‘82 
‘History. 
—— 
-on the source of the oxygen, and ,he found that, by co- 
vering the water with a stratum of oil, and thus exclu- 
ding the atmosphere, the — of oxidation was re- 
tarded. This fact. he adduces as a powerful argument 
in favour of the chemical hypothesis. He concludes, 
that the oxygen in these cases cannot be derived from 
the water, because were the water decomposed there 
would be a liberation of hydrogen. The effect that is 
produced on the senses of vision and of taste, he attri- 
butes to the formation of new chemical compounds, 
-which act in a peculiar manner upon the organs; an 
‘ opinion which may be true, to a certain extent, so far 
‘Discovery 
of the pile 
by Volta, 
1800. 
‘Description. 
PLatTEe 
CCLXIU. 
Fig. 1. 
Hffects. 
as respects the tongue, but it is not easy to conceive 
how it could cause the flash of light which is excited in 
the eye by the contact of the metals. See Journal de 
Physique, xlix. 348, 
abroni’s paper did not appear to excite much atten- 
tion at the time when it was published, as it directly op- 
posed the current of popular opinion. But many of the 
statements have been since verified by succeeding phi- 
losophers ; and when we consider that it was writ- 
ten before the discovery of the pile, it must be regarded 
as displaying much sagacity and nice observation. 
In this state, the science of galvanism remained un- 
til the year 1800. It was generally admitted, that the 
immediate agent in producing the phenomena was the 
electric fluid, and that the actions exhibited by the ani- 
mal body depended merely upon its extreme sensibili- 
ty to small quantities of this fluid. The experiments 
principally consisted in different combinations of con- 
ducting substances with parts of the animal body, com- 
posing what was called the galvanic are or circle. The 
chemical effects had been little attended to, except by 
Fabroni; and his remarks, although truly ingenious, 
‘must be regarded rather as the first glance of a series 
of important facts, than as constituting their complete 
developement. 
Sect. II. Experiments from the Discovery of the Pile to 
the Decomposition of the Alkales. 
- Thesecond period of the history of galvanism commen- 
ces with the important discovery made by Volta, of the 
instrument which has been called the galvanic or vol- 
taic pile, Volta, as we have seen above, adopted the 
idea, that the action excited by the two metals, depend- 
ed upon an alteration in their respective states of elec- 
tricity, or in a destruction of its equilibrium. The ef- 
fect produced by one pair of plates could only be com- 
paratively small; but he supposed that by interposing 
a conductor between several pairs of plates, it might be 
multiplied and concentrated in an indefinite degree. 
He accordingly provided a number of silver coins, and 
pieces of zinc of similar dimensions ; these were dispo- 
sed in pairs, and between each pair was placed a piece 
of card soaked in water ; and thus a pile or column was 
formed, in which the three substances silver, zinc, and 
water, existed in regular rotation. The effect of the 
combination fully justified the expectations of the dis- 
coverer. All the phenomena that had been excited by 
a single pair of metals were far exceeded by those of 
the pile, while by touching the two ends of it at the 
same time, it was found that a distinct shock was felt in 
the.arms. This fully established the opinion that had 
been formed, and was generally ado Hy of the identi- 
ty of electricity and galvanism ; although there were 
still some circumstances connected .with the latter, 
& 
GALVANISM. 
which appeared not to be completely analogous to the Hist 
usual operations of the electric fluid. ee . 
He found, that 40 pairs of the metallic discs, with Galva 
the proper number of pieces of moistened card interpo- shock. 
sed, were sufficient to produce a shock, which was very i 
distinctly felt in the hands and arms, and that by in- 
creasing the number of pairs, the power of the pile was 
proportionally augmented. In order to produce the 
full effect, it was found necessary that two pieces of me- 
tal, either composing the extremities of the instrument, 
or in contact with them, should be firmly grasped by 
the two hands; and the shock might, in this case, be 
repeated for any number of times, as long as the paste- 
board between the two metals remained suificiently 
moist. Volta conceived, that the newly invented ap-« 
paratus was analogous in its action to the electrical or- 
gan of the torpedo. The experiments that he perform. 
ed with it, were almost exclusively confined to the ani- 
mal body ; and he appears to have entertained no idea 
of the important use which would afterwards be made 
of the pile, as an instrument of chemical analysis. It is 
indeed a little remarkable, that after making so curi- 
ous a discovery, he should have rested there, and not’ 
have proceeded with the farther prosecution of the sub- 
ject. It would be unjust not to acknowledge, in the 
warmest terms, the obligation under which the scienti- 
fic world was laid by the discovery of Volta; but, at 
the same time, it must be admitted, on the other hand; 
that the benefit of the discovery has been obtained by 
others. An account of the pile was written by Volta, 
in the form of two letters to Sir Joseph Banks, which 
were published in the Philosophical Transactions o 
London for the year 1800. 
No sooner was the discovery of the galvanic pile 
announced, than the English experimentalists } 
their operations with it, and almost at the first trial of 
its effects, made some important and interesting observa« 
tions. Sir Joseph Banks, on the receipt of the letters, 
having communicated the information to his scientific 
friends, a pile was formed by Messrs Nicholson and Nichol 
Carlisle, with which they began to repeat the experi- and C 
ments of Volta. They arranged the substances in the lisle 
order of silver, zine, fluid; silver, zinc, fluid, &c.: an ar- 
rangement which it is necessary to attend to, in speak- 
ing of what have been called the silver and zine ends 
of the apparatus. Volta, it appears, had satisfied him- 
self that the action of the pile was electrical, because 
it produced the shock ; but Messrs Nicholson and Car- & 
lisle applied to, it the instrument called the revolving Disc 
doubler, (See ELectricity, p. 526), and by this means “"* ~ 
decidedly proved it to be the case: They found, that 
the silver end was in the minus, and the zinc end in 
the plus state of electricity. tly 
In the course of the experiments, a part of the cir- pec 
cuit between the upper and lower ends of the pile was tion 
formed by water ; and it was observed, that there was ter in 
a disengagement of gas, at the where the wire ™ 
came in contact with the fluid. is gas was thought “ 
to have the odour of h en ; and it led them to no- 
tice, with more attention, the effect produced by cau- 
sing the electricity to pass through a tube of water, into 
the two ends of which wires were inserted, which com- 
municated with the extremities of the pile. We shall 
relate this very important experiment in Mr Nichol- 
son’s own words. ‘ On the 2d of May we inserted a 
brass-wire through each of two cocks, inserted in a 
glass tube of half an inch internal diameter. The tube - 
was filled with new river water, and the distance be- 
