Copper and brass vessels are tinned inside, to prevent the formation of that poisonous substance called verdigris. The mode of tinning them is as follows:--They are cleaned inside by means of vitriol, and then made hot, fine grain-tin and a little rosin being put into them, and turned about and brushed over the surface with a ball of tow: by this means, the tin is equally spread over the inner surface of the vessel. Tin-tacks, buckles, and other small articles, receive a coating of tin by being put into an earthen pot together with some grain-tin and a substance called “sal ammoniac,” and the pot being heated over a fire sufficiently to melt the tin, is then shaken up till the articles inside have received a coating of tin. Iron plates have lately been coated with melted zinc instead of tin, and the surface thus covered enables them to be used for various purposes and in situations where they are exposed to the action of the weather, as on housetops, &c. The plates, thus treated, are called “galvanised iron,” and they are generally used in a corrugated form. They withstand the action of the weather very much better than simple iron plates would, for the latter would be very soon eaten into holes from rusting. GLASS. This most useful and elegant material--now an article of almost universal application, in various forms--is made on a very large scale by fusing together sea-sand and alkali (either potash, soda, or lime), and, in the case of “crystal,” or “flint-glass,” oxide of lead. The following is about the composition of the chief kinds of glass in use:-- FLINT GLASS. PARTS. PLATE GLASS. PARTS. Pure white sea-sand 52 Pure white sand 55 Potash 14 Soda 35 Oxide of lead 34 Nitre 8 ------ Lime 2 100 ----- 100 CROWN GLASS. PARTS. GREEN BOTTLE GLASS. PARTS. Fine white sand 63 Sea-sand 80 Chalk 7 Salt 10 Soda 30 Lime 10 ---- ---- 100 100