S04 
a negative end ; or that in every complete 
galvanic circle, the electric fluid circulates 
iii one way only. Thus, if two simple com- 
binations are disposed as in fig. 14, this ar- 
rangement will not have any galvanic power, 
because the actions of the two simple com- 
binations, or the two currents of electricity, 
are opposed to each other ; the two positive 
ends being called p, and the two nega- 
tive ends n. But if those fixed bodies are 
disposed as in fig. 15, then the combination 
will be very active ; because, according to 
the hypothesis, the direction of the electric 
fluid in each simple arrangement tends the 
same way, and probably the one accelerates 
the other. 
What has been said above of the arrange- 
ment of two simple galvanic combinations, 
must be likewise understood to hold good 
with respect to the connection of any num- 
ber of the same ; viz. that they must not 
counteract each other ; or, if a certain num- 
ber of them counteract each other, then the 
remaining only form the active part of the 
battery. For instance, if a battery consists 
of 40 simple combinations, and if 12 of 
them are placed in a direction contrary to 
the others; then these 12 will counteract 12 
others, and of course the whole battery will 
have no more power than if it consisted of 
16 simple combinations properly disposed. 
This points out a method of comparing 
the powers of two batteries ; for if those bat- 
teries are connected in an inverted order, 
viz. the positive end of one to touch the 
negative end of the other ; then, on connect- 
ing the two other extremities, or on apply- 
ing them to proper instruments, the whole 
power will be annihilated, if the separate 
batteries had equal power ; otherwise the 
power of the whole will be the excess of the 
power of the most powerful battery above 
that of the weakest ; and the direction, viz. 
its being positive or negative, will shew to 
which battery it belongs. It must be ob- 
served, with respect to the inactive arrange- 
ment of fig. 14, that if one of the separate 
bodies Z, is removed, then the remaining 
jive bodies will form an active combination ; 
for in that case, W, W, become one body, 
and S, S, likewise act as one body. 
It is almost superfluous to observe, that 
(as has been said with respect to simple 
circles) in a galvanic battery the interpo- 
sition of conductors that have no particular 
action, or of the conductors of the same 
class as the adjoining bodies, does not alter 
the effect of the battery. 
Thus far we have stated the general laws, 
which have been pretty well ascertained 
with respect to galvanic combinations. We 
shall now proceed to describe the practical 
construction, and the effects of those com- 
binations, especially of the compound ar- 
rangements or batteries. 
The simplicity of single galvanic circles 
is so great, that nothing more need be said 
with respect to their construction ; for 
when the three bodies are selected, the oper- 
ator needs only take care that their contact 
is perfect. 
Galvanic batteries have been constructed 
of various shapes, and they may be end- 
lessly diversified. But the most usual forms 
are represented by figs. 16, 17, and 19. Those 
of figs. 16 and 17 are more easily construct- 
GALVANISM. 
ed ; that of fig. 16, however, is the most com- 
modious. 
The battery, fig. 16, consists of several 
glasses, or china cups, full ofwater, or of wa- 
ter containing salt, &c. ; and two plates un- 
connected with each other, viz. a plate of 
zinc and a piate of silver, are plunged in the 
fluid of each cup, excepting the first and 
last cups ; but each of those plates must have 
a sort of tail or prolongation, by which they 
are so connected that the silver plate of one 
cup communicates with the zinc plate of 
the next, and so on. 
The battery, fig. 17, consists of pieces of 
silver, about as big as half-crowns, pieces of 
zinc, of an equal size to those of silver, and 
pieces of card, or cloth, or leather, or other 
bibulous substance, a little smaller in dia- 
meter than the metallic pieces, and soaked 
in water or in other proper fluid. 
Those pieces are disposed in the order of 
silver, zinc, and wet cloth, &c. as indicated 
by the letters S, Z, W. The pieces of 
card, or cloth, &e. must be well soaked in 
the fluid ; but before they are applied, they 
should be squeezed, in order that the superflu- 
ous fluid may not run down the outside of the 
pile, or insinuate itself between the contigu- 
ous pieces of silver and zinc. Those pieces, 
especially if soaked in plain water, lose their 
moisture pretty soon, so that they can hardly 
serve longer than for a day or two ; after 
which time the pile must be decomposed, 
the metallic pieces cleaned, those of cloth or 
card soaked again, and the whole arranged 
as before. 
The three rods R, R, R, are of glass or of 
baked wood ; and the piece of wood, O, 
slides freely up or down the rods. This 
serves to prevent the falling of the pieces. 
When such battery is to be very powerful, 
viz. is to consist of numerous pieces, the 
best way | is to form two or three or more 
piles, and to join them by pieces of metal, 
as c c in fig. 18, where two piles are joined 
together, so that a is the negative extremity, 
and b is the other or positive extremity of 
the whole arrangement, or of the two piles 
considered as one. 
The battery, fig. 19, consists of a strong 
oblong vessel of baked wood, about three 
inches deep and about as much broad. In 
the sides of this vessel grooves are made op- 
posite to each other, and about one-eighth 
of an inch in depth. In each pair of oppo- 
site grooves a double metallic plate, viz. a 
plate of zinc and a plate of silver soldered 
together at their edges, are cemented ; by 
which means the wooden vessel is divided 
into several partitions, or cells, about half 
an inch broad, as is sufficiently indicated by 
the figure. The cementation of the metallic 
pieces into the sides and the bottom of the 
wooden vessel, must be so accurate as not to 
permit the passage of any fluid from one 
cell into the next. The cement proper for 
this purpose is made by melting together 5 
parts of resin, 4 parts of bees’-wax, and 2 
parts of powdered red ochre. 
Those cells are afterwards filled almost to 
the top with water, or any other fluid, ac- 
cording to the foregoing table ; and thus the 
whole will form a battery, consisting of va- 
rious repetitions of silver, zinc, and fluid. 
Two or more of such batteries may be join- 
ed, as has been said of the preceding battery. 
See fig. 24. 
It need hardly be observed, that instead of 
zinc, copper, and water, other combinations 
may be made according to the table. At 
present the last- described batteries are con- 
structed with copper, zinc, and water mixed 
with a small proportion of nitric or muriatic 
acid. For the construction of such batte- 
ries it is immaterial whether the metals are 
quite pure or slightly alloyed. 
The action of all these batteries is greatest 
when they are first completed or filled with 
the fluid; and it declines in proportion as the 
metal is oxidated, or the fluid loses its power. 
Hence, after a certain time, not only the 
fluid must be changed, but the metallic 
pieces must be cleaned by removing the 
oxidated surface ; which is done either by 
filing or by rubbing (hem with sand or sand- 
paper, or by immersing them for a short 
time in diluted muriatic acid, and then wip- 
ing them with a coarse doth. The metal- 
lic pieces of the battery, fig. 19, may be 
cleaned by the last method, and may be 
wiped by introducing a stick with a rag into 
the cells. 
Thus much may be sufficient with respect 
to the construction of simple and compound 
galvanic arrangements. It is now neces- 
sary to state the effects of those combina- 
tions. Indeed, the mode of applying single 
galvanic circles, and their principal effects, 
have already been described; yet, for the 
sake of assisting the memory, it will be use- 
ful to collect those effects under the four fol- 
lowing heads, in explanation of which we 
shall add such farther experiments and obser- 
vations as could not with propriety be men- 
tioned before. 
(1) The action of a single galvanic circle 
affects the organs of living animals, or of 
animals recently dead, especially when one 
end of the combination is connected with a 
nerve, and the other end is connected with 
a muscle of the same limb. 
(2) That action may be transmitted thro’ 
good conductors of electricity, but not thro’ 
electrics, or through less perfect conductors. 
(3) Jt affects the electrometer by the inter- 
mediation of other instruments. 
(4) That action increases, cr otherwise 
modifies, the chemical agency of the bodies 
concerned, upon each other. 
The limbs of animals, especially of frogs 
recently dead, are the most sensible instru- 
ments of galvanic powers; and, in fact, the 
simplest galvanic circles will affect them, 
when they will not produce any other deci- 
sive electrical effect. 
. The various powers of different simple 
circles may be ascertained by applying them 
to such animal preparations as have their vi- 
tality or irritability more or less exhausted. 
Thus Mr. Volta, in his letter to Gren, says, 
“ If you take a frog, the head of which has 
been cut off, and which has been deprived of 
all life by thrusting a needle into the spinal 
marrow, and immerse' it without skinning, 
taking out the bowels, or any other prepara- 
tion, into two glasses ofwater, the rump into 
one, and the legs into the other as usual ; it 
will be strongly agitated and violently con- 
vulsed when you connect the water in both 
glasses by a bow formed of very different 
metals, such as silver and lead, or, what is 
better, silver and zinc ; but this will by no 
means be the case when the two metals are 
less different in regard to their powers, such 
