100 
it with the conductor or rubber of the electrical ma- 
chine; and yet its operationis not in any degree affected. 
Healso contrived an apparatus, in which there were three 
wires placed between the extremities of the pile, two 
of them connected with the ends of the pile, and the 
third in the centre; the wires having water interposed 
between them, and electrometers so situated, as to as- 
certain the electric condition of the wires. In the or- 
dinary state of the apparatus, the terminating wires were 
one positive and the other negative, corresponding to the 
ends of the pile to which they were attached, while the 
central wire was neutral; yet the ends of this neutral 
wire produced opposite electrical effects, one separating 
oxygen, and the other hydrogen. By altering the 2 
paratus, the-electrical state of the wires were altered ; 
the central wire was rendered at one time positive, and 
afterwards negative, and the state of the terminating 
wires was reversed ; yet no change took place in the 
chemical action of the wires, each of them continuing 
to evolve oxygen and hydrogen as at first, and the two 
ends of the central wire separating oxygen and hydro« 
gen respectively at its extremities, in the same man- 
ner, whether the wire itself was positive, negative, or 
neutral. See Nicholson’s Journ. xxvi. 
Mr Singer has proposed an ebjection to Sir H. = 
hypothesis, very similar to this of M. De Luc’s. If a 
number of metallic wires are placed in a line, with their 
extremities immersed in a fluid, and the whole con- 
nected with the pile, each wire will evolve oxygen at 
one end, and hydrogen at the other. Now, he con- 
ceives it impossible that every wire can have an oppo- 
site electricity at its two extremities, when it is sur- 
rounded by a conducting fluid; for no metallic body 
can be made polar, 7. e. one end positive and the other 
negative, but by the temporary disturbance of the equi- 
librium of its natural electricity ; an event which can 
only happen when they are separated by a non-con- 
ducting substance.. But he observes, “© No one can 
maintain, that water, or any saline fluid or acid mix- 
ture, is a non-conductor, either of the chemical or elec- 
trical effects of the voltaic apparatus ; yet the usual che- 
mical changes produced by voltaic electricity occur at 
every interruption of the metallic circuit in such fluids.” 
See Singer’s Elem. p. 376. 
There appears to us to be considerable weight in 
these objections ; and we confess, that the ideas of Sir 
H. Davy produce a shock to our usual associations on 
the subject of electricity, which it is not easy to over- 
come. However, as we have already remarked, it 
would be foreign to the object of this article to pursue 
the discussion any farther; nor do we conceive, that 
we are at present in possession of sufficient facts to 
warrant us in coming to any definite conclusion re- 
specting it. 
We shall here conclude our account of the theory of 
galvanism. Our readers will perceive, that much dis- 
cordance of opinion still exists u the subject, and 
that some strong objections attach to every hypothesis 
which has yet been proposed. The most important 
points to ascertain are, the difference between electri- 
city, as excited by the friction of the common machine, 
and that modification of it which is strictly called gal- 
vanism. For this purpose, the nature of electric in- 
tensity should be farther investigated ; for it would ap- 
that if we were able to attach a more precise idea 
to this term, a considerable insight would be gained 
inte the cause of this difference. Experiments somes 
1 
GALVANISM. 
what similar to those of M. De Luc should be proses ‘Theory 
cuted, in which the electrical and chemical effects of ~-~~ 
the pile are separated from-each other, and a moreace = 
curate measure of the galvanic power should, if | 
possible, be obtained, than any of which we are now 
possessed. The conducting power of the fluids con< 
cerned in the galvanic apparatus should be carefully 
examined, and the relation of their chemical action to 
their teres power should be ascertained. But it 
is unnecessary for us to enlarge one these topics: the 
rapid succession of discoveries which have been made 
in this erate of science, and the very general at« 
tention which it has obtained from the first philoso-« 
hers of the age, afford every reason to , that the ) 
arther investigation of it will be followed by no less 
success, than that which has hitherto its pro< 
gress. 
Description of the Figures in Plate CCLXIII. ag 
— 
a 
Fig. 1. The galvanic pile, as originally constructed b PLate 
— tenance’ e letters C, Z; and F denote the aap COLXIff 
o zinc, and the pieces of cloth or paste- Fig. 1. 
bata seule in fluid. The hile has four rods placed 
round it, to keep it in the perpendicular direction. The 
lower end was called the copper, and the upper the 
zine end. . uy 
Fig. 2. When the number of plates is very consider Fig. 2, 
able, Volta divides it into two or more parts, each be- : 
ing connected by slips of metal. In this case, it is es« 
sential that the same order of parts be observed from Ke 
one end to the other, up the first pile, down the se- ‘ 
cond, up the third, and, lastly, down the fourth. a 
Fig. 3. This was a modification of the galvanic ap- Fig. 3. 
paratus that was formed by Volta, which he called cous a 
ronne des tasses, where the zinc plates Z and é 
lates C are not in contact, but are connected by metal- i 
ic rods, and then immersed a a fluid. eg 
Fig. 4. represents the tro apparatus invented by fie, 4, 
Mr Ulekaeanders the plates‘of sie and copper are sol« +o 
dered together, and are then cemented into a wooden 
frame, leaving intervals between the double plates, to 
receive the fluid which is intended to act upon the zinc. 
It is provided with wires at each end, which are in 
posite states of electricity, and may be applied to any 
substance which it is proposed to subject to its influ- 
ence. 
Fig. 5. represents the battery of Mr Children, which Fig. 5. 
is a combination of the couronne des tasses of Volta and 43 
the trough of Cruickshanks. The plates are not in 
contact, but each pair is connected by slips of metal, 
and the whole is attached to a beam, so as to be lifted 
out of the cells at pleasure. The trough and partitions 
may be formed of either wood or earthen ware, and 
contain the fluid that is to act on the zine plates. ] 
Fig. 6. is the apparatus for receiving in separate ves- Fig. 6. 
sel the gases which are evolved by the action of gal- 
vanism upon water. . The two small jars have metal- 
lic wires inserted at their upper end, one of which is 
connected with the positive, and the other with the 
negative extremity of the pile. They are filled with 
water and inverted in the same fluid; and the ends of 
the wires are so situated, that the gas disengaged from 
them rises to the top of the jar. 
Fig. 7. 4 cone the apparatus in which the gases Fig, 7. 
disengaged from water may be reconverted into water 
by checslectaia spark, 
Fig. 8. are the agate cups, connected by amianthus, Fig. 8. 
