern hedge, and 290 feet from the stile in the corner of it.

Epwell, a village in Oxfordshire. The station is on the apex
of the hill, and may easily be found, by measuring 17 feet from
the stile, and 14, feet from the hedge which runs across the hill.
N.B. The station is west of the hedge.

Brill on the Hill, Buckinghamshire. The station ison Muzzle
Hill, near the town. There is but one field on this hill: it is on
the highest part of it. The station is situated in the centre of the
field, and in the middle of a rising, once the site of a windmill.
_ Arbury Hill. This hill is still surrounded with the remains of
an ancient fortification. The station is on the north-west corner
of it, and near the brow, but cannot be easily found, from the
want of proper objects to which measurements may be made.

Wendover, Buckinghamshire. The station is on the down
south of the town, and contiguous to the village of Ellesborough,
A road from Wendover, to Sir J oun RUSSELL’S seat, Checquers,
runs over the down: but, as there are no marks on it, its pre-

580 The Account of a.

cise situation cannot be easily pointed out by measurement. It
may, however, be observed, that it is 14, feet peer
the decayed parapet on the top of the hill. PIG: 4, b rt

Quainton, Buckinghamshire. The station is on the high
ground, north of this town. It cannot very easily be found,
because the hill is destitute of objects; yet it may, probably, be
discovered, by looking for it on the green ridge which divides
the land: it is in the middle of that boundary, and about 200
feet westward of the pathway. —

Kinsworth, a village near Dunstable. The station is on the
summit of a hill, about half a mile north of the village. A hedge
runs across the hill, from which the station is 40 feet north-
west : it is likewise close to the road. 92

Lillyboe, Hertfordshire. The station is on a sonically
eminence, having the Icknield way at the foot of it. There are no
objects on this hill, therefore the precise situation cannot be
pointed out by means of measurement : it is towards the north-
west corner of the hill. aol |

Stanmore. This station is on the southern extremity of the
range above the town: it is near the trees, and a sin to the
westward of the broken ground.

Bushy Heath, near Stanmore, The station cannot be aby
found : it is about 1000 feet from the road, but there areno ob-
jects near enough to determine it by measurement. |

Wrotham. This station is 2054 feet north-east of the old
station: it may be easily found, with the assistance of a theodo-
lite, Severndroog Tower making an angle of 94° 19’ = the
new Station.

Gravesend. The station is on Windmill Hill, and on the western
side of it: it is about 50 feet south of the stile, and near the brow.

Trigonometrical Survey. 581

Gad’s Hill, Kent. The station is very easily found, being in
the middle of the tumulus.

Sheppey, Isle of. The station is on the bare hill, westward of,
and contiguous to, the high range: it cannot be found through
means of measurement.

Hampstead. The station is on the heath, but cannot easily be
found, on account of the rugged and broken ground which sur-
rounds it: it is situated 40 feet from the road, and among the
sand holes.

Langdon Hill, Essex. The station is in the middle of the field
on the top of this hill: it is about 400 feet from either of the
stiles.

Hadleigh, The station is on a remarkable hill, in shape very
like a barrow, and is abouta mile south-west of the town.

Southend. The station is in the second field westward from the
terrace: it cannot be easily found.

Interior Stations.

Hope's Nose, the north projecting point of Torbay. The only
spot fit fora station in this part is the one chosen: it can easily
be found, for it is the high and bare rising, just above the Nose.

Ball’s Obelisk. This object is on the eastern part of Great
Haldon, in Devonshire. The station can be easily found, for it
is close to the gate of the inclosure, and on the only spot not
covered with heath.

Evercrutch, in Somersetshire. The hill on which the station
is, commands an extensive view, and is not far from the town of
Evercrutch. Bruton is also near it. The station isin the middle
of the flat place on the top of the hill.

Crouch Hill, near Banbury, in Oxfordshire. . The hill is well

MDCCC. AF |

582 The Account of a

known, and the station easily found; for the apex of the hill
appears as if it were truncated, and in the middle of the smooth
part is the station.

Cumner Hill, near Oxford. The station is about 130 feet
westward from the centre of the clump of trees.

Whitebam Hill, Oxfordshire. There are a few trees contiguous
to the station, which bear eastward from it, and are about 80
feet distant. The station is on the highest and smoothest part
of the hill.

Lidlingion, a village near Ampthill in Bedfordshire. This
station can easily be found, for a tumulus, whose centre is the
station, has been erected, to render it conspicuous.

Trusler Hill, in Woburn Park. The station is on a tumulus
likewise ; and can be found without any difficulty.

Stations in Essex, Suffolk, and Hertfordshire.

Prittlewell Steeple.

Rayleigh Steeple. The station is in the north-east corner, 20
inches from the north parapet, and 4, feet from the eastern one.

Danbury Steeple. The instrument was placed in the four
angles of the Steeple, as circumstances rendered it necessary.
The points are readily found, as there is scarcely room in the
corners to place an instrument. Stations were also selected on
the following Steeples, &c.

Canewden Steeple. West Mersea St. Little Bentley St.
Frierning St. Colchester, St. Mary’s Staircase. | Woodbridge St.
Tillingham St. Tattingstone St. ~ Butely St.
Thorp St. Rushmere St. Otley St.

Stoke St. Great Tey St. Henley St.
Dover Court St. St. Osyth Priory, Flagstaff. Falkenham St.

Peldon St. Shoebury Ness, Staff. Copdaock St.

Trigonometrical Survey §83

Naughton St. Beauchamp Roding St. Westham St.
Lavenham St. - Hornchurch St. Barking, Staireasé.
Balmer St. Naseing St. Berkhampstead, Ga-
Giemsford St. Henham onthe Mount St. _—_zebo.

Toppesfield St. Thorley St. .. Gallywood Common.
Twinestead St. Albury St. Purfleet Cliff.
Southweald St. Elmdon St. Babraham Mount.
Pleshley St. Rickling St. Epping Mill, Base.
High Easter St. Thaxted St. Brentwood Spire, sur-
HatfieldBroad Oak St. Balsham St. veyed round,

Stations in Kent.

Frant Steeple. Station of 1787. Seal Chart. Ash St.

Botley Hill. Do. __ Tunbridge St. North Fleet St.
Chiddingstone St. Oxford Mount. Stockbury St.
Mount Sion. Silverden Farm. Hernhill St.
East Peckham St. Well Hill.

Tudely St. Crayford St.

The stations chosen for the survey of Essex, and parts of the
adjoining counties, as also for completing the survey of Kent,
are mostly towers, as may be seen from the above. When the

tops of the towers have been smooth and even, the stations
were always in the centres of them; but, when they were covered
with roofs, or had spires upon them, stations were chosen in the
most convenient places, and staffs always erected. I have
omitted giving the measurements by which the stations may
be exactly found, Rayleigh and Prittlewell excepted, in order
to avoid swelling this article to an inconvenient length.

4,F 2

xe Lhe Account of a

Art. vitt. Particulars relating to. the Base on King’s Sedgemoor,
and the Reduction of that Base. Pilate XXVIII.

Comparisons of the Chains.

As the chains, after the measurement on Salisbury Plain,
-were oiled, and laid up in the Tower, no apprehensions were
entertained that either of them was elongated by the rusting of
the joints. It was, however, our wish to have compared them
with each other, previous to the commencement of this operation,
and attempts were made, but rendered unsatisfactory, from the
want of sufficient firmness in the soil. It was not till we arrived
at the 7oth chain, that a good opportunity presented itself:
the measuring chain A, was then compared with the standard
B, and found to be thirteen divisions of the micrometer head,
attached to the brass scale, in excess. In these trials, the tem-
perature remained constant; the mercury in FAHRENHEIT’s
thermometer being at 662°. |

The 50-feet chain, spoken of in a former article, came from
the hands of Mr. Ramspen without being very accurately mea-
sured ; therefore it now became proper to ascertain its length,
by means of the standard chain. This was accordingly done at
the present time; when B was found to exceed twice the length
of the 50-feet chain, by 14 divisions of the micrometer screw ;
the thermometer, at the time of trial, standing at 69”.

At the conclusion of the measurement, the chains were again
compared, when the working chain A, was found to exceed the
standard, 174 divisions on the micrometer head : this was after
273 chains were measured. Now, when 70 chains only had
been measured, the difference between A and B was 13 of those

Trigonometrical Survey, 585

divisions; consequently 174— 13,4, divisions, was the wear of
B, in measuring 203 chains. Therefore, the whole wear is
found by this proportion, viz. 203 : 44 :: 273 : 5,223 divisions,
== ;2, ofan inch; which very inconsiderable quantity, like the
wear on Salisbury Plain, no doubt, arose from the pivots and
pivot holes of the joints being polished by continual use.
This supposition seems just; as the wear oi the chain, after
the measurement on Hounslow Heath, was found to be much
greater.

The length of the chain A, as well as that of the standard B,
‘was accurately ascertained by Mr. RamspEn, in the year 1793,
as particularly shewn in the Philosophical Transactions for 1795.
In the temperature of 54°, A was found to exceed 100 feet,
+425 of an inch; therefore, adding the wear which took
place on Salisbury Plain, wiz. 52, part of an inch, we get the
length of A at the commencement of the measurement on
Sedgemoor = 100,01009 feet.

From repeated trials, as before observed, the standard B was
found to exceed the length of twice that of the new fifty-feet
chain, 14 divisions of the micrometer head; and, after the mea-
surement, the same chain fell short of A, 17Lof those divisions :
hence, A exceeds twice the length of the 50-feet chain, 31+ divi-
sions. Therefore the length of the short chain, in the temperature
of 54°, may be taken at 50,00075 feet.

586 The Account of a

Art. 1x. Table of ithe Measurement of the Base of Verification
on King’s Sedgemoor.

Spaces Mean Spaces Mean Spaces
Days. | measured. | temp. by Days. | measured. | temp. by Days. | measured.
Yards. 15 therm, Yards. 15 therm. Yards,
July 100 | 69,7 3200 | 79,27 6300
200 | 65,56 3300 | 79,96 6400
iI 300 | 62,73 25 3400 | 62,06 6500
400 | 67,40 |}. 3500 | 65,90 6600
500 | 64,10 26 3600 | 67,63 6700
iz 600 | 65,30 3700 | 65,83 6800
700 | 73,40 Zz, 3800 | 67,72 6900
800 | 69,36 3900 | 75553 7000
g20 | 68,06 4000 | 71,40 7190
13 1000 | 66,05 AIOO | 71523 7200
1100 | 70,30 4200 | 67,14 7300
1200 | 69,33 31 4300 | 66,56 7400
1300 | 62,83 ||Aug. I 4400 | 71,16 7500
14 1400 | 63,93 2 4500 | 64,60 7600
1500 | 61,40 4600 | 65,16 7700
1600 | 57,03 4700 | 68,16 7800
16 1709 | 66,36 4800 70,16 7900
1800 | 65,80 4900 | 76,23 8000
1900 71,03 5@00 70,06 8100
17 2000 | 75,70 5100 | 64,23 82c0
2100 | 80,43 3 5200 | 64,46 8300
2200.1) 77554 5300 | 63,96 8400
18 2300 | 65,96 5400 | 63,86 8500
2400 | 69,79 5500 | 67,13 8600
2500 | 69,56 - 4 5600 | 73,53 8700
2600 | 68,16 5700 | 73,84 ‘8800
19 2700 | 68,19 5800 | 69,83 8900
2800 | 72,66 5g00 | 65,86 gooo
2900 | 69,23 6000.| 61,50 1 g100
21 3000 | 70,76 6100 | 76,46 16 |9225,4943

3100 | 79,68 6200 | 84,26

|

Trigonometrical Survey.

Art. x. Reduction of the Base.

_ The overplus of the 273d chain was measured
by Mr. Ramspen, and found to be 29,517 feet;

§87

Feet.

wherefore, the apparent length of the base was = 27676,4830

From the measurement in the Riding-house of
his Grace the Duke of Marisoroveu, the chain
A was found to exceed 100 feet, in the temperature
of 54°, 0,11425 parts of an inch; to which, add-
ing the wear by the measurement on Salisbury
Plain, viz. +45, and also balf the wear by the
measurement of this base, wz. ;4, part of an inch,

=" for the excess of the chain’s length

we se

above 100 dg therefore,“ x 279,8 = 29,7075

feet ; which add = = a =
The sum of all the degrees gat Mal the ther-

mometer was 98511; wherefore," — 54 x 272,8

° a

== 3,1069 feet; which ae add iy

Reatte from the comparison of the s50-feet chain
with the standard B, it appeared that the excess
above 50 feet, in the temperature of 54°, was0,0g075
9,09075

parts of an inch; therefore, x 8 = 0,0605

parts of a foot. This likewise add -
The sum of all the degrees shewn by the ther-
mometers placed by the sides of the s0-feet chain,

was 1372; therefore “> — 54 x 4x2 = 0,0365

parts of a foot: and this add - -

+ 257075

+3,1069

+0,0605

+0,0365

27682,3944,

588 The Account of a
| 276823944
And, for the reduction of the base to the tempe-
rature of 62°, viz. for 8° on the brass scale, we have
oclagy Keree xe ==2,2497 feet ; which subtract —2,24.97
Therefore, the length of the base is - 2 feet 27680,1447

which, neglecting decimals, may be taken at 27680 feet.

As to the probable error of the above conclusion, I know not
how to form a just opinion. On ground sufficiently hard, and
otherwise favourable, I think a base of 5 miles might be mea-
sured so accurately, as to afford a result not differing from the
truth more than three inches : but, on this occasion, I should
not suppose the error can be less than six, nor more than nine
inches. Motives for adopting this supposition, have been related
in a foregoing article.

ART. x1. Calculation of the Sides of certain principal Triangles in
Cornwall and Devonshire. Plate XXVII.

Distance from Hensbarrow to St. Agnes Beacon, 97084,8 Feet. Phil. Trans. 1797. p+ 461.

No. of ‘Observed : Spheri-
easels Names of stations. angles, Diff. ne

EXCCSS, |

Angles corrected}
Error. | for calculation, | Distances.

o 46 7] 7) a u oO 4 v7] Feet.
1. |St. Agnes Beacon 47 10 0575 |—0,15 47 10 3,25
Hensbarrow - - | 67 6 13,25{—0,58 67,6413
Trevose Head - 65 43 47. |—0,57 65 43 43:75
180 oO 1 1,31 |—0,31
ieesinate Agnes Beacon - 98108,1
Trevose Head from { Hensbarrow a -, | .78099.9

are ec

Trigonometrical Survey. 589

Distance from Hensbarrow to Bodmin Down, 4733752 Feet. Phil. Trans. 1797. p- 460.

No. of : Observed Spheri= Angles corrected
triangles Names of stations. angles, cal trror. | for calculation, 4 Distances.
| EXCESS.
Se | coerce | RSS eee
oO 44 7) Feet.
tr. |Hensbarrow + - | 77 20 18,5 77 20 17, 5
Bodmin Down - | 68 21 58,25 | 68 21 57525
Trevose Head - 34 17 4555 34. 17 45525
180 ° 2525 0,86 Lae
Bodmin Down - 81967,6
Trevose Head from { Panebatrow 78093

Mean distance from Hensbarrow to Se Head, 78096,4 feet.

111. ?Trevose Head - 42 33 52 —0,32] 42 33 os 25
Bodmin Down - 7155 27. |—0,43 Py 55 26575
Cadon Barrow -f[ .. . 65 30 42,0

revose Head - 85625
Cadon Barrow from {r Bedwin Down °C 63 925
iv. |Bodmin Down - | 30 58 13 |-0,05 30 §8 12,75
Cadon Barrow - -| 43 49 50,5 |—0,04 43 49 50
Brown Willy - - = iss ie lak, ites Il 57:25
‘ Bodmin Down : - | 43722
Brown Willy from { tie Dit owe te 4 32488

Distance from Carraton Hill to Maker Heights, 82600,3 feet, Phil. Trans. 1797. p..458-

v. arraton Hill - -|74 § 22,5 |—0,60 74° 5° 21758
Maker Heights - 53 429 |—0,48 34 28575
Black Down - + | 52 50 9,75|—0,48 52 50 955
180 O 1,25 1 1,57|~0,32
Maker Heights - = | 99680
Black Down from { Carraton Hill < = $2860,4.

MDCCC. »
4G :

590 The Account of a

Observed f Spheri-
angles. Diff. cal | Error,

€XCess.

Angles corrected

No. of
for calculation.

triangles Names of stations,

° <p te -
48 57 9,25
39 44 38,5

48 57 $,25|—0,24
39:44 39) Oe hei 2e
QI 18 12,75

vr, |[CarratonHill - -
Black Down. - -
St. Stephen’s Down

180 0 0 0,89 |—0,89

an Carraton Hill
St. Stephen’s Down from { Black Down

gt 18 12,25

5299153
62 eb;

Distance from Carraton Hill to Kit Hill, 33427 feet. Phil. Trans. 1797. p. 459-

vir, {Carraton Hill - - | 70 15 32 |—o,14 70 15 32525
St. Stephen’s Down | 37 1 56 |—0,11 37 byl Save
Kit Hill - - ohne Les 72 42 32

ce fe | ee | eee

St. Stephen’s Down from { roe Hill - “

Mean distance from St. Stephen’s Down to Carraton Hill, 52292,7 feet.

541613 |—0,19 fF a 4 ee i 5
52 57 37. ~|—0.19 52 57 36.5
B anole 72 46 1

Viir, {St. Stephen’s Down
Black Down - -~
Kit Hill - =

Kit Hill = - is ~

Black Down from St. Stephen’s Down -

53128
62509,2

Hence the mean distance from Black Down to St. Stephen’s Down, is 62508 feet.

In the third triangle, the angle at Cadon Barrow is supplemen-
tary. When the observations were made at that station, a direction-
post at Bodmin Down was mistaken for the staff, (to which it was
similar in shape,) erected at no great distance from it. This error
was not detected till long after: and, although it has been a maxim
to which we have generally adhered, of observing all the angles of

Trigonometrical Survey. 591

each triangle, yet, for the reasons assigned in the preface, I have
chosen to depart from it on the present occasion. In another
principal triangle, the angle at Brown Willy is also supplementary :
it has already been mentioned, that an instrument cannot be got on
the top of it. As to the angles at Kit Hill, in the two last triangles,
being inferred ones, it may be proper to mention, that Black Down
was chosen for a station, after the observations were made at the
former. To have visited Kit Hill a second time would have been
unnecessary, because there are not any distances, except to interior
objects, which depend upon those triangles.

art. x11. Calculation of the Sides of a Set of principal Triangles,

_ carried on from the Side which joins the Stations on Beacon Hill,

near Amesbury, and Wingreen Hill, near Shaftsbury, towards the
Base of Verification on King’s Sedgemoor. Plate XXIX.

Distance from Beacon Hill to Wingreen Hill, 114522,4 Feet. Phil. Trans. 1795. p. 501.

ae of i? BF ataitane. Observed - Dif, Spheri- | prroz, [Angles corrected Wiskanccs.
riangles i angles. cal for ealculation.
7 excess,
ovMiaa ie #7) 7] u a Oneal Feet.
1x. |Wingreen Hill - | 89 57 37275|—0,97 89 57 37
Beacon Hill - 32 11 43,25|—0,48 ; 3z II 43
Bradley Knoll 57 5° 38,25 |—0,48 57-50 40
179 59 59225 1,93 {|—z,68
Wingreen is = 72074.
Bradley Knoll from Bee Eh cus. 13527293
x. |Bradley Knoll - 40°43 52 i=-0,26 “ 1140 43 5155
Wingreen - 96 26°37 ~|—0,65 96 20 36,25
Bull Barrow + ‘ | 42 55 32,75|—0.25| © A2 55 32,25
180 Os T75 Tel Gn [20,55
Bradley Knoll -~ 105180
Bull Barrow from{ Wingreen y - | 6905 3,6

In the Philosophical Transactions for 1797, p. 455, the distance from Bull Barrow to
Wingreen is said to be 69058, being 44 feet greater than the above conclusion.

4G 2

No of .
vriangles| Names of stations.

Bull Barrow - | 40 38 47,75
x1. |Bradley Knoll

Ash Beacon -

|~0,28!
45 43 3.25
93 38 11,5

Whew oa le: sara,
TSO, OC 8575) 1,25 |42,50

Bradley Knoll “ | 68650,6
Ash Beacon from { Bull Bert ow ; 75451
x11. [Beacon Hill = - 23° 4:15 J-=0,68 23 4 14575
Bradley Knoll 42 43 29,75 |4+0,07 42 43 28,25
Westbury Down 114 12 18,5 |—0,97 ' 114.12 17
180 © 3,25 1517 |42,08
f Beacon Hill - 100625 ,1
Westbury Down from{ Bradley Knoll 4 58118,2

| 4° 48 175

x111.|Westbury Down {40 48 1,75|—0,12
Bradley Knoll - |101 23 59 |—0,48. 101 23 59,75
Mendip Hills - | 37 47 58,5 |—0,16 37 47 5855
179 59 59225 0:77 [71552
7 ae: Westbury Down - 92954,0
Mendip Hills from{ Bradley Knoll it 61961,1

7

Base of verification—Greylock’s Foss to Lugshorn Corner, 27680 feet.

xiv. {Lugshorn Corner [107 44 31 107 44 31.
Greylock’s Foss - 8 30 0 yor 8°30 Gaeht
Dundon Beacon - | 63 45 29 63 45 29

180 0 Oo Oo]
Lugshorn Corner ~ 4561,5

Dundon Beacon from{ Greylock’s Foss 29393

Trigonometrical Survey. 593

Angles corrected]
Error. | for calculation, | Distances.

cal
excess,

OL TS

} “ ° 4 n Feet.
xv. |Greylock’s Foss - 105 40 0,5
Moor Lynch - 59 58 1455
Dundon 14 21 45
—1,0
| Greylock’s Foss - 8421,5
Moby Lymeli from{ Dundon Beacon - 32688,7

xvi. |Lugshorn Corner - | 13 51 59 13 51 58,75
Greylock’s Foss - |114 9 59 | : J114 9 58,5
Moor Lynch + 51.58 g625% §UAGSL 42575
[180 © 1,25 41525
Lugshorn Corner -- 32061,3
NpoCe Lommel from{ Greylock’s Foss 2 8421,8

| 93 52 34525
8 oO 10,75

7 sig ag

Lugshorn Corner - | 93 52 33,75!
Moor Lynch - 8 0 10,25
Dundon Beacon - | 78 7 1455

179 59 5855

f Lugshorn Corner
| Moor Lynch -

Dundon Beacon from

Hence the mean distance from Moor Lynch to Dundon Beacon is 32688,85 feet.

xvi11.\Moor Lynch - | 54 38 50 |—0,07 54 38 49,5
Dundon Beacon + |101 22 54,5 |—0,32 IOI 22 53575
Mendip Hills = - | 23 58 17 |—0,10 23 58 16,75

180 0 Ls | 0,5 |+1,0

Moor Lynch - - 78876,8

Mendip Hills from{ mutdon Beacon Z 6562257

59A The Account of a-

Angles corrected

No. of Observed Spheri-

triangles} | Names of stations. angles. Diff. cal | Error. } for calculation. Distapces
excess.
oO wae of r) a Ona Feet.
x1X~ |Moor Lynch - 54. 3 22,5 |—0,42 ‘S43 22) -¥H
Mendip Hills - | 69 26 48,25 |—0,49 69 26 47
Ash Beacon - 56 29 51,5 |—0,42 56 29 51
WOO! 01.125 2i5 ‘| 1533!-4+0,92
Moor Lynch - - 88 71
Ash Beacon from Mendip Hills z 76851
xx, |Mendip Hills - 58 16 22 |—0,30 1 58° 16 21,504 <i
Ash Beacon . 50 8 45,5 |—0,28 ~ | 50 8 45,25}
Bradley Knol! - [971 94 55 '|==0396 71/34 54,25
180 O 2,5 O,951-4+1,55
} Mendip Hills - 61963;
Bradley Knoll from{ aie ere | | gees

The distance from Bradley Knoll to the station on Mendip Hills,
and also to that on Ash Beacon, is given in the preceding triangles,
independent of the above values. The first is 61961,1, and the second
68650,6 feet: these distances have their origin in the base on
Salisbury Plain. The other distances are 61963,5, and 68653,6 feet;
and these depend on the base of verification on King’s Sedgemoor.
There is, therefore, a difference of 24, feet between the values of
one distance, (12 miles nearly,) and g feet between those of the
other, which is about 13 miles in length. If the computations had
been carried on from one base to another, the difference between the
measured base on Sedgemoor and the computed base, would have
appeared to be one foot nearly. 1 have already delivered it as my
opinion, that an error of nine inches may exist in the new base:
therefore, these results must be considered as satisfactory enough.
A different correction of the observed angles, or another selection of

eS

Trigonometrical Survey. . 595

the angles themselves, might afford a closer agreement; but I can-
see no just reason for making arty alterations in one or the other.

I shall now take the means of the distances, as derived from both

bases, and consider 68652,2 feet as the true distance from Ash

Beacon to Bradley Knoll; and 61962, feet for that between Bradley

Knoll and the station on Mendip Hills.

In one of the foregoing triangles, (Bull Barrow, Bradley ‘Knoll,
and Ash Beacon, ) the distance between Ash Beacon and Bull Barrow
is found to be 75451 feet. If the mean distance between Bradley
Knoll and Ash Beacon, viz. 61962,93 feet, be now used, 75452,7
feet becomes the distance between those stations; and this I shall
use, in computing the sides of the two triangles which immediately

follow. x
No. of} | : Observed : Spheri- Angles corrected] _.
triangles} Names of stations. angles. Diff. cal Error. | forcalculation, | Distances.
excess.
‘i rm Ooh es ; n a a wn Oar aur Feet.
xxi. |Ash Beacon -+ (| 34 18 56,25|—0,14 34 18 55,754.
Bull Barrow > 51 26 42. |—0,13 51 26 41,75
' Mintern - - | 94 14 23 |—0;32 94 14 2255
) -|180. 0 1,25 | 0559 -+0,66
. HitiBeacon!. 77991 0,4 ' 59166,6
pee Or { Bull Barrow . = e __—,: | 4265347

SSS

_ Semre, (Pilsden! Oo! id [eR liigh uo) tojew i 135° 3 (05751
Ash Beacon - AQ 21 38,25 |—o,24 49 21 38
Mintern— - 95) 135,22... .\—0,60 95 35 21,25
180 O 1,25 | 1,08 40,17
: Ash. Beacon = “ 102535
Pilsden from { Minteta Ds Heee 8177.6

In our last account, (see Phil. Trans. 1797. p. 455 and 456.) the distance from Bull Barrow
to Mintern was found to be 42653,4 feet; and the distance from Pilsden to Mintern 78177
feet. The distances derived from.the above triangles are very nearly the same; a difference
of a few inches only existing between them.

596 _- The Account of a

No. of Observed Angles corrected

triangles} | Names of stations. angles. Diff. for calculation. | Distances.
Ole tn Vis “ eee LP) Feet.
xx111.{Moor Lynch - 57 19 325 |—-0,64 57 19 255
Ash Beacon “ 76 2 36,5 {—0,39 76 2 36
Pilsden - = Li peas et 46 38 21,5
Pilsden from Moor Lynch - - 118230

But Pilsden was also observed from Dundon Beacon ; from which, and the angle observed
at Moor Lynch, between Dundon Beacon and Pilsden; results the following triangle.

xx1iv.|Moor Lynch: - = | 56 43 36,75|+0,03 56 43 3655

Dundon Beacon - {108 1 52 |—0,64 108 1 $1575

Pilsden - - Eee ty 15 14 31575
Pilsden from Moor Lynch = = awe 118233,6..

Hence, the mean distance from Moor Lynch to Pilsden is 118231,8
feet; and this is the side from which the series about to be carried
on, for the survey of the north of Devonshire, is to originate. _

In the triangle formed by the stations on Mendip Hills, Bradley
Knoll, and Westbury Down, the distance between the first and last
is 92954,0 feet; but, computing with the mean distance from
Mendip to Bradley Knoll, (61962, feet, ) as found from both bases,
the distance from Mendip to Westbury Down proves to be 92955,9 _
feet; which distance is used in the remaining principal triangles in
this quarter. dtmall

xxv. |Farley Down - - | 77 21 53,75 |-=0,44 77 21 S295

Westbury Down - | 63 42 51,25 }—0,34 63 42 49,75
Mendip Hills - 38 55 1725 }—0,3° , 38 55 1735
180 O 255 1,1@|-+ 1,40
Mendip from Farley Down - - - } 85412,2

Westbury Down - - 9295 509

Trigonometrical Survey. 597

Jv

No. of f Observed | Spheri- Angles corrected]
triangles. Names of stations. angles Diff. cal Error. | for calculation. | Distances.
excess.
OM TN ys ” a a Oath Feet.
xxvi. [Mendip - - | 60 36 15,5 |—0,40 60 36 15
Dundry - - | 69 52 22 “|—0,44 69 52 22
Farley Down - | 49 31 23,5 |—0,37 49 31 23
130 0" FT 1,21 |—0,21 ;
Farley Down - - © | 7925553
Dundry from {Mendip ke z 69196
xxV1II.|Mendip - - | 41 3 58,5 |—o,25 41 3 58,25
Dundry - - | 83 34 18 |—0o,40 83 34 1755
Lansdown - -]| . : 55 21 44,25
Lansdown from Neeoiire i pais 8357352

5524902

xxvit1.j]Dundry - - 13 41 56,25 |—0,09 13 41 56
|Farley Down - 27 5 27,5 |—0,11 27. > 27325
Lansdown - -| .. .

139 12 36,75

ec | ee | me |

Farley Down - 2873054
Lansdown from iad es is - | 55248,7

Wherefore, the mean distance from Dundry to Lansdown is 52248,9 feet.

ART. x11. Calculation of the sides of certain principal Triangles,

carried on from the side Bagshot Heath and Highclere, towards the
north, Plate XXXI.

Distance from Bagshot Heath to Highclere, 142952,6 feet. Phil. Trans. 1795. p. 496.

xx1x. |Bagshot Heath - | 55 32 26 |—o,89) 55 32 25,25
Highclere - 46 10 18,25 |—0,83 46 10 17375].
Nuffield - - | 78 17 18,25 |—1,20 Zo LF Uz

180 ©O 2,5 2,94 |—0,43

Nuffield an eee Heath - = |105321,2
Highclere - ° 120374

MDCCC. 4H

598 The Account of a

No. of i Observed ! Spheri- Angles corrected} _.
triangles. Names of stations. angles. Diff. cal Error. | for calculation, | Distances.

excess.

B pean 1 y, Fi ee Lbs Bah Feet.
xxx, |White Horse Hill | 63 7 53,25 |—0,94 63. 7 53:5
Highclere - - | 63 18 16,75 |—0,94 63 18 17 :
Nuffield - - | 53 33 49.5 |—0,86 63 33 4995
179, 59 5955 204 Weig2* 4
é i Nuffield - - 120557,7
White Horse Hill from Highclere ¢ 10856351

Distance from Beacon Hill to Highclere, 98694,4 feet. Phil. Trans. 1795. p. 497.

xxxI, |Beacon Hill - - | 17 42 38,5 |—0,12 17 42 38,25
Highclere - -| 56 0 29,75|+0,08 56 0 29,25 "
Inkpin Hill - + |106 16 53,25|—0,47 106 16 52,5
180 0 155 0,50 }+41,0
dai? Highclere - = 31278,8
Inkpin Hill from 4 po >on Hill wwe iia
xxx. |Highclere - - | 34 27 50,75|+0,38 34 27 50,75
Inkpin Hill - 133 27 57,5 |—9.91 e133) 27.55 ‘
White Horse Hill | 12 4 11,5 |+0,04 IZ 4 11525
179 59 5975 0,49 |—1,24 ‘
White Horse Hill from ip itecn he z i 108565,5
Inkpin - - - | 84647,1

In the following computations, I shall use 120557,” feet for the dis-
tance between White Horse Hill and Nuffield: this is derived from
the base on Hounslow Heath. By the last triangle, White Horse Hill,
from Highclere, is distant 108565,5 feet; which is computed from
the base on Salisbury Plain. ‘The distance between those stations,
found by the second of the above triangles, is 108563,1 feet. “There-
fore, whether the distance between White Horse Hill and Nuffield
be founded on the base measured on Salisbury Plain, or Hounslow
Heath, nearly the same conclusion is derived: the difference will

Trigonometrical Survey. 599

not amount to four feet; a small quantity in a side of three-and-
twenty miles. I shall, however, use 120557,7, because I think it
the most accurate determination.

No. of
triangles,

Spheri- Angles corrected) _.
cal Error. | for calculation. | Distances.

excess,

Observed
angles.

Names of stations.

° 7) ] ° DA fh Meet
xxx1t1.|White Horse Hill | 38 43 Tapes —0,67 38 48 12,5
Nuffield - = | 86 4 16,25|—1,21 86 4 15
2) Mane Pb)
| 2,6 |+0,4
White Horse Hill - - |146603,2
Numeldy| b= >= 9208555
XxXxIV. {Brill - - 5° 14 44,5 |—1,18 50 14 45
White Horse Hill | 64 45 43.75|—1,34 64 45 42,5
Stow on the Wold | 64 59 32 |—1,35 6459 45
180 0 0,25 3,88 |—3,63
f White Horse Hill - - |124365,6
c Stow from { Mais a $ - 146326,3

«

32 34 43 |—0.41
60 56 6,25 |—0,64

xxxv. {Brill - - 32) AA zs25
60 56 5,5

86 29 12,25

2537 1+0,38

.

Stowsvad-i wee :2slsrie oi 78938,2
Epwell from ) 23) a J = 128140

xxxvi. |Epwell - - 38 10 44 |—0,25 . 38 10 42,75

| Stow a;-;. |- 72 38 49,5 |—9,34 72 38 47,5
Broadway Beacon | 69 10 31,75|—0,32 69 10 29,75
180 O 5,25 if 0,92 +4533
Broadway Beacon from £ pill RAR peeree

4H 2

Goo The Account of a —

No. of : Observed Spheri- Angles corrected| —_
triangles, | Names of stations. angles. ‘ cal -for-calculation, | Distances.
excess.

—— ee

aw A oO. pue Feet.
xxxXV11.|Broadway Beacon | 56 32 45 56 32 44,75
Epwell —- 95 34 25525 95 34 24575
Corley = = | 27 52 49,75 27 52 50,5
180 0 Oo 1,58|—1,58
Corley from Broadway Beacon - - = |171568
xxxv1it.[Brill - - 34.23 5855 |—-O,05 34 23 5795
Epwell - 85 0 18,5 |—1,10 a5 “orryes
Arbury Hill - 60 35.4535 |—0,70)-> 60.35 $755
180 0 2,5 2,46 |—0,04
: Epwell - 83098,4
Arbury Hill from Ball i it 140530

89 57 535
54 45 18,25
35 17 36,25

xxxix.{Arbury Hill - | 89 57 4,5
Epwell == 54 45 18,75 |—0.57
Corley - 35 17 36,75 |—0.57

2,29

Arbury Hill - 117463
Corley from { Epwell s - = /143827,8

By the triangle Broadway Beacon, Epwell, Corley, (see the above) the distance from
Corley to Broadway Beacon is the only distance computed; and this has been obtained
through the means of two observed angles only. When the observations were made at
Broadway Beacon, it was not imagined Corley could be seen; and the contrary was not known
till the party arrived at the latter place. In so large a triangle, it would certainly be right to
observe all the angles: but I-have given the angles as they now stand, because the distance
from Epwell to Corley comes out 143831 feet, which determination differs only three feet
from the same distance found by the last triangle.

i A ES

x. |Bow Brickhill - | 68 22 56,75|—1,21 ~ | 68 227%q
Arbury Hill - 43 16 55,5 |—0,99 43 16 54,5
Brill - ° 68 20 7,75|—1,22 68 20 6,5

180 0 oO 3243 1-343

Arbury Hill - - {146481

Bow Brickhill from { Boll: - — 1108058,9

Trigonometrical Survey. 601

It will now be expedient to compute the distance from Bow Brick-
hill to Brill, by means of another set of triangles. And it was
for the express purpose of verifying this distance found by the last
triangle, that Scutchamfly Barrow, in Berkshire, and the station
above Wendover, were chosen. The base on which these triangles
are to rest, is the distance between Nuffield and White Horse Hill,
VIZ. 120557,7 feet.

No. of ; Observed } Spheri- Angles corrected] _.
triangles Names of stations. angles. Diff. cal Error. } for calculation. | Distances.
excess,
OM t 7] r) “ r o 8 ) Feet.
xu1. |Nuffield > - | 62 32 5425 |—0,53 62°32 6
White Horse Hill 35 34 23.25 —0,47 35 34 24
Shotover Hill - 81 53 29:75 —0,74 81 53 30
179 59 58,25| 1575|—3>5

White Horse Hill - 108050,2

Shotover Hill from { Nuffield i f 7084251

xLit. |Shotover Hill - z0° S48 —~0,12 20) o8
White Horse Hill 42 4/'2 |—0,04 A2: Abe 2
Scutchamfly Barrow |111 47 50 |—0o,70 Ill 47 50
180 0 Oo | | 0,86 }|—0,86
White Horse Hill = - 51261,9
Scutchamfly Barrow from Shotover Gill 2 - 77968;3
xL111,|Shotover Hill - {117 30 56 |—1,41 117 30 55,25
Scutchamfly Barrow {| 34 26 52 |—o,o1 34 26 52
Wendover - 28 2 12,75 |—0,09 28 2,412,798
4180 0 0,75 | 1,52 |—0,77

Scutchamfly Barrow = |147113,3
Wendover from { SiStover : i 93828,6

602 The Account of a

Angles corrected
for calculation.

Observed
angles.

Distances.

/ " 7] Pe 7) Feet.
XLIV.|Wendover - 23123 57,5 23 23 57,25
Shotover Hill - 48 30 39,75 48 30 40,5

A Wendover - - 1739493

Beil tem { Shotover Hill 39200,2

xLv. |Wendover - 80 11 9,25
Brill - - BEAR Tint
Bow Brickhill - | 42 23 50,75

80 11 8,5
5.25. 237-9
e235 575

180 O 1,51 1,58 |—0,07

Rieter } Wendover - “ 92400,7
Bow Brickhill from { Brill t Di 108055

According to the first determination, the distance from Bow Brickhill to Brill is 108058,9
feet, and by the last, 108855 feet. There is, therefore, a difference of 4 feet nearly ; a quan-
tity which must be deemed inconsiderable ; hence, 108056,9 feet may be taken for the true
distance.

xLvi.{Kinsworth - 62 55. 38375 62° ik 5* 2855
Bow Brickhill - 88 42 0 88 4I 59,25
Brill - = 2 hear 28 22 22,25

—_- |§ ———— | — | ——__—_

caste Brill - - 121322,
LSS OED Teh { Bow'Brickhill: “20 ©.) Rae
xivi1|Wendover - 33 26 48 33 26 49
Quainton - = - | 94 58 37 94 58 38
| Brill: Ga - - 51 34 33 51 34 33
179 59 58 0355 |—2555

Brill - - pele
Quainton from { Wendover E 2 58146,4

Trigonometrical Survey. 603

Angles eorrected
for calculation,

Error. Distances.

No. of ' Angles -, | Spheri-
triangles} . observed, eae cal
: excess.

ee | ee oe

° , v7) 7] “ o 1 7] Feet.
xLvizi|Bow Brickhill - 38 51 40,75 38 51 40,75
- = | 46 44 2955 46 44 29,25
Ot 23-50225 Dine
180 0 1,25 0,83 |+0,42
c Wendover - - 58146,9
pois { Bow Brickhill - 6749153

In the above triangle, I have computed the distances of Wendover and Bow Brickhill from
Quainton with 92400,7 feet, the side Wendover and Bow Brickhill, as determined in a
former triangle?

xL1x.|Bow Brickhill - 85 9 5275 Siva, Qasiz
Kinsworth - ges UGE eal 52 17 56
Quainton - = IC eh ie, 8 42 32 12

5 Kinsworth - a 84997
Quainton from Bow Brickhill - 67490,3

Therefore, 67490 may be considered as nearly the true distance, in feet, between Quainton
and Bow Brickhill.

L. {Bow Brickhill - | 42 10 36,75 AZ 1040.5
Kinsworth —_ - 82 50 30,5: 82 50 30
Lillyhoe = = = | 54 38 53 54 38 53,5
180 O 0,25 1,26 |—1,50
: Kinsworth = 47278,7
Lallyboe irom { Bow Brickhill = [69867

s

As the stations Lidlington, Trusler Hill, together with Crouch Hill, Cumner Hill, and
Whiteham Hill, have been used for purposes of greater importance than secondary ones have
been generally applied to, I shall insert the triangles formed by their intersections in this
article.

604, The Account of a

No. of 5 Ob d ;
siianigled Names of stations. ate Diff. pine ea Distances.
1 7) “ Feet.
Li. |Kinsworth - 7 45 re
Bow Brickhill - | 80 39 37,25
Lidlington - 68 16 22,25
180 0 4,5 0,42 |+4,92
zy. Bow Brickhill —- 32035,6
Lidlington from te chee ‘i 6125543
Li. |Lillyhoe - + | 78 58 26 78 58 26
Kinsworth - 51 46 22 51 46 22
Lidlington - adh, 2 . 49 15 12
. Kinsworth - - 47280
Lillyhoe from Lidlington 2 49025

The distance from Lillyhoe to Kinsworth, as found in a former triangle, is 47278,1 feet,
and by the last 47280 feet ; therefore, 47279,3 may be taken for the true distance in feet.

Litt. [Bow Brickhill - 38 28 56. 38 28 56
Lillyhoe - - | 23 59 31 23 59 31
Lidlington - a) den 117 31/33
oi Lidlington - - 4902753
cynoe mom 4 Bow Brickhill é 69869

And this triangle, with that preceding it, gives the mean distance between Lillyhoe and
Lidlington = 49026,1 feet; and, with the triangle Lillyhoe, Kinsworth, and Bow Brickhill,
it assigns 69868 feet for the mean distance between Lillyhoe and Bow Brickhill.

Liv. {Lillyhoe - - 5 52 I15 5 52 11,5

Bow Brickhill - TA 54 4.2575 14 54 42575

Trusler Hill cS Oi Mab ips a tt 159 13 5575
Teele Aron Bow Brickhill - | 209g8}7

Lillyhoe - - 5067 3,6

Trigonometrical Survey. 6os

eNoiGE) Mame oftaions, | Omerwed | pig / Seber] so, Andis cas ance.
| €XCess.
; : J , Feet.
Liv. |Crouch Hill = 145 23 26,25 4 J : 14s 23 26
' {Epwell - - 27 93. 10 27. 3:10
Brill - - Sipe “keen Sich 7 33 24
, Brill iS si 102608
Crouch Hill from{ Epwell : Yi 29668,8
-Distance from White Horse Hill to Shotover Hill 108050,2 feet.
tv. |Shotover Hill - 48 5 32,75 48 § 32,25)
White Horse - 16 59 5375 16 59 $3525
|Whiteham Hill - |114 54 34,75 114A 54 3455
180 O 15325
; : White Horse Hill - 88662,2
Whitcham Hill from{ Mie Sh pt c He'd
tvi. |Whiteham Hill + | 55 52 35 55 52 36
Shotover Hill - 24 37 36 ZAG Br a7
Cumner Hill - 99 29 48,5 rae 99 29 47
179 59 $995
‘ Shotover Hill 2 - 29231,
Cumner Hill from { Whiteham Hill - Rie pe

And, because the Observatory of his Grace the Duke of Mart-
BorouGH, at Blenheim, together with that at Oxford, have been
observed with the same care and attention as the principal stations,
and also because precise determinations of the situations are of
great importance, I shall here insert the triangles formed by their
intersections.

. MDCCC. 41

606 The Account of a

No. of Observed Spheri- Angles corrected

triangles Names of stations. angles. Diff cal . | for calculation, | Distances.
: | excess. sees
‘ ©. el a a 7] u CT ae Feet.
Lvii. |Shotover Hill - - | 23 11 5 24°. @
Cumner Hill - - | 29 23 33 1 29 27°93
The Atlas on the top 12) 25 22
‘of the Observatory
at Oxford
Cumner Hill - - | 14492
Oxford Observatory from 4 cyotover Hill - e 8665.1
Lvi11.|Whiteham Hill - [131 25 36,5 13% 25 35395
White Horse Hill - | 10 30 43,5 10 30 43575
Blenheim Observatory . 38 3.40575
: White Horse Hill - 107831,9
Blenheim Observatory from { Whiteham Hill - - | 26237,6

ART. XIV. Triangles for connecting the Series carried on from Scut-
chamfly Barrow and White Horse Hill, in Berkshire, into Bucking-
hamshire and Bedfordshire, with the Series carried on for the Survey
of Essex.

The angle at St. Ann’s Hill, between the station on Hanger Hill
Tower and Hampton Poor House, inferred from General Roy’s
Account, is 25° 33’ 58,5. In 1799, the angle between the staff on
Pen Church Tower and Hampton Poor House was taken, and
found = 95° 57’ 34,5; therefore, the angle between Pen Tower
and Hanger Hill is 70° 29’ 36”.

The distance from St. Ann’s Hill to Pen is determined i

a" «. we

Trigonometrical Survey. 607 *

the following triangle, in which the distance between St. Ann’s
Hill and Bagshot Heath, viz. 46955,3 feet, (see Phil. Trans.
for 1795, p. 496,) is used for the base.

Angles corrected

Observed *
al ‘| Error. | for calculation. | Distances.

No. of .
triangles} Names of stations. angles,

Fect.

Lix. {St, Ann’s Hill 80 43 48 80 43 48
Bagshot - = | 70 30 37 70 30 37
Pen Tower - BT gst ats 28 45 35
St. Ann’s Hill - © | gz000,5
Seto co Bagshot Heath - - 96318

_ The distance from St. Ann’s Hill to Hanger Hill Tower is
68895,8 feet: this is derived from the mean length of the base
on Hounslow Heath. This side, together with St. Ann’s Hill
and Pen, using the included angle at St. Ann’s Hill, as found
above, give 94640,5 feet, for the distance between Pen and
Hanger Hill Towers.

The angle at St. Ann’s Hill, between Bagshot Heath and
Hanger Hill Tower, is 151° 7' 24",25: this, with the sides
Bagshot Heath and. St. Ann’s, St. Ann’s and Hanger Hill,
give 17° 13’ 48”, for the angle at Bagshot Heath, between
Hanger Hill Tower and St. Ann’s Hill: hence we have the
following triangle.

Bagshot Heath - - 16° 45' 43”

Hanger Hill - - 103 18 23

Stanmore - - BQ 5 5A
le |

608 The Account of a

Which triangle gives 37431 feet, for the distance between Stan-
more and Hanger Hill Tower.

The angle at the station on Bow Brickhill, (see the ocd
article,) between Wendover and Kinsworth, is 46° 18’ 8”,5;
and the distances from it to these stations are 92402,2 feet, .
and §7668 feet respectively: these give the following triangle.

Bow Brickhill ts AG. 13° 8 oe
Wendover - - 38 25 21,25
Kinsworth - - 95 16 30,25

From which the distance between Wendover and Kinsworth
is found = 67090,7 feet. The observed angle at Wendover,
between Bow Brickhill and Stanmore, is 102° 29” 99”; from
which, subtracting 98° 25’ 21,25, the angle between Bow Brick-
hill and Kinsworth, we get 63° 57' 7,75, for the angle between
Kinsworth and Stanmore. Again, the observed angle at Kins-
worth, between Bow Brickhill and Stanmore, is 173° 37 44)";
from which, subtracting the angle between Bow Brickhill and
Wendover, we get 78° 21’ 19”,75, for the angle between Stan-
more and Wendover. If these computed angles are actually
such as might be observed, were Kinsworth and Wendover
visible from each other, the angle at Stanmore between those
stations ought to be 97° 41’ 39”, nearly: but the observed angle
was 37° 41’ 41”,75; which is so nearly the computed one, as to
leave little doubt of the accuracy of those data from which the
angles are derived. The distance from Wendover to Kinsworth
is 67090,7 feet.

Wendover = 63 57 7075
Kinsworth - 78 21 13,75 | which, corrected for calcula-
Stanmore - - 37 41 41,75{ tion, becomes,

180 0 3,25}

Trigonometrical Survey. 6og

Wendover - 63 37 >
Kinsworth - 78 21 12
Stanmore - 37 41 4A which triangle gives
Wendover = 1074641 foet.
Kinsworth = 98577,5

In consequence of Bushy Heath intercepting the view towards
the east from Stanmore, it became necessary to choose a station
on the former. ‘To determine the distance, the angles at the
two stations were taken very accurately; they were as follows,

the distance of Stanmore from{

Stanmore - 42 11 21,5
Bushy Heath 135 35 40,5
Kinsworth, : . . which gives 5489, feet for the

required distance.
To determine the distance of the station on Pen Church Tower,
we have two angles in the following triangle, viz.

Wendover - 38 13 18 pt corrected for calcula-

Stanmore - 23 44 48 tion, becomes,

Pen Tower - 118 1 54

Wendover - 38 13 18,25
Stanmore - 23 44 48,25
Pen Tower - 118 1 54,5 which triangle gives

the distance of Pen from Canmore, me leet
tanmore == 75325,4

With this distance of Stanmore from Pen, found from the
last triangle, and also that between Stanmore and Hanger Hill,
derived from the triangle, Bagshot Heath, Hanger Hill, and
Stanmore, together with the included angle at Stanmore, viz.
‘109’ 28’ 29”,5, we get the distance of Pen to Hanger Hill
Tower = 9461.8 feet. The same distance has been found
-before, in a shorter and more direct way, being 9464.0,5 feet :
the difference is only 8,7 feet; a sufficient proof that the distances
given for the survey of this intricate and woody country, are

G10 The Account of a

sufficiently correct. It will be more convenient to show how
these triangles are connected with those to the eastward, when
I arrive at that part of the work which treats of the survey of
Essex, than at present. I shall, therefore, proceed to the fol-
lowing article, after observing, that by the help of Harrow Spire,
(the situation of which has been determined by General Roy,)
and by observations hereafter to be made with the small instru-
ment on Pen Tower, less difficulty will occur in rt interior
survey than was at first expected.

ART. xv, Triangles formed by the intersections of Churches,
Windmills, and other Objects.

Triangles, Angles Distances of the Stations from the
observed. intersected Objects.
ee ee a ene erm ce
} Feet.
Little Haldon - - 23 54 so [} 18974
Ball’s Obelisk - - - {132 41 } Great wie Li L] 19366

Great Haldon, secondary station

Great Haldon from Ball’s Obelisk 19366 feet.

_ Great Haldon - - . 68 0 35
Ball’s Obelisk = - Fl 32°30
Topsham Steeple

28316

} Topsham Steeple - { 27679

Little Haldon from Furland 72776 feet.

Little Haldon - - 18.2.2 > 37656
Furland - - 18 42 53 }Hop pe ee q 39028
Hope’s Nose; secondary station

Bodmin from Trevose 81967,6 feet.
Bodmin - - 15 48 43 : eae
"Treveee t eg % {21 28 36 St. Minvern Steeple —s_ 36806

St. Minvern Steeple

Bodmin > 12 pe Minvern Windmill {| 34852

Trevose - - 3 Hn 48478
St. Minvern Windmill

Trigonometrical Survey. 611°

Trevose from Cadon Barrow 85624,8 feet.

Triangles, : Angles Distances of the stations from the
observed. intersected objects»
ee ee ee [ ceiemeneneaetmemael
T te} 3 W ' 56
revose Cre - - 55 3 59 i 4 292

Cadon Barrow - = 19 15 48 bse. Isey Steeple { 73216
St. Isey Steeple

Trevose - - 58 41 39 Shaye 10894
Cadon Barrow - - 6 38 22 }st. MA eset oa { 80504

St. Merian Steeple
Black Down from St. Stephen’s 62506,7 feet.

Black Down - - 4 46-37— “ 61289
St. Stephen’s Down” - - 74, 20 14 } Werrington Ss ily 5301
Werrington Steeple

Black Down - - 15 18 49 69897
St. Stephen’s - - 104 53 9 } Boyton oe % { sauce
Boyton Steeple

Black Down - & Tus ae ; 60448
St. Stephen’s re Pewee se Stephen’s Steeple { 2395
St. Stephen’s Steeple

Black Down - - OK O18) . 77698
St. Stephen’s - i 153 13 23 } North Petherwin Steeple { abhno

North Petherwin Steeple

Carraton from St. Stephen’s 52994 feet.

Carraton siles - 50 40 15 : : | 32886
St. Stephen’s 4 38 21 4 }stokeclimsland Steeple { pet
Stokeclimsland Steeple

Carraton ss - - Gime \7
St. Stephen’s - - 55 32 16
Launceston Steeple

} Launceston Steeple { cee

Carraton - - - | § 58 26
St. Stephen’s = - - - 53.4 70a5

} Launceston Chapel = { 49404
Launceston Chapel

6427

Long Knoll from Westbury 58118,2 feet.
SSeS
L 5g BPR oot aia

one one 7 Die } Frome Steeple - { 33765

Westbury ~ - - - | 34 53 50

Frome Steeple . 41793

612 The Account of a

= ew +. om,

Lansdown from Farley Down 28730,4 feet.

Triangles. Angles Distances of the stations from the o
observed. IDkeréeCEed ODJCCLs. ane eee
Lansd 6 43 16 ibe
ansdown - ° 56 43 1 ‘ 13563
Farley Down iid 3 =P 28) i2iae } Cold Aston { 24120
Cold Aston
Moor Lynch from Dundon 32688,8 feet.
Moor Lynch - - 15 54 56 : i 20406
Bondo iy ” 23-19 6 Walton Windmill — - { 14213"
Walton Windmill ;
Moor Lynch ~ - £22 0O AU1 } 17688
Duties ? 19-18 55 Westonzoyland Steeple 44848
Westonzoyland Steeple
Moor Lynch - - =) Note 5 96 : 15691 |
Bunce i i “8 a -260 Middlezoy Steeple - { a

36530
Middlezcy Steeple ‘

Moor Lynch - - - 153 53.50 } 4 { 19454
Banden 4 - it 939 13 Chedzoy Steeple 29556
Chedzoy Steeple

Moor Lynch - - 29 20 18 } : ne 24457
Dances ‘ R y U6 God: Highham Windmill 16618

Highbam Windmill

Moor Lynch - - 36 25 56 } : : { 21567
Dundon 4 Fi 3 - | 39 51 57. Highham Steeple : 19982
Highbam Steeple

Moor Lynch - - 147 57 0 } . . - { 33656
Dundon 5 y ~ | 16 15 14 Bridgewater Spire 63768
Bridgewater Spire i ee eee
Moor Lynch - - 69 52 39 } : { 40063
Dupdeeeee rey ‘ 63 18 59 Burton Present Obelisk 42101
Burton Pynsent Obelisk } ee ere
Moor Lynch - - IZ 12 41 } ‘ { 40792
Dundon - * - -}129 45 57 Somerton Steeple a Wa ee ee

Somerton Steeple

Trigonometrical Survey.

Dundry from Lansdown 55248,9 fect.

613

Angles

Triangles. Distances of the stations from the
observed. intersected objects.

: aay Feet.
Dundry~- - - i a 16 54757
Pease se r z 8s 25\ 0 } Puckle Church Steeple 21819
Puckle Church Steeple
Dundry - - = 30 37 18 : ft { 61842

~ Lansdown - - - | 86 18 39 } westleigh ohegute 31566
Westleigh Steeple : ;
Dundry - - - Cb a) C0) ih { 21920
Gasca re _ 22 23 ; | } Bristol Cathedral 44935
Bristol Cathedral
Dundry~ - - - 44 18 9g - " { 22096
ee ae 2 - | 21 a2 24 | Redclift Steeple 42346
Redcliff Steeple
Dundry pte aie - | 78 18 2 a ’ 13883
Reason il 4 - 14 32 } Long Aston Steeple 54168
Long Aston Steeple
Dundry - - = OZ 33h Gk 5 : : 12860
is ell Pa aA [Ep Clitden Windmill” ~~ { | 2008"
Clifden Windmill
Dundry : = Seehpay 5 ign Jey 38391
Sousa 4, " 39.7 35 } Blaze Castle - { 58032
Blaze Castle
Dundry - - - 89 10 18 35391
BLAS z f - | 32 52 56 }Penpole Park Gazebo { aes
Penpole Park Gazebo
Dundry a 32, LOb 3 , . 32391
pei & 5 31 49 52 }st. George’s Steeple - { au7oy
St. George’s Siecble -

Dundry = - ~ 4454 50 . , . 1168
Lapilown : : 48 5 4 | Duke of Beaufort’s House { Eaaat
Duke of Beaufort’s House, Stoke | House; Stoke
Dundry - - - 57°15) 32 35182
Incbaa. , - | 39 14 57 } Marfeld Steeple - { aire
Harfield Steeple

MDCCC. 4K

614 The Account of a

Distances of the Stations from the
intersected Objects.

Triangles.

o pha Feet.
Dundry , - -- 13 58 bab ‘e 66541
Lansdown - = =, 1kz0. Obs Daskpaevieenr . 18573
Durham Steeple
Dundry~- - - f | 56512
Tansdowa a 7. z } Knowle Steeple - { ; ited
Knowle Steeple
Dundry - - ~ 29 42 10 47845
Lansdown dn a ~ 459-59 447 }Mangotsfield Steeple - { 27376
Mangotsfield Steeple
Dundry - - - 46 12 31 : 55045
Tansdown i i 166 38 49 }Winterbourn Steeple - { 43280
Winterbourn Steeple

Mendip from Dundry 69196 feet.
Dundry - - - 15 0 54 : . 76847
Meidip |. ¥ a 104 10 15 \ Leigh Steeple on Mendip 20533
Leigh Steeple on Mendip ¥
Dundry - - ° go 22 22 {| 1417
Mendip - - - | 1 10 22 } Dundry ag a | 69221
Dundry Steeple -
Mendip from Long Knoll 61962,3 feet,
Long Knoll - - 7-20-24 : : {| 49286
Mendip ¥ 2 2 25 42 22 }Doulting Spire { 14517
Doulting Spire
Farley Down from Westbury 59849,5 feet,
Westbury - - - “81 25 20 . 51197
Farley Down - > a ager ee }Devizes Steeple - { odaee
Devizes Steeple '
Whitehorse from Scutchamfly 51261,9 feet.

Whitehorse - - - 32 55 51 : : 72898
Scutchamfly =. hier eines) (9 27 Abingdon Spire ¥ { 40852

Abingdon Spire

Trigonometrical Survey. 615

Triangles. Angles Distances of the Stations from the
observed. intersected Objects.
ONG Feet.
Whitehorse - - - | 10 39 30 101693
Scutchamfly - r 158 52 26 } Wallingford Steeple - { 52185
Walling ford Steeple

Whitehorse - - -
Scutchamfly =

oe if #a 8 | bGreat Coxwell Windmill { hee
Great Ch cwell Windmill

21 71834

Whitehorse - ne Cos mare e 38449
Scutchamfly : fe ah ot ‘6 } Highworth Steeple = - { 87355
Highworth Steeple

Whitehorse > - —f 28-699 63991
Scutchamfly = B ye 99 45 45 }Drayton Steeple - { 40586
Drayton Steeple

Whitehorse - - - 348-57 81618
Scutchamfly ieee r., IECG.233,.80 }Radley SuENe = { 48624
Radley Steeple

Whitehorse - - - Fis 7 118
Sculichamély j & . ia a BS } Buckland ye - { pai
Buckland Steeple :

Whitehorse - - - : 22
Scutchamfly - - - - } Witney ERG ( dhe
Witney Steeple .
Whitehorse - - - 9° 57 40 8992
Scutchamfly - 4 g | 48 27 50 } Bampton Steeple - : anne
Bampton Steeple

Whiteham from Brill 62066,1 feet.
Whiteham - - - 19 47 } : 28983
es ee — tp 40 Islip Steeple - n { ee
Islip Steeple
Whiteham - - - 78 47 27956
Brill Z k - Gees 33 Woodjtock Steeple - { 64725
Woodstock Steeple
Whiteham - - - 38 39 25 = : 24677
Brill 1 ‘i x e 18 59 22 Kidlington Spire { 47373
Kidlington Spire

4 Ka

616 The Account of a

Whitehorse from Brill 146603,2 feet,

Triangles. Angles Distances of the Stations from the
observed. intersected Objects,

i

a

Feet.

a 2 i 9 i is sos v5 } Witchwood Forest Beacon { ace

Witchwood Forest pond

Broadway from Epwell 80611,4 feet.

Broadway - - - 46 51 21 : . 109337
Epwell J i . 85 48 34 } Warwick Steeple + { 79992
Warwick Steeple

Broadway - - - 49 43 19 524 158205
Epwell - a5 . 1600-10-49 st. Martin’s, Coventry - { 122627

St. Martin’s Spire, Cory

Broadway - - : 71 52 32

Epwell - - . == 174-5355
Soleybull Spire

Corley - - - - | 10 17 47 } ae ee { 70621
Arbury - a 18 145 Dun Church Windmill 44249
Dun Church Windmill.
Corley - - - - |107 11 { 106471
Arbury - : 34 20 2 2 | } Gazebo on Bardon Hill 180344
Gazebo on Burdon Hill, Leices-
tersbire
Corley - - - - 100 41 54 } ; ; e { 103373
Arbury Ls “ - | 36 37 26 Markfield Windmill me ;
Markfield Windmill
Coney oe aay or ren a wioaer ote } Newnham Windmill ~ - { 118771
Arbury : - 101 33 35 5845
Newnham REDD J
Corley from Broadway 171570 feet.
Breen - were r ga" 2A } Building on Breadon Hill, ye oe
Corley = - "14 33 '9 | | 182682

Building on Breadon Hill

Trigonometrical Survey. 617

Epwell from Crouch Hill 29668,8 fect,

Distances of the Stations from the
intersected Objects.

Triangles. Angles

observed.

ee es eee | | ee ee +.

OS mig | Feet
Epwell - - - - 24 43 28 } . - 47493
See rel .. if ~ }r2q- 8 31 Deddington Steeple Weaade

Deddington Steeple

Epwell - - - = 22°. 2057 2 : { 31887
Crouch Hill - - - 89 27 20 } Bloxham ee 11971
Bloxham Spire

Epwell - - = <1, D2 4.0 go } ayy { | 60070
Crouch Hill - - - 1ig5-28-44 eee joieeple L | 31802
Aynoe Steeple

Epwell - - - 1Z, 45 23 3 y 43823
Crouch Hill - - = ft43 29°30 Adderbury Spine 16265
Adderbury Spire

Epwell - - - 9:33 429 ; 64520
Crouch Hill - - 162 29 20 Harthingo'stceple 35005

Farthingo Steeple

Epwell from Arbury Hill 83098,4 feet.

Epwell - - - 27 30 20235
Arbury Hill 3 8 9 42 a Rand House, Edge Hills { 65816
Round House, Edge Hills
Epwell - - = - 150 9 8 Belg 122636:
Arbury Hill - z r 87 15 6 }se. Martin’s, Coventry { 94262
St. Martin’s, Coventry é
Epwell - - - - | 28 31 46 SPaaieae 18576
Rey Fill . Sl 6 }Round House Windmill { 67364
Round House Windmill, Ede ‘
Hills

Brill from Quainton 40908,6 feet.
Brill - - - - 19 36 52 7
Quainton - b “ a 140-7 a \wingrove Steeple - { aad
Wingrove Steeple
Brill - = -- - 16 25 48 ne
Quainton & - |128 12 5 | Hardwick Steeple - { a

Hardwick Steeple

618 The Account of a

Triangles. Angles Distances of the Stations from the
observed. intersected Objects.
Bail 2 me i Feet
ri r c = 16 42 12 8710.
: Quatifon | 4 . : 4 24 16 Luggersal Steeple - 32664
Luggersal Steeple

Brill - - - - 8 30 43
Quainton - - |144 20 22
Granborough Steeple

Granborough Steeple - f

Brill - - - - 105 7 30 ‘ 2122
Quainton 4 Ps ‘j wT aa On FS Bicester Steeple ‘agi
Bicester Steeple
ae ALD Oar RIN ~ | 17 37 3? | (House at Wooton 14793
Quainton = - Q) 28.57, a 27181
Centre of the xen House at

Wooton

Stow from Broadway 52203,2 feet.

Stow -
Broadway > 3 a
Sarsden Chapel

Stow = une - ‘| 56 10 42 :
Broadway 2 . - | 49 34.47 ‘ Walford Spire - j
Walford Spire

Stow - - If 3 44 32926
Broadway - 21 32 40 \ Bourton Chars A ; 21786
Bourton Chapel

Stow from Epwell 78938,2 feet.
Stow - - rseergmes| | ro 30 20 9876
Epwell - i 6 37 9 1 stow on the Wold - } 74573
Stow on the Wold Steeple

Wendover from Brill 92400,7 feet.
aa ‘ a os ae eee t Pitehcot Windmill - { 53739
Wendover - - - 46137 | 4. 5ogo1

Pitchcot Windmill

Trigonometrical Survey. 619

Triangles. | Angles Distances of the Stations from the
observed, intersected Objects,

ll ° ‘ a Fest
Bri - - - 24. Kea m2 : : 99003
Wendover - - - “NIL 33 40, }winghoe SEC | L| 43577
Ivinghoe Spire |
_ if tne “766 36 4) \padbury Steeple - Wisi
Wendover - 46 32 33 y P g2401
Padbury Steeple (doubtful)

1 ee ROO ERY ae | 39009
oaoual: | - fi a a 1 48 } Quainton Steeple - { 55056
Quainton Steeple

Wendover from Quainton 72889,4 feet.

Wendover - - - 34. 46 37 . 63 { 52487
Quainton - - - 45 9 20 NvangpStceple 42230
Wing Steeple

Wendover Fa then = 44 58 11 : : : 66472
Quainton - : -\6r-- ato: }crindon Windmill - { 5 3026

Crindon Windmill

Quainton from Bow Brickhill 67490,6 feet.

Quainton - = - 75 15 34 58876
Bow Brickhill 4 - | 47 19 Southern Obelisk - 77449
Southern Obelisk, Stow Park, Bucks

Quainton > - 75 4 46 3 61881

Northern Obelisk, Stow Park

Wendover from Kinsworth 84462 feet.

Kinsworth - - - 69 56 52
Wendover - - | 31 6 26

Leighton Buzzard - { 35317
Leighton Bucart Spire.

64215,

Kinsworth from Quainton 84996,3 feet.

Kinsworth 2 - ae fey dae f-| 70886
Opaintod | - i =; bgte 9514 daylesbury Steeple - { 27879
Aylesbury Steeple

620

The Account of a

Bow Brickhill from Lidlington 32035,6 feet.

Triangles, Angles
observed,

Bow Brickhill = + - - 57 43 21 21
Lidlington - - 65 40 39
North Crawley pire
Bow Brickhill - - - 45 8 47
Lidlington - - - + -[I12-13 11
Pavenbam Spire
Bow Brickhill - - - 24. 15 25
Lidlington = - - 137 19 21
St. Paul’s Spire, Beare
Bow Brickhill - - 48 2 42
Lidlington - - = 111, 8 0g
Sharnbrook Spire i
Bow Brickhill - - - 38 42 47
Lidlington - = 19 39 20

Woburn Market Bout

Distances of the Stations from the
intersected Objects.

Feet.

}wvorth Crawley Spire - { Lege!

} Pavenham Spire - { his.

S , 68727
}se. Paul’s, Bedford - peta

} sharnbrook Spire - { | aa

| Woburn Market House ( pest

Bow Brickhill - - - Rigas oe ; / {
Lidlington i e i 10 6 1 | p Ridgemont Station

Ridgemont Station

Bow Brickhill - - - 25. §1|\29 } : y { 46959
Lidlington - - - 116 31/15 Rigo tor aie 22889
Wootton Spire

Bow Brickhill - - - 36 40 14 2 { 29599
Lidlington = - - - 64 51 26 } Cranfield Spas - 19526
Cranfield Spire

Lillyhoe from Lidlington 49026,1 feet.

Lillyhoe - - See 3. ATT 25
Lidlington - . - - 3 2.16
Pollux Hill Spire

Lillyhce ° - - 234031123

Lidlington - - - {11g 15 11
Bow Brickhill Steeple
Lillyhoe - - :
Lidling'on ~ -
Colmworth Spire

49°54 3
- |100° 30 33

} Pollux Hill Spire

race 70224

} Bow Brickhill Steeple { 31738
. d 97617
}colmworth Spire { 759044

Trigonometrical Survey. 621

Wrest Garden Obelisk

Lillyhoe + - - 63 39 11
Lidlington - - -| 88 31 51
St. Neot’s Steeple

Triangles. ; Angles Distances of the stations from the
observed. intersected objects.
Oat We Feet,
Lillyhoe - - - 23.97 30 : ch 25599
Lidlington = - - -| 22 4 36 i aed % 27658
Silsoe Spire
Lillyhoe - - a 11 46 23 : 30008
Lidlington - - -| 17 18 29 ; a ; 20580
Flitton Steeple
Lillyhoe = - St ee ai 57 56 38 i 16857
Lidingran ‘ a ae et Shillington Steeple 4ekag
Shillington Steeple ;
Lillyhoe - - - 14 35 24 : 32242
Lidlington = - - - | 24 29 56 Eom, ie Shea ps Oe 19586
Westoning Steeple
Lillyhoe - - - 23 40 47 4 . 23770
Lidlington : n | 19 18 12 Wrest Garden Obelisk 8880

St. Neot’s Steeple -

Kinsworth from Lidlington 61255,3 feet.

Kinsworth = ie oa ey, oo : : 666
Lidlington eye 23 a ; \ Hartington Steeple = ; 37

Harlington Steeple

Kinsworth - - - | 17 22 11
Lidlington - - oy a 3
Maulden Steeple

oF
i Maulden Steeple - } 63165

Kinsworth = - or -| 3532 a te Gave
Lidlington e iz 73 16 4 * illbrook Steeple - } 7

Millbrook Steeple ,

Kinsworth = - - - 36 15 30
Lidlington - = = pm ME 5)

1 streatly Steeple - { 36167
Streatly Steeple “

Kinsworth = 2 3 34 29 11 “ ' ae
Lidlington - « ame 166 a Py + Hanslop Spire = } Bare 3
Hanslop Spire

MDCCC, 4 L

622 The Account of a

Kinsworth from Bow Brickhill 57668 feet.

Triangles. Angles Distances of the Stations from the -
observed. intersected Objects.

Bow Brickhill 1 31 2 pe

ow Brickhi - - 131 31 Bo : ie 93229
Kinsworth - - ~ | 30 17 44 } Souldrope an { 138367
Souldrope Spire ;
Bow Brickhill = - - QI 22 55 ane 31623
ee | ha " - | 28-24 oe } Sauldon Windmill - { 66434
Sauldon Windmill
Bow Brickhill = - - 70 9 33 a 32706
Kinowortn) © 5 rs 33.27 4 }stewkley Windmill = - { 55812

Stewkley Windmill

Bow Brickhill - -
Kinsworth = iS a
Tharfield Windmill

Sie arfield Windmi 139157
93 36 13 } Tharfield Windmill - 123073

Bow Brickhill = -
Kinsworth - - -
Tottenhoe Station

4 13 44 Stati 2 . 43177
14.47 27 } Tottenhoe Station { 13049

Bow Brickhill - - te 55 14 }chalgrave Steeple - { 43590

Kinsworth - - mn Agi ee 23699
Chalgrave Steeple b

Bow Brickhill - - 85 441.3 ways : ; 28814
Kanenneth Z rn - | 27 23 29 }Lidlington Windmill - { 62442
Lidlington Windmill -

Bow Brickhill - : 116 46 10 : r 107275
Kinsworth - - siti senn 6 | A } Keysoe ae { 142850

Keysoe Spire

Lillyhoe from Trusler Hill 50673,6 feet.
a

118536

. ee . 3 4 " 6 2
Lillyhoe Lae bd ke } Knotting Green Elm Tree { 95981

Trusler Hill - - 103 29 55
Knotting Green Elm Tree

Lillyhoe BHM -
Trusler Hill = -
Sundon Windmill

36 45 37 } - dune { 25692
27 4 Sundon Windmill 33799

-
aad) eae

’ Trigonometrical Survey. 623
Bow Brickhill from Trusler Hill 20138,7 feet.
Triangles, Angles Distances of the stations from the
observed. intersected objects,
* ° / I
Bow Brickhill = - = LA Dy ts GA 15998
Trusler Hill - Sah res 5O 16 225i\. Srv teyratceple 3867

Crawley Steeple

Bow Brickhill * - 93 18 15 } Moulshoe Steeple Hl { 25136

Trusler Hill - - - | 49 17 46 33101
Moulshoe Steeple

Bow Brickhill es 1g 2707. s i { 12432
Trusler Hill - - - | 19 46 14 Woden sterle 8552
Woburn Steeple

Bow Brickhill from Lillyhoe 69867 feet.

Bow Brickhill - - 60 57 17 } Renlold Steeple i { 84608

Lillyhoe te - | 68 43 59 79373
Renbold Steeple

Bow Brickhlll - - 64.55 32 85825
Lillyhoe = - - - | 66 41 24 }Ravensden Steeple - { 84640
Ravensden Steeple

Kinsworth from Lillyhoe 47278,7 feet.

Kinsworth . - - | 43 44 48 we fe 49849
Lillyhoe a i= 3 71 53 53 \ Plitwick Steeple = { 36264
Flitwick Steeple

624, The Account of a

SECTION SECOND.

Determination of the Latitudes and Longitudes of the Stations on
Black Down, in Dorsetshire, Butterton, in Devonshire, and St.
Agnes Beacon, in Cornwall.

Art. xvi.—Calculation of the Distance between Black Down and
Dunnose in the Isle of Wight.

To complete this distance, I shall have recourse to the xxvith
and xxviith triangles, published in the Philosophical Transac-
tions of 1795, and uid and tivth of the Trans. for 1797,
together with the observations made at Black Down, in the
latter year. (See also Pl. XXX. Fig. 1.).

The most eligible method of calculating with these ri
seems to be that of first finding the cross-distance between
Black Down and Dean Hill. To do this, we have the angle at
Nine Barrow Down, between Black Down and Dean Hill, and
the respective distances from the first to the latter stations,
together with the newly observed angle between Dunnose and
Nine Barrow Down; from which we obtain the angles of a tri-
angle, constituted ny Dunnose, Nine Barrow Down, and Black
Down.

The distance from’ Nine Barrow Down to Dean Hill is
166497 feet, and, from the same station to Black Down, the dis-
tance is 126782 feet, (see Phil. Trans. for 1795, p. 502, and for
1797, p. 455,) and the angle comprehended by those distances
= 110° 30’ 13” ,25. The difference between the horizontal angle
and that formed by the chords is 3",25, which, substracted from
110° go’ 19”,95, leaves 110° go’ 10”: computing with this

Trigonometrical Survey. 625

angle and the sides spoken of, there results the following tri-
angle, viz.

Nine Barrow Down - |. 110° go’ 10”
Black Down - - 40 6 54y75
Dean Hill -. - - 29 22 55,75

This, using the side Nine Barrow and Dean Hill, ( 166497
feet,) gives 24,0236,7 feet, for the distance between Black Down
and Dean Hill.

The angle at Dean Hill, between Nine Barrow Down and
Dunnose, is 647° 50’ 19”, (see Phil. Trans. for 1795. p. §01,) and
the angle between Black Down and Nine Barrow, as just found,
is 29° 22’ 55",75, which, increased by the proper correction for
the difference between the chord and horizontal angles, becomes,
29° 22’ 57,5. The sum of these angles ,94° 13’ 16”, 5, is the hori-
zontal angle between Black Down and Dunnose.

The angle at Black Down, between Dunnose and Nine Bar-
row Down, deduced from observations made in 1797, is found
to be 4° 30’ 25”,75: this, subtracted from the angle between
Dean Hill and Dunnose, leaves 35° 36’ 29”, for the angle at
Black Down; which, corrected for the purpose of reduction
to their respective chord angles, become 94° 19’ 11”,5, and 35°
360’ 25",75, from whence we get the angle at Dunnose = 50°
10' 22,75. We have, therefore, the following triangle, viz.

Dean Hill yi. =) igg? re" 4155!
‘Black Down - es 35, 36 25,75
Dunnose_ - bs ~ 50 10 29,75

The distance between Dean Hill and Dunnose is 1834,96,2:
feet, (Phil. Trans. for 1795, p. 501,) and that between Black
Down and Dean Hill, according to the foregoing computation, is
240236,7 feet : these, applied to the angles.of the above triangle.

6s) The Account of a

give 314309,6, and 314305,4 feet, respectively, for the distance
between Black Down and Dunnose: wherefore, the mean
314307,5 feet, = 59,528 miles, may be considered as the true
distance between those stations.

Direction of the Meridian at Black Down.

On the 18th of April, in the forenoon, the
angle between the Pole Star, when at its
greatest apparent elongation from the meri-

dian, was observed, and found to be - 104° 19’ 19,25 ©
And on the 1gth, in the afternoon - 98 42 47
Half their sum is the angle between the :

meridian and Abbotsbury staff - == - 101 31 8

On the goth of April, in the forenoon, the
angle between the Pole Star, when at its
greatest apparent elongation from the meri-

dian, was observed, and found to be - 104, 19 25,25
And on the 1gth, in the afternoon - 98 42 35,5
Half their sum is the angle between the

meridian and Abbotsbury staff - - 101 31 0,5

Therefore, 101° 31’ 2” may be taken for the angle between
the meridian and Abbotsbury staff.

Art. xvil.—Latitude and Longitude of Black Down.

The angle between Dunnose and the Abbotsbury Staff was
observed, and found = 164° 26’ 3525; and the angle between
the meridian and the same staff; by double azimuths of the
Pole Star, 101° 31’ 2”. Wherefore their sum, subtracted from
360°, leaves g4° 2’ 22”,75, the angle which Dunnose makes

_with the meridian. Lend

Trigonometrical Survey. 627

In Fig. 4. Plate XXX. let Z be the zenith, B the station on
Black Down, and ZBA its meridian; also, let D be Dunnose,
and ZD its meridian; likewise, suppose BC to be an arc of a
great circle, perpendicular to the meridian at B, and DA ano-
ther arc of a great circle, perpendicular to the meridian at D,
BF and ED being the parallels of latitude at Black Down and
Dunnose. .

In the spherical triangle BZD, the angles at B and D are
given, the first being 94° 2’ 22”,75, and the second 84° 54/ 53”;
therefore, in the triangle ABD the angle at B is 85° 57’ 36”,75,
and, in the triangle BDC, the angle at D = 84° 54/ 53": hence,
_ the angles of these triangles, when reduced to those formed by
the chords, are as follows :

DDC = 84 54! 52,5"
In the triangle BDC {cpp SS Oar as 4.475
| DY a Aina 2 29.

ABD = 85 57 36,75
And in the triangle ent BAD = 88 57 16,95
BDA= 5 5 7

Now the distance between Black Down and Dunnose, BD,
has been already found to be 314307,5 feet; therefore, using
the above angles with that distance, (after the proper corrections
are applied for reducing the horizontal angles to those formed
by the chords, ) we get,

; : BC = 313128
In the triangle BCD {ep conta sy ee

| § ’ AD= 319581,2 !
| And in the triangle ABD { AB i S653 \ feet

Again, in the two small triangles formed by the parallels
BF and ED, the perpendiculars BC and DA, and the small
arcs CF and AEF, we have the angles at C and A given, the

628 The Account of a

first being 91° 2' 4.5”,75, and the last 88° 57'15"; which angles,
however, are augmented by the addition of the differences be-
tween the horizontal angles and those formed by the chords,
We have therefore, .
BCP = gi 245
In the triangle BCF { BEc =a 88 on 5855
FBC= 0.81 29.75

EAD = 88 57 17 7
And in the triangle AED ; AED = go 31 21,5
ADE = 0 381 21,5

And, using BC and AD, as found above, we get

CF = 28509,1
And EA = aor 8} eet

Therefore FD = DC + CF = 22146,9 + 2859,1 = 25006
feet. And BE=BA=EA= 27864,5 — 2859,8 = 25004,7
feet. The mean, 25005,3 feet, may be considered as very nearly
the true distance between the parallels of Black Down and
Dunnose. This method is the same as that made use of in the
Phil. Trans. for 1795, p. 521, and affords the means of very
accurately determining the distance between the parallels of
latitude of the two stations, when the angles were observed with
precision, and the direction in which the stations lie, is not
much removed from east and west.

This small space, 25004,7 feet, corresponds to 4/ 6”,5, in
which I use 60851 fathoms for the length of a degree of the
meridian in 50° 41’. See Phil. Trans. for 1795, p. 537- |

‘Now the latitude of Dunnose is 50° 37’ 7”,3, and its longitude
1°11/ 36”; (Phil. Trans. for 1795, p. 536;) therefore, 50° 37/73
+ 4/ 6",5 = 50° 41’ 19,8, is the latitude of Black Down.

This method of finding the latitude seems to be more correct _

than by spherical computation; yet, by this latter, nearly the’

Trigonometrical Survey. Gag

same conclusion is derived; for, the bearing of Black Down
west of Dunnose being 84° 54 52,5, we get the distance of
that station from the meridian of the latter = 319072 feet,
and from the perpendicular, 27861 feet ; which, converted into
parts of an arch, according to the lengths of their respective
degrees, gives 50° 41’ 14” for the latitude, and 1° 20’ 46”,4, for
the longitude west of Dunnose. According to the troublesome
yet ingenious method recommended by M. Sgyjour, in his
Traité Analytique des Mouvemens apparens des Corps Célestes, the
latitude of Black Down comes out 50° 41' 13,9, and the longi-
tude 1° 20’ 45”,75. We may, therefore, admitting the supposi-
tion of Dunnose being situated in 50° 37’ 7’’,3, safely take 50°
41’ 13,8 for the latitude, and 2° 32' 22”,4, for the longitude, of
Black Down; that of Dunnose being 1° 11’ 36” west of the
meridian of Greenwich.

Art. xvii. Calculation of the Distance between the Stations on
Black Down, in Dorsetshire, and Rippin Tor, in Devonshire.

For the calculation of this distance, we must have recourse
to the xiviith, x:vimth, xirxth, and uth triangles. (See Phi-
losophical Transactions for 1797, and Plate XXX, Fig. 1 of this
Volume.) Inthe two first, we have the whole angle at Pilsden, be-
tween Dumpdon and Black Down = 152° 3%’ 2%"’,95, which, re-
duced to the angle formed by the chords, becomes 152° 37'2.4)”,25.
The sides forming this angle, are Dumpdon and Pilsden, Pilsden
and Black Down: the distance between the two first stations
being 78459,3 feet, and between the two last 79110,7 feet.
From these data, the distance between Dumpdon and Black
Down is found to be 153095,7 feet, the triangle for computa-
tion being,

MDCCc. 4,M

630 The Account of a
Pilsden - - 152° 37! 24,25
Black Down - = 13 37 50 45
Dumpdon - = ~ 13 44 45 325

But this side may be also found, by computing with the whole
angle at Charton Common, which angle, when reduced to the
plane of the chords, becomes 141° 93’ 53”,75. The two sides
are 581012,5 feet, and 103345 feet; which data give the fol-
lowing triangle :

Charton - = 141° 33’ 53",5
Dumpdon - 24 48 39 ,25
Black Down - 193 37 2% ,25; from whence we

find the distance from Dumpdon to Black Down = 153094.6
feet. Wherefore, the mean, 153095,2 feet, maybe considered
to be very nearly the true distance.

In the th triangle, (Cawsand Beacon, Dumpdon, and Little
Haldon) the angle at Cawsand Beacon is 43° 14/ 21”,25; and
in the List, (Rippin Tor, Cawsand Beacon, and Little Haldon)
the angle at the same station is 25° 30’ 39,75; their sum is 68°
45’ 1”, and, adding 1” for the necessary correction, it becomes
68° 452". Computing with this angle, and the including sides,
(64020,5 and 18334 feet,) we obtain the following triangle :

Rippin Tor - - 90°34! 95”
Cawsand Beacon - 6845 2 -
Dumpdon_ - - 20 40 23, which gives the

distance from Dumpdon to Cawsand Beacon = 169014, feet.
In the xxrxth triangle, the observed angle at Dumpdon is
found to be 86° 39’ 8”5, and, by adding to it the horizontal
angle at Dumpdon, between Rippin Tor and Little Haldon,
and also that between Black Down and Charton Common, we
get 125° 54 30,5, for the horizontal angle between Rippin

Trigonometrical Survey. 631

Tor and Cawsand Beacon. To reduce this angle to that formed
by the chords, 6” must be subtracted; therefore, 125° 54/ 24,5
is the angle for computation. The sides Dumpdon and Rippin
Tor, Dumpdon and Black Down, (169014, and 153095,2 feet, )
with this angle, give the following triangle:

Rippin Tor - - 25°36! 4,5
Dumpdon - 125 54 24,5
Black Down - 28 29 31, which gives the

distance from Rippin Tor to Black Down = 286973,9 feet.

On referring to the observations made in 1797, on Black
Down, it will be seen that the angle between Rippin Tor and
the staff erected near Abbotsbury, was 3° 8’ 52”,5, and the
angle between Pilsden and the same staff 45° 16’ 19”; their
difference, 42° 7’ 20”,5, is the angle between Rippin Tor and
Pilsden. Now, if the angles of the triangles, five in number, used
in finding the distance between Rippin Tor and Black Down
have been observed correctly, and the calculations properly
made, the computed angle at Blackdown, between those sta-
tions, should be, of course, the same; but the angle formed by
the chords of the arcs between Blackdown and Pilsden and
~ Dumpdon, has been found = 193° 37’ 50”,5, (which is very
nearly the same.as the horizontal one,) and the angle between
Dumpdon and Rippin Tor = 282 29’ 31”, which it is also un-
necessary to correct: their sum is 42° 7' 21”,5, the very angle
observed. It is not, perhaps, proper to dismiss this considera-
tion, without observing that this agreement affords a strong
proof of the excellence of our instrument, as the triangles, from
their magnitude and nature, are not so disposed as to favour the
comparison.

4M 2

632 The Account of a

ArT. x1x. Latitude and Longitude of Rippin Tor.

The angle at Blackdown, between the staff at Abbotsbury and
the meridian, has been found = 101° 91’ 1”,5, nearly, and that

between Rippin Tor and the same staff == 9° 8' 50,53 there=

fore, 98° 22’ 8” is the angle which Rippin Tor makes with the
meridian, and this, taken from 180°, leaves 81° 37’ 52”, the
bearing of Rippin Tor SW from Black Down.

This angle, with the distance found above, gives 28 585,3 feet,
for the distance of Rippin Tor from the meridian of Black Down,
and 56086,0 feet, for that from its perpendicular ; therefore, the
latitude is 50° 39’ 59”,1, and the longitude west from Black
Down, 1° 13’ 3,8; consequently, its longitude west of Green-
wich is 3° 45° 26’.

Direction of the Meridian at Butterton Hill,

On the 6th of May, in the afternoon, the angle
between the Pole Star, when at its greatest ap-
parent elongation from the meridian, and the staff
on Hemmerdon Ball was observed, and found

to be - - - - - 91° 29' 1375
And on the 7th, in the afternoon - - 97 4A 14
Half their sum is the angle between the meri-

dian and the staff on Hemmerdon Ball - 94 16 44

Again, on the 7th, in the afternoon, the angle

between the Pole Star, when at its greatest appa-

rent elongation from the meridian, and the staff

on Hemmerdon Ball was observed, and found

to be - - - - ~ gi 29 12
Half the sum of this, and the angle observed

Trigonometrical Survey. 633

in the forenoon of the same day, (97° 4 14\’)
git oak ney ss 7 g4° 16' 43”

Hence, 94° 16’ 44)’ may be considered as the true angle be-
tween the meridian and the staff on Hemmerdon Ball.

The angle between the station on Rippin Tor and Hemmer-
don Ball, is 121°17' 7,75; therefore, 121° 17° 7,75 — 94° 16°
AA! = 27° 0! 29,75, is the bearing of Rippin Tor, north-east of
Butterton. This angle, with 62951 feet, gives 28585,2 feet, and
56086,6 feet, for the distance of Rippin Tor from the meridian
and perpendicular ; which, using 61182 and 60847 fathoms, for
the lengths of degrees on the meridian and perpendicular, re-
spectively become 4 40”,3, and 9’ 13”. Therefore, in the right
angled spherical triangle BPT, (Plate XXX, Fig. 2,) in which B
is Butterton, P the pole, T Rippin Tor, and R the point where
the parallel to the perpendicular cuts the meridian, we have the
co-latitude of T, or Rippin Tor, = 39° 26’ 0”,9, and RT = 4/
40',3, We have, consequently, cosine 4/ 40”,3 : radius : : cosine
39° 26’ 0,9 : cosine 39° 26’ 0,7, the co-latitude of the point
R. So PB = PR + RT= g9° 26’ 0",7 + 9/ 19" = 39 35!
13,7; therefore,-the latitude of Butterton is 50° 24/ 46,3, and
its longitude west from Greenwich, 3° 52’ 4,7”,5.

ArT. xx. Calculation of the Distance between Hensbarrow and
Butterton.

The most convenient, as well as the most accurate mteans of
computing this distance, will be by referring to the tvith, rvith,
and ixivth triangles, in the series of 1796, where the sum of the
observed angles at Carraton Hill is 136° 52’ 43”. The correc-
tion for reducing this angle to that formed by the chords, is 4’:
therefore, 136° 52’ 39" is the proper angle for computation¢

634 The Account of a.

The distance from Hensbarrow to Carraton Hill, is 100416
feet, and from Butterton to that station 131576 feet. (See Phil.
Trans. for 1797, p. 458, 460.) These data give the following
triangle, viz.

Carraton Hill - - 136° 52’ 39”
Hensbarrow - - 24 35 5755
Butterton - - 18 31 23,5, which gives

21602 feet, for the distance between Hensbarrow and Butterton
Hill:

The angle between Carraton Hill and Rippin Tor was ob-
served in 1796, and found = 101° 9’ 44/’,25. (See Phil. Trans.
1797.) The angle between Hensbarrow and Rippin Tor is
119° 35’ 3,25; therefore, 18° 31’ 19” is the angle between
Hensbarrow and Carraton. The difference between the hori-
zontal and chord angle is 0,25 nearly; this, added to 18°
31' 23”,5, gives 18° 31’ 23”,75, which is nearly the same as the
observed angle. This agreement proves, that the angles of the
triangles connecting Butterton and Hensbarrow have been ob-
served correctly.

ART. xxI. Latitude and Longitude of Hensbarrow.

The angle between Hensbarrow and Hemmerdon, (see Ob-
servations made at Butterton, ) was 1° 52’ 4,",5; therefore, as the
angle between the latter and the meridian = 94° 16’ 44,”, we get
92° 24/ 39”,5, for the angle which Hensbarrow makes with the _
same meridian. The distance from Hensbarrow to Butterton,
as found above, is 21602 feet; this, with the angle g2° 24/ 39,5,
gives the distance of Hensbarrow from the meridian = 215871
feet, and from the perpendicular go8g feet; these, converted
into parts of degrees, become 35’ 17,1, and 1’ 29’,62. There-

Trigonometrical Survey. 635

fore, the latitude of Hensbarrow is 50° 29’ 3,3, and its longi-
tude, west of Butterton, 55’ 20,2 ; consequently, its longitude,
west of Greenwich, is 9° 52! 47,5 + 55/ 20,2 = 4° 48! 7,7.

ART xxl. Direction of the Meridian at St. Agnes Beacon.

On the g2d of May, in the forenoon, the angle
between the Pole Star, when at its greatest
elongation from the meridian, and the staff
near Peranzabulo, was observed, and found

to be - - - - - 38° 26 1,5
And on the ged, in the afternoon - Ad © 33,25
Half their sum is the angle between the meri-

dian and staff - - - Al 13-1755

The angle between the staff at Peranzabulo and the station
Hensbarrow, was also observed at the same station, and found
to be 31° 50’ 55,5; wherefore, 41° 19 17”",5 -- 31° 50’ 554.5
= 73° 4/ 13”, is the angle between Hensbarrow and St. Agnes
Beacon.

ART. xxl. To find the Latitude and Longitude of St. Agnes
' Beacon.

In Plate XXX. Fig. 3. Let A be the station at St. Agnes, P
the pole, H Hensbarrow, and B the point where the parallel to
the meridian of St. Agnes cuts that meridian, BHP being a
right angled spherical triangle on the earth’s surface.

PH has been already found = 39° 36’ 56”,7; and, as BH, the
distance of Hensbarrow from the meridian, = 92878, and AB,
the distance from the perpendicular, = 28271, we get BH =15'
10,9, and AB = 4/ 38,8; which arcs are found by using
61182 and 60845 fathoms, for the length of their respective

636 The Account of a

degrees. From these data, the latitude of the point B is easily
derived; for cosine 15’ 10”,9 : radius :: cosine 39° 36’ 56”,7:
cosine 39° 36’ 54,",2, the co-latitude of B; hence 39° 36’ 54/",2
+ 4/ 38”,8 = 39° 41' 33”,0 the co-latitude of A; hence 50° 18’
27" is the latitude of St. Agnes. Its longitude, west from
Hensbarrow, is also found by a simple proportion; sine 39° 36’
54,2 : radius : :-sine 15’ 10,9: sine 0° 29’ 48"; therefore,
4 48" 7",7 + 0° 23/ 48” = 5° 11’ 55,7, is the longitude of
St. Agnes, west of Greenwich. |

ART. Xx1V.— Remarks.

I have shewn, with attention to minuteness, the manner in
which the latitudes and longitudes of the stations on which
directions of meridians have been observed are determined. It
now remains to be considered, how far the uncertain state
in which we remain, with respect to the figure of the earth, may
affect the accuracy of those conclusions.

If the earth were homogeneous, it would necessarily be an
ellipsoid; and, were its diameters known, the longitudes and
latitudes of places on its surface might be accurately computed,
provided their geodetical situations were correctly ascertained,
and the latitude of one station in the series of triangles truly
determined.

As there is, however, great reason to suppose that the earth
is not any regular geometrical figure, from the impossibility of
reconciling the results of the various measurements for ascer-
taining the lengths of degrees of latitude, some uncertainty must
remain with respect to our deductions; but there seems to be
reasons for supposing the errors, thence resulting, are confined
within moderate limits.

Trigonometrical Survey. 637

In making computations on a given hypothesis of the earth’s
figure, the truth of the conclusions, as well as the ease with
which they are found, materially depends on the distances of the
‘objects from their respective fixed meridians.

If the difference of longitude approaches nearly to, or exceeds
3°, to compute that longitude, and also the latitude, it is necessary
the precise figure should be understood; because the analogy
does not hold good, in that case, between the equality of the
sums of the angles of spherical and spheroidical triangles on
the earth’s surface. With regard to latitudes, more particularly
when the distances are diminished by means of frequent new
directions of meridians, a knowledge of the exact length of a
degree of a great circle is not necessary ; because the determi-
nation of those latitudes, by means of spherical computation,
being true as to sense, the cosines of those small arcs will remain
the same.

As there cannot be a doubt justly entertained of the latitude
of Greenwich being very accurately determined, as particularly
set forth by the Astronomer Royal in his reply to M. Cassin1,
it is reasonable to suppose, that if any errors do exist in the
latitudes of those stations, they can only have arisen from the
computations being made with erroneous lengths of degrees on
the meridian.

In our former Papers on this subject, we have taken it for
granted, that the length of a degree of the meridian at the
middle point between Greenwich and Paris, (50° 10’,) is 60842
fathoms, (which supposition may be considered just, provided
the latitude of Paris, 48° 50’ 14’, be as near the truth as 51° 28’
40” is to that of Greenwich, ) and afterwards added g fathoms,

MDCCC. 4,N

638 The Account of a

ners it 60851, in order to get the length of the degree in
50° 41’; (see Phil. Trans. 1795, p. 5373) these g fathoms,
however, were not arbitrarily assumed, but computed. If the
latitude of Paris be 48° 50’ 15", (Conn. des Tems, 1797-98,
p- 373.) the length of the degree will be about 7 fathoms
greater, which will make the degree in 50° 41’, 60849 instead
of 60842 fathoms. .

The latitude of the station on Beachy Head, 50° 44/ 23,7,
was found by using 60861 fathoms for the length of a degree
on the meridian in 51° 6’; but, if it be true that 48° 50’ 15” is
the latitude of Paris, the latitude of Beachy Head will be about
one-third.of a second greater. This seems to be the limit of the
probable error in the computed latitude of this station ; since its
proximity to the meridian of Greenwich, obviates any doubt of
the conclusions being affected by any uncertainty respecting the
length of the degree of the great circle perpendicular to the
meridian.

The latitude of Dunnose was determined by computing the
distance between the parallels of that station and Beachy Head ;
(see Phil. Trans. for 1795, p. §22;) which method is very exact,
and preferable to any other, since the small space between the
parallels was determined with great accuracy, leaving not a
doubt of a greater error than g feet, a quantity corresponding
to about =4d part of a second. And, since the same method
has been “adugnea to find the difference of latitude between
Black Down and Dunnose, it is highly probable that the lati-
tude of the former station is not removed more than —+ths of a
second from the true one, that of Beachy Head wer supposed

= 50° 44! 23",7.

Trigonometrical Survey. 639

. It would have been fortunate, had the difference of latitude
between Black Down and Butterton, and Butterton and St.
Agnes Beacon, been determined in the same manner, since the
latitudes of all these important stations would, in that case, have
been found with evident accuracy ; but, whoever has leisure and
inclination to go through these calculations, will find that, by
means of the directions of meridians at Butterton and St. Agnes
Beacon, the latitudes of those stations may be found to within
halfasecond. By this I mean, that, allowing the latitude of Black
Down to be 50° 41’ 13,8, the latitude of Butterton, 50° 24/ 46,3,
will not deviate more than half a second from the truth; and the
same may be said with respect to the latitude of St. Agnes, that of
Butterton being admitted as correct. Supposing, therefore, the
latitude of Greenwich to be 51° 28’ 40”, we may rely on the
assurance of the latitude of St. Agnes Beacon being determined
within 12” of the truth. ;

With respect to the longitudes of these stations, their accu-
racy entirely depends on the observations made at Dunnose
and Beachy Head, for determining the length of a degree of a
great circle perpendicular to the meridian. The truth of the
deduction drawn from those observations rests on their accuracy $
and it can scarcely be deemed presumptuous to assert, that an
error of more than 1” cannot have existed in either of the
angles. On this account, therefore, I should suppose, that the
difference of longitude between those stations, has been found
so nearly as to leave no greater error than 1”. The whole of
the operation to which I now allude, was performed with great
care; the directions of the meridians having been determined by
means of double azimuths of the Pole Star, confirmed by com-
puted azimuths. In returning to the consideration of this sub-

4Ne

640. The Account of a

ject, I do not perceive any source of error likely to affect the
conclusions, unless it be that to which all astronomical obser-
vations, made with instruments adjusted by plumb-lines or levels,
areliable. In determining differences of longitude through these
means, the direction in which any lateral attraction must act,
to produce a maximum of error, is at right angles to the meri-
dian. If the attraction be in the plane of it, it is obvious the
double azimuth, although the telescope of the theodolite does
not move ina vertical, will nevertheless give, almost exactly,
the true direction of the meridian.

The high lands about St. Catherine’s Light-House, in the Isle
of Wight, are about six miles from Dunnose, and nearly west
of it; but it does not appear that the effect of their lateral attrac-
tion can have produced any sensible error; since it may be
shewn, that the plumb-line of the sector at Schehallien would
have deviated only a small part of a second from the true ver-
tical, had the sector itself been placed at that distance from
the hill. Beachy Head is situated at the eastern extremity of
the South Downs; a defect of matter towards the east imme-
diately taking place. This circumstance renders the observa-
tions liable to some small errors, on account of the superior
lateral attraction in the opposite direction ; but, notwithstanding
it is very probable that an error induced by either of these
attractions, is so very small as to render the subject scarcely
worth consideration, yet, as both lie the same way, it is satisfac-
tory to consider that they mutually tend to correct the errors
which may result from either; we may, therefore, safely con-
clude, that 1° 11’ 36” is very nearly the true longitude between
the station on Beachy Head and that on Dunnose.' Under this
persuasion, I consider it probable that the longitude of Black |

Trigonometrical Stievey. 641

Down cannot err in excess or defect more than 9”; that of But-
terton 5”; and that of St. Agnes Beacon 6”.

The latitudes and longitudes of these important stations,
brought under one point of view, will be as follows :

Latitude. Longitude west from Greenwich.
In degrees. In time.

Black Down - 50°41’ 13,8 2° 32! 99/4 10’ 9",5
Butterton Hill - 50 24 46,3 3 52 N75 15 31,2
St. Agnes Beacon 50 18 27 § 115557 20 47,7

Note. It may probably be expected, that I should determine the directions of the
meridians at Black Down, Butterton Hill, and St. Agnes Beacon, by calculation, and’
afterwards compare them with the observed ones. I have desisted from the measure in
the body of the work, and reserved the little I have to say for this note.

’ If the earth were a perfect sphere, or an ellipsoid of known diameters, the direction
of the meridian, at any station not very remotely situated from the parallel of another,
might be determined, provided the direction of the meridian at that station were ob-
served, and the value of the arc subtended by the space between them pretty accurately
ascertained, and also the latitude of the station, at which the angle is given, nearly
obtained.

Thus, if it be required to find the angle at Dunnose, between Beachy Head and the
meridian, from the observed angle at the latter station, and the arc between them, we
shall. have 39° 15’ 36”,3, the co-latitude of Beachy Head, and 55’ 28",7 for the oblique
arc. These data (two sides and an included angle) give 1° 26’ 48”,4, for the difference
of longitude between Beachy Head and Dunnose, and 81° 56'§2",6, for the angle which
the meridian at the latter makes with the former station. The difference of longitude
found in a rather more:correct way, has been heretofore shewn to be 1° 26’ 47",93, (see
Philos. Trans. 1795. p. 523,) and the angle at Dunnose was also shewn to be 81°
56 53”, from observation, which may be considered the same with that found: by this
mode of computation. In all cases in which the data were equally correct, no doubt
the direction of meridians might be computed, without fear of the results deviating
much from the truth ; but, if it be required to find the angle at Black Down, from
the observed direction of the meridian at Dunnose, a different method must be used.
It is, however, less accurate than the former one, and it has been expressly for this:
reason, that Ihave not introduced this subject into. the account. |

The Account of a

In the adjoining diagram, suppose B, Black Down; D;
Dunnose ; and, N, Nine Barrow. Down. also, let RB, the me-
ridian of Black Down, be prolonged to M, and DM be drawn,
PM being — —PD. Then we shall have three spherical tri-

found from observations to be 4° 30’ 28", and BND 172°
27' 33'55 3 these give the angle BDN = 3° 1’ 59",5, nearly, be-
cause the excess of the three angles above 180° is 1". The

observed angle at D, Dunnose, between Nine Barrow. Down
and the meridian DP, or PDN, was 87°56' 53”; therefore, 87° 56’ 53” — 3°1' 59,5 =
84° 54’ 53",5, is the angle at D, between the meridian and the station on Black Down.

Now, the difference of longitude between‘B and D,.or the angle at P, has been
already found = 1° 20’ 46",4; and, since BP is very nearly = PD, and BD is small,
we shall have rad. ; tang. P :: cosine DP ; cosine BMD = 89° 28’ 47”.. But the
angle PDB has been found = 84° 54'53",53 therefore, 89° 28! 47" — 84° 54'53",5
= 4° 33' 53,"5, the angle BDM; hence, 180° o! 2”-— 94° 2'40",5 = 85° 57' 21,"5,
or MBD ; therefore, 94° 2' 38,"5, or DBP, is the angle at Black Down obtained in
this way, which differs nearly 16" from the observed one, viz. 94° 2’ 22",75. It is
probable, some portion of this arises from defects in the observation made at Dunnose,
on the lights fired at Nine Barrow Down: only two lights were seen; and, as the ob-
servations differed 5” from each other, some degree of doubt exists, as to the accuracy
of the angle. The angle at Nine Barrow Down, between Black Down and Dunnose,
is not absolutely to be depended on for purposes of this kind, although there can be
no doubt of its being sufficiently near the truth, for that to which it has been before
applied. In the correction of the angles at that station, in our former accounts, we
proceeded on the supposition of their being less satisfactory than the other angles of
the triangles to which. Nine Barrow Down is a common station. For these reasons, I
am of opinion the computed angle cannot be applied as a test to the observed .one ;
and it also appears to me, that greater objections lie against similar comparisons be-
tween the computed and observed angles at Butterton and St. Agnes; as those stations

could not be seen from each other, nor the latter from Black Down. Although the.

computed directions of the meridians differ some seconds from the observed ones, I am
by no means doubtful of the truth of the latter; as the double azimuths of. the Pole
Star, found from computation, agree very satisfactorily with those which have been
used in obtaining the directions of the several meridians. In finding the value of the
oblique arc, or the line which joins Black Down and Dunnose, as used in the first
method of computation, I have had recourse to the following correct expression, Viz.

pS ENE et ; where d is the length of the required degree, p that of the great
Pm —p - S$?

circle perpendicular to the meridian, m that of a degree of the meridian itself, and s

the sine of the angle constituted by the oblique arc and the meridian.

angles BPD, BND; and BMD. Now, the angle NBD was

Trigonometrical Survey. 643

Art. xxv. Bearings of the Stations in the Series of 1795 and1796,
from the Parallels to the Meridians of Black Down, Butterton
Hill, and St. Agnes Beacon ; likewise their Distances from those

Mertdians, and from their Perpendiculars.

Meridian of Black Down.

Bearings from the Parallel to the Meridian, earns AL, pains:
: ; o NE Nn Feet. Feet.
Bull Barrow - Black Down] 42 z 30 NE 5 3643,2 5948957
Mintern - - - - 10:36 33 NE 10996,8 58709
Pilsden - - - - | 56 14 48 NW 65775,6 | 439554
Charton Common - - vts3- go 3 NW 502681 11697,5
Dumpdon - Charton Common} 45 4 o NW 143749 52670,9
Rippin Tor —- - = £3)°81 37 52°SW
Meridian of Butterton,
Rippin Tor == Butterton | 27 023 NE 28585,3 | 56086,6
Furland - = - 78 37 39 SE 78066, 3 15883
Bolt Head = = - 14 49 48 SE 1855153 7006554
Maker Heights - 7o 36 g SW 71467,9 | 25164,3
Kit Hill —- - - 67 12 12 N Wi 93081,9 | 39121,7
Carraton Hill - - a 7353 22 NW 126408,9 36511,3
Cawsand Beacon - Rippin Tor} 35 35 29 NW 86744,4 | 108147,5
Little Haldon - Furland 425 2 NE 8457154. 56675,8
Bindown - - Maker 70 448 NW 52926,6 19180,1
Hensbarrow — - - - 87 35 18 SW 92878,0 28271,0

"Meridian of ‘SE. Agnes Beacon.

28279,9

Hensbarrow - St. Agnes Beacon] 73 4 13 NE 9287734
Deadman = - 722427 SE 9729235 30849
Karnbonellis - - - 3 27 27 SW 274147 453792
Karnminnis - - 61 13 58 SW 741681 40719
eae i £ Ecasbaccon 37 ap 45 NE 12170352 65825,8
c 75 29 51 SE 1529453 | 12733,5
St. Burian Karnbonellis 67 20 59 SW 94831,5 83807,3
Pertinney - - Kar: minnis 39 25 32 SW 100465,1 72704,4.
Sennen - - Pertinney 40 50 18 SW 113674,4 | 879868

644 The Acchunt of a~

Art. xxvi. Latitudes and Longitudes of the Stations in the Series

of 1795 and 1796.

Meridian of Black Down. ¢

Names of Stations.

eres

Bull Barrow - -
Mintern - -
Pilsden - - -
Charton - -
Dumpdon - -
‘Rippin Tor - =

Meridian of Butterton Hill.
Furland = =
Little Haldon ss =
Cawsand Beacon -
Bolt Head - =
Maker - - -
Kit Hill 5 -
Carraton Hill a =
Bindown - ae
Hensbarrow S 2

Meridian of St. Agnes.

Lansallos > é

Bodmin Down - -
Deadman - -
Karnbonellis ° - | 50
Karnminnis - ° 50
St. Burian - 50
Pertinney : . 50
Sennen - © - | 50

Latitude.

”
5° 5° 5955
50 50 52,8

IO o4
Il 43,8
4 37:9
6 27,0

3 55,6

In degrees.

WwNN BNO

PPP ARWWWw

‘ie MAMMA pp

18 29,2
29 31,6
49 23,1

Longitude from | Longitude west of Greenwich.

In time,

m. Ss.

9 14

9 58,1
Il 1755
Il 5555
14 38,3
15 1;7

14 10,3
14 451
15 40,1
5 12,2
I 5)
ib
17 4bI
17 3857
19 12,5

18 11,0
18 42,6
19 38,3
20 5035
22 355
22 2453
22 30,5
22 4355

Trigonometrical Survey. 645

¢

Art. xxvil. Bearings of the intersected Objects, from the Stations
in the Series of 1795 and 1796, from the Parallels to the Meri-
dians of Black Down, Butterton Hill, and St. Agnes Beacon ; and
likewise their Distances from these Mertdians.

Meridian of Black Down.

Distances Distances
from merid. | from perp.

Bearings from the Parallels to the Meridian.

At Bull Barrow. fee By Feet. Feet.
Portland Light House - 19 47 16 SE 21581 59985
Noil Windmill - - 10 12 56 NE 72842 166029
Noil Steeple - - - = 2u 53). 29 NE 86610 1415 34.
Holy Trinity, - Shaftsbury| 25 41 52 NE 81081 116506
St. Rumbold’s Steeple, Ditto 28 12 51 NE 80486 109522
Maypowder Steeple - - 85 17 11 NW 29526 61479
Stourhead House - - - o 27 46 NW 52881 153806
Mr. Frampton’s Obelisk ° 10 3 4SE 63588 3384.
Mere Steeple - 6 40 55 NE 63893 146984.
Mrs. Thornhill’s Obelisk | - 22 18) 51 NW 40391 91778
Odcomb Spire - . 70 25 oNW 35474. g1194
Milborne Port - - e 38 21 20 NW 20110 101865

At Black Down. :
Puncknoll Flagstaff - 89 957 NW 25612 373
Lambert’s Castle - - 65 17 36 NW 67269 30950
Lyme Cobb = - 82 21 29 NW 89547 12015

At Pilsden.
Golden Cape - - 444 3SW 68239 14209
Glastonbury Tor - - 14 19 23 NE 34314 167176
Bridport Beacon - 8 19 55 SW 72199 9!
Lord Rolle’s Barn, near Sidmouth 64 34 38 SW 101743 26859
At Dumpdon.

Naval Flagstaff, Whitlands - 32 45 10 SE 116249 9920
Catherstone Lodge - - 22945 NE 140940 117131
Lord Lisburne’s Obelisk - 46 47 34 SW 225502 24119
Sir J. de la Pole’s Flagstaff - - 52 342 SE 86622 8137
Honiton Steeple - = 12 24 9 SW 146681 39339
St. Mary Ottery Steeple - - 42 21 56 SW 179904 13028
Sir Robert Palk’s Tower - 58 56 2SWw 242012 6526

MDCCC. 4,0

646 The Account of a

Meridian of Butterton.

Bearings from the Parallels to the Meridian. oes a, fribiglee.

At Little Haldon. Bie, Feet. Feet.
North Bovey - - - a1 44 23 NW | agane 70289
Eastern Karn = - - - 56 27 52 NW 41145 85459
Western Karn - - - 53 12 toy Ww. 40730 89472
West Down Beacon - - - 63 59 14 NE 126152 76968
Woodley’s Summer House - - 83 39 47 SW 29448 50555
Berry Head Flagstaff - - 1022 16 SE 95740 4350
Brixen Steeple - - - 229 4 SE 87435 9331
Ipplepen Steeple - - 22 i o SW 68413 17180
Three Barrow Tor - - 68 43 3 SW 8667 27109
Brent Beacon - - 5O il 17 SW 15460 10390

At Butterton.

Chudleigh Steeple - - 44 444 NE 67688 69900
Froward Flagstaff - - - | 95 © 28 SE 84342 22587
Start Point Flagstaff - - 39 22 33 SE 56544 68897
Marlborough Steeple - - | 16 42 32 SE 18429 61393
Bolt Head Flagstaff = - - 1457 7SE 18739 70173
Mewstone, highest point - - 52 45, 23 sow _ 49825 38108
Cupola, Hospital, Plymouth - 76 47 30 SW 66891 15699
St. John’s Steeple - - -| 79 3444 S5SW 83991 15447 |
Saltash Steeple - - 89 37 12 SW 73707 489
Penlee Beacon - - - 64 59 49 SW 69758 32532
Plymstock Steeple - 5 73 4615 SW 49217 14326 © .
Statten Barn - - - 64 43 53 SW 53270 25145
Mount Baiton - - 70 50 51 SW 58651 20370
Flagstaff, Plymouth Garrison - 72 OT 17 0S Wa~ 57021 17591
New Church, Plymouth - - 75 25 49 SW 56521 14691
Old Church, Plymouth - =|) 75 11. 56"S Wi 57505 15374
West Chimney, Governor’s House 75 42 15 SW 64497 164.35
Flagstaff on Mount Wise - - 75 40 55 S W 65281 16662,
Chapel, Plymouth Dock - 77 33 23 SW 67040 14792
Obelisk, Crimhill Passage, Plymouth ah 7 9h SW) 66728 18984
Mount Edgecumbe House - 72 18 23 SW 65827 | 21001
Flagstaff, Maker Tower - - 70 53 41 SW 68224 23632
Naval Signal Staff, Maker Tower 70 54 37S W 68232 23626
Eddystone Light House - - 46 1 27 SW 87190 “| 84127

’

At Butterton.

Stonehouse Steeple = - 65 32 37°S W 53078 24140
Puslinch Obelisk - - - 45 17 46 SW 27480. 27223
Flagstaff, Rame Head - 65 13 44 5 W. 76935 35774

At Rippin ue
Great Haldon - - - 52 27 “oO NE 72023 89479

Trigonometrical Survey. 64,7

Bearings from the Parallels to the Meridian. aes goes

oa es Cs Se ee are eee ee | ee

At Maker. 1h Feet. Feet.

Hemmerdon Ball - - 62 10 37 NE 27722 2077
Brent Tor - - 5 27 45 NE 62385 69820
Blockhouse Flagstaff - 27 51 26 NE 64005 11043
Rame Steeple - - = 20 20 12 SW 74388 33043
Chapel, Dockyard - - 23 “650 NE 67042 14795
Flagstaff, Statten Battery - - 83°49 5 SE 54278 25719
Windmill, Plymouth Dock - 29 47 35 NE 65963 15549
; At Kit Hill.

St. Stephen’s Steeple - - 19 29 31 SE 78182 2979
St. Ive Steeple - e 56 20 4SW 114213 25047
Callington Steeple - - 43 014 SW 98219 33013
Linkinghorn Steeple - - | 69 8 31 NW LIIA17 46108
St. Dominic Steeple - - 27 19 41 NE 89512 46030
South Petherwin Steeple - - 34 618 NW 115216 71807
South Hill - - 7457 40 NW 108044 43142
St. Cleer Steeple - - 7442 9 SW 133492 27795

At Carraton Hill.
Cheese Rings - - - 44. 0 29 NW 133198 43540
Liskeard Steeple - ~ - |° 15 19 39 SW 132155 15546
Landrake Steeple - - 46 1 2SE 92463 3750
Duloe Steeple - - - 15 23 3S W 137923 5330
Menheniot Steeple - - 11 59 44 SE 121941 15479
Polparrow Flagstaff - - zo 8 5 SW 138871 2521
Lord Camelford’s Obelisk: - 48 33 15 SW 163992 3324.
Boconnock Steeple - - 4434 58 SW 158753 3692
Roach Steeple = - - 66 30 33 SW 218318 3434
Roach Rock - - 65 58 15 SW 217204 3969
Meridian of St. Agnes.
At Lansallos.
Lanlivery Steeple ° . 56 48 14 NW 119848 34388
Helmen Tor - = GALS 53 55°17 NW 113818 41243
Mr. Tremaine’s Summer House - 67 21 40 SW 96548 10787
Gorran Steeple - - -| 5855 59 SW 95877 21647
Flagstaff, Deadman = - 51 46 44 SW 97959 31278
Gwineas Rocks - - 53 9 oSW 106551 22037
At Hensbarrow.

Hendellion Steeple - - - 22659 NW 89918 97463
Stone, St. Braeg’s Down - 17 31 12 NW 81868 63145
St. Dennis Steeple - - 83 625 NW 77630 30114
Lansallos Steeple - = 7343 28 SE 149787 11656
Gerrans Steeple - 20° 23°53 S W 55357 46773
St.Michael Carhayes Steeple - 9 39 51 SW 84768 19353

4,0 2

648 The Account of a

Distances Distances
from merid,| from perp. -

Bearings from the Parallels to the Meridian.

a ee ee pee

Of Ps oD Feet, Feet,
St. Kivern Steeple - - 29 647 SW. 30611 93398
Flagstaff, Blackhead - - 24.50 30 SW 31214 104917 |
Windmill, near Fowey - - 67 244 SE 134347 10797 .
Menabilly House - - 60 26 48 SE 123516 10899
Old Tower at Polruan - 64 44 37 SE 35892 7978 .
Flagstaff, St. Anthony’s Head (.*) 26 35 45 SW 48664 60038

At the Deadman.

St. Veep’s Steeple - - 39 429 NE 140146 21930
At St. Agnes.

St. Columb Minor Steeple - 44757 NE 40698 -41950 |
Peranzabulo - - 41 54 34 NE 19354 21563
St. Eval Steeple - - = 37 52 39 NE 50275 64632
Cubert Steeple - - 42 26 53 NE 23773 25991
Flagstaff; Pendennis Castle - - 34 19 23 SE 39999 58586
Windmill, St, Mawe’s - = 45 52 9 SE 48079 46642
Karnbre Castle - - - | I) 53 47°98 W 6480 30760 .
Illugan Steeple - - 30 1 2SW 11865 20537
St. Paul’s Steeple - - 20 21 16 SW 38457 103660 |
Lord Dunstanville’s House - 40 33 25 SW 19726 23050 |
Gwinear Steeple - - 39 33 34 SW 39578 47911
Cow and Calf - - - 23 47 22°NE 37174 87044
Camborn Steeple - - 30 16 51 SW 19881 34048
St. Erme Steeple - - 88 42 22 NE 44657 1009
St. Allen Steeple - - 85 13 35 NE 36688 3064
Ludguan Steeple - - 47 39 58 SW 64737 58976

At Karnboneliis,
Lizard Windmill - - 147 24SE 573 114785
Grade Steeple - - OAL 7S Be | 5710 117451
Ruan Major Steeple —- - 3 46 21 SE 1486 109496
St. Hilary Steeple - 66 19 33 SW 49009 65664.
Mr. Rogers’s Tower, near St. fees =i), 383 23 ROUS Wi 18396 47102
Madern Steeple - - 76 53 40 SW 81542 63725
Parklough Flagstaff = - 6 55 1S W 10735 111240

At Karuminnis.
St. Buryan Steeple - - 25 45 25 SW 95205 84320

At St. Buryan. .
Chapel Karnbury - - 3 25 16 NW 95472 73098
Flagstaff; St. Leven’s Point - 77 29 40 SW 114449 88158
Sennen Steeple - - -| 83 44 37 SW 112202 85712

At Pertinney. :

Stone, Lann’s ExD = ~~ = 48 5 30S W 116222 86847

* The letter D is added (as in the former accounts) to those places respecting
which any doubts are entertained.

Trigonometrical Survey. 64.9

Art. xxvill. Latitudes and Longitudes of such intersected Objects,
in the Series of 1795 and 1796, as have been referred to the Meri-
dians of Black Down, Butterton Hill, and St. Agnes.

: - ongitude from |Longitude west of Greenwich.
Bae tes se pieciae iS Taek Down, Th degrees In ae
j OW o «4 4 o 7) m. Ss.
Portland Light House “eel sO 2y 22,2) 1 0 5) 22.0 B | 2 26 4935 9 4753
Noil Windmill - Sat hE) 2055) | OS 5057 bl, 2 13) 24,7 8 53,0
Noil Steeple - - 51 4 27,1 |o 22 31,8 E] 2 19 50,6 | 9g 1953
Holy Trinity, - Shaftsbury|] 51 0 20,7 |o 21 3,6E| 2 11 18,8 8 45,3
St. Rumbold’s Steeple, Ditto | 50 59 11,8 | o 20 53,9 E| 2 11 28,5 8 45,3
Maypowder Steeple - 50 51 19,7 |}0 7 38,6E] 2 24 43,8 9 33,9
Stourhead House - - 51 6 29,5 | 0 13 46,0E| 2 18 36,4 | 9 14,4
Mr. Frampton’s Obelisk =''50 41 46,0 1.0 VO 2450 EB) 2) 15'257,9, | (9 13,5
Mere Steeple Gr 5 2h Ob VO, 37,01 | 2 skin) AA,8 9 2:9
Mrs, Thornhill’s Obelisk - | 50 56 17,5 |0 10 28,6E] 2 21 53, 9 27,6
Odcomb Spire - - 50 56 12,6 | 0 9 12,1 W| .2 41 3454 | 10 46,3
Milborne Port - - BO 57 5050.0. 5 1355 Kl 2.27 19.3 9 48,6
Puncknoll Flagstaff = - 5° 41 17,3 | 0 6 36,4.W| 2 38 58,8 | 10 35,9
Lambert’s Castle - = | 50 46 17,7 | 0 17 23,1 W| 2 49 45,5] BI 19
Lyme Cobb - ° 5° 43 10,0 |e 23 7, WI 2 55 29,4 | II 41,9
Golden Cape - - | 5° 43 32,5 |0 17 37:2 W] 2 49 §9,6 |] Ir 20
Glastonbury Tor - Gt S 47,7 10. 8 56,4.W] 2 AI 48,0 | LO 45,2
Bridport Beacon - 5° 41 13,2 | o 18 37,6 W|] 2 50 59,9 | II 24
Ld. Rolle’s Barn, near Sidmouth 5° 45 35:6 | o 26 17,2 W] 2 58 39,6 | 11 54,6
Naval Flagstaff, Whitlands LO 42 47,7 | 0 30:.20,4 Wi 3 2 2258 | 127, 9,5
Catherstone Lodge - - | 51_ 0 23,0 | o 36 36,6W| 3 8 59,0 | 12 35,9
Lord Lisburne’s Obelisk - ROU 97 1153 4) 0.59. 0530 Wl 3. 30,2050 | 4 1,9
Sir J. de la Pole’s Flagstaff - | 50 42 31,9 | o 22 21,4 W| 2 54 43,8 | 11 3839
Honiton Steeple - - OVA. Sigsk Ons 7 Gon 7 Wily (3 kOoRS,E it Teva s2
St. Mary Ottery Steeple - 50 43 12,9 | o 46 26,8 W] 3 18 49,2 | 13 15,3,
Sir Robert Palk’s Tower = | 50 39 52,5 | 1 2 24,6W] 3 34°47, 14 1951.

Meridian of Butterton Hill.

Names of Objects.

North Bovey Steeple (p.) +
Eastern Karn - -
Western Karn - -
West Down Beacon -
Woodley’s Summer House
Flagstaff, Berry Head, Torbay
Brizen Steeple - -
Ipplepen Steeple -
Three Barrow Tor - -
Brent Beacon, near Ashburton
Chudleigh Steeple -
Froward Flagstaff -
Flagstaff, Start Point = -
Marlborough Steeple -
Flagstaff, Bolt Head - -
Mewstone, highest point -
Cupola of Plymouth Hospital
St. John’s Steeple (p.) =
Saltash Steeple - -
Penlee Beacon - -
Plymstock Steeple - -
Statten Barn
Mount Batten -
Flagstaff, Plymouth Gartner
New Church, Plymouth -
Old Church, Plymouth -
Eddystone Light House -
West Chimney, Governor’s
House, Plymouth Dock -
Flagstaff, Mount Wise -
‘Chapel, Plymouth Dock -
Obelisk, Crimhill Passage
Mount Edgecumbe House
Flagstaff, Maker Tower
Naval Flagst. near Maker Tow.
Stonehouse Steeple - -
Puslinch Obelisk - -
Rame Head - -
Great Haldon - -
Hemmerdon Ball - -
Brent Tor -
Flagstaff, Blockhouse,Plymouth

The Account of a

Latitude.

Lye)
5°
59°
5°
50
50

Longitude from | Longitude west of Greenwich,
Butterton Hill.

01,0010. 0. (0'O OOO O| G10_0 0%00 OO) (O00) O 0 OOO) On

O00000000000 0.0

i a

11; pF
10 36,3 E
10 30,1 E
32 30,0E
7 3458
24 331 E
22 24,8 E
17 33,8E
2 13,5 K
3 58,1 E
17.2559) &
21 36,3 E

ADOOAORPADDAHRH HPAHRPRADR DARA REWLOWWWWWWWWHWWOY O

In degrees.

bt

In time.

Trigonometrical Survey. 651

Names of Objects.

ea ines Longitude from |Longitude west of Greenwich.

Butterton Hill. In degrees, In time.
‘OF ay a Onin, a“ oo" 7] m. S.

Rame Steeple - - 50 19 18,7 | 0 37 59,8 W| 4 30 47.3 | 18 3,1
Flagstaff, Statten Battery 50 20 3158.4 © 13°54,1 W) 4 6 41,6 | 16 26,8
Windmill, Plymouth Dock 50 22 11,6 | 0 16 54,2W| 4 9 41,7 | 1€ 38,8
St. Stephen’s Steeple - 50124 15,1 © 20 3,0W| 4°12 50,5 | 16 51,3
St. Ive Steeple - - 50 28 49 ON29u20,2.W|-47°22 757 "17 26,5
Linkinghorn Steeple - 5© 32 1753 | 08 28)30,2:W| “4 21 26,7 | 17 25,8
St. Dominic Steeple (v.) =hgO 32 17564 © 23° 1,2) 4 15 4857 | 17 3,2
South Petherwin Steeple - 50 36 30,4 | 0 29 40,4W] 4 22 27,5 | 17 29,8
South Hill Steeple - 50 31 48,3 | 0 27 46,9W| 4 20 34,4 | 17 22,3
St. Cleer Steeple - - 50 29 15 O 34 33,1 W| 4 27 20,6 | 17 49,4
Callington Steeple - FOIZO 14,90) CO 25014.4 Wi 4 18 “9-97 1251
Cheese Rings - - GO Zu HOMO) 3424.14.90 WI 34°27" 2.4" 17 48,1
Liskeard Steeple - - 50 27 14,4 | 0 33 55:5 W] 4 26 43,0 | 17 46,8
Landrake Steeple - ROlL2G 26,7 4) 0* 23843,3 W| 4 16,3058 | 17 “6
Duloe Steeple - - 50 23 48,0 | 0-35 21,.9W] 4 28 9,4 | 17 52,6
Menheniot Steeple - GOl27 W464 © 39218,3, Wi 4624 5,8) 17 36.4
Polparrow Flagstaff — - 5O: 25 | Ssh) Hl Ol 359 37.4. WW” 4 282459") 57 53:0
Lord: Camelford’s Obelisk 50-25 11,1 | o'42 4,2W| 4 34 51,7 “| 18. 19,4,
Boconnock Steeple - FO. 26 Wihssic| oO 40rA3,7 Wil 4 3393152 "18 14,1
Roach Rock = - 5OI2G 5354 | © 55°41,8 W| 4 48 29,4 | 19 13,9
Roach Steeple - - 50 23 53,7 | ©%55°59,1 W) 4 48 46,6 | 19 15,1

Names of Objects.

Lanlivery Steeple
Heimen Tor -

Mr. Tremaine’s Summer House

Gorran Steeple =
Flagstaff, Deadman
Gwineas Rocks -
Hendellion Steeple

Stone, St, Braeg’s Down

St. Dennis Steeple

St. Michael Carhayes Steeple
St. Kivern Steeple -

Flagstaff, Blackhead
Windmill, near Fowey
Menabilly House -
Old Tower at Polruan
Flagstaff, St. Anthony’s

St. Veep’s Steeple -
St. Columb Minor Steeple

Peranzabulo -

re Se ee

Longitude from | Longitude west of Greenwich.
St. AgnesBeacon.| In degrees. In time.

- ° 30 44,0 E 4 41 157 18 44,8

- © 29 11,9E|] 4.42 43,8 | 18 50,9

O'Z4 41,0 E) 4 47 14,1 | 19 ° 8,9

= © 24 30,4E) 4 47 25,3 | 19 9,6

; © 24 47,7E| 447 8,0 | 19 8,5

- 0 27 14,FE| 4 44 41,6.| 18 58,8

- © 23 8,5E| 4°48 47,2 | 19 15,1

- O21 1,7E| 4 50 54,0 | 19 23,6

- © 19 54,5E| 4 52 1,6 | 19 28,1
O 21 40,2E| 4 50 15,5 | 19 21

ON 7 ag5 BG. A 8,2 [Zo 16,5

© 7 56.4E} 5 3 59.3 | 20 15,9

- © 34 24,.2E| 4 37 31,5 | 18 30,1

Og 4750 4 94, AO 17.0) | arson t

: © 34 47.7E) 4 37 8,0 | 18 28,5

Head O 12 24,7E} A $9 31,0 | 19 58,1

6 35 Sa4.75| 4.396) 80 || TS! 24,3

© 10 26,4E) 5 1 29:3 | 20 5,9

- 50 21 59.4 10 4 57,6E} 5 6 §8,2 | 20 27,9

652 | ~The Account of a

, ; Longitude from] Longitude west of Greenwich,

Nemes eae atte si Antes Beacon. Ti degtes. In time.

ER ACL Oy te Cy “ erable )

St. Eval Steeple - 50 29 3,5 |012 549E| 4 59 0,8 | 19 56 .
Cubert Steeple - 5° 22 43,0 | of 6: 5,6E |} ~hs5 gon 41 20 aage
Flagstaff, Pendennis Castle 50 8 48,7 | 0 10 12,1 E| 5 (1 43:6 | 20°°6,9
Windmill, St. Mawes - 50 10 46,3 | 0 12 16,3E| 4 59 39:4 | 19 58,6
Karnbre Castle - - 50°13 23:0 | ov 2539.3 Wh 5-23 35301) ZOmgaoe j
Illugan Steeple - 59 15 4410 3 1.9W) 5 14°5736 | zo hos8
St. Paul’s Steeple - 50 1 24,3 | 0 9g 47,0W| § 21 42,7 |\2Rizbe
Lord Dunstanville’s House 5° 14 39.4 |0 5 255W) 5 16 58,2 | 21 7,8
Lansallos Steeple - 5° 20 15,3 | 0 38 16,2E| 4 33 39,5 | 18 14,6
Gerrans Steeple - 50 10 44,8 |o0 14 7,7E| 4 57 48,0 | 19 51,2
Gwinear Steeple - - 50 10 34, |-0 10 6,0W| 5 22 4857 | 21 28,5
Cow and Calf - - 5° 324458 | o 9 33.7 HE) 5 2 :22,0)1 207 sgES
Camborn Steeple - 59 12 51010. § 4,7W) 5 17 sejQ jean
St. Erme Steeple - 50 18 36,3 | o-11°25,7 E}. 5 0 30;0)) zou
St. Allen Steeple : - 50 18 56,8 | o 9g 23,6E | °5 -2 32,1) 20 wove
Ludguan Steeple - 50 8 44,1 | © 16 30,7W| 5 28 26,4 | 21 53,8
Windmill, Lizard - 49 59 3551 |0 0 8,7E} 5 12 4,4 | 20 48,3
Grade Steeple - - 49 59 8,8. | 0 1 27;1E] 5 10°28;6 | 20 4159
Ruan Major Steeple - 50° 0 27,2 | o 0)22,6F) 5 11 295% | 2enagre
St. Hilary Steeple - 50 7 3857 | o112 20,7 W) 5. 24-254 0oT egy
Mr. Rogers’s Tower - 50 10 42,4 |o 4 41,7W) 5 16 37,4 | 21 655
Madern Steeple - - 59 7 56,0 |.0 2094755 W| .5 32. 43.2 | 2mm
Park Lough Flagstaff 50 9 9,9 |0 2 43,8 Wi) 5 14 39,5 | 20 58,6
Lizard Flagstaff - - 49.57 55:8 |o o 381 E| 5 11 17,7 | 20 455
St. Buryan Steeple - 50 4 32,8 | o 24 14,8 W| 5 36 10,5 | 22 24,7
Karnbury Chapel - 50°» 6 2355 |-0-24- 1958 Wieers 36 1S | eee
St. Leven’s Point, Pingslag, 50 3 53:8 | 0 29 8.5 Wl 5 4t 4,2 | 22 aaee
Sennen Steeple - 50 4 18,0 | 0 28 36,6 W| 5 40 29,9 | 22 41.9
Stone, Lanv’s Enp ~ 50 4 6,6 | o 29 35.8 W|. 5-41 3155 | >22eqer

Notwithstanding almost the whole of the above latitudes and longitudes belong to
objects near the sea coast, yet I have distinguised those which are actually upon it, from ’
those more remotely situated, by Italics. ;

Trigonometrical Survey. 653

ART., XXIX. Bearings of the Stations in the Series of 1797 and
1798, from the Parallels to the Meridians of Black Down, But-
terton Hill, and St. Agnes Beacon ; and likewise their Distances

from those Meridian s

Meridian of Black Down.

Names of the Stations. Beartages pane meee
ai Heacos Ts alae Moor Lynch - “a 3 23 Ne i 71070 162067
Moor Lynch 5 - t Ash Beacon - 59 54 e sr t 5544 117624
Ash Beacon - t EOE Ob 46. 45 3 NE i 55557 164953
Moor Lynch ~ |. Danton od | ee see | 2968 | 245307
Ash Baron = Mendip = 4) 38 NE,]F sozr | royore
dane t ocontit - 4/8 HE ANE [Pages | 88
Metio . ¢ Westbury - | 39 44 34N5 |f 92715 | 209344
bit ol au Farley Down ; eA be ae 577522) 257920
Merde on’. Dundey - 4/3859 NWT ssass | asso
Bang? > f andor = 4] NEL} sou | arcu

Meridian of Butterton Hill.

re ree a aaa
St. Stephen’s i Black Down - } 76°92 26 SE b suz97 72555

4

Meridian of St. Agnes Beacon.

St. Agnes Beacon * 25 54 12 NE

Hensbarrow = i Trevose Head { 39 49 34 NW 42858 88250
Trevose Head 62 18 48 NE
Redeeis, Down i EE LO: Fit eae 119364 126702

Bodmin Do = ‘ 8 46 20 NE
i i Brown Willy - 9] 16“) 42 SE biaz74s 104145

MDCCC. 4,P

O54 The Account of a

ART, XXX. Bearings of the Stations in the Series of 1799, from
the Parallels to the Meridians of Dunnose and Greenwich; and
likewise their Distances from those Meridians.

Meridian of Dunnose.

" Names of the Stations. Bearings. Fig 3 pi
POUR CEL eee dd) a Se ees ee ee
Beate 2AR, Feet.
{ Bagshot Heath - | 81 40 58 NE 108275 274173
Highclere - 4 Nuffield - - 35 30 40 NE 351480
| White Horse Hill - | 27 47 37 NW 349533
{ Stow on the Wold 14 29 27 NW] 114915 469942
Brill - - 50 16 17 NE 443235
White Horse Hill Shotover Hill - 53 30 7 NE 413801
Scutchamfly - | 84 25 51 SE 344558
(Whiteham Hill - 36 30 13 NE 4agber
Broadway - - | 33 3 55NW|]. 143396 | 513693
Stow on the Wold Epwell ; : 39 34 55 NE 530781
Shotover Hill - Cumner Hill - 76 58 3SW 40720g
Corley Hill - 6 6 NW } 673637
Epwell - - y 39 5 3
P Arbury Hill —- 48 5 23. NE 586288
: Crouch Hill ~~ - 39 20 49 NW 522584
Bull 5 sek J Quainten - = 61 40 13 NE 462648
Meridian of Greenwich.
eal ee } Wendover - { ee i é ae } 174338 100986
i f - aretinnge 6 46 : '
ae Hill x. } Bow Brickhill { a a 8 Me }rsrang 190493
i 2 - 85 8 30 NE
cpeekcwonn if } Kinsworth = - { ie 55 “ SE }rz0910 141gb2
Bow Brickhill - ; z 74 6 27 SE } 4
Kinsworth —- S lealiytae { 50 54 40 NE B4215 171367
neste z \ Lidlington - { 2 yee = } 121834 202802
Lae > Wee Taustecetal t= { &9 oe ak pigxars 1g01ss

KR

Trigonometrical Survey. 655

Art. xxx1. Latitudes and Longitudes of the Stations in the Sertes
of 1797 and 1798, referred to the Meridians of Black Down,
Butterton Hill, and St. Agnes Beacon.

Meridian of Black Down.

Longitude from | Longitude west of Greenwich,

Names of the Stations. Latitude. Black Do In degrees. Taine:
Va Cray) 7] oO 4 4 OM aire! mess

Moor Lynch - - Sie Das 21-1 OO nZO,0 Wil 2 7505s Al TT 2,6
Ash Beacon - - GIO 003855 42Gh'1! 26,4 EB] 2 30 56 10 357
Long Knoll - - FES*SO1D; 2, PORT 412843 LE} 2 7 545% g 11,6
Dundon - - SNHogIOnSS 6,5. kereiigo7 Wr 2 43 39st). PaoNg4s2
Mendip - - 5IOLZIO FB koi 0895.9 Hi 2'392 Oss | renvessg
Beacon Hill = - - GIXITG 2,6,)20049°206E|- 1 43 +158 6 5258
Westbury - - GESISOZ5 A Abohedi aH Eh 2) 8 °G,4 8 32,6
Farley Down = = 8102303574 QUE51I7,6 EF 2°17-14,8 9 8,9
Dundry - - ENIRG1O23052,2-110UR5 47,70W 2 98 Ost p tows alo
Lansdown ~ - §1027050,4. 0} 8'30,6E]. 2 23 51,8 9 3554

Mertdian of Butterton Hill.

, 5 Longitude from | Longitude west of Greenwich.
Names of the Stations. anaes: Butterton Hill, In degrees. In time.
A CoE a Oars ye Ly Oe Hal Me 5:
St. Stephen’s - - 502. O,7. 1 OU ZB So°GNVi al ei ae ta 2
Black Down - - 50 36 40,9 | 0 13 20,5Wi 4 6 8,0 | 16 24,5

Meridian of St. Agnes Beacon.

Winseote? tie Stations, atinasle, ep opeitude from | Longitude west of Greenwich.
t. AgnesBeacon.| In degrees. In time,
Ss me fo) a o , r] m. S$.
Trevose Head + - 5c 32 56,5 | o 11 155 BE -i5" oO Gaztiteo 356
Cadon Barrow - - | 50 39 12,1 | 0 30 46,5E| 4 41 9,2 | 18 44,6
Brown Willy - - 5° 35 27,9 | © 36 45,3 EE} 4 35 10,4] 18 20,6

4Pe

656 The Account of a

Art. xxxut. Latitudes and Longitudes of the Stations in the |
Series of 1799, referred to the Meridians of Dunnose and
Greenwich.

Meridian of Dunnose.

Longitude from | Longitude west of Greenwich.

Names of the Stations. Latitude. mehaats In degrees. Sn dime:
° 4 ° , 4 u m. Se
Nuffield = - - -~ | 51 34 52,2 |o g 39,9 E rt 56,1 “terogney 9
White Horse Hill - 51 34 31,6 |o 22 1,7W| 1 33 37.7 | © 1455
Stow onthe Wold -~ - 51 54 16,3 | 0 30 26,7W) 1 42 2,4 | 6 48,1
Broadway - - 52 1 25:6 | o 38 5,3W] 1 49 41,3 | 7 18,7
Brill - - - 51 49 56,6 |o 7 394E| 1 3 56, 4 1557
Scutchamfly - - | 51 33 44.1 |0 8 37 Wi] 1 20 13,0 | 5 20,8
Shotover Hill = - 51 45 6,7 |o 0 48,5E]| 1 10 47,5 | 4 4351
Whiteham Hill - - 151 46 15,4 |o 8 12,1W] 1-19 48,1 5 19,2
Cumner Hill - - | 51 44 155 |o 6 42,4W] 1 18 18,4 | § 13,2
Epwell - = - 52 4 19,8 |0 17 10,8W| 1 28 46,8 | 5 55,8
Corley Hill - = 51 50 2853 | o 9 39.9W] 1 21 15,9 | 5 2530
Arbury Hill = - - 52 13 26,6 |0 0 44,4W| 1 12 20,4 | 4 4953
Crouch Hill - - 52 2 58,7 |o 9g 35,0W| 1 21 11,6 | § 2457
Quainton - - 51°53 7.2 | 0 17-121 EB)" © 54 23,9 |~ 3 S75

Meridian of Greenwich.

Longitude west of Greenwich.

Names of the Stations. Latitude. In depres, Inte
Wendover - - 51 45 6.4 ° 46 14
Bow Brickhill —- E 51 59 50,5 | 0 40 152
Kinsworth : -— 51 51 50,8 | o 31 59,9
Lillyhoe = Se remnenrnt neil Vn BA BaF sO eA
Lidlington - - 52 1. 54;0 1 of 392 121.7

Trusler Hill - ° 51 59 48,0 | 0 34 50,5

Trigonometrical Survey. 657

Art. xxxi. Bearings of intersected Objects, from the Stations in
the Series of 1797 and 1798, from ibe Parallels to the Meridians
of Black Down, Butterton Hill, and St. Agnes Beacon; and

likewise their Distances from those Meridians.

: “Meridian of Black Down.

Distances Distances
from merid.| from perp.

Bearings from the Parallels to the Meridian.

es Se

At Moor Lynch. - sok tba Feet. ” Feet.
Walton Windmill - é 7512 31 SE 51340 156858
Westonzoyland Steeple - - 63 42 36 SW 46928 154235
Middlezoy Steeple - - 31 48 21 SW 79339 148733
Chedzoy Steeple -" - -| 85 18 45 NW 90459 |» 163658
Higham Windmill - - 29-57 17 SE 58858 140880
Higham Steeple = - - -|. 22 §1 39 SE 62691 142196
Bridgewater Spire - - 88 39 25 SW 104717 161280
Somerton Steeple - - 47 454 SE 41197 134292
Burton Pynsent Obelisk + - 10 35 4S W 78428 “| 122688
At Dundry. —
Puckle Steeple - - - 55 19 25 NE 26010: 292363
Westleigh Steeple - - 46 49 23 NE 23610 301818
Bristol Cathedral - - | 26.7 30 N-E 11836 279184:
Redcliff Steeple = - - 33. 832 NE 9407 278007:
Long Aston - - o 51 38 NW 21696 273385
Clifden Windmill - - - 952 50NE 19281 272172
Blaze Castle - - - | 149 16 NE [f° 20268 297874
Penpole Park Gazebo - -| 11 43 37 NW 28680 294155
Duke of Beaufort’s House, Stoke: 32 31 51 NE 651 294212
Durham Steeple -- - 63 28 33 NE 38049 289219
Knowle Steeple - - 13 41 30 NE 8112 314410
Mangotsfield Steeple - - 47 44 31 NE 13923 291677
Winterbown Steeple - - | 31 14 10 NE 7056 306569
Harfield Steeple - 2. 2a, 11 g NE 93478 292526
Leigh on Mendip ——- - 3359 55 SE 21483. 195794
Dundry Steeple - - -| 71 23 20S W 22831 259052
At Long Knoll.
Doulting Spire - - -| 68 59 5u NW 9544. 182322
' Frome Steeple - - 5 20 25 NW 52415 198272

At Farley Down.

Devizes Steeple - - 7951 30 SE 129342. 24.5113,
Cold Aston Steeple - - - 33 43 21 NW 44302 277983

658 The Account of a

‘

Meridian of Butterton Hill,

Distances

Bearings from the Parallels to the Mendin’ from mds aeeneal
At Furland. Pa ate Feet. Feet.
Hope’s Nose kak : 23 755 NE. 93759 18745
At St. Stephen’s. . a.
Werrington Steeple - - - 29 37 23 NE 109839 92242
Boyton Steeple - - - 6.55 35. NW 112767 106733
St. Stephen’s Steeple - | - 45 55 4SE 110738 85968
North Petherwin Steeple - -. |. 49 15 49 NW 125044 98473
At Carraton Hill,
Stokeclimsland Steeple - - 65.546 zNE 96381 49922
Launceston Steeple - - - 21,26 54 NE 108267 82689
Launceston Chapel - - 211413 NE 108513 | 82564

Meridian of St. Agnes Beacon.

At Bodmin.
St. Minvern Steeple - - 58 18 36 NW 79549 91845
St. Minvern Windmill - - 61 51 46 NW 90966 82260
At Trevose Head.
St. Isey Steeple - - Gls! 212 SE 68456 | 74082
St. Merian Steeple - Sa- 57.59 32 SE 52096 82476

Art. xxxiv. Bearings of intersected Objects, from the Stations in
the Series of 1799, from the Parallels to the Meridians of
Dunnose and Greenwich; and likewise their Distances from.
those Meridians.
| Meridian of Dunnose.

At Epwell.
Warwick Steeple - - - 16 25 48 NW 87242 607508
St. Martin’s, Coventry 2.342 NW 69c28 | 653327
Soleyhul Spire = - - - 31.3 35 NV 128826 654971

At Arbury Hill.
Dunchurch Windmill - - 23 55 48
Breadon Hill, Summer House - 37 an

NW 20724 — 626734 t
NW 26706 765038

Trigonometrical Survey. 659

; DE Distances Distances
Bearings from the Parallels to the Meridian. from merid.| from perp.

os

i OMe ake vir Feet Feet.

Markfield Windmill - - 5 20 7 NW 18608 75581g

Newnham Windmill - - = SG) 4a IN 2261 589244
At Corley Hill.

Gazebo, Breadon Hill — - - 35 45 58 SW 188086 525408
At Crouch Hill. :

Deddington Steeple ~ He 6 0. SE 28646 499771

Bloxhaina Spire - - 16 35 11 S W 39519 511110

Aynoe Steeple : - 49 26 2SE 11944 501goz

Adderbury Spire - - - 37 26 59 SE 26213 509671

Farthingo Steeple - - - | 56 26 49 SE 6431 502904

At Arbury Hill.

Round House, Edge Hills - 50 5 5 SW 57501 549724
Windmill, near the Round House 55 39 29 SW 58398 543286
At Brill.
Wingrove Steeple - - 80375 NE 103826 454713
-“Hardwick Steeple —_- - - #816, 1 NE. 83299 454687
Luggersal Steeple - - 44 56 1 NE 35106 449401
Granborough Steeple . - 53) tg 30 NB 70782 474574
Bicester Steeple - - - 43 27 16 NW 6854 466560
Marq. Buckingham’s House, Wooton] 79 17 25 NE 43490 445984
Islip Steeple - - - 84 26 3S W 8944 439540
Woodstock Steeple 2 - 85 25 45 NW 35563 448393
Kidlington Spire - - 88 29 39 SW 13401 441989
Witchwood Beacon 5 - 89 11 34 SW 76971 444726

At Whiteborse Hill.

Abingdon Spire - - 62 38 13 NE 19054 383037
Wallingtord Steeple - - 84 54 39 NE 17497 358560
Great Coxwell Windmill - - 25 45 11 NW 96959 376819
Drayton Steeple : _- - 67 28 o NE 24691 374055
Highworth Steeple - - 57 49 55 NW 116343 370003
Witney Spire - - = 14°14 57 NE 64.737 424386
Bampton Steeple - - - 4 36 29 NE 79056 408 334
Radley Steeple - - - 61-25 12 NE 12123 388578
Buckland Steeple - - - zo 812 NE 69616 388204
At Stow. >
Stow on the Wold Steeple - 20 55 25 NW 118442 479166
At Broadway. »
Sarsden Chapel - - - 52 29 “SSE 86195 469777 -
Bourton Chapel - - - > 4 54 36 35 SE 125636 501076
Walford Spire - - - j 92 3842 SE 92704 507924

660 The Account of a

Meridian of Greenwich.

Bearings from the Parallels to the Meridian. Petsagveart wea a.
-| from perp

At Wendover. we Pin Feet. Feet
Pitchcot Windmill —- - 19 11 59 NW 191077 149055
Ivinghoe Spire - - 45 44 37 NE 143127 131397
Quainton Steeple - - 3447 15 NW 205750 146203
Leighton Buzzard Spire - 2141 12NE 150616 160663

At Quainton.
Southern Obelisk, Stow Park = - 22 1 36NW 227554 204673
Northern Obelisk, ditto - 21 50 48 NW 228505 207532

’ At Kinsworth.
Aylesbury Spire - - 77 56 58 SW 190234 126763 »
Maulden Steeple - - 16 30 28NE 102962 202124
Harlington Steeple ~ - 16 12 37NE 110395 177730
Millbrook Steeple - - 3 ir 41-NE 117732 201645
Stretley Steeple =) ge 35 23 47 NE 99961 171044 ©
Sauldon Windmill - - 60 20 46 NW 178643 174431
At Bow Brickbill.
Hanslope Spire - - 38 58 48 NW 185668 232843
North Crawley Steeple - 941 15NE | 145529 224901
Pavenham Spire - 22 15 49NE 122215 261812
St. Paul’s Spire, Bedford. - 43 9 11NE 104408 240631
Sharnbrook Spire = We- 19 21 54NE 123533 269816
Woburn Market-House = 73 52 37SE 139255 186978
Ridgemont Station - - 7z 28 11 NE 130927 196964
Wootton Spire - - 41 33 7NE 120265 225635
Cranfield Spire - - 30 44 22 NE 136284 215933
Husborne Crawley Steeple - 65 44 5StNE 136827 197064
Woburn Steeple - - on 22° FSS E 139373 187394
Souldrope Spire - - 16 32 49 NE 124861 279861
Windmill near Tharfield - 86 612NE 12577 199950
Tottenhoe Station - - 27 42 7SE 130412 150494.
Chalgrave Steeple - ~ - 53 G11 SE 116215 164780
Keysoe Spire - - 31 17 59NE 95682 282155
Moulshoe Steeple - - 2 19 30 NW 152432 215608
Renhold Spire - - 44 56 16NE g1651 250385
Lidlington Windmill - 62 30 ONE 125855 203797
At Lillyboe. ‘ :

Knotting- Green Elm ‘Tree - 16 17 56NW 117482 285139
Ravensden Steeple == - 7 25 0.2N 95142 255 304.
Bow Brickhill Steeple - 73 20 18 NW 151490 19150

a4

Trigonometrical Survey. 661

Bearings from the Parallels to the Meridian. ; f Distances Distances
rom merid. | from perps«
ce oe Feet, Feet.
Colmworth Spire ¢ «. - o 12 52zNW 84580 268984
Sundon Windmill - - 75 0 6SW 109032 164718
Silsoe Steeple - - 26 9 25 NW 95501- 194345
Flitton Steeple - - 38 20 32 NW 102831 194903 -
Shillington Steeple - 749 43 NE 81919 188066
Westoning Steeple - ° 64 42 19 NW 113366 185143
Wrest-Garden Obelisk 2 26 26 83NW 94797 192652
_-Flitwick Steeple NG AER 57 11 27 NW 114694 | 191016
Ampthill Steeple - - ago 13 NW 109957 203041
St. Neot’s Steeple = - - 13 32 16NE 59630 273475
Pollux Hill Steeple - - 47 5 30NW 102236 188118

Art. xxxv. Latitudes and Longitudes of such Places, in the
Series of 1797 and 1798, as have been referred to the Meridians
of Black Down, Butterton Hill, and St. Agnes Beacon.

Bs ty 8-2 Meridian of Black Down. .
Names ofthe Objects: | tattude, | Hgnsinde fom | Longtnde wes of Greenwich
43, " Onna, O. 54, o 4 a m. 5S.

Walton Windmill - 51 6 59.5 | 0 13 22,1W| 2 45 44.5 | IL 2,9
Westonzoyland Steeple - 51 6 33,8 | 0 12.12,9W] 2 44 35,3] 10 58,3
Middlezoy Steeple - 5M 85.5003 | © 20 3858 W) 253 0.2) FL 32,5
Chedzoy Steeple = - - GIseSo. FsB h-O-23039337 W| .2 55-5 Oba old) 4957
Higham Windmill | - 51 4 21,8 | 0 15 18,6W] 2 47 41,0 | 11 10,7
Higham Steeple - 51 4 34,6 | 0 16 18,5 W| 2 48 40,9 | 11 14,7
Bridgewater Spire - 51 7 40,7 |.0. 27. 16,3W!| 2 59 38,7 | 11 58,6
Somerton Steeple §t 3.1753 | O 10 42,7W) 2 43 551 | 10. 52,3
Burton Pynsent Obelisk. - 51 1 21,6 | O 20 22,7W] 2 52 45,1 | 11 31

Westleigh Steeple - 51 30 49.4 | 0 6 12,0E}] 2 26 10,4] 9 44,7
Bristol Cathedral - ST 27 Ome 93 O.27M). 2351 28,4 [eto\2d,9
Redcliff Steeple —- - 51 26 54,8 | 0 2 28,0W) 2 34 50,4 | 10 19,3
Long Aston - - 52 26..0,8 fo. 5 ig WP YO! 98 457° Y- re" 42,2
Clifden Windmill - 5h cheers One te W) 62 87 257 | 10. 20,7
Blaze Castle = - - ("| 5% gO 1o,@ | O° G 16,3 W| 2 37 41,7 |. 10 30,8
Penpole Gazebo - SY 293937 | O07 37 9 S457 16 39,6
Duke of Beanfort’s House, Stoke] 51 29 34,5 | 0 © 10,2H| 2 32 12,2 | 19 8,8
Durham Steeple - - 51 28 44,8 | 0 9 59,0E| 2 22.23,4 | g 29,5
Knowle Steeple - - BY- 325 4y7— Oo —2---7,9 WI ~2-34-30r3 -|- 10-18 -
Mangotsfield Steeple - EL 206.9% ko. 3 392 2 28 43:2 | 9 54,8
Winterbown Steeple - So gn 636.4. p@OR 52,2H | 2 30. 3%,2 tol 251
Harfield Steeple - - 51 29 15,3 | 0 24 32,2W) 2 56 54,6 | 11 47,6
Leigh. Steeple on Mendip 51 13 24, ,0 5 36,3E]-2 26 46,1 9 4751
Dundry Steeple - bl 23 47,7 |O °5 58.8W]- 2 38 21,2 | £0) 33,4

MDCCC. "4.9

662

The Account of a

Names of the Objects. Latitude.

Doulting Spire = - - 5 Lit 1154
Devizes Steeple - 51 21 25,5
Frome Steeple - - 51 13 4759
Cold Aston -— - 51 26 53,9
Puckle Steeple - | 51 29 -16,z

Longitude from | Longitude west of Greenwich.

Black Down. In degrees.

° 4 a“ ae a”

© 2 29,3 E] .2 29 ggst!
O 33 51,2 E|] 2 58 31,2

© 13 40,8 E] z 18 41,6
O11 38,0E} 2 20 44,4 |
0 649,6E{ 2

Meridian of Butterton Hill.

25 32,3 |

es
9 42,2

Names of Objects. Latitude.
Hope’s Nose, Torbay _- 50. 27 48; 5
Werrington Steeple 2 50 39 52,2
Boyton Steeple - - | 50 42 14,9
North Petherwin - 50.40 52,5
St. Stephen’s Steeple - 50 38 50,3
Stokeclimsland Steeple - 50 32 55,8
Launceston Steeple - 50 38 18,1
Launceston Castle - 50 38 16,8

Longitude from | Longitude west of Greenwich.

Butterton Hill.

26 44 E
28 19,4 W
z9 6,1W
32 15,3 W
28 32,6W
24. 47,5 W
27 5441 W
27 57.9 W

000000000

In degrees.

° UJ ”

3 26 43,1
421 6,9
4 21 53,6
4 25 2,8

4 21 20,1 |

4°77 35:2
4 20 41,6

- 4 20 454

Meridian of St. Agnes Beacon.

Names of Objects. _ Latitude.
St. Minvern Steeple - 50 33 30,6
St. Minvern Windmill - 5° 31 5555
St. Isey Steeple - 50 30 36,0
St. Merian Steeple - 5° 31 5953

Longitude from | Longitude west of Greenwich,

St. Agnes Beacon.

20 28,1 E
23 23.5 E
17 36,6 E
13 23,8 E

oaooo0o°o

In degrees.

er | a
4 51 27,6
4 48 32,2
4 54 2051
4 58 31,9

In time.

m. s.

19 25,8
19 14,3
19 3723

19 54st

Art. xxxvi. Latitudes and Longitudes of such Places, in the
Series of 1799, as have been referred to the Meridians of

Dunnose and Greenwich.’

Meridian of Dunnose.

Names of Objects. Latitude.

° ‘ a
Warwick Steeple - 52 16 53,0
St. Martin’s Spire, Coventry | 52 24 25,4
Soleyhull Spire - - 52 2 30,4
Dunchurch Windmill —- 52 20 4,6

Longitude from | Longitude west of Greenwich.

Dunnose.

es

18 29,5 W

34 13,8 W
5 32.5 W

00000

4a
23 18,3 W)-

In degrees. —

In time.

aA s.
19,6
6 03

9 353-
5 8,6

Meridian of Greenwich.

Trigonometrical Survey. 663
a 5 ongitude Longitude west Of Greenwich.
Manitecr Objects. Latitude, fibre Sunni2: Ue dastees, In time.
Pius 7) oP os 7] ° 1 " m. S.
Gazebo, Bardon Hill* - 52 42 47,6 |}o 7 12,2W| 1 18 48,2 5 15,2
Markfield Windmill - - | 5241 16,8 }o 5 1,0W| 1 16 37,0 5 6,5
Breadon Hill Building ¢ - 52 £36.70 40 50,7 W| 2-29 9557; 8 6,4
Newnham Windmill - 52 13 55.7 | 0 Oo 36,2E| 1 10 59,8 4.4359
Deddington Steeple - - | 51 59-13.9 |0 7 36,1 W| 1 Ig 12,1 5 16,8
Bloxham Spire - 34 520.5 6 sa 10: 2g G22) 1557 5 28,4
Aynoe Steeple - - 51 59 3552 | 0 3 10,2W! 1 14 46,2 4 59>%
Adderbury Spire - | Se AGtsRo led O-" 339 Willi 27 30,7 5 10,6
Farthingo Steeple — - 51 59 4551 | O 1 42,4W) 1 13 18,4 2 a 4
Round House, Edge Hills 52 7 25,6 | 0 15 18,4 Wi 1 26 54,4 5 47,6
Round House Windmill - 5207114. 50 Th 3256 W) wm 27048; 5 48,6
Wingrove Steeple - gr 51 46,8 | 0 27 28,7E| 0 44 7,3 2 5655
Hardwick Steeple _—- - | 51 51 47,8 | 0 22 2,6E] 0 49 3354 3 18,2
Luggersal Steeple, Bucks FEeQOes7sawhinS eo n7.2 B | o2imhays Ai 2
Granborough Steeple - ~| 51 55 4:3 | 0 18 45,2E] 0 52 50,8 73154.
Bicester Steeple = - = | 51 53 46,8 |}o 1: 48,9E] 1 9 47,1 4 39.1
Abingdon Spire - -| 510% 3,8 )0 5 -1,2W] 216 3752 S655
Wallingford Steeple - 51 36 2,4 10 4 36,2E|-1 6 59,8 4 2739
Great, Coxwell Windmill 51°38 59,8 | 0 25 32,4 W| 1 37 8,4 6 28,5
Drayton Steeple - - | 51 38 35 ° 30,1 W) 1 18 6,1 5 12,4
Highworth Steeple - 51 37 51,4 | 0 30 38,1 W) 1 42 14,1 6 48,9
Witney Spire - - 51 46 49,9 | 0 17 6,9 W] 1 28 42,9 5 54,8
Bampton Steeple - - | 51 44 11,2 | 0 20 51,9 W| 1 32 27,9 6 9,8
Radley Steeple L SE 0058.3 .0-0 3t 6754 WI) tag agin 6 54,2
Buckland Steeple - ~ | 5% 40/5953 (| O 18 21,1 W] i 29 57,811 115 59,8
Witchwood Beacon - 151 50 9,8 | O 20 21,6W| 1 31 57,6 6 7,8
Stow on the Wold - - | 51 55 46,9 | 0 31 23,6 W] 1 42 59,6 6 5159
Sarsden Chapel = - 51 54 16,4 | 0 22 49,9 W] 1 34 25,9 17,7
Bourton Chapel = = - | 51 59 22,5 | 0 33-2057 WI 1 44 56,7 6 59,8
Walford Spire - - 52 0.9830 a 26 12,5 W] 1:37 4855 6 31,2
Islip Steeple - - 51 49 20,7 | 0 2 21,9 W| 1 13 5759 4 55,8
Woodstock Steeple - 51 50 47,4 | 0 9g 24,5 Wl] 1 21 O 5 24
Kidlington Spire = -| 51 49 44,0 | 0 4 51,9W| 1 16 27,9 pane

Longitude west of Greenwich.

Names of Objects. Latitude. In degrees. enititat

" “ . CS as para amt acai alana TMs... Ss
Pitchcot Windmill - - | 51 52 5855 © 50 3555 3) 2254
Ivinghoe Spire - - 151 50 gpI O 37 555240 2 Sikes
‘Quainton Steeple - 51 52 28,7 | © 54 28,0 3.3728
Southern Obelisk, Stow Park | 52 2 2,2 b O 27,5 f 4 ise
Northern Obelisk, ditto - 50 2 30,2 1 © 42,9 | 4, 2,8

* In page 658, this is, by mistake, called Breadon Hill Summer House.
+ In page 659, this building is called Gazebo.

4.Q 2

664,

Names of Objects.

Leighton Buzzard Spire
Aylesbury Spire -
Hanslope Spire - -

North Crawley Spire -

Pavenham Spire -
St. Paul’s Spire, Bedford
Sharnbrook Spire -
Woburn Market-House
Woburn Steeple -
Ridgemont Station -
Wootton Steeple -
Cranfield Spire -

Husborne Crawley Steeple

Souldrope Spire -
Windmill near Tharfield
Tottenhoe Station -

Chalgrave Steeple -

Keysoe Spire -
Moulshoe Steeple
Renhold Spire -

Lidlington Windmill -

Maulden Steeple -
Harlington Steeple =
Millbrook Steeple -
Stretley Steeple -
Sauldon Windmill -

Knotting-Green Elm Tree

Ravensden Steeple -
Bow Brickhill Steeple
Colmworth Spire -

Sundon Windmill =

Silsoe Steeple -.
Flitton Steeple -
Shillington Steeple -
Westoning Steeple = -
Wrest-Garden Obelisk

’ Flitwick Steeple 7

Ampthill Steeple —-
St. Neot’s Steeple -
Pollux Hill Steeple ~

eee a

The Account of a

Latitude.

—

2 5 I

- 52

In degrees,

G& 0.0 © O«8 0-'O'O"0"0' 00" 6" 0' O06" 0-0 6'0 OO 0 00 0 0 O'0 000 06 OC Os

Longitude west of Grecnwich,

In time.

He NED EE DE NORD HNN NDE NNONDHHRNNKHNHKHKHODDHE

Ss.
39,6
23,2
17,2
3495
8
529
11,2
279
2Z

aN
See
af

Eeotu
“SI coo ©

Trigonometrical Survey. 665

Arr. xxxvit, Latitudes and Longitudes of some remarkable Places,
not contained in the preceding Tables.

St. Nicholas’s or Drake’s Island, in Plymouth Sound.

_ The bearing of Kit Hill, from the meridian of Butterton, is
67° 12’ 12”, and the angle between it and the flagstaff on
Drake’s Island, 41° 40 8”; therefore, the bearing of the latter
from the meridian is 71° 7’ 40”; consequently, its distance from
the meridian is 60591 feet, and from the perpendicular 20692
feet, which respectively subtend 9’ 53'’6, and 3' 24,5. These,
with the latitude and longitude of Butterton, 50° 24/ 46,3
and 3° 52’ 47",5, give 50° 21’ 21",1 for the latitude, and 4° 8’
17,9 for the longitude, of the flagstaff on Drake’s Island.

The latitude and longitude of this spot was determined by
Mr. Bay ey, in the year 1792. The observations for the former
were as follows :

BBO 1°90" 24 'SBVPEE.
50 21 90,5 ditto.
50 21 31 ~~ ditto.
50 21 29) a@ Aquilz.
50 21 26,5 « Ophiuchi.
50 21 55 ©’suu. The mean of these is 50°21'28", 5.

The place chosen by Mr. Bay ey, as I have been lately in-
formed, was a few feet northward of the staff; therefore, 7”, 4,
may be taken for the true difference between our determinations,

The longitude of Mr. BayLey’s. station, found by the moon’s
transit, was 4° 18’ 52"; but* the longitude deduced from the
recent operations, is 4° 8’17”,9; there is, therefore, a difference:
of 10’ 34,1 between the two determinations.

666 The Account of a

St. Andrew’s or the Old Church, at Plymouth.

The angle at Butterton, between the Old Church tower and
Kit Hill, is 37° 45' 5,2; its bearing, therefore, south-west from —
the meridian, is 75° 1’ 56”; consequently, its distance from the
meridian is 57505 feet, and from the perpendicular 1 5374 feet.
These Buses ie subtend 9! 24)", and 9! go",1: hence, its ati-
tude becomes 50° 22’ 19”,6, and longitude 4° 7’ 31”, hes 16%
3o’,1 in time, west of Greenwich.

As it is of very great importance that the truths of the con-
clusions given in this Work should receive support, wherever
I can find it, I think it right to mention the result of his
Excellency the Count de Brunu’s endeavours to ascertain the
longitude of Plymouth, by means of chronometers.. The fol-
lowing is a copy of his communication, made in the year 1795-

Journey from Plymouth to London.

Green Timekeeper.
June 8th, Mr. Mupce’s clock* at Plymouth, fast for mean time 0” 32',15

1783. "1 Timekeeper faster than Mr. Mupe#’s clock - 0 25,6

bye { Timekeeper slower than London clock - 14 29 94

40+ 4 London clock slow for mean time - - © 36.5
Difference of longitude - 16 3,65

Blue Timekeeper.

June 8th, Mr, Mupcs’s clock at Plymouth, fast for mean time 0” 32°,15

| Timekeeper faster than Mr. Mupcsx’s clock - 0 37,44

byte { Timekeeper slower than London clock - 14 17,2
. {London clock slow for mean time - - © 3655
Difference of longitude - 16 3425

Mean difference - - 16 3355

The longitude of St. Paul’s, west of Greenwich, is 23°; 1 in

* Itis, perhaps, right to observe, that Mr. T. Mupce’s transit, at Pisuouti. was
made by the late Mr. Brrp, and properly set up between stone pillars. The clock, the
entire work of his own hands, was a most excellent one.

~

Trigonometrical Survey. 667

time; and Mr. DutTon’s house in Fleet-street is about 2° west
of St. Paul’s ;* wherefore, its longitude west of Greenwich is
25°: consequently, 16" 95,55 + 25° = 16" 28,55, is the dif-
ference of longitude between Greenwich and Plymouth, as
shewn by the timekeepers.

Now the meridian of Mr. Mupce’s transit-room, at Plymouth,
passed only 35 feet to the eastward of the centre of St. Andrew’s
Tower, his northern meridian mark being on the church itself;
therefore, the longitude of the church and transit-room may be
considered the same. From the survey, we find it to be
16" 30°,1; and, from Count Bruut’s determination, making a
just allowance for the difference of longitude between the late
Mr. DuttTon’s house and Greenwich, 16™ 28°,5.

It is left for the public, and this learned Society in parti-
cular, to determine how far the near agreement of these several
methods, tends to corroborate the assertion I have advanced, of
the dependence which may be placed on the deductions drawn
from the observations made at Beachy Head and Dunnose. If
there had been-only one watch employed on the occasion, the
result would not have been so satisfactory as the circumstance
of two being used seems to make it. As the occasion calls for
the remark, before I dismiss this article, I must observe, that
the highest advantages would accrue to geography, were the
ideas of the Astronomer Royal carried into execution, (and which
I shall endeavour to do at some future period,) respecting the
discovery of the difference of longitude between Greenwich
and some very remote point on the western side of the island,
(St. David’s Head for instance,) by means of timekeepers,

* According to Horwoop’s Mapof London, the distance from the centre of St. Paul’s
to Bolt Court, at the corner of which Mr. Durron’s house is situated, is 31 chains.

668 _ The Account of a

carried backwards and forwards in the mail coaches. If this
excellent scheme were executed, and the watches employed
equal to the best now made, it is probable that the true diffe-
rence of longitude would shortly be determined. The geodetical
situation of St. David’s Head will, ere long, be ascertained from
a prosecution of the survey : a knowledge, therefore, of its true
longitude would be attended with eminent advantages.

Lizard Light- Houses.

The light-houses on this head-land were observed from Per-
tinney and Karnbonellis. At the latter, Pertinney bears 74,
22' 41" south-west, from the parallel to the meridian of St.
Agnes; and, as the angle between the western light-house and
Pertinney is 78° 40! 5”, it follows, that the bearing of the light-
house from the said parallel is 4° 17’ 24/’ south-east. Computing
with this angle and the distance from Karnbonellis to the light-
house, we get 3344, feet, and 126499 feet, for the distances of
that object from the meridian and perpendicular of St. Agnes:
therefore, admitting the length of the degree in the meridian, in
the middle point between St. Agnes and, the light-house, to be
60850 fathoms, and 61182 for the length of a degree of a great
circle perpendicular to it, we get 20’ 47,4, and g2”,8, for the
small arcs which those spaces respectively subtend. These
data, with the latitude and longitude of St. Agnes, 50° 18’ -
27”, and 5° 11' 55”57, give the latitude of the light-house=
40° 57' 44’, and longitude west of Greenwich 5 Ly 4", 8, in
time, 207 4.45,3.
This light-house was also observed from the station on
Karnminnis. The triangle resulting from that observation,
together with the angle at Karnbonellis, is

Trigonometrical Survey. 669

Karnminnis ay erigde 946"

Karnbonellis - - 98 1 go

Western Light-house 37 48 44; which gives 81342
feet, for the distance between the station Karnbonellis and the
Light-house. This distance is said, in the Philosophical Trans-
actions for 1797, p. 501, to be 81948 feet, which differs only
6 feet from the above determination ; but it is. probable the dis-
tance first given is most correct, as the two light-houses appear-
ing nearly in the same line at Karnminnis, was the means of
preventing us from clearly distinguishing the apex of either,
and it was principally on this account that we preferred the ob-
_ servation made at Pertinney. The agreement however proves,
hat no inconsistency can be found to obtain with respect to the
data before given, for settling the situation of this important
headland.

In the Philosophical eiheapcons for 1797, page 502, it is:
mentioned, that the distance from the spot where the late Mr..
BraDLEy made his observations, to the place where his meridian
mark was fixed, was 800 feet. But there appears to be some in-
consistency in this particular; as Mr. BRADLEy’s own words, in.
an extract of a letter now before me, are, zt was just 480 feet.
Adding to this, 24, feet, the distance between the place of the
meridian mark and the line joining the centre of the light-
houses, we get the distance of the point O, or the place of the
_ Observatory, (see Phil. Trans. 1797, p. 502,) from the line join-
ing the light-houses W, E, = 504 feet; a space corresponding
to 5” of latitude, nearly ; therefore, from the trigonometrical.
operations, we get,

ay Se ' Pees | a
as be i * is Pe ve longitude £of Mr. BRADLEY’S station.
MDCCC. 4R

670 The Account of a

Mr. BraDLey’s observations for finding the latitude, were
made with a quadrant of one foot radius, the workmanship of
Mr. Birp; they were as follows.
Nine meridional altitudes of the sun’s limb, the

extreme results of which were 49° 57 27",5 and

49 57' 44’, gave for the latitude of the Obser- i

vatory . < 49° 57 35"
Six meridional observations of the Pole Star be- |

-low the Pole, the extreme results of which were

49° 57' 35" and 49° 57' 20,4, gave for the la-

titude ~ - - - 49 57 23,2
Thirteen observations of Arcturus, « Coronz Bo- |

realis, and « Serpentis, the extreme results of

which were 49° 57! 54,7 and 49° 57’ 2",7, gave

for the latitude - - - 49 57 29
Fifteen observations of «, @, » Draconis, the ex-

treme results of which were 49° 57‘ 22”,2 and

49° 57°27, gave for the latitude - AQ 57 33

The mean of which is - 49 57 30

According to the trigonometrical operations, the latitude is
49° 57’ 44’; there is, therefore, a difference of 14’ between the
results ; a quantity so large as justly to excite surprise, if it were
not generally understood, that much dependance cannot be
placed on observations made with an astronomical quadrant
precisely similar to that made use of by Mr. Braptey. The
extreme results in the above, differ so widely as to authorise the
truth of the supposition on this occasion. —

The longitude of the Lizard was determined by the transit
of Venus, Sun’s eclipse, transit of the Moon, and two emersions

Trigonometrical Survey. 671

of Jupiter’s first satellite, as particularly set forth in the Preface
to the Nautical Ephemeris of 1791. The conclusions were as
follows:

Four transits of ou Moon, lau by Mr. xs

gave for the longitude - - 20" 30 ,6
Two emersions of Jupiter’s first satellite, calculated
by ditto : ‘ i 4 21 14 65

{Doctor MASKELYNE 20 57 ,O
ee of Venus, calculated by¢ Mr. WiTcHELL - 20 56 ,5

racer - dyi2© §7is0
Mr. WITCHELL = 20 44 55
Mr. SEJOUR = 20 45 51
Mr. EuLER - 20 59 ,0
Mr. LEXxEL - 20 51,0

Sun’s eclipse, calculated by |

Mean of the whole - 20 52 ,12

From the trigonometrical operations, we find the longitude
in time to be 20” 4,4°,3 ; there is, therefore, a difference of 7°,82
between these different determinations: this is, probably, as
near as we could have expected to find it; yet it can scarcely
be supposed, that of this difference, more than 2° can be laid to
the account of the survey.

In the Philosophical Transactions for 1797, p. 502, it is ob-
served, that angles were taken at the Lizard Light-house and
Naval Signal-Staff, to determine the situation of the Poznt it-
self. This Point, marked P in the diagram, makes an angle
of 2° 23’ 16” S W, with the parallel to the meridian of St. Agnes
at the station on Karnbonellis, and is therefore 636,6 feet
from that meridian, and 126394, feet from the perpendicular;

therefore 49° 57' 40,6 is the latitude . ,
and 5 11 46 the longitude es ae

4R 2

679 The Account of a

Scilly Islands...

To determine the distances of the objects in these islands,
from the stations near the Land’s End, with sufficient accuracy,
proper corrections were made for reducing the horizontal angles
to those formed by the chords. On the present occasion, it will
be right to use the horizontal, and not the chord angles ;' the
distances from the meridians, and from their perpendiculars,
being computed on the supposition of the earth’s surface being a
plane, which, within the limits of our fixed meridians, may be
considered as true.

The angles for finding the distances of these objects are given
in the Philosophical Transactions for 1797, p. 503; from whence,
and the data contained in this Work, we get the bearing of
the Day-mark in the Island of | St. Buryan 75° 44/ 52" SW

cme Pertinney , 71 14 22 SW
St. Martin’s from - ether eo os Ww

which, combined with the distances of the stations from the
meridian of St. Agnes, give

2G Ioe ee for the distance of the Day-mark from the

246804, «ae .
246821 meridian of St. Agnes ;

and 122409
122410 pfeet, for the distance of it sian the perpendiaulas,
1224.14,

The mean of the first is 246809 feet, and the mean of the last
122411 feet; but the latter becomes 122419, because a line
drawn from the Day-mark, perpendicular to the meridian of
St. Agnes, cuts that meridian eight feet below the parallel.

Again, we get the bearing of

the Windmill - - - in the Island of St. f Povagres, - 65°32' 307 SW
the Flagstaff of the Fort Mary, from Pertinney - 6653 5 SW

Trigonometrical Survey. 673

from whence, after a similar correction with that just made, we
find the distance of _

the Windmill 256304 | feet from. the f 143597 | feet from the perpendicular of
the Flagstaff 260152 f. meridian, and | 140876 f . St. Agnes.

From the same page, and the data fonnhed in this work,
we'also find the bearing of .
St. Agnes Light-fSennen - 68°6' 54'°S W

House from .. |St. Buryan, 69 § 56 SW; which gives
265865 | |

265879 Veet, for the distance from ae meridian, and

Fas oa fleet for the distance from the perpendicular of St. Agnes.

The mean of the first is 265872 feet, and the mean of the last,
when corrected, 149139 feet.
With the above data, and also the latitude and longitude of

St. Vd we get
- Day-mark in St..Martin’s. ~ ' 49°58’ 2",9
Windmill, St. Mary’s —- - 49:54 3257
) Flagstaff, ditto.» -. - 49°54 59.1
_ St. Agnes pis Eiouse - - 49.53 36,8

the labile of -

In Time.
_¢ 6° 14' 38",8 , 24™58°,6

and longitude west J’ Windmill 5 ~~ 3,2: ge thecmieric 6 416 58737) 25% <7 “9
from St. Agnes. | Flagstaff 16 2,7. ‘wich. fers, G17; S7 od 25 Ul. oD
Light House 1 7 27; 7 4 6 19234 25 20 55

Dayemark _ 1° 2’ 43751

sd is the Requisite Tables, published By order of the Board of Longitude, the lati-
tude of the Scilly Lights is said to be 49" 56’0", and longitude 6° 460". The
latitude, Acordes to the survey, is 49° 53' 36,8, and longitude 6° 19'23°,4. An
error of 2' 23” in the latitude, may not perhaps be considered extraordinary; but
how, in a maritime Poewleoe like our own, where chronometers are in such constant use,
so great an error-as 26’ 37" (1™ 46° in time) in the longitude, should have remained
undetected, excepting by one person, is surprising. J. Huppart, Esq. visited the
Scilly Isles, having with him a watch made by Arnotp, and obtained his time at
that spot in the island of St. Mary where the body of Sir Ctoupstey SHovEL
is said to have been thrown ashore, by means of equal altitudes of the Sun’s limb;
he then found, comparing his time with that shewn by the watch, that ot 2 5™ 18° was
the difference between the meridians of Greenwich and this spot in St. Mary’s. Now
St. Agnes Light-house is about 2’ of adegree west of the place to which Mr. Huppart
alludes ; therefore, 25/18” + 8” ='25'26" is the longitude of St. Agnes, through these
means; which differs only 4',5 in time from that found by the survey.

674, The Account of a

The Observatory of bis Grace the Duke of Matorover, at
Blenheim.

The staff erected over the quadrant, was observed from
White Horse Hill and Whiteham Hill. At the former station,
the latter makes an angle of 36° 30' 13”,5, with the parallel to
the meridian of Dunnose. The staff, therefore, bears from the
parallel 25° 59’ 29”,75 NE.; consequently, its distance from the
meridian of Dunnose is 36540 feet, and from the perpendicular
4,464.58 feet. These respectively subtend 5’ 58’,3, and 1°13’21”,4;
therefore, the latitude of the Observatory is 51° 50’ 28”,3, and its
longitude 9’ 39”,9 from Dunnose: but 1°11’ 36” is the longitude
of that station; therefore, 1° 21’ 15”,9, or 5’ 25,2 in time, is the
longitude of the Observatory west from Greenwich.

As the meridian of Dunnose passes at no great distance from
that of Blenheim, I have deduced the latitude and longitude from
the former, to avoid the errors which creep in, when computa-
tions are carried on from remote meridians. It may be worth
while, however, to show that the extent of those errors would
not be great, were the meridian of Dunnose neglected, and
- the Observatory at Blenheim referred to the meridian of
Greenwich, _

The distance of White Horse Hill from the meridian of Green-
wich is found to be 356050 feet, and from. its perpendicular
39425 feet; the bearing of Nuffield, from the parallel at that
station, being 89° 59’ 27” SE. Blenheim will, therefore, be found
to bear 26° 55'95” NE from the parallel at White Horse Hill;
consequently, its distance from the meridian of Greenwich is
307204, feet, and from its perpendicular 135569 feet. These
give the arcs 50’ 19”,4, and 22’ 16”,1; from. whence we get
51° 50’ 28,1 for the latitude, and 1° 21’ 16” for the longitude,

Trigonometrical Survey. 675

of the Observatory west of Greenwich. Either of these deter-
minations may be taken for the true result, but I shall prefer
2 Sa
Being favoured by his Grace with the latitude and longitude
derived from astronomical observations, we have the following
comparisons : ;
Degrees. Time.

“2, 4. f observed 51°50! 24,9 Longitude west {1° 21’ 6",0 5™ 24%,4
Tatiride Sa SI 50 28 51 from Greenwich. 1 211559 5 25 51

'

Observatory at Oxford.

The angle at the station on Shotover, between the Atlas on
the top of the Observatory and the parallel to the meridian of
Dunnose, is 79° 50’ 51”,75 N W: therefore, its distance from
the meridian is 14,719 feet, and from the perpendicular 416985
feet. The figure representing Atlas is 33 3 feet due east of the
Quadrant Room; consequently, no correction will be required
in the computed latitude. The space 14719 feet subtends an arc
= 2’ 24"’,3, and 416985 feet an arc of 1° 8’ 30’,8._ These data,
with the latitude and longitude of Dunnose, give 51° 45’ 38”
for the latitude, and 1° 15’ 29”,2 for the longitude, of the Obser-
vatory. As in the former case, with respect to Blenheim, so in
the present instance, it is immaterial whether the calculations
be carried on from the meridian of Greenwich or that of Dun-
nose, as differences of only o”,1 in both the latitude and longitude
are found in the results.

The latitude and longitude of this Observatory are given in
the Requisite Tables; the first is 51° 45’ 38”, and the last
1° 15' 30", or 5™ 2° in time. Doctor Hornsspy, however, has
furnished me with what he conceives to be more accurate

676 The Account of a
determinations ; from which, and the above, we have the follow-
ing comparisons : :

Degrees. Time.
Latitide “(oad fy do ka eee a a
2 -L1 15 29 52 5 ia %1s9
I conclude this article with expressing an opinion, that the
coincidence between the computed and, no doubt, accurately
observed longitude of this Observatory, affords strong reason
for supposing, that the operations at Beachy Head and Dunnose,
in 1794, for finding the length of a degree of a great circle
perpendicular to the meridian on the earth’s surface, were made
with the required accuracy.

SECTION THIRD.

Trigonometrical Surveys of the Northern and Western Parts of
Kent, the County of Essex, and Parts of the. adjoining Counties,

Suffolk and Hertford, executed in the Years 1798 and 1799.

(See Plate XXXII. )

It will be convenient to treat of the operations carried on in

the north of Kent and Essex, before we speak of those executed

in the western parts of the former county.
In a former article I have observed, that from the old station
at Wrotham, (General Roy’s,) the view towards the north is ob-
structed, and also that it became necessary to select a new one:
this station was found to be 205,5 feet from the other; the dis-
tance was accurately measured, and afterwards the. angle taken
at the old station, between the staff on Severndroog Tower,

Trigonometrical Survey. . 674
Shooters Hill, and the one newly chosen; this angle subtended
94 19' 0",5.

The distance from Severndroog Tower to the old station at
Wrotham, is 79960 feet. But, it must be observed, this dis-
tance is not precisely the same as that given by General Roy,
because an allowance is made for the error in the reduction of
the bases, in the surveys of 1787 and 1788.

With the distances 79960 feet and 20,5 feet, and the included
angle, 94° 19’ 0”,5, we find the distance of the Flag-staff on
Severndroog Tower, from the new station = 79944, feet; with
this distance, a part of the AG triangles have their sides

computed.
ART. XXXVIII. ‘Principal Triangles.

Names of stations. Observed angles. } / Distances of the stations.

Onn Feet
Wrotham - - 62 54 33 ( 45578
Gravesend - - 82 spi2trloi »>Gravesend = -
Severndroog Tower | 71762
Gravesend : - 95 53 59 44886
Langdon Hill sa 8y i, ma) 54 47 125 »p Langdon Hill - 7
Severndroog Tower. 88470
Gravesend - - BAe BIRR 64076
Hadleigh Steeple - ALT eaten Steeple -
Langdon Hill - - 37171
Gravesend - -- 3° 24 19—21 44839
Hadleigh F 7 it 46 233 pHalstow Steeple - { 34004,
Halstow = - x 107 49. 5— 6

a ee

44 27959057 wie ) ;

Gravesend. oh Rte 31 48 bt aoe
Haltom ne LAG2! x. \eeplegth g Or Mea co. {
Gadshill’ ; ,

Halstow - ere ‘ 59 18 6 — { 49409
Hadleigh Steeple - 49 13 ee 3] }shep ey ~ Mtoe 64387"
Sheppey Isle - - 31 28 24 —23

MDCCC. 4.8

678 | The Account of a

The distances of Gadshill from Halstow, and from Halstow to the Isle of Sheppey, in
the following triangle, viz.

Halstow 128 34 28

Sheppey 18 18 3

Gadsbill give the distances between Gadshill and the station
in the Isle of Sheppey 70687 and 70685 feet: the mean, 70686 feet, may be taken for
the true distance. ,

Names of stations. Observed Distances.
angles.
’ 4 of & ;
Hadleigh - - 38 43 29 ; 27596
Southend - - 11g 20 5] pSouthend = - - -
Sheppey | - 46204

To find the distance between Langdon Hill and the spindle of the weather-cock on
Rayleigh Steeple, we have the following quadrilateral.
Langdon Hill 122° 2! 46"
Gravesend © 64 56 14

Halstow © III 20 14 ne

Rayleigh - 61 40 46

360 0 o,which gives the distance from the centre of
Rayleigh Steeple to the staff on Langdon Hill = 44131 feet; but the point on the top -

of Rayleigh Tower, over which the instrument was placed, was just 7 feet farther from ,

Langdon Hill than the: spindle; therefore, 44131 -+ 7 = 44138 feet, is the distance

between Langdon Hill and the station on the steeple.—The angles in the following tri-

angles,
Hadleigh - 134° 11' 55,”

Sheppey 16 26 30
Langdon Hill

Langdon Hill 4D 8 ake
Sheppey - 27 4 46

Rayleigh give the distance of a.

the Spindle on Rayleigh Tower from ; roa Hill re er 2 1 rec

From the preceding quadrilateral, the distance between the spindle on Rayleigh’ Tower
and the station on Langdon Hill, was found = 44131 feet, which is the same as the
other determination. :

Ww

7&8

‘ Trigonometrical Survey. 679,

Names of stations, 1 Observed’ Distances,

angles.
OF ie i E Feet
Halstow + eRe? 2 95 46 § \ spindle c } ; 49413
Sheppey - - | 42 6 39 73313
Rayleigh Tower Spindle
Halstow - - - 35 18 . 46820
Hadleigh 3 7 - ag--gtig i Prittlewell = - - j 27206
Prittlewell Steeple
i as Se i Prittlewell - - j qoez3
Sheppey = hatte 55 24 34 51243
Prittlewell
Halstow —s - - 73 2 71201
Shenneae fos = 6% ‘ Canewden = - - ; 74461
Canewden Steeple
Rayleigh - - - G2 5, tO 31438
Prittlewell = - Spree | 7341 30 angyees " y 26189
Canewden
Hadleigh = - Saas 52 52 24 51846
Halstow - - - | 86 10 13 age te ” } 34060
Flagstaff of the Garrison, .
_ Sheerness
Severndroog Tower - - 17 48 23 . 404.23
Gravesend = - - 20 22 40 = easeo/ See eons 35498
Purfleet Cliff - - -~ |I4t 48 57
. 180 0 Oo
Ragliee |) - ee 97 7 27 ; 2 47514
Langdon Hill - - 43 18 2 aay I 68746
Danbury Spire
Severndroog Tower = - - | 26 24 33. = 103659
Langdon Hill - - . 95 25 0 tenn j A ; 46312
Frierning Steeple - - 58 10 27 |
Langdon Hill - 2 88 14. 19 : 46314
Frierning = tie = 44 13 19 | -Frierning - *
Rayleigh : 63270

45 2

680 . The Account of a.

Mean distance from Langdon Hill to Frierning Steeple 46313 feet.

Observed Distances,

angles.

on Feet.

Frierning etn mee 92 15---6 49020
Langdon Hill - - 45 26 17 | Danbury ' bi { 68748
Danbury Steeple
Langdon Hill - - 24 297-23 p 83902
Rayleigh == - |132 52 23 } Signal aa a { 47408
Signal Staff, Shoehune ness
Triptree, old station - - | 47 850
Rayleigh - = - | 73 45,24
Frierning i ;
Triptree, old station, from | roe Rewer iq re th x: 43
Triptree - - - 31 59 21
Danbury - ie 124 20 48
Rayleigh

Danbury Spire from Triptree Heath 36000
Triptree, old station - Ico 28 19
Tillingham Steeple - - | 30 14 40
Danbury. Spire

Titngham fom Peewee - = | stage

Tillingham = - 84 52 34 | 42469
Peldon - - - 62 39 36| -Peldon - -
Danbury ene -
Tillingham - - - 148 58.
Peldon - 83 42

Flagstaff on St. Osytb ine

Peldon - - = 20°49

Thorp - - | 32 47 af
Flagstaff, St. Osyth Priory -
Peldon - - - ; {

Thorp - - ~

Stoke Steeple
Peldon = - - 71 48 20 43475
Great Tey - - - {75 51 12 | pGreat Tey - -

Danbury - - . 77204

Trigonometrical Survey. 681

Names of the Stations. Observed __ Distances,

angles.
- PM A 4: 1 6 Feet. ‘
Peldon - - - P AGL TAN Z a { 3941*
Great Tey = - - -| 9056 9 } Stoke hi 4 46182

: Stoke

From a former triangle, the distance between Peldon and Stoke Steeple was found to be
63931 feet; wherefore, 63936 feet, the mean, may be taken for the true distance.

Thorp - - z

20481
Little Bentley - - Little Bentley -
Dover-Court-. - - 42981

Thorp - - - 41 12 53
Little Bentley - - {123 30 18 | -Little Bentley -
Peldon - = = ; 51205
Tillingham - - g6 57 20 28924
Danbury Spire - - 61 46 57 } West 4 ae a { 79173
West. Mersea , :
Rayleigh == Be - (| 54 27 44 96701
West Mersea - - 29 13. © | -West Mersea -
Danbury - - - ie : 79170
nS ERR 1 NAR 2 AN i en a tera mt oe a am
Great Tey - - 52 11 44 .
Stoke - - - A5 12 57
Staircase, St. Mary’s Steeple, Col-
chester

St. Mary’s Steeple from Stoke —— = = - 36796-
Little Bromley - - GA Likes 44356
Stoke - - - 47 58 26 | Little Bromley —- “
St. Mary’s, Colchester - 33706
Dover Court - os 18 58 I9 } . . 38946
Stoke . 2 z 1453 50 Tattingstone - fn { e260
Tattingstone j
Thorp 5 a - - 27 ea 49 . o6g0
StoRacte Pre : Baler i }Tattingstone - { ed
Tatting stone
ne ee eee
Dover Court - - 50 26 54 J 1651
Rushmere - ° -" 1538,.25 120 }Palkenham i { Som

Falkenbam Steeple

The distance from Dover Court Steeple to Stoke Steeple is 84425 feet, and from Rush-
mere Steeple to Stoke Steeple 75955 feet ; the included angle at Dover Court Steeple is 62°
38°20". These give the distance of Dover Court Steeple from Rushmere, 50921 feet.

682 - The Account of a

Names of Stations, Observed Distances.
‘ _ angles. 4
D c t ; ° t nf a Ae
over Cour - - 43 40 51 . m 39949
Rusienes , 5 Be Tattingstone 35232

Tatting stone

Dover Court = = sal fig 13 a
Rushmere a ok “ 3 30 1 Woodbridge - ;

Woodbridge Steeple - =| 57°397

Falkenham~ - er 41 25 50 : 33761
Rushmere - - | 58 0 10 Bvondbrmge : } 26342*
Woodbridge
:
Falkenham - - - 48 42 0 2 45013
Woodbridge - - - 83 10 oO } Butley : } 34058
Butley Steeple ’
Falkenham - - - 21 58 1 . 60589
Buoy i m ” ~ 1516 14159 1 orford Light House - } 25207
Orford Light Hous .
Rushmere_ = : - 62 45 1 - 29238
Woodbridge = = - = | 63 30 1-0 + ottey ” ; | 2g044

Otley Steeple - - -

Rushmere - = = | 40 25 30 i

“rover.

Otley - = - - | 46 2570 Hime) ® ki } 18988
Henley Steeple emia O51. 923°

180 0 0
Dover Court - = - 12 43 40 |?) Obelisk 4 ae 26766 ‘i
Rushmere —« - - | 13 22 10 | 4 i (25503),
Obelisk, Woolverstone Park
Rushmere - -" - 61 35 58 28984
Copdock Steeple - - 153 5 10 | pCopdock - - tho Vaca
Obelisk a 28057
Rushmere - = - 85 25 oO a 21209
Copdock = - + - | 37 46 © i eal ae 34520
Henley = - - 56 49 oO | ea

Trigonometrical Survey. 683

Names of Stations. Observed Distances,
" angles,
H | 7 . 4 ‘ 4
enley - - > 58 32 42—40
Copdock = - - 74. 30 LI—10 | Naughton y x
Naughton Steeple - - | 46 $7 11=10

Naughton - - 7h Al 2

Stoke - p - | 45 58 58 Lavenham -

Lavenham Steeple - EQ) 37 mao

i ie tao ee A oh

Lavenham - - - 67 48 30 30837
Stoke Pi asters - | 44 59 10 panes os } 4
Bulmer Steeple 67 12 20

poceulere sey sz te ss) Glemsford - 25746
Bulmer - - = 27086

Glemsford Steeple

Lavenham - - 18 22 0
Bulmer - - - |142 15 20
To pplesfield

Lavenham - - - 51 36 4o
Stoke - = SASSO. (SVS
pe Steeple

Stoke - + - 50 4 48
Great Tey - - - 56 15 56
Twinestead

Frierning a - 156 42 10,
Danbury > VP TS gO FO
Souibweald Steeple

Danbury = - - 1g1 18 36
Triptree, old Station - - | 12 © 34
Gallywood Common. =) - 0 oho O
Triptree, old Station = 37 41 44
Gallywood =- = aay eae
Plesbley Steeple Di
Danbury - - es

Gallywood - - 3

Plesbley

Gallywood - - 15 45 30
Pleshley - - |114°49 0
High Easter Steeple

684 The Account of a

= eee

Names of stations. Observed } Distancessisei2 to somevl
angles.

[enema

Feet.

Danbury = : neg Fe Scop
Plushies iS 3 _ AZ £39 | } Hatfield Broad Oak - tbh

39058

Hatfield Broad Oak Steeple vi

Danbury - - - 20 nc.
High Easter - - 29 43 54

}rhaxted - - { 101330
Thaxted Spire

53429

Hatfield Broad Oak - 54.20 51
Pleshley - - 39.25 oO

} Beauchamp Roding - { 24853:
Beauchamp Roding Spire

31806

The angle observed from the station on Danbury Steeple, between Hatfield Broad
Oak and Thaxted, was 30° 33’ 40”; this, with the including sides, 85094 and 101330
feet, gives the following triangle :

Danbury - 302133 40"

Hatfield Broad Oak g2 24 0

Thaxted - 57. 2 20,which gives the distance between Thaxted
and Hatfield Broad Oak = 51566 feet.

Danbury - - - 27 24 19 sabe
Peldon = - - 118 2 28 } Stoke : = 6395"
Stoke

Again, the angle observed at Danbury, between Thaxted and Stoke was 66° 43 3;
this, with the sides which form it, ra pee and Thaxted, Danbury and she gives the
following triangle:

Danbury - 66° 43' 8"

Stoke - OMNAB 25116 a oat

Thaxted oh Gar er 36, from atl we find 124430 mira for the dis.
tance from Thaxted to Stoke.

The angle at Lavenham Steeple, between Stoke and Thaxted, was likewise observed, ,
and found to be 89° 10’ 30", which, with the distances of these latter. stations, from
Lavenham, 48039 and 124430 feet, gives
Lavenham = - 89° 10' 30” Pi H wet 09 a Ss
Stoke = = 6817.4 oben’ ae est
Thaxted - 22 42) 80, from which we find 11 5480 feet to be e the

distance from Thaxted Spire to Lavenham Steeple. " | : dat ‘"q ;

i 4 A , +. Vi

Trigonometrical Survey. 685

The angle at Danbury, between Southweald and Hatfield Broad Oak, was found to be
54° 44 30". The distances from Danbury to Southweald and Hatfield Broad Oak have
been already found, the former being 77622 feet, and the latter 85096 feet ; from these
we get the triangle,

Danbury” - 54° 44! 30"
Southweald - 67 42 5
Hatfield Broad Oak 57 33 25, which gives 75104 feet, for the
distance between Hatfield Broad Oak and Southweald Steeples.

In order to connect the preceding triangles with those carried on for the survey of the
south-western part of Essex, and of Hertfordshire, stations were selected on Hampstead
Heath, and on Highbeech in Epping Forest, to which the great theodolite was taken, as
related in the article detailing the particulars of the operations in 1799. The triangles
making this connection are the following. The first, namely,

Severndroog Tower 28° 58' 10”

Southweald - 9449 5

Langdon Hill - 56 12 45, is had from the included angle
at Severndroog Tower, 28° 58’ 10”, and the sides Severndroog Tower and Southweald,
Severndroog Tower and Langdon Hill: the first is 73787 feet, and the second 88470 feet.
From these data, we obtain the distance between the station on Langdon Hill and that on
Southweald Steeple = 43001 feet.

Names of Stations. Observed Distances.

angles.

P F = O; eet Feet.

everndroog Tower - 24 24 35 a 73553*
Langdon Hill - cli ch NagasGr an \ Brentwood { 36016
Brentwood Steeple
Severndroog Tower - 4 33 29 78553*
Southweald - - aa tie) } Brentwood 7” { 7706
Brentwood :

Foot of the cross on the dome of St. Paul’s from the station on Severndroog Tower 39962".
Phil. Trans. for 1787. p. 250.

Severndroog Tower - 53539 4 . 71534
St.Paul’s - 2 - | 51 24 12 } Highbeech oi { 61919

Highbeech

Severndroog Tower - 44 34 28 , *
Highbeech = - - - | 69 53 13 }southweald Fe { ee

Southweald

MDCCC, es

686 The Account of a

From the last triangle, we find the distance from Severndroog ‘Tower to the station on
Southweald Steeple to be 73795 feet; this, it will be perceived, is deduced from the
distance between the cross on the dome of ‘St. Paul’s and Severndroog Tower; but
73791 feet has been found by the triangle, which is derived from the distance between the
latter station and Wrotham. A difference of 4 feet on such a distance, all things consi-
dered, is not a large quantity. : 3 ute

Names of Stations. . ' Observed : Distances. etre
Angles.
Severndroog T 5 8 'r ly | ogecee
everndroog Tower - 4 I ‘8558*
Highbeech - - - on 16 44 ep a i A! ¥ { be
Breniwood Spire 3
Severndroog Tower - RIP Zqriziy 6485
Highbeech bs ? -| 58 29 19 } Hampstead Heath - { “3 424
Hampstead Heath
Highbeech - - -| 24 36 5 roa 6181
Hampstead - - 4|- 33 ei 1 Ta hse. ae I x { » 25966
St. Paul’s ; wie.

As it became necessary to ascertain the situation of a high building near Berkhamstead,
which, for distinction sake, I shall style the Gazebo, the instrument was removed from
the station on Highbeech, to another farther west of it, as some trees obstructed the view
of this object from the former. To get the distance from St. Paul’s to this new station,
the distance between it and the old one was measured, and found = 460 feet: the angles
in the following triangle were also observed. - — 2

Highbeech, old station 66° 32° 47”

Highbeech, new station 113-3 46° 5

St. Paul’s __ which gives the distance from
St. Paul’s to the new station 61738 feet. Ce"

— ———

Highbeech, new station == 105 21 44 | - moat 49631
Berkhamstead Gazebo - Ar og "2b" -A@azepO * ~ ee
St. Pauls - . f 88872
- - 4o \ , M _
Sovuthweald - + - 16 46 15 ; ba So 46717
Highbeech, old station - 52 16 51 } Bpping Bondi d { 17042*
Siand of Epping Windmill : eae:
Severndroog Tower S: 10 68 44 |, A eg : 81891
Highbeech - - - {122 10 45 }pping Windonlll ‘. ( 17043*
Siand of Epping Windmill

Trigonometrical Survey. 687

Names of Stations. | Observed ~ Bs Distances.
angles. _ :
i a | OL ap ey Feet.
Highbeech, old station - 99 19 16 }Eppin z Windwill i : bee

Berkhamstead Gazebo - 17°41 25
Stand of Epping Windmill

At the new station on Highbeech, the angle between the staff on the Gazebo
at Berkhamstead and the old station was observed, and found to be 141? 45 50".
This angle, with the measured distance between the stations, and also the distance
from the Gazebo to the new station, which are respectively 460° and 49628 feet, gives
49987 feet, for the distance between the new station on Highbeech and Berkhamstead
Gazebo.

Hatfield Broad Oak Steeple - [59 1 0 87140
Berkhamstead Gazebo - 43.12 50 | Hatfield Broad Oak = 60219
Epping Windmill - Pineeositba

¥

Berkhamstead Gazebo - 249 55 4 3917
Hatfield Broad Oak = - = =«|:'17 19 38 }Naseing i: . { epi

Naseing Steeple

Hatfield Broad Oak - 107 3 § bdo 26
Berkhamstead Gazebo - 20 i 14 |} Henham See aoe { ace
Henbam on the Mount Steeple

Hatfield Broad Oak © - FI 28» 242
Henham onthe Mount - 36 6 x } Thorley X 7 { file
Thorley Steeple

Henham on the Mount - B5ei25 0 882
Thorley Steeple _—- - | 69 33 0 j} Atterbury ¥ r { te
Atterbury Steeple wie

Henham on the Mount - 87°20 0 anya: 17816
Thorley ©. - - = 24.57 50 }Rickling 7 i { 42169
Rickling Steeple
Henham on the Mount - 20-54-05 527
Rickling - - 146 35 0 }Bmdon . . { see
Elmdon Steeple

4 Te

688 The Account of a

The angle between Albury and Elmdon Steeples was observed, at Henham on the
Mount, and found to be 72° 47' 38’. The distances from the former stations to the
latter are 37882 and 45275 feet, which give the following triangle : -

Henham - hw 47' 38”
Albury - 60 28 27
Elmdon - = 46 43 35, from whence we get ae distance
between Albury and Elmdon = 49701 feet.

) of Tat?

Names of Stations. Observed Distances.
angles.

h h 6 30: se 988
Henham on the Mount - 106 30 50 , 2298
Elmdon 3 - - -| 23 2 40 }rhaxted - { 56302
Thaxted Steeple
Elmdon~ - - - 71 54 10 } A 55262
Thaxted - - - | 53 28 44 Babee . { 65504
Balsham Steeple

Elmdon - - - 43559
Balsham - - - 23255
Babrabam Mouni Station

Elmdon - S ~ 29 46 30 y : wf a { 24.806
Babraham Mount - - =| 32 56 30} it plow 29185
Triplow Steeple

~The angle at Henham on the Mount, between Hatfield Broad Oak and Thaxted Steeples,
is 109° 10° 44”; and the distances of the latter stations from the former one are 39266

and 22988 feet ; from these data we have the triangle, ts
pate Henham = = - = ~— 409° 10’ 44"
Thaxted - - 45 56 29

Hatfield Broad Oak - 24 52 47, which gives 51608 feet for

the distance of Thaxted from Hatfield Broad Oak.

Hatfield Broad Oak - = 51 24858 4
Beauchamp Roding - - | 64 i; a | Nan Raitt nine (| 44h
High Easter Steeple et
Severndroog Tower - =" 23 - f | 50989
Langdon Hill » - - 24 10 20 9 | | Hornchur ee a (| 44832*
Hornchurch Steeple

Langdon Hill - - - 177 57 33 44837”
Gravesend s+ - =} 50.59 © Hortichurch " { 56438

Hornchurch Steeple

Trigonometrical Survey. 689

Observed Distances.

angles.

Names of Stations.

a —

See tee Se ee vetoes | ener ee

a os, he Feet.

Gravesen - - - 24. 32 30 : 4 35517
Hornchurch - é 3 Zi 26,22 } Purfleet Cliff { 23282
Purfleet Cliff Station

Severndroog Tower - - 39 44 2 . 25383
Hornchurch - - | 27 16 44 } Barking o w 35404

Staircase of Barking Steeple

Severndroog Tower. = = | 39 41 fe 28046
St, Paul’s - - = - 144 15 27 > |} Westham m = { 25662
Westham Steeple

ArT. xxx1x. Secondary Triangles.

St. Paul’s from Severndroog Tower 39962 feet.
Severndroog Tower - Beer ee | { 26371
St. Paul’s - - - - | 22 36 4 } Limehouse ‘ 15456
Limehouse Steeple
Severndroog Dongs - - 9 15 30 . : 2 57757
Highbeech - - - | 32 36 38 } Chigwell { 17242
Chigwell Steeple
Severndroog Tower = - - | 11.57.\,6.) Low. bite IOOILO
Prierning =) = - | 74 34 30 } Billericay y { 21506
Billericay Chapel
Westham Steeple - - 45 58 o 15640
Staircase of Barking Steeple - | 68 35 0 } Station 7 % { 12077
Station on Bank of the Thames
Station on Bank of the Thames f 41 21 131Z0
Westham Steeple - - 56 15 t10 S| pPerry SSS SE { 10424
Perry's Mast House
Hornchurch — - - 14 3% 20 33236
Staircase of Barking Steeple 68 52 ¢ | } Chimney i { 9005
Chimney of Public House at Bark-

ing Creek

Purfleet Cliff - - -154 57 0 21002
Hornchurch - - 46 40 © }Guzzard y . { 23638

Guzzard Station

Ggo The Account of a

Names of Stations. Observed

angles.

Distances,

o ¢ a
34 11 30
gz) o

Purfleet Cliff - - -
Hornchurch - = =
Rainham Steeple

}Rainham -

Purfleet Cliff == - - | 81 9 o . 16212
Hornchurch - | 31 50 50 }ReWvidere : a ( 30369
Lord Page, S, Belvidere

Purfleet Cliff - - 42 18 30 10971
Rainham - | 41 45 0 } cold a ae { 11090
Station at Cold Eaybour : :
Guzzard - - - 56 8 20 . 21436
Hornchurch - - - | 56 43 20 } Aveley Ml a 4 { 21302
Aveley Mill

Purfleet Cliff = - - - | 34 2 40 3630
Hornchurch E = | os 37140 } Valence ae " { —
Valence Tree :

Gravesend ° - - 79 39 30 17008
Severndroog Tower = - | 13 41 10 } Chadwell -, i 70717
Chadwell Steeple @
Gravesend. - - - 35 39 0 18479
Chadwell Steeple a a | 79 31 20 Ree J * { 10953
Greys Steeple ,
Gravesend - - - 37 46 oO ; | 22880 |
Chadwell Steeple - 94 24 0 ee ae —— { 14054
Flagstaff on Mr. Button’s s Bowe

Gravesend - - - fist 43hh0
Chadwell Steeple - - 80 2 30 } west Thurrock - {

West Thurrock Steeple

Gravesend - “ 49 8 30 gajaet®
Hornchurch 2 - 136 7 5 } Horndon - 2 { as,
Horndon Spire

Gravesend - - - | 18 52 o :

Chadwell = - - 59 26 30 } West Tilbury me { 14956
West Tilbury Steeple

Gravesend ia - | 69 31 27] 7 8955
Chadwell - - - 30 27 42 } Northfeet 7 ° { 16179

Northflect Steeple

Trigonometrical Survey. 691

Names of Statione. Observed Distances.
angles.

fe) 1 7] , ae
Gravesend = = as 57 16 0 Py 2 { 1632
Chadwell = = 59 13 30 } Base Tilbury 159387
East Tilbury Flagstaff .
Chadwell - : - 51 23 0 + iy ‘ " { 26526
Mr. Button’s Flagstaff = - g5 22 gor } Station x 20031
Station near Ockendon =
Mr. Button’s Flagstaff - | 54.20 30 }orset a hae { 17360
Station near Ockendon - 54 54 3° 17240
Orset Steeple
Gravesend - - 45 9 13 . ae , {| 41433
Halstow —_- = 2 62 a 1@ [fe PPE L| 33270
Fobbing Steeple
Hadleigh Station ——- 65 31 12 \ 5 ‘ ” { 26221
Halstow - - - 45 48 50 popes 33279
Fobbing Steeple
Halstow - = 10I 39 27 Be { 41342
Guneead - 37° 10 ho j Thundersley
Thundersley Steeple -
Halstow ~—— — | 7 53 10 } ; " ¥ { 5713
Hadleigh - - 117 13 23 eich 37028

Hadleigh Spire - =

‘ Hadleigh =} - 89 20 40 } oR { 15735
Halstow | to - 24 54 27 pesh fi N 37357
Leigh Steeple itease -
Halstow - - 74. 23 37359
Sheppey Station - 42 a °3 } Leigh P 7 { 53325
Leigh Steeple Staircase
Halstow - - IBA 45 41434.
Sheppey 46 5 47 j ehgervess ; { 13063

Sheerness Fort F ectage

Hadleigh | }south Church | -

eppey
South Church Steeple

Hadleigh | = ¥, weed Be sf Joes
Sheppey Station 2 80 16 46 } Pritelewel ae {

’ Prittlewell Steeple

692 The Account of a

Names of Stations. Observed . Distances. —
angles.
Canewden Steepl 15 gO 38:
anewden Steeple : 45 50 0 : a { 23850
Prittlewell == 60 46 30 } Lite i Manes 19003 .

Little Wakering Steeple

Prittlewell = e s
Bank Flagstaff

Prittlewell - 5

Station on Bank
Shoebury-ness

Canewden - : 32 51 30 35481 |
Bank Flagstaff —- a 81 20 0 }Foul-ness : o- { 19473
Foul-ness Chapel

fe: si Le } Shoebury-ness - {

Canewden A « |

Rayleigh - - 47 28 6 ‘ 71622 ©
Peldon \ ‘ 43 45 33 } signal Staff -« - { “baad
Foul-ness Signal Staf

Tillingham Steeple - 139 21 10 ‘ e { 13990
Peldon - 9 44 29 } Signal Staff 5gROe.)
Signal Staff, Filing bam Ga

Tillincham - c 43 27 58 } : 5 f 18802
Peldow - 24 10 18 Signal Staff 31591
Signal Staff, Bi aiwell Point

Tillingham - - 31 2 40 fl eo
Peldon 2 m 100 56 20 } Brightlingsea
Brightlingsea Steeple

Tillingham - < 39 48 40 } 2
West Mersey Steeple = 57 33 33 Tolesbury

Tolesbury Steeple

nae | ee eee ee |

Tillingham - é 63a5h 16 } ud : { 31946
Triptree, old Station - ete a Althors Z 49330
Altborn Church én

Tillingham - -
Althorn - - “
Burnham Steeple

\ " 3
j Burnham {

Peldon 3 ts 56 33 25 }Toleshunt

Tolesbunt Major Steeple

Trigonometrical Survey. 692

Observed
angles.

Names of stations. Distances.

ees mene, | A en | a ES YE SS SE

ont; Feet
Prittlewell Steeple - 33 10 21208
Bank Flagstaff - - 39 20 SignaliStaff_ - ‘ 18302
Signal Staff; Shoebury-ness
Triptree, new Station = 38.05) 18 19425
Danbury - - - jo. 1 27 } Maldon i 7 ; 23829
Maldon Spire
Triptree, new Station - 36 48 30 36118
Danbury - - - 2 @ Purleigh yi p: j 22734
Purleigh Steeple
Danbury Pr: - =
Purleigh Steeple -
Steple Steeple
Danbury - - e
Canewden - - Fr 8.46 \ Hockley ; 23555
Hockley Steeple
Danbury - mY haa 27.21) 50 41400
Rettenden - - - [0g 22 0 | Hockley e z } rotGe

Hockley Steeple

Danbury - = 3
Canewden - ~
_ Rettenaen Steeple

Rettenden =
Canewden

Bait & | Stow, St. Mary’s = } 2500s
Stow, St. Mary’s ‘Steeple

Joma 4 O

Rayleigh - - - FSD 18 20760
Langdon Station - ~ = 27 38 45 bRettenden i tf } 126
Rettenden Steeple

Rayleigh - : - 51.8) td 2120
Langdon - - 28 10 20 Runwell 2 i } aie
Runwell Steeple

Danbury - - - 48 57 22 : 2
Rayleigh - 72 39 17 oe Fier ; yes
Great. Burgbstead Steeple

Danbury - - - II . 666
Gallywood Station - He 40 ie \ Hanningfield 2 { 24843
East Hanning field Steeple

MDCCC. A, U

694 The Account of a

Names of stations. Observed Distances,
angles.
Frierning Steep! 6 "7 4 6826
rierning Steeple - - 36 7 48 1682
Danbury - - - 15 38 36 BES : 36793
Stock Steeple
Triptree, old Station - 18 38 11 55°75
Tillingham Steeple - 83 33 14 17711
Southminster Steeple
Peldon Steeple - - 7 ace ot 20180
Tillingham - 23 54 4 j pie poe y 49369
Layer Marney Steeple
Peldon - - - 80 20 6 : 60701
Tillingham 61 39 24 t signal ae : } 67990
Signal Staff, St. Osyth Point
Thorp Steeple 2 a: 143.1 75 20 21517
Little Bentley - 18 54 29 + signal pra ¥ 39344
Great Clackton Signal Staff
Thorp - © - DPS BE BS 18920
Peldon - - 16 58 13 SEES EOS: i ; 61508
Great Clackton Steeple
Dover Court Steeple - 24 36 48 38998
Thorp - - os gz 26 41 IEE Fr . 16257
Finton Steeple ;
Dover Court - - 39 16 34 : : 34686
Thorp - 70 11 16 SRE CEE 23340
Finton Signal Stafe
Dover Court - - 53 15 26 ? 26275
Thorp - - - 47 52.22 ies 28389
Walton Tower or Sea-mark
Dover Court - - 133 57 30 : F ¢ ; 15085
Thorp _ - - 13 29 57 | § ~uPOM 46517
Cupola, Verndeuard Fort :
Thorp - - - 46 16 17 ; : 7 7 { 47494
Peldon - - - 47 1 34 ee 46901
Ardleigh Steeple ‘5
Peldon - - 106 10 16 ‘ 7 35433
Great Tey Steeple - 32 32 11 } Prating 3 { 63274

Frating Steeple

Trigonometrical Survey. 695

Names of Stations.” AEN A Distances,
angles.
oer ET ee
Thorp - - - 30, 1m7" 45'S au 23390
Little Bentley Steeple - go 41 23 pSetmupren 12053

Thorrington Steeple

Dover Court - - 22 10 12
‘Thorp - = c 59 48 37
Kirby Steeple

Little Oakley -

Dover Court - - 33
Kirby Steeple - - 18
Little Oakley Steeple

Layer de la Hay Steeple = - 45 2
Toleshunt Major Steeple

Dover Court - -
Tattingstone Steeple - -
Brantham Steeple

Dover Court - - | 70) 520 58
2

; 19946
Rushmere Steeple - - | 16 51 Blanlstead a 35319
Harkstead Steeple
Dover Court - - 33 17 30 13053
Tattingstone Sent aes -|14 20 0 Arwarton i ‘ ; 28941
Arwarton Steeple
Tattingstone - - - | 66 10 o 20998
Arwarton Steeple - - | 43.12 0 Bene ik (- ; 28059
Bradfield Steeple
Dover Court - - 72 48 50 : 8881
Rushmere : - - 9 58 0 amc 3 f ; 49036
Harwich Spire
Dover Court - - 56 48 20 57475
Rushmere - - - | 67 58 30 Hollesley y ji j 51881
Hollesley Steeple
Dover Court - - 47. 7 40 t 3%. 52205
Rushmere - - - | 68 4 20 HS . j 41224
Shottisbam Steeple
Dover Court - - 65.59 785 61
Rushmere - : - | 52 42.10 } Bawdsey = " / fou
Bawdsey Steeple

¢

696 The Account of a
Names of Stations. ele Distances,

: 4 ae
Dover Court - - 52 48 i a ¥ sé ou 289
Woodbridge Steeple - 28 31 Felixstow 48262
Felixstow Signal Staff
Dover Court - - 45. 12-155 } . 42265
Woodbridge - - 4453 0 BUGS] 42510

Bawdsey Signal Staff

Rushmere - - - |, AS Aa 5, J ti 75267
Falkenham Steeple - 1037'"'52) 10 orford 55472
Orford Steeple

Woodbridge - - 28 29 110 a { 21686
Butely Steeple - - 34° 37) 10 J} Rendlesham 18204
Rendlesham Steeple

Butely - - - 15323 0 a { 15762
Rendlesham - - IZ 209 j Orford 33057
Orford Steeple

Dover Court - - 8 2616 i f { > 7371
Rushmere - o 1 664) 10 | Kesgrave 48505
Kesgrave Steeple

Dover Court - - 34 14 16 } Pe 7 { 45360
Rushmere - - - | 62 15 50 a Saveucie 28841
Waldring field Steeple

Dover Court - - 30 58:10 } ‘ { 40331
Kesgrave Steeple - - | 56 8.30 pine tad 24993
Whertstead Steeple

Falkenham - - -| 30 59 0 } c ~ { 25098
Rushmere - - = *1°36"-" 2) 50 ALE 21959
Nacton Steeple

Dover Court - - 13 29 58] 1 = a {| 55220
Stoke a - : ZZ 45 20 yes: L| 33325
Capel Steeple

Stoke - ° - 24 14 18 . A { 40790
Capel Steeple - LTO3 0, 44. hepa 17186
Hintlesham Steeple

Stoke - - - 29 43°10 . i? ; 42238
Lavenham Steeple - - ¥'6r'31 40 ee 23821

Bildestone Steeple

Trigonometrical Survey. 697

Names of Stations. ey Distances.

iss Hey , ‘i z Feet,
Stoke - - - 33 53 40 ; 4 ‘ . j 32055
Bildestone Steeple - - | 48 50 10 algbai 23746
Aldham Steeple
Lavenham - - =. || 20.99) 50 : , is } 42673
Naughton - - 93 17 20 Hadleigh 21154
Hadleigh Spire :
Layenham - - - | 31 40 10 : a i | 25138
Naughton Steeple - 42 21 50 \ Lindsey 19537
Lindsey Steeple
Stoke - - - 23-7 30 : :, } 27153
Lavenham - - - | 24 48 40 ewpon 25413
Newton Steeple
Stoke - - - 27 14 10 " E 19660
Newton - - - |42 49 0 + Groton j 13140

Grotton Steeple.

Bulmer Steeple - Lo 67 27 4o . i j 25637
Glemsford Steeple - = 1°53 37150 } Waldingfild 29407
Walding field Steeple
Lavenham - : - 56 59 Oo 7 a j 14065
Glemsford - - 33) 850 Acton 21097
Acton Steeple
Lavenham = Z - | 26 13 10 ]2 41546
Bulmer - gi 21 20 | § Peaemp : ; 18360
Beauchamp Church, St. Poul?s
Lavenham - - 12.30 150 F 59359
Topplesfield Steeple - 27 20 Hedingham Castle } 16316 -
High western part aged ban :
Castle i |
Lavenham - - - | 26° 57%0 : 4 62325
Bulmer - - 123 32 © | Ridgew a4 ‘ } 33886
Ridgewell Steeple
Stoke Steeple - - IOl 57 15 sa si 17904
Nauzhton Steeple - ZO 22) 45 } Langham ™ { 49907
Langham Steeple :
Stoke Steeple - - 21 17 20 : 13615
Great Tey Steeple - - 8 23 40 } Great Boy) { 33859

Great Horksley Steeple

.

698 The Account of a

Names of Stations. - Observed Distances.
angles.

Stoke - - - 71 21

Twinestead Steeple - 19 53

Great Horksley Steeple

Stoke - - - 44. 24

Great Horksley - ~ 109 43

Mount Bures Steeple

Stoke = - = 62 30 40 ‘ ks 47756
St. Mary’s, Colchester - 70 48 oO Eatles (Colne 44860

Earles Colne Steeple

Great Tey - = - | 24 47 20 : re 21357
St. Mary’s Colchester - 23° 148 10 BY of Bexpholt ; 16339
West Bergholt Steeple ij

Danbury - - i 6 6° 0 pe mr 41358
Great Tey - - -| 6 56 40 Brajied 36349

Brazxted Steeple

Braxted Steeple > - 11 43 36

10407
Kelvedon Steeple

Great Tey - - - | 30 14 50 . Bes 3 223g0
Kelvedon - - - | 58 32 0 Messing 13223
Messing Steeple

Great Te - - - | 51 43 10 p 15462
Kavedon - - -| 36 4 0 Het lier 20616
East Thorp Steeple

Danbury - - - 50 48 o : 51487
Triptree, new station =~ 85 12 30 BESO 40039

Black Notley Steeple

{

t

{
ie
gale - - )egeliuee

;

{

Danbury - - 23 51 34 : a a

Triptree, old station - - 177 29 26 MRSS 14852
Witham Steeple

Danbury - _— - . 47 47 25 : i 31874
Triptree, old station - 58 17 35 Tne 27751
Tarling Spire

Danbury - - - 51 43. 0 : si . 58918
Triptree, old station - go 45 50 Braise 46252

Braintree Steeple

Trigonometrical Survey. 699

Names of Stations. ie a
. “ Qo 1 “
Triptree, new station ° 56 13 54
Gallywood station - - | 64 47 51
Feltstead Steeple
Danbury - - - 26 31 30
Feltstead Steeple - - | 73 49 10
Braintree Steeple
Danbury - - -
Pleshley Steeple - -

Feltstead Steeple

Triptree, new station + 274.23020
Danbury - 27, 35530

S. Spire of Hatfield Pever el Abbey

Pleshley -
Feltstead -
Great Leigh Steeple

Danbury = 4l 29 44
Pleshley - i6 39 0
Great Baddow Steeple

Danbury - - 23 59
Pleshley - - - 20 21
Chelm ford Spire

Danbury - - 32 38 36
Pleshley - - - 4l 51 20
Whittle Steeple

Danbury - - 19 16 20
Hatfield Broad Oak - 35 29 15
Willingale Spain Steeple

Pleshley - - - 36.1250
Gallywood station - 26.14 36
Roxwell Steeple

Pleshley - - » 103 44 45

Gallywood station = - | 34 9 50

White Roding Steeple

Southweald Steeple - 27 51 51
Frierning Steeple - - { 30 14 50
Doddinghurst Steeple

Distances,

‘ Feltstead

} Braintree

h Feltstead

} Hatfield Peverel -

} Great Baddow =
Chelmsford - -

} whittle 4 ‘s

{
t
t
Tat a oe
{
{
{

}witlingate Spain os ( 60488

} Roxwell = © { | B6630
} White Roding - { 33489
57926

} Doddinghurst zi { 17880

700 The Account of a

Cupola of a house at Woodford

Names of stations. Observed Distances.

angles,* ,

Oe TT a Feet
Southweald - - 349 0 31098
Epping Windmill - 7.31| 0 ee . 15824
Theydon Mount Steeple
Southweald - - 49 23°) Off? 9656
Theydon Mount Steeple —- 16 26 0 ieee + oes 25846
Navestock new Windmill
Southweald 7 - - 58 po 37107
Theydon Mount - - 149 43. 0 \ Pheydon eannan . } 6797
Theydon Garnon Steeple
Theydon Mount - - Ill 19 30 21090
Theydon Garnon— - - 53 3870 1 Havering P ‘ ; 24397
Havering Steeple
Severndroog Tower - 5 40 20 52260
Highbeech Station 14 49 4 i Crea. a= - ‘ 20197

Southweald - - 36 20 20 : 51340
Highbeech - - 65 36 20 Ruins " 33405
Ruins near Ilford

Highbeech - - 102 38 o|)? 34702
St. Paul’s - - 2608 2 Wo jo uesbant - a ; 77151
Cheshunt Station

Berkhamstead Gazebo : 3157
Naseing Steeple - - i Hunsdon is ; 18911
Hunsdon Steeple

Naseing - - - O4a3s © 13899
Hunsdon Steeple - — - 34 41 gitae green : 24348
Broxbourn Steeple

Berkhamstead Gazebo - 8 33 28 62528
Hatfield Broad Oak Steeple 20 11 Il ; Dae Sheep Ne : ; 26964.
Harlow Steeple

Hatfield Broad Oak - 19 44 10 . 21054.
Naseing : 11 48 5 Sabridgeworth 34763

Sabridgeworth Steeple

Thorley Steeple - -
Albury Steeple = =
Great Hadbam Steeple

45.17 ©

40 29 0 + Great Hadham - j 13253

Trigonometrical Survey.

701

Names of stations. Observed Distances.

angles.

° , @
Henham on the Mount Steeple 31 43 34 :
Albury Steeple 3 " eaha4 6 Bishop Stortford -
Bishop Stortford Steeple

i
Henham on the Mount - 42 32 24 16575
Albury z 2335 3 } Stanstead Mountfitchet } 28009
Stustent Mountfitcbet Steeple
Henham on the Mount - Bony © 24419
Stanstead Mountfitchet - TOM 2) O i Nancsiain a * ; 13323
Farnham Steeple
Henham on the Mount - 38 33 0 39054
Albury - - - 73 13 10 oe j 25421
Meesdon Windmill
Henham on the Mount - 40 10 40 21677
Elmdon Steeple - - 25 58 10 } Octagon wig ‘ } 31938
Chimney on an octagon Lodge
Balsham Steeple - - 75 Tsu s 23740
Elmdon-— - - 25 Zz a are Fe j 53410
Shady Camps Steeple i
Balsham =~ = : 7 10 30778
Shady Camps - - 2 19 0 } ashdon 5 me j 16120
Ashdon Steeple
Danbury - - - Q 35 7646
Thaxted Spire - - 26 an ae i ; 7e8sG
Litile Saling Steeple -
Elmdon - - - 22 27,0 26492
Rickling Steeple - - 64 25 0 {Newport i E { rae
Newport Steeple
Danbury - - - 7. 5.3.06 71826
Little Saling Bole - 61 38 0 haa a ; T1198
Stebbing Sieeple

-MDCCC. 4%

=

702 The Account of a

Art. xL. Principal Triangles for the Survey of the Western Part
of Kent. Plate XXXIII.

Frant Steeple from Botley Hill 90362,4 feet.

Names of stations. Observed Distances.

angles.

Frant Steeple : -
Botley Hill - -

3 7
phi hala } Sevenoaks - - { ba da
32 52 47

Sevenoaks old Windmill

Frant - - 22 17 10 «yas 42875
Sevenoaks Windmill - 40 52 50 } Chiddingstone 2 { 24858
Chidding stone Steeple -

Frant - - - 35 217 . 57874
Chiddingstone —- : 07 43 43° } Mount pion to oe {

Mount Sion Station

Frant - - - 31 28 30°
Mount Sion - 76 9g 30
East Peckham Steeple

Mount Sion = is
East Peckham - ia
Tudely Steeple

Botley Hill -
Sevenoaks Wmadiill -
Seal Chart Station

Seal Chart - -
Sevenoaks Windmill -
Tunbridge Steeple

Seal Chart - - 78 1
Sevenoaks Windmill -
Station on Otford Mount

°

Sevenoaks Windmill - - | 69 27
Otford Mount - - 61 24
Silverden Farm Station

re)

} Silverden Pann i

fo}

Norwood from Severndroog Tower 39155 feet.

Norwood > - 538 7°40 : f
Severndroog Tower - 84 8 © j wen By ie 5 vi 46155
Well Hill Station

Trigonometrical Survey. 703

Names of stations. Observed Distances.
_angles.
s d T ° eit pees
everndroog lower - 5 I4- 2

Well Hill : a8 ae + Crayford iy phe
Crayford Steeple
Well Hill = = 77 37 40 | 34738
Crayford - - - 48 8 40 j ap . ; i 45555
Ash Steeple
Ash - - - 10 | 32237
Crayford - sd "3 38 Fe 4 1 North fleet - - } ees

_ Northfleet Steeple
Ash - - - 15 3G A= 266
Northfleet - = 3s if g \ Gravesend 3 ii } py
Gravesend Station ; ;

Ash : - 47 33 3° : 56308
Northfleet - - 97 53 4° } Belvidere % é { 41951
Lord Eardley’s, Belvidere *

Gravesend from Halstow 44836 feet.

_ Gravesend - - 31 38 20 : | 22276
Halstow = - tz : 24 18 20 } Gadshill a y ; 28388
Gadshbill Station
~ Sheppey - - 13 18
Gadshill Sheppey from Gadshill

LEDS: iit Clade
Hernhill Steeple - -
Stockbury Steeple

Halstow - - - © 34 28 ;
| 71603

i Stockbury - j 43144

Frinstead Steeple Sh 65 27 18 Ak 57820
“Sheppey - = : 65a Hernhill - « { 38439
Hernhill Steeple

ART. XLi. Secondary Triangles.

Frant Steeple - - 26 37 20
Botley Hill Station - 9 52 49
Bidborough Steeple

26066
‘| 68071

Frant - - =
Chiddingstone Steeple -
Station near Bidborough Church

20. 52 Bo ; 27227
29 5 © { Station ; } 19953

4X 2

7OA The Account of a

Names of stations. Observed — Distances.

angles.
: ee
rant - - - : 24pm
Botley Hill ; al es i Remarkable Tree - j 99201

Remarkable Tree near Kibben’ Ss
Cross

Frant -
Station near Bidborough Church
Cowden Steeple

Station near Bidborough Church
Chiddingstone Steeple -
Mount Sion Station :

Station near Bidborough Church
Mount Sion - -
Leigh Steeple

Frant L = 2
Chiddingstone - -
Ide Hill Station

Chiddingstone - - 67 42 0
Ide Hill - 49 43. 0
Edenbridge Steeple

Seal Church Steeple - 15132
Otford Mount - - 17766
Sevenoaks Steeple ‘
Mount Sion Station. - 20 36 0 25291
Peckham Steeple — - - 47 56 0 \ Hadlow 7 - 11987
Hadlow Steeple

Seal Chart Station - 50 45 0 . 29804.
Otford Mount ~— - - toa olf oe s ‘ 23131

Sundrich Steeple
LL LL LLL ILL LLL OL
Otford Mount - e 94. 17
Silverden Station -
Seal Steeple

Well Hill Station
Norwood
Windmill, Reston Giniion

Well Hill - -
Severndroog Tower - 37 39 («0
Flagstaff on Hayes Common

Trigonometrical Survey. 7O5

Norwood from Severndroog Tower 32155 feet... Between the triangles

Names of Stations. Observed

Distances.
angles.
OCT te Feet
Norwood - - = i 65.53 30 } ze , aaa 30718
Severndroog Tower 2 46 30 0 Hlagstalt 38654"
Hayes Common

Norwood - - - | 34 27 30

Hayes Common - 30) 41, 50

Flagstaff on Addington Common

Well Hill - - - | 56 11 40 } 4 " { 20860

Norwood - - mI 22* Aidt 5 Sheng) 48958

Cudbam Steeple
Well Hill from Otford Mount 19206 feet.

Otford Mount - - 52 13 22860

Well Hill “4 73 58 0 S | }Knockholt Beeches - { 18790

Knockbolt Beeches, East End.

- Well Hill - - =" |) 22122) 26
Crayford Steeple - - Al 17 10

}Race House - { aed
Dome of a Race House

Well Hill - = Sided Wane. vm

Norwoed - 39 30 24

Windmill, Bromley Ciiniien

Well Hill - - - |59 1 11650
Severndroog Tower - 13 58 © ¢ | } Farborough na { 41381
Farnborough Station

Well Hill - - - | 58 52 o ’ 17255
Farnborough - 2 AQ 3210 }se. ES Bae yi ( 15019
St. Mary’s Cray Steeple

Well Hill - - 79 42 26 8653
Norwood 8 4 «| } Halstead : 5 { 56492
Halstead Steeple.

Norwood - - - | 36 36 4o 22696
Severndroog Tower ~~ - 32 52 50 } Bromley a q { 24932
Bromley Steeple

Well Hill . - - | 32 29 oO 36198
Severndroog Tower - ch 130 { Bromley ag F ; 22938

Bromley Steeple

706 The Account of a

.
~
-

Names of Stations. wrsiiag Distances.
iH 3 Ecet,
Well Hill = - ~ =eienil 2 ~ 4 ; 3
Bromiley - - = - Bl 25) 2 Hay g8o5
Hayes Steeple
Bromley - - 45-48 Ob Ls asters a os 19640
Severndroog Tower - 51 28 0 17846

Lewisham Steeple
Severndroog Tower from Chiselhurst Steeple, 36778.

Severndroog Tower - }
Chiselhurst Steeple -

New Cross Station

Severndroog Tower j

New Cross. - - - 14496
Eastcombe Point Station

Severndroog Tower - 49 39 0 : i " j 9628
Eastcombe Point - = "1 38 55, 0 Wicosict 13879
Woolwich Steeple

Severndroog Tower - 15 1 30 a h, ;
Crayford - - | 57 48 20] Bexley

Bezley Steeple

Well Hill ~— - 2 al SES Ke) : 3 j 22835
Crayford - - - | 36 39 0 + Charlton 33714
Charlton Farm

Crayford - - ~- | 23 17 10 i r » 20374
Charlton Farm - - | 28 14 0 Diaten 17026
Darent Steeple

Ash Steeple —- 2 12 56 49 : 2 33636
Crayford - - - | 30 32 18 Dartford Baa 14830

Dartford Brent Mill

Crayford - - - 16 16 18 21153
Stone Steepie - - gi.) 0

Dartford Brent 8069
te fal 15.44 5°. |) stetley a init
Northfleet Steeple - - 4 56 20 24750
Hartley Steeple

Northfleet = ~ 8 40 40 : A 7 33675
Ash - - = 101 42 0 t Ridley 5189

Ridley Steeple

Trigonometrical Survey. 707

Observed

Names of Stations. adglen Distances
Northfleet e = : 90 16 30 }
Gravesend Station - 4g 26 6 Southfleet <

Southfleet Steeple

Gadshill - - = : 119539
Sheppey Isle AS My } Strottenden Mill - { 7g
Shottenden Windmill

‘Gravesend Station - - | 4046 7 } : . 30549
Gadshill - - -| gz 28 1 Cliff Ss { 19967
Cliff Steeple

Gravesend Station - - . 14115
Gadshill < - } Higham -. % { 23489

Higham Steeple

Gravesend Station - = 86 16 16 3373
Halstow Station - - 4 18 ig } Gravesen g i { 44.747
Gravesend Steeple

Gravesend - - - 11621
Halstow - = = 6
Chalk Steeple ee
Gravesend - - - | 59 21 48 . 2828
Gaishitt | | - 92 5 «57 } Lower Hope Point - { = oat
Lower Hope Point, letamuch of

the Guard Room
Gravesend - = : ; 6
Gadshill = - - } Titbury oe ‘ t Ayres

Flagstaff, Tilbury F ont

Gadshill - - -
Sheppey - = &
Rainham Steeple

28 52 26 } Rainham =

Gadshill = aie - 1128 37 56 2
Halstow - = 4 29 12 53 + Swanscombe - 2 ; 3°747

Swanscombe Spire

Gadshill - - 124 43 26 10
Halstow ~ - - | 28 58 21 { Northflee 4 ; paeee
Northflect Steeple

Halstow - - - 4 37 23 36
Gravesend . 159 53 20 + Southfleet 7 { an

Southfleet § teeple

708 The Account of a

Names of Stations, Observed Distances,
angles.
G d ren ee Feet.
ravesen - - - | 38 36 50 : say
Habtow toe «7 3 Pee FP Sbone anit "7 a

Shorn Mill

48453°
Stockbury — - - -|'79'3te's 31257

Sheppey = : Tol eSONRZB AAD eit eects
Gillingham Steeple ‘

Sheppey = = =) Og ag P52
Gillingham ~~ 24 34 17

}se. James’s Church
St. Fames’s Church, Isle af Grain

Halstow -
Sheppey
Gillingham Steeple

Bat zs } Gillingham = =

a

Gadshill - - =
Sheppey - -
Friendsbury Steeple

23 35 24
4 10 33

11049

23822
48453*
| 60721

OV

Halstow -
Sheppey
Chimney of the ‘Star iy

73239
35 45 47

Halstow -
Sheppey
High Staff at the Upper Bell itive

a
a
BS ous [RE
BEF
rae ie =

Twinestead = -
Hove Steeple

Gadshill - = 4

Sheppey - 3 =

Upchurch Spire

Gadshill —- Sie agen (uz ial as 60739
Sheppey - - =" Wilt 20) 2 Bobbing z 3 26212

Bobbing Spire

Sheppey - -
Halstow ~~ =
Flagstaff, Sheerness Cagsan

52765
15656

Sheppey = e a
Frinstead a é :

Hucking Spire

_ Trigonometrical Survey. 709

Observed
-Angles.

—e

Names of Stations. Distances$

ees BU ence

anamemmenmnmntad

moa? Feet
Sheppey - - + ~ | 29 27 6 : A 58439
East Church Station - 136 15 56 Bernipill i 41564.

Hernbill Steeple

East Church - - - 44. 20 17 F
Sheppey —- yp 95 42 22 i Peas e

Milton Steeple

Sheppey ace
Milton - = é a i Iwade 5 ay Fon
Iwade Steeple

Hernhill So . 3 728 0 : \ piety
Frinstead = a a 45 6 35 t Witchling e« = a Z

Witchling Steepl

Hernhill = - - PASI Bh)
Sheppey - - > - | 25 51 16

; Tenham - é
Tenbam Steeple

Sheppey - - - S 24 42 40

Bapchild Spire

Sheppey : 4 = Zi) 320A : 56869
Hernhill = - 2 - 175 8 0 + sheldwich < é ace
Sheldwich Steeple

Sheldwich 2 4 x re
Sheppey - = = anne
Queenborough Steeple

Hadleigh = = o ZI 19 45 oi 69035
Sheppey - fa a 114 38 31 Minster a ey
Minster Steeple

Halstow = = 25 cae
Hadleigh s & me Maes

St. Mary’s Steeple

i
i
i
ee a | re roy
1
i
t

Hernhill - - - 29.UH, 0" 15630
BREREEG) my ee =) “hy. gOuz 44537
Feversham Spire

Tenham bi - - 41 29 0 20617
Hernhill - — - 2 36 6 o |g Hartey . - 22906
Hartey Steeple

MDCCC, 4%

710 The Account of a

Observed

Names of Stations. Distances.

Hernhill = =
East Church -
Sea Salter Steeple

Tenham - =
Sheppey - -
Whitstable Steeple

SECTION FOURTH.

Determination of the Altitudes of the Stations above the Level of
the Sea; and the mean Refractions deduced from observed Angles
of elevation and depression.

Art. xu. Elevations and Depressions.
At Trevose Head.

The ground at Cadon Barrow - - - elevated 39! 24"
Bodmin Down - - - - elev. 10 48
St. Agnes - 4 ice: - depressed 6 39
Hensbarrow - - - - elev. 29 2

At Bodmin Down.

The ground at Carraton Hill - - - - elev. 27 49
Trevose Head - - - - depr. 22 33
Cadon Barrow - - - - elev. 16 0
Brown Willy - - - - elev. 54 24

Cadon Barrow.

The ground at Trevose Head - - - depr. 36 49
Brown Willy - - - - elev 36 3°

The horizon of the sea in the direction of Trevose Head depr. 30 56 —

Ditto in the direction north - “Ge i} - -. depe GL

St. Stephen’s Down.
The ground at Black Down - - - = elev. 25 21
Carraton Hill - - - elev. 35 18
Brown Willy - aa. 2a - elev. 42 Qo

Trigonometrical Survey. 714

Black Down, near Lydford.

The ground at Maker Heights = - - - depr. 32' 8"
Carraton Hill - - - depr. 3 46

St. Stephen’s Down - - - depr. 35 18

Mendip Hills.

The ground at Bradley Knoll - - - - depr. 6 12
Westbury Down - - - depr. 14 59

Farley Down - - - depr. 18 21

Lansdown ° - ° depr. 14 4

Moor Lynch oe - - depr. 34 53

Dundry - - : ~ depr. 15 45

Dundon Beacon - - - depr. 38 24

Ash Beacon - - - - depr. 20 45

Dundry.

The ground at Mendip - - - - - elev. 5 8
Farley Down = - = - depr. 10 1

Lansdown - - - - depr. 3°19

Lansdown.
The ground at Dundry~—s- - - - depr. 5 44
Mendip - = - - depr. 1 39
- Farley Down.

The ground at Westbury’ - - - « depr. o 12
Mendip - - - - elev. § 51

Dundry = - - . - depr. 1 46

Bradley Knoll.

The ground at Bull Barrow = - “ - depr. 8 59
Ash Beacon - - - - depr. 20 18
Westbury = - n - depr. 4 36

Westbury Down.

The ground at Beacon Hill, Amesbury - - depr. 10
Bradley Knoll - - - elev. 7 4
Mendip - - - - elev, 1 28
Farley Down - - oes depr. 9 9

4Y 2

712 _ ‘The Account ofa
Dundon Beacon. ‘
The ground at Moor Lynch - -- - = depr. ° 6 3"
Lugshorn Corner - - - depr. 3 56 13
Mendip - - - - . elev. 28 18°
Pilsden =: ae - - elev. 8 38
Moor Lyncb.
The ground at Greylock’s Foss-way - = - depr. 59 14
Lugshorn Corner = - : depr. 32 45
Dundon Beacon : - - elev. 0 9
Mendip - - - - elev. 23°50
Pilsden - - - - - elev. 9 2
Ash Beacon - - - elev. 6 57

Greylock’s Foss-way.

The ground at Moor Lynch - - - - elev. 1 53 56
Dundon Beacon - - - elev. 34 48
Top of the staff (20 feet high) at Greylock’s Foss-way - elev. © 34

Lug shorn Corner.

The ground at Moor Lynch - - - - elev. 27 21
Dundon Beacon - - - elev. 1 20 58
Top of the staff (20 feet high) at the west end of the base depr, ro}

Beacon Hill, Amesbury.

The ground at Westbury : - - = depre 4 36
Inkpin - - - : elev. 6 22

" Inkpin Hill.

The ground at White Horse Hill = - - - depre 10 54
Highclere - - 2 depr. 15 ©

Beacon Hill, Amesbury - - 18 24

White Horse Hill. 7 ats!
The ground at Highclere - - - - depr, 7 39
Nuffield - - 2 at) ae cain 2.
Shotover Hill - - - -- depr, 37 6

Trigonometrical Survey. 713
Scutchamfly Barrow.

The ground at Wendover “ 2 - - depr. 5' 36"
Whiteham Hill = -. - - - depr. 11 20

At Shotover Hill.
The ground at Scutchamfly Barrow - - elev. © 20
Nuffield 2 - - ~ elev. 1 27
Wendover - - - - elev. 2 58
White Horse Hill rh ee - elev. 1 36

Brill on the Hill.
The ground at Nuffield ° - - . depr. 4 48
Wendover © E: - elev. -3 55
Bow Brickhill - - - depr. 10 44
Epwell - ~ - - depr. 6 57
Stow - - -" - depr.§ 7° 6
White Horse Hill - - * depr. 5 45
Nuffield. ;
The ground at White Horse Hill =) siA depr.. 4 45
SE of the Staff at Brill on the Hill, Staff 1 3 feet highs) depr. 6 2
Bagshot » - = - - depr. 6 43
Highclere - - ~ depr. 4 12
N. B. The half stage belonging to the Royal Society was used at this station.
Wendover.

The ground at Brill on the Hill - - * depr. 14 59
Shotover Hill . - S =a Udepne 7) 2%
Bow Brickhill - = 2 depr. 17 28
Stanmore - - 2 2 depr. 19 57

Stow on the Wold.
‘Fhe ground at Shotover - ve S - depr. 13 48
White Horse Hill - ae - depr. 7 30
_ Broadway Beacon” - - - elev. 11 29
Brill on the Hill - - - depr. 14. 45
Epwell - - = - depr. 8 oO

Broadway Beacon.
The ground at Stow —s_ - - ay ay depr. 19 0
Epwell - = ~ - 5 depr. 17 25

714 The Account of a

Epwell.
The ground at Stow . - - depr. 3°53"
Arbury Hill - - - - depr. 6 39
Brill on the Hill - - - - depr. 11 §1
Corley - - - - depr, 20 8
Broadway Beacon <= - - elev. 8 31

Arbury Hill.

The ground at Epwell - - - - depr. 14 25
| Bow Brickbill.
The ground at Wendover - - - =» ¢ety.693 56
Kinsworth = : - ot elev. 5 35
Brill on the Hill - -. - depre 5§ 28
Kinsworth. Bi,
The ground at Brill on the Hill 2 - * depr. 12 37
Bow Brickhill - - - - depr. 17 25
Arbury Hill - - - depr. 13 44
Stanmore - . - - depr. 17 4
Lillyhoe - - - - depr. 23 44.
Bagshot Heath.
The ground at Nuffield ~ - - - - elev. 1 29
Stanmore - - - - depr. 7 28
Stanmore. ‘
The ground at Bagshot Heath - - - depr. 9 34

ArT. xt. Heights of the Stations.

Ground above low water mark.

Stations. Feet.
Trevose Head = - . - - - 274
St. Agnes Beacon - - - “ - 621
Hensbarrow - - - rn = ke - 1034
Bodmin Down - - - - ene 645
Black Down - - - - 1160
St. Stephen’s Down - - 2 » - 605
Bradley Knoll ei ae - = - * 973

ArT. xLIV. Mean Terrestrial Refractions.

Between : Mean Refractions.
Bodmin Down and Cadon Barrow - - a
Bradley Knoll and Westbury Down - - z
Maker Heights and Black Down - - - S
Highclere and Inkpin - - = = =
St. Agnes Beacon and Trevose Head - - 5
Moor Lynch and Lugshorn Corner ° - —

Hensbarrow and Trevose Head 5 = sat SR

Trigonometrical Survey. 715
Stations. Ground above Jow water mark,

, Feet.
Mendip or oe - - - - 999
Westbury Down - - - <1 75
Dundry—- - ° - 4 79°
Lansdown _ - - - - - 813
Farley Down - - - - 700
Moor Lynch - - - - - 330
Dundon Beacon - - - - 360
Lugshorn Corner 2 - - 2 49
Greylock’s Foss-way 3 ie - - 42,
Ash Beacon _ - - - 655
Cadon Barrow - - - - 1011
Brown Willy = . 5 J 1368
Inkpin - - - - - IOII
Nuffield - mn - ~ - 957
White Horse Hill. - ~ 2 Co e $93
Shotover Hill - - - = 599
Muzzle Hill, (Brill station) - - aut aa
Whiteham Hill - - R - 576
Wendover, ground above - - - 905
Bow Brickhill co a = x 683
Kinsworth = i Le - 5 - 904
Lillyhoe = Seige ot = - = 664
Stow onthe Wold. = - a 5 iS 883
Epwell Hill - - - = - 836
Broadway Beacon - - - - « 1086
Arbury Hill - - - - - - 804

716

The Account of a ,

Wingreen and Bradley Knoll - - - igi
Bodmin Down and Trevose Head = - - —
Carraton Hill and Black Downs + © - - Os
Westbury Down and Mendip~ - - - ay
-Carraton Hill and St. Stephen’s Down - aritea
Farley Down and Mendip - : - v8
Beacon Hill and Westbury Down - - - wv
Dundry and Farley Down - - - -
Dundon Beacon and Mendip . - - vy
Bradley Knoll and Mendip - - - a
Lansdown and Mendip - - - - is
Moor Lynch and Dundon Beacon - - <a
Dundry and Mendip - - - - 6
Westbury Down and Farley Down - B a
St. Stephen’s Down and Black Down ~ - - os
Moor Lynch and Dundon Beacon - - - dr
Dundon and Lugshorn Corner - - - =
Moor Lynch and Greylock’s Foss-way ~ = Sele
°

Lugshorn Corner and Greylock’s Foss-way -

Cadon Barrow and horizon of the sea in the direction of

Trevose Head > pee zs y Bate
Ditto in a northern direction ~ - =: . =
Brill and Nuffield ~ - = 7 2 clea
Broadway and Stow - _ - . =
Epwell and Broadway = - at iy L om
Highclere and White Horse Hill = aah ie a
Nuffield and White Horse Hill “ 2s oo
Nuffield and Bagshot - “4” - “. ay
Epwell and Stow - * - * ae
Brill and Stow on the Wold - ny - THA
Wendover and Bow Brickhill : = . a5
Kinsworth and Bow Brickhill _ - - 7 ot
Shotover and White Horse Hill =5~ 2 £ —
Epwell and Brill = rete - - er
Bow Brickhill and Brill = - - 4 a

Trigonometrical Survey. a7

Ant. xiv. Particulars respecting the Altitudes of ihe Stations.

The height of the station on Trevose Head, above the surface
of the sea at low water, was determined in 1797, by levelling.
The transit instrument was used for the purpose; and there is
reason to believe the result, 274%. feet, is within a very few
inches of the truth.

In the Philosophical Transactions for 1797, p. 4'71, the height
of the station on Maker Heights is said to be 402 feet; this was
also found by levelling. The altitude of St. Agnes Beacon, deter-
mined from that station, is 599 feet; (see the same volume and
page;) but, if the calculation be made from the base of alti-
tude at Trevose Head, the height of that station, above the level
of the sea, will be 621 feet, which gives a difference of 22 feet.
It must be recollected, however, that in the first result, the com-
putation was carried through two intermediate stations, which
gave three arcs, and as many mean refractions; and, consider-
ing the extreme variableness to which refractions are liable, we
are assuredly not to consider 22 feet deviation from the truth
as a large quantity.

Besides St. Agnes Beacon, the altitudes of Cadon ee
Brown Willy, Hensbarrow, and Bodmin Down, have been de-
termined from that of Trevose Head. Of the remaining stations,
some are derived from Maker Heights, others from Dunnose :
most of them are mean results, that is, each station has gene-
rally been found two ways; and, as it will serve to shew what
errors proceed from irregularity of refraction, and imperfection
of observation, I shall exhibit a few particulars in relation to
them.

MDCCC, ~ 4 Z

718 The Account of a

Height of deduced from Feet.

Maker Heights = 1 169 Mean.

Black Down 1160
Carraton Hill - - 1152
Black Down - 609

St. Stephen’s Down 605
Carraton Hill - 600
Bradley Knoll - 779

Westbury Down 775
Beacon Hill ~ abe i 4
i Mendip Hills - 703

Farley Down 700
| Westbury Down - 696
Mendip Hills - = 335

Moor Lynch | 339
Ash Beacon - 325
Dundon Beacon - 46

Lugshorn Corner 49
Greylock’s Foss-way 52
Highclere - - 1014

Inkpin Beacon 1011
Beacon Hill ~ 1009
Bull Barrow ~ - 653

Ash Beacon 655

Bradley Knoll - 657

The above will sufficiently shew, what dependence is to be
placed on the heights deduced from observed angles of eleva-
tion or depression; the results are, indeed, often less consistent,
and frequently unsatisfactory; but, generally, they run on a
parallel with these. ‘The data from which all the heights
have been computed, accompany this article.

The measurement of the base on Sedgemoor, shewed a fall of
about 7 feet, from Lugshorn Corner to Greylock’s Foss-way :

Trigonometrical Survey. 719

therefore, supposing that fall to be gradual and constant, all the
way from the latter station to the surface of the sea at Bridge-
water Bay, we shall get 24 feet, for the height of Lugshorn
Corner from the surface of the sea. The altitude of this sta-
tion, deduced from that of Trevose Head, is 49 feet ; and, sub-
tracting 9 feet from it, (the height of the bank on which the
instrument stood above the moor,) we get 46 feet for the height
of the moor at Lugshorn Corner, above the level of the sea at
Bridgewater Bay. But this height, supposing the fall regular, is
proved to be 24 feet. There is, therefore, a difference of 22
feet, granting the whole of this to be an error on the side of the
survey: but, as the general surface of the moor at Bridgewater
Bay is several feet above the surface of the sea, we may take a
moiety of 24, feet, for the error of the computed height of the
station at Lugshorn Corner. :

Art. xiv. Matters relaling to Refraction.

The refractions contained in this account, like those in our
former Papers, tend to prove, that when rays of light pass hori-
zontally, and considerably distant from the surface of the earth,
they are less bent or refracted from their rectilinear courses,
than theory and opinion have laid down as fact. It is very cer-
tain, however, that objection lies against particular conclusions
drawn from such data as we possess; because the angles of
elevation and depression of corresponding stations are observed
at different times, and almost always, therefore, under different
circumstances ; but, with the experience and continual practice
of thus obtaining means of computing these refractions, although
we may not be able to determine the refracting power of the
air under given circumstances, yet, as the causes which render

422

720 The Account of a

it variable, are as likely to predominate when the angles of de-
pression or elevation are observed from low stations as when
observed from high ones, we may be enabled to make some
general deductions.* | |

When the instrument formerly made use of by General Rox
was intrusted to my care, I possessed the means of deter-
mining, in a more accurate manner than had yet been done,
the refractive power of the air near the horizon. . To devote
much time to it, has not, as yet, been in my power; because a
more rapid extension of the survey was an object of greater

* As many instances of strong atmospherical refraction have been related, and inge-
niously accounted for, in some of the late publications of the Royal Society, I think it
right to mention, by way of note, a very extraordinary instance of its variability.

In the month of June, 1795, when the instrument and party were. stationed at
Pilsden Hill, in Dorsetshire, on a particular day, at about the hour of four, I em
ployed myself in observing the angles of depression or elevation of the surrounding
hills. After I had done all that was necessary in this matter, I turned the telescope to
Glastonbury Tor, and observed the depression of it. ‘The air was so unusually clear,
that, desirous of proving to a gentleman then with me in the observatory tent, the
excellence of the telescope, I desired him to apply his eye to it: this he did, and, agrees
ably to a desire he expressed, I again took the depression of the upper part of the old
building, which I was enabled to do with gréat accuracy, and found it 2” different ;
the first being 30',0’, and the last 39',2”. The unusual distinctness of this object, led
me to keep my eye along time at the telescope ; and, whilst my attention was engaged,
I perceived the top of the building gradually rise above the micrometer wire, and so
continue to do, till it was elevated 10',45” above its first apparent situation ; it then
remained stationary, and as night drew on, the object became indistinct. The follow-
ing evening, I observed the depression again, and found it 29’,50”. To what cause this
extraordinary change in the refraction could be owing, I am at a loss to conjecture.
The former part of the day had been warm, with little wind, and cloudy. The thermos
meter, at the time of observation, was 65°, and continued stationary for a considerable
time. The sky was cloudy, but yet, as I have before observed, the air was remarkably
clear. The top of Glastonbury Tor, I suppose, is about 200 feet from the surface of
Sedgemoor, over a considerable tract of which, the line joining Pilsden with that object
passes. The gentleman of whom I speak, as being with me in the tent, was Captain
Darcy, of the Royal Engineers, who, no doubt, well remembers the circumstance. |

Trigonometrical Survey. 721

importance, I did not, however, lose any opportunity which the
subsequent season offered; the first was, when the instruments were
at White Horse Hill and Whiteham Hill; the second, when one was
stationed at Brill and the other at Arbury Hill; and the third op-
portunity offered itself, when one party was stationed at the latter
place and the other at Wendover.

On these occasions, the instructions which I communicated to
Mr. Wootcort, and by which I governed myself, were to observe
the elevation or depression of the corresponding station at the expi-
ration of every hour, beginning at six A. M. and to have the watch
well regulated from observed altitudes of the sun’s limb. I requested
him also to be very minute in entering on his book the state of the
weather; to keep the instrument properly sheltered from the wind ;
to be always cautious to adjust his level; and also to insert the state
of the air, as to temperature and density, by noting the thermometer
and barometer.

During the time we were at the two first stations, White Horse
and Whiteham Hills, there was only one day when the air was suf-

‘ficiently clear for the purpose; this was the 6th of June. On that
day, the following observations were made at the same time as shewn
by signal.

Whitebam Hill. Sfune 6th, 1799.

—

Hours. |Wh. Horse ?hessec Thermo-

Elevated. ter. meter. Bemeret.
rh In. pts |Degrees,

3 6 4 29,730} 60,3 | Light airs at SW. Sun not shining; remarkably clear. .

4 6 24 29,724) 62,5 Ditte. Ditto ditto,

5 6 14 29,728] 58,7 Ditto. Ditto ditto.

6. 6 Io 29,732] 5855 Ditto. Ditto ditto.

7 6 11 29,728] 5735 Ditto. Ditto . ditto.

8 6 21 29,7321 57 Very calm, and cloudy, but clear.
#9 537 29,736] 55.7 Ditto. Lamp at Shotover very bright, Dew falling.
#10 5 39 29,740] 55,5 Ditto. Ditto.

The Account of a

White Horse Hill. fune 6th.
a

Hours.

Depressed. ter.

meter.

In. pts.| Degrees.

3 18 21 |29,412) 5757
4 | 18 16 29,408) 59,5
5 18 24 | 29,410) 57,6
6 18 20 |29,412] §5,5
y) 18 25 © |29,412|) 5555
8 18 15 |29,438) 54,2
* 9 18 10 | 29,438) 5354
*1I0 18 25 |29,438) 53,2

Whiteham H, |Barome-|Thermo-

Remarks.

Light airs at SW. Sun not shining; very clear.
Ditto. Ditto ditto.
Ditto. Sun shining a little; not so clear.
More wind. Sun not shining, and darker.
Calm and cloudy.
Quite calm, and a little dew falling.
Ditto. Fine night. Lamp at Whiteham very distinct.
Ditto, but lamp rather indistinct.

Similar observations were also made when the instruments were at
Brill and Arbury Hill: they were as follows.

Arbury Hill. ‘Fuly 11th, 1799. Watch regulated.

Brill, Barome-{Thermo-

Remarks,

Hobrs Depressed.| ter. meter.
” In. pts.|Degrees. SY

gA.M.| 11 15 |29,180| 65 ,5 | Light airs at SW. Cloudy, but sun shining now and then.
to Il 15 |29,200] 70 ,0 Ditto. Cloudy.

11 Il 15 | 29,200} 70 57 Ditto. Ditto.

12 11 6 |29,199| 70 ,2 Ditto. Ditto.

3P.M. 11 6 | 29,162] 68 ,o Ditto. Ditto. Very clear. 4

4 TO) 35 1 295108|| 7.2 ok Ditto. Sun shining a little, yet free from any tremor.
*g 10 30 | 29,132] 63 ,0 Ditto. Lamp at Brill perfectly distinct.

Brill on the Hill. 7fuly 11th, 1799. Watch regulated.

Hours. Arbury H. |Barome-|Thermo-

Depressed.| ter. meter.

nk In. pts.|Degrees.

gA.M.| 8 40 |29,10c} 61 0
10 8 36 | 29,210) 67 55
iM 8 36 | 29,210) 67 55
12 8 36 | 29,210] 65 5,0
3P.M.| 8 36 |29,210] 71 20
Ps. 8 46 29,250] 71 55
#9 8 48 |29,200} 61.75

Remarks.

Light airs at SW. Appearances of rain from SW. Cloudy.
Ditto. Clearer, but cloudy. Arbury Hill very distinct.
Ditto. More cloudy and equally clear. [round,.

The air remarkably clear and free from tremor. Cloudy all
Ditto ditto. More cloudy.

Ditto ditto. Not so cloudy. -

The lamp at Arbury H. very bright. Avery fine quietnighte

Trigonometrical Survey. 729

The next opportunity which offered, was at the former station and —
~ Wendover: the observations were as follows.

Arbury Hill. ‘fuly 27th, 1799. Watch regulated.

‘Wendover.|Barome-|Thermo- Remarks

Hours.
~ |Depressed.| ter. meter.

oe

In, pts.| Degrees. {and there.

12 8 28,728] 62 ,0 | Fresh wind from SW. Rather dark weatier, sun shining here

Ll

2

I 12 3 | 28,734] 64 ,2 Ditto. . Airtremulous, ditto.

2 1Z 11 | 28,740) 64 50 Ditto, Ditto, ditto.

3 12 10 | 28,738] 63 45 Ditto. Air more steady, ditto. Clearer.
4 12 22 | 28,740) 64 50 Ditto. Very steady. Sun shining a little,
5 II 50 | 28,740| 64 ,2 Ditto. Ditto. Ditto,

12 17 | 28,740] 61 ,0 | Less wind, and the air very clear. Wendover perfectly distinct.

Wendover. ‘Fuly 27th, 1799. Watch regulated.

Hout | Arbory Bazan ero Remarks

ny In. pts |Degrees
5 A.M.} 16 12 [29,030] 53 ,2 | Wind at SW, rather fresh; sun shining, and air very clear.
6 16 12 | 29,030] 53 ,0 Ditto, ditto.
7 15 26 | 29,030] 54 ,5 | Less wind, and the air very steady. Arbury Hill very distinct.
8 14 44 | 29,100}54 ,0| Little wind. Dew falling very fast. Ditto.

Another opportunity for making contemporary observations occurred,
when the parties were on Broadway Beacon and Epwell: I place
them last, because I think them inferior to the others.

Epwell. “Fune 26th, 1799. Watch regulated.

Broadway B.|Ba -|Th =
ae Bloat. a a ie Romarkse
*% v In. pts.|Degrees. : : ‘ :
12 6 29,100| 60,5 | Wind SW. Cloudy. Much rain preceding night.
1P.M| 6 8 |29,100| 63,2 | Ditto, but calmer; sun not shining at Broadway.
2 6 12 | 29,208] 60,7 | Very calm, and-cloudy all round.
3 6 20 |29,100| 59,0 | Ditto. Appearances of rain in SW quarter.
4. 8 32 29,100| 57,5 | Foggy, but easily perceive the tent at Broadway Beacon.
Broadway Beacon. ‘fune 26th, 1799. Watch regulated.
Epwell. Ch -
Bers Derctsicds ae Remarks.
i Pr Degrees. -
2 19 0 57,5 | Light airs from SW. [Inclinable to rain.
3 Oey 5735 Ditto. Still more so.
4 IQ 3 57>5 Ditto, but misty. Barometer tube broken.

724, The Account of a

To determine the refractions on the first arc, White Horse
and Whiteham Hills, we have the distance between those stations
== 88662,2 feet, which subtends an are of 14’ 32" nearly.

To determine those on the second, we have the distance be-
tween Brill and Arbury Hill == 146530 feet, subtending an
arc of 24’ 3”,9: those on the third, Wendover and Arbury Hill,
210628 feet = 34! 35’; and, for finding the refractions from
the two last tables, we have the distance from Broadway Bea-
con to Epwell = 80611,4 feet, which subtends an arc of
13/11” nearly.

The depressions and elevations were all taken to the ground,
excepting those which are marked with asterisks. At White
Horse Hill and Whiteham Hill, lamps were used at the hours of
g and 10: they were also made use of at Arbury Hill and
Brill at g o'clock. In the first instances, the lamps were placed
(the centres of them) 14 feet from the bottoms of the respec-
tive instruments; and in the last 2+ feet.

The height of the transit telescope above the ground was always
5+ feet; therefore, an allowance must be made, at each station,
for the angle which that space subtends at its corresponding one;
this premised, the refraction will be found from one of the two
following rules, viz. if A be the contained arc, and D d the ob-

served depressions, the quantity answering to the refraction, R,

will be expressed by 2s, or, if one of the angles should

be an elevation, e, then R = mitas : these rules give the
refractions in the following table.

725

StS S65) ot

: fo}
6 [SS 96a) 25 6

° ¢ ¢ 66
= V 19‘SS 96a fe)
S Wd joLoS'6a) Se L,
za i?
os SOLE G65} = 9
NS 9's ‘
S SLG 6s) ; LTE °Q¢ ere “ g
“s ‘ c ue ¢ ¢ ous ve
Ss 2 99 ILS ae & |S*tg |g ‘8° i 19 eat a v

8°0 ‘
= PbS-66s | . — . G6s| — was
= e *sqjd “ul g ‘sid ‘ut
0 a beet eee
: ; ‘1B *JUOD °sid] , 5 E "212 *]U09 *s3d| : b “sid “DIR ¢ i

Ny ULIOY TL ulo1eg ‘uoTqaeay sino}yy wis y woleg coated *sInOFL mI9y J, “‘woleg S uctiaeubiee ®siNO Fy “WOU TL “WIO1e ee *SINO Fy

‘lJandq pue uoorag ACID EOE

ony“ TERY MA 29 [ET 8STOFT OTM

‘OD 'F

*1aAOpua AA puR Ine Ainqiy
Siyes

‘IH Ainqiy pur [lg
“21 °Z

‘uoisaidagy pun uoyvaary fo sasup Suipaoasd aqy wodf punof suonov.ifay

5A

MDCCC.

726 The “Account of a

On examining the refractions obtained on the first arc, we
perceive them to have been tolerably regular from g o'clock
till 8; the mean being —2— part of the contained arc. The
height of Whiteham Hill is 576 feet, and that of White Horse
Hill 893 feet, above the level of the sea: the ray passes, there-
fore, through a tract of air considerably elevated, as the country
between the stations is, for the most part, flat and low.

The air is not often clear enough, or sufficiently free from tre-
mulous motions, for these delicate observations. On the present
occasion, however, the state of it was highly fit for the purpose;
and, as care was taken, I am of opinion an error of more than
3”, taking that of the arch of altitude into the account, cannot
have obtained in any of the angles. The refractions at 9
and 10 o'clock are less than at the preceding hours; but
this does not appear to have been owing to any change in the
refractive power of the air throughout the whole extent of the
ray, because the depression of Whiteham Hill, from the other
station, varied little at those hours. These changes in the ob-
served angles of elevation at Whiteham, ( 44,” and 42” being the
differences, ) without corresponding ones at White Horse Hill,
prove that some partial alteration, from floating strata, had taken
place in the refraction near the former station. Whoever con-
siders the matter, must perceive a case may be constructed in
which this will take place, causing a great variation in one of
the angles, whilst the other apparently remains the same: and
this suggested the idea, that to afford any accurate conclusions
in this way, a long series of observations would be necessary.
It furthermore appears, that dew could not have caused these
differences at Whiteham Hill, since the same cause would
equally operate to vary the observed angles at White Horse
Hill; but those remained nearly the same.

Trigonometrical Survey. 727

The refractions on the second and third arcs, I consider as
most accurate, on account of the great distance between the
stations ; and also as more to be depended on, from the circum-
stance of the ray generally passing 300 feet above the ground.

The fourth arc affords another instance of the refraction
varying at one station, and remaining constant at the other.
This; no doubt, was owing to the intervention of ‘some partial
stratum of air, nearer to: Epwell than Broadway Beacon. The
refractions, deduced ‘from ‘these contemporary observations are
certainly inconclusive. The mean refractions, (neglecting the
fourth arc) brought under one point of view, will be as follows.

Arcs. Barom. | Therm.

; in. pts.

1. White Horse Hill and Whiteham. | 734, = 4 2.925).5759
2. Arbury H. and Brillys first refracs,) 774. |= « |:2932] 67,8
3. Arbury Hill and Wendover. -. |. 28,8} 58,1

If the air had been in a quiescent state, previous to and also
at the times when these observations were made, it might be
expected that the differences of altitudes in the stations would
be obtained, tolerably near the truth, barometrically. The re-
marks in the tables appertaining to the first and second arcs,
shew that such opportunities offered ; but those which belong to
the third, prove the wind to have been fresh ; and, as the space
between the stations which constitute the extremities of that
arc is 34, miles, nearly, it is not to be expected that a true result
should be obtained. The differences of altitudes of the stations
constituting the extremities of the two first arcs, obtained by
means of the observed angles of elevation and depression, as well

5A2

728 The Account, &c.

as from the heights of the mercury in the barometer, will be as
follows. |
Arcs. Obs. Ang. _— Barom. Diff. .
1 317 282 835
2 60 15 Ab
The little done on this subject, points out the necessity of

doing more; it therefore remains with me to observe, that I
shall lose no opportunity of employing the apparatus committed
to my charge in the best and most diligent manner, both as
relating to matters of refraction, and to all others connected with

the Trigonometrical Survey.

In the Introduction, page 540, it is stated that this Account would be comprized in
three Sections, but it was afterwards thought more convenient to divide it into four,

In Page 583, line penult. dele and Prittlewell.
——— 665, —- 14, for 1792, read 1772+

Lhilos. trans. MV)C CC. Plate RXV fies

+5 "
GS SEDGEMOUZoun.
Nellore Gate
+ ok j
%, Moorlyneh Gat
7
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d re
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eal

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se (0 the URIGON OME TRMCAL SUhVEY, 1790.

ZA Philos. trans. MVCCC. Hale XXNX p jee

© White Horse Mill

\

arley Down

o Devizes

Westbury Down

o Frome
|
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ea
| i Lees,
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FILAIN of the — Lrenipial . Langley the TRIGDNOMETRIVAL SURVEY, 1790.
¢ Chiles. Trans MYCCC Hale XX1X p28

& White Horse Tilt

Bristol Cathedral 5

_ gq luunsitown

Duniiy Beacon a= :
y Sq Marley Down

Inkpin Beacon ),
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|
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pal

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10 a5 20

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| Brack Down
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ay = aaesh - ‘ a ’ i
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‘ if =
pO © RAIN eT -sepeetatenes dite r > HTT E vag RRS EN ONE ARREST «ANI ARNE Tap Pree a ena AaNae mY, fas
‘ ) : oo . - J

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Dean Hill

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Bull Barrow

« BLACK Down

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DUNNOSE

\ ; \
IT art Perea, HS aes tie ep LaNat, ce 30! hie Fa HraT Aaem Ty da DMPA egy ene VT IER, owt te Nays nett pes
alice eal “ noe ~ wan fiat oe 1S See rm Siem he whe we cenlpe or yea

7 Yh, r ey, 4 y /
iG the TRIGONOMETRIC UA ne AGNES BAC ON. Philos Trans MDC CC. ialeX¥NN pp. 728

&
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= PLAN of the PRINCIPAL TRIANGLES in the TRIGONOMETRICAL SURV

Philos Trans MDC CC.PateXXNIL p. 728

a Ningreen

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ll

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Meridian of Greenwich

oLekhanpsttad Gagebo

é Hampficad

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PO)

TLL of tie RIN CTP ALT RTAN ELE St Vie TRLGONOMETHICAL STRVEV3 1797 -

Philos. Trans MDC CC. Lite XXM 7725

Corley Hill

*
o Coventry

Meridian of Durnnese

@ Crouch Mill

ratway Beacon

a

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G99.

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Vrdathectahe Paderio Da ieloadey
J ~s '

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Persian Lyrics, or scattered Poems, from the Di-
wan-i-Hafiz. London, 1800. A?

A Journal of Natural Philosophy, by W. Nichol-
son. No. 40

"The Doctrine of Phlogiston established, and that

of the Composition of Water refuted, by J
Priestley. Northumberland, 1800.
Compendium Flore Britannice, auctore J. =
Smith. Londini, 1800. 8°
A. H. Macdonald, Disputatio inaug. de Necrosi ac
Callo. Edinburgi, 1799. 8°
Memoranda of the State if the Thermometer at
Sidmouth, Devonshire, from Dec. 11. 1799 to
Apr. 15, 1800. MS. 4°
An Introduction to Harmony, by William Shield.
London, 1800.
A Journal of Natural Philosophy, by W. Nichol:
son, No. 41.

A

DONORS.

The Royal Society of
Edinburgh.

James Edward Smith,
M. D. F. R.S.

Mr. William Nicholson.

The Rev. George Whit-
more, B. D. F.R.S. _

The Rey. Francis Wol-
laston, LL.B. F.R.S.

Professor Comparetti of
Padua.

Mr. Pearson.

Sir John Call, Bart.
F,R.

TheRev.WilliamTooke,
F.R.S.

The Rev. Herbert
Marsh, B. D.

Mr. William Renwick.

The Royal Humane So-
ciety.

Sir John Cox Pi shee
Bart. F.R.S$

Gibbes Walker Jordan,
Esq. F. R.S.

John Haddon Hindley,

Esq.
Mr. William Nicholson.

The Rev. Joseph Priest-
ley, LL. D. F. R.S.

James Edward Smith,
M. D. F.R.S.

Alexander Herman Mac-
donald, M. D.

White Melville, Esq.

William Shield, Esq.
Mr. William Nicholsons

INDEX

TO THE

PHILOSOPHICAL TRANSACTIONS

FOR THE YEAR 1800.

A 7 page

Acrp, carbonic, remarks on, - a = - 202
—- fluoric, remarks on, - - - - 202
- muriatic, experiments to decompose it, - ~ 188
Air, on the quantity of it discharged through an aperture, = 107
on the direction and velocity of a stream of it, - 109
Albumen, experiments on, - - - 375» 387, 396
Alcyonium, experiments on various species of, - 354, 364
Antipathes, experiments on various species of, - 351, 364

_ Arteries, on a peculiarity in those of slow-moving animals, L
Astronomy, physical, second appendix to the improved solution of
a problem in, 3 % 4 a 86

B

Barker, Tuomas, Esq. Abstract of a register of the barometer,
thermometer, and rain, at Lyndon, in Rutland, for the year 1798, =

Barometer, Register of, at Lyndon, in Rutland, - -

Birds, on their organ of hearing, - = - 6, a

Blood, remarks on, = = x = 401

Bradypus didactylus, remarks on its arteries, - - 100
- tridactylus, remarks on its arteries, - - 99

Brig hiness, remarks on, - - - 51

C

Candle, on the reflection of its heat, - = - 297

on the refraction of its heat, - 308

Car.iste, Mr. ANTHONY. Account of a peculiarity in 1 he
distribution of the arteries sent to the limbs of slow-moving ani-

mals; together with some other similar facts, - = 98
Cartilage, experiments on, - - - - 383
Cavities, sonorous, observations on, - - - 116
Chords, on their vibrations, = = Me is 134
Cochlea of the Ear, remarks on, - - - 18

MDCCC. 5B

INDEX.

; page
Coorer, Mr. Astiey. Observations on the effects which take 7
place from the destruction of the membrana tympani of the ear, 1 5t

Corallina Opuntia, experiments on, - - 334, 362
Cruickshank, Mr. on the matter remaining after the explosion of
gunpowder, - - - = “ 237
E
Ear, on its membrana tympani, = = = 1, 1514
on the uses of its different parts, 4 2 ns
Eel, electrical, on its electric apparatus, - - 429
Electricity, its effect on carbonic acid, - - ~ 202
on fluoric acid, 4 > a 202
on muriatic acid, = = a 190
on that excited by the contact of conducting substances, 403
Elephant, on its organ of hearing, a = = 2,19
F .
Feather, experiments on, - = = > 372
Fire-beat, on its reflection, - - = 300, 305
on its refraction, = - - 311, 315
on its transmission, = ~ = 476, 524
Fish, experiments on their light, atl = i 163
on their organ of hearing, - - - 15
Flame-heat, on its transmission, ms = - 462, 524
Fluids, elastic, on the vibrations of different ones, = 124
Flustra foliacea, experiments on, - - 334, 362
Focus, on that of the rays of heat, = — = - - 444
G
Gas, muriatic acid, effects of electricity on it, + a 190
effects of electrifying it with inflammable sub-
stances, - - - - = 194
Gelatin, remarks on, = 2 = 366, 376, 396
Glow-worms, experiments on their light, ~ ~ 178, 180
Gorgonia, experiments on various species of, =i; 338, 362
Gunpowder, comparison of its strength with that of fulminating
mercury, - miaris - - 207, 236
on the matter remaining after its explosion, - 237
lo
Hair, remarks on, = - - - 371

Hartcuett, Cuarwes, Esq. Chemical experiments on zoo-
phytes; with some observations on the component parts of

_ membrane, - - - - aap i
Heat, on its different refrangibility, - - 255, 271, 438

on the solar and terrestrial rays which occasion it, 293, 437

INDEX.

5Be2

page
Heat, on the laws to which it is subject, ~ 296
on the reflection of that of the sun, - 296, 298, 302
ee of that of a candle, - - 297
— — of that of hot iron, - ~ 299, 306
nee - of that of fire, - 300, 305
—— on the refraction of that of the sun, - 284, 308, 310, 317
_—— of that of a candle, - - 308
—— of that of fire, ~ - 311, 315
—— of that of hot iron, - 313, 319
—— on the focus of its rays, ' ~ - - 444
—— on the transmission of heat-making rays, - 445, 520
— of terrestrial flame-heat, = 462, 524
— — of the solar heat which ts of equal re-
peneiellity with red rays, - ~ 470, 520
of that ae fire, - “ 476, 524
—— of invisible solar heat, 2 485, 520
fees ——_—_————. of invisible terrestrial heat, - 490, 524
—— on its transmission through colourless substances, ~- 449
— —=—_—_—_-—- through coloured glasses, - 453
—_— through liquids, - ! 456
— through scattering substances, -~ 458
—— on the scattering of solar heat, - 497
whether it be occasioned by the same rays as light, or by dif-
ferent ones, - - 506
Heavens, on the time it would take t to sweep them, = 84
He Luins, THE Rev. Joun. A second appendix to the improved
solution of a problem in physical astronomy, inserted in the Phi-
Josophical Transactions for the year 1798, containing some further
remarks, and improved formule for computing the coefficients A
and B; by which the arithmetical work is considerably shortened
and facilitated, - - - - 86
Henry, Mr. Wittiam. Account of a series of experiments, un-
dertaken with the view of decomposing the muriatic acid, - 188
Hrerrings, experiments on their light, - 163
Herscuer, Wittiam, LL.D. On the power of penétrating into
space by ‘telescopes ; with a comparative determination of the
extent of that power in natural vision, and in telescopes of va-
rious sizes and constructions ; illustrated by select observations, 49
SS Investigation of the powers of the
prismatic colours to heat Ne illuminate objects; with remarks,
that prove the different refrangibility of radiant heat. To which
is added, an inquiry into the method of viewing the sun advan-
tageously, with telescopes of large apertures and high magnifying
powers, - - = - - 255

INDEX.

age
Herscuer, Wittiam, LL.D. Experiments on the refrangibility i
of the invisible rays of the sun, > . - - 284
—_—_— Experiments on the solar, and on
the terrestrial rays that occasion heat; with a comparative view
of the laws to which light and heat, or rather the rays which occa-
sion them, are subject, in order to determine whether they are the
same, or different, - - “. - 293, 437
Home, Everarp, Esq. The Croonian Lecture. On the structure --
and uses of the membrana tympani of the ear, es — 1
Some additional remarks, on the mode
of hearing in cases where the membrana tympani has been de-
stroyed, - - - - - 159
Some observations on the head of the
Ornithorhynchus paradoxus, - - - 432
Hoof, experiments on, - - - - 374
Horn, experiments on, = ie = - 372
Horse, remarks on its membrana tympani, - - 6
Howarpb, Epwarp, Esq. Ona new fulminating mercury, 204

Hume, Natuaniet, M.D. Experiments and observations on
the light which is spontaneously emitted, with some degree of.

permanency, from various bodies, - - - 161-
I
Illuminating power, on that of coloured rays, ~ < 262
Images, on double ones caused by atmospherical refraction, - 239
Iron, bot, on the reflection of its heat, - - 299, 306
on the refraction of its heat, 4 = 313, 319
— on the transmission of its heat, we 490, 524
Isis, experiments on various species of, - - 335, 362
L,

Latitude, on that of various places, - 624, 644, 649, 655, 661
Lecture, Croonian, Pe ~ - - - 1
Lemur Loris, remarks on its arteries, ee = - 100
tardigradus, remarks on its arteries, - = 98
Lig bt, experiments and inquiries respecting it, - - 106
- on the analogy between it and sound, - - 125
- on the laws to which it is subject, - ~ 295

whether it be occastoned by the same rays as heat, or by
different ones, - 5 - adie 506

- on the transmission of terrestrial scattered light through va-
rious substances, - - - 528

——-- on the scattering of terrestrial light by various substances, §33
——- spontaneous, experiments and observations on the kind of

light so called, ~ - - - 161

INDEX.

page

Light, spontaneous, on the degree of putrescence necessary for its
emission, - a - - 163
——- On its separation and preservation, 165, 171
—- —————_ 0 its extinction and revivification, 171,47,
—- ———-——- effects of motion on it, - - 175
—- ——-———_ does not affect the thermometer, - 176
—- ——_——- effects of cold on it, = = £97
——- — of heat on it, ~ - 179

- —- of the human body and animal fluids
on it, = a = — ra 184
Lion, remarks on its carotid artery, = Es 102
Longitude, on that of various places, - 624, 644, 649, 655, 661
Luminous bodies, remarks on, E 49

M

Mackerels, experiments on their light, “noses - 164
Madrepora, experiments on various species of, - 329, 360
Magnifying power, remarks on, = - - 8
Membrana tympani, on its structure and uses, - - 1
on the effects arising from its destruction, 151, 159
Membrane, observations on its component parts, - 327, 366
Mercury, fulminating, on a new one, - - 204
method of preparing it, “ 205, 214
— effects of concussion on it, = 206
—_—___—____ effects of electrical shocks on it, - 206
. temperature at which it explodes, - 207

ee comparison of its strength with that of gun-
‘powder, - - = - 207, 236
on its constituent principles, - 216
- on its characteristic properties, 230, 237
Miillepora, experiments on various species of, © - 331, 362

Morean, Witi1am, Esq. On the method of determining, from
the real probabilities of life, the values of contingent reversions
in which three lives are involved in the survivorship, - 22
Munpece, Caprain Wicxtiam. An account of the trigonome-
trical survey, carried on in the years 1797, 1798, and 1799, by
order of Marquis Cornwallis, Master-General of the ordnance, 539

Muscular fibre, experiments on, - - -, 391
N

Nail, iron, remarks on its appearance in a microscope, 2 263

—— human, experiments on, 2 d a 374

Nicholson, Mr. Remarks on his opinion respecting the electric
apparatus of the torpedo, &c. - ~ - 429

INDEX.
age
O pant: 298
Ornitborbyncbus paradoxus, observations on its head, a 432
|
Pipes, on their harmonic sounds, - “ “ 121
Plates, on their vibrations, - = e ~ 140
Poker, bot, on the reflection of its heat, ~ = 299, 306
Presents received by the Royal Society, from November 1799 to
July 1800, - - q = = P29
Prismatic colours, experiments on their heating power, « 256
————— experiments on their illuminating power, 262
—_———— on the reflection of the heat that accompanies
them, - = - = be * 298
—————-—-— onthe refraction of the heat that accompanies them, 310
: R
Rain, register of, at Lyndon, in Rutland, - 2 - 46
Rays, on the solar and terrestrial ones that occasion heat, 293, 437
—-— on the heating power of coloured ones, - - 256
—-— on the illuminating power of coloured ones, = 262
—-— on the reflection of invisible ones, e = 302, 304
—-— on the refraction of invisible ones, - 284, 317; 319
—-— on the condensation of invisible ones, - 304, 317
—-— on the different refrangibility of those of heat, it 271, 438
—-— on the focus of those of heat, = St ee 444
—-— on the transmission of heat- making ones, _ "445, 520
—— ——— of invisible ones, - 405, 520
—-— whether light and heat be occasioned by the same, or by
different ones, - - - - - 506
Refraction, atmospberical, on double images caused by it, - 239
oo extraordinary instance of, - 720
Reversions, contingent, on determining the values of those in which
three lives are involved in the survivorship, - - 22
Rods, on their vibrations, 6 Bs . . 140
S
Scale, horny, experiments on, = - - - 374
Scales of fish, experiments on, - - -"% 373
Shells, observations on, - = - - 3275 357
Skin, experiments on, - - - - 369, 378
Silver, on a fulminating one, - - - - 233
Soap, Chaptal’s, remarks on, - - - - 392
Sound, experiments and inquiries respecting it, - - 106
—--— ocular evidence of its nature, = - ~ 115,
—-— on its velocity, : : . rs . 116

INDEX,

page

Sound, on sonorous cavities, : - - E 116
—-— on its divergence, - . - - 118
on its decay, - - = - 120

—-— on the harmonic sounds of pipes, - - 121
—-— on the vibrations of different elastic fluids, = 124
—-— on the analogy between light and sound, - - 125
on the coalescence of musical sounds, - - 130
—--— on the frequency of vibrations constituting a given note, 133
—--— on the vibrations of chords, - - - 134
—--—— on the vibrations of rods and Pits - - 140
on the human voice, - - 141
—-— on the temperament of nftisieat intervals, - 143
Space, on penetrating into it by telescopes, - - 49, 64
Sponge, experiments on various species of, - - 352, 364
Sun, on viewing it advantageously, 2 - 255, 273
on the refrangibility of its invisible rays, - - 284

See Heat and Rays.
Survey, trigonometrical, carried on in the years 1797, 1798, and

1799, account of, = bins ta LgAG - 539
— particulars RENE to the operations of the
year 1797, - - - 542
— ——_——. angles len in the year 1797, - 549
nn particulars relating to the operations of the
year 1798, - - - - 555
— ——-—-—— angles taken in the year 1798, 559
_ —— —— particulars elaine to the operations of the
year 1799; ; 563
—————--——_-—— _ angles taken in the year 1799) = 569
———_—_————-— situations of the stations, : 576
———— particulars relating to the base on Sedgemoor, 584
_— — principal triangles, - 588, 677, 702
—_————____— secondary triangles, - 610, 689, 703
—— latitudes and longitudes of various places, 624,
644, 649, 655, 661
—_____-_——_— bearings of the stations from various paral-
lels, : - - - 643, 653
——__.-—_—_—__ ——_ bearings of intersected objects from various
parallels, - - - 645, 657
——_—_. ————. survey of the northern and western parts
of Kent, Essex, &c. - - - 676
——_—__—_—_ altitudes of the stations, - 7103 717
mean terrestrial refractions, - 715, 719

Survivorship. See Reversions.

: ié
INDEX.
é
ni pag
Tadpoles, experiments on their light, - - 168
Tanning principle, remarks on, na a A 382
Telescopes, on penetrating into space by them, - 49, 64
on their magnifying power, - - é 68
on viewing the sun advantageously with mie 255, 273
experiments with them, - - 277
Temperament, on that of musical intervals, 4 - 143
Thermometer, register of, at Lyndon, in Rutland, : - 46
Thermometers, on their sensibility, “ - - 447
Torpedo, remarks on its electric apparatus, ~ 416, 429
Tortoise shell, experiments on, = - FS 375» 397
Trig onometrical survey. See Survey.
Tubipora musica, experiments on, - - - 333, 362
Vv
Vibrations, on those of different elastic fluids, - - 124
- on the frequency of those constituting a given note, 133
- on those of chords, - - - 134
- on those of rods and plates, - - 140.
Vision, observations on, - - aI - 49
Voice, human, remarks on, - - - : 141
Votta, Mr. ALExanpeER. On the electricity excited by the
mere contact of conducting substances of different kinds, - 408
WwW
Weather of 1798, remarks on, - - - - 47
Willow, remarks on its bark, - - - - 382
Wottaston, Witt1am Hype, M.D. On double images
caused by atmospherical refraction, - - - 239
Wood, shining, experiments on its light, - - 1775-179"
Y
Yolk of egg, remarks on, ~ 389
Youne, Tuomas, M. D. Outlines of experiments and i squires
_respecting sound and light, - - - - 106
Z
Zoopbytes, chemical experiments on, a jtsied «ne - 327
From the Press of a

W. BULMER & Co.
Cleveland-Row, St. Fames’s.

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