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is discontinued, being replaced by an application of the Pohle air-pump. All four of the solutiontanks are connected underneath by a 3 in. lead pipe, which joins a pipe of similar size leading down under the floor below (to give the solution a certain amount of head), then turning and leading up, over, and into the settling-tanks. Just beyond the lower elbow a lead air-pipe is introduced. When it is desired to move the solution the method of procedure is as follows : The valves of the solutiontanks are opened, allowing the liquid to flow through the piping, air-pressure is turned on, and the rising bubbles of air suck the solution along with them. The operation is entirely automatic and requires little or no attention. The second settling-tanks and the precipitating-tanks are connected by a similar continuance. All solution is allowed to stand twelve hours in the solution-tanks and twelve hours in the second settling-tanks before being pumped over for precipitation, thus insuring the complete settling of all slimes. Precipitation of the gold is accomplished by the use of sulphur-dioxide and hydrogensulphide, the resulting sulphides being collected in a filter-press, dried, roasted, and melted. Some metallurgical features developed in actual working may be of interest. Before taking charge of the mill the writer had been informed that Boulder County ores should be roasted at a very low heat, not only on account of the loss of gold by volatilisation along with the tellurium, but because marcasite and the ferro-tellurides were so apt to form non-porous black oxide of iron under a high heat. The latter condition does not seem to have been attained any more than in roasting iron-pyrite. A very careful and exhaustive system of checking by bullion returns and by assays shows that there has not been any appreciable loss by volatilisation since the mill started. An average of all daily assays made on ore entering arid leaving the roaster has shown a slight increase in value instead of a loss, as it should, owing to the loss in weight incurred in roasting. This increment is 0-03 oz. on 1 oz. to 3 oz. ore. It was at first deemed necessary to maintain a moderate fire in the first fire-box of the roaster, and apply the greater part of the heat through the second and third box. This practice was found to diminish the capacity; the three fire-boxes are now fired alike, and are crowded to the utmost, a steam-jet being used under the grates to aid combustion. The average contents in sulphur of the ore treated has been 2-5 per cent. ; this must be reduced to a trace or a few hundredths to give a 95-per-cent. extraction. Hence the necessity of a very great heat. In the light of our experience here, remembering also that nearly every member of the tellurium family has occurred in the ore treated, it would seem that the loss of gold in roasting tellurium-ores has been overrated, certainly on material ranging from 1 oz. to 3 oz. in value. Occasional lots of even much higher grade have been treated without any sensible loss. After numerous experiments, the least amount of chemicals that was safe to use was found to be 10 lb. chloride of lime and 15 lb. sulphuric acid 66° for the barrel-charge per ton of ore ; andf lb. sulphur, f lb. iron-sulphide, and 1J lb. sulphuric acid per ton for precipitation.

TEMPERATURE IN AMALGAMATION. [From the Engineering and Mining Journal, New York.] Some months ago Mr. Thomas J. Grier, manager of the Homestake Company's mines in the Black Hills, in South Dakota, ascertained by experiment that the cooling of the water used in the stamp-mill batteries very considerably increased the yield of gold from the Homestake ore. The difference was in the saving of the fine gold—the coarse gold taking care of itself—which was apparently much greater at lower than at higher temperatures. The facts, as communicated to us through the courtesy of Dr. Franklin R. Carpenter, of Deadwood, are that two batteries side by side were run upon the same ore, one with the water at a temperature of about 50 deg. Fahr., and the other at a higher temperature of 60 deg. to 70 deg. There was no possible doubt of the increased yield from the colder battery. It was supposed that more fine gold amalgamated at the lower temperature —the coarse gold not being lost at any temperature. Mr. Grier desired to make the facts public for the benefit of mill-men, and we do so with much pleasure, hoping to draw out discussion on the causes of this difference, as well as notes of the experience in other mills. The first theory propounded by those to whom the facts were submitted was that at the lower temperature there was either less oxidation of the mercury or that there was less decomposition of iron-pyrites or other minerals contained in the ore to foul the quicksilver. Either of these causes would, of course, interfere with the amalgamation of the fine gold. In answer to a suggestion that in warming the water by waste steam small particles of oil might be carried to the batteries, Dr. Carpenter obtained from Mr. Allan J. Clark, assayer for the company, a statement that the mill water, while the higher temperature was used, was never in contact with any oil or grease. The steam from the cylinders was passed through a series of pipes, with which the mill water was held in contact for a period of time sufficient to give the desired temperature. The condensed steam was discarded. Mr. Clark also added to the facts in the case the statements, from his personal observations, that in the Golden Star Mill the water of a single battery was cooled by contact with pipes containing a freezing mixture placed immediately below the first row of plates, so that the water on the second row of this battery was about 10 deg. Fahr. below that on the adjacent plates presumably receiving the same quality of ore. The recovery of amalgam was decidedly better than from the other plates. In the Highland plate-house (third row plates) the recovery of amalgam would diminish during a period of warm weather, and perhaps for twenty-four hours after. There seems to be no doubt about the correctness of Mr. Grier's observations, nor about the fact that better results were obtained in amalgamating Homestake ore when the water was at a temperature of 50 deg. than when it was at 60 deg. or over. Whether the explanation is that given above, whether there is really a temperature at which the affinity of quicksilver for gold is at a maximum or whether the effect is only mechanical, does not seem to be decided,