10. In taking casts from such a mould, the internal surface is oiled to prevent adhesion, and then plaster mixed with water is poured into it through a small orifice. The mould is afterwards turned in every direction, that the plaster may cover every part of the surface; and when a sufficiency of it has been distributed to produce the requisite strength, and the plaster has acquired the proper solidity, the several pieces are removed from the cast, which, of course, is an exact resemblance of the subject on which the mould was formed. 11. Superfluous portions of the material, produced by the seams in the mould, are removed with suitable instruments, and applications of fresh plaster are made, where necessary to repair blemishes. The cast is finished by dipping it in a varnish made of soap, white wax, and water, and afterwards rubbing it with soft linen. The polish produced in this manner, approaches that of marble. 12. The durability of plaster casts, exposed to the weather, is greatly increased by saturating them with linseed oil combined with wax or rosin. They are made to resemble bronze by the application of a soap composed of linseed oil and soda, and colored with the sulphate of copper and iron. 13. Moulds are, also, formed of a warm solution of glue, which hardens upon cooling, and such are called _elastic_ moulds. This material is sometimes preferred on account of its more easy separation from irregular surfaces. For small and delicate impressions in bas-relief, melted sulphur is sometimes employed; also a strong solution of isinglass in proof spirits. All three of the substances last mentioned yield sharper impressions than plaster of Paris. 14. Statues designed to occupy situations in which they may be exposed to the weather and mechanical violence, are often made of bronze cast in moulds. The external portions of the mould are made on the pattern, out of plaster, brick-dust, and water. The mould is then covered on the inside with a coating of clay as thick as the bronze is intended to be, and the several pieces are afterwards put together, or _closed_. The internal cavity is next filled with a composition like that on the other side of the clay. 15. When this has been done, the several pieces forming the outside of the mould are separated, and the clay carefully removed. These having been again united, and the core or internal portion of the mould secured in its true position, the whole is bound with iron hoops, and thoroughly dried. The melted bronze is poured into the cavity formed by the removal of the clay, through an aperture made for the purpose. The cast is afterwards rendered smooth by mechanical means.