Science Siftings

New Zealand Tablet, Volume XXXVI, Issue 3, 30 January 1908, Page 35

Science Siftings

By 'Volf

A Curious Pact About Brass. It is a curious fact, which has hitherto puzzled " the most) clever - philosophers, that common 'brass which is subjected for some time to constant tension occasionally undergoes a remarkable change. It" loses its tenacity and in a short time becomes almost as brittle as glass. Eye -Photographs. An image impressed upon the retina of the eye re^ mains there an. appreciable time. This is the reason why a torch swung rapidly seems to be a circular flame. The sensibility of "the retina is different at different times of the day. Everyone has noticed how. on waking in the morning and looking at the bright window, then closing the -eyes, he will ■ observe an impression or phantom of the window for an appreciable time after his eyes are closed. Elevated "Rivers. The most elevated river in the world Is the .Desaguadero, in Bolivia. It is of a considerable depth, and its whole length, from, the village of Desaguadero, at the south extremity of Titicaca, to the north end of the Lake Aullagas, is about 180 miles. The average elevation of the valley or tableland of Desagua/dero above the level of the sea is about 13,000 feet. The river whose source lies highest is the Indus, which rises on the north of the Kailas Parbat. mountain, in Tibet, 22,000 feet above sea level. Diamond Cutting. Although the Cullinan diamond weighs over 3000 carats in its present natural state, he would be a rash man who would venture to say what its weight will be when cut. The Koh-i-noor was reduced by an unskilled stone-cutter from 793f, carats to. 280 carats f a second cutting brought it down to 186 1-16 carats, and a third to 106 1-16 carats, or less than a seventh cf its original size. How delicate a matter this diamond cutting is was proved in the case of the ' Great Mogul.' In the rough state this stone, according to Tavernier, weighed 787i carats. It was Hortensio Borgis who cut it, for which he was also badly paid. When it was cut he was reproached for having spoilt the stone, which might have remained heavier, and instead of rewarding him the King fined him 10,000 rupees.' Some Old Trees. The cocoanut palms of Brazil live from 600 to 700, years, and the Arabs assert that the date palm frequently reaches the age of 200 to 300 years. Wallan's' oaV, near Paisley, Scotland, is known to be more than 700 years old, and there are eight olive trees on the Mount of Olives, near Jerusalem, which are known to have been flourishing in 1099. The yews T at Fountain Abbey, Yorkshire, England, were old trees when, in 1132, the abbey was built, and a redwood in Marip'osa Grove, California, is a manifold centenarian. Baobab trees of Africa have been computed to be more than 5000 years old, and the deciduous cypress in Cbapultepec, Mexico, is considered to be of a still greater age. Hunnboldt said that the Dracena Draco, in Orota/va, on Teneriffe, was one of the- oldest inhabitants of the earth. ' " * ' Breath Drawings. Some curious experiments may be made - with the breath. On a pane of glass or a mirror that has not been polished just beforehand trace a figure or a letter or a name with your finger. Nothing will be visible. But breathe on the glass, and the tracing will at once appear. Now, on a freshly polished plate of metal or glass place a coin. After a few moments remove the coin, and nothing will be seen on the surface, but breathe on it where the coin was lying, and an image of it will appear. If you polish the coin instead of the metal or glass the same effect will be produced when you breathe on the surface. If you have a plate of glass that has been against an engraving for several years breathe on that side of it, and the lines of the engraving will become visible. This may fail sometimes, but rarely. Does all this sound like magic ? The explanation is " a natural one. On the surface of all solids a layer of gas, vapor, and fine dust' gathers. When you polish the object the layer is removed or it is altered by the contact of other solids. If the object is breathed upon the breath , condenses more easily on some parts ,than it does on others, according to the condition ,or state of this layer, and therefore any marks made on it will become visible.