Glass for mirrors is sometimes tinned instead of being silvered. M. Gulley, of France, has invented a process by which the tin is protected from injury by means of a coat of metal. It is done in the following manner :mdash; Lay a coat of varnish on the tin, and over this another of plumbago, when dry place the glass immediately in a vessel containing a so-. ution of sulphate of copper, a battery arranged in the usual manner, is applied to this solution, and by this means a coat of copper is deposited on the tinned side of the glass.