Tin. This is a very difficult ore to reduce, but the addition of a little cyanide of potash to the powdered ore will make it easier. Fuse, after moistening on the charcoal, in the oxidizing flame, and you will probably obtain small globules of tin. Silver. Make a paste of the ore with carbonate of soda; add a small piece of lead and fuse into a button. Make a second paste of bone ash and water, and after you have dried it with a gentle flame place the button of silver and lead on the bone ash, and turn on the oxidizing flame. The lead will disappear, leaving a silver globule. Should it not be pure white, but more or less tinged with yellow, it probably contains gold; and if the button be dissolved in nitric acid, whatever remains behind is gold. Sometimes it is desirable to determine whether tellurium is present in an ore. This is very easy to find out. All that is required is a blow-pipe, alcohol lamp and a porcelain dish. Break off a small piece of the ore, place it in the dish previously warmed, blow upon the ore with the blow-pipe until it is oxidized, then drop a little sulphuric acid on the ore and dish. If tellurium be present, carmine and purple colors on the assay will proclaim the fact. Bismuth ores are very heavy; usually they have more or less antimony associated with them, which is a drawback, as the separation is an expensive matter and the returns are less than they would be from a low grade pure ore. In testing for this metal, dissolve a crushed sample in nitric acid and then add potash in excess. If the ore is one containing bismuth, you should have a white precipitate; if it contains cobalt, you will get a bluish-green coloration. Bismuth is worth about fifty cents a pound if pure and free from antimony. Galena is often mistaken for other ores, specular iron ore for instance. If the ore be crushed and heated in nitric acid until dissolved, some water added, and an addition made to the solution of a few drops of ferrocyanide of potassium, a dark blood-red precipitate is thrown down. If the ore were galena, there would be no coloration. The so-called steel galena which carries a little zinc is generally richer in silver than the ordinary cube galena, though the reverse is sometimes the case. If lead ore be dissolved in nitric acid, the solution diluted, and some hydrochloric acid added, a white precipitate is thrown down. Add ammonia and the precipitate remains unaltered. The blow-pipe operator has to learn to breathe and blow at the same time; the breathing he does through the nostrils, the blowing is produced by the natural tendency of the cheeks to collapse when distended with air. A skillful operator can blow for many minutes at a time without the slightest fatigue. To identify cinnabar, the ore from which quicksilver is obtained, make a paste of the substance in powder and carbonate of soda. Heat in the open tube, and a globule of mercury will result.