The experiments of M. Becquerel show that electricity is a power which makes the atoms of matter aggregate in crystalline forms; for he has succeeded in forming crystals of gold, silver, cobalt, nickel, platinum, and a variety of the gems undistinguishable from those in nature, by exposing saturated solutions of these substances for a very long time to feeble voltaic electricity; and crystals of earthy matter have been obtained in the same manner. The electric and magnetic state of mineral veins in mines which contain a vast variety of crystals, metallic and non-metallic, strongly favours this view of the origin of crystalline form. M. Regnault has proved that the ratio between the specific heat and the weight of the atoms of matter is intimately connected with the mode of their aggregation; and indeed if it be considered that the atoms have not only specific heat and weight, but specific affinity, electricity, magnetism, consequently polarity, and probably specific forms, these peculiar forces must necessarily influence the structure of crystals according as they combine with or oppose the natural or artificial forces acting upon them, or upon their dissimilar faces, and this may be the cause of the great variety of forms that matter appears under. Carbonate of lime alone assumes more than 1,200 different modifications of its primitive type, but whatever be the variety of forms which any one substance may take, they are found to be all compatible with and derivative from a common type. The circumstances which have caused dimorphous crystals to deviate from the general law have not yet been explained. It is very singular that when chlorate of soda is dissolved in water the solution does not possess the property of circular polarization, but when evaporated and allowed to crystallise, some of the crystals turn light to the right, and others to the left. Now if all the crystals that have the same property be picked out and dissolved in water a second time, the liquid will still have no circular polarization, but when allowed to crystallise, some of the crystals make light revolve through them to the right and others to the left as before. From this it is supposed that the atoms of liquids, which are free to move in every direction, already possess part of the characters which the change to solidity renders evident and permanent.