Science Siftings

New Zealand Tablet, 12 September 1912, Page 59

Science Siftings

By Volt.’

, i Deepest Spot in the Ocean. The German navy’s surveying ship has discovered in the vicinity of the Philippines the deepest known spot in the ocean, 9780 metres, or 406 feet more than six miles. This record sounding was made about 46 miles off the north coast of Mindanao. The greatest depth hitherto known, 9365 metres — under six miles-was found by the United States cable steamer in 1901 to the south of the island of Guam. . . Hard and Soft Pencils. What makes a pencil hard or soft ? Graphite, which composes the writing crayon in the pencil, is, as everybody knows, so soft that it will not scratch the most highly polished surface of burnished gold. Yet there are pencils so hard that they actually scratch the paper. A pencil is hard or soft in proportion to the amount of clay added to the graphite. A pencil cannot be composed wholly of graphite, for the reason that it would fall into powder. Hence the use of clay as a binding element. . Sometimes the clay is not evenly distributed through the mass, and then one strikes a place that sets one’s nerves on edge. That does not happen so much as was the case a few years ago. Graphite is pure carbon, like that contained in the diamond. The clay used is the finest that can be found and without grit.

The Force of Plants.

The force exerted by plants in the course of their growth was recently exemplified by a stretch of tar macadam pavement at Shoeburyness. The surface became covered with what may be called ‘ blisters,’ raised -a little above the common level. From each of these, in a few days, a series of cracks appeared, extending themselves in rays from a centre. Finally came up a broad, soft shoot, looking extremely well pleased with itself and its work, which proved to be so old and well-known a friend as the thistle. The contrast between the soft, yielding shoot, which the slightest pressure crushes, and the hard material it pierced was almost ridiculous.

The Cutting of Diamonds.

The great Cullinan diamond, the most valuable and once the largest brilliant in the world, is now no longer in existence. Since it has been split into fragments its very name has —officially, at all events - consigned to oblivion. The two largest portions are now known as the ‘ Stars of Africa.’ The other very much smaller pieces, mere chips from the cuttings, have been utilised in the regalia in various ways, and have largely lost their identity. It has been the same with many historic diamonds in the past. Indeed, people owning these treasures seem often to be possessed by a perfect mania for altering their size and shape; sometimes, as in the case of the Cullinan, by slicing them in halves, but more frequently by recutting them. In this latter way the Koh-i-noor has been reduced from 800 carats to a trifle over 100; seven-eighths of the gem, in other words, have been whittled and ground away at different periods by its various owners. In the same way the magnificent Rajah of Mattan diamond has been reduced from 787 carats to 367, the Pitt or Regent diamond from 410 to 136, and the Star of the South from 254 to 127; while the Tavernier, the first’ blue diamond seen in Europe, was deliberately sawn in halves, like the Cullman. Of course, the idea in dealing in this way with these gems is to increase their beauty, and thereby their -value. But the desired result is not always obtained. Experts are agreed, for instance that Hortensio Borghese, the Venetian lapidary who first cut the Koh-i-noor, thereby reducing it from 800 to 279 carats, bungled his work so badly as to reduce the value of the jewel by more than two-thirds.