THE DIAMOND.

Waipukurau Press, Issue 306, 10 September 1908, Page 2

THE DIAMOND.

Sir William Crookes, the dislanguished physicist, writes in the “North American Review” —A word as to the hardness of diamonds. They vary much in this — respect ; even different parts of the same crystal differ in their resistance to cutting and grinding. So hard is diamond in comparison to glass that a ; suitable splinter of diamond will plane curls off a glass plate as a carpenter’s tool ■will plane shavings off a deal board. Another experiment that will illustrate its hardness is to place a diamond on the flattened end of a conical block of steel, and upon it bring 'another similar cone of steel. If I force them together with hydraulic power I can force the stone into the steel blocks without injuring the diamond in the least. The pressure which I have brought to bear in this experiment has been equal to 170 tons a square inch of diamond. The only serious rival of the diamond in hardness is the metal tantalum. In an attempt to bore a hole through a plate of this metal a diamond drill was used, revolving at the rate of five thousand revolutions a minute. This whirling force was continued ceaselessly for three days and nights, when it was found that only a small point, one hundredth of an inch deep, had been drilled, and it was a moot point which had suffered most damage, the diamonnd or the tantalum. After exposure for some time to the sun, many diamonds glow in a dark room. One beautiful green diamond in my collection, when phosphorescing in a vacuum, gives almost as much light as a candle, and you can easily read by its rays. But the time has hardly come when we can use diamonds as domestic illuminants. Mrs Kunz, wife of the well-known New York mineralogist, possesses perhaps the most remarkable of all phosphorescing diamonds. This prodigy diamond will phosphoresce in the dark for some minutes after being exposed to a small pocket electric light, and if rubbed on a piece of cloth a long streak of phosphorescence appears.