_By Scorification._--Ore taken, 3 grams. Silver got. 0.0425 gram Silver from slag 0.0022 " Silver lost in cupellation 0.0020 " ------ 0.0467 " Deduct silver in lead 0.0015 " ------ Silver in ore 0.0452 " = 492.2 ozs. per ton. ~Determination of Silver in Silver Precipitate.~--This substance contains, in addition to metallic silver and gold, sulphates of lead and lime; oxides of zinc, copper, and iron; and more or less organic matter. The sample as received is generally free from "water at 100° C."; and, since it rapidly absorbs water, care should be taken in weighing it. Since it contains combined water it is not suited for scorifying; therefore the determination of silver and gold (fine metal) is made by pot assay. Weigh up 5 grams of the precipitate, mix with 100 grams of litharge and 1 gram of charcoal. Melt in a crucible at a moderate heat and pour. Detach the slag, replace in the crucible, and, when fused, add a mixture of 20 grams of litharge and 1 gram of charcoal. When the fusion is again tranquil, pour; and cupel the two buttons of lead. In a sample worked in this manner the mean of four determinations gave 0.6819 gram of "fine metal"; deducting 1 milligram for the silver contained in the oxide of lead, and adding 8 milligrams for the cupellation loss, there is got 0.6889 gram or 13.778 per cent. of silver (and gold) in the sample. ~Determination of Silver in Burnt Ores.~ _By Pot Assay._--Roasted cupriferous pyrites containing small quantities of gold and silver comes under this heading. The following mixture will give a fluid slag which is heavy and tough when cold:-- Ore. Borax. Sand. Litharge. Charcoal. 100 50 50 100 7 Mix; place in a large crucible; cover with salt; and melt down under cover. When fused drop in an iron rod for a few minutes, and about a couple of minutes after its withdrawal, pour the charge quickly into a large conical mould. The button of lead should weigh about 50 grams. Cupel and weigh the silver. The litharge may be replaced by red lead, in which case another gram of charcoal powder must be added. In our experience the results obtained by this method are about 20 per cent. less than the actual content of the ore. The results of two assays, after deducting for the silver in the litharge used, were 3.9 and 4.1 milligrams; and a third assay, in which 5.4 milligrams of silver had been added, gave 9.2, which, after deducting the added silver, leaves 3.8 milligrams. The average of the three results is 3.9 milligrams from the 100 grams of ore. Two lots of 100 grams of the same ore treated in the wet way gave 5.2 and 5.0 milligrams of silver. Burnt ores from Spanish pyrites carry about 0.005 per cent. of silver. WET METHODS.