GALVANISM. 
made, the metal in solution became re- 
duced. Thus, when iron and silver were 
placed in a solution of copper, the iron im- 
mediately began to reduce the copper in 
solution, while the silver had not the slight- 
est action. Upon bringing the two metals 
in contact, however, the silver became 
coated with copper. Dr. Wollaston attri- 
butes the curious phenomenon, above de- 
scribed, to a change of states in the electri- 
city of the metals ; and in order to confirm 
this idea, he attempted the same by means 
of common electricity, in which he suc- 
ceeded to his utmost satisfaction. He sup- 
poses that the chemical affinities are so alter- 
ed by the presence or absence of electricity, 
as to induce the anomalous appearances, 
which took place in the above experi- 
ments. The silver wire became coated 
with copper, and at the same time appeared 
to have the power of decomposing water. 
The only mystery we observe in these ex- 
periments, is the liberation of the hydrogen 
in a situation where no oxygen is mani- 
fested either in the form of gas, or in 
any other state. Nor does the new doctrine, 
lately advanced by Mr. Davy, throw much 
light on this subject. The zinc in this ex- 
periment, is said to be positively electrified, 
and the copper or silver to be negative. 
That the zinc, on that account, attracts the 
oxygen of the w T ater, and the silver the hy- 
drogen. That the constituent parts of wa- 
ter are by the same law made to appear in 
situations where the decomposition did not 
take place, is very evident ; hence it would 
appear that the hydrogen is carried by 
some means from the zinc to the silver. Or 
that the oxygen passes from the silver to the 
zinc, or according to Mr. Davy’s hypothesis, 
the decomposition of the water takes place' 
between the metals, the oxygen passing 
inevitably to the zinc, and the hydrogen in 
a similar way ..to the silver. To the latter 
there are several objections, which will ap- 
pear from the following experiments. 
Let a tube of three feet in length be 
filled with dilute muriatic acid, and corked 
at both ends, having a wire of zinc inserted 
in one end, and one of silver or platina in 
the other. The zinc will immediately be- 
gin to give out hydrogen, but no effect will 
be observed at the silver wire. Let a com- 
munication be established between the 
wires on the outside of the tube. The sil- 
ver does not immediately give out bubbles, 
as was the case in the experiments of Dr. 
Wollaston, nor does that effect take place, 
till a few seconds after the contact of the 
VOL. III. 
metals. Can-we for a moment suppose that 
the slight negative and positive electricity, 
produced by the contact of two small wires, 
which would not affect the most delicate 
electrometer, can have the power, the one 
of attracting oxygen, and the other hydro- 
gen, at the distance .of eighteen inches, 
reckoning from the middle of the tube. 
If the same tube be bent in the middle 
to an acute angle, like the letter V, ac- 
cording to Mr. Davy’s hypothesis, the 
appearance of the hydrogen at the silver 
wire ought to take place as soon after the 
contact, as with the straight tube ; but what 
is very singular, it will not take place at all. 
This experiment would seem to prove, that 
one of the constituents of the water is car- 
ried through the whole length of the tube ; 
and that by some law which differs from 
those of electricity, since the angle of the 
tube appeared to interrupt its passage. The 
interruption is still greater, even with a 
shorter tube, when the tube is bent in dif- 
ferent places, forming a sort of zig-zag. 
The idea that hydrogen is carried from 
the zinc to the copper wire, is strongly fa- 
voured by another experiment. Take the 
glass tube, AB, fig. 2, filled with dilute 
muriatic acid, having a cork at B, through 
which the wires, z and c are passed, z be- 
ing a wire of zinc, and c a wire of platina, 
silver, or copper. So long as the wires re- 
main unconnected at z, the platina-wire ap- 
pears unchanged; but, as soon as the con- 
tact is formed, bubbles of hydrogen are 
first seen at d; they then very slowly begin 
to appear in the lower parts of the wire ; but 
what is singular, the moment they begin to 
appear at /, they are also seen at s, and 
some seconds are elapsed before any bub- 
bles are seen at g. if the hydrogen in the 
last experiment were attracted by the ne- 
gative state of the platina-wire, since the 
metal is the best conductor, it would seem, 
that the point, s, wouM be the last part to 
have parted with its electricity; and, of 
course, the bubbles of hydrogen ought to 
have appeared the last at that point, which 
is contrary to fact. It therefore appears, 
more likely that the hydrogen has been 
held in combination by the electricity, the 
latter of which is taken by the nearest me- 
tallic conductor in the circuit, leaving the 
hydrogen in its gaseous form : the law, how- 
ever, by which it moves along the liquid, 
does not appear to agree with any known 
properties of electricity, since the hydrogen 
is some seconds in reaching the point'#-. 
It will appear, from the above experi- 
IS 
