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of no importance whatever. Therefore in the treatment of tailings very dilute solutions can be used, the only limit being a sufficient amount of cyanide to dissolve the gold satisfactorily. Moreover, however acid the solution may be, when entering the boxes the precipitation takes place equally well, the same amount of gold being recovered as from a neutral or alkaline solution. There are none of the complications arising from the formation of lime and alumina and hydrate of iron, which, under similar circumstances, sometimes occasions so much trouble in the zinc process. Every one here present is aware that a solution containing 0-03 of cyanide will dissolve gold just as effectively as a solution containing 0-3 per cent., provided a longer time is allowed for treatment. In the first case the decomposition of cyanide in the tailings is much less than in the second, and a corresponding economy is effected. The moisture in the original tailings being usually about the same as that contained in the residues, there is, as a rule, no chance to give a large water-wash after the cyanide treatment is finished. The residue discharged contains 10 to 15 per cent, moisture, carrying about 0-1 to 0-05 per cent, cyanide solution when the zinc process is employed. This is equivalent to -Jib. of cyanide per ton of tailings. This loss may be reduced to by using as weak wash a solution containing o*ol per cent, cyanide, which strength will be perfectly suitable for electrical precipitation—though difficult to deal with by the chemical method. Having described the principles involved in this process, it only remains to give some details as to the practical working results obtained at the Worcester works. There are now in use five leaching-vats of 2ft. in diameter with 10ft. staves, each holding 2,700 cubic feet. One tank is discharged and filled every day. The strong solution used contains from o'os to 0-08 per cent, cyanide, and the weak washes 0-01 per cent. The actual extraction of fine gold has averaged 70 per cent., while the consumption of cyanide has been Jib. per ton of tailings treated. The precipitation plant consists of four boxes 20ft. by Bft. by 4ft. Copper wires are fixed along the top of the sides of the boxes, and convey the current from the dynamo to the electrodes. The anodes are iron plates 7ft. long, 3ft. wide, and -Jin. thick. They stand on wooden strips placed on the bottom of the box, and are kept in vertical position by wooden strips fixed to its sides. In order to effect circulation in solutions passing through the box, some of the iron sheets rest right down on the bottom, while others are raised about one inch above the level of the solution, thus forming a series of compartments similar to those of a zincbox, the difference being that the solution passes alternately up and down through successive compartments. The sheets are covered with canvas to prevent short circuit. The lead sheets are stretched between two iron wires, fixed in a light wooden frame, which is then suspended between the iron plates. The boxes are kept locked, being opened once a month for the purpose of the ' cleanup,' which is carried out in the following manner : The frames carrying the lead-cathodes are taken out one at a time. The lead is removed and replaced by a fresh sheet, and the frame returned to the box, the whole operation taking but a few minutes for each frame. By this means the ordinary working is not interrupted at all, and the cleaning-out of the boxes, which is necessary in the zinc process, is only required at very long intervals. The lead, which contains about 2 to 12 per cent. of gold, is then melted into bars and cupelled. The consumption of lead is 7501b. per month, equal to 1-Jd. per ton of tailings. The working-expenses, including filling and discharging tanks, come to 3s. per ton. When working on a larger scale the expenses will, of course, be reduced. After the facts mentioned in this paper it will, ilo doubt, be conceded that electrical precipitation has emerged from its experimental infancy and grown up into a healthy manhood, and proved itself to be a technical and commercial success, and that it is in every respect at least as good a method of precipitation as the zinc process. Anyway, it exists as a tangible fact, which cannot be explained away by argument or ignored by commercial men, who require the best work at the cheapest rate. It is to be regretted that the time available has not allowed such a fully detailed account as could be wished, but sufficient has been said, and figures enough given, to place the Siemens and Halske process within the category of practical precipitants of gold from cyanide solutions. " In the course of the short discussion which ensued it was stated that the costs at the Worcester worked out as follows : Filling and discharging, lOd. per ton ; cyanide, 6d.; lime, l-2d.; caustic soda, 0-5 d.; lead, 1-ld.; iron, 2-2 d.; white labour, s'2d. ; native wages and food, l-9d.; coals, 4-6 d.; stores and general charges, 3'2d. : total, 3s. " Mr. Butters observed that the charges for white lahour —namely, sd. per ton—were very high. They were only treating at the Worcester 100 tons per day. If they were treating 8,000 tons per month instead of 3,000 tons the cost would be the same, and white labour should only be one-fifth of the present charge. The high rates were for white labour and coal. Coal would be nearly constant for additional plant; but, while white labour would not be constant with a larger plant, coal would perhaps be a penny cheaper, and white labour would come down to Id. per ton instead of sd. That meant a saving of 4d. per ton in larger works. In the case of the MacArthur-Forrest process the cost of zinc came to 2-J-d. on every ton. The new process had lead and iron and coal as heavy items against cyanide, zinc, and coal in the MacArthur-Forrest process. Mr. Yon Gernet had. taken iron at 2-2 d., but he had written the cost off by depreciation in one year ; whereas it would last probably for three years, but all the costs they had taken at the outside. They thought the total cost would come down to 2s. 6d. per ton with an ordinary cyanide plant of from 6,000 to 8,000 tons per month. Of course the gain of the process was in the lesser cost of cyanide. Anybody could work at 4s. per ton, but they thought they could reduce that by Is., or may be Is. 6d. If they could bring down the cost to 2s. 6d. there would be an enormous gain. As the boxes had only to be opened once a month, that represented a great advantage in various ways."