The precious metals are gold, silver, and platinum. They are so called because they are rare and costly. Platinum is the most rare, and is used only to a very moderate extent. Gold is more plentiful; and silver much more abundant, though sufficiently rare to be considered a precious metal. [Illustration: BATTERY FOR SILVER-PLATING.] We do not often hear of articles of table service of solid gold, though solid silver is comparatively common. But, with the help of electricity, skilled workmen are able to cover the cheaper metals with one or more coatings of gold or silver, and the articles thus treated, look like solid gold or silver. A very small quantity of the precious metals will plate a large number of articles; but even with this small amount of gold, the gold-plated substances are too costly to be in general use; though it is quite common to line silver-plated articles with a thin plate of gold. Exceedingly beautiful things are made of silver-plated ware, for table service especially, but it is also much used for ornaments, and even statues and statuettes are made of it, as well as a great variety of useful things. As you are in the habit of seeing so many silver-plated articles I think you will be interested if I tell you, briefly, how the plating is done. But you will understand my description better if you know something about the galvanic battery, and the laws which govern its action, and if you have not studied this matter, any one of your acquaintance who possesses an electrical machine, will no doubt take pleasure in explaining it to you. I am supposing you did not know before that the same agent which causes the lightning to flash from the clouds, puts the silver on your tea-spoons. After the article to be silver-plated has been formed out of some cheap metal, or a metallic composition, it is thoroughly cleansed; for there must not be the very slightest taint of greasiness or dirt upon the surface. The method of cleaning depends upon the metal; some are burned in the fire, and some are purified with alkalies. They are next washed in acids, then scoured with sand or pumice stone, and washed, and brushed. They are now clean, and are dried in sawdust to avoid handling and soiling. All of these operations have to be carefully done. They are generally performed by women. They are then taken to the gilder to receive their deposit of metal, whether zinc, copper, gold, or silver. Our articles, you know, are to be silver-plated. They are therefore placed in a fluid chemical mixture contained in a box of wood, stoneware, or some other non-metallic substance, which is called the bath.