806 
GALVANISM. 
prehend how this compensation does not take 
place in all cases. 
Having mentioned above, that the charge 
of a battery may be communicated to a com- 
mon electrical battery, it is almost ‘super- 
fluous to observe, that the same may be com- 
municated to a condenser, or to a multiplier, 
and from it to the electrometer. If the bat- 
tery consists of 200 repetitions, the electro- 
meter will be affected by the simple contact. 
The spark, or the discharge of a galvanic 
battery^ when sent through thin inflammable 
bodies that are in contact with common or 
oxygen air, sets them on fire, and consumes 
them with wonderful activity, It fires gun- 
powder, hydrogen gas, phosphorus, and other 
combustibles; it renders red-hot, fuses, and 
consumes very slender metallic wires and 
metallic leaves. The mode of applying the 
power of the battery for such purposes is 
shewn in fig. 21, where AB represents a pow- 
erful galvanic battery; ACDF is a wire 
which communicates with the last plate of tin? 
battery at A; BKIHG is another wire which 
communicates with the last plate at B. DL, 
III, are two glass tubes, through which those 
w ires pass, and into which they are fastened 
sufficiently steady. Those tubes serve to 
move the wires by ; for if the operator ap- 
plies his fingers to the middlemost parts of 
those tubes, he may move the wires where- 
•ever he pleases, without the fear of receiving 
a shock. If the two extremities F,G, are 
brought sufficiently near to each other, the 
spark will be seen between them. It is be- 
tween those extremities that the combustible 
substances, or metallic leaf, &c. is to be 
placed, in order to be fired or consumed. 
This figure represents the situation of the 
wires in the act of inflaming gunpowder. A 
battery consisting of 200 pairs of metallic 
platgs (viz. copper and zinc, each five inches 
S(juare) melted .23 inches of very fine iron 
wire. A platina wire about inch in dia- 
meter, was melted into a globule. Fig. 24 
is the representation of a compound battery 
■of the same kind, fastened together with iron 
cramps a, b, e. 
Under the exhausted receiver of the air- 
pump, the galvanic battery acts less power- 
fully than in the open air; but in oxygen air 
it acts with increased power. 
The flash of light which appears before 
the eye of the experimenter, when the eye 
itself, or some other part not very remote 
from it, is put in the circuit of a galvanic 
combination, does not appear much greater 
when a battery is employed than when two 
plates are applied in the manner which has 
been already mentioned ; but when the bat- 
tery is used, the sensation of a flash may be 
produced in various ways. If one hand or 
both be placed in perfect contact with one 
extremity of the battery, and almost any 
part of the face brought into contact with the 
other extremity of the battery, the flash will 
appear very distinctly, the experimenter being 
in the dark, or keeping his eyes shut. This 
flash appears very strong, when a wire which 
proceeds from one extremity of the battery 
is held between the teeth, and rests upon the 
tongue, whilst the other wire is held in the 
hand. In this case the lips and the tongue 
are convulsed, the flash appears before the 
■eyes, and a very pungent taste is perceived 
in the mouth. 
If any part of the human body, forming 
part of the circuit of a galvanic battery, is 
kept sometime in that situation, the irritation 
or numbness is more or less distinct, and 
more or less painful, according to the sensi- 
bility of the parts concerned. 'This applica- 
tion is likely to prove most useful as a reme- 
dy in various disorders. It is said that it has 
already proved beneficial in deafnesses and 
in rheumatisms. It highly deserves to be 
tried by medical persons. See fig. 25. 
The ’most extraordinary phenomena of a 
galvanic battery are the chemical ellects 
and the modifications which are produced 
by it upon the bodies concerned, or upon 
such as are placed in the circuit. We shall 
first describe the simplest mode of exhibiting 
the principal of those phenomena, namely, 
the evolution of gas from water, from which 
the mode of conducting similar experiments 
is easily derived; then shall transcribe the 
various particulars which relate to those che- 
mical effects, from the Journals of the British 
Royal Institution, where they are concisely 
expressed. 
AB, fig. 22, exhibits a glass tube full of 
distilled water, and having a cork at each 
extremity. EF is a brass or copper wire, 
which proceeds from one extremity of a gal- 
vanic battery, and, passing through the cork 
A, projects within the tube. I1G is a simi- 
lar wire, which proceeds from the other ex- 
tremity of the battery, and comes with its ex- 
tremity G within the distance of about an inch 
or two from the wire F. 
In this situation of things, you will find 
that bubbles of gas proceed in a constant 
stream from the surface G of the wire which 
proceeds from the negative end of the bat- 
tery; these bubbles of gas, ascending to the 
upper part of the tube, accumulate by de- 
grees. This gas is the hydrogen, and may 
be inflamed. At the same time the other 
wire F deposits a stream of oxide in the form 
of a stream or cloud, which gradually accu- 
mulates in a greenish form in the water, or 
on the sides of the tube, and is a perfect ox- 
ide of the brass. The wire F is readily dis- 
coloured and corroded. If you interrupt 
the circuit, the production of gas and of ox- 
ide ceases immediately. Complete the cir- 
cuit, and the production of gas re-appears, 
This production of gas may be observed 
even where the battery consists of not more 
than six or eight repetitions of silver, zinc, 
and water. In short, if the power of the 
battery is sufficient to oxidate one of the 
w ires of communication, the other wire will 
afford hydrogen gas ; both extremities of the 
wires being in water. 
In this experiment it seems that the hydro- 
gen is separated from the water, and is con- 
verted into a gaseous state by the wire con- 
nected with the negative extremity of the 
battery ; whilst the oxygen unites with and 
oxidates the wire connected with the positive 
end of the battery. If you connect the posi- 
tive end of the battery with the lower wire of 
the tube, and the negative with the upper, 
then the hydrogen proceeds from the upper 
wire, and the lower wire is oxidated. 
If two wires of gold or platinum are used, 
which are not oxidable; then the stream of 
gas issues from each, the water is diminished, 
and the collected gas is found to be a mix- 
ture of hydrogen and oxygen, it explodes 
violently. 
Those two different elastic fluids may be 
obtained separate from each other by the fol- 
lowing means: Let the extremities of the 
two wires winch proceed from the battery, 
be immersed in water, at the distance of 
about an inch from each other, and place 
over each of them a small glass vessel in- 
verted and full of water, as in fig. 23. 
Dr. Priestley, however, who denies the 
convertibility of water into hydrogen and 
oxygen air, thinks that the elastic fluid 
in these experiments originates from the air 
which is contained in the water ; “ since,’* 
says he, “ if by means of oil upon the water, 
or a vacuum, access to the atmosphere is cut 
off, the whole production of gas ceases.” Nor 
is any air produced when the water has been 
exhausted of it. 
In the above described apparatus, a little 
hole must be made in the lower cork B, for 
the purpose of giving exit to the water in 
proportion as the gas is formed. 
In all batteries of the first order, when the 
connexion is completed, changes take place 
which denote the evolution of influences ca- 
pable of producing from common water oxy- 
gen and hydrogen, acid and alkali, in diffe- 
rent parts of the body. 
Thus in the battery with a series of zinc 
plates, silver wires, and common water, oxide 
of zinc is formed on all the plates of zinc, 
whilst hydrogen is produced from the silver 
wires; and it the water in contact with them 
is tinged with red cabbage juice, it becomes 
green. 
And in the battery with silver, gold, and 
weak nitric acid, the silver is dissolved, whilst 
the acid becomes green, and slowly evolves 
gas at its points of contact with the gold. 
The chemical agencies exerted in the 
compound batteries of the first order can be 
best observed by the substitution of single 
metallic wires for some of the plates ; for, in 
this case, the changes taking place in the sc- 
ries with wires, will be exactly analogous to 
those produced in the series, with plates ; sil- 
ver, and all the more oxidable metals, oxi- 
dating in water, in the usual place, and gold 
and platina evolving oxygen gas. 
Thus, when into two small glass tubes, 
connected by a moist animal substance, and 
filled with distilled water, two gold wires are 
introduced from a large battery in the pro- 
per order, oxygen is produced in one quan- 
tity of water, and hydrogen in the other, 
nearly in the proportions in which they are 
required to form water by combustion : and 
if the process is continued for some time, the 
apparatus being exposed to the atmosphere, 
the water, in the oxygen-giving tube, will be- 
come impregnated with an acid (apparently 
the nitrous) ; whilst that in the hydrogen- 
giving tube will be found to hold in solution 
an alkali, which, in certain cases, has appear- 
ed to be fixed. 
From some experiments it would appear 
probable, that the quantities of hydrogen, 
produced in series, are small, and the quan- 
tities of alkali great, in proportion as the sur- 
faces of contact of the least oxidable metals 
with the water are more extended. 
All the oxygenated solutions of bodies 
possessing less affinity,, for oxygen than na- 
scent hydrogen, are decomposed when ex- 
posed to the action of the metal occupying 
the place of the least oxidable part, of the 
series in the compound circle. 
Thus, sulphur may be produced from sul- 
phuric add; and copper and other metals 
precipitated in the metallic form from their 
solvents. 
