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Sec. II, Ch. 12: The Carbonado Diamond

Sec. II, Ch. 12: The Carbonado Diamond Page of 366 Sec. II, Ch. 12: The Carbonado Diamond Text size:minus plus Restore normal size   Mail page  Print this page
144                                 Carbonado.
Carbonado, in operations for gold-mining and other pur­poses, has caused it to rise in price from 2s. 6d. to £8 or even to .£10 per carat.
THE DIAMOND DRILL.
If steel is used to cut rocks, a percussive and not a rubbing or cutting motion must be given to it ; otherwise,, owing to its deficient hardness, the steel itself would be worn away rather than the rock, as popularly exemplified in the ordinary grindstone. Where deep borings for exploring purposes have to be made, it becomes a difficult mechanical problem to construct a machine, which shall satisfactorily impart a striking motion to a heavy steel tool. Moreover,, the difficulties and chances of failure increase very rapidly with the distance from the surface, whereas, with a continuous rotatory motion, it is comparatively easy to bore to any depth. Borings have been effected to a depth of several thousand feet with the aid of carbon, not much greater difficulty being experienced at the end than at the commencement of the operations.
Selected pieces of carbon are firmly embedded in a ring of steel, called a crown, of the size corresponding to that of the perforation which it is desired to bore. This ring is screwed to a series of long hollow tubes, which are lengthened as the work proceeds ; these tubes or rods are kept rotating by steam power, and their weight is so adjusted, that a pressure of half a ton can be brought to bear on the crown, when it is boring a 4-in. hole in native or living rock. The crown rotates some 250 times a minute, and water is continually pumping through the hollow rods, passing under the cutting face of the crow.i, to keep the Diamonds cool, and to wash off and upward
Sec. II, Ch. 12: The Carbonado Diamond Page of 366 Sec. II, Ch. 12: The Carbonado Diamond
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