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ELECTRIC LIGHT

ITS PRODUCTION AND USE

BY THE SAME AUTHOR. Crown Bto, 51 cloth.

ELECTRO-PLATING :

PRACTICAL HANDBOOK, INCLUDING THE
PRACTICE OF ELECTROTYPTNG.

Carefully thought out."— Engineer.

A thoroughly practical manual."— Inm.

Any amateur will find no difficulty in nnderltanding the book

«."-» fe»jM* Journal,
& Co., 7, Stationers' Bail Court, E.C.

Gramme's Combined Exciting and Dividing; Machine. [See p. iij.]

/*) Z8-

ELECTRIC LIGHT

7ZS* PRODUCTION AND USE

EMBODYING

PLAIN DIRECTIONS FOR THE WORKING OF

GALVANIC BATTERIES, ELECTRIC LAMPS,

AND DYNAMO-ELECTRIC MACHINES

Br j! W. _yRQUHART, C.E.

AUTHOR OF "ELECTRO-PLATING: A PRACTICAL HANDBOOK

EDITED BY

F. C. WEBB, M.I.C.E., M.S.T.E.

WITH NINETY*FOUR ILLUSTRATIONS

(a*%Is

LONDON

CROSBY LOCKWOOD AND CO.

7, STATIONERS' HALL COURT, LUDGATE HILL

1880

LONDON :

PRINTED BY VIRTUE AND CO., LIMITED,

CITY ROAD.

PREFACE.

^ The following pages contain a general account of
the means adopted in producing electric light.
The author's intention was originally to speak

q only of electric light as obtained from voltaic or
galvanic batteries. But the rapid development of
other and more generally applicable methods has
induced him to extend the limits of the work, and
to treat at some length, from a practical point of
view, of the dynamo-electric machine in several of
its forms. Of electric lamps and other apparatus
used in connection with dynamo-electric machines,
the book contains several examples.

No attempt has been made to teach the science
of electricity, but in the first portion of the book
such particulars of the voltaic battery as may lead
to a correct idea of its use for electric light pro-
duction have been given. The work is, moreover,
not designed for a text-book, and the author
makes no pretension to teach electricians the art
or science of electric lighting; but it is hoped
that some portions of its contents may be read
with advantage by many persons engaged in

V1U PREFACE.

producing electric light. Practically considered,
the art of electric lighting is of such recent date
that the whole subject is as yet only partially
developed and understood. On account of this,
and in view of the imperfections and shortcomings
of his work, necessarily due to the same cause, the
author asks for the kind forbearance of his readers.
He has to acknowledge having received able assis-
tance from Mr. F. C. Webb, member of the Society
of Telegraph Engineers, who kindly undertook the
arrangement and supervision of the work in its
progress through the press, and has made many
valuable suggestions and additions.

J. W. URQUHART.

London, April, 1880.

NOTE BY THE EDITOR.

In revising for the press Mr. Urquhart's little
work, I have endeavoured to arrange the matter, where
possible, in the order which appeared to me most
in accordance with the history of the subject, and I
have here and there made a few additions which I
thought would be interesting to the reader, on historical,
theoretical and experimental points.

F. C. WEBB.

Palace Chambers, Bridge Street, Westminster,
• April, 1880.

CONTENTS.

CHAPTER I.
Introduction i — 5

PARE

CHAPTER II.
Voltaic Batteries 6 — 46

CHAPTER III.

Thermo-Electric Batteries . . . 47 — 52

CHAPTER IV.

Magneto-Electric Generators . . . 53 — 91

CHAPTER V.

Electro-Magneto Electric Machines . 92 — 97

CHAPTER VI.

Dynamo-Electric Machines . . . 98 — 149

CHAPTER VII.

General Observations on Machines . . 150 — 165

CONTENTS.

CHAPTER VHL
Electric Lamps and Candles .

PAGE

. 166 — 252

CHAPTER IX.
Measurement of Electric Light

. 253—261

CHAPTER X.

Mathematical and Experimental Treat-
ment of the Subject .... 262 — 272

CHAPTER XI.

Application and Cost of the Electric

Light 273—285

LIST OF TABLES.

PAGB
III

Table relating to Gramme's Machines .

Siemens' Machines . . . 123

the Wallace-Farmer Machine . .147

Work of various Machines . .151
Experiments of the Franklin Institute 259

„ „ Trinity Board . 259

Effects of different kinds of Glass . 276

Cost of the Electric Light . .281

„ at the British Museum . . 284

LIST OF ILLUSTRATIONS.

FIG.

i. Binding-screws and Clamps

2. Simple Voltaic Cells .

3. Battery Cells

4. Small Bichromate Cell

5. Bichromate Cells

6. Six-cell Lifting Battery

7. Bunsen Cell

8. „ Cells

9. Battery Carbon

10. Pair of Bunsen Cells, showing connections

11. Zinc Cylinder .

12. Grove's Cell

13. Pots for Grove's Cell

14. Zinc for Grove's Cell

15. Platinum Plate

16. Ten-cell Grove's Battery .
17- Bichromate Pneumatic Battery

18. Thermo-Electric Bars

19. Faraday's Experiment

20. Induction Experiment

21. Clarke's Machine

22. Commutator: End .

23. „ Section

PAGE
IO

14
16

23
29

30
3°

35
36

36
36

37
42

47
55
56

58
58
58

xii

LIST OF ILLUSTRATIONS.

fin.
34.

»5-

26.

37-

38.
39.
30.

31.
33.

33-
34-
35-
36-

37-
38.

39-

40.

41.
43.

43-
44.

45-
46.

47-
48.

49.

5°-
5i-
52-
53-

Stohrer's Machine ....
Electro-Magnet ....
The Alliance Magneto-Electric Machine
Siemens' Armature ....
Varley's Machine ....
Gramme's Ring ....
Section of Gramme's Ring
Gramme Hand Magneto-Electric Machine

n » tt

Small Gramme Magnet

Gramme Ring and Contact Drum

Contact Springs and Drum

Wilde's Magneto-Electric Electro-Magneto

trie Machine

Wilde's Armature

First Form of Ladd's Machine .

■

Ladd's Machine
Small Gramme Machine .
Gramme Machine : Section
Large Gramme Machine .
Gramme's Combined Machine .

Siemens' Machine

»>

Plan

Section .

with Fixed Armature : Section
Siemens' Alternating Current Machine
Maxim's Machine ....
Wilde's Dynamo-Electric Machine : Front Eleva
tion

Elec

PAGE

63
66

74
76

77
78

94
96

I02
I03

I06
I08
114

"5
116

118

119

120

122

126

128

list of illustrations.

Xlll

FIG.

PAGE

54. Wilde's Dynamo-Electric Machine: !

End Eleva-

tion . . . . . . . .129

55. Weston's Machine

• 1 S 1

56. „ „ Section

. i3 2

57. „ Commutator

. 132

58. „ New Machine

■ 134

59. „ Armature ....

• 135

60. Trouv^'s Machine ....

• 137

61. „ „ End

133

62. Lontin's Exciting Machine

139

63. „ Distributing Machine .

140

64. „ Exciting Machine

, 141

65. „ „ „ Plan

. 141

66. Brush's Machine

142

67. „ Ring ....

• 143

68. Wallace-Farmer Machine .

• 145

69. Siemens' Circuit " Regulator " .

162

70. Carbon Points ....

. 169

71. Serrin's Lamp ....

■ J 75

72. Archereau's Lamp

176

73. Bobbin for Archereau's Lamp .

178

74. Gaiffe's Lamp

, 180

75. Lamp Rack-work ....

•

. 181

76. Detent of Duboscq's Lamp

, 182

77. Siemens' Lamp ....

, 184

78. „ Differential Lamp

189

79. Brush's Lamp

*95

80. Thomson-Houston Lamp .

200

81. The Wallace-Farmer Lamp

202

82. Rapieffs Lamp ....

204

83. Urquhart's Lamp : End

208

84. „ „ Side

209

XIV

LIST OF ILLUSTRATIONS.

FIG.

85. Werdermann's Lamp

86. Carbon Rods ....

87. Complete Candle

88. Jablochkoff Candle .

89. From Photo of half-burnt Candle

90. Jablochkoff Candle-holders

9 1, J) 99

92. Wilde's Candle .

93. Jamain's Blowpipe Candle .

94. Edison's Platinum-Iridium Lamp

PACK
220

225

226

227

232

234
242

ELECTRIC LIGHT.

CHAPTER I.

INTRODUCTION.

If conductors leading from the two poles of a
powerful source of electricity are made to termi-
nate in points which are brought into contact, a
light will be produced when the contact is broken ;
and if the source is sufficiently powerful the points,
or electrodes as they are termed, can be separated
to a certain distance, depending on the electro-
motive force of the source, without interrupting
the current of electricity, which continues across
the intervening space through the conduction
afforded by the heated air between them. A
brilliant belt of light is produced between the
electrodes, which has been termed the voltaic arc.
If the pointed electrodes are made of carbon the
effect is greatly increased. The light in this case
is supposed by some to be partly due actually to
combustion of the carbon, particles of which fly off
from one carbon to the other. On the other hand
it has been pointed out that the incandescence is

'«• B

2 ELECTRIC LIGHT.

still more intense in a vacuum, or in any of the
gases that do not support combustion, than in the
ordinary atmosphere, so that the phenomenon is
not to be considered as one of simple combustion.
A brilliant light can also be obtained by passing"
powerful currents through metals of low conducting*
power, such as platinum, or through thin pieces of
carbon. In all cases it will be found that a great
resistance to the current in a small space has to be
overcome by the source of electricity.

The date of the earliest production of the electric
light is somewhat uncertain, but in 1810 Sir Hum-
phry Davy, with a battery of 2,000 elements, ex-
hibited at the Royal Institution the electric light
with an arc 3 inches long between carbon points.

The following is the account given in the Philo-
sophical Magazine, vol. xxxv., for Jan. to June, 1810,

p. 463 :—

"In the concluding lecture at the Royal Insti-
tution, the large voltaic apparatus, consisting of
2,000 double plates of four inches square, was put
into action for the first time. The effect of this
combination, the largest that has ever been con-
structed, was, as might be expected, of a very
brilliant kind.

" The spark, the light of which was so intense as
to resemble that of the sun, struck through some
lines of air, and produced a discharge through
heated air of nearly three inches in length and of a
dazzling splendour. Several bodies which had not
been fused before were fused by this flame; the

INTRODUCTION. 3

new metals discovered by Mr. Tennant, iridium
and the alloy of iridium and osmium, zircon, and
alumine, were likewise fused ; charcoal was made
to evaporate, and plumbago appeared to fuse in
vacuo ; charcoal was ignited to intense whiteness
by it in oxymuriatic acid gas, and volatilised in it,
but without effecting its decomposition."

With regard to this, Professor Daniel, whose
elegant and careful writing is still worth quoting
at the present day, remarks:* — "The disruptive
discharge of the voltaic battery through air is de-
pendent upon precisely the same principles as that
of the Leyden battery; but the phenomena are
modified by the lower intensity, greater quantity,
and perpetual renewal of the force. When passing
between two charcoal points, its duration renders
it the most splendid source of light which is under
the command of art. When the poles of a powerful
battery are gradually separated after contact, the
discharge takes place through an interval which
increases with the heating of the air by the ignited
charcoal. With the original battery of the Royal
Institution of 2,000 plates, the discharge passed
through four inches of air ; and with the constant
battery of 70 cells the flame is much more volumi-
nous, and extends to the distance of one inch.

"It would, however, appear that the air is not
the only form of matter which is concerned in the
phenomena, but that particles of the solid electrodes
contribute to the general effect by convection. It

* " Chemical Philosophy," p. 460.

4 ELECTRIC LIGHT.

is probable that the superior brilliancy of the phe-
nomena with charcoal may be owing to the larger
number of its solid particles which its small cohesion
enables it to throw off in the process. The colour
of the light varies with the substances between
which the discharge passes. Gold leaf gives white
tinged with blue ; silver, a beautiful emerald green ;
copper, bluish white light with red sparks ; lead, a
purple ; zinc, white fringed with red.

" The arc takes place with great brilliancy under
the surface of distilled water; some electrolytic
effect will at the same time occur, but the greater
part of the charge will pass in a brilliant stream of
light."

For many years the light only remained a little
more than a scientific toy, being occasionally used
for lecture purposes, or for the illumination of the
microscope; but the discovery of the means of pro-
ducing electricity in large quantities from mechani-
cal motion through the intervention of magnetism,
instead of by chemical action, gave this branch of
electric science a new starting-point, and at the
present day electric lights on a large scale are
entirely produced by currents generated by the
rapid movement of insulated wires. In all arrange-
ments for the production of the electric light we
require first a source or generator of electricity;
secondly, conducting wires; and thirdly, an ar-
rangement of carbons or metals, at which the light
is actually emitted, called the lamp. We shall com-
mence, therefore, by descriptions of the generators

INTRODUCTION. 5

employed ; and as electricity from voltaic batteries
-was first employed for the electric light, it will be
more in accordance with the history of the subject to
commence by describing this means of producing
electricity, notwithstanding that the production of
the light by the currents produced by what may be
termed electro-mechanical means, is, at the present
day, of the greater importance.

We shall, however, again allude to the voltaic
arc when treating of the various arrangements of
lamps.

CHAPTER II.

VOLTAIC BATTERIES.

Although voltaic electrical generators are at
present quite inapplicable to the production of an
electric light to replace gas permanently, they are,
nevertheless, where properly handled as the author
will endeavour to explain, of the greatest use for
numerous minor applications of electricity as light.

For magic-lantern exhibitions, and the working
of a very great number of other optical instru-
ments, the electric light is often absolutely neces-
sary to secure even approximately good results,
and it is at present idle to suppose that in such
instances the light could as a rule be produced by-
means of the dynamo-electric machine, although it
is probable that everyj lecture-room of any note
will shortly provide for the use of lecturers the
necessary dynamo-electric plant.

In short displays of the light, whether for pur-
poses of pleasure-ground illumination at night or
advertisement, there is as yet no better or cheaper
source of the current than a properly arranged
voltaic battery.

For the purposes of the photographer, who often

VOLTAIC BATTERIES. 7

requires a brilliant electric light in actual por-
traiture, or in making enlargements, the author
has devised a handy and economical adaptation of
Byrne's generator, which will be found to give a
light of surpassing power even from so few as 1 2
cells; and 6 cells may be caused to produce a
light suited to ordinary work. It will be well to
understand, however, that this apparatus is only
fitted for the production of light during a number
of minutes under 15, but in most cases no such
continuance of the light will be necessary.

Rudimentary expositions of the theories and
actions concerned in the working of voltaic cells
will not be found in this treatise. After careful
consideration, and judgments upon an extensive
experience with all kinds of generators, it is but
too obvious that elementary instruction of this
kind is often misplaced in works having a practical
bearing, and is therefore really not wanted.
Almost any one, after reading the description of
them, can set in action and even make use of the
ordinary kinds of battery, and such as want an
electric light quickly and at small cost, for some
useful purpose, have again no need to know the
theory of the voltaic battery, while those of a
different turn of mind will find it given in any of
the many excellent text-books on electricity now
published.

Voltaic batteries of a type suited to the produc-
tion of the electric light are few in number. The
batteries that are generally employed in working

8 ELECTRIC LIGHT.

telegraphs or ringing house bells, or even in
electro-plating, are all too weak for our purpose.

We require a battery of small size to supply for
a short period a very energetic current of electri-
city. We also must have a generator that will not
vary much in power during about two hours. It
must be cheap at first, and its cost of working must
be low, while it should not give any trouble during
the time the light is required. It must not waste
its materials, but give all the benefit derived from
the consumption of zinc as current.

Directions for the construction of all the most
suitable generators will be given, and with the
help of a few carefully prepared engravings it is
hoped that the subject will be made clear.

All batteries consist of one or more cells, in
which are placed two substances, the one more
oxidisable than the other, and acted on by acids
more or less diluted. The most oxidisable sub-
stance is termed the positive element, and the
other the negative element. Electricity of opposite
name is believed to flow off" in contrary directions
in equal quantities from the surface of generation,
viz., the junction of the liquid with the positive
plate; but for convenience, the current is sup-
posed to flow from the positive element through
the liquid to the negative element, thence from the
terminal on the negative element through the ex-
ternal circuit of wire, earth, or other conductor
back to the terminal of the positive element. The
current is supposed, therefore, to leave the battery

POSITIVE ELEMENTS. 9

at the terminal attached to the negative element, and
this terminal, or the end of any wire attached to it,
is termed the positive pole.

In the same way the terminal or wire attached to
the positive element is termed the negative pole.

Positive Elements. — In nearly all batteries the
oxidisable metal, or positive plate or element, is
of zinc, and the current is therefore produced by
the slow consumption or combustion of zinc, which
is, therefore, our fuel. Its cost is about fourpence
per lb. The best zinc to use is that known as
rolled Belgian. All such plates or cylinders should
be about -^ths of an inch in thickness, and in
electric light batteries must be amalgamated ; that
is, coated with a closely adherent film of mercury.
Zinc, when new from the rolling mill, is greasy,
and this film should be scrubbed or dissolved off
with hot water and soda. To cut zinc plates to
size is a more difficult matter than is generally
supposed. The simplest way is to make a deep
scratch at the place of separation, repeat this on
the opposite side, and run mercury into the cut.
This will soak nearly through in a few minutes,
and the plate may be divided by bending over the
edge of a table. To bend zinc plates into cylinders
it is only necessary to heat them as hot as can be
borne in the hands by the aid of a duster, when
the bending will be easily done over a wooden
roller fixed in the vice, or a mallet may be used.

A question now arises as to whether the zinc
plate is to be provided with a binding-screw, or is it

ELECTRIC LIGHT.

*Jfi

~ll B-LF

®U

to have a copper strap soldered to it ? Binding-
screws are procurable of all kinds. Some are
made for soldering to zinc plates, and others for
screwing upon them.

Fig. i shows some specimens of binding-screws,
of which the smallest, with rounded head, is best
suited for screwing upon plates and cylinders of

zinc. For soldering,
the same screw is
made with and with-
out plain tangs. Such
screws — of the first
kind — are procur-
able at 4s. per dozen,
and those of the se-
cond kind at 3s. per
dozen, or singly, as
required. Conducting straps of copper should be
cut from sheet, and of uniform width, with a length
of 5 inches. They are usually attached to zinc
cylinders, for use in Bunsen's cell. It is by far
best to make a hole in the zinc and strap, and to
securely rivet the latter to the cylinder. The joint
should be quite firm, the copper where it touches
must be clean, and a coating of japan or other
varnish will protect the joint from corrosion.

To solder, a copper " soldering bolt " is required,
with a piece of tinman's solder. The surfaces must
be clean, the bolt heated to the dullest red, cleaned
on the point by filing, touched with hydrochloric
acid ("spirit of salt") and then with the solder,

Fig. z. — Binding-screws and Clamps.

NEGATIVE ELEMENTS. II

which may also be wetted with acid. This is
"tinning" the bolt. Touch the brass and zinc to
be soldered together with the acid, place in posi-
tion, and, taking a drop of solder on the bolt, a
little care will run a good joint. The solder should
perfectly amalgamate with the brass and zinc, if
there is a sufficiency of heat and acid. Do not use
"killed spirit," as hydrochloric acid with zinc dis-
solved in it is called, except for joints when zinc is
absent.

To amalgamate, dip the plate for a minute in
acidulated water, one to ten; pour the mercury
upon a plate, and, while the zinc surface is wet, rub
the mercury on with a pad of cotton or rags, or a
cork, until a perfect surface is secured, and the
mercury covers the plate. If there are parts where
the mercury will not " take," dip the plate again
into the solution and repeat, set up to drain, and
go on with the remainder.

If amalgamating is not done, "local action"
will reduce the current in strength and waste a
great deal of the zinc. The mercury connects the
hard and soft parts together, and prevents the local
action from starting. After use, if the plates show
black patches, they should be re-amalgamated.

Negative Plates. — Receiving or negative plates in
electric light batteries are usually of the dense
variety of carbon known as graphite, found in gas
retorts after gas-making. It may be scaled off,
and is to be had at gas-works for a mere trifle,
as it is, otherwise than for batteries, of little use.

12 ELECTRIC LIGHT.

The best carbon, which assists the current, is very
hard, of a grey colour and dense crystalline
structure. It is, therefore, very difficult to cut, and
unless proper appliances be at hand, in the shape
of a revolving disc of iron, fed with silver sand
and water, it will be found cheaper to buy the
plates and blocks from the instrument-dealers.

Excitants are, as a rule, sulphuric acid diluted
with much water. Sulphuric acid is procurable at
about 3d. per pound.

Containing Cells. — The containing cells hold from
half a pint to a gallon. Quart size is very well
suited for electric - light batteries. The single
liquid cells have only one containing pot, while
those that are double have two. Outer pots may
be made of glass, but, as a rule, glazed earthen-
ware is stronger and more suitable. It will be
well to mention that instrument-dealers charge as
much as 1 s. 6d. for containing pots, while the real
cost of production is about 2d. ; and the wholesale
price of ten less than 4d. For these reasons it is
always best to obtain any considerable number of
pots, if possible, from the manufacturer, or of
wholesale houses.

Porous pots are of unglazed earthenware. They
are made usually in two shapes — round tubes, long
and narrow, and in oblong form, for use in Grove's
battery. They are placed inside the zinc cylinder,
or bent plate, and usually contain the carbon block,
or plate, or, in Grove's cells, a strip of platinum
foil.

COMPOSITION OF CELLS. 1 3

Such pots, to be suitable for electric light pur-
poses, must not be hard and dense, while the
thickness of the sides should in no. case be
over -^ths of an inch. The softest are of redware ;
but better pots, and soft enough, are made from
white clay. A test of the porosity should be
taken by placing water in the pots, and allowing
them to stand for some time. If, after about 15
minutes, a dew does not appear on the outside of
the pot, it is probably too hard or thick, and will
offer too great a resistance to the current. If, on
the other hand, the water actually runs off the
side, the pot is too porous, and will stop the action
of the battery by too rapid transfusion of the liquids
into each other. / This mixing action is often called
endosmos, although it is also applied to the peculiar
creeping of solutions of metallic salts, such as the
copper sulphate used in Daniell's cell. Porous
cells are easily procurable of instrument-dealers at
a cfreap rate.

Composition of a Cell. — A voltaic cell must be
composed of two dissimilar metals or materials
immersed either in one or two liquids. The one-
liquid cells, although handy enough for short ex-
periments, so rapidly acquire a film of gas upon
their plates, that all further action of the exciting
liquid is put a stop to, and consequently such cells,
unless agitated in some way, are unfitted for
supplying current for any length of time together.

Two^liquid cells, on the other hand, cannot, on
account of the porous separation, acquire a film of

14 ELECTRIC LIGHT.

gas upon their plates, and the action goes on,
without the necessity for any disturbance, for a
length of time dependent upon the bulk of liquids
employed and the size of the plates.

Two-liquid cells are, however, more troublesome,
and may be set aside in favour of single liquid
ones for many short experiments.

Bichromate Cells.

Fig. 2 shows, in principle, the way in Which
three or more of the bichromate of potash cells
are made up. They are composed of two carbon
plates, having be-
tween them a zinc
plate, amalgamated
as usual. The plates
are contained by a
glass or earthenware
pot of the shape

^^^TUUiCA ShOWD > aIld * d0Zen

or two of such cells,
about six inches high, form a very powerful and
useful battery in short experiments. This engrav-
ing was, however, only prepared to illustrate the
make-up of single cells, and how they are joined

) plates are used in a single cell,
and are held 7\ a brass clamp, such as that shown
in the illustratiVi of binding-screws, they must be
separated from cVntact with each other by having

BICHROMATE BATTERIES. 1 5

placed between their upper edges a strip of wood,
pasteboard, or other non-conducting material. The
three cells here shown form a battery of three cells
joined in series, that is, zinc to carbon and zinc to
carbon throughout. The two carbon plates are
connected together by a strip of copper, and there-
fore one wire from any one of them takes off all
the current. Both sides of the zinc give off elec-
tricity, which passes through the liquid to the
carbon plates, and so by the negative plate wire,
as shown by the arrow and marked P. Thus the
negative plate wire is the positive wire or pole,
while the zinc plate wire, being the receiving or
returning end of the battery, is called the negative
wire or pole, as shown by N, and the arrow indi-
cating the flow of the current.

Two wires thus come from a coupled-up battery
of cells, and scarcely any action commences within
the battery until the ends of these conductors are
brought together in metallic contact, or until some
conducting circuit, such as through an electric
lamp, is provided for the electricity to flow from
and back to the battery.

For electric light purposes it is always best, up
to 50 cells, to join up in series — zinc, carbon, zinc,
carbon ; but this will be further spoken of in con-
nection with Bunsen's cell.

A plate of zinc between two plates of carbon
then forms a single cell. A brass clamp may hold
the whole together, the zinc being prevented from
contact with the carbon by strips of wood as thin

1 6 ELECTRIC LIGHT.

as possible, while the two carbons are joined as
one by the brass clamp. Elements, or sets thus
made up, can be charged with dilute sulphuric acid
only, and for bell-ringing or telegraphy with a
solution of sal-ammoniac, but for electric light pur-
poses, requiring a powerful current, the containing
pot should be three-fourths filled with a mixture as
follows :

Crystals of bichromate of potash 3 01.

Warm water I pint.

And (when cool) sulphuric acid 2 oz.

When this liquid is fresh, it causes the pairs
immersed in it to give off a great deal of electricity
— that is, a strong current. The potash salt is in
reddish crystals, and costs about is. per lb.

Pairs of bichromate of potash cell plates should
not be immersed in the solution until the current
is really required
and all is ready. Of
course, all the pairs,
joined up by spirals
of wire, may lie near
the cells until the
time comes for plac-
ing them in the li-
quid; but a far better
plan, and a most con-
venient and cheap

Fi K . 3 .-B a t tE rjCelii. , . f

containing cell, is
shown in Fig. 3. Bottles of this shape, and to
hold about a quart, are easily procurable ; the size

BICHROMATE BATTERIES. 1 7

of neck is sufficient to admit the pairs of plates,
while the liquid is not readily splashed over the
top. On the cell to the right is shown a stout
brass collar, A, soldered around the neck tightly.
To this is soldered securely an upright stout brass
wire, bent as shown at B. The object is, of course,
to provide a convenient hook upon which to hang
the pairs of plates when out of the liquid. All the
cells should have this arrangement, and may be
put out of action in a moment by pulling up and
hooking the plates by their wire or in a loop
soldered on the clamp.

Fig. 4 exhibits a more expensive and elaborate
form of the bichromate of potash cell. It is very
handy for experiments, requir-
ing little attention after the
liquid is put in. The pair of
carbon plates reach from the
wooden or ebonite cover of the
bottle to the bottom, and re-
main permanently in the li-
quid. This does the carbon
no harm. The liquid will keep
any length of time, but the Fig ._ 4 _ SnMll Bichromate
time it will work is, of course, CdL

limited to perhaps 1 5 minutes, if the bulk be small.
The zinc plate is attached to a sliding rod, mov-
able in a split brass tube fastened to the cover,
and may thus be lifted clear of the liquid as soon
as the current is not wanted. This saves the zinc
and the solution.

IS ELECTRIC LIGHT.

The carbon plates are made fast by screwing or
riveting to stout angular pieces of copper, and these
coming together, and having soldered to them the
tang of a binding-post, one wire serves as before
for both plates. The split tube is connected by a
strip of copper or brass to the other binding-screw.
The ebonite cover — or a wooden cover will do
equally well — has a brass collar to fit over the
neck of the bottle.

Fig. 5 shows another shape of bottle, of larger
size, and also exhibits the connecting up arrange-
ment in such cells. The zinc should be as large as
possible, and its top should hold a piece of ebonite
cut to fit between the carbon plates, to prevent the

BICHROMATE BATTERIES. 1 9

zinc from twisting and closing the circuit within
the cell.

The amateur may make such cells himself, as
they usually cost as much as 8s. for pint size, when
bought. For electric light purposes, however, if
the operations go above 8 or 10 cells, the first hook
arrangement will be found much more economical
and even better in use, because the zinc plate may
be much larger.

The art of working bichromate cells consists,
first, in never leaving or placing the zinc in the
solution when the current is not needed, pulling it
out the instant the experiment is performed, and
not leaving it in the liquid for over five minutes
without either disturbing the cell or moving the
plate. The great defect of such cells is the want of
circulation in the liquid, so that, when the liquid is
quite still, the current is soon weakened. If heat
can be applied, so as to give some circulation, the
current will come off almost in full even flow until
the solution is exhausted. Exhausted solutions
may be thrown away, or they may be spontaneously
evaporated, when the chrome alum formed in the
action may be recovered. This salt is of value in
dyeing.

All the connecting wires should be of cotton-
covered wire, at least as stout as No. 16 Birming-
ham wire gauge. All connections must be clean
and metallic ; electricity will not pass through dirt,
coatings of oxide, or cotton covering. Connecting
points in clamps should be occasionally looked to,

20 ELECTRIC LrGHT.

to prevent bad contact. Bad connections will
often utterly weaken the current, and sometimes
stop it altogether. To give some convenient elas-
ticity, the connecting wires may be wound on a
rod to make a spiral ; but too much wire must not
in this way be introduced into the circuit, or the
current will be weakened by its resistance. All
connections to lamp or instruments should be
strong, or No. 1 2 copper wire. All uninsulated wires
must, of course, be kept from contact together,
otherwise the circuit may be closed outside the
battery before it reaches the electric lamp or other
instrument.

Fig. 6 is a form of bichromate battery in much
favour, as it admits of a great number of plates
being placed in and withdrawn from the liquid
at once. The arrangement also allows of the easy
agitation of the liquid. The author has seen a

BICHROMATE BATTERIES. 21

battery of this kind of 25 quart cells give a beau-
tiful electric light for a considerable time by an in-
genious arrangement of a weight, wheel, and lever
rocked by a crank applied to the lifting-crank. In
this way the plates were lifted a little way, and
then dropped every second, thus agitating the
liquid — the result being a steady current.

A is a wooden frame, holding as many oblong
glazed pots as may be required. The plates are all
attached to a wooden holder above them as shown,
above which come the binding-posts as in other
forms of the cell. This holder is capable of sliding
up and down upon A, by means of the handle and
spindle with cords, B and C.

Number of Bichromate Cells required. — This will
all depend upon the light required. A light will
be given by 6 cells of quart size, but it will be a
small light, and will not permit any actual sepa-
ration of the carbon points; 12 cells will give
much more than double the light, and 24 will admit
of actual separation, giving the true voltaic arc and
a very brilliant light ; 50 cells will give rise to a
voltaic arc of great splendour, probably equal to
1,500 candles.

It may be said that, up to 50 cells of the quart
size, it is generally advantageous to join up in series
with ordinary lamps.

The electromotive force of 50 cells is usually
sufficient, and any cells over should be connected
in parallel circuit to an equal consecutive number
of cells of the 50 elements, so as to reduce the

22 ELECTRIC LIGHT.

internal resistance of the battery whilst maintain-
ing a sufficient electromotive force. Thus, if there
are ioo cells, each 50 should be joined up in series,
and then the negative wires from both should lead
to one screw of the lamp, and both positives to the
other screw. Thus the electromotive force of the
battery is not increased, but the resistance of the
elements that are doubled is halved. But of course
the most advantageous mode of grouping a given
number of elements must depend on the resistance
of the external part of the circuit ; for with a given
number of elements they should be so joined that
their internal resistance shall equal the external
resistance. It will be unwise to expect over half-
an-hour's continuous light from any bichromate of
potash battery ; and there must be agitation of the
liquid to get even this amount of light. The
solution may be refreshed afterwards by the ad-
dition of other 2 oz. of sulphuric acid to the pint ;
but acid further than this will do no good.

Constant Lights. — Bunsen's Battery.

The original battery invented by Bunsen really
consisted of a cylinder of carbon for the negative,
and the zinc, in the form of a cylinder also, was
put inside the porous cell. This form is expensive
to make, and also more expensive to use than that
now known as the Bunsen cell.

Fig. 7 is a view of a Bunsen cell of approved
construction. The outer pot in the view is of glass,

BUNSEN BATTERIES. 23

to make the interior more clear. The positive
element consists of a cylinder of thick sheet zinc,
to fit easily into the outer pot. A is a projection
left upon the zinc while cutting it to size ; it serves
to give a fastening to the binding-screw clear of

the liquid. The screws are of brass. Inside the
zinc cylinder is a pot of porous earthenware, as
before indicated, and into the porous pot, com-
pleting the cell, is put a cylindrical or square
block of gas carbon, with a binding-clamp, b,
fastened to it.

24 ELECTRIC LIGHT.

It maybe as well to preface further remarks upon
this generator with the assurance that, with one
exception, it is the only real producer of voltaic
currents that can be cheaply applied and depended
upon in the production of electric light. Its current,
once started, is almost perfectly constant for about
4 hours, and a good light may, with confidence, be
depended upon for 3 hours and over.

The roll of zinc, A, should not be a complete
cylinder. The edges should not come quite to-
gether ; a division, however narrow, should be left
while bending. Both inside and outside of the
cylinder should, and indeed must, be amalgamated,
as is done with flat plates, and care is necessary to
renew the amalgamation as soon as black patches
are seen.

As to the actual making up of Bunsen generators,
as here shown, the outer pots should hold nearly a
quart of liquid at least. They are best made of
brown well-glazed earthenware, as before recom-
mended. The 2inc cylinders should be cut to the
size in the flat sheet, leaving the " tang " for the
screw upon them for good connection, and then
bent over a wooden former while hot. The porous
pots should be higher than the zinc, and this should
be higher than the outer cell. A soft porous pot is
best, of white or red materials. Inside the porous cell
is placed the carbon block, which should be highest
of all, and may be either round or square ; but
square blocks are almost always in use, and are
easily procurable at about f d. per inch in height,

BUNSEN BATTERIES. 25

retail. A hard, clear grey carbon should be chosen,
and black and porous varieties rejected, because
they add to the resistance of the circuit and reduce
the force otherwise.

It is a common practice simply to clamp the
carbon by a binding-clamp of brass for the con-
nection. This is, however, when the cell is to be
used much, a bad and decidedly troublesome way
of getting contact. It is by far better to give the
block a heading of lead. To do this, dry the head,
cut a notch or two around it J in. from the end.
Melt the lead and pour it into some square holder*
such as a cavity made in hard putty or plaster of
Paris. Before the lead sets, dip in the carbon end,
and allow the whole to solidify before removal.
While still hot, the binding-screw may be soldered
on, and before it cools the whole should receive a
good coating of melted pitch; or, what is much
better, dip the head in melted (solid) paraffin,
which, when cool, will effectually defend the con-
nection from outside attacks of the acid.

A better way still, although not so quickly ac-
complished, is to electrotype a heading of copper
upon the rods, to insure the best possible connec-
tion. To do this, partly fill a porous pot with acidu-
lated water, place this in an outer cell containing
crystals of copper sulphate dissolved in warm
water. Heat the rods, and give them a coating of
paraffin, driven in with a hot iron, between where
the liquid will reach up to and where the heading
will reach down to. If any paraffin goes upon the

2b ELECTRIC LIGHT.

end, drive it back by heating; cut now a few
notches in the head as before, and drill a hole right
through, in which place tightly a piece of stout
copper wire, having \ in. of the end projecting at
each side. Tie to this a wire, at the end of which
fasten a strip of zinc, which .place in the porous
cell, while the carbon head dips into the copper
solution. As soon as this is done, a deposit of
copper will begin to form upon the wire and
carbon, and when it has attained a thickness of
good brown paper, remove, drill two holes right
through the copper and carbon, soak a little time
in warm water, dry off, and place for some time in
melted paraffin to obtain an efficient protection.
The binding-screw may be soldered to the copper,
which will be found of the greatest value as a head-
ing that cannot give trouble.
The exciting solutions or liquids are : —

In the outer cell, with the zinc • . I part sulphuric acid ; water, 4.
In the porous cell, with the carbon • strong nitric acid only.

This "charge" will work the cell for about 4
hours. After this the outer acid will have exr
hausted itself; but the nitric acid, which will have
turned from a clear liquid to a reddish colour,
may be used again. The second time of using
will turn it green, and the third time quite
clear again, when it should be thrown away and
replaced by fresh. It is no economy to use nitric
acid of inferior quality ; it should be concentrated,
and will cost, when good, about iod. per lb. retail.

The Bunsen, while at work, gives off the fumes

BUNSEN BATTERIES. 27

of the nitric acid, which renders it necessary that
it should be placed out of doors, or in a place
where there is a draught of air. These fumes are in-
jurious to breathe ; they are worst while the porous
cells are being emptied into the nitric acid stock
bottle, but may be quite avoided in the open air.

In the working of large batteries of the Bunsen
cell, some special arrangements are required to
enable the attendant to get through the work of
charging quickly and accurately. First, then, the
sulphuric acid mixture must be prepared in a large
bottle beforehand, by pouring the acid into the
water — not the reverse — and stirring. It is
most convenient to have a graduated measure, by
meaiis of which the correct quantity of nitric acid
may be determined before placing in the cell. This
is of more importance than might at first seem to
be necessary, but a measure that can be quickly
and easily filled to a known point, and as speedily
emptied into the cells, will not only be cleanly, but
will prevent spilling the nitric acid into the zinc
compartment, an accident which sets up violent
local action upon the zinc. It will first be neces-
sary to find how much liquid will fill the porous
pots to within one inch of the top when the car-
bons are in them, and then to fill all the cells with
the carbons and zincs near at hand. It is further of
consequence to have the liquid within the porous
cell at the same height as that in the outer pot.

This filling up should not be done until near the
time when the light is wanted ; a dish of water

28 ELECTRIC LIGHT,

should be at hand in the case of accident by burn-
ing the hands with nitric acid, and it is well to have
in use the oldest clothes, because nitric acid will,
if dropped upon them, destroy the part. Quickly
place the zincs and carbons in their respective cells
first, and then go backwards over the series, making
the connections with certainty. See that each
screw is well home, and that there is no bad con-
nection throughout. As to the time such opera-
tions occupy, a battery of 50 Bunsens may be un-
packed, acid mixed, and the light produced within
twenty minutes.

Again, in pulling the battery to pieces after
operations, all the connections should first be
loosened ; then the zincs should be placed one by
one in a bucket of water to wash off the acid.
The carbons are next similarly treated, and after
putting a funnel in the neck of the nitric acid
bottle, the porous pots should be emptied one by
one, and then plunged in water. The outer liquid
may be thrown away, as it is useless, or nearly so.
Porous pots should, after once being used, be kept
in water for a few hours to soak out any nitric acid
or zinc sulphate, which while dry would crack
them. All connections should be well washed and
dried, and before again using should be looked to
for dirt or bad contact points, which must be
scraped bright or filed.

Zinc cylinders showing black patches should be
again amalgamated, but this will probably be un-
necessary until after the third time of using.

BUNSEN BATTERIES. 29

The force of the Bunsen will increase after set-
ting up for about an hour, and the full effect will
not be attained until the acid soaks through the
porous pot. Carbons, as in bichromate batteries,
are not affected in the least, and will last any
length of time. The zinc is consumed slowly,
through the mercury coating.

Twenty-five cells of the Bunsen will give a very
brilliant light, and 50 will produce an arc of great
power, while 100 will, when coupled in two
parallel circuits of 50 each, so as to give an
electromotive force of 50 and a resistance of only
25, produce effects of the most splendid character.
The conducting wires must be stout — about No. 12,
and even stouter conductors should be employed
when 100 cells are used, joined up in parallel cir-
cuits of 50 each.

ELECTRIC LIGHT.

Fig. 8 shows three of the Bunsen generators of
the cheap kind, in glass pots, and con-
nected properly in series. The zinc
cylinders have straps of copper riveted
to them, and the carbon connections are
brass clamps, with screws on the top
for holding the ends of the straps, which,
for this kind of clamp connector, should
be slotted out.

Fig. o shows the carbon rod, with
another kind of binding-screw soldered
to a neater brass heading.

Copper straps are, however, the best
%«■-!"■ connection in a battery of any size, be-
cause small wires get hot and offer great
resistance to the passage of the current. It is wise
to solder as well as rivet the straps of the zincs.
Fig. io is a view of a pair of superiorly finished
Bunsen cells, for la-
boratory use. They
are fitted with remov-
able screws upon
both the carbons and
zincs. The contain-
ing pots are of glass.
This engraving exhi-
bits the separation
which should be
made between the

Fig. id.— Pair of Bunsen Celli, showing

connections. edges ot the zinc

cylinder. This separation is chiefly for the purpose

IRON CELLS. 31

of preventing the formation of local currents in the
zinc, while it also assists the outer liquid to more
freely circulate.

Various arrangements of the Bunsen cells may-
be adopted in making up a handy battery. The
framework and lifting arrangement spoken of in
connection with the bichromate cell is also applic-
able to the Bunsen. There is, however, one disad-
vantage in the two liquid cells, and it consists in
the mixing tendency of the two liquids whether the
cells are in action or not. It is thus almost im-
practicable to arrange a rackwork frame for the
Bunsen, so as to obtain the convenience of the
arrai\gement to the extent previously described in
the bichromate. It is better, however, to have the
means of lifting them out, as it is useful when the
battery is put into action for short experiments ex-
tending to about one and a half hours. During
this time no great mixture will have taken place,
and the zincs and carbons, arranged on the lifting-
board just above their respective pots, may be
lowered as required. There are some advantages
in the frame used in this way. Bunsen cells are
also best put up in long boxes while in action.

Iron Cells.

With the primary idea of effecting economical
working, a cell has been tried, the invention of
Mr. Slater, and others. All that can be here said
of it, as well as of every other form of cell in
which iron is employed yet introduced, is that it

32 ELECTRIC LIGHT.

is entirely unfitted for use in inexperienced hands.
It has many objections, but its chief one would
appear to be the tendency of the acid in the iron
compartment to boil over when least expected.
Such cells are, moreover, false economy, as will
be found on working them for electric light,
although the first cost may be lower than that of
the Bunsen.

Chromate of Lime Cells.

To replace the potash salt with greater economy
and equal power in working, a cell of the double
liquid kind has been devised which has proved to be
about as constant as the Bunsen, while it is almost
as effective in working, and is undoubtedly cheaper
when properly made.

The chief point in the construction is to secure
as large a negative surface as possible, and, by
means of a soft porous cell, to reduce the internal
resistance of the combination.

Several forms of make-up have been tried. The
best is a cylinder of carbon surrounding a large
porous cell holding the zinc as a cylinder. Car-
bon cylinders are difficult to make. The graphite
must be ground finely, or that deposited as powder
upon the retorts may be used direct. It must be
mixed into a stiff dough with water and sugar
syrup, then baked until hard, and, while still hot,
plunged in a strong solution of sugar or tar, and
finally heated to whiteness and cooled slowly.

A make-up of this cell devised and used by the

CHROMATE OF LIME BATTERIES. 33

author is much more simple, and to all appear-
ance as effective in use, while it is incomparably-
cheaper.

A large soft porous cell is taken, in which is
placed centrally a thin rod of carbon, or a Bunsen
rod, with a screw affixed. Around the rod is packed
a quantity of broken carbon in lumps as large
as hazel nuts. Over the top is run melted pitch,
and a conical hole is left for the introduction of the
liquid. The outer pot, as in the Bunsen, contains
a cylinder of zinc, and its diameter should be only
just enough to admit the porous pot freely: the
object being to have the zinc near to the porous
pot. In order to allow the outer liquid greater
freedom of action, the zinc cylinder should have a
separation of about J in. It is also a good plan to
bore several J-in. holes in the zinc cylinder. The
cell is thus a carbon and zinc one, like Bunsen's.
The exciting solutions are, however : —

For Porous Cell.

Chromate of lime 2 ounces.

Warm water 5 „

Sulphuric acid 5 „

For the Outer Cell.

Water 1 pint.

Sulphuric acid 3 ounces.

The action will be found to give off little or no
fames. The electro-motive force is slightly greater
than that of the Bunsen ; but the internal resist-
ance is also greater.

This same cell is available for use with another

34 ELECTRIC LIGHT.

excitant, which will be found to work even with
greater force, and give little or no fumes for the
first two hours : —

For the Porous Cell.

Bichromate of potash .... 2 ounces.

Nitric acid 10 „

Sulphuric acid 2 „

In the outer cell the solution is the same as for
the Bunsen. This will be found to work with
greater power than the Bunsen, and the internal
resistance is less, but the cost of working is in-
creased about 25 per cent. After use the porous
cells should be emptied of their contents, and kept
in water until again wanted. The same solution
may be used two or three times, and if there be
any appearance of a poverty of potash salt, add
more.

Various modifications of such cells may be
used. As a rule it is best to provide a strongly
acid mixture for the carbon compartment. Thus
the cell I have spoken of, as its construction is
virtually the same as the Bunsen, may be used
with great advantage as a Bunsen, and it will give
a greater current than the common forms, while
the cost of construction is very little more.

Cells Too Weak.

Avoid attempting to produce the electric light
with the following cells : — Daniell, Smee, Man-
ganese, Sulphate of Lead, Sulphate of Mercury,
Chloride of Silver, Marie Davy (mercury sulphate

GROVE BATTERIES. 35

cell), Copper-Zinc (simple), Minotto (modification
of Daniell), Leclanche, Grenet, Highton, Clark's
Mercury, Peroxide of Iron, Perchloride of Iron,
Calland's, Spiral Cell, Meidenger (modification of
Daniell), and, in short, aircclls used for telegraphy
or bell-ringing.

The Grove Cell.

This cell admits of a very large and powerful
battery being placed in a very small compass.
Grove's cell is like the Bunsen, except that plati-
num foil is employed instead of carbon. The solu-
tions are the same — that is, strong nitric acid in
the porous pot with the platinum foil, and acidu-
lated water in the zinc cell. To get the greatest
power, it is best made up in pots like the Bunsen.

Fig. 1 1 represents the zinc cylinder of a Grove
cell.

Another, make-up, adapted to the purposes of

lecturers and where great portability is necessary,
is shown in Fig. 12, where A is the zinc plate, in a

36 ELECTRIC LIGHT.

flat outer cell, and B the platinum foil plate, in a
flat porous pot.

Fig. 13 shows these pots more clearly. Porous
pots of this kind are more expensive than round
ones. They should be thin in the sides, but the
ends and bottoms for strength may be stouter with

Fig. 14 shows how the zinc plate should be bent,
.0 that it may embrace the porous cell closely.

1. Fig. 15.

Platinum Plata.

The generator has thus a great deal of zinc sur-
face. To increase the otherwise somewhat small
surface of the platinum plate, it should be corru-
gated, or simply very much wrinkled ; but it is
better to corrugate it in the direction of its length,
which will both increase the effective surface and
add to its stiffness. Fig. 15 shows the plate
arranged for the cylindrical zinc of Fig. 11. A is a
cover of wood or ebonite to which the plate is made
fast, and a connecting strip leads to the binding-
screw holder, B, which is of brass or copper sheet,
bent at right angles, and secured to the wooden

GROVE BATTERIES. 37

cover by two screws. It is a mistake to purchase
platinum foils too thin. There is no waste, but
foil that is like tissue-paper is a constant trouble.

The chief objection to the use of platinum is its
great cost, as it is not procurable as sheet or wire
under £ i 10s. per oz. ; but an ounce of platinum
will go a long way in foil of sufficient thickness for
use in the Grove cell. The connection may be
soldered on, but it is usually better to solder on a
clamp-piece of sheet-copper first, across the top
edge ; and to protect this metal from the fumes of
nitric acid, it should be coated, while warm, with
Brunswick varnish, or sealing-wax dissolved in
warm methylated spirit of wine. Any kind of
clamps or screws may be used, but it is most
convenient to have them removable.

Fig. 1 6 shows a ten-cell Grove battery, as used
by lecturers for the production of small electric

. Fig. i5.- -Ten-cell Grove's Battery.

lights. It is composed of the flat cells, and the foils
are clamped by plain clamps to the zincs through-
out.
The resistance of Grove's battery is very small,

38 ELECTRIC LIGHT.

and on this account it will give, size for size, a
stronger current than the Bunsen when the ex-
ternal resistance is small, although the difference
does not warrant the extra expenditure except
for travelling purposes, or when space is limited.
A Grove's cell will cost about three times as
much as a Bunsen. Twenty Grove's cells, or two
cases of ten as the one shown, will give a good
light, and five such cases of ten, coupled up in
series, will produce effects of great grandeur.

It is of greater importance than with most other
cells to have the conductors and connections used
in Grove's batteries very stout and of good soft
copper. The time it will remain in action is about
the same as that given by the Bunsen. The Grove
cells may be smaller than the Bunsen to produce
the same effects. The same care is necessary in
keeping the zinc amalgamated, and the bottom, or
bend, is usually better rounded and well watched.
Less nitric acid than is used in Bunsen's will be
sufficient in the Grove pots. The author has used
Bunsen cells made up in Grove pots with every
success for operations extending over i\ hours.
Plates of carbon must, of course, be used instead of
blocks, and they should be as thin as may be con-
venient. This make-up is more expensive than
that of the common shape of Bunsen. Grove porous
pots should have a lip at one corner for conveni •
ence in pouring out the contents.

PNEUMATIC BATTERIES, 39

Battery for Photographer's Light.

It has long been known that the electric light is
rich in actinic rays, and on this account it is of much
value to the photographer in securing views of
places and objects not reached by the light of the
sun, or in the practice of portraiture.

It may be said that a good electric light will be
found to work the rapid dry plates of to-day almost
as easily as daylight at noon.

Since the introduction of cheap dynamo-electric
machines, and the new gas-engines of Crossley and
Otto, photographers in various cities have taken
up the new light, and just now it is an easy matter
to get a portrait taken at dead of night in more
than one place in Regent Street and elsewhere.
Very few photographers, however, can afford to go
to the necessary outlay of about ^110 for a gas-
engine and machine with lamp.

The author has devised, in a modification of Dr.
Byrne's negative plate cells, a voltaic generator free
from most of the objections generally urged against
the application of batteries. It is at first inexpen-
sive, is easily managed and certain in results, and
its maintenance low enough in cost to warrant its
extensive use. It is, further, very portable, and
may be made use of in travelling to secure photo-
graphs of caves and such places. It is not pro-
curable commercially, and the intending user is
therefore recommended to make it for himself, for

40 ELECTRIC LIGHT.

which purpose full instructions are given, with an
illustration of the apparatus.

Assuming that the reader, from glancing at pre-
vious pages, is sufficiently acquainted with the
usual make-up of a voltaic cell to understand
readily minor details not here mentioned, it will be
best to premise further remarks with an explana-
tion of the nature of this new generator. It is,
then, a simple bichromate of potash cell, with
negative plates of a peculiar construction, and so
arranged that a very powerful current may be
obtained from even 6 cells by the aid of much
agitation by air.

Each negative plate consists of a plate of copper,
to one surface of which, as well as to its edges, a
sheet of platinum foil, compact and free from pin-
holes, is soldered, and to the opposite surface or
back, a sheet of lead — the three metals being so
united that the copper shall be effectually protected
from the action of acids. The lead back and edges
are then coated with asphaltum varnish, acid-proof
cement, or any other like substance; and lastly,
the platinum face, being first rubbed over gently
with emery cloth, is to be thoroughly platinised.

To Platinise. — Fill a containing pot and a porous
cell with acidulated water, and place the porous
cell within the large pot. Tie a strip of zinc by a
clean wire to the plate to be platinised ; dip the
zinc in the porous cell, and the plate in the outer
cell, and drop into the outer cell, while stirring, a
solution of platinic chloride in water. Add drop

PNEUMATIC BATTERIES. 41

by drop, with agitation, until the platinum surface
is seen to turn dark, and to have acquired a granu-
lar deposit of platinum. Upon this surface depends
to a great degree the power of the generator. If
any difficulty is experienced in securing a good
deposit, dip only a little of the zinc in the solution
at first, and increase as the coating is seen to form*
Dry carefully, and do not scratch the plate or
remove the deposit, which it is not difficult to do
before it is dry.

Each cell contains two such plates, between
which a single zinc is suspended, and when the
elements are immersed so that the exciting fluid
reaches to within an inch of the top, a large nega-
tive surface is brought into action.

It will thus be seen that the platinum alone is
the negative, or receiving metal, and the copper
core a conducting body merely; while the lead,
being almost passive, serves no other purpose than
to protect the copper, so that any other, and, best
of all, a non-metallic substance capable of resisting
the action of bichromate solutions, might, with
advantage, be substituted for the lead. The ex-
citing solution to use in this cell is prepared as
follows : —

Bichromate of potash .... 2 ounces.

Warm water I pint.

And, when cool, sulphuric acid . . 4 ounces.

Chromate of lime will give even a higher electro-
motive force.
Fig. 17 represents a six-cell generator of this

ELECTRIC LIGHT.

kind. The cells are the ordinary brown glazed
earthenware oblong ones used for the Grove and

other batteries. They should be capable of holding
at least a pint, and quart cells will be found more
economical. There are three plates in each cell,

PNEUMATIC BATTERIES. 43

two platinised plates, and one amalgamated zinc
between them. They are separated at their top
edges by slips of wood or ebonite, against which
they are securely clamped by stout brass clamps as
shown. Thus the brass clamp, being in metallic con-
tact with the lead, with clean scraped surface, repre-
sents them both as the positive pole. To the rinc
plate in the centre is soldered a common binding-
screw. Very stout and soft copper wires—about
No. 1 2 — must be used to connect up the elements
in series zinc to platinum, zinc to platinum, and so
on, with clean contacts. The sets of plates are
fastened to a framing of wood, made to slide up
and down the side uprights by means of an over-
head shaft, cords, and handle F. This allows of
the plates being drawn out of the solution the
instant they are out of action to save zinc and
solution, as previously described for common
bichromate batteries. A ratchet wheel should be
put upon the spindle, with adjustable pawl, to
hold the plates in position when drawn up. For
quart cells the plates may be 8 in. long by 4 J
wide.

Now for the air-distributing arrangements of this
apparatus. A A A is a piece of inch lead piping,
fastened to the back of the framework, from which
lead, as shown, 6 smaller tubes (J inch) of rubber
or varnished lead. These extend to the bottom of
the cells, and then run parallel with and directly
under the plate edges. The ends are closed, and
the horizontal portion is perforated with many

44 ELECTRIC LIGHT.

small holes. B B is a rubber pipe slipped over the
end of A, its other end being made secure to the
outlet, C, of a hand-pump D, worked by the
handle E.

There must be a valve at C to close the passage
to A when the handle is drawn up ; otherwise the
solution would be pumped out of the cells. The
whole should be screwed to the floor, or have a
projection upon which to place the foot for steadi-
ness. It is better to use one of Fletcher's foot-
blowers.

If these elements are lowered . into the solution
simply, it will be found that a much greater power
is obtainable from them than that given by zinc-
carbon batteries, previously mentioned. The full
effect, however, for which this valuable battery is
remarkable can only be got by pumping in air by
the small tubes. A great disturbance of the liquid
results, and the current is so much augmented
in power that even a 6-cell battery will give a
light equal to that given by a 30-cell Bunsen or
Grove.

The air disturbance has no effect upon the electro-
motive force of the battery although the volume of
current given off is enormously increased, and any
other means of effecting the required agitation would
probably answer the purpose equally well. The
suggestion of Professor Adams as to the air effect-
ing a free circulation in the fluid, by which the
metallic surfaces are kept constantly clear, is un-
doubtedly the correct explanation. The wonderful

PNEUMATIC BATTERIES. 45

effects are in great part due to the low internal
resistance of the cell, owing to the peculiar arrange-
ment of negative plate, partly to the peculiar effect
of a rapid flow of air upwards through the liquid,
and partly to the production of heat. The action
of the air flow is principally mechanical, but by
hastening the combustion of the zinc it tends to
generate heat, which in turn reduces the resistance.
The mechanical action of the air is to remove from
the neighbourhood of the negative plate the chrome
alum which is formed there, and from the surfaces
of the zinc plate the zinc sulphate, formed by its
union with the sulphuric acid; and to bring a
fresh supply of solution constantly to the sur-
faces.

With a battery of ten cells, a platinum wire,
32 in. long, of No. 14 gauge (-o89-in. in diameter),
was gradually brought to a glowing red heat, which
ebbed and flowed with the cessation or renewal of
the air flow. A brilliant electric light is maintained
between two carbon points, which similarly varies
in intensity with the flow of air, so that it is impor-
tant to pump the air in regularly ; and when this
can be done by a crank attached to a heavy fly-
wheel, almost perfect regularity is secured. The
effects which are ordinarily produced by 60 or 70
Grove or Bunsen cells were obtained from ten cells
of this battery in the laboratory of Mr. Spottis-
woode, F.R.S., at Sevenoaks.

To prevent the possibility of any disappointment
in the Use of this apparatus, it will be as well to tell

46 ELECTRIC LIGHT.

the reader at once that for every 15 minutes or so
of electric light the cells will be nearly exhausted,
and to continue at full power ought to be refilled.
The light is, however, usually cheap enough for
ordinary working.

CHAPTER III.
THERMO-ELECTRIC BATTERIES.

Much has been done, and much more remains to
be accomplished in the generation of electricity for
illuminating purposes by heat and combinations of
metals.

A current of electricity is produced in a cir-
cuit composed of two different metals when their
junction is heated. The metals which exhibit this
property to the greatest degree are bismuth and

% Fig. 18. — Thermo-Electric Bars.

antimony. If two bars of bismuth, B and C, and one
of antimony, A, are placed as in Fig. 1 8, and heat
applied at one junction while the other is cooled
by radiation or otherwise, a current will flow into
the wires and through the galvanometer.

48 ELECTRIC LIGHT.

The two most efficient thermo-electric piles in
use up to 1876 were probably those of MM. Clamond
and Noe ; great numbers of such pairs being em-
ployed to multiply the force and current.

By the expenditure of 2 1 lbs. of coke per hour,
M. Clamond, of Paris, has succeeded in maintain-
ing four electric lights, each having an illuminating
power of 220-standard candles. This is vouched
for by the Count du Moncel; and, indeed, there
should be nothing impossible, or even difficult, in
the accomplishment of such a result. Sixty couples
will yield, when well constructed, a current equal
to a gallon Bunsen cell, and less than 3,000 ele-
ments will give the effects of 50 Bunsens with an
expenditure of 80 cubic feet of gas per hour. Such
results are reported of the couples of M. C. A.
Faure.

M. J. E. M. Sudre, who has been working in
conjunction with M. Clamond, has taken out a
patent for the following advances in the make-
up of thermo-electric batteries.

1. For the construction and arrangement of
thermo-electric chains composed of couples, the
resistance of which has been reduced to a mini-
mum.

2. The combination and arrangement of the
chains with two metallic plates of which the op-
posing surfaces are coated with an insulating layer ;
which plates form part of two metallic systems, one
serving to collect and communicate the heat, and
the other to abstract and diffuse it.

THERMO-ELECTRIC BATTERIES. 49

3. The combination and arrangement for bind-
ing, coupling, and insulating the thermo-electric
chains, when several are mounted side by side
between the two plates.

4. The application and use of the collector and
difiuser to any description of thermo-electric piles,
so as to maintain the necessary difference of tem-
perature between the extremities of the couples

without lateral waste of heat.

One of the main features of the invention, as
described, is the maintenance of the necessary
difference of temperature between the two solder-
ings of each couple by placing those couples
between two surfaces from which they are elec-
trically insulated. It is stated that in the construc-
tion of thermo-electric couples and chains, an iso-
lated thermo-electric couple is ordinarily composed
of a prism in metal or alloy casting and of a
polar plate of iron, copper, German silver, or other
suitable metal soldered to each of its extremities.
The plates do not ordinarily interfere in the slightest
with the electric force obtained, and it is the bar,
such as that of antimony and zinc, which produces
the effect.

When it is desired to use two metals or energetic
alloys of which the effects are combined, and which
are easily fusible, such as bismuth and antimony,
the couple is then formed of two bars, which are
joined together by a cross bar which binds them
and is soldered to each of them.

The total resistance of a couple is composed,

50 ELECTRIC LIGHT.

i st, of the resistance of the connecting plate; 2nd,
of the resistance of the bar, ordinarily composed
of alloys sufficiently resistant, and 3rd, of a par-
ticular resistance at the points of contact or solder-
ing between the plates and the bar. The metallic
plates should be of a metal sufficiently conductive,
such as copper, iron, German silver, &c, and
should be sufficiently large and thick to present but
a feeble resistance. They should also be as short
as possible. These conditions, it is claimed, are
realised in the improvements of M. Sudre. Again,
the bar should have very little resistance under a
small volume. The inventor takes as a datum the

formula R=k ~ in which k is a specific co-efficient

for the metal employed, L the length of the bar,
and s its section. As the resistance depends on

the ratio -, the volume of the couple may be dimin-

ished by diminishing the length and sectional
area in equal degrees, in which case the resistance
will not be affected.

The length which should be given to the bar
depends upon the difference of temperatures em-
ployed. For differences of temperature between
io° and 120 (Centigrade), M. Sudre gives to the
couples a length of 10 or 12 millimetres, whilst if
the higher temperature reaches 300 the length
varies from 20 to 30 millimetres. The resistance at
the points of contact or soldering is of the highest
importance. The junction should be made so that

THERMO-ELECTRIC BATTERIES. 5 1

the plate is in contact with the whole section of the
bar. The plate should penetrate to a very little
depth within the bar, so as not to diminish too much
the electro-motive force of the couple ; for the really
effective difference of temperature is that of the
two solderings, and this difference diminishes as
the plates penetrate more deeply into the bar, and
thus approach one another.

In constructing the couples M. Sudre cuts the
extremities of the connecting plates in the form of
a comb, the teeth of which are afterwards twisted
so as to present a helicoidal surface, which holds
the plates, as it were, screwed into the bars. The
cut portion of the plates is so adjusted in a mould
that the teeth become embedded in the bar when
this is cast. A considerable number of bars are cast
simultaneously, and constitute a thermo-electric
chain. The external portion of the plates is coated
with asbestos-paper, mica, terra-cotta, or other
suitable insulating material, which may be cemented
to the metallic, surfaces by means of silicate of soda
solution.

The chains are arranged in battery between two
metal plates, which may be plane or curved.
Each of the plates is kept cool on one of its sur-
faces by means of a thin layer of some bad con-
ductor of heat. One of these plates constitutes the
collector and the other the diffuser. In order to
maintain the diffusing surface at a low tempera-
ture, M. Sudre employs a cooling-box of water,
fed from a tank.

52 ELECTRIC IilGHT.

An important question remains yet to be solved
as regards this pile, and that is the amount of main-
tenance and repairs required by it. Should these
be of low cost, a generator very well suited to pur-
poses of artificial illumination will result.

■1

{

CHAPTER IV.
MAGNETO-ELECTRIC GENERATORS.

In the year 1 83 1 Professor Michael Faraday made
one of those brilliant discoveries which have im-
mortalised his name, and has formed the starting
point of all those ingenious electro-mechanical
engines of the present day for converting the energy
stored in fuel into light. Arguing that as from
electricity in the electro -magnet he obtained
magnetism, so from magnetism there must be a
means of obtaining electricity, he experimented
with his usual skill and patient perseverance, and
was rewarded by the discovery of what has been
termed magneto-electricity. He found that if a
magnet was moved near a coil of insulated wire
forming a circuit, a current of electricity was
induced in the circuit during the movement of the
magnet.

Fig. 19 illustrates, in a simple way, the manner in
which the generation of an electric current may be
brought about by means of a magnet and coiled
wire, with a galvanometer, or current measure, to
prove its existence. A is a bobbin of insulated
copper wire, having attached to its ends, or in

54 ELECTRIC LIGHT.

circuit, a common galvanometer, B. When a per-
manent steel bar magnet, C, is quickly passed into
the coil by the central aperture, a current is
caused to circulate in the wire, and its direction
will be indicated by the direction in which the
galvanometer needle moves. This current is, how-
ever, only momentary, that is, it lasts just as long
as the magnet is in motion within the coil, and
ceases as soon as the motion ceases. If, however,
the magnet is now withdrawn, another current will
be caused to circulate in the coil, and its direction
will be opposite to that of the first. This will be
shown by the needle of the galvanometer, B, being
deflected to the left.

This simple experiment contains the first of all
the laws of magneto-electric induction, and is,
in fact, the base or principle of every dynamo-
electric machine noticed in this work.

Were it possible or practicable to make the
magnet move backwards and forwards within the
coil rapidly by means of any mechanical contriv-
ance, we should have a magneto-electric machine on
a small scale. The currents would be alternating
in direction, just like those from the machine now
used to burn the " electric candles," and would be
induced in the coil just as long as the motion was
kept up. Again, were it possible to cause an
endless magnet to move in one direction in the
coil continuously, we should have a machine yield-
ing a constant current of electricity in one direc-
tion only.

MAGNETO-ELECTRIC INDUCTION. 55

The necessary materials for the practical illus-
tration of this important principle may consist
of a 3-inch long paper bobbin, wound with five
layers of No. 22 B. W. G. cotton- or silk-covered
copper wire ; a galvanometer, or current detector,
composed of a magnetised sewing-needle, hung by
its centre, by a thread, within an oblong coil (say
ten turns) of the wire. The needle must, of course,
be held parallel with the wire coil. A steel bar
magnet of the common kind, and 8 inches long,
■will complete the apparatus practically as exhi-
bited in Fig. i<).

Fig. 19.— Fareday's Eiperiment

This is called magneto-electric induction. It is
more difficult to move the magnet in the coil
when the circuit is closed than when it is open.
The action that takes place may perhaps be ex-
plained as follows : — The movement of the magnet

56 ELECTRIC LIGHT.

induces a current in the coil, forming it 'into a
magnet with its poles in a position such as to
attract the poles of the moving magnet in the
reverse direction to that they are moving in, and
thus opposing the motion of the magnet. This
opposition has to be overcome by force, and the
energy thus expended, less that dissipated in heat,
reappears in the form of current in the coil circuit.
The magnetism thus forms a connecting link
between the movement of the magnet and the
current produced.

Fig. 20 illustrates an experiment in another kind
of induction — current induction. Some electric

generators have been constructed upon this prin-
ciple ; they are not the most successful, but it is
important that the reader should understand, as

FIRST MAGNETO-ELECTRIC MACHINE. 57

bearing upon the whole art of dynamo-electric
machine construction, that a bobbin A, coiled with
wire and connected to a current detector B, has
induced in it currents in opposite directions as the
wire bobbin c, drawing current from the voltaic
cell D, is moved up and down in it. The principle
is identical with that shown by the first experi-
ment, the connecting link between the energy and
the current produced being, in this case, not mag-
netism but electricity itself. All that can be done by
the magnet maybe done with the current bobbin C

The materials to illustrate practically this second
phase of the first law may consist of the same
larger bobbin and galvanometer, with a ruler,
coiled with two layers of No. 22 wire, connected
to one of the bichromate of potash cells already
mentioned.

First Magneto-Electric Machine. — A year after
the publication of Faraday's experiment, a magneto-
electric machine was brought out by Pixii, who
caused the magnet to revolve its poles near to the
iron cores of a pair of bobbins forming an electro-
magnet. He, in fact, caused by mechanical means
a permanent magnet to induce currents in the wire
of an electro-magnet.

It comes to exactly the same end, whether the
electro or permanent magnet is moved. Saxton, in
1833, improved the arrangement: he placed the
whole apparatus horizontal, fixed the compound
horse-shoe magnet, and rotated the armature in
front.

58 ELECTRIC LIGHT.

E. M. Clarke, in 1836, designed the construction
exhibited in Fig. 21. He placed the magnet
vertically and revolved the coils about a horizontal

Fig. II— Clarke's Machine.

axis, and added a commutator to make the currents
flow in one direction, which the author has en-
deavoured to make plain in Figs. 22, 23.

'HPf

^H B." B L^i

In Fig. 22 are shown the two halves of a metallic
cylinder, insulated from each other by some non-

CLARKE'S MACHINE. 59

conducting material as shown. A A are two contact
springs for collecting the currents. Let us suppose
that a constant current is being supplied to the two
halves of the cylinder : in this case, as long as the
cylinder remains in the position shown a direct
current will pass to the springs, but if the cylinder
is turned halfway round, the current will flow in the
opposite direction in the springs, because the ends
of the circuit connected to the cylinder remain the
same, and communicate now with reverse springs.
This is supposing a current in one direction, and
as long as the cylinder rotates, the current will be
reversed at each half-turn. The machine Fig. 21,
v however, gives alternating currents to the cylinder,
and as these currents change direction just at the
point where the commutator reverses, it is obvious
that the alternating currents will now be made to
flow in the springs always in one direction.

In practice, the common commutators are made
like B and c, Fig. 24, which shows Stohrer's machine
of 1836. B is a cylinder, an explanation of the con-
struction of which is given at Fig. 23, and C is a
pair of contact forked springs. A and A in Fig. 23
represent the ends of the pair of springs c, just
spoken of, and the cylinder is made up as shown
in section. There are two metal tubes on the
spindle, and they are insulated from each other by
a tube of ebonite or wood, shown black. The metal
tubes are connected to the wire coils as shown. B
and C are projections on these tubes. They go
half round the circle, B and c (bottom) on one side,

6t> ELECTRIC LIGHT.

and B and C (top) on the other. At each half
revolution, therefore, as the coil changes the direc-
tion of its current, so do the cylinder and springs,
the result being a constant current in one direction.

Fig. 24. — Stohrer'a Machine.

The current is strongest, of course, just as the coils,
with their iron cores, pass the poles. In these
machines, therefore, we have simply an electro-
magnet revolved before the poles of a permanent
magnet.

Clarke's machines are usually employed for
" shocking " or medical purposes, and as no shocks
would be felt upon grasping handles fixed to the
wire ends were the currents continuous, it is usual
to arrange an interrupter in the circuit. This may
be done either by employing a third spring, work-
ing on a brass tube split, so as to give a break of
circuit, at its centre, or by making the half-rings in
Fig. 23 overlap on the tube — that is, making them
slightly pass the central line. The result will be
that the current at each half-turn will pass for an
instant by the fork of the spring, so cutting it for
the same period of time from the outside circuit.

STOHRER'S MACHINE. 6 1

Concerning the practical construction of these
machines, it is not the author's intention to dwell
upon it at great length, on account of their simpli-
city, and because he has other, better, and newer
information on constructing a useful machine to
give. It will, however, be useful to state that the
iron used in these revolving electro-magnets, as
cores and backs, should be as soft and pure as pos-
sible, so that it may with rapidity change its
magnetical polarity. Hard iron will develop only
weak currents. The material usually employed is
Swedish iron, made soft by soaking in a blood-red
fire for some hours, and then cooling very slowly
by burying in the hot ashes or allowing the fire to
go out. The parts of iron to be screwed together
must be quite clean, and in order to secure a good
connection they should be quite flat.

The size and number of layers of wire must be
regulated by the purpose for which the machine is
intended. If high electro-motive force be required,
as for a shocking machine, the wire should be fine,
to give a great number of turns ; but if the currents
are required to do work in an external circuit of
low resistance, a thick wire is to be employed.
The electro-motive force and resistance of that
part of the circuit formed by the moving coil will
depend upon the number of turns of the wire, and
upon its size. The greater the number of turns,
the higher the electro-motive force, and the stouter
the wire, the less the resistance.
. The amount of current or quantity passing in a

62 ELECTRIC LIGHT.

given time in the circuit depends on the resistance
of the whole circuit, as well as on the electro-
v motive force ; and, therefore, if the portion of the
'circuit external to the machine is of small resist-
ance the wire of the coils should be large, and if
the external circuit is of great resistance the wire
should be small and have many turns.

The principle is to some extent analogous to that
of the voltaic battery, for when the cells are in-
creased in size the internal resistance of the bat-
tery is decreased, and if the external resistance is
small, the decrease in the total resistance of the
circuit thus obtained more than counterbalances
any decrease in electro-motive force. If the number
of elements is increased the electro-motive force is
increased, and if the external resistance is great
compared to that of the battery, this more than
counterbalances the increase of the battery resist-
ance.

It is important that this should be borne in mind
as bearing on the voltaic arc. Great electro-
motive force will give a longer arc than a small
electro-motive force ; but if we get very small inter-r
nal resistance we can produce with a given electro-
motive force an arc which, though having a very
small length, may, from the magnitude of the cur-*
rent passing, have a greater volume of light than
with the greater length of arc. The exact relation,
however, between all these elements of the ques-
tion are not as yet entirely understood. Despretz,
in a paper communicated to the French Academy

THE ELECTRO-MAGNET. 63,

published in the Comptes Rendus of 1850, describes
some experiments on the subject. He found that
the length of arc increased more rapidly than the
number of elements in series, and that by coupling
given groups of batteries in parallel circuits (or as
it sometimes is termed for quantity) very small arcs
as regards length were obtained, but the amount of
light given is not stated.

For medical machines, from No. 18 to 32 wire,
cotton or silk-covered, will answer, according to
the tension required. No. 22 or 24 will usually be
found suitable, and as many as from five to ten
layers may be wound on the reels. All connec-
tions must be soldered to prevent bad contact, and
care is necessary that the wire passes from one
reel to the other like the letter S (A, Fig. 25),

a ^ B

Fig. 25.— Electro-Magnet.

• >

so that, in appearance, the winding may be in
opposite directions. B, Fig. 25, exhibits the iron
back and the coils.

Magnets of the permanent kind for such machines
must be of good steel only. It is, indeed, impera-
tive that the steel should be of the finest kind if the
best effects are sought, and if it is required that
the magnet should retain its force for many years.
Steel of indifferent quality will soon become weak
in magnetism.

64 ELECTRIC LIGHT.

The soft steel should be heated to a dull red, and
then bent into the horse-shoe shape required. It
should then be finished up, and again heated to a
blood-red and plunged, bend first, in cold water.
This should make it so hard that a file will not act
upon it, when it is ready for magnetisation. This

may either be done by a permanent or electro-
magnet larger than the new one, or by a few cells
of the strong batteries, such as the bichromate or
Bunsen. In magnetising by battery, the legs must
be coiled with insulated wire. Four layers of
No. 1 6 will be sufficient on each, and one minute of
passing the current will suffice. The circuit should
be broken two or three times during the operation.
The process of magnetising by a magnet is by
rubbing it upon the steel, pole following pole, from
end to end, in one direction. A piece of soft iron
must cross the poles of such magnets when not in
use or being magnetised.

Large Magneto- Electric Machines.
Some eighteen years passed without any great
advance being made in the use of magneto machines,
or any increase in their size, although several
patents were taken out, some of which we shall
have to allude to farther on.

The "Alliance" Machine.
In 1 850 Professor Nollet, of the Military School
of Brussels, commenced the design of a powerful
magneto-electric machine, with the view of decom-
posing water and procuring oxygen and hydrogen

THE ALLIANCE MACHINE. 65

for the lime light. In 1853 a company for this pur-
pose was formed in Paris called the Soci6t6 G6n6-
rale de TElectricit6, and a large machine by Nollet
was experimented on in Paris. The experiments
failed as regards the lime light, but experiments
on the electric light made by Mr. F. H. Holmes
with this machine, altered to a continuous current
machine by means of a commutator, were so far
successful as to lead to further experiments both
in France and England. About 1859 the Com-
pagnie de T Alliance was formed for the manufac-
ture of electric light machines. In the machines
made by this company the commutator of Holmes
was removed and the alternate current again
adopted, and the machine was known as the
4t Alliance Machine," Fig. 26. Mr. Van Malderon
had much to do with the success of these machines,
which were used afterwards in the French light-
houses. From what was known when this machine
was invented it was not possible, perhaps, to pro-
duce a better magneto-electric generator.

To a central shaft is made fast a series of copper
or bronze discs, carrying each at its outer edges
as many as 16 Coils of wire with iron cores. The
whole of this system, which may consist of as
many discs as may be required, is caused to re-
volve by attaching the central shaft to a steam-
engine. To an outside frame is secured a number
of compound steel magnets : 8 sets of magnets are
provided, and the coils revolve between each pair
of magnet poles. The actual construction has been

66 ELECTRIC LIGHT.

varied many times ; and not only for this reason,
but because the author does not consider the
matter of sufficient importance on account of re-
cent advances, no detailed account will be given.

The currents given off are collected, one sign
from the axis and the other from a brass ring upon,
and insulated from, the axis. Alternate impulses
are of course produced, and as there are as many

changes of direction as coils, the machine gives 16
alternate currents per minute ; the shaft being
driven at 400 revolutions, there must be at least
6,000 to 7,000 alternate impulses and changes of
■ direction per minute.

As a matter of course, the parts, on account of
these rapid magnetic reversals, become heated,
but the way in which the parts are arranged causes

holme's first machines. 67

them to act as a wind fan, which not only does
away with much power, but keeps the machine
cool enough for continuous working.

It was a modification of this class of machine
which first illuminated the south lighthouse at Cape
LaHfeve, in 1863, and the same apparatus, slightly
improved, was put down at the north lighthouse
in 1865. Two 8 horse-power steam-engines drive
a pair of the machines at each lighthouse. The light
from one is equivalent to 1,900 candles. The same
machine is fixed at Cape Gris-nez.

The Holmes Permanent Magnet Machines*

Mr. Holmes gave further attention to the sub-
ject, and in 1857 a large machine, made under his
superintendence for the Trinity Board, was experi-
mented on at Blackwall under the direction of
Professor Faraday. In this machine the magnets,
36 in number, mounted on six wheels, rotated, and
the coils were fixed and arranged in 5 rings of 24
each. Direct currents were produced by means of
a commutator.

The experiments were satisfactory, and two larger
machines were made for the South Foreland light-
house. In these machines the magnets were fixed
and the coils rotated as in the earlier Alliance
machine. The machine contained 60 compound
horse-shoe magnets mounted radially in their
vertical planes, the poles of the magnets being
turned away from the centre. The coils, 160 in
number, were mounted on two wheels about 9 feet

68 ELECTRIC LIGHT.

diameter, 80 to each wheel. By means of a com-
mutator direct currents were obtained. The power
absorbed was 2f horse-power to each machine. On
the 8th of December, 1858, the electric light pro-
duced from permanent magnets was shown on the
sea for the first time at the South Foreland high
lighthouse. These machines were afterwards re-
moved from the South Foreland lighthouse and
placed in Dungeness lighthouse, where the light
was exhibited in February, 1862. Another machine
was made by Holmes in 1867, afterwards used at
Soutar Point lighthouse in 1871, in which the
magnets were fixed but turned with their poles
towards the centre. There were in this machine
7 rings of 8 magnets each, and between the rings
of magnets revolved 6 wheels on the shaft, having
1 6 coils each. This machine had no commutator,
and the alternate currents were taken off by brushes.
It is, in fact, nearly a return to the Alliance machine,
viz. permanent magnets, horse-shoe magnets turned
with their poles towards the shaft, the coils revolv-
ing, and no commutator. Professor Holmes after-
wards designed other machines which do not be-
long to the permanent magnet class, and will be
described farther on.

The Siemens' Armature.

In 1 856 Mr. C. W. Siemens patented an armature
of great merit for magneto-electric machines, and
which has been, and is still, extensively used in mag-
neto machines of various descriptions. It consists

SIEMENS' ARMATURE.

6 9

of a long iron bar, deeply grooved on two opposite
sides, lengthwise. In this deep channel the wire
is wound lengthwise of the bar, over its ends and
along its sides. One end of the wire is soldered to
the iron armature itself, and the other to a metal
ring (insulated) on the driving spindle. This
arrangement occupies the place of the electro-mag-
net in Clarke's machine, and it is rotated, by suit-
able means, between the poles of a strong magnet.

Fig. 27, which will further explain this, shows a
cross section of the armature, with
the wire in position. The sides of
the armature are solid and rounded.
Two cheeks, hollowed out, are shown
attached to the poles of the magnet.
These embrace the armature, which
revolves very closely to them. It
is usual in practice to wind the wire
until it nearly completes the circu-
lar form of the sides. Rings of
brass are then put over all, to prevent the wire
from being forced out of position by the force of
rotation. The pole cheeks are long, to embrace a
considerable length of armature. There is very
little churning of the air, as in Clarke's machines.
This form of Siemens' armature has been employed
by Mr. Siemens in a magneto-electric machine,
with a number of magnets arranged parallel to one
another, and by several other makers, among
whom may be mentioned Mr. Wilde, of Man-
chester, and Mr. Ladd, of London.

Fig. 27.— Siemens'
Armature.

70 ELECTRIC LIGHT.

The armature, and several modifications of it,
have been employed in magneto-electric telegraphic
machines, and in the better class of medical
apparatus. These forms of the machine do not,
however, concern us here, although they are,
historically, of much interest.

Breguet's Machine.

M. Breguet, a well-known manufacturer of elec-
trical apparatus in Paris, constructs a machine
which is composed of a pair of large permanent
steel magnets, passing between the poles of which
is a shaft carrying a stout iron disc, upon the face
of which is secured, at right angles to it, a series of
iron cores wound with wire. These cores are so
arranged that both magnets act upon them, one
magnet upon their free ends, and the other upon
the ends fixed to the iron disc.

The apparatus is simply an extension of Clarke's
principle, but the number of bobbins admits of a
continuous current being given off. The coils are
joined up as a battery in series. As the system is
caused to revolve, all the bobbins on one side of
the poles will give off direct currents, while those
on the opposite side will give off inverse currents.
These currents are properly collected by a pair of
springs at the changing or neutral line. The con-
tact slips are disposed readily from the central
parts of the disc, and to each strip are joined the
two adjacent ends of each pair of coils.

There is no actual break of circuit during the

VARLEY'S MACHINES. J I

revolution, because the contact springs are always
bearing upon two or more of the radial slips.

On a large scale the machine, would doubtlessly-
work very well, and is adapted for the rapid
dissipation of heat generated by the magnetic
reversals. But the same advantage is again a
disadvantage, because the coils, being some way
from the axis, act as a fan, and so consume power
in churning the air.

C. F. Varley's Machines.

In the machines constructed upon the designs of
Mr. C. F. Varley, actual, or nearly actual, contact is
maintained between the armatures and the poles of
the inducing magnets. The magnets themselves,
together with the intermediate cores, surrounded by
coils of wire, form a complete ring, link, or circuit
of iron, or iron and steel. These permanent or
inducing electro-magnets have their respective
north and south poles continuously or nearly con-
tinuously closed, notwithstanding the movement
of the armature or armatures ; but the armatures,
when rotated or moved to and fro along the iron
or link, affect the direction of the currents.

In arranging a machine on these principles in
the simplest and most elementary form, two horse-
shoe magnets are placed opposite to each other,
and between their poles are two soft-iron cores, on
which are wound coils of insulated wire. The poles
of the magnets are placed, the north opposite the
south. Together with these, which are the fixed

72 ELECTRIC LIGHT.

parts of the apparatus (Fig. 28, A, b), an armature
is employed, E, to which a reciprocating motion is
given, which places it first in contact or nearly so
with the two poles of one magnet, and then trans-
fers it to a corresponding position with respect to
the other magnet. The faces of the magnets and
of the armature may be grooved to increase the
area of the surfaces in contact or in close
proximity.

In place of a reciprocating armature, a rotating
one may be employed, so formed as to connect the

Fig. iS.-Varlty'i Machine.

north pole of one magnet with the south pole of the
other, and, as it rotates, to couple the poles
alternately.

In the figure a shaft is shown, C, reciprocally
moved by the crank and power "pulley, D. In ad-
dition to this design of a dynamo-electric machine,
Mr. Varley has invented various other pieces of
apparatus for the production of single or multiple
circuits of current.

GRAMME'S MAGNETO-ELECTRIC MACHINES. 73

M. Gramme's Magneto-Electric Machines.

M. Gramme, of Paris, introduced about the year
1870 an entirely new kind of armature, which is
essentially different from any of the forms pre-
viously in use.

It is a complete ring of iron, and the wire is wound
upon it without a break all round the circle. If
an iron ring has thus wound upon it an insulated
wire, forming a complete coil, the ends of which are
connected by soldering together, and if this coil
and ring are caused to rotate upon a central axis
between the poles of a magnet, there will be
developed in the coils a curious electric state. Two
currents are constantly flowing in the wire, such
that as each point in the circuit arrives at a spot
equidistant from the two poles of the magnet, that
point in the wire has a maximum positive poten-
tial, whilst the point in the coil exactly oppo-
site to this has a maximum negative potential.
If now the exterior turns of the wire are de-
nuded of covering, and a pair of springs made
to press, one on each side of the ring, on a line
directly between the poles, a constant current,
similar to a constant fall of water, will pass in any
outside circuit connected to the springs.

A Gramme ring may be made to work just as
described, but in practice a different way of making
up the ring is adopted.

M. Gramme makes his ring armature up as
shown in Fig. 29, where A and A are the ends

74 ELECTRIC LIGHT.

of a coil or ring, composed of a great number of
soft iron wires.

B B B are the coils of wire used by M. Gramme
to cover the ring, it being found more convenient
to make up the endless coil in sections, and then
join them properly together, than to wind the wire
from end to end and take the currents from the
bared exterior. The upper part of the ring is seen
fully coiled, while the lower side is being filled with
coils. C C are the ends of the coils of wire, which

are taken out for connecting up after the ring is
complete. At D is shown a number of copper
plates radiating from the centre, and having fixed
to them, in notches and with soldering, the ends of
the completed coils of wire. These radiating plates
are simply for the purpose of carrying the currents
along the wooden axis to the point where they are
taken off by a pair of contact pads or springs.
When the ring is complete, it will be entirely

gramme's ring. 75

covered with coils of insulated wire, and each coil
will be connected to a copper plate. The connec-
tion is made up, however, in this way : — No. i coil
has its inside end connected to No. i copper plate,
and to the same plate is connected the outside or
commencing end of No. 2 coil. The other end of
No. 2 coil is then connected to No. 2 plate, and to
the same plate is joined the outside end of No. 3
coil. This is continued around the circle, and the
plates act exactly as if the wire was simply bared,
and the currents collected direct. These radiating
copper plates are also exhibited in the following
views of the machine and its parts. The centre of
the ring, after its ends have been drawn together,
is filled up with a block of wood, through which
runs the central spindle, and into slits in which the
copper plates fit. It has been said, to aid the
imagination, that the ends of the ring are drawn
together, but the actual best mode of construction
is to make up the ring of complete rings, or of cut
wires, cut circularly and put into position so that
there is no actual break at any part.

The length of wire in each coil will depend upon
the size of the machine and upon the size of the
wire. For No. 12 wire, well insulated, as much as
12 yards may be placed in each coil, and it is im-
portant that those coils are not very thick. They
should be so thin as to allow about fifty to be
placed on a 5-inch ring ; but a great deal will
depend upon the amount of care employed. Every
part of the ring must be covered, and it will be

7 6

ELECTRIC LIGHT.

found best, as convenient in making up the central
space equal to the exterior, to coat the copper
plates with gutta-percha and varnish at their outer
edges, and to place them between the coils against
the ring itfeelf. Fuller particulars for actual con-
struction will, however, be found farther on.

Fig. 30 exhibits a section of the wire ring and
coils, B B, upon a central spindle, c c. A A are the
magnetic pole-pieces between which the ring re-

Fig. 30*— Section of Gramme's Ring.

volves. It will be observed that there are lock-
nuts to secure the central portion in position.

Gramme's magneto-electric machines are now
manufactured by M. Breguet, Boulevard Mont
Parnasse, 81, Paris, in two or thiree forms to suit
hand-power. The machines are very useful in
laboratories, where a powerful current of electricity
is often required. The best type are those with
Jamain's laminated magnets.

Fig. 31 is a view of this machine. It will be
seen that, as in all other forms of the Gramme ma-

THE HAND GRAMME. 77

chine, the currents are collected upon the neutral
line, that is on a line passing between the poles of
the magnet, vertically.

The following are a few instructions by which
the amateur may be enabled to make for himself a
very useful hand magneto-electric machine. The

Fig. 31.— Gramme Hand Magneto -Electric Machine,

construction is not difficult, and doubtlessly will
be undertaken by very many in want of some
clean and handy apparatus to supersede the
troublesome and often unwholesome battery.
Fig. 32 represents another hand-machine with

ELECTRIC LIGHT.

the Gramme armature. At present a similar
machine is in the market from the laboratory of

Fig. ]1.-G™im Hand Jlagatto-Electric Machine.

M. Breguet, at the price (in England) of £42. It
the machine became known, and the demand were
thus increased, there is no reason why the same

THE HAND GRAMME. 79

apparatus could not be made and sold for much
less, and there is really nothing to prevent the
handy amateur from making one for himself at
an outlay of, at most, one-fifth of this.

The magnet is a permanent steel one. Some
idea of the effect obtainable from the current, while
the hand-wheel is driven at about 80 turns per
minute, may be gathered from the fact that 14 in.
of No. 36 B. W. G. platinum wire is brought to a
white, glowing heat in a few seconds, and the
turning of the handle at a fairly uniform speed
may be easily kept up for almost any time re-
quired in ordinary experiments.

The general arrangement of the parts is indi-
cated by the figure, in which M M is the permanent
magnet, w the driving-wheel, gearing in a pinion
on the spindle of F F, the Gramme ring. Screws
are shown on the face of the magnet. These are
employed when the magnet is made of two or more
sections or layers of steel. A solid steel magnet
is used in the machine made by M. Breguet, but it
is undoubtedly better to make it up from two or
more layers, although in this case constructional
difficulties are much augmented. The teeth of M.
Breguet's driving-wheel are cut obliquely upon the
wheel rim. This is supposed to both decrease the
noise and the risk of breakage ; but the common
wheel and pinion will be found to work the ring
quite well. The base is solid, and it is imperative
that it should be of some heavy dia-magnetic
substance, if the machine cannot be clamped or

80 ELECTRIC LIGHT.

screwed to a table; this insures steadiness. The
bearings or standards for the driving-wheel spindle
also bear the ring spindle, and are of gun metal,
and stout. The driving-wheel may be of brass,
as, although cast-iron would do, it is very apt to
give way at the toothed portion ; brass or gun-
metal is, therefore, to be recommended. The
magnet should be of the best steel only, because
steel of indifferent quality will not only fail to take
up sufficient magnetism, but will lose its little
strength quickly. Even the best steel will, in a
few years, lose some of its magnetic strength, but
it is no difficult matter to re-magnetise it. The wire
used in the construction of the ring should be of
the softest iron procurable, and the wire from which
the coils are made should be of good copper of
high conductivity. A high degree of accuracy is
not necessary except in the making up of the ring,
which must be truly circular and somewhat equally
weighted.

Construction: the Magnet — This part of the
machine may be constructed in more ways than
one. What is really wanted is a concentration of
magnetic power at the ring-cheeks, p fi, Fig. 33.
Various forms of magnet might be employed to
effect this, exclusive of electro-magnets ; but as
space in height is of little moment, and as the
steel is most conveniently arranged vertically,
the form of magnetic arrangement exhibited by-
Fig* 33 will be found to answer the purposes of the
amateur best.

THE HAND GRAMME. 8 1

Fig. 33 shows the magnetic horse-shoe M M ; the
concaved cheeks, p p, may form part of the same
mass of metal, but it will be found most easy in
practice to make them of cast iron, and to screw
them to the magnet legs as shown at the dotted
lines on either side.
The feet or basis of the
bent bar will be most
easily screwed on from
underneath, on account
of the difficulty of get-
ting wire coils upon
the magnet in the pro-
cess of imparting the
necessary magnetic
strength. The length
of the bar complete
may be 3 ft., its width
3 in., and its thickness
\ in. It is best bent
from rolled steel, of flat
bar shape, although
any other shape of steel

Will answer the pur- Fig. 33 .-Sma]! Gramme Magnet.

pose. It iswell to know,

however, that if the thickness be greater than £ in.,
the extra metal will be simply thrown away, for
thick bars do not carry more magnetism than
thin ones, and the difficulty of hardening will be
greatly increased.

The bar should first be bent to horse-shoe shape,

82 ELECTRIC LIGHT.

with two legs of equal length, and a space between
them of 6J in. It may then be finished up, and
have the screw holes for the cheeks and feet drilled.
The screws may be ordinary f in. bolts or screws.
The hardening and tempering should then be pro-
ceeded with. It will be best to harden in a good
charcoal fire, which must be of equal heat through-
out the space occupied by the steel. As soon as a
good blood-red heat is attained, plunge it into
water, bend first, vertically. If this is not done as
directed, it is probable that the bend will be softer
than the other parts. The steel should be so hard
that a file will scarcely cut it. Leave the " skin "
on, and coat with sealing-wax or other varnish,
except where the cheeks, p p, are to bear. If the
magnet is to be magnetised by rubbing with
another, do not yet coat with varnish.

Magnetism may be obtained in tw6 .ways : these
are, first, by .rubbing with a sufficiently strong
electro-magnet ; second, by passing round the steel
a strong current of electricity. Very few people
possess electro-magnets of sufficient strength to
impart much vitality to so large a mass of steel, so.
that it will be best in most cases to use the voltaic-
current. It will be necessary to place upon the
steel legs a pair of long coils of stout cotton-covered
wire. No. 1 6 B. W. G. wire will answer very well,
and as many as four layers ought to be in each
coil, if its length does not cover the straight part of
the steel. The battery power to employ may con-
sist of just as many quart Bunsen's or bichromate

THE HAND GRAMME. 83

cells over 6 as the maker may possess. The more
battery power the more magnetism, usually up to
20 cells. Ten cells of the simple bichromate
battery in series will answer very well. The cur-
rent may be passed for about a minute, and the
circuit should be broken several times during this
minute. The bar will be more difficult to magne-
tise, as it is harder ; but the magnetism will last
longer without variation. The poles should be
crossed by a piece of iron during magnetism. Care
should be taken that the wire from one leg crosses
to the other like the letter S ; if this is not attended
to, and the wire is not wound as it is upon com-
mon electro-magnets, the magnetisation will be a
failure and must be repeated under different con-
ditions. If the wire be coiled upon the steel direct,
it will be safest for the amateur to continue the
coiling over the bend, when the direction must be
correct.

The cheeks p p are of cast iron. They should be
6 in. high by 5 in. wide, and thick enough to allow
of the 5 J in. circle, S, being cut from them. The
space between their faces will thus be about half
an inch or more. It will be best to have them cast
to pattern, and then turned out. If there is con-
venience for annealing the cast iron, this may be
done in a charcoal fire by heating to redness and
cooling slowly. The circular space, S, should be as
true as possible, for it is upon the nearness of the
iron to the ring that the effects, to a great extent,
depend. The backs must be made flat, to bear

84 ELECTRIC LIGHT.

flatly upon the clean flat surface of the magnet
itself.

If the base is to be of iron, and the feet of the
magnet are to be secured to it direct, they must be
of brass, and brass screws must be used. If a
wooden base is to be employed, the feet and screws
may be of any metal. It will thus be seen that
care is necessary not to close the magnetic circuit
of the horse-shoe by any iron prolongations. The
magnetic arrangement must be made steadily fast
to the base, in position, and the rest of the work
may be proceeded with.

The Ring, or A rmature. — In the Gramme machine,
the best form of ring consists of a flat bundle of
soft iron wires, as is exhibited by Fig. 29, p. 74.
The bundle of wires is a little more difficult to
arrange in practice than one ring of iron. A good
plan is to make it up of three 2-in. wide lengths
of soft iron, one over the other. The innermost
layer must be shorter than the second layer, and
it must, in turn, be shorter than the outside layer.
They are to form an almost complete ring, except
a gap of 1 J inch wide, to allow the coils of wire, B,
to be slipped on. This gap, when all the ring is
coiled, is then to be filled up with a piece of iron
having a coil of wire upon it. This will complete
the ring, the iron body of which must be con-
tinuous. The diameter of the ring, outside, is to be
3 J in., and its diameter inside will thus be about
2% in., its width will be 2 in., and this size of ring
will, when coiled with wire, give an outside ring

THE HAND GRAMME. 85

of 5 in. diameter or a little over, to fill the space
S, Fig. 33, with clearance room.

The coils of wire, B B, Fig. 29, p. 74, are to con-
sist of four layers of No. 16, silk or cotton covered.
Silk will give the best coil, but cotton will answer,
if well dried and steeped in melted solid paraffin.
The layers of wire are to be 1 J or rather less in
width. They should be first coiled upon a former,
or mandrel, having the same size as the ring body,
and may be kept in shape by tying with silk
thread and steeping in paraffin. They are to be
slipped on, entering at the gap A A, Fig. 29, p. 74,
until the ring is quite full, and their ends, c C, are
to go to one side. The last coil, filling up the gap
in the ring, is to be placed upon the piece of iron
filling up the gap. This iron piece should fit into
the ends so as to spring them apart, and must have a
catch or taper filed upon it to keep it in place when
it is tightly pressed in.

We have now the ring, with the wire upon it,
and all the coil ends coming out at one side. There
will be spaces at the outside not filled with wire,
and they should be filled up completely with some
such substance as melted pitch, to which some
gutta-percha has been added. Concerning this, it
should be remarked that these spaces will not
exist if the contact plates of copper (D, Fig. 29)
are placed within the ring, as there shown. It will,
however, be easier for the amateur to leave the
ends as they are, and to proceed to finish the ring
as follows : — Turn a box or hard-wood drum to fit

ELECTRIC LIGHT.

the centre of the ring tightly. Let it be very slightly
tapered and somewhat rough, to give a hold to the
cement. Its length should be 7 in., and it should
have a central hole to hold a tightly driven spindle
of £-in. round iron, of length over all 9 in. Let
the wooden drum go through the ring until its
thickest end is nearly flush with the wire coil and
the small end projects considerably. Mark this
place, take off, and in the wooden drum — com-
mencing at the mark reached by the coils — make

•

S
S

€

3
S

Fig. 34.— Gramme Ring and Contact Drum. . '

a number of slots or cuts with a saw. These cuts
must be equal in number to the coils, and must
radiate from the centre. Fig. 34 is intended to
represent this. Now turn down the wooden drum
for 2 in. at one end ; reduce until the diameter is
1 in; D, Fig. 34, will now represent this end so
reduced. The depth of slots will be reduced
also.

Into these slots must fit tightly pieces of thick
sheet copper, D, Fig. 29, p. 74. These radiating
slips must be driven in, and their edges should be

THE HAND GRAMME. 87

flush with the wood drum, both at the wide and
reduced parts.

Now finish off, with a file, the edges, and connect
the coils with the slips, and, to fasten on the ring,
press the ring firmly on the spindle or drum.
Melt a quantity of pitch and a little gutta-percha
together, and fill in between the ring and the drum
with it while very hot. When this sets it will keep
the ring in position. Bring out all the cleaned
ends of the coils, and commence by soldering the
finishing or outside end of No. 1 coil to No. 1
copper slip ; solder also to No. 1 slip the inside or
beginning end of No. 2 coil. Solder the finishing
end of this coil to No. 2 slip, and* to the same slip
the commencing or inside end of No. 3 coil. Con-
tinue thus until all the coils are joined to the
copper slips, paint over with hot gutta-percha and
pitch, and the ring with its connections is com-
plete.

Fig. 34 will render this more clearly, where E E
is the ring upon its axis, s s the coils, F F the ends
of these joined to the copper slips, which lead
along the drum, as the lines indicate, to D, which
is the reduced end spoken of, with the slips having
their edges flush with it.

Fig- 3°> P- 76, will make the whole still more
intelligible ; but there are joints shown here which
are intended to represent the way in which Gramme
mounts the ring upon its spindle.

The actual construction of the spindle and the
mounting are ordinary mechanical operations. The

88 ELECTRIC LIGHT.

toothed driving-wheel may conveniently have a
diameter of 10 inches, and the pinion a diameter
of i J inches. The number of teeth is a matter of
little consequence, but the pinion and wheel must
agree as to pitch of the teeth, otherwise they will
not run together. It will be found best to provide
a gun-metal pinion, and to drive a pin right through
its hub and the spindle. The height of the stand-
ards must be regulated nicely, to allow the 5-in.
ring to revolve freely in the space S, Fig. 33.
Nothing further should be done until this part is
very exactly fixed in position. The distance be-
tween the centres of both spindles must be marked
off on the uprights, and will always afterwards be
correct. The lower spindle must be so set that the
ring occupies as nearly as possible the central
portion of the cheeks//, Fig. 33.

As to the side of the machine at which the
reduced or " contact " end of the wood drum pro-
jects, it is of little consequence; but it will be
found most convenient to project it from the side
opposite to the driving-wheel, because arrange-
ments are to be fixed here for holding a pair of
contact springs for collecting the current from the
copper slips, as they project at D, Fig. 34.

When the ring is caused to revolve without the
contact brushes passing upon the slips, there can
be no circuit for currents, so that no currents are
induced in the ring by the magnet.

Reference to Fig. 35 will render clear the way in
which the contact spring should be arranged. One

THE HAND GRAMME. 89

presses upon the upper side of the drum end, and
the other on the under side of the same. The edges
of the radiating slips being flush with the circum-
ference, there is not a heavy contact, but it is
sufficient to collect the impulses as they are given
off. These currents are constantly in one direction,
and in this respect resemble a fall of water*

The springs shown at Fig. 35 are best made up
from a number of stiff copper wires; but brass
wires will answer, although they will be burned
sooner if there is much sparking. The springs
ppp

Fig* 35* — Contact Springs and Drum.

should be adjustable, through the screws fastening
them, to expose fresh surface to the friction when
necessary; and the thumbscrews shown serve to
cause them to bear more or less heavily upon the
axis. This part must be oiled.

From these contact springs the wires are taken
to the binding-screw exhibited by Fig. 31. Stout
covered wires should be employed to connect the
machine to any piece of apparatus. M. Breguet
supplies with the machine two rings, with stout
and fine wire, for quantity and tension currents.

90 ELECTRIC LIGHT.

The currents must always be collected upon the
neutral line.

De Meritens' Machine.

The construction of this machine provides for
the armature a wheel, with a rim composed of
segments of soft iron, wound as usual with wire at
right angles to the iron segments, which are sepa-
rated magnetically by strips of copper. All the seg-
ments are wound in one direction, but the outside
end of one coil is joined to the outside end of the
next, and the inside end is joined to the inside of
the preceding coil.

This ring-tire armature is made to revolve inside
the poles of a number of permanent steel magnets,
arranged around in a circle parallel to the shaft
of the revolving wheel. There is thus a regular
succession of poles in the ring — N.S.N.S.

By this arrangement of coils, and the size of the
coils in relation to the distance between the
magnets, as one coil is approaching a north pole
the next is approaching a south pole. Currents in
opposite direction in these two coils are therefore
produced, but by the mode of coupling the ends of
the coils described above, these currents become in
the circuit in the same direction. The current,
however, is of course reversed, as any one magnet
approaches and then recedes from any one pole,
thus the machine produces currents which alternate
in their direction.

The terminations of the wheel coils are soldered

DE MERITENS** MACHINE. 9 1

to a pair of brass or copper rings upon, and insu-
lated from, the central spindle. From these rings
the current is taken off by copper brushes, usually
composed of springy wire of large size.

It has been found that this machine produces re-
markably strong currents in comparison with other
machines of the same type. Were the sections
composing the circular armature not insulated
magnetically from each other as they are, some
comparison might be made with the Gramme mag-
neto machine, for the currents are induced under
similar conditions, except that De Meritens em-
ploys a number of small magnets.

It is questionable if there really is any advantage
in the De Meritens wheel armature, or in the insu-
lating of the segments composing it, since such
excellent work is done by the Gramme, with its
complete ring.

CHAPTER V.

ELECTRO- MAGNETO ELECTRIC MACHINES.

Hitherto we have only alluded to magneto-electric
machines in which the current was produced by-
revolving coils of wire placed on soft iron cores,
near fixed permanent magnets, or vice versa, re-
volving permanent magnets near fixed coils. It
will be evident, however, that electro-magnets
excited by currents from some source of electricity
may be substituted for fixed permanent magnets ;
and, in fact, in 1845 Professor Wheatstone patented
the substitution of electro-magnets for permanent
magnets in magneto-electric machines for tele-
graphic purposes, and in 1852 Watt, in a patent,
mentions the same idea; but no particular use
seems to have been made of these suggestions.

Wilde's First Machine.

In 1 863 Mr. H. Wilde, of Manchester, took out a
patent for a machine for obtaining electric currents
in which a large electro-magnet was excited by
means of a battery, or by the current from the
armature of a small magneto-electric machine, both

WILDE'S FIRST MACHINE. 93

machines having Siemens' armatures, a commutator
being arranged on the small machine, so as to give
a current in one direction round the electro-magnet
of the large machine. Mr. H. Wilde constructed a
large machine on this principle, and appears to
have first brought the principle before the public in
two papers, readat the Royal Society on April 26th,
1866. "1. On some new and paradoxical pheno-
mena in electro-magnetic induction, and their re-
lation to the principle of Conservation of Physical
Force. 2. On a new and powerful Generator of
Dynamic Electricity,"

The machine described consisted of a small
magneto-electric machine, in which the magnets
were permanent magnets, and the armature a Sie-
mens' armature, standing on a large magneto
machine, in which the magnets were electro-mag-
nets, these electro-magnets being excited by the
current from the armature of the smaller machine.
The current from the large armature was conse-
quently very powerful.

Fig. 36 shows an end elevation of this machine.
M m' is the small permanent magneto machine with
its Siemens' armature C ; r and / are the terminals
connecting the commutator brushes of the small
machine to the insulated copper bands of the
large electro-magnet E E\ The wires z and z' show
the external circuit connected to the contact
brushes of the armature of the large electro-
magnet.

Mr. Wilde carried his principle further, and made

94 ELECTRIC LIGHT.

and described a machine where the current from the

o Electric Macbin.

first excited the electro-magnets of a second, and
the current from the second excited the electro-

WILDE'S MACHINE. 95

magnets of a third, the diameters of the Siemens'
armatures being respectively if inches, 5 inches,
and 10 inches.

The magnets of the small magneto-electric
machine consist of six magnets weighing 1 lb.
each, and the magnets of the 10-inch machine
weighed 3 tons. The machine was furnished with
two armatures, one for the production of "in-
tensity/* . and the other for the production of
" quantity," effects.

The intensity armature was coiled with a bundle
of thirteen No. n copper wire 376 feet in length,
and weighing 232 lbs.

The quantity armature was wound with copper
plate 67 feet long, weighing 344 lbs.

The armatures were driven at the rate of 1,500 /
revolutions per minute.

When the large machine was excited by the
medium, which in its turn was excited by the
smallest machine, enormous effects were produced,
and a piece of iron 15 inches in length, and J of an
inch in diameter, was melted. This was with the
quantity armature. With the intensity armature
the current produced melted 7 feet of No. 1 6 iron,
and made a length of 2 1 feet red hot. The intensity
armature was used for the electric light, with gas
carbon half inch square, and the light evolved was /
sufficient to cast a shadow from the flames of the
street lamps a quarter of a mile distant.

In March, 1867, Mr. Wilde exhibited a large
machine of this description at the conversazione

ELECTRIC LIGHT.

of the Royal Society at Burlington House. The
electric light was shown in great splendour, and

iron rods 15 inches long and J inch
in diameter were fused.

Wild J s Armature. — Although the
distinctive features of Wilde's machine
lie in its magnets and arrangement,
the make of Siemens' armature adopted
by him calls for further explanation.

Fig* 37 exhibits this construction.
The metallic portion of the armature
is shown in the end view with cross
section lines and the wire wound upon
it in three layers. This cast-iron body
extends from A to A, and in its longi-
tudinal side grooves the wire is wound.
The length of covered copper wire
wound on is about 50 feet, and after
the wire is on, a wooden packing serves
to keep it in place and make up the
circular form of the armature. Straps
of brass encircle the armature at dif-
ferent intervals along its length ; this
prevents the coils from being forced
outwards by centrifugal force. These
are sunk in grooves made for them in
the cast-iron body and wooden pack-
ing E. Two ends of brass are fitted to the ends
of the armature, and to these brass caps are made
fast the steel axis ends C c. D is the pulley by
which motion is given to the armature from a strap.

Fig. 37

WILDE'S MACHINE. 97

The Commutator is of simple construction, and is
shown at B. It is composed of two rings or sections
of steel, fitted upon the steel shaft, c, and insulated
from each other. Upon this commutator or current
reverser press the contact springs which take off
the currents. One-half of the commutator is con-
nected to the commencing end of the coil, and the
other to the finishing end. As soon as the arma-
ture begins to move, a current begins to be induced
in it, and for each revolution two opposed currents
are given rise to in its coil. If the springs press
upon the commutator, it will be seen, since the
latter is separated by an oblique cut, that the springs
must exchange parts at each half revolution, and
as this exchange takes place at the moment when
the armature reverses its current, the springs take
off the current in one continuous direction.

CHAPTER VI.
DYNAMO-ELECTRIC MACHINES.

THE machine made by Mr. Wilde was an im-
mense step in advance of all previous means of
obtaining electricity from motive power, but a
further step was very shortly to be made of still
greater importance.

About the end of 1866, or beginning of 1867, the
idea of employing the current, or a portion of the
current, from -an electro-magnetic electric machine
to excite the electro-magnets themselves, thus dis-
pensing with voltaic batteries or any primary ex-
citing machine, occurred to Messrs. Varley, Siemens,
and Wheatstone. Mr. Cornelius Varley patented
this principle in 1866. In January, 1867, Mr. Werner
Siemens communicated this principle to the
Academy of Science at Berlin, and in February,
1867, Dr. W. Siemens communicated the same to
the Royal Society. About the same time Professor
Wheatstone published a similar idea. But all these
gentlemen were, as far as printed publication went,
long anticipated by Soren Hjorth, of Copenhagen,
who in 1854 had patented this principle very dis-
tinctly, giving drawings in his specifications.

DYNAMO-ELECTRIC MACHINES.

Mr. Murray also, in the Engineer of July
1866, states that he, using only a single machine,
passes the currents from its armatures through
wires coiled round the permanent magnets in such
a direction as to intensify their magnetism, which
in its turn reacts upon the armatures and intensi-
fies the current.

On February 14, 1867, two papers on this subject
were read before the Royal Society. The first,
received February 4, was " On. the Conversion of
Dynamical into Electrical Force without the aid
of Permanent Magnetism," by C. W. Siemens,
F.R.S.

The author says, " An experiment has been sug-
gested to me by my brother, Dr. Werner Siemens, of
Berlin, which proves that permanent magnetism is
not requisite in order to convert mechanical into
electrical force ; and the result obtained by this
experiment is remarkable, not only because it
demonstrates this hitherto unrecognised fact, but
also because it provides a simple means of produc-
ing very powerful electrical effect." After describ-
ing the principle of a dynamo machine, in which a
single element of a battery was used to start the
magnetism, he says, "The co-operation of the bat-
tery is only necessary for a moment of time after
rotation has commenced, in order to introduce
the magnetic action which will thereupon continue
to accumulate without its aid. The mechanical
arrangement best suited for the production of these
currents is that originally proposed by Dr. Werner

IOO ELECTRIC LIGHT

Siemens in 1857 (see *Du Moncel sur TElectricit^/
1862, page 248), consisting of a cylindrical keeper
hollowed at two sides for the reception of insulated
wire wound longitudinally, which is made to rotate
between the poles of a series of permanent magnets,
which latter are at present replaced by electro-
magnets.* On imparting rotation to the armature
of such an arrangement, the mechanical resistance
is found to increase rapidly to such an extent that
either the driving strap commences to slip, or the
insulated wires constituting the coils are heated to
the extent of igniting their insulating silk covering.

" It is thus possible to produce mechanically the
most powerful electrical or calorific effects without
the aid of steel magnets."

The second paper, received February 14, was
" On the Augmentation of the Power of a Magnet
by the reaction thereon of currents induced by the
Magnet itself," by Charles Wheatstone, F.R.S.

The author states, " In the present note I intend
to show that an electro-magnet, if it possess at the
commenceirient the slightest polarity, may become
a powerful magnet by the gradually augmenting
currents which itself originates." He then de-
scribes a machine the same as the electro-magnetic
part of Mr. Wilde's machine, and then goes on to
show that little effect is produced by temporarily
exciting the electro-magnet if the circuits of the
armature and magnet are separate. But if the

* It being understood that the current from the armature is by
suitable commutator led round the electro-magnet coils.

DYNAMO-ELECTRIC MACHINES. IOI

wires of the two circuits {ue. the electro-magnet
and armature coils) be so joined as to form a single
circuit, in which the currents generated by the
armature, after being changed to the same direction,
act so as to increase the existing polarity of the
electro-magnet, very different results will be
obtained. The force required to move the machine
will be far greater, showing. a great increase of
magnetic power in the horse-shoe ; and the exist-
ence of an energetic current in the wire is shown
by its action on a galvanometer, by its heating
4 inches of platinum wire -0067 in, diameter, by its
making a powerful electro-magnet, by its decom-
posing water and other tests.
*

The principle thus brought prominently forward
by Dr. Siemens and Professor Wheatstone, and
previously patented by Soren Hjorth and Cornelius
Varley, and published by Murray, was soon brought
to bear in the construction of an infinite variety of
machines for obtaining electricity from mechanical
motion without the aid of permanent magnets
or batteries, and the name of dynamo-electric
machine has been given to them in distinction from
magneto-electric machines, where permanent mag-
nets are employed. Dr, Siemens' machine, con-
structed to show the principle, consisted of flat
electro-magnets like Wilde's, with the Siemens'
armature, only the machine was laid horizontal
instead of vertical.

Mr. Wilde soon adapted this principle of re-
action to his machines, dispensing with the per-

102 ELECTRIC LIGHT.

manent magnets, but still using a small electro-
magneto electric machine, as well as a large one,
the current from the armature of the small machine
being made to pass round the wire of both machines
to excite their electro-magnets. The current from
the armature of the large electro-magnets was
used alone for external purposes.

As the heat is sometimes great, some of Wilde's
machines have the central shaft hollow, and a
current of cold water is caused to pass through it,
and also through the tubular large electro-magnet.

These machines have had their chief application
in electro-metallurgy, but they have also been used
for the production of electric lights,

Ladd's Dynamo-Electric Machines.

Mr. Ladd, of London, made a machine, Fig. 38,

which differed from Wilde's in having two flat

Fig. 38.— Fint Form of Li

electro-magnets, B, placed parallel, with Siemens'
armatures, C C, revolving at each end of the system,
Fig. 38. The current from one of the armatures

LADD'S MACHINES. 103

excited the electro-magnets, and the current from
thaother was used for external purposes. Mr. Ladd
also constructed the form of machine 'exhibited in

Fig. 39, with two armatures fastened upon one
shaft, one armature is used to excite the electro-
magnet and the other is reserved for outside
work.

104 ELECTRIC LIGHT.

Holmes's Dynamo-Electric Machine.

In 1869 Professor Holmes made a dynamo-electric
machine for the Trinity House. The machine con-
sisted of ten electro-magnets fixed to a revolving
shaft, the poles of the magnets, turned outwards
from the shaft, passing as the shaft revolved by
fixed coils. A part of the current from the coils
was passed along the shaft to the coils of the
electro-magnet. It was intended for use in the
South Foreland, and gave 2,800 candle power, but
was not used.

From this point the author does not pretend to
give descriptions of the various machines in the
order of the date of their invention.

Gramme's Dynamo-Electric Machine,

The Gramme magneto-electric machine has been
described; the Gramme ring armature being the
essential feature of the arrangement. In the
Gramme dynamo-electric machine the ring is the
same in principle and form, but the magnets are
electro-magnets, formed by bars magnetically joined
by the frame of the machine, and the insulated wire
on them is wound in such a way that the mass of
metal joined to the centres of the bars, or groups of
bars, are the magnetic poles when the magnets are
excited. The current from the coil is led through
the electro-magnet coils as in most dynamo-electric
machines.

GRAMME S DYNAMO MACHINES. 105

Kg. 40 is a view of a complete Gramme machine
of the smaller type. It is much used in electro-
plating (see the writer's "Electro-plating"), and in
illuminating workshops. Its power is over 2,000
candles. Its weight is 1 cwt. 2 qrs. The armature
should make 1,600 revolutions per minute, with a
horse-power of ij. Its price is ^60 to^70.

DD are electro-magnets, connected through the
framework, and this brings the poles to the cast-
iron cheeks which embrace the ring above and
below. The system composes, therefore, one
electro-magnet, a is the ring, c c the collecting
brushes, B the driving pulley. The height of this

106 ELECTRIC LIGHT.

machine, as shown, is 23 inches. Length 25 in.,
width, 13 in.

Fig. 41 is an end sectional view of a Gramme
machine of a small size. A a' are bars, of the elec-
tro-magnets, wound with stout copper wire. These
bars form the two poles of a magnet, as they are

Fi e . 41.— Gramme Machine. Section.

connected together at their ends, through the frame-
work of the machine, bb' are the pole pieces, or
cheeks, which embrace the ring for about seven-
eighths of its circumference. The ring revolves very
near to them. C c' are the collecting pads, brushes,
or springs. These usually consist of a bundle of

gramme's dynamo machines. 107

hard copper slips, or hard copper wires, passed
through, secured by, and regulated as to length
through the holders shown. These brushes need
attention about once a day, when the machine is in
constant action. They must riot press heavily upon
the axis, but the pressure should be increased until
most of the sparking is taken up. These sparks,
given off by slight breaks in the circuit, soon burn
the brushes and contact pieces.

Gramme's machines are now made in several
sizes, to give from 2,000 to 16,000 candle lights,
with horse-power required of from 1 J to 6, and
in weight from 1 to 8 cwts. Cost, from £70 to
£300.

Fig. 42 illustrates one of the large machines
constructed by Gramme, for electro-plating and
cognate purposes. It has 6 bar magnets, 2 rings,
and weighs 1,540 lbs. The copper wire upon all
the magnet bars weighs 400 lbs., and upon the ring
80 lbs. It is found to give an electric light of about
4,000 candles, but is not well adapted for electric
illumination or for very high speeds.

Two of Gramme's 1 6,000-candle power machines
are employed to burn the electric candles on the
Thames Embankment. One of these machines
burns 20 " candles/' The connections in the
ring of this larger machine are not made all on
one side. There are 1 20 radiating slips, 60 on each
side of the ring. These lead to two collecting
cylinders, and four collecting pads press upon these
cylinders to take up the currents.

108 ELECTRIC LIGHT.

Work of the Gramme. — In a communication to
the Academy of Sciences, M. Tresca gives an
account of a series of experiments which he had
instituted for the purpose of determining the work
performed by the dynamo-electric machines of

Fig. 42^-Large Gramme Machine.

M. Gramme. His experiments had reference to two
machines emitting light equivalent to 1,850 and
300 Carcel candles respectively. These particulars
will be found in Van Nostrandts Magazine for June,
1876.

gramme's dynamo machines. 109

A similar series of experiments were carried
out at the French Northern Railway depot, with
Gramme machines of 50, 100, and 150 Carcel lamp
power respectively, The power necessary to drive
the machines was ascertained by a comparison
with engines driven by gas or steam, of 2, 3, or 4
horse-power, used either separately or coupled.
Previous determinations, carefully ascertained,
however, with a Prony dynamometer, had given
the relative volume of gas consumed to the power
derived (*.*., useful work), all the conditions remain-
ing the same.

The lamps employed in the experiments were of
the Serrin type, and answered the purpose remark-
ably well. The following results were obtained.
The horse-power is given in Force de Cheval =
0*9876 of a horse-power.

Dynamo-Electric Machine of

50-Candle 100- Candle 150-Candle
Number of revolutions of bobbin per Power. Power. Power.

minute 1,650 800 800

Power necessary to secure a steady light —

With carbons 0*007 m * apart ... 2*2 ch. 2*4 ch. 2*5 ch.
Ditto 0*009 m. apart . * • » 2*6 ch. 27 ch.

Consumption of carbons, including waste —

With carbons 0*007 m. apart —

At Positive Pole „ 0-090 m. \ m

Ditto at Negative Pole ... „ 0*045 m. J

With carbons 0*009 m. apart —

At Positive Pole „ 0*060 m. \ ^

Ditto at Negative Pole ... ,, 0*030 m. J

The following figures will be of interest as ex-
hibiting the comparative cost of electric lights

110 ELECTRIC LIGHT.

and gas, as ascertained through the experiments
undertaken by the Northern Railway Company of
France.

Taking, for example, the lamp of 150 Carcel
• candles, and allowing it to emit light for 10 con-
secutive hours in some spacious hall or railway
depot : 1 50 Carcel candles will require a consumption
of 150 x 0*105 mc. of gas per hour, equal to 1575 m.,
which, at the rate of 0*36 fr. per cubic metre, would
constitute an expense of 570 firs. In the use of
electricity for the illumination, 150 Carcel candles
require 27 ch., which, at the rate of 0*09 fr. per
horse-power per hour, including cleaning and lubri-
cation, the expense would amount to 0*24 fr. Add-
ing to this 0*09 fr. for carbons, o'45 fr. for wages
to the employ^, and 0*20 fr. for the interest and
liquidation of the expense of instalment, the total
, amount would be 0*98 fr., or, in other words, be-
tween one-fiftieth and one-sixtieth of the expense
involved when using gas for the illumination.

An electric light of 1 50 Carcel candles lights up
advantageously a circle of about fifty metres in
diameter, and it is evident the illumination by
electricity, being so much superior in intensity,
ought to be more economical than gas, since the
illumination of the same area requires the light of
more than twenty-five gas jets, consuming 105 litres
per hour.

The best make of Gramme machine now pro-
duced, of the 6,000-candle type, is, length, 1 ft. 1 1 in. ;
breadth, 1 ft. 3 in.; height, 1 ft. 8 in.; weight,

gramme's distributor machine.

Ill

3 cwt. i qr. 22 lb., horse-power absorbed, 2*5 ; revo-
lutions per minute, 850 ; light in standard candles,
condensed beam, 6,400 ; diffused beam, 4,000 ; light
produced per horse-power, in standard candles, con-
densed beam, 2,560; diffused beam, 1,600.

The following are a few particulars given by the
British Electric Light Company of Gramme
Dynamo-Electric Machines.

•

3
D

Light in

Standard

Candles.

Horse-
power
required.

Revolu-
tions per
Minute.

•

• m*

Extreme Dimensions.

•
V

•c

60
60

Length.

Breadth.

Height.

800
2,000
6,000

fi5,ooo

*25,000

f25,ooo
♦45,000

5
8

8
13

1,600
I,6oO
900
700)
1,200)

300)
500/

cwts.

ij
if

ft. in.

1 6

2 4

2 5

3 2

ft. in.

I 2
I 2

1 4

1 10

2 8

ft. in.

1 4

1 11

2 2
2 8

t Tension.

• Quantity.

The intensity of light here quoted is approxi-
mately that given by a machine working with a
Serrin lamp in good order. When other lamps
are used, the intensity of light may differ from the
above results. The figures are given as a guide
only.

Gramme's Distributor Machine.

For the Jablochkoff candle, consisting of two
carbons placed parallel and insulated from one
another, which will be described farther on, alter-
nate currents are required, and for this purpose, and
for producing currents in several separate circuits,

112 ELECTRIC LIGHT.

M. Gramme devised a machine called the "dis-
tributor," which is used in conjunction with an
ordinary Gramme machine.

The machine in external appearance resembles a
wooden drum fixed by feet and bolts to a firm base*

Directly inside the drum surface is a flat ring of
iron, divided into 8 sections, and half of each
section is coiled alternately right and left with
covered wire. The whole outside system is there-
fore simply 8 flat curved electro-magnets. Within
this circle, projecting from the axis of the machine
like the spokes of a wheel, are 8 wide and flat
electro-magnets, which are also wound with wire
alternately right and left, their exterior poles
being thus alternately north and south. This
central system is caused to rotate, and into
the coils of the magnets is passed the current
from an ordinary Gramme, generator. There is no
actual connection between the revolving system
and the outer 8-section ring. The electro-magnets
act as usual by induction upon it, and cause each
section to give off alternate currents. These sec-
tions may be subdivided again into right and left
subsections. The subsections may also be wound
in one direction as in the Gramme ring. The wires
of the central rotating electro-magnets form one
continuous circuit, and the current is simply passed
into it by a pair of copper wire brushes pressing
upon two copper rings connected to the ends of the
circuit. The speed is from 300 to 600 revolutions
per minute, with horse-power of from 10 to 16, and

GRAMME'S COMBINED MACHINE. 113

it is usual to drive both generatbrs and distributors
from one engine. These machines give no trouble
whatever, and may be had to cut a current into 32
parts or circuits for as many or more lights.

Taking two notable examples of the application
of this machine, it was the one used to distribute
the main currents to JablochkofFs candles as em-
ployed lately in Paris. It is the machine in use
in the illumination of the Thames Embankment.
In this latter instance of electric illumination, the
main generators (of which there are two) are
1 6,000-candle power Grammes ; the current from
these is passed into the distributing machines,
which send alternate currents into 4 circuits, in
each of which there are 5 candles.

Gramme's Combined Exciting and Dividing

Machine*

This is a new form of the Gramme apparatus
recently introduced. In it the exciting ring and
"distributing" or "dividing" coils are combined
and form one machine. Figs. 43, 44, 45, and 46
represent this apparatus.

The machine, a general view of which is shown
by Fig. 43, is arranged as follows : On a cast-iron
foundation are fixed two plates of the same metal,
almost circular in shape, forming the standards
upon which the electrical parts are mounted. They
are connected together by six square bolts, and
are provided with bearings for the main shaft (see

114 ELECTRIC LIGHT.

longitudinal section shown in Fig. 44). One of
these plates is furnished on the inner side with a
circular rib on which are mounted the electro-
magnets for exciting the ring, as shown by the
cross section Fig. 45. As in the model previously
described, the coil for the alternating currents rests
on the square bolts connecting the end plates of the
frame with packing pieces of hard wood. One end

of the frame thus carries the electro-magnets of the
exciter, while the central portion supports in posi-
tion the large flat coils of the distributor, shown in
cross section in Fig. 46. Upon the main shaft is
mounted, at one end, the exciting coil, which re-
volves between the poles of the fixed electro-
magnet, see Fig. 45. The central portion of the
main shaft carries a hexagonal sleeve upon which

GRAMME'S COMBINED MACHINE. 115

are bolted the six electro-magnets of the large
distributing coil, shown in cross section in Fig. 46.
The shaft thus carries at one end the exciting coil
and upon its central portion the six electro-
magnets, radially arranged, which induce the cur-
rents in the distributing coils, see Fig. 44. Wide
bearings are employed, and in the larger machines
a system of automatic lubrication is in use.

An arm carrying a wire brush, shown in the

Fig. 4 4.— Gramnw's Combined Machine.

longitudinal section, Fig. 44, serves to place in com-
munication the coils of the moving electro-magnets
with the exciting ring. The current is collected
and transmitted by small brushes of silvered copper
wire. The brushes are worked by means of a small
endless screw. For regulating the power of the
machine, a copper wire, the length of which can be
varied at will, is introduced between the exciter
and the electro-magnets. The method of coiling

Il6 ELECTRIC LIGHT.

the wire differs slightly from that adopted in the
other machines, as instead of winding only one
wire two are coiled, in order to obtain by this mode
of coupling tension currents for small lights, or
quantity currents for large ones. Two types of this
machine are now manufactured. The smaller
weighs 616 lbs., and supplies 12 candles of from
20 to 30 Carcel burners, or 8 candles of from 40

Figs- 45 and 46.— Gramme"! Combined Machine.

to 50 burners. The larger machine weighs 990 lbs.,
and furnishes power of 24 candles of 20 to 30
burners, or 16 of 40 to 50. The following table
contains the results of some recent experiments
with these machines : —

Number of revolution! Hoise-power Number of Power of each light

43 -O

4*5

48*0

SIEMENS' MACHINE. 117

With a machine specially arranged for small lights,
there have been obtained, with a speed of 1,250
revolutions, 14 lights of 20 Carcel burners each,
with an expenditure of 4*66 horse-power. The
candles employed had carbons 3 mm. (*i2 in.)
in diameter. In all the experiments made a much
steadier light was obtained than that given by the
machines employing an independent exciter.

A recent application of this machine has been
made on board the Cosmos, a ship recently built by
Messrs. Inglis & Co., of Glasgow and Greenock, for
the Messageries Fluviales a Vapor, in South America,
for running on the rivers Plata and Uruguay. The
machine employed is capable of producing 8 large
or 12 small lights, and running at a speed of 1,500
revolutions per minute, maintains 8 lights of 50
Carcel power, each with an expenditure of 6 horse-
power. The lights are distributed as follows: —
Three in the upper saloon, three in the lower saloon,
one on the landing of the stairway leading from the
upper to the lower saloon, and one over the gang-
way. The machine, which is fixed on deck amid-
ships and under the paddle-wheel shaft, is driven by
a vertical engine with a cylinder 4 \ in. in diameter,
and 4^ in. stroke. The experience obtained at the
trial of this light was in every way satisfactory.

Siemens' Machine.

This machine has gained considerable praise,
especially in England, by its excellent perform-
ances at the trials at the South Foreland lighthouse

Il8 ELECTRIC LIGHT.

by the Trinity Board. The apparatus is made in
several sizes; the largest giving a luminous inten-

sity of 14,000 candles, and the smallest 1,200
candlelight.

Fig. 47 represents the smallest machine, and the
principle upon which its parts are arranged being.

SIEMENS' MACHINE. 1 19

the same as the other sizes, the same view will
serve for all.

B E are the flat bobbins of wire around a series
of bent iron bars, A, crossing from one side of the
machine, and curving over the armature to the
other. There is, in fact, one large electro-magnet,

made up from 5 iron bars above and 5 below. The
ends of these bars are secured, as shown, to the
side frames by 10 screws on each side as seen.
There are thus four flat bobbins of wire, and the
poles of the large electro-magnet are, one directly
above the armature, and the other directly beneath.
The end of the armature, which is of somewhat

120 ELECTRIC LIGHT.

peculiar construction, is also exhibited, and upon
its axis is the collecting drum, against which the
contact pads of copper slip press, to take off the
currents.

Fig. 48 is a plan of the same machine, where 7
electro-magnet bars are shown, the machine being
sometimes made with 7 bars. The wire bobbins
will be clearly seen in position. B is the end of
the armature, and c the collecting drum as before
mentioned. The armature in this machine is a

cylinder of iron, and the wire is coiled upon it
lengthwise, the ends of the different coils being
fastened to copper radiating slips at C. This
cylinder of iron is hollow, and is arranged so as
to revolve with the central shaft ; thus the whole
central wire-coiled cylinder revolves, while the
electro-magnet remains fixed.

Fig. 49 is a sectional end view of the machine,
where the true shape of the electro-magnet bars
will be seen. They are curved so as to embrace
the armature very closely, as shown, and the flat

SIEMENS' MACHINE. 121

bobbins of wire encircle them. These wire bobbins
are shown, the right-hand pair in section. In the
central chamber is the armature, the half of which
is in section to show the wire coils, and the left-
hand half with the ends of the left-hand coils shown
fastened to the tops of the radial slips of the collect-
ing drum. The wire is wound on the armature in
a longitudinal direction, and in a peculiar grouping
invented by Hafner-Alteneck. Each convolution is
parallel to the axis of the cylinder, and the wire is
wound in six sections of two coils each, leaving
twenty-four ends which are connected up, so that
two of these ends are brought to each of the seg-
ments of a circular commutator having twelve
divisions. But all the coils are connected to the
several segments of the commutator in such a
manner that the whole six double sections form a
continuous circuit, but are not joined in the mere
succession in which they are placed on the arma-
ture, but in a peculiar way difficult to explain
without diagrams.

The joining is so arranged all round the arma-
ture, that the coils are placed in proper relation to
each other, so that their impulses may be collected
by the contact brushes, which are placed as far
from the neutral line (neutral magnetic line) as is
found to give the strongest current with the least
amount of sparking.

Fig. 50 shows another kind of armature as
fitted to Siemens' large 14,000-candle machine.
In this machine the iron of the armature is itself

122 ELECTRIC LIGHT.

fixed, and the wire coils, arranged and made fast to
a cylinder of German silver, revolve over it. The
difference is not much, but the machine is rendered,
in the opinion of its inventor, cooler and more
effective in use, because in this case both the poles
and the iron of the armature remain fixed. The wire
coiling is almost the same, but there are double
sets of supports ; that is, a pair of bearings in which
the ends of the central shaft, to which the armature
cylinder is made fast, are fixed, and a pair of

with Fixed Armati

ordinary bearings in which revolve the ends of the
German silver or wire cylinder over the fixed one.
The figure shows the real bearings only, also the
embracing electro-magnet bars.

Although the large flat electro-magnet of the
Siemens' machine is to all intents a closed electro-
magnetic mass, with no terminal poles, as ordi-
narily found in electro-magnets, poles exist in a
line passing vertically through the centre of the
armature and the machine, the same way as in the
Gramme the poles are in the masses attached to

SIEMENS' MACHINE.

123

the centre of the bars. When the machine is set
in motion there is little resistance, but a few turns
of the armature is sufficient to collect in its coils,
from the feeble induction of the residual magnet-
ism, enough electricity to greatly strengthen the
magnetic poles, which induce stronger currents in
the coils, and this goes on, on the principle of
mutual accurtiulation, until the magnet is saturated
and the machine gives its strongest current.

The magnetic poles act strongest upon the coils
just as they pass the vertical line passing through
the axis, and the weakest currents are produced as
the coils pass the horizontal line. These are called
the maximum and minimum points. Currents are
thus induced as the convolutions of wire approach
either of the magnetic poles. The currents are at
once taken off by the contact brushes, and pass in
a constant direction through all the coils of the
electro-magnet, from the two ends of which the
current is taken for the external circuit in the usual
way. All the wires employed are, of course, insu-
lated, or covered with gutta-percha, tarred hemp,
or cotton and silk.

The new Siemens* machine is made in three
sizes, designated by the makers as A, B, and C, to
which the following figures refer :

Revolutions
per minute.

Horse-power
required.

Light effect,
standard can.

Weight,
cwt. qrs.

Cost,

£l

"A."
" B."
« C."

850
650
360

' 2

4
8

1,200

6,0OO

14,000

2 2

3 3
II 2

112
250

124 ELECTRIC LIGHT.

Several lighthouses are now illuminated solely
by the above machines. The smallest size would
appear to be in most favour, as they may be readily-
coupled together, which is often required in thick
weather to produce a powerful light, which would
be unnecessary in clear weather. They have been
adopted by the Trinity Board, at the Lizard light-
house, where six of the small machines are fixed
Of the competitive trial brought about by the
Trinity Board, to determine the most economical
machine for lighthouses, superintended by Professor
Tyndall and Mr. Douglas, engineer to the Board,
it will be unnecessary here to speak at length.
The Siemens is known to have given the best
results, but would doubtlessly have been run very
closely by the Gramme had not the specimen of
that machine tried been of an inferior type to those
now produced.

Of the working of Siemens' machines the author
has had practical experience, and can testify to
their excellent performance with one lamp in
circuit. The machines keep cool, which is a great
advantage in continuous working.

The Siemens' Alternating Current Machine.

Dr. Siemens in 1878 patented an alternating cur-
rent machine, Fig. 51. It consists of a central disc
carrying bobbins. This disc is on a shaft and re-
volves between two sets of electro magnets ranged
in circles on each side of the disc, having their
axis parallel to the shaft. The bobbins have no

SIEMENS' ALTERNATING MACHINE. 125

iron cores, and the heating caused by the mag-
netising and de-magnetising of the iron is thus

avoided. The electro-magnets are excited by a
small Siemens' continuous current dynamo machine.

Maxim's Machine.

Fig. 52 represents a dynamo-electric machine,
patented by Mr. Hiram S. Maxim, of New York.

It will not be difficult to trace in the arrangement
of the parts a distinct resemblance to the Siemens'
machine.

The curved electro-magnet bars are bolted to a

126 ELECTRIC LIGHT.

stout cast-iron projection from the base, and form,
in fact, the framework of the machine. They
extend upwards, are curved at the middle to pro-
vide a cylindrical chamber for the armature, and
are finally bolted to a metallic plate forming the
crown of the machine. Just above the base are
placed a pair of fiat wire bobbins, closely embrac-
ing the electro-magnet bars, and above the curved
central portion are
fixed another similar
pair of bobbins. This
forms the electro-
magnetic system of
the apparatus, which
is very simple so
far.

Along the sides
of the bars, just op-
posite to the central
line horizontally, are
bolted two stout side

Fig. 51.— Maxim's Machine. r _-_

frames, inese carry
between their ends the supports or bearings of the
central spindle.

The armature in this machine is similar to that
of the Hafner-Alteneck armature in the Siemens'
machine. It is a hollow cylinder of iron. The
wire is coiled upon it lengthwise in sections, and
these sections are connected to radial metallic con-
tacts, as in Gramme's armature. The brushes are
fastened in a very well-arranged frame, which is so

WILDE'S DYNAMO-ELECTRIC MACHINE. 1 27

mounted as to be adjustable, so that the machine
may give the minimum of sparking. The collectors
themselves are of thin sheet hard-rolled copper,
in several layers to give elasticity. Hard-drawn
copper wire is also used, and is, perhaps, better in
wear than copper sheet. The collecting pads, or
brushes, thus, made up, are clamped by two bolts
in position as required to press slightly or strongly
upon the collecting axis. This machine is very
compact, occupies even less space, power for power,
than the smaller Siemens, and is well adapted for
the dissipation of heat. The horse-power required
is about 2. This would appear to be the machine to
which the United States Electric Light Company
have pinned their faith.

Wilde's Dynamo-Electric Machine.

Mr. Wilde, in 1866, took out a patent which
forms the basis of a dynamo-electric machine, which
he eventually completed in its design in 1873. It
consists, for the framework, of two cast-iron circu-
lar plates, placed vertically and kept the requisite
distance apart by stay rods. Each plate carries,
projecting from its inner face, a series of electro-
magnets, sixteen in number. These fill up the
greater part of the space between the frames.
Through the centres of the frames is passed the
shaft, which carries a large cast-iron disc, rotating
between the two sets of electro-magnets. This
cast-iron rotating disc carries sixteen soft iron coils,

128 ELECTRIC LIGHT.

passed through the disc. The projecting ends of
each coil are wound with wire; thus they form
32 armature electro-magnets. These are connected
so as to form eight groups of four each, and the cur-
rent from one of these groups is used to excite the
circles of electro-magnets, whilst the remaining
seven groups are employed to give the current for
external use. By an arrangement of commutators
the currents produced can be obtained direct or

Fi (f- S] - -Wilde's Dynamo-Electric Machine. Front Elevation.

alternating. This machine is extensively used by
the Admiralty in the large ironclads, where it is
driven by a Brotherhood engine connected direct
to the shaft.

Figs. 53 and 54 exhibit the arrangement of the
parts in this new machine.

rapieff's machine.

129

RapiefFs Machine.

What would appear to be a novel idea is em-
bodied in the specification of M. Rapieff.

He proposes to construct a machine composed of
several rings, placed side by side, and revolving
every alternate ring, while the remaining ones are
fixed. In what way the wire is to be arranged

Fig. 54. — Wilde's Dynamo-Electric Machine. End Elevation.

upon these ring magnets and inductors, or in what
manner M. Rapieff is to get magnetism into rings
for his purpose, is not made clear. The inventor
calls these rings two-sided inductors, and it is
supposed that an advantage is secured by thus
arranging the parts to secure magnetic or electric
effect from both sides at once.

The inventor speaks also of the induction of

130 ELECTRIC LIGHT.

currents being generally produced in dynamo-in-
duction machines by means of setting some arma-
tures in motion with respect to some inductors, or
inversely coiled rings, prisms, or cylinders can be
applied to such machines, either as both electro-
magnets and armatures, or only as electro-magnets
and armatures. The ring-shaped apparatus in which
the currents are induced, or armatures, and the in-
ductors or electro-magnets of the same construction
through which the currents are sent, can be com-
bined together in several ways ; but these various
modifications may be considered as arrangements
of the construction just spoken of.

As far as the author is aware, the apparatus has
not been applied to the production of currents for
electric illumination, nor has a public demonstra-
tion of the machine's capabilities been made. No
particulars as to the way in which the inductors
and electro-magnetic rings should be made, or the
manner of arranging the coils of wire, are given, so
that the author is unable to place before his readers
fuller particulars of this machine or the principle
on which it is to act.

The Weston Machine.

The makers of an excellent machine for electro-
plating purposes — the Weston, of American manu-
facture — intend to apply it to the generation of
currents suitable for the electric light. The machine
is well adapted for this purpose, and with suitable

1 win
f age

WESTON S FIRST MACHINE. 131

wire upon its armature and magnets will constitute

a good generator.

u Fig. 55 exhibits the external appearance of this

apparatus.

Fig. 56 shows the central arrangement of mag-
nets. There are two sets, the inner, on the shaft,
and the outer, fixed to the cast - iron drum.
Each set is composed of six magnets. They are

arranged in pairs, forming three pairs of horse-shoe
magnets. The length, of course, is less for the
inside set than for the outside set, which is made
fast to the iron drum by screws as shown. These
magnets are composed of malleable cast iron, and
they have a shape which gives them great induc-
tive strength in little space. It will be seen that,
with reference to the outside set of magnets, the

132

ELECTRIC LIGHT.

Fig. 56.— Weston's Machine.
Section.

cylinder or drum itself forms the magnetic con-
necting link between them. The drum being of
cast iron, of considerable hardness, always retains,
as indeed do the magnets themselves, sufficient re-
siduary magnetism to start the machine in action

as soon as the central system
is put in motion.

After coiling, the wires are
taken off in three pairs.
Those wires from the N poles,
for example, are carried to
one portion of the commuta-
tor, Fig. 57, and those from
the S poles to the other
portion. The wire is finer
for the inner than for the
outer set of magnets.

After the currents are generated in the central
set constituting the armature, they pass, of course,
to the contact brushes, and from these they are at
once led into the circuit of the outside set of magnets
by the ends of the wire shown discon-
nected in Fig. 56. This can be done
because the outside system circuit is
complete, the wire being wound, with-
out break, over each bobbin in succes-
sion. One contact brush is joined to
one end of the outer magnet circuit, and
the other is connected to one end of the external
resistance, the second end of which is connected
to the remaining end of the magnet portion of

Fig. 57.

Weston's

Commutator.

to!

ioc
gin

:o
i-

WESTON'S NEW MACHINE. 1 33

^ the circuit. The contact brushes are shown at D D,

Fig- 55-

Much care is taken so to adjust and turn up the

faces of the two sets of magnets that they may pass

each other as near as possible without actually

touching.

The polarity of the armature system is continu-
ally being changed when the machine is in motion,
because the outside magnets always have like
polarity, and by induction change the poles of the
inner system six times in one revolution. The
inner system should always, in these machines, be
of the softest and finest iron, because the changes
of magnetic polarity are exceedingly rapid, and
much heating, with loss of current and power,
must result in the employment of cast or hard
iron.

Six impulses are given off at each revolution,
and as these are in alternate directions, they are
converted into three direct impulses by the com-
mutator. Because these currents are not constant
in strength throughout each revolution, the speed
should be high in employing the machine for elec-
tric light.

The idea is specially applicable to the electro-
plating vessel. For electro-plating, the machine is
provided with an ingenious contrivance by which
the reversal of polarity of the magnets, by counter-
currents from the. vats, is impossible.

Weston's New Machine. — Since the foregoing
particulars of the recognised Weston machine were

134 ELECTRIC UGHT.

written, Mr. Ladd, of London, has communicated
to the British Association (1879 meeting) a descrip-
tion with illustrations of an entirely new machine,
specially for electric light purposes, devised and
carried out with much success by Weston.

The general arrangement of the machine is ex-
hibited in Fig. 58, where A A are the magnet coils.

It will be seen that this part of the apparatus is
very like Siemens'. The pole pieces, or plates,
crossing the armature and embracing it for part of
its circumference, are composed of iron plates,
placed side by side in a mould, but separated a
uniform distance from each other. As the plates
are thus set in the mould, the iron magnets on
which the wire is to be wound are cast on to
"lugs," or projections, on the ends of the plates.
The two cast-iron ends and uniting plates form one
magnet ; the upper and lower magnets are alike,

WESTON'S NEW MACHINE. 1 35

and when joined together by the perforated vertical
supports, the inner curved edges of the field-plates
embrace about two-thirds of the circle in which the
armature is to revolve.

It will be thus seen that the inventor prefers to
employ cast iron and malleable plate in his mag-
nets, making the crossing curved prolongations
only from boiler or other rolled plate.

Fig* 59 shows the armature, or revolving portion
of the machine. It is built up of plates which are

Fig. 59. — Weston's Armature.

somewhat like a cogged wheel in shape. These
plates are stamped out of sheet iron, and when
mounted on the shaft are separated from each other
at a uniform distance. The radial projections are
then arranged in lines, so that the whole forms a
very broad cogged wheel, or cylindrical structure,
having longitudinal grooves with transverse spaces
at regular distances. The longitudinal grooves
are for carrying the wire, and it will be observed
from the nature of the structure that the wire lies
in channels three sides of which are iron, so that
the mutual effect upon each other is increased as
much as possible.

The ends of the wire are connected to the com-
mutator in much the usual way, the currents

136 ELECTRIC LIGHT.

travelling in one direction only to the field magnets.
The commutator is fitted on a portion of the shaft
which projects beyond the bearings: this admits
of its easy removal, and a new one being fitted in
a few minutes.

Another important feature in the construction is
the arrangement for ventilation ; the separation
between the pole plates of the field magnets, the
perforation in the vertical supports of the magnets,
and the light framework of the armature are all for
this purpose. The air enters the centre of the
armature, and is driven out between the layers of
wire through the spaces formed by the separated
poles of the armature and field magnets, and thus
prevents any part from becoming unduly heated.
Machines of this description are made of various
sizes and strengths, to give from one to sixteen
lights in a single circuit.

This armature should furnish a very good return
for the power expended in driving it, but the
stamping of its structural parts from sheet iron
is a mistake. Sheet iron is always hard, as rolled
by the common process, and unless it is very care-
fully annealed to secure a softer structure, the
magnetic poles of such an armature would not
change polarity readily from N. to S., or the
converse, in revolution. No doubt, however, the
thinness of the various parts composing this
ingenious armature will greatly aid its perform-
ance in practice, and the arrangement of wire
is in a certain sense to all appearance superior to

TROUVl'S MACHINE. I37

that adopted in the newest form of Siemens' arma-
ture.

Trouv^'s Machine.

This machine is the result of an idea that a
great gain in power would be obtained by doing
away entirely with the space necessary in other
machines between the moving and the fixed parts.
M. Trouve" makes the large inducing magnet

Fig. fo.— Tnmv6- S Machint

actually touch the cores of the induction coils, and
by these means causes the induction coils to re-
volve also.

Figs. 60 and 6i represent a machine on this prin-
ciple, where the large central drum is composed of
an iron core and ends, wound with wire as usual.
This drum-like electro-magnet is surrounded with
a frame of spokes at each end, and these frames
carry two or more bundles of long, thin induction

138 ELECTRIC LIGHT.

coils, which revolve in bearings as shown. This
motion is caused by friction between the electro-
magnet and the small cores. All the cores ap-
proaching the large magnet on one side of their
circle have, say, negative currents induced, and
those receding from it positive. A commutating
arrangement is fixed to the axis of each bundle,
and from this the currents are taken off, to be used
separately (from each bundle) or in combination
with those from other
bundles of cores actu-
ated by the same elec-
tro-magnet.

This machine is,
without doubt, theore-
tically good ; but it is
just as surely a step in
the wrong direction
when looked at from a
practical point of view.
The friction of the parts

Fig. (Si.— TrouvS's Machine. End. r

is a very great objec-
tion, and will consume a great deal of power
with great disengagement of heat and much wear.
The noise is also very great, and the whole appa-
ratus exceedingly complicated, . and in large size
necessarily costly. If the inventor had struck upon
the idea of obtaining actual contact by means of
endless steel bands, he would have been nearer the
practical solution of this problem. The same
principle is applied to a machine similar to the

LONTIN'S MACHINES. 139

Gramme, and it is said that this type of machine,
which it is not worth the time to describe here,
gives a light equal to 600 Carcel burners ; but the
power necessary to secure this unlikely light is not
given.

Lontin's Machine.

The machines identified with the name of M,

Lontin are intended to produce currents in a

number of circuits from one source. They consist

of a generating or exciting and a distributing
machine.

Fig. 62 will give some idea of one of Lontin's
first exciting machines, in which several bobbins
are arranged on a cylinder and revolve between the
poles of the fixed electro-magnets. A commutator
is arranged so as to give continuous currents.

The dividing or distributing machine is com-
posed of a series of electro-magnets, M M, Fig. 63,

140 ELECTRIC LIGHT.

radiating from a shaft or drum. These electro-
magnets are excited by the continuous current from
the machine above described, and cause in their
rotation induced currents to flow in the coils wound
over the soft-iron blocks or cores B B, the circuits
being taken from the bobbins B B direct ; and those

Fig. 6j.— Lontin'j Distributing Machine

bobbins may be joined in pairs or otherwise, as
may best suit the outside resistance to be worked
through. The machine is provided with a key-
board, upon which are fixed the binding screws
and switches, to cause the currents to be subdivided
to a number of lights. This machine, it will be
seen, gives alternating currents.

LONTIN S MACHINES. 141

If there are as many as 10 induction bobbins
fixed to the outside frame F F, there will be a
possibility of pro-
ducing 10 lights in
as many circuits ;
or, all those bobbins
may be combined to
produce one large
light, or any number
up to 10, as may be
required. In this

respect the Lontin ****•*■■** =«w-B *"■*"*
machine is of much value. It is, in fact, a distri-
buting machine.

In the latest machines of this maker the exciting
machines have a
number of bobbins
upon a drum ar-
ranged in diagonal
lines, as shown in
Figs. 64 and 65, re- J
volving between the '
fixed electro mag-
nets. By this ar-
rangement the cur-
rent is maintained

more uniform in its rig _ 65 ^ Loatin , t ElcitinE Machine . ^
strength.

142 ELECTRIC LIGHT.

Brush's Machine.

This is an American machine, and it may be
said that it is an attempt — a skilful one, certainly
— to improve upon the well-known armature of
M, Gramme.

The armature is a ring with a series of depres-
sions sunk in each side, and in these depressions
only the wire is wound. The armature is thus

only partially covered with the wire coils, and not
wholly enveloped, as in Gramme's armature.

Fig. 66 is a longitudinal section representing the
way in which the machine is arranged. Two power-
ful electro-magnets act upon the armature as shown.
These electro-magnets are fed from the armature,
either by the whole current or by part only, and
need .not occupy our attention further, since the
play of induction is the same as in other machines.

brush's machine. 143

Fig. 67 is intended to represent the armature,
coiled with wire. The projecting portions aid
greatly in dissipating any heat generated in the
coils, with the additional advantage of presenting
portions of the armature which may be brought very
near to the poles of the magnets, and so take up a
greater inductive strain. Concerning this, how-
ever, it must not be forgotten, in comparing this
armature with the Gramme, that, while Brush
gains magnetic effect by nearness to the poles, the
armature of the Gramme is entirely covered with
wire coils, and that for arma-
tures of the same size the
Brush has not so many coils
or sections of wire as the
Gramme.

In joining up the sections
of wire upon the armature, it
is usual to connect diametri- Fi 6 _Bn»h'. Ri DS
cally opposite sections, by
their first and last ends, together, and to carry the
remaining ends to two of the insulated contact
sections upon the commutator drum. These con-
tact sections should be diametrically opposed to
each other on the drum.

In this way all the sections are joined up, and
the currents are collected, as usual, by a pair of
brushes passing upon the drum at opposite sides.
The number of contact slips carried by the drum is,
of course, less than that upon or in Gramme's
drum.

144 ELECTRIC LIGHT.

It is usual, in constructing the Brush machine,
to lay upon the electro-magnets, before the main
stout coils are put on, a layer or two of fine wire.
The ends of these layers are arranged so that both
electro-magnets are in one circuit of fine wire, and
through this wire, when the machine is running",
but doing no work, or when it is at work, a portion
of the current induced is passing. This idea was
adopted by Mr. Brush so that the magnets might
always be maintained in a magnetic condition, and
is especially useful when the machine is used in
electro-plating, the risk of reversal of polarity being
great. Weston's idea is even better.

At the competitive trial brought about by the
Franklin Institute, United States, the Brush was
compared with the Gramme. The Brush machine
(small), at 1,400 revolutions per minute, with 3*76
horse-power, gave a light of 900 standard candles,
while the Gramme, at 800 revolutions per minute,
with 1*84 horse-power, gave a light of 705 candles.
It must be considered by all really practical men
that there is nothing here in favour of the Brush.

The Wallace-Farmer Machine.

Fig. 68 is a view of this machine. It is of
American manufacture, and has been much spoken
of as that employed by Mr. Edison, of Menlo
Park, in his electric light experiments.

The inducing magnets are flat in shape, and are
two in number, attached to the frame. This ma-
chine is in reality only an extension of the prin-

THE "WALLACE-FARMER MACHINE. 145

ciple upon which Clark arranges his two-bobbin
armature, and like it the Wallace-Farmer machine
has many defects, due to the way in which the
armature is arranged.

Instead of the armature being a straight bar,
carrying a pair of bobbins and cores before the
magnet poles, two iron discs about an inch apart
are employed, studded all round with bobbins and

cores, one set to each disc. The poles of the in-
ducing electro-magnet are thus as far apart from
each other as the diameter of the bobbin wheel, or
nearly so. There are four brushes and two contact
parts upon the axis where the currents are taken
off. The bobbins may be coupled up for tension
or quantity. The shaft is carried through, and
runs in bearings in, the side uprights.

The impulses given off by each bobbin are of

-V

146 ELECTRIC LIGHT.

necessity of very short duration, but as the speed
is high, these combine to give rise to a fairly con-
tinuous current. The construction presents a large
-f surface to the cooling effects of the air, but this
also introduces a disadvantage, as the various parts
act as a fan, which causes the air to act an appre-
ciable part in consuming the driving power neces-
sary. The high speed — 800 per minute — causes the
armature wheel to give out a humming sound when
in motion, proving the fan-like action of the bobbins.

Heat is developed in such quantity that, despite
the cooling by air, sealing-wax may be melted
upon the armature wheel when the machine has
been some time at work. This temperature is
never attained in the machines of Gramme or
Siemens.

Variously different arrangements of the magnets,
connections, and commutators may be made in this
machine. The practice, however, is to oppose to
each other the poles of the magnets, so that the
poles of the bobbin cores change polarity during
every half-revolution. Connecting up is done by
passing the currents from the coils, after they have
been commuted to one direction, through the in-
ducing magnets, as in other forms of dynamo-elec-
tric machine. The collecting points are arranged
similarly to those in Gramme's machine, the wires
being connected to metallic sectors insulated from
each other. Appended are some useful particulars
of the wires employed and the work done. The
machine is made in two sizes : —

EDISON'S MACHINE. 1 47

1
Copper Wire on Armature. 1

Copper Wire on Magnets.

Large Wallace .
Small ,,

0-42 in.
0'43 »

50 lbs.
19 »

• 1 14 in.
•096 „

125 lbs.
41 »

Work. — The weight of the large Wallace ma-
chine is 600 lbs., of the smaller size 350 lbs. The
armatures or bobbin wheels revolve, 800 revolu-
tions in the large per minute, and 1,000 revolutions
in the small machine. The horse-power required
is, for the large 4^, and 3 J for the small machine.
The illuminating power, in standard candles, is, for
the large machine, 823, and for the small, 440. Or,
per horse-power, 113 for the smaller machine, that
given by the large machine not having been deter-
mined.

j Figures concerning the consumption of carbon

I by these machines are given by the committee ap-
j pointed by the Franklin Institute to test them, but
I they are really of little value, since one quality of
carbon is known to burn as fast again as another.
The diameter of carbon rods used for the larger
machine was f in., and J in. for the smaller.

Edison's Machine.

Some time prior to Mr. T. A. Edison's discoveries
and inventions relating to telephones and phono-
graphs, there appeared in the scientific press a
notice of a new idea in electro-motors suggested or
worked out by the above able electrician. This
thing was called a " harmonic engine," but for
what reason it is difficult to conjecture.

148 ELECTRIC LIGHT.

A tuning-fork with legs as long as three feet was
provided. It was massive and heavy, and was
secured by bolts by the bend to a firm base. This
fork would, of course, vibrate to a distance of about
| in. from the centre when struck. Mr. Edison's
idea was to keep it vibrating by means of a pair of
electro-magnets of small size, with very little
current indeed, and to employ the vibratory motions
in working a pair of extremely small water-pumps,
or at other work.

The whole matter seems to be a mistake, for the
vibrations of a fork in no way aid levers to over-
come mechanical resistances ; nor does it appear to
be advantageous to turn electro-magnetic power
into vibratory movements in a large mass of metal
before applying the power to the work, which
would obviously be best done direct.

The author has gone thus far in explaining an
idea which is doubtlessly the parent of a machine
which has been called Edison's " dynamo-electric
machine." In this generator the large fork is also
employed, as also the small electro-magnets, in
duplicate ; also a pair of permanent magnets to
induce currents in the electro-magnets. It is pro-
posed to make the great fork vibrate, either by
crank and steam-power, or by means of gas or air
engines or cylinders connected to the legs direct,
which latter device appears to be preferred by the
inventor.

It is stated that the length of the legs in a fork
for a practicable machine should be about 2 yards,

EDISON'S MACHINE. 1 49

or 6 feet. It would appear to the author, when it is
remembered that such a fork will vibrate only once
at least in two seconds, that this machine would
utterly fail to produce currents of any value for the
purposes of electric illumination.

CHAPTER VII.

GENERAL OBSERVATIONS ON MACHINES.

Measurement has been made by Dr. J. Hopkin-
son and by Mr. L. Schwendler, independently, of
the energy obtained in the form of current from a
Siemens machine as compared with the energy
shdwn to be consumed in driving it, and the result
showed that only from 12 to 13 per cent, of the
energy is wasted, but as lamps are usually adjusted,
only half the energy of the current appears in the
arc, or 44 per cent, of the energy transmitted by the
strap.

Work to Expect of Machines.

Many machines churn the air to such an extent
that a continuous humming noise is produced, and
from 1 to 25 per cent, of the total driving power is
thus expended upon the air alone. One machine
examined wasted 1 7 per cent., and it is probable
that such types of generators would heat to an in-
convenient extent were it not for this air-churning.

With regard to the amount of light produced
per horse-power this varies considerably in dif-
ferent machines. Experiments were made at the

WORK OF MACHINES. 151

South Foreland by the Engineer to the Trinity
Board, the results of which are given in Mr. Doug-
las's paper read at the Institution of Civil Engineers
in March, 1879. The following are a few of the
results obtained.

Light produced

per H.P. in
standard candles,
Machine* mean of

experiments*
Holmes's Magneto-Electric .... 475

Alliance ,, 543

Gramme. No. I 758

No. 2 758

Siemens' Large 911

Small 954

Small 1,254

Thus it will be seen that a good machine should give
about 1,000 or 1,200 standard candles per horse-
power ; but the measurement of the light is, in fact,
rather a difficult and doubtful matter, owing to
the errors caused by the varying position of the
carbon points.

Some of the machines will give over this, and
some under ; but when the light falls much below
700 candle-power for each horse-power required,
it is reasonable to judge the machine as inferior.
It will be understood that this is the light ordi-
narily obtainable from separated carbons in the
Serrin pr other equally good voltaic arc lamp.

So high an illuminating power will not, in all
probability, be obtainable from any lamp of the
incandescent type, although incandescent lamps
may be found more serviceable on account of
steadiness.

152 ELECTRIC LIGHT.

Management of Machines.

Skill or knowledge of electrical apparatus is not
necessary on the part of the intelligent workman
to be employed upon the care of a dynamo-electric
machine.

Having obtained a machine, the first considera-
tion should be its fixing. A dry place should, if
possible, be selected, and the machine should be
so fixed to a firm raised framework of wood that
its commutating brushes may be at least 3 ft.
above the floor level. The speed to be given to it
must then be considered, and such a pulley em-
ployed as will produce, at the normal speed of the
shafting or engine, the normal speed stated as ap-
plicable to the machine with full current. Broad,
stout, and well-stretched belts should be employed,
and powdered resin employed upon them if there
is slipping with ordinary tightness. It is of no use
to test these questions while the circuit of the ma-
chine is open — the machine must be connected by
stout wires either to its lamp or to a coil of fine
iron wire, measuring, say, from 20 to 200 ft., accord-
ing to the resistance of the machine. When a
suitable resistance is fixed upon, start the machine
with open circuit, and when the full speed is at-
tained, close the circuit through the resistance,
either by inserting the conductor end in the bind-
ing-screw, or by screwing up a previously disen-
gaged contact brush.

Now is the time to test the speed, and for this

MANAGEMENT OF MACHINES. 1 53

purpose one of the small speed indicators now-
used will be found very useful. An engine may
run 100 revolutions with the machine at open cir-
cuit, and this may fall to 70 on closing the circuit.
If there be so great a fall as this, the engine gover-
nor is defective. It will, of course, be necessary to
open or close the throttle valve upon the governor,
until the machine gives, with closed circuit, the
proper number of revolutions per minute.

It must be distinctly understood that a dynamo-
electric machine will give less than its maximum
current if the outside resistance, in wire or lamp,
is not proportionate to the internal wire resistance
of the machine — that is, if the outside resistance is
too great, the current set up around the magnets
will be small, owing to the resistance, and the ma-
chine can only, in such a circuit, produce a small
current. If the outside resistance is small — that is,
if large short conductors are used, with a proper
lamp, the machine will not only give maximum
current, but must be controlled by the engine, for
upon increasing the speed too much the machine
will heat.

Again, never place the machine at full speed on
short circuit This is of much importance. If the
circuit between the binding screws be closed by a
short and stout wire only, all the current will be
dissipated as heat in the machine itself and the
result will probably be to destroy the machine by
burning the insulating covering of the wire. Never,
then, allow an inexperienced person to experiment

154 ELECTRIC LIGHT.

with the machine. Always see that the outside
circuit gives some work to do outside the machine.
If there is work to do, a light to produce, metal to
electrically deposit, water to decompose, electric
motor to drive, or large magnets to magnetise, or
resistance to overcome in a long, thin wire, the
machine will be kept cool, and with very high resist-
ance the speed may even be increased.

All the electric light machines now constructed —
Siemens, Gramme, Wilde, Ladd, Weston, Wallace-
Farmer, and several others described in this work
— have internal resistances of wire, suited to the
production of one powerful light with any of the
good lamps mentioned, such as the trustworthy
Serrin as an example. This resistance will suit
them, with as much as ioo feet or over of stout
conducting cable, to carry the current to the lamp.

Cables or conductors may be composed of a No. 8
copper wire, insulated with gutta-percha and tarred
hemp, or paraffined cotton only — solid paraffin,
melted ; but it is usually more convenient to make
use of a more flexible conductor, composed of from
4 to 8 No. 1 6 wires twisted together, and covered
with gutta-percha and tarred hemp. If the dis-
tance between the machine and lamp is over 50
feet, the thickest conductor should be used, so as
to reduce the resistance; and if the distance be
small, a smaller conductor will serve. These cables
are now obtainable of dealers in electrical machines.
Their price varies from 2d. to 6d. per yard, accord-
ing to the size and covering.

MANAGEMENT OF MACHINES. 1 55

Two conductors are necessary in almost every
case. Before fixing the ends in the screws of
the lamp and machine, see that the covering is
scraped off, and then screw down fast. Before
starting, either keep one of the conductors out of
its screw, or unscrew one of the brushes. Then
turn on steam, and as soon as the motion is up
close the circuit. The lamp will then at once show
light, and will separate its carbons to the proper
distance ; nothing further should be necessary, and
the lamp should burn steadily until the carbons are
consumed.

If there is jumping or flickering of the light the
carbons are bad, or this may be caused by the
engine not having a sufficiently sensitive governor
to keep up a steady motion. If the carbons are
bad, there is more need for a sensitive governor,
and the engine, however good, will not keep up a
steady current.

Dynamo-electric machines, when working upon
a voltaic arc lamp circuit, vary much in the strain
they put upon the engine. This variation is mostly
due to the difference in resistance presented every
moment by the carbons of the lamp. If the engine
is not provided with a heavy fly-wheel or a sensitive
governor, always employ one of greater power than is
really needed. Thus, speaking of common engines —
perhaps of the agricultural type — if 2 horse-power is
necessary for the machine, use a 3^ or 5 horse-power
engine ; and if another fly-wheel can be fixed to
the opposite end of the shaft, let it be done ; also

156 ELECTRIC LIGHT.

keep the governor well oiled, to give freedom to its
motions.

In the case of driving off shafting, the main
look-out is the provision of steadiness in the
machine's motion. Large mill shafting, when the
revolutions are quite regular, will be found to work
dynamo-electric machines to perfection, as will also
a large engine of any kind. It will be seen from
this that the dynamo-electric machine needs steadi-
ness in driving if a steady light be required. Brother-
hood's direct-acting 3-cylinder engine is applicable
and very suitable.

Gas engines answer fairly well, but they should
always be of large size. Otto and Crossley's 8 horse-
power gas-engine is probably the best in the market,
and is practically as handy in every way as the
best steam-engine, but more expensive in working.
An engine of the above power will drive two of the
small Gramme or Siemens machines steadily, as
will also a steam-engine of similar power. Two
machines may be driven off one pulley by using
two belts, one above the other, the machines
being placed at different distances from the en-
gine and in a line with the driving pulley. The
author has steadily driven three of Siemens'
small machines (1,200 candle-power each) from
one engine of the agricultural class of 10 horse-
power. An additional fly-wheel had to be put
on; two machines were worked off one of the
wheels, and the third off the other. The motion
was quite steady enough for all practical pur-

MANAGEMENT OF MACHINES. 1 57

poses, and three of Serrin's lamps were kept steadily
burning.

Water motors of the small type are at present,
at least in towns, much too expensive.

Turbines and water-wheels of different kinds are
perfectly applicable to the driving of dynamo-
electric machines, and where there is a good supply
of water at no cost, the expense of illumination in
this case would not reach 25 per cent, of that of
gas or oil illumination, necessarily of inferior
quality. This is reckoning the wages of an atten-
dant, and expense of carbons by the lamp system.

Oil and Lubricating. — For dynamo-electric ma-
chines sperm oil only should be used. Every
machine should have upon each bearing a "needle"
lubricator — that is, a bottle of oil, with a wire
working loosely through a hole in its wooden
cork. The motion of the " needle," rubbing upon
the shaft, liberates the oil as long as the machine
runs.

Heating of Machine in Work. — If a dynamo-
electric machine should heat to any inconvenient
degree within the first two hours of working, there is
something wrong either within the machine or in
the lamp. If the lamp is adjustable as to distance
of carbons, it will be well to increase the length
of the arc, which will reduce the heating. A
machine that heats much is not properly con-
structed, and may be improved by taking a layer
of wire off the electro-magnet. If the heat rises
so high — very near to the electro-magnet, or upon

158 ELECTRIC LIGHT.

its body — as to melt sealing-wax, it will be wise to
stop working and to increase the outside resistance;
and if it should heat with the ordinary external
resistance in circuit, the machine should be con-
demned. A machine should, however, heat very
rapidly when upon short circuit ; if it does not, it is
not of much value in the production of light. Care
must be taken that the insulation be not injured in
an experiment of this kind.

Steadiness may be tested in various ways. Per-
haps the most generally applicable test is a Bell
telephone. Pass the current, at full speed of
machine, through about 500 feet of cable, or 100
feet of stout iron wire. Cut 5 feet of insulated
wire, and bind it to the main wire by a cord,
fastening its ends on the screws of a Bell telephone.
Currents corresponding to the impulses (if any)
given off by the machine will thus circulate, by
induction, through the telephone coil. By placing
the ear to the telephone mouthpiece, any augmen-
tation or reduction of working power may be
noted by the noise in the telephone becoming
greater or less ; and if the machine does not give
a steady current, the fact will at once be noted.
Sudden rushes, ending in a slower succession of
impulses — as whir-r-r-r, whir-r-r — will, in all
probability, be due to want of sensibility in the
driving-engine's governor. With a constant re-
sistance the current should be almost perfectly
steady. If there be an unsteady light with a steady
current, it will be due to a fault in the lamp, or

MANAGEMENT OF MACHINES. 1 59

more probably to bad carbons, or both. The light
should slightly increase in brilliancy as the carbons
become shorter, in the case of rod carbons like
those used in the Serrin lamp.

Commutators, or Contact Brushes. — Almost every
machine has a pair of contact or collecting brushes,
to connect the armature wires through the electro-
magnet wires to the external part of the circuit,
as in the Siemens machine, where the brushes are
connected to two ends of the electro-magnet wires.
At the other two ends of the magnet wires are the
terminals for connecting the external resistance to
the machine. Or it may be, in some constructions,
that there are 4 brushes pressing upon the collect-
ing axis — 2 for the outside circuit and 2 for the
electro-magnets.

But contact brushes, for whatever specific pur-
pose, are the same in all machines, although their
shape and the material may be different. As far
as experience has indicated, the best brush in use
would appear to be a copper one ; it is generally
composed either of sheet or wire copper. The
sheet employed is cut into thin narrow slips, and
as the material is thin, a bundle of from 10 to 50 is
employed. Such brushes press upon the collecting
drum in a slanting position, and all the free ends
of the bundle are arranged in a slant, or to
form an angle of about 20 deg. with the brushes'
plane.

Copper- wire so used is rendered hard by repeated
drawing, and the bundle is placed in most cases

l60 ELECTRIC LIGHT.

with the ends equal, and right under or above the
axis or at the sides, to right and left, as maybe
required.

The object of all collecting arrangements is to
take off the currents just at the point where there
is least sparking, and also to do this with little
pressure, because heavy pressure causes much wear
and tear of the drum. When commutators and
brush-holders are adjustable round the collecting
drum, care must be taken to so fix them that the
loss by sparking is reduced to its minimum, and
when this spot is found, the points of strongest
discharge will also be under the brushes. To
adjust the brushes, set the machine in motion, and
make one just touch the axis, then screw up the
other until a moderate pressure is given, and the
sparking is very little. Adjust then the opposite
one in the same way ; but one brush will be found
to set off a greater number of sparks than the
other. What is really wanted is the minimum of
pressure with the minimum of sparking. Use com-
mon oil, free from grit, upon the commutating
drum. Shift the brushes when they become worn
or burnt.

Regulators of Current.

Many attempts have been made to invent or
introduce some device by means of which currents
from dynamo-electric machines might be automati-
cally regulated or governed, as the steam supply is
in steam-engines*

MANAGEMENT OF MACHINES, l6l

. There is much use for such an addition to exist-
ing generating machines, and a considerable ad-
vance towards the general applicability of electric
lights will have been made when an efficient
regulator has been introduced. For example, the
electric light without a steady current is very
unsteady, and as constant strength of current
depends in a great degree upon the motor itself,
it is found that common steam-engines, unless of
greater power than is really required, are not the best
for the working of electric-light machines. Nowthere
is a want of perfection at three points concerned in
the production of an electric light. The engine
seldom has a sufficiently sensitive governor; the
lamp is at present unsteady on account of various
defects in the carbons ; and the machine itself is
entirely without a means of regulating its supply
of current to the needs of the outside circuit.

These faults combined have done much to render
the introduction of electric illumination difficult
where a perfectly steady source of light is required.
Staite and Edwards patented, so long ago as
1855, an electric regulator based upon the heating
and expansion of metals by the current to be

regulated. The metal used was platinum, in the

•

form of wire ; this was attached to a lever ampli-
fying its movements, and the lever in turn moved
a resisting coil of wire. This coil was a common
naked helix, having some spring, and the action
depended upon more or less turns of the wire being

pressed together, so diminishing the resistance or

162

ELECTRIC LIGHT.

augmenting it as the expansion and contraction of
the platinum wire demanded. This idea, beautiful
in itself, is really the origin of the regulators used
to-day, and the selfsame principle is employed by
Mr. Edison, in his attempts to construct a self-
regulating lamp. This device is, however, to a
great extent a failure from various causes con-
sidered under the description given of the lamp.

Dl Siemens has constructed a regulator worked
by the expansion and contraction of a strip of

To Lamp

From Machine

Fig. 69.— Siemens' Circuit " Regulator.

»»

platinum ; but the apparatus, so far, has not been
practically applied. The action is the same as
that employed in Messrs. Staite and Edwards*
device. The resistance coils used are put in
or out of circuit by the amplified movements of a
lever.

Fig. 69 is a view of the working parts of perhaps
the best regulator yet put into use generally. It is
issued by the makers of the Siemens machine.

MANAGEMENT OF MACHINES. 163

A is an electro-magnet in the circuit of the
machine and lamp ; B is a contact point in connec-
tion with the main circuit through the resistance
coil shown only. Normally, the electro-magnet
attracts the armature and the current passes right
through the instrument without resistance; but
should the lamp by any accident go out or break
circuit, the machine cannot be damaged by the
engine racing when the load is taken off. The
resistance coil is equivalent to that of the lamp
when burning, and to keep it cool it is immersed
in a small tank of water in the base of the regu-
lator.

It will at once be seen that this is far from being
a regulator, in the true sense of the word, because
it is only useful in the case of any excessive change
in the current strength. It is, however, no doubt a
valuable adjunct to the dynamo-electric machine,
as much harm cannot be done to either engine or
machine when this is in circuit. It is joined up in
the usual way, .by cutting the conductor near to the
machine, and connecting one end to C, and the other
to the same point, but, of course, on the opposite
side of C, so that when the machine is working the
current may pass direct to the lamp. The other
connections, c l and c 2 , are made by cutting the
remaining conductor, and joining up as shown.
The instrument may be regulated for strong and
weak currents by the antagonistic spring screw
and by the contact screw.

In all regulating apparatus intended to regulate

1 64 ELECTRIC LIGHT.

the current by actual breaking of the circuit, a very
great objection is introduced by the charge spark-
ing at the contact. A word of explanation as to
what this really is will not be unnecessary to the
untrained worker.

When two short wires are attached to any
electric source, their ends touched and then sepa-
rated, an exceedingly feeble spark only is noted ;
but when the wires are long, a large spark of great
brilliancy is produced, and when the same wires are
coiled up, especially around iron, the spark is still
further increased in size and length. This is
usually spoken of as the " extra" current spark, and
is due to electro-magnetic induction.

Any regulator, then, depending upon actual
breaking of circuit for its action, must so far be a
failure, because no contact points yet discovered or
tried will withstand the burning power of the
electric spark. Edison's lamp was to work by the
constant making and breaking of the circuit, and
as no contact points could stand this for over a few
minutes and retain their sensibility, the idea was
thoroughly impracticable, and is only of use in the
case of Siemens' check just illustrated.

Dr. Siemens also described, in January, 1879, a
regulator based upon the curious property, dis-
covered by Hughes and Edison, that carbon when
under pressure will conduct better than when free
from pressure. Thus Siemens proposed to place a
number of carbon discs in an insulating tube, pass
the current through them, and by means of a

MANAGEMENT OF MACHINES. 1 65

variable expansion of platinum, as in Staite and
Edwards' apparatus, to vary, by more or less
pressure, the conductivity of the carbon series.
There is no positive break here, and something
remains to be done with the idea.

CHAPTER VIII.
ELECTRIC LAMPS AND CANDLES.

An electric lamp is the apparatus at which the
electric current is actually converted into light.
Generally it consists of an arrangement of two
carbons for forming the electric arc between them,
but endeavours have also been made to obtain
light by the mere heating of a short piece of
carbon or metal, and in that case the lamp consists
of an arrangement for this purpose.

When two pointed sticks of carbon attached to the
two poles of a source of electricity, such as any of
those previously described, are touched together, a
current will pass, and the carbons may then be
separated a certain distance without interrupting the
current, which is carried on by the intermediate air
heated by the current, and an exceedingly brilliant
light, which is termed the voltaic arc, will be pro-
duced between the carbons.

Particles of burning carbon are projected from
one carbon to the other and a portion of the light
is attributed to this flow of burning matter, but the
greater portion is due to a conversion of electric
current into light, as inexplicable as that pro-

THE VOLTAIC ARC. 1 67

duced in a spark discharge between two con-
ductors, or in a flash of lightning.

The positive carbon, or that from which the
current comes, is consumed very fast, while the
negative or receiving carbon is acted upon very
slightly, and becomes pointed. Carbon rods will
burn at the rate of about 5 in. per hour, according
to their size, and as they burn away must be fed
up to each other, if it is desired to continue the
light. This was formerly done by hand, but now
it is done by such perfect automatic lamps that the
light is not only perfectly steady, but gives no
trouble for several hours together, and needs no
attention whatever. It is no difficult matter to feed
carbons by hand, by means of a screw attached to one
of the pencils, and for taking photographs by quick-
acting plates this will answer very well, but a lamp
is the only satisfactory means by which ordinary
carbon sticks can be burned for general purposes.

In another class of lamps the carbons are kept
actually in contact. Thus, if pointed rods of
carbon, or one pointed and one flat carbon, are
attached to the poles of a source of electricity and
the carbons are brought together, a bright light
will be produced at the point of actual contact,
and will remain practically steady as long as the
carbons are kept together. This principle is
adopted in several different kinds of holders or
lamps. The light is partly due to the incande-
scence of the carbon and partly to the voltaic arc
produced round the point of contact.

1 68 ELECTRIC LIGHT.

Another way is to join the two ends of a power-
ful current wire by a thin strip or coil of some
difficultly fusible metal, or by a strip or thin pencil
of carbon itself. In either case the resistance of
the material, it being small in bulk, causes the
passing energy to heat it to a point past white
heat, when it emits a light of considerable brilliancy.
The metal generally used in such burners is plati-
num, sometimes alloyed with other metals, chiefly
iridium.

This is called light from incandescence, and there
are in use various devices by means of which the
principle works perfectly well.

Such lights are not so brilliant as those produced
when the carbon pencils are actually separated.

As early as 1843 experimenters were at work
upon the useful production of electric lights, and
the celebrated Foucault produced the light from
rods of gas carbon and a battery of Bunsen cells.
Previously to this wood carbon was frequently used,
and among others by Sir Humphry Davy, at the
beginning of the present century, when he produced
his (and the first) voltaic arc over the Royal Insti-
tution, from a battery of 2,000 cells.

It was soon found that the electric light was not
only independent of air or oxygen for support, but
possessed the properties of sun-light in showing all
colours as they should be seen. It was also found
that no vapours, smoke, or appreciable (diffused)
heat were given off by it, and that its chief peculiarity
was exceeding brilliancy difficult of diffusion.

THE VOLTAIC ARC. 169

Fig. 70 is an enlarged view of the carbon points
as they actually appear when their image is thrown
upon a screen for examination. P is the positive
or feeding end, and N the negative or receiving.
The nodules observed chiefly on the lower carbon
are impurities in the substance, which melt and
stick to the points. The light itself is not only
produced by electricity itself, but by millions of
highly incandescent particles car-
ried from the positive to the nega-
tive carbon.

The stronger the current under p
these conditions the stronger the
light, and the greater distance
will the carbons admit of being
separated without extinguishing
the light. m

The power of electric lights is
usually expressed in terms of
standard candle power, and varies Fig. 70.

Carbon Point*,

from, say, 100 candle power to
16,000, above which it has not as yet been found
convenient to go in one light, as carbons are at
once split up with higher power.

It would appear that about the year 1 845 the first
patents were applied for in electric lamps or
burners. The names of King and Wright are the
first concerned in the invention of patented appara-
tus of this kind. King's patent was for an incan-
descent burner of platinum, and Wright used re-
volving discs of carbon. Probably the best attempt

170 ELECTRIC LIGHT.

at obtaining a steady light shortly after this date
(1846) was that of Staite and Edwards, who made
a lamp in which two rods of carbon were pressed
together at an angle upon some badly conducting*
substance. Greener, Staite, and Petrie then pro-
duced lamps of various kinds, and in 1 848 a self-
regulating lamp was made by Foucault.

It will be unnecessary to give particulars of all
the numerous, and often useless, pieces of apparatus
invented since 1845; hut the author will describe
those only which have been well tested by elec-
tricians in practice.

Carbons.

As has been before stated, rods of charcoal were
first employed as the points in the production of
electric light. This burns too fast, and is too easily
split, although, when well prepared, it gives a
steady light.

The scale of deposit found in the interior of gas
retorts after trial was found to be well adapted for
the purposfe. This substance is cheap enough, as it
may usually be obtained for the trouble of carrying
away ; but it is not, in its^^de state, well suited
to the production of steadyN^ws. It is very im-
pure, containing various f<aH| earthy matters,
sometimes metals ; but silica is the -most trouble-
some constituent, as it is more difficult of fusion
than the pure graphite. A good gas carbon is of a
fine texture, and a clear grey colour. It is very
difficult to cut or shape on account of its hardness.

MANUFACTURE OF CARBONS. 171

Many attempts have been made since 1846 to
obtain a perfectly pure powder of graphite or other
substance suited to the steady production of light.

Staite and Edwards* Carbons. — These were in use
for a considerable time before other inventors came
into the field. They were made by finely powdering
the best gas carbon, mixing with a little sugar
syrup, kneading and compressing in the shape of
rods. They are then gently heated and saturated
with a strong solution of sugar, when they are
heated to whiteness, and are found to burn with
tolerable uniformity in good lamps. The same
method, with the substitution of tar for the syrup
and the addition of ground charcoal, was patented
by Le Molt a few years later.

ArchereatHs Method consists of mixing with the
ground and selected graphite some magnesia,
which is supposed to render the light more steady.

Carr&'s Carbons. — These are, and indeed have
been, the standard carbon rods in use. He mixes
with the substance certain proportions of potash
and soda, which slightly lengthen the arc and add
to its brilliancy. Good carbons are made from
the powdered carbon, lamp black, and syrup of
cane-sugar, with a little gum. The proportions
may vary, but the following are recommended : —
Carbon powder, 15 parts; calcined lamp black,
5 ; syrup, 7. These substances are perfectly mixed,
with a very little water added, when the mass
is well pressed and rounded by being passed
through a draw-plate. They are then baked dry,

172 ELECTRIC LIGHT.

and while still hot are put into a solution of cane
sugar or a strong syrup, which is pressed into their
pores, and they are then again heated to a high
temperature. Carr6 would appear to prefer coke
dust, as found in retorts, to ground carbon.

Many attempts have been made to improve the
conducting power and steadiness of carbons by-
coating with metals. They are almost all failures,
and lamps are now in use by which the current is
not caused to travel the whole length of the carbon.
A great many mixtures have been tried both in-
side and outside the carbons.

Carbon rods frequently crack and split at the
points, putting out the light for an instant. This
usually results from the use of inferior carbons,
and by employing them of too small a body for
the current. Carbons should be selected to suit
the current to be passed through them. If they
are irregular in composition they will crack, and
whether regular or not they will crack when the
current is too strong for their size. M. Gramme
mixes with the powders nitrate of bismuth, which
is of use in preventing cracking and augmenting
the steadiness and power of the light. The average
price charged for good carbon rod, $-in. in dia-
meter, is iod. per foot.

Lamps with Automatic Regulators for Arc.

When the electric light is obtained by carbons
separated a certain distance so as to produce the
voltaic arc the carbons consume away, and thus

AUTOMATIC ELECTRIC LAMPS. 1 73

increase the length and electric resistance of the
column of heated air between them. As the re-
sistance increases, the current of course decreases ;
this decrease of current again lessens the heat
of the column of air which has already been
lengthened, thus the rapid increase of resistance
soon causes the arc to cease altogether suddenly.
To overcome this the carbons must be kept con-
stantly at the same distance apart. At first this
was done by hand adjustment, but this was evi-
dently an incomplete arrangement, and the atten-
tion of electricians was turned towards some means
of overcoming the difficulty by mechanism that
should act automatically.

In 1846 Staite used clockwork to bring the
carbons together, the rate of the clock being pre-
viously regulated to suit approximately the con-
sumption of the carbons, but this was not found to
answer, as the carbons burn irregularly.

Attempts to make the decrease of current itself
adjust the carbons were soon made. It is difficult
to give the date of the earliest invention for this
purpose, but Staite as early as 1847 patented a lamp
in which the clockwork for moving the lower
carbon is controlled by a movable weighted soft
iron core acted on by a hollow electro-magnet.

Perhaps the Foucault and Wilson lamps were
amongst the earliest. But the author cannot pre-
tend to place the various lamps in chronological
order, but commences with the Serrin lamp, as a
good type of the clockwork or self-regulating kind.

174 ELECTRIC LIGHT.

The Serrin Lamp.

This lamp is, in all probability, one of the best con-
trivances of the mechanical kind ever constructed for
the perfect regulation of the electric light, as pro-
duced between a pair of vertical rods, end to end.
It is in more extensive use than any other lamp of
the kind, and experience has shown that there is
really no better automatic lamp in existence for
producing the light by this particular method.
Serrin's lamp, as made by M. Breguet, is used in
the lighthouses, and for almost every electric light
of the single kind yet established. Its price is
high, £21, but a glance at its construction and
efficiency in use places it far before others at lower
prices.

Fig. 71 is an illustration of the interior of this
lamp. A is an] electro-magnet ; B its armature,
which, when the current passes, is attracted, and
through its connection with the sliding bar of the
lower carbon, E, pulls it down, and makes the
separation. The apparatus is put in motion, not
by a spring, but by the weight of the upper car-
bon holder constantly tending downwards, which
pressure communicates motion to the train of
wheels by its toothed rack, as shown. The rate
of descent in the upper carbon with its rack is, of
course, regulated by its [setting the wheel train in
motion, which brings a check, connected to the
left side of the lower carbon holder, to bear upon
the arms of the radial fly-wheel lowest in the train

THE SERBJN LAMP. 1 75

of wheels. This locks
the length of the arc
until from burning
away the current be-
comes weak, and the
armature is allowed
to go upwards with
its lower carbon
bolder. This it is
enabled to do by the
springs constantly
pulling it away from
the magnet. When
the lower carbon can
thus move upwards,
the upper, its wheel
train being free, by
the check being
taken off the radial
fly, falls until the
current is strong
enough to again pull
down the lower
holder and to again
bring the check to
bear upon the radial
fly, thus locking the
distance. F is an
adjusting screw, and

the two upper screws ' rig. 7 ,.-seiTi n 'a Lun P .

are for the same purpose. This lamp gives no

176 ELECTRIC LIGHT.

trouble, and may be set in action by the most
ordinary workman. It will take any length of
carbon rods up to about 12 inches.

Archereau's Lamp.
Fig. 72 represents the lamp invented by M.
Archereau. It
is very simple
in construction
and action, and
forms one of the
best regulators
forshort periods
in use.

■The author
can especially
recommend this
form of lamp to
the notice of
amateurs, or
those requiring
a simple regu-
lator, easily
Fi i -Arch ■ l» made and man-

aged for short
periods. It will be found very well suited for the
production of electric light in magic-lantern and
other similar apparatus, while it is also suitable for
larger displays or the illumination of buildings.

It consists of a bobbin of No. 12 silk-covered
wire, providing one layer, or two at most, for

ARCHEREAU'S LAMP. 1 7 J

weak currents, A; having within it a column of
metal, B. This is best made of one half (top)
copper, and the other half (bottom) of soft iron*
The upper end, B, carries the lower carbon rod,
which is fastened in its end by the set screw
shown. The connection to this coil of wire is from
the binding-screw to one end, while the other end
of the coil has soldered to it a thin copper spring
pressing gently upon the copper part of the
interior column. The current thus passes to the
lower carbon, while the other connection is made
to the metallic upright at D. This metallic pillar
may be of brass, arid it must carry a right angle
arm, to which the upper carbon holder is made
fast as shown. A counterpoise weight, C, is
supported by a cord, which passes over the
central pulley, and, going to the inner side of the
metallic column in the wire coil, supports it in
position, with a gentle pressure between the points.
The connection with the electric source must be
so made as to draw down the iron cylinder by the
induced magnetism. The action is, then, this :
the current passes into the coil, up through the
carbons, and at once, separates them. If the sepa-
ration has been too sudden or far, the weight will
bring the points nearer to each other again. The
arc is established as soon as the current passes,
and the weight should so counterbalance the
column that its action may not be too strong for
the current. It will be found best to have the
counterpoise adjustable in weight.

178 ELECTRIC LIGHT.

Fig. 73 represents a coil and bobbin of wire for
this lamp, having within it the copper and iron
column, with the carbon rod fixed in the top. For
a lamp to burn, say, for 1^ hours, with a light of
500 candles, the wire may-
be No. 12, and it should be
silk-covered.

The bobbin should be of
hard wood, with a thin tube.
It may be 5 inches long,
and the central hole may be
f in. in diameter, while the
diameter of the sliding
column may be \ in. or even
less. The upper portion
will do if of copper tube
only, and it will be found
most convenient to make
the lower half of soft-iron
bar. The total length of the
column may be 7 inches,
and it should be provided
with a brass or iron socket,
having a |-in. hole in its
Fi K . 7 j.— Bobbin forArcbereau's end for the reception of car-
bons of different sizes.
The total height may be 13 inches, and the cord
pulley must be placed above the middle portion of
the main pillar, as shown, in a slot cast or cut for it.
It will be found convenient to have the right-angle
arm adjustable around the main pillar as an axis by

gaiffe's lamp. 179

a thumb-screw ; and a good plan is to have the top
carbon screw or socket drilled right through, so
that the carbons may be pushed downwards from
the top.

The base must be solid and firm. It will be
found best in most cases to provide one of cast
iron, and to insulate the binding -screw from it by
fastening in a block of wood in a -J-in. hole cast in
the base.

Of carbons, the size will depend altogether upon
the strength of current to be used in the produc-
tion of the light. This lamp is very well suited to
the current as obtained from voltaic batteries, and
it will prove useful to give sizes of carbons best
suited to different strengths of such currents.

A current from 50 cells of the Bunsen, or 40 of
the bichromate of potash cell, will consume from
i to T Vin. carbon rods, and if the cells are large
the carbons may be ordinary § rods ; for smaller
numbers of cells the J-in. rods will be found quite
large enough, and round rods are better in work
then square. They should be pointed on com-
mencing the light.

Gaiffe's Lamp.

This lamp bears a strong resemblance in prin-
ciple to the regulator devised by Archereau, pre-
viously described.

It has a vertical coil of stout wire (Fig. 74), into
which the lower carbon bar, A, is drawn when the
current passes. This bar, unlike that used in

1 86 ELECTRIC LIGHT.

Archefeau's lamp, is toothed throughout a portion
of its length, and
actuates a wheel of
25 teeth, the spindle
of which carries
another wheel of 50
teeth, insulated from
the spindle. The
second, or largest,
wheel engages an-
other racked bar, B,
actuating the upper
carbon, and any mo-
tion of the first bar
in its coil gives a
rate of approxima-
tion of 2 : 1 to the
bars, the upper hav-
ing, of course, to
move the faster to
make up for the
greater length burnt.
Fig. 75 shows the
racks, E and E; F is
a pair of wheels
bearing the ratio 2 :
1 to each other's
effect upon the racks.
The rack actuating
iove the faster, because
: than the lower point.

tion ™

GAIFFE'S LAMP. l8l

In order to maintain the contact between the
carbons when the current is not passing, a clock-
spring is provided upon the spindle of the wheels,
and this constantly urges the carbons together.
The strength of this spring is such, that the pull of
the bobbin upon the lower bar, when the current
passes, will overcome it, and separate the carbons
to the required distance for the production of a
brilliant light.

All the parts of each carbon holder are, of course,
insulated from each other. There is a
great advantage in this arrangement as
applied to such purposes as require the
light to occupy one point continually,
such as in lighthouse illumination and
the working of various instruments, in-
cluding magic-lanterns. It is a well-
constructed and arranged lamp, and on
account of its simplicity can be under-

Fie* <je t

stood at a glance ; while the cost of con- Lamp Rack

° work.

structiori and the market price is much
lower than that of Serrin's lamp, before spoken of.
The lamp maybe obtained through English houses
at about £8, while the Serrin costs about £21.
The Gaiffe lamp is not, however, adapted for the
consumption of very large and long carbons.
Otherwise it may be said to possess all the advanr
tages claimed for the Serrin, and is certainly more
manageable when anything goes wrong in un-
trained hands. It is fixed upon a steady base, and
a circular metallic case encloses the working parts.

1 82 ELECTRIC LIGHT.

Duboscq's Lamp.
The regulator connected with the name of Du-
boscq was invented originally by Foucault, though
the mechanism has been considerably improved by
Duboscq. This lamp is well known in England,
as it was for a long time the only efficient regu-
lator of vertical carbons obtainable. It has had
considerable application in the production of elec-

Fig. 76.— Detent of Duboscq's Lamp

trie lights for demonstrating purposes, such as the
experiments of lecturers and occasional displays.

It has the same kind of regulating arrangement
as Gaiffe's lamp. The racks are, however, in this
arrangement actuated entirely by a clockwork
spring and train, and the current only performs
the part of stopping and releasing this train when
the carbons are apt to go too near to each other,
or the current is too weak by too great separation
of the points.

SIEMENS' LAMP. 1 83

Fig. 76 exhibits the arrangement adopted for
stopping and releasing the train as required. A
is a metallic finger or detent, which stops or
releases the mechanism contained in a case above.
B is a soft-iron armature to which the detent is
attached; c is an electro-magnet, by which the
current is enabled to control the movement of the
parts as required. D is an arrangement control-
ling the spiral spring shown, which balances the
attractive force of the magnet when in work.

The current may be said to have almost perfect
control over the movements of the points, and per-
mits approximation to each other until the arc or
separation for light is of a suitable length for the
current to maintain. The arrangement D, acting
upon the antagonistic spring, enables the adjust-
ment of the lamp to any given strength of current
to be easily made by hand before commencing
work. In this lamp also the points are kept as
nearly as possible in one position, and for this
reason the arrangement is suitable for lighthouse
work, but it is undoubtedly inferior to Serrin's and
Gaiffe's.

Siemens' Lamp.

This lamp was originally devised by Herr Hafner
von Alteneck, who was the inventor of the par-
ticular mode of winding the wire on the armature
in the Siemens' dynamo-electric machine in its
present form.

As in several other lamps, Siemens' apparatus

1 84 ELECTRIC LIGHT.

has the carbon holders racked, and the pinions of the
racks are on one axle and of such diameters that
the upper carbon has double the run of the lower.
Fig. 77 exhibits the chief peculiarity of this lamp.
It will be seen that it con-
sists of an electro-magnet
arrangement, A, L, T, through
which motion may be com-
municated to the , ratchet
wheel, u, by the pawl s. l
is the fulcrum of the magnet
armature, which is caused
■ . to oscillate opposite the

I poles of the electro-magnet,
' E, by reason of a contact-
breaking arrangement being
situated ate, with an adjust-
able platinum-tipped screw.
The armature is pulled from
the magnet poles by an an-
tagonistic spring, f. When
the spring is enabled, by the
cessation of magnetism in
the magnet, to pull to itself
Fi K . 77 ._Si«n>™-L ain p. the armature, the pawl, S,
is compelled by a pin to
leave the teeth of the ratchet wheel, u, and the
upper rack may then descend, causing, as it does
so, the under rack to ascend at half the speed.
The current goes, as indicated by the arrow, up
one wire and rack and down the other.

SIEMENS' PENDULUM LAMP. 1 85

This lamp is suited to work either with alternating
or direct currents, but if alternating currents are
used, there is no need for the contact-breaking
stop, C, the change of polarity in the connections
giving the required motion.

In the case of a direct current, the action is as
follows: — As soon as the current passes, a small
light is shown at the point of contact of the carbons,
and this passage of current causes the electro-
magnet to work the armature with an oscillating
motion until the pawl has separated the carbons
through the rotation of wheel u. When the
separation is sufficient the current is weakened,
and the antagonistic spring prevents the weakened
magnet from giving further motion to the wheel.
A continuous check is thus kept upon the falling
tendency of the rack with the upper carbon. This
lamp is admirably suited for lighthouse and general
purposes.

The Siemens and Hafner-Alteneck Pendulum

and Differential Lamps.

This lamp, the invention of Herr Hafner von
Alteneck, recommends itself at once by the almost
total absence of wheels and the simplicity of its
moving parts. The lower carbon-holder is in this
lamp a fixture, and the upper carbon-holder is
formed by a rack, which in sinking down will turn
a pinion. In order to moderate the speed with
which this pinion turns, a common escapement-
wheel with its pendulum is fixed to the same axle.

1 86 ELECTRIC LIGHT.

A movable frame, serving as a guide to the upper
carbon-holder, carries the pinion and the pendulum,
being lifted, more or less, by a solenoid acting on
an iron core connected to the framing. During
the normal burning of the lamp, a small lever fixed
to the movable frame catches the pendulum, pre-
venting it from moving, and thus keeping the
upper carbon-holder stationary. When the arc
becomes too large, or the current is weakened by
other causes, the solenoid will let the frame drop a
certain distance, the free end of the little lever is
arrested by a projection of the lamp casing and the
pendulum is free to move. The upper carbon will
then at once descend, but as soon as the distance
between the carbons is diminished, the strength of
current will increase, lift the frame, and the little
lever will again stop the downward motion of
the upper carbon-holder. In order to lessen the
suddenness of the motion of the framing, an air-
pump is connected with it, and a spiral spring is
attached to the core, by which the attractive force of
the solenoid can be more or less assisted according
to the strength of the current. In practical work
this form of lamp has proved to be very efficient,
as its management is easily understood, and hardly
any part of it can get out of order. Six such lamps
have been in use at Blackpool, a watering-place in
Lancashire, during two months in all sorts of
weather, and never failed after a few mechanical
imperfections had been removed. Similar lamps
are at work in the British Museum, where all the

SIEMENS' PENDULUM LAMP. 187

apparatus has been managed, after the first fort-
night, by the Museum authorities themselves, and
no difficulty has been experienced by them in
maintaining the regulators in good working order.
At present these lamps are being exchanged for
others which work on the same principle, but have
the case containing the solenoid and the moving
frame above the point of light* This modification
has been adopted because it facilitates the construc-
tion of suitable lanterns, but it does not differ from
the form first described in the way of regulating the
approach of the carbons.

In the lamps just described, as in most of those
of other makers, the strength of current regulates
the distance of the carbons, and the consequence is,
that it is not possible to connect two or more of them
in one circuit. To overcome this difficulty, Mr. v.
Alteneck used another principle, which in some
respects resembles the pendulum lamp. The upper
carbon is attached to a similar rack moving in a
slide, and turning a pinion with pendulum attached,
but the motion of the movable frame is governed by
two solenoids instead of one. The frame is attached
to a lever, which carries a double iron core reach-
ing into the two solenoids. One of these acts in
the same way as the solenoid of the pendulum
lamp, separating the carbons whenever a current
passes through it. The other one consists of fine
wire having a high resistance, and forms a shunt to
the main circuit, the ends of the fine wire being
connected direct to the terminals of the lamp, and

1 88 ELECTRIC LIGHT.

by attracting its wire it brings the carbons together
or releases the pendulum respectively. The action
of these solenoids will, therefore, be balanced when
the difference of potential on the two sides of the
arc is of a certain magnitude, depending on the
relative position of the two coils and the resistance
of the wire on them. By this arrangement the
quantity of the current flowing through the lamp
has no influence on the relative position of the
carbons, and nothing prevents a large number of
them being inserted into one circuit. In producing
light by alternate currents as many as 24 of these
lamps have been worked in series, and their
behaviour was all that could be desired. In order
to make these lamps independent of each other a
little contact piece is attached to the movable frame,
which makes a short circuit from one terminal to
the other whenever the frame is in its lowest
position.

The principle of the action in this differential
lamp is exhibited by Fig. 78, where g and k indicate
the carbons held respectively in the sockets a and
by and provided with means of feeding as they are
consumed. One socket, a, is attached to one arm, (f,
of a lever pivoted at d, and having its opposite arm,
c, connected to a piece of non-magnetic material
uniting a pair of iron cores, s s / . The core, s, is free
to play up and down within a solenoid R, the coil of
which is of large wire offering small resistance, and
forms part of the lamp circuit. The core j / is free to
play up and down within a solenoid X, having a coil

SIEMENS' DIFFERENTIAL LAMP.

189

of smaller wire offering a greater resistance than
the coil of R. The coil of T is in a circuit external to
the lamp, that is to say, joining the conductors
L l', excluding the carbons. When the solenoid
R, being excited, draws in its core s y the points ot
the carbons are separated ; when on the other hand
the solenoid T draws in its core /, the carbons are
caused to approach each other. As the relative
force of the two solenoids depends upon the
strengths of the cur-
rents of electricity C ~
passing respectively
through the coils,
and as this depends
upon the relative re-
sistance of their re-
spective circuits, the
one circuit, consist-
ing of the coil T and
its connections to
the main circuit of
L l', and the other

consisting of the coil R, the two carbons and the arc
between them, that portion of the latter which
consists of the arc being dependent on the distance
of the carbons apart, this distance will become
adjusted automatically by the action of the two
solenoids, so as practically to maintain constant the
action of the lamp. If, for example, the carbons
should be too near together, a larger proportion of
the electric current passing through coil R than

Fig. 78. — Siemens' Differential .Lamp.

IQO ELECTRIC LIQHT.

through coil T will cause the superior attraction of
the core s, separating the carbons, and thereby in-
creasing the resistance of the arc between them,
and so lessening the quantity of electric current that
passes through them. If, on the other hand, the
ans should be too far apart, then the coil R,
% less excited than the coil t, will exert less
ctive force on its core s, permitting the other
/ to be drawn into its coil, and thus causing
pproach of the carbons which will lessen the
tance of the arc between them, and so permit
passage of a larger proportion of the current
lgh them ; thus the regulation of the lamp
j dependent only on the resistance of its voltaic
ind independent of the strength of current, the
n of any one lamp in a circuit will not affect
of other lamps in the same circuit, and conse-
tly a number of such lamps can, by means of
invention, be effectually worked in one and the
) circuit. .

>th in the "pendulum" and in the "differen-
lamp the lower carbon is fixed, the focus of
light will therefore gradually descend. For
! purposes it is, however, necessary to keep the
; in the same place, and Dr. William Siemens
suggested a simple contrivance to attain this
The lower carbon is enclosed in a tube and,
aeans of a fine wire, a roller and a weight,
shed against a screw fixed to the upper end of
ube. As the carbon wastes away by the action
e current fresh carbon is fed upwards by the

LONTIN'S LAMP. 191

weight, and the shape which the carbon assumes
admits of the screw being far enough away from the
arc to prevent its being injuriously affected by the
heat It is obvious that in such a case much longer
carbons can be used, and that the time during
which a lamp can remain alight without removal
of carbons, is thereby very materially increased.

This " abutment " pole is employed for both elec-
trodes in the last form of lamp invented by Dr.
William Siemens, but the screw, against which the
carbons are pressed, has been replaced by a knife-
edge, which appears to give better results. In this
lamp the carbons are placed horizontally, and their
tubes are attached to Bell crank-levers, the other
ends of which support the core of a solenoid, on
which fine wire is wound, forming a high resistance
shunt from one terminal to the other. The action
of the lamp is very simple ; the weight of the core,
which can be varied at will, keeps the carbons
apart when no current passes. As soon as a
current arrives the solenoid will lift the core, the
carbons touch for a moment and the arc is esta-
blished, the further regulation depending again on
the difference of potential only, and being indepen-
dent of the strength of the current. No wheels
whatever enter into the construction of this lamp,
and all its parts are exceedingly simple.

Lontin's Lamp.

M. Lontin, inventor of the Lontin dynamo-
electric machine, has sought to improve upon the

192 ELECTRIC LIGHT.

well-known Serrin lamp by introducing parts for
its working of greater simplicity than hitherto.

It would appear that this inventor bases one part
of his improvement upon the Serrin lamp upon the
expansion of a metallic bar by the passage of the
current through it, and by substituting this bar for
the electro-magnet employed in Serrin's lamp.
Up to the time of going to press, however, no
further particulars of this apparatus are obtainable,
and it must be as yet considered as under the ex-
amination it deserves.

M. Lontin has also invented a form of lamp in
which any length of carbon rods may be employed.
The lamp and carbons in this invention are hori-
zontally placed, instead of vertically, as in most
other lamps. The carbon holders are hollow
throughout, so that any required length of rod may
be inserted in them.

One of the carbons, as it passes through its
support, is moved by a pair of rollers bearing with
gentle pressure against it. This rotation is kept
up by bevel wheels actuated by a spring and clock
movement in the case of the lamp.

There is a disadvantage, however, in placing the
carbons horizontally, as they are found to give much
less light than vertical ones.

This lamp is not quite new. An invention
brought out several years ago employed the tubular
holders and the driving by clockwork ; and the
mechanism was, perhaps, as effective in use as that
here spoken of, while the position selected *<vas a

CARRE'S LAMP. 193

vertical one, which is certainly superior to the
horizontal plan, when the light power from a given
current is considered.

Carry's Lamp.

The inventor of the Carr6 induction (high tension)
machine has produced a lamp which is judged by
some to be an improvement on Serrin's lamp. He
employs a double solenoid instead of an electro-
magnet, which is supplied with an armature of S
shape. This armature is caused to oscillate round
a spindle, or pivot axis at its centre, and the two
ends enter a curved bobbin. When, from any
cause, the current is interrupted, this armature is
withdrawn by springs as usual, a detent releases
the mechanism, and the carbon points come into
close contact, so re-establishing the current. As in
Serrin's lamp, the mechanism of Carre's device is
actuated by the falling weight of the upper carbon
holder.

When the current passes, the ends of the arma-
ture are sucked into the solenoid, and the carbon
points are at once separated to the distance re-
quired to produce the voltaic arc.

Girouard's Lamp.

M. Girouard invented the device bearing his
name in 1876, so that it is an attempt to improve
upon the apparatus previously in use. The appa-
ratus consists, essentially, of two distinct parts :

194 ELECTRIC LIGHT.

the lamp itself, with its clockwork mecha
effecting the regulation of the carbon pc
an instrument intended to act as a relay,
lator of the current, which is fixed to t
This relay is actuated by the current
portable voltaic battery. The second
part of the lamp controls the mechanis:
lamp proper, and through it the length of
which is, of course, produced by anothe:
obtained from a stronger voltaic batte
dynamo-electric machine. The idea in
good, but it cannot be said to be well cs
in this lamp.

Brush's Lamp.

This is an American invention, by M
who is also the inventor of the well-knoi
dynamo-electric machine. Like some of
efficient electrical apparatus in use, its coi
is exceedingly simple, and its parts are so arranged
as ' to make it very certain in action as well as
prompt to respond instantly to changes of current
strength.

Fig. 79 is an illustration of its chief part only.
Its under parts, such as the base and lower c
holder, are constructed like most other 1
There is no mechanism in the under arrangi
of simple base and holder, and the part ;
herewith has the action of the lamp entirely
control.

A is a coil of stout insulated wire, cons

brush's lamp, 195

of 2 or more layers. Its interior provides a cylindri-
cal vertical aperture, and the bobbin is fixed upon
a supporting plate,
as shown.

B is an iron hol-
low core, fitting
easily into the
aperture in A.
This core is able
to move up and
down a 'short dis-
tance. Within the
core, B, is a brass
or iron rod, C,
which is also the
upper carbon-
holder. This rod
is loose in the
aperture of B. At
D is shown a bent
finger attached to
B, the under end
of which is bent
and catches un-
derneath a brass

washer, D, placed Fie . J9 ._b™h', l.« p .

somewhat loosely

on the rod, c. This washer is otherwise quite
free.

E is a set screw, which is moved by hand. It
is intended to control the movements of the

196 ELECTRIC LIGHT.

washer, D, by being screwed more or less down
upon it.

If one wire from the dynamo-electric machine or
battery is connected to the lower carbon, while, tlie
other is connected to the commencing end of the
wire coil, A, the finishing end of which communi-
cates with the upper carbon-holder, the current
will pass from the lower carbon through the upper
as fastened at C, through the wire coil, and the
circuit is complete. The core cylinder, B, is then,
by the force of the magnetism created, drawn up
into the interior of A. By means of the lifting-
finger, D, it raises that edge of the washer, until,
by the washer's angular pressure upon it, it lifts
this rod upwards, and will raise it to such a height
as may be determined by the height of the thumb-
screw, E. As long, then, as the magnetism remains
the same, the rod C, with its upper carbon, will
remain fixed. While the current is not passing,
the rod, c, is quite free to descend until its carbon
point is supported by the lower carbon. This is
the condition of the parts when the lamp is out of
action, or when, by accident, the circuit is broken.

As soon, however, as the current passes, the
core, B, is sucked into the cylindrical cavity of the
bobbin, A, and in being raised also raises the
washer by its finger, D, and with it the rod and
upper carbon, C, until the voltaic arc is established
and the light produced.

A pair of springs is shown, one on either side of
the core, B. The action of those spirals of steel is

BRUSH'S LAMP. 1 97

ssd£to support the weight of the core, B, with the aid of
the induced magnetic attraction when the current
passes. As the carbons are consumed the length
iifciof the voltaic arc increases, and with the resist-
offance the current diminishes in strength. This
m weakens the magnetic pull of the wire coil, and the
sffl core, B, with the rod, C, and upper carbon move
g| downwards by the action of gravity, until the con-
i i. sequent shortening of the voltaic arc so diminishes
(A the resistance and increases the strength of the
Hj current that this downward movement is stopped
'fa by the increasing pull of the magnetic helix, A.
After some time, however, the clutch washer, D,
will reach its floor or plate, and its downward
movement will be stopped, when any downward
movement of the core, B, however slight, will at
te once affect the rod, C, allowing it to slide through
i the washer until arrested by the upward movement
of the core, B, due to an increase of magnetism.
The working of this lamp is very steady, and there
is very little sluggishness in responding to changes
in the strength of the current.

Experiments with this lamp and the machine
invented by Mr. Brush have shown the practicability
of working as many as 6 to 10 of the lights in one
circuit. It is further stated by the inventor that
lights of 2,000 candle-power each have been pro-
duced in each lamp under the above conditions^
The system allows of great electric power being
worked upon the circuit, even up to 30,000 standard
candlelight.

198 ELECTRIC LIGHT.

The Thomson- Houston Lamp.

Professors Thomson and Houston, of the Phila-
delphia High School, having been engaged in an
extended series of experimental researches on
dynamo-electric machines and their application to
electric lighting, have had their attention directed
to the production of a system that will permit the
use of a feebler current for producing an electric
light than that ordinarily required, or, in other
words, the use, when required, of a current of in-
sufficient intensity to produce a continuous arc of
the light.

When an electrical current, which flows through
a conductor of considerable length, is suddenly
broken, a bright flash, called the extra spark,
appears at the point of separation. This extra
spark will appear although the current is not suffi-
cient to sustain an arc of an appreciable length at
the point of separation*

In their system one or both of the electrodes,
which may be ordinary carbon rods, are caused to
vibrate to and from each other. The electrodes
are placed at such a distance apart that in their
motion towards each other they touch, and after-
wards recede a distance apart which can be regu-
lated. These motions or vibrations are made to
follow one another at such a rate that the effect of
the light produced is continuous, for, as is Well
known, when flashes of light follow one another
at a rate greater than 25 to 30 per second, the

THE THOMSON-HOUSTON LAMP. 199

effect produced is that of a continuous light. The
vibrating motions may be communicated to the
electrodes by any suitable device, such, for example,
as mechanism operated by a coiled spring, a
weight, compressed air, &c> but it is evident that
the current itself furnishes the most direct method
of obtaining such motion.

In a practicable lamp, instead of vibrating both
electrodes, it is found necessary to give motion to
but one, and since the negative electrode may be
made of such size as to waste very slowly,
motion is imparted to it in preference to the posi-
tive. The carbon electrodes may be replaced by
those of various substances of sufficient conducting
power. In this system, when desired, an inde-
pendent current is employed to control the extinc-
tion and lighting of each lamp. The following is
a description of one of the forms of electric lamp
which Messrs. Thomson and Houston have devised
to be used in connection with their system of
electric illumination.

Fig. 80 exhibits the construction. A flexible
bar of metal, 3, is firmly attached at one of its ends
to a pillar, fi y and bears at its free end an iron
armature, a y placed over the adjustable pole piece
of the electro-magnet, m. A metal collar, c, sup-
ports the negative electrode, the positive electrode
being supported by an arm, /, attached to the
pillar, p. The pillar, /, is divided by insulation at
i into two sections, the upper one of which conveys
the current from the binding-screw marked + to

200

ELECTRIC I2GHT.

the arm /, and the rod R, supporting the positive
electrode.

The magnet, m, is placed as shown by the dotted
lines, in the circuit which produces the light. The
pillar, p, is hollow, and has an insulated conducting*

wire enclosed, which
connects the circuit
closer, v, to the bind-
ing - screw marked
— . The current is
conveyed to the ne-
gative electrode
through b y and the
coils of the magnet,
m. When the elec-
trodes are in contact
the current circu-
lating through m
renders it magnetic,
and attracts the ar-
mature, a y thus sepa-
rating the electrodes ;
when, on the weak-
ening of the current,
the elasticity of the
rod, by again restores the contact.

During the movement of the negative electrode,
since it is caused to occur many times in a second,
the positive electrode, though partially free to
fall, cannot follow the rapid motions of the nega-
tive electrode, and, therefore, does not rest in

Fig. 80. — Thomson-Houston Lamp.

THE WALLACE-FARMER LAMP. 201

permanent contact with it. The slow fall of the
positive electrode may be insured either by properly
proportioning its weight, or by partly counter-
poising it. The positive electrode thus becomes
self-feeding. The rapidity of movement of the
negative electrode may be controlled by means of
the rigid bar, /, which acts, practically, to shorten
or lengthen the part vibrating. In order to obtain
an excellent but free contact of the arm, /, with
the positive electrode, the rod, R, made of iron or
other suitable metal, passes through a cavity filled
with mercury, placed in electrical contact with the
arm,/. Since the mercury does not wet the metal
rod, R, or the sides of the opening through which
it passes, free movement of the rod is allowed
without any escape of the mercury.

In order to prevent a break from occurring in
the circuit when the electrodes are consumed, a
button, u, is attached to the upper extremity of the
rod, R, at such a distance that when the carbons
are consumed as much as is deemed desirable, it
comes into contact with a tripping lever, T, which
then allows two conducting plugs attached to the
bar, v y to fall into their respective mercury cups,
attached respectively to the positive and negative
bind-posts by a direct wire. This action practi-
cally cuts the lamp out of circuit.

The Wallace-Farmer Lamp.

Fig. 8 1 is an illustration of this lamp. Various
devices have been resorted to, to cause the carbons

202 ELECTRIC LIGHT.

of ordinary shape to automatically approach each
other as they are consumed, and the Wallace lamp
is not only of an improved description, but its
automatic arrangement is of the most perfect kind
yet tried.

A A are two plates of carefully prepared carbon,
and the object of this invention is to so cause the

light to burn between them, that the automatic
adjustment so often necessary in other lamps is here
only necessary about every half-hour. The plates
in the latest form of this lamp are about 9 in. long,
5 broad, and the upper is double the thickness of
the under — this thickness in turn depending upon
the strength of current to be employed. The

THE WALLACE-FARMER LAMP. 203

lower plate is fixed to the frame, but the upper
plate is under the control of an electro-magnet
through the rod B. This provides for the contact
between or separation of the plates, as the current
may require, to produce the maximum amount of
light. The electro-magnetic arrangement, C, con-
sists of an ordinary electro-magnet, having its
poles downwards, and the rod D B has attached to
it a soft-iron armature. When no current passes,
the electro-magnet has no effect, and one carbon
rests upon another ; but when the current is passed,
the arc of light forms where there is least resist-
ance, and the electro-magnet at the same instant
pulls up the upper carbon and makes the required
separation. The distance between the plates may
be regulated to a nicety to suit any current.

The light, as has been said, starts at the point of
least resistance, and it burns its way horizontally
along the carbon edges and back again until the
distance is too great, when it is necessary to screw
down the rod D a turn or two. In this way the lamp
may burn for nearly 100 hours at a time. As many
as 10 of these lamps have been maintained in cir-
cuit of a Wallace-Farmer machine. It has been
well tried in England, and gives every satisfaction.
It is, however, unsuited to purposes requiring the
light to be kept in one point.

This lamp really supersedes almost every other
arrangement for general purposes, and its simpli-
city is a feature of the greatest importance. The
author can speak of its performance as almost

204

ELECTRIC LIGHT.

perfect for outside or inside diffused illumina-
tion.

RapiefFs Lamp.

The leading peculiarity of M. RapiefFs lamp

consists of the duplex carbons used.
Most other lamps employ only one
solid carbon rod for each burning
point ; but Rapieff uses two — that
is, four altogether. These rods are
inclined to each other to form one
upright and one inverted V, and at
the point of intersection the electric
arc is produced as in other lamps.
The rods used by this inventor are
necessarily of half the sectional area
they would have if not double.

Fig. 82 will give some definite
idea of these arrangements, where
the four rods are seen in the interior
of a glass globe nearly in contact.
The upper pair of rods are always
the longer, because they burn away
the faster. The duplicate arrange-
ment of the rods has the advantage
that one of them may be removed
and renewed without extinguish-
ing the light, and this is the chief advantage of the
whole arrangement. As soon as the lamp has
nearly burnt its carbons, they may be renewed
without much disturbing the light. This inventor

Fig. 82.— RapieflPs
Lamp.

RAPIEFF'S LAMP. 205

also recognises the advantage of making the elec-
trical contact with the rods as near to their points
as possible. This has the effect of greatly decreas-
ing the resistance of the lamp.

The upper carbons are free to slide in their
holders, and as their points come into actual con-
tact, they are stopped from further motion. As far
as this end of the circuit is concerned it is self-
feeding, for as fast as the points burn away the
length is renewed by their weight pressing them
downwards.

When the current is stopped, the two pairs of
points come together by movement on the part of
the lower pair only. As long as the current does
not pass, a light spring supports the lower pair,
and gently presses them against the upper pair.
Fastened to the free end of both upper carbons is
a silk thread, which passes over a pulley and is
attached to a sliding-weight in the supporting-
pillar of the lamp. As soon as the current passes
the lower pair of carbons is caused through its
spring to be separated the required distance to
produce the voltaic arc. There is communication
between the vertical rod actuating the lower
carbons and an electro-magnetic arrangement con-
cealed in the base of the lamp.

This consists simply of two electro-magnets, one
of which is fixed to the base while the other is
pivoted or hinged, and by its approach to the fixed
one moves the vertical rod controlling the lower
carbons, and these are thus drawn away from the

206 ELECTRIC LIGHT.

upper pain When the current ceases to #ass, the
spring before spoken of causes the hinged magnet
to fall into its normal position, and the lower
carbons ^t the same time touch the upper pair to
be in readiness to start the light when the current
next passes.

Another good feature of the Rapieff lamp is its
arrangement (also concealed in the foot) for throw-
ing a resistance of wire, equivalent to that of the
lamp, into circuit when, through any cause, the
circuit has been interrupted in the lamp. When
the hinged magnet falls back, it instantly closes
the circuit of this resistance of wire, and the
machine is not affected, nor does it (the supposed
accident) affect any other lamps in the same circuit,
since the resistance must remain constant, or very
nearly so. There is also employed in these lamps
a resistance consisting of a pencil of carbon, and
through this, the resistance of which is equal to
that of the lamp, the current passes when the
lamp breaks circuit.

By means of these carefully thought out arrange-
ments, as many as 6 and 8 lamps of this type
have been kept alight upon one circuit only, and
any accident to one lamp did not affect the others ;
or aiiy lamp might be extinguished and relighted
without any effect being apparent upon the main
circuit.

This system has been in practical use in the
composing-room of the Times newspaper, and
gas is thus entirely replaced by electric • lights.

URQUHART'S LAMP. 20?

Electricians and others are appreciative of the
energy with which the proprietors of the Times
brought M. RapiefFs system into actual use. The
construction of the lamp is not so well carried
out as the plan, and the parts are unnecessarily
delicate, which should not be the case in a practic-
able lamp for general use. M. Rapieff has also
brought into use a lamp in which both pairs of
carbons pass up from underneath, forming an in-
verted V. The arc impinges upon a piece of lime,
which increases the light. M. Rapieff has also
invented a " candle."

Urquhart's Lamp.

From a somewhat extensive acquaintance with
the various systems of electric-lighting, the author
has been able to judge of their advantages and de-
merits, and to come to some positive conclusions
on the chief questions. Most of the best electric
lamps in use are far too delicate for general
handling, and but too apt to get out of order when
most wanted to produce a steady light. Even the
Serrin, about which so much has been said, is
exceedingly delicate, and although it may give
little trouble, if at any time it should go wrong in
inexperienced hands, the result is an entire stop-
page of operations, and another lamp will not in
such a case be probably at hand.

As a brief introduction to the author's design, it has
been invented to suit his ideas of a lamp suitable
to almost any application of electric light. He has

208 ELECTRIC LIGHT.

sought to produce a steady lamp, and one that will
give little trouble, that will cast no shadows, and a
regulator that may be understood and worked or
fed at once by any man of ordinary intelligence.

Figs. 83 and 84 are views of the lamp. The same
letters refer to the same parts in both figures.

Fig;. 8}- — Urquhari's Lamp. End.

Fig. 83 is an end view of the lamp, and Fig. 84 a
side view.

A A are a pair of carbon plates, carefully made
from the best materials used in the composition of
rod carbons. These plates are of any suitable
length, and 6 inches broad. The length may con-
sequently be 1 2 inches. These plates are of differ-
ent thicknesses, the positive one being the thicker
because it burns away the faster. They are made

URQUHART S LAMP. 209

to slide freely through the hollow cores of a pair
of flat electro-magnets, b b, which are fastened
together hy a strong bridge of hard wood, c, pro-
vided with a ring for suspending the lamp. The
carbon plates pass downwards until they meet at
the point where the light is shown, thus forming a
V shape. The plates pass also through two hollow
armatures, E E, provided with set screws by which

Fig. 8.].— Uiqnl*ut'< Lamp : Side.

the plates and armatures may be made fast to-
gether,. The armatures are fixed to the magnet
cores by a pair of long brass springs, but this
might be dispensed with. Fig. 84 will show more
clearly how each plate is made to pass through the
electro-magnet system. The whole arrangement is
exceedingly simple.

When it is required to put carbons in the lamp,
plates of suitable size, and about £-in. in thickness

210 ELECTRIC LIGHT.

for common currents, are selected, passed through
the magnets until they touch at their lower edges,
and there fastened by the screws, E E. Thus the
carbon plates and the armatures are as one, and
are free to move up and down to the point where
the plates meet. The current enters at F +, passes
through the coil of stout wire, B, and is then made
to pass to the core of the magnet — including, of
course, the armature, which is metallically con-
nected by a spring, and passes down the positive
plate, up the negative plate (as shown by the
arrows), through the coil of the left-hand magnet,
and back to the generator by F.

Suppose that the lamp has been " trimmed ;"
the plates will be in contact at their lower edges,
and the current has a free circuit of little resist-
ance. When it passes, it instantly makes B and B
magnetic, which attract the armatures, E E ; and,
the plates rising with them, the voltaic arc is
established, and of such length as may suit the
current passing. It is not found necessary to start
the arc at one end by inserting a carbon chip.

The arc forms at the point of least resistance
between the near edges of the plates, as in the
Wallace -Farmer lamp, and from this " point it
creeps along the edges of the plates to the farthest
extremity. The time occupied in doing this will
depend upon the strength of current at work, but
it may be taken at one hour or so at 2,000 candle-
power. When the arc has burned its way from
end to end of the plates, the voltaic arc becomes

URQUHAKT'S LAMP. 211

too long, the current weakens, the magnets release
their hold slightly, and the arc is re-established at
the length it first had. Thus the action of the
lamp is quite motionless for periods of at least half
an hour each, and only controls the length of the
arc by keeping a constant up-pull upon the plates.
It is only about every half-hour that the plates
move at all, and when they do move downwards to
make up for burnt carbon, the distance for each
is very small, or only half that burned off the plate
edges.

When the lamp has given light for about 6
hours or more, and it is required to continue for
other 6 hours, it is only necessary to slightly
lower the plates by the screws in the armatures,
E E. In practice this cannot be done just as
directed, because the freed armature, having the
weight of the plate off it, would be instantly and
powerfully attracted, and the current would have
to be stopped to free it. The simplest way in
which to lower the carbon plates for further con-
sumption is to throw the coil at the required side
out of circuit ; and to do this it is only necessary
to scrape the insulation of a little of the wire
leading the current to the binding screw, and to
give the bared wire a twist around the pinch screw
at E. Thus the magnet will be powerless on that
side, and the light will not be extinguished. The
screw at E may then be slackened, and the plate
tapped downwards a little. It is found that about
T^th of an inch will suffice for 5 hours' work. In

212 ELECTRIC LIGHT.

order to obviate the necessity to even thus far
disturb the lamp, the pinch screw may be set
"easy" — that is, not hard against the plate; and
when it is required to lower the latter, a tap or two
with any wooden handle will suffice.

This lamp will burn without any attention, and
quite steadily, for at the least 6 hours, and often
for 12 hours. If it is looked to every 6 hours or
thereabouts, and the plates tapped a little down-
wards, it will burn for periods ranging from 50 to
1 20 hours with plates of moderate size.

It gives little resistance to the current, as the
magnets are coiled with one layer of No. 10 wire
only, and the size of the carbon plates permits of
a very low resistance in that direction. There is,
further, the advantage that the resistance of this
lamp is almost constant, and does not vary, like
Serrin's regulator, from perhaps 5 ohms to 10
ohms in a few hours. The resistance here is more
constant than that obtained in RapiefFs lamp.

There is no fear that the plates may be lowered
too far in adding to the length for further work.
If the plates are too near to each other, the current
will be strengthened, and the magnets will respond
by pulling them up to the required length of arc,
if the length is not obviously excessive.

w, in the first figure, is a reflecting surface of
polished metal or other suitable material ; it serves
to throw any light diffused upwards in a condensed
beam through the carbon separation ; and, to
insure that no light is lost, this reflected portion

URQUHART'S LAMP. 213

may be thrown downwards quite clear of the arc
itself, by making one end of the reflector slightly
higher than the other.

The author has found it best in practice, and con-
ducive to steady working, to employ between the
pole pieces and the armatures a brass spring, made
from a few turns of hard brass wire, as exhibited
by the first figure.

The plates slide quite freely through the magnet
cores, and would do the same through the arma-
tures if not pinched by the set screws. These
magnet cores, being hollow, are best made from
pattern in malleable cast iron, and the armatures
may also be of this material. The wire is wound
upon the core direct, and the flanges shown are
cast with the core as one. The aperture provided
through the core is 6 J inches long, and -§• in. wide ;
so that any size of carbon, up to 6 in. wide and
nearly -jj- in. thick, may be burned.

The wooden bridge is of this material to com-
pletely insulate the two sides from each other. It
is 7 inches long, and is bolted to the bobbin ends
or flanges. The reflector, W, must not connect
these together metallically, but must have wooden
or rubber ends.

Binding screws, F, F+, are provided as usual.
They are insulated from the metallic flange by
being screwed into a block of wood or ebonite, set
in a dove-tailed aperture cut in it. One end of the
coil, B, is connected to the screw, and the other to
the metal of the magnet itself; to secure which

214 ELECTRIC LIGHT.

connection it is only necessary to strip the com-
mencing end, lay it in metallic contact with the
magnet, and wind the wire over it, the finishing
end being made fast to the screw.

As the carbon plates slide within the cores, and
in metallic connection therewith, there is an elec-
trical communication here ; but as the armature is
apt to hold the thinner plates clear of the magnet
altogether, various devices may be adopted to
insure a metallic contact with the carbon. It will
be found that the spring employed between the
armature and magnet will insure this without
further trouble.

This spring should, for convenience, be fastened
to the magnet core and the armature, and the author
finds it most convenient to make a recess in the
upper face of the armature to receive the coils of the
spring when they are compressed by strong mag-
netism. The armatures are thus always connected
by the springs to the cores, and cannot' get lost,
while this relationship renders the fitting of new
plates very easy. The inexperienced workman has
only to push down the plates until their edges meet
at the point indicated, or simply until their edges
meet, and then to screw up the pinches, E E, when
the lamp is ready for work and may be left by
itself for hours together.

It will be noted that remarks are made in pre-
ceding pages concerning the fact that a hori-
zontal arc does not give so much light as a vertical
one. It may be thought that the lamp shown with

ROTATING DISC LAMPS. 21$

this description will give a horizontal light or arc ;
but this is not the case, because one carbon is
always, from causes affecting the attraction, above
the other, and the light takes place in a diagonal
line. The lamp will also burn in a horizontal
position when required. It is strong, cannot pos-
sibly get out of working condition, since there is
no mechanism, and otherwise is fitted for general
illumination by electricity. It is best hung from
some point above the space to be illuminated, and
it will be found in this position to cast no shadow
whatever downwards or to either side under it.
The bridge, c, may be of iron if it is insulated by
wood or rubber packing from the metal work at one
end only.

In using very light carbons, it may be necessary
to weight them a little by slipping a piece of bent
sheet lead over the top. This may remain on until
the carbon is consumed. It is not necessary to
have the upper half of the plate of carbon ; it may
be of brass. This will save carbon.

Rotating Disc Lamps.

Many attempts have been made since 1846 to
produce a good lamp having rotating discs of
carbon instead of the usual rods. Wright was the
first to employ this idea, and it has been copied by
several others, with modifications and improve-
ments from time to time.

The discs revolve regularly upon two metal
axles, put in connection with the poles of the

2l6 ELECTRIC LIGHT.

battery or other generator of electricity, and pre-
sent successively, by the combined rotation and
approximation provided, all the extreme points of
their circumferences to the production and emis-
sion of the electric light. At each revolution of
the discs, they are caused to approach each other
by the distance they have burned inwards from the
edge, to make the length of the arc constant.

Many different kinds of apparatus may be
employed to cause the discs both to regularly
rotate, and also at each revolution to approach
each other by the exact distance consumed. It
has been done by means of clockwork and a spring-
or weight, and electro-magnetism is, of course,
also available for the same purpose. Le Molt,
whose lamp was produced and patented in 1849,
produced the motion by the first method, and he
employed cams upon a large brass disc to make up
for the burnt portion of the carbon discs employed.
This lamp would burn for over twenty hours at a
time.

A great objection to this class of lamps lies in
the fact that it is almost impossible to produce
discs of sufficient purity to burn equal spaces in
equal times, so that a regular motion is in practice
of no use. The motion, however it is produced,
must be under the direct control of the current
itself, so that any augmentation of space burnt
over may be compensated for by greater speed in
the discs, and a decrease of carbon space burnt by
less speed. Arranged vertically, one disc edge

REYNIER'S LAMP. 217

above the other, and thus controlled, there is no
reason why this should not make a good continuous
lamp.

Lamps in which the Carbons touch.

In the lamps previously mentioned, the carbons
are, by clockwork, electro-magnets, or weights kept
automatically at a distance apart, so as to form the
voltaic arc ; in another class of lamps the carbons
actually touch, and the light is emitted through the
incandescence of the carbon at and near the points
of contact, and also by arcs formed between points
immediately around the points of contact, the
resistance at the point of contact being sufficient
to cause a portion of the current to form a belt
of heated air forming the arc between the portions
of the carbon situated near the point of contact.

Reynier's Lamp.

Reynier's improved lamp works with a rod and
a disc of carbon. The rod is placed vertically as
usual in other lamps, and fixed to the upper arm.
This upper arm of the lamp is movable as in
Serrin's lamp, and is also toothed. The sup-
port and the carbon rod thus move downwards
together.

The racked bar, as it descends by its own
weight, carrying its carbon rod, is made to impart
motion to a pinion, which in turn rotates, through
a larger wheel, the carbon disc employed. Thus
the disc rotates in obedience to the descent of the

2l8 ELECTRIC LIGHT.

upper carbon, and it will be evident that the car-
bon rod also acts as a brake upon the rotating disc
to prevent too free a motion.

One peculiarity of the Reynier lamp is its em-
ployment of incandescence in the rod used. This
carbon pencil is small although long, and the cur-
rent is not made to traverse the whole of its length.
The current is communicated to it a little way
above its contact with the revolving carbon disc,
and the part of the rod between where the contact
is made with the conductor and its end is made
white hot, and emits considerable light and heat.

It will be inferred that the unequal burning away
of the disc, as it is softer or harder, must cause irre-
gularities in the light, and this is in the foregoing
construction really the case.

Some recent improvements made by the inventor,
however, make the light almost perfectly steady.
The revolution of the turning disc is obtained
from the tangential component of the pressure
of the carbon pencil on the circumference of the
disc. Thus the burning end of the pencil never
leaves the moving contact, and it is said that all
previous causes of irregularity are thus obviated.
There is a brake retarding the progress of the rod,
and it is operated thus : — The contact wheel is car-
ried by a lever. The pressure exerted by the car-
bon on the wheel causes a shoe to press upon the
face of a wheel, which is revolved by means of the
weight of the holder rod through its rack and
pinion. This lamp is suited for the weakest cur-

werdermann's lamp. 219

rents and displays of light, down to the current
from 5 Bunsen cells.

Werdermann's Lamp.

The principle embodied in the construction of
this lamp is of much value. It is almost a true in-
candescent lamp, and in this respect may be com-
pared to the Reynier apparatus.

Fig. 85 represents the Werdermann regulator.
A is a rounded block of carbon, connected to the
negative wire from the machine or battery. B is a
rod of carbon, constantly urged upwards against A
by a weight, G, acting through a cord over a pulley
as shown. It will thus be seen that the lamp is
altogether of very simple construction, and has no
clockwork or other regulating mechanism.

The inventor states that there is a repulsion be-
tween the carbon block and the point sufficient to
cause a slight separation, so that the lamp is not
simply an incandescent one, but possesses some of
the peculiarities and advantages of open circuit
lamps. When the current is passed, the carbon
rod, at its extreme upper end, becomes white, and
glows with a clear, steady light. For this purpose
a thin rod is used.

The chief advantage claimed by the inventor
lies in the fact that several of these lamps may be
placed in one circuit, or, more correctly, in multiple
arc connection with the electric source. This connec-
tion is made by taking two straight wires from the
machine, but not joining their ends, and then

220 ELECTRIC LIGHT.

placing the lamps so that they may connect the
two wires together through them. The current is
thus divided between the lamps, and the result is,
or should be, an almost perfect subdivision of the
currents. The number placed in one circuit is

.Fig. Ss.-WeniermWi Lamp.

limited, however, for when too many are in, the
subdivision does not hold good unless the main
conductors increase in size with the number.

As many as from 9 to 12 lights of 50-candle
power have been maintained with so small a cur-

CROMPTON'S LAMP. 221

rent as that from a Gramme plating-machine.
When only 2 lamps were upon the circuit they
gave, each, a light equal to 320 standard candles.
This lamp is decidedly a considerable advance in
electric light production. It has been repeatedly
exhibited in London.

Crompton's Lamp.

In this lamp the inventor has aimed at reducing
the weight of those parts that require movement for
the more delicate and final adjustment of the
distance between the carbons. In its latest form
the mechanism is above the light. The negative
carbon is below the positive, and attached by an
arm to a rod fast to the armature of the magnet. A
spring keeps the armature and rod up, when the
magnet is not acting. The positive carbon is fast
to a rod which by its weight constantly tends to
descend towards the negative carbon, and in doing
so by means of a rack causes a train of wheels
to work.

On the top of the armature of the magnet is
hinged a smaller piece 0$ iron or jockey armature
carrying a brake which can act on the train of
wheels. A small light spring keeps the brake from
touching the wheels until a current sufficiently
strong causes, not only the armature to be drawn
down and come in contact with the magnet, but
also causes the smaller jockey piece on the top of
it to be drawn down and apply the brake. The
action is as follows: 1. When no current is circu-

222 ELECTRIC LIGHT.

lating, the positive descends and touches the
negative. 2. On a current being established the
electro-magnet draws down the armature, thus
lowering the negative away from the positive and
establishing the arc. 3. The positive then begins
to fall until the current becomes sufficiently strong
to attract the small jockey armature, causing the
brake to be applied and stopping the descent of
the positive. The lamp is very sensitive, as,
instead of having several pounds to be thrown in
and out of motion for each adjustment, the portion
to be moved by the change of current is only a few
grains. The adjustment consequently takes place
every few seconds. The price of this lamp is
£12 10s.

The Brougham-Andr£ Lamp.

In this lamp a carbon rod, weighted, falls on to a
cone of copper, the carbon being the positive elec-
trode and the copper the negative. The carbon rod
is inside a brass tube, and the copper cone is fast to
an arm connected by a rod to another tube outside
the one containing the carbon rod, and insulated
from it. The outer brass tube is joined to a brass
disc, to which is fastened the glass case enveloping
the light, and this is kept air-tight by being
immersed in a second glass case filled with water.
Thus an air-tight joint is obtained and the light
soon exhausts the oxygen, leaving gases which do
not combine with carbon.

While the carbon burns away at the rate of six

ELECTRIC CANDLES. 223 N^p/^J

inches per hour in the open air, it burns only one-
eighth of an inch per hour when in the water-
covered globe.

Lugo's Carbons.

This patented arrangement of carbons is the in-
vention of Orazio Lugo, of Flushing, N.Y. It
consists chiefly in making the carbon rods hollow,
so that air may pass through them to keep down
the temperature. The inventor also mentions the
possibility of increasing or modifying the intensity
of the light by the introduction of various fluids or
substances through such apertures. It is not, how-
ever, very clear as to what these fluids are to consist
of. The air may also be forced.

Electric Candles.

In all the arrangements previously described
some means of moving the carbons, either by
springs or gravity, is employed, but if two rods of
carbon are placed parallel, the arc, it is found, can
be maintained between them, if the currents are
used alternately in different directions so as to con-
sume the carbons equally. This idea first occurred
to M. Jablochkoff, and is called an electric candle,
as the carbons consume away from one end in the
same way as the wick and wax of a candle. It
was first thought necessary to have an insulating
material between the rods, but this has been found
unnecessary.

224 ELECTRIC LIGHT.

M. Jablochkoff s Candle.

In March, 1876, this "candle" was patented
and introduced, and a remarkable movement to-
wards the application of electric lights to public
purposes was in consequence instituted. In Paris
it took the form of lighting the Avenue de TOp6ra,
the Place de TOp6ra, the Place du Th6cttre Fran-
9ais, and numerous public buildings ; and in conse-
quence of the success attending these applications
of the new light, it was tried successfully in work-
shops, railway depots, and other places on the
Continent and in America, while the same impetus
carried the electric light to the Thames Embank-
ment and other public places in London and the
provinces.

The "candle" just mentioned consists of two
rods of manufactured carbon, placed side by side,
and insulated from each other by a strip of plaster
of Paris, or kaolin, which was at first used for the
purpose. Figs. 86 and 87 show the rods and the
complete candle. The rods used are about -^ths of
an inch in diameter, and from 5 to 15 inches in
length. They are stuck in a pair of brass tubes,
which are held together by a cement of earthy
matter, B. Across the top is a chip of carbon
fastened in place by carbon powder and gum,
and when the alternating currents pass this is
fused and the true electric arc instituted.

Fig. 88 shows a burning candle, and Fig. 89 is
from a photograph of a candle partly burnt on the

ELECTRIC CANDLES.

22 5

Thames Embankment. Both
rods burn equally, on ac-
count of the alternating cur-
rents, which must always be
employed with the candle
with this very object, and
the plaster of Paris
fused as the candle burns
down.

The candles most in use
are ten inches long, and
burn for about i£ hours;
and if a candle goes out it
cannot again be conveni-
ently relighted — that is, it
will not relight itself, as a
good lamp or some other
candles will. Four candles
are placed in one lamp,
which has usually a cover
of opalescent glass to tone
down the intense glare.
When one candle goes out,
or before it goes out, another
is switched into the circuit,
either by hand or by an
automatic arrangement—
which, however, does not
appear to have had extensive «*■ '%£!** *&£ c£aE
application. Twenty of the

lamps on the Thames Embankment are self-light-

226 ELECTRIC LIGHT.

ing as the candles burn down, and twenty are
switched by hand.
Figs. 90 and 91 represent holders for the candles.
They consist simply of
two cheeks insulated from
each other, one fixed, A,
and the other on a joint
with a holding spring, B.
The binding-screws, C C,
carry the current to the
holder.

The automatic switch
consists of a metallic
finger, which is pressed
against the candle by a
spring, so that when the
candle is consumed down
to this point the finger
will fall through it, and
by its holder underneath
switch another candle into
circuit. Other more or
less complicated arrange-
ments are in use, but they
do not carry the same
evidences of mature
Fi * 8S c _ M^ I e ocbkoff F pl;>ta 'of*™ thought as the candle it-
baint candle, self would appear to have
induced. Jablochkoff s candle must inevitably
give place to other and better devices lately intro-
duced.

]

WILDE'S ELECTRIC CANDLE. 227

Wilde's Candle.
The maker and inventor of the well-known
dynamo-electric machine (Mr. Henry Wilde, of
Manchester) has also invented a candle and holder
superior in many respects to that of M. Jablochkoff.
From his experiments in connection with the Jab-

Figs, go and gi.-Jablocl.kofFs Candle-boldera.

lochkoff system he deduces several very important
conclusions, bearing practically upon the question
of electric burners of this type. One of the con-
ditions necessary for producing a constant light
from the candle, in its most recent form, was
that the strength of the alternating current
should be such that the carbons consume at

228 ELECTRIC LIGHT.

a rate of from 4 to 5 inches per hour. If the
electric current is too powerful, the carbons become
unduly heated, and present additional resistance
to the passage of the current. The points at the
same time lose their regular conical form. If, on
the other hand, the current be too weak, the electric
arc plays about the points of the carbons in an
irregular manner, and the light is easily extin-
guished by currents of air.

In the course of his experiments, Mr. Wilde was
struck by the apparently insignificant part which
the insulating material plays in the maintenance of
the light between the carbon points; and it oc-
curred to him to try the effect of covering each of
the carbons with a thin coating of hydrate of lime,
and mounting them parallel to each other in
separate holders, without any insulating material
between them. The use of the lime covering was
intended to prevent the light from travelling down
the contiguous sides of the carbons. On com-
pleting the electric circuit the light was maintained
between the two points, and the carbons were con-
sumed in the same regular manner as when the
separation was by means of plaster of Paris.

Two plain cylindrical rods of carbon, -^ths of
an inch in diameter and 8 inches long, were now
fixed on the holders, parallel to each other as
before, and £th of an inch apart. The strength of
the alternating current was such that it would fuse
an iron wire 0*025 in. in diameter and 8 feet in
length. On establishing the electric current through

WILDE'S ELECTRIC CANDLE. 229

the points of the carbons, by means of a conduct-
ing paste composed of carbon and gum, the light
was produced, and the carbons burnt steadily
downwards as in the first trials.

Four pairs of naked carbons mounted in this
manner were next placed in series on the circuit
of a four-light machine, and the light was pro-
duced from th^se carbons simultaneously, as when
the insulating material was used between them.
The light from the naked carbons was also more
regular than that from the insulated ones, as the
plaster of Paris insulation did not always consume
at the same rate as the carbons, and thereby
obstructed the passage of the current. This was
evident from the rosy tinge of the light produced
by the volatilisation of the calcium simultaneously
with the diminution of the brilliancy of the light
from the carbons. The only function, therefore,
which the insulating material performs in the
electric candle, as shown by these experiments, is
that it conceals the singular and beautiful property
of the alternating current to which attention has
been directed.

This simple method of burning the carbons will
greatly further the development of the electric
light, as carbons can be used of much smaller
diameter than has hitherto been possible. They
may also be of any desired length, for as they are
consumed they may be pushed up through the
holders without interrupting the light. One of
these developments will be a better method of

230 ELECTRIC LIGHT.

lighting coal and other mines. In this application
the alternating currents or waves from a powerful
electro-magnet induction machine may be used for
generating, simultaneously, alternating secondary
currents or waves in a number of small induction
coils, placed in various parts of the mine. The
light may be produced in the secondary circuits
from pairs of small carbons enclosed in a glass
vessel, having a small aperture to permit the ex-
pansion of the heated air within. Diaphragms of
wire gauze may be placed over the aperture to
prevent the access of explosive gas. By generat-
ing secondary currents or waves, without inter-
rupting the continuity of the primary circuit, the
contact breaker is dispensed with, and the subdivi-
sions of the light may be carried to a very great
extent.

In the course of his experiments, it was observed
by Mr. Wilde that when the electric circuit was
completed at the bottom of a pair of carbons close
to the holders, the arc immediately ascended to the
points, where it remained so long as the current
was transmitted. His first impression of this
peculiar action of the arc was, that it was due to
the ascending current of hot air by which it was
surrounded. This, however, was found not to be
the cause, as the arc travelled towards the points
in whatever position the carbons were placed,
whether horizontally or \vertically in an inverted
position. Moreover, when a pair of carbons was

held in the middle by the holders, the arc travelled

WILDE'S ELECTRIC CANDLE. 23 1

upwards or downwards to the points, according as
the circuit was established above or below the
holders. The action was in fact recognised to be
the same as that which determines the propagation
of an electric current through two rectilinear and
parallel conductors submerged in contact with the
terrestrial bed, which was described by the same
experimenter in the scientific papers of August,
1868.

In all the arrangements in general use for regu-
lating the electric light, when the light is required
the ends of the carbon pencils are brought into
momentary contact, and are then separated a short
distance to enable the light to form between them.
The peculiar behaviour of the electric arc when the
carbons are placed parallel to each other suggested
to Mr. Wilde the means of lighting the carbons
automatically, notwithstanding the fact that they
could only be made to approach each other by a
motion laterally, and to come into contact at their
adjacent sides.. To accomplish this object, one of
the carbon holders is articulated (jointed) or hinged
to a small base plate of cast iron, Fig. 92, C, which
is so constructed as to become an electro-magnet
when coiled with a few turns of insulated wire, E.
The carbon holder, B B, is made in the form of a
right-angled lever, to the short horizontal limb of
which is fixed an armature, D, placed over the poles
of the electro-magnet, E. When the movable and
fixed carbon holders are brought into juxtaposition,
and the carbons inserted in them, the upper parts

232 ELECTRIC LIGHT.

of the two carbons are always in contact when no
current is transmitted through them, as shown by
the dotted lines in the engraving.

The contact between the carbons is maintained
by means of an antagonistic spring, inserted in a
recess in one of the poles of the electro-magnet,

;ure.
St is
bon

s in
ie of
.ted..

, jamain's blowpipe lamp. 233

The coils of the electro-magnet are thus placed in
the same circuit as the carbon pencils.

When the alternating current from a dynamo-
electric machine is transmitted to the carbons, the
electro-magnet attracts the armature and separates
the upper ends of the carbons, which bring them
into this normal position, and the light is imme-
diately produced. When the circuit is interrupted
the armature is released, the upper ends of the
carbons come into contact, and the light is pro-
duced as before. When several pairs of carbons
are placed in the same circuit, they are by these
arrangements lighted simultaneously.

Jamain's Blowpipe Lamp.

A curious application of Mr. Wilde's electric
candle has been devised by M. Jamain, who,
in a communication to the French Academy of
Sciences, gives details from which the following
description has been deduced : — Wilde's candle, as
is well known, consists of a pair of thin carbon
rods separated from each other, the arc forming
between them as mentioned in the description given
in this work. M. Jamain takes the negative elec-
trode leading from the electrical generator, and,
instead of fastening it in the binding-screw at
once, makes it describe one or two turns around
the candle, from top to bottom, as in Fig. 93, where
A is the candle, and the negative electrode is
wound one turn round the candle longitudinally,

236 ELECTRIC LIGHT.

in a vacuum. It will be understood from this that
the production of electric light needs no aid from
the oxygen of the air, as do almost every other
kind of light. It is as easily produced in a vacuum
as in free air.

Owing to the fact that a saving is effected when
the light is produced in vacuo, many inventors
have turned their attention to this section of the
subject, which when first suggested promised much,
but the attendant complications gradually over-
came the advantages, and the methods were
failures.

It was then thought that carbon in the form of
thin pencils, enclosed in a glass globe exhausted
of air, might, by being rendered highly incandes-
cent by passage of the electric current, afford a
permanent source of light, since it was believed
that carbon would not burn and waste in vacuo.
These attempts, although not few in number or
undertaken by unskilled hands, have as yet failed,
because the carbons always do burn and perish. So
long ago as 1845 an American inventor, Mr. King,
patented there and in England a lamp involving
this principle. His light was produced in a
vacuum, to prevent the oxidation of the incandes-
cent carbon or metal, and was extremely promising
for its beauty, brilliancy, and steadiness. But it
failed to be permanent and economical from various
defects and deficiencies, some of which have, of
course, been removed by the increased power and
economy of modern dynamo-electric machines, and

INCANDESCENCE IN VACUO AND GAS. 237

by recent advances in the art of subdividing the
electric current.

Messrs. Sawyer and Mann, of New York, have
secured patents for a lamp based upon the ex-
haustion of a glass globe of air, and filling it with
pure nitrogen gas, in which the material is to
glow permanently. The light is produced by the
incandescence of a slender pencil of carbon. The
light-giving apparatus is separated from the lower
part of the lamp by three diaphragms to shut off
downward heat radiation. The copper standards
of the lamp are so shaped as to give great radiating
surface, so that the conduction of heat downwards
to the mechanism of the base is wholly prevented.
No detailed description of this lamp will be neces-
sary, further than to say that the electric current
enters from below, follows the line of metallic
conductors to the burner, thence downwards on
the other side to the return circuit. The light-
producing portion is, of course, completely insu-
lated, and also sealed at the base gas-tight.

A fatal defect in all previous lamps depending
on incandescent carbon has arisen from what has
been called the " vaporising " of the carbon. This
Mr. Sawyer holds to be an absurdity, since the
carbon is not even fused. The wastage of the
carbon in mercurial vacuo and in atmospheres
of compound gas is due, he holds, to chemical
decomposition. Many gases, indifferent to carbon
at ordinary temperatures, attack it destructively
at temperatures obtained in the electric lamp;

238 ELECTRIC LIGHT.

and the process is continuous, the carbon taken
from the burner being redeposited on the glass
case, and the gas left free to continue its depre-
dation.

Mr. Sawyer claims to have overcome this diffi-
culty by his method of charging the lamps with
pure nitrogen gas only, and by providing for
fixing of any residual oxygen left in the lamp.
In this way it is claimed that an unwasting*
carbon is secured. Another stumbling-block, upon
which many inventors have come to a standstill,
has been the crumbling or disintegration of the
carbon burner. This is usually caused by sudden
heating when the lamp is first lighted. This is
avoided in the Sawyer-Mann lamp by a kind of
switch, with the use of which it is impossible to
turn all the current on at once, or otherwise than
gradually. This, however, the inventor holds, is
not the only nor the chief advantage of the switch.
It is claimed to be the key to the entire problem,
Mr. Sawyer holds,of practicable electric distribution.

A dynamo-electric light company has been
formed in America to supply lights upon the
Sawyer-Mann system, and they claim for it the
following advantages: — It is well known that an
electric current will exactly and readily divide
among circuits of equal resistance ; accordingly, if
the resistance of a sub-circuit be maintained con-
stant, no matter what may be going on in it,
whether a lamp is not lighted at all or lighted to
a mere taper, or to any intermediary stage up to

INCANDESCENCE IN VACUO AND GAS. 239

full brilliancy, it is obvious that no other lamps in
circuit will be affected.

The greater part of the illumination produced on
this system is the product of a small part of the
current. When the light is well on, a very slight
increase in the current increases the light enor-
mously. It is here that the great loss occasioned
by dividing a fixed current among several lamps
finds its explanation.

A current that suffices in one lamp to produce a
light, say, of 100 candles, will, if divided between
2 lamps, give in each, perhaps, no more than 20
candles, or even 10, making a loss of 80 candles
in the sum total. But if the current be doubled,
each lamp will give a light of 100 candles, and the
sum total will be 200 candles instead of 20. Hav-
ing brought a candle or a system of candles up to
the point of feeble incandescence, a (proportion-
ally) small addition to the current will make them
all brilliant. If at 6,000° Fahr. a given carbon
will produce a light of 3 candles, at 12,000° Fahr.
it will give 9 candles, and at 24,000° Fahr. it will
give 81 candles; the illuminating power increas-
ing with vastly greater rapidity than the tempera-
ture. The wires supplying the current may be
run through existing gas pipes, each lamp being
provided with a switch placed conveniently in the
wall: and by simply turning a key the light is
turned up and down, off or on. So long as the
house is connected with the main, it makes no
difference to the producer whether all the lights

240 ELECTRIC LIGHT.

are on or off, since the existence of the entire house
resistance remains the same ; though a difference
will be caused to the consumer, since a meter
records the time that each lamp is on, and the
charge is rated accordingly.

When the main is tapped for a sub-circuit, a
shunt is introduced so as to throw so much of the
current as may be needed into the derived circuit.
The resistance of, say, ioo added lamps will be
about 1,000 ohms. By giving to the shunt a re-
sistance of 10 ohms, iooth of the current will be
diverted, and the lamps supplied. Where a large
number of lamps are required in a circuit, a com-
bination of two plans indicated is employed. The
diversion of any portion of the electric supply into
an added circuit, whether one house or a group of
houses, necessarily increases the aggregate resist-
ance of the electric district, and calls for more
work from the generator. To meet such contin-
gencies automatically, Messrs. Sawyer and Mann
have invented and patented a regulator, which
responds instantly to any increase or diminution
in the demand, thereby securing an absolutely
uniform volume of current.

This regulator so controls the steam or other
power actuating the generator of electricity, that
the amount of power supplied is increased or
diminished in exact proportion to the demand,
either by changing the volume of steam produced,
or by coupling on or detaching different gene-
rators, or parts of a simple generator in circuit.

EDISON'S LAMPS. 24 J

This system does not appear to have had an
extended trial, and it is very doubtful whether the
carbon pencils will, in "pure nitrogen," be per*
fectly permanent, The light obtained by incan-
descent pencils is much less than that from the open
arc with the same current, and the incandescent
lamp is in this respect costly, even although a
perfectly permanent pencil could be arranged.
There is an obvious defect, too, in the Sawyer-
Mann system when the resistance of the circuit,
and consequently the expenditure, is always the
Same, whether the lamps are burning or not. This
could, no doubt, be obviated.

Such is the best incandescent lamp of this kind
that has been invented. M. Fontaine has likewise
made many experiments with carbon pencils, but
the best of them were consumed as usual in air in
15 minutes. Konn has also invented an incan-
descent lamp, in which a vacuum is maintained.
Other inventors have also produced lamps of little
use in practice.

Edison's Lamps.

Much interest has been taken in the sensational
and often absurd announcements concerning, the
apparatus in course of perfection by Mr. T. A.
Edison, of Menlo Park, New York. This inventor
is well known by his talking phonograph and tele-
phones, and it was in some quarters thought that
when he had set himself to the task of inventing an
efficient subdivision of the electric light circuit,

242

ELECTRIC LIGHT.

something would in all probability be done. Un-
fortunately, however, as far as can be learned up
to this date (July, 1879), the attempts have proved
almost complete failures ; but it is to be hoped that
if Mr. Edison continues his investigations the ulti-
mate outcome may be of much value.

Edison's lamp, Fig. 94 (for only one is deserving
of notice), is based upon a very old idea— the
incandescence of platinum, which was employed by

various inventors,
and by King, as
early as 1845. All
such lamps have so
far been failures, and
have proved wasteful
of current, inasmuch
as the true arc gives
much more light for
the same expendi-
ture of power in the
circuit. Edison's
device, however, would appear to depend almost
altogether for its usefulness upon an automatic regu-
lator attached to it, and it has proved that automatic
apparatus of this class work very indifferently.
He employs, first, a strip of an alloy of platinum
and iridium, A. This is fastened between two
holders, the lower one of which is a lever, B, jointed
at one end. This lever is provided with a spiral
spring, D, constantly stretching the platinum-iridium
strip, and under its end is a contact point, C. When

Fig. 94.— Edison's Platinum-iridium Lamp.

EDISON'S LAMPS. 24$

the current passes the strip is made white hot, and
gives out considerable light before it fuses. The
expansion consequent upon this allows the antago-
nistic spring to put the strip out of circuit for
an instant when it is in danger of being fused
by the strength of current. Unfortunately, how-
ever, the expansibility of platinum is extremely
small, and although the lever provided multiplies
the expansion into a considerable movement, the
platinum-iridium strip is very often fused before it
can act. It is>, in fact, extremely doubtful whether
any regulator of current upon this principle will
ever be devised.

It must not be forgotten, also, that any contact
points in the circuit of a dynamo-electric machine
will never work well. There is a powerful discharge
of stored-up electric energy as soon as the circuit
is broken, and what contact points will withstand
such sparks ? If there is to be regulation of circuit
at all, it must be by means of some substance upon
which pressure acts to increase or decrease the
resistance, and not by open contact. It is, in short,
not difficult to see that the obstacles which stand
in the way of inventing a useful lamp on this
system are of a kind difficult of removal. The
expansion of this lamp itself when it becomes
heated would suffice to render useless any contacts
or adjustments previously made. The apparatus
is too delicate, and may be said to be useless in
any but skilled hands. The idea of regulating the
current has been tried in various pieces of appa-

244 ELECTRIC LIGHT.

ratus intended to automatically govern the circuit
of a dynamo-electric machine, and which are here
spoken of under " Regulators of Current/' p. 160.

Edison's lamp has been tried in England, but the
results were anything but satisfactory, considering 1
that it was originally intended to be applicable to
general household purposes.

The Times of March 22nd, 1879, went so far as to
say that Mr. Edison never did accomplish more
than to maintain 400 coiled iron wires in a state of
partial incandescence with current derived from the
powe^of a 16 horse-power engine. This is wrong.
Mr. Edison has produced several lamps of the
platinum description, and with them some real sub-
division has been effected, and it is very improbable
indeed that iron wire would be chosen by him from
which to obtain light by incandescence.

From private experiments made with Edison's
apparatus, and modifications of it, the greatest care
was found to be necessary to prevent the instant
melting of the incandescent strip, and if the regulator
is not adjusted with the greatest accuracy, the strip
disappears under the energy in a twinkling.

Mr. Edison has also employed lamps made with
platinum wire spirals, regulated again by expan-
sion, and a break in the circuit. He also proposes
the use of secondary currents and induction coils,
and also secondary batteries in circuit.

With regard to the platinum-iridium spirals for
use in Mr. Edison's lamps, a communication by the
inventor himself, read before the American Asso-

EDISON'S EXPERIMENTS. 245

ciation for the Advancement of Science, contains
some interesting particulars of a new method by
which they may be prepared for use in electric
illumination.

In the course of his experiments on electric light-
ing he has developed some striking phenomena
arising from the heating of metals by flames and
by the electric current, especially wires of platinum,
and platinum alloyed with iridium. These experi-
ments are still in progress. The first fact observed
was that platinum lost weight when treated in a
flame of hydrogen, that the metal coloured the
flame green, and that these two results combined
until the whole of the platinum in contact with the
flame had disappeared. A platinum wire, 20,000th
of an inch in diameter, was wound in the form of
a spiral one-eighth of an inch in diameter and half
an inch in length. The two ends of the spiral were
secured to clamping posts, and the whole apparatus
was covered with a glass shade. Upon bringing
the spiral to incandescence for 20 minutes, that
part of the globe in line with the sides of the spiral
became slightly darkened ; in five hours the deposit
became so thick that the incandescent spiral could
not be seen through the deposit.

This film, which was most perfect, consists of
platinum, and Mr. Edison has no doubt but large
plates of glass might be coated economically by
placing them on each side of a large sheet of
platinum, kept incandescent by the electric current.

This loss in weight, together with the deposit

246 ELECTRIC LIGHT.

upon the glass, presented a very serious obstacle
to the use of metallic wires for giving light by in-
candescence ; but this was easily surmounted after
the cause was ascertained. He coated the wire
forming the spiral with the oxide of magnesium by
dusting upon it finely powdered acetate of magne-
sium. While incandescent the salt was decomposed
by the heat, and there remained a strongly adherent
coating of the oxide. This spiral so coated was
covered with a glass shade and brought to incan-
descence for several minutes; but instead of a
deposit of platinum upon the glass, there was a
deposit of the oxide of magnesia. From this and
other experiments Mr. Edison became convinced
that this effect was due to the washing action of
the air upon the spiral ; that the loss of weight in
and the colouration of the hydrogen flame was
also due to the wearing away of the surface of the
platina, by the attrition produced by the impact of
the stream of gases upon the highly incandescent
surface, and not to volatilisation, as commonly sup-
posed.

He further describes other and far more impor-
tant phenomena observed in his experiments. If
a short length of platinum wire, i,oooth of an inch
in diameter, be held in the flame of a Bunsen
burner, at some part it will fuse and a piece of
the wire will be bent at an angle by the action of
the globule of melted platinum ; in some cases there
are several globules formed simultaneously, and
the wire assumes a zig-zag shape. With a wire

EDISON'S EXPERIMENTS. 247

4,000th of an inch in diameter this effect does not
take place, as the temperature cannot be raised to
equal that of the small wire, owing to the increased
radiating surface and mass. After heating, if the
wire be examined under a microscope, that part
of the surface which has been incandescent will
be found covered with innumerable cracks. If
the wire be placed between clamping posts, and
heated to incandescence for 20 minutes by the
passage of an electric current, the cracks will be so
enlarged as to be seen with the naked eye ; the wire
under the microscope presents a shrunken appear-
ance, and is full of deep cracks.

If the current is continued for several hours, these
effects will so increase that the wire will fall to
pieces. This disintegration has been noticed in
platinum long subject to the action of a flame, by
Professor Draper. The failure of the process of
lighting invented by the French chemist, Tessi6-du-
Motay, who raised sheets of platinum to incandes-
cence by introducing them into a hydrogen flame,
was due to the rapid disintegration of the metal.
Mr. Edison has ascertained the cause of this phe-
nomenon, and has, he says, succeeded in eliminating
that which produces it, and in doing so has produced
a metal in a state hitherto unknown, and which is
absolutely stable at a temperature when nearly all
substances melt or are consumed ; a metal which,
although originally soft and pliable, becomes as
homogeneous as glass and as rigid as steel. When
wound in the form of a spiral, it is as springy and

248 ELECTRIC LIGHT.

elastic when at the most dazzling incandescence as
when cold, and cannot be annealed by any process
now commonly known. For the cause of this
shrinking and cracking of the wire is due entirely
to the expansion of the air in the mechanical and
physical pores of the platinum, and the contraction
upon the escape of the air. Platinum as sold in
commerce may be compared to sandstone, in which
the whole is made of a great number of particles
with many air spaces. The sandstone upon melt-
ing becomes homogeneous, and no air spaces exist.
With platinum or any metal the air spaces may be
eliminated and the metal made homogeneous by a
very simple process.

This process is then described by Mr. Edison*
He made a large number of platinum spirals, all of
the same size and form and the same quality of
wire ; each spiral presented to the air a radiating
surface of 3^ of an inch ; 5 of these were brought
by the electric current up to the melting-point, the
light was measured by a photometer, and the
average light was equal to 4 standard candles
for each spiral just at the melting-point. One of
the same kind of spirals was placed in the receiver
of an air-pump, and the air exhausted to 2 milli-
metres ; a weak current was then passed through
the wire to warm it slightly, for the purpose of
assisting slightly the passage of the air from the
pores of the metal into the vacuum. The tempera-
ture of the wire was gradually augmented at
intervals of ten minutes until it became red. The

EDISON'S EXPERIMENTS. 249

object of slowly increasing the temperature was to
allow the air to pass out gradually and not ex-
plosively. After which the current was increased at
intervals of fifteen minutes. Before each increase
in the current the wire was allowed to cool, and
the contraction and expansion at these high tem-
peratures caused the wire to weld together at the
points previously containing air. In one hour and
forty minutes this spiral had reached such a tem-
perature without melting that it was giving a
light of 25 standard candles, whereas it would
undoubtedly have melted before it gave a light of
5 candles had it not been put through the above
process. Several more spirals were afterwards
tried, with the same result. One spiral which
had been brought to these high temperatures
more slowly gave a light equal to 30 standard
candles. In the open air this spiral gave nearly
the same light, although it required more current
to keep it at the same temperature. Upon exami-
nation of those spirals which had passed through
the vacuum process, by the aid of a microscope no
cracks were visible : the wire had become as white
as silver, and had a polish which could not be
given it by any other means. The wire had a
smaller diameter than before treatment, and it was
exceedingly difficult to melt in the oxy-hydrogen
flame as compared with the untreated platinum ;
it was found that it was as hard as the steel wire
used in pianos, and that it could not be annealed
at any temperature His experiments with many

250 ELECTRIC LIGHT*

metals treated by this process have proved to his
satisfaction, and he has no hesitation in stating
that which is known as annealing of metals to make
them soft and pliable is nothing more than the
cracking of the metal. In every case where a hard-
drawn wire had been annealed, a powerful micro-
scope revealed myriads of cracks in the metal.
Since the experiment just mentioned was made,
further investigations, with the aid of Sprengel
mercury pumps, produced higher exhaustions, and
by consuming five hours in excluding the air from
the wire and intermitting the current a great num-
ber of times, the result is stated to be the light of
8 standard candles from a spiral of wire with a
total radiating surface of -j^th of an inch, or a sur-
face about equal to a grain of buckwheat. With
spirals of this small size which have not passed
through the process the average amount of light
given out before melting is less than one standard
candle. Thus Mr. Edison has been enabled, by the
increased capacity of platinum to withstand high
temperatures, to employ small radiating surfaces,
and thus reduce the energy required for electric
light.

He now claims to have obtained 8 separate jets,
each giving out an absolutely steady light, and
each equal to 16 standard candles or a total of 128
candles, by the expenditure of 30,000 foot-lbs. of
energy, or less than one horse-power. As a matter
of curiosity he made spirals of other metals, and
excluded the air from them in the manner stated.

EDISON'S EXPERIMENTS. 2$ I

Common iron wire may be made to give a light
greater than platinum not treated.

The latest outcome of Mr. Edison's praiseworthy-
labours to obtain a constant burner by electric
agency, is a small lamp in the form of a glass
globe, exhausted of air, and containing in the
electric circuit a horseshoe-shaped strip of car-
bonised cardboard.

This horse-shoe is stamped from "Bristol board,"
and is then placed in a wrought-iron mould and
raised to such a temperature that the volatile con-
stituents of the paper are driven off, the result
being a miniature horse-shoe (2 in. long) composed
of charred paper. Through this, when the contain-
ing globe has been exhausted by the air-pump, the
current is passed from pole to pole by connections
of platinum wire. It is claimed that this substance,
which becomes highly incandescent and yields a
brilliant light, is unchangeable by heat in vacuo,
and that a lamp may be produced at an outlay of
25 cents.

A number of these lamps were seen burning in
the inventor's laboratory by correspondents of the
press, English and American, during the month of
December, 1879. The result is stated to be so
satisfactory that Mr. Edison intends to illuminate,
on a practical scale, the village of Menlo Park,
and then to extend the system to New York.

There is little probability, however, that this
lamp will prove constant. Burnt paper in various
forms' has been repeatedly tried before, and it is

252 ELECTRIC LIGHT*

assuredly not constant in the best possible vacuum
obtainable. Moreover, the resistance of such a
substance is very much greater than that of pure
carbon in the graphite form. Carbon obtained,
from paper is obviously very'impure, and cannot,
therefore, prove constant while incandescent under
the electric current, while a strong discharge of
electricity throughout the circuit would in all pro-
bability split every horseshoe therein. Some time
has elapsed since Mr. Edison announced his inten-
tion to light Menlo Park, and no further progress
can be reported. We may, indeed, rest assured
that, upon further reflection, Mr. Edison will
abandon this imperfect burner.

Up to the time of going to press (April, 1880) it
is reported that Mr. Edison continues his experi-
ments with the carbon loops, and that he is build-
ing and fitting a model electric light station,
capable of maintaining 500 lights, to demonstrate
the practicability of his scheme.

CHAPTER IX.
MEASUREMENT OF ELECTRIC LIGHT.

Photometric measurements, as applied to the
light produced by electricity between two carbon
points, are not so easily obtained accurately as may
be supposed. The value is usually given in terms
of comparison with the standard sperm candle,
burning, as nearly as possible, 1 20 grains per hour.
London gas, with a burner consuming about
5 cubic feet of gas per hour, gives an average
illuminating power of 15 standard candles, Liver-
pool gas 16, and the gas of other towns varies in
quality so greatly that gaslight should never be
employed as a standard of measurement unless its
actual value has been determined. In France the
measurement is usually made by comparing with
the light of a Carcel lamp, burning 648 grains of
pure oil per hour. An ordinary gas jet, burning
4 \ cubic feet per hour, is equal to i-iV** 1 °f a Carcel
light as above. A burner consuming 7 feet per
hour is equal to 172 Carcel lights — taking 16-candle
gas.

The intensity of the beam of electric light varies
considerably according to the relative positions of

254 ELECTRIC LIGHT.

the carbons. Thus, if a carbon having a square
section be placed so that its axis corresponds with
the line of one of the angles of the other carbon,
the beams of light in different directions will vary-
as much as the ratio of 38 to 287, and even when
the axis of one carbon lies properly in a prolonga-
tion of the axis of the other, the beam will vary
with the angle formed by the beam with the axis
of the carbons. Thus it is stated that the beam at
right angles to the axis has measured 970 candles
only, whilst that measured at 45 with the axis of
the carbons has been 2,000 candles. The light
should, therefore, always be measured on a beam
at right angles to the axis of the carbons.

Rumford's Photometer is one of those often used,
and its simplicity recommends it to the practical
electrician. It consists simply of a calico or other
screen, in front of which, and about a foot from it,
is placed, vertically, an opaque rod of any material,
such as blackened wood. The lights to be com-
pared, for example a candle and a gas jet, are
placed at different distances from the rod, and the
gas jet is moved until the shadow it casts from the
rod upon the screen is equal in intensity to that
produced by the candle, which will, of course, be
much nearer to the rod. The intensity of a light
diminishes as the square of the distance or in
other words, the intensity of the light is inversely
proportional to the square of the distance. Since the
intensity of a light at twice the distance is one-
fourth, and at three times the distance one-ninth, it

MEASUREMENT OF ELECTRIC LIGHT. 255

is obvious that if two sources of light, of which one
is placed at a certain distance from a surface while
the other is placed at a distance twice or three
times as great, produce equal degrees of illumina-
tion, the illuminating power of the more distant
light must be four or nine times as great compared
with the illuminating power of the light which is
nearer to the surface. From this it is clear that
when two sources of light produce equal intensities
of light upon two surfaces at unequal distances,
their illuminating powers are in the ratio of the
square of their distances from the illuminated
surfaces.

Unfortunately, a difficulty is introduced in such
work by the redness of a candlelight and the in-
tense violet rays given off by the electric light.
For electric light measurements it is found better to
use Bunsen's photometer, which enables the inten-
sities to be compared with greater accuracy than is
possible by the use of the opaque rod and screen.
The difficulty consists in the very different appear-
ance presented by a shadow cast by the reddish
candle, and that given from the brilliant electric
light.

Bunsen's Photometer consists of a square wooden
frame, over which is stretched a piece of white paper,
having a circular grease-spot in the centre. When
lights are to be compared, a straight line is drawn
upon a flat surface, the paper screen is placed
vertically upon it with its centre on a level with the
two lights, which are arranged upon either side of

256 ELECTRIC LIGHT.

it. The stronger light is moved away upon the
line until the grease-spot is not visible, and then
as before, by measuring the distances between the
lights and the screen and comparing them, the
power may be accurately arrived at. A grease-
spot is best made by dropping melted stearine upon
the paper, removing it with a knife, and weakening
the strength of the spot by passing blotting-paper
on either side of it under a hot iron. If the spot be
too strong, it will be difficult to arrive at a correct
estimate of the values.

Equal advantages should be given to both lights.
For example, if the electric light be thrown upon
the screen from a parabolic reflector, the candle-
light should be also provided with a similar backing.
If the electric light be diffused, the candle light
should also be diffused, and care is necessary to
have the back, grounds, and sides near to the lights
equal in colour or reflective power. Care is also
necessary that the experiment be made in an other-
wise dark place.

In the experiments undertaken by the Committee
of the Franklin Institute, to determine the effi-
ciency of the dynamo-electric machines placed in
their hands, namely, the large and small Brush,
the Wallace-Farmer, large and small, and one of
Gramme's machines, care was taken, in order to
make the measurements as accurate as possible, so
to arrange the apparatus that no reflected or dif-
fused light should fall on the photometer, and thus
introduce an element of error.

MEASUREMENT OF ELECTRIC LIGHT. 257

The electric lamp was enclosed in a box open at
the back for convenience of access, but closed with
a non-reflecting and opaque screen during the
experiments. Projecting from a hole in the front
of the box was a wooden tube, 6 in. square inside
and 8 ft. long, with its inner surface blackened to
prevent reflection, thus allowing only a small beam
of direct light to leave the box.
• The beam of light passed into a similar wooden
tube, placed at a proper distance from the first
(about 30 ft.), and holding in its farther end the
standard candle. This tube also held the dark box
of a Bunsen photometer, mounted on a slide, so as
to be easily adjusted at the proper distance between
the two sources of light. A slit in the side of the
tube enabled the observer to see the diaphragm
and grease-spot. The outer end of the second tube
was also covered by a non-reflecting opaque hood,
and the room was, of course, darkened when photo-
metric measurements were taken. The rigid exclu-
sion of all reflected or diffused light is believed to
be the only trustworthy method of obtaining true
results, and will, no doubt, account in a great
degree for the lower candle power obtained in these
experiments than that given by many previous
experimenters.

The difficulties encountered in the measurement

of the light, arising from the difference in colour,
were at first thought to be considerable, but further
practice and experience enabled the observer to
overcome them to such an extent, that the error

258 ELECTRIC LIGHT.

arising from this cause is inconsiderable, being*
greatly less than that due to the fluctuations of the
electric arc itself.

The Franklin Institute Committee considered
what advantage would be gained by using a larger
source of light than the standard candle, but after
making several experiments with gas flames and
the oxy-hydrogen light, they determined to use a
standard candle only, making corrections for any
variations in the rate of consumption of 120 grains
per hour.

In determining the light-giving power of the
current produced by the different machines, a con-
tinuous run of from 4 to 5 hours was made, and great
care was taken to keep the axis of the two carbons
of the lamp in the same line. To facilitate obser-
vations, a lens was placed in the side of the electric
lamp box, in line with the carbon points. The axis
of the lens was at right angles to the beam of light
going to the photometer, and an image projected
upon a screen, from the lens, enabled the observer
to note the condition of the carbon points without
distressing the eye. Photographic views of the
carbon points were' also taken at the moment of
making the photometric observations, and care was
observed that, at the moment of making the
measurement, there was no fluctuation or moving
from side to side of the electric arc.

The first of the following tables exhibits the results
obtained by the Franklin Institute from their photon
metric measurements of the lights from the Brush

MEASUREMENT OF ELECTRIC LIGHT.

259

thof

bon

imed

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Size
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in Standard

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Horse
Power.

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Revolu-
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minute.

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Field Magnets.

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Small Brush . .
Large Wallace .
Small Wallace '.
Small Gramme .

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260 ELECTRIC LIGHT. j]

machines, large and small; the Wallace-Farmer
machines, large and small, and the small machine of
Gramme, made by Breguet, and sent by him to the
Philadelphia Exposition. The latter machine was
lent by Prof. Wiley, of Purdue University, La-
fayette, Indiana, and the others were sent in by
their makers — the Brush by the Telegraph Supply
Company of Cleveland, Ohio, and the Wallace by
Wallace and Sons, of Asonia, Conn. The second
table gives some particulars of the experiments
made at the South Foreland by Mr. Douglass, the
engineer to the Trinity Board, in 1876 and 1877.

The measurements of electric lights made by the
Franklin Institute, and those by the Trinity House
authorities, thus include particulars of the chief
machines at present in use.

It is but fair to the proprietors of 'the Gramme
machine, as tested by the Trinity Board, to state
that the type of apparatus tried was not the best
in use, and that the Gramme has since been found
in practical working to very nearly reach the candle
power per horse power of the smaller Siemens,
while it is more compact.

According to Messrs. Sautter and Lemonnier and
Co/s experiments, made by them in Paris, they give
for the Gramme machines : —

A type 2,400 \

C type 2,800 > Standard candles per H. P.

D type 3,125 )

The superiority of the Siemens and Gramme
machines over all other inventions yet in use in

MEASUREMENT OF ELECTRIC LIGHT. 26 1

England and America is not difficult to find a
reason for when the constructional details are
examined. These machines are also cool in working.
As far as the author can learn, the new dynamo-elec-
tric machine invented by Weston, being somewhat
similar in construction to the Siemens apparatus,
runs both Siemens 5 and Gramme's machines very
closely in point of efficiency, and it is one of the
, coolest machines in use— there is, however, a slight
loss over churning the air.

In the photometric measurements of the Trinity
Board, the standard of comparison was the 6-wick
colza-oil lamp of the Board, and it was placed at a
distance of 100 feet from the electric lamp. It was
found that when two of Siemens' machines were
coupled together, they gave a larger candle power
than when worked separately. Working separately
the aggregate light was equal to 12,403 candles,
while the illuminating power rose to 14,134 candles
when the machines were joined to one cable and
driven at the same speed as before.

CHAPTER X.

MATHEMATICAL AND EXPERIMENTAL
TREATMENT OF THE SUBJECT.

Dr. Hopkinsoris Investigations. — Dr. Hopkinson,
in April, 1879, read a valuable paper on "Electric
Lighting" before the Institution of Mechanical
Engineers. In this communication he gives the
results of experiments on one of Siemens' con-
tinuous current dynamo-machines to establish the
relation between the electro-motive force, resistance
of the circuit and current, and also between the
energy transmitted, measured by dynamometer,
and that appearing as current. The curve formed
by taking the current as abscissaa and the electro-
motive force as ordinates when different resistances
are in circuit, is given, the quantities being reduced
to a common rate of 720 revolutions a minute, it
being taken that electro-motive force, with the
other elements constant, is proportional to the
speed. From this curve various problems can be
solved. It will determine what current will flow at
any given speed of rotation of the machine, and
under any conditions of the circuit, whether of
resistances or of opposed electro-motive forces.

MATHEMATICAL DEDUCTIONS. 263

Mr. Schwendler* s Experiments. — With regard to
the relation of speed to currents and electro-motive
force, Mr. Schwendler* states: "The current pro-
duced by a dynamo-electric machine through a
given constant total resistance in circuit increases
permanently with the speed of the induction
cylinder. This increase of current for low speeds
is more than proportional to the speed, afterwards
it becomes proportional, and for high speeds the
increase of current is less than proportional to the
speed. The current has, however, no maximum
for any speed, but reaches its greatest value at
an infinite speed. This same law, as the total
resistance in circuit is supposed to be constant,
of course holds good also for the electro-motive
force."

With regard to the influence of ■ external resis-
tance, Mr. Schwendler further states : " Keeping
the speed constant, the electro-motive force de-
creases rapidly with increase of external resistance.
This decrease is more rapid the smaller the internal
resistance of the machine. Hence the currents
must decrease much more rapidly than proportional
to the total resistance in the circuit. As in the case
of speed the electro-motive force has no maximum
for a certain external resistance, but approaches
permanently its greatest value for an external
resistance equal to nil."

Mr. W. H. Preecds Investigations. — Mr. W. H.

* Precis of report to the Board of Directors of the East India Rail-
way on electric light experiments.

264 ELECTRIC LIGHT.

Preece, in a paper on the Electric Light in the
Philosophical Magazine of January, 1879, investi-
gates mathematically the question of grouping
lights in multiple arc and in series, and arrives
at the conclusion that " beyond certain limits when
the current is produced by a dynamo-machine if n
lamps be joined in series the total light becomes

diminished by — , and the light emitted by each

lamp becomes diminished by — r If they are joined
up in multiple arc the total light is diminished
by -J and the light emitted by each lamp —3. In

the latter case the rapid diminution in the light
emitted is due to the fact that the heat is developed
in the machine itself instead of in the resistances
external to it."

Mr. Preece then goes on to say, " We have as-
sumed w [i.e. the work done in the steam-engine
in unit time) to be constant; but this is only
the case when the velocity of the rotating coils
in the dynamo machine has attained a maximum.
This limit will vary with each dynamo machine
and each kind of lamp used. With the Wallace-
Farmer machine the limit appears to be reached
when six lamps are connected up in series. With
the Gramme alternating machine and Jabloch-
koff candles the limit appears to be five lamps.
Beyond these limits the above laws will be true.
It is partial success in multiplying the light that

MATHEMATICAL DEDUCTIONS. 265

has led so many sanguine experimenters to antici-
pate the ultimate possibility of its extensive sub-
division — a possibility which this demonstration
shows to be hopeless, and which experiment has
proved to be fallacious."

Mr. Alexander Siemens' Paper at the Society of
Telegraph Engineers. — Mr. "A. Siemens has pointed
out, in a paper read before the Society of Telegraph
Engineers in March, 1880, that in the ordinary
dynamo machines as generally used, " the intensity
of the magnetic field in which the armature re-
volves varies very much, being greatest when the
external resistance is smallest, and vice versa. If
therefore the lamps producing the light are not
working very regularly, their action re-acts con-
tinually on the machine in the most unfavourable
wa y> by weakening the magnetic field when the
resistance is greatest and the current most wanted,
and by inducing the most powerful currents when
the least resistance is to be surmounted." This
often destroys the insulation of the wire.

To obviate this the electro-magnet circuit has
been made a parallel circuit to the external
resistance circuit, one circuit acting as a shunt to
the other. In this case, as the external resistance
increases the E. M. F. rises, as more current passes
through the electro-magnet circuit.

But although this causes the E. M. F. to vary in
the right direction it still causes fluctuation, and
the variation in the strength of the field magnets
causes a variation in the power absorbed, and

266 ELECTRIC LIGHT*

also displaces the most favourable point for tlie
brushes.

A constant and permanent magnetic field is
therefore recommended by using a separate ma-
chine for exciting the electro-magnets.

It is also pointed out that length of leading-
wires, by adding to the resistance of the circuit,
diminishes the fluctuations in the current caused
by the variation in the resistance of the arc.

Alternate current machines appear, according*
to Mr. Siemens, to stand wear and tear better
than the continuous current machine, and in those
made by Mr. Siemens an important improvement
has been introduced by omitting the iron cores of
the revolving coils. The heating effects of the
cores caused by the incessant reversing of their
polarity is thereby avoided, and the intensity of
the magnetic field scarcely affected.

Mr. Fitzgerald's Investigations. — It has been re-
marked by so able an investigator of electrical
phenomena as Mr. Fitzgerald, that there is no
force in nature varying simply as the number of
cells in series of a battery or corresponding with
what is known as electro-motive force, and no
inertia varying according to what is defined as
electrical resistance.

Further, it is observed that the effects of varying
those " current elements " are very different in the
two cases of the dynamo-electric and the voltaic
currents. The law of Ohm, as previously applied
to the current effects of voltaic batteries, was thought

MATHEMATICAL DEDUCTIONS. 267

by some to be inapplicable in certain points to the
dynamo-electric machine and its currents. This
does not mean, however, that the well-known law
of Ohm is incorrect as a law of phenomena— an
expression indicating a necessary relation — but
from a physical point of view as empirical as other
mathematical laws in which causation is lost
sight of.

In the case of any electro-motor the equation

I = - is perfectly applicable. In the voltaic bat-
tery, however, a variation of R does not of necessity
affect E, which is altogether independent of such
variation when this occurs in the external portion

of the circuit. Thus we have generally 1 oc -, or

XV.

current varies inversely as the resistance in circuit.
A variation of E does not necessarily affect R ;
and, when the external resistance of the circuit
bears a high ratio to the battery resistance, a varia-
tion of the electro-motive force from E to E 1 — an
addition to, or diminution of, the number of cells
in series — causes the current to vary approximately

E 1

in the ratio -— . Accurately, the variation in any

E 1 R

case is determined by the ratio , where p

E R -p E p

is the resistance of the cells added or subtracted.

Thus,

E E l R E 1

R ER + Ep R+ p

In the case of a telegraph circuit, for instance,

268 ELECTRIC LIGHT.

we have approximately I oc E. On the other hand,
in the dynamo-electric machine, converting into

electrical work a given horse-power, I oc - — , since,
the ratio — being constant, E 2 ocR, e oc -/ R» and

— oc i. — = —1= . Thus any variation of R in this

case necessarily affects E.

Again any variation of E necessarily affects R ;
and, the product E I being constant, we have

I oc _, a somewhat startling result, which, to some

observers, has appeared contradictory to the law of
Ohm. With this, however, it is in perfect accord

— in effect, since E oc ^ r, r oc e 2 , and

E E I
R E* E

or, when E is varied, the current varies inversely
as the electro-motive force, because the resistance
varies as the square of this value.

It will be seen that R oc E 2 = 4 • and that the

same quantity of work will be done by the current
whatever may be the resistance in the circuit.

If h. p. be taken to express the total horse-
power converted into electrical work (in the whole
circuit), under the best conditions, with a Gramme
machine of the form experimented with at the
Franklin Institute,

H. P. =h. p. x i*39,

MATHEMATICAL DEDUCTIONS. 269

and the efficiency of the machine is expressed by

^ = 72 (nearly).

Or the machine can convert into electrical work
72 per cent, of the energy expended upon it.

Let E = electro-motive force, in volts, acting in
a circuit.

R the total resistance, in ohms, of the circuit.

r = resistance of the voltaic arc obtained.

H. P. = h. p. of the prime motor working the
dynamo-electric machine.

h. p. = the h. p. absorbed in the production of
electrical work in the circuit.

X = the intensity, as standard candles, of the
electric light so arranged as to illuminate equally
in all directions.

A = intensity of the light in one particular
direction; the light being arranged to give the
maximum illumination (without reflectors) in this
direction.

The energy of the current, or the mechanical
equivalent of the work and heat produced by it per
hour, will be

E» X 2654 ft> . lbs . = tfXI-18 ft . tons#
R R

Horse-power absorbed in the current

( energy in ft.-lbs. *\
33,000 x time in min.y

will be

, E 2
n. p. = ,

R X 747

270 ELECTRIC LIGHT.

The ratio =/£ is the measure of the efficiency

Jti. jr.

of dynamo-electric machines. In the case of

Gramme's machine, under the best conditions we

have

H. P. =h. p. x 1*39.

The horse-power absorbed in the arc itself is

h. p. x —

* R

The ratio of this latter value to h. p., or

_r h. p. x r x 747

R — E 2

is the measure of the efficiency of the electrical

circuit in the production of the greatest quantity

of light with a given quantity of electrical energy.

In the experiments with the Gramme machine

made by the Committee of the Franklin Institute,

the light, in standard sperm candles, produced by

the voltaic arc was

A = h. p. x — x 1,044 (candles) . . . (1)

when the intensity of the light was approximately
equal in every direction. But, when the carbons
are so adjusted as to give the best effects with the
photometer in a given position, we may multiply
the former value by 2*87, and we have

A = h. p. x — x 2,996 (candles) ...(11)

Expressing these equations in a different form,

we have

\ = i 2 r x i'4 • • • • (10)
A x I 2 r X 4 .... (1 1 a)

MATHEMATICAL DEDUCTIONS. 27 1

It should be remembered that these values are
obtainable only under. the most carefully arranged
conditions.

Although the light cannot be subdivided without
very considerable loss, it is not to be admitted that,
if a given total quantity of light be produced with
one hundred lamps, it is one hundred times as
expensive as if it were produced by one lamp. If
we use two lamps instead of one, and put them in
series, the original arc resistance, /, is not neces-
sarily doubled ; indeed it may be preserved con-

C 2 /

stant, in which case we should have for

each light, and the original value, C 2 /, for the two.

And if we place four lamps in parallel circuit, the

total resistance may be reduced nearly fourfold,

so that we may obtain twice the original current

with half the electro-motive force in action. Thus

E 2

C 2 /, or -=s- / becomes

K\J 4 P 4

The theoretical value for each light being

C 2 /

CD'-

and that from the four C 2 /. The loss, when the
light is subdivided, is doubtless due to an increase
in the quantity of heat which must be expended
before any luminous effect is produced.

272 ELECTRIC LIGHT.

Equational numbers required in reducing results. —
The particulars given herewith will be found of
value in any experiments upon dynamo-electric
machines, circuits, or lamps.

One horse-power is equal to 1,980,000 foot-lbs.
per hour, or 33,000 per minute ; that is, 33,000 lbs.
weight falling one foot in a minute, or 1 lb. weight
falling 33,000 feet per minute.

1 horse-power is maintained in modern steam-
engines with 3^ lbs. of coal per hour.

1 heat unit = 772 foot-lbs.

Therefore, 1 horse-power = 2,565 units of heat
per hour, and ^£^ = 6| units of heat per candle
of light.

1 standard candle (of sperm) burns 120 grains
per hour, and equals \ cubic feet of gas per hour.

1 lb. gas coal produces 4 cubic feet of gas, 0*85
lb. of gas coke, and 0*05 lb. of tar. In a pound of
gas coal there are 15,000 units of heat, in the coke
13,000, in the gas tar 20,000 units of heat.

The power expended by a dynamo-electric
machine producing current for the light of a
standard candle is about 90 lbs. falling through
one foot in a minute.

1 calorie (kilogramme of water heated i° Centi-
grade) is equal to 424 kilogramm&tres, which equals
3*9683 units (Fahrenheit).

1 kilogrammfetre equals 7*2331 foot-lbs.

CHAPTER XL

PRESENT APPLICATION AND COST OF THE

ELECTRIC LIGHT.

So extensive has been the introduction of elec-
tric lights that to enumerate and dwell upon them
in detail would in itself almost fully occupy the
pages of this little treatise. The more note-
worthy instances can pnly, therefore, be briefly
glanced at.

Interior Illumination of Large Buildings. — Suck
places as theatres, before and behind the scenes,
halls, and picture-galleries, are most effectually
illuminated from above. There are various ways
of doing this, and of diffusing the light. Perhaps
the best is that of sending the fall rays through a
large sheet of frosted glass.

This should be set in the centre of the ceiling, if
convenient at the same height as the ceiling. Its
size will depend upon the size of the building. For
a medium-sized theatre, a glass surface 6 feet
square will be found sufficient. Directly above
this frosted glass surface is to be placed the electric
light. The lamp should be hung by a cord and
counterpoise, and if it be of the form described at
page 207, no other arrangement will be necessary,

2 74 ELECTRIC LIGHT.

because the rays of light from this lamp are all
thrown downwards. If another form of lamp be
used, it will be necessary to reflect the light down-
wards from it by means of wooden covers, about
6 feet square, covered with sheets of tin plate.
Two of these will be found sufficient. They should
be set at an angle, rising from the edges of the
frosted glass until quite over the lamp. Any rays
then thrown upwards will be reflected upon the
frosted glass.

Light sent over a building in this way is beauti-
fully diffused, and is very soft and agreeable. It
will be necessary to have free access to the lamps
from above. In some cases it will be found very
advantageous to enclose the lamp in a ground-
glass case, and to suspend this near to a white
ceiling. But a better plan still is to have a pyra-
midal case of ground-glass made, to fasten the
base of this to the ceiling, and to lower the lamp
into it from above. The result is perfect diffusion
of the light, which must of course be reflected
downwards into the glass case by reflecting boards
or a whitened ceiling.

Workshops are usually illuminated by setting-
the lamp over a reflector on the floor, screened
by some cover, and projecting the rays from the
reflector upon the white-washed ceiling. This is
what is usually done, and is found to answer the
purpose very well* A great objection to the Serrin
and such lamps is the base containing the move-
ment, which, when the lamp is suspended, throws

APPLICATIONS OF ELECTRIC LIGHT. 275.

downwards a great deal of shadow; but this is
entirely prevented by the use of slanting re-
flectors.

In the extensive chocolate works of M. Menier
the Serrin lamps are in use, and the proprietor has
devised a means of access to the suspended lamps
without the use of ladders or a separate suspension
cord. A windlass is used, having a dry wooden
drum with cast-iron cheeks. A cable with two in-
sulated and stout wires is made fast to the drum,
and the ends of it to the cheeks ; this cable leads
upwards to the roof, over a pulley, and on the other
side hangs the lamp. It can thus be lowered by
the windlass with ease without in any way disturb-
ing the connections. The cheeks of the winding
drum are, of course, connected to the terminals of
the dynamo-electric machine through the separated
bearings.

Electric lights are in extensive use in all out-of-
door works of magnitude, such as bridge and dock
construction, and it is found, as was proved in the
case of the great Tay bridge, that operations may
be carried on at night with the greatest facility.
For such purposes, the light should be so arranged
that a power of about 2,000 candles is thrown
around every 600 feet of space — that is, an ordinary
2,000 electric light, placed upon a 20-feet standard,
should give sufficient illumination at a radius of
300 feet. In some cases the standard is thus inad-
missible, and the light may have to be thrown upon
the work from a parabolic reflector. All such lights

278 ELECTRIC LIGHT.

from a perusal of any one instance, little trust can
be placed in them.

The Gaslight and Coke Company, whose works
are at Westminster, tried the electric light to test
the question of cost. Their experiment was carried j
on for 1,000 hours; they used a 6 horse-power
engine, which cost 1$. bd. per hour for fuel alone —
that is, about 40 lbs. of coal per horse-power per
hour : this engine must have been singularly ineffi-
cient. The light produced from a Siemens' ma-
chine was of 2,000-candle power, and in their ex-
periment replaced 4 sun-burners of 63 jets each,
consuming in the aggregate 760 feet of gas per
hour. The result is that they give the cost of the
electric light as double that of the gas. Very \
little consideration of the following figures will j
suffice to show what this light ought to have cost
the gas company. It cost them 4s. 6d. per hour,
while any electrician will undertake to produce a
light of double the power at is. iod. per hour, in
continuous work.

This is a case in point, the facts of which the
public are free to investigate as far as the report
goes.

On the other side another case of actual applica-
tion may be mentioned. At the St. Lazare station
of the West of France Railway there are six electric
lights of 480-candle power each, on the Lontin
system. They are produced by the power from a
common agricultural engine with 9|-in. cylinder of
I3j-in. stroke. The carbons for the lamps cost

COST OF ELECTRIC LIGHT. 279

altogether 8d. per hour, and the real working ex-
penses are : —

s. d.
Coal at 32s. per ton 12

Carbons .......08

Attendance . . . . . . o 10

Per hour . 28

This is for six electric lights, in aggregate power
2,880 candles. Let this be compared with 4s. 6d.,
the cost of a 2,000-candle light with coals at 20s.
per ton as above.

In numerous other such cases may the facts be
learned, where the light has been in use for years
(since 1877), and in every application where the
arrangements are properly carried out, and where
the light has replaced gas or oil, except in street
lighting alone, the price is greatly in favour of
electricity.

The cost of illuminating the streets by gas is, as
is generally known, exceedingly low, especially in
London, and this, of course, told against electricity
when an attempt was made to introduce it for that
purpose.

To put down new plant and electrically light a
street, then to compare the cost with that of gas
at street price, is obviously not consistent with
ordinary fair working : and this is what was done
in Paris, and in High Holborn, nearer home. Gas
has been established for years, has every advantage
<rf long experience in working, it comes from a
manufactory where the quantity produced renders
the supply to one street very insignificant in point

*8o ELECTRIC LIGHT.

of cost, and yet it was thought to be a wise thing
to place electricity side by side with it and compare
the costs. It will not yet pay, as far as experience
has shown, to light only one street by electricity ;
it must be done upon a larger scale or not at all.

Gas for private users costs so much that, in the
case of workshops, yards, theatres, picture gal-
leries, and numerous other places where there is
real work for a surpassingly brilliant and powerful
light or two, electricity is without the shadow of a
doubt the cheaper, not to speak of its additional
advantages, and the fact that colours are not falsely
represented by it as by gas light

Where electricity replaces gas at is. gd. per 1,000
cubic feet, a saving will undoubtedly be effected, even
as the light now stands, not to speak of greater
perfection, which will assuredly be attained.

For the splendid illumination of skating ponds
and pleasure grounds at night, the electric light is
not by any system expensive, because the same
effects could not at any cost be obtained by gas
or oil lamps.

In almost every case of street illumination the
Jablochkoff candle has been used. This necessitates
the production of alternating currents, and alter*
nating currents are extremely wasteful of power in
long circuits. If a good direct system were tried,
there is every prospect that street lighting by
electricity would prove itself at least as cheap as
gas, while fewer lamps and fittings would be
needed, and a better light secured.

COST OF ELECTRIC LIGHT. 28 1

Let the various expenses in establishing ap-
paratus for the production of one electric light by
the open circuit method, or six, by a method such
as Werdermanri's, and of 5,500-candle power, be
tabulated at the highest figures of to-day :—

£ s. d.
One dynamo-electric machine of 6,000-candle power . 75 o o

. The most expensive lamp in use, or 6 incandescent

lamps, with cables and fittings • • • 25 o o

One 6 horse-power steam-engine and boiler, complete 150 o o

Cost of Plant , 250 o o

Working Expenses.

(Per year, of 1,200 hours' working.)

£ s. d.
Interest on cost of plant, say 15 o o

Wear and tear in machine and lamps . . • 800

„ „ engine and boiler • . • . 1200
Labour, attending to engine, machine, and lamps at

7d. per hour (one year of 1,200 hours) . • 35 o o
Fuel at 4 lbs. per horse-power per hour, with coal at

20s. per ton, say 24 tons 24 o o

Carbons for the lamp 25 o o

Oil, and other items . . . . . • . 5 10 6

Cost of a 5,500-candle light for 1,200 hours . 124 10 6

Such a light should replace, in most applica-
tions, over 400 gas jets burning 5 cubic feet per
hour each, the cost of which, at 3s. per 1,000 cubic
feet, would be 6s. per hour, or about, for 1,200 hours
light, £350.

The prices quoted for plant will be found higher
than the actual prices, and those given for working
expenses will also be over the average in most
places in England; while the price of gas con-
sidered is lower than the average in England.

._ j

282 ELECTRIC LIGHT.

The cost of an outfit to give a 1,200 candle light
is £180: —

5 horse-power engine and boiler complete •
Dynamo-electric machine and lamp, with fittings .

100

180

Dynamo-electric machines and lamps are be-
coming cheaper as time goes on and as competi-
tion is beginning to be felt, and a higher return for
power expended may yet be expected.

Outfits for the exhibition of electric lights as
advertisements or otherwise are easily to be had
on hire, at low enough charges.

The places where the electric light may now be
seen in constant use are so numerous that to quote
particulars of the cost would involve a recapitula-
tion of what has been already said.

The cost of illuminating by voltaic generators
is always high, but for short displays this is com-
pensated for by the convenience.

Mr. A. Siemens, in his paper read before the
.Society of Telegraph Engineers, March, 1880, gives
the following particulars as regards comparative
cost of electric light and gas. In making the com-
parison it is assumed that a hundred-candle Sugg
gas-burner will consume 23 cubic feet of gas
per hour, costing 3s. 6d. per 1,000 cubic feet:
further, that a 400-candle alternate current light
requires ^ horse-power, and that it consumes
3 inches of carbon per hour, costing 4 Jd. per foot ;
and that a 6,000-candle continuous current light

COST OF ELECTRIC LIGHT. 283

requires 4 horse-power, consuming 3 inches of car-
bon per hour, costing 8d. per foot. When the
-electrical machines are driven by a gas engine
consuming 26 cubic feet of gas per hour per horse-
power, the relative cost of maintaining a light of
6,000-candle power is as follows : —

For gas 4s. iod.

For alternate current electric lights (fifteen 400-
candle lights) : —

s. d.
200 cubic feet of gas for the motor . . . o 8 J

3 feet 9 inches of carbon, at 4jd. per foot . L 4 J

Attendance >...>.. 6

d.
41

2 7

Showing a saving of 47 per cent, over gas.
For continuous current light : —

114 cubic feet of gas for the motor .
3 inches of carbon, at 8d. per foot .
Attendance ...,.,.,

o 7£

Showing a saving of 87 per cent, over gas.

At the Albert Hall a saving in gas is effected
of 25,000 cubic feet per night, or £4 7s. 6d., while
the five electric lights cost £1 10s. 6d. for fuel,
attendance, and carbons. In this case a pumping
engine is used for driving the machinery, which
consumes a very large quantity of fuel, and never-
theless a saving of 66 per cent, is effected.

At the British Museum the electric light was used
for 360 J hours between 28th Oct, 1879, and the end
of February, 1 880. Two 8 horse-power engines

284

ELECTRIC LIGHT.

are used. There are four lights in the reading
room, of 4,000 candle power each, and in the halls
seven of 400 candles each. There are four con-
tinuous current machines for the reading room
lamps, one to each lamp, in separate circuits. One
alternate current machine works the other seven
lights. Another machine of continuous current
type excites the electro-magnets of all the other
five. The machines are tried in the morning, and
then the fires of the engines are banked up so as to
be ready at 10 minutes' notice.
The cost for 360 hours is as follows :—

Carbons

23 tons of coal, at 15s. .
18 gallons of oil, at 4s. 6d.
54 lbs. of waste, at 6d. .
2 sets of brushes, at 5s. .
1 set of commutator plates
Engine-driver, 18 weeks at 37s.

Total cost

This gives us cost per hour :-

For carbons •
Other charges

£108

s. d.

2 9

3 3

6 o

for a light of 18,800 candles; which amount of
light produced by gas would cost at least 15s. per
hour, the saving effected being 60 per cent.

The following facts as to the lighting of the
Thames Embankment will be of interest. The first

COST OF ELECTRIC LIGHT. 285

experiment with 20 lights was commenced on the
13th of December, 1878, the second with 40 on
the 1 6th of May, 1879, the third with 55 lights on
the 10th of October, 1879. The length of the
circuit on the west side of Waterloo Bridge is
6,007 ft. ; of that on the east side 6,062 ft. The total
length of conducting wire is 17 miles 361 yards.
The ten new lights on Waterloo Bridge are worked
by a 20-light Gramme machine in two circuits.

The following are a few particulars of Messrs.
Siemens' machines, &c. : —

Alternating current machine, large size.

Dimensions, 29^" X 27j" X 34".

Weight, 8 cwt. o qrs. 13 lbs. £

Speed, 600 revolutions per minute. Price . . 137
Small dynamo-machine for magnetising the above. Speed

1,000 revolutions per minute. Price. ' . . . 45

Capacity for 12 lamps in one .circuit, or two cir-
cuits of 6 lamps each. Each lamp of 400 candle
power. Total power absorbed about 9 horse-
power.

Smaller alternating current machine.
Dimensions, 28" X I9j" X 24".

Weight, 5 cwt. o qrs. 20 lbs. £

Speed about 700 revolutions per minute. Price • 87

Small dynamo-machine for magnetising ... . 38

This machine feeds 6 lamps of 400 candles each
in one circuit, and absorbs 5 horse-power.

INDEX.

A IR battery, 42
A Albert Hall, electric light at,

283
Alliance machine, 64
Alternating current machine, Sie-
mens', 124
Siemens', cost of, 285
Amalgamation of zinc plates, 1 1
Applications of the light, 273
Arc, the voltaic, 166
Archereau's lamp, 176
Armature, Siemens' first type of,

Gramme's, 73
Wilde's, 96
Ladd's, 103
Weston's, 135
Brush's, 143
Automatic electric lamps, 172

"DATTERIES, voltaic, 6—46
composition of, 8
simple, 14
bichromate, 14
Bunsen's, 22
Grove's, 35—38
Dr. Byrne's, 39
for photographer's light, 39

Batteries, air, 42

pneumatic, 42

thermo-electric, 47
Bichromate cells, 14

hanger for, 16

to use, 19

number required, 21
Binding-screws, 10
Breguet's machine, 70
British Museum, electric light at,

Brougham-Andre" lamp, 222
Brush's machine, 142

lamp, 194
Brushes for machines, 159
Bunsen's batteries, 22

zinc cylinders for the, 24

connections for the, 25

liquids for, 26

management of large batteries
of, 27

number of cells required, 29

cells in Grove pots, 38
Byrne's battery, 39

liquids for, 41

/~* ANDLES, electric, 223
Jablochkoff's, 223

c
J

INDEX.

287

Candles, "Wilde's, 227

De Meriten's, 234

Siemens', 235

RapiefPs, 235
Carbons, manufacture of, 170
Carry's lamp, 193

carbons, 171
Cells, 12

porous, 12

iron, 31

lime chromate, 32

too weak, 34 — 35
Clamps and screws, 10
Clarke's machine, 58
Commutator construction, 58

Wilde's, 97
Composition of batteries, 8
Conductors, 154

Connection, Bunsen's carbons, 25
Contact drum, Gramme's, 86
Containing cells, 12
Cost of electric light, 277
Crompton's lamp, 221
Current induction, 56

regulators of, 160
Cylinders for the Bunsen battery,
24

J)ANI£LL, Dr., views of, on

voltaic arc, 3
Davy, Sir Humphry, 2

large battery of, 2
De Meritens' machine, 90

candle, 234
Deductions, mathematical, 262
Differential lamp, Siemens', 187
Direction of the current, 8
Distributor machine, Gramme's,

in
Double and single cells, 13
Double armature, Ladd's, 103
Driving machines off engines, 155

shafting, 156
Duboscq's lamp, 182
Dynamo-electric machines, 98

TJDISON'S machine, 147
lamps, 241
experiments, 245
Electric lamps and candles, 166
candles, 223

light, measurement of, 253^
cost of, 277
Electro-magnet, 63

Electro-magneto-electric machines
92

Endosmos, 13 '

Equational numbers, 272

Excitants for batteries, 12

Experiments, Edison's, 244

Schwendler's, 263

TJ*ARADAY, discovery of mag-
neto-electricity by, 53
First production of electric light, 2
magneto-electric machine, 57
Fitzgerald, investigations of, 266

QAIFFE'S lamp, 179

Girouard's lamp, 193
Gramme's magneto - electric ma-
chine, 73
ring armature, 73
hand machine, 79
contact drum, 86
dynamo-electric machine, 1,04
large machine, 108
machine, power of, no
distributor machine, in
combined exciting and dividing
machine, 114
Grove's battery, 35
zinc for, 36
platinum in, 37

cell pots used for Bunsen's
battery, 38

T_T AND Gramme machine, 77
Heating of machines, 157
Holme's machines, 67

288

INDEX.

Holme's dynamo-electric machine,

104
Hopkinson's investigations, 262

TLLUMINATION of buildings,

273

Incandescence in vacuo and gas, 235

Induction, magneto-electric, 53

current, 56
Instructions for making Gramme

machine, 79
Introduction, 1 — 5
Iron cells, 31

JABLOCHKOFF'S candles, 223
Jamain's blowpipe lamp, 233

T ADD'S machines, 102

armature, 103
Lamps and candles, 166

automatic, 172

Serrin's, 174

Archereau's, 176

Gaiffe's, 179

Duboscq's, 182

Siemens 1 , 183

pendulum, 185
differentia], 187

Lontin's, 191

Gfrouard's, 193

Carry's, 193

Brush's, 194

Thomson-Houston, 198

Wallace-Farmer, 201

Rapieff's, 204

Urquhart's, 207

rotating disc, 215

Reynier's, 217

Werdermann's, 219

Crompton's, 221

Brougham-Andr€, 222

Jamain's blowpipe, 233

Sawyer-Mann's, 237

Edison's, 241

Large magneto-electric machines,

buildings, illumination o( 273
Leading wires, 154
Lifting battery, 20
Lime chromate cell, 32

liquids for, 33—34
Liquids for chromate of lime cells,

33
Lontin's machines, 139

lamp, 191

Lubricating machines, 157

Lugo's carbons, 223

AT ACHINE, Clarke's magneto-
electric, 58

Stohrer's, 59

large magneto-electric, 64

the Alliance, 64

Holme's, 67

Breguet's, 70

Varley's, 71

the hand magneto • electric
Gramme, 73

De Meritens', 90

Wilde's first, 93

Ladd's, 102

Gramme dynamo-electric, 104

Holme's dynamo-electric, 104

Gramme's exciting and divid-
ing, 114

Siemens', 117

alternating current, 124

Maxim's, 125

Wilde's dynamo-electric, 127

Rapieff's, 129

Weston's first, 130
new form of, 133

Trouv6's, 137

Lontin's, 139

Brush's, 142
. Wallace-Farmer, 144

Edison's, 147

work of, 150

management of, 152

INDEX.

289

Machine, heating of, in work, 157

steadiness of, 158

Siemens' alternating current,
cost of, 285
Magneto-electric generators, 53

machine, first, 57
large, 64
Management of large batteries, 27
Manufacture of carbons, 170
Mathematical deductions, 262
Maxim's machine, 125
Measurement of electric light, 253

J^EGATIVE pole, 9

Negative elements, 1 1 '
.Number of bichromate cells re-
quired, 21
Bunsen cells required, 29

£\RIGINATOR of the dynamo-
^"^ electric machine, 98

pENDULUM lamp, 185

Photographer's light, battery
for, 39

Platinum in Grove's cells, 37

Platinising, 40

Pneumatic battery, 42
power of, 45 "

Porous cells, 12 4

Positive pole, 9
elements, 9

Preece, investigations of, 263

Present applications of electric light,

273

Production of electric light by

Davy, 2

"DAPIEFF'S machine, 129
lamp, 204
candle, 235
Regulators of current, 160
Reynier's lamp, 217

Ring, Gramme's, 73
Rotating disc lamps, 215

C AWYER-MANN lamp, 237

Schwendler's experiments, 263
Screws and clamps for batteries,

10
Serrin's lamp, 174
Siemens' armature, first form of,
69

machine, 117
power of, 123

alternating current machine, 124

lamps, 183

pendulum lamps, 185

differential lamp, 187

candle, 235

Mr. Alexander, paper of, 265

alternating machine, cost of,

Simple voltaic cells, 14
Single and double cells, 13
Sliding zinc bichromate cells, 17
Soldering, 10
Soren Hjorth, inventor, 98
Steadiness of machines, 158
Stohrer's machine, 59
Sulphuric acid, 12

T^HERMO - ELECTRIC bat-
teries, 47
Thomson-Houston lamp, 198
Trouve*'s machine, 137

TTRQUHART'S lamp, 207

Useful equational numbers,
272

"\7ACUO and gas, incandescence

"1,235
Varley's machine, 71
Voltaic batteries, 6—46

arc, the, 166

290

^fALLACE - FARMER
chine, 144

lamp, 201
Weak cells, 34
Werdermaiixx's lamp, 219
Weston's first machine, 130

new machine, 133

armature, 135
Wilde's first machine, 92

armature, 96

INDEX.

ma-

Wilde's commutator, 97

dynamo-electric machine, 127
candle, 227 .

Wires for conductors, 154 I

Work of machines, 150

7INC plates, to cut, 9
to amalgamate, 11

for Grove's cell, 36

THE END.

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" To highway and town surveyors this book will have the utmost value, and as con-
taining the largest amount of information in the shortest space and at the lowest price,
we may predict for it a wide circulation." — Journal of Gas Lighting.

Steam Boilert

A TREATISE ON STEAM BOILERS : their Strength, Con-
struction, and Economical Working. By R. Wilson, C.E.
Fifth Edition. i2mo, 6s. cloth.

" The best work on boilers which has come under our notice. H — Engineering.
"The best treatise that has ever been published on steam boilers." — Engineer.

Practical Ttinnelling.

PRACTICAL TUNNELLING: Explaining in detail the Setting
out of the Works, Shaft-sinking and Heading-Driving, Ranging
the Lines and Levelling under Ground, Sub- Excavating, Timbering,
and the Construction of the Brickwork of Tunnels with the amount
of labour required for, and the Cost of, the various portions of the
work. By Frederick Walter Simms, M. Inst. C.E., author
of "A Treatise on Levelling." Third Edition, Revised and Ex-
tended. By D. Kinnear Clark, M. Inst. C.E. Imp. 8vo, with
21 Folding Plates and numerous Wood Engravings, 30J. cloth.

" Mr. Clark's additional chapters on the Mont Cenis and St. Gothard Tunnels contain
minute and valuable experiences and data relating to the method of excavation by
compressed air, the heading operations, rock-boring machinery, process of enlarge-
ment, ventilation in course of construction by comoressed air, labour and cost, &c. "
— Building News.

" The estimation in which Mr. Simms' book on tunnelling has been held for over
thirty years cannot be more truly expressed than in the words of the late Professor
Rankine : — ' The best source of information on the subject of tunnels is Mr. F. W.
Simms' work on " Practical Tunnelling." ' — The Architect.

PUBLISHED BY CROSBY LOCKWOOD & CO. 7

Locomotive-Engine Driving.

LOCOMOTIVE-ENGINE DRIVING ; a Practical Manual for
Engineers in charge of Locomotive Engines. By Michael
Reynolds, Member of the Society of Engineers, formerly Loco-
motive Inspector L. B. and S. C. R. Fourth Edition, greatly
enlarged. Comprising A KEY TO THE LOCOMOTIVE
ENGINE. With Illustrations and Portrait of Author. Crown
8vo, 4s. 6d. cloth.

" Mr. Reynolds deserves the title of the engine driver's friend." — Railway Nc7us.

" Mr. Reynolds has supplied a want, and has supplied it well. We can confidently
recommend the book not only to the practical driver, but to every one who takes an
interest in the performance of locomotive engines." — The Engineer.

" Mr. Reynolds has opened a new chapter in the literature of the day. This
admirable practical treatise, of the practical utility of which we have to speak in
terms of warm commendation." — Athemettm.

T/te Engineer, Fireman, and Engine-Boy.

THE MODEL LOCOMOTIVE ENGINEER, FIREMAN,
AND ENGINE-BOY : comprising a Historical Notice of the
Pioneer Locomotive Engines and their Inventors, with a project
for the establishment of Certificates of Qualification in the Running
Service of Railways. By Michael Reynolds, Author of
"Locomotive- Engine Driving." With numerous Illustrations,
and a fine Portrait of George Stephenson, "the Father of Rail-
ways." Crown 8vo. 4s. 6d. cloth. [Just published.

Levelling.

A TREATISE on the PRINCIPLES and PRACTICE of
LEVELLING ; showing its Application to Purposes of Railway
and Civil Engineering, in the Construction of Roads ; with Mr.
Telford's Rules for the same. By Frederick W. Simms,
F.G.S., M. Inst. C.E. Sixth Edition, very carefully revised, with
the addition of Mr. Law's Practical Examples for Setting out
Railway Curves, and Mr. Trautwine's Field Practice of Laying
out Circular Curves. With 7 Plates and numerous Woodcuts. 8vo,
&r. 6d. cloth. \* Trautwine on Curves, separate, $s.

" One of the most important text-books for the general surveyor, and there is
scarcely a question connected with levelling for which a solution would be sought but
that would be satisfactorily answered by consulting the volume." — Mining Journal.

" The text-book on levelling in most of our engineering schools and colleges."—
Engineer.

The High-Pressure Steam Engine.

THE HIGH-PRESSURE STEAM ENGINE ; an Exposition
of its Comparative Merits, and an Essay towards an Improved
System of Construction, adapted especially to secure Safety and
Economy. By Dr. Ernst Alban, Practical Machine Maker,
Plau, Mecklenberg. Translated from the German, with Notes, by
Dr. Pole, F.R.S., M. Inst. C.E., &c, &c With 28 fine Plates,
8vo, 1 dr. 6V. cloth.

" A work like this, which goes thoroughly into the examination of the hlgh-pMssure
engine, the boiler, and its appendages, &c, is exceedingly useful, and deserves a place
in every scientific library. "—-Steam Shipping Chronic te.

8 WORKS IN ENGINEERING, SURVEYING, ETC.,

Slate and Slate Quarrying.

A TREATISE ON SLATE AND SLATE QUARRYING,
Scientific, Practical, and Commercial. By D. C. Davies, F.G.S.,
Mining Engineer, &c. With numerous Illustrations and Folding
Plates. Crown 8vo, 6s. cloth.
"A useful and practical hand-book on an important industry." — Engineering.
" There is no other book which contains so much information concerning the pro-
cedure observed in taking quarries, the processes employed in working them, and
such full statistics of the present and past position of the great slate trade of
Wales."— The Architect.

Metalliferous Mining.

A TREATISE ON METALLIFEROUS MINERALS AND
MINING. By D. C. Davies, F.G.S., author of "A Treatise on
Slate and Slate Quarrying." Illustrated with numerous wood en-
gravings, crown 8vo. [/« preparation.

Hydraulics.

HYDRAULIC TABLES, CO-EFFICIENTS, and FORMULA
for finding the Discharge of Water from Orifices, Notches, Weirs,
Pipes, and Rivers. With New Formulae, Tables, and General
Information on Rain-fall, Catchment-Basins, Drainage, Sewerage,
Water Supply for Towns and Mill Power. By John Neville,
Civil Engineer, M.R.I.A. Third Edition, carefully revised, with
considerable Additions. Numerous Illustrations. Cr. 8vo, 14J. cloth.

"Undoubtedly an exceedingly useful and elaborate compilation." — Iron.

" Alike valuable to students and engineers in practice." — Mining Journal.

Strength of Cast Iron, &c.

A PRACTICAL ESSAY on the STRENGTH of CAST IRON
and OTHER METALS. By Thomas Tredgold, M.I.C.E.,
Author of " Elementary Principles of Carpentry." Fifth Edition,
Edited by E. Hodgkinson, F.R.S. With 9 Engravings and
numerous Woodcuts. 8vo, 12s. cloth.

Minings Surveying and Valuing.

THE MINERAL SURVEYOR AND VALUER'S COM-
PLETE GUIDE, comprising a Treatise on Improved Mining
Surveying, with new Traverse Tables ; and Descriptions of Im-
proved Instruments ; also an Exposition of the Correct Principles
of Laying out and Valuing Home and Foreign Iron and Coal
Mineral Properties. By William Lintern, Mining and Civil
Engineer. With four Plates of Diagrams, Plans, &c, i2mo,4J. cloth.

" Contains much valuable information given in a small compass, and which, as far
as we have tested it, is thoroughly trustworthy." — Iron and Coal Trades Review.

%* The above, bound with Thoman's Tables. (See page 21.)
Price 7s. 6d. cloth.

Common Sense for Gas- Users.

COMMON SENSE FOR GAS-USERS : a Catechism of Gas-
Lighting for Householders, Gasfitters, Millowners, Architects,
Engineers, &c, &c. By Robert Wilson, C.E., Author of "A
Treatise on Steam Boilers. " Second Edition. Crown 8vo, sewed,
with Folding Plates and Wood Engraviugs, 2s. 6a 1 .

PUBLISHED BY CROSBY LOCKWOOD & CO. 9

Coal and Coal Mining.

COAL AND COAL MINING : a Rudimentary Treatise on. By
Wabington W. Smyth, M.A., F.R.S., &c, Chief Inspector
of the Mines of the Crown. New edition, revised and corrected.
l2mo, with numerous Illustrations, 4s. cloth boards.

"Every portion of the volume appears to have been prepared with much care, and
as an outline is given of every known coal-field in this and other countries, as well as
of the two principal methods of working, the book will doubtless interest a very
large number of readers." — Mining- Journal.

Earthwork.

EARTHWORK TABLES, showing the Contents in Cubic Yards
of Embankments, Cuttings, &c, of Heights or Depths up to an
average of 80 feet. By Joseph Broadbent, C. E., and Francis
Campin, C.E. Cr. 8vo, oblong, 5*. cloth.

"The way in which accuracy is attained, by a simple division of each cross
section into three elements, two of which are constant and one variable, is in-
genious." — A thenamm.

Trigonometrical Surveying.

AN OUTLINE OF THE METHOD OF CONDUCTING A
TRIGONOMETRICAL SURVEY, for the Formation of Geo-
graphical and Topographical Maps and Plans, Military Recon-
naissance, Levelling, &c, with the most useful Problems in Geodesy
and Practical Astronomy. By Lieut. -Gen. Frome, R.E., late In-
spector-General of Fortifications. Fourth Edition, Enlarged, and
partly Re- written. By Captain Charles Warren, R.E. With
19 Plates and 115 Woodcuts, royal 8vo, 16s. cloth.

Fire Engineering.

FIRES, FIRE-ENGINES, AND FIRE BRIGADES. With
a History of Fire-Engines, their Construction, Use, and Manage-
ment ; Remarks on Fire- Proof Buildings, and the Preservation of
Life from Fire ; Statistics of the Fire Appliances in English
Towns ; Foreign Fire Systems ; Hints on Fire Brigades, &c, &c
By Charles F. T. Young, C.E. With numerous Illustrations,
handsomely printed, 544 pp., demy 8vo, 1/. 4s. cloth.
" We can most heartily commend this book." — Engineering.

" We strongly recommend the book to the notice of all who are in any way in-
terested in fires, fire-engines, or fire-brigades."— Mechanics' Magazine.

Manual of Mining Tools.

MINING TOOLS. For the use of Mine Managers, Agents,
Mining Students, &c. By William Morgans, Lecturer on Prac-
tical Mining at the Bristol School of Mines. Volume of Text
l2mo, 3j. With an Atlas of Plates, containing 235 Illustrations.
4to, 6s. Together, gs. cloth boards.

" Students in the Science of Mining, and Overmen, Captains, Managers, and
Viewers may gain practical knowledge and useful hints by the study of Mr.
Morgans' Manual." — Colliery Guardian.

" A very valuable work, which will tend materially to improve our mining litera-
ture"— Mining J<mrn^.

io WORKS IN ENGINEERING, SURVEYING, ETC.,

Engineering Fieldwork.

THE PRACTICE OF ENGINEERING FIELDWORK,
applied to Land and Hydraulic, Hydrographic, and Submarine
Surveying and Levelling. Second Edition, revised, with consider-
able additions, and a Supplementary Volume on WATER-
WORKS, SEWERS, SEWAGE, and IRRIGATION. By W.
Davis Haskoll, C.E. Numerous folding Plates. Demy 8vo, 2
vols, in one, cloth boards, i/. 5-r. (published at 2/. 4s.)

Waterworks for Cities and Towns.

WATERWORKS for the SUPPLY of CITIES and TOWNS,
with a Description of the Principal Geological Formations of
England as influencing Supplies of Water. By Samuel Hughes,
C.E. New and enlarged edition, i2mo, 4s. 6d. cloth.

" One of the most convenient, and at the same time reliable works on a subject,
the vital importance of which cannot be over-estimated. — Bradford Observer.

Steam.

THE SAFE USE OF STEAM : containing Rules for Unpro-
fessional Steam Users. By an Engineer. 4th Edition. Sewed, 6V.

" If steam-users would but learn this little book by heart, boiler explosions would
become sensations by their rarity."— English Mechanic.

Field-Book for Engineers.

THE ENGINEERS, MINING SURVEYOR'S, and CON-
TRACTOR'S FIELD-BOOK. By W. Davis Haskoll, C.E.
Consisting of a Series of Tables, with Rules, Explanations of
Systems, and Use of Theodolite for Traverse Surveying and Plotting
the Work with minute accuracy by means of Straight Edge and Set
Square only ; Levelling with the Theodolite, Casting out and Re-
ducing Levels to Datum, and Plotting Sections in the ordinary
manner; Setting out Curves with the Theodolite by Tangential
Angles and Multiples with Right and Left-hand Readings of the
Instrument ; Setting out Curves without Theodolite on the System
of Tangential Angles by Sets of Tangents and Offsets ; and Earth-
work Tables to 80 feet deep, calculated for every 6 inches in depth.
With numerous wood-cuts. Fourth Edition, enlarged. Crown 8vo.
12s. cloth.

" The book is very handy, and the author might have added that the separate tables
of sines and tangents to every minute will make it useful for many other purposes, the
genuine traverse tables existing all the same." — Athenaum.
" TSfafl* 01 ^ forms a handsome pocket volume, and cannot fail, from its portability
vehave ttJt be extensively patronised by the engineering profession. —J/wwi/

as we

V The ab

Price p. 6d. cio T » f Measurement and Calculation of.

Common S^ on EARTHWORK. By Alex. J. S. Graham,

/^^AyrAyrrvxT oVivEngineer, Forest of Dean Central Railway. With
COMMON SEtfr,* . ^^

Lighting for House ' , _ f ,...,,

i?«n-; n oiU St,* Xr* preference, we know of no work equal to it ; and the
j&ngineers, «c, etc. D}.^ d in the measurement ^ calculation of earth-
Treatise on bteam .Boilers, -tical information very admirably arranged, and
with Folding Plates and Wood i as well as for the more exact calculations

•<?." — Artizau.

PUBLISHED BY CROSBY LOCKWOOD & CO. 1 1

Bridge Construction in Masonry, Timber \ & Iron.

EXAMPLES OF BRIDGE AND VIADUCT CONSTRUC-
TION OF MASONRY, TIMBER, AND IRON ; consisting of
46 Plates from the Contract Drawings or Admeasurement of select
Works. By W. Davis Haskoll, C.E. Second Edition, with
the addition of 554 Estimates, and the Practice of Setting out Works,
illustrated with 6 pages of Diagrams. Imp. 4to, 2/. 12s. 6d, half-
morocco.

" One of the very few works extant descending to the level of ordinary routine, and
treating on the common every-day practice of the railway engineer. . . . A work of
the present nature by a man of Mr. Haskoll's experience, must prove invaluable to
hundreds. The tables of estimates appended to this edition will considerably enhance
its value."— Engineering.

Drawing for Engineers y &c.

THE WORKMAN'S MANUAL OF ENGINEERING

DRAWING. By John Maxton, Instructor in Engineering

Drawing, Royal Naval College, Greenwich, formerly of R. S. N. A.,

South Kensington. Third Edition, carefully revised. With upwards

of 300 Plates and Diagrams. i2mo, cloth, strongly bound, 4J.

" Even accomplished draughtsmen will find in it much that will be of use to them.
A copy of it should be kept for reference in every drawing office."— Engineering.
" Indispensable for teachers of engineering drawing."— Mechanics* Magazine.

Oblique Arches.

A PRACTICAL TREATISE ON THE CONSTRUCTION of
OBLIQUE ARCHES. By John Hart. Third Edition, with
Plates. Imperial 8vo, 8j. cloth.

Oblique Bridges.

A PRACTICAL and THEORETICAL ESSAY on OBLIQUE

BRIDGES, with 13 large folding Plates. By Geo. Watson

Buck, M. Inst. C.E. Second Edition, corrected by W. H.

Barlow, M. Inst. C.E. Imperial 8 vo, 12s. cloth.

" The standard text book for all engineers regarding skew arches is Mr. Buck's
treatise and it would be impossible to consult a better."— Engineer.

Wealds Dictionary of Terms.

A DICTIONARY of TERMS used in ARCHITECTURE,
BUILDING, ENGINEERING, MINING, METALLURGY,
ARCHAEOLOGY, the FINE ARTS, &c. By John Wealk.
Fifth Edition, revised and corrected by Robert Hunt, F.R.S.,
Keeper of Mining Records, Editor of " Ure's Dictionary of Arts,"
&c. i2mo, cloth boards, 6s.

" The- best small technological dictionary in the language."— Architect.

"There is no need now to speak of the excellence of this work ; it received the ap-
proval of the community long ago. Edited now by Mr. Robert Hunt, and published
in a cheap, handy form, it will be of the utmost service as a book of reference scarcely
to be exceeded in value." — Scotsman,

" The absolute accuracy of a work of this character can only be judged of after
extensive consultation, and from our examination it appears very correct and very
complete."- Mining Journal.

12 WORKS IN NAVAL ARCHITECTURE, ETC.,

NAVAL ARCHITECTURE AND
NAVIGATION, ETC.

♦

Pocket Book for Naval Architects & Shipbuilders.

THE NAVAL ARCHITECT'S AND SHIPBUILDER'S
POCKET BOOK OF FORMULA, RULES, AND TABLES
AND MARINE ENGINEER'S AND SURVEYOR'S HANDY
BOOK OF REFERENCE. By Clement Mackrow, Naval
Draughtsman, Associate of the Institution of Naval Architects.
With numerous Diagrams, &c 12 mo, strongly bound in leather,
with elastic strap for pocket, I2j. 6d. {Just ready.

Grantham s Iron Ship-Building.

ON IRON SHIP-BUILDING ; with Practical Examples and
Details. Fifth Edition. Imp. 4to, boards, enlarged from 24 to 40
Plates (21 quite new), including the latest Examples. Together
with separate Text, also considerably enlarged, l2mo, cloth limp.
By John Grantham, M. Inst. C.E., &c 2/. 2s. complete.

" A very elaborate work. . . . It forms a most valuable addition to the history
of iron shipbuilding, while its having been prepared by one who has made the subject
his study for many years, and whose qualifications have been repeatedly recognised,
will recommend it as one of practical utility to all interested in shipbuilding." — Army
and Navy Gazette.

" Mr. Grantham's work is of great interest. • . . It is also valuable as a record
of the progress of iron shipbuilding. ... It will, we are confident, command an
extensive circulation among shipbuilders in general. ... By order of the Board
of Admiralty, the work will form the text-book on which the examination in iron ship-
building of candidates for promotion in the dockyards will be mainly based."—
Engineering.

Pocket-Book for Marine Engineers.

A POCKET BOOK FOR MARINE ENGINEERS. Con-
taining useful Rules and Formulae in a compact form. By Frank
Proctor, A.I.N. A. Second Edition, revised and enlarged.
Royal 32mo, leather, gilt edges, with strap, 4^.
"We recommend it to our readers as going far to supply a long-felt want."—
Naval Science.
"A most useful companion to all marine engineers." — United Service Gazette.
" Scarcely anything required by a naval engineer appears to have been for-
gotten." — Iron.

Light-Houses.

EUROPEAN LIGHT-HOUSE SYSTEMS ; being a Report of
a Tour of Inspection made in 1873. By Major George H.
Elliot, Corps of Engineers, U.S.A. Illustrated by 51 En-
gravings and 31 Woodcuts in the Text. 8vo, 21;. cloth.

Surveying (Land and Marine).

LAND AND MARINE SURVEYING, in Reference to the

Preparation of Plans for Roads and Railways, Canals, Rivera,

Towns' Water Supplies, Docks and Harbours ; with Description

and Use of Surveying Instruments. By W. Davis Haskoll, C. E.

With 14 folding Plates, and numerous Woodcuts. 8vo, I2j. 6d. cloth.

"A most useful and well arranged book for the aid of a student" — Builder.

" Of the utmost practical utility, and may be safely recommended to all students

who aspire to become clean and expert surveyors." — Mining Journal.

PUBLISHED BY CROSBY LOCKWOOD & CO. 13

Storms.

STORMS : their Nature, Classification, and Laws, with the
Means of Predicting them by their Embodiments, the Clouds.
By William Blasius. With Coloured Plates and numerous
Wood Engravings. Crown 8vo, iar. 6d. cloth boards.

Rudimentary Navigation,

THE SAILOR'S SEA-BOOK: a Rudimentary Treatise on Navi-
gation. Part I. How to keep the Log and Work it off. Part II.
On Finding the Latitude and Longitude. By James Green-
wood, B. A. To which are added, the Deviation and Error of the
Compass ; Great Circle Sailing ; the International (Commercial)
Code of Signals ; the Rule of the Road at Sea ; Rocket and Mortar
Apparatus for Saving Life ; the Law of Storms ; and a Brief
Dictionary of Sea Terms. With numerous woodcuts and coloured
plates of flags. New, thoroughly revised and much enlarged
edition. By W. H. Rosser, Author of the "Deviation of the
Compass considered practically," "The Yachtsman's Handy-Book
for Sea Use," &c, &c. i2mo, 3<f. cloth boards, [Just published.

Mathematical and Nautical Tables.

MATHEMATICAL TABLES, for Trigonometrical, Astronomical,
and Nautical Calculations ; to which is prefixed a Treatise on
Logarithms. By Henry Law, C.E. Together with a Series of
Tables for Navigation and Nautical Astronomy. By J. R.
Young, formerly Professor of Mathematics in Belfast College.
New Edition. i2mo, 4^. cloth boards. [Just published.

Navigation (Practical), with Tables.

PRACTICAL NAVIGATION : consisting of the Sailor's Sea-
Book, by James Greenwood and W. H. Rosser ; together
with the requisite Mathematical and Nautical Tables for the Work-
ing of the Problems. By Henry Law, C.E., and Professor
J. R. Young. Illustrated with numerous Wood Engravings and
Coloured Plates. i2mo, 7-f. strongly half bound in leather.

[Jut t published.

WEALE'S RUDIMENTARY SERIES.

The following books in Naval Architecture, etc. , are published in the

above series.

MASTING, MAST-MAKING, AND RIGGING OF SHIPS. By
Robert Kipping, N.A. Fourteenth Edition. Illustrated.
l2mo, 2 j. 6d. cloth boards.

SAILS AND SAIL-MAKING. Tenth Edition, enlarged, with an
Appendix. By Robert Kipping, N.A. Illustrated. i2mo, 3*.
cloth boards.

NAVAL ARCHITECTURE. By James Peake. Fourth Editien,
with Plates and Diagrams. i2mo, 4^. cloth boards.

MARINE ENGINES, AND STEAM VESSELS. By Robert
Murray, C.E. With a Glossary of Technical Terms, and their
Equivalents in French, German, and Spanish. Seventh Edition.
Illustrated. i2mo, 3*. 6d. cloth boards.

14 WORKS IN ARCHITECTURE, ETC.,

ARCHITECTURE, &c.

♦

Construction.

THE SCIENCE of BUILDING : An Elementary Treatise oa
the Principles of Construction. By E. Wyndham Tarn, M.A.,
Architect. With 47 Wood Engravings. Demy 8vo. &r. 6d. cloth.
" A very valuable book, which we strongly recommend to all students. "-—Builder
" No architectural student should be without this hand-book." — Architect.

Beaton s Pocket Estimator.

THE POCKET ESTIMATOR FOR THE BUILDING
TRADES, being an easy method of estimating the various parts
of a Building collectively, more especially applied to Carpenters'
and Joiners' work, priced according to the present value of material
and labour. By A. C. Beaton, Author of * ' Quantities and
Measurements." Second Edition. Carefully revised. 33 Wood-
cuts. Leather. Waistcoat-pocket size. is. &/.

Beaton's Builders 9 and Surveyors 9 Technical Guide.

THE POCKET TECHNICAL GUIDE AND MEASURER
FOR BUILDERS AND SURVEYORS: containing a Complete
Explanation of the Terms used in Building Construction, Memo-
randa for Reference, Technical Directions for Measuring Work in
all the Building Trades, &c. By A. C. Beaton. Second Edit.
With 19 Woodcuts. Leather. Waistcoat-pocket size, is. 6d.

Villa Architecture.

A HANDY BOOK of VILLA ARCHITECTURE ; being a
Series of Designs for Villa Residences in various Styles. With
Detailed Specifications and Estimates. By C. Wickes, Architect,
Author of " The Spires and Towersof the Mediaeval Churches of Eng-
land," &c. 31 Plates, 4to, half morocco, gilt edges, il. is.
* # * Also an Enlarged edition of the above. 61 Plates, with Detailed

Specifications, Estimates, &c. 2/. 2s. half morocco.
" The wJtoteof the designs bear evidence of their being the work of an artistic
architect and they will prove very valuable and suggestive. — Building News.

House Painting.

HOUSE PAINTING, GRAINING, MARBLING, AND
SIGN WRITING : a Practical Manual of. With 9 Coloured
Plates of Woods and Marbles, and nearly 150 Wood Engravings.
By Ellis A. Davidson, Author of "Building Construction," &c
Second Edition, carefully revised. i2mo, 6s. cloth boards.
'• Contains a mass of information of use to the amateur and of value to the practical
man." — English Mechanic.

Wilsons Boiler and Factory Chimneys.

BOILER AND FACTORY CHIMNEYS ; their Draught-power
and Stability, with a chapter on Lightning Conductors. By Robert
Wilson, C.E., Author of "Treatise on Steam Boilers," &c, &c.
Crown 8vo, 3^. 6d. cloth.
"A most valuable book of its kind, full of useful information, definite in statement
and thoroughly practical in treatment." — The Local Government Chronicle.

PUBLISHED BY CROSBY LOCKWOOD & CO. 15

A Book on Building.

A BOOK ON BUILDING, CIVIL AND ECCLESIASTICAL.

By Sir Edmund Beckett, Bart., LL.D., Q.C., F.R.A.S.,

Author of " Clocks and Watches and Bells," &c. Crown 8vo,

with Illustrations, Js. 6d. cloth.
*' A book which is always amusing and nearly always instructive. Sir £. Beckett
will be read for the raciness of his style. We are able very cordially to recommend
all persons to read it for themselves. The style throughout is in the highest degree
condensed and epigrammatic."— 77>««.

" We commend the book to the thoughtful consideration of all who are interested
in the building art."— Builder.

Architecture, Ancient and Modern.

RUDIMENTARY ARCHITECTURE, Ancient and Modern.
Consisting of VITRUVIUS, translated by Joseph Gwilt,
F.S.A., &c, with 23 fine copper plates; GRECIAN Archi-
tecture, by the Earl of Aberdeen ; the ORDERS of
Architecture, by W. H. Leeds, Esq. ; The STYLES of Archi-
tecture of Various Countries, by T. Talbot Bury; The
PRINCIPLES of DESIGN in Architecture, by E. L. Garbett.
In one volume, half-bound (pp. 1,100), copiously illustrated, 12s.
*+* Sold separately, in two vols., as follows —

ANCIENT ARCHITECTURE. Containing Gwilt's Vitruvius
and Aberdeen's Grecian Architecture. Price 6s. half -bound.

N.B.— This is the only edition of VITRUVIUS procurable at a
moderate price.

MODERN ARCHITECTURE. Containing the Orders, by Leeds ;
The Styles, by Bury ; and Design, by Garbett 6s. half-bound.

The Young Architect's Book.

HINTS TO YOUNG ARCHITECTS. By George Wight-
wick, Architect, Author of " The Palace of Architecture," &c, &c
New Edition, revised and enlarged. By G. Huskisson Guil-
laume, Architect. Numerous illustrations. i2mo, cloth boards, 4s.
" Will be found an acquisition to pupils, and a copy ought to be considered as
necessary a purchase as a box of instruments." — Architect.

" Contains a large amount of information, which young architects will do well to
acquire, if they wish to succeed in the everyday work of their profession. "—English
Mechanic,

Drawing for Builders and Students.

PRACTICAL RULES ON DRAWING for the OPERATIVE
BUILDER and YOUNG STUDENT in ARCHITECTURE.
By George Pyne, Author of a " Rudimentary Treatise on Per-
spective for Beginners." With 14 Plates, 4to, Js. 6d. boards.

Builder's and Contractors Price Book.

LOCKWOOD & CO.'S BUILDER'S AND CONTRACTOR'S
PRICE BOOK for 1879, containing the latest prices of all kinds
of Builders' Materials and Labour, and of all Trades connected
with Building, &c, &c. The whole revised and edited by
Francis T. W. Miller, Architect and Surveyor. Fcap. 8vo,
strongly half-bound, 4*-.

1 6 WORKS IN ARCHITECTURE, ETC.,

Handbook of Specifications.

THE HANDBOOK OF SPECIFICATIONS; or, Practical
Guide to the Architect, Engineer, Surveyor, and Builder, in drawing
up Specifications and Contracts for Works and Constructions-
Illustrated by Precedents of Buildings actually executed by eminent
Architects and Engineers. Preceded by a Preliminary Essay, and
Skeletons of Specifications and Contracts, &c, &c. By Professor
Thomas L. Donaldson, M.I.B.A. With A Review of the
Law op Contracts. By W. Cunningham Glen, of the
Middle Temple. With 33 Lithographic Plates, 2 vols., 8vo, 2/. 2s.
" In these two volumes of 1,100 pages (together), forty-four specifications of executed
works are given, including the specifications for parts of the new Houses of Parliament,
by Sir Charles Barry, and for the new Royal Exchange, by Mr. Tite, M.P.
Donaldson's Handbook of Specifications must be bought by all arcnitects."— Builder,

Taylor and Crtsys Rome.

THE ARCHITECTURAL ANTIQUITIES OF ROME. By
the late G. L. Taylor, Esq., F.S. A., and Edward Cresy, Esq.
New Edition, thoroughly revised, and supplemented under the
editorial care of the Rev. Alexander Taylor, M.A. (son of
the late G. L. Taylor, Esq.), Chaplain of Gray's Inn. This is
the only book which gives on a large scale, and with the precision
of architectural measurement, the principal Monuments of Ancient
Rome in plan, elevation, and detail. Large folio, with 130 Plates,
half-bound, 3/. 3J.
* # * Originally published in two volumes, folio, at 18/. i&r.

Specifications for Practical Architecture.

SPECIFICATIONS FOR PRACTICAL ARCHITECTURE :

A Guide to the Architect, Engineer, Surveyor, and Builder ; with

an Essay on the Structure and Science of Modern Buildings. By

Frederick Rogers, Architect. With numerous Illustrations.

Demy 8vo, 15J. cloth. (Published at 1/. icv.)

\* A volumeof specifications of a practical character being greatly required, and the

old standard work of Alfred Bartholomew being out of print, the author, on the basis

of that work, has produced the above. He has also inserted specifications of works

that have been erected in his own practice.

The House- Owner's Estimator.

THE HOUSE-OWNER'S ESTIMATOR ; or, What will it
Cost to Build, Alter, or Repair? A Price- Book adapted to the
Use of Unprofessional People as well as for the Architectural
Surveyor and Builder. By the late James D. Simon, A.R.I.B. A.
Edited and Revised by Francis T. W. Miller, Surveyor. With
numerous Illustrations. Second Edition, with the prices carefully
corrected to present time. Crown 8vo, cloth, 31. 6d.

" In two years it will repay its cost a hundred times over." — Field.

" A very handy book for those who want to know what a house will cost to build,
alter, or repair." — English Mechanic.

Useful Text- Book for Architects.

THE ARCHITECT'S GUIDE : Being a Text-book of Useful
Information for Architects, Engineers, Surveyors, Contractors,
Clerks of Works, &c, &c. By Frederick Rogers, Architect,
Author of "Specifications for Practical Architecture," &c With
numerous Illustrations. Crown 8vo, 6s. cloth.

PUBLISHED BY CROSBY LOCKWOOD & CO. 17

CARPENTRY, TIMBER, MECHANICS.

TredgoUFs Carpentry, new and cheaper Edition.

THE ELEMENTARY PRINCIPLES OF CARPENTRY :
a Treatise on the Pressure and Equilibrium of Timber Framing, the
Resistance of Timber, and the Construction of Floors, Arches,
Bridges, Roofs, Uniting Iron and Stone with Timber, &c To which
is added an Essay on the Nature and Properties of Timber, &c,
with Descriptions of the Kinds of Wood used in Building ; also
numerous Tables of the Scantlings of Timber for different purposes,
the Specific Gravities of Materials, &c. By Thomas Tredgold,
C.E. Edited by Peter Barlow, F.R.S. Fifth Edition, cor-
rected and enlarged. With 64 Plates (1 1 of which now first appear
in this edition), Portrait of the Author, and several Woodcuts. In
1 vol., 4*0, published at 2/. 2s., reduced to 1/. $s. cloth.

" Ought to be in every architect's and every builder's library, and those who
do not already possess it ought to avail themselves of the new issue. — Builder.

"A work whose monumental excellence must commend it wherever skilful car-
pentry is concerned. The Author's principles are rather confirmed than impaired by
time. The additional plates are of great intrinsic value."— Building News.

Grandy's Timber Tables.

THE TIMBER IMPORTER'S, TIMBER MERCHANTS,
and BUILDER'S STANDARD GUIDE. By Richard E.
Grandy. Comprising : — An Analysis of Deal Standards, Home
and Foreign, with comparative Values and Tabular Arrangements
for Fixing Nett Landed Cost on Baltic and North American Deals,
including all intermediate Expenses, Freight, Insurance, &c, &c. ;
together with Copious Information for the Retailer and Builder.
Second Edition. Carefully revised and corrected. i2mo, 31. 6d.
cloth.

" Everything it pretends to be : built up gradually, it leads one from a forest to a
treenail, and throws in, as a makeweight, a host of material concerning bricks, columns,
cisterns, &c. — all that the class to whom it appeals requires." — English Mechanic.

" The only difficulty we have is as to what is not in its pages. What we have tested
of the contents,taken at random, is invariably correct." — Illustrated Builders Journal.

Tables for Packing-Case Makers.

PACKING-CASE TABLES ; showing the number of Superficial

Feet in Boxes or Packing-Cases, from six inches square and

upwards. Compiled by William Richardson, Accountant.

Second Edition. Oblong 4to, 3s. 6d. cloth.

"Will save much labour and calculation to packing-case makers and those who use
packing-cases."— Grocer. " Invaluable labour-saving tables." — Ironmonger.

Nicholson 9 s Carpenters Guide.

THE CARPENTER'S NEW GUIDE ; or, BOOK of LINES
for CARPENTERS : comprising all the Elementary Principles
essential for acquiring a knowledge of Carpentry. Founded on the
late Peter Nicholson's standard work. A new Edition, revised
by Arthur Ashpitel, F.S.A., together with Practical Rules on
Drawing, by Georqe Pyne. With 74 Plates, 4to, 1/. is. cloth.

18 WORKS ON CARPENTRY, TIMBER, ETC.,

Dowsing f s Timber Merchant's Companion.

THE TIMBER MERCHANT'S AND BUILDER'S COM-
PANION ; containing Nev7 and Copious Tables of the Reduced
Weight and Measurement of Deals and Battens, of all sizes, from
One to a Thousand Pieces, and the relative Price that each size
bears per Lineal Foot to any given Price per Petersburgh Standard
Hundred ; the Price per Cube Foot of Square Timber to any given
Price per Load of 50 Feet ; the proportionate Value of Deals and
Battens by the Standard, to Square Timber by the Load of 50 Feet ;
the readiest mode of ascertaining the Price of Scantling per Lineal
Foot of any size, to any given Figure per Cube Foot. Also a
variety of other valuable information. By William Dowsing,
Timber Merchant. Third Edition, Revised and Corrected. Crown
8vo, 3J. cloth.
"Everything is as concise and clear as it can possibly be made. There can be no
doubt that every timber merchant and builder ought to possess it" — Hull Advertiser.

Timber Freight Book.

THE TIMBER IMPORTERS' AND SHIPOWNERS'
FREIGHT BOOK : Being a Comprehensive Series of Tables for
the Use of Timber Importers, Captains of Ships, Shipbrokers,
Builders, and all Dealers in Wood whatsoever. By William
Richardson, Timber Broker. Crown 8vo, 6s, cloth.

Hortoris Measurer.

THE COMPLETE MEASURER ; setting forth the Measure-
ment of Boards, Glass, &c, &c ; Unequal-sided, Square-sided,
Octagonal-sided, Round Timber and Stone, and Standing Timber.
With just allowances for the bark in the respective species of
trees, and proper deductions for the waste in hewing the trees,
&c. ; also a Table showing the solidity of hewn or eight-sided
timber, or of any octagonal-sided column. By Richard Horton.
Third edition, with considerable and valuable additions, i2mo,
strongly bound in leather, $s.
"Not only are the best methods of measurement shown, and in some instances
illustrated by means of woodcuts, but the erroneous systems pursued by dishonest
dealers are fully exposed The work must be considered to be a valuable addi-
tion to every gardener's library. — Garden.

Superficial Measurement.

THE TRADESMAN'S GUIDE TO SUPERFICIAL MEA-
SUREMENT. Tables calculated from 1 to 200 inches in length,
by 1 to 108 inches in breadth. For the use of Architects, Surveyors,
Engineers, Timber Merchants, Builders, &c By James Haw-
kings. Fcp. 3j. 6d. cloth.

Practical Timber Merchant.

THE PRACTICAL TIMBER MERCHANT, being a Guide
for the use of Building Contractors, Surveyors, Builders, &c,
comprising useful Tables for all purposes connected with the
Timber Trade, Marks of Wood, Essay on the Strength of Timber,
Remarks on the Growth of Timber, &c. By W. Richardson.
Fcap. 8vo, 3J. 6d. cloth.

PUBLISHED BY CROSBY LOCKWOOD & CO. 19

The Mechanics Workshop Companion.

THE OPERATIVE MECHANIC'S WORKSHOP COM-
PANION, and THE SCIENTIFIC GENTLEMAN'S PRAC-
TICAL ASSISTANT. By William Templeton. Twelfth
Edition, with Mechanical Tables for Operative Smiths, Millwrights,
-Engineers, &c. ; and an Extensive Table of Powers and Roots,
&c, &c. 11 Plates. i2mo, $s. bound.

" As a text-book in which mechanical and commercial demands are judiciously met
Tbmpleton's Companion stands yxativalled.'*— Mechanics' Magazine.

'* Admirably adapted to the wants of a very large class. It has met with great
success in the engineering workshop, as we can testify ; and there are a great many
men who, in a great measure, owe their rise in life to this Little work. " — Building News,

Engineer's Assistant.

THE ENGINEER'S, MILLWRIGHT'S, and MACHINIST'S
PRACTICAL ASSISTANT ; comprising a Collection of Useful
Tables, Rules, and Data. Compiled and Arranged, with Original
Matter, by William Templeton. 6th Edition. i8mo, 2s. 6d.
cloth.

" So much varied information compressed into so small a space, and published at a
price which places it within the reach of the humblest mechanic, cannot fail to com-
mand the sale which it deserves. With the utmost confidence we commend this book
to the attention of our readers." — Mechanics' Magazine.

"A more suitable present to an apprentice to any of the mechanical trades could not
possibly be made." — Building- News.

Designings Measuring ', and Valuing.

THE STUDENT'S GUIDE to the PRACTICE of MEA-
SURINGand VALUING ARTIFICERS' WORKS; containing
Directions for taking Dimensions, Abstracting the same, and bringing
the Quantities into Bill, with Tables of Constants, and copious
Memoranda for the Valuation of Labour and Materials in the re-
spective Trades of Bricklayer and Slater, Carpenter and Joiner,
Painter and Glazier, Paperhanger, &c. With 43 Plates and Wood-
cuts. Originally edited by Edward Dobson, Architect. New
Edition, re-written, with Additions on Mensuration and Construc-
tion, and useful Tables for facilitating Calculations and Measure-
ments. By E. Wyndham Tarn, M.A., 8vo, ior. 6d. cloth.

" We have failed to discover anything connected with the building trade, from ex-
cavating foundations to bell-hanging, that is not fully treated upon. ' — The Ar'tizan.

" Altogether the book is one which well fulfils the promise of its title-page, and we
can thoroughly recommend it to the class for whose use it has been compiled. Mr.
Tarn's additions and revisions have much increased the usefulness of the work, and
have especially augmented its value to students."— Engineering.

Plumbing.

PLUMBING ; a text-book to the practice of the art or craft of the
plumber. With supplementary chapters upon house-drainage, em-
bodying the latest improvements. By William Paton Buchan,
Sanitary Engineer. i2mo, with 300 illustrations. 3s. 6d. cloth.

"Will be welcomed as the work of a practical master of his trade." — Public Health.

" The chapters on house-drainage may be usefully consulted, not only by plumbers,
but also by engineers and all engaged or interested in house- building. ' — Iron.

"A book containing a large amount of practical information, put together in a very
intelligent manner, by one who is well qualified for the task." — City Press.

ao WORKS IN MATHEMATICS, ETC.,

MATHEMATICS, &c.

Gregory's Practical Mathematics.

MATHEMATICS for PRACTICAL MEN ; being a Common-

J)lace Book of Pure and Mixed Mathematics. Designed chiefly
or the Use of Civil Engineers, Architects, and Surveyors. Part I.
Pure Mathematics — comprising Arithmetic, Algebra, Geometry,
Mensuration, Trigonometry, Conic Sections, Properties of Curves.
Part II. Mixed Mathematics — comprising Mechanics in genera],
Statics, Dynamics, Hydrostatics, Hydrodynamics, Pneumatics,
Mechanical Agents, Strength of Materials. With an Appendix of
copious Logarithmic and other Tables. By Olinthus Gregory,
LL.D., F.R. A.S. Enlarged by Henry Law, C.E. 4th Edition,
carefully revised and corrected by J. R. Young, formerly Profes-
sor of Mathematics, Belfast College ; Author of " A Course of
Mathematics," ftc. With 13 Plates. Medium 8vo, \l. is. cloth,

" The engineer or architect will here find ready to his hand, rules for solving nearly
every mathematical difficulty that may arise in his practice. The rules are in all cases
explained by means of examples, in which every step of the process is clearly worked
out."— Builder.

"One of the most serviceable books to the practical mechanics of the country.

In the edition just brought out, the work has again been revised by

Professor Young. He has modernised the notation throughout, introduced a few
paragraphs here and there, and corrected the numerous typographical errors which
have escaped the eyes of the former Editor. The book is now as complete as it is
possible to make it. It is an instructive book for the student, and a Text*
book for him who having once mastered the subjects it treats of, needs occasionally to
refresh his memory upon them." — Building 1 News.

" As a standard work on mathematics it has not been excelled." — Artisan.

The Metric System.

A SERIES OF METRIC TABLES, in which the British
Standard Measures and Weights are compared with those of the
Metric System at present in use on the Continent By C. H.
Dowling, C. E. Second Edition, revised and enlarged. 8vo,
iar. 6d. strongly bound.

" Mr. Dowling*s Tables, which are well put together, come just in time as a ready
reckoner for the conversion of one system into the other." — Atkenteum.

" Their accuracy has been certified by Prof. Airy, Astronomer-Royal. w — Builder.

" Resolution 8. — That advantage will be derived from the recent publication of
Metric Tables, by C H. Dowling, C.E."— Report of Section F, Brit. Assoc., Bath,

Comprehensive Weight Calculator.

THE WEIGHT CALCULATOR; being a Series of Tables
upon a New and Comprehensive Plan, exhibiting at one Reference
the exact Value of any Weight from lib. to 15 tons, a': 300 Pro-
gressive Rates, from 1 Penny to 168 Shillings per cwt., and con-
taining 186,000 Direct Answers, which, with their Combinations,
consisting of a single addition (mostly to be performed at sight),
will afford an aggregate of 10,266,000 Answers ; the whole being
calculated and designed to ensure Correctness and promote
Despatch. By Henrv Harben, Accountant, Sheffield, Author
of "The Discount Guide." An entirely New Edition, carefully
revised. Royal 8vo, strongly half-bound, 1/. $s. \Just published*

PUBLISHED BY CROSBY LOCKWOOD & CO. 21

Comprehensive Discount Guide.

THE DISCOUNT GUIDE : comprising several Series of Tables
for the use of Merchants, Manufacturers, Ironmongers, and others,
by which may be ascertained the exact profit arising from any mode
of using Discounts, either in the Purchase or Sale of Goods, and
the method of either Altering a Rate of Discount, or Advancing a
Price, so as to produce, by one operation, a sum that will realise
any required profit after allowing one or more Discounts : to which
are added Tables of Profit or Advance from I J to 90 per cent.,
Tables of Discount from 1 \ to 98I per cent., and Tables of Commis-
sion, &c, from \ to 10 per cent. By Henry Harben, Accountant,
Author of " The Weight Calculator." New Edition, carefully Re-
vised and Corrected. Demy 8vo (544 pp.), half-bound, ^1 5*.

Inwood's Tables, greatly enlarged and improved.

TABLES FOR THE PURCHASING of ESTATES, Freehold,
Copyhold, or Leasehold; Annuities, Advowsons, &&, and for the
Renewing of Leases held under Cathedral Churches, Colleges, or
other corporate bodies ; for Terms of Years certain, and for Lives ;
also for Valuing Reversionary Estates, Deferred Annuities, Next
Presentations, &<x, together with Smart's Five Tables of Compound
Interest, and an Extension of the same to Lower and Intermediate
Rates. By William Inwood, Architect. The 20th edition, with
considerable additions, and new and valuable Tables of Logarithms
for the more Difficult Computations of the Interest of Money, Dis-
count, Annuities, &c, by M. F£dor Thoman, cf the Socie'te'
Credit Mobilier of Paris. I2mo, &r. cloth.

" Those interested In the purchase and sale of estates, and in the adjustment of
compensation cases, as well as in transactions in annuities, life insurances, &c. T will
find the present edition of eminent service." — Engineering.

" ' Inwood's Tables' still maintain a most enviable reputation. The new issue has been
enriched by large additional contributions by M. Fe'dor Thoman, whose carefully
arranged Tables cannot fail to be of the utmost utility."— Mining Journal.

Geometry for the Architect, Engineer, &c.

PRACTICAL GEOMETRY, for the Architect, Engineer, and

Mechanic ; giving Rules for the Delineation and Application of

various Geometrical Lines, Figures and Curves. By E. W. Tarn,

M.A., Architect, Author of " The Science of Building," &c.

With 164 Illustrations. Demy 8vo. 1 2s. 6d. cloth.

" No book with the same objects in view has ever been published in which the
clearness of the rules laid down and the illustrative diagrams have been so satis-
factory. M — Scotsman.

Compound Interest and Annuities.

THEORY of COMPOUND INTEREST and ANNUITIES ;
with Tables of Logarithms for the more Difficult Computations of
Interest, Discount, Annuities, &c, in all their Applications and
Uses for Mercantile and State Purposes. With an elaborate Intro-
duction. By FfcDOR Thoman, of the Socie'te' Credit Mobilier,
Paris. 3rd Edition, carefully revised and corrected. 12010,4*. 6d. cl.

A very powerful work, and the Author has a very remarkable command of his
subject." — Professor A. de Morgan.
"We recommend it to the notice of actuaries and accountants."— Athenaum,

22 WORKS IN SCIENCE AND ART, ETC.,

SCIENCE AND ART.

Dentistry,

MECHANICAL DENTISTRY. A Practical Treatise on the
Construction of the various kinds of Artificial Dentures. Com-
prising also Useful Formulae, Tables, and Receipts for Gold
Hate, Clasps, Solders, etc., etc. By Charles Hunter. With
numerous Wood Engravings. Crown 8vo, Js. 6d. Cloth.

" The work is very practical" — Monthly Review of Dental Surgery.

" An authoritative treatise Many useful and practical hints are scattered

throughout the work, while its value as a text book is enhanced by numerous illus-
trations. We can strongly recommend Mr. Hunter's treatise to all students pre-
paring for the profession of dentistry, as well as to every mechanical dentist." —
Dublin Journal of Medical Science.

Brewing.

A HANDBOOK FOR YOUNG BREWERS. By Herbert
Edwards Wright, B.A. Crown 8vo, $s. 6d. cloth.

" A thoroughly scientific treatise in popular language. It is evident that the
author has mastered his subject in its scientific aspects." — Morning Advertiser.

" We would particularly recommend teachers of the art to place it in every pupil's
hands, and we feel sure its perusal will be attended with advantage." — Brewer.

The Military Sciences.

AIDE-MEMOIRE to the MILITARY SCIENCES. Framed
from Contributions of Officers and others connected with the dif-
ferent Services. Originally edited by a Committee of the Corps of
Royal Engineers. Second Edition, most carefully revised by an
Officer of the Corps, with many additions ; containing nearly 350
Engravings and many hundred Woodcuts. 3 vols, royal 8vo, extra
cloth boards, and lettered, 4/. ioj.

«<

1 A compendious encyclopaedia of military knowledge. w — Edinburgh Review.
" The most comprehensive work of reference to the military and collateral sciences.
— Volunteer Service Gazette.

Field Fortification.

A TREATISE on FIELD FORTIFICATION, the ATTACK
of FORTRESSES, MILITARY MINING, and RECON-
NOITRING. By Colonel I. S. Macaulay, late Professor of
Fortification in the R. M. A., Woolwich. Sixth Edition, crown
8vo, cloth, with separate Atlas of 12 Plates, I2J. complete.

Dye- Wares and Colours.

THE MANUAL ot COLOURS and DYE-WARES : their
Properties, Applications, Valuation, Impurities, and Sophistications.
For the Use of Dyers, Printers, Drysalters, Brokers, &c By J.
W. Slater. Post 8vo, Js. 6d. cloth.

A complete encyclopaedia of the materia tinctoria. The information is ful
and precise, and the methods of determining the value of articles liable to sophistica-
tion, are practical as well as valuable." — Chemist and Druggist.

PUBLISHED BY CROSBY LOCKWOOD & CO. 23

~ - - I 1 I I _ II II.IBII - J

Text-Book of Electricity.

THE STUDENT'S TEXT-BOOK OF ELECTRICITY. By
Henry M. Noad, Ph.D., F.R.S., F.C.S. New Edition, care-
fully Revised. With an Introduction and Additional Chapters
by W. H. Preece, Vice-President of the Society of Telegraph
Engineers, &c. Illustrated with 470 Illustrations. Crown 8vo,

I2j. 6d. cloth. [Just published,

"A reflex of the existing state of Electrical Science adapted for students." —
W. H. Preece, Esq., vide " Introduction."

" We can recommend Dr. Noad's book for clear style, great range of subject, a
good index, and a plethora of woodcuts. Such collections as the present are indis-
pensable." — Athena itm.

" An admirable text-book for every student— beginner or advanced — of electricity."
— Engineering.

" A most elaborate compilation of the facts of electricity and magnetism. " — Popular
Science Review.

Electricity.

A MANUAL of ELECTRICITY ; including Galvanism, Mag-
netism, Diamagnetism, Electro-Dynamics, Magno-Electricity, and
the Electric Telegraph. By Henry M. Noad, Ph.D., F.C.S.,
Fourth Edition, with 500 Woodcuts. 8vo, 1/. 4^. cloth.
" The accoun' s given of electricity and galvanism are not onlvcomplete in a scientific
sense, but, which is a rarer thing, are popular and interesting.— Lancet.

Rudimentary Magnetism.

RUDIMENTARY MAGNETISM : being a concise exposition
of the general principles of Magnetical Science, and the purposes
to which it has been applied. By Sir W. Snow Harris, F.R.S.
New and enlarged Edition, with considerable additions by Dr.
Noad, Ph.D. With 165 Woodcuts. i2mo, cloth, 4s.

" As concise and lucid an exposition of the phenomena of magnetism as we believe
it is possible to write."— English Mecht, nic.

" The best possible manual on the subject of magnetism." — Mechanics* Magazine.

Chemical Analysis.

THE COMMERCIAL HANDBOOK of CHEMICAL ANA-
LYSIS ; or Practical Instructions for the determination of the In-
trinsic or Commercial Value of Substances used in Manufactures,
in Trades, and in the Arts. By A. Normandy, Author of " Prac-
tical Introduction to Rose's Chemistry," and Editor of Rose's
" Treatise on Chemical Analysis." New Edition. Enlarged, and
to a great extent re-written, by Henry M. Noad, Ph. D., F.R.S.
With numerous Illustrations. Cr. 8vo, I2J. 6d. cloth.
" We recommend this book to the careful perusal of every one ; it may be truly
affirmed to be of universal interest, and we strongly recommend it to our readers as a

Side, alike indispensable to the housewife as to the pharmaceutical practitioner."—
edical Times.

" Essential to the analysts appointed under the new Act. The most recent results
are given, and the work is well edited and carefully written." — Nature.

Mollusca.

A MANUAL OF THE MOLLUSCA ; being a Treatise on
Recent and Fossil Shells. By Dr. S. P. Woodward, A.L.S.
With Appendix by Ralph Tate, A.L.S., F.G.S. With numer-
ous Plates and 300 Woodcuts. 3rd Edition. Cr. 8vo, ys. 6d. cloth.

14 WORKS IN SCIENCE AND ART, ETC.,

Gold and Gold-Working.

THE PRACTICAL GOLD- WORKER ; or, The Goldsmith's
and Jeweller's Instructor. The Art of Alloying, Melting, Re-
ducing, Colouring, Collecting and Refining. The processes of
Manipulation, Recovery of Waste, Chemical and Physical Pro-
perties of Gold, with a new System of Mixing its Alloys ; Solders,
Enamels, and other useful Rules and Recipes, &c. By George
E. Gee. Crown 8vo, *js. 6d. cloth.

"A good, sound, technical educator, and will be generally accepted as an
authority. It gives full particulars for mixing alloys and enamels, is essentially a book
for the workshop, and exactly fulfils the purpose intended." — Horological Journal.

" The best work yet printed on its subject for a reasonable price. We have no
doubt that it will speedily become a standard book which few will care to be with-
out."— Jeweller and Metalworker.

Silver and Silver Working,

THE SILVERSMITH'S HANDBOOK, containing full In-
structions for the Alloying and Working of Silver, including the
different modes of refining and melting the metal, its solders, the
preparation of imitation alloys, methods of manipulation, preven-
tion of waste, instructions for improving and finishing the surface
of the work, together with other useful information and memoranda.
By George E. Gee, Jeweller, &c. Crown 8vo, with numerous
illustrations, *js. 67/. cloth.

" This work is destined to take up as good a position in technical literature as the
Practical Goldivorker, a book which has passed through the ordeal of critical ex-
amination and business tests with great success." — Jeweller and Metalworker.

Clocks, Watches, and Bells.

RUDIMENTARY TREATISE on CLOCKS, and WATCHES,
and BELLS. By Sir Edmund Beckett, Bart, (late E. B.
Denison), LL.D., Q.C., F.R.A.S., Author of " Astronomy with-
out Mathematics," &c Sixth edition, thoroughly revised and
enlarged, with numerous Illustrations. Limp cloth (No. 67,
Weale's Series), 4s. 6d. ; cloth boards, 5«r. 6d.

" As a popular and practical treatise it is unapproached." — English Mechanic.

" The Dest work on the subject probably extant. The treatise on bells is un-
doubtedly the best in the language. To call it a rudimentary treatise is a misnomer,
at least as respects clocks and hells. It is the most important work of its kind in
English. "— Engineering.

"The only modern treatise on clock-making." — Horological Journal.

" This admirable treatise on clocks, by the most able authority on such a subject,
is completely perfect of its kind." — Standard.

Science and Scripture.

SCIENCE ELUCIDATIVE OF SCRIPTURE, AND NOT
ANTAGONISTIC TO IT ; being a Series of Essays on— 1.
Alleged Discrepancies ; 2. The Theory of the Geologists and
Figure of the Earth ; 3. The Mosaic Cosmogony ; 4. Miracles in
general — Views of Hume and Powell ; 5. The Miracle of Joshua —
Views of Dr. Colenso : The Supernaturally Impossible 5 6. The
Age of the Fixed Stars— their Distances and Masses. By Professor
J. R. Young. Fcap. 8vo, 5*. cloth.

" Distinguished by the true spirit of scientific inquiry, by great knowledge, by keen
logical ability, and by a style peculiarly clear, easy, and energetic." — Nonconform^

PUBLISHED BY CROSBY LOCKWOOD & CO. 25

DR. LARDNER'S POPULAR WORKS.
ZDr. Lardner* s Museum of Science and Art.

THE MUSEUM OF SCIENCE AND ART. Edited by
Dionysius Lardner, D.C.L., formerly Professor of Natural Phi-
losophy and Astronomy in University College, London. With up-
wards of 1200 Engravings on Wood. In 6 Double Volumes.
Price £1 1 j., in a new and elegant cloth binding, or handsomely
bound in half morocco, 31J. 6d.

" The ' Museum of Science and Art ' is the most valuable contribution that has
ever been made to the Scientific Instruction of every class of society." — Sir David
Brewster in the North British Review.

" Whether we consider the liberality and beauty of the illustrations, the charm of
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there is hardly to be found among the new books, one that would be welcomed by
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* # * Separate books formed from the above, suitable for Workmen's

Libraries, Science Classes, &*c.

COMMON THINGS EXPLAINED. Containing Air, Earth, Fire,
Water, Time, Man, the Eye, Locomotion, Colour, Clocks and
Watches, &c. 233 Illustrations, cloth gilt, $s.

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POPULAR GEOLOGY. Containing Earthquakes and Volcanoes,
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POPULAR PHYSICS. Containing Magnitude and Minuteness, the
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STEAM AND ITS USES. Including the Steam Engine, the Lo-
comotive, and Steam Navigation. 89 Illustrations, cloth gilt, 2s.

POPULAR ASTRONOMY. Containing How to Observe the
Heavens. The Earth, Sun, Moon, P.'anets. Light, Comets,
Eclipses, Astronomical Influences, &c. 182 Illustrations, 4s. 6d.

THE BEE AND WHITE ANTS : Their Manners and Habits.
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trations, cloth gilt, 2s.

THE ELECTRIC TELEGRAPH POPULARISED. To render
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Scientific Class-Books, by Dr. Lardner.

NATURAL PHILOSOPHY FOR SCHOOLS. By Dr. Lardner.
328 Illustrations. Sixth Edition. 1 vol. y. 6d. cloth.
" Conveys, in clear and precise terms, general notions of all the principal divisions ■
of Physical Science." — British Quarterly Review.

ANIMAL PHYSIOLOGY FOR SCHOOLS. By Dr. Lardner.
With 190 Illustrations. Second Edition. 1 vol. y. 6d. cloth.
" Clearly written.well arranged, and excellently illustrated. "—Gardeners' Chronicle.

28 WORKS IN SCIENCE AND ART, ETC.,

Delamotte' s Works on Illumination & Alphabets.

A PRIMER OF THE ART OF ILLUMINATION ; for the
use of Beginners : with a Rudimentary Treatise on the Art, Prac-
tical Directions for its Exercise, and numerous Examples taken
from Illuminated MSS., printed in Gold and Colours. By F. Dela-
motte. Small 4to, 9J. Elegantly bound, cloth antique.

" A handy book, beautifully illustrated ; the text of which is well written, and cal-
culated to be useful. . . . The examples of ancient MSS. recommended to the student,
which, with much good sense, the author chooses from collections accessible to all, are
selected with judgment and knowledge, as well as taste." — Atheiutunt.

ORNAMENTAL ALPHABETS, ANCIENT and MEDIEVAL ;
from the Eighth Century, with Numerals ; including Gothic,
Church-Text, large and small, German, Italian, Arabesque, Initials
for Illumination, Monograms, Crosses, &c. &c, for the use of
Architectural and Engineering Draughtsmen, Missal Painters,
Masons, Decorative Painters, Lithographers, Engravers, Carvers,
&c. &c. &c. Collected and engraved by F. Delamotte, and
printed in Colours. New and Cheaper Edition. Royal 8vo,
oblong, 2 s. 6d. ornamental boards. \fjust published.

"A well-known engraver and draughtsman has enrolled in this useful book the
result of many years' study and research. For those who insert enamelled sentences
round gilded chalices, who blazon shop legends over shop-doors, who letter church
walls with pithy sentences from the Decalogue, this book will be useful."— -Athetueum.

EXAMPLES OF MODERN ALPHABETS, PLAIN and ORNA-
MENTAL ; including German, Old English, Saxon, Italic, Per-
spective, Greek, Hebrew, Court Hand, Engrossing, Tuscan,
Riband, Gothic, Rustic, and Arabesque; with several Original
Designs, and an Analysis of the Roman and Old English Alpha-
bets, large and small, and Numerals, for the use of Draughtsmen,
Surveyors, Masons, Decorative Painters, Lithographers, Engravers,
Carvers, &c. Collected and engraved by F. Delamotte, and
printed in Colours. New and Cheaper Edition. Royal 8vo,
oblong, 2j. 6d. ornamental boards. \Just published.

" To artists of all classes, but more especially to architects and engravers, this very
handsome book will be invaluable. There is comprised in it every possible shape into
which the letters of the alphabet and numerals can be formed, and the talent which
has been expended in the conception of the various plain and ornamental letters is
wonderful. "-Standard.

MEDIAEVAL ALPHABETS AND INITIALS FOR ILLUMI-
NATORS. By F. Delamotte, Illuminator, Designer, and
Engraver on Wood. Containing 21 Plates, and Illuminated Title,
printed in Gold and Colours. With an Introduction by J. Willis
Brooks. Small 4to, dr. cloth gilt.

" A volume in which the letters of the alphabet come forth glorified in gilding and
all the colours of the prism interwoven ana intertwined and intermingled, sometimes
with a sort of rainbow arabesque. A poem emblazoned in these characters would be
only comparable to one of those delicious love letters symbolized in a bunch of flowers
well selected and cleverly arranged."— Sun.

THE EMBROIDERER'S BOOK OF DESIGN ; containing Initials,
Emblems, Cyphers, Monograms, Ornamental Borders, Ecclesias-
tical Devices, Mediaeval and Modern Alphabets, and National
Emblems. Collected and engraved by F. Delamotte, and
printed in Colours. Oblong royal 8vo, \s. 6d. in ornamental boards.

PUBLISHED BY CROSBY LOCKWOOD & CO. 29

AGRICULTURE, GARDENING, &c.

Potato Culture.

POTATOES, HOW TO GROW AND SHOW THEM; A
Practical Guide to the Cultivation and General Treatment of the
Potato. By James Pink, Author of " How to Grow One Thou-
sand Pounds of Potatoes from 1 lb. of Seed. " With Illustrations.
Second Edition. Cr. 8vo, 2s. cloth. \jfust published.

" A well written little volume. The author gives good practical instructions
under both divisions of his subject" — Agricultural Gazette.

"Cordial praise must be given to Mr. Pink for his thoroughly practical and useful
work/* — Daily Chronicle.

Kitchen Gardening.

KITCHEN GARDENING MADE EASY. Showing how to

prepare and lay out the ground, the best means of cultivating every

known Vegetable and Herb, with cultural directions for the

management of them all the year round. By George M. F.

Glen NY, Editor of •' Glenny's Illustrated Garden Almanack," &c.

With Illustrations, i2mo, 2s. cloth boards. [Just Published.

"As a guide to hardy kitchen gardening, tbis book will be found trustworthy and
useful to the many who cannot spare the time to consult more comprehensive and
detailed works."— North British Agriculturist.

Bulb Culture.

THE BULB GARDEN, or, How to Cultivate Bulbous and

Tuberous-rooted Flowering Plants to Perfection. A Manual

adapted for both the Professional and Amateur Gardener. By

Samuel Wood, Author of "Good Gardening," etc. With

Coloured Illustrations, Plans, and numerous Wood Engravings.

Crown 8vo, 3-r. 6d. cloth.

" Supplies the want which has hitherto existed of any sufficiently modern work of
the kind. The book contains practical suggestions as to the arrangement of
the flowers, and the growth of flower-roots for the trade, as well as for amusement."
—Saturday Review.

Production of Meat.

MEAT PRODUCTION. A Manual for Producers, Distributors,
and Consumers of Butchers' Meat. Being a treatise on means of
increasing its Home Production. Also comprehensively treating
of the Breeding, Rearing, Fattening, and Slaughtering of Meat-
yielding Live Stock ; Indications of the Quality ; Means for Pre-
serving, Curing, and Cooking of the Meat, etc., etc. By John
Ewart, author of "The Land Improvers Pocket Book," etc.
With numerous Illustrations. Cr. 8vo, $s. cloth.
" A compact and handy volume on the meat question, which deserves serious and
thoughtful consideration at the present time, when the question of the food supply of
the country has become one of the leading topics of the day." — Meat and Provision
Trades* Review.

History, Structure, and Diseases of Sheep.

SHEEP ; THE HISTORY, STRUCTURE, ECONOMY,
AND DISEASES OF. By W. C. Spooner, M.R.V.C, &c.
Fourth Edition, with fine engravings, including specimens of New
and Improved Breeds, 366 pp., 4*. cloth. [Just published.

3o WORKS ON AGRICULTURE, GARDENING, ETC.,

Good Gardening.

A PLAIN GUIDE TO GOOD GARDENING ; or, How to
Grow Vegetables, Fruits, and Flowers. With Practical Notes on
Soils, Manures, Seeds, Planting, Laying-out of Gardens and
Grounds, &c. By S. Wood. Third Edition, with considerable
Additions, &c, and numerous Illustrations. Cr. 8vo, $s. cloth.
" A thoroughly useful guidebook for the amateur gardener."— Daily Telegraph.
" A very good book, and one to be highly recommended as a practical guide.
The practical directions are txceWenV—Athen&um.

Gainful Gardening.

MULTUM-IN-PARVO GARDENING; or, How to make One
Acre of Land produce ^"620 a year, by the Cultivation of Fruits
and Vegetables ; also, How to Grow Flowers in Three Glass
Houses, so as to realise £176 per annum clear Profit. By Samuel
Wood, Author of '• Good Gardening," &c 3rd Edition, revised.
With Wood Engravings. Cr. 8vo, 2s. cloth.
" We are bound to recommend it as not only suited to the case of the amateur and
gentleman's gardener, but to the market grower." — Gardener's Magazine.

Culture of Fruit Trees.

FRUIT TREES, the Scientific and Profitable Culture of. From
the French of Du Breuil, revised by Geo. Glenny. 187
Woodcuts. i2mo, 4s. cloth.

Scott Burn's System of Modern Farming.

OUTLINES OF MODERN FARMING. By R. Scott Burn.
Soils, Manures, and Crops — Farming and Farming Economy—.
Cattle, Sheep, and Horses — Management of the Dairy, Pigs, and
Poultry — Utilisation of Town-Sewage, Irrigation, &c. New Edition.
In 1 vol. 1250 pp., half-bound, profusely illustrated, I2j.
"There is sufficient stated within the limits of this treatise to prevent a farmer
from going far wrong in any of his operations."— Observer.

Ewarfs Land Improvers Pocket-Book.

THE LAND IMPROVER'S POCKET-BOOK OF FOR-
MULAE, TABLES, and MEMORANDA, required in any Com-
putation relating to the Permanent Improvement of Landed Pro-
perty. By John Ewart, Land Surveyor and Agricultural Engineer.
Royal 32mo, oblong, leather, gilt edges, with elastic band, 4s.
" A compendious and handy little volume."— Spectator.

Hudson's Tables for Land Valuers.

THE LAND VALUER'S BEST ASSISTANT: being Tables,
on a very much improved Plan, for Calculating the Value of
Estates. With Tables for reducing Scotch, Irish, and Provincial
Customary Acres to Statute Measure, &c. By R. Hudson, C.E.
New Edition, royal 32mo, leather, gilt edges, elastic band, 4*.
' 'Of incalculable value to country gentlemen and professional men. "—Farmers Journal.

Complete Agricultural Surveyors Pocket-Book.

THE LAND VALUER'S AND LAND IMPROVER'S COM-
PLETE POCKET-BOOK ; consisting of the above two works
bound together, leather, gilt edges, with strap, *]s. 6d.
" We consider Hudson's book to be the best ready-reckoner on matters relating to

the valuation of land and crops we have ever seen, and its combination with Mr.

Ewart's work greatly enhances the value and usefulness of the latter-mentioned . .

It is most useful as a manual for reference." — North of England Farmer.

PUBLISHED BY CROSBY LOCKWOOD & CO. 3!

Youatt and Burtts Complete Grazier.

THE COMPLETE GRAZIER, and FARMER'S and CATTLE-
BREEDER'S ASSISTANT. A Compendium of Husbandry.
By William Youatt, Esq., V.S. 12th Edition, very con-
siderably enlarged, and brought up to the present requirements of
agricultural practice. By Robert Scott Burn, Author of "The
Lessons of My Farm," &c One large 8vo volume, 860 pp. with 244
Illustrations. 1/. is. half-bound.

" The standard and text-book, with the farmer and grazier. "—Farmer's Magazine.

"A treatise which will remain a standard work on the subject as long as British
agriculture endures." — Mark Lane Express.

Donaldson and Burns Suburban Farming.

SUBURBAN FARMING. A Treatise on the Laying Out and
Cultivation of Farms adapted to the produce of Milk, Butter and
Cheese, Eggs, Poultry, and Pigs. By the late Professor John
Donaldson. With considerable Additions, Illustrating the more
Modern Practice by Robert Scott Burn. With numerous
Illustrations. Crown 8vo, 6j. cloth.
"An admirable treatise on all matters connected with the laying-out and cultivation
of dairy farms." — Live Stock Jourttal*

Scott Burn's Introduction to Farming.

THE LESSONS of MY FARM : a Book for Amateur Agricul-
turists, being an Introduction to Farm Practice, in the Culture of
Crops, the Feeding of Cattle, Management of the Dairy, Poultry,
Pigs, &c. By R. Scott Burn. With numerous Illus. Fcp. 6s. cl.

" A complete introduction to the whole round of farming practice." — John Bull.

Auctioneer's Assistant.

THE APPRAISER, AUCTIONEER, BROKER, HOUSE
AND ESTATE AGENT, AND VALUER'S POCKET AS-
SISTANT, for the Valuation for Purchase, Sale, or Renewal of
Leases, Annuities, and Reversions, and of property generally;
with Prices for Inventories, &c By John Wheeler, Valuer, &c.
Fourth Edition, enlarged, by C. Norris. Royal 32010, cloth, $s.

" A neat and concise book of reference, containing an admirable and clearly-
arranged list of prices for inventories, and a very practical guide to determine the
value of furniture, &c n — Standard.

The Management of Estates.

LANDED ESTATES MANAGEMENT: Treating of the
Varieties of Lands, Peculiarities of its Farms, Methods of Farming,
the Setting-out of Farms and their Fields, Construction of Roads,
Fences, Gates, and Farm Buildings, of Waste or Unproductive
Lands, Irrigation, Drainage, Plantation, &c. By R. Scott Burn,
Fcp. 8vo. numerous Illustrations, 3*. 6d.

"A complete and comprehensive outline of the duties appertaining to the manage-
ment of landed estates.' ' — Joui nal of Forestry.

* * A very useful vade-mecum to such as have the care of land." — Globe.

"Should be in the hands of all young men whose pursuits are in any way con-
nected with land." — Estates Gazette.

" A valuable and important work on a subject of imperative moment, as there is a
large and daily increasing demand for farm produce of all kinds.'*— Farmer's Herald*

3« WORKS PUBLISHED BY CROSBY LOCKWOOD & CO.

"A Complete Epitome of the Laws of this
Country."

EVERY MAN'S OWN LAWYER; a Handy-Book of the Prin-
ciples of Law and Equity. By A Barrister. 16th Edition,
Revised to the end of last Session. Including a Summary of the
principal Acts of the past Session (1878), viz. : — The Bills of Sale
Act, The Weights and Measures Act, The Dentists Act, The
Public Health Act (as to the Supply of Water to Dwelling-
houses), The Matrimonial Causes Act (as to aggravated Assaults
upon Wives), &c, &c With Notes and References to the Au-
thorities. Crown 8vo, price dr. Sd. (saved at every consultation),
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COMPRISING THE LAWS OF

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" No Englishman ought to be without this hook."— Engineer.

" What it professes to be — a complete epitome of the laws of this country, thoroughly
intelligible to non-professional readers. The book is a handy one to have in readiness
when some knotty point requires ready solution." — Bell's Life.

" A concise, cheap, and complete epitome of the English law, so plainly written
that he who runs may read, and he who reads may understand." — Figaro.

" A useful and concise epitome of the law, compiled with considerable cart."—
Law Magazine.

" Full of information, fitly expressed without the aid of technical expressions, and
to the general public will, we doubt not, prove of considerable worth." — Ecottomist.

Auctioneering.

AUCTIONEERS : THEIR DUTIES AND LIABILITIES.
By Robert Squibbs, Auctioneer. Demy 8vo, ior. 6a. cloth.

\Just published.
" Mr. Squibbs writes with evident knowledge of his subject and shrewd common
sense. His book should be useful to young auctioneers, and serviceable for
reference even to old ones." — Scotsman.

House Property.

HANDBOOK OF HOUSE PROPERTY : a Popular and Prac-
tical Guide to the Purchase, Mortgage, Tenancy, and Compulsory
Sale of Houses and Land ; including the Law of Dilapidations and
Fixtures ; with Explanations and Examples of all kinds of Valua-
tions, and useful Information and Advice on Building. By Edward
Lance Tarbuck, Architect and Surveyor. i2mo, 5J. cloth boards.

"We are glad to be able to recommend it." — Builder.
" The advice is thoroughly practical." — Law Journal.

Bradbury, Agnew, ft Co., Printers, Waitefriais, London.

Wte&W %fctgimntta rg Verted.

PHILADELPHIA, 1876.
THE PRIZE MEDAL

Was awarded la the Publishers for

Book) : Rudimentary Scientific,
"WEALE'S SERIES," ETC.

A NEW LIST OF

WEALE'S SERIES

RUDIMENTARY SCIENTIFIC, EDUCATIONAL,
AND CLASSICAL.

LONDON, 1862.
THE PRIZE MEDAL

Was awarded to the Publishers of

"WEALE'S SERIES."

These popular and cheap Si
commended lo the notice of En

department of Science, Art, ,
rinrrrs, Architects, Builder,, Artis.

ins. and Students

generally, as well as to those

IntenattJ IN Workmen's Librane.

L iterary and Scientific Instil,

■sses, &-c., Jw.

N.B.—ln ordering from thi
the titles and prices.

t List it is recommended, as a -mea.
9 quote the numbers affixed to the v.

-*-s

doth boards for DO. el

RUDIMENTARY SCIENTIFIC SERIES.

No ARCHITECTURE, BUILDING, ETC.

16. ARCHITECTURE— ORDERS— The Orders and their -fEithetic

Principles. By W. H. Letos. Illustrated, is. 6d.

17. ARCHITECTURE—STYLES— Tht History and Description of

the Styles of Architecture of Various Countrios, from ths Earliest to the
Present Period. By T. Talbot Bust, F.R.I. B.A., Stc. Illustrated. 11.

18. AicSe^£CTL r 'kB—j^SJON—T^s?A^i3stt''Si Design in

Architecture, a, deducible from Nature and exemplified In the Works of the

Greet and Gothic Architects. Bv E. L. GAKBiiri, Architect. Illustrated, n
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42. COTTAGE BUILDING. By C. Bruce Allen, Architect.

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128. VITRUVIUS — THE ARCHITECTURE OF MARCUS

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130. GRECIAN ARCHITECTURE, An Inquiry into the Principles
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156. QUANTITIES AND MEASUREMENTS, How to Calculate and
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182. CARPENTRY AND JOINE R I— The Elementary Prin-
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189. THE RUDIMENTS OF PRACTICAL BRICKLAYING.

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192. THE TIMBER IMPORTER'S, TIMBER MERCHANTS,

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CIVIL ENGINEERING, ETC.

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