96 GALVANISM. 
Theory. these cases, it is retained by them for a certain space of 
—y—" time only, and is continually passing off, more or less 
rapidly, to all the surrounding bodies. 
But besides this temporary transfer from one body to 
another, without their undergoing any farther altera- 
Electricity 
the primary effect, and, consequently, is to be consi-~ 
of the pile. ' ‘. ' 
The two 
electricities 
tion, they occasionally experience a more permanent 
change rf their Savttical “yes; when, in consequence 
of their acquiring different physical and chemical pro- 
— their capacity for electricity is entirely altered. 
hen their capacity is diminished, a more ual, 
but more continued discharge of the electric fluid takes 
place ; and in this appears to consist the essential action 
of the pile, as contrasted with that of the machine. In 
the action of the machine, by which the electric fluid 
is set at liberty, and transferred from one body to ano- 
ther, no change appears to take place in the substances 
employed, except the alteration in their respective 
antities of electricity. Their attraction for it is nei- 
ther increased nor diminished ; and, consequently, they 
have a tendency, the one to lose, and the other to ac- 
quire, the electricity which has been thus, as it were, 
forced into the one, and out of the other. According 
to the nature of the action by which the electricity is 
evolved, whether the substances experience any per- 
manent change in their capacity, or whether their equi- 
librium is merely disturbed in a temporary manner, the 
state of the fluid appears to be affected, so as to causea 
difference in its intensity. 
When we employ the machine, the electricity that 
we procure appears to be in a highly elastic state, its 
particles strongly repulsive of each other, and at the 
same time not disposed to enter into a permanent union 
with other bodies. The galvanic electricity which we 
procure from the pile, is more readily united to other 
bodies, and has a tendency to form new combinations 
with them, which is so powerful as to counteract some 
of the strongest chemical affinities. At the same time, 
it exhibits less of what may be called mechanical ac- 
tion : its particles are less repulsive of each other; its 
motions appear less rapid ; it causes less commotion in 
its passage from one body to another ; and although its 
ultimate effects are more powerful, it seems to act with 
less violence. The one may be compared to a small 
quantity of an agent highly concentrated ; the other to 
a larger quantity, but in a state of greater dilution. The 
phenomena of electricity, as excited by the common 
machine, depend upon the attraction and repulsion of 
the electric fluid, and its passage from one body to ano- 
ther; while the most important actions of galvanic elec- 
tricity result from the chemical changes that it produces 
in the composition of bodies. The excitation of com- 
mon electricity is not necessarily attended with any 
permanent alteration in the state of the substances that 
are employed in producing it. It is usually developed 
by the mechanical aid of friction, and the same appa- 
ratus may continue to’ be employed for an indefinite 
length of time. Friction, on the contrary, has no ef- 
fect in the production of galvanic electricity ; it requires 
a chemical change in some part of the apparatus ; and 
the individual parts which have been employed in ge- 
nerating it acquire new properties, and are incapable 
of any farther galvanic action. 
6 After these general observations, 
inconclusive as they are, appear to be all that our pre- 
sent knowledge upon the subject will warrant, we must 
proceed to examine more minutely into the nature of 
the action that is exercised by the galvanic apparatus. 
From the remarks that have been already made, it will 
be obvious, that in the operation of the pile, there are 
compared. 
Action of 
which, scanty and 
the pile, 
sophers, ee the electrical hypothesis ; while there 
are several distinguished experi ists in thi 
who maintain, that the chemical action is the one whi 
ives rise to all the changes that are produced, and there 
fore constitutes the pri action of oe len gta 
In all the experiments were performed with Volta, 
two metals, previous to the discovery of the pile, with — 
the exception of those of Fabroni, which seem to have electric 
been but little attended to, the only point in discussion Pothesi 
was, whether the effects were to be referred to the-elec« 
tric fluid, or to a new agent inherent in the animal 
body. Volta strenuously adopted the opinion, 
simply upon common electricity, 
accounted for them by supposiig that the contact of 
the two metals had the power of altering the 
of electricity which was natural to them, addi 
tion of it to the one, and subtracting it from 
pairs of metal, by i ing between each pair a con« 
ing substance, which, without altering the electric 
state of the metals, might increase the effect, by trans« 
mitting it through a number of successive stages. What- 
ever we may think of the hypothesis, the experin 
to which it gave rise was most fortunate; for it led to 
the construction of the pile; an apparatus by means of 
which the most curious and i discoveries have , 
Loeestwray ine wlan xesedbr brs may 4 
: t % 
Although Volta completed the discovery of the pile, 4 
and fully cadecianeh trupdeortie ths cate body, yet tice 
it is not a little remarkable, that he limited his’ inqui- mical 
ries to this object, and seems to have been totally ig- fects. — 
norant of the farther powers of the instrument of which 
he was possessed. is circumstance must a the 
more remarkable, snare recollect that New 
very first employment of it by Messrs Ni 
Carlisle, choy pavcatveld its chemical action, and became 
aware of its importance as an agent in the d 
tion of bodies. Cruickshanks, Davy, Wolluutony then: 
ry, and the other English philoso , farther deve~ 
loped its powers in this r which had so com- 
pletely escaped the notice of Volta, and they were con- 
sequently led to form a different idea of the mode of its 
operation. Dr Wollaston seems to have been the first 
who decidedly adopted the opinion, that the chemical 
action of the pile is the primary origin of all the 
changes which it experiences, and is the cause of the 
electrical effects ; and the same idea was embraced by 
Sir H. Davy, although he has since abandoned it for 
the hypothesis of electric energies. ‘ 
We must now to examine the two leading 
theories of the galvanic action, as exhibited in the pile, 
with more minuteness ; and we shall in with that 
of Volta’s, or the one which s i 
a. ae, metals to be the primary cause the] 
its operation. This philosopher has given a state- 
ment of his opinions on the subject, ist covers lettits 
which he wrote to his friends, and which have been 
An 
of 
tric 
