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UNIVERSITY OF CALIFORNIA
AT LOS ANGELES

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iLtbrarp of electrical Science

I'OLUME ONE

A DICTIONARY OF

E LECTRIC AL

WORDS, TERMS and PHRASES

EDWIN J. HOUSTON, A.M., PH.D.

EMERITUS PROFESSOR OF NATURAL PHILOSOPHY AND PHYSICAL GEOGRAPHY

IN THE CENTRAL HIGH SCHOOL OF PHILADELPHIA J PROFESSOR OF

PHYSICS IN THE FRANKLIN INSTITUTE OF PENNSYLVANIA ;

ELECTRICIAN OF THE INTERNATIONAL ELECTRICAL

EXHIBITION, ETC., ETC., ETC.

P ART ONE A to S

NEW YORK
P. F. COLLIER fcf SON

1902

APPENDIX B

BY EDWIN J. HOUSTON

S05T
WtflcL

PREFACE TO THE FIRST EDITION.

THE rapid growth of electrical science, and the almost daily addition to it of new
words, terms and phrases, coined, as they too frequently are, in ignorance of
those already existing, have led to the production of an electrical vocabulary that is
already bewildering in its extent. This multiplicity of words is extremely discourag-
ing to the student, and acts as a serious obstacle to a general dissemination of elec-
trical knowledge, for the following reasons :

1. Because, in general, these new terms are not to be found eve^ in the unabridged
editions of dictionaries.

2. The books or magazines, in which they were first jroposed, are either inac-
cessible to the ordinary reader, or, if accessible, are often written in phraseology un-
intelligible except to the expert.

3. The same terms are used by different writers in conflicting senses.

4. The same terms are used with entirely different meanings.

5. Nearly all the explanations in the technical dictionaries are extremely brief as
regards the words, terms and phrases of the rapidly growing and comparatively new
science of electricity.

In this era of extended newspaper and periodical publication, new words are often
coined, although others, already in existence, are far better suited to express the same
ideas. The new terms are used for a while and then abandoned ; or, if retained,
having been imperfectly defined, their exact meaning is capable of no little ambiguity;
and, subsequently, they are often unfortunately adopted by^different writers with such
varying shades of meaning, that it is difficult to understand their true and exact
significance.

Then again, old terms buried away many decades ago and long since forgotten, are
\ dug up and presented in such new garb that their creators would most certainly fail
to recognize them.

It has been with a hope of removing these difficulties to some extent that the author
r has ventured to present this Dictionary of Electrical Words, Terms and Phrases to his
^$ brother electricians and the public generally.

He trusts that this dictionary will be of use to electricians, not only by showing the
sjt wonderful extent and richness of the vocabulary of the science, but also by giving the
eral consensus of opinion as to the significance of its different words, terms or
phrases. It is, however, to the general public, to whom it is not only a matter of
interest but also one of necessity to fully understand the exact meaning of electrical
literature, that the author believes the book will be of the greatest value.

In order to leave no doubt concerning the precise meaning of the words, terms and
phrases thus defined, the following plan has been adopted of giving :
(i.) A concise definition of the word, term or phrase.

(2.) A brief statement of the principles of the science involved in the definition.
J VOL. 1

853927

(3.) Where possible and advisable, a cut of the apparatus described or employed
in connection with the word, term or phrase denned.

It will be noticed that the second item of the plan makes the Dictionary ap-
proach to some extent the nature of an Encyclopedia. It differs, however, from
an Encyclopedia in its scope, as well as in the fact that its definitions in all cases
' are concise.

Considerable labor has been expended in the collection of the vocabulary, for
which purpose electrical literature generally has been explored. In the alphabetical
arrangement of the terms and phrases defined, much perplexity has arisen as to the
proper catch-word under which to place them. It is believed that part of the
difficulty in this respect has been avoided by the free use of cross references.

In elucidating the exact meaning of terms by a brief statement of the principles
of the science involved therein, the author has freely referred to standard textbooks on
electricity, and to periodical literature generally. He is especially indebted to works
or treatises by the following authors, viz. : S. P. Thompson, Larden, Gumming,
Hering, Prescott, Ayrton, Ayrton and Perry, Pope, Lockwood, Sir William Thom-
son, Fleming, Martin and Wetzler, Preece, Preece and Sivewright, Forbes, Max-
well, De Watteville, J. T. Sprague, Culley, Mascart and Joubert, Schwendler,
Fontaine, Noad, Smee, Depretz, De la Rive, Harris, Franklin, Cavallo, Grove,
Hare, Daniell, Faraday and very many others.

The author offers his Dictionary to his fellow electricians as a starting point only.
He does not doubt that his book will be found to contain many inaccuracies, ambig-
uous statements, and possibly doubtful definitions. Pioneer work of this character
must, almost of necessity, be marked by incompleteness. He, therefore, invites
the friendly criticisms of electricians generally, as to errors of omission and commis-
sion, hoping in this way to be able finally to crystallize a complete vocabulary of
electrical words, terms and phrases.

The author desires in conclusion to acknowledge his indebtedness to his friends,
Mr. Carl Henng, Mr. Joseph Wetzler and Mr. T. C. Martin, for critical exami-
nation of the proof sheets ; to Dr. G. G. Faught for examination of the proofs of
the parts relating to the medical applications of electricity, and to Mr. C. E. Stump
for valuable aid in the illustration of the book ; also to Mr. George D. Fowle,
Engineer of Signals of the Pennsylvania Railroad Company, for information concern-
ing their System of Block Signaling, and to many others.

EDWIN J. HOUSTON.

CENTRAL HIGH SCHOOL, PHILADELPHIA, PA.,
SEPTEMBER, 1889.

PREFACE TO THE SECOND EDITION.

THE first edition of the "Dictionary of Electrical Words, Terms and Phrases" met
with so favorable a reception that the entire issue was soon exhausted.
Although but a comparatively short time has elapsed since its publication, electrical
progress has been so marked, and so many new words, terms and phrases have been
introduced into the electrical nomenclature, that the preparation of a new edition has
been determined on rather than a mere reprint from the old plates.

The wonderful growth of electrical science may be judged from the fact that the
present work contains more than double the matter and about twice the number of
definitions that appeared in the earlier work. Although some of this increase has
been due to words which should have been in the first edition, yet in greater part it
has resulted from an actual multiplication of the words used in electrical literature.

To a certain extent this increase has been warranted either by new applications of
electricity or by the discovery of new principles of the science. In some cases, how-
ever, new words, terms or phrases have been introduced notwithstanding the fact that
other words, terms or phrases were already in general use to express the same ideas.

The character of the work is necessarily encyclopedic. The definitions are given
in the most concise language. In order, however, to render these definitions intel-
ligible, considerable explanatory matter has been added.

The Dictionary has been practically rewritten, and is now, in reality, a new book
based on the general lines of the old book, but considerably changed as to order of
arrangement and, to some extent, as to method of treatment.

As expressed in its preface, the author appreciates the fact that the earlier book
was tentative and incomplete. Though the wide scope of the second edition, the
vast number of details included therein, and the continued growth of the electrical
vocabulary must also necessarily make this edition incomplete, yet the author ventures
to hope that it is less incomplete than the first edition. He again asks kindly criti-
cisms to aid him in making any subsequent edition more nearly what a dictionary of
so important a science should be.

The order of arrangement in the first edition has been considerably changed. The
initial letter under which the term or phrase is defined is in all caSjes that of the noun.

For example, "Electric Light " is defined under the term " Light, Electric " ;

" Diameter of Commutation " under "Commutation, Diameter of , " "Alter-
nating Current Dynamo- Electric Machine" under "Machine, Dynamo-Electric,
Alternating Current ." As before, the book has numerous cross references.

Although the arrangement of the words, terms and phrases under the initial letter
of the first word, term or phrase, as, for example, " Electric Light" under the letter E,
might possess some advantages, yet, in the opinion of the author, the educational value

of the work would be thereby considerably decreased, since to a great extent such an
arrangement would bring together incongruous portions of the science.

Frequent cross references render it possible to use the Dictionary as a text-book in
connection with lectures in colleges and universities. With such a book the student need
nuke notes only of the words, terms or phrases used, and afterwards, by the use of the
definitions and explanatory matter connected therewith, work up the general subject
matter of the lecture. The author has successfully used this method in his teaching.

In order to separate the definitions from the descriptive matter, two sizes of type
have been used, the definitions being placed in the larger sized type.

In the descriptive matter the author has not hesitated to quote freely from standard
electrical works, electrical magazines, and periodical literature generally. Among the
numerous works consulted, besides those to which reference has already been made
in the preface to the first edition, he desires to acknowledge his indebtedness espe-
cially to "The Alternating Current Transformer," by J. A. Fleming ; to various works
of John W. Urquhart ; to "Modern Views of Electricity," by Prof. O. J. Lodge; to
"A Text-book of Human Physiology," by Landois & Sterling; and to "Practical
Application of Electricity in Medicine and Surgery, " by Liebig & Rohe.

The cuts or diagrams used in the book have either been drawn especially for the
work or have been taken from standard electrical publications.

The chart of standard electrical symbols and diagrams has been taken from Prof.
F. B. Crocker's paper on that subject.

The definition of terms used in systems of electric railways have been taken
mainly from a paper on " Standards in Electric Railway Practice," by O. T. Crosby.

The author desires especially to express his obligations to Prof. F. B. Crocker of
the Electrical Engineering Department, Columbia College, New York, and to Carl
Hering, of Philadelphia, for critical examination of the entire manuscript and for many
valuable suggestions ; also to The Electrical World and the Electrical Engineer of New
York, and to Prof. Elihu Thomson, Edward Caldwell, T. C. Martin, Dr. Louis Bell,
Joseph Wetzler, Nikola Tesla, Wm. H. Wahl, Prof. Wm. D. Marks, Prof. A. E.
Dolbear, C. W. Pike, John Hoskin, and numerous others, for aid in connection with
new words or phrases. So far as they relate to the medical applications of electricity,
the proof sheets were revised by Dr. G. G. Faught, of Philadelphia.

The author desires to thank critics of the first edition and the electrical fraternity in
general for valuable suggestions. He presents this second e lition of his Dictionary in the
hope that it may to some extent properly represent the vocabulary of electrical science.

CENTRAL HIGH SCHOOL, EDWIN J. HOUSTON.

PHILADELPHIA, May, 1892.

PREFACE TO THE THIRD EDITION.

THE second edition of the "Dictionary of Electrical Words, Terms, and Phrases"
was exhausted in such a comparatively short time that the publishers believed
that what new matter might be required for a third edition could best be added in
the form of an appendix.

Although not quite two years have elapsed since the issue of the second edition,
yet the growth of electrical science has continued at so rapid a pace, and new words,
terms, and phrases have of necessity been introduced so rapidly, that fully twenty per
cent., both of new words and new matter, have been found necessary for the third
edition. Had this fact been known in time, it might have been better to have
developed the additional matter throughout the text, rather than placing it at the end
of the book as an appendix.

Should a demand be made for a fourth edition, the author contemplates re-
writing and re-arranging the entire volume. He is thoroughly aware of the inaccuracies
and incompleteness of many of the definitions in the second edition, and hopes, in
the event of a demand for a fourth edition, to produce a volume more nearly ap-
proximating to what an electrical dictionary should be. In the meantime, he again
asks the kindly criticisms of his fellow laborers in the electrical field to aid him in the
work.

In order to facilitate the use of the cross-references, all words, terms, and phrases
referred to in the appendix are so marked; i. e., (See Appendix Insulation, Kilo-
metric, of Cable. ) All references not so marked will be found in the main text of the
dictionary.

The author desires to express his obligations to numerous authors and technical
journals for information as to new words, terms, and phrases, and to the significance
generally given to them in actual use. He desires especially to acknowledge his
obligations to his colleague, Mr. A. E. Kennelly, and to Professors R. A. Fessenden,
C. Wellman Park; to Messrs. C. P. Steinmetz, J. F. Kelly, O. B. Shallenberger, Carl
Hering, H. W. Frye, W. D. Weaver, W. F. C. Hasson, Townsend Wolcott, J. B.
Cahoon, and many others, for reading of proof sheets and suggestions.

The author presents this third edition of the Dictionary with the hope that it
may prove of value to the electrical fraternity.

EDWIN J. HOUSTON.
PHILADELPHIA, May, 1894.

PREFACE TO THE FOURTH EDITION.

TN preparing the fourth edition of his " Dictionary of Electrical
1 Words, Terms and Phrases," the author soon found that the
recent marvellous growth in the electrical vocabulary was such that
it would be impossible to add, in the shape of a separate appendix,
the new words, terms and phrases only, that it was necessary to
introduce into the book. This will be evident from the fact that
the added words exceed in number those already contained in the
first, second and third editions. Since it was deemed inadvisable
by the publisher to recast the entire book, the only course left open
to the author was to alphabetically arrange all the old and new
words, and to present them in concise definitions without any ency-
clopaedic matter, referring the reader to the matter contained in
the earlier editions for illustration and detail.

It has also been thought advisable to introduce a change in the
manner of arrangement, the words, terms and phrases being alpha-
betically arranged according, either to the word, or to the first word
of the term or phrase. This has permitted the entire suppression
of all cross references, which, in view of the author's past expe-
rience, he believes will prove an advantage.

The author desires to acknowledge the very valuable assistance
afforded him by his colleague, Dr. A. E. Kennelly, in the prepa-
ration of the matter for the fourth edition, both in collecting new
terms, as well as in preparing the definitions, and reading the
proof.

The author trusts, that the fourth edition of his electrical Diction-
ary will prove of benefit not only to the electrical world but to the
reading public generally.

All criticisms will be gladly received.

EDWIN J. HOUSTON.

PHILADELPHIA, December, 1897.

A DICTIONARY

ELECTRICAL

WORDS, TERMS AND PHRASES.

A. or An. An abbreviation sometimes used
in medical electricity for anode. (See Anode.)

A. C. C. An abbreviation used in medical
electricity for Anodic Closure Contraction.
(See Contraction, Anodic Closure.)

A. D. C. An abbreviation used in medical
electricity for Anodic Duration Contraction.
(See Contraction, Anodic Duration)

A. 0. C. An abbreviation used in medical
electricity for Anodic Opening Contraction.
(See Contraction, Anodic Opening.)

Abscissa of Rectilinear Co-ordinates. A
line or distance cut off along axis of abscissas.

The abscissa of the point D, Fig. i, on the curve
O D R, is the distance D I, or its equal A 2,
measured or cut off on the line A C, the axis of
abscissas; or, briefly, A 2, is the abscissa of the
point D.

Abscissas, Axis of One of the

axes of co-ordinates used for determining the
position of points on a curved line.

Thus the position of
the point D, Fig. i, on
the curved line O D R,
is determined by the per-
pendicular distances, D I
and D 2, of such point
from two straight lines,
A B and A C, called the
ax fs of co-ordinates. AC, A 2 C

is called the axis of ab- F *- r ; **<**/ Co-ordinate*,
scissas, and AB, the axis of ordinates. The point

A, where the lines are considered as starting or
originating, is called fat point of origin, or, gen-
erally, the origin.

The use of co-ordinates was first introduced by
the famous mathematician, Des Cartes.

Absolute. Complete in itself.

The terms absolute and relative are used in
electricity in the same sense as ordinarily.

Thus, a galvanometer is said to be calibrated
absolutely when the exact current strengths re-
quired to produce given deflections are known ;
or, in other words, when the absolute current
strengths are known ; it is said to be calibrated
relatively when only the relative current strengths
required to produce given deflections are known.

The word absolute, as applied to the units em-
ployed in electrical measurements, was introduced
by Gauss to indicate the fact that the values of
such units are independent both of the size of the
instrument employed and of the value of gravity at
the particular place where the instrument is
used.

The word absolute is also used with reference
to the fact that the values of the units could
readily be redetermined from well known con-
stants, in case of the loss of the standards.

The absolute units of length, mass, and time
are more properly called the C. G. S. units, or
the centimetre-gramme-second units. (See Units,
Absolute.)

An absolute system of units based on the milli-
gramme ^ millimetre, and second, was proposed by
Weber, and was called the millimetre -milli-
gramme-second units. It has been replaced by

Abs.]

[Ace.

the C. G. S. units. (See Units, Centimetre-
Gramme- Second. Units, Fundamental.)

Absolute Block System for Railroads.

(See Block System for Railroads, Absolute)

Absolute Calibration. (See Calibration,
Absolute)

Absolute Electrometer. (See Electrome-
ter, Absolute?)

Absolute Galvanometer. (See Galva-
nometer, Absolute?)

Absolute Unit of Current. (See Current,
Absolute Unit of.)

Absolute Unit of Electromotive Force.
(See Force, Electromotive, Absolute Unit
of.)

Absolute Unit of Inductance. (See In-
ductance, Absolute Unit of)

Absolute Unit of Resistance. (See Re-
sistance, Absolute Unit of)

Absolute Unit of Self-induction. (See
Induction, Self, Absolute Unit of)

Absolute Units. (See Units, Absolute.)

Absolute Vacuum. (See Vacuum, Ab-
solute)

Absorption. The taking, or, literally,
drinking in, of one form of matter by another,
such as a gas, vapor or liquid by a solid ; or
of the energy of sound, light, heat, or elec-
tricity by ordinary matter.

Absorption, Acoustic The taking

in of the energy of sound waves produced by
one sounding or vibrating body by another
vibrating body.

Acoustic absorption may result in the dissipa-
tion of the absorbed energy, as heat, or in sym-
pathetic vibrations. (See Vibrations, Sympathetic.)

Absorption, Electric The appar-
ent soaking of an electric charge into the
glass or other solid dielectric of a Leyden jar
or condenser. (See Condenser.)

The capacity of a condenser varies with the
time the condenser remains charged and with the
time taken in charging. Some of the charge
acts as if it soaked into the solid dielectric, and
this is the cause of the residual charge. (See
Charge, Residual.) Therefore, when the con-

denser is discharged, less electricity appears than
was passed in ; hence the term electric absorption.

Absorption, Luminous The ab-
sorption of the energy of light in its passage
through bodies.

When sunlight falls on an opaque colored body,
such for example as a red body, all the colors but
the reds are absorbed. y The reds are then thrown
off and thus cause the color. In the same manner,
when sunlight falls on a transparent colored body,
such for example as red, all colors but the reds are
absorbed, and the reds are transmitted.

When sunlight falls on a phosphorescent body,
a part of the light is absorbed as heat ; another
part is absorbed by the molecules being set into
motion sufficiently rapid to cause them to emit
light or to become luminous.

A mass of glowing gas or vapor absorbs waves
of light of the same length as those it itself emits.
This is the cause of the dark lines of the solar
spectrum, called the Fraunhoffer lines.

The amount of light absorbed by the glass globe
of an incandescent lamp, according to Urquhart,
is as follows, viz.:

Clear glass 10 per cent.

Ground glass 35 "

Opalescent glass 50 "

Absorption, Selective The absorp-
tion of a particular or selected character of
waves of sound, light, heat, or electricity.

Absorption, Thermal The ab-
sorption of heat energy in its passage through
a body.

The phenomena of thermal absorption are
similar to those of luminous absorption. A sub-
stance that is transparent to heat, or which allpws
heat waves to pass through without absorption,
is called diathermanous, or diathermanic, or
is said to be transparent to heat.

Absorptive Power. (See Power, Absorp-
tive)

Acceleration. The rate of change of
velocity.

Acceleration is thus distinguished from velocity:
velocity expresses in time the rate- of- change of
position, as a velocity of three metres per second ;
acceleration expresses in time the rate-of-change
of velocity, as an acceleration of one centimetre
per second.

Since all matter is inert, and cannot change its

Ace.]

[Ace.

condition of rest or motion without the applica-
tion of some force, acceleration is necessarily due
to some force outside the matter itself. A force
may therefore be measured by the acceleration it
imparts to a given mass of matter.

Acceleration is positive when the velocity is in-
creasing, and negative when it is decreasing.

Acceleration, Dimensions of The

value of the acceleration expressed in terms
of the length or of distance by the time. (See
Acceleration, Unit of.}

Acceleration, Unit of That ac-
celeration which will give to a body unit-
velocity in unit-time; as, for example, one
centimetre-per-second in one second.

Bodies falling freely in a vacuum, and ap-
proximately so in air, acquire an acceleration
which in Paris or London, at the end of a second,
amounts to about 981 centimetres per second, or
nearly 32.2 ft. per second.

V
A = , or, in other words,

The acceleration equals the velocity divided by
the time.

But, since velocity equals the Distance, or the

Length traversed in a Unit of Time, V = t .

L
Therefore, A = X = -I. = ^ , O r

The acceleration equals the length, or the dis-
tance passed through, divided by the square of the
time in seconds.

These formulae represent the Dimensions of
Acceleration.

Accumulated Electricity. (See Electri-
city, Accumulated^}

Accumulating 1 Electricity. (See Electri-
city, Accumulating?)

Accumulation of Electricity. (See Elec-
tricity, Accumulation of.}

Accumulator. A -word sometimes applied
to any apparatus in which the strength of a
current is increased by the motion past it of a
conductor, the currents produced in which
tend to strengthen and increase the current
which causes the induction.

The word accumulator is sometimes applied to
Sir Wm. Thomson's Electric Current Accumu-
lator.

Current accumulators operate on the reaction
principle of dynamo-electric machines. In this
sense, therefore, a dynamo-electric machine is an
accumulator. (See Machine, Dynamo-Electric,
Reaction Principle of.}

Fig. 2. Barltrw's Whtel.

The copper disc D, Fig. 2, has freedom of
rotation, on a horizontal axis at O, in a magnetic
field, the lines of force of which, represented by
the dotted lines in the drawing, pass downward
perpendicularly into the plane of the paper.

If, now, a current from any source be passed
in the direction A, O, B, C, A, through the circuit
A, O, B, C, A, which is provided with spring
contacts at O, and A, the disc will rotate in the
direction of the curved arrow. This motion is
due to the current acting on that part of the disc
which lies between the two contacts A and O.
This apparatus is known as Barlow's Wheel.

If, when no current is passing through the
circuit, the disc be turned in the direction of the
arrow, a current is set up in such a direction as
would oppose the rotation of the disc. (See
Law, Lenz's.)

If, however, the disc be turned in the opposite
direction to that of the arrow, induction currents
will as before be produced in the circuit. As
this rotation of the disc tends to move the circuit
O A, towards the parallel but oppositely directed
circuit B C, these two circuits being parallel and
in opposite directions tend to repel one another,
and there will thus be set up induced currents
that tend to oppose the motion of rotation, and
the current of the circuit will therefore increase
in strength. (See Dynamics, Electro.} Should
then a current be started in the circuit, and the
original field be removed, the induction will be
continued, and a current which, up to a certain
extent, increases or accumulates, is maintained in
the circuit during rotation of the disc. (Larden.)

Barlow's Wheel, when used in this manner, is
known as Thomsons Electric Current Accumu-
lator.

Acc.]

[Ace.

Accumulator. A word often applied to
a Leyden jar or condenser, which permits the
gradual collection from an electric source of
a greater charge than it would otherwise be
capable of containing.

A condenser. (See Condenser?)

The ability of a source to accumulate an in-
creased charge when connected to a condenser is
due to the increased capacity which a plate or
other conductor acquires when placed near
another plate or conductor. (See Condenser.
Jar, Leyden.}

Accumulator, Capacity of -- The

capacity of a condenser, expressed in micro-
farads. (See Condenser, Capacity of.)

Accumulator or Condenser ; Laws of Ac-
cumulation of Electricity. Sir W. Snow
Harris, by the use of his Unit-Jar and Elec-
tric Thermometer, deduced the following
laws for the accumulation of electricity, which
we quote from Noad's " Student's Text-Book
of Electricity," revised by Preece :

(l.) "Equal quantities of electricity are given
off at each revolution of the plate of an electrical
machine to an uncharged surface, or to a surface
charged to any degree of saturation."

(2. ) "A coated surface receives equal quantities
of electricity in equal times ; and the number of
revolutions of the plate is a fair measure of the
relative quantities of electricity, all other things
remaining the same."

(3.) " The free action of an electrical accumula-
tion is estimated by the interval it can break
through, and is directly proportional to the quan-
tity of electricity."

(4.) " The free action is inversely proportional
to the surface."

(5.) " When the electricity and the surface are
increased in the same ratio, the discharging in-
terval remains the same ; but if, as the electricity
is increased, the surface is diminished, the dis-
charging interval is directly as the square of the
quantity of electricity."

(6.) " The resistance of air to discharge is as
the square of the density directly. "

According to some later investigations, the
quantity a plane surface can receive under a given
density depends on the linear boundary of the
surface as well as on the area of the surface.

" The amount of electrical charge depends on

surface and linear extension conjointly. There
exists in every plane surface what may be termed
an electrical boundary, having an important rela-
tion to the grouping or disposition of the electric
particles in regard to each other and to surrounding
matter. This boundary in circles or globes is
represented by their circumferences. In plane
rectangular surfaces, it is by their linear extension
or perimeter. If this boundary be constant, their
electrical charge varies with the square root of
the surface. If the surface be constant the charge
varies with the square root of the boundary. If
the surface and boundary both vary, the charge
varies with the square root of the surface multi-
plied into the square root of the boundary."

These laws apply especially to continuous sur-
faces taken as a whole, and not to surfaces divided
into separate parts.

By electrical charge Harris meant the quantity
sustained on a given surface under a given elec-
trometer indication ; by electrical intensity, he
meant the indication of the electrometer corre-
sponding to a given quantity on a given surface.

(See Condenser, Capacity of. Capacity, Elec-
trostatic. Capacity, Specific Inductive. )

Accumulators of this character are now
generally called Condensers. (For more modern
principles concerning their construction and
capacity see Condenser. Condenser, Capacity of.)

Accumulator, Secondary or Storage
Cell -- Two inert plates partially sur-
rounded by a fluid incapable of acting cham-
ically on either of them until after the passage
of an electric current, when they become
capable of furnishing an independent electric
current.

This use of the term accumulator is the one
most commonly employed. A better term for
such a cell is a secondary or storage cell. (See
Cell, Secondary or Storage.)

Commercially, an accumulator consists of a
single jar and its electrolyte, in which a single
set of positive and negative plates is properly
placed.

Accumulator, Water-Dropping --
An apparatus devised by Sir W. Thomson for
increasing the difference of potential between
two electric charges.

The tube X Y, Fig. 3, connects with a reser-
voir of water which is maintained at the zero
potential of the earth. The water escapes from

Ach.]

the openings at C and D, in small drops and falls
on funnels provided, as shown, to receive the
separate drops and again discharge them.

The vessels A, A', and B,
B', which are electrically
connected as shown, are
maintained at a certain small A hj
difference of potential, as
indicated by the respective
-f- and signs.

Under these c i r c u m -
stances, therefore, C and D, A '
will be charged inductively Fi S- 3- Water-Drop-
with charges opposite to t ing Acatmulator -
those of A and B, or with and -f- electricities
respectively. As the drops of water fall on the
funnels, the charges which the funnels thus con-
stantly receive are given up to B' and A', before
the water escapes. Since, therefore, B, B', and
A, A', are receiving constant charges, the differ-
ence of potential between them must continually
increase. This apparatus operates on the same
principle as the replenisher. The drops of water
act as the carriers, and A, A', and B, B', as the
hollow vessels. (See Replenisher.)

Achromatic. Free from false coloration.

Images formed by ordinary lenses do not pos-
sess the true colors of the object, unless the edges
of the lenses are cut off by the use of a diaphragm ;
i. f., an opaque plate with a central circular
opening. The edges of the lenses disperse the
light like an ordinary prism, and so produce rain-
bow colored (prismatic) fringes in the image.
The use of an achromatic lens is to obviate this
false coloration.

Achromatizable. Capable of being freed
from false coloration.

Achromatize. To free from false color-
ation.

Achromatizing. Freeing from false color-
ation.

Acid, Spent A battery acid, or other

acid, that has become too weak for efficient
action.

In a voltaic cell the acid of the electrolyte
becomes spent by combining with the metal of
the positive plate.

Acidometer. A special form of hydrom-
eter used in determining the specific gravity
of the acid liquid in a secondary or storage

cell. (See Areometer or Hydrometer. Cell.
Storage?)

The scale on the acidometer tube is made to in-
dicate the density according to the distance the
floating instrument sinks in the liquid.

Aclinic Line. (See Line, Aclinic)

Acoustic Absorption. (See Absorption,
Acoustic?)

Acoustic Engraving. (See Engraving,
Acoustic?)

Acoustic Telegraphy. (See Telegraphy,
Acoustic?)

Acoustic Tetanus. (See Tetanus, Acous-
tic:)

Acoutemeter, Electric An ap-
paratus for electrically testing the delicacy of
hearing.

The Acoutemeter is one of the many applica-
tions of Hughes' sonometer. It consists of three
flat coils placed parallel to one another on a grad-
uated rod, passing through their axes. The
central coil, which is used as the primary of an
induction coil, is fixed. The other two, which are
employed as secondary coils, are movable. (See
Sonometer, Hughes*. Coil, Induction. Micro-
phone.} A microphone, electrical tuning fork,
switches, plugs, and other accessories, are suitably
placed and connected. The subject whose hear-
ing is to be tested is placed with his back to tke
apparatus, and with two telephone receivers tightly
fixed to his ears. As various sounds are produced,
the outer or movable coils are moved gradually
away from the central coil, until no sound is
heard in the telephone receivers. This distance
is in the inverse ratio of the delicacy of hearing of
the individual.

Actinic Photometer. (See Photometer,
Actinic?)

Actinic Ray. (See Ray, Actinic?)

Actinism. The chemical effects of light,
as manifested by the decomposition of various
substances.

Under the influence of the sun's light, the car-
bonic acid absorbed by the leaves of plants is de-
composed in the living leaves into carbon, which is
retained by the plant for the formation of its
woody fibre or ligneous tissue, and oxygen, which
is thrown off.

Act,]

[Act.

The bleaching of curtains, carpets, and other
fabrics exposed to sunlight is caused by the actinic
power of the light. The photographic picture is
impressed by the actinic power of light on a plate
covered with some sensitive metallic salt.

Actinograph. An apparatus for measur-
ing and recording the intensity of the chemi-
cal effects of light.

Actinography. The method of measuring
and recording the intensity of the chemical
effects of light.

Actinometer. A word sometimes applied
to a pyrheliometer. (See Pyrheliometer)

Actinometer, Electric An appa-
ratus for electrically measuring the intensity
of the chemically active rays present in any
luminous radiation.

The rays from the luminous source are per-
mitted to fall on a selenium resistance, and their
intensity determined by the change observed in
the resistance as indicated by the deflections of a
galvanometer placed in circuit with the selenium
resistance. Or, a thermo-electric pile is employed,
and the amount of heat present determined by the
indications of a galvanometer placed in its
circuit.

Action, Cataphoric The action

of electric osmose or cataphoresis. (See
Cataphoresis.)

Action Currents. (See Currents, Action?)

Action, Inductive, Lines of

Lines within the space, separating a charge
and a neighboring body, along which elec-
trostatic inductive action takes place.

Lines of electrostatic force.

Lines of inductive action pass through the
dielectric, separating the two bodies, and termi-
nate on the surfaces of the conductor. According
to the now generally received notions, the elec-
trostatic charge exists in the mass of the dielectric,
and not in that of the conductor. The lines of
inductive action terminate against the surfaces,
one at the positive, and the other at the negative
surface. A true E. M. F. exists in the space
traversed by lines of inductive action. A con-
ductor brought into this space becomes electri-
fied, or is strained in such a manner that a
momentary current is produced by the rearrange-

ment of the electrification brought about by
electrostatic induction.

Action, Local, of Dynamo-Electric Ma-
chine The loss of energy in a dy-
namo-electric machine by the setting up of
eddy currents in its pole pieces, cores, or
other conducting masses. (See Currents,
Eddy.}

In a dynamo-electric machine local action is
obviated by a. lamination of the pole pieces, arma-
ture core, etc. (See Core, Lamination of.)

Action, Local, of Voltaic Cell

An irregular dissolving or consumption of the
zinc or positive element of a voltaic battery, by
the fluid or electrolyte, when the circuit is
open or broken, as well as when closed, or in
regular action.

Local action is due to small particles of such
impurities as carbon, iron, arsenic, or other
negative elements, in the positive plate. These
impurities form with the positive element minute
voltaic couples, and thus direct the corrosive
action of the liquid to portions of the plate near
them. Local action causes a waste of energy.
It may be avoided by the amalgamation of the
zinc. (See Zinc, Amalgamation of.)

Action, Magne-Crystallic A term

proposed by Faraday to express differences
in the action of magnetism on crystalline
bodies in different directions.

A needle of tourmaline, if hung with its axis
horizontal, is no longer paramagnetic, as usual,
but diamagnetic. The same is true of a crystal
of bismuth. Faraday concluded from these ex-
periments that a force existed distinct from either
the paramagnetic or the diamagnetic force. He
called this the magne crystallic force.

Pltlcker infers from these phenomena that a
definite relation exists between the ultimate form
of the particles of matter and their magnetic be-
havior. The subject may be regarded as yet
somewhat obscure. (See Polarity, Diamagnetic.}

Action of a Current on a Magnetic Pole.

(See Current, Action of, on a Magnetic
Pole)
Action, Refreshing, of Current

The restoration, after fatigue, of muscular and
nervous excitability obtained by the action of

Act.]

voltaic alternatives. (See Alternatives, Vol-
taic)

Activity. The work done per second by
any agent. (This term is but seldom used.)

Work-per-second, or, as generally termed
in the United States, Power, or Rate of
Doing Work. (See Power.)

Activity, Unit of A rate of work-
ing that will perform one unit of work per
second.

In C. G. S. units, the activity of one erg per
second.

The C. G. S. unit of activity is very small.
One Watt, the practical unit of activity or power,
is equal to ten million ergs per second. (See
Watt.)

The unit of activity generally used for mechan-
ical power is the horse-power, or 746 watts.
(See Horse- Power.)

Actual Cautery. (See Cautery, Actual)

Acute Angle. (See Angle, Acute)

Adapter. A screw nozzle fitted to an elec-
tric lamp, provided with a screw thread to en-
able it to be readily placed on a gas bracket
or chandelier in place of an ordinary gas
burner.

Adherence. The quality or property of
adhering. (See Adhesion)

Adherence, Magnetic Adhesion be-
tween surfaces due to magnetic attraction.

Magnetic adhesion has been applied, among
other things, to a brake action on car wheels,
either by causing them to adhere directly to the
track or to a brake-block.

Adhesion. The mutual attraction which
exists between unlike molecules. (See At-
traction, Molecular?)

The phenomena of adhesion are due to the
mutual attraction of dissimilar molecules.

Adhesion, Electric Adhesion be-
tween surfaces due to the attraction of unlike
electrostatic charges.

Molecular adhesion must be distinguished from
the attraction which causes a piece of dry and
warmed writing paper, that has been rubbed by a
piece of india-rubber, to stick to a papered wall.
In this latter case the attraction between the wall

[Aer.

and the paper is due to the mutual attraction of
two dissimilar electrostatic charges. Molecular
adhesion must also be distinguished from the at-
traction of opposite magnetic poles.

Adhesion, Galvanoplastic -- The ad-

hesion of a galvanoplastic deposit or coating
to surfaces subjected to electroplating. (See
Plating, Electro)

Adiathermaiicy. Opacity to heat.

A substance is said to be diathermanous when
it is transparent to heat. Clear, colorless crys-
tals of rock salt are very transparent both to light
and to heat. Rock salt, covered with a layer or
deposit of lampblack or soot, is quite transparent
to heat. An adiathermanous body is one which
is opaque to heat.

Heat transparency varies ndt only with differ-
ent substances, but also with the nature of the
source from which the heat is derived. Thus, a
substance may be opaque to he it from a non-
luminous source, such as a vessel filled with boil-
ing water, while it is comparatively transparent
to heat from a luminous source, such as an incan-
descent solid or a voltaic arc.

A similar difference exists as regards transpar-
ency to light. A colorless glass will allow light
of any color to pass through it. A blue glass will
allow blue light to pass freely through it, but will
completely prevent the passage of any red light ;
and so with other colors.

Adiathermauic. Possessing the quality of
adiathermancy. (See Adiathermancy)

Adjustable Condenser. (See Condenser,
Adjustable)

Adjuster, Cord --- A device for ad-
justing the length of a pendant cord.

Adjustment. Such a regulation of any
apparatus as will enable it to properly perform
its functions.

.Epinus' Condenser. (See Condenser,

Aerial Cable. (See Cable, Aerial)
Aerial Cable, Suspending Wire of

(See Wire, Suspending, of Aerial Cable)
Aerial Line. (See Line, Aerial.)
Aerolites. A name sometimes given to

meteorites.
Meteorites are masses of solids which pass

Aff.]

[Ago.

through the upper portions only of the earth's
atmosphere on their approach to the orbit of the
earth, or which fall through the air on the earth's
surface from the sky. They are luminous at
night and are followed by a train of fire. The
luminosity is due to heat produced by friction
through the air. Meteors frequently burst from
the sudden expansion of their outer portions.

Some meteorites are composed of nearly pure
iron alloyed with nickel. The majority of them,
however, are merely stones or oxidized sub-
stances. Their average velocity is about 26 miles
a second.

Affinity, Chemical Atomic attrac-
tion.

The force which causes atoms to unite and
form chemical molecules.

Atomic or chemical attraction generally results
in a loss of the characteristic qualities or proper-
ties which distinguish one kind of matter from
another. In this respect chemical affinity differs
from adhesion, or the force which holds unlike
molecules together. (See Adhesion. Attraction,
Molecular.} If, for example, sulphur is mixed
with lampblack, no matter how intimate the
mixture, the separate particles, when examined
by a magnifying glass, exhibit their peculiar color,
lustre, etc. If, however, the sulphur is chemi-
cally united with the carbon, a colorless, transpar-
ent, mobile liquid, called carbon bisulphide, re-
sults, that possesses a disagreeable, penetrating
odor.

Chemical affinity, or atomic combination, is in
fluenced by a variety of causes, viz. :

(I.) Cohesion. Cohesion, by binding the mole-
cules more firmly together, opposes their mutual
atomic attraction.

A solid rod of iron will not readily burn in the
flame of an ordinary lamp ; but, if the cohesion be
overcome by reducing the iron rod to filings, it
burns with brilliant scintillations when dropped
into the same flame. In this case the increase of
surface and the increased temperature of the
smaller particles also contribute to the result.

(2.) Solution. Solution, by giving the molecules
greater freedom of motion, favors their chemical
combination.

(3.) Heat. Heat sometimes favors atomic com-
bination possibly by decreasing the cohesion, and,
possibly, by altering the electrical relations of the
atoms. If too great, heat may produce decom-
position. There is for most substances a critical

temperature below wh^h chemical combination
will not take place. (See Thermolysis. )

(4.) Light. Decomposition, or the lessening of
chemical affinity, through the agency of light, is
called Actinism, Light also causes the direct
combination of substances. A mixture of equal
volumes of hydrogen and chlorine unites explo-
sively when exposed to the action of full sunlight.
(See Actinism.)

(5.) Electricity. An electric spark will cause
an explosive combination of a mixture of oxygen
and hydrogen. Electricity also produces chemi-
cal decomposition. (See Electrolysis.)

Helmholtz accounts for the electro-chemical
attraction of oxygen for zinc by supposing that all
substances possess a definite amount of attraction
for electricity, and that the attraction of zinc in
this respect exceeds that of copper and the other
metals. He thus regards the zinc as attracting
its electric charge rather than as attracting the
oxygen. Since both zinc and copper are dyad
metals, this view, as will be seen, is at variance
with later views.

Chemical affinity may be caused by the opposite
attractions of electrical charges naturally possessed
by the atoms of matter. This would appear to be
rendered probable by the law of electro-chemical
equivalence. (See Equivalence, Electro-Chemical,
Law of. Electricity, Atom of.)

After Currents. (See Currents, After.}

Aging of Alcohol, Electric (See

Alcohol, Electric Aging of.)

Agonal. Pertaining to the agone. (See
Agone.)

Agone. A line connecting places on the
earth's surface where the magnetic needle
points to the true geographical north.

The line of no declination or variation of
a magnetic needle. (See Needle, Magnetic,
Declination of.)

As all the places on the earth where the mag-
netic needle points to the true north may be ar-
ranged on a few lines, it will be understood that
the pointing of the magnetic needle to the true
geographical north is the exception and not the
rule. In many places, however, the deviation
from the true geograpical north is so small that
the direction of the needle may be regarded as
approximately due north.

Agonic. Pertaining to the agone.

Air.

[Ala.

Air-Blast for Commutators. An inven-
tion of Prof. Elihu Thomson to prevent the
injurious action of destructive flashing at the
commutator of a dynamo-electric machine.

A thin, forcible blast of air is delivered through
suitable tubes at points on the three-part commu-
tator cylinder of the Thomson- Houston dynamo,
where the collecting brushes bear on its surface.
The effect is to blow out the arc or prevent its for-
mation and thus avoid its destructive action on
the commutator segments. The use of the air-
blast also permits the free application of oil, thus
further avoiding wear.

Fig. 4. Air-Blast on Commuta
The blast-nozzles are shown at B 3 , B 8 , Fig. 4,
near the collecting brushes.

The air-supply is obtained from a blower at-
tached directly to the shaft of the machine. Its
construction and operation will be readily under-
stood from an inspection of Fig. 5, in which the

Fig. f. The Thomson Blower.

top is removed for ready examination of the
interior parts.

Air Churning. (See Churning, Air)

Air Condenser. (See Condenser, Air)

Air Field. (See Field, Air)

Air-Gap. (See Gap, Air)

Air-Line Wire. (See Wire, Air-Line)

Air Magnetic Circuit. (See Circuit, Air
Magnetic)

Air-Pump. (See Pump, Air)

Air-Pump, Oeissler's Mercurial

(See Pump, Air, Geissler's Mercurial)

Air-Pump, Mechanical (See Pump,

Air, Mechanical)

Air-Pump, Mercurial (See Pump,

Air, Mercurial)

Air-Pump, Sprengel's Mercurial

(See Pump, Air, SprengeFs Mercurial)

Air-Space Cut-Out (See Cut-Out, Air-
Space)

Alarm, Burglar A device, generally

electric, for automatically announcing the
opening of a door, window, closet, drawer, or
safe, or the passage of a person through a
hallway, or on a stairway.

Electric burglar-alarm devices generally consist
of mechanism for the operation of an automatic
make -and -break bell on the opening or closing of
an electric circuit. The bell may either continue
ringing only while the contact remains closed, or,
may, by the throwing on of a local circuit or
battery, continue ringing until stopped by some
non-automatic device, such as a hand-switch.

The alarm-bell is stationed either in the house
when occupied, or on the outside when the house
is temporarily vacated, or may connect directly
with the nearest police station.

Burglar-alarm apparatus is of a variety of
forms. Generally, devices are provided by means
of which, in case of house protection, an annunci-
titor shows the exact part where an entrance has
been attempted. (See Annunciator, Burglar-
Alarm) Switches are provided for disconnecting
all or parts of the house from the alarm when so
desired, as well as to per-
mit windows to be partly
raised for purposes of ven-
tilation without sounding
the alarm. A clock is fre-
quently connected with the
alarm for the purpose of
automatically disconnect-
ing any portion of the
house at or for certain in-
tervals of time.

Fig. 6 shows a burglar- Fig. 6. Burglar-Alarm
alarm with annunciator, Annunciator.

switches, switch-key, cut-off, and clock.

Alarm, Burglar, Central-Station

A burglar-alarm, the contact points of which
are placed in the places to be protected, and

Ala.]

[Ate.

connected by suitable circuits with alarms
placed in a centrally located station.

In a system of central-station burglar-alarms, a
number of houses, factories, banks, etc., are all
connected telegraphically with the nearest police
station, or other central station, constantly pro-
vided with police officers. A series of contacts are
placed on doors, windows, safes and money draw-
ers, and connected with alarms and annunciators
placed in the central station. An unauthorized
entrance, therefore, is automatically telegraphed
to the central station and its exact location indi-
cated on the annunciator. Systems of central-
station fire-alarms are constructed on a similar
plan.

Alarm, Electric An automatic de-
vice by which attention is called to the occur-
rence of certain events, such as the opening
of a door or window; the stepping of a person
on a mat or staircase; the rise or fall of tem-
perature beyond a given predetermined point;
or, a device intended to call a person to a tel-
egraphic or telephonic instrument.

Electric-alarms are operated by means of the
ringing of an electro-magnetic or mechanical bell,

Fig. 7. Electrically Started Mechanical Alarm.

which is electrically called into action by either
closing or opening an electric circuit, generally
the former.

Electric-alarms may be divided into two classes,
viz.:

(I.) Mechanically operated alarms, or those in

which the alarm is given by clock-work, started
by means of an electric current.

(2.) Those in which the alarm is both set in ac-
tion and operated by an electric current.

In Fig. 7 is shown the general construction of
an electrically started mechanical alarm. The
attraction of the armature B, by the electro-mag-
net A, moves the armature lever pivoted at C,
and thus releases the catch e, and permits the
spring or weight connected with the clock move-
ment to set it in motion and strike the bell.

Electrically actuated alarm-bells are generally
of the automatic make-and-break form. The
striking lever is operated by the attraction of the
armature of an electro-magnet, and is provided
with a contact-point, so placed that when the
hammer is drawn away from the bell, by the ac-
tion of a spring, on the electro-magnet losing its
magnetism, a contact is made, but when the ham-
mer is drawn towards the bell the contact is open-
ed. When, therefore, the hammer strikes the
bell, the circuit is opened, and the electro-magnet
releases its armature, permitting a spring to again
close the contact by moving the striking lever
away from the bell. Once set into action, these
movements are repeated while there is battery
power sufficient to energize the magnet.

In Fig. 8, in which is shown an electrically ac-
tuated alarm-bell, the battery terminals are con-

Fig. 8. Automatic Make-and-Break.

..ected with the right and left hand binding-posts,
P and M. The hammer, K, is connected with a
striking lever, which forms part of the circuit,"
and which is attached toihe armature of the elec
tro-magnet e. A metallic spring, g, bears against
the armature when the latter is away from the
magnet, but does not touch the armature when
it is moved towards the magnet. A small spring
draws the lever away from the magnet when no
current is passing. The movements of the arma

[AlCo

ture thus automatically open and close the circuit
of the electro-magnet.

This form of make-and-break is called an auto-
matic make-and-break.

Alarm, Electrically Operated An

alarm that is maintained in operation by the
electric current. (See Alarm, Electric^)

Alarm, Electro-Mechanical - - A
mechanically operated alarm that is started
or set in operation by means of an electric
current. (See Alarm, Electric^)

Alarm, Fire, Automatic An in-
strument for automatically telegraphing an
alarm from any locality on its increase in tem-
perature beyond a certain predetermined point.

Fire-alarms are operated by thermostats, or by
means of mercurial contacts; i. e., a contact
closed by the expansion of a column of mercury.
(See Thermostat. Contact, Mercurial.)

In systems of fire-alarm telegraphs, the alarm
is automatically sounded in a central police sta-
tion and in the district fire-engine house. (See
Telegraphy, Fire-Alarm. )

Alarm, Mercurial Temperature

An instrument for automatically telegraphing
an alarm by means of a mercurial contact on
a predetermined change of temperature.

The action of mercurial contacts is dependent
on the fact that, as the mercury expands more
than glass by the action of heat, the mercury level
reaches a contact-point placed in a glass tube and
thus completes the circuit through its own mass,
which forms the other or movable contact.
Sometimes both contacts are placed on opposite
sides of a tube and are closed when the mercury
reaches them.

Mercurial temperature or thermostat alarms
are employed in hot-houses, incubators, tanks
and buildings for the purpose of maintaining a
uniform temperature.

Alarm, Telegraphic An alarm-bell
for calling the attention of an operator to
a telegraphic instrument when the latter is of
the non-acoustic or needle type.

In acoustic systems of telegraphy the sounds
themselves are generally sufficient.

Alarm, Telephonic An alarm-bell

for calling a correspondent to the receiving
telephone.

These alarms generally consist of magneto-
electric bells. (See Bell, Magneto-Electric.)

Alarm, Temperature An electric
alarm automatically operated on a change of
temperature. (See Alarm, Fire, Automatic)

Alarm, Thermostat An electric
alarm that is thrown into action by a thermo-
stat. (See Thermostat)

Alarm, Water or Liquid Level

A device for electrically sounding an alarm
wnen a water surface varies materially from
a given level.

An electric bell is placed in a circuit that is au-
tomatically closed or broken by the movement of
contact-points operated by the change of liquid
level.

A form of electric alarm for a water-level is
shown in Fig. 9. The float is provided with
contacts for closing an electric circuit, when it
either rings a bell, or, by its action on some form
of automatic cut-off, stops the water.

Fig: 9. Water- Level Alarm. Fig. 10.

When arranged with a double float, as shown
in Fig. 10, the alarm may be made to signal
either a too high or a too low water level.

Alarm, Yale-Lock-Switch Burglar
An apparatus whereby the opening of a
door by an authorized party provided with the
regular key will not sound an alarm, but any
other opening will sound such alarm.

Fig. n. Yale-Lock-Switch.

A Yale-lock burglar-alarm switch is shown in
Fig. II.

Alcohol, Electric Aging of A pro-
cess for the rapid aging of alcohol, by rx-

Ale.]

[All.

posing it to the action of electrically produced
ozone.

Instead of the ordinary process of aging alco-
hol, by exposing it in partially closed vessels to
the action of air, it is exposed to the action of
ozone, electrically produced.

The ozone employed is obtained in substan-
tially the usual way by the passage of a rapid
succession of electric sparks through air.

Alcohol, Electric Rectification of

A process whereby the bad taste and odor of
alcohol, due to the presence of aldehydes,
are removed by the electrical conversion of
the aldehydes into true alcohols through the
addition of hydrogen atoms.

An electric current sent through the liquid
between zinc electrodes liberates oxygen and hy-
drogen from the decomposition of the water.
The nascent or atomic hydrogen converts the
aldehydes into alcohol and deprives the pro-
ducts of their fusel oil, while the oxygen forms
insoluble zinc oxide.

Algebraic Co-efficient (See Co-efficient,
Algebraic?)

Algebraic Notation. (See Notation, Al-
gebraic?)

All-Night Arc Lamp. (See Lamp, All-
Night Arc?)

All-Night Electric Lamp. (See Lamp,
All-Night Arc.}

Allotropic. Pertaining to allotropy. (See
Allotropy.}

Allotropic State. (See State, Allotropic).

Allotropy. A variation of the physical
properties of an elementary substance with-
out change of composition of its molecules.
(See State, Allotropic.)

Alloy. A combination, or mixture, of two
or more metallic substances.

Alloys in most cases appear to be true chemi-
cal compounds. In a few instances, however,
they may form simple mixtures.

The composition of a few important alloys is
here given:

Solder, plumber's; Tin 66 parts, Lead 34 parts.

Pewter, hard; Tin 92 parts, Lead 8 parts.

Britannia metal; Tin 100 parts, Antimony 8
parts, Copper 4 parts, Bismuth, I part.

Type metal; Lead 80, Antimony 20 parts.
Brass, white; Copper 65, Zinc 35 parts.
Brass, red; Copper 90, Zinc I o parts.
Speculum metal ; Copper 67, Tin 33 parts.
Bell metal; Copper 78, Tin 22 parts.
Aluminium bronze; Copper 90, Aluminium 10
parts.

Alloy. To form a combination or mixture
of two or more metallic substances.

Alloy, German Silrer An alloy

employed for the wires of resistance coils,
consisting of 50 parts of copper, 25 of zinc,
and 25 of nickel.

German silver wire is suitable for resistance
coils, because its resistance varies but slightly with
changes of temperature. It is cheaper than plati-
num-silver alloy, and is therefore employed ex-
tensively. Platinum silver alloy, however, has
more resistance for a given size of wire, and its re-
sistance varies somewhat less than German silver
with changes of temperature, and is therefore used
where greater accuracy is desired.

Alloy, Palladium An alloy of pal-
ladium with other metals.

Palladium forms a number of useful alloys with
various metals. Some of the palladium alloys are
as elastic as steel, are unaffected by moisture or
ordinary corrosive agencies, and are entirely de-
void of paramagnetic properties; that is to say,
they cannot be magnetized after the manner of
iron.

These properties have been utilized by their
discoverer, Paillard, in their employment for the
hair-springs, escapements and balance wheels of
watches, in order to permit the watches to be car-
ried into strong magnetic fields without any ap-
preciable effects on the rate of the watch. A
number of careful tests made by the author, by
long continued exposure of watches, thus pro-
tected by the Paillard alloys, in extraordinary
fields, show that the protection thus given the
watches enables them to be carried into the strong-
est possible magnetic fields without appreciably
affecting their rate.

The Paillard palladium alloys have the follow-
ing composition, viz.:

Alloy No. i.

Palladium 60 to 75 parts.

Copper 151025 "

Iron i to 5 "

All.]

[Alp.

Alloy No. 2.
Palladium .............. 50 to 75 parts.

Copper 20 to 30 "

j ron c to 20 "

Alloy No. j.
Palladium .............. 65 to 75 "

Copper ................ 151025 "

Nickel ................ ito 5 "

Gold .................. ito 2*

Platinum ............... i to 2 "

Silver .................. 3 toio

Steel .............. i to 5 "

Alloy No. 4.

Palladium .............. 45 to 50 "

Silver .................. 201025 "

Copper ................ l 5 to2 S <

Gold ................... 2 to 5 "

Platinum ............... 2 to 5 "

Nickel ................. 2105 "

Steel ................... 2 to 5 "

The great value of the palladium alloys, when
employed for the hair-springs of watches, arises
not only from their non -magnetizable properties,
and their inoxidizability, but particularly from the
fact that their elasticity is approximately the same
for comparably wide ranges of temperature.

Alloy, Platinum-Silver -- An alloy
consisting of one part of platinum, and two
parts of silver.

Platinum- silver alloy is now extensively em-
ployed for resistance coils from the fact that
changes in temperature of the alloy produce but
comparatively small changes in its electrical re-
sistance. (See Alloy, German Silver.}

Alphabet, Telegraphic -- An arbi-
trary code consisting of dots and dashes,
sounds.deflections of a magnetic needle, flashes
of light^ or movements of levers, following one
another in a given predetermined order, to
represent the letters of the alphabet and the
numerals.

Alphabet, Telegraphic: International

n A T-i. j t if i

Code -- The code of signals for letters,

etc., employed in England and on the Euro-
pean continent generally.

Similar symbols are employed for the numerals
and the punctuation marks.

It will be observed that it is mainly in the

characters of the American Morse, in which spaces
** used > that the Continental characters differ
from the American. This is due to the use of the
needle instrument, with which a space cannot well
be represented. A movement or deflection of the

S ' nK ' e *"**

Printing Needle Printing .Needle

* x/ n <\

* '- o --- "/
c ~* /X/N p --- *'' x
'- ---- ^

International Telegraphic Code.

needle to the left signifies a dot; a movement to
the ri g ht a dash -

Alphabet, Telegraphic : Morse's __

Varkms ^ of dots and dashes> Qr

deflections of a ma tic needle to the rf ht
^ ^ ^.^ represent ^ lettere Q ^

alphabet or other signs.

In t^ Morse alpha bet dots and dashes are em-
ployed in recording systems, and sounds of
varying intervals, corresponding to the dots and
dashes, in the sounder system.

A dash is equal in length of time to three dots.
The space between the separate characters of a
single letter is equal to one dot, except in the
American Morse, in which the following letters
contain longer spaces: c> o> R? Y> and z . The

lengt hened spaces are equal to two dots. L is
one an d a half times the length of T.

The sound produced by the down stroke of the
sounding lever in the Morse sounder is readily
distinguishable from the up stroke. When these
differences are taken in connection with the inter-
vals between successive sounds there is no diffi-

culty in reading by sound.
(For methods of recdving the alphabet> see

Sounder , Morse Telegraphic. Recorder, Morse.
Recorder, BaMs Chemical. Recorder, Siphon.
Relay. Magnet, Receiving. ) In the needle tele-
graph, the code is similar to that used in the Morse
Alphabet. (See Telegraphy, Single-Needle.}

Alt.]

AMERICAN MORSE CODE.
ALPHABET.

h ---.

o - -

r - --

& - ---

NUMERALS.
i

PUNCTUATION MARKS.

Period

Comma

Interrogation

Exclamation

Printing

SingJe Needle
X ////

xx ///
xxx //
xxxx/

Period ------ NX \\ \x

Comma ______ x A A /

Interrogation ______ xx / / \\

Exclamation ______ /Ax//

Colon ______ ///NNN

Semicolon ______ /\/\/\

Alteration Theory of Muscle or Nerve
Current (See Theory, Alteration, of
Muscle or Nerve Current?)

Alternating Arc. (See Arc, Alternat-
ing.}

Alternating Current Circuit. (See Cir-
cuit, Alternating Current?)

16 [Alt.

Alternating Current Condenser. (See
Condenser, Alternating Current?)

Alternating Current Dynamo-Electric
Machine. (See Machine, Dynamo-Electric,
Alternating Current?)

Alternating Current Electric Motor.

(See Motor, Electric, Alternating Current?)

Alternating Currents. (See Currents,
Alternating?)

Alternating Currents, Distribution of
Electricity by (See Electricity, Dis-
tribution of, by Alternating Currents?)

Alternating Discharge. (See Discharge,
Alternating?)

Alternating Dynamo-Electric Machine.
(See Machine, Dynamo-Electric, Alternat-
ing Current?)

Alternating Electrostatic Field. (See
Field, Alternating Electrostatic?) ,

Alternating Electrostatic Potential.
(See Potential, Alternating Electrostatic?)

Alternating Field. (See Field, Alternat-
ing?)

Alternating Influence Machine, Wims-
hurst's (See Machine, Wimshurst's
Alternating Influence?)

Alternating Magnetic Field. (See Field,
Alternating Magnetic?)

Alternating Magnetic Potential. (See
Potential, Alternating Magnetic?)

Alternating Potential. (See Potential,
Alternating?)

Alternating Primary Currents. (See
Currents, Alternating Primary?)

Alternating Secondary Currents. (See
Currents, Alternating Secondary?)

Alternation. A change in direction or
phase.

Alternations. Changes in the direction of
a current in a circuit.

A current that changes its direction 300 times
per second is said to possess 300 alternations per
second.

Alternations, Complete A change
in the direction of a current in a circuit from its

Alt]

[A mm.

former direction and back again to that
direction. A complete to-and-fro change.

Complete alternations are sometimes indicated
by the symbol ~.

Alternations, Frequency of A

phrase employed to denote the number of al-
ternations per second.

Alternative Path. (See Path, Alterna-
tive^

Alternatives, Yoltaic A term used

in medical electricity to indicate sudden re-
versals in the polarity of the electrodes of a
voltaic battery.

An alternating current from a voltaic bat-
tery, obtained by the use of a suitable com-
mutator.

Sudden reversals of polarity produce more
energetic effects of muscular contraction than do
simple closures or completions of the circuit.

The muscular contraction produced by a voltaic
current is much stronger when the direction of the
current is rapidly reversed by means of a com-
mutator than when the current is more slowly
broken and the poles then reversed.

The effect of voltaic alternatives is to produce
quick contractions that are in strong contrast to
the prolonged contractions that result from the
faradic current. In the faradic machine, the
reversals are so rapid that the muscle fails to
return to rest before it is again contracted.

Voltaic alternatives are sometimes indicated by
the contraction V. A.

Alternator. A name commonly given to
an alternate current dynamo. (See Machine,
Dynamo-Electric, Alternating Current?)

Alternator, Compensated Excitation of

An excitation of an alternating current
dynamo-electric machine, in which the field is
but partially excited by separate excitement,
the remainder of its exciting current being
derived from the commuted currents of a
small transformer placed in the main circuit
of the machine.

The object of compensated excitation of an
alternator is to render the machine self-governing.

Amalgam. A combination or mixture
of a metal with mercury.

Amalgam, Electric A substance

with which the rubbers of the ordinary fric-
tional electric machines are covered.

Electric amalgams are of various compositions.
The following formula produces an excellent
amalgam :

Melt together five parts of zinc and three of
tin, and gradually pour the molten metal into
nine parts of mercury. Shake the mixture until
cold, and reduce to a powder in a warm mortar.
Apply to the cushion by means of a thin layer of
stiff grease.

Mosaic gold, or bisulphide of tin, and powdered
graphite, both act as good electric amalgams.

An electric amalgam not only acts as a con-
ductor to carry off the negative electricity, but,
being highly negative to the glass, produces a far
higher electrification than would mere leather or
chamois.

Amalgamate. To form into an amalgam.

Amalgamating. Forming into an amal-
gam.

Amalgamation. The act of forming into
an amalgam, or effecting the combination of
a metal with mercury.

Amalgamation of Zinc Plates of Yoltaic
Cell. (See Plates, Zinc, of Voltaic Cell,
Amalgamation of,}

Amber. A resinous substance, generally
of a transparent, yellow color.

Amber is interesting electrically as being be-
lieved to be the substance in which the proper-
ties of electric attractions and repulsions, imparted
by friction or rubbing, were first noticed. It was
called by the Greeks r/\Enrpov, from which the
word electricity is derived. This property was
mentioned by the Greek, Thales of Miletus, 600
B. c., as well as by Theophrastus.

American System of Telegraphy. (See
Telegraphy, American System of.)

American Twist-Joint (See Joint,
American Twist?)

American Wire Gauge. (See Gauge,
Wire, American?)

Ammeter. A form of galvanometer in
which the value of the current is measured
directly in amperes. (See Galvanometer?)

An ampere-meter or ammeter is a commercial
form of galvanometer in which the deflections* of

Amm.J

[Amp.

a magnetic needle are calibrated or valued in am-
peres. As a rule the coils of wire in an ammeter
are of lower resistance than in a voltmeter. The
magnetic needle is deflected from its zero position
by the field produced by the current whose strength
in amperes is to be measured. This needle is held
in the zero position by the action of a magnetic
field, either of a permanent or an electro-magnet,
by the action of a spring, or by a weight under the
influence of gravity. There thus exist a variety
of ammeters, viz. : permanent-magnet ammeters,
electro-magnetic ammeters, spring ammeters and
gravity ammeters.

In the form originally devised by Ayrton and
Perry, the needle came to rest almost imme-
diately, or was dead-beat in action. (See Damp-
ing.') It moved through the field of a permanent
magnet. The instrument was furnished with a
number of coils of insulated wire, which could
be connected either in series or in multiple-arc by
means of a commutator, thus permitting the scale
reading to be verified or calibrated by the use of a
single voltaic cell. (See Circuits, Varieties of.
Commutator. Calibration, Absolute. Calibra-
tion, Relative.) In this case the coils were
turned to series, and a plug pulled out, thus intro-
ducing a resistance of one ohm.

Fig. ra. Ayrton and Perry Ammeter.

Fig. 12 represents an ampere-meter devised by
Ayrton and Perry. A device called a commutator
for connecting the coils either in series or parallel
is shown at C. Binding-posts are provided at
P, PS, and S. The dynamo terminals are con-
nected at the posts P, PS, and the current will
pass only when the coils are in multiple, thus
avoiding accidental burning of the coils. In this
case the entire current to be measured passes
through the coils so coupled. The posts S and
PS, are for connecting the single battery cell cur-
rent.

A great variety of ampere-meters, or ammeters,
have been devised. They are nearly all, how-

ever, constructed on essentially the same general
principles.

Commercial ammeters are made in a great va-
riety of forms. When the currents to be meas-
ured are large, as is generally the case in electric
light or power stations, they consist of a coil of
insulated wire, often of a single turn, or even of
but a part of a turn, having a balanced core of
iron or steel capable of moving freely within it.

Ammeter, Electro-Magnetic A

form of ammeter in which a magnetic needle is
moved against the field of an electro-magnet
by the field of the current it is measuring.
(See Ammeter?)

Ammeter, Gravity A form of am-
meter in which a magnetic needle is moved
against the force of gravity by the field of the
current it is measuring. (See Ammeter?)

Ammeter, Magnetic- Vane An

ammeter in which the strength of a magnetic
field produced by the current that is to be
measured is determined by the repulsion ex-
erted between a fixed and a movable iron
vane, placed in said field and magnetized
thereby. (See Voltmeter, Magnetic- Vane.}

Ammeter, Permanent-Magnet A

form of ammeter in which a magnetic needle
is moved against the field of a permanent mag-
net by the field of the current it is measuring.
(See Ammeter?)

Ammeter, Reducteur for (See Re-

ducteur, or Shunt for Ammeter?)

Ammeter, Spring A form of am-
meter in which a magnetic needle is moved
against the action of a spring by the field of
the current it is measuring. (See Ammeter.}

Amorphous. Having no definite crys-
talline form.

Mineral substances have certain crystalline
forms, that are as characteristic of them as are the
forms of animals or plants. Under certain cir-
cumstances, however, they occur without definite
crystalline form, and are then said to be amor-
phous solids.

Amperage. The number of amp&res pass-
ing in a given circuit.

The current strength in any circuit as indi-
cated by an ampere-meter placed in the circuit.

Amp.]

[Amp.

Ampere. The practical unit of electric
current.

Such a rate-of-flow of electricity as trans-
mits one coulomb per second.

Such a current (or rate-of-flow or trans-
mission of electricity) as would pass with an
electromotive force of one volt through a cir-
cuit whose resistance is equal to one ohm.

A current of such a strength as would
deposit .005084 grain of copper per second.

A current of one ampere is a current of such
definite strength that it would flow through a cir-
cuit of a certain resistance and with a certain
electromotive force. (See Force, Electromotive.
Volt. Resistance. Ohm.}

Since the ohm is the practical unit of resistance,
and the volt the practical unit of electromotive
force, the ampere, or the practical unit of current,
is the current that would flow through unit resist-
ance, under unit pressure or electromotive force.

To make this clearer, take the analogy of water
flowing through a pipe under the pressure of a
column of water. That which causes the flow is
the pressure or head ; that which resists the flow
is the friction of the water against the pipe, which
will vary with a number of circumstances. The
rate-of-flow may be represented by so many cubic
inches of water per second.

As the pressure or head increases, the flow in-
creases proportionally; as the resistance increases,
the flow diminishes.

Electrically, electromotive force corresponds to
the pressure or head of the water, and resistance
to the friction of the water and the pipe. The
ampere, which is the unit rate-of-flow per second,
may therefore be represented as follows,

viz. : C = _, as was announced by Ohm in his
R

law. (See Law of Ohm.}

This expression signifies that C, the current in
amperes, is equal to E, the electromotive force in
volts, divided by R, the resistance in ohms.

We measure the rate-of-flow of liquids as so
many cubic inches or cubic feet per second that is,
in units of quantity. We measure the rate-of-flow
of electricity as so much electricity per second.
The electrical unit of quantity is called the Coul-
omb. (See Coulomb.} The coulomb is such a
quantity as would pass in one second through a
circuit in which the rate-of-flow is one ampere.

An ampere is therefore equal to one coulomb per

The electro-magnetic unit of current is such a
current that, passed through a conducting wire
bent into a circle of the radius of one centimetre,
would tend to move perpendicular to its plane a
unit magnetic pole held at its centre, and
sufficiently long to practically remove the other
pole from its influence, with unit force, i. <?., the
force of one dyne. (See Dyne.) The ampere, or
practical electro-magnetic unit, is one-tenth of
such a current ; or, in other words, the absohite
unit of current is ten amperes.

An ampere may also be defined by the chemical
decomposition the current can effect as measured
by the quantity of hydrogen liberated, or metal
deposited.

Defined in this way, an ampere is such a cur-
rent as will deposit .00111815 gramme, or
.017253 grain, of silver per second on one of the
plates of a silver voltameter, from a solution of
silver nitrate containing from 15 to 30 per cent, of
the salt (See Voltameter], or which will decompose
.00009326 gramme, or .001439 grain of dilute
sulphuric acid per second, or pure sulphuric acid
at 59 degrees F. diluted with about 15 per cent, of
water, that is, dilute sulphuric acid of Sp. Gr. of
about I.I. The present scientific and commercial
practice is to take the ampere to be such a current
as will deposit 4. 024 grammes of silver in one hour.

Ampere Arc. (See Arc, Ampere?)
Ampdre-Feet. (See Feet, Ampere.}
AmpSre-Hour. (See Hour, Ampere.}

Ampere-Meter. An ammeter. (See Am-
meter.}

Ampere-Meter, Balance or Neutral Wire

An ampere-meter placed in the cir-
cuit of the neutral wire, in the three-wire sys-
tem of electric distribution, for the purpose of
showing the excess of current passing over
one side of the system as compared with the_
other side, when the central wire is no longer
neutral.

Ampere-Minute. (See Minute, Ampere}
Ampere Ring. (See king, Ampere?)
Ampere-Second. (See Second, Ampere?)
Ampdre Tap7 (See Tap, Ampere?)
Ampere-Turn. (See Turn, Ampere?)

Ampere-Turn, Primary (See Turn,

Ampere, Primary?)

Amp.]

[Ane.

Ampere-Turn, Secondary (See

Turn, Ampere, Secondary?)

Ainpdre-Yolt. A watt, or the -7-5^ of a
horse-power.

This term is generally written volt-ampere.
(See Volt-Ampere.}

Ampdre-Winding. (See Winding, Am-
pere)

Ampere's Bule for Effect of Current on
Needle. (See Rule, Amperes, for Effect of
Current on Needle?)

Ampere's Theory of Magnetism. (See
Magnetism, Ampere's Theory of)

Amperian Currents. (See Currents, Am-
perian)

Amplitude of Vibration or Wave. (See
Vibration or Wave, Amplitude of)

Ammunition-Hoist, Electric An

electrically operated hoist for raising ammu-
nition to the deck of a ship.

In the electric ammunition-hoist the electric
motor which moves the hoist is made to follow the
motions of the operator's hand, both as regards
direction and speed. The motion of a crank, or
wheel, causes a switch to start an electric motor in
a certain direction, which tends to close the switch,
thus necessitating a race between the operator
and the motor. Shpuld the operator begin to
close the switch more slowly, the motor will over-
take him, will partially close the switch, and thus
* lower the speed of the motor.

Analogous Pole. (See Pole, Analogous)

Analysis. The determination of the com-
position of a compound substance by separ-
ating it into the simple or elementary sub-
stances of which it is composed.

Analysis, Electric The determin-
ation of the composition of a substance by
electrical means.

Various processes have been proposed for elec-
tric analysis; they consist essentially in decompos-
ing the substance by means of electric currents,
and are either qualitative or quantitative. (See
Electrolysis . )

Analysis, Electrolytic A term

sometimes used instead of electric analysis.
(See Analysis, Electric)

Analysis, Qualitative A chemical

analysis which merely ascertains the kinds of
elementary substances present.

Analysis, Quantitative A chemical

analysis which ascertains the relative propor-
tions in which the different components enter
into a compound.

Analyzable. Separable into component
parts.

Analyze. To separate into component
parts.

Analyze, Electrically To separate

electrically into component parts.

Analyzer, Electric A gridiron of

metallic wires which is transparent to electro-
magnetic waves, when its length is perpendic-
ular to them, but opaque to them /. e.,
possessing the ability to reflect them when
rotated 90 degrees from its former position.

The electric analyzer, it will be observed, is
analogous to an analyzer for polarized light. A
reflecting surface, for example, being able to re-
flect polarized light in a given position, and unable
to reflect it when rotated 90 degrees from such
position, is capable of acting as an analyzer for
pjlarized light.

Analyzer, Gray's, Harmonic Telegraphic

An electro-magnet, the armature of

which consists of a steel ribbon stretched in
a metallic frame and capable through regula-
tion, as to tension, by means of a screw, of
being tuned to a certain note.

The steel ribbon is thrown into vibration when-
ever pulsations from the transmitting instruments
are sent over the line corresponding to the rate of
motion of the ribbon, but is not set into vibration
by any others. If, therefore, a number of different
analyzers, tuned to different notes, are placed on
the same line, each will be operated only by the
pulsations sent into the line corresponding to its
rate of motion, and thus multiple transmission in
the same direction is possible. In order to
strengthen the tones of the analyzers, each is pro-
vided with a resonant air column. (See deton-
ator. Telegraphy, Multiplex)

Analyzing. Separating into component
parts.

Anelectric. A word formerly applied to
bodies (conductors) which it was believed
could not be electrified by friction.

Ane.]

[Ani.

This term is now obsolete. Conductors are
easily electrified, when insulated.

Anelectrotonic State. (See State, Anelec-
trotonic)

Anelectrotonic Zone. (See Zone, Anelec-
trotonic^)

Anelectrotonus. In electro-therapeutics,
the decreased functional activity which occurs
in a nerve in the neighborhood of the anode,
or positive electrode, when applied therapeu-
tically. (See Electrotonus)

Anemometer, Electric An appa-
ratus to electrically record or indicate the direc-
tion and intensity of the wind.

In the electric recording anemometer, the force
or velocity of the wind, or both, are recorded on
a moving sheet of paper, on which the time is
marked, so that the exact time of any given
change is known.

Anemoscope. An instrument which indi-
cates, but does not measure the intensity or
record the direction of the wind.

The word is often, though improperly, used in-
terchangeably for anemometer.

Angle. The deviation in direction between
two lines or planes that meet.

Angles are measured by arcs of circles. The
angle at B A C, Fig. 13, is the deviation of the

straight line A B, from A
C. In reading the let-
tering of an angle the
letter placed in the mid-
dle indicates the angle
referred to. Thus B A

C, means the angle be- D~

tween A B and A C ; B A Fig- 13- Angles.

D, the angle between B A and A D. Angles are
valued in degrees, there being 360 degrees in an
entire circumference or circle. Degrees are in-
dicated thus: 90, or ninety degrees.

Angle, Acute An angle whose value

is less than a right angle or 90 degrees.

B A E, or E A D, in Fig. 13, is an acute angle.

Angle, Complement of What an
angle needs to make its value 90 degrees, or a
right angle.

Thus in Fig. 13, B A E, is the complement of
the angle E A D, since BAE4-EAD = 9O
degrees.

Angle, Obtuse An angle whose

value is greater than a right angle or 90
degrees.

E A C, Fig. 13, is an obtuse angle.

Angle of Declination or Variation. (See
Declination, Angle of. Variation, Angle of.)

Angle of Difference of Phase Between
Alternating Currents of Same Period.
(See Phase, Angle of Difference of, Between
Alternating Currents of Same Period?)

Angle of Dip. (See Dip. Dip or Incli-
nation, Angle of)

Angle of Inclination. (See Dip or Incli-
nation, Angle of)

Angle of Lag of Dynamo-Electric Ma-
chine. (See Lag, Angle of, of Dynamo-
Electric Machine)

Angle of Lead. (See Lead, Angle of)

Angle of Variation. (See Variation,
Angle of.}

Angle, Plane An angle contained

between two straight lines.

Angle, Solid An angle contained

between two surfaces.

Angle, Supplement of What an

angle needs to make its value 180 degrees, or
two right angles.

Thus in Fig. 13, E A C, is the supplement of
E A D, because EAD-f-EAC = i8o degrees,
or two right angles.

Angle, Unit An angle of 57.29578

or 57 17' 44.8" nearly. (See Velocity, An-
gular.)

Angnlar Currents. (See Currents, An-
gular.)

Angular Velocity. (See Velocity, Angu-
lar)

Animal Electricity. (See Electricity,
Animal)

Animal Magnetism. (See Magnetism,
Animal)

Anion. The electro-negative radical of a
molecule.

Literally, the term ion signifies a group of
wandering atoms. An union is that group of
atoms of an electrically decomposed or electro lyzed

Ani.]

[Ann.

molecule which appears at the anode. (See
Electrolysis. Anode. )

As the anode is connected with the electro-
positive terminal of a source, the anion is the
electro-negative radical or group of atoms, and
therefore appears at the electro-positive terminal.

A kathion, or electro-positive radical, appears
at the kathode, which is connected with the
electro-negative terminal of the battery. Oxygen
and chlorine are anions. Hydrogen and the
metals are kathions.

Anisotropic Conductor. (See Conductor,
Anisotropic?)

Anisotropic Medium. (See Medium,
Anisotropic?)

Annealing, Electric A process
for annealing metals in which electric heating
is substituted for ordinary heating.

Annual Inequality of Earth's Magnet-
ism. (See Inequality, Annual, of Earth's
Magnetism.

Annual Variation of Magnetic Needle.
(See Needle, Magnetic, Annual Variation
of.)

Annunciator, Burglar-Alarm An

annunciator used in connection with a system
of burglar-alarms. (See Alarm, Burglar?)

Annunciator Clock, Electric -
(See Clock, Electric Annunciator?)

Annunciator Drop. (See Drop, Annun-
ciator?)

Annunciator Drop, Automatic
(See Drop, Automatic Annunciator?)

Annunciator, Electro-Magnetic

An electric device for automatically indicating
the points or places at which one or more
electric contacts have been closed.

The character of the annunciator depends, of
course, on the character of the places at which
these points, places or stations are situated.

Annunciators are employed for a variety of
purposes. In hotels they are used for indicating
the number of a room the occupant of which
desires some service, which he signifies by push-
ing a button, thus closing an electric circuit.
This is indicated or announced on the annuncia-
tor by the falling of a drop, on which is printed a
number corresponding with the room, and by the

ringing of a bell to notify the attendant. The num-
ber is released by the movement of the armature
of an electro-magnet. The drops are replaced in
their former position by some mechanical device
operated by the hand. In the place of a drop a

Fig. 14. Electro -Magnetic Annunciator.

needle is sometimes used, which, by the attraction
of the armature of an electro-magnet, points to
the number signaling.

Annunciators for houses, burglar-alarms, fire-
alarms, elevators, etc., are
of the same general con-
struction.

Annunciators are general-
ly operated by electro-mag-
netic attraction or repulsion,
and are therefore some-
times called electro -magnetic
annunciators.

Fig. 14 shows an annun-
ciator suitable for use in
hotels.

The numbers 28 and 85
are represented as having
been dropped by the closing
of the circuit connected
with them.

Annunciator, Eleva-
tor An annuncia-
tor connected with an
elevator to indicate the
floor signaling.
One form of elevator annunciator is shown in
Fig. 15.

Fig. z$. Elevator
Annunciator.

Ann.]

[Ann.

Annunciator, Fire-Alarm An

annunciator used in connection with a system
of fire-alarms.
Annunciator, Gravity-Drop An

annunciator whose signals are operated by
the fall of a drop.

Fig. ib. Gravity-Drop Annunciator.

A form of gravity-drop annunciator is shown
in Fig. 16. The armature mechanism for the
release of the drop will be understood by an in-
spection of the drawing.

Annunciator, Hotel An annun-
ciator connected with the different rooms of a
hotel.

A hotel-annunciator is generally provided with
a return bell and guest-call.

Annunciator, House An annun-
ciator connected with the rooms of a house.

Annunciator, Needle An annun-
ciator, the indications of which are given by
the movements of a needle instead of the fall
of a drop.

A form of needle-annunciator is shown in
Fig. 17.

Annunciator, Oral or Speaking Tube

An annunciator electrically operated

by means of a puff of breath transmitted
through an ordinary speaking tube.

The oral-annunciator is a contrivance whereby
a central office is placed in communication with a
number of speaking tubes coming from different
points in a hotel or other place. A person
in any room, who wishes to cpmmunicate
with the central office, blows through the
speaking tube in his room, and thus, by
effecting an electric contact, rings a bell and
operates a drop at the annunciator, thus indicat-
ing the exact tube at which the attendant is to
receive the message. The attendant can thus be
placed in easy communication with each of the
rooms whose speaking tubes connect with the
annunciator.

Annunciator, Pendulum or Swinging
An annunciator, the indicating arm of
which consists of a pendulous.or swinging arm,

Fig. 77. Needle- Annunciator.

which, when at rest, points vertically down-
ward, and which is moved to the right or left
by the action of the current.

Pendulous, or swinging-annunciators are gen-
erally so arranged as to need no replacement.

Ano.]

[App.

On the cessation of the current the indicator arm
drops vertically downward.

A relay is preferably used with pendulum-
annunciators, since the rapid makes and breaks
of the current by the bell alarm interfere with
their satisfactory action.

Anodal. Pertaining to the anode. (See
Anode)

Anodal Diffusion. (See Diffusion,

Anode. The conductor or plate of a de-
composition cell connected with the positive
terminal of a battery, or other electric source.

That terminal of an electric source out of
which the current flows into the liquid of a
decomposition cell or voltameter is called the
anode.

That terminal of an electric source into
which the current flows from a decomposition
cell or voltameter is called the kathode.

The anode is connected with the carbon or
positive terminal of a voltaic battery, and the
kathode with the zinc, or negative terminal.
Therefore the word anode has been used to
signify the positive terminal of an electric source,
and kathode, the negative terminal, and in this
sense is employed generally in electro-thera-
peutics. It is preferable, however, to restrict the
use of the words anode and kathode to those
terminals of a source at which electrolysis is
taking place.

The terms anode and kathode in reality refer
to the electro-receptive devices through which
the current flows. Since it is assumed that the
current flows out of a source from its positive
pole or terminal, and back through the source at
its negative pole or terminal, the pole of any
device which is connected with the positive pole
of a source is the part or place at which the
current enters and flows through it, and that
connected with the negative pole, the part at
which it leaves. Hence, probably, the change
in the use of the words already referred to.

Since the anion, or the electro-negative radical,
appears at the anode, it is the anode of an electro-
plating bath, or the plate connected with the
positive terminal of the source, that is dissolved.

When the term anode was first proposed by
Faraday, voltaic batteries were the only available
electric source, and the term referred only to the

positive terminal of a voltaic battery when
placed in an electrolyte.

Anodic. Pertaining to the anode. (See
Anode)

Anodic Electro-Diagnostic Reactions.

(See Reactions, Kathodic and Anodic Elec-
tro-Diagnostic?)

Anodic Opening Contraction. (See Con-
tration, Anodic Opening.)

Anomalous Magnet. (See Magnet, An-
omalous)

Anomalous Magnetization. (See Mag-
netization, Anomalous)

Anti-Induction Cable (See Cable,

Anti-Induction)

Anti-Induction Conductor. (See Con-
ductor, Anti-Induction)

Antilogous Pole. (See Pole, Antilogous)

Anvil. The front contact of a telegraphic
key that limits its motion in one direction.
(See Key, Telegraphic)

Aperiodic Galvanometer. (See Galva-
nometer, Aperiodic)

Apparatus, Faradic-Induction

An induction coil apparatus for producing
faradic currents.

A voltaic battery is connected with the primary
of an induction coil, and its current rapidly
broken by an automatic break, or by a hand
break. The alternating or faradic currents thus
produced in the secondary coils are used for
electro-therapeutic purposes. (See Coil, Induc-
tion.)

Faradic-induction apparatus is made in a great
variety of forms. They all operate, however, on
essentially the same principles.

Apparatus, Faradic, Magneto-Electric

A small magneto-electric machine

employed in electro-therapeutics for producing
faradic currents.

Magneto-electric faradic machines consist essen-
tially of a coil of wire wrapped on an armature
core that is rotated before the poles of permanent
magnets. No commutator is employed, since it is
desired to obtain rapidly alternating currents.

Apparatus, Interlocking Devices
for mechanically operating from a distant signal

App.]

[Arc.

tower, railroad switches and semaphore signals
for indicating the position of such switches,
by means of a system of interlocking levers,
so constructed that the signals and the
switches are so interlocked as to render it
impossible, after a route has once been set up
and a signal given, to clear a signal for a
route that would conflict with the one previ-
ously set up. (See Block System for Rail-
roads^)

Apparatus, Magneto-Electric Medical
A term applied to small magneto-
electric machines employed in medical elec-
tricity for the production of uncommuted
or faradic currents. (See Apparatus, Fara-
dic, Magneto-Electric)

Apparatus, Registering-, Electric

Devices for obtaining permanent records by
electrical means.

Apparatus, Registering, Telegraphic

A name sometimes given to a telegraphic
recorder. (See Recorder, Chemical, Bain's,
Recorder, Morse. Recorder, Siphon?)

Apparent Co-efficient of Induction.

(See Induction, Apparent Co-efficient of.)

Arago's Disc. (See Disc, Arago's)

Arc. A voltaic arc. (See Arc, Voltaic)

Arc. To form a voltaic arc.

A dynamo-electric machine is said to arc at the
commutator, when the current passes as visible
sparks across the spaces between adjacent seg-
ments.

This action at the commutator is more gener-
ally called sparking or burning.

Arc, Alternating A voltaic arc

formed by means of an alternating current.

In order to avoid the extinction of the arc a
certain number of alternations per second is nec-
essary. The alternating arc produces a loud
singing noise. At very high frequencies, how-
ever, the noise disappears.

The alternating arc, not possessing a fixed posi-
tive crater, requires to be covered by a good
reflector to throw the light downward.

Arc, Ampe're A single conductor

bent in an arc of a circle, and used in electric
balances for measuring the electric current.

Arc Blow-Pipe. (See Blow-Pipe, Elec-
tric Arc.}

Arc, Compound An arc formed

between more than two separate electrodes.

Arc, Counter Electromotiye Force of

An electromotive force generally be-
lieved to be set up on the formation of a
voltaic arc, opposed in direction to the electro-
motive force maintaining the arc. (See Force,
Electromotive, Counter?)

This counter electromotive force is believed to
have its origin partly in the energy absorbed at
the crater of the positive carbon, where the car-
bon is volatilized, and given out at the nipple on
the negative carbon, where it is deposited or
solidified. It is to be noted in this connection
that the apparent resistance of the carbon voltaic
arc is not directly proportional to the length of
the arc.

Arc, Electric A term sometimes

used for the voltaic arc. (See Arc, Voltaic)

Arc, Frying of A frying sound at-
tending the formation of a voltaic arc when
the carbons are too near together.

The cause of the frying sound is probably the
same as that of hissing. (See Arc, Hissing of '.)

Arc, Hissing of A hissing sound

attending the formation of voltaic arcs when
the carbons are too near together.

The cause of the hissing is not entirely under-
stood. Prof. Elihu Thomson suggests that it is
due to a too rapid volatilization of the carbons.

Arc Lamp. (See Lamp, Arc)

Arc Lamp, Electric (See Lamp,

Electric Arc)

Arc Lamp, Triple Carbon Electric

(See Lamp, Arc, Triple Carbon Electric)

Arc Lighting. (See Lighting, Arc)

Arc, Metallic A voltaic arc formed

between metallic electrodes.

When the voltaic arc is formed between metallic
electrodes instead of carbon electrodes, a flaming
arc is obtained, the color of which is characteristic
of the burning metal ; thus copper forms a brill-
iant green arc. The metallic arc, as a rule is
much longer than an arc with the same current
taken between carbon electrodes.

Arc Micrometer. (See Micrometer, Arc)

Arc.]

[Arc.

Arc, Noisy A voltaic arc, the

maintenance of which is attended by frying,
hissing, or spluttering sounds.

Arc, (Juiet A voltaic arc which is

maintained without sensible sounds.

Arc, Roaring of A roaring sound
attending the formation of a voltaic arc when
the carbons are too near together and a very
powt rf ul current is used.

Arc, Simple An arc formed be-
tween two electrodes.

Arc, Spluttering of A spluttering

sound attending the formation of a voltaic
arc.

Prof/Elihu Thomson suggests that the cause of
spluttering is due to the presence of impurities in
the carbons, or from the sudden evolution of gas
from insufficiently baked carbons.

Arc, Yoltaic The brilliant arc or
bow of light which appears between the elec-
trodes or terminals, generally of carbon, of a
sufficiently powerful source of electricity, when
separated a short distance from each other.

The source of light of the electric arc lamp.

It is called the voltaic arc because it was first
obtained by the use of the battery invented by
Volta. The term arc was given to it from the
shape of the luminous bow or arc formed between
the carbons.

To form the voltaic arc the carbon electrodes
are first placed in contact and then gradually
separated. A brilliant arc of flame is formed be-
tween them, which consists mainly of volatilized
carbon. The electrodes are consumed, first, by
actual combination with the oxygen of the air;
and, second, by volatilization under the combined
influence of the electric current and the intense
heat.

As a result of the formation of the arc, a crater
is formed at the end of the positive carbon, and
appears to mark the point out of which the
greater part of the current flows.

The crater is due to the greater volatilization
of the electrode at this point than elsewhere.
It marks the position of highest temperature of the
electrodes, and is the main source of the light of
the arc. When, therefore, the voltaic arc is em-
ployed for the purposes of illumination with
vertically opposed carbons, the positive carbon
should be made the upper carbon, so that the

focus of greatest intensity of the light may be
favorably situated for illumination of the space
below the lamp. When, however, it is desired to
illumine the side of a building above an arc lamp,
the lower carbon should be made positive.

The positive carbon is consumed about twice as
rapidly as the negative, both because the negative
oxygen attacks the points of the positive carbon. '
and because the positive carbon suffers the most
rapid volatilization.

The electric current passes through the space
occupied by the voltaic arc because

(I.) The heated arc is a partial conductor of
electricity.

(2.) Because small charges of electricity are
carried bodily forward from the positive to the
negative carbon through the space of the voltaic
arc, by means of the minute particles which are
volatilized at the positive electrode.

S. P. Thompson has shown that the tempera-
ture of the light-emitting surface of the carbon is
the temperature of the volatilization of carbon,
and is therefore constant/

Dr. Fleming found that " A rise of potential
along the arc takes
place very suddenly,
just in the neighbor-
hood of the crater. ' '

The crater in the
end of the positive car-
bon is seen in Fig. 18.
On the opposed end
of the negative carbon
a projection or nipple
is formed by the de-
posit of the electrical-
ly volatilized carbon.
Fig. r8. Voltaic Arc. The rounded masses
or globules that appear on the surface of the elec-
trodes are due to deposits of molten foreign mat-
ters in the carbon.

The carbon, both of the crater and its opposed
nipple, is converted into pure, soft graphite.

Arc, Voltaic, Resistance of The
resistance offered by the voltaic arc to the
passage of the current.

As in all other conductors, the ohmic resistance
of the arc increases with its length, and decreases
with its area of cross-section. The apparent
resistance, however, is not directly proportional
to the length. An increase of temperature de-
creases the resistance of the voltaic arc.

Arc.]

[Arm.

The total apparent resistance of the voltaic arc
is composed of two parts, viz. :

(I.) The true ohmic resistance. (See Resist-
ance, Ohtnic.)

(z.) The counter electromotive force, or spuri-
ous resistance. (See Resistance, Spurious.)

Arc, Watt A voltaic arc, the elec-
tric power of which is equal to a given number
of watts.

The ordinary long-arc, as employed in arc
lighting, has a difference of potential of about 45
volts and a current strength of about 10 amperes.
It is, therefore, a 45O-watt arc.

Arch, Auroral The archlike form

sometimes assumed by the auroral light. (See
Aurora Borealis?)

Arcing. Discharging by means of voltaic
arcs. (See Arc, Voltaic?)

Arcing at the commutator of a dynamo-electric
machine not only prevents the proper operation
of the machine, but eventually leads to the de-
struction of the brushes and the commutator.

Areometer, Bead A form of are-
ometer suitable for rapidly testing the density
of the liquid in a storage cell.

The bead areometer consists of a glass tube,
open at both top and bottom, containing a few
glass beads, so weighted as to float at liquid
densities such as 1.105, 1.170, 1.190
and 1. 200. To use the instrument,
it is immersed in the liquid of the
storage cell, and then withdrawn.
The finger being kept in the upper
opening, the liquid does not escape
through the small opening at the
bottom. The density is then ascer-
tained by noting the beads that
float.

Areometer or Hydrometer.
An instrument for determin-
ing the specific gravity of a liquid.

A common form of hydrometer
consists, as shown in Fig. 19, of a
closed glass tube, provided with a
bulb, and filled at the lower end V

with mercury or shot, so as to in-

sure its vertical position when Fig. 19. Hy-
floating in a liquid. When placed drometer.
in different liquids, it floats with part of the tube
out of the liquid. The lighter the liquid, the
2 Vol. 1

smaller is the portion that remains out of the
liquid when the instrument floats. The specific
gravity is determined by observing the depth to
which the instrument sinks when placed in different
liquids, as compared with the depth it sinks when
placed in water.

Areometry. The measurement of specific
gravity by means of an areometer.

Argand Burner, Electric Hand-Lighter
-(See Burner, Argand, Electric Hand-
Lighter?)

Argand Burner, Electric Plain-Pendant
(See Burner, Plain Pendant, Argand,
Electric?)

Argand Burner, Electric Ratchet-Pen-
dant (See Burner, Ratchet-Pendant,
Argand) Electric?)

Argyrometry. The art of determining
the weight of electrolytically deposited silver.
(See Balance, Plating?)

Arm, Balance One of the resist-
ances of an electric balance. (See Arms,
Bridge or Balance. Bridge, Electric?)

Arm, Bridge A bridge arm. (See
Arms, Bridge or Balance?)

Arm, Cross A horizontal beam at-
tached to a pole for the support of the in-
sulators for telegraph, electric light or 'other
electric wires.

A telegraphic arm. (See Arm, Tele-
graphic?)

Arm, Rocker An arm on which the

brushes of a dynamo or motor are mounted
for the purpose of shifting their position on
the commutator.

Arm, Semaphore The movable

arm of the signal apparatus employed in block
systems for railroads, for the purpose of in-
forming engineers of trains of the condition
of the road as regards other trains.

In the absolute block system, as used on some
roads, there are two positions for the semaphore
arm, viz. :

(i.) For Danger when in a horizontal position,,
or at 90 degrees with the vertical supporting pole.

(2. ) Clear when dropped below the horizontal
position through an angle of 75 degrees.

In the Permissive Block System, a third position

Arm.]

[Arm.

intermediate between the ist and the zd, or at an
angle of 37 degrees 30 minutes with the horizontal
position, is used for caution. (See Block System
for Railroads. ,)

Arm, Signal A semaphore arm.

(See Arm, Semaphored)

Arm, Telegraphic A cross-arm
placed on a telegraphic pole for the support
of the insulators.

These arms are generally called cross-arms.

Armature. A mass of iron or other
magnetizable material placed on or near the
pole or poles of a magnet.

In the case of a permanent magnet, the arma-
ture, when used as a keeper, is of soft iron and is
placed directly on the magnet poles. In this case
it preserves or keeps the magnetism by closing
the lines of magnetic jorce of the magnet through
the soft iron of the armature, and is then called a
keeper. (See Force, Magnetic, Lines of.}

In the case of an electro-magnet, the armature
is placed near the poles, and is moved toward
them whenever the magnet is energized by the
passage of the current through the magnetizing
coils. This movement is made against the action
of a spring or weights, so that on the loss of
magnetism by the magnet, the armature moves
from the magnet poles. (See Magnet, Permanent.
Magnet, Keeper of .}

When the armature is of soft iron it moves to-
ward the magnet on the completion of the circuit
through its coils, no matter in what direction
the current flows, and is then called a non-polar-
ized armature. (See Armature, Non-Polarized. )

When made of steel, or of another electro-mag -

Fig.2O. Bi-polar Armature.

net, it moves from or toward the poles, accord-
ing to whether the poles of the armature are of
the same or of a different polarity from those of
the magnet. Such an armature is called a
polarized armature. (Set Armature, Polarized.)

Armature, Bi-polar An armature

of a dynamo-electric machine the polarity of
which is reversed twice in every revolution
through the field of the machine.

A form of bi-polar armature is shown in Fig. 20.
The word bi-polar armature is not generally
employed. The term applies rather to the field-
magnet poles than to the armature.

Armature Bore. (See Bore, Armature.}

Armature Bore, Elliptical (See
Bore, Elliptical Armature?)

Armature Chamber. (See Chamber,
Armature?)

Armature Coils, Dynamo - (See
Coils, Armature, of Dynamo-Electric Ma-
chine?)

Armature Core, Dynamo - (See
Core, Armature, of Dynamo-Electric Ma-
chine?)

Armature, Cylindrical A term
sometimes applied to a drum armature.
(See Armature, Drum. Armature, Dy-
namo-Electric Machine?)

Armature, Cylindrical Ring. A ring
armature with a core in the shape of a com-
paratively long cylinder.

Armature, Disc An armature of a

dynamo-electric machine, in which the arma-
ture coils consist of flat coils, supported on
the surface of a disc. (See Armature, Dy-
namo-Electric Machine?)

Armature, Dissymmetrical Induction of

Any induction produced in the arma-
ture of a dynamo-electric machine that is un-
equal in amount on opposite halves, or in sym-
metrically disposed portions of the armature.

Dissymmetrical induction in the armature may
cause annoying or injurious sparking at the com-
mutator. It may arise

(i.) From a lack of symmetry in the amount of
the armature windings.

(2.) From a lack of symmetry in the arrange-
ment of the armature windings on the armature
core.

(3. ) From a lack of symmetry of the pole pieces
of the machine.

(4.) From an improper position of the brushes

Aroi.]

[Arm,

as regards the neutral point on the commutator,
causing a temporary short-circuiting of one or
more of the armature coils.

Armature, Drum An armature of
a dynamo-electric machine, in which the
armature coils are wound longitudinally over
the surface of a cylinder or drum. (See
Armature, Dynamo-Electric Machine?)

A form of drum-armature is shown in Fig. 21.

Fig. 21. Drum- Armature.

Armature, Dynamo-Electric Machine

The coils of insulated wire together

with the iron armature core, on or around
which the coils are wound.

That part of a dynamo-electric machine in
which the differences of potential which
cause the useful currents are generated.

Generally, that portion of a dynamo-elec-
tric machine which is revolved between the
pole pieces of the field magnets.

The armature of a dynamo-electric machine
usually consists of a series of coils of insulated
wire or conductors, wrapped around or grouped
on a central core of iron. The movement of
these wires or conductors through the magnetic
field of the machine produces an electric cur-
rent by means of the electromotive forces so gen-
erated. Sometimes the field is rotated ; some-
times both armature and field rotate.

The armatures of dynamo-electric machines
are of a great variety of forms. They may for
convenience be arranged under the following
heads, viz.:

Cylindrical or drum-armatures, disc-arma-
tures, pole or-radial armatures, ring armatures,
and spherical- armatures . For further particulars
see above terms. Armatures are also divided

into classes according to the character of fee
magnetic field through which they move viz.:
unipolar, bipolar, and multipolar- armatures.

The English sometimes use the word cylindrical
armature as a synonym of ring-armature.

A unipolar-armature is one whose polarity is
never reversed. A bipolar-armature is one in
which the polarity is reversed twice in every
rotation; multipolar armatures have their po-
larity reversed a number of times in every rota-
tion.

The term armature as applied to a dynamo-
electric machine was derived from the fact that
the iron core acts to magnetically connect the
two poles of the field magnets in the same
manner that an ordinary armature connects the
poles of a magnet.

Armature, Flat Ring A ring-arma-
ture with a core in the shape of a short cylin-
drical ring.

Armature, Girder An armature

with an H -shaped or girder-like core.

An H -shaped armature.

Armature, Intensity An old term
for an armature with coils of many turns and
of a comparatively high resistance.

Armature, Lamination of Core of
A division of the iron core of the armature
of a dynamo-electric machine or motor, so as
to avoid the formation of eddy-currents
therein. (See Core, Lamination of. Cur-
rents, Eddy.)

Armature, Mnltipolar A dynamo-
electric machine armature whose polarity is
reversed more than twice during each rotation
in the field of the machine.

Armature, Neutral A non-polarized

armature. (See Armature, Non-Polarized.)

Armature, Neutral-Relay A relay

armature, consisting of a piece of soft iron,
which closes a local circuit whenever its elec-
tro-magnet receives an impulse over the main
line. (See Artnature, Polarized?)

This term is applied in contradistinction to a
polarized relay armature.

Armature, Non-Polarized An

armature of soft iron, which is attracted toward
the poles of an electro-magnet on the comple

Arm.]

[Arm.

tion of the circuit, no matter in what direc-
tion the current passes through the coils.

The term non-polarized is used in contradistinc-
tion to polarized armature. (See Armature,
Polarized.}

Th. non-polarized armature of a relay magnet
is generally called the neutral -relay armature.

Armature of a Cable, or Cable-Armature.

A term sometimes employed for the sheath-
ing or protecting coat of a cable.

The term armor sheathing or coating is prefer-
able.

Armature of a Condenser, or Condenser
Armature. A term sometimes applied to
the metallic plates of a condenser or Leyden
jar.

The use of this term is unnecessary and ill-
advised. The term coating or plate would appear
to be preferable.

Armature of Holtz Machine, or Holtz-
Machine Armature. The pieces of paper
that are placed on the stationary plate of the
Holtz and other similar electrostatic induction
machines.

Armature Pockets. (See Pockets, Arma-
ture)

Armature, Polarized An armature

which possesses a polarity independent of
that imparted by the magnet pole near which
it is placed.

In permanent magnets the armatures are made
of soft iron, and therefore, by induction, become
of a polarity opposite to that ol the magnet poles
that lie nearest them. They have, therefore, only
a motion of attraction toward such pales. (See
Induction, Magnetic. )

In electro-magnets the armatures may either be
made of soft iron, in which case they are attracted
only on the passage of the current; or they may
be formed of permanent steel magnets, or may be
electro-magnets themsehes, in which case the pas-
sage of the current through the coils of the elec-
tro-magnet, or electro-magnets, may cause either
attraction or repulsion, according as the adjacent
poles are of opposite polarity or are of the same
polarity.

Armature, Pole An armature the
coils of which are wound on separate poles

that project radially from the periphery of a
disc, drum or ring.
A pole-armature showing the arrangement of

Fig. Z2. Pole- Armature.

the coils and their connection to the commutator
segments is seen in Fig. 22.

Armature, Quantity An old term

for an armature wound with but a few coils
of comparatively low resistance.

Armature, Radial A term some-
times used instead of pole-armature. (See
Armature, Pole.)

Armature, Ring A dynamo-electric

machine armature, the coils of which are
wound on a ring-shaped core.
c

Fig- 23- Ring-Armature.

A ring-armature is shown in Fig. 23, together
with the disposition of the coils and their connec-
tion to the segments of the commutator.

Armature, Shuttle A variety of

drum armature in which a single coil of
wire is wound in an H -shaped groove formed
in a bobbin shaped core.

The old form of Siemens-armature.

Armature, Single-Loop A closed

conducting circuit consisting of a single loop,
capable of revolving in a magnetic field so as
to cut its lines of force.

Armature, Spider. (See Spider, Arma-
ture)

Arm.]

Arr.

Armature, Spherical A dynamo-
electric machine armature, the coils of which
are wound on a spherical iron core.

The Thomson- Houston dynamo, which is the
only machine employing an armature of this type,
has its armature formed by wrapping three coils
of insulated wire on a core of iron so shaped as
to insure an approximately spherical armature
when wrapped.

Armature, Toothed-Ring An ar-
mature, the core of which is in the shape of
a ring, provided with a number of teeth in the
spaces between which the armature coils are
placed.

Armature, Unipolar A dynamo-
electric machine armature whose polarity is
not reversed during its rotation in the field
of the machine.

Armature, Ventilation of A pro-
cess for insuring the free passage of air
through the armature of a dynamo-electric
machine in order to prevent overheating.

Armor of Cable. (See Cable, Armor of.)

Armored Cable. (See Cable, Armored?)

Armored Conductor. (See Conductor,
Armored!)

Arms, Bridge or Balance The
electric resistances, in the electric balance or
bridge. (See Bridge, Electric!)

Zn C
Fig. 24. Arms of Balance.

An unknown resistance, such, for example, as
D, Fig. 24, is measured by proportioning the
known resistances, A, C and B, so that no current
flows through the galvanometer G, across the
circuit or bridge M G N.

Arms, Proportionate The two re-
sistances or arms of an electric bridge whose
relative or proportionate resistances only are
required to be known in order to determine,

in connection with a known resistance, the
value of an unknown resistance placed in the
remaining arm of the bridge.

Thus is Fig. 24, A and B, are the proportionate
arms.

Arrangement or Deyice, Electromotive

A term sometimes employed to rep-
resent a dynamo-electric machine, voltaic cell
or other electric source, by means of which
electromotive force can be produced.

Electric sources do not produce electric cur-
rents, but differences of potential or electro-
motive force. Electric sources are therefore very
properly termed electromotive devices.

Arrester, Lightning A device by
means of which the apparatus placed in any
electric circuit is protected from the destruc-
tive effects of a flash or bolt of lightning.

In the phenomena of lateral induction and
alternative path, we have seen the tendency of a
disruptive discharge to take a short-cut across an
intervening air space, rather than through a
longer though better conducting path. Most
lightning arresters are dependent for their opera-
tion on this tendency to lateral discharge. (See
Induction, Lateral. Path, Alternative.}

A form of lightning arrester is shown in Fig. 25.

Fig. 23- Comb Lightning- Arrester.

The line wires, A and B, are connected by two
metallic plates to C and D, respectively.

These plates are provided with points, as shown,
and placed near a third plate, connected to the
ground by the wire G. Should a bolt strike the
line, it is discharged to the .earth through the
wire G.

Various forms are given to lightning arresters
of this type. The projections are sometimes placed
on the ground-connected plate as well as on the
plates connected to line wires. This form is
sometimes called a comb arrester, or protector.

Arr.]

[Ast.

Arrester, Lightning, Comb - A

term sometimes applied to a lightning ar-
rester in which both the line and ground
plates are furnished with a series of teeth,
like those on a comb. (See Arrester, Light-
ning)

Arrester, Lightning, Counter-Electro-
motive Force A lightning arrester,
in which the passage of the discharge through
the instruments to be protected is opposed
by a counter-electromotive force, generated
by induction on the passage of the discharge
of the bolt to earth.

The counter-electromotive force lightning ar-
rester is an invention of Professor Elihu Thomson.

It assumes a variety of forms. In the shape
shown in Fig. 26, the line circuit of the dynamo,

Fig. 26. Counter-Electromotive Force Lightning
Arrester.

D, has one end connected to ground, and the
other end has two conducting paths to ground.
One of these paths is through the ordinary comb-
protector at P, by the ground plate E; this cir-
cuit includes a few turns
of wire C'. The other
path is through a corres-
ponding coil C, either
interior or exterior to C',
so as to be within its in-
ductive field. As will be
[ E I seen from the figure, C, is

Fig. 27. Counttr-Elec- connected through the
tromotive force Light- machine to the ground.
ning Arrester. The induction coils C

and C', are thoroughly insulated from each
other.

Should a lightning flash or other static discharge
pass through the circuit C', which is of compara-
tively low self-induction, a counter-electromotive
force is produced in the other coil C, which
protects the line circuit.

In the form of lightning arrester shown in
Fig. 27, the coil in the path of the direct light-
ning discharge is formed into an exterior mesh or
net work surrounding the dynamo to be pro-
tected. In this case, the coils of the dynamo act
as the secondary coils in which the counter elec-
tromotive force is set up.

Arrester, Lightning, Transformer

A form of lightning arrester designed for
the protection of transformers.

The Thomson arrester for transformers oper-
ates on the same principle as his arc-line pro-
tector. In the latter the arc, when formed,
is blown out by the action of the field of an
electro-magnet. This arc is formed on curved
metallic bows, one of which is connected to line
and the other to earth. The arc is formed at the
smallest interval between the bows, and is extin-
guished by being driven by action of a magnetic
field toward greatest interval.

Arrester Plate of Lightning Protector.
(See Plate, Arrester, of Lightning Pro-
tector^

Arrester Plates. (See Plates, Arrester^

Articulate Speech. (See Speech, Articu-
lated,

Artificial Carbons. (See Carbons, Arti-
ficial^

Artificial Illumination. (See Illumina-
tion, Artificial.}

Artificial Line. (See Line, Artificial.}

Artificial Magnet (See Magnet, Arti-
ficial.}

Asphyxia. Suspended respiration, result-
ing eventually in death, from non-aeration of
the blood.

In cases of insensibility by an electric shock a
species of asphyxia is sometimes brought about.
This is due, probably, to the failure of the nerves
and muscles that carry on respiration. The exact
manner in which death by electrical shock results
is not known. (See Death, Electric. }

Assy m metrical Resistance. (See Resist-
ance, Assymmetrical.)

Astatic. Possessing no directive power.

Usually applied to a magnetic or electro-mag-
netic-device which is free from any tendency to
take a definite position on account of the earth's
magnetism.

Ast,]

[Ato.

Astatic Circuit. (See Circuit, Astatic}

Astatic Couple. See Couple, Astatic.}

Astatic Galvanometer. (See Galvanom-
ster, Astatic.)

Astatic Needle. (See Needle, Astatic.}

Astatic Pair. (See Pair, Astatic}

Astatic System. (See System, Astatic}

Astronomical Meridian. (See Meridian,
Astronomical}

Asymptote of Curve. (See Curve, Asymp-
tote of}

Atmosphere, An A unit of gas or

fluid pressure equal to about 1 5 pounds to the
square inch.

At the level of the sea the atmosphere exerts a
pressure of about 15 pounds avoirdupois, or,
more accurately, 14.73 pounds, on every square
inch of the earth's surface. This value has there-
fore been taken as a unit of fluid pressure.

For more accurate measurements pounds to the
square inch are employed.

In the metric system of weights and measures
an atmosphere is considered equal to 1,033
grammes per square centimetre.

Atmospheric pressures are measured by instru-
ments called Manometers. (See Manometer.)

Atmosphere, Residual The traces

of air or other gas remaining in a space which
has been exhausted of its gaseous contents
by a pump or other means.

It is next to impossible to remove all traces of
air from a vessel by any known form of pump or
other appliance. (See Vacuum, Absolute.)

Atmosphere, The The ocean of

.air which surrounds the earth.

The atmosphere is, approximately, composed,
by weight, of oxygen 23 parts, and nitrogen 77
parts. Besides these there are from 4 to 6 parts
in 10,000 of carbonic acid gas (or about a cubic
inch of carbonic acid to a cubic foot of air), and
varying proportions of the vapor of water.

The oxygen, nitrogen and carbonic acid form
the constant ingredients of the atmosphere, the
vapor of water the variable ingredient. There
are in most localities a number of other variable
ingredients present as impurities.

Atmospheric Electricity. (See Electric-
ity, Atmospheric.)

Atmospheric Electricity, Origin of

(See Electricity, Atmospheric, Origin of.)

Atom. The smallest quantity of elemen-
tary or simple matter that can exist.

An ultimate particle of matter.

Atom means that which cannot be cut. It is
generally believed that material atoms are abso-
lutely unalterable in size, shape, weight and den-
sity ; that they can neither be cut, scratched,
flattened, nor distorted ; and that they are un-
affected in size, density, or shape, by heat or
cold, or by any known physical force.

Although almost inconceivably small, atoms
nevertheless possess a definite size and mass.
According to Sir William Thomson, the smallest
visible organic particle, 1-4000 of a millimetre in
diameter, will contain about 30,000,000 atoms.

Atom, Closed-Magnetic Circuit of

(See Circuit, Closed-Magnetic, of Atom}

Atom, Gramme - Such a number
of grammes of any elementary substance as is
numerically equal to the atomic weight of
the substance.

The gramme-atom of a substance represents
the number of calories required to raise the tem-
perature of one gramme of that substance through
I degree C. (See Heat, Atomic. Calorie.) Thus,
in the case of chlorine, whose atomic weight is
35.5, its gramme-atom is 35.5 ; consequently
35.5 small calories of heat would be required to
raise one gramme-atom of chlorine through i
degree C.

Atom of Electricity. (See Electricity,
Atom of}

Atom, Vortex A number of particles

of the universal ether moving in the manner
of a vortex ring.

The theory of vortex atoms, so formed from
vortex rings, was propounded by Sir William
Thomson in order to explain how a readily mov-
able substance, like the universal ether, could be
made to possess the properties of a rigid solid. If
it be granted that a vortex motion has once been
imparted to the universal ether, Thomson shows
that such rings would be indestructible. (See
Matter, Thomson's Hypothesis of.)

Atomic Attraction. (See Attraction,
Atomic}

Ato.]

[All.

Atomic Capacity. (See Capacity, Atom-
ic)

Atomic Currents. (See Currents, Atom-
ic)

Atomic Energy. (See Energy, Atomic)
Atomic Heat (See Heat, Atomic)

Atomic or Molecular Induced Currents.

(See Currents, Induced, Molecular or
Atomic)
Atomic Weight. (See Weight, Atomic)

Atomicity. The combining capacity of
the atoms.

The relative equivalence of the atoms or
their atomic capacity.

The elementary atoms do not always combine
atom for atom. Some single atoms of certain
elements will combine with two, three, four, or
even more atoms of another element.

The value of the atomic capacity of an atom is
also called its quantivalence or valency.
Elements whose atomic capacity is

One, are called Monads, or Univalent.
Two, " Dyads, " Bivalent.

Three, " Triads, " Trivalent.

Four, " Tetrads, " Quadrivalent.

Five, " Pentads, " Quinquivalent

Six, " Hexads, " Sexivalent.

Seven, " Heptads, " Septivalent.

Atomization. The act of obtaining liquids
in a spray of finely divided particles.

In most cases the term is not literally correct,
as each of the smallest particles so obtained usu-
ally consist of many thousands of atoms.

Atomize. To separate into a fine spray by
means of an atomizer. (See Atomizer)

Atomizer. An apparatus for readily ob-
taining a finely divided jet or spray of liquid.

A jet of steam, or a blast of air, is driven across
the open end of a tube that dips below the surface
of the liquid to be atomized. The partial vacuum
so formed draws tip the liquid, which is then
blown by the current into a fine spray.

Attract. To draw together.
Attracted-Disc Electrometer. (See Elec-
trometer, Attracted-Disc)

Attract ins?. Drawing together.

Attraction. Literally the act of drawing
together.

In science the name attraction is given to a
series of unknown causes which effect, or are as-
sumed to effect, the drawing together of atoms,
molecules or masses.

Attraction and repulsion underlie nearly all
natural phenomena. While their effects are well
known, it is doubtful if anything is definitely
known of their true causes.

Since attraction, pure and simple, necessitates
the belief in action at a distance, an action which
is now generally discredited, we must, strictly
speaking, regard the term attraction as being but
a convenient substitution of the effect for the
cause.

It would appear much more reasonable to re-
gard the effects of attraction as produced by a
true push exerted from the outside of the bodies.
According to this notion, two masses of matter
undergoing attraction are pushed together rather
than drawn or attracted together.

It has been suggested that gravitation may per-
haps be an effect of a longitudinal motion or vibra-
tory thrust in the universal ether. If this is the
case, and the ether is sensibly incompressible, the
velocity of gravitation, it would appear, should be
almost infinite.

Attraction, Atomic The attraction
which causes the atoms to combine. (See
Affinity, Chemical)

In the opinion of Lodge, atomic attraction is
the result of the attraction of dissimilar charges of
electricity possessed by all atoms, which are capa -
ble of uniting or entering into chemical combi-
nation. (See Electricity, Atom of)

Attraction, Capillary The molec-
ular attractions that are concerned in
capillary phenomena. (See Capillarity)

Attraction, Electro-Dynamic The
mutual attraction of electric currents, or of
conductors through which electric currents
are passing. (See Dynamics, Electro)

Attraction, Electro-Magnetic The
mutual attraction of the unlike poles of
electro-magnets. (See Magnet, Electro.}

Attraction, Electrostatic - The
mutual attraction exerted between unlike
electric charges, or bodies possessing unlike
o'ectric charges.

Alt.]

[Aur.

For example, the pith ball supported on an in-
sulated string is attracted, as shown at A, Fig. 28,

Fig. 28. Electrostati
Attraction.

Fig: 29. Electrostati
Repulsion.

by a bit of sulphur which has been briskly rubbed
by a piece of silk. As soon, however, as the ball
touches the sulphur and receives a charge, it is
repelled, as shown at B, Fig. 29.

These attractions ai d repulsions are due to the
effects of electrostatic induction. (See Induction,
Electrostatic.}

Attraction, Magnetic The mutual
attraction exerted between unlike magnet
poles.

Magnetic attractions and repulsions are best
shown by means of the magnetic needle N S,
Fig. 30. The N. pole of an approached magnet

Fig. 30. Magnetic Attraction.

attracts the S. pole of the needle but repels the
N. pole.

The laws of magnetic attraction and repulsion
may be stated as follows, viz.:

(i ) Magnet poles of the same name repel each
other; thus, a north pole repels another north
pole, a south pole repels another south pole.

Fig. 31. floating
Magnet.

(2.) Magnet poles of unlike names attract each
other; thus a north pole
attracts a south pole, or
a south pole attracts a
north pole.

A small bar magnet,
N S, Fig. 31, laid on the
top of a light vessel floating on the surface of a
liquid, may be readily employed to illustrate the
laws of magnetic attraction and repulsion.

Attraction, Mass The mutual at-
traction exerted between masses of matter.
(See Gravitation}

Attraction, Molar A term some-
times employed for mass attraction.

Gravitation is an example of mass attraction,
where the mass of the earth attracts the mass of
some body placed near it. (See Gravitation.}

Attraction, Molecular The mutual

attraction exerted between neighboring
molecules.

The attraction of like molecules, or those of the
same kind of matter, is called Cohesion ; that of
unlike molecules, Adhesion.

The tensile strength of iron or steel is due to
the cohesion of its molecules. Paint adheres to
wood, or ink to paper, by cohesion or the attrac-
tion between the unlike molecules.

Attraction of Grayitation. A term gen-
erally applied to the mutual attraction be-
tween masses. (See Gravitation^)

Attractions and Repulsions of Currents.
(See Currents, Attractions and Repulsions
of}

Audiphone. A thin plate of hard rubber
held in contact with the teeth, and maintained
at a certain tension by strings attached to one
of its edges, for the purpose of aiding the
hearing.

The plate is so held that the sound-waves from
a speaker's voice impinge directly against its flat
surface. It operates by means of some of the
waves being transmitted , to the ear directly
through the bones of the head.

The audiphone is sometimes called a denti-
phone.

Aural Electrode. (See Electrode, Aural}

Aurora Australis. The Southern Light.

A name given to an appearance in the south-

Aur.]

[Aut.

ern heavens similar to that of the Aurora
Borealis. (See Aurora Borealis.}

Aurora Borealis. The Northern Light.

Luminous sheets, columns, arches, or pillars
of pale, flashing light, generally of a red color,
seen in the northern heavens.

The auroral light assumes a great variety of ap-
pearances, to which the terms auroral arch, bands,
cor once, curtains and streamers are applied.

The exact cause of the aurora is not as yet
known. It would appear, however, beyond any
reasonable doubt, that the auroral flashes are due
to the passage of electrical discharges through the
upper, and therefore rarer, regions of the atmos-
phere. The intermittent flashes of light are prob-
ably due to the discharges being influenced by the
earth's magnetism.

Auroras are frequently accompanied by mag-
netic storms. (See Storm, Magnetic. )

The occurrence of auroras is nearly always
simultaneous with that of an unusual number of
sun spots. Auroras are therefore probably con-
nected with outbursts of the solar energy. (See
Spots, Sun.)

The auroral light examined by the spectroscope
gives a spectrum characteristic of luminous gaseous
matter, i. e., contains a few bright lines; but, ac-
cording to S. P. Thompson, this spectrum is pro-
duced by matter that is not referable with cer-
tainty to that of any known substance.

Whatever may be the exact cause of auroras,
their appearance is almost exactly reproduced by
the passage of electric discharges through vacua.

Aurora Polaris. A general term some-
times applied to aurora in the neighborhood
of either pole, or in either the northern or
the southern hemisphere.

Auroral Arch. (See Arch, Auroral?)

Auroral Bands. (See Bands, Auroral}

Auroral Coronse. (See Corona, Au-
roral?)

Auroral Curtain. (See Curtain, Au-
roral.}

Auroral Flashes. (See Flashes, Auroral.}

Auroral Light (See Light, Auroral?)

Auroral Storm. (See Storm, Auroral}

Auroral Streamer. (See Streamer, Au-
roral}

Auroras and Magnetic Storms, Peri-

odicity of Observed coincidences be-
tween the occurrence of auroras, magnetic
storms, and sun-spots.

The occurrence of auroras, or magnetic storms,
at periods of about eleven years apart, corre-
sponds to the well-known eleven-year sun-spot
period.

The period also agrees with a variation in the
magnetic declination of any place, which, accord-
ing to Sabine, occurs once in every eleven years.

Austral Magnetic Pole. (See Pole, Mag-
netic, Austral}

Autographic Telegraphy. (See Teleg-
raphy, Autographic}

Automatic Annunciator Drop. (See
Drop, Annunciator, Automatic}

Automatic Bell. , See Bell, Automatic
Electric}

Automatic Contact Breaker. (See Con-
tact Breaker, Automatic}

Automatic Cut-Out. (See Cut-Out, Au-
tomatic}

Automatic Cut-Out for Multiple-Connect-
ed Electro-Receptive Devices. (See Cut-
Out, Automatic, for Multiple-Connected
Electro-Receptive Devices}

Automatic Cut-Out for Series-Connected
Electro-Receptive Devices. (See Cut-Out,
Automatic , for Series-Connected Electro-Re-
ceptive Devices}

Automatic Drop. (See Drop, Auto-
matic}

Automatic Electric Burner. (See Burn-
er, Automatic Electric}

Automatic Electric Safety System for
Railroads. (See Railroads, Automatic Elec-
tric Safety System for}

Automatic Fire-Alarm. (See Alarm,
Fire, Automatic}

Automatic Gas Cut-Off. (See Cut-Off,
Automatic Gas}

Automatic Indicator. (See Indicator,
Automatic}

Automatic Make-and-Break. (See Make-
and-Break, Automatic}

Automatic Oiler. (See Oiler, Automatic.

Aut.]

[B. A, U.

Automatic Paper-Winder. (See Winder,
Telegraphic Paper.}

Automatic Regulation. (See Regulation,
Automatic.)

Automatic Regulator. (See Regulator,
Automatic?)

Automatic Search-Light. (See Light,
Search, Automatic?)

Automatic Switch for Incandescent Elec-
tric Lamp. (See Switch, Automatic, for
Incandescent Electric Lamp?)

Automatic Telegraphy. (S e e Teleg-
raphy, Automatic?)

Automatic Telephone Switch. (See
Switch, Telephone, Automatic?)

Automatic Time Cut-Outs. (See Cut-
Out, Automatic Time?)

Automatic Variable Resistance. (See
Resistance, Variable, Automatic?)

Automatically Regulable. (See Regula-
ble, Automatically?)

Automobile Torpedo. (See Torpedo, Au-
tomobile?)

Average or Mean Electromotive Force.
(See Force, Electromotive, Average, or
Mean?)

Axes of Co-ordinates. (See Co-ordinates,
Axes of?)

Axial Magnet. (See Magnet, Axial?)

Axis, Magnetic The line around

which a magnetic needle, free to move, but
which has come to rest in a magnetic field,
can be turned without changing the set or
direction in which it has come to rest.

Axis, Magnetic, of a Straight Needle

A straight line drawn through the magnet,
joining its poles.

The magnetic axis of a straight needle may be
regarded as a straight line passing through the
poles of the needle and its point of support.

The magnetic axis may not correspond with
the geometric axis of the
needle. This leads to
an error in reading the
true direction in which
the needle is pointing,
which must be cor-
rected. Thus, the nee-
dle N S, Fig. 32, points
to 31 degrees on the
scale. In reality, if the
magnetic axis of the
needle lies in the line
N' S', the true deflec-
tion of the needle is only
28 degrees.

Fig-. 33. Magnet!
Axis.

Axis of Abscissas. (See Abscissas, Axis
of?)

Axis of Ordinates. (See Ordinates, Axis
of?)

Azimuth. In astronomy, the angular dis-
tance between an azimuth circle and the
meridian.

The azimuth of a heavenly body in the North-
ern Hemisphere is measured on the arc of the
horizon intercepted between the north point of
the horizon and the point where the great circle
that passes through the heavenly body cuts the
horizon.

Azimuth Circle. (See Circle, Azimuth?)

Azimuth Compass. (See Compass, Azi-
muth?)

Azimuth, Magnetic The arc inter-
cepted on the horizon between the magnetic
meridian and a great circle passing through
the observed body.

B. A contraction used in mathematical
writings for the internal magnetization, or the
magnetic induction, or the number of lines of
force per square centimetre in the magnetized
material.

This contraction for internal magnetization is,

in most mathematical treatises, printed in bold-
faced type.

B. A. Ohm. (See Ohm, B. A?)

B. A. U. A contraction sometimes em-
ployed for the British Association unit or ohm.

B. W. G.]

[Bal.

B. W. G. A contraction for Birmingham
wire gauge. (See Gauge, Birmingham
Wire.)

A contraction sometimes used for the new
British wire gauge.

Back Electromotive Force. (See Force,
Electromotive, Back?)

Back-Stroke of Lightning. (See Light-
ning, Back- Stroke of.)

Bain's Chemical Recorder. (See Re-
corder, Chemical, Bain's.)

Bain's Printing Solution. (See Solution,
Bain's Printing.)

Balance Arms. (See Arms, Bridge or
Balanced)

Balance, Bi-fllar Suspension An

instrument similar in construction to Cou-
lomb's torsion balance, but in which the
needle is hung by two separate fibres instead
of by a single one. (See Balance, Coulomb's
Torsion. Suspension, Bi-filar.)

Balance, Centi-AmpSre An arr-

meter in the form of a balance, whose scale is
graduated to give direct readings in centi-
amperes.

Ampere balances giving readings in various
decimals or multiples of amperes have been de-
vised by Sir William Thomson. The strength of
current passing is determined by the action on a
movable ring or coil, placed between two fixed
rings or coils.

The movable ring is in a horizontal plane
nearly midway between the two fixed rings.
The fixed rings are traversed by the current
in opposite directions, so that one attracts
and the other repels the movable ring. The
movable ring is attached to one end of a horizon-
tal balance arm, and a similar movable ring, also
provided with attracting and repelling fixed rings,
is attached to the opposite end of the balance arm.
In order to avoid disturbance of horizontal com-
ponents of terrestrial, or of local magnetic force,
the current is sent in the same direction through
the two movable rings. The balancing is effected
by means of a weight, sliding on a nearly hori-
zontal arm attached to the balance. A counter-
poi^e weight is used in connection with the sliding
weight.

A standard Thomson centi-ampere balance
is shown in Fig. 33. In measuring a current,

F 'S- 33- Centi-Amplre Balance.
the weight is moved along the scale until the
balance comes to rest.

Balance, Composite A balance

form of ammeter devised by Sir William Thom-
son, which can be used for an ampere-meter, a
watt-meter, or a volt-meter, according to the
manner in which its sets of fine and coarse
wire coils are connected. (See Balance,
Centi- Ampere.)

Balance, Coulomb's Torsion An

apparatus to measure the force of electric or
magnetic repulsion between two similarly
charged bodies, or between two similar mag-
net poles, by opposing to such force the tor-
sion of a thin wire.

The two forces balance each other ; hence the
origin of the name.

Fig. 34. Coulomb's Torsion Balance.

Fig. 34 represents a Coulomb torsion bal-
ance, adapted to the measurement of the force

Bal.]

[Bal.

of electrostatic repulsion. A delicate needle of
shellac, having a small gilded pith ball at one of
its ends, is suspended by a fine metallic wire. A
proof -plane, B, is touched to the electrified surface
whose charge is to be measured, and is then
placed as shown in the figure. (See Plane, Proof.)
There is a momentary attraction of the needle,
anvx t ..^~ a repulsion, which causes the needle to
be moved a ^.'^in distance from the ball on the
proof-plane. This distance is measured in degrees
on a graduated circle a a, marked on the instru-
ment. The force of the repulsion is calculated by
determining the amount of torsion required to
move the needle a certain distance toward the
ball of the electrified proof-plane.

This torsion is obtained by the movement of the
torsion head D, the amount of which motion is
measured on a graduated circle at D. The
measurement is based on the fact that the force re-
quired to twist a wire is proportional to the angle
of torsion.

Balance, Deci-Ampere An ammeter

in the form of a balance, whose scale is
graduated to give direct readings in deci-
amperes. (See Balance, Centi-Ampere^)

Balance, Deka-Ampere An am-
meter in the form of a balance, whose scale is
graduated to give direct readings in deka-
amperes. (See Balance, Centi-Ampere^)

Balance, Electric A term fre-
quently used for Wheatstone's electric bridge.
(See Bridge, Electric!)

The electric bridge is sometimes called a balance
because, when in use in measuring resistances,
one resistance or set of resistances balances an-
other resistance or set of resistances.

Balance, Hekto-Ampdre An am-
meter in the form of a balance, whose scale
is graduated to give direct readings in hekto-
amperes. (See Balance, Centt'-Ampere.)

Balance Indicator. (See Indicator, Bal-
ance.)

Balance, Induction, Hughes'

An apparatus for the detection of the presence
of a metallic or conducting substance by the
aid of induced electric currents.

Hughes' induction balance is shown in Fig. 35.

A, B, C and D are bobbins, wound with about
300 feet of No. 32 copper wire. The coils are

connected as shown, A and B, in the circuit of a
battery, and C and D, in the circuit of a telephone.
The coils, A and B, and C and D, are placed at

Fig 33. Hughes' Induction Balance.

such a distance apart as to prevent any mutual
induction occurring between them. The coils
are so joined that the direction of the induction
of A, on C, is opposite to that of B, on D.

The coils, A and B, then act as primaries, and C
and D, as secondaries. In the battery circuit is an
interrupter I, which is caused to continually make
and break the circuit.

The coils are so adjusted that the opposing
secondary coils produce but little noise to one
listening at the telephone. This can readily be
done by the adjusting of a single pair of coils.

If a single coin or mass of metal be introduced
between either A and C, or B and D, or even
above one of the coils, as at d, the balance
will be disturbed, since some of the induction is
now expended in producing electric currents in
the interposed metal, and a sound will therefore
be heard in the telephone. But if precisely similar
metals are placed in similar positions, between A
and C, and B and D, no sound is heard in the
telephone, since the inductive effects due to the
two metals are the same.

The slightest difference, however, either in
composition, size or position, destroys the balance,
and causes a sound to be heard in the telephone.

A spurious coin is thus readily detected when
compared with a genuine coin.

A somewhat similar instrument has been em-
ployed to detect and locate a bullet or other for-
eign metallic substance in the human body.

In order to determine the amount of the dis-
turbance, an instrument called a sonometer is .
used (See Sonometer, Hughes'), in which a single
secondary coil, placed in the circuit of a telephone,
slides on a graduated bar between two fixed
primary coils, so wound as to exert equal and op-
posite inductions on the secondary. When, there-
fore, the secondary is exactly in the middle of the

Bal.]

[Bal.

graduated bar, and consequendy exactly midway
between the two fixed primary coils, no sounds are
heard in the telephone, but when moved to one
side or the other the sounds are heard. Switches
are so arranged that the telephone can be readily
switched from the induction balance to the tele-
phone, or vice versa. When, therefore, a metallic
disc is> placed in one of the coils of the induction
balance, and a noise is heard in the telephone,
the coil of the sonometer is shifted so that the
noise heard in this telephone is judged by the
ear to be equal, and the comparison can then be
made by means of simple calculations.

The following table gives, in arbitrary values,
the results of various experiments as to the sensi-
tiveness in this respect of discs of different
metals, of various sizes and shapes :

Silver, chemically pure 125

Gold 117

Silver, commercial 115

Aluminium 112

Copper too

Zinc 80

Bronze 75

Tin 74

Iron, ordinary 53

German silver 5

Iron, pure 40

Copper, alloyed 40

Lead ; 58

Antimony 35

Bismuth IO

Zinc, alloyed 6

Carbon 2

; (Fleming.)

An inspection of this table shows that the values
found for different metals do not correspond with
their electric conducting power, although, roughly
speaking, the best conductors stand at the top of
the table, and the worst at the bottom. The
effects appear to be dependent for their action on
the phenomena of magnetic screening, for

(i.) If slots are cut in the middle of the plate
its disturbing action is either removed or very
much decreased.

(2.) If a flat coil of copper wire replaces a disc
of metal no effect is produced on the induction
balance when its ends are open, bui when closed
the coil acts just like a disc, or continuous plate
of metal.

(3.) The difference between various metals in-

serted as discs in the induction balance is less at
high speeds of reversal than at low speeds.

Balance, Kilo-Ampere An am-
meter in the form of a balance, whose scale is
graduated to give direct readings in kilo-am-
peres. (See Balance, Centi- Ampere.}

Balance of Induction in Cable. _o
Induction, Balance of, in Cab! . J

Balance, Plating An automatic
device for disconnecting the current from
the article to be plated, as soon as a certain
increase in weight has been obtained.

The objects to be plated are suspended at one
end of a balance, and when a certain increase in
weight has been gained, the balance tips and
breaks the circuit Edison's electric meter is
based on this principle.

Balance, Thermic, or Bolometer. An

apparatus constructed on the principle of the
differential galvanometer, devised by Professor
Langley for determining small differences of
temperature. (See Galvanometer, Differen-
tial)

A coil composed of two separately insulated
wires, wound together, is suspended in a mag-
netic field, and has a current sent through it.
Under normal conditions, this current separates
into two equal parts, and runs through the wires
in opposite directions. It therefore produces no
sensible field, and suffers no deflection by the field
in which it is suspended.

Any local application of heat producing a dif-
ference in temperature in these coils, causing a
difference in resistance, prevents this equality. A
field is therefore produced in the suspended coil,
which, though extremely small, is rendered meas-
urable by means of the powerful field produced
in the coil, within which the double coil is sus-
pended.

Differences of temperature as small as one-
fourteen thousandth of a degree Fahrenheit are
detected by the instrument.

Balance, Wheatstone's Electric A
name often given to the electric bridge or
balance. (See Bridge, Electric.}

Balanced-Metallic Circuit. (See Circuit,
Balanced-Metallic)

Balanced Resistances. (See Resistances,
Balanced^

Bal.

[Bar.

Balata. An insulating material.
Balata, when prepared for use as an insulating
material, is somewhat like gutta-percha.

Ball, Electric Time A ball, sup-
ported in a prominent position on a tall pole,
and caused to fall at the exact hour of noon,
or at any other predetermined time, for the
purpose of thus giving correct time to an
entire neighborhood.

The release of the ball is effected by the closing
of an electric circuit, either automatically, or
through the agency of an observer.

Ball, Fire A term sometimes ap-
plied to globular lightning. (See Lightning,
Globular?)

Ball Lightning. (See Lightning, Ball.}
Ballistic Curve. (See Curve, Ballistic}

Ballistic Galvanometer. (See Galva-
nometer, Ballistic.}

Balloon, Electric A balloon, or

air ship, provided with electric power so as
to be able to be steered or moved against the
direction of the wind.

Electric balloons have been moved against the
wind and steered with a certain amount of success,
by the use of electric motors driven by storage
batteries. All that is needed to make aerial navi-
gation a commercial success is the ability to ob-
tain great power with a small weight. The storage
battery does this to a limited extent.

Bearing in mind the high efficiency of the elec-
tric motor, it would appear that the problem of
successful aerial navigation will be solved when
the discovery is made of means for directly con-
verting the chemical potential energy of coal into
electrical energy.

Balloon Signaling for Military Pur-
poses. (See Signaling, Balloon, for Mil-
itary Purposes}

Balls, Pith Two balls of pith, sus-
pended by conducting threads of cotton to
insulated conductors, employed to show the
electrification of the same by their mutual
repulsion.

The pith balls connected with the insulated
cylinder A B, Fig. 36, not only show the electri-
fication of the cylinder, but serve also to roughly

indicate the peculiarities of distribution of the
charge thereon.

Fig. 36. Pith Ball Cylinder.

Bands, Anroral Approximately

parallel streaks of light sometimes seen
during the prevalence of the aurora. (See
Aurora Borealis^)

Bank of Lamps. (See Lamps, Bank of}
Banked Battery. (See Battery, Banked}

Bar, Detorsion A bar placed in a
magnetic instrument called a declinometer for
the purpose of removing the torsion of the
suspending thread of the magnet.

The detorsion ^ar of the declinometer is gen-
erally made of gun metal of the same weight as
that of the suspended magnet. A small magnet
is placed in a rectangular aperture in the middle
of the bar.

Bar Electro-Magnet. (See Magnet,
Electro, Bar}

Barad. A unit of pressure proposed by
the British Association.

One barad equals one dyne per square centi-
metre.

Barometer. An apparatus for measuring
the pressure or weight of the atmosphere.

Barometric Column. (See Column, Baro-
metric.)

Bars, Bus Omnibus bars. (See

Bars, Omnibus}

Bars, Krizik's Cores of various

shapes, provided for solenoids, in which the
distribution of the metal in the bar is so pro-
portioned as to insure as nearly as possible a
uniform attraction or pull while in different
positions in the solenoid.

Ban]

[Bat.

Krizik's bars of various shapes are shown in
Fig. 37. It will be observed that in all cases the

Fig. 37. Krizik's Bars.

mass of metal is greater toward the middle of
the core than near the ends.

When a core of uniform diameter is drawn into
a solenoid, the attraction or pull is not uniform in
strength for different positions of the bar. When
the bar is just entering the solenoid, the pull is
strongest ; as soon as the end passes the middle of
the core the attraction decreases, until, when the
centres of the bar and core coincide, the motion
ceases, since both ends of the solenoid attract
equally in opposite directions. By proportioning
the bars, as shown in the figure, a fairly uniform
pull for a considerable length may be obtained.

Bars, Negative-Omnibus The

bus-bars that are connected with the negative
terminal of the dynamos. (See Bars, Omni-
bus)

Bars, Neutral-Omnibus The bus-
bars that are connected with the neutral
dynamo terminal in a three-wire system of
distribution.

Bars, Omnibus Heavy bars of con-
ducting material connected directly to the
poles of dynamo-electric machines, in electric
incandescent light or electric railway installa-
tions, and therefore receiving the entire current
produced by the machine.

Main conductors common to two or more
dynamos in an electrical generating plant.

The terms bus and omnibus bars refer to the
fact that the entire or whole current is carried by
them.

Bars, Positive-Omnibus The bus-
bars that are connected with the positive
terminal of the dynamos.

Bath, Bi-polar An electro-thera-
peutic bath, the current applied to which
enters at one part of the tub, and leaves at
another part.

The electrodes for the bi-polar bath consist of
suitably shaped copper plates, generally called
shovel electrodes.

Bath, Copper An electrolytic bath
containing a readily electrolyzable solution
of a copper salt, and a copper plate acting as
the anode, and placed in the liquid near the
object to be electro-plated, which forms the
kathode. .(See Plating, Electro)

The sulphate, the cyanide and the acetate of cop-
per are used for copper baths. The use of the sul-
phate is objectionable. The cyanide is expensive.
The acetate is therefore very generally employed.
Wahl gives the following formula for a copper
bath, viz. :

Water i ,000 parts.

Acetate of copper, crystal-
lized 20 "

Carbonate of soda 20 "

Bisulphite of soda 20 "

Cyanide of potassium (pure) 20 "

Bath, Electro-Plating Tanks con-
taining metallic solutions in which articles
are placed so as to be electro-plated. (See
Plating, Electro)

Strictly speaking a plating bath includes not
only the vessel and its metallic solution, but also
the metallic plate acting as the anode and the
article to be plated forming the kathode.

Bath, Electro-Therapeutic A bath
furnished with suitable electrodes and used
in the application of electricity to curative
purposes.

Such baths should be used only under the advice
of a regular physician.

Bath, Gold An electrolytic bath

containing a readily electrolyzable solution of
a gold salt and a gold plate acting as the
anode, and placed in the liquid opposite the
object to be plated, which forms the kathode.
(See Plating, Electro)

Electro gilding may be accomp'islied either with
or without the aid of heat. Hot gilding appears
to give a smoother and cleaner deposit.

The following is a fairly good solution for a
gold bath:

Water 1,000 parts.

Cyanide of potassium, pure. . 20 "

Gold 10 "

(Wahl.)

Bat.]

[Bat.

The gold is first converted into neutral chloride
by dissolving it in 25 parts of pure hydrochloric
acid to which 12.5 parts of pure nitric acid has
been added. When the gold is completely dis-
solved, the liquid is heated until of a dark red
color, in order to expel any excess of acid.

Bath, Head, Electric A variety

of electric breeze, applied therapeutically to
the head of the patient.

The patient is placed on an insulating stool and
connected with one pole of an electrostatic induc-
tion machine, the other pole of which is con-
nected to a circle of insulated points suspended
over the head.

Bath, Hydro-Electric A bath in

which electro-therapeutic treatment is given
by applying one electrode to the metallic lining
of the tub, and the other electrode to the body
of the bather.

Bath, Multipolar-Electric An

electro-therapeutic bath, in which more than
two electrodes are employed.

It is not clear that the multipolar-electric bath
possesses any decided advantages over the bi-polar
bath.

Bath, Nickel An electrolytic bath

containing a readily electrolyzable salt of
nickel, a plate of nickel acting as the anode
of a battery and placed in the liquid near the
object to be coated, which forms the kathode.
(See Plating, Electro)

The double sulphate of nickel and ammonium
(from 5 to 8 parts dissolved in 100 parts of water)
is used for the bath. Some prefer to add
sulphate of ammonium and citric acid to the above
solution.

Bath, Shower, Electric A shower

bath in which the falling drops carry 'electric
charges to the patient subjected thereto.

The water is rendered slightly alkaline. One
pole is immersed in the alkaline water and the
other connected to a metallic stool on which the
patient is placed.

Bath, Silver An electrolytic bath

containing a readily electrolyzable salt of
silver and a plate of silver acting as the
anode of an electric source and placed in the
liquid near the object to be coated, which
forms the kathode. ^See ^lating, Electro?)

The double cyanide of silver and potassium
is the salt usually employed in the silver bath.

The following bath is recommended by Rose-
leur:

Water 1,000 parts.

Cyanide of potassium (pure) 50 "
Pure silver 25 "

The silver (granulated) is treated with pure nitric
acid (43 degrees Beaum) and converted into
nitrate of silver. The solution is then heated to
drynessand subsequently fused. The fused nitrate
so obtained is dissolved in fifteen times its weight
of distilled water and treated with a solution of
cyanide of potassium (10 per cent, of the cyanide),
by means of which silver cyanide is thrown down
as a precipitate. This precipitate is then sepa-
rated and washed. It is added to the 1,000 parts
of water, dissolved, and the cyanide of potassium
afterward added, thus forming the double cyan-
ide required for the bath.

Bath, Stripping A bath for remov-
ing an electro-plating of gold, silver, or other
metal, either by simple dipping or by electric
action.

Bath, Ungilding A stripping bath
suitable for the removal of a coating of gold.
(See Bath, Stripping)

Bath, Unipolar-Electric An electro-
therapeutic bath, the water of which forms
one of the electrodes of the source, and the
other electrode is attached to a metallic rod
fixed at a convenient height above the tub.

The bath tub is formed of non-conducting sub-
stances. The terminals of the electrode con-
nected with the water terminate in metal plates
located at suitable points in the tub. The cur-
rent is applied by the patient making and break-
ing contact at the vertical metal rod with his
hands.

The unipolar-electric bath is employed instead
of local galvanization where it is desired to limit
the application to especial organs or particular
parts of the body. In general galvanization the
patient is placed on an electrode of large sur-
face, formed of a large spxjnge- covered metallic
plate, on which he sits or rests. This electrode is
connected with the kathode of the battery. The
anode is connected with a large sponge electrode,
which is moved regularly over the body of the
patient; sometimes the moistened hand of the
operator is used in place of the sponge electrode.

Bat.]

[Bat.

Bath, UnsilTering A stripping bath
suitable for the removal of a coating of silver.
(See Bath, Stripping^

Bathometer. An instrument invented by
Siemens for obtaining deep-sea soundings
without the use of a sounding line.

The bathometer depends for its operation on
the varied attraction of the earth for a suspended
weight in parts of the ocean differing in depth.
As the vessel passes over deep portions of the
ocean, the solid land of the bottom, being further
from the ship, exerts a smaller attraction than it
would in shallow parts, where it is nearer; for,
although in the deep parts of the ocean the water
lies between the ship and the bottom, the smaller
density of the water as compared with the land
causes it to exert a smaller attraction than in the
shallower parts, where the bottom is nearer the
ship. The varying attraction of the earth is
caused to act on a mercury column, the reading
of which is effected by means of an electric con-
tact.

Battery, Banked A term some-
times applied to a battery from which a num-
ber of separate circuits are supplied with cur-
rents.

The term banked-battery is sometimes ap-
plied to a multiple-arc connected battery.

Battery, Cautery A term some-
times employed in electro-therapeutics, for a
multiple connected voltaic battery adapted for
producing electric incandescence for cautery
effects.

Battery, Closed-Circuit - A voltaic
battery which may be kept constantly on
closed-circuit without serious polarization.

The gravity battery is a closed -circuit battery.
As employed for use on most telegraph lines, it is
maintained on a closed circuit. When an operator
wishes to use the line he opens his switch, thus
breaking the circuit and calling his correspondent.
Such batteries should not polarize. (See Cell,
Voltaic, Polarization of.)

Battery, Connection of, for Quantity

A term, now generally in disuse, formerly
employed to indicate the grouping of voltaic
cells, now known as parallel or multiple.

The arrangement or coupling of a number of
voltaic cells in multiple reduces the internal resist-

ance of the battery, and thus permits a greater
current, or quantity, of electricity to pass ; hence
the origin of the term.

Battery, Dynamo The combina-
tion or coupling together of several separate
dynamo-electric machines so as to act as a
single electric source.

The dynamos may be connected to the leads
either in series, in multiple, in multiple-series or
in series-multiple.

Battery, Dynamo, Electric Machine

A dynamo battery. (See Battery, Dy-
namo?)

Battery, Electric A general term

applied to the combination, as a single source,
of a number of separate electric sources.

The separate sources may be coupled either in
series, in multiple, in multiple-series, or in series-
multiple. ( See Circuits, Varieties of.)

The term battery is sometimes incorrectly ap-
plied to a single voltaic couple or cell.

Battery, Floating, De la Rive's A

floating voltaic cell, the terminals of which are
connected with a coil of insulated wire, em-
ployed to show the attractions and repul-
sions between magnets and movable electric
circuits.

The cell, shown in Fig. 38, consists of a vol-

Fig. 38. Floating Cell.

taic couple of zinc and copper, the terminals of
which are connected to the circular coil of insu-
lated wire, as shown, and the whole floated by
means of a cork, in a vessel containing dilute sul-
phuric acid.

When the current flows through the coil in the
direction shown by the arrows, the approach of
the N-seeking pole of a magnet will cause the
cell to be attracted or to move towards the mag-
net pole, since the south face or end of the coil is
nearer the north pole of the magnet. If the other

Bat.]

[Bat.

end were nearer, repulsion would occur, the cell
turning round until the south face is nearer the
magnet, when attraction occurs.

This is, strictly speaking, a floating cell, and
not a battery. (See Battery, Voltaic.}

Battery, Galvanic Two or more

separate voltaic cells so arranged as to form
a single source.

This is more correctly called a Voltaic Battery.
(See Battery, Voltaic.)

Battery, Gas A battery in which

the voltaic elements are gases as distinguished
from solids.

The electrodes of a gas battery generally con-
sist of plates of platinum, or other solid substance
which possesses the power of occluding oxygen
and hydrogen. The lower parts of these plates
dip into dilute sulphuric acid, and the upper parts
are respectively surrounded by oxygen and hydro-
gen gas derived from the electrolytic decompo-
sition of the dilute acid.

A gas battery consisting of plates of platinum
dipping below into acid liquid, and surrounded
in the space above the liquid by hydrogen and
oxygen H, H' and O, O', etc., respectively is
shown in Fig. 39.

Fig- 39- Gas Battery.

In charging this battery an electric current is
sent through it until a certain quantity of the
gases has been produced. If, then, the charging
current be discontinued, a current in the oppo-
site direction is produced by the battery. The
gas battery is in reality a variety of storage bat-
tery. (See Electricity, Storage of. Cell, Secon-
dary. Cell, Storage.")

Gas batteries can also be made by feeding con-
tinually into the cell a gas capable of acting on
the positive elements.

Battery Gauge. (See Gaugi, Battery?)

Battery, Leyden Jar The combina-
tion of a number of separate Leyden jars so
as to act as one single jar.

A Leyden jar battery is shown in Fig. 40,

Fig. 40, Leyden Jar Battery.

where nine separate Leyden jars are connected
as a single jar by joining their outer coatings by
placing them in the box P, the bottom of which
is lined with tin foil. The inner coatings are
connected together by the metal rods B, as
shown.

A discharging rod A, may be employed for
connecting the opposite coatings. The handles
are made of glass or any other good insulating
material.

A number of Leyden jars can be coupled in
series by connecting the inner coating of the first
jar to the outer coating of the second, the inner
coating of the second to the outer coating of the
third, and so on. The battery so obtained is
then discharged by connecting the outer coat,
ing of the first jar with the inner coating of the
last.

Battery, Local A voltaic battery

used at a station on a telegraph line to
operate the Morse sounder, or the register-
ing or recording apparatus, at that point
only. (See Telegraphy, American or Morse
System of.)

The local battery is thrown into or out of action
by the telegraphic relay. (See Relay.}

Battery, Magnetic -The combina-
tion, as a single magnet, of a number of sep-
arate magnets.

A magnetic battery, or compound magnet, is

Bat.]

[Bat.

Fig, J.T, Magneti
Battery, or Com

shown in Fig. 41. It consists of straight bars of
steel, p, p, p, with their similar poles placed near
together and inserted in
masses of soft iron, N and
S, as shown.

Battery, Main

The battery, in a system
of telegraphic communi-
cation, that is employed
for sending the signals
over the main line, as dis-
tinguished from any bat-
tery employed for any
other particular work,
such, for example, as that
of the local battery. (See
Battery, Local.)

Battery, Multiple-Con- found Magnet.

nected A battery the single cells of

which are connected to one another and to the
mains or conductors in multiple. (See Cir-
cuit, Multiple)

Battery, Open-Circuit A voltaic

battery which is normally on open-circuit,
and which is used continuously only for com-
paratively small durations of time on closed-
circuit.

Leclanche'-cells form an excellent open-circuited
battery. 'They have a comparatively high electro-
motive force, but rapidly polarize. They cannot
therefore be economically used for furnishing
currents continuously for long durations of time.
When left on open-circuit, however, they readily
depolarize. They therefore form an excellent
battery for such work as annunciator bells, burg-
lar alarms, etc., where the current is only
required for short periods of time, separated by
comparatively long intervals of rest. (See Cell,
Voltaic, Leclanche.)

Battery Plates of Secondary or Storage

Cell, Forming of (See Plates of

Secondary or Storage Cell, Forming of.)

Battery, Plunge A number of

separate voltaic cells connected so as to form
a single cell or electric source, the plates of
which are so supported on a horizontal bar
as to be capable of being simultaneously
placed in, or removed from, the exciting
liquid.

The plunge battery shown in Fig. 42, consists

Fig. 42. Plunge Battery,

of a number of zinc-carbon elements immersed in
an electrolyte of dilute sulphuric acid, or in elec-
tropoion liquid, contained in separate jars, J, J.
(See Liquid, Electropoion.)

The mode of support to the horizontal bar
will be understood from an inspection of the
drawing.

Battery, Primary The combina-
tion of a number of separate primary cells so
as to form a single source.

The term primary battery is used in order to
distinguish it from secondary or storage battery.
(See Cell, Secondary. Cell, Storage.)

Battery, Secondary The combina-
tion of a number of separate secondary or
storage cells, so as to form a single electric
source. (See Electricity, Storage of.)

Battery, Selenium The combina-
tion of a number of separate selenium cells so
as to form an electric source. (See Cell,
Selenium.)

Battery, Series-Connected A bat-
tery, the separate cells of which are con-
nected to one another and to the line or
conductor in series. (See Circuit, Series.)

Battery Solution. (See Solution, Bat-
tery)

Battery, Split A voltaic batten'

connected in series, but having one of its
middle plates connected with the ground.

By the employment of the device of a split-
battery, the poles of the battery are maintained
at potentials differing in opposite directions from
the potential of ihe earth.

Battery, Storage A number of
separate storage cells connected so as to
form a single electric source.

Bat.]

[Bel.

A cell of a storage battery is shown in Fig.

43-

Fig. 43. Storage Battery.

Battery, ' Storage, Element of A

single set of positive and negative plates of a
storage cell connected so as to be ready for
placing in the acid liquid of the jar or cell.

A term sometimes applied to one of the
storage cells in a storage battery.

This latter use of the term element is unfortu-
nate, since from the analogous case of a primary
cell, an element would consist of a single plate,
either positive or negative, and not of both. That
is, every voltaic couple consists of two elements,
the positive and the negative.

Battery, Thermo A term often

applied to a thermo-electric battery. (See
Battery, Thermo- Electric)

Battery, Thermo-Electric The

combination, as a single thermo-electric cell,
of a number of separate thermo-electric cells
or couples. (See Couple, Thermo-Electric)

Battery, Voltaic The combina-
tion, as a single source, of a number of sepa-
rate voltaic cells.

Battery, Water A battery formed

of zinc and copper couples immersed in an
electrolyte of ordinary water.

Any voltaic couple can be used, the positive
element of which is slightly acted on by water.
When numerous couples are employed consider-
able difference of potential can be obtained.

Water batteries are employed for charging
electrometers. They are not capable of giving
any considerable current, owing to their great in-
ternal resistance.

Bead Areometer or Hydrometer. (See
Areometer, Bead.)

Bec-Carcel. The Carcel. or French unit
of light. (See Carcel)

Bell, Automatic-Electric An elec-
tric bell furnished with an automatic contact-
breaker. (See Contact-Breaker, Automatic)

A form of automatic-electric bell is shown m
Fig. 44. The relation of the electro- magnet, its
armature and the bell
lever, will be readily
understood from an in-
spection of the draw-
ing.

Bell, Call

An electric bell used
to call the attention
of an operator to the
fact that his corre-
spondent wishes to
communicate with
him.

Bell, Circular

A bell so construct-
ed that all its moving

parts are contained in Figt 44 , Automa tic EUctrii
the gong. Bell.

Bell, Continuous-Sounding Electric

An electric bell, which, on the completion
of the circuit, continues striking until stopped
either by hand or automatically.

On the completion of the circuit, the attraction
of an armature throws a catch off from a lever,
and thus permits the lever to fall and complete a
contact and allows the current to ring the bell; or
the bell is rung by clockwork, which is thrown
into action by the passage of a current through an
electro-magnet. (See Bell, Electro-Mechanical.}

Bell, Differential Electric An

electric bell, the magnetizing coils of which
are differentially wound.'

Differential winding is ot advantage where a
very strong current is required, as this winding
decreases the sparking at the contacts, on the
opening of the circuit.

Bell, Electro-Magnetic, Siemens-Arma-
ture Form A form of electro-mag-

Bel.]

[Bel.

netic bell in which the movements of the bell
armature are obtained by the reversal of
polarity that takes place when alternating cur-
rents are pass-
ed through the
coils of a sim-
ple, single coil,
Siemens - arma-

ture> Fig. 4$. Siemens-Armature Form

The details of Electro-Magnetic Bell.

will be readily understood from an examination
of Fig. 45.

Bell, Electro-Mechanical A bell,

the striking apparatus of which is driven by
a weight or spring, called into action by the
movement of the armature of an electro-
magnet. (See Alarm, Electric?)

Bell, Extension-Call A device for

prolonging the sound of a magneto call.

An alarm bell is automatically connected with

Fig. 46. Extension-Call Bell.

the circuit of a local battery by means of the cur-
rent generated by the magneto-call, and continues
sounding after the current of the magneto call
has ceased.

A form of extension-call bell is shown in Fig. 46.

Bell, Indicating- An electric bell

in which, in order to distinguish between
different bells in the same office, a number
is displayed by each bell when it rings.

Bell, Magneto-Electric An electric

bell, the curre.it employed to operate or
strike which is obtained by the motion of a
magneto-electric machine.

Bell, Night In a telephone ex-
change, a bell, switched into connection with
the shunted circuit of an annunciator case, and
intended, by its constant ringing, to call the
attention of the night operator to the falling
of a drop.

Bell, Belay, Electric --- An electric
bell in which a relay magnet is employed to
switch a local battery into the circuit of the
sounding apparatus of the bell.

The relay bell is suitable for use when the bell
to be sounded is situated at a great distance. As
the current from the 1 ine, when this is long, is
too weak to ring the bell, it throws into action a
local battery by the action of a relay.

Relay bells were used in the early forms oi
acoustic telegraphs as employed in England with
relay sounders.

The dots and dashes of the Morse alphabet were
indicated by the sounds of two bells, a tap on
one bell indicating a dot, and a tap on the other
a dash. This system is now practically aban-
doned.

Bell-Shaped Magnet. (See Magnet, Sell-

Bell, Shunt, Electric -- An electric
bell, the magnetizing coils of which are placed
on the line in shunt.

In the case of shunt-connected electric bells,
one of the bells must make and break the circuit
for all the rest. The series-connected electric
bell is used where the distance between the sepa-
rate bells is great, in order to save the expense of
multiple connections.

In most cases, where a number of electric bells
are to be simultaneously sounded, connection in
multiple is adopted.

Bell, Single-Stroke Electric --- An

electric bell that gives a single stroke only for
each make of the circuit.

Kg. 47. Single-Stroke Bell.

Since the bell gives a single stroke for each
completion of the circuit, its use permits of ready
communication between any two places by any

Bel.]

[Bla.

system of prearranged signals. A buzzer may be
used for the same purpose. A form of single-
stroke bell is shown in Fig . 47 . On completing the
circuit, the current, through its coils, attracts the
armature and causes a single stroke of the bell.

Bell, Telephone-Call - A call bell
used to call a correspondent to the telephone.

The telephone-call bell is generally a magneto-
electric bell.

Bell, Trembling A name some-
times given to a vibrating or an automatic
make-and-break bell. (^ezMake-and-Break,
Automatic )

Bell, Yibrating A trembling bell.
(See Bell, Trembling)

Bias of Relay Tongue. (See Tongue,
Relay, Bias of.}

Bichromate Toltaic Cell. (See Cell, Vol-
taic, Bichromate.)

Bi-fllar Suspension. (See Suspension,
Bi-filar.}

Bi-fllar Suspension Balance. (See Bal-
ance, Bi-filar Suspension)

Bi-fllar Winding. (See Winding, Bi-
filar)

Binary Compound. (See Compound, Bi-
nary)

Binding Coils. (See Coils, Binding)

Binding-Post (See Post, Binding)

Binding-Screw. (See Screw, Binding)

Binding Wire for Telegraph Lines. (See
Wire, Binding, for Telegraph Lines)

Biology, Electro That branch of

electric science which treats of the electric
conditions of living animals and plants, and
the effects of electricity upon them.

Electro-Biology includes :

(I.) Electro-Physiology.

(2.) Electro-Therapy, or Electro-Therapeutics.

Bioplasm. Any form of living matter pos-
sessing the power of reproduction.

Bioscopy, Electric The determina-
tion of the presence of life or death by the
passage of electricity through the nerves and
muscles.

Bi-polar. Having two poles.

Bi-polar Armature. (See Armature,
Bi-polar)

Bi-polar Bath. (See Bath, Bi-polar)

Birmingham Wire Gauge. (See Gauge,
Wire, Birmingham)

Bi-Telephone. (See Telephone, Bi)

Bitite. A variety of insulating material.

Black Electro-Metallurgical Deposit
(See Deposit, Black Electro-Metallurgical)

Black Lead. A variety of carbon em-
ployed in various electrical processes.

Black lead is also termed plumbago or graphite.
(See Plumbago. Graphite)

The term black lead is a misnomer, since the
substance is carbon and not lead. The term is an
old one, and is still very generally used.

Blasting, Electric The electric
ignition of powder or other explosive material
in a blast. (See Fuse, Electric)

The current required for the ignition of the
fuse is generally obtained by means of a magneto-
electric machine. In the form of magneto-blast-
ing machine, shown in Fig. 48, the movement

Fig. 48. Magneto-Blasting Machine.

of the handle shown at the top of the figure
causes the rapid rotation of a cylindrical armature
constructed on the Wheatstone and Siemens prin-
ciple. The magnets are of iron, and are furnished

Ble.J

[Boa.

with coils of insulated wire. On the rotation of
the armature the current developed therein in-
creases the field of the field magnet, and, when
of the proper degree of intensity, is thrown into the
outer circuit, and ignites the fuse.

Bleaching, Electric Bleaching pro-
cesses in which the bleaching agents are
liberated, as required, by the agency of electro-
lytic decomposition.

In the process of Naudin and Bidet, the cur-
rent from a dynamo-electric machine is passed
through a solution of common salt between two
closely approached electrodes. The chlorine and
sodium thus liberated react on each other and
form sodium hypochloride, which is drawn off
by means of a pump and used for bleaching.
(See Electrolysis.)

Block, Branch A device em-
ployed in electric wiring for taking off a branch
from a main circuit. (See Wiring.)

A form of branch-block, with its fuses attached,
is shown in Fig. 49.

Fig. 49. Branch-Black.

Block, Cross-Over A device to

permit the safe crossing of one wire over
another in molding or cleat wiring.

Block, Fuse A block containing

a safety fuse or fuses for incandescent light
circuits. (See fuse, Safety.)

Block System for Railroads. (See Rail-
roads, Block System for.)

Block Wire. (See Wire, Block)

Blow-Pipe Electric A blow-pipe
in which the air-blast is obtained by a stream
of air particles produced at the point of a

charged conductor by a convection dis-
charge.
The candle flame, Fig. 50, is blown in the di-

Fig. 50. Convection Blow-Pipe.

rection of the stream of air particles passing off
from the point P. (See Convection, Electric.)

Blow-Pipe, Electric-Arc A de-
vice of Werdermann for cutting rocks, or
other refractory substances, in which the heat
of the voltaic arc is directed* by means of a
magnet, or a blast of air, against the substance
to be cut.

The cartons are placed parallel, so as to readily
enter the cavity thus cut or fused. This inven-
tion has never been introduced into extensive
practice.

In the welding process of Benardos and
Olzewski, the welding temperature is obtained by
means of an electric arc taken between two suit-
ably shaped electrodes.

In t!ie electric-arc
blow - pipe, shown in
Fig. 51, the voltaic arc,
taken between two ver-
tical carbon electrodes,
is deflected into a hori-
zontal position under the
influence of the inclined
poles of a powerful elec-
tro-magnet.

The highly heated car-
bon vapor which consti-
tutes the voltaic arc is deflected by the magnet in
the same direction as would be any other mov-
able circuit or current.

Board, Cross-Connecting' In a

system of telegraphic or telephonic communi-
cation, a board to which the line terminals are
run before entering the switchboard, so as to

Fig. 5f. Electric- Arc
Blmv-Pipe.

Boa.]

[Boa.

readily place any subscriber in connection
with any desired section of the switchboard.

Board, Fuse A board of slate or

other incombustible material on which all
the safety fuses in an installation are as-
sembled.

The fuse board is used for avoiding accidents
from the firing of the fuses.

Board, Hanger A form of board

provided for the ready placing or removal of
an arc lamp from a circuit.

Fig, <fs* Hanger- Board.

A hanger-board contains a switch or cut-out for
the ready opening or closing of the circuit. A
form of hanger-board is shown in Fig. 52.

Board, Key Any board to which

are connected electric keys or switches.

Board, Legging-Key A key boaid

employed for the purpose of legging an
operator into a circuit connecting two or more
subscribers. (See Leg.)

Board, Multiple Switch A board

to which the numerous circuits employed in
systems of telegraphy, telephony, annunciator
or electric light and power circuits are con-
nected.

Various devices are employed for closing these
circuits, or for connecting or cross-connecting
them with one another, or with neighboring cir-
cuits.

A multiple switchboard, for example, for a tele-
phone exchange, will enable the operator to con-
nect any subscriber on the line with any other
subscriber on that line, or on another neighbor-

ing line provided with a multiple switchboard.
To this end the following parts are necessary:

(I.) Devices whereby each line entering the ex-
change can readily have inserted in its circuit a
loop connecting it with another line. This is
accomplished by placing on the switchboard a
separate spring-jack connection for each sepa-
rate line. This connection consists essentially
of one or two springs made of any conducting
metal, which are maintained in
metallic contact when the plug
key is not inserted, but which are
readily separated from one another
by the introduction of the plug-
key, Fig. 53, the terminals, a and
b, of which are insulated from
each other, and are connected to
the ends of a loop coming from
another line. As the key is in- Fis ' 53 ^ e Plug '
serted, the metallic spring or
springs of the spring-jack are separated and the
metallic pieces, a and b, are brought into good
sliding contact therewith, thus introducing the
loop into the circuit. (See Spring- Jack.)

(2.) As many separate annunciator-drops as
there are separate subscribers. These are pro*
vided so as to notify the Central Office of the par-
ticular subscriber who desires a connection.
Alarm-bells to call the operator's attention to the
calling subscriber, or to the falling of a drop, are
generally added. (See Bell, Call.)

(3. ) Connecting cords and keys for connecting
the operator's telephone, and means for ringing
subscribers' bells, and clearing out drops.

Fig. S4- Multiple Switchboard 1 for Electric Light.

In Multiple Switchboards for the Electric Light
or Distributing Switches, spring-jack contacts are
connected with the terminals of different circuits.

Boa.]

[Bod.

and plug switches with the dynamo terminals.
By these means, any dynamo can be connected
with any circuit, or a number of circuits can be
connected with the same dynamo, or a number
of separate dynamos can be placed in the same
circuit without interference with the lights.

Board, Switch A board provided

with a switch or switches, by means of which
electric circuits connected therewith may be
opened, closed, or interchanged.

Board, Switch, Telegraphic A

device employed at a telegraph station by
means of which any one of a number of tele-
graph instruments, in use at that station, may
be placed in or removed from any line con-
nected with the station, or by means of which
one wire may be connected to another.

The ability to readily connect one wire with
another is of use in case of interruption to tele-
graph lines, in which case a through circuit may
be made up of sections of
different circuits.

In the switchboard shown
fa Fig. 55, the upper left-
hand binding-post is con-
nected to earth; the four
remaining binding - posts
are connected to two sepa- Fig. ss- Telegraphic
rate instruments the sec- Switchboard.

ond and third from the top to one instrument,
and the fourth and fifth to another instrument.
The four posts at the top of the figure are con-
nected to two lines running east and west.

Various connections are made by the insertion
of plug keys in the various openings.

Board, Switch, Trnnking A

switchboard in which a few subscribers only
are connected with the operator, thus enabling
him to obtain any other subscriber by means
of trunk wires extending to the other sections.
(See Wire, Trunk)

Boat, Electric A boat provided

with electric motive power.

Electric power has been applied both to ordi-
nary vessels and to submarine torpedo boats.

Boat, Submarine Electric A boat

capable of being propelled and steered while
entirely under water.

The motive power of such boats is generally

electricity. The requisite buoyancy is obtained
by means of an air chamber. Artificial ventila-
tion is maintained, the fresh air requisite for
breathing being derived from a compressed air
cylinder.

Boat, Torpedo A boat used for

carrying and discharging torpedoes. (See
Torpedo)

Bobbin, Electric An insulated coil

of wire for an electro-magnet.

Body, Charged A body containing

an electric charge.

Charges are bound or free. ' (See Charge,
Bound. Charge, Free.}

Body, Electrified A body con-
taining an electric charge.
Body, Human, Resistance of

The resistance which the human body offers to
the passage of an electric current.

The resistance of the human body to the passage
of a current varies with the time. The re-
sistance rapidly decreases after a short time.

"The resistance diminishes because of the con-
duction of water in the epidermis under the action
of the constant current and the congestion of the
cutaneous blood vessels in consequence of the
stimulation. ' ' ( Landois and Stirling. )

The resistance also varies markedly with the
condition of the surface, the condition of the skin,
and with the shape, area, position and material
of the electrodes by which the current is led into
and carried out of the parts. It very seldom is
less than 1,000 ohms under the most favorable
conditions, and with ordinary contacts is many
times that amount.

The muscles offer nearly nine times the resist-
ance in a direction transverse to the fibres than
longitudinally to them. (Hermann.)

The resistance of the epidermis is greater than
that of any other tissue of the body.

The human body probably possesses a true
assymmetrical resistance; that is to say, when
taken after the current has been passing for some
time, its resistance is different in different direc-
tions. This variation in the apparent resistance
is believed by some to be due to polarization
effects.

Body, Insulated A body sup-
ported on an insulator, or non-conductor of
electricity.

Bod.]

[Box.

Body-Protector, Electric . A de-
vice for protecting the human body against the
accidental passage of an electric discharge.

To protect the human body from the acciden-
tal passage through it of dangerous electric cur-
rents, Delany places a light, flexible, conducting
wire, A A B L L, in the posi-
tion shown in Fig. 56, for
the purpose of leading the
greater part of the current
around instead of through
the body. The body-pro-
tector thus provides a by-
path, or shunt of low resist-
ance, around the body, and
protects it from the effects
of an accidental discharge, f'f- S6. Electric
The resistance of the con- Body-Protector.
tacts of the protecting conductor with the skin
may interfere somewhat with the efficacy of the
device. Inside insulating shoe-soles for lessening
the danger from accidental contacts through
grounded circuits have also been proposed.

Boiler-Feed, Electric A device

for automatically opening a boiler-feed appar-
atus electrically when the water in the boiler
falls to a certain predetermined point.

Boiling of Secondary or Storage Cell.
(See Cell, Secondary, or Storage, Boiling of,}

Bole. A unit, seldom or never used, pro-
posed by the British Association.

One bole is equal to one gramme-kine. (See
Kine.)

Bolometer. An apparatus devised by
Langley for measuring small differences of
temperature.

A thermal balance. (See Balance, Ther-
mic)

Bpmbardment, Molecular The

forcible rectilinear projection from the nega-
tive electrode, of the gaseous molecules of the
residual atmospheres of exhausted vessels on
the passage of electric discharges. (See
Matter, Radiant, or Ultra-Gaseous)

Bonsalite. An insulating substance.

Bore, Armature The space pro-
vided between the pole pieces of a dynamo
or motor for the rotation of the armature.

Boreal Magnetic Pole. (See Pole, Mag~
netic, Boreal?)

Bot. A term sometimes used as a con-
traction for Board of Trade unit of electric
supply, or the energy contained in a current
of 1 ,000 amperes flowing in one hour under a
pressure of one volt.

The term appears inadmissible. If used at all,
it should be B. O. T. The usage of giving the
names of distinguished dead electricians to new
units is a good one, and should be followed here.

Boucherize. To subject to the boucheriz-
ing process. (See Boucherizing?)

Boucherizing. A process for the preser-
vation of wooden telegraph poles, by inject-
ing a solution of copper sulphate into the
pores of the wood. (See Pole, Telegraphic?)

Bound Charge. (See Charge, Bound)

Box Bridge. (See Bridge, Box)

Box, Cable A box placed on a

large terminal pole and provided to receive the
separate conductors where the air-line wires
join a cable.

The wires are distributed in the cable box so
as to be readily attached to the air-line wires.

Box, Cooling, of Hydro-Electric Ma-
chine. A box provided in Armstrong's
hydro-electric machine for the steam to pass
through before leaving the nozzle.

In passing through the cooling-box some of the
steam suffers condensation. The cooling-box,
therefore, always contains some water, the pres-
ence of which seems to be necessary to the opera-
tion of the machine.

Box, Distributing, of Conduit. A name
generally applied to a handhole of a conduit.
(See Handhole of Conduit)

Box, Distribution, for Arc Light Cir-
cuits. A device by means of which arc
and incandescent lights may be simultane-
ously employed on the same line from a con-
stant-current dynamo-electric machine or
other source of constant currents.

A portion of the line circuit, whose difference
of potential is sufficient to operate the electro-
receptive device, as, for example, an incandescent
lamp, is divided into such a number of multiple

Box.]

[Box.

circuits as will provide a current of the requisite
strength for each of the devices. For example, if
the normal current on the line is seven amperes,
then each of the seven multiple-connected electro-

Fig. J7. Series- Multiple Circuit.
receptive devices shown in Fig. 57 will have a cur-
rent of one ampere passing through it, provided
the resistance of each branch is the same,

In order to protect the remaining devices from
variations in the current on the extinguishment of
any of the devices, automatic cut-outs are pro-
vided, which divert the current thus cut off
through a resistance equivalent to that of the
device.

A variety of distribution boxes are in use. (See
Circuits, Varieties of.)

Box, District-Call A box by

means of which an electric signal is auto-
matically sent over a telegraphic line and
received by an electro-magnetic device at the
other end of the line.

motion by the pulling of a lever, makes and
breaks an electric circuit and sends over the line
a succession of electric impulses of varying length,
separated from one another by varying intervals
of time. These impulses may be received at the
central station as a series of dots and dashes, or
may, by means of a Morse sounder, produce suc-
cessive sounds. By pulling the lever or handle
through different distances, different signals may
be sent to the central station and serve as calls for
various services, such as messenger boys, fire
alarm, police, special, etc.

The general appearance of a four-call district
box is shown in Fig. 58. In order to transmit
a call for any particular one of these four services
the handle is pulled until it comes opposite to the
letters indicating the required service, and is then
released. The service required is then indicated
at the receiving, or central station, through the
varying signals sent over the line by the move-
ment of the break-wheel, on the release of the
handle.

Box, Fire-Alarm Signal A signal
box provided for the purpose of automatically
sending an alarm of fire.

The fire-alarm box shown in Fig. 59, operates

Fig. 38. District Call Box.

A system of district calls includes a number of
call boxes connected by telegraphic lines with a
central station, A wheel, or its equivalent, set in

Fig. j-p. Fire- Alarm Signal-Box.

on the same principle as the district call box. The
movement of the handle in the direction of the
arrow drives a wheel that makes and breaks a
circuit at certain intervals.

The fire-alarm signal boxes are connected

Box.]

[Box.

either with a central station, or with the engine
houses of the district in which the alarm is
sounded, or with both.

Box, Fire- Alarm Telegraph An

automatic-call signal-box employed for send-
ing an alarm of fire to a central station.

A form of fire-alarm telegraph box is shown in
Fig. 60. It consists essentially of a circuit-breaker

Fig. 6O. Fire- Alarm Telegraph Box.
that is moved by pulling down a lever. The
release of the lever repeats the signal to the fire
department at the central station a certain number
of times. The box also contains a relay bell,
lightning arrester and signal-bell key.

Box, Fishing A term sometimes

used instead of junction box. (See Box,
Junction. )

Box, Flush A box or space, flush

with the surface of a road-bed, provided in a
system of underground wires or conduits,
to facilitate the introduction of the conduct-
ors into the conduit, or for the examination
of the conductors.

Box, Fuse The box in which the

fuse-wire of a safety-fuse is placed.

The fuse-box should be formed of moisture-
proof, Incombustible, insulating materials.

Box, Junction A moisture-proof

box provided in a system of underground con-

the feeders and the mains, and from which
the current is distributed to the individual
consumer. (See Feeder. Main, Electric^)

A form of junction box for coupling lengths of
conductors is shown in Fig. 6l.

Box, Patrol Alarm An automatic-
signal call-box provided for use on the out-
side of buildings.

The call-box is placed inside a box, the outer
door of which is furnished with a Yale lock.

Fig. 6 1. Junction Box.

ductors to receive the terminals of the feed-
ers, in which connection is made between

Fig. 62. Patrol Box.

A form of patrol box is shown in Fig. 62.

Box, Resistance A box containing

a number of separate coils of known resist-
ances employed for determining the value of
an unknown resistance, and for other pur-
poses. (See Bridge, Electric, Box Form of.)

Box-Sounding Relay. (See Relay, Box-
Sounding)

Box-Sounding Telegraphic Relay. (See

Relay, Box-Sounding Telegraphic.)

Box, Splice A box provided for

holding splice joints and loops, and so ar-
ranged as to be readily accessible for exami-
nation, re-arranging, cross-connecting, etc.

Splice-boxes vary in shape and construction
according to the purposes for which they are
designed.

Box, Splice, Four-way A splice-
box piovided with four ways or tubular con-
duits.

Box, Splice, Two Way A splice-

Box.J

[Bra.

box provided with but two tubular conduits or
ways.

Box, Tumbling A rotating box

in which metallic articles that are to be
electroplated are placed so as to be polished
by attrition against one another.

Boxing the Compass. (See Compass,
Boxing the?)

Bracket, Lamp, Electric A de-
vice similar to a bracket for a gas burner for
holding or supporting an electric lamp.

Fig. 63. Lamp Bracket. Fig. 6 4. Lamp Bracket.
Lamp brackets are either fixed or movable.

Fig. 6j. Lamp Bracket, Movable Arms.
Those shown in Figs. 63 and 64 are fixed. That
shown in Fig. 65 is movable.

Bracket, Telegraphic A support

or cross piece placed on a telegraph pole
for the support of the insulators of tele-
graphic lines.

Telegraphic insulators are supported either on
wooden arms, or on iron or metal brackets.

Fig. 66 shows a form of iron bracket. Fig. 67
shows a form of wooden arm.

Fig. 66. Telegraphic
Bracket.

Fig. 67. Telegraphic
Cross- Arm.

Various well known modifications of these
shapes are in common use. (For details, see Fole,
Telegraphic. )

Braid, Tubular A braid of fibrous

insulating material, woven in the form of a
tube, and provided for drawing over a splice
after two wires have been connected.

Braided Wire. (See Wire, Braided)

Brake, Electro-Magnetic A brake

for car wheels, the braking power for which
is either -derived entirely from electro-magnet-
ism, or is thrown into action by electro-mag-
netic devices.

Electro-magnetic car brakes are of a great va-
riety of forms. They may, however, be arranged
in two classes, viz. :

(l.) Those in which magnetic adhesion, or the
magnetic attraction of the brake to the wheels, is
employed.

(2.) Ordinary brake mechanism in which the
force operating the brake is thrown into action by
an electro-magnet.

Brake, Friction A name some-
times given to a Prony brake. (See Brake,
Prony.)

Brake, Magneto-Electric A device

for checking the swing of a galvanometer, in
which a slight inverse current is sent through
the coils of the galvanometer.

The Frey magneto-electric brake, as shown in
Fig. 68, consists of a small coil, connected by a

Fig. 68. Electric Brakt.

contact-key with the galvanometer terminals. A
small adjustable magnet coil is provided for
regulating the action ot the inverse current. To
avoid disturbance, the brake is placed at least
4 or 5 feet from the galvanometer. Manipulation
of the ordinary galvanometer key attains the same
end in a much simpler manner.

Brake, Prony A mechanical de-
vice for measuring the power of a driving
shaft.

Bra.j

[Bre.

An inflexible beam, Fig. 69, is provided at one
end with a clamping device for clamping the
driving shaft or pulley, and at the other end A,
with a pan for holding weights.

If the brake be arranged as shown in Fig. 69,
and the shaft rotate in the direction of the arrow,
the tendency will be to carry the beam around
with the shaft, placing it at some given moment

Fig, 69, Pr any Brake.

in the position shown by the dotted line. If a
sufficiently heavy weight be placed at x, in a pan
hung at A, the beam will assume a position ver-
tically downwards. If, however, the torque, or

Fig. 70. Prony

twisting force of the driving shaft, be balanced by
the weight, the bar will remain horizontal. The
power can then be calculated by multiplying the
weight in pounds by the circumference in feet of
the circle of which the bar is a radius, and this
product by the number of turns of the driving
shaft per minute. The product will be the num-

Fig. 7 TC Prony Brake.

ber of foot-pounds per minute, and, when divided
by 33,000, will give the horse-power.

Some modified forms of the Prony brake are
shown in Figs. 7 and 71.

A simple form of brake consists of a cord passed
over the pulley of the machine to be tested. A
weight is hung at one end of the cord. The other

end of the cord is attached to the top of a spring
balance, the other end of which is fastened to the
floor. A reading of the spring balance is taken
while the pulley is at rest and when it is in motion,
and the result calculated.

Branch. A term applied to any principal
distributing conductor from which outlets
are taken or taps made.

Branch-Block. (See Block, Branch)

Branch Conductors. (See Conductor,
Branch)

Branch Fuse. (See Fuse, Branch.}

Branch, Sub A distributing con-
ductor taken from a branch.

Branding, Electric - - A process
whereby the branding tool is heated by elec-
trical incandescence instead of by ordinary
heat.

The branding tool consists essentially of a small
transformer with devices for regulating the cur-
rent strength by switches and choking coils.

Brassing, Electro Coating a sur-
face with a layer of brass by electro-plating.
(See Plating, Electro)

The plating bath contains a solution of copper
and zinc ; a brass plate is used as an anode.

Break. A want of continuity in a circuit.

Break, Circuit Loop A device for
introducing a loop in any part of a line
circuit.

A form of circuit loop-break is shown in Fig. 7 2 -

Fig. T3. Circuit Loop Break.

It consists essentially of a rigid frame with two
porcelain or other suitable insulators for the sup-
port of the loop wires.

Bre.]

[Bri.

Break-Down Switch. (See Switch,Break-
Down?)

Break-Induced Current. (See Current,
Break-Induced?)

Break, Mercury A form of circuit
breaker operated by the removal of a conduc-
tor from a mercury surface.

Mercury breaks assume a variety of forms. One
end of the circuit is connected with the mercury,
and the other with the conductor.

Break Shock. (See Shock, Break\

Breaker, Circuit Any device for

breaking a circuit.

Breaking the Primary. (See Primary,
Breaking the.)

Breaking Weight of Telegraph Wires.
(See Wires, Telegraph, Breaking Weight
of.)

Breath Figures. (See Figures, Breath?)

Breeze, Electric A term some-
times employed in electro-therapeutics for a
brush discharge.

One of the electrodes, consisting of a single
point or a number of points, is held near the
parts to be treated so that the con vective discharge
is received thereon. The other electrode is con-
nected to the body of the patient.

Breeze, Electro-Therapeutic An

electric breeze. (See Breeze, Electric?)

Breeze, Head, Electro-Therapeutic
A form of electric convective discharge,
or electric breeze, applied to the head. (See
Breeze, Electric?)

Breeze, Static An electric breeze
obtained by the convective discharge of an
electrostatic charge.

Bridge-Arms. (See Arms, Bridge or
Balance?)

Bridge, Box A box of resistance

coils so arranged as to be capable of being
used directly as a Wheatstone electric balance.
(See Bridge, Electric, Box Form of?)

The commercial form of Wheatstone's
balance.

Bridge, Electric A device for

measuring the value of electric resistances.

The electric bridge is also called the Electric
Balance.

This is called a bridge because the wire M, G,
N, bridges or joins points of equal potential.

A, B, C and D, Fig. 73, are four electric re-
sistances, any one of which can be determined in
ohms, provided the absolute value of one of the
others, and the relative values of any two of the
remaining three are known in ohms.

A voltaic battery, Zn C, is connected at O
and P, so as to branch at P, and again unite at

Zn C
Fig. 13. Electric Balance.

Q, after passing through the conductor D C, and
B A.

A sensitive galvanometer, G, is connected at
M N, as shown.

The passage of a current through any resistance
is attended by a fall of potential proportional to
the resistance. (See Potential, Electric.) If, then,
the resistances A, C and B, are so proportioned
to the value of the unknown resistance D, that no
current passes through the galvanometer G, the
two points, M and N, in the two circuits, Q M P
and Q N P, are at the same potential. That is to
say, the fall of potential along Q M P and Q N P,
at the points M and N, is equal. Since the fall
of potential is proportional to the resistance, it
follows that

A : B : : C : D,
or A X D = B X C,

">=(!)

If then we know the values of A, B and C, the
value of D, can be readily calculated.

By making the value iL some simple ratio, the

value of D, is easily obtained in terms of C.

The resistances A, B and C, may consist of
coils of wire whose resistance is known. To
avoid their magnetism affecting the galvanometer
needle during the passage of the current through
them, they should be made of wire bent into two

Bri.]

[Bri.

parallel wires and wrapped in coils called resist-
ance coils; or a resistance box may be used. (See
Coil, Resistance. Box, Resistance,)

There are two general forms of Wheatstone's
Bridge, the box form, and the sliding form.

Bridge, Electric, Armg of The

resistances of an electric bridge or balance.
(See Bridge, Electric)

Bridge, Electric, Box Form of

A commercial form of bridge or balance in
which all the known arms or branches of the
bridge, except the unknown arm, consist of
standardized resistance coils, whose values are
given in ohms. (See Coil, Resistance?)
The box form of bridge or balance is shown in

Fig. 74. Box Balance.

perspective in Fig. 74, and in plan in Fig. 75.
The bridge arms, corresponding to the resistances

Fig.

Box Balance.

A and B, of Fig. 73, consist of resistance coils of
10, 100 and 1,000 ohms each, inserted in the
arms q z, and q x, of Fig. 75. These are
called the froportional coils. The arm corre-
sponding to resistance C, of Fig. 73, is composed
of separate resistances of I, 2, 2, 5, 10, 10, 20, 50,
loo, 100, 200, 500, 1,000, 1,000, 2,000 and 5,000
ohms. In some forms of box bridges additional
decimal resistances are added.

The resistance coils are wound, as shown in
Fig. 76, after the wire has been bent on itself in
the middle. This is done in order to avoid the
effects of induction, among which are a disturb-
ing action on a galvanometer used near them,
and the introduction of a spurious resistance in
the coils themselves. (See Resistance, Spurious.}

3 Vol. 1

To avoid the effects of changes of resistance oc-
casioned by changes of temperature, the coils are
made of German silver, or, preferably, of alloys
called Platinoid or Platinum silver. Even when
these alloys are used, care should be taken not to
allow the currents to pass continuously through
the resistance coils longer than a few moments.

The coils, C, C', are connected with one another
in series by soldering their ends to the short

Fig. 76.

ce Coils.

thick pieces of brass, E, E, E, Fig. 76. On the in-
sertion of the plug-keys, at S, S, the coils are cut-
out by short-circuiting. Care should be taken to
see that the plug-keys are firmly inserted and free
from grease or dirt, as otherwise the coil will not be
completely cut out. As each plug-key is inserted
it should be turned slightly in the opening, so
as to insure good contact.

The following are the connections, viz.: The
galvanometer is inserted between q and r, Fig. 77,

Jit

Fig. 77. Electric Balance.

the unknown resistance between z and r ; the bat-
tery is connected tox and z. , A convenient pro-
portion being taken for the value of the propor-
tional coils, resistances are inserted in the arm C,
until no deflection is shown by the galvanometer
G. The similarity between these connections and
those shown in Fig. 75 will be seen from an
inspection of Fig. 77. The arms, A and B, corre-
spond to q x and q z, of Fig. 75; C, to the arm

Bri.]

[Bri.

x r, Fig. 75 ; and D, to the unknown resistance.
We then have as before:

A:B::C:D, orAxD = BxC. .-. D = f\ Q.

The advantage of the simplicity of the ratios, A
and B, or 10, 100 and 1,000 of the bridge box,
will therefore be manifest. The battery terminals
may also be connected to q and r, and the gal-
vanometer terminals to x and z, without disturb-
ing the proportions.

Bridge, Electric, Commercial Form of

A name sometimes given to the box

form of Wheatstone's electric balance. (See
Bridge, Electric, Box Form of.)

Bridge, Electric Duplex An ar-
rangement of telegraphic circuits in the form
of a Wheatstone electric bridge for the pur-
poses of duplex telegraphy. (See Teleg-
raphy, Duplex, Bridge Method of )

Bridge, Electric, Proportionate Arms
of (See Arms, Proportionate)

Bridge, Electric, Slide-Form of

A balance in which the proportionate arms of
the bridge are formed of a single thin wire, of
uniform diameter, generally of German silver,
of comparatively high resistance. The length
of this wire is usually one metre ; hence this
apparatus is often called the metre bridge.

A Sliding Contact Key slides over the wire; one
terminal of the key is connected with the galva-
nometer and the other with the wire when the key
is depressed. As the wire is of uniform diameter
the resistances of the arms, A and B, Fig. 78, will

Fig

be directly proportional to the lengths. A scale
placed near the wire serves to measure these
lengths. A thick metal strip connected with the
slide wire has four gaps at P, Q, R and S.

When in ordinary use, the gaps at P and S, are
either connected by stout strips of conducting ma-
terial or by known resistances, in which latter case
they act simply as ungraduated extensions of the
slide wire, and, like lengthening the slide wire,
increase the sensibility of the instrument.

The unknown resistance is then inserted in the
gap at Q, and a known resistance, generally the
resistance box, in that at R. The galvanometer
has one of its terminals connected to the metal
strip between Q and R, and its other terminal to
the sliding key. The battery terminals are con-
nected to the metal strips between P and Q, and
R and S, respectively.

These connections are more clearly seen in the
form of bridge shown in Fig. 79. The slide wire,
w w, consists of three separate wires each a metre

Fig. 79. SuU Form of Bridge.

in length, so arranged that only one wire, or two
in series, or all three in series, can be used. Mat-
ters being now arranged as shown, the sliding
key is moved until no current passes through the
galvanometer when the key is depressed.

The slide form of bridge is not entirely satis-
factory, since the uncertainty of the spring-con-
tact causes a lack of correspondence between the
point of contact and the point of the scale on
which the index rests.

The loss of uniformity in the diameter of the
wire, due to constant use, causes a lack of corre-
spondence between the resistance of the wire and
its length. With care, however, very accurate
results can be obtained by the slide form.

Bridge, Inductance An appara-
tus for measuring the inductance of a circuit
similar to a Wheatstone bridge. (See /</?/-
tance)

Professor Hughes employed an inductance
bridge of the following description:

Four resistances, Q, S, R and P, arranged as
shown in Fig. 80, form the bridge. The re-
sistances, Q, S and R, consist of sections of Ger-
man silver wire, one metre in length, each of
the resistance of 4 ohms. P, is a coil of wire pos-
sessing sensible inductance. The object of tha

Bri.]

[Bri,

bridge is to measure the value of this inductance.
I, is an interrupter placed in the circuit of the
battery B.

Suppose the interrupter, I, be placed in the tele-
phone circuit between T and c. By shifting the
sliding contact so as to alter the value of R, a bal-

Fig. 80. Inductance Bridge.

ance can be effected and silence obtained in the
telephone.

Now remove the interrupter and place it in the
battery circuit between b and a, as shown in Fig.
80. If now, the interrupter, I, be made to rapidly
interrupt the battery current, this balance is
destroyed, and cannot be again obtained by any
variation in the value of the resistance, R.

The reason of this is evident. On the closing
or opening of the battery current, the inductance
of P, produces a counter electromotive force in
P, which produces differences of potential between
a and c. If an attempt be made to prevent this,

Fig. St.

Bridge.

by altering the value of R, the steady balance is
destroyed, and the telephone wfll be traversed by
a current during the time the currents have be-
come steady. In order to obtain a balance
during rapid alternations of the battery current,
Professor Hughes placed a pair of mutually in-

ductive coils in the battery and the telephone
circuits, as shown in Fig. 81.

The resistances, Q, S, R and P, are the same
as already described. The mutually inductive
coils, M 1 and M 2 , are placed respectively in the
telephone and battery circuits in the manner
shown. The coil M 2 , in the battery circuit is
fixed, while that in the telephone circuit is so
arranged that it can be maintained, with its centre
coincident with that of M 3 , while its axis can be
placed at any desired angle with M 2 . When the
axes of the coils are at right angles, the inductance
is zero. When they are co-linear, the inductance
is at its maximum.

When the coils M lf and M 8 , are in any inter-
mediate position, the inductive electromotive
force produced in the telephone circuit can, if
the value of R, be changed, be made to balance
the impulsive electromotive force due to the in-
ductance of P, and the value of this latter can,
therefore, be inferred.

Bridge, Magnetic An apparatus in-
vented by Edison for measuring magnetic
resistance, similar in principle to Wheatstone's
electric bridge.

The magnetic bridge is based on the fact that
two points at the same magnetic potential, when
connected, fail to produce any action on a mag-
netic needle. The magnetic bridge consists, as
shown in Fig. 82, of four arms or sides made of

Fig. 82. Magnetic Bridge.

pure, soft iron. The poles of an electro-magnet
are connected to projections at the middle of
the short side of the rectangle. By this means
a difference of magnetic potential is main-
tained at these points. Thetwo long sides are
formed of two halves each, which form the four
arms of the balance. Two of these only are
movable.

Two curved bars of soft iron, of the same area
of cross-section as the arms of the bridge, rest on
the middle of the long arms, in the arched shape
shown. Their ends approach near the top of the

Bri.]

[Bru.

arch within about a half inch. A space is hol-
lowed out between these ends, for the reception of
a short needle of well-magnetized hardened steel,
suspended by a wire from a torsion head.

The movements of the needle are measured on
a scale by a spot of light reflected from a mirror.

The electro-magnet maintains a constant dif-
ference of magnetic potential at the two shorter
ends of the rectangle. If, therefore, the four
bars, or arms of the bridge, are magnetically
identical, there will be no deflection, since no
difference of potential will exist at the ends of the
bars between which the needle is suspended. If,
however, one of the bars or arms be moved even
a trifle, the needle is at once deflected, the motion
becoming a maximum when the bar is entirely
removed. If replaced by another bar, differing
in cross-section, constitution, or molecular struc-
ture, the balance is likewise disturbed.

The magnetic bridge is very sensitive. It was
designed by its inventor for testing the magnetic
qualities of the iron used in the construction of
dynamo-electric machines.

Bridge Method of Duplex Telegraphy.^

(See Telegraphy, Duplex, Bridge Method
of.)

Bridge Method of Qnadrnplex Teleg-
raphy. (See Telegraphy, Quadruples,
Bridge Method of.)

Bridge, Metre A slide form of

Wheatstone's electric bridge, in which the
slide wire is one metre in length. (See
Bridge, Electric, Slide Form of.)

Bridge, Resistance A term some-
times applied to an electric bridge or balance.
(See Bridge, Electric)

Bridge, Reversible A bridge or

balance so arranged that the proportionate
coils can be readily interchanged, thus per-
mitting the bridge coils to be readily tested by
reversing.

Bridge, Wheatstone's Electric

A name given to the electric bridge or balance.
(See Bridge, Electric)

Bridges. Heavy copper wires suitably
shaped for connecting the dynamo-electric
machines in an incandescent light station to
the bus-rods or wires.

Bright Dipping. (See Dipping, Bright?)
Bright Dipping Liquid. (See Liquid,
Bright Dipping :)

Britannia Joint. (See Joint, Britannia)
Broken Circuit. (See Circuit, Broken)

Bronzing, Electro Coating a sur-
face with a layer of bronze by electro-plating.
(See Plating, Electro)

The plating bath contains a solution of tin and
copper.

Bmsh-and-Spray Discharge. (See Dis-
charge, Brush-and-Spray)

Brush Discharge. (See Discharge,
Brush)

Brush Electrode. (See Electrode, Brush)

Brush, Faradic An electrode in

the form of a brush employed in the medical
application of electricity.

The bristles are generally made of nickelized
copper wire.

Brush-Holders for Dynamo-Electric Ma-
chines. Devices for supporting the collecting
brushes of dynamo-electric machines.

As the brushes require to be set or placed on
the commutator in a position which often varies
with the speed of the machine, and with changes
in the resistance of the external circuit, all brush -
holders are provided with some device for moving
them concentrically with the commutator cylin-
der.

Brush Rocker. (See Rocker, Brush)

Brush, Scratch A brush made

of wire or stiff bristles, etc., suitable for clean-
ing the surfaces of metallic objects before
placing them in the plating bath.

Scratch brushes are made of various shapes and
are provided with wires or bristles of varying
coarseness.

Some forms of scratch and finishing brushes
are shown in Fig. 83. They are circular in outline

Fig. 83. Scratch Brushes.

and are adapted for use in connection with a
lathe.

Bru.J

[Bui.

Brush, Scratch, Circular A

scratch brush of a circular shape, so fitted as
to be capable of being placed in a lathe and
set in rapid rotation.

Brush, Scratch, Hand A scratch

brush operated by hand, as distinguished
from a circular scratch brush operated by a
lathe.

Brushes, Adjustment of Dynamo-Electric

Machines Shifting the brushes into

the required position on thr commutator
cylinder, either non-automatically by hand, or
automatically by the current itself. (See
Regulation, Automatic, of Dynamo-Electric
Machines?)

Brushes, Carbon, for Electric Motors

Plates of carbon for leading current

to electric motors. (See Brushes of Dynamo-
Electric Machine?)

These are generally known simply as brushes.

Brushes, Collecting, of Dynamo-Electric

Machine Conducting brushes which

bear on the commutator cylinder, and take off
the current generated by the difference of
potential in the armature coils. (See Brushes
of Dynamo-Electric Machine?)

Brushes, Lead of The angle through

which the brushes of a dynamo-electric ma-
chine must be moved forward, or in the
direction of rotation, in order to diminish
sparking and to get the best output from
the dynamo.

The necessity for the lead arises from the coun-
ter magnetism or magnetic reaction of the arma-
ture, and the magnetic lag of its iron core. (See
Lead, Angle of.)

The position of the brushes on the commutator
to insure the best output is practically the same
in a series dynamo for any current strength.
In shunt and compound dynamos it varies with
the lead.

Brushes of Dynamo-Electric Machine.
Strips of metal, bundles of wire, slit plates of
metal, or plates of carbon, that bear on the
commutator cylinder of a dynamo-electric
machine, and carry off the current generated.

Rotary brushes consisting of metal discs are
sometimes employed. Copper is almost univer-

Fig. 84. Brushes

sally used for the brushes of dynamo-electric
machines. Carbon brushes are often used for
dynamo-electric motors.

The brush shown at B, Fig. 84, is formed of
copper wires, soldered
together at the non-
bearing end. A copper
plate, slit at the bear-
ing end, is shown at C,
and bundles of copper
plates, soldered together
at the non-bearing end,
are shown at D.

The brushes should
bear against the com-
mutator cylinder with
sufficient force to pre-
vent jumping, and con-
sequent burning, and
yet not so hard as to
cause excessive wear.

Brushes, Rotating, of Dynamo-Electric

Machines Discs of metal, employed

in place of the ordinary brushes for carry-
ing off the current from the armatures of
dynamo-electric machines.

Brushing, Scratch Cleansing the

surface of an article to be electroplated, by
friction with a scratch brush.

Scratch brushing is generally done with the
brushes wet by various solutions.

Buckling. Irregularities in the shape of
the surfaces of the plates of storage cells, fol-
lowing a too rapid discharge.

Bug. A term originally employed in quad-
ruplex telegraphy to designate any fault in
the operation of the apparatus.

This term is now employed, to a limited extent,
for faults in the operation of any electric appa-
ratus.

Bug-Trap. A device employed to over-
come the " bug " in quadruplex telegraphy.

Bulb, Lamp The chamber or

globe in which the filament of an incan-
descent electric lamp is placed.

The chamber or globe of a lamp must be of
such construction as to enable the high vacuum
necessary to the operation of the lamp to be main-
tained.

Bun.]

(54

[Bur.

Bunched Cable. (See Cable, Bunched?)
Bunched Cable, Straightaway

(See Cable, Bunched, Straightaway?)

Bunched Cable, Twisted - (See
Cable, Bunched, Twisted?)

Bunsen Yoltaic Cell. (See Cell, Voltaic,
Bunsen's)

Buoy, Electric A buoy on which

luminous electric signals are displayed.

Burglar Alarm. (See Alarm, Burglar?)

Burglar Alarm Annunciator. (See An-
nunciator, Burglar Alarm?)

Burglar Alarm Contacts. (See Contacts,
Burglar Alarm.)

Burglar Alarm, Yale Lock Switch for

(See Alarm, Yale-Lock-Switch Burglar)

Burner, Argand Electric An ar-

gand gas-burner that is lighted by means of
an electric spark.

The argand electric burner assumes a variety
of forms, such as the plain pendant, the ratchet-
pendant and the automatic. They are also used
in systems of multiple gas lighting.

Burner, Argand Electric, Automatic

An argand burner arranged for automatic
electric lighting. (See Burner, Automatic-
Electric:)

Burner, Argand Electric, Hand-Lighter

A plain-pendant electric burner

adapted for lighting an argand gas-burner.
(See Burner, Plain-Pendant Electric?]

Burner, Argand-Electric, Plain-Pendant

A plain-pendant electric burner

adapted for lighting an argand gas burner.
(See Burner, Plain-Pendant Electric?)

Burner, Argand-Electric, Ratchet-Pend-
ant A ratchet-pendant electric burner

adapted for lighting an argand gas-burner.
(See Burner, Ratchet-Pendant Electric?]

Burner, Automatic-Electric An

electric device for both turning on the gas
and lighting it, and turning it off, by alter-
nately touching different buttons.

The gas-cock is opened or closed by the motion
of an armature, the movements of which are con-
trolled by two separate electro-magnets. One
push-button, usually a white one, turns the gas on

by energizing one of the electro-magnets and,
at the same time, lights it by means of a suc-
cession of sparks from a spark coil. Another
push-button, usually a black one, turns the gas
off by energizing the other electro-magnet.
The turning on or off of the gas is accom-
plished by positive
motions. Automatic
burners are also made
with a single button.

An Argand Electric
Burner is shown in
Fig. 85.

Burner, Electric
Candle - A
device for electri-
cally lighting a gas
jet in a burner sur-
rounded by a por-
celain tube in imita-
tion of a candle.

Electric candle bur-
ners are either simple
or ratchet candle bur-
ners.

Burner, Hand-
Lighting Electric
A name sometimes applied to a plain-
pendant electric burner. (See Burner, Plain-
Pendant Electric?)

Burner, Jump-Spark A term

sometimes applied to a gas burner in which
the issuing gas is ignited
by a spark that jumps be-
tween the metallic points
placed on it.

Jump-spark burners are
used in systems of multiple
gas lighting. (See Light-
ing, Electric Gas.)

Burner, Plain-Pen-
dant Electric A

gas - burner provided

with a pendant for the

purpose of lighting the

gas by means of a spark, F ig. 8t>. Plain.

after the gas has been Burner.

turned on by hand.

The gas is first turned on by hand at the ordi-

Fig. Sj. Argand Electr
Burner.

Bur.]

[But

nary key, and is then lighted by pulling the pend-
ant C, Fig. 86. A spark from a spark coil ignites
the gas.

This is sometimes called an electric hund-
Jighting burner,

Burner, Ratchet-Pendant Candle Elec-
tric A burner for both lighting and

extinguishing a candle gas jet.

Burner, Ratchet-Pendant Electric

A gas-burner in which one pulling of a
pendant turns on the gas and ignites it by
means of an electric spark from a spark coil,
and the next pulling of the pendant turns off
the gas.

A ratchet-wheel and pawl are operated by the
motion of the pendant. The first pull of the
pendant chain moves the ratchet so as to open a
four- way gas cock, and at the same time light
the gas at the burner tip by a wipe-spark from a
spark coil. On the next pull ot the pendant, the
four- way cock is turned so as to turn off the g?s.
Alternate pulls, therefore, light and extinguish
the gas.

Burner, Simple Candle Electric

A plain-pendant electric burner. (See Bur-
ner, Plain Pendant Electric?)

Burner, Thumb-Cock Electric

An electric gas-
burner, in which
the turning of an
ordinary thumb-
cock turns on the
gas, and ignites it
by a spark pro-
duced by a wiping
contact actuated
by the motions of
the thumb-cock.
A form of thumb-
cock burner is
shown in Fig. 87.

Burner, Vi-
brating-Elec-

triC An Fig. 87. Thumb- Cock Burner.

electric gas-burner in which the gas is lighted
after it is turned on by hand, by means of the
spark from a spark coil produced on the rapid

making and breaking of the circuit by a
vibrating contact.

The vibrating-electric burner has a single elec-
tro-magnet. It is operated by means of a button
or switch, and may be used on single lights or on
groups of lights. It bears the same relation to
the automatic burner that the plain-pendant
burner does to the ratchet burner.

Burnetize. To subject to the Burnetizing
process. (See Burnetizing?)

Burnetizing. A method adopted for the
preservation of wooden telegraph poles by
injecting a solution of zinc chloride into the
pores of the wood. (See Pole, Telegraphic?)

Burning at Commutator of Dynamo.

An arcing at the brushes of a dynamo-elec-
tric machine, due to their imperfect contact,
or improper position, which results in loss of
energy and destruction of the commutator
segments.

Bus. A word generally used instead of
omnibus. (See Omnibus?)

Bus-Bars. (See Bars, Bus?)

Bus-Rod Wires. (See Wires Bus-Rod.)

Bus-Wire. (See Wire, Bus?)

Butt Joint. (See Joint, Butt?)

Button, Carbon A resistance of

carbon in the form of a button.

A button of carbon is used as an electric resist-
ance in a variety of apparatus; its principal use,
however, is in the transmitting instrument of the
electric telephone. In the telephone transmitter,
the button is so placed between contact-plates that
when the plates are pressed together by the
sound-waves, the electrical resistance is decreased
by a decrease in the thickness of the carbon button,
an increase in its density, and an increase in the
number of points where the carbon touches the
plates. Rheostats, or resistances, have been
made by the use of a number of carbon buttons or
discs piled one on another and placed in a glass
tube. Discs of carbonized cloth form excellent
resistances for such purposes.

Button, Press A push button.

(See Button, Push?)

Button, Push A device for closing

But]

[Cab.

In electric circuit by the movement of a
button.
A button, when pushed by the hand, closes the

Buzzer, Electric A call, not as

loud as that of a bell, produced by a rapid

Fig. 88. Push Button. Fig, 89. Push Button.

contact, and thus completes a circuit in which
some electro-receptive device is placed. This
circuit is opened by a spring,
on the removal of the pressure.
Some forms of push-buttons are
shown in Figs. 88, 89 and 90.

A.floor-push for dining-rooms
and offices is shown in Fig.
90.

Fig. 88 shows the general
appearance of an ordinary bell-
push. The arrangement of the
interior spring contacts will be
understood by an inspection of Fig. 91

Fig. 9 /. Spring Contact of Bell Push.

automatic make-and-break. (See Make-and'
Break, Automatic?)

The buzzer is generally pkced inside a resonant

Fig. 90. Floor
Push.

Fig. 92. Buzzer.

case of wood in order to strengthen the sound by
resonance. A form of buzzer is shown in Fig. 92.

C. An abbreviation for centigrade.

TIUS, 20 degrees C. means 20 degrees of the
centigrade thermometric scale. (See Scale, Cen-
tigrade Thermometer.')

C. A contraction for current.

Generally a contraction for the current in

amperes, as C = ^.

C. C. A contraction for cubic centimetre.
(See Weights and Measures, Metric System
of.)

C. G. S. Units. A contraction for centi-
timetre-gramme-second units. (See Units,
Centimetre-Gramme- Second.)

C. P. A contraction for candle power.
(See Candle, Standard.)

Cable. An electric cable. (See Cable,
Electric.)

Cable. To send a telegraphic dispatch,
by means of a cable.

Cable, Aerial A cable suspended

in the air from suitable poles.

Cable, Anti-Induction, Waring

A form of anti-induction cable.

In the Waring an ti- induction cable the separate
conductors are covered with a fibrous insulator,
from which all air and moisture is expelled, and
the fibre then saturated with an insulating ma-

Cab.]

[Cab.

terial called ozite. The conductors are then pro-
tected from the inductive effects of neighboring
conductors by a continuous sheath of lead alloyed
with tin.

Where the cables are bunched, the bunches
are sometimes again surrounded by insulating
material, and the whole then covered by a con-
tinuous lead sheathing ; generally, however, the
separately insulated conductors are bunched,
and then covered by a single sheathing of lead
alloyed with tin.

Cable, Armature of The armor of

a cable. (See Armature of a Cable)

Cable, Armor of The protecting

sheathing or metallic covering on the outside
of a submarine or other electric cable.

Cable, Armored An electric cable

provided, in addition to its insulating coat-
ing, with a protective coating or sheathing,
generally of metal tubing or wire.

Cable-Box. (See Sox, Cable.)

Cable, Bunched A cable contain-
ing more than a single wire or conductor.

Some forms of bunched, lead-covered cables,
are bhown in Fig. 93.

Fig. 93. Bunched Cables.

Cable, Bunched, Straightaway

A bunched cable the separate conductors of
which extend in the direction of the length of
the cable without any twisting, being placed
in successive layers.

In arranging the separate conductors in suc-
cessive layers an advantage is gained in testing
for a given wire in order to make a loop, splice,
or branch with the next adjoining section. This is
rendered still easier by giving the conductors
of the successive layers some distinctive form of
braiding in the fibrous insulating material, or
some distinctive color.

Cable, Bunched, Twisted A

bunched cable, the separate conductors of
which are twisted-pairs placed in successive
layers.

Each twisted-pair of a bunched cable acts as a
metallic circuit, and, moreover, possesses the ad-
vantage of avoiding the ill effects of induction, so
disadvantageous in telephone circuits.

In laying up the twisted-pairs in successive
layers in a bunched cable, the direction of twist-
ing is reversed in each successive layer. This
form is especially desirable on all long cable lines.

In the case of twisted cables for telephone lines,
the twists are sometimes made as frequent as one
in every three or four inches. In such cases the
cross-talk of induction is inappreciable.

Cable, Capacity of The quantity

of electricity required to raise a given length
of a cable to a given potential, divided by the
potential.

The amount of charge for a given potential
that any single conductor will take up with
the rest of the conductors grounded. (See
Capacity, Electrostatic^)

The ability of a wire or cable to permit a
certain quantity of electricity to be passed
into it before acquiring a given difference of
potential.

Before a telegraph line or cable can transmit a
signal to its further end, its difference of potential
must be raised to a definite amount dependent on
the character of the instruments and the nature of
the system.

The first effect of electricity being passed into a
line is to produce an accumulation of electricity
on the line, similar to the charge in a condenser.
Cables especially act as condensers, and from the
high specific inductive capacity of the insulating
materials employed, permit considerable induc-
tion to take place between the core and the
metallic armor or sheathing, or the ground.

The capacity of a cable depends on the capacity
of the wire ; *. e. , on its length and surface, on
the specific inductive capacity of its insulation,
and its neighborhood to the earth, or to other
conducting wires, casings, armors, or metallic
coatings. Submarine or underground cables
therefore have a greater capacity than air lines.

This accumulation of electricity produces a re-
tardation in the speed of signaling, because the
wire must be charged before the signal is received
at the distant end, and discharged or neutralized
before a current can be sent in the reverse direc-
tion. This latter may be done by connecting
each end to earth, or by the action of the reverse
current itself.

Cab.J

[Cab.

The smaller the electrostatic capacity of a cable,
therefore, the greater the speed of signaling. (See
Retardation. )

The capacity of a cable is measured in micro-
farads. (See Farad, Micro.)

Cable Clip. (See Clip, Cable)

Cable-Core. (See Core of Cable)

Cable, Core-Ratio of The ratio be-
tween the diameter of the insulation of a cable
and the mean diameter of the strand.

The core- ratio is represented by ^-; where D,

is the diameter of the insulation, and d, the mean
diameter of the strand. Should the extreme
diameter of the strand of a cable be used in cal-
culations for insulation resistance, inductive capa-
city, etc., erroneous values would be obtained.
The measured diameter of the copper conductor
is consequently decreased some five per cent., and,
in this way, correct values are approximately
obtained. (Clark <&> Sabine.)

Cable, Duplex A conductor con-
sisting of two separate cables placed parallel
to each other.

The duplex cable is used especially in the al-
ternating current system.

Cable, Electric The combination

of an extended length of a single insulated
conductor, or two or more separately insu-
lated electric conductors, covered externally
with a metallic sheathing or armor.

Strictly speaking, the word cable should be
limited to the case of more than a single con-
ductor. Usage, however, sanctions the employ-
ment of the word to indicate a single insulated
conductor.

The conducting wire may consist of a single
wire, of a number of separate wires electrically
connected, or of a number of separate wires in-
sulated from one another.

An electric cable consists of the following parts,
viz.:

(i.) The conducting wire or core.

(2.) The insulating material for separating the
several wires; and

(3.) The armor or protecting covering, consist'
Ing of strands of iron wire, or of a metallic coat-
Ing or covering of lead.

As to their position, cables are aerial, sub-
marine, or underground. As to their purpose,

they are telegraphic, telephonic, or electric light
and power cables. As to the number of their
conductors they are single-wire or bunched
cables. Bunched cables are straightaway or
twisted.
Fig. 94 shows a form of submarine cable the

Fig. 94. Electric Cablt.

armor of which is formed of strands of iron
wire.
Cable, Electric Light or Power

A cable designed to distribute the electric cur-
rent employed in electric light or power sys-
tems.

Electric light cables are generally underground.
They may be submarine. (See Cable, Electric.)

Cable, Flat A cable, the separate

conductors of which are laid-up side by side
so as to form a flat conductor.

A flat cable is suitable for house work as being
less objectionable in appearance when placed OB
the outside of ceilings or walls.

Cable, Flat Duplex A flat, laid-up

cable containing two wires.

Cable-Grip. (See Grip, Cable)
Cable-Hanger. (See Hanger, Cable)

Cable-Hanger Tongs. (See Tongs, Cable-
Hanger)

Cable Laid-TJp in Layers. A term applied
to a cable, all the conducting wires of which
are in layers.

Cab.]

[Cab.

Cable Laid-TJp in Reversed Layers. A
term applied to a cable in which the conduct-
ors, in alternate layers, are twisted in opposite
directions. (See Cable, Bunched, Straight-
away)

Cable Laid-Up in Twisted Pairs. A term
applied to a cable in which every pair of wires
is twisted together. (See Cable, Bunched,
Twisted?)

Cable Lead. (See Lead, Cable}.

Cable, Multiple-Core A cable corn-

tainir.g more than a single core.

Cable-Protector. (See Protector, Cable?)

Cable-Serving. (See Serving, Cable)

Cable, Single-Wire A cable con-
taining a single wire or conductor.

Cable, Sub-Aqueous An electric

cable designed for use under water.

The term submarine is more frequently em-
ployed.

Cable, Submarine A cable designed

for use under water.

Submarine cables are either shallow-water, or
deep-sea cables. Gutta-percha answers admirably
for the insulating material of the core. Various
other insulators are also used.

Strands of tarred hemp or jute, known as the
cable-serving, are wrapped around the insulated
core in order to protect it from the pressure of the
galvanized iron wire armor afterwards put on.
To prevent corrosion the iron wire is covered
with tarred hemp, galvanized, or otherwise
Coated.

Submarine cables are generally employed for
telegraphic or telephonic communication. (See
Cable, Electric.')

Cable, Submarine, .Deep-Sea A

submarine cable designed for use in deep
water.

This form of cable is not so heavily armored as
the shallow-water submarine cable.

Cable, Submarine, Shallow- Water

A submarine cable designed for use in shallow
water.

This cable is provided with a heavier armor or
sheathing than a deep-sea cable to protect it
from chafing due to the action of the waves and
tides in shallow water. (See Cable^ Submarine.)

Cable Support, Underground (See

Support, Underground Cable.}

Cable Tank.- (See Tank, Cable)

Cable, Telegraphic A cable de-
signed to establish telegraphic communication
between different points.

Telegraphic cables may be aerial, submarine,
or underground. (See Cable, Electric.)

Cable, Telephonic A cable de-
signed to establish telephonic communication
between different points.

Telephonic cables may be aerial, submarine,
or underground, (See Cable, Electric.)

Cable-Terminal. (See Terminal, Cabled

Cable, Torpedo A cable, in the

circuit of which a torpedo is placed. (See
Torpedo, Electric)

Cable, Twisted-Pair A cable

containing a single twisted pair, suitable for
use as a lead and return, thus affording a
metallic circuit.

Cable, Two, Three, Four, etc., Conductor

A cable containing two, three, four,

or more separate conducting wires.

Cable, Underground An electric

cable placed underground.

The conducting wires of an underground cable
are surrounded by a good insulating, water-proof
substance, and protected by a sheathing or armor.
A coating of lead is very generally employed for
the sheathing or armor. Underground cables, in
order to be readily accessible, should be placed
in an underground conduit or subway. (See
Cable, Electric, Conduit^ Underground Electric.
Subway^ Electric.)

Cable- Worming. (See Worming, Cable)

Cablegram. A message received by means
of a submarine telegraphic cable.

Cables, Lajlng-Up The placing or

disposing of the separate cables or conduc-
tors in a bunched cable. 1

The separate conductors in cables may be laid-
up "straightaway" or "twisted." (See Cable,
Bunched* Twisted. Cable % Bunched, Straight-
away. )

Cabling. Sending a telegraphic dispatch
bv means of a cable.

CaL]

[Cal.

Calahaif s Stock Printer. (See Printer,
Stock, Calahan's.)

Calamine, Electric A crystalline

variety of silicate of zinc that possesses pyro-
electric properties. (See Electricity, Pyro.)

Cal-Electricity. (See Electricity, Cal)

Calibrate. To determine the absolute
or relative value of the scale divisions, or of
the indications of any electrical instrument,
such as a galvanometer, electrometer, vol-
tameter, wattmeter, etc.

Calibrating. The act of determining the
absolute or relative value of the deflections,
or indications of an electric instrument.

Calibration, Absolute The deter-
mination of the absolute values of the read-
ing of an electrometer, galvanometer, volt-
meter, amperemeter, or other similar instru-
ment.

The calibration of a galvanometer, for ex-
ample, consists in the determination of the law
which governs its different deflections, and by
which is obtained in amperes, either the absolute
or the relative currents required to produce such
deflections.

For various methods of calibration, see stan-
dard works on electrical testing, or on elec-
tricity.

Calibration, Invariable, of Galvanom-
eter In galvanometers with absolute

calibration, a method for preventing the oc-
currence of variations in the intensity of the
field of the galvanometer, due to the neigh-
borhood of masses of iron, etc.

Calibration, Relative The deter-
mination of the relative values of the reading
of an electrometer, voltmeter, amperemeter,
or other similar instrument.

Caliper, Mi-

erometer

A name some-'
times given to a
vernier wire
gauge. (See
Gauge, Vernier

Wire) Fig, 95. Micrometer Califer.

A form of micrometer caliper is shown in Fig. Q

Call-Bell, Extension (See Sell,

Extension Call.)
Call-Bell, Magneto-Electric An

electric call-bell operated by currents pro-
duced by the motion of a coil of wire before
the poles of a permanent magnet.

A well known form of magneto call-bell is shown

Fig. 96. Magneto Call Bell.

in Fig. 96. The armature is driven by the rota-
tion of the handle.

Call-Bell, Telephone An electric

bell, the ringing of which is used to call a
person to a telephone.

Call, Electric Bell An electric

bell sometimes used to call the attention of an
operator to the fact that his correspondent
wishes to communicate with him, or to notify
an attendant that some service is desired.

Call, Messenger A district call-
box. (See Box, District Call.)

Call, Thermo-Electric An instru-
ment for sounding an alarm when the tem-
perature rises above, or falls below, a fixed
point.

In one form of thermo-electric call a needle is
moved over a dial by a simple thermic device and
rings a bell when the temperature for which it
has been se is attained. The thermo-call is appli-
cable to the regulation of the temperature o/

Cal.]

[Cal.

dwellings, incubators, hot houses, breweries, dry-
ing rooms, etc.

Callaud Voltaic Cell. (See CeH, Vol-
taic, Callaud's.}

Calling-Drop. (See Drop, Calling.}

Calorescence. The transformation of
invisible heat-rays into luminous rays, when
received by certain solid substances.

The term was proposed by Tyndall. The light
from a voltaic arc is passed through a hollow
glass lens filled with a solution of iodine in bisul-
phide of carbon.

This solution is opaque to light but quite trans-
parent to heat.

If a piece of charred paper, or thin platinum
foil, is placed in the focus of these invisible rays,
it will be heated to brilliant incandescence. (See
Focus.)

Caloric. A term formerly applied to the
fluid which was believed to be the cause or
essence of heat.

The use of the word caloric at the present time
is very unscientific, since heat is now known to
he an effect of a wave motion and not a material
thing. (SeeA^a/.)

Calorie. A heat unit.

There are two calories, the small and the large
calorie.

The amount of heat required to raise the tem-
perature of one gramme of water from o degree
C. to I degree C. is called the small calorie.

The amount of heat required to raise 1,000
grammes, or a kilogramme, of water from o de-
gree C. to I degree C. is called the great calorie.
The first usage of the word is the commoner.

This word is sometimes spelled calory.

Calorie, Great The amount of

heat required to raise the temperature of one
kilogramme of water from o degree C. to I
degree C.

Calorie, Small The amount of

heat required to raise the temperature of one
gramme of water from o degree C. to I
degree C.

Calorimeter An instrument for measur-
ing the amount of heat or thermal energy
contained or developed in a given body.

Thermometers measure temperature only. A

thermometer plunged in a cup full of boiling
water shows the same temperature that it would
in a tub full of boiling water. The quantity of
heat energy present in the two cases is of course
greatly different, and can be measured by a cal-
orimeter only.

Various forms of calorimeters are employed.

In order to determine the quantity of heat in
a given weight of any body, this weight may be
heated to a definite temperature, such as the boil-
ing point of water, and placed in a vessel con-
taining ice. The quantity of ice melted by the
body in cooling to the temperature of the ice, is
determined by measuring the amount of water
derived from the melting of the ice. Care must
be observed to avoid the melting of the ice by ex-
ternal heat.

In this way the amount of heat required to
raise the temperature of a given weight of a body
a certain number of degrees, or the capacity of
the body for heat, may be compared with the
capacity of an equal weight of water. This ratio
is called the specific heat. (See Heal, Specific.)

The heat energy, present in a given weight of
any substance at a given temperature, can be de-
termined by means of a calorimeter; for, since a
pound of water heated i F. absorbs an amount
of energy equal to 772 foot-pounds, the energy can
be readily calculated if the number of pounds of
water and the number of degrees of temperature
are known. (See Heat, Mechanical Equivalent
of-}

Calorimeter, Electric An instru-
ment for measuring the heat developed in a
conductor or any piece of electrical apparatus,
in a given time, by an electric current.

Fig. 97. Electric Calorimeter.

A vessel containing water is provided with a
thermometer T, Fig. 97. The electric currenl

Cal.]

[Can,

passes for a measured time through a wire im-
mersed in the liquid.

The quantity of heat is determined from the
increase of temperature, and the weight of the
water heated.

According to Joule, the number of heat units
developed in a conductor by an electric current
is proportional:

(I.) To the resistance of the conductor.

(2.) To the square of the current passing.

(3.) To the time the current is passing.

(See Heat Unit, English.)

The heating power of a current is as the square
of the current only when the resistance remains
the same. (See Heat, Electric.)

Calorimetric. Pertaining to or by means

of the calorimeter.

Calorimetric measurement is the measurement
of heat energy made by means of the calorimeter.
(See Calorimeter.}

Caloriinetrically. In a Calorimetric man-
ner.

Calorimetric Photometer. (See Photom-
eter, Calorimetric)

Calorimotor. A name applied to a defla-
grator. (See Deflagrator^

Calory. A term used for calorie.

Calorie is the preferable orthography. (See
Calorie.)

Cam, Electro-Magnetic A form

of magnetic equalizer, which depends for its
operation on the lateral approach of a suita-
bly shaped polar surface. (See Equalizer,
Magnetic?)

Cam, Listening In a telephone

exchange system, a metallic cam by means of
which an operator is placed in circuit with
a subscriber.

Candle. The unit of photometric intensity.

Such a light as would be produced by the
consumption of two grains of a standard
candle per minute.

An electric lamp of 1 6 candle-power, or one of
2,coo candle-power, is a light that gives respect-
ively 16 or 2,000 times as much light as one stand-
ard candle.

Candle Bnrner, Electric (SeeJBur-

ner. Electric Candle^

Candle, Electric A term applied

to the Jablochkoff candle, and other similai
devices. (See Candle, Jablochkoff,')

Candle, Foot A unit of illumina-
tion equal to the illumination produced by a
standard candle at tlv distance of i foot.

According to this unit, the illumination pro-
duced by a standard candle at the distance of
2 feet would be but the one-fourth of a foot-
candle; at 3 feet, the one-ninth of a foot-candle,
etc.

The advantage of the proposed standard lies in
the fact that knowing the illumination in foot-
candles required for the particular work to be
done, it is easy to calculate the position and
intensity of the lights required to produce the
illumination.

Candle, Jablochkoff An electric

arc light in which the two carbon electrodes are
placed parallel to each other and maintained
a constant distance apart by means of a sheet
of insulating material placed between them.

The Jablochkoff electric candle consists of twa
parallel carbons, separated by a layer of kaolin or
other heat-resisting insulating material, as shown
in Fig. 98. The current is passed into and out of
the carbons at one end of the
candle, and forms a voltaic arc at
the other end. In order to start
the arc, a thin strip called the
igniter, consisting of a mixture of
some readily ignitable substance,
connects the upper ends of the
carbons.

An alternating current is em-
ployed with these candles, thus
avoiding the difficulty which Fig - <)S Ja "
would otherwise occur from the ****** Candu '
more rapid consumption of the positive than the
negative carbon. (See Current^ Alternating.)

Candle, Metre The illumination pro-
duced by a standard candle at the distance of
one metre. (See Candle, Foot?)

Candle-Power. (See Power, Candle.)

Candle-Power, Bated (See Power,

Candle, Rated.)

Candle -Power, Spherical (See

Power, Candle, Spherical?)

Candle, Standard A candle of

Cao.]

definite composition which, with a given con-
sumption in a given time, will produce a light
of a fixed and definite brightness.

A candle which burns 120 grains of sperma-
ceti wax per hour, or 2 grains per minute, will
give an illumination equal to one standard candle.

Unless considerable care is taken, erroneous re-
sults will be obtained from the use of the stand-
ard candle. According to SJingo and Brooker
the following are among the most important
causes of these errors :

(i.) Defective forms of candle which cause a
varying consumption of the material per second,
and consequently a varying light for the standard
candle.

(2.) Variations in the composition of the sper-
maceti of which the candle is composed. Sper-
maceti is not a definite chemical compound, but
consists of a mixture of various substances ;
therefore, even if the consumption is maintained
constant, the light-giving power is not necessarily
constant.

(3.) Variations in the composition and charac
ter of the wick, such as the number and size of
the threads of which it is formed and the closeness
of the strands, all of which circumstances influence
the amount of light given off by the candle.

(4.) The light emitted in certain directions va-
ries in a marked degree with the shape of the
wick. The mere bending of a wick may, there-
fore, cause the amount of light to vary consider
ably.

(5.) The light varies with the thickness of the
wick. Thick wicks give less light than thin
wicks.

(6.) The light given by the standard candle va-
ries with the temperature of the testing-room.
As the temperature rises the light given by the
standard candle increases.

(7.) Currents of air. by producing variations
in the amount of melting wax in the cup of the
candle, vary the amount of light emitted.

These difficulties in obtaining a fixed amount of
light from a standard candle, together with the
difficulty of comparing the feeble light of a single
candle with the light of a much more powerful
source, such as an arc lamp, coupled with the
additional difficulty arising from the difference in
the colors of the lights, have led to the use of
other standards of light than those furnished by
the standard candle.

Caoutchouc, or India-Rubber. A resin-

[Cap.

ous substance obtained from the milky juices
of certain tropical trees.

Caoutchouc possesses high powers of electric
insulation, and is used either pure or combined
with sulphur.

Cap, Insulator A covering or cap

placed some distance above an insulator, but
separated from it by an air space.

Insulator caps are intended for protection of the
insulators from injury by the throwing of stones
or other malicious acts. Insulator caps are gen-
erally made of iron. They are highly objection-
able, owing to the facility they offer for the ac-
cumulation of dust and dirt.

Capacity, Atomic The quantiva-

lence or valency of an atom. (See Atomi-
city)

Capacity, Dielectric A term em-
ployed in the same sense as specific inductive
capacity. (See Capacity, Specific Indwtive.}

Capacity, Electro-Dynamic A

term formerly employed by Sir William
Thomson for self-induction. (See Induction,
Self.}

Capacity, Electrostatic The quan-
tity of electricity which must be imparted to a
given body or conductor as a charge, in order
to raise its potential a certain amount. (See
Potential, Electric.}

The electrostatic capacity of a conductor is not
unlike the capacity of a vessel filled with a liquid
or gas. A certain quantity of liquid will fill a
given vessel to a level dependent on the size or
capacity of the vessel. In the same manner a
given quantity of electricity will produce, in a
conductor or condenser, a certain difference of
electric level, or difference of potential, dependent
on the electrical capacity of the conductor or
condenser.

Or, taking the analogous case of a gas-tight
vessel, the quantity of gas that can be forced into
such a vesssl depends on the size of the vessel
and the pressure with whfch it is forced in. A
tension or pressure is thus produced by the gas
on the walls of the vessel, which is greater the
smaller the size of the vessel and the greater the
quantity of gas forced in.

In the same manner, the smaller the capacity
of a conductor, the smaller is the charge required

Cap.]

[Cap.

to raise it to a given potential, or the higher the
potential a given charge will raise it.

The capacity K, of a conductor or condenser,
is therefore directly proportional to the charge Q,
and inversely proportional to the potential V; or,

K.2.

From which we obtain Q = KV; or,

The quantity of electricity required to charge a
(onductor or condenser to a given potential is
tqual to the capacity of the conductor or condenser
multiplied by the potential through which it is
raised.

Capacity, Electrostatic, Unit of

Such a capacity of a conductor or condenser
that an electromotive force of one volt will
charge it with a quantity of electricity equal
to one coulomb.

The farad. (See Farad?)

Capacity of Cable. (See Cable. Capacity

of)

Capacity of Condenser. (See Condenser,
Capacity o/.)

Capacity of Leyden Jar. (See Jar,
Leyden, Capacity of.)

Capacity of Line. (See Line, Capacity

tt
Capacity of Polarization of a Voltaic

Cell. (See Cell, Voltaic, Capacity of Polar-
ization of.)

Capacity, Safe Carrying, of a Conductor

The maximum electric current the

conductor will carry without becoming unduly
heated.

Capacity, Specific Inductive

The ability of a dielectric to permit induction
to take place through its mass, as compared
with the ability possessed by a mass of air of
the same dimensions and thickness, under
precisely similar conditions.

The relative power of bodies for trans-
mitting electrostatic stresses and strains
analogous to permeability in metals.

The ratio of the capacity of a condenser
whose coatings are separated by a dielectric
of a given substance to the capacity of a
similar condenser whose plates are separated
by a plate or layer of air.

The inductive capacity of a dielectric is com-
pared with that of air.

According to Gordon and others, the specific
Inductive capacities of a few substances, com-
pared with air, are as follows:

Air i. oo

Glass 3.013 to 3.258

Shellac 2.740

Sulphur 2.580

Gutta-percha 2.462

Ebonite 2.284

India-rubber 2.220 to 2.497

Turpentine 2.160

Petroleum 2.030 to 2.070

Paraffin (solid) 1.994

Carbon bisulphide 1.810

Carbonic acid 1.00036

Hydrogen 0.99967

Vacuum 0.99941

Faraday, who proposed the term specific in-
ductive capacity, employed in his experiments a
condenser consisting of a metallic sphere A, Fig.
99, placed inside a large
hollow sphere B.

The concentric space
between A and B was filled
with the substance whose
specific inductive capacity
was to be determined.

Capacity, Specific

Magnetic A term

sometimes employed in
the sense of magnetic
permeability.

Conductibility for lines
of magnetic force in the
same sense that specific
inductive capacity is con-
ductibility for lines of
electrostatic force.

This term has received
the name of specific mag- ' f "'
netic capacity in order to distinguish it from specific
inductive capacity. The velocity of propagation
of waves in any elastic medium is proportional to
the quotient obtained by extracting the square
root of the elasticity of the medium divided by
the square root of its density; or,

Cap.]

[Car.

Similarly, the speed with which inductive waves
travel depends on the relation between the elas-
ticity and the density of the medium. Calling ^,

the electric elasticity, then its reciprocal, K, corre-
sponds with the dielectric capacity. The elec-
trical density, /*, corresponds with the magnetic
permeability. The velocity of wave transmission
is therefore,

Capacity, Storage, of Secondary Cell

(See Cell, Secondary or Storage, Capa-
city of.)

Capillarity. The elevation or depression
of liquids in tubes of small internal diameter.

The liquid is elevated when it wets the walls,
and depressed when it does not wet the walls of
the rube.

The phenomena of capillarity are due to the
mutual attractions existing between the mole-
cules of the liquid for one another, and the
mutual attraction between the molecules of the
liquid and those of the walls of the tube.

In capillarity, therefore, the approximately
level surface caused by the equal attraction of all
the molecules towards the earth's centre is dis-
turbed by the unequal attraction exerted on each
molecule by the walls of the tube and by the re-
maining molecules.

Capillarity, Effects of, on Toltaic Cell

. Efrects caused by capillary action
which disturb the proper action of a voltaic
cell.

These effects are as follows:

(i.) Creeping, or efflorescence of salts. (See
Creeping, Electric. Efflorescence.)

(2. ) Oxidation of contacts and consequent in-
troduction of increased resistance into the battery
circuit. The liquid enters the capillary spaces
between the contact surfaces and oxidizes them.

Capillary. Of a small or hair-like diame-
ter or size.

A capillary tube is a tube of small hair-like di-
ameter. (See Capillarity.)

Capillary Attraction. (See Attraction,
Capillary)

Capillary Contact-Key. (See Key, Cap-
illary Contact?)

Capillary Electrometer. (See Electrom-
eter, Capillary)

Carbon. An elementary substance which
occurs naturally in three distinct allotropic
forms, viz.: charcoal, graphite and the dia-
mond. (See Allotropy)

Carbon-Brushes for Electric Motors.

(See Brushes, Carbon, for Electric Motors)

Carbon Button. (See Button, Carbon)
Carbon-Clutch or Clamp of Arc Lamp.

(See Clutch, Carbon, of Arc Lamp)

Carbon-Electrodes for Arc Lamps. (See
Electrodes, Carbon, for Arc Lamps)

Carbon-Holders for Arc Lamps. (See
Holders, Carbon, for Arc Lamps)

Carbon Points. (See Points, Carbon)

Carbon Transmitter for Telephones.
(See Transmitter, Carbon, for Telephones)

Carbonic Acid Gas. (See Gas, Carbonic
Acid)

Carboning Lamps. (See Lamps, Carbon-
ing)

Carbonizable. Capable of being carbon-
ized. (See Carbonization, Processes of)

Carbonization. The act of carbonizing,
(See Carbonization, Processes of)

Carbonization, Processes of

Means for carbonizing material.

The carbonizable material is placed in suitably
shaped boxes, covered with powdered plumbago
or lamp-black, and subjected to the prolonged
action of intense heat while out of contact with
air.

The electrical conducting power of the carbon
which results from this process is increased by the
action ot the heat, and, probably, also, by the de-
posit in the mass, ot carbon resulting from the
subsequent decomposition of the hydro-carbon
gases produced during carbonization.

When the carbonization is for the purpose of
producing conductors for incandescent lamps, in
order to obtain the uniformity of conducting
power, electrical homogeneity, purity and high
refractory power requisite, selected fibrous ma-
terial, cut or shaped in at least one dimension

ar.J

[Car.

prior to carbonization, must be taken, and sub-
jected to as nearly uniform carbonization as pos-
sible.

Carbonize. To reduce a carbonizable ma-
terial to carbon. (See Carbonization, Pro-
cesses of.)

Carbonized Cloth Discs for High Resist-
ances. (See Cloth Discs Carbonized, for
High Resistances)

Carbonizer. Any apparatus suitable for
reducing carbonizable material to carbon.

Carbonizing. Subjecting a carbonizable
substance to the process of carbonization.
(See Carbonization, Processes of)

Carbons, Artificial Carbons ob-
tained by the carbonization of a mixture of
pulverized carbon with different carbonizable
liquids.

Powdered coke, or gas-retort carbon, some-
times mixed with lamp-black or charcoal, is made
into a stiff dough with molasses, tar, or any other
hydro-carbon liquid. The mixture is molded
into rods, pencils, plates, bars or other desired
shapes by the pressure of a powerful hydraulic
press. After drying, the carbons are placed in
crucibles and covered with lamp-black or pow-
dered plumbago, and raised to an intense heat at
which they are maintained for several hours. By
the carbonization of the hydro-carbon liquids, the
carbon paste becomes strongly coherent, and by
the action of the heat its conducting power in-
creases.

To give increased density after baking, the
carbons are sometimes soaked in a hydro-carbon
liquid, and subjected to a re-baking. This may
be repeated a number of times.

Carbons, Concentric-Cylindrical

A cylindrical rod of carbon placed inside a hol-
low cylinder of carbon but separated from it
by an air space, or by some other insulating,
refractory material.

Jablochkoff candles sometimes are made with a
solid cylindrical electrode, concentrically placed
in a hollow cylindrical carbon.

Carbons, Cored A cylindrical carbon

electrode for an arc lamp that is molded
around a central core of charcoal, or other
softer carbon.

Much of the unsteadiness of the arc light is due
to changes in the position of the arc. Cored car-
bons, it is claimed, render the arc light steadier,
by maintaining the arc always at the softer carbon
and hence af. the central point of the electrode.

A core of harder carbon, or other refractory
material, is sometimes provided for the negative
carbon.

Carbons, Flashed Carbons which

have been subjected to the flashing pro-
cess, (See Carbons, Flashing Process for)

Carbons, Flashing Process for A

process for improving the electrical uniformity
of the carbon conductors employed in in-
candescent lighting, by the deposition of car-
bon in their pores, and over their surfaces at
those places where the electric resistance is
relatively great.

The carbon conductor or filament is placed in
a vessel filled with the vapor of a hydrocarbon
liquid called rhigolene, or any other readily de-
composable hydrocarbon liquid, and gradually
raised to electric incandescence by the passage
through it of an electric current. A decomposi-
tion of the hydrocarbon vapor occurs, the car-
bon resulting therefrom being deposited in and on
the conductor.

As the current is gradually increased, the
parts of the conductor first rendered incandes-
cent are the places where the electric resist-
ance is the highest, these parts, therefore, and
practically these parts only, receive the deposit
of carbon. As the current increases, other
portions become successively incandescent and
receive a deposit of carbon, until at last the
filament glows with a uniform brilliancy, in-
dicative of its electric homogeneity.

A carbon whose resistance varies considerably
at different parts could not be successfully em-
ployed in an incandescent lamp, since if heated
by a current sufficiently great to render the points
of comparatively small resistance satisfactorily
incandescent, the temperature of the points of
high resistance would be such as to lower the life
of the lamp, while if only those portions were
safely heated, the lamp would not be economical.
The flashing process is therefore of very great
value in the manufacture of an incandescent
lamp.

The name " flashing " was applied to the pro-
cess by reason of the flashing light emitted by the

Car.]

[Cas.

carbons when they have been sufficiently treated.
The process requires so little time that the dull red
which first appears soon flashes to the full lumin-
osity required.

The term "flashing" is sometimes applied to
the electrical heating to incandescence, while the
carbons are in the lamp chambers, and on the
pumps. This flashing is for the purpose of
driving off all the gases occluded by the carbon,
so that these gases may be carried off by the
operation of pumping. This process is more
properly called the process for driving off the
occluded gases.

The carbons are sometimes flashed in the liquid
itself instead of in its vapor.

Carbons, Paper Carbons, of textile

or fibrous origin, obtained from the carboniza-
tion of paper.

The carbonization of paper is readily effected
by submitting the paper to the prolonged action
of a high temperature while out of contact with
air.

For this purpose the paper is packed in retorts
or crucibles, and covered with lamp-black, or
powdered plumbago, in order to exclude the air.

Since paper consists of a plane of material uni-
formly thin in one direction, formed almost en-
tirely of fibres of pure cellulose, the greatest
length of which extends in a direction nearly par-
allel to that in which the paper is uniformly thin,
it is clear that sheets of this substance, when car-
bonized, should yield flexible carbons of unusual
purity and electrical homogeneity, since such
carbons are structural in character, and are uni-
formly affected by the heat of carbonization to an
extent that would be impossible by the carboniza-
tion of any material in a mass.

Carcase of Dynamo-Electric Machine.
(See Machine, Dynamo-Electric, Carcase of.)

Carcel. The French unit of light. The
light emitted by a lamp burning 42 grammes
of pure colza oil per hour, with a flame 40
millimetres in height.

The bec-carcel. One carcel = 9.5 109.6 stand-
ard candles.

Carcel Lamp. (See Lamp, Carcel)

Carcel Standard Gas Jet. (See/?/, Gas,
Carcel Standard.)

Card, Compass A card used in the

mariner's compass, on which are marked the

four cardinal points of the compass N, S, E
and W, and these again divided into thirty-
two points called Rhumbs. (See Compass,
Azimuth.)

Cardew Voltmeter. (See Voltmeter,
Cardew.)

Carriage, Pen The carriage in an

electric chronograph which holds the pen and
moves over the sheet of paper on which the
record is made. (See Chronograph, Elec-
tric.)

Carriers of Replenisher. (See Replen*
isher, Carriers of.)

Cascade, Charging Leyden Jars by

A method of charging jars or condensers
by means of the free electricity liberated by
induction from one coating, when a charge is
passed into the other coating.

The jars are placed as shown in Fig. 100, with
the inside coating of the first jar connected with
the outside coating of the one next it. There is in

Fig. 100. Cascade Charging of Leyden Jars.
reality no increase in the entire charge obtained
in charging by cascade, since the sum of the
charges given to the separate jars is equal to
the same charge given to a single jar separately
charged.

The energy of the discharge in cascade can be
shown to be less than that of the same charge
when confined to a single jar. This i= of course
to be expected, since it is energy that 'P charged
in the jar and not electricity, and, of course, the
energy charged in the jar can never exceed the
energy employed in charging the jar. There is
a small loss for each jar, and this increases ne-
cessarily with each jar added.

Cascade, Connection of Electric Sources
in A term sometimes used for series-
connection of electric sources.

The term series -connection is the preferable
one. (See Connection^ Series^)

Case-Hardening, Electric Super.

ficially converting a piece of wire into steel
by electrically produced heat.

Cas.]

[Can.

In electric case-hardening, the superficial layers
of a piece of iron are converted into steel by
electrically heating the same, while surrounded
by a layer of case-hardening flux and carbonaceous
substances such as animal charcoal, shavings of
horn, leather cuttings or other similar substances.

In the case of a readily oxidizable metal like
iron, oxidation is prevented by surrounding the
metal by a hydrocarbon gas, which, when suffi-
ciently heated, deposits on the surfaces a pro-
tective coating of carbon. This layer of carbon
gradually carbonizes the iron.

Case Wiring. (See Wiring, Case.)

Cataphoresis. A term sometimes em-
ployed in place of electric osmose. (See Os-
mose, Electric?)

The word cataphoresis applies to the cases where
medicinal substances, such as iodine, cocoaine,
quinine, etc., are caused to pass through organic
tissues in the direction of flow of an electric cur.
rent, or from the anode to the kathode. This
action is probably due to an electrolytic action.

Cataphoric Action. (See Action, Cata-
phoric.)

Catch, Safety A wire, plate, strip,

or box of readily fusible metal, capable of con-
ducting, without fusing, the current ordinarily
employed on the circuit, but which fuses and
thus breaks the circuit on the passage of an
abnormally large current.

Safety -catches are generally placed on multiple,
arc and multiple -series circuits. (See Fuse %
Safety.)

Catelectrotonns. An orthography some-
times applied to Kathelectrotonus. (See
Kathelectrotonus.)

Cathetometer. An instrument for the ac-
curate measurement of vertical height.

The cathetometer consists essentially of an
accurately divided vertical rod which carries a
sliding support for a telescope. The telescope is
provided with two spider lines at right angles to
one another, so placed as to be seen in front of
the object whose height is to be measured. From
observations taken in different positions, the
measurement of the true vertical height is readily
obtained.

Cathlon. A term sometimes used instead
ul Kathion.

More correctly written Kathion. (See
Kathion)

Cathode. A term sometimes used instead
of Kathode.

Catoptrics. That branch of optics which
treats of the reflection of light.

Causty, Galvano A term some-
times used for galvano-cautery. (See Cautery,
Galvano)

Cauterization. The act of cauterizing, or
burning with a heated solid or caustic sub-
stance.

Cauterization, Electric Subject-
ing to cauterization by means of a wire elec-
trically heated. (See Cautery, Electric.}

Cauterize. To subject to cauterization, or
burning with a heated solid or caustic sub-
stance.

Cauterizer, Electric A term some-
times applied to an electric cautery. (See
Cautery, Electric.)

Cautery, Actual A burning or sear-
ing with a white-hot metal.

Cautery Battery. (See Battery, Cautery .)

Cautery, Electric An instrument

used for electric cauterization.

In electro-therapeutics, the application ol
variously shaped platinum wires heated to in-
candescence by the electric current in place
of a knife, for removing diseased growths, ot
for stopping hemorrhages.

The operation, though painful during applies-
tlon, is afterward less painful than that with a
knife, since secondary hemorrhage seldom occurs,
and the wound rapidly heals.

Electric cautery is applicable in cases where
the knife would be inadmissible owing to the
situation of the parts or their surroundings.

Cautery, Galvano A term fre-
quently employed in place of electric cautery.
(See Cautery, Electric)

Cautery, Galvano Electric An

electric cautery. (See Cautery, Electric)

Cautery, Galvano Thermal A

term sometimes used for an electric cautery.
(See Cautery, Electric*

tail, f

[CeL

Cautery-Knife Electrode. (See Electrode
Cautery- Knife.}

Cautery, Thermal A cautery

heated by heat other than that of electric ori-
gin, as distinguished from an electric cautery.
(See Cautery, Electric)

Ceiling Rose. (See Rose, Ceiling}

Cell, Depositing An electrolytic

cell in which an electro-metallurgical deposit is
made (See Metallurgy, Electro}

Cell, Electrolytic A cell or vessel

containing an electrolyte, in which electrolysis
is carried on.

An electrolytic cell is called a voltanuter when
the value of the current passing is deduced from
the weight of the metal deposited.

Cell, Impulsion A photo-electric

cell whose sensitiveness to light may be re-
stored or destroyed by slight impulses given
to the plates, such as by blows or taps, or elec-
tro-magnetic impulses.

An impulsion cell may be prepared by pasting
pieces of tin-foil, the opposite faces of which are
respectively polished and dull, on the opposite
faces of a plate of glass, so as to expose dissimi-
lar sides to the light, when the cells are dipped
in alcohol.

Cell, Photo-Electric A cell capa-
ble of producing differences of potential
when its opposite faces are unequally exposed
to radiant energy.

Photo -voltaic cells are made in a variety of
forms, both with selenium and with different me-
tallic substances. (See Cell, Selenium.}

Cell, Porous A jar of unglazed

earthenware, employed in double-fluid voltaic
cells, to keep the two liquids separated.

The use of a porous cell necessarily increases
the internal resistance of the cell, from the de-
crease it produces in the area of cross section of
liquid between the two elements. When the bat-
tery is dismantled, the porous cells should be
kept under water, otherwise the crystallization of
the zinc sulphate or other salt is apt to produce
serious exfoliation, or scaling off, or even to
crumble the porous cell.

A porous cell is sometimes called a diaphragm,
but only properly so when the cell is reduced to
a single separating plate. (See Cell, Voltaic.}

Cell, Secondary A term sometimes

used instead of storage cell.

The term secondary cell is used in contradis-
tinction to primary or voltaic cell.

Cell. Secondary or Storage, Boiling of

A term sometimes applied to the

gassing of a storage cell. (See Cell, Storage,
Gassing of}

Cell, Secondary or Storage, Capacity of

The product of the current in am-
peres, by the number of hours the battery is.
capable of furnishing said current, whea
fully charged, until exhausted.

The capacity of storage cells is given in ampere-
hours. A storage battery with a capacity of i,ooa
ampere-hours can furnish, say a current of fifty-
amperes for twenty hours, or a current of one
hundred amperes for ten hours ; or a current of
twenty-five amperes for forty hours.

Cell. Secondary or Storage, Gassing of

An escape of gas due to the decom-
position of water on passage of too strong a
charging current.

Cell, Secondary or Storage, Renovation

of The revivifying or recharging of a

run-down, or discharged storage cell.

Cell, Secondary or Storage, Time-Fall

of Electromotive Force of (See

Force. Electromotive of Secondary or
Storage Cell, Time-Fall, of}

Cell, Secondary or Storage, Time-Ris^

of Electromotive Force of (See

Force, Electromotive of, Secondary or
Storage Cell, Time-Rise, of}

Cell, Selenium A cell consisting

of a mass of selenium fused in between two
conducting wires or electrodes of platinized
silver or other suitable metal.

A convenient manner of forming a selenium
cell is to wind two separate spirals of platinized
silver wire around a cylinder of hard wood, tak-
ing care to maintain them a constant distance
apart, so as to avoid contact between them. The
space between these wires is filled with fused sele-
nium, which is allowed to cool gradually.

Exposure to sunlight reduces the resistance of
a selenium cell to about one-half its resistance ia-

lei.]

[del.

the dark, but neither the resistance nor the reduc-
tion ratio long remains constant.

A selenium cell produces a difference of poten-
tial, or electromotive force, when one of its elec-
trode faces is exposed to light, while the other is
kept in darkness.

According to Von Uljanin, who experimented
with selenium melted in between two parallel
platinized piates, cooled under pressure, and then
reduced from the amorphous to the sensitive crys-
talline variety by gradual cooling after two or
three heatings in a paraffine bath up to 195 de-
grees, the following peculiarities were observed:

(I.) Exposure of one of the electrodes to sun-
light produced an electromotive force which
causes a current to flow from the dark to the
illumined electrode.

(2.) The maximum electromotive force was
o.i 2 volt.

(3.) The electromotive force disappeared instan-
taneously and completely on the darkening of the
electrodes^

(4.) A slight difference in the electromotive
force was observed when the positive and nega-
tive electrodes were alternately exposed to the
light, the maximum electromotive force being
attained by the exposure of the negative electrode.
(5.) If both electrodes are similarly illumined
the resulting current strength is decreased and
may reach zero.

(6.) The action of light is instantaneous.
(7.) Most of the selenium cells experimented
with exhibited an electromotive force of polariza-
tion.

(8.) The electromotive force of polarization is
diminished by exposure to light.

(9.) The electrical resistance and sensitive-
ness to light as regards the production of an
electromotive force decrease with time. This
is probably due to a gradual change in the allo-
tropic state of the selenium. (See State, Allo-
tropic.)

(10.) The electromotive force produced is pro-
portional to the intensity of the illumination only
when the obscure rays or heat rays are absent.

(II.) Of different wave lengths the orange-yel-
low rays in the diffraction spectrum, and the
greenish-yellow in the prismatic ppectrum pro-
duced the greatest effect.

Among some of the more recent applications
of selenium cells are the following:

(i.) A selenium cell is so placed in a circuit
containing an electro-magnet and switch, that on

one of its electrodes being exposed to the de-
creased illumination of coming night it automat-
ically turns on an electric lamp, and, conversely,
on the approach of daylight, and the consequent
illumination of the electrode, turns it off.

(2.) A device whereby the presence of light,
as for example that carried by a burglar, auto-
matically rings an alarm and thus calls the atten-
tion of the watchman of the building.

Cell, Standard (See Cell, Voltaic,

Standard?)

Cell, Storage Two relatively inert

plates of metal, or of metallic compounds,
immersed in an electrolyte incapable of acting
considerably on them until after an electric
current has been passed through the liquid
from one plate to the other and has changed
their chemical relations.

A single one of the cells required to form
a secondary battery.

Sometimes, the jar containing a single cell
is called a storage cell.

This latter use of the word is objectionable.

A storage cell is also called an accumulator.

On the passage of an electric current through
the electrolyte, its decomposition is effected and
the electro-positive and electro- negative radicals
are deposited on the plates, or unite with them,
so that on the cessation of the charging current,
there remains a voltaic cell capable of generating
an electric current.

A storage cell is charged by the passage through
the liquid from one plate to the other of an elec-
tric current, derived from any external source.
The charging current produces an electrolytic de-
composition of the inert liquid between the
plates, depositing the electro-positive radicals, or
katkions, on the plate connected with the negative
terminal of the source, and the electro-negative
radicals, or anions, on the plate connected with
the positive terminal.

On the cessation of the charging current, and
the connection of the charged plates by a con-
ductor outside the liquid, a current is produced,
which flows through the liquid from the plate
covered with the electro-positive radicals, to that
covered with the electro -negative radicals, or in
the opposite direction to that of the charging cur-
rent.

The simplest storage cell is Planters cell, which,
as originally constructed, consists of two plates of

Cel.]

[Cel.

lead immersed in dilute sulphuric acid, H 2 SO 4 .
On the passage of the charging current, the plates
A and B, Fig. 101, dipped in H 2 SO 4 , are covered
respectively with lead peroxide, PbO 2 , and finely
divided, spongy lead. The peroxide is formed on
the positive plate, and the metallic lead on the
negative plate. The acid and water should have
a specific gravity of about 1.170. When the cell
is fully charged the acid solution loses its clear-
ness and becomes milky in appearance, and the

Figs. 10 1 and 102. Storage Cell.

specific gravity increases to 1. 195. This increase
is a good sign of a full charge.

When the charging current ceases to pass, the
cell discharges in the opposite direction, viz.,
from B' to A', that is, from the spongy lead plate
to the peroxide plate through the electrolyte, as
shown in Fig. 102.

As a result of this discharging current the per-
oxide, PbOg, on A', gives up one of its atoms of
oxygen to the spongy lead on B', thus leaving
both plates coated with a layer of PbO, lead
monoxide, or litharge. When this change is
thoroughly effected, the cell becomes inert, and
will furnish no further current until again charged
by the passage of a current from some external
source.

In order to increase the capacity of the storage
cells, and thus prolong the time of their discharge,
the coating of lead monoxide thus left on each
of the plates, when neutral, is made as great as
possible. To effect this, a process called ' 'forming
the plates 11 is employed, which consists in first
charging the plates as already described, and
then reversing the direction of the charging cur-
rent, the currents being sent through the cell in
alternately opposite directions, until a consider-
able depth of the lead plates has been acted on.

It will be noticed that during the action of the
charging current, the oxygen is transferred from
the PbO, on one jjlate, to the PbO, on the other
plate, thus leaving one Pb, and the other PbO,;
and that on discharging, one atom of oxygen is

transferred from the PbO z , to the Pb, thus leav-
ing both plates covered with PbO. In reality
this is but the final result of the action, hydrated
sulphate of lead, PbO, H 4 SO 4 , being formed,
and subsequently decomposed. Other com-
pounds are formed that are but imperfectly un-
derstood.

In order to decrease the time required for form-
ing, accumulators, or secondary cells, have been
constructed, in which metallic plates covered with
red lead Pb 3 O 4 replace the lead plates in the
original Plant< cell. On charging, the Pb 8 O 4
is peroxidized at the anode, i. e., converted into
PbO z , and deoxidized, and subsequently con-
verted into metallic lead at the kathode. Or, in
place of the above Pb 3 O 4 , red lead is placed on
the anode and PbO, or litharge, on the kathode.

Plates of compressed litharge have also been
recently used for this purpose. Storage cells so
formed have a greater storage capacity per unit
weight than those in which a grid is employed,
but a higher resistance.

In all cases where a metal plate is employed
various irregularities of surface are given to the
plates, in order to increase their extent of surface
and to afford a means for preventing the separa-
tion of the coatings. The metallic form thus
provided is known technically z&z.grid.

Unless care is exercised, the plates will buckle
from the difference in the expansion of the lead
and its filling of oxide. This buckling is attended
with an increase in the resistance of the cell and
the gradual separation of the oxides that cover ot
fill it.

Cell, Thermo-Electrlo A name

applied to a thermo-electric couple. (See
Couple, Thermo-Electric^

Cell, Voltaio The combination of

two metals, or of a metal and a metalloid,
which, when dipped into a liquid or liquids
called electrolytes, and connected outside the
liquid or liquids by a conductor, will produce
a current of electricity.

Different liquids or gases may take the place of
the two metals, or of the metal and metalloid.
(See Battery ', Gas.)

Plates of zinc and copper dipped into a solu-
tion of sulphuric acid and water, and connected
outside the liquid by a conductor, form a simple
voltaic cell.

If the zinc be of ordinary commercial purity:

Cel.]

[Cel.

and is not connected outside the liquid by a con-
ductor, the following phenomena occur:

(i.) The sulphuric acid or hydrogen sul-
phate, H Z SO 4 , is decomposed, zinc sulphate,
ZnSO 4 , being formed, and hydrogen, H,, liber-
ated.

(2.) The hydrogen is liberated mainly at the
surface of the zinc plate.

(3.) The entire mass of the liquid becomes
heated.

If, however, the plates are connected outside
the liquid by a conductor of electricity, then the
phenomena change and are as follows, viz. :

(i.) The sulphuric acid is decomposed as be-
fore; but,

(2.) The hydrogen is liberated at the surface of
the copper plate only.

(3.) The heat no longer appears in the liquid
only, but in all parts of the circuit.

(4.) An electric current now flows through the
entire circuit, and will continue so to flow as long
as there is any sulphuric acid to be decomposed,
and zinc with which to form zinc sulphate.

The energy which previously appeared as heat
only, now appears in part as electric energy.

Therefore, although the mere contact of the
two metals with the liquid will produce a differ-
ence of potential, it is the chemical potential
energy which became kinetic during chemical
combination that supplies the energy required to
maintain the electric current. (See Energy,
Kinetic. Energy, Potential.)

A voltaic cell consists of two plates of different
metals, or of a metal and a metalloid (or of two
gases, or two liquids, or of a liquid and a gas),
each of which is called a
voltaic element, and which,
taken together, form what is
called a voltaic couple.

The voltaic couple dips in-
to a liquid called an electro-
lyte, which, as it transmits
the electric current, is de-
composed by it. The ele-
ments are connected outside
the electrolyte by any con-
ducting material.

Direction of the Current. la. any voltaic cell
the current is assumed to flow through the liquid,
from the metal most acted on to the metal least
acted on, and outside the liquid, through the out-
side circuit, from the metal least acted on to the
metal most acted on.

Fig. 103. Voltaic
Couple.

In Fig. 103 a zinc-copper voltaic couple is
shown, immersed in dilute sulphuric acid. Here,
since the zinc is dissolved by the sulphuric acid,
the zinc is positive, and the copper negative in
the liquid. The zinc and copper are of opposite
polarities out of the liquid.

There is still a considerable difference of opinion
as to the exact cause of the potential difference of
the voltaic cell. There can be no doubt that a
true contact force exists, but the chemical poten-
tial energy of the positive plate is the source
of energy which maintains the potential differ-
ence.

The difference in the polarity of the zinc and
copper in and out of the liquid is generally de-
nied by most of the later writers on electricity,
since tests by a sufficiently delicate electrometer
show that the entire zinc plate is negative and
the entire copper plate positive. Remembering,
however, the convention as to the direction of
the flow of the current, since the current flows
from the zinc to the copper through the liquid,
we may still fairly regard the zinc as positive and
the copper as negative in the liquid. It will be
remembered, that in every source the polarity
within the source is necessarily opposite to the
polarity outside it. The copper plate is there-
fore called the negative plate, and the wire con-
nected to its end out of the liquid, the positive
electrode. Similarly, the zinc plate is called the
positive plate, and the wire connected to it the
negative electrode.

It will of course be understood that in the
above sketch the current flows only on the com-
pletion of the circuit outside the cell; that is,
when the conductors attached to the zinc and
copper plates are electrically connected.

Amalgamation of the Zinc Plate. When zinc
is used for the positive element, it will, unless
chemically pure, be dissolved by the electrolyte
when the circuit is open, or will be irregularly
dissolved when the circuit is closed, producing
currents in little closed circuits from minute vol-
taic couples formed by the zinc and such impuri-
ties as carbon, lead, or iron, etc., always found
in commercial zinc. (See Action, Local, of Vol-
taic Cell.) As it is practically impossible to ob-
tain chemically pure zinc, it is necessary to amal-
gamate the zinc plate; that is, to cover it with a
thin layer of zinc amalgam.

Polarization of the Negative Plate. Since the
evolved hydrogen appears at the surface of the
negative plate, the surface of this plate, unless

Cel.J

means are adopted to avoid it, will, after a while,
become coated with a film of hydrogen gas, or
as it is technically called, will become polarized.
(See Cell, Voltaic, Polarization of,)

The effect of this polarization is to cause a fall-
ing off or weakening of the current produced by
the battery, due to the formation of a counter,
electromotive force produced by the hydrogen-
covered plate; that is to say, the negative plate,
now being covered with hydrogen, a very highly
electro-positive element, tends to produce a
current in a direction opposed to that of the
cell proper. (See Force, Electromotive, Coun-
ter.)

This decrease in current strength is rendered
still greater by the increased resistance in the cell,
due to the bubbles of hydrogen, and to the de-
creased electromotive force, due to the increase
in the density of the zinc sulphate, in the case of
zinc in hydrogen sulphate.

In the case of storage cells, the counter-elec-
tromotive force of polarization is employed as the
source of secondary currents. (See Electricity,
Storage of. Cell, Secondary. Cell, Storage.)

In order to avoid the effects of polarization in
voltaic cells, and thus insure constancy of cur-
rent, the bubbles of gas at the negative plate are
mechanically carried off either by roughening its
surface, by forcing the electrolyte against the
plate as by shaking, or by a stream of air; or else
the negative plate is surrounded by some liquid
or solid substance which will remove the hydro-
gen, by entering into combination with it. (See
Cell, Voltaic, Polarization of .)

Voltaic cells are therefore divided into cells
with one or with two fluids, or electrolytes, or
into:

(I.) Single-fluid cells; and

(2.) Double-fluid cells.

Very many forms of voltaic cells have been de-
vised. The following are among the more im-
portant, viz. : Of the Single-Fluid Cells, the
Grenet, Poggendorff, or Bichromate, the Zinc-
Copper, the Zinc- Carbon and the Smee. Of the
Double-Fluid Cells, Grove's, Bunsen's, Callaud
or Gravity, DanielFs, Leclanche, Siemens- Hals ke
and the Meidinger,

Of all the voltaic cells that have been devised
two only, viz., the Gravity, a modified Daniell,
and the Leclanche, have continued until now in
very general use, the gravity cell being used on
closed-circuited lines, and the Leclanche on open-
circuited lines ; the former being the best suited

of all cells to furnish the continuous constant cur.
rents employed in most systems of telegraphy,
and the latter for furnishing the intermittent cur-
rents required for ringing bells, operating annun-
ciators, or for similar work.

Cell, Voltaic, Absorption and Genera-

tion of Heat in (See Heat, Absorption

and Generation of, in Voltaic Cell.)

Cell, Yoltaic, Bichromate A zinc-
carbon couple used with an electrolyte
known as electropoion, a solution of bichro-
mate of potash and sulphuric acid in water.
(See Liquid, Electropoion^}

Bichromate of sodium or chromic acid are
sometimes used instead of the bichromate of
potassium.

The zinc, Fig. 104, is amalgamated and placed
between two carbon plates.
The terminals connected
with the zinc and carbon
are respectively negative
and positive. In the form
shown in the figure, the zinc
plate can be lifted out of
the liquid when the cell is
not in action.

The bichromate cell is
excellent for purposes re-
quiring strong currents
where long action is not
necessary. As this cell
readily polarizes it cannot
be advantageously employ-
ed continuously for any
considerable period of time. It becomes depolar-
ized, however, when left for some time on open
circuit

The following chemical reaction probably takes
place when the cell is furnishing current, viz. :

jo 4. Bichromate
Cell.

K 8 S0 4 -f 3 ZnS0 4 + Cr 8 3(So 4 ) -j- 7 H 2 O.
This cell gives an electromotive force of about
1. 9 volts.

Cell, Voltaic, Bunsen's A zinc-
carbon couple, the elements of which are
immersed respectively in electrolytes of dilute
sulphuric and strong nitric acids.

Bunsen's cell is the same as Grove's, except
that the platinum is replaced by carbon. The
zinc surrounds the porous cell containing the car-

Cel.]

[Cel.

bon. The polarity is as indicated in Fig. 105.
(See Cell, Voltaic, Grove.)

Fig. 1 03. Bunsen Cell.

The Bunsen cell gives an electromotive force
of about 1.96 volts.

Cell, Voltaic, Callaud's A name

sometimes given to the gravity cell. (See
Cell, Voltaic, Gravity.)

Cell, Toltaic, Capacity of Polarization of

The quantity of electricity required

to be discharged by a voltaic cell in order to
produce a given polarization. (See Cell, Vol-
taic, Polarization of.)

During the discharge of a voltaic cell an electro -
motive force is gradually set up that is opposed
to that of the cell. The quantity of electricity
required to produce a given polarization de-
pends, of course, on the condition and size of
the plates. Such a quantity is called the capacity
of polarization.

Cell, Yoltalc, Closed-Circuit A

voltaic cell that can be left for a considerable
time on a closed circuit of comparatively
small resistance without serious polarization.

The term closed-circuit voltaic cell is used in
contradistinction to open-circuit cell, and applies
to a cell that can only be kept on closed circuit
for a comparatively short time.

Daniell's cell and the gravity cell are closed-cir-
cuit cells. Leclanchd's is an open-circuit celL

Cell, Voltaic, Contact Theory of

A theory which accounts for the production
of difference of potential or electromotive
force in the voltaic cell by the contact of the
elements of the voltaic couple with one an-
other by means of the electrolyte.

The mere contact of two dissimilar substances
through the electrolyte will produce a difference
of potential, but the cause of the current which a
voltaic cell is able to maintain is the chemical
potential energy which becomes kinetic during
combination. (See Cell, Voltaic. Series, Contact,)

Most authorities explain the difference of
potential produced by the contact of different
metals by the fact that the metals are sur-
rounded by air. They point out the fact that the
order of the metals in the contact-series is
almost identical with the order of their electro-
chemical power as deduced from their chemical
equivalents, and their heat of combination with
oxygen. It would appear, therefore, that the
difference of potential between a metal and the
air which surrounds it, is a measure of the tend*
ency of the metal to become oxidized.

The origin of the electromotive force of a zinc-
copper couple, in an electrolyte of hydrogen sul-
phate, is the superior affinity of the zinc for the
oxygen, over that of the copper for the oxygen.

Cell, Voltaic, Creeping in The

formation, by efflorescence, of salts on the sides
of the porous cup of a voltaic cell, or on the
walls of the vessel containing the electrolyte.
Paraffining the portions of the walls out of the
liquid, or covering the surface of the liquid with
a neutral oil , obviates much of this d ifficulty . (See
Efflorescence.)

Cell, Voltaic, Daniell's A zinc-
copper couple, the elements of which are im-
mersed respectively in electrolytes of dilute
sulphuric acid, and a saturated solution of
copper sulphate.

In the form of Daniell's cell, shown in Fig. 106,
the copper element is made in the form of a cylin-
der c, and is placed in a porous cell. The cop-
per cylinder is provided with a wire basket near
the top, filled with crystals of blue vitriol, or cop-
per sulphate, so as to maintain the strength of the
solution while the cell is in use. The zinc is in
the shape of a cylinder and is placed so as to sur-
round the porous celL This cell gives a nearly
constant electromotive force.

The constancy of action of Daniell's cell
depends on the fact that for every molecule of
sulphuric acid decomposed in the outer cell, an
additional molecule of sulphuric acid is supplied
by the decomposition of a molecule of copper sul-
phate in the inner cell. This will be better un-

Cel.]

ICel.

derstood from the following reactions which take

place, viz.:

Zn + H 2 S0 4 = ZnS0 4 -f- H,
H -f CuS0 4 = H 3 S0 4 + Cu.
The H 8 SO 4 , thus formed in the inner cell,

passes through the porous cell, and the copper is

deposited on the surface of the copper plate.

Fig 1 06. Daniell s Cell.

The Daniell cell gives an electromotive force
of about 1.072 volts.

A serious objection to this form ot cell arises
from the fact that the copper is gradually de-
posited over the surface and in the pores of the
porous cell, thus greatly increasing its resistance.
This difficulty is avoided in the gravity cell. (See
Cell, Voltaic, Gravity.)

Cell, Voltaic, Double-Fluid A

voltaic cell in which two separate fluids or elec-
trolytes are employed.

One of the elements of the voltaic couple is
dipped into one ot the fluids and the other ele-
ment into the other fluid. In order to keep the
fluids separate and distinct, they are either sep-
arated by means of porous cells, or by the action
of gravity. (See Cell, Porous. Cell, Voltaic,
Gravity.)

In the double-fluid cell the negative element is
surrounded by a liquid which is capable ot pre-
Yenting polarization by combining chemically
with the substance that tends to collect on its
surface. In the Daniell cell this substance is the
same as that of the negative plate. (See Cell,
Voltaic^ Polarization of.)

Cell, Yoltaic, Dry A voltaic cell

in which a moist material is used in place of
the ordinary fluid electrolyte.

The term dry cell is in reality a misnomer,
since all such cells are moistened with liquid
electrolytes.

The dry cell, like other cells, is made in a
variety of forms. The ab-
sence of free liquid permits
the cell to be closed. A well
known form of dry cell is|
shown in Fig. 107.

Cell, Yoltaic, Effects of I
Capillarity in (See

Capillarity, Effects of. m \
Voltaic Cell.)

Cell, Yoltaic, Exciting
Liquid of The elec-
trolyte of a voltaic cell. n g , f07 . Dry ceil

A voltaic cell may have a single electrolyte, in
which case it is called a single-fluid cell, or it may
have two electrolytes, in which case it is called a
double-fluid cell.

Cell, Yoltaic, Fuller's Mercury Bichro
mate A zinc-carbon couple im-
mersed in an electrolyte of electropoion liquid.

The zinc is attached to a copper rod by being
cast thereto, and is placed at the bottom of a
porous .cell, where it is covered by a layer of
mercury. The carbon plate is placed in electro-

Pig. M08 Fuller's Mercury Bichromate Cell.
poion liquid, diluted with wajer in the proportion
of three of the former to two of the latter,, The
zinc is generally placed in pure water, which
rapidly becomes acid.

The mercury effects the continuous amalgama-
tion of the zinc.

A Fuller mercury bichromate cell is shown
in Fig. 108.

Cel.J

[CeL

Cell, Toltaic, Gravity A zinc-
copper couple, the elements of which are em-
ployed with electrolytes of dilute sulphuric acid
or dilute zinc sulphate, and a concentrated
solution of copper sulphate respectively.

The use of a porous cell is open to the objection
of increased internal resistance. Moreover, the
porous cell is apt to receive a coating of copper
which often deposits on the cell instead of on the
copper plate. The gravity cell was devised in
order to avoid the use of a porous cell. As its
name indicates, the two fluids are separated from
each other by gravity.

The copper plate is the lower plate, and is sur-
rounded by crystals of copper sulphate. The
zinc, generally in the form of an open wheel, or
crow-foot, is sus-
pended near the top
of the liquid, as
shown in Fig. 109.

When the cell is
set up with sul-
phuric acid, the re-
actions are the same
as in the Daniell
cell. When copper
sulphate and zinc
sulphate alone are
used, zinc replaces
the copper in the
copper sulphate.
The action is then
merely a substitution process. (See Cell, Voltaic,
Daniels.)

A dilute solution of zinc sulphate is generally
used to replace the dilute sulphuric acid. It
gives a somewhat lower electromotive force, but
ensures a greater constancy for the cell.

Cell, Toltaic, Grenet A name

sometimes given to the bichromate cell. (See
Cell, Voltaic, Bichromate!)

Cell, Voltaic, Grove A zinc-plati-
num couple, the elements of which are used
with electrolytes of sulphuric and nitric acids
respectively.

The zinc, Z, Fig. HO, is amalgamated and
placed in dilute sulphuric acid, and the platinum,
P, in strong nitric add (HNO t ) in a forous tell
to separate it from the sulphuric acid. (See C ell,
Porous.) In the Grove cell the current is moder-
ately constant, since the polarization of the plati*

Fig. 109. The Gravity Cell.

num plate is prevented by the nitric acid, which
oxidizes and thus removes the hydrogen that
tends to be liberated at its surface. The con-
stancy of the current
is not maintained for
any considerable time,
since the two liquids
are rapidly decom-
posed, or consumed,
zinc sulphate forming
in the sulphuric acid,
and water in the nitric
acid.

The chemical reac-
tions are as follows,
viz.:
Zn + H a SO 4 =

ZnSO 4 + H 8 ;
6H -f 2HNO 8 =

4H 8 O -f- 2NO;
2NO + O, = N 8 4 .

Nitrate of ammo-
nium is sometimes formed when the nitric acid
becomes dilute by decomposition. The reaction
is as follows :

2HNO, -f 4 H, = 3H 8 + NH 4 NO,.

The cell gives an electromotive force of 1.93
volts.

When the porous cell is good, the resistance of
the Grove cell may be calculated according to
the following formula of Ayrton:

Grove's Cell.

R =

ohms,

where d, is the distance in inches between the
platinum and zinc plates, and A, the square inches
of the immersed portion of the platinum plate.

Cell, Yoltaic, LeclanchS A zinc-
carbon couple, the elements of which are used
in a solution of sal-ammoniac and a finely
divided layer of black oxide of manganese
respectively.

The zinc is in the form of a slender rod and
dips into a saturated solution of sal-ammoniac,
NH 4 C1.

The negative element consists of a plate of car-
bon, C, Fig. ill, placed in a porous cell, in which
is a mixture of black oxide of manganese and
broken gas-retort carbon, tightly packed around
the carbon plate. By this mean? a greatly ex
tended surface of carbon surrounded by black

CeL]

oxide of manganese, MnO,, is secured. The entire
outer jar, and the spaces inside the porous cell are
filled with the solution of sal-ammoniac.

Fig. in. The Ledanchl Cell.

This cell, though containing but a single fluid,
belongs, in reality, to the class or type of double-
flwd cells, being one in which the negative ele-
ment is surrounded by an oxidizing substance,
the black oxide of manganese, which replaces the
nitric acid or copper sulphate in the other double-
fluid cells.

This reaction is generally given :

Zn + 4NH 4 C1 + 2Mn0 2 = ZnCl, -j- 2NH 4 Cl
+ 2NH 8 -f- Mn 8 8 -1- H 8 0.

This reaction is denied by some, who believe
the following to take place :

Zn + 2(NH 4 Cl) = ZnCl a + aNH, + H 2 .
The ZnCl 2 and NH 8 react as follows :
ZnCl, -|- 2(NH 3 ) = 2 (NH Z ) ZnCl 2 + H,.

2H -f 2(Mn 2 O 2 ) = H 2 O -f Mn a O 3 ;
or, possibly, 4H -f 3MnO a = Mn a O -f- 2H,O.

The Leclanche' cell gives an electromotive force
of about 1.47 volts. It rapidly polarizes, and
cannot, therefore, give a steady current for any
prolonged time. When left on open circuit, how-
ever, it quickly depolarizes.

Cell, Toltaic, Local Action of

(See Action, Local, of Voltaic Cell.)

Cell, Yoltaic, Meidinger A zinc-
copper couple, the elements of which are em-
ployed with dilute sulphuric acid, or solution
of sulphate of magnesia, and strong nitric
acid, respectively.

The Meidinger cell is a modification of the
Daniell cell. The zinc-copper couple is thus ar-
ranged : Z Z, Fig. 112, is an amalgamated zinc
ring placed near the walls of the vessel, A A,
constricted at b b. The copper element, c, is
similarly placed with respect to the walls of the
vessel d d. The glass cylinder h, filled with

[Cel.

crystals of copper sulphate, has a small hole in
its bottom, and keeps the vessel, d d, supplied
with saturated so- 4.

lution of copper
sulphate. The cell
is charged with di-
lute sulphuric acid,
or a dilute solution
of Epsom salts, or
magnesium sul-
phate.

Cell, Voltaic,
Open-Circuit

A voltaic

cell that cannot be
kept on closed cir-
cuit, with a com-
paratively small

resistance, for any Fig. 112. The Meidinger Cell.

considerable time without serious polariza-
tion.

A Leclanch^ cell is an open-circuit cell. The
term open-circuit cell is used in contradistinc-
tion to closed-circuit cell, such as the Daniell.
^See Cell, Voltaic, Closed-Circuit.)

Cell, Voltaic, Poggendorff A

name sometimes given to the Grenet cell. (See
Cell, Voltaic, Grenet.)

Cell, Voltaic, Polarization of The

collection of a gas, generally hydrogen, on the
surface of the negative element of a voltaic
cell.

The collection of a positive substance like hydro-
gen on the negative element or plate of ? voltaic
cell sets up a counter -electromotive force, which
tends to produce a current in the opposite direc-
tion to that produced by the cell. (See Force,
Electromotive, Counter.)

Polarization causes a decrease in the normal
current of a voltaic cell:

(l.) On account of the increased resistance of
the cell from the bubbles of gas which form part
of its circuit.

(2.) On account of the counter-electromotive
force, produced by polarization.

There are three ways in which the iH effects of
the polarization of a voltaic cell can be avoided.
These are :

(i.) Mechanical. The negative plate is fur-
nished with a roughened surface which enables the

CeL]

[Cel.

bubbles of gas to escape from the points on such sur-
face ; or, a stream of gas, or air, is blown through
the liquid against the plate and thus mechanically
brushes the bubbles off.

(2.) Chemical. The surface of the negative
plate is surrounded by some powerful oxidizing
substance, such as chromic or nitric acid, which
is capable of oxidizing the hydrogen, and thus
thoroughly removing it from the plate.

The oxidizing substance may form the entire
electrolyte, as is the case of the bichromate solution
employed in the zinc-carbon couple. Generally,
however, it has been found preferable to employ
a separate liquid, like nitric acid, to completely
surround the negative plate, and another liquid for
the positive plate, the two liquids being generally
kept from mixing by a porous cell, or diaphragm.
Such cells are called double-fluid cells. (See
Cell, Voltaic, Double-Fluid.)

(3.) Electro-Chemical. This also necessitates a
double-fluid cell. The negative element is im-
mersed in a solution of a salt of the same metal as
that forming the negative plate. Thus, a cop.
per plate, immersed in a solution of copper sul-
phate, cannot be polarized, since metallic copper
is deposited on its surface by the action of the
hydrogen which tends to be liberated there.

The constancy of action of a Daniell cell depends
on a deposition of metallic copper on its copper
plate as well as on the formation of hydrogen
sulphate, and the solution of additional copper
sulphate from the crystallized salt placed in the
cell (SeeO//, Voltaic, Daniell's.)

Cell, Voltaic, Primary, Exhaustion of

The inability of a primary voltaic

cell to furnish any further current, unless
fresh electrolyte, or fresh positive element, or
both, are supplied to it.

In the case of exhaustion of a primary voltaic
cell the stock of fresh energy is supplied to the
cell from the chemical potential energy of the
positive element, or of the electrolyte or elec-
trolytes. (See Energy, Chemical Potential.)

In most voltaic cells a marked decrease in the
current strength is observed soon after the cir-
cuit is closed, and, therefore, long before the
cell is exhausted. This decrease is due

(i.) To the increased internal resistance due to
the bubbles of hydrogen on the negative plate.

(2.) To the counter-electromotive force of po-
larization, where zinc is employed with an elec-
trolyte of sulphuric acid.

(3.) To the decrease in the electromotive force
due to an increase in the density of the zinc sul-
phate.

Cell, Voltaic, Secondary, Exhaustion of

The inability of a secondary cell to

furnish any further current, unless fresh
electro-positive and electro-negative materials
are formed in it by the passage of the
charging current.

In the case of the exhaustion of a secondary
voltaic cell, the stock of fresh energy supplied
to the cell is derived from the electric energy
of the charging current. (See Energy, Electric.)

Cell, Voltaic, Siemens-Halske -
A zinc-copper couple, the elements of which
are employed with dilute sulphuric acid and
saturated solution of copper sulphate respect-
ively.

The Siemens-Halske cell is a modification of
Darnell's. A ring of zinc, Z Z, Fig, 113, sur-

Fig IT3. Siemens-Halske Cell.

rounds the glass cylinder, c c. The porous
cell is replaced by a diaphragm, ff, of porous
paper, formed by the action of sulphuric acid on
a mass of paper pulp. Crystals of copper sul-
phate are placed in the glass jar, c c, and rest
on the copper plate, k, formed of a close copper
spiral. Terminals are attached at b and h. The
entire cell is charged with dilute sulphuric acid.
The resistance of the cell is high ,

Cell, Voltaic, Silver Chloride A

zinc and silver couple immersed in electro-
lytes of sal-ammoniac or common salt and
silver chloride.

Cel.]

[Cel.

The zinc acts as the positive element, and a
silver wire, around which a cylinder of fused
silver chloride is cast, as the negative element.
The zinc, and the silver wire and silver chloride,
are placed in a small glass test-tube and covered
with the sal-ammoniac or common salt, and
the tube closed by a cork of paraffin, to prevent
the evaporation of the electrolyte. When sal-
ammoniac is used, the strength of the solution is
that obtained by dissolving 23 grammes of pure
sal-ammoniac in I litre of water. The silver
chloride acts as a depolarizer.

This cell is used as a standard cell, known as
De la Rue's standard cell, from its inventor,
Warren De la Rue. Its electromotive force is
1. 068 volts.

Cell, Voltaic, Simple Any voltaic

cell formed of a single couple immersed in a
single exciting liquid.

Cell, Voltaic, Single-Fluid A vol-
taic cell in which but a single fluid or elec-
trolyte is used.

Single-fluid voltaic cells possess the disadvan-
tage of polarizing during action. This polariza-
tion is due to the electro-positive element of the
electrolyte collecting on the surface of the nega-
tive plate, or within its mass. For example,
where dilute sulphuric acid is the electrolyte,
hydrogen gas collects on the negative plate and
lowers the electromotive Jorce produced by the
cell, by a counter -electromotive force thereby
generated. (See Force, Electromotive. Force,
Electromotive, Counter.)

Cell, Voltaic, Smee A zinc-silver

couple used with an electrolyte of dilute sul-
phuric acid, H 2 SO 4 .

A form of Smee cell is shown in Fig. 1 14. Here
the plate of silver is placed between two zinc
plates.

The silver plate is roughened and covered with
a coating of metallic platinum, in the condition
known as platinum alack. (See Platinum Black. )
This cell was formerly extensively employed in
electro-metallurgy but is now replaced by dynamo-
tlectric -machines. (See Metallurgy, Electro.
Machine, Dynamo -Electric. )

A zinc -carbon couple is sometimes used to re-
place the zinc-silver couple. A couple of zinc-
lead is also used, though not very advanta-
geously.

The Smee cell was one of the earliest forms
of voltaic cells.

In the zinc-silver couple the chemical reaction
that takes place when the
cell is furnishing current is
as follows, viz. :
Zn -f H a S0 4 = ZnS0 4

+ H 2 .

The Smee cell gives an
electromotive force of about
.65 volt.

Cell, Voltaic, Stand-
ard A voltaic cell

the electromotive force of
which is constant, and Fig. IT 4. Smee Cell.
which, therefore, may be used in the measure-
ment of an unknown electromotive force.

Absolute constancy of electromotive force is
impossible to attain, but if the current of the
standard cell is closed but for a short time the
electromotive force may be regarded as practically
invariable.

Cell, Voltaic, Standard, Clark's

The form of standard cell shown in Fig. 115.

Latimer Clark's standard cell assumes a
variety of forms. The H-form is arranged as
shown in Fig. 115. The vessel to the left con-
tains, at A, an amal-
gam of pure zinc. The
other vessel contains,
at M, mercury covered
with pure mercurous
sulphate, Hg 8 SO 4 .
Both vessels are then
filled, above the level
of the cross tube, with
a saturated solution of
zinc sulphate Z, Z, to
which a few crystals
of the same are added.
Tightly fitting corks
C, C, prevent loss by Fig. 113. Clark's Stand-
evaporation. *rd Cell.

The voltage of this cell in* legal volts is 1.438
[10.00077 (t IS degrees C.)] (Ayrton.)

The value t, is the temperature in degrees of
the centigrade scale.

Cell, Voltaic, Standard, Kayleigh's Form

of Clark's A modified form of Clark's

cell.

Ccl.]

[Cel.

Il(> _ Ray leigh'*
Form of Clark's

Standard Cell.

Lord Rayleigh's form of Clark's standard cell
is shown in Fig. 1 16. The electrodes pass respect-
ively through the bottom and top of the test tube
of glass. On the lower
electrode a layer of mer-
cury, Hg, is placed. On
this rests a layer of mercu-
rous sulphate paste made
sufficiently semi-fluid with
a solution of zinc sulphate
to form an approximately
level surface. The zinc,
Zn, is attached to the up-
per electrode and is im-
mersed in this semi-fluid
paste.

The mercurous sulphate
appears to act to keep the
mercury free from impuri-
ties.

The electromotive force j
of this cell has been care-
fully determined by Ray-
leigh. Its value in true

Volts is :

E= 1.435 t 1 -00077 (t 15)] when t, is the
temperature in degrees Centigrade.

This cell is often called Clark's normal element.

Cell, Voltaic, Standard, De la Rue's -
A form of silver-chloride cell. (See Cell,
Voltaic, Silver-Chloride.}

Cell, Voltaic, Stand-
ard, Fleming's --
The form of standard
cell shown in Fig. 117.

The U-tube, Fig. 117,
is connected, as shown,
by means of taps, with
two vessels filled with
chemically pure solutions
of copper sulphate of sp.
gr. i.i at 15 degrees C.,
and zinc sulphate of sp.
gr. 1.4 at 15 degrees C.
respectively. To use the
cell the zinc rod Zn, con-
nected with a wire pass-
ing through a rubber
stopper, is placed in the
left-hand branch. The tap A, is opened and
the entire U-tube is filled with the denser
zinc sulphate solution. The tap at C, is then

Fig. z if. Fleming's
Standard Cell.

opened, and the liquid in the right-hand branch
above the tap is discharged into the lower vessel,
but, from this part only. The tap C, is then
closed, and the tap B, opened, and the lighter
copper sulphate allowed to fill the right-hand
branch above the tapC. The copper rod Cu, fitted
to a rubber stopper and connected with a con-
ducting wire, is then placed in the copper solution.

Tubes are provided at L and M, for the recep-
tion of the zinc and copper rods when not in use.
The copper rod is prepared for use by freshly
electro-plating it with copper. The electro-
motive force of this cell is 1.074 volts. If the line
of demarkation between the two liquids is not
sharp, the arms of the vessels are emptied, and
fresh liquid is run in.

Cell, Voltaic, Standard, Lodge's

A form of standard Daniell cell.

Lodge's standard cell is shown in Fig. 118.
Through the tube T, in a
wide mouthed bottle, is
passed the glass tube, in the
mouth of which is placed a
zinc rod. To the bottom of
the tube T, a small test-tube
t, containing crystals of cop -
per sulphate, is fastened by
means of a string or rubber
band. The uncovered end
of a gutta-percha insulated
copper wire projects at the
bottom of t, through a tube
in a tightly fitting cork, and
forms the copper electrode. The bottle is partly
filled as shown with a solution of zinc sulphate.

The internal resistance of this cell is so high
that it is only employed in the use of zero methods
with a condenser.

Cell, Voltaic, Standard, Sir William

Thomson's A form of standard

Daniell cell.

Fig. 118. Lodge's
Form of Daniel!' t Cell.

Fig. u<). Thomson's Form of Daniell' s Cell.
Sir Wm. Thomson's standard cell is shown in
Fig . 1 1 9. A zinc disc is placed at the bottom of the

Cel.]

cylindrical vessel and a solution of zinc sulphate
of sp. gr. 1.2 poured over it. By means of the
funnel F, a half-saturated solution of copper
sulphate is carefully poured over this and floats
on it owing to its smaller density. The electro,
motive force of this cell is 1.072 true volts at
15 degrees C.

Cell,Yoltaic, Standardizing a De-
termining the exact value of the electromotive
force of a voltaic cell, in order to enable it to
be used as a standard in determining the
electromotive force of any other electric
source.

Cell, Voltaic, Two-Fluid A term

sometimes employed in place of double-fluid
cell. (See Cell, Voltaic, Double-Fluid)

Cell, Voltaic, Water A voltaic

cell in which the exciting liquid is merely
water.

Any voltaic couple can be used, the positive
element of which is acted on by water. (See
Battery, Voltaic.)

Cell, Voltaic, Zinc-Carbon A

cell in which zinc and carbon form the posi-
tive and negative elements respectively.

A name sometimes given to the bichro-
.nate cell.

Cell, Voltaic, Zinc-Copper A

cell in which zinc and copper form the posi-
tive and negative elements respectively.

Cell, Voltaic Zinc-Lead A zinc-
lead couple sometimes used, though not very
advantageously, to replace the zinc-silver
couple in a Smee cell. (See Cell, Voltaic,
Smee?)

Cells, Coupled A number of sep-
arate cells connected in any way so as to
form a single source.

Cells, Voltaic, Series-Connected

A number of separate voltaic cells connected
in series so as to form a single source. (See
Circuit, Series.)

Cement-Lined Conduit. (See Conduit.
Cement-Lined?)

Cements, Insulating Various

mixtures of gums, resins and other substances,
possessing the ability to bind two or more
4 Vol. 1

[Ch*

substances together and yet to electrically in-
sulate one from the other.

Cent!. (As a prefix) The one-hundredth
part of.

Centi-Ampdre. One-hundredth of an am-
pere.

Centi-AmpSre Balance. (See Balance.
Centi-Ampere?)

Centigrade Thermometer Scale. (See
Scale, Centigrade Thermometer?)

Centigramme. The hundredth of a
gramme

One centigramme equals 0.1544 grains avoir-
dupoise. (See Weights and Measures^ Metric
System of.)

Centilitre. The hundredth of a litre.

One centilitre equals 0.6102 of a cubic inch.
(See Weights and Measures, Metric System of.)

Centimetre. The hundredth of a metre.

One centimetre equals 0.3937 inch. (See
Weights and Measures, Metric System of.)

Centimetre-Gramme-Second Units. (See
Units, Centimetre-Gramme-Second?)

Central Galvanization. (See Galvaniza-
tion, Central?)

Central Station. (See Station, Central?)

Central Station Burglar Alarm. (See
Alarm, Burglar, Central Station?)

Central Station Lighting. (See Light-
ing, Electric Central Station?)

Centre of Gravity. (See Gravity, Centre
of.)

Centre of Oscillation. (See Oscillation,
Centre of.)

Centre of Percussion. (See Percussion
Centre of)

Centrifugal Force. (See Force, Centrifu-
gal?)

Centrifugal Governor.-t-(See Governor
Centrifugal?]

Chain Lightning. (See Lightning,
Chain?)

Chain, Linked Magnetic and Electric

A chain of three links, the separate

links of which consist of the primary circuit.

Cha.j

LCha.

the magnetic circuit, and the secondary cir-
cuit respectively, of an induction coil.

The conception of a linked magnetic and elec-
tric chain, in studying the action of an induction
coil, was first developed by Kapp. A linked
magnetic and electric chain is shown in Fig. 120.

Fig. 120. Linked Magnttic and Electric Chain.

tf, in such a case, the magnetic core or circuit is
of varying magnetization, when one of the electric
circuits has a periodic current passed through
it, the various phenomena of the induction coil
are produced. (See Coil t Induction.)

Chain, Molecular A polarized chain

oi molecules that is supposed to exist in an
electrolyte during its electrolytic decomposi-
tion, or in a voltaic cell on closing its circuit.
(See Hypothesis, Grotthus.)

Chain Pull. (See Pull, Chain)

Chamber, Armature The armature

bore. (See Bore, Armature?)

Chamber of Lamp. (See Lamp, Cham-
hrof.)

Change, Chemical Any change in

matter resulting from atomic combination
and the consequent formation of new mole-
cules.

Some chemical changes are caused by atomic
combinations and the formation of new molecules.
They are necessarily attended by 9 loss of the spe-
cific identity of the substances involved in the
change. Thus carbon, a black solid, combined
with sulphur, a yellow solid, produces carbon
disulphide, a colorless, odorous liquid. (See
Atom.)

Change, Physical Any change in

matter resulting from a change in the relative
position of its molecules, without the forma-
tion of new molecules.

Ice, when heated, is turned into water; steel,
when stroked by a magnet, is rendered perma-
nently magnetic; a piece of vulcanite or hard

rubber stroked by a piece of cat skin becomes
electrified. In all these cases, which are instances
of physical changes, the substances retain their
specific identity , This is true in all cases of phys-
ical changes. (See Molecule.)

Changing-over Switch. (See Switch,
Changing-over?)

Changing Switch. (See Switch, Chang-
ing.']

Characteristic Curve. (See Curve,
Characteristic^)

Characteristic Curve of Parallel Trans-
former. (See Citrve, Characteristic, of
Parallel Transformer!)

Characteristic Curve of Series Trans-
former. (See Cur've, Characteristic, of
Series Transformer?)

Characteristics of Sound. (See Sound,
Characteristic of.)

Charge, Bound The condition of

an electric charge on a conductor placed near
another conductor, but separated from it by
a medium through which electrostatic induc-
tion can take place. (See Induction, Elec~
trostatic?)

When a charged conductor is placed near an-
other conductor, but separated from it by a di-
electric or medium through which induction can
take place, a charge of the opposite name is in-
duced in the neighboring conductor. This charge
is so held or bound on the conductor by the mu-
tual attraction of the opposite charge that it is
not discharged on connection with the earth
unless both conductors are simultaneously touched
by any good conductor. The bound charge was
formerly called dissimulated or latent electricity.
(See Electricity, Dissimulated or Latent. )

Charge, Density of The quantity

of electricity per unit of area at any point on
a charged surface.

Coulomb used the phrase surface density to
mean the quantity of electricity per unit of area
at any point on a surface.

Charge, Dissipation of The gradual
but final loss of any charge by leakage, which
occurs even in a well insulated conductor.

This loss is more rapid with negatively charged
conductors, than with those positively charged.

[Cha.

Crookes, of England, has retained a charge on
conductors for years, without appreciable leakage,
by placing the conductors in vessels in which a
high vacuum was maintained. (See Vacuum,
pi.)

Charge, Distribution of The vari-
ations that exist in the density of an electrical
charge at different portions of the surface of
all insulated conductors except spheres.

The density of charge varies at different points
of the surface of conductors of various shapes. It
is uniform at all points on the surface of a sphere.

It is greater at the extremities of the longer
axis of an egg-shaped body, and greatest at the
sharper end.

It is greater at the corners of a cube than at
the middle of a side.

It is greatest around the edge of a circular disc.

It is greatest at the apex oi a cone

Charge, Electric The quantity of

electricity that exists on the surface of an in-
sulated electrified conductor.

When such a conductor is touched by a good
conductor connected with the earth, it is <#*-
charged. (See Condenser.)

Charge, Free The condition of an

electric charge on a conductor isolated from
any other conductor.

It is impossible to obtain a perfectly free charge,
since it is impossible to complete!; isolate an
insulated conductor. The charge, however, can
be comparatively free.

The charge, on a completely isolated conductor,
readily leaves it when it is put in contact with a
good conductor connected with the ground. (See
Charge, Bound.}

Charge, Induced Electrostatic

The charge produced by bringing a body

into an electrostatic fiel

In order to obtain a permanent charge, i. e., a
charge which will be maintained when the body
is withdrawn from an electrostatic field, it is nec-
essary to connect the body with the earth so that
it may lose, or'part with, a charge of the same
mame as the inducing charge. Then, on the with-
drawal of this charge, it will possess a charge op-
posite in name to the inducing charge. (See
Condenser. )

Charge, Influence A charge pro-

duced by electrostatic induction. (Sec /
duction, Electrostatic)

Charge, Negative According to the

double-fluid hypothesis, a charge of negative
electricity.

According to the single-fluid hypothesis,
any deficit of an assumed electrical fluid.

Charge, Positive According to the

double-fluid hypothesis, a charge of positive
electricity.

According to the single-fluid hypothesis,
any excess of an assumed electrical fluid.

Charge, Residual The charge pos-
sessed by a charged Leyden jar for a few
moments after it has been disruptively dis-
charged by the connection of its opposite
coatings.

The residual charge is probably due to a species
of dielectric strain, or a strained position of the
molecules of the glass caused by the charge.
Such residual charge is not present in air con
densers. In other words, a Leyden jar does not
give up all the electric energy charged in it, on a
Single disruptive discharge.

Charge, Return A charge induced

in neighboring conductors by a discharge of
lightning.

Under the influence of induction a lightning
stroke produces during its discharge an electric
shock in the human body, or a charge in neigh*
boring bodies, which is called the back or re-
turn stroke of lightning. (See Stroke^ Light-
ning, Back or Return.}

Charged Body. (See Body, Charged)

Charging Accumulators. Sending an
electric current into a storage battery for the
purpose of rendering it an electric source.

There is, strictly speaking, no accumulation of
electricity in a storage battery, such, for example,
as takes place in a condenser, but a mere storage
of chemical energy, which may .afterward become
electric. (See Cell, Storage.)

Charging Leyden Jars 1>7 Cascade. (See

Case ad*, Charging Leyden Jars by)

Chart, Inclination A map or chart

on which the isoclinic lines are marked. (See
Map or Chart, Inclination. Lints, Isocltnie)

Cha.]

[Chr.

Chart, Isodynamie A map or chart

on which the isodynamic lines are marked.
(See Map or Chart, Isodynamic. Lines,
Isodynamic?)

Chart, Isogonal An isogonic chart.

(See Map or Chart, Isogonal)

Chart, Isogonic A map or chart

on which the isogonic lines are marked. (See
Map or Chart, Isogonic. Lines, Isogonic)

Chatterton's Compound. (See Com-
pound, Chatterton's)

Chemical Change. (See Change, Chem-
ical)

Chemical Effect. (See Effect, Chemical)

Chemical Equivalent. (See Equivalent,
Chemical)

Chemical Galvano-Cautery. (See Cau-
tery, Galvano-Chemical)

Chemical Phosphorescence. (See Phos-
phorescence, Chemical)

Chemical Photometer., (See Photometer,
Chemical)

Chemical Potential Energy. (See En-
ergy, Chemical Potential)

Chemical Recorder, Bain's (See

Recorder, Chemical, Bains)

Chemistry, Electro That branch

of electric science which treats of chemical
compositions and decompositions effected by
the electric current. (See Electrolysis. De-
composition, Electrolytic)

That branch of chemistry which treats of
combinations and decompositions by means
of electricity.

Electro-chemistry treats of the formation of
new molecules, by the combination of atoms under
the electric force, as well as the decomposition of
molecules by electricity.

The action of a series of sparks passed through
air, in forming nitric acid, is an instance of the
former, and electrolytic decompositions fax gen-
eral afford instances of the latter.

Chimes, Electric Bells rung by

the attractions and repulsions of electrostatic
charges.

The bells B and B, Fig. 121, are conductively
connected to the prime or positive conductor -\-,

of a frictional machine. The bell C, is insulated
from this conductor by means of a silk thread,
but is connected with the ground by the metallic
chain. Under these
circumstances th e
clappers, 1, 1, insu-
lated by silk threads,
t, t, are attracted to
B, B, by an induced
charge and repelled
to C, where they lose
their charge only to
be again attracted to
B, B. In this way
the bells will con-
tinue ringing as long
as the electric ma-
chine is in operation.

Choking Coil. (See Coil, Choking)
Chronograph, Electric An elec-
tric apparatus for automatically measuring
and registering small intervals of time.

Chronographs, though of a variety of forms,
generally register small intervals of time by
causing a tuning fork or vibrating bar of steel,
whose rate of motion is accurately known, to
trace a sinuous line on a smoke-blackened sheet
of paper, placed on a cylinder driven at a uni-
form rate of motion by clockwork. If the fork
is known to produce, say, 256 vibrations per
second be used, each sinuous line will represent
y|3 part of a second.

Fig. tSf. Electric Chimes.

Fig. 122. Electric Chronograph.

An electro-magnet is used to make marks on
the line at the beginning and the end of the
observation, and thus permit its duration to be
measured.

In the form of electric chronograph shown

Clir.]

[Cir.

in Fig. 122, an electro-magnet, the armature of
which carries a pen, is supported on a carriage
moved by clockwork over a sheet of paper
wrapped on a rotating cylinder. A clock is so
connected with the circuit of the electro-magnet
that it makes or breaks the circuit at the end of
every second second, and so moves, or displaces,
the armature, as to cause an elevation or depres-
sion in the otherwise continuous sinuous line, that
would be drawn on the paper by the double
motion of its rotation and the movement of the
pen-carriage.

When it is desired to know with great precision
the exact time of occurrence of any event,
such, for example, as the transit of a star over the
meridian, the observer, who carries in his hand a
push button, or other form of electric key, closes
or opens the circuit at the exact moment and so
superposes an additional mark on the sinuous
line. Since the exact time of starting the clock
is known, and the intervals between the regular
successive marks are two seconds each, it is easy to
estimate from its position between any two such
marks the exact value of the additional mark inter-
posed. Fig. 122, taken from Young, shows a form
of chronograph by Warner & Swasey. The de-
tails of this apparatus will be understood from
an inspection of the drawing.

Chronograph Record. (See Record,
Chronograph)

Chronoscope, Electric An appa-
ratus for electrically indicating, but not
necessarily recording, small intervals of time.

This term is often used for chronograph.

The interval of time required for a rifle ball
to pass between two points may be determined
by causing the ball to pierce two wire screens
placed a known distance apart. As the screens
are successively pierced, an electric circuit is
thus made or broken, and marks are registered
electrically on any apparatus moving with a
known velocity.

Cigar-Lighter, Electric (See

Lighter, Cigar, Electric)

Cipher Code. (See Code, Cipher)

Circle, Azimuth The arc of a

great circle passing through the point of the
heavens directly overhead, called the Zenith,
and the point directly beneath, called the

Nadir.

Circle, Dipping A term some-
times applied to an inclination compass. (See
Compass, Inclination)

Circle, Galvanic A term some-
times used for galvanic circuit. (See Circuit,
Galvanic)

Circle of Reference. The circle, by refer-
ence to which simple harmonic motion may
be studied, by comparison with uniform mo-
tion around such circuit. (See Motion,
Simple Harmonic)

Circle, Voltaic A name formerly

employed for voltaic cell or circuit. (See
Cell, Voltaic. Circuit, Voltaic)

Circuit, Air-Magnetic That part

of the path of a line of magnetic induction
which takes place wholly through air.

Circuit, Alternating Current A

circuit in which an alternating current of
electricity is flowing. (See Current, Alter-
nating)

Circuit, Astatic A circuit consist-
ing of two closed curves enclosing equal sur-
faces.

Such a circuit is A

not deflected by the *jL

action of the earth's _|[l

field. The circuit dis- J
posed, as shown in
Fig. 1 23, is astatic and
produces two equal
and opposite fields at
S and S'. (See Mag- Fig. 123. Astatic Circuit,
netism, Ampere's Theory of.)

Circuit, Balanced-Metallic A me-
tallic circuit, the two sides of which have
similar electrical properties.

Circuit Breaker. (See Breaker, Circuit)

Circuit, Broken An open circuit.

A circuit, the electrical continuity of which
has been disturbed, and through which the
current has therefore ceased' to pass.

Circuit, Closed A circuit is closed,

completed, or made when its conducting
continuity is such that the current can pass.

Circuit, Closed Iron-Magnetic

The name applied to the path of any line

dr.]

[Cir.

of magnetic force, which takes place entirely
through iron, steel, or other paramagnetic sub-
stance.
Circuit, Closed-Loop Parallel A

variety of parallel circuit in which the lead
and the return circuit are arranged in the
form of concentric circuits, with the recep-
tive devices placed radially between them.

Circuit, Closed-Magnetic A mag-
netic circuit which lies wholly in iron or other
substance of high magnetic permeability.

All lines of magnetic force form closed circuits.
The term closed-magnetic circuit is used in con-
tradistinction to a divided circuit, or one in which
an air gap exists in the substance of high mag-

Fig. 124.* Closed-Magnetic Circuit.
netic permeability forming the remainder of the
circuit. This introduces so high a resistance that
such a circuit is sometimes called an open-mag-
netic circuit. An iron ring, such as shown in
Fig. 124, forms a closed -magnetic circuit.

Circuit, Closed-Magnetic, of Atom

A closed-magnetic circuit, or closed lines
of magnetic force supposed to lie entirely in
the atom itself.

The assumption of closed lines of magnetic
force in atoms or molecules was made in order to
explain the original polarity of the same, and to
account for some of the other phenomena of
magnetism.

When the atom is subjected to a magnetizing
force, such, for example, as the field of an electric
current, these closed lines of force are assumed
to open out and produce lines of polarized atoms.
According to Lodge, for every single line of force
produced by the current passing through a coil
of wire surrounding an iron core, some 3,000
lines of magnetic force are added to it from the
iron. Therefore an iron core greatly increases
the magnetic strength of a hollow coil of wire.

Circuit, Closed-Magnetic, of Molecule

A closed-magnetic circuit assumed to lie
wholly within the molecule.

As it is not known whether the assumed mag.
netic circuit lies within the atom or the molecule,
it is called indifferently the closed-atomic or
closed-molecular circuit. (See Circuit, Closed-
Magnetic, of Atom.)

Circuit, Completed A closed

circuit.

A circuit, the conducting continuity of
which is unbroken.

A completed circuit is also called a made or
closed circuit.

Circuit, Compound A circuit con-
taining more than a single source, or more
than a single electro-receptive device, or both,
connected by conducting wires.

The term compound circuit is sometimes ap-
plied to a series circuit. (See Circuit, Series.)
The term, however, is a bad one, and is not
generally adopted.

Circuit, Constant-Current A cir-
cuit in which the current or number of am-
peres is maintained constant notwithstanding
changes occurring in its resistance.

The series-circuit, as maintained for arc-lamps,
is a constant-current circuit. (See Regulation,
Automatic.)

Circuit, Constant-Potential A
circuit, the potential or number of volts of
which is maintained approximately constant.

The multiple-arc or parallel circuit is an ap-
proximately constant-potential circuit.

Circuit, Derivative A derived or

shunt circuit. (See Circuit, Shunt.)

Circuit, Derived

A term applied to a shunt
circuit.

If, in addition to the galva-
nometer G, the conductor S,
Fig. 125, be connected with
the circuit of the battery B, a
derived circuit will thus be
established, and a current will
flow through S, diminishing
the current in the galvanom-
eter. (See Circuit, Shunt.)

J2j. Derivtd
Circuit.

Cir.]

[Cir.

Circuit, Divided-Magnetic A

magnetic circuit which lies partly in iron, or
qther substance of high magnetic perme-
ability, and partly in air.
A divided-magnetic circuit is shown in Fig. 126.

Fig. I2b. Divided Magnetic Circuit.
Where the iron ring is separated by the air gap,
a high magnetic resistance is introduced, owing
to the fact that the iron is at these points replaced
by air, whose magnetic reluctance is great.

Circuit, Double-Wire A term

sometimes used for a simple multiple circuit
with two conductors or wires. (See Circuit,
Multiple')

The term double-wire circuit is used in contra-
distinction to single-wire circuit. (See Circuit,
Single -Wire.-)

Circuit, Earth A circuit in which

the ground or earth forms part of the con-
ducting path.

Circuit, Earth, Telegraphic '-

That portion of a telegraphic circuit which is
completed through the earth or ground.

Circuit, Electric The path in

which electricity circulates or passes from a
given point, around or through a conducting
path, back again to its starting point.

All simple circuits consist of the following
parts, viz.:

(I.) Of an electric source which may be a
voltaic battery, a thermopile, a dynamo-electric
machine, or any other means for producing elec-
tricity.

(2.) Of leads or conductors for carrying the
electricity out from the source, through whatever
apparatus is placed in the line, and back again to
the source.

(3.) Various electro-receptive devices, such as
electro-magnets, electrolytic baths, electric
motors, electric heaters, etc., through which

passes the current by which they are actuated or
operated.
Circuit, Electrostatic The circuit

formed by lines of electrostatic force.

Lines of electrostatic force, like lines of mag.
netic force, form closed circuits. Hence the
origin of the phrase electrostatic circuit. (See
Force, Electrostatic, Lines of.)

Circuit, External That part of a

circuit which is external to, or outside the elec-
tric source.

The circuit external to the source consists of
two distinct parts, viz. :

(i.) The conductors or leads.

(2.) The electro-receptive or translating de-
vices.

It is in the external circuit only that useful
work is done by the current.

Circuit, Forked A term sometimes

used in telegraphy for a number of circuits
that radiate from a given central point.

Circuit, Galvanic A term some-
times employed instead of voltaic circuit.

The term galvanic in place of voltaic is unwar-
ranted by the facts of electric science. (See Cir-
cuit, Voltaic. )

Galvani thought he had discovered the vital
fluid or source of animal life. Volta first pointed
out the true explanation of the phenomena ob-
served in Galvani's frog, and devised means
for producing electricity in this manner. The
terms voltaic battery, cell, circuit, etc., are there-
fore preferable.

Circuit, Ground A circuit in which

the ground forms part of the path through
which the current passes.

As the ground is not always a good conductor,
the terminals should be connected with the gas or
water pipes, or with metallic plates, called ground
plates. Such connection, or any similar ground
connection, is usually termed the ground or earth.

Circuit, Ground, Telegraphic

An earth circuit used in any system of telegra-
phy. (See Circuit, Earth, Telegraphic!)

Circuit, Grounded A ground cir-
cuit.

Circuit, Incomplete An open 01

broken circuit.

Cir.]

A circuit whose conducting continuity is
incomplete.

Circuit, Inductive Any circuit in

which induction takes place.

Circuit, Internal That part of a

circuit which is included within the electric
source.

The electric current passing through the inter-
nal circuit does no useful work.

Circuit, Leg of One part of a

twisted or metallic circuit.

Circuit, Line The wire or other

conductors in the main line of any telegraphic
or other electric circuit.

Circuit, Line, Telegraphic The

conductor or line connecting different tele-
graphic stations.

Circuit, Local-Battery The cir-
cuit, in a telegraphic system, in which is
placed a local battery as distinguished from a
main battery. (See Telegraphy \ American
or Morse System of.)

Circuit, Loop A term sometimes

applied to a circuit in parallel or multiple-arc.
(See Circuit, Multiple^

Circuit Loop Break. (See Break, Circuit
Loop.)

Circuit, Made A completed circuit.

A circuit, whose conducting continuity is
unbroken.

A made circuit is often called a completed or
closed circuit. (See Circuit, Closed.)

Circuit, Magnetic The path through

which the lines of magnetic force pass.

All lines of magnetic force form closed circuits.

[Cir.

is often placed around the magnet. The magnet
is then said to be iron-clad.

The armature of a magnet lowers the magnetic
resistance by affording a better path for the lines
of magnetic force than the air between the
poles.

The magnetic circuit always tries to shorten its
path, or to render itself as compact as possible.
This is seen in the action of an armature drawn
towards a magnet pole.

Circuit, Main-Battery A term

sometimes used for line circuit. (See Circuit.
Line) .

Circuit, Metallic A circuit in which

the ground is not employed as any part of the
path of the current, metallic conductors being
employed throughout the entire circuit.

Circuit, Multiple A compound cir-
cuit, in which a number of separate sources
or separate electro-receptive devices, or both,
have all their positive poles connected to a
single positive lead or conductor, and all their
negative poles to a single negative lead or
conductor.

The connection of three Bunsen cells, in mul.
tiple, is shown in Fig. 128, where the three car-

Fig. t2j. Magnetic Circuit.

In the bar magnet, shown in Fig. 127, part of
this path is through the air. In order to reduce
or lower the resistance of a magnetic circuit, iron

Fig. 1 28. Batteries connected in a Multiple Circuit.

bons, C, C, C, are connected together so as to form
the positive, or -\- terminal of the battery, and
the three zincs, Zn, Zn, Zn, are similarly con-
nected together so as to form the negative, or
terminal.

The electromotive force is the same as that of
a single cell, or source. The internal resistance
of the source is as much less than the resistance of
any single source as the area of the combined
negative or positive plates is greater than that of
any single negative or positive plate ; or, in othet
words, is less in proportion to the number of cells,
or other separate sources so coupled.

The connection of six cells in multiple or
parallel circuit, is shown in Fig. 129.

Cir.J

[Cir.

In the case of the six cells, the current would
be,

where E, is the electromotive force, r, the in-
ternal, and r', the external resistance.

1 H fl2fi 031} 848 ISB M

Fig. 129. Six Cells Connected in Multiple.

In the case of voltaic cells the effect of multiple
connection on the internal resistance of the source
is to increase the area of cross-section of the
liquid in the dirert proportion of the number of
cells added, and consequently to decrease the re-
sistance in the same proportion.

When strong or large currents of low electro-
motive force are required, connections in multi-
ple-arc are generally employed.

The multiple-arc connection was formerly
called connection-f or -quantity. This term is now
abandoned.

The total resistance for the parallel circuit is
obtained as follows: calling the separate resist-
ances of the separate electro-receptive devices,
R', R", R'", etc., etc., etc., total resistance,
R' X R" X R'"

R' R"

R" R'" R' R'"

or, what is the same thing, the conductivity is the
sum of the reciprocal of the separate resistances,

Conductivity

The joint resistance of only two separate resist-
ances joined in a multiple-circuit is equal to the
product of the separate resistances divided by
their sum.

When the separate resistances joined in multiple
arc are all of the same value, the joint resistance is
equal to the resistance of one of them divided by
their number.

Circuit, Multiple- Arc A term often

used for multiple circuit. (See Circuit, Mul-
tiple^

Circuit, Multiple-Series . A com-
pound circuit in which a number of separate

sources, or separate electro-receptive devices,
or both, are connected in a number of sepa-
rate groups in series, and these separata
groups subsequently connected in multiple.
In Fig. 130, a multiple-series circuit of six
_ _ _ _ c

Fig. 130. Mulliple-Series-Connected Cells.

sources is shown, in which three separate groups
of two series-connected cells are coupled in multi-
ple. The current takes the paths indicated by the
arrows. The electromotive force of the source
will be increased in proportion to the number of
cells in series, and the internal resistance de-
creased in proportion to the number in parallel.

Fig. 13 r. Cells Connected in Multiple- Series.
c _ 3E

In Fig. 131, six cells are arranged in two
groups of three series-connected cells, and these
three groups connected in parallel.

Calling r, the resistance of each separate cell,
the total resistance for the multiple-series circuit
for a circuit containing three cells in parallel and
two in series is,

for three in series and two in parallel,

If, therefore, the circuit of this battery be
closed by a resistance equal to r, the current
would be in the case of Fig. 130,
c _ 2E

Cir.]

100

[Cir.

Circuit, Negative Side of The side

olt a circuit opposite to the positive side.
(See Circuit, Positive Side of.)

That side or half of a circuit connected to or
leading from the positive terminal of the source of
Current.

Circuit, Open A broken circuit.

A circuit, the conducting continuity of
which is broken.

Circuit, Open-Iron Magnetic

The path of a line of magnetic induction,
which passes partly through iron, and partly
through an air space.

The magnetic circuit is always closed, that is
the lines of magnetic force always form closed
paths. The term " open " is used in contradis-
tinction only to "closed " iron magnetic circuit,
in which the entire path of a line of force passes
through iron. (See Circuit, Magnetic.)

Circuit, Parallel A name some-
times applied to circuits connected in mul-
tiple. (See Circuit, Multiple.)

Circuit, Parallel-Tree A form of

parallel circuit in which the receptive devices
are placed in parallel between the leads and
returns, and the branches and sub-branches
arranged in a tree-like form.

Circuit, Positive Side of That side

of a circuit, bent in the form of a circle, in
which, if an observer stood with his head in
the positive region, he would see the current
pass round him from his right hand towards
his ldt(Dam'etZ.)

Circuit, Recoil A term sometimes

applied to the circuit that lies in the alterna-
tive path of a discharge. (See Path, Alter-
native^

Circuit, Return That part of a

circuit by which the electric current returns to
the source.

In a multiple-circuit the lead that is con-
nected to the negative terminals of the
separate sources.

Circuit, Series A compound cir-
cuit in which the separate sources, or the sep-
arate electro-receptive devices, or both, are so
placed that the current produced in each, or
passed through each, passes successively

through the entire circuit from the first to the
last.

The six cells, shown in Fig. 132, are connected
in series by joining the positive pole of each cell
with the negative pole of the succeeding cell, the
negative and positive poles at the extreme ends

Fig. 132. Series Circuit.

being connected by conductors with the external
circuit.

The connection of three Leclanche' cells iit
series is clearly shown in Fig. 133. The carbons,

- C +Z- C >

Altaic Cells Connected in Series.

C, C, of the first and second cells are connected to
the zincs, Zn, Zn, of the second and third cells,
thus leaving the zinc, Zn, of the first cell, and the
carbon, C, of the third cell, as the terminals of
the battery. The direction of the current is
shown by the arrows.

The resistance of such a connection is equal to
the sum of the resistances of all of the separate
sources.

The electromotive force is equal to the sum of
the separate electromotive forces.

If the electromotive force of a single cell is
equal to E, its internal resistance to r, and the
resistance of the leads and electro -receptive de-
vices to r', then the current in the circuit,

If six of such cells are coupled in series, the cur-
rent becomes

If, however, the internal resistance of each cell be
so small as to be neglected, the formula becomes

r 6E -
C=_,

Cir.]

101

[Cir.

or the current is six times as great as with one
cell.

The total resistance of the separate sources or
electro-receptive devices of the series circuit is
as follows, calling R', R", R'", etc., the-separate
resistance and R, the total resistance,
R = R' -f R" + R "', etc.

The series connection of battery cells is used
on telegraph fines, where a high electromotive
force is required in order to overcome a consider-
able resistance in the circuit, or in similar cases
where the resistance in the external circuit is
great, on account of a number of electro-receptive
devices being connected to the line in series.

The series connection was formerly called
connection for intensity. The term is now aban-
doned.

Circuit, Series-Multiple -- A com-
pound circuit, in which a number of separate
sources, or separate electro-receptive devices,
or both, are connected in a number of sepa-
rate groups in multiple-arc, and these sepa-
rate groups subsequently connected in series.

In the series-multiple circuit the resistance of
each multiple group is equal to the resistance of
a single branch divided by the number of branches.

If, for example, r, is the resistance of each sepa-
rate branch of say seven parallel circuits in each
of the separate groups of multiple circuits, then
the resistance, R, of each separate multiple
group is

The total resistance of the series-multiple cir-
cuit is equal to the sum of the resistances of the
separate multiple groups. The total resistance of
the three groups is -

R' = ^ + JL + Jl^JL.
777 7

An example of the series-multiple circuit is
shown in Fig. 134, which is the method adopted

Fig. 134- Series-Multiple Circuit.
in the use of distribution boxes. Here a number
c multiple groups or circuits are connected with
each other in series, as shown. (See Box, Dis-
tribution, for Arc Light Circuits. )

Circuit, Short A shunt, or by-path.

of comparatively small resistance, around the
poles of an electric source, or around any
portion of a circuit, by which so much of the
current passes through the new path, as vir-
tually to cut out the part of the circuit around
which it is placed, and so prevent it from re-
ceiving an appreciable current.

Circuit, Shunt A branch or addi-
tional circuit provided at any part of a cir-
cuit, through which the current branches or
divides, part flowing through the original cir-
cuit, and part through the new branch.

A shunt circuit is in multiple circuit with the
circuit it shunts.

In the case of branch circuits each of the cir-
cuits acts as a shunt to the others. Any number
of additional or shunt circuits may be thus pro-
vided. (See Lams, JGrcAAofs.)

Circuit, Simple A circuit containing

a single electric source, and a single electro-
receptive device, connected by a conductor.

The term simple circuit is sometimes applied
to a multiple circuit. The term is not, however,
a good one, and is not in general use.

Circuit, Single- Wire A term some-
times used for a grounded circuit. (See
Circuit, Grounded?)

The single-wire circuit is sometimes used in the
distribution of incandescent lamps in multiple-arc.
One pole of the dynamo is put to ground, and the
other pole to a single wire or lead. The electro-
receptive devices have one of their poles con.
nected to this lead and the other pole to earth.
The single-wire circuit is a very objectionable
circuit so far as safety is concerned.

It is frequently used, however, in the wiring of
ships.

Circuit, Through A telephonic or

telegraphic circuit that has been completed
through to a given station by cutting out inter-
ruptions or breaks in the line by the connec-
tion together of sections of different wires.

Circuit, Time-Constant of The

time in which a current due .to a constant
electromotive force will rise in a conductor
to a definite fraction of its maximum value.
The ratio of the inductance of a circuit to

its resistance.

Cir.J 1

The time required from the moment of
closing the circuit, for a current to rise to

a value equal to e * of the full value, or

.632 of the maximum value.

In the above, e, equals 2.71828, or the base of
the Napierian system of logarithms.

The time-constant is proportional to the con-
ductivity of the circuit and its formal resistance.

Approximately the time constant of a circuit is
the time from closing the circuit, in which the
current rises to two-thirds of its maximum value,
this maximum value being determined by the

formula, C = -.
R

The time- constant of a circuit may be reduced

(i.) By decreasing the self-induction of the cir-
cuit.

(2.) By increasing the resistance.

In the case of a magnetic conductor the time-
constant is proportional to a quantity (the perme-
ability) which is determined by the capacity of
the conductor to utilize part of the energy in
producing magnetization of its substance. (Flem-
ing-)

Circuit, Voltaic The path through

which the current flows out from a voltaic cell
or battery, through the translating devices
and back again to the cell or b?>tery.

Circuits, Forked A term employed

in telegraphy to indicate circuits that radiate
from any single point.

Forked circuits are employed in simultaneously
transmitting messages to several stations.

Circuits, Varieties of Conducting

paths provided for the passage of an electric
current.

Electric circuits may be divided, according to
their complexity, into

(i.) Simple.

(2.) Compound.

According to the peculiarities of their connec-
tions, into

(i.) Shunt or derived.

(2.) Series.

(3.) Multiple, multiple-arc or parallel.

(4.) Multiple-series.

(5.) Series-multiple.

Either the circuits, the sources, or the electro-

[Cle.

receptive devices may be connected in series, in
multiple, in multiple-series or in series-multiple.

According to their resistance, circuits are
divided into

(i.) High-resistance.

(2.) Low-resistance.

According to their relation to the electric
source, into

(I.) Internal circuits.

(2.) External circuits.

According to their position, or the work done,
circuits are divided into very numerous classes;
thus, in telegraphy, we have the following, viz.:

(i.) The line-circuit.

(2.) The earth or ground circuit.

(3.) The local-battery circuit.

(4.) The main -battery circuit, etc.

Circular Bell. (See Bell. Circular)
Circular Units. (See Units, Circular)'

Circular Units (Cross-Sections), Table

of (See Units, Circular (Cross-Sec-

tions), Table of)

Clamp, Carbon A carbon clutch,

(See Clutch, Carbon, of Arc Lamp)

Clamp for Arc Lamps. A clamp for
gripping the lamp-rod, /. e., the rod that sup-
ports the carbon electrodes of arc lamps.
(See Lamp, Electric, Arc.)

Clamp, Rod A carbon clutch. (See

Clamp for Arc Lamps)

Clark's Compound. (See Compound,
Clark's)

Clark's Standard Voltaic Cell. (See

Cell, Voltaic, Standard, Clark's)

Clark's Standard Voltaic Cell, Ray-

leigh's Form of (See Cell, Voltaic,

Standard, Rayleigh's Form of Clark's)

Clay Electrode. (See Electrode, Clay)

Cleansing, Fire The removal of
grease from metallic articles, that are to be
electro-plated, by subjecting them to the action
of heat.

This cleansing is for the purpose of obtaining \
uniform, adherent coating.

Clearance-Space. (See Stace. Clearance)

Cle.]

103

[Clo.

Clearing-Out Drops. (See Drops, Clear-
ing-Out)

Cleat, Crossing A cleat so arranged

as to permit the crossing of one pair of wires
under or over another pair without contact
with each other.

Cleat-Wiring. (See Wiring, Cleat)

Cleats, Electric Suitably shaped

pieces of wood, porcelain, hard rubber or
other non-conducting material used for fasten-
ing and supporting electric conductors to
ceilings, walls, etc.

A simple form of wooden cleat is shown in
Fig. 135-

Fig- '35' Wooden Cleat.

Clepsydra, Electric An instrument

for measuring time by the escape of water or
other liquid under electrical control.

Climbers, Pole

Devices employed by
linemen for climbing
wooden telegraph poles.

A climber with straps
for attachment to the leg
and foot is shown in Fig.
I 3 6.

Clip, Cable A

term sometimes used for
cable hanger. (See
Hanger, Cable?)

Clock, Electric

A clock, the works of

which are moved, COn- Fig. 136. Climber and

trolled, regulated or *"**

wound, either entirely or partially, by the elec-
tric current.

Electric clocks may be divided into three
classes, viz.:

(i.) Those in which the works are moved en-
tirely or partially by the electric current.

(2.) Those which are controlled or regulated
by the electric current

Fig. Jjf. Controlling
Clock.

(3-) Those which are merely wound by the
current.

A clock moving independently of electric power
is prevented from gain-
ing or losing time, by
means of a slight re-
tardation or acceleration
electrically imparted .
The entire motion of
the balance wheel is
sometimes imparted by
electricity.

An example of one of
many forms of controll-
ing electric clocks is
shown in Fig. 137,
where the split battery
(See Battery, Split), P
N, is connected, as
shown, to the spring
contacts S and S'. In this way currents are sent
into the circuit in alternately opposite directions.

The pendulum bob, Fig. 138, of the con-
trolled clock is formed of a hollow coil of insu-
lated wire, which encircles one or both of two
permanent magnets, A and A', placed with their
opposite poles facing each other.

When the pendulum of the controlling clock is
in the position shown in Fig. 137, the current
passes in the direction E P Sn W, etc., and through
the coil C, Fig. 138. When the pendulum of the
controlling clock is in con-
tact with S', the current
flows through Wn S' N E,
etc., and through the coil
C in the opposite direc-
tion. In this manner a
slight motion forwards or
backwards is imparted to
the pendulum, which is
thus kept in time with the
controlling clock.

Mercury contacts are
sometimes employed in
place of the springs S and
S'. Induction currents may A
also be employed.

Clocks of non-electric ac- Fig. 138.
tion may be electrically
controlled, or correctly set at certain intervals,
either automatically by a central clock, or by the
depression of a key operated by hand from an
astronomical observatory.

Controlled
Clock '

Clo.]

104

[Clo,

In a system of time-telegraphy, the controlling
clock is called the master clock, and the con-
trolled clocks, the secondary clocks.

Secondary clocks are generally mere dials, con-

Fig. 139. Mechanism of Secondary Clock.

taining step-by-step movements, for moving the
hour, minute and second hands, as shown in
Fig. 139-

In Spellier's clock, a series of armatures H,
Fig. 140, mounted on the circumference of a

Fig. 140. Spellier's Electric Clock.

wheel, connected with the escapement wheel,
pass successively, with a step-by-step movement,
over the poles of electro-magnets. On the com-
pletion of the circuit, they are attracted towards
the magnet, and on the breaking of the circuit
they are drawn away by the fall of the weight F,
placed on the lever D, pivoted at E. A pulley at
E, runs over the surface of a peculiarly shaped
cog on the escapement wheel.

Clock, Electric Annunciator A

clock, the hands or works of which, at cer-
tain predetermined times, make electric con-
tacts and thus ring bells, release drops, trace
records, etc.

Clock, Electrical-Controlling In

a system of time telegraphy, the master clock,
whose impulses move or regulate the second-
ary clocks. (See Clock, Electric.}

Clock, Electrically-Controlled In

a system of time telegraphy, a secondary
clock, that is either driven or controlled by
the master clock. (See Clock, Electric.}

Clock, Electrolytic, Tesla's A time

piece in which the rotation of the wheel work
is obtained by the difference in weight of the
two halves of a delicately pivoted and well-
balanced wheel placed in an electrolytic
bath.

In the electrolytic clock of Nikola Tesla, a deli- '
cately formed and balanced disc of copper is sup-
ported on a horizontal axis at right angles to the
shortest distance between the two electrodes, and
placed in a bath of copper sulphate. Its two
halves become respectively electro-positive and
electro-negative when a current is passed through
the bath, and consequently metal is deposited on
one half and dissolved from the other half. The
rotation of the disc under the influence of gravity
is caused to mark time.

An electrolytic clock could therefore be made
to answer roughly as an electric meter.

Clock, Master The central or con-
trolling clock in a system of electric time-dis-
tribution, from which the time is transmitted
to the secondary clocks in the circuit. (See
Clock, Electric.}

Clock, Secondary Any clock in a

system of time telegraphy that is controlled
by the master clock. (See Clock, Electric.}

Clock, Self-Winding A clock that

at regular intervals is automatically wound by
the action of a small electro-magnetic motor
contained within it.

This motor is usually run by one or more vol-
taic cells, concealed in the case of the clock.

Cloged-Circuit. (See Circuit, Closed)

Closed-Circuit Battery. (See Battery,
Closed-Circuit)

Closed-Circuit, Single-Current, Signal-
ing (See Signaling, Single-Current,

Closed-Circuit^

Clo.]

105

[Coe.

Closed-Circnit Thermostat. (See Ther-
mostat, Closed-Circuit)

Closed-Circuit Voltaic Cell. (See Cell,
Voltaic, Closed-Circuit)

Closed-Circuit Voltmeter. (See Volt-
meter, Closed-Circuit)

Closed-Circuited. Placed in a closed or
completed circuit.

A voltaic battery, or other source, is closed- cir-
cuited when its poles or terminals are electrically
connected with each other.

Closed-Circuited Conductor. (See Con-
ductor, Closed-Circuited)

Closed-Circular Current. (See Current,
Closed- Circular)

Closed-Coil Disc Dynamo-Electric Ma-
chine. (See Machine, Dynamo-Electric,
Closed-Coil Disc)

Closed-Coil Drum Dynamo-Electric Ma-
chine. (See Machine, Dynamo-Electric,
Closed-Coil Drum)

Closed-Coil Dynamo-Electric Machine.
(See Machine, Dynamo-Electric, Closed-
Coil)

Closed-Coil Ring Dynamo-Electric Ma-
chine. (See Machine, Dynamo-Electric,
Closed-Coil Ring)

Closed-Iron-Circuit Transformer. (See
Transformer, Closed-Iron-Circuit)

Closed-Loop Parallel-Circuit. (See Or-
ttu't, Closed-Loop Parallel)

Closed-Magnetic Circuit. (See Circuit,
Closed-Magnetic)

Closed-Magnetic Core. (See Core, Closed-
Magnetic)

Closure. The completion of an electric
circuit.

Cloth Discs, Carbonized, for High Re-
sistances Discs of cloth carbonized by

heating to an exceedingly high temperature
in a vacuum, or out of contact with air.

After carbonization the discs retain their flex-
ibility and elasticity and serve admirably for high
resistances. When piled together and placed in
glass tubes, they form excellent variable resist*
> vrhen subjected to varying pressure.

Club-Footed Magnet. (See Magnet,
Club-Footed)
Clutch, Carbon, of Arc Lamp A

clutch or clamp attached to the rod or other
support of the carbon of an arc lamp, pro-
vided for gripping or holding the carbon.
(See Lamp, Electric Arc)

Clutch Rod. (See Rod, Clutch)

Coating, Metallic A covering or

coating of metal, usually deposited from
solutions of metallic salts by the action of an
electric current . (See Plating, Electro)

Coating of Condenser. A sheet of tin
foil on one side of a Leyden jar or condenser,
directly opposite a similar sheet on the other
side for the purpose of receiving and collecting
the opposite charges. (See Jar, Leyden.
Condenser)

Coatings of Leyden Jar. The sheets of
tin foil or other conductor on the opposite
sides of a Leyden jar or condenser. (See
Jar, Leyden. Condenser)

Code, Cipher A code in which a

number of words or phrases are represented
by single words, or by arbitrary words or syl-
lables.

The message thus received requires the posses-
sion of the key to render it intelligible.

Code,Telegraphic The pre-arranged

signals of any system of telegraphy. (See
Alphabet, Telegraphic. Alphabet, Tele-
graphic, Morse's. Alphabet, Telegraphic,
International Code)

Co-efflcient, Algebraic A number

prefixed to any quantity to indicate how
many times that quantity is to be taken.

The number 3, in the expression 33, is a co-
efficient and indicates that the a, is to be taken
three times, asa4-a4-a = 3a.

Co-efficient, Economic, of a Dynamo-
Electric Machine The ratio between

the electrical energy, or the electrical horse-
power of the current produced by a dynamo,
and the mechanical horse-power expended in
driving the dynamo.

The economic co-efficient is usually called the
efficiency.

Coe.]

106

[Coi.

The efficiency may be the commercial effi.
ciency, which is the useful or available energy in
the external circuit divided by the total mechan-
ical energy; or it may be the electrical efficiency,
which is the available electrical energy divided
by the total electrical energy.

The efficiency of conversion is the total elec-
trical energy developed, divided by the total
mechanical energy applied.

If M, equals the mechanical energy,
W, the useful or available electrical energy,

and
w, the electrical energy absorbed by the

machine, and
m, the stray power, or the power lost in

friction, eddy currents, air friction, etc.
Then, since

The Commercial Efficiency

_ W_. W

~~ "M ~~ W + w -f m"
The Electrical Efficiency
W

The Efficiency of Conversion

^ W + w = W -f w

M W + w -f m'

Co-efficient of Electro-Magnetic Inertia.

(See Inertia, Electro-Magnetic, Co-effi-
cient of.)

Co-efficient of Expansion. (See Expan-
sion, Co-efficient of.)

Co-efficient of Expansion, Linear --

(See Expansion, Linear, Co-efficient of)

Co-efficient of Magnetic Induction. (See
Induction, Magnetic, Co-efficient of.)

Co-efficient of Magnetization. (See
Magnetization, Co-efficient of.)

Co-efficient of Mutual- Inductance. (See
Inductance, Mutual, Co-efficient of.)

Co-efficient of Mutual-Induction. (See
Induction, Mutual, Co-efficient of)

Co-efficient of Self-induction. (See In-
duction, Self, Co-efficient of)

Coercitive Force. (See Fora, Coerci-
tive)

Coercive Force. (See Force, Coercive)

Coil, Choking -- A coil of wire so

wound on a core of iron as to possess high
self-induction.

Choking-coils are used to obstruct or cut oft an
alternating current with a loss of power less than
with the use of a mere ohmic resistance.

Fig. 141 shows a choking-coil. It consists of
a circular solenoid of insulated wire, wound
on a core of soft iron wire. A thorough divis-
ion of the core is obtained by forming it of coils
of insulated iron wire. In this way, no eddy
currents are produced in the coil. When a simple
periodic electromotive force is applied to the
terminals of such a coil, if
the magnetic permeability
of the coil is constant, a
simple periodic current is
produced, which lags be-
hind the phase of the im-
pressed electromotive force
by a constant angle. If Fig. 14.1. Choking-
the impressed electromo-
tive force is sufficiently great to more than satu-
rate the core, the choking coil ceases to choke
the current. The higher the periodicity the
greater is the choking effect of a given coil, or the
smaller the coil may be made to produce a given
effect.

Since an open-magnetic circuit requires a
greater current to saturate it than a closed-mag-
netic circuit, the complete throttling or choking
power of such a coil is increased by forming its
core of a closed -magnetic circuit, z\ e., of a circuit
in which there is no air space or gap. (See Circuit,
Divided-Magnetic. Circuit, Closed- Magnetic.)

Coil, Electric A convolution of in-
sulated wire through which an electric current
may be passed. (See Magnet, Electro?)

The term coil is usually applied to a number
of turns or to a spool of wire.

Coil, Impedance A term sometimes

applied to a choking-coil. (See Coil, Chok-
ing)

Such a coil has a high self-induction. Its im-
pedance is therefore high. (See Induction, Self.
Impedance. )

Coil, Induction An apparatus con'

sisting of two parallel coils of insulated wire
employed for the production of currents by
mutual induction. (See Induction, Mutual.
Induction, Electro-Dynamic)

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107

[Coi.

A rapidly interrupted battery current, sent
through a coil of wire called the primary coil,
induces alternating currents in a coil of wire called
the secondary coil.

As heretofore made, the primary coil consists of
a few turns of a thick wire, and the secondary
coil of many turns, often thousands, of fine wire.
Such coils are generally called Ruhmkorff coils,
from the name of a celebrated manufacturer of
them.

In the form of Ruhmkorff coil, shown in Fig.
142, the primary wire, wound on a core formed

Fig . 142. Ruhmkorff Coil.

of a bundle of soft iron wires, has its ends brought
out as shown at f, f. The fine wire, forming the
secondary coil, is wrapped around an insulated
cylinder of vulcanite, or glass, surrounding the
primary coil. This wire is very thin, and in some
coils is over one hundred miles in length.

If the core of an induction coil were made solid
it would heat considerably and therefore cause a
loss of energy. The core is therefore laminated,
usually by forming it of a bundle of soft iron wire.

Too great a division of the core, however, is
inadvisable, since, although the eddy currents
therein are thereby avoided, yet, too great a
division of the core acts practically so to
decrease the magnetic permeability that the
greatest efficiency cannot be obtained.

The ends of the secondary coil are connected
to the insulated pillars A and B.

The primary current is rapidly broken by
means of a mercury break, shown at L and M.

The commutator, shown to the right and front
of the base, is provided for the purpose of cutting
off the current through the primary, or for chang-
ing its direction. When a battery which produces
a comparatively large current of but a few volts
electromotive force is connected with the pri-
mary, and its current rapidly interrupted, a
torrent of sparks will pass between A and B,
having an electromotive force of many thousands
of times the number of volts of the primary cur-

rent, but of a correspondingly smaller current
strength.

In such cases, excepting losses during conver.
sion, the energy in the primary current, or C E,
is equal to the energy in the secondary current,
or C' E'. As much therefore as E', the electro-
motive force of the secondary current, exceeds E,
the electromotive force of the primary current,
the current strength C', of the secondary, will ba
less than the current strength C, of the primary.
This is approximately true only, and only in in.
duction coils possessing a closed magnetic circuit.
(See Transformer.')

Fig. 143 shows diagramatically the arrange.

Fig. 143. Circuit Connections of Induction Coil.
ment and connection of the different parts of an
induction coil.

The core II', consists of a bundle of soft iron
wires, each of which is covered with a thin insu-
lating layer of varnish or oxide. A primary wire
P P, consisting of a few turns of comparatively
thick wire, is wound around the core, and a
greater length of thin wire S S, is wound upon the
primary. This is called the secondary. So as
not to confuse the details of the figure it is repre-
sented as a few turns.

The terminals of the battery B, are connected
to the primary wire, through the automatic inter-
rupter, in the manner shown. It will be seen that
the attraction of the core I.I', for the vibrating
armature H, will break contact at the point o, and
cause a continued interruption of the battery
current

The condenser c c', is connected as t>>.own. It
acts to diminish the sparking at the contact points
on breaking contact, and thus, by making the
battery current more sudden, to make its in-
ductive action greater.

The reactions which take place when a simple

Coi.]

108

[Coi.

periodic electromotive force is impressed on the
primary of an induction coil are substantially
thus stated by J. A. Fleming :

(i.) The application of a simple periodic im-
pressed electromotive force produces a simple
periodic current, moving under an effective elec-
tromotive force of self-induction, and brings into
existence a counter-electromotive force of self-
induction, which causes the primary current to
lag behind, by an angle called the angle of lag.

(2.) The field around the primary, and, there-
fore, the induction through the secondary, is in
consonance with the primary current, and the im-
pressed electromotive force in the secondary is
in quadrature with the primary current. (See
Consonance. Quadrature, In.}

(3.) The secondary-impressed electromotive
force gives rise to a secondary current moving
under an effective electromotive force and creat-
ing a counter electromotive force of self-induc-
tion.

(4. ) This secondary current reacts in its turn
on the primary, and creates what is called the
back -electromotive force, or the reacting-induc-
tive-electromotive force of the primary circuit.

(5.) There is then a phase-difference between
the primary and secondary currents, and also be-
tween the primary-impressed electromotive force
and the primary current.

If, as in Fig. 144, two electric circuits are

Fig. 144. Electric and Magnetic Link.

linked with a magnetic circuit, and a small
periodic electromotive force be impressed on the
primary, the following phenomena occur:

(I.) A periodic primary current is set up in
the primary circuit, which, though of the same
periodic time as the impressed electromotive
force, differs from it in phase.

(2.) A wave of counter electromotive force is
produced in the primary circuit by the inductive
action, which does not coincide either with the
impressed electromotive force, nor with the
primary current.

(3.) A wave of magnetization is produced in
the iron core, which lags behind the primary

current by somewhat less than 90 degrees of
phase.

(4.) A wave of impressed electromotive force
is produced in the secondary circuit, due to and
measured by the rate of change of magnetic in-
duction in the core, and lagging 90 degrees, o*
more, behind the magnetization wave.

(5.) A wave of secondary current, lagging be-
hind the secondary electromotive force in phase;
except where the circuit consists of a few turns o!
conductor, or is connected with an external cix -
cuit of practically no inductance. (Fleming.)

Coil, Induction, Inverted An

induction coil in which the primary coil is
made of a long, thin wire, and the secondary
coil of a short, thick wire.

By the use of an inverted coil, a current of high
electromotive force and comparatively small cur-
rent strength, /. t., but of few amperes, is con-
verted or transformed into a current of compar-
atively small electromotive force and large cur-
rent strength. For advantages of this conversion
see Electricity* Distribution of, by Alternating
Currents.

Inverted induction coils are called converters or
transformers. (See Transformer.)

Coil, Induction, Medical An

induction coil used for medical purposes.

A form of induction coil used for medical pur*
poses is shown in Fig. 145.

Fig. 145. Medical Induction Cmt.

Coil, Induction, Microphone Ar

induction coil, in which the variations in the
circuit of the primary are obtained by means
of microphone contacts. (See Microphone^

The carbon -button telephone transmitter is a
microphone in its action, its electric resistance
varying with the varying pressure caused by the
sound waves. The carbon-button is in the prim-
ary circuit of an induction coil, variations in

Coi.]

109

[Coi.

primary of which, under the influence of the
sound waves, produce corresponding variations
in the currents induced in the secondary.

Coil, Kicking A term sometimes

applied to a Choking-Coil. (See Coil, Chok-
ing^

The term kicking-coil has arisen from the fact
that the impedance due to self-induction opposes
the starting or stopping of the current somewhat
in the manner of an opposing kick.

Coil, Magnet A coil of insulated

wire surrounding the core of an electro-mag-
net, and through which the magnetizing cur-
rent is passed. (See Magnet, Electro^)

Coil, Primary - That coil or con-
ductor of an induction coil or transformer,
through which the rapidly interrupted or alter-
nate inducing currents are sent.

In the Ruhmkorff induction coil the primary
coil consists of a comparatively short length of
thick wire, the secondary coil being formed of
a comparatively great length of fine wire. In
the transformer or converter, the primary coil
consists of wire that is longer and thinner than
that in the secondary coil. In other words, the
transformer or converter consists of an inverted
induction coil. (See Coil, Induction. Trans-
former. )

Coil, Reaction A magnetizing coil,

surrounded by a conducting covering or
sheathing, which opposes the passage of
rapidly alternating currents less when directly
over the magnetizing coil than when a short
distance from it.

A term often used for choking-coil. (See
Coil, Choking?)

Coil, Reaction, Balanced A coil

employed in a
system of distri-
bution by means
of transformers
for maintaining
a constant cur-
rent in the sec-
ondary Circuit, Fi S- Z 4(>- Balanced-Reaction Grit.

despite changes in the load placed therein.
A balanced -reaction coil is shown in Fig. 146.

A reaction coil is placed in the circuit of lamps in
series in a constant potential system. The sheath-
ing of this coil is maintained in a balanced position
by the counter weight P, and the spring S. If now
a lamp is extinguished in the circuit, the increase
of current, due to decreased resistance, causes the
sheath to be deflected, and, thus increasing the
self-induction of the coil, reduces the lamp current
to its normal value.

Coil, Resistance A coil of wire

of known electrical resistance employed for
measuring resistance.

In order to avoid self-induction and the mag-
netizing effects of the coils on the needles of the
galvanometer used in electric measurements, as
well as the disturbing effects of self-induction, the
wire of the resistance coil is doubled on itsell
before being wound, and its ends connected
with the brass bars, E, E, Fig. 147. The inser-

Fig. f4J. Connections of Resistance Coils.

tion of the plug -key cuts the coil out of the cir-
cuit by short-circuiting. (See Box, Resistance.
Bridge. Electric. Coil, Resistance, Standard.)

The coils are made of German silver, or plati-
noid, the resistance of which is not much
affected by heat.

Coil, Resistance, Standard A coil

the resistance of which is that of the stand-
ard ohm or some multiple or sub-multiple
thereof.

The standard ohm, as issued by the Electric
Standards Committee of England, has the form
shown in Fig. 148. The coil of wire is formed of
an alloy of platinum and silver, insulated by silk
covering and melted pararfine. Its ends are sol-
dered to thick copper rods, r, r', for ready con-
nection with mercury cups. The coil is at B.
The space above it, at A, is filled with paraffine.
A hole, at t, runs through the coil for the readv

Coi.]

110

[Coi.

insertion of a thermometer. The lower part of
the coil, B, is immersed in water up to the shoul-
der of A, and the water stirred from time to

Fig, 148. Standard Ohm.

time. Since the coil is heated by the current, sue-
cessive observations should be at least ten minutes
apart. Only mild currents should be passed
through the coils.

Coil, Resistance, Standardized

Resistance coils whose resistances have been
carefully determined by comparison with a
standard ohm or other standard coils.

Coil, Ruhmkorff A term some-
times applied to any induction coil, the
secondary of which gives currents of higher
electromotive force than the primary. (See
Coil, Induction?)

Coil, Secondary That coil or con-
ductor of an induction coil or transformer,
in which alternating currents are induced by
the rapidly interrupted or alternating currents
in the primary coil. (See Coil, Induction.
Transformer?)

Coil, Shunt A coil placed in a de-
rived or shunt circuit, (See Circuit, Shunt)

Coil, Spark A coil of insulated wire

connected with the main circuit in a system
of electric gas-lighting, the extra spark pro-

Fig. 149. Spark Coil.

duced on breaking the circuit of which is em-
ployed for electrically igniting gas jets.
Spark coils are employed where the number of

gas jets to be simultaneously lighted is not too
great. When this number exceeds certain limits,
the spark from an induction coil is more advan-
tageously used.

A spark coil is shown in Fig. 149.

Coils, Armature, of Dynamo-Electric

Machine The coils, strips or bars that

are wound or placed on the armature core.

To avoid needless resistance the wire, or other
conductor, of the armature coils, should be as
short and thick as will enable the desired electro-
motive force to be obtained without excessive
speed of rotation.

The armature coils should enclose as many
lines of force as possible (/. e., they should have
as nearly a circular outline as possible). In
drum-armatures, the breadth of the armature is
frequently made nearly equal to its length, unless
other considerations prevent.

When the armature wire consists of rods or
bars, it should be laminated or slit in planes
parallel to the lines of force so as to avoid
eddy currents. Other things being equal, the

Fig. 1^0. Series Connection of Armature Coils.

greater the number of coils, the more uniform
the current generated. The separate coils should
be symmetrically disposed; otherwise irregular in-
duction, and consequent sparking at the commu-
tator results.

The coils of pole-armatures should be wound near
the poles rather than on the middle of the cores.
In order to avoid undue heating, spaces for
air ventilation are not inadvisable. Various con-
nections of the armature coils are used.

In some machines all the coils are connected in
a closed circuit. In some, the coils are independ-
ent of one another, and, either for the entire
revolution, or for part of a revolution, are on an
open-circuit.

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Ill

[Col.

In alternating current dynamos in order to ob-
tain the rapid reversals or alternations of current,
which in some machines are as high as 12,000
per minute, a number of poles of alternate polar-
ity are employed. The separate coils that are
used on the armature may be coupled either in
series or in multiple-arc.

Where a comparatively low electromotive force
is sufficient, such as for incandescent lamps in
multiple-arc, the separate coils are united in
parallel; but for purposes where a considerable
electromotive force is necessary, as for example,
in systems of alternate current distribution, with
converters at considerable distances from the
generating dynamo, they are often connected in
series, as shown in Fig. 150.

Coils, Binding Coils of wire wound

on the outside of the armature coils, and at
right angles thereto, to prevent the loosening
of the armature wires by the action of cen-
trifugal force.

The binding coils are generally made of hard
brass wire.

Coils, Compensating' A term some-
times applied to the series coils placed on a
shunt-wound dynamo.

Coils, Conjugate Two coils so

placed, as regards each other, that an interrup-
tion of the current in one produces no induced
current in the other.

When two coils are conjugate to each other, the
lines of force of one do not pass through the other.
Consequently such coils can produce no induc-
tion in one another.

Coils, Henry's A number of sepa-
rate induction coils so connected that the
currents induced in the secondary wire of
the first coil, are caused to induce currents
in the secondary wire of the second coil, with .
whose primary it is connected in series, and
so on throughout all the coils.

A series of three of Henry's coils is shown in
Fig. 151. An intermittent battery current is sent

secondary, d, of the second coil, is connected with
the primary, e, of the third coil, and the cur-
rents finally induced in f, are employed for any
useful purpose, such as the magnetization of a
bar of iron at g.

The current in b, is sometimes called a Secon-
dary Current, or a Current of the Second Order;
that induced by this secondary current in d, is
called a Tertiary Current^ or a Current of the
Third Order ; that in f, a Current of the Fourth
Order. Henry carried these successive induc-
tions up to currents of the Seventh Order.

Henry's coils in reality consist of separate in-
duction coils, connected, as above explained, in
series.

In Fig. 152, the tertiary current induced in

Fig, I J '2. Tertiary Currents of Coils.
IV, may be employed to give shocks to a person
grasping the handles, e and f.

Coils, Proportional Pairs of re-
sistance coils, generally of 10, 100 and 1,000
ohms each, forming the proportional arms of
the balance or bridge, and employed in the box,
or commercial form of Wheatstone's bridge.
(See Bridge, Electric, Commercial Form
of.}

Cold, Production of, by Electricity

An absorption of energy and consequent
reduction of temperature at a thermo-electric
junction by the passage of an electric current
across such junction in a certain direction.

When an electric current passes across a thermo-
electric junction, the junction is either heated or
cooled. In the case of an antimony-bismuth
couple, if the current passes from the antimony

Fig. Jjr. Henry's Coils.

into a, the secondary, b, of which is connected
with the primary, c, of the second coil. The

A B

Fig. fjf. Freezing of Water by Electricity.

to the bismuth the junction is heated ; if it passes
from the bismuth to the antimony it is cooled.
In the apparatus shown in Fig. 153, the antimony-
bismuth couple is arranged as shown for the

Col.]

112

[Com.

freezing of water by means of the electric cur-
rent. A and B, represent plates of antimony and
bismuth respectively. A small cavity, at E, serves
to hold a drop of water. When a current has
passed in the direction shown by the arrows, a
drop of water, previously cooled to the tempera-
ture of melting ice, is solidified by the lowering
of the temperature at the junction.

Collecting Brushes of Dynamo-Electric
Machine. (See Brushes, Collecting, of
Dynamo-Electric Machine?)

Collectors, Electric Devices em-
ployed for collecting or taking off electricity
from a moving electric source.

Collectors of Electric Frictional Ma-
chines. The metallic points that collect the
charge from the glass plate or cylinder of a
frictional electric machine.

Collectors of Dynamo Electric Machines.
The brushes that rest on the commutator
cylinder, and carry off the current generated
on the rotation of the armature.

Collectors are properly called commutators
when they are employed to cause an alternate
current to become continuous, or to flow in one
and the same direction.

Colloids. One of the two classes into
which substances are separated by dialysis.

By dialysis bodies are separated into crystal-
loids, or bodies capable of crystallizing, and col-
loids or jelly-like bodies, incapable of crystallizing.
Colloids possess great cohesion and but slight
diffusibility. (See Dialysis.)

Colombin. An insulating substance, con-
sisting of a mixture of sulphate of barium
and sulphate of calcium, placed between the
parallel carbons of the Jablochkoff candle.

Column, Barometric A column,

usually of mercury, approximately 30 inches
in vertical height, sustained in a barometer,
or other tube, by the pressure of the atmos-
phere.

The space above the barometric column con-
tains a vacuum known as the Torricellian vac-
uum. (See Vacuum, Torricellian.)

Column, Electric A term formerly

applied to a voltaic pile. (See Pile, Voltaic.}

Colza Oil. (See Oil, Colza.)

Combination Gas Fixtures (See Fix-
tures, Gas, Combination?)

Combined Tangent and Sine Galvanom-
eter. (See Galvanometer, Combined Tan
gent and Sine.)

Comb Lightning Arrester. (See Arrester,
Lightning, Comb.)

Comb Protector. (See Protector, Comb.)

Commercial Efficiency. (See Efficiency,
Commercial?)

Commercial Efficiency of Dynamo.
(See Efficiency, Commercial, of Dynamo?)

Commercial Form of Electric Bridge.
(See Bridge, Electric, Commercial Form of.)

Communicator, Electric A term

formerly employed for a telegraphic key. (See
Key, Telegraphic?)

Commutating Transformers, Distribu-
tion of Electricity by (See Elec-
tricity, Distribution of, by Commutating
Transformers?)

Commutation. The act of commuting, as
of currents.

Commutation, Diameter of In a

dynamo-electric machine a diameter on the
commutator cylinder on one side of which
the differences of potential, produced by the
movement of the coils through the magnetic
field, tend to produce a current in a direction
opposite to those on the other side.

That diameter on the commutator cylinder
of an open-circuited armature that joins the
points of contact of the collecting brushes.

Thus in Fig. 154, the directions of the induced
electromotive forces are indicated by the arrows.
The diameter of commutation is therefore the line
n n'. The term neutral line is also sometimes
given to this line. It lies at right angles to the
line of maximum magnetization m m.

In a closed-circuited armature, that is, in an arm.
ature the coils of which are connected in a closed
circuit, the collecting brushes rest on the commu-
tator cylinder at the neutral line, or on the diame*
ter of commutation.

In an open-circuited armature, however, where
the coils are independent of each other, the
collecting brushes must be set at m m, at right
angles to the neutral line n n. The term diame-

Com.]

113

[Com.

ter of commutation is, therefore, often applied to
this second position. According to this use of the

Fig. 134. Diameter of Commutation.
term, the diameter of commutation is that diameter
on the commutator which joins the points of con-
tact of the collecting brushes.

The neutral linenn', Fig. 154, it will be noticed
does not occupy a vertical position, but is dis-
placed somewhat in the direction of rotation, thus
necessitating the shifting of the brushes forward
in the direction of rotation. This necessary shift-
ing of the brushes is known technically as the
lead of the brushes. (See Lead, Angle of.)

It will thus be seen that the term diameter of
commutation is used in two different senses.

In reality, the term refers to the position of cer-
tain points on the commutator as distinguished
from points on the armature coils. On the com-
mutator, the diameter of commutation is the line
drawn through the two commutator bars at which
the currents from the two sides are opposed to
each other.

It is evident that the commutator may be inten-
tionally twisted with respect to the armature, so
as to bring its diameter of commutation into any
desired convenient position.

Commutation, Dissymmetry of

A commutation in which the neutral line does
not coincide with a diameter of the commu-
tator. (See Commutation, Diameter of.)

Commutator. In general, a device for
changing the direction of an electric current.

Commutator, Burning* at Arcing

and consequent destructive action on the
commutator segments of a dynamo-electric
machine.

When the arcing is pronounced, the intense
heat soon destroys the commutator.
Commutator Cylinder, Neutral-Line of

(See Line, Neutral, of Commutator

Cylinder^

Commutator, Dynamo-Electric Machine
That part of a dynamo-electric ma-
chine which is designed to cause the alter-
nating currents produced in the armature to
flow hi one and the same direction in the ex-
ternal circuit.

One end of an armature coil is connected with
A', Fig. 155, and the
other with A. The brushes
are so set that A, and A',
are in contact with B',
and B, respectively, as .1
long as the current flows
in the same direction in the
armature coil connected
therewith, but enter into
contact with B, and B', Fig. 155. Commutator
when the current changes of Dynamo - Electric
its direction, and continue Machine.
in such contact as long as it flows in this direc-
tion. J3y the use of a commutator the furrent
will therefore flow throttgh any circuit connected
with the brushes in one and tJie same constant
direction.

Two-fart Commutator

In action, the commutator is subject to wear
from the friction of the brushes, and the burning
action of destructive sparks. The commutator

Fig. 1ST- Two-part
Commutator.

Fig. 158. Two-part
Commutator.

segments are, therefore, made of comparatively
thick pieces of metal, insulated from one another

Com.]

114

[Com.

and supported on a commutator cylinder usually
placed on the shaft of the armature.

The ends of the armature coils are connected
to commutator strips or segments.

The number of metallic pieces or segments, A.
and A', on the commutator cylinder depends on
the number, arrangement and connection of the
armature coils, and on the
disposition of the magnetic
field of the machine.

Figs. 156, 157 and 158
show the connections of an
armature coil to the plates of
a two-part commutator.

A four-part commutator
for a ring-armature, and the
connections of the coils
thereto, are shown in Fig. 159.

The commutator strips may either connect the
separate coils in a closed-circuited armature, in
which the coils are all connected with one an-
other, or, in an open-circuited armature, in which
the separate coils are independent of one another.

Commutator, RuhmkorfTs A name

given by Ruhmkorff to a device placed on his
induction coil for the purpose of changing or
reversing the direction of the battery current
through the primary.

This reverser is shown in Fig. 160. (See
Coil, Ruhmkor/.}

Fig. 1 60. Ruhmkorjf's Commutator

Two metallic strips, V, V, supported on a
cylinder of insulating material, are in contact with
the battery terminals A, and D, through Iwo
vertical springs that bear on them. On a half
rotation of the cylinder by the thumb screw L,

the strips V, V, change places as regards the ver-
tical springs, and thus reverse the direction oi
the battery current.

Commuted Currents. (See Currents,
Commuted)

Commuter, Current Any appa-
ratus by means of which electrical currents,
flowing alternately in different directions,
may be caused to flow in one and the same
direction.

A Commutator.

Commuting. Causing to flow in one and
the same direction.

Commuting Currents. (See Currents,
Commuting)

Compartment Manhole of Conduit. (See
Manhole, Compartment, of Conduit)

Compass, Azimuth A compass

used by mariners for measuring the horizon-
tal distance of the sun or stars from the mag-
netic meridian. (See Azimuth, Magnetic)

A mariner's Compass.

A single magnetic needle, or several magnetic
needles, are placed parallel to one another on the
lower surface of a card, called the compass card.
This card is divided into the four cardinal points,
N, S, E and W, and these again subdivided into
thirty-two points called Rhumbs.

In the azimuth compass these divisions are sup-
plemented by a further division into degrees.

A form of azimuth compass is shown in Fig.
l6l. In order to maintain the compass box in a

Fig. 1 6 1. Azimuth Compass.

horizontal position, despite the rolling of the ship,
the box, A B, is suspended in the larger box, P
Q, on two concentric metallic circles, C D, and

Com.

115

[Com,

E F. pivoted on two horizontal axes at right angles
to each other. This kind of support is technic-
ally termed Gimbals. Sights G, H, are provided
for measuring the magnetic azimuth of any ob-
ject.

Compass, Boxing the Naming,

Consecutively, all the different points or
rhumbs of the compass from any one of them.
(See Compass, Points of.)

Compass-Card. (See Card, Compass)

Compass, Inclination A magnetic

needle moving freely in a single vertical plane,
and employed for determining the angle of
dip at any place.

An Inclinometer. (See Inclinometer^
A dipping circle. (See Circle, Dipping)
The needle M, Fig. 162, is supported on knife

Fig. 162. Inclination Cbmpast.

tdges so as to be free to move only in the vertical
plane of the graduated vertical circle C C. This
circle is movable over the horizontal graduated
circle H H. In order to determine the true angle
of dip, the vertical plane in which the needle is
free to move must be placed exactly in the plane
of the magnetic meridian.

To ascertain this plane the vertical circle is
moved until the needle points vertically down-
wards. It is then in a plane 90 degrees from the
magnetic meridian. The vertical circle is then
moved over the horizontal circle 90 degrees, in
which position it is in the plane of the magnetic
meridian, when the true angle of the dip is read off.

For an explanation of the reason of thib see

Component^ Horizontal and Vertical, of tht
Earth's Magnetism.

Compass, Mariner's A name often

applied to an azimuth compass. (See Com-
fass, Azimuth?)

Compass, Points of The thirty-two

points into which a compass card is divided.

Sixteen of these points are shown in Fig. 163.

Fig. 163. Points of Compass.

The position of the remaining points will be
readfly seen by an inspection of the figures.
These points are as follows:

1. North. 17. South.

2. N. by E. 18. S. by W.

3. N. N. E. 19. S. S. W.

4. N. E. by N. 20. S. W. by S.

5. N. E. 21. S. W.

6. N. E. by E. 22. S. W. by W.

7. E. N. E. 23. W. S. W.
& E. by N. 24. W. by S.
9. East. 25. West.

10. E. by S. 26. W. by N.

11. E. S. E. 27. W. N. W.

12. S. E. by E. 28. N. W. by W.

13. S. E. 29. N. W.

14. S. E. by S 30. N. W. by N.

15. S. S. E. 31. N. N. W.

16. S. byE. 32. N.byW.

Boxing the Compass consists in naming aD
these points consecutively from any one of them.

The direction in which the ship is sailing is de.
termined by means of a point fixed on the inside ol
the compass box, directly in the line of the ves-
sel's bow.

Compass, Rhumbs of The points
of a mariner*3 compass. (See Compass
Points <?/.)

Com.]

116

[Com.

Compensated Alternator. (See Alter-
nator, Compensated)
Compensated Excitation of Alternator.

(See Alternator, Compensated Excita-
tion of.)

Compensating Coils. (See Coils, Com-
pensating)

Compensating Magnet (See Magnet.
Compensating)

Complement of Angle. (See Angle, Com-
plement of.)

Completed-Circuit (See Circuit, Com-
pleted.)

Component. One of the two or more sep-
arate forces into which any single force may
be resolved ; or. conversely, the separate forces
which together produce any single resulting
force.

When two or more forces'act simultaneously to
produce motion in a body, the -body will move

,'D

Fig. 164. Composition of Forcet.

with a given force in a single direction called the
resultant. The separate forces, or directions of
motion, are called the components*

Two forces acting simultaneously on a body at
A, Fig. 164, tending to move it in the direction

B E

Fig.tbf. Rttfluiion o/Fortts.

of the arrows, along A B, and A C, with Intensl-
tiesproportioned to the lengths of the lines A B,
and A C, respectively, wfll move It in the dlrec-
tion A D, obtained by drawing B D, and D C,

parallel to A C, and A B, respectively, and then
drawing A D, through the point of intersection,
D. This is called the Composition of Forces.
A D, is the resultant force, and A B and A C,
are its components.

Conversely, a single force, acting in the direc.
tion of D B, Fig. 165, against a surface, B C,
may be regarded as the resultant of the two sep-
arate forces, D E, and D C, one parallel to C B,
and one perpendicular to it. D E, being parallel
to C B, produces no pressure, and the absolute
effect of the force will, therefore, be represented
by CD.

This separation of a single force into two or
more separate forces is called the resolution of
forces, the force, D B, being resolved into the
components, D E and D C.

Component Currents. (See Currents,
Component)

Component, Horizontal, of Earth's Mag-
netism That portion of the earth's

directive force which acts in a horizontal di-
rection.

That portion of the earth's magnetic force
which acts to produce, motion in a com-
pass needle free to move in a horizontal plane
only.

Let A B, Fig. 166, represent the direction and
magnitude of the earth's magnetic field on a mag-
netic needle. . The magnetic force will lie in the
plane of the magnetic merid-
ian, which will be assumed to
be the plane of the paper C A
D. The earth's field, A B, can
be resolved into two compo-
nents, A D, the horizontal com-
ponent, and A C, the vertical
component

In the case of a magnetic
needle, like the ordinary com-
pass needle, which is free to
move in ahorizontal plane only,
the horizontal component alone
directs the needle. A weight
is applied to balance the vertical Magnetism .
component.

When the needle Is free to move in a vertical
plane, and this plane corresponds with that of
the magnetic meridian, the entire magnetic force,
A B, acts to place the needle, supposed to be
properly balanced, in the direction of the lines of
force of the earth's magnetic field at that point.

Com.]

117

[Con.

Component, Tertical, of Earth's Magnet-

ism -- That portion of the earth's
directive force which acts in a vertical direc-
tion.

In the vertical plane at right angles to the plane
of the magnetic meridian, the vertical component
alone acts, and the needle points vertically down-
wards, in no matter what part of the earth it
may be. In Fig. 166, A C, is the vertical com-
ponent of the earth's directive force.

Composite Balance. (See Balance. Com-

Composite-Field Dynamo. (See Dynamo.
Composite-Field)

Composition of Forces. (See Forces,

Composition 0f.)

Compound Arc. (See Arc, Compoztnd^
Compound, Binary -- In chemistry,

a compound formed by the union of two

different elements.

Water is a binary compound, being formed by
the union of two atoms of hydrogen with one
atom of oxygen. Its composition is expressed in
themical symbols, H 2 O, which indicates that two
atoms of hydrogen are combined, or chemically
united, with one atom of oxygen. Water is
therefore a binary compound, because it is formed
of two different elementary substances.

Compound, Chatterton's -- A com-
pound for cementing together the alternate
coatings of gutta-percha employed on a cable
conductor, or for filling up the space between
the strand conductors.

The composition of Chatterton's compound is
as follows:

Stockholm tar ........ I part by weight.

Resin ............... I " "

Gutta-percha ......... 3 "' "

(Clark & Sabine.)

Compound Circuit. (See Circuit, Com-
pound^

Compound, Clark's -- A compound
for the outer casing of the sheathing of sub-
marine cables.

The composition of Clark's compound is as fol-
lows:

Mineral pitch 65 parts by weight.

Silica 4.30 '

Tar 5

(Clark S> Sabine.)

Compound - Horseshoe Magnet. (See
Magnet, Compound-Horseshoe)

Compound Magnet. (See Magnet, Com-
pound?)

Compound Radical. (See Radical, Com-
pound?}

Compound- Winding of Dynamo-Electric
Machines. (See Winding, Compound, ef
Dynamo- Electric Machine?)

Compound-Wound Dynamo-Electric Ma-
chine. (See Machine, Dynamo-Electric,
Compound- Wound?)

Compound-Wound Motor. (See Motor,
Compound- Wound.)

Concentration of Lines of Force. (See

Force, Lines of, Concentration of.)
Concentric Carbon Electrodes. (See

Electrodes, Concentric Carbon.)
Concentric Cylindrical Carbons. (See

Carbons, Concentric Cylindrical)

Condenser. A device for increasing the
Capacity of an insulated conductor by bring-
ing it near another insulated earth-connected
conductor, but separated therefrom by any
medium that will readily permit induction to
take place through its mass.

A variety of electrostatic accumulator.

If the conductor A, Fig. 167, standing alone

Fig: r67. &pirtus Air Condenser.
and separated from other conductors, be con-
nected with an electric machine, it will receive
only a very small charge.

Con.]

118

[Con.

If, however, it be placed near C, but separated
from it by a dielectric, such as a plate of glass
B, and C, be connected with the ground, A, will
receive a much greater charge. (See Dielectric.')

Suppose, for example, that A, be connected
with the positive conductor of a frictional electric
machine, it will by induction establish a negative
charge on the surface C, nearest it, and repel
a positive charge to the earth. The presence of
these two opposite charges on the opposed sur-
faces of A and C, permits A, to receive a fresh
charge from the machine. (See Induction,
Electrostatic. )

The charge in a condenser in reality resides
on the opposite surfaces of the glass, or other
dielectric separating the metallic coatings, as can
be shown by removing the coatings after charg-
ing.

The condenser resulted from the discovery of
the Leyden jar. (See Jar^ Ley/den.}

The capacity of a condenser is measured in
microfarads. (See Farad.}

In practice condensers are made of sheets of
tin foil, connected to A and B, respectively, and
separated from one another by sheets of oiled
silk, paraffined paper, or thin plates of mica, as
shown in Fig. 168.

Fig. rb8. Condenser.

A Leyden jar or condenser does not store elec-
tricity any more than a storage battery does.
The same quantity of electricity passes out of the
opposite coating of the jar that is passed into the
other coating. The jar, therefore, possesses no
store of electricity. What it really possesses is a
store of electrical energy.

According to Ayrton, if the capacity of a con-
denser,' in farads, be F, and the difference of po-
tential, with which it is charged, be V, volts, the
store of electric energy it possesses, or the work it
can do when discharged, is,

In order to obtain a comparatively wide range
of adjustability, a condenser is composed of say
four separate sections: consisting of one of 2
microfarads, one of I microfarad and two of }
microfarad, thus making in all 4 microfarads.

Condenser, JEpinus A name given

to an early form of condenser. (See Con-
denser?)

Condenser, Air A condenser in

which layers of air act as the dielectric.

A form of air condenser is shown in Fig. 169.

Work

2.712

foot-pounds.

Condenser, Adjustable A con-
denser, the plates of which can be readily
adjusted so as to obtain the same capacity
as that of the conductor to be measured.

Fig. 769. Air Condenser.

It consists essentially of one set of thin plates of
glass partially coated on both sides with sheets of
tin foil, so as to leave uncoated a space of about
one inch around the edge of the glass. The glass
plates do not act as dielectrics, but merely as sup.
ports for the tin foil, hence the foil on both sides
of the plates is connected electrically.

Another set of plates alternating with the above
have the tin foil placed over the whole surface of
the glass.

These plates are placed, alternately, over one
another on a stand between guide rods of vuIcan-
ite E, E, E, E, in the manner shown, and are
separated from one another by fragments of glass
of the same thickness. The plates with the foil
over their entire surface are all connected to-'
gether and to the terminal B, to form the outer
coating, and the plates with the foil over nearly
all their surfaces are all connected together and
to the terminal A, to form the inner coating oi
the condenser.

There is thus formed a condenser in which
practically two extended conducting surfaces an

Con.]

119

[Con.

separated from each other by a thin layer of air,
which acts as the dielectric.

Condenser, Alternating-Current --
A condenser suitable for use in connection with
a system for the distribution of electric energy
by means of alternating currents.

Alternating-current condensers must have a very
thin dielectric in order to avoid too great bulk.
This, of course, introduces a difficulty as regards
liability of failure of insulation, which must be
carefully avoided.

Condenser, Armature of -- (See Arm-
ature of a Condenser?)

Condenser, Capacity of ---- The quan-
tity of electricity in coulombs a condenser is
capable of holding before its potential in volts
is raised a given amount.

The ratio between the quantity of electric-
ity in coulombs on one coating and the poten-
tial difference in volts between the two coat-
ings. (Ayrton.)

The capacity is directly proportional to the
charge Q, and inversely proportional to the po-
tential V, or,

or, since Q = K V, the quantity of electricity re-
quired to charge a condenser to a given potential
is equal to the capacity of the condenser multi-
plied by the potential through which it is carried.

The capacity of a condenser increases in direct
proportion to the increase in the area of its coat-
ings.

When the Coatings are plane and parallel to
each other, the capacity of the condenser is in the
inverse ratio to the distance between the coatings.

Condenser, Coating of -- (See Coat-
ing of Condenser.}

Condenser, Plate - -A condenser, the
metallic coatings of which are placed on
suitably supported plates.

Condenser, Poles of - - (See Poles of
Condenser.}

Condenser, Time-Constant of --
The time in which the charge of a condenser
falls to the 1-2.71828 part of its original
value.

Condensers, Distribution of Electricity
by Means of -- .(See Electricity. Distrt

button of. by Alternating Currents, by means
of Condensers . Electricity, Distribution of,
by Continuous Currents, by means of Con-
densers!)

Conduct. To pass electricity through con-
ducting substances.

To determine the general direction in which
electricity shall pass through the ether or
dielectric surrounding the so-called conduct-
ing substance. (See Conduction, Electric.)

Conductance. A word sometimes used in
place of conducting power.
Conductivity.

Conductance, Magnetic A word

sometimes used instead of magnetic permea-
bility. (See Permeability Magnetic.)

The magnetic conductance is equal to the total
induction through the circuit divided by the
magnetizing force.

Conducting Cord. (See Cord, Conduct-
ing.)

Conducting, Electrical Possessing

the power of passing electricity through any
conducting substance.

Possessing the power of determining the
direction in which electricity shall pass through
the ether surrounding a substance. (See
Conductor.)

Conducting Power. (See Power. Con-
ducting.)

Conducting Power for Electricity. (Se*

Power, Conducting, for Electricity.)

Conducting Power for Lines of Mag
netic Force. (See Force, Magnetic, Lines
of. Conducting Power of.)

Conducting Power, Tables of

(See Power, Conducting, Tables of.)

Conduction Current. (See Current, Con-
duction^

Conduction, Disruptive A species

of conduction in which the resistance of ?*
conductor is suddenly overcome.

Disruptive conduction is seen in the disruptive
discharge of a condenser, or Leyden jar.

Conduction, Electric The so

Con.]

120

[Con.

called flow or passage of electricity through
a metallic or other similarly acting substance.

The ability of a substance to determine the
direction in which electric energy shall be
transmitted through the ether surrounding it.

The ability of a substance to determine the
direction in which a current of electricity
passes from one point to another.

When a conducting wire has its ends connected
with an electric source, a current of electricity is,
in common language, said to flow through the wire,
and this was formerly believed to be a correct
statement. According to modern views, however,
the electric energy is believed to pass through the
ether or other dielectric surrounding the con-
ductor, the so-called conductor forming merely
a sink, where the electrical energy dissipates
itself. The conductor simply acts to direct the
current.

Since, however, the energy practically passes
by means of, and in the general direction of the
conductor, there is no objection in speaking of
the electricity as flowing through the conductor.

Conduction, Electric, Disruptive

A conduction of electric energy which ac-
companies a disruptive discharge. (See
Discharge, Dismpti've^

Conduction, Electric, Metallic A

conducting of electric energy of the same char-
acter as that which occurs in metallic sub-
stances.

Conduction, Electrolytic A terra

sometimes employed to indicate the passage
of electricity through an electrolyte.

There is no passage of electricity through an
electrolyte in the same sense as through an ordi-
nary conductor.

When, through electrolysis, an electromotive
force is brought to bear on a molecule of say
HC1, it is assumed by some that the liberated
hydrogen atoms travel on the whole in one di-
rection, and the liberated chlorine atoms in the
opposite direction. The atoms thus moving
through the liquid may by their electric charges
be assumed to convey electricity, and this fact
has given rise to the term electrolytic conduc-
tion.

In electrolytic conduction the charges are
necessarily equal, but the speeds of their motion
are unequal. In a given liquid, each atom has

its own rate of motion, no matter with what it
has been combined. Hydrogen travels faster
than any other kind of atom. The conductivity
of a liquid depends on the sum of the speeds with
which the two opposed atoms travel.

This assumed double stream of oppositely mov-
ing atoms is denied by most physicists. (See
Hypothesis , Grot t hits.)

Cond uctive-Discharge. (See Discharge.
Conductive^

Conductivity, Electric The recip-
rocal of electric resistance.

Since the conductivity is greater the less the re-
sistance, the conductivity will be equal to the recip.
rocal of the resistance, and may be so defined. The

conductivity is therefore equal to B

Conductivity, Equivalent A con-
ductivity equal to the sum of several conduc-
tivities.

Conductivity per Unit of Mass. The re-
ciprocal of the resistance of a substance per
unit of mass.

Conductivity per Unit of Volume. The
reciprocal of the resistance of a substance
per cubic centimetre or per cubic inch.

The resistance is measured from one face of
the cube to the opposite face.

Conductivity Resistance. (See Resist-
ance, Conductivity?)

Conductivity, Specific The par-
ticular conductivity of a substance for elec-
tricity.

The specific or particular resistance of a
given length and unit of cross-section of a
substance as compared with the same length
and area of cross-section of some standard
substance.

Conductivity, Specific Magnetic

The specific or particular permeability of a
substance to lines of magnetic force.

The specific magnetic conductivity is measured
by the ratio of the magnetization produced to tke
magnetizing force which produces it.

The specific magnetic conductivity is the an-
alogue of specific inductive capacity, or conduc-
tivity for lines of electrostatic force. It is also th
analogue for specific conducting power for heat*

Con.]

121

[Con.

Conductor. A substance which will per-
mit the so-called passage of an electric current.

A substance which possesses the ability of
determining the direction in which electricity
shall pass through the ether or other dielec-
tric surrounding it.

Some electrolytes, such, for example, as vari-
ous mixtures of sulphuric acid and water, possess
a true power of conducting electricity, and there-
fore have a specific resistance. Generally, how-
ever, the passage of the electrolyzing current is
regarded as different from that of a current which
merely heats the conductor.

The space or region around a conductor
through which an electric current is passing has
a magnetic field produced in it.

The term conductor is opposed to non-conductor,
or a substance which will not permit the passage
of an electric current through it after the manner
of a conductor.

The terms conductors and non-conductors are
only relative. There are no such things as
either perfect conductors or perfect non-con-
ductors.

Conductors in general, are distinguished from
electrolytes, in that the latter do not allow the
electricity to pass save by undergoing a chemical
decomposition.

Conductor, Anisotropic A con-
ductor which, though homogeneous in struc-
ture like crystalline bodies, has different
physical properties in different directions, just
as crystals have different properties in the
direction of their different crystalline axes.

Anisotropic conductors possess different powers
of electric conduction in different directions.
But in opposite directions along the same axis their
conductivity is equal. They differ in this respect
from isotropic conductors. (See Conductor, Iso-
tropic.)

Conductor, Anti-Induction A con-
ductor so constructed as to avoid injurious
inductive effects from neighboring telegraphic
or electric light and power circuits.

Such anti-induction conductors sometimes con-
sist of a conductor for constant currents and a
metallic shield surrounding the conductor, and
designed to prevent induction from taking place
in the wire itself.

The anti-induction conductor generally con-

sists of twin conductors surrounded by ordinary
insulation and sometimes enclosed by some form
of metallic shield, in order to prevent the action
of electrostatic induction.

When a periodic current is to be transmitted
through a conductor, the most effective way of
annulling its inductive effects on neighboring cir-
cuits is to place the lead of the conductor in the
axis of another conductor, used as a return. In
other words, to employ concentric cylinders, in-
sulated from one another and from the earth.
Under these conditions, calling the current in one
direction positive, and in the other direction
negative, the shielding action will be perfect
when the algebraic sum of the currents in the
core and sheath are zero.

The same effect is obtained in metallic circuits,
by placing the leads parallel to the return, and
crossing and recrossing the wires repeatedly.
(See Connection, Telephonic Cross.)

Elihu Thomson renders ordinary telephone
conductors, arranged as single lines with earth
returns, free from induction by means of the
counter-electromotive force produced in a coil of
wire by the disturbing cause.

In applying this system to the case of an elec-
tric arc or power line passing alongside a tele-
phone line, a wire coil, whose turns are pro-
portioned in number to the induction to be bal-
anced, is introduced into the electric light line
and placed near another coil of finer wire inserted
as a loop in the telephone circuit. The second coil
is placed parallel to or inclined at an angle to the
first coil. In practice, the second coil is inclined
until the counter-induction set up in the tele-
phone wire is equal to that produced in the main
line, and silence is thus produced, so far as in-
duction is concerned, in the telephone.

Conductor, Armored A conduc-
tor provided with a covering or sheathing of
metal placed over the insulating covering for
protection from abrasion or external wear.

Armored conductors are used in situations
where the conductor is exposed to abrasion or
other external wear.

Conductor, Branch A conductor

placed in a shunt circuit. (See Circuit,
Shunt.)

Conductor, Closed-Circuited A

conductor connected as a closed or com-
pleted circuit.

Con.]

122

[Con.

Conductor, Conjugate In a system

of linear conductors, any pair of conductors
that are so placed as regards each other that
a variation of the resistance or the electro-
motive force in the one causes no variation in
the current of the other.

Conductor, Earth-Circuited A

conductor connected to the ground, or to an
earth-connected circuit.

Conductor, House-Service A term

employed in a system of multiple incan-
descent lamp distribution for that portion of
the circuit which is included between the ser-
vice cut-out and the centre or centres of dis-
tribution, or between this cut-out and one or
more points on house mains.

Conductor, Isotropic A conduc-
tor which possesses the same powers of elec-
tric conduction in all directions.

An electrically homogeneous conducting
medium.

Conductor, Leakage A conductor

placed on a telegraph circuit for the purpose
of preventing the disturbing effects of leakage
into a neighboring line by providing a direct
path for such leakage to the earth.

The leakage conductor, as devised by Varley
consists of a thick wire attached to the telegraph
pole. The lower end of the conductor is grounded,
and its upper end projects above the top of the
pole.

There exists some doubt in the minds of expe-
rienced telegraph engineers whether it is well to
apply leakage conductors to telegraphic or tele-
phonic lines of over 12 or 15 miles in length,
since such conductors greatly increase the electro-
static capacity of the line, and thus cause serious
retardation.

Conductor, Lightning A term

sometimes used for a lightning rod. (See
Rod, Lightning?)

Conductor, Open-Circuited A con-
ductor arranged as an open or broken circuit.

Conductor, Potential of The rela-
tion existing between the quantity of elec-
tricity in a conductor and its capacity.

A given quantity of electricity will raise the

potential of a conductor higher in proportion as
the capacity of the conductor becomes less.

Conductor, Potential of, Methods of

Tarying The potential of a conductor

may be varied in the following ways :

(I.) By varying its electric charge.

(2.) By varying its size or shape without alter-
ing its charge.

(3.) By varying its position as regards neigh-
boring bodies.

This resembles the case of a gas whose tension
or pressure may be varied as follows, viz. :

(I.) By varying the quantity of gas.

(z.) By varying the size of the gas holder in
which it is kept, and

(3.) By varying the temperature.

Difference of potential, therefore, correspondsr-

(I.) With difference of level in liquids.

(2. ) With difference of pressure in gases.

(3.) With difference of temperature in heat.
(Ayrton,)

Conductor, Prime The positive

conductor of a frictional electric or electro-
static machine. (See Machine, Frictional
Electric?)

Conductor, To Short-Circuit a

To shunt a conductor with a circuit of com-
paratively small resistance.

Conductor, Underground An elec-
tric conductor placed underground by actual
burial or by passing it through underground
conduits or subways.

Underground conductors, though less unsightly
than the ordinary aerial conductors, require to
be laid with unusual care to render them equally
safe, since, when contacts do occur, all the wires
in the same conduit are apt to be simultaneously
affected, thus spreading the danger in many dif-
ferent directions. They are, however, less liable to
dangers arising from occasional accidental crosses
or contacts.

Conductors, Service Conductors

employed in systems of incandescent lighting
connected to the street mains and to the
electric apparatus placed in the separate
buildings or areas to be lighted.

Conduit, Cement-Lined A cable

conduit, the separate ducts of which are sur-
rounded by any suitable cement.

Con.]

123

[Con.

Conduit, Handhole of (See Hand-
hole of Conduit)

Conduit, Manhole of (See Man-
hole of Conduit?)

Conduit, Multiple A conduit

formed of concrete or other insulating mate-
rial, and furnished with a number of separate
ducts.

Conduit, Open-Box A conduit

consisting of an open box of wood placed in
a trench and closed with a wooden cover
after the introduction of the cable.

Cables or wires may be drawn through such
conduits in the usual manner.

Conduit, Rodding a Introducing a

wire or rope into the duct of a closed conduit
preparatory to drawing the cable through.

Various methods are in use for rodding a con-
duit One much followed consists in using sec-
tions of gas pipe, the ends of which are furnished
with screw threads.

The sections are about four feet in length. One
section is pushed into the duct at one manhole
and the successive sections are introduced into
the duct and screwed onto the section in the duct
and pushed through until a sufficient length is
obtained to reach the next manhole, a rope or
cable is then pulled through from one manhole to
the next.

Conduit, Underground Electric

An underground passageway or space for
the reception of electric wires or cables. (See
Subway, Electric?)

Congelation. The act of freezing, or the
change of a liquid into a solid on loss of heat,
or change of pressure.

Conjugate Coils. (See Coils, Conjugate)

Connect. To place or bring into electric
contact.

Connecting. Placing or bringing into elec-
tric contact.

Connection for Intensity. Connection in
series. (See Connection, Series)

This term is now nearly obsolete.

Connection for Quantity. Connection in
multiple. (See Connection, Multiple)

This term is now nearly obsolete.
5 Vol. 1

Connection, Mercurial A form

of readily adjustable connection obtained by
providing the poles of one piece of electric
apparatus with cups or 'cavities filled with
mercury, into which the terminals of another
piece of apparatus are dipped in order to
place the two in circuit with each other.

This form of connection is used particularly
when a very perfect contact or one free from
friction is desired.

Connection, Multiple Such a con-
nection of a number of separate electric
sources, or electro-receptive devices, or circuits,
that all the positive terminals are connected
to one main or positive conductor, and all the
negative terminals are connected to one main
or negative conductor.

In the multiple connection of a number of
electro-receptive devices, when the devices are
connected as above described to positive and
negative leads that are maintained at a constant
difference of potential, the current passes through
the devices from one lead to the other by branch-
ing and flowing through as many separate cir-
cuits as there are separate receptive devices,
and the opening or closing of one of these cir-
cuits does not affect the others. (See Circuits,
Varieties of. )

Connection, Multiple-Series Such

a connection of a number of separate electric
sources, or separate electro-receptive de-
vices, or circuits, that the sources or devices
are connected in a number of separate groups
in series, and each of these groups connected
to main positive and negative conductors or
leads in multiple arc. (See Circuits, Varie-
ties of)

Connection of Battery for Quantity.
(See Battery, Connection of , for Quantity)

Connection of Electric Sources in Cas-
cade. (See Cascade, Connection of Electric
Sources in)

Connection of Toltaic Cells for Inten-
sity. (See Intensity, Connection of Voltaic.
Cells for)

Connection, Series The connec-
tion of a number of separate electric
sources, or electro-receptive devices, or cir-

Con.]

124

[Con.

cuits, so that the current passes successively
from the first to the last in the circuit. (See
Circuits, Varieties of.}

Connection, Series-Multiple Such

a connection of a number of separate electro-
receptive devices, that the devices are placed
in multiple groups or circuits, and these
separate groups connected with one another
in series.

Connection, Telephonic Cross

A device employed in systems of telephonic
communication for the purpose of lessening
the bad effects of induction, in which equal
lengths of adjacent parallel wires are alter-
nately crossed so as to alternately occupy the
opposite sides of the circuit.

Connector. A device for readily con-
necting or joining the ends of two or more
wires. (See Post, Binding?)

Connector, Double
A form of bind-
ing screw suitable for
readily connecting two
wires together.

A form of double con-
nector is shown in Fig.
170.

Conning Tower.
(See Tower, Conning.)

Consequent Points. (See Points, Conse-
quent)

Consequent Poles. (See Poles, Conse-
quent)

Conservation of Energy. (See Energy,
Conservation of)

Consonance, "In Consonance." A term
employed to express the fact that one simple
periodic quantity, /. e., a wave or vibration,
agrees in phase with another.

Constant. That which remains invariable.
Constant-Current. (See Current, Con-
stant)

Constant-Current Circuit. (See Circuit,
Constant Current)

Constant-Current, Distribution of Elec*
trieity by (See Electricity, Distri-
bution of, by Constant Currents)

Fig. i TO. Double
Connector.

Constant, Dielectric A term some-
times employed in place of specific inductive
capacity. (See Capacity, Specific Inductive)

Constant, Galvanometer The

numerical factor connecting the current pass-
ing through a galvanometer with the deflec-
tion produced by such current.

Sometimes a distinction is made between the
galvanometer constant and the reduction factor,
the former being used to indicate the relation
between the current and the geometrical constant
of the galvanometer, while the latter is used in
the sense just defined of galvanometer constant.

Constant Inductance. (See Inductance,
Constant)

Constant Potential. (See Potential,
Constant)

Constant-Potential Circuit. (See Cir-
cuit, Constant-Potential)

Constant, Time, of Electro-Magnet

The time required for the magnetizing

current to rise to the of its final value.

Contact-Breaker, Automatic A

device for causing an electric current to
rapidly make and break its own circuit.

The spring c, Fig. 171, carries an armature of
soft iron, B, and is
placed in a circuit in
such a manner that
the circuit is closed
when platinum con-
tacts placed on the
ends of D and B,
touch each other. In
this case the arma-
ture, B, is attracted to
the core A, of the
electro-magnet, thus
breaking the circuit
and causing the magnet to lose its magnetism.
The elasticity of the spring C, causes it to fly back
and again close the contacts, thus again energiz-
ing the electro-magnet and again attracting B,
and breaking the circuit. The makes and breaks
usually follow each other so rapidly as to produce
a musical note. (See Alarm, Electric)

Contact, Dotting An electric con

Ftg. 17 r. Automatic
Contact Breaker.

Con.]

125

[Con.

tact obtained by the approach of one con-
tact point towards another.

The term dotting contact is used in contradis-
tinction to a rubbing contact. The rubbing
contact is generally to be preferred, since it tends
automatically to remove dust and keep the con-
tact surfaces polished and free from oxides.

Contact Dynamo. (See Dynamo. Con-
tact)

Contact Electricity. (See Electricity,
Contact.}

Contact, Fire- Alarm A contact so

arranged that an alarm is given when any
predetermined temperature is reached.

Fire-alarm contacts are generally operated by
the expansion of a metal or of a conducting fluid,
such as mercury. (See Thermostat.)

Contact Force. (See Force, Contact)

Contact, Fnll-Metallic A contact,

which from its small resistance establishes a
good or complete connection. (See Contact,
Metallic)

Contact, Intermittent The occa-
sional contact of a telegraphic or other line
with other wires or conductors by swing-
ing, or by alternate contraction or expansion
under changes of temperature.

Contact, Metallic A contact of

a metallic conductor produced by its coming
into firm connection with another metallic
conductor.

Contact, Partial A contact of a

telegraphic, or other line, arising from defect-
ive insulation, bad earths, or connection with
an imperfect conductor.

Contact, Rolling -A contact con-
nected with one part of an electric circuit,
that completes the circuit by being rolled over
a conductor connected with and forming
another part of the circuit.

Rolling contacts are employed on electric rail-
roads. (See Railroad, Electric.)

Contact, Rubbing A contact

effected by means of a rubbing motion,

Contact Series. (See Series, Contact!)

Contact, Sliding A contact con-
nected with one part of a circuit that closes

or completes an electric circuit by being slid
over a conductor connected with another
part of the circuit.

Sliding contacts are employed in electric rail-
roads, in rheostats, switches, and a variety of other
apparatus. (See Railroad, Electric. Rheostat.
Key, Discharge.)

Contact, Spring A spring-sup-
ported contact connected with one part of a
circuit that completes said circuit by being
moved so as to touch another contact con-
nected with the other part of the circuit.

The movement required to bring the two con-
tacts together may be non-automatic, as in the case
of a push-button, or automatic, as in the case of
a thermostat (See Button, Push. Thermostat.')

Contact Theory of Yoltaic CelL (See

Cell, Voltaic, Contact Theory of)

Contact, Yibrating A spring con-
tact, connected with one part of a circuit and
so supported as to be able to vibrate towards
and from another contact connected with
another part of the circuit, thus automatically
closing and opening said circuit.

A vibrating contact is used in the automatic
contact-breaker in which the movement of aa
armature towards an electro-magnet is caused to
break the circuit of the coils of the electro-magnet,
and, on its movement away from the magnet, to
close another contact which again completes the
circuit of the electro-magnet. (See Coutect
Breaker, Automatic.)

Contact, Wiping A contact ob-
tained by a wiping movement of one con-
ductor against another.

The spark for electrically igniting a gas jet \s
obtained by means of a wiping contact of a spring
moved by the motion of the pendant. (See
Burner, Plain-Pendant Electric. )

Contacts. A variety of faults occasioned
by the accidental contact of a circuit with any
conducting body.

The word contacts as employed above is in die
sense of accidental contacts as distinguished from
predetermined contacts.

Contacts of an accidental character are of the
following varieties, viz.:

(I.) Full, or metallic, as when the circuit is

Con.]

126

[Con.

Accidentally placed in firm connection with *n-
other metallic circuit.

(2.) Portia/, as by imperfect conductors being
placed across wires, or bad earths, or defective
insulation.

(3.) Intermittent, as by occasional contacts of
swinging wires, etc.

Contacts, Burglar Alarm Con-
tacts fitted to windows, doors, tills, steps,
floors, etc., so that a movement of the parts
from their natural position gives an alarm by
sounding a conveniently located bell.

Contacts, Lamp Metallic plates or

rings connected with the terminals of an incan-
descent lampf or ready connection with the line.

Contacts, Mercurial Electric con-

tacts that are opened or closed by the ex-
pansion or contraction of a mercury column.

In the commonest forms of mercurial con-
tacts, on the expansion of the mercury by heat it
reaches a contact point placed in the tube, and
thus completes the circuit through it own mass.

Or, on contraction it breaks a contact, and thus
disturbing an electric balance, sounds an alarm.

Continental Code Telegraphic Alphabet.
(See Alphabet. Telegraphic, International
Code)

Continuity of Current (See Current,
Continuous.)

Continuous Current (See Current, Con"
tinuous)

Continuous Current, Distribution of
Electricity by (See Electricity, Dis-
tribution of, by Constant Currents)

Continuous Current, Dynamo-Electric
Machine (See Machine, Dynamo-
Electric, Continuous Current)

Continuous-Sounding Electric Bell.
(See Bell, Continuous-Sounding Electric.)

Continuous Wires or Conductors. (See
Wires or Conductors, Continuous)

Contraction, Anodic Closure The

muscular contraction observed on the closing
of a voltaic circuit, the anode of which is placed
over a nerve, and the kathode at some other
part of the body.
This term is generally written A. C. C.

Contraction, Anodic Duration

The length of time the muscle continues in
contraction on the opening or closing of a
circuit, the anode of which is placed over the
part contracted.

This term is generally written A. D. C.

Contraction, Anodic Opening

The muscular contraction observed on the
opening of a voltaic circuit, the anode of which
is placed over a nerve, and the kathode at
some other part of the body.

This term is generally written A. O. C.

When the anode is placed over a nerve and a
weak current is employed, if the circuit be kept
closed for a few minutes, it will be noticed that,
on opening the circuit the contraction will be
much greater than if it had been opened after
being closed for only a few seconds. The effect
of the A. O. C. therefore depends not only on the
current strength, but also on the time during
which the current has passed through the nerve.

Contraction of Lines of Magnetic Force.
(See Force, Magnetic, Contraction of
Lines of)

Contractures. In electro-therapeutics,
prolonged muscular spasms, or tetanus, caused
by the passage of electric currents.

Contraplex Telegraphy. (See Telegra-
phy, Contraplex)

Controlled Clock. (See Clock, Electric)

Controller. A magnet, in the Thomson-
Houston system of automatic regulation,
whose coils are traversed by the main cur-
rent, and by means of which the regulator
magnet is automatically thrown into or out of
the main circuit on changes in the strength
of the current passing. (See Regulation,
Automatic)

Controlling Clock. (See Clock, Electric)

Controlling Magnet (See Magnet, Con-
trolling)

Convection Currents. (See Currtnts.Con-
vection)

Convection, Electric The air par-
ticles, or air streams, which are thrown off
from the pointed ends of a charged, insulated
conductor.

Con.]

[Cop.

Convection streams, like currents flowing
through conductors, act magnetically, and are
themselves acted on by magnets. The same thing
is true of the brush discharge, of the voltaic arc,
and of convective discharges in vacuum tubes.

Convection, Electrolytic A term

proposed by Helmholtz to explain the appa-
rent conduction of electricity by an electro-
lyte, without consequent decomposition.

Helmholtz assumes that the atoms of oxygen or
hydrogen, adhering to the electrodes during elec-
trolysis, are mechanically dislodged and diffused
through the liquid, thus carrying off the elec-
tricity by the charges received while in contact
with the electrodes.

Convection of Heat, Electric (See
Heat, Electric Convection of.)

Convection Streams. (See Streams, Con-
vection^)

Convective Discharge. (See Discharge,
Convective?)

Conversion, Efficiency of, of Dynamo

The total electric energy developed by a
dynamo, divided by the total mechanical
energy required to drive the dynamo. (See
Co-efficient, Economic, of a Dynamo-Electric
Machine?)

The efficiency of conversion

W-f w _ W + w

M~~ ~~ W + w + m,

where W, equals the useful or available electrical
energy, M, the total mechanical energy, w, the
electrical energy absorbed by the machine, and
m, the stray power, or the power lost in friction,
eddy currents, air friction, etc.

Converted Currents. (See Currents,
Converted.)

Converter. The inverted induction coil
employed in systems of distribution by means
of alternating currents.

A term sometimes used instead of trans-
former. (See Transformer?)

Converter, Closed-Iron Circuit

A closed-iron circuit transformer. (See
Transformer, Closed-Iron Circuit.)

Converter, Constant-Current

A constant-current transformer. (See Trans-
former, Constant-Current.)

Converter, Efficiency of The effi-
ciency of a transformer. (See Transformer,
Efficiency of.)

Converter Fuse. (See Fuse, Converter.)

Converter, Hedgehog A form of

transformer. (See Transformer, Hedgehog.)

Converter, Multiple A multiple

transformer. (See Transformer, Multiple.)

Converter, Open-Iron-Circuit An

open-iron-circuit transformer. (See Trans-
former, Open-Iron-Circuit.)

Converter, Series A series trans-
former. (See Transformer, Series.)

Converter, Step-down A step-down

transformer. (See Transformer, Step-down.)

Converter, Step-up A step-up

transformer. (See Transformer, Step-up?)

Converter, Welding A welding

transformer. (See Transformer, IVelding.)

Converting Currents. (See Currents,
Converting.)

Cooling Box of Hydro-Electric Machine.
(See Box, Cooling, of Hydro-Electric
Machine?]

Co-ordinates, Axes of The axes of

abscissas and ordinates.

The two straight lines, usually perpendicular
to each other, to which distances representing
values are referred for the graphic represen-
tation of such values. (See Abscissas, Axes of.)

Copper Bath. (See Bath, Copper?)

Copper Plating. (See Plating, Copper?)

Copper Ribbon. A variety of strap cop-
per. (See Copper, Strap?)

Copper, Strap Copper conductors

in the form of straps or flat bars.

Strap copper is used on the armatures of some
dynamos. Heavy copper conductors for such
purposes are divided into strap copper so as to
avoid eddy currents. The straps are placed
alongside one another and insulated by a coating
of varnish.

Copper Wire, Hard-Drawn (See

Wire, Copper, Hard-Drawn?)

Copper Wire, Soft-Drawn (See

Wire, Copper, Soft-Drawn.)

Cop.]

128

[Cor.

Copper Voltameter. (See Voltameter,
Copper.)

Coppered Plumbago. (See Plumbago,
Coppered.)

Coppering, Electro Electro-plating

with copper. (See Plating, Electro.)

Cord-Adjuster (See Adjuster, Cord.)

Cord, Conducting A small flexible

cable, usually containing several conductors
separated from one another by insulating ma-
terial.

Cord, Electric A flexible, insulated

electric conductor, generally containing at least
two parallel wires.

Electric cords are named from the purposes for
which they are employed, battery cords, dental
cords, lamp cords, motor cords, switch cords, etc.

Fig. 172. Flexible Cord.

A two-conductor flexible cord, in which each
cord is composed of a number of bare copper wires
placed parallel to and in contact with one another,
is shown in Fig. 172. The several separate wires
give flexibility to the cord.

Cord, Pendant A flexible conductor

provided for conveying the current to a hang-
ing electric lamp supported by it,

Cords, Telephone Flexible con-
ductors for use in connection with a tele-
phone.

Fig' '73- Telephone Cards.

Telephone cords, attached to an articulating
telephone, are shown in Fig. 173.

Core, Armature, Filamentous

An armature core, the iron of which consists
of wire.

Core, Armature, H An armature

core in the shape of the letter H, generally
known as the shuttle armature, and some-
times as the girder armature.

This form is also called an I armature.

The H armature core was the form originally
given to the Siemens armature. In this form a
single coil of wire was secured on the cross-bar
of the H armature core, so as to fill up the entire
space inside the letter, and the ends of the wire
connected to a two-part commutator,

Core, Armature, Lamination of

The subdivision of the core of the armature
of a dynamo-electric machine into separate
insulated plates or strips for the purpose of
avoiding eddy or Foucault currents.

This lamination must always be perpendicular
to the direction of the eddy currents that would
^otherwise be produced. (See Currents, Eddy.}

Core, Armature, of Dynamo-Electric

Machine The iron core, on, or around

which, the armature coils of a dynamo-electric
machine are wound or placed.

The armature core is laminated for the pur-
pose of avoiding the formation of eddy or Fou-
cault currents.

In drum, and" in ring-armatures, the laminae
should be in the form of thin insulated discs or
plates of soft iron; in pole-armatures they should
be in the form of bundles of insulated wires.

The iron in the cores should be of such an area
of cross-section, as not to be readily o versa turated.

Core, Armature, Radially-Laminated

An armature core, the iron of which

consists of thin iron washers.

Core, Armature, Ribbed A cylin-
drical armature core provided with longi-
tudinal projections or ribs that serve as
spaced channels or grooves for the reception
of the armature coils.

Core, Armature, Tangentiallj -Laminated

An armature core, the iron of which

consists of a coiled ribbon.

Core, Armature, Ventilation of

Means for passing air through the armature

Cor.]

129

[Con.

cores of dynamo-electric machines in order to
prevent undue accumulation of heat.

A properly proportioned dynamo-armature
may need no ventilation, since in such the
amount of heat generated is small as compared
with the extent of the radiating surface.

Since, however, in practice all armatures tend
to heat at full load, especially in certain installa-
tions in heated situations, ventilation of the ar-
mature is desirable.

Core, Closed-Magnetic A mag-
netic core so shaped as to provide a complete
iron path or circuit for the lines of magnetic
force of its field.

Core, Laminated A core of iron

which has been divided or laminated, in order
to avoid the injurious production of Foucault
or eddy currents.

Core, Lamination of Structural

subdivisions of the cores of magnets, arma-
tures, and pole-pieces of dynamo-electric
machines, electric motors, or similar appa-
ratus, in order to prevent heating and subse-
quent loss of energy from the production of
local, eddy or Foucault currents.

These laminations are obtained by forming the
cores of sheets, rods, plates, or wires of iron in-
sulated from one another.

The cores of dynamo-electric machine arma-
tures should be subdivided in planes at right
angles to the armature coils; or in planes parallel
to the direction of the lines of force and to the
motion of the armature; or, in general, in planes
perpendicular to the currents that would otherwise
be generated in them.

Pole-pieces should be divided in planes per-
pendicular to the direction of the currents in the
armature wires.

Magnet cores should be divided in planes at
right angles to the magnetizing current.

Core of Cable. The conducting wires of
an electric cable. (See Cable, Electric?)

Core, Open-Magnetic Any mag-
netic core so shaped that the lines of magnetic
force of its field complete their circuit partly
through iron and partly through air.

Core Ratio of Cable. (See Cable, Core
Ratio of.)

Core, Ring 1 A hollow, cylindrical

core of short length.

Core, Ring, Elongated A hollow,

cylindrical core of comparatively great length.

Core, Solenoid A core so arranged

as to be drawn into a solenoid on the passage
of the current through its coils, and to be
withdrawn therefrom, on the stopping of the
current by the action of a spring or weight.
(See Solenoid?)

Core, Stranded, of Cable The

conducting wire or core of a cable formed of
a number of separate conductors or wires in-
stead of a single conductor of the same weight
per foot as the combined conductors.

Core Transformer. (See Transformer,

Core.}

Cored Carbons. (See Carbons, Cored.)

Cored Electrodes. (See Electrodes,
Cored.)

Coronae, Auroral A crown-shaped

appearance, sometimes assumed by the auro-
ral light. (See Aurora JBorealis.)

Corposant. A name sometimes given by
sailors to a St. Elmo's Fire. (See Fire, St.
Elmo's.)

Correlation of Energy. (See Energy,
Correlation 0f.)

Corresponding Points. (See Points, Cor-
responding?)

Cosine. One of the trigonometrical func-
tions. (See Trigonometry?)

Cotangent. One of the trigonometrical
functions. (See Trigonometry?)

Coulomb. The unit of electrical quantity.

A definite quantity or amount of the thing
or effect called electricity.

Such a quantity of electricity as would pass
in one second in a circuit whose resistance is
one ohm, under an electromotive force of
one volt.

The quantity of electricity contained in a
condenser of one farad capacity, when sub-
jected to an electromotive force of one volt.

The quantity of electricity that flows per
second past a cross-section of a conductor

Con.]

130

[Coii.

conveying an ampere. (Ayrton.) (See Am-
pere. Farad. Volt.)

Coulomb's Torsion Balance. (See Bal-
ance, Coulomb's Torsion.)

Coulomb-Volt. A Joule, or .7373 foot-
pound.

The term is generally written volt-coulomb.
(See Volt-Coulomb.)

Counter, Electric A device for

counting and registering such quantities as
the number of fares collected, gallons of water
pumped, sheets of paper printed, revolutions
of an engine per second, votes polled, etc.

Various electric devices are employed for this
purpose. They are generally electro-magnetic
in character.

Counter-Electromotive Force. (See
Force, Electromotive, Counter?)

Counter Electromotive Force Lightning
Arrester. (See Arrester, Lightning, Coun-
ter-Electromotive Force.)

Counter-Electromotive Force of Convec-
tive Discharge. (See Force, Electromotive,
Counter, of Connective Discharge?)

Counter-Electromotive Force of Mutual
Induction. (See Force, Electromotive,
Counter, of Mutual Induction?)

Counter-Electromotive Force of Self-in-
duction. (See Force, Electromotive, Coun-
ter, of Self -Induction?)

Counter-Electromotive Force of Self-In-
duction of the Primary. (See Force,
Electromotive, Counter, of Self-Induction of
the Primary?)

Counter-Electromotive Force of Self-In-
duction of the Secondary. (See Force,
Electromotive, Counter, of Self-induction of
the Secondary?)

Counter-Electromotive Force of the
Primary. (See Force, Electromotive,
Counter, of the Primary?)

Counter Inductive Effect. (See Effect,
Counter Inductive?)

Couple. In mechanics, two equal parallel
forces acting in opposite directions but not in
the same line, and tending to cause rotation.

The moment, or effective power of a couple, is

equal to the intensity of one of the forces multiplied
by the perpendicular distance between the direc-
tions of the two forces.

Couple, Astatic Two magnets of

exactly equal strength so placed one over the
other in the same vertical plane as to com-
pletely neutralize each other.

An astatic couple has no directive tendency. A
pair of magnets combined as an astatic couple is
called an astatic needle. (See Needle, Astatic.)

Couple, Magnetic The couple which

tends to turn a magnetic needle, placed in the
earth's field, into the plane of the magnetic
meridian.

If a magnetic needle is in any other position
than in the magnetic meridian, there will be two
parallel and equal forces acting at A and B, Fig.
174, in the directions shown by the arrows.
Their effect will be to ro-
tate the needle until it
comes to rest in the mag-
netic meridian N S.

The total force acting
on either pole of a needle
free to move in any direc-
tion, is equal to the
strength of that pole mul-
tiplied by the total inten-
sity of the earth's field at
that place ; or, if free to move in a horizontal
direction only, is equal to the intensity of the
earth's horizontal component of magnetism at
that place, multiplied by the strength of that pole.

The effective power or moment of a magnetic
couple is equal to the force exerted on one of the
poles multiplied by the perpendicular distance,
P Q, between their directions.

Couple, Moment of The effective

power or force of a couple.

The moment of a couple is equal to the inten-
sity of one of the forces multiplied by the perpen-
dicular distance between the direction of the
forces.

Couple, Thermo-Electric Two dis-
similar metals which, when connected at their
ends only, so as to form a completed electric
circuit, will produce a difference of potential,
and hence an electric current, when one of the
ends is heated more than the other.

Thus if a bar of bismuth be soldered to a bar

Fig. 174. Magnttic
Couple.

Con.]

131

[Cre.

of antimony the combination will form a thermo-
electric couple, and the circuit so formed will
have a current passing through it when one junc-
tion is hotter or colder than the other.

There is, according to Lodge, a true contact
force, at a thermo-electric junction, as is shown by
the reversible heat effects produced when an
electric current is passed across such junction; for,
in one direction more heat is produced, and in the
opposite direction less heat. This, as is well
known, differs from the irreversible heat produced
by a current through a homogeneous metallic
conductor. The reversible heat effects, or as they
are called the Peltier effects, may overpower and
conceal the heating effects. But, in addition to
these effects, since a difference of potential, called
a Thomson effect, exists in a substance unequally
heated, currents are so produced, and these are
also influential in causing the difference of poten-
tial of a thermo-electric couple.

" There are then," says Lodge, " in a simple
circuit of two metals with their junctions at differ-
ent temperatures, altogether four E. M. Fs., one
in each metal, from hot to cold, or vice versa, and
one at each junction, and the current which flows
around such a circuit is propelled by the resultant
of these four." * * * "These four forces,
two Thomson forces in the metals, and two Peltier
forces at their junctions, may some of them help
and some hinder the current. " * * * "When-
ever they help, the locality is to that extent cooled ;
whenever they hinder, it is to that extent
warmed."

The action of a thermo-electric couple in pro-
ducing a difference of potential is therefore a
complicated one, and depends on Peltier and
Thomson effects, as well as on the thermo-electric
effect. (See Effect, Peltier. Effect, Thomson.
Effect, Tkermo-Electric.)

Couple, Yoltaic Two materials,

usually two dissimilar metals, capable of
acting as an electric source when dipped in
an electrolyte, or capable of producing a
difference of electric potential by mere con-
tact.

Liquids and gases are capable of acting as
voltaic couples.

All voltaic cells have two metals, or a metal and
a metalloid, or two gaseous or liquid substances
which are of such a character that, when dipped
into the exciting fluid one only is chemically
acted on.

Each one of these two substances is called an
element of the cell, and the two taken collectively
form a voltaic couple.

The elements of a voltaic couple may consist of
two gases or two liquids. (See Battery, Gas.)

Coupled Cells. (See Cells, Coupled)

Coupler, Yoltaic Any device by

means of which voltaic cells may be readily
coupled or connected in different forms of
circuits. (See Circuits, Varieties of)

Coupling of Voltaic Cells or Other
Electric Sources. A term indicating the
manner in which a number of separate
electric sources may be connected so as to
form a single source. (See Circuits, Varie-
ties of)

Cramp, Telegrapher's An affec-
tion of the hand of a telegrapher due to im-
moderate and excessive use of the same
muscles, somewhat similar to the disease
known as writer's cramp.

Telegrapher's cramp, like writer's cramp, may
be defined as a professional neurosis of co-ordina-
tion. It appears not only in certain groups of
muscles, but is limited to such groups, only when
they are performing certain complicated opera-
tions. For example, telegrapher's cramp is
practically a paralysis of certain muscles of the
hand and wrist of the operator. These muscles,
when called on to perform the somewhat delicate
movements required in sending a telegraphic dis-
patch, are incapable of performing their proper
functions, but when called on to perform in part
other similar actions, provided all these actions
are not required to be used, appear to be un-
affected.

The ability of the operator to send with either
hand would lessen the liability to this disease.

Crater in Positive Carbon. A depression
at the end of the positive carbon of an arc
lamp which appears when a voltaic arc is
formed. (See Arc, Voltaic?)

Creep, Diffusion The flow of an

electric current in portions of a conducting
substance, outside the parts that lie in the
direct lines between the points where the
terminals of the same are applied to the con-
ducting substance.

Oe.J 132

Creeping, Electric A term some-
times applied to the creeping of a current.
(See Current, Creeping of.)

Creeping in Yoltaic Cell. (See Cell, Vol-
taic, Creeping in.)

Creeping of Current. (See Current,
Creeping of, Electric.)

Creeping, Saline The formation

of salts by efflorescence on the walls of a solid
immersed in a solution of a salt.

Creosoting. A process employed for the
preservation of wood, as, for example, tele-
graph poles, by injecting creosote into the
pores of the wood. (See Pole, Telegraphic.)

Crith. A term proposed by A. W. Hoff-
man, as a unit of weight, or the weight of
one litre, or cubic decimetre, of hydrogen at
O^ C. and 760 mm. barometric pressure.

Critical Current. (See Current^ Crit-
ical.)
Critical Current of a Dynamo. (See

Current, Critical, of a Dynamo^

Critical Distance of Lateral Discharge
through Alternative Path. (See Distance,
Critical, of Lateral Discharge through
an Alternative Path.)

Critical Speed of Compound-Wound Dy-
namo. (See Speed, Critical, of Compound-
Wound Dynamo.)

Crookes' Dark Space. (See Space, Dark,
Crookes'.)

Crookes' Electric Radiometer. (See Ra-
diometer, Electric, Crookes'?)

Cross Arm. (See Arm, Cress.)

Cross-Connecting Board. (See Board,
Cross-Connecting?)

Cross, Electric A connection, gen-
erally metallic, accidentally established be-
tween two conducting lines.

A defect in a telegraph, telephone or other
circuit caused by two wires coming into
contact by crossing each other.

A swinging or intermittent cross is caused by
wires, which are too slack, being occasional^
blown into contact by the wind.

[Cro.

A weather cross arises from defective action ot
the insulators in wet weather.

Cross, Swinging or Intermittent

An accidental contact, generally metallic,
caused by wires being brought into occasional
contact with one another, or with some other
conductor, by the intermittent action of the
wind.

Cross, Weather A contact or leak

occurring in a telegraphic or other line dur-
ing wet weather, from the defective action of
the insulators.

Crossing Cleat (See Cleat, Crossing.)

Crossing, Live-Trolley A device

whereby a trolley moving over a line that
crosses a second line at an angle is enabled
to maintain its electrical connection with the
line while crossing.

A live-trolley crossing is necessitated where one
line of electric railway crosses another. The
upper line must, of course, provide a space or
opening for crossing the lower line at the points
of intersection. This is effected in the Bagnall
live-trolley crossing, shown in Fig. 175, by attach -

Fig'175- Livt- Trolley Crossing.
ing to the upper trolley wire a bridge piece of
light lathe casting, provided at its centre with a
gap through which the trolley wire passes. This
bridge piece is insulated from the trolley wire by
means of a disc of insulating material at the cen-
tre of the bridge, which is provided with a hinged
curved lever, that in its normal position rests un-
der the influence of gravity in the position shown
in the figure. The passage of the trolley wheel
along the wire carries the line under it and thus
bridges the gap, as shown by the position of the
dotted lines.

Crossing Wires. (See Wires, Crossing.)

Cross-Over Block. (See Slock, Cross-
Over.)

Cross-Over, Trolley A device by

means of which a trolley is enabled to pass
over the points where different lines cross one
another without serious interruption.

Cro.]

133

[Cur.

A trolley cross-over, for trolley lines, is shown
in Fig. 176.

Fig. 176. Trolley Cross Over.

Crow-foot Zinc. (See Zinc, Crow-foot.')

Crucible, Electric A crucible in

which the heat of the voltaic arc, or of elec-
tric incandescence, is employed either to per-
form difficult fusions, or for the purpose of
effecting the reduction of metals from their
cres or the formation of alloys. (See Fur-
nace, Electric?)

Crystal. A solid body bounded by sym-
metrically disposed plane surfaces.

A definite form or shape is as characteristic of
an inorganic crystalline substance as it is of an
animal or plant. Each substance has a form in
which it generally occurs. There are, however,
certain modifications of the typical forms which
cause plane surfaces to appear curved, and the
eymmetrical airangement of the faces to disap
pear. These modifications often render it ex
tremely difficult to recognize the true typical
fornv

For the different fundamental crystalline forms,
or systems of crystals, see any standard work on
chemistry.

Crystal, Heniihedral A crystal

whose shape or form has been modified by
the replacement of half its edges or solid
angles,

A hemihedral crystal possesses different forms
at the ends or extremities of its axes. Hemi
hedral Crystals, when unequally heated, develop
electrical charges.

Electricity produced in this way was formerly
called pyro-electricity. (See Electricity, Pyro.)

Crystal, Holohedral A crystal

whose shape or form has been modified by
the replacement of all its edges or solid
angles.

Crystalline Electro-Metallurgical De-
posit. (See Deposit. Crystalline. Electro-
Met allurgic al.)

Crystallization. Solidification from a state
of solution or fusion in a definite crystalline
:orm

The crystallization of a dissolved solid is fa-
vored by any cause that gives increased freedom
of movement to its molecules, such for example as
solution, fusion, sublimation, or precipitation,

Crystallization by Electrolytical Decom-
position. The crystalline deposition of vari-
ous metals by the passage of an electric cur-
rent through solutions of their salts under
certain conditions.

A strip of zinc immersed in a solution of sugar
of lead (acetate of lead) soon becomes covered
with bright metallic plates of lead, that are elec-
trolytically deposited by the weak currents due to
minute voltaic couples formed with the zinc by
particles of iron, carbon, or other impurities in
the zinc. The deposit assumes at times a tree-
like growth, and is therefore called a lead tree.
(See Couple, Voltaic.}

Crystallization, Eletro Crystalli-
zation effected during elect rolytic deposition.

Crystallize. To separate from a liquid
or vapor, in the form of a crystalline solid.

Crystalloid. Those portions of a mixed
substance subjected to dialysis, that are capa-
ble of crystallization. (See Dialysis.)

Cube, Faraday's An insulated

room cubic in shape, covered on the inside
with tin foil, which, when charged on the
outside gives no indications to an observer on
the inside, though furnished with delicate in-
struments.

Faraday's cube illustrates the fact that an elec-
trostatic charge resides on the outside of an insu-
lated conductor. (See Net, Faraday* s.)

Cup, Mercury A cup or cavity

filled with mercury and connected with the
pole of an electric apparatus for the ready
placing of the same in circuit with other elec-
tric apparatus.

To connect apparatus it is only necessary to
insert the free terminal of one apparatus in the
mercury cup of the other.

Cup, Porous A porous cell. (See

Cell, Porous)

Curb, Double A device for in-
creasing the speed of signaling, by means of
which the line is rid of its charge before the
next signal is sent, by sending an opposite
charge, then another in the same direction,

Cur.]

134

[Cur.

then finally another in the same direction
before connecting with the ground.

The effect of the third charge is to reduce the
potential of the line more nearly to zero at the
end of the signal.

Curb, Single A device for in-
creasing the speed of signaling telegraphic-
ally by ridding the line of its previous charge
by sending a reversed current through it be-
fore connecting with the ground.

In single-curb signaling the operator in dis-
charging the line before sending another signal
through it, before putting the line to earth, re-
verses the battery, and then connects to earth.

Current, Absolute Unit of A cur-
rent of 10 amperes. (See Ampere. Units,
Practical)

A current of such a strength that when
passed through a circuit of a centimetre in
length bent in the form of an arc of a circle
one centimetre in radius, will act with the
force of a dyne on a magnetic pole of unit
strength, placed at the centre of the arc.

The ampere, the practical unit of current, is
but ^5 the value of the absolute unit of current.

Current, Action of, on a Magnetic Pole
An attraction or repulsion depend-
ent on the name of the pole and the direction
of the current.

Two currents of electricity attract or repel each
other according to the direction in which they
are flowing, and the mutual positions of their
circuits. A current and a magnetic pole exert an
action on each other which, strictly speaking, is
neither attraction nor repulsion, but which is ro-
tation, that may, however, be regarded as being
produced by the combined action of attraction
and repulsion.

Current, Alternating A current

which flows alternately in opposite directions.

A current whose direction is rapidly re-
versed.

The non-commuted currents generated by the
differences of potential in the armature of a
dynamo-electric machine are alternating or
simple-periodic-currents.

In a characteristic curve of the electromotive
forces of alternating currents, positive electro-
motive forces, or those that would produce cur-

rents in a certain direction, are indicated by
values above a horizontal line, and negative elec-
tromotive forces, by values below the line.
The curves A B C, and C D E, Fig. 177, are

Fig. 177. Curve of Electromotive Forces of Alternating
-Currents.

often called phases, and represent the alternate
phases of the current.

Current, Alternative A voltaic

alternative. (See Alternatives, Voltaic.)
Current, Assumed Direction of Flow

of The direction the current is as-
sumed to take, z*. e., from the positive pole of
the source through the circuit to the negative
pole of the source.

The electricity is assumed to come out of the
source at its positive pole, and to return or flow
back into the source at its negative pole. This
convention as to the direction of the electric cur-
rent is in accordance with the assumption of the
direction of flow of lines of magnetic forces.

The old idea'of a dual or double current flowing
in opposite directions is still maintained by some.
(See Force, Lines of, Direction of.)

Current, Axial In electro-thera-
peutics a current flowing in a nerve in the
opposite direction to the normal impulse in
the nerve.

Current, Break-Induced The cur-
rent induced by a current in its own, or in
another circuit, on breaking or opening the
same.

The current induced in the secondary on
the breaking of the primary circuit.

The break-induced current set up by a current
in its own circuit is sometimes called the direct-
induced current.

Lord Rayleigh has shown that within certain
limits the break-induced current has a greater
effect in magnetizing steel needles, the smaller
the number of turns of wire in the secondary. In

Cur.]

135

[Cur.

the case of a galvanometer, it is well known that
the opposite is true. The deflection of the gal-
vanometer needle depends on the strength of the
whole current. The magnetizing power depends,
for the greater part, on the strength of the cur-
rent at the beginning of its formation.

Current, Closed-Circular A cur-
rent flowing in a circular circuit.

A small closed-circular current may be replaced
magnetically by a thin disc of steel, magnetized in
a direction perpendicular to its lace, and the edge
of which corresponds to the edge of the circular
conductor.

Current-Commuter. (See Commuter,
Current?)

Current, Conduction The current

that passes through a metallic or other con-
ducting substance, as contradistinguished
from a current produced in a non-conductor
or dielectric. (See Current, Displacement)

Current, Constant A current that

continues to flow in the same direction for
some time without varying in strength,

This term is sometimes used to mean a con
tinuous or direct current m contradistinction to
an alternating current, but it ought to be applied
only to unvarying currents, such, for example as
a constant current of 10 ampdres.

Current, Continuous An electric

current which flows in one and the same
direction.

Although the term continuous current is used
as synonymous with constant current, it is not
entirely so; a continuous current flows constantly
in the same direction. A constant current not
only flows continuously in the same direction, but
maintains an approximately constant current
strength

This term continuous current is used in the
opposite sense to alternating current, and in the
same sense as a direct current.

Current, Creeping of Electric

A change in the direction of path of a current
from the direct line between the points of
connection with the source.

When the terminals of any electric source are
placed in contact with any two points of a metallic
sheet of conducting material, the flow of the cur-
rent is not confined to the direct line between the

points of contact, but creeps or diffuses into por-
tions of the conducting plate surrounding this
direct line. (See Current ', Diffusion of.)

In a somewhat similar manner, the current
is said to creep, or to establish a partial short-
circuit around the poles of a poorly insulated
voltaic battery, or other electric source.

Current, Critical

The current at which a
certain result is reached,

Current, Critical, of a

Dynamo That value

of the current at which the

characteristic curve begins

to depart from a nearly -^

straight line. (Silvanus Fig 178. Critical

P. Thompson.} &** & Dynatno

In Fig. 178 the critical

current is shown in three different cases, as oc-
curring where the dotted vertical line cuts the
characteristic curves.

The speed at which a series dynamo excites
itself is often called the critical speed.

Current, Demarcation A term

sometimes applied to an electric current ob-
tained from an injured muscle.

" Every injury of a muscle or nerve causes at
the point of injury a dying surface, which benaves
negatively to the positive intact substance."
(Landois dr Stirling.)

Current Density. The current of elec-
tricity which passes in any part of a circuit as
compared with the area of cross-section of
that part of the circuit.

In a dynamo- electric machine the current den-
sity in the armature wire should not, according to
Silvanus P. Thompson, exceed 2,500 ampdres
per square inch of area of transverse section of
conductor.

The current density in a dynamo wire, of
necessity depends on the sectional area of the
coils. If, for example, a current of 50 ampdres
be safe in an armature section of eight tu.us it
may be safely increased to 100 amperes ii the
conductors are cross- sectioned so as to make but
four turns. (Urquhart.)

In electro-plating, for every definite current
strength that passes through the bath, or in other
words, for a definite number of coulombs, a
definite weight of metal is deposited, the charac-

Cor.]

136

[Cur:

ter of which depends on the current density. The
character of an electrolytic deposit will therefore
depend on the current density at that part of the
circuit where the deposit occurs.

-The following table from Urquhart gives the
practical working value for the current density
for electro-metallurgical deposits :

CURRENT DENSITY (OR AMPERES ON
CATHODE).

Amperes
Solution of per square foot.

Copper, acid bath 5 . o to 10.0

Copper, cyanide bath 3.0 " 5.0

Silver, double cyanide 2.0 " 5.0

Gold, chloride in cyanide i.o " 2.0

Nickel, double sulphate 6.0 " 8.0

Brass, cyanide 2.0 " 3.0

Tin

Current, Diacritical - Such a
strength of the magnetizing current as pro-
duces a magnetization of an iron core equal
to half-saturation.

The diacritical current is the current which,
flowing through the diacritical number of ampere-
turns, will bring up the magnetism produced to
half -saturation.

The diacritical number of ampere-turns is such
a number of ampere-turns as would reduce the
magnetic permeability to half its iull value.

Current, Diffusion of A term em-
ployed to designate the difference in the
density of current in different portions of a
conductor. (See Current, Creeping of, Elec-
tric.)

Current, Diffusion of Electro-Therapeu-

fic The difference in the density of

current in different portions of the human
body between the electro-therapeutic elec-
trodes.

When the electrodes are placed at any two
given points of the human body, the current
branches through various paths, extending in a
general direction from one electrode to the other,
according to the law of branched or derived cir-
cuits, and flowing in greater amount, or with
greater density of current, tlirough the relatively
better conducting paths. (See Current Density.)

This is sometimes called the creeping of the
current. (See Current, Creeping of .)

Current, Direct A current con-

stant in direction, as distinguished from an
alternating current.

A continuous current.

Current, Direct-Induced The cur-
rent induced in a circuit by induction on it-
self, or self-induction, on breaking or opening
the circuit. (See Currents, Extra?)

This is called the direct-induced current because
its direction is in the same direction as the induc-
ing current.

Current, Direction of The direc-
tion an electric current is assumed to take
out from one pole of any source through the
circuit and its translating devices back to the
source through its other pole.

Conventionally, the current is assumed to come
out from the positive pole of the source and to go
back to the source at the negative pole.

Current, Displacement The rate
of change of electric displacement.

A brief conduction current produced in a
dielectric by an electric displacement. (See
Displacement, Electric?)

This is called a displacement current in order
to distinguish it from a conduction current in any
conductor.

The displacement current continues while the
displacement of electricity is going on. Dis-
placement currents have all the properties of con-
duction currents, and, like the latter, produce a
magnetic field; in fact, they resemble extremely
brief conduction currents.

The difference between conducting substances
and dielectrics, lies in the fact that the conducting
substances do not possess an elastic force, en-
abling them to resist electric displacement. In
other words, conducting substances possess no
electric elasticity, and can have no true displace-
ment current established in them. (See Elasti-
city, E let trie.}

A displacement current, like a conduction cur-
rent, possesses a magnetic field, or is encircled by
lines of magnetic force. (See Field, Magnetic, of
an Electric Current. )

Current, Electric The quantity of
electricity which passes per second through
any conductor or circuit.

The rate at which a definite quantity of elec-
tricity passes or flows through a conductor or
circuit.

Car.]

137

[Cur.

The ratio existing between the electro-
motive force, causing the current, and the
resistance which may, for convenience, be
regarded as opposing it, expressed in terms
of quantity of electricity per second.

The unit of current, or the ampere, is equal to
one coulomb per second. (See Ampere. Coulomb. )

The word current must not be confounded
with the mere act of flowing; electric current
signifies rate of flow, and always supposes an
electromotive force to produce the current, and a
resistance to oppose it.

The electric current is assumed to flow out
from the positive terminal of a source^ through
the circuit and back into the source at the nega-
tive terminal. It is assumed to flow into the
positive terminal of an electro-receptive device
such as a lamp, motor, or storage battery, and
out of its negative terminal ; or, in other words,
the positive pole of the source is always con-
nected to the positive terminal of the electro-re-
ceptive device.

Professor Lodge draws the following com-
parison between the motions of ordinary mat-
ter, heat and electricity: "Consider the modes
in which water may be made to move from place
to place; there are only two. It may be pumped
along pipes, or it may be carried about in jugs.
In other words, it may travel through matter, or,
it may travel with matter. Just so it is with heat,
also. Heat can travel in two ways: it can flow
through matter, by what is called ' conduction, '
or, it can travel with matter, by what is called
'convection.' There is no other mode of con-
veyance of heat." * * * "For electricity
the same is true. Electricity can travel with
matter, or it can travel through matter, by con-
vection, or by conduction, and by no other way."

In the above, the radiation of heat is apparently
lost sight of.

In the opinion of some, an electric current con-
sists of two distinct currents, one of positive and
the other of negative electricity, flowing in oppo-
site directions. Each of these currents is supposed
to be equal in amount to the other.

The electric current is now regarded as passing
through the dielectric surrounding the conductor,
rather than through the conductor itself. (See
Current, Electric, Method of Propagation of,
Through a Circuit.')

The current that flows or passes in any circuit
is, in the case of a constant current, equal to the

electromotive force, or difference of potential,
divided by the resistance, as

f. See Law of Ohm.)

Current, Electric, Method of Propagation

of, Through a Circuit When an

electric current is propagated through a wire
or other conductor, it is not sent or pushed
through the conductor, like a fluid through
a pipe or other conductor, but is, so to speak,
rained down on the surface of the conductor
from the medium or dielectric surrounding it.

Poynting, who has carefully studied this mat-
ter, remarks as follows, viz.: "A space contain-
ing electrical currents may be regarded as the
field where energy is transformed at certain points
into the electric or magnetic kind, by means of
batteries, dynamos, thermopiles, etc., and in
other parts of the field this energy is being again
transformed into heat, work done by the electro-
magnetic forces, or any other form yielded by
currents.

"Formerly the current was regarded as some-
thing traveling in the conductor, and the energy
which appeared at any part of the circuit was
supposed to be conveyed thither through the
conductor by the current But the existence of in-
duced currents and electro-magnetic actions have
led us to look on the medium surrounding the
conductor as playing a very important part in the
development of the phenomena. If we believe in
the continuity of the motion of energy, we are
forced to conclude that the surrounding medium
is capable of containing energy, and that it is
capable of being transferred from point to point.
We are thus led to consider the problem, how
does the energy about an electric current pass
from point to point; by what paths does it travel,
and according to what laws? Let us take a spe-
cific case. Suppose a dynamo at one spot gen-
erates an electric current, which is made to operate
an electric motor at a distant place. We have
here, in the first place, an absorption of energy
from the prime motor into the dynamo. We find
the whole space between and around the conduct-
ing wires magnetized and the seat of electro-
magnetic energy. We have further a retrans-
formation of energy in the motor. The question
which presents itself for solution is to decide how
the energy taken up by the dynamo is trans-
mitted to the motor, by what path it travels

Cur.]

138

[Cur.

and according to what laws ? Briefly stated, the
tendency of recent views is that this energy is
conveyed through the electro-magnetic medium
or ether, and that the function of the wire is to
localize the direction or to concentrate the flow in
a particular path, and thus provide a sink or place
in which the energy can be dissipated. * * * "

Taking again, for instance, the case of the dis-
charge of a condenser by a conductor. He says:
"Before the discharge we know that the energy
resides in the dielectric, between the conducting
plates. If these plates are connected by a wire,
according to these views, the energy is transferred
outwards along the electrostatic, equipotential sur-
faces, and moves on to the wire and is there con-
verted into heat. According to this view we
must suppose the lines of electrostatic induction,
running from plate to plate, to move outwards, as
the dielectric strain lessens, and while still keep-
ing their ends on the plates, to finally converge
in on the wire and be there broken up and their
energy dissipated as heat."

In other words, some of the energy of the ex-
panding lines of induction is changed into mag-
netic energy; this energy is contained in ring-
shaped tubes of force, which expand outwards
from between the plates and then contract on
some other part of the conductor.

The time of the discharge, then, consists of the
following steps, viz. :

(I.) The time during which the energy of the
charge is nearly all electrostatic and is repre-
sented by the energy contained in the lines or
tubes of electrostatic induction, running from
plate to plate of the condenser.

(2.) The time during which the discharge is at
its maximum and the energy consists of two parts,
viz.: energy associated with the outward ex-
panding lines of electrostatic induction, and energy
associated with the closed lines or tubes of mag-
netic force, which at first are expanding and after-
wards contracting.

(3.) The time when the energy has been ab-
sorbed, or the period in which the energy in the
wire or the conductor has either been dissipated
in the form of non -luminous radiation or obscure
heat.

(4.) The time during which this non-luminous
heat gives up its energy again to the surrounding
medium in the shape of heat waves.

Current, Electro-Therapeutic Polarizing

The current which produces the

phenomena of electrotonus. (See Electro-
tonus.)

Current, Element of A term

employed in mathematical discussions to in-
dicate a very small part of a current for ease
in considering its action on a magnetic needle
or other similar body.

Current, Faradic In electro-
therapeutics, the current produced by an in-
duction coil, or by a magneto-electric machine.

A rapidly alternating current, as distin-
guished from a uniform voltaic current.

A voltaic current that is rapidly alternated by
means of any suitable key or switch is sometimes
called a voltaic alternative. The discharge from
a Holtz machine is sometimes called a Franklinic
Current. (See Alternatives, Voltaic. Current,
Franklinic.}

Current Filaments. (See Filament,
Current)

Current, Franklinic A term some-
times used in electro-therapeutics for a cur-
rent produced by the action of a frictional
electric machine.

The term, Franklinic current, is used in con-
tradistinction to Faradic current, or that produced
by induction coils, or, in contradistinction to a
galvanic or voltaic current, or that produced by
a voltaic battery.

Current, Generation of, by Dynamo-Elec-
tric Machine The difference of

potential developed in the armature coils
by the cutting of the lines of magnetic
force of the field by the coils, during the rota-
tion of the armature.

If a loop of wire whose ends are connected to
the two-part commutator, shown in Fig. 179, be
A

Fig. ifQ. Induction in Armature Loop.

rotated in the magnetic field between the magnet
poles N and S, in the direction of the large arrow,
differences of potential will be generated which

Car,]

139

[Cur.

will cause currents to flow in the direction indi-
cated by the small arrows during its motion past
the north pole from the top to the bottom, but in the
opposite direction during its motion past the south
pole from the bottom to the top. If, now, col-
lecting brushes rest on the commutator in the
positions shown in the Fig. 1 80. the vertical line
18P1...

Fig. 180. Action of Commutator.

of the gap between the poles corresponding with
the vertical gap between the commutator seg-
ments, the currents generated in the loop will be
caused to flow in one and the same direction, and
B', will become the positive brush, since the end
of the loop is connected with it only so long as it
is positive. As soon as it becomes negative, from
the current in the loop flowing in the opposite
direction, the other end, which is then positive,
is connected with the positive brush.

A similar series of changes occur at the nega-
tive brush B.

Theoretically, the neutral points, where the
brushes rest, would be in the vertical line coincid -
ing with that of the gap between the poles. An
inspection of the figure shows that the neutral
line, or the diameter of commutation, is dis-
placed in the direction of rotation. (See Commu-
tation, Diameter of.) The displacement of the
brushes, so necessitated, is called the lead.

The cause of the lead is the reaction that occurs
between the magnetic poles of the field magnets

Fig i8r Cause of Lead of Brushes.
and those of the armature, the result of which is
to displace the field magnet poles, and to cause a
change in the density in the field. This is shown
in Fig. 181, where the density of the lines offeree
indicates the position of the diameter of commu-

tation as being near, or at right angles to the di-
ameter of greatest average magnetic density.
(See Lead, Angle of. Lag, Angle of.)

Current-Governor. (See Governor, Cur-
rent.)

Current, Homogeneous Distribution of

Such a distribution of a current through

any conductor in which there is an equal
density of current at all portions of any
cross-section of the conductor.

When the flow of a constant current is estab-
lished in a solid conducting wire, there is a
homogeneous distribution of current in that con-
ductor.

Current, Induced The current

produced in a conductor by cutting lines of
force.

The induced current results from differences of
potential produced by electro-dynamic induction.
(See Induction, Electro- Dynamic.)

Current Induction. (See Induction,
Current.)

Current, Intensity of An old

term sometimes employed to indicate the
current which resulted from a considerable
difference of potential, or a great electromotive
force.

This term was also formerly used as synony-
mous with strength of current.

This use of the term is now abandoned.

Voltaic batteries, connected in series so as to
give a considerable difference of potential, were
spoken of as being connected for intensity.

This term has also been used for the quantity
of electricity conveyed per second across a unit
area of cross -section.

Intensity of current is more properly called
density of current. (See Current Density.)

Current, Intermittent A current

that does not flow continually, but which flows
and ceases to flow at intervals, so that elec-
tricity is practically alternately present and
absent from the circuit.

Current, Inverse-Secondary The

make-induced current. (See Current, Make-
Induced?)

Current. Jacobi's Unit of -Such

a current that when passed through a volta-
meter will liberate a cubic centimetre of

Cur.J

140

[Cur.

oxygen and hydrogen at O degrees C. and
760 mm. barometric pressure.

One Tacobi's unit of current equals

10.32
ampere. (Obsolete.)

Current, Make-Induced The

current induced by a current in its own circuit
on making or closing the same.

The current produced in the secondary of
an induction coil on the making or com-
pletion of the circuit of the primary.

The make-induced current is also called the
inverse-secondary current, because its direction
is opposite to that of the inducing current.

Current, Make or Break Induced, Dura-
tion of The time during which the

induced inverse or direct -secondary currents
continue.

Blaserna made a number of experiments, which
he claims shows :

(i.) The greater the distance apart of the pri-
mary and the secondary, that is, the less their
mutual-induction, the less the maximum value of
the secondary current, and the greater the delay
in establishing that maximum.

(2.) The delay in establishing the maximum of
the break or direct -secondary current is not as
great as in the case of the make, or inverse-sec-
ondary current.

(3.) When the coils are near together, the in-
duced currents at starting are established by a
series of electric oscillations.

(4 ) The primary current establishes itself by a
series of electrical oscillations.

(5.) That the interposition of dielectric sub
stances, such as glass between ^.he coils, reduces
the time between tht making or breaking of the
primary current and the beginning of the sec-
ondary current. This last conclusion was nega
tived by some experiments of Bernstein,

Blaserna determined in the case of certain ex -
periments the following value for the durations of
the secondary currents :

In verse -secondary current lasts .000485 second.

Direct -secondary current lasts .000275 second.

Helmholtz contradicts the results of Blaserna,
and asserts :

(I.) That no perceptible difference in the zero
points of the currents is produced by varying
the distance between the primary and secondary .

(2.) That the sparks produced by the breaking

of the primary last for an appreciable time, some

thing like T5 4 5ff to

a second.

(3.) The duration of the break-spark is never
constant, but depends in great part on the amount
of platinum given off from the contacts at each
spark.

Current- Meter. A form of galvanometer.
(See Galvanometer,}

Current, Momentary - A current
that continues to flow but for a short time.

Current, Multi-Phase - A rotating
current, (See Current, Rotating.)

Current, Muscle -- In electro-thera-
peutics, the current flowing through a muscle.

Muscle currents are produced either by stimu
lation, or during activity of a muscle. According
to L. Hermann, uninjured muscles, or perfectly
dead muscles, yield no currents, but such cur-
rents result only from an injury. (See Current,
Demarcation . )

Current, Non- Homogeneous Distribution

of - Such a distribution of current pass-
ing through a conductor in which there is an
unequal density of current at all portions of
any cross-section of the conductor.

When a rapidly alternating current is passed
through any solid conductor, the current density
is greater at the surface and less towards the
centre. The current distribution in such a con
ductor is non homogeneous, and the want of uni
formity of current density is greater as the rapid
ity of alternation or periodicity is greater.

Current, Outgoing - The current
sent out over the line from a station provided
with a duple < or quadruplex transmission, as
distinguished from the received current. (See
Current, Received?)

Current, Periodic - A simple
periodic current. (See Currents, Simple
Periodic!)

Current, Periodic, Power of -- An

amount of work, per second, equal to the
product of the electromotive force taken at
successive moments of time during a com-
plete cycle, multiplied by the current strength
taken at the corresponding moments during
the cycle.
Since the electromotive force and current in

Cur.]

141

[Cur.

a periodic circuit may be represented by two
simple harmonic functions, the mean value of
the two, when of different amplitude and phase,
is equal to the product of their maximum value
by the cosine of their difference of phase divided
by two.

Current, Polarization In electro-
therapeutics, the constant current which when
passed through a nerve produces in it the
electrotonic stite. (See Elecfrolonus.}

Current. Pulsating A pulsatory

current. (See Current, Pulsatory?)

Current, Pulsatory A current, the

strength of which changes suddenly.

The pulsatory current usually consists of sudden
and distinct impulses, or rushes of current, in
contradistinction to an undulatory or harmonically
varying current.

Current, Received The current

received from the distant end of the line at a
station provided with a duplex or quadruplex
transmission as distinguished from the out-
going current.

A term sometimes used in telegraphy to
distinguish between currents that come in over
the line from a distant station, and those
that are sent out to a distant station.

Current. Rectilinear A current

flowing through straight or rectilinear por-
tions of a circuit.

In studying the effects of the attractions or repul-
sions produced by electric currents the name ex-
pressing the peculiarity of shape of any part of
the circuit is often applied to the current flowing
through that part of the circuit. Thus we speak
of a rectilinear current, a sinuous current.

Current, Reverse-Induced - The

current induced by a current in its own cir-
cuit at the moment of making or closing the
circuit.

The current induced in the secondary on
closing or making the circuit of the primary.

This is called the reverse-induced current, be-
cause its direction is opposite to that of the current
in the inducing circuit.

Current, Reversed A current whose

direction is changed at intervals. (See Cur-
rent, Alternating.}

Current Reverser. (See Reverser, Cur-
rent.}

Current, Reversing a Changing the

direction of an electric current.

Current, Rotating A term applied

to the current which results by combin-
ing a number of alternating currents, whose
phases are displaced with respect to one an-
other.

A rotating current is sometimes called a poly-
phase or multiple-phase current, particularly if
there are three or more currents combined.

The rotating current is employed by Tesla,
Dobrowolsky and others in a system of distribu-
tion by transformers in place of the ordinary
alternating current. In practice, three alternating
current are combined. The currents and their
combination are obtained by means of a specially
constructed alternator. When three currents are
combined the displacement between each set of
phases is 120 degrees. A rotating current, unlike
an alternating current, possesses, in a certain
sense, a definite direction of flow. Its effect on a
magnetic needle is to cause rotation. Hence
motors constructed on the principle of rotating
currents will start with a load.

Current, Rotatory Phase Alternating

A term sometimes employed for a

rotating electric current. (See Current, Ro-
tating^)

Current, Secretion In electro-
therapeutics, a current following stimulation
of the secretory nerves.

Current, Simple-Harmonic A term

sometimes used instead of simple-periodic
current. (See Currents, Simple Periodic.}

Current, Sinuous A term some-
times applied to currents flowing through a
sinuous conductor.

Sinuous currents exert the same effects of attrac-
tion or repulsion on magnets, or on neighboring
circuits, as would a rectilinear current whose
length is that of the axis of such sinuous current.

This can be shown by approaching the circuit
A' B', Fig. 182, consisting of the sinuous con-
ductor A', and rectilinear conductor B', to the
movable conductor A B C, on which it produces
no effect. The current A', therefore, neutral-

Car.]

142

[Cur.

izes the effects of the current B'; or, it is equal to
it in effect.

Fif. 182. Rectilinear Equivalent of Sinuous Current.

In calculating the effects of sinuous currents it
is convenient to consider them as consisting of a

Fig. 183. Sinuous Currents.
succession of short, straight portions at right an-
gles to one another, as shown in Fig. 183.

Current, Steady A current whose

strength does not vary from time to time.

In a steady current the quantity of electricity
flowing through each unit of area of the equi-
potential surface of the conductor is the same for
each succeeding interval of time. Such a current
is sometimes called a uniformly distributed cur-
rent.

Current Streamlets. (See Streamlets,
Current^

Current Strength. The product obtained
by dividing the electromotive force by the
resistance.

The current strength for a constant current
according to Ohm's law is

r _E
C_ R .

Current strength is proportional to the amount
of the magnetic or chemical (electrolytic) effects
it is capable of producing.

For a simple-periodic current, the current
strength necessarily varies from time to time.

The average current strength of a simple-
periodic current is equal to the average impressed
electromotive force divided by the impedance.
(See Impedance. )

The maximum current strength is equal to the
maximum impressed electromotive force divided
by the impedance.

Current, to Transform a To

change the electromotive force of a current
by its passage through a converter, or trans-
former.

To convert a current.

Current, Transforming a Chang-
ing the electromotive force of a current by its
passage through a converter or transformer.

Current, Undulating An undu-

latory current. (See Currents, Undulatory^

Current, Uniformly-Distributed .

A term sometimes employed in the same
sense as steady current. (See Current.
Steady.)

Current, Unit Strength of Such

a strength of current that when passed
through a circuit one centimetre in length,
arranged in an arc one centimetre in radius,
will exert a force of one dyne on a unit mag-
net pole placed at the centre.

This absolute unit is equal to ten amperes or
practical units of current (See Ampere.)

Current, Variable Period of

The period which exists while an electric
current is being increased or decreased in
strength, or while it is being reversed.

Currents, Action Physiological cur-
rents obtained during the activity of a muscle
or nerve.

Currents, After In electro-thera-
peutics, currents produced in nervous or
muscular tissue when a constant current,
which has been flowing through the same,
has been stopped.

After currents are due to internal polarization.

Currents, Alternating-Primary

The currents employed in the primary of a

Cur.]

143

[Cnr.

transformer to induce alternating currents in
the secondary. (See Transformer)

Currents, Alternating-Secondary

The currents induced in the secondary of a
transformer by the alternating currents in the
primary. (See Transformer)

Currents, Alternating, Shifting of Phase

of (See Phase, Shifting of, of Alter-
nating Currents?)

Currents, Ampdrian The electric

currents that are assumed in the amperian
theory of magnetism to flow around the mole-
cules of a magnet. (See Magnetism, Amperes
Theory of.)

The amperian currents are to be distingu