The India-rubber, or caoutchouc, now imported to the enormous extent of six or seven hundred thousand pounds annually, reaches this country in masses of varied shape, but mostly of a dark color. In its imported state it is used for very few purposes; considerable modifications being necessary for its adaptation to practical service. It requires to be transformed into cakes, or sheets, or tissues, or tubes, or solutions, preparatory to its ultimate use; and this transformation requires operations of a somewhat peculiar kind, owing to the necessity of rendering the whole mass homogeneous in substance. The bottles, and masses, and fragments, as imported, have much inequality in texture, and are, moreover, contaminated with much dirt and refuse. To separate these, the India-rubber is first cut into very small fragments, and then steeped in warm water, by which the dirt is precipitated. The fragments are dried, and are then thrown into a kind of kneading machine, where immense pressure is employed to bring them to one homogeneous mass. The India-rubber, though put in cold, becomes so hot by the agitation that it could not be safely touched by the hand; it is necessary to supply the machine with cold water, which is made nearly to boil by the caloric driven out of the elastic mass. So thoroughly is the mass pressed, rolled, pricked, cut, and kneaded, by the severe turmoil which it undergoes, that all dirt, air, water and steam are expelled, and it presents the appearance of a dark colored, uniform, smooth mass. It is put into cast iron moulds of great strength, and brought, by hydraulic or screw pressure, to the form of blocks, slabs, or cylinders, according to the purpose to which it is to be applied. MACKINTOSH CLOTH.