Before giving examples of the production of electricity in the phenomenon of crystallization, it will be well to examine, beforehand, the different circumstances under which electricity acts as the determining cause of crystallization or intervenes among the causes that bring about the phenomenon. In the first place, two words concerning crystallization itself: We know that crystallization is the passage, or rather the result of the passage, of a body from a liquid or gaseous state to a solid one. It occurs when the substance has lost its cohesion through any cause whatever, and when, such cause ceasing to act, the body slowly returns to a solid state. Under such circumstances, it may take on regular, 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).