Suspended from the rod are anodes of gold, silver, or copper or whatever metal from which a deposit is desired. The other plates of the battery or the negative elements, are connected with another rod across the trough, to which are suspended the articles to be plated.
Electrotyping.—This is the process by which, type, wood cuts, etc., are reproduced in copper by the process of electroplating. A mould is first made of the set type in wax; this mould is next coated with black lead to give it a metallic surface, as the wax is an insulator; the mould is then subjected to the process of electro deposition, resulting in the formation of a film of copper on the prepared surface.
The copper shell is removed from the mould by applying hot water; the shell is then backed up with electrotype metal to render it strong enough for use.
Almost all the illustrations in this book, for example, are printed from electrotype copies, and not from the original wood blocks, which would not wear so well.
CHAPTER IX
MAGNETISM
Magnetism.—The ancients applied the word “magnet,” magnes lapes, to certain hard black stones which possess the property of attracting small pieces of iron, and as discovered later, to have the still more remarkable property of pointing north and south when hung up by a string. At this time the magnet received the name of lodestone or “leading stone.” It is commonly, though incorrectly, spelled loadstone.
Ques. Describe two kinds of magnetism.