of the unamalgamated metal. Again, as
Davy has shown[A], if amalgamated and unamalgamated zinc be put in contact,
and dipped into dilute sulphuric acid, or other exciting fluids, the former
is positive to the latter, i.e. the current passes from the amalgamated
zinc, through the fluid, to the unprepared zinc. This he accounts for by
supposing that "there is not any inherent and specific property in each
metal which gives it the electrical character, but that it depends upon its
peculiar state--on that form of aggregation which fits it for chemical
change."

[A] Philosophical Transactions, 1826, p. 405.

1005. The superiority of the amalgamated zinc is not, however, due to any
such cause, but is a very simple consequence of the state of the fluid in
contact with it; for as the unprepared zinc acts directly and alone upon
the fluid, whilst that which is amalgamated does not, the former (by the
oxide it produces) quickly neutralizes the acid in contact with its
surface, so that the progress of oxidation is retarded, whilst at the
surface of the amalgamated zinc, any oxide formed is instantly removed by
the free acid present, and the clean metallic surface is always ready to
act with full energy upon the water. Hence its superiority (1037.).
1006. The progress of improvement in the voltaic battery and its
applications, is evidently in the contrary direction at present to what it
was a few years ago; for in place of increasing the number of plates, the
strength of acid, and the extent altogether of the instrument, the change
is rather towards its first state of simplicity, but with a far more
intimate knowledge and application of the principles which govern its force
and action. Effects of decomposition can now be obtained with ten pairs of
plates (417.), which required five hundred or a thousand pairs for their
production in the first instance. The capability of decomposing fused
chlorides, iodides, and other compounds, according to the law before
established (380. &c.), and the opportunity of collecting certain of the
products, without any loss, by the use of apparatus of the nature of those
already described (789. 814. &c.), render it probable that the voltaic
battery may become a useful and even economical manufacturing instrument;
for theory evidently indicates that an equivalent of a rare substance may
be obtained at the expense of three or four equivalents of a very common
body, namely, zinc: and practice seems thu