THE SANDS OF THE SEA.

King Country Chronicle, Volume VI, Issue 448, 16 March 1912, Page 7

THE SANDS OF THE SEA.

SOME PECULIAR DISCOVERIES. Many very instructive matters were touched upon during the lecture of Mr. C. E. S. Phillips, F.R.S.E., at the meeting of the Royal Institution. He told his audience that the colour of the sand of Alum Bay, I. W., is due to a layer of iron oxide with which each sand grain is coated, but iron is present in even the whitest sand. The black ironsands of New Zealand consists mainly of magnetite, while the black sand of the Isle of Wight is chielly silicate of iron. Sand from the Sahara, with its wealth of marine shells, proves that this arid desert was once the bed of a huge ocean. The uses of sand were next touched upon, the chief topic being glassmaking, and to illustrate the subject a red-hot crucible containing molten glass was brought into the lecture theatre and the contents poured out on a slab. On cooling a crystal-clear disc of glass was held up for inspection. Sand has an important place in warfare, as a bank of sand twenty inches thick is proof against modern rifle-shots. The electrical properties of sand are interesting. A jet of sand was allowed to fall in turn on a square of metal, paper, and wood, these being connected with an electrostatic voltmeter. Wood gives the best effect; metal soon "tires," this being due to the surface becoming pitted and retaining a protecting layer of sand. The electricity of sand is positive, but, curiously, a rod of silica—sand is chiefly silica— shows negative electricity. WHY WET SAND DRIES UNDERFOOT. Those who have walked on *. stretch of wet sand have noticed the singular drying effect which occurs when the sand is pressed by the foot. This is due entirely to the alteration in the piling of the sand grains. Normally the grains are close together, but abnormal piling is brought about by pressure of the • foot—that is, the space between tht 2dges of the grains is enlarged and :he water drained away. If the pressure of the foot is continued the sand becomes wetter than ever, the partial vacuum quickly bringing water from the surrounding sand. The various theories of quicksands were also referred to by Mr. Phillips. He favours the theory that the moving character of the sands is due to the imprisonment between the grains of gases from organic matter. The practicability of this theory was shown by comparing the properties of ordinary wet sand and an artificial quicksand, produced by adding sodium peroxide to the sand before adding the same amount of water as in the blank' experiment. The terrible properties of the Goodwin Sands were shown experimentally to be due to the exhaustion oi air beneath the ship, the effect being compared to that exhibited by the leather suckers by which boys lift heavy stones. Boring operations show that the Goodwin Sands are 80 feet deep and rest on solid chalk. . The amount of sand in a tube has, curious to state, no effect on the rate of flow out of a nozzle at the bottom of the tube. This is due tc the way the sand grains interlock. Shrieking sands derive their name from sounds emitted by certain sands when they are struck. Som< shrieking sand in a mortar was pressed by a pestle and gave out a squeal almost human in its tone. Mr. Phillips amused his audience by playing on a sand organ composed of four long tubes of sand, each oi which gave out a different note—the dampness and method of packing be j ing other factors accounting for the variation in tone.—'"Popular Science liftings."