VOLTAIC ELECTRICITY.
In describing the various means by which electricity may be obtained, it
was stated that "Chemical Action" was a most important source of this
remarkable agent; at the same time it must be understood that it is not
every kind of chemical action which is adapted for the purpose; there
are certain principles to be rigidly adhered to--first, in the
generation of the force; and secondly, in carrying it by wires so as to
be applicable either for telegraphic purposes, or for the highly
valuable processes of electrotyping and electro-silvering, plating, and
gilding.
A lighted candle, or an intense combustion of coal, coke, or charcoal,
no doubt involves the production of electricity, but there are no means
at present known by which it may be collected and conducted; when that
problem is solved, the cheapest voltaic battery will have been
constructed, in which the element decomposed is charcoal, and not a
metal, such as iron or zinc. The first and most simple experiment that
can be adduced in proof of electrical excitation by chemical means, is
to take a bit of clean zinc and a clean half-crown, and placing one on
the tongue and the other below it, as long as they remain separate no
effect is observed, but directly they are made to touch each other,
whilst in that position, a peculiar thrill is rendered evident by the
nerves of the tongue, which in this case answers the same purpose as the
electroscope already described, and in a short time a peculiar metallic
taste is perceptible.
It has been stated over and over again that it was to a somewhat similar
circumstance we owe the discovery of voltaic electricity, and the story
of the skinned frogs agitated and convulsed by an accidental
communication with two different metals, or, as some say, with the
electricity from an ordinary machine, has been repeated in nearly every
work on the science. Professor Silliman, however, asserts that the
galvanic story is doubtful, and is a fabrication of Alibert, an Italian
writer of no repute, and that greater merit is due to Galvani than that
of being merely the accidental discoverer of this kind of electricity,
because he had been engaged for _eleven_ years in electro-physiological
experiments, using frogs' legs as electroscopes. It was whilst
experimenting on animal irritability, Galvani noticed the important fact
that when the nerve of a dead frog, recently killed, was touched with a
steel needle, and the muscle with a silver one, no convulsions of the
limb were produced until the two different metals were brought in
contact, and he explained the cause of these singular after-death
contortions by supposing that the nerves and muscles of all animals were
in opposite states of electricity, and that these nervous contractions
were caused by the annihilation, for the time, of this condition, by the
interposition of a good conductor between them.
This theory of Galvani had several opponents, one of whom, the [Page
194] celebrated Volta, succeeded in pointing out its fallacy; he
maintained that the electrical excitement was due entirely to the
metals, and that the muscular contractions were caused by the
electricity thus developed passing along the nerves and muscles of the
dead animal.
To Volta we are indebted for the first voltaic battery, and the
distinguished philosopher may truly be said to have laid the foundation
of this now _commercially_ valuable branch of science.
_First Experiment._
If a plate of clean bright zinc is placed in a vessel containing some
dilute sulphuric acid, energetic action occurs from the oxidation of the
metal, and its union as an oxide with the acid, and the escape of a
multitude of bubbles of hydrogen gas. After the action has proceeded
some time, the zinc may be removed, and if a little quicksilver is now
rubbed over the surface with a woollen rag tied on the end of a stick,
it unites with the metal, and the surface of the zinc assumes a
brilliant silvery appearance, and is said to be amalgamated. In that
condition it is no longer acted upon by dilute sulphuric acid, and for
the sake of economy this is the only form in which zinc should be
employed in the construction of voltaic batteries or single circles. If
a clean plate of copper, with a wire attached, is now placed in the
dilute acid opposite to and not touching the amalgamated zinc plate,
which may also be furnished with a conducting wire, no bubbles of
hydrogen escape until the wires from the two metals are brought in
contact, and then, singular to relate, the hydrogen escapes from the
copper plate, whilst the oxygen is rapidly absorbed by the zinc, and a
current of electricity will now be found to pass from the zinc through
the fluid to the copper, and back again through the wire to the starting
point, and if the wires are disconnected, the chemical action ceases,
and no more electricity is produced. (Fig. 179.)
[Illustration: Fig. 179. A single voltaic circle, consisting of a zinc
and copper plate (marked Z and C) in dilute acid. The arrows show the
direction of the current.]
The passage of the current of electricity is not discoverable by the
electroscope, because it is adapted only to indicate electricity of high
tension or intensity, such as that produced from the electrical machine,
which will pass rapidly through a certain thickness of air, and cause
pith balls to stand out and repel each other; such effects are not
producible by a single voltaic circle, or even an ordinary voltaic
battery, although one comprising some hundreds of alternations would
produce [Page 195] an effect on a delicate electrometer; hence voltaic
electricity is said to be of low intensity, and this property makes it
much more useful to mankind, because it has no desire to leave a
metallic path prepared for it, and does not seize the first opportunity,
like the electricity from the electrical machine, to run away to the
earth through the best and shortest conductor offered for it. If
electricity had only been producible by friction, we should never have
heard of electrotyping, and the other useful applications of electrical
force of low intensity.
_Second Experiment._
To ascertain the passage of a current of voltaic electricity, the
instrument called the galvanometer needle is provided, which consists of
a coil of copper wire surrounding a magnetic needle, so as to leave the
latter freedom of motion from right to left, or _vice versâ_. When this
coil is made part of the voltaic circle it becomes magnetic, and
reacting on the magnetized needle, deflects it to one side or the other,
according to the direction of the current. (Fig. 180.)
[Illustration: Fig. 180. A galvanometer needle, consisting of a coil of
covered copper wire, the ends of which terminate at the binding screws.
The magnetic needle is suspended on a point in the centre, and the coil
is surrounded with a graduated circle.]
_Third Experiment._
If a number of simple voltaic circles, such as the one described in the
first experiment, are connected together, they form a voltaic battery,
in which of course the quantity of electricity is greatly increased.
Batteries of all kinds, from the original Volta's pile, consisting of
round zinc and copper plates soldered together with interposed cloth
moistened with dilute sulphuric acid, or his _couronne des tasses_,
consisting of zinc and silver wires soldered together in pairs, and
placed in glass cups containing dilute acid, to the improved batteries
of Cruikshank, Wilkinson, Babington, Wollaston, and the still more
perfect arrangements of Daniell, Mullins, Shillibeer, and Grove, have
been from time to time recommended for their own peculiar features.
Amongst these several inventions, none will be found more useful than
the _constant_ battery of Daniell for electrotyping, silvering, gilding,
and other purposes, and Grove's battery for all the more brilliant
results, such as the deflagration of the metals or the production of the
electric light. The construction of the Daniell and Grove batteries will
therefore be described. The former consists of a cylindrical vessel made
of copper, in which is suspended or placed (as it is open at the top) a
membranous, brown-paper, canvas, or porous earthenware tube, containing
an amalgamated rod of zinc. To charge this arrangement, a strong
solution of sulphate of copper, with some sulphuric acid, is poured into
the copper vessel, which is provided usually with a sort of [Page 196]
colander at the top to hold crystals of sulphate of copper, and in the
porous tube containing the zinc rod is poured dilute sulphuric acid. A
number of these cylinders of copper, twenty inches high and three inches
and a half in diameter, arranged in wooden frames to the number of
twenty, afford a quantity of electricity sufficient to demonstrate all
the usual phenomena. (Fig. 181.)
[Illustration: Fig. 181. A A. Copper cylindrical vessel with colander to
hold the crystals of sulphate of copper. B. The amalgamated zinc rod
inside the porous cell C C. D. A series of single cells forming a
Daniell's battery.]
Professor Grove's battery consists of a flat glazed earthenware vessel
containing a flat porous cell. An amalgamated zinc plate is placed
outside the porous cell, and a platinum plate inside the latter. The
arrangement is put in action by pouring dilute sulphuric acid round the
zinc and strong nitric acid inside the porous cell. A set of Grove's
nitric acid battery, as manufactured by Messrs. Elliott, Brothers, of
30, Strand, with fifty pairs of sheet platinum, five inches by two
inches and a quarter, and double amalgamated zinc plates, flat porous
cells, and separate earthenware troughs for each pair, and stout
mahogany stand, arranged in ten series of five pairs, will evolve with a
proper voltameter one hundred cubic inches of the mixed gases per minute
from the decomposition of water, and will exhibit a most brilliant
electric light, when arranged as a single series of fifty pairs of
plates. Even thirty pairs exhibit the most splendid effects, whilst
forty may be regarded as the happy medium, giving all the results that
can be desired. (Fig. 182.)
The advantage of employing amalgamated zinc is very prominently
illustrated whilst using any powerful arrangements of either Daniell's
or Grove's batteries, as they will remain for hours quiescent, like a
giant asleep, until the terminal wires of the series are brought in
contact [Page 197] either through the intervention of some fluid under
decomposition or by means of charcoal points. The author had the
pleasure of witnessing at King's College some of the effects of an
enormous battery, prepared by the late Professor Daniell, and consisting
of seventy of his cells.
[Illustration: Fig. 182. A A. Amalgamated zinc plate in flat earthenware
trough. Attached to a binding screw is the platinum plate in porous
cell, C C. D. A series of single cells forming a Grove's battery.]
A continuous arch of flame was produced between two charcoal points,
when distant from each other three quarters of an inch, and the light
and heat were so intense that the professor's face became scorched and
inflamed, as if it had been exposed to a summer heat. The rays collected
by a lens quickly fired paper held in the focus.[C]
[Footnote C: By the light from the same battery photogenic drawings were
taken, and the heating power was so great as to fuse with the utmost
readiness a bar of platinum one-eighth of an inch square; and all the
more infusible metals, such as rhodium, iridium, titanium, &c., were
melted like wax when placed in small cavities in hard graphite and
exposed to the current of electricity.]
_Fourth Experiment._
It is by "chemical action" the electricity is produced, and as action
and reaction are always equal, but contrary, we are not surprised to
find that the electricity from the voltaic battery will in its turn
decompose chemically many compound bodies, of which water is one of the
most interesting examples. It was in the year 1800, and immediately
after Volta's announcement to Sir Joseph Banks of his discovery of the
pile, that Messrs. Nicholson and Carlisle constructed the first pile in
England, consisting of thirty-six half-crowns, with as many discs of
zinc and pasteboard soaked in salt water. These gentlemen, whilst
experimenting with the pile, observed that bubbles of gas escaped from
the platinum wires immersed in water and connected with the extremities
of the Volta's pile, and covering the wires with a glass tube full of
water, on the 2nd of May, 1800, they completed the splendid discovery of
the fact that the Volta's current had the power to decompose water and
other chemical compounds.
[Page 198]
In 1801, Davy had succeeded to a vacant post in the Royal Institution,
and on Oct. 6th, 1807, made his transcendent discovery of potassium with
the aid of the voltaic battery, and from that and other experiments
inferred that the whole crust of the globe was composed of the oxides of
metals. To exhibit the decomposition of water, two platinum plates with
proper connecting wires, passing to small metallic cups full of mercury,
are cemented inside a glass vessel, which is then filled with dilute
sulphuric acid. Just above the platinum plates and over them, stand two
glass tubes also containing the same fluid in contact with the battery.
Two measures of hydrogen are found in one tube, and one of oxygen in the
other. (Fig. 183.)
[Illustration: Fig. 183. A A. A finger glass with two holes drilled to
pass the wires through, which are imbedded in cement up to the platinum
plates. B B. Glass tubes, closed at one end and open at the other, which
are placed over the platinum plates to receive the liberated oxygen and
hydrogen. The scale at the side shows the respective volumes of two of H
to one of O.]
To measure the quantity power of the voltaic battery, an important
instrument invented by Faraday is used. It consists of separate platinum
plates cemented in a wooden stand, and over which a capped air-jar with
a bent pipe is also cemented. This apparatus contains dilute sulphuric
acid of the same strength as that used in the battery under examination,
and by taking the time, the quantity of the mixed oxygen and hydrogen
gases producible by a battery per minute is accurately determined, the
gases of course being collected in a graduated jar. (Fig. 184.)
[Illustration: Fig. 184. A. Gas jar with cap and bent tube passing to
the graduated tube C; the jar is cemented in the same stand which
carries the connecting cups, wires, and platinum plates, which are bent
round each other to improve the action of the voltameter.]
[Page 199]
_Fifth Experiment._
By grouping the simple circles forming a voltaic battery in various
numerical relations, the _quantity_ and _intensity_ effects are
modified.
Thus, if a series of thirty pairs of Grove's battery are all connected
together in consecutive order, the smallest _quantity_ and the largest
_intensity_ effect is produced.
If changed to two groups of fifteen each, the quantity is doubled--that
is to say, it will produce double the quantity of the mixed gases from
the voltameter with half the intensity.
If arranged in three groups of ten each, it is trebled with a
proportional loss of intensity, until the grouping reaches six series of
five each, when a maximum supply of the mixed gases is obtained from the
voltameter.
In arranging the groups, all the zinc ends of each series are connected,
and all the platinum ends are likewise joined by proper wires.
_Sixth Experiment._
A plate-glass trough, containing a few grains of iodide of potassium
dissolved in water with some starch, is quickly decomposed into its
elements by placing in two platinum plates and connecting them with the
wires of the voltaic battery. If the glass trough is divided in the
centre with a bit of cardboard, the purple colour of the iodine and
starch is shown very beautifully on one side, but not on the other, as
iodine is liberated at one pole and the alkali at the other. (Fig. 185.)
[Illustration: Fig. 185. A A. A glass trough containing the salt
dissolved in water, and divided temporarily with a bit of cardboard, B.
C C are the two platinum plates connected with the battery, and the
shaded side is supposed to represent the liberation of the iodine.]
_Seventh Experiment._
Some solution of common salt coloured with sulphate of indigo and placed
in the trough is decomposed into chlorine, which bleaches one side of
the indigo solution, and the alkali liberated on the other does not
affect it.
_Eighth Experiment._
Some nitrate of potash dissolved in water and coloured with litmus
placed in the glass trough, changes red on one side of the cardboard by
the liberation of acid, and is not affected on the other.
In these experiments the oxygen, iodine, chlorine, and nitric acid are
liberated at the electro-positive pole, and are hence termed
electro-negative bodies, whilst hydrogen and the alkalies are set free
at the electro-negative pole, and are therefore called electro-positive
bodies. [Page 200] Faraday has modified these terms, and calls the two
classes "_anions_" and "_cathions_," and the two poles "anodes" and
"cathodes."
Anode, from [Greek: _ana_], up, and [Greek: _hodos_], a way: the way which
the sun rises. Anions, from [Greek: _ana_], up, and [Greek: _eimi_], to go:
that which goes up; a substance which passes to the anode during the
passage of a current of electricity. Cathode, from [Greek: _kata_], down,
and [Greek: _hodos_], a way: the way which the sun sets. Cathion, from
[Greek: _kata_], down, and [Greek: _eimi_], to go: that which goes down; a
substance which passes to the cathode during the passage of electricity
from the anode to the cathode.
_Ninth Experiment._
In the process of the electrotype is presented a valuable application of
the chemical power of the voltaic circle or battery, and it may be
conducted either as a single cell operation or by distinct batteries. In
the former case the most simple arrangement will suffice; the only
articles necessary are--a large mug or tumbler; some brown paper and a
ruler; a bit of amalgamated zinc, four inches long and half an inch
wide; a short length of copper wire; some black lead, blue vitriol, and
oil of vitriol.
The mould from which the electrotype is to be taken can be made of
common sealing wax, plaster of Paris, white wax, gutta percha, or
fusible alloy. Supposing the first to be selected--viz., a common seal,
it is first thoroughly black-leaded,[D] then one end of the copper wire
is bent round the top of the amalgamated zinc, and the other is gently
warmed and melted into the side of the seal, leaving a small portion
uncovered by the wax, which is then well black-leaded. A few ounces of
blue vitriol are dissolved in boiling water, and when cold the solution
is poured into the tumbler, and the porous cell to contain the mixture
of eight parts water to one of sulphuric acid is made by rolling the
brown paper three or four times round the ruler and closing the end, and
fixing the side with a little sealing wax. The porous cell of brown
paper is now filled with the dilute acid, and placed in the tumbler
containing the solution of blue vitriol, the amalgamated zinc being
arranged in the paper cell, and the attached seal in the copper
solution; in about twelve hours a good deposit of copper is produced,
and a perfect cast in metal of the seal obtained. (Fig. 186.)
[Footnote D: The application of plumbago, or black lead, for electrotype
purposes, was first made by the late lamented Mr. Robert Murray.]
[Illustration: Fig. 186. A A. The tumbler containing the solution of
sulphate of copper. B B. The brown paper cell containing the dilute
sulphuric acid, inside which is the amalgamated zinc with wire attached
to the seal D.]
[Page 201]
Messrs. Elliott provide every kind of convenient vessel for the purpose,
and in the picture below it will be noticed that the single cell
apparatus, though not so economical as the simple tumbler arrangement
already described, is perhaps more convenient for electrotyping. (Fig.
187.)
[Illustration: Fig. 187. A. Single cell apparatus with proper vessel,
porous tube, and binding screws. B. A large trough divided by a
diaphragm of biscuit-ware or very thin porous wood.]
_Tenth Experiment._
[Illustration: Fig. 188. A. A single cell, Daniell's, attached to B, the
trough containing the mould and the plate of copper. Below is a Smee's
battery ready to be attached to a larger trough for the purpose of
electrotyping a great number of moulds at the same time.]
A single cell apparatus is only adapted to produce small electrotypes,
but when larger ones are required, a separate battery of three or four
[Page 202] Daniell's or Smee's cells is required; and it is usual to
place the mould to be copied in a separate wooden trough, attaching it
to the cathode wire, whilst a copper plate is connected with the anode,
so that as the solution of sulphate of copper undergoes decomposition by
the passage of the electricity, it is kept almost in a normal state, in
consequence of the oxygen of the water and the acid passing to the
copper plate, which they attack and dissolve as fast as the oxide of
copper and hydrogen are liberated at the cathode, where the latter
deoxidizes the oxide of copper, and by a secondary action deposits
metallic copper; the object being to dissolve fresh metal as the copper
is deposited on the mould. (Fig. 188.)
_Eleventh Experiment._
To silver electrotypes or other brass and copper articles, the first
attention must be paid to the cleanness of them; and when an electrotype
is just removed from the copper solution, and washed in clean water, it
is at once ready to receive the coating of silver; otherwise, if it has
been handled, or is slightly greasy, it should be first boiled in a
solution of common washing soda, and then the oxide removed by passing
it rapidly in and out of some "Dipping Acid," which is prepared by
mixing together equal parts of oil of vitriol and nitric acid; when
removed from the "Dipping Acid," it must be well washed in water, and
may remain under the surface of the water until the silvering solution
is ready. A silver solution may be prepared by dissolving a sixpence in
some nitric acid contained in a flask; it is then poured into a solution
of common salt, which precipitates the chloride of silver, and leaves
the copper in solution--the latter is poured off when the chloride has
subsided, and after being well washed in some boiling water, is
dissolved in a solution of cyanide of potassium. If a clean electrotype
is plunged into this solution, it is immediately covered with a very
thin coating of silver, which of course would soon wear off, and in
order to increase the thickness of the silver deposit, a single cell
arrangement may be constructed of a large gallipot containing a wide
porous cell and a circle of amalgamated zinc around it; the arrangement
is set in action by pouring a solution of salt (or, still better, sal
ammoniac) into and around the porous vessel, and the silvering solution
into the latter; a connecting wire passes from the zinc, and the article
being attached to it, is now plunged into the porous cell, when a
current of electricity slowly passes and deposits the silver on the
copper article. (Fig. 189.)
[Illustration: Fig. 189. The gallipot containing the solution of sal
ammoniac, with the circular amalgamated zinc with wire and binding screw
to which the medal is attached, and contained in the porous vessel
holding the silvering solution and medal.]
[Page 203]
_Twelfth Experiment._
Separate batteries and large troughs containing a solution of cyanide of
silver in cyanide of potassium are used on a grand scale in the
electro-plating establishment of Messrs. Elkington of Birmingham, where
the finest specimens of the art are to be obtained; a plate of silver
being attached to the anode to supply the loss of silver in these
troughs.
_Thirteenth Experiment._
The art of gilding by the agency of electricity is quite as simple as
the processes already described, although greater care is necessary to
avoid any loss of the precious metal. A small bit of gold is dissolved
in a mixture of three parts muriatic acid and one of nitric acid, which
forms the chloride of gold. This is then digested with an excess of
calcined magnesia, and the gold is precipitated as an oxide of the
metal; the latter is collected and washed, and then boiled in strong
nitric acid to remove the magnesia clinging to it, and being again
thoroughly washed with water, is dissolved in a solution of cyanide of
potassium, forming a solution of cyanide of gold and potassium, which
may be placed in the porous cell of the single cell arrangement already
described in the Eleventh Experiment.
_Fourteenth Experiment._
The safest and surest mode of making a gilding solution is to dissolve
some cyanide of potassium in water in a gallipot, and having placed a
porous vessel therein containing the same solution, put a plate of
copper into the porous cell, and some thin foil of pure gold into the
gallipot; connect the gold with the anode of a single cell of Daniell,
and the copper in the porous cell with the cathode, and in a few hours
sufficient gold will be dissolved for the purpose of gilding.
It is usually recommended to warm the gilding solution till it reaches a
temperature of about 150° Fahr., and a very moderate battery power is
employed in Electro Gilding. Indeed the same arrangement, shown in the
Eleventh Experiment, Fig. 189, will also answer for the gilding
solution. After being gilt, the articles may be rubbed with a little
tripoli, or burnished (with taste) by the handle of a key.
_Fifteenth Experiment._
Passing on to the more brilliant results obtainable from a powerful
voltaic battery (of at least thirty pairs of Grove), the beautiful
incandescence of platinum wire may first be noticed. If a wire of this
metal is stretched between the brass standards of two ring stands, the
length must be proportioned to the power of the battery; the adjustment
can be made very conveniently by twisting the platinum wire on one ring
stand, and then leaving the other end loose, the second ring stand may
be brought nearer and nearer to the first, until the desired intensity
of [Page 204] light from the incandescent wire is obtained. (Fig. 190.)
If the wire is contained in a glass tube the cooling effect of currents
of air is prevented, and a much greater length of wire can be made hot.
[Illustration: Fig. 190. A A. Two ring stands with the battery wires B B
(which should be a convenient length) attached. C. Platinum wire, fixed
end. D. The other end held in one hand and shortened as the stand is
moved by the other hand.]
_Sixteenth Experiment._
With the same arrangement, a chain composed of alternate links of silver
and platinum wire presents a very pretty effect, every alternate link of
platinum being incandescent, whilst the silver, from its excellent
conducting power, remains comparatively cool.
_Seventeenth Experiment._
Fireworks or gunpowder, arranged in proper cases, are fired at a great
distance from the voltaic battery by heating a thin iron or platinum
wire contained within them by the passage of the electricity; and
submarine and other explosions of gunpowder by the same agency have
become a common engineering operation. (Fig. 191.)
[Illustration: Fig. 191. A. A Gerb firework with two holes punctured,
through which the bit of iron wire passes, and is wound round the
battery wires tied to the outside of the case. C. A gut bladder
containing the thin wire and powder for a miniature submarine
explosion.]
During the operation of blasting the hard marl rocks in the River Severn
by Mr. Edwards, C.E., a number of holes were made side by side in the
bed of the river, and cartridges formed of strong duck or canvas,
tapered at the bottom, were filled with charges of powder from two to
four pounds, according to the depth of the marl; thus, two pounds for
four feet, three pounds for four feet six inches, and four pounds for
five feet. Into the bag were conveyed the wires of the voltaic battery,
or Bickford's fuse, and being then coated with pitch and tallow, and
finally greased all over and dusted with whitening, they rarely failed,
and were all fired simultaneously under water. The pitch and tallow
first, and afterwards the simple tallow, effectually excluded the water
from the gunpowder contained in the canvas bag.
[Page 205]
_Eighteenth Experiment._
The burning of various metals by the battery is displayed with great
effect by De la Rue's discharger, as also the incandescence of the
charcoal points producing the _electric light_. The illuminating power
derived from a forty-cell Grove's battery of the ordinary size is about
equal to the light of 500 candles.
[Illustration: Fig. 192. De la Rue discharger, containing a series of
six pairs of different substances, such as charcoal, iron, lead, zinc,
copper, antimony, in six pair of crayon holders, and turning on a
centre, so as to be changed at pleasure.]
Fizeau and Foucault have made a careful comparison of the light obtained
from 92 carbon couples as arranged in a Bunsen's battery, and of the
oxy-hydrogen, or Drummond Light, as compared with that of the sun, and
they state that "On a clear August day, with the sun two hours high, the
electric light (assuming the sun as unity) bore to it the ratio of one
to two and a half--_i.e._, the sun was two and a half times more
powerful, while the Drummond Light was only 1/146th that of the sun."
Bunsen found the light from 48 carbons equal to 572 candles. In Bunsen's
battery carbon is substituted for the platinum in Grove's arrangement;
and simultaneously with Bunsen, Cooper (in England) had applied charcoal
for the same purpose.
At night the giant ship (Polyphemus like) is to have an electric light
at the mast-head whilst steaming across the Atlantic.
[Illustration: Fig. 193. _Great Eastern_, with electric light.]
[Page 206]