GALVANISM. 
605 
as gold and silver, silver and copper, copper 
and iron, tin and lead. But what is more, 
tire effect will be fully produced on this so 
little prepared frog, when you immerse in 
one of the two glasses the end of a bow 
merely of tin or zinc, and into the other glass 
the other end of this bow which has been 
rubbed over with a little alkali. You may 
perform the experiment still better with an 
iron bow, one end of which has been covered 
with a drop or thin coating of nitrous acid; 
and beyond all expectation, when you take 
a, silver bow, having a little sulphuret of pot- 
ass adhering to its extremity.” 
When a single powerful galvanic combi- 
nation of the second order is applied with 
one end-to the tongue, and with the other 
fluid end to some other sensible part of the 
body, an acid taste is perceived on the tongue, 
which taste, by continuing the contact, be- 
comes less distinct, and is even changed into 
an alkalin,e taste. 
If a tin bason is filled with soap-suds, lime- 
water, or a strong ley, which is still better ; 
and if you then lay hold of the bason with 
both your hands, having first moistened them 
with pure water, and apply tire tip of your 
tongue to the fluid in the bason, you will 
immediately be sensible of an acid taste upon 
your tongue, which is in contact with the 
alkaline liquor. This taste is very percep- 
tible, and, for the moment, pretty strong; 
but it is changed afterwards into a different 
one, less acid, but more saline and pungent, 
until at last it becomes alkaline and sharp, 
in proportion as the fluid acts more upon the 
tongue. 
Mr. Davy observes, that if zinc and silver 
are made to form a circle with distilled water, 
holding in solution air, for many w'eeks, a 
considerable oxidation of the zinc is perceived, 
without the perceptible evolution of gas ; 
and the water, at its point of contact with 
the silver, becomes possessed of the power of 
tinging green, red cabbage juice, and of ren- 
dering turbid, solution of muriate of magnesia. 
The chemical action of bodies upon each 
other is increased by the galvanic arrange- 
ment so much, that some of them are by that 
means enabled to act upon bodies that other- 
wise they would haye no action upon. Fig. 
20. represents a glass tube about four inches 
long. Two corks are thrust into its apertures 
A and B. An oblong piece of zinc, CD, is 
fixed into one of the corks, and is made to 
project within and without the tube. EFG 
is a silver wire, which, being fixed into the 
other cork, projects with the extremity E 
within the tube ; and its other extremity is 
bent so as to come near the projecting part 
of the zinc C. 
Remove one of those corks, and fill the 
tube with water, in which you must mix a 
drop or two of muriatic acid; then replace 
the cork, and you will find that the zinc is 
acted upon by the diluted acid, is oxidated 
by it, and bubbles of gas are evolved from 
it ; but the silver wire E remains untouch- 
ed, and no gas whatever is evolved from 
it. Now, if you bend the silver wire EG, so 
that its end G may touch the zinc at C, then 
the galvanic circle of silver, zinc, and di- 
luted acid is completed, in consequence of 
which the diluted acid is enabled to act 
stronger upon the zinc D, which is mani- 
fested by the more copious evolution of gas, 
and is besides enabled to act upon the silver 
2 
wire; for now you will observe the evolution 
of gas from the silver E also. Break the 
contact between G and C, and the silver E 
will cease to yield gas. Form it again, and 
gas will again proceed from the silver. 
Instead of silver, zinc, and diluted muriatic 
acid, you may in the same, manner use gold, 
tin, and diluted nitric acid ; and by com- 
pleting the circle, the acid will be enabled to 
act upon the gold. 
It has been observed, that whenever an 
oxidating influence is exerted at one of the 
places of contact of the perfect and imper- 
fect conductors, a deoxidating action appears 
to be produced at the other place. Thus 
when iron, which oxidates rapidly when 
forming a circle with silver and common 
water, is arranged with zinc and common 
water, it remains perfectly unaltered, whilst 
the zinc is rapidly acted upon. 
Such are the facts which have as yet been 
discovered with respect to the power of sin- 
gle galvanic circles. They form a remark- 
able addition to the science of electricity, 
and open a vast field of speculation and ex- 
perimental investigation; yet we are unable 
to form a theory sufficient to account for the 
original cause, or for the action of that very 
remarkable power ; and we can only wait 
with patience for the probable elucidation, 
which may be afforded by farther discove- 
ries. 
If the effects of single circles are very re- 
markable, the collected power of several sin- 
gle circles, or of the battery, cannot fail of 
surprising the least reflecting mind. 
The battery not only convulses the pre- 
pared limbs of a frog, or produces the ap- 
pearance of a flash of light before the human 
eye ; but it shews all the phenomena of elec- 
tricity in a very considerable degree. It 
gives the shock; it affects the electrometer ; 
shews a luminous spark, accompanied with 
an audible report; it burns metallic and 
other combustible bodies; and continues in 
action for a very long time, viz. until the 
chemical action between the component 
parts of the battery is quite exhausted. The 
following paragraphs contain a more parti- 
cular, yet concise, enumeration of those won- 
derful effects. 
When the galvanic battery of the first or- 
der consists of 20 repetitions of simple com- 
binations, if you touch with one hand one 
extremity of the battery, as at b, in any one 
of the above-described batteries (see figs. 
17, 18, 19.), and apply your other hand to 
the other extremity of the battery, as at a, 
you will feel a very slight shock, like that 
which is communicated by a Leyden phial 
weakly charged, and it will be hardly felt 
beyond the fingers, or at most the wrists. 
This shock is felt as often as you renew’ the 
contact. If you continue the hands in con- 
tact with the extremities b and a , you will 
perceive a slight but continued irritation ; 
and, when the hand or other part of the 
body, which touches the extremity of the 
battery, is excoriated or wounded, this sen- 
sation is disagreeable and rather painful. 
The dry skin of the human body is seldom 
capable of conducting this shock; therefore 
the touching fingers should be well moisten- 
ed with water. It will be belter to immerse 
a wire that proceeds from one extremity of 
the battery, in a bason of water, wherein you 
may plunge one of your hands ; then grasp- 
ing with your other hand well moistened a 
large piece of metal, for instance a large 
silver spoon, touch the other end of the bat- 
tery with it, and the shock will be felt more 
distinctly. By this means the shock has been 
felt when the battery consisted of less than 
20 repetitions. 
Instead of one person, several persons may 
join hands (which must be well moi tened 
with water), and on completing the circuit, 
they will all feel the shock at the same in- 
stant. But the strength of the shock is much 
diminished by its passing through the several 
persons, or, in general, by passing through 
less perfect conductors. 
r j he shock from a battery consisting of 50 
or 60 repetitions of the most active com- 
binations of the first order may be felt as far 
as the elbows; and the combined force of five 
or six such batteries will give a shock per- 
haps much stronger than most men would be 
willing to receive. The prepared limbs of a 
frog or other animal are violently convulsed, 
but soon exhausted of their irritability by the 
action of a galvanic battery. 
This shock is similar to that of a large 
common electrical battery weakly charged, 
and not to that of a small Leyden phial fully 
charged. The difference consists in this, viz. 
that the latter contains a small quantity of 
electric fluid highly condensed; hence" its- 
discharge will force its way through perhaps 
an inch of air; whereas the former contains 
a vast quantity of electricity but little con- 
densed; hence its spark, viz. its course thro’ 
the air, is so very short/that the fingers must 
be brought almost into perfect contact in or- 
der to receive the shock; and such is the 
case with the galvanic battery: for the 
shock from a very powerful battery of this 
sort will hardly ever force its way through 
the air, when the extremities of the circle of 
communication are more than a fortieth of an 
inch distant, even when those extremities 
consist of perfect conductors. In this case a 
small but very vivid spark is seen at that ex- 
tremity, accompanied with an audible but not 
strong report. There is no perceptible dif- 
ference of appearance between the spark of 
the positive and that of the negative end of 
the battery. 
If a wire proceeding from one extremity 
of a pretty strong battery is made to commu- 
nicate with the inside coating, and a wire, 
which proceeds from the other extremity of 
the battery, is made to communicate with 
the outside coating of a common large jar 
or electrical battery ; the latter will be- 
come weakly, but almost instantaneously, 
charged, in the same manner as if it had been 
charged by a few turns of a common electri- 
cal machine ; and with that charge you may 
either give the shock or affect on electrome- 
ter, &c. 
In short, every tiling conspires to prove 
that a galvanic battery produces a vast 
quantity of electric fluid, but which is little 
condensed; and indeed it would be impos- 
sible to suppose that the electric fluid could 
proceed in a very condensed state from an 
arrangement of bodies, which, whether more 
or less, are however all good conductors of 
electricity; for if the fluid was much con- 
densed at one extremity of the battery, and 
much rarefied at the other extremity, the 
condensation would soon be made tlirough 
the pile itself. Indeed, it is difficult to coia- 
