gular, geometrical forms
called crystalline. Such conditions are brought about by different
processes--fusion, volatilization, solution, the dry way, wet way, and
electric way. Further along, we shall give some examples of the last
named means.

Let us add that crystallization may be regarded as a general property
of bodies, for the majority of substances are capable of
crystallizing. Although certain bodies seem to be amorphous at first
sight, it is only necessary to examine their fracture with a lens or
microscope to see that they are formed of a large number of small
juxtaposed crystals. Many amorphous precipitates become crystalline in
the long run.

In the examination of the various crystallizations that occupy us, we
shall distinguish the following: (1) Those that are produced through
the direct intervention of the electric current; (2) those in which
electricity is manifestly produced by small voltaic couples resulting
from the presence of two different metals in the solution experimented
with; (3) those in which there are no voltaic couples, but in which it
is proved that electricity is one of the causes that concur in the
production of the phenomenon; (4) finally, those in which it is
rational, through analogy with the preceding, to infer that
electricity is not absent from the phenomenon.

I. We know that, by means of voltaic electricity or induction, we can
crystallize a large number of substances.

Despretz tried this means for months at a time upon carbon, either by
using the electricity from a Ruhmkorff coil or the current from a weak
Daniell's battery. In both cases, he obtained on the platinum wires a
black powder, in which were found very small octohedral crystals,
having the property of polishing rubies rapidly and perfectly--a
property characteristic of diamonds.

The use of voltaic apparatus of high tension has allowed Mr. Cross to
form a large number of mineral substances artificially, and among
these we may mention carbonate of lime, arragonite, quartz, arseniate
of copper, crystalline sulphur, etc.

As regards products formed with the concurrence of electricity
(oxides, sulphides, chlorides, iodides, etc.), see "Des Forces
Physico-Chimiques," by Becquerel (p. 231).

There is no doubt as to the part played by electricity in the chemical
effects of electro-metallurgy, but it will not prove useless for our
subject to remark that when, in this operation, the current has become
too weak, the