SCIENCE NOTES.

Otago Witness, Issue 3249, 21 June 1916, Page 69

SCIENCE NOTES.

A Wonderful Mine. — Situated in the beautiful Kaap "Valley, in the Jamestown district of Barberton, Iransvaal. there is a mine known by the name of Verdite. The name was given to it on account of the peculiar greenstone found in the mine, which is unknown in any other part of the globe. Articles of jewellery and ornaments ore made of verdite, and it has been called the lucky greenstone of South Africa. This greenstone is a silicate of magnesia, or talc, coloured green by nature in tho course of its formation. Other silicates of magnesia may bo mentioned hero—peridots, serpentine, meerschaum, and steatite. The mine—or, rather, hillconsists of three varieties of talc—green, white, and black. But a peculiar fact is that in tho black talc there is present pure gold. Some of the finest specimens of goldbearing rock have been found at this mine. Everyone knows that gold is found in quartz, pyrites, or even in sea-water, but scarcely ever has it been mentioned in books "that gold exists in talc. When the verdite rock has gone through the ordinary process of crushing, and the gold has been extracted, the waste (or what is called the slimes from a gold mine) is used in the manufacture of soap, grease, paint, paper, toilet-powders, gas-jets, electric insulators, crayons, and many other articles of everyday use —in fact, one might say that everything got from this mine can be used for some commercial purpose. —An Expanding Boring Cutter. —

A tool which cannot fail to appeal to engineering shops is the new adjustable cutter of the double-ended typo for finishing bored holes. The cutter consists of two high-speed tool-stool ends, with a centre ooui.ection of a special soft metal alloy. This centre-piece ;s partly banded by an iron or brass clip of U-shape. When the cutter, as a result of use, shows signs of wear, it can bo extended to its original dimensions by hammering the alloy centre, the result of which is to compress the alloy thus forcing the ends outwards. Those can be brought dead to the gauge by tho hammering process, and the U-band round the centre facilitates the true setting of the cutter to the original dimensions. It will be observed that this can bo dono by the man himself at his machine, so that visits to the tool shop are rendered unnecessary, thereby materially saving time. When the alloy centre has been compressed to its maximum, it can be given a now lease of life by the insertion of a fresh centre. The outstanding advantage of this cutter, apart from the saving of time, is< that the nature of the cutter is not affected, as is the case with the conventional tool, as a result of its visits to the tool shop; consequently this adjustable, expansible tool ensures a saving in tool steel. The tool has been subjected to searching and prolonged tests, and it has proved to be as stiff under the heaviest work as the solid steel-cutter. In one particular test a cutter of this type finished 200 Sin by lOin holes in steel castings, every one of which was dead true to gauge. Cobalt a "Curiosity Metal." —

For many years the metal cobalt was regarded as a curiosity by scientists and as a" nuisance" by those engaged in exploiting the mineral resources of the country around the town of Cobalt, in Northern Ontario. The only utilisation of this mineral was in the preparation of the pigment known as cobalt blue. But times have changed. From a curiosity cobalt has passed into one of the most valuable alloys for increasing the strength and toughness of steel, cobalt steel,, in fact, being now recognised as one of the greatest rivals to vanadium steel. Cobalt steel., which is a British production, has been subjected to several searching tests, and in tho making of tool etoel for turning, planing, slotting, drilling, and milling iron and steel has proved exceedingly successful. In one test with a gin twist drill the cobalt steel tool drove 15.200 holes through a iin malleable casting before needing to be ground, the drill running at 820 revolutions per minute. In the preparation of the cobalt for combination with the steel, what is known as the a.lumino-thermic process is practised. Although this is not the cheapest process for reducing commercial cobalt oxide, it has the advantage of giving an absolutely carbon-free metal. The oxide is combined with powdered aluminium, the mixture then being placed in a furnace of conical shape. The chemical action is started by lighting a fuse, and upon tho furnace" being fired the contents are ra.ised to a white heat. The aluminium reduces the cobalt oxide, lib of the former metal reducing and melting 21b of metallic cobalt.—Chambers's Journal.