OTAGO INSTITUTE.

Otago Witness, Issue 2892, 18 August 1909, Page 12

OTA GO INSTITUTE.

PROFESSOR WATERS'S LECTURE. The Otago Institute met in the Museum, on the 10th inst Professor Park (president of the institute) occupied the chair The Chairman stated that Mr F V. Morris had been elected a member, and on his motion Messrs /E. R. Green and T M. Gillies were elected members. He aJUiounced that a number of new books had been added to the library, includingone which was a bibliography of the literature relating to New Zealand, compiled and written by Dr T. M. Hocken.—(Applause.) .The chairman remarked that this was a work of immense value to science and literature, and a work which no one else in New Zealand was better qualified to undertake than was Dr Hocken. The latter had spent years on the book, which had involved a very great deal of laborious research.

Mr G. M. Thomson, M.P., stated thai the new vclume of the "Transactions of the New Zealand Institute " had been out of his hands for the past two or three months, and the delay in publication and printing was due, as usual, to the Government Printing Office. The volume would be issued in due course, however, and it would be sent to members by post. The Chairman said this delay in publication was very unsatisfactory, especially in view of the fact that Mr Thomson had done his work so well and promptly. The Chairman announced that a, special meeting of the institute would be held on the evening of August 24th for the reading and consideration of papers on the sub' ject of glaciation, by Professor Marshall and himself.

THE PEINCIPLES OF OBE CONCENTRATION

Professor Waters delivered an address on. " The Principles of Ore Concentration." He explained that ho was speaking of the extraction of metals from their ores — not as might have been supposed, the concentration of the metals themselves before they left the earth. He said that the art of treating ores was very ancient, and that the processes in vogue then did not differ materially from some of those of to-day — which, in view of the fact that a knowledge of chemical reaction was the basis of any system of extraction, was not surprising-. Going on to deal with the various methods of treating ores, the professor said that he did not propose to deal with the various chemical processes, but with methods of preparing ore for chemical treatment. The most important thing was to concentrate good ore; another was to so separate ore that contained two valuable minerals as to allow both to be profitably treated. In concentrating ore, the commonest and most primitive method was hand-picking : separating, by colour and weight, the valuable ore from the remainder. In another method they were separated by their difference in specific gravity — heavy ore being: carried one way by a rushing stream o£ water, and light ore another way But this did not separate ores lilts tin OXlde and wolfram, between the weiglrte of wind* there was little difference, and so, in these cases, a strong magnet was employed. Wolfram was attracted by magnetism, and! tin oxide repelled, and on that basis a. fairly satisfactory method of concentrating ores was obtained. But even this system had its limitations. For instance, something special, was required for the separation of quartz and galena,, and a system ofi oil concentration was used: by passing- the ore over a greased table, diamonds were separated from valueless minerals having; the same specific gravity. At Broken Hill, the problem of separating zinc ore from rhodonite and garnet defied solution for years, until if was partly solved by the flotation process. Even this was not entirely a success, but a combination of the oil and flotation processes promised better things. The last word in ore concentration was the electrostatic separation process, which waa based on the fact that while the metals o£ certain ores were conductors of electricity, others were not.

On the motion of the Chairman, Professor Waters was cordially thanked for his interesting *nd valuable address.

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