183 
ART. IV. Experiments on exciting Galvanism, with compound 
and simple substances, at high temperatures. By K.T. Kemp, 
Esq. Lecturer on Chemistry, &c. &c. 
Gatvanic electricity has been invariably produced by liquids of 
a compound nature, and its developement has accordingly been re- 
garded by those who adopt the chemical theory, as the necessary 
consequence of the decomposition of the liquid which is interposed 
between the metallic plates. According to the theory of Volta, on 
the other hand, the chemical action has been regarded as entirely 
accidental, and quite unconnected with the developement of the 
electricity set in motion by the battery ; and the supporters of this 
theory attribute it to the contact of the metals by which the elec- 
trie equilibrium is disturbed, and that the liquid only acts the part 
of again restoring the equilibrium between the plates. 
It is to be little wondered at, however, that these two theories 
so opposite should still continue to hold im the different countries’ 
in which they originated, when we consider that the modes adopted 
for exciting galvanism have been so similar ; and that various. sub- 
stances have been altogether overlooked, which, had they been em- 
ployed, might have thrown considerable light on this obscure sub- 
ject. 
: In illustration, I performed the following experiments with sub- 
stances which have not hitherto been employed for exciting gal- 
vanie electricity. 
Having procured a small sized black lead crucible, and having 
perforated a hole in the bottom of it sufficient to allow of the pas- 
sage of a copper wire, which I inserted so as to project within the 
inside of the crucible, and rendered the whole tight by cement. 
A circular plate of copper was then cut, so as to enter easily into 
the mouth of the crucible, having also a copper wire soldered to 
its centre. . 
The crucible having been thus prepared was placed in a fur- 
nace, and a quantity of lead put into it ; as the metal became melted, 
additional portions of it were successively added, until the liquified’ 
mass filled the crucible till within an inch of the top. During 
this part of the operation the furnace was raised to a red heat, and 
the extremity of the wire coming from the bottom of the crucible, 
was connected with the one side of an apparatus containing a sus- 
pended magnetised needle, the other extremity of the wire being” 
in contact with the melted lead within the crucible. 
A quantity of nitrate of potass, likewise heated to redness, was 
now poured over the melted lead in the crucible. ‘The extremity 
of the wire, which had been soldered to the centre of the circular 
copper plate, was connected with the other side of the needle appa- 
ratus, so as to form a continuous wire passing under the needle. 
The copper plate itself, by means of the wire attached to it, was 
carefully placed into the crucible, so as to be in contact with the 
