444 
ELECTRICITY. 
their changes are trivial when compared to thofe of a 
combination of filver or copper with zinc. Tire latter of 
thefe metals oxydates fo readily, as to give out its com¬ 
bined eleftricity with greater facility than any other me¬ 
tal. In an extenfive battery, (liver plates would become 
expenfive; and, as copper only lofes one-fifth of the 
power, or, in other words, as eighty plates of filver and' 
zinc are equal in power to about 100 plates of copper and 
zinc, the difference is amply compenfated by the laving. 
Soon after the important communication of Volta on the 
felf-charging power of his moto-eleftric apparatus, the'ce¬ 
lebrated French chemifls, Fourcroy, Vauquelin, and The- 
nard, fuppoling, a priori , that the effefts would be in 
proportion to the metallic furfaces expofed, conftrufted 
plates of zinc and copper about nine or ten inches in dia¬ 
meter. The plates which had been previouily employ¬ 
ed, rarely exceeded the (ize of half-a-crown. As one of 
thefe large plates expofed a furface about forty times 
greater than that of the fmall plates, it was expected 
that tire eilefts produced from ten fuch plates would 
have equalled the efte£ls of four hundred of the fmaller 
ones ; but, to their great furprife, they found that the 
fenfations were the fame, from an equal number of each ; 
and that the extent of furface did not make any fenfible 
difference. The power appeared to be regulated by the 
number of the plates, and not to be influenced by the 
furfaces expofed. They were equally furprifed, when 
they found that a feries of ten large plates, the effefts of 
which on the human frame could with difficulty be per¬ 
ceived, pofieffed a power of burning finely-drawn wires, 
and of deflagrating laminated metals, fuch as gold and 
filver leaves, equal to that of four hundred fmaller plates, 
the fum of whole furfaces was equal to the furface of the 
larger ones. Thefe curious fafts led to an important de- 
duftion, that “ the influence of the galvanic fluid on the 
human frame, is in proportion to the feries, or number of 
the plates employfcd ; while its etfefts on metals are in 
the ratio of the furfaces expofed.” 
In difeharging a galvanic battery, the fenfation will be 
in proportion to the number of plates between the points 
of contaft. We will fuppofe the trough, A B C D, fig. 
31, to confift of fixty plates. If, between B and 1, there 
are fifteen plates ; and between 1 and 2 ; 2 and 3 ; and 3 
and C, the fame number ; and if one of the hands be ap¬ 
plied at B, and the other at C, the whole force of the 
battery will be communicated. But if one of the hands 
be applied at B, and the other at 1, only one-fourth of 
the (hock will be felt; and it is consequently in propor¬ 
tion to the number of the plates between the two hands, 
in this way a given power of eleftricity is divided into 
any required minute portions, with an accuracy which 
cannot be imitated on the common eleftrical apparatus. 
When a communication is formed between B and C, 
it appears, on a tranlient view, to controvert what has 
been already dated, relative to the neceffity of connedf- 
mg the zinc fide and the copper fide of the fame inden- 
tical plate, in order to produce a difcharge ; feeing that 
the charges of all the plates are thus, communicated. 
Upon a little reflection, it will, however, be obvious, 
that this is a neceffary refult, and a powerful confirma¬ 
tion of the doftrine already laid down. When one of the 
Iiands is applied at B, fuppofing the latter to be what is 
termed the copper part of the trough, and the end C the 
zinc part, the hand at B is not only in contaft with the 
copper furface of the firft plate, but, on account of the 
regular chain of conducting media, it is alfo connected 
with the copper furfaces of the other plates. In the 
lame way the hand at C, which touches the zinc furface 
of the lame plate, is, by a fimilar channel of communi¬ 
cation, in conducting-union with the zinc furfaces of all 
the plates towards B. Let us fuppofe the plates alone, 
from B to 1,. to be under the galvanic action 3 and the 
cells from 1 to C to be filled with pieces of charcoal : 
upon forming the communication between B and C, the 
united powers of only fifteen plates will he tranfmitted. 
Now, the plates from 1 to C, in this cafe, aft merely as- 
condufting media. It is precifely the fame when all the 
cells are filled with an acid folution. This fluid keeps 
up the conneftion of the chain from plate to plate ; and* 
they then reciprocally aft as conducting media to each 
other. From thefe obfervations may be perceived the 
neceffity of the cells being infulated in fuch a way as 
that the fluid cannot pals from one to the other. If 
fuch a communication (hould exifi, there would then be 
a connecting medium from the copper furface to the zinc 
furface of the fame plate. On this account it is necef- 
fary that each plate (hould be well cemented in the ap¬ 
paratus. When a battery is carelefsly made, the appear¬ 
ance of the plates will evince the non-infulation of the 
cells. As was before obferved, the oxvdifying procefs 
can only continue in,proportion as the decompofed elec¬ 
tricity is difengaged. Tims the plates which confiantly 
have a connecting and conducting medium from the cop¬ 
per furface to the zinc furface, are rapidly oxydated ; 
while the other plates merely undergo changes, at each 
of the inftants when the circuits are completed. 
In combining feveral batteries, care ffiould be taken 
that they be nearly of equal force. If an imperfeft bat¬ 
tery be interpofed, the united power of the whole will 
be merely equal to the fame feries of the imperfect one. 
In precedes of deflagration, a battery confiding of fmali 
plates ffiould not be ranged with a battery having large- 
large plates, the effefts of the latter being diminiflied" 
confiderably by the former. 
In difeharging the Voltaic pile, as ffievvn at fig. 22, in 
the engraving, the whole charge goes off at once. If one’ 
hand be placed at f, and the other at g , the whole (hock 
isindantly communicated. This pile Volta calls a nioto- 
eleftric apparatus : its power of electrification continues 
as long as the pieces or difes of cloth or pafteboard re¬ 
main moift; as foon as they become dry, its power ceafes. 
This pile has been improved by Mr. Nicholfon, for the 
more obvious operation of decompofing water. It oc¬ 
curred to him, that if the (hock were to be tranfmitted' 
through an interrupted circuit in water, the faft of the 
decompofition would be clearly afeertained. With this 
view lie conftruftcd an apparatus, reprefented at fig. 23, 
in which AB reprefents the Voltaic pile, and CD a glafs 
tube filled witli water, a wire proceeding from the upper 
part of the pile into the tube at C, and ending at <?, while 
another wire paffes from the bottom of the pile through ' 
the end D towards f leaving an interruption oppolite 
ef. The apparatus having been thus arranged, one of- 
the wires was obferved rapidly to give out a gas, which, 
on examination, proved to be hydrogen ; while the other 
became oxydated. When wires of gold or platina were 
employed, thefe being non oxydable metals, oxygen was, 
as well as the hydrogen gas, given out. It was invaria¬ 
bly remarked, that the wire connefted with the zinc end 
of the battery gave out oxygen, and the other wire hy¬ 
drogen, gas; as more particularly deferibed in the expe¬ 
riments made by Meffrs. Carlifie and Nicholfon, men¬ 
tioned above. Perhaps the arrangement reprefented as 
affixed to the trough, fig. 31, may be more convenient. 
A wire, r, which Aides on one of the plates, fupports a 
brafs cup, in the center of which is a pair of brafs pin-- 
cers holding a piece of. gold wire; over thefe pincers a. 
glafs tube is placed, having, at its extremity, 0, a piece 
of gold wire fealed in with a glafs, which (hould not 
touch the wire at p. The tube and brafs cup being filled 
with water, a wire, orm, connefted with the top of the 
glafs tube, joins the other end of the battery, by which 
means the circuit is completed, and the decompofition 
goes on. As the gafes are difengaged, they rile up to 
tire top of the glafs tube, and, preffing the water into tiie 
cup, the procefs will go on till the whole of it is preflfed. 
beneath the upper wire. The operation then ceafes. 1 
The decompofition of water by eleftricity, according 
to the mode adopted by Van Marum, is a very tedious 
procefs. Dr. Wollafton’s method above deferibed, by 
i the 
