DISCUSSION OF MR. H. LIPSON HANCOCK'S PAPER Mr. H. LIPSON HANCOCK (Moonta Mines, South Australia) wrote that following mechanical concentration and smelting, the wet treatment of vein-stuff containing sulphide copper-ores (especially those associated with iron-pyrites, and these were probably more common than those that were free from the latter mineral) was essentially required, and present-day experience was proving that this style of treatment would be more widely adopted in the future than it had been in the past. It had gradually grown in connection with the operation of the Wallaroo and Moonta mines, and he hoped at an early date to attain an extrac tion in this department of over 2,000 tons per year, providing an ample supply of acid is available. Of course, this output would be obtained from treating a large quantity of crushed veinstuff, which had accumulated during a number of years; nevertheless it indicated the importance attaching to the process. There was no doubt that this means of extraction, in which the assistance of sulphuric acid played an important part, would be still further improved. He (Mr. H. Lipson Hancock) might repeat that the tailings at the Moonta mines are chiefly felsite-porphyry, with a small percentage of copper-pyrites and a little bornite. The assay for copper in recent years was about 07 or 08 per cent., although the average of the full heaps under lixiviation might be set down at 09 per cent. There is only a very small percentage of ironpyrites in the material of the Moonta mines under treatment, so that it causes a dearth of iron in the liquors. In order, therefore, to facilitate the leaching operations, it will be necessary shortly to use a small percentage of sulphuric acid; this will enable the liquors to attack the proto-salts of copper as they are formed, and lead to higher extraction. New tailings from the concentrating plants, after dumping, are periodically soused for some weeks, and then allow to rest for 3 or 4 months, according to circumstances. They are then drenched again; and, after a further short rest, they are generally in a sufficiently oxidized state for leaching, as indicated above. The precipitate is washed against a stream of fresh water, and * Trans. Inst. M. E. 1901, vol. xxii., page 461. divided into three classes, the coarser and heavier being separated as the best. The first and second classes are melted in a reverberatory-furnace, with other coarse copper from the concentrating ores. There is only a small percentage of the third-class precipitate, and this has to pass through two furnaces in the smelting. There was, he might say, a freedom from impurities in the material, and good copper known as the Wallaroo brand resulted therefrom. DISCUSSION OF MR. J. J. MUIR'S PAPER ON THE "TREATMENT OF LOW-GRADE COPPER-ORES IN AUSTRALIA."* Mr. H. LIPSON HANCOCK (Moonta Mines, South Australia) wrote that there is no doubt that sulphuric acid is useful in connection with the wet treatment of sulphide ores of copper, especially when oxidation has more or less set in. This may be the result of natural weathering, but it is generally a slow operation. If, however, the ore be properly dumped and soused periodically with liquors containing salts of iron, and is allowed to rest and dry for some time, oxidation is very much promoted. Sulphuric acid applied at this stage is a powerful solvent, and its use has led to very satisfactory results. DISCUSSION OF MR. F. J. NORMAN'S PAPER ON "BORING IN JAPAN."+ Mr. F. J. NORMAN (Calcutta) pointed out the following errata in his paper:-On page 685, line 6 should read "depths of 300, 480 and 720 feet below sea-level, and the depths increase the farther one goes inland." On page 690, line 8 should read "depth of from 5 to 8 feet," etc; and line 13, "bottomless tub or box," etc. Page 691, line 17 should read " (Zelkowa acuminata)." Mr. WILLIAM CHARLTON read the following paper on the "Use of Ratchet and other Hand-machine Drills in the Cleveland Mines": * Trans. Inst. M.E., 1902, vol. xxiii., page 517. + Ibid., 1902, vol. xxiii., page 685. VOL. XXIV.-1902-1903. 35 35 USE OF RATCHET AND OTHER HAND-MACHINE BY WILLIAM CHARLTON, Assoc.R.S.M. Some twenty years ago, almost the whole of the Cleveland ironstone was won by the chisel-pointed hand-drill, with a swelled end to add weight to the blow, and well known to all interested in mining as the "jumper-drill." So established had this mode of drilling become that the old practical miner of that time naturally considered it necessary for working the Cleveland stone that the holes should have the triangular shape A, and that it was only by his skill in drilling, with the jumper-drill, a hole with a "flat-back" or "flat-front," "flat-top," or "flat-bottom," that the stone could be successfully mined. Experiments, however, had been made with rotary drills, which showed conclusively that a round hole could work the stone; and the millions of holes which have since been drilled by the compressed-air and electric drills, so successfully introduced by Mr. William Walker and Mr. A. L. Steavenson, are more than ample proof of their suitability. Since 1880, mining by power-machines has made great progress and at the present time about one-third of the Cleveland ironstone is won by such machinery. Until 1888, very little use had been made of the hand-machine drills. The late Mr. George Lee had tried some at the Liverton mines, and the late Mr. T. Allison, of Guisborough, had introduced a few ratchet-machines into the Belmont and Spawood mines of the Weardale Iron & Coal Company, Limited. In 1884, owing to depression in the iron-trade, the Slapewath mines of Sir B. Samuelson & Co. were closed. It being absolutely necessary that steps should be taken to reduce the cost of winning the ironstone, on restarting the mines in 1886, a thorough and exhaustive trial of the ratchet-machine was instituted. The first machines were of crude construction, being fitted with loose brasses in the barrel and thick-edged drills; and, when drilling the hole, the machine was set against a prop fixed between the roof and the floor. It was soon found that a great drawback to the use of the machine was the time spent in setting these props or stands, a considerable portion of the time saved in drilling the hole being spent in the preliminary setting of the props and in changing In many instances, the stone thrown down by the the drills. |