Roasting dishes, scorifiers and cupels are required. The cupel is made of the ashes of burnt bone, and it is better to make them on the spot, as the bone ash may be carried anywhere without damage, whereas the cupels are very fragile. The bone ash is moistened with water, stamped in a cupel mould, and allowed to dry slowly. A good one will absorb its own weight of lead, but it is better to calculate on its absorbing but three-quarters of that amount. [Illustration: SCORIFICATION FURNACE.] [Illustration: SCORIFICATION MOULD.] The crucible, scorification and cupel tongs, a couple of hammers, iron pestle and mortar, sieves from 20 to 100 mesh, and scorification mould complete the requisite tools. [Illustration: HAMMER.] [Illustration: HORN SPOON.] [Illustration: STEEL MORTAR.] [Illustration: ALCOHOL LAMP.] In addition, however, the assayer will require quite a bulky lot of apparatus, reagents and chemicals. All dealers keep lists of assayers' supplies on hand, and a full and complete assortment will cost about $200 in New York or Chicago. Quart bottles, with glass stoppers; ordinary corked bottles, ring stands, alcohol lamps, wash bottles, test tubes, horn spoons, iron pans, parting flasks, annealing cups, glazed black paper--these will suffice, provided the assayer has, as well, the outfit recommended for blow-pipe work. [Illustration: TEST TUBE.] Dry reagents, such as litharge, borax (crystallized), silica, cyanide of potassium, yellow prussiate of potash, argol, charcoal, starch, metallic iron, pure lead, nitre, powdered lime, sulphur, carbonate of ammonia and common salt are necessary. As solvents and precipitants, distilled water, sulphuric, nitric and hydrochloric acids, chloride of sodium, nitrate of silver and sulphuretted hydrogen are also indispensable. This will seem rather a formidable list, and so, under certain conditions, it may be; indeed, where means of transport is limited, all regular assay work must be postponed until the return to civilization. Assaying is not, however, difficult, being mostly a matter of rule of thumb, and correct results may be arrived at without a deep knowledge of chemistry, although such knowledge will never come amiss. A preliminary examination will show what the ore probably is. The blow-pipe is especially useful, though to the skilled assayer often unnecessary. The ore is first powdered, and any metallic flakes picked out and tested separately. A fair sample must be selected, otherwise all the work will be thrown away and the result be valueless. The next step is weighing the ore and the reagents. Moisture is drawn off by heating in a crucible, a low heat being sufficient. Roasting will eliminate sulphur, antimony, arsenic, etc., and must take place in a flat dish, so that the air may have free access. The powder should be stirred frequently. Reduction is the operation of removing oxygen, and it takes place usually in a crucible or scorifier.