MODERN SCIENCE.

New Zealand Herald, Volume LXII, Issue 19061, 4 July 1925, Page 7 (Supplement)

MODERN SCIENCE.

ITEMS OF INTEREST. MIGHTY STAR CLASSIFIED. THE MOST LUMINOUS KNOWN. A star 600,000 times as; bright as the «un and moro than 185,000,000 miles in diameter has been classified by the Harvard University Observatory, according to bulletin recently issued by the director, Mr. Harlow Shapley. This star, which is known in the catalogues as S. Doradtis, is the most luminous now known—possibly the brightest object in the entire universe. .S. Doradtis is located in the large Magellanic cloud, in the constellation Dorado, near the south pole of the heavens, and is visible only to observers south of tho equator. It is a variable star, ranging in apparent magnitude from 8.2 to 9.4—(an increase or decrease of slightly more than three times in brightness) and is invisible to the naked eye, although visible in telescopes of small aperture. The faintness to an observer on the earth is due to its enormous distance—more than 100.000 light years —and the investigations of Harvard Observatory have, determined that its true brightness or mean absolute magnitude is minus 8.9, ■or 14.5 magnitudes brighter than the sun. This moans that if it were located whore ■the sun is it would shine with 600,000 times the sun's brightness. SUN'S JOURNEY THROUGH SPACE. Astronomers estimate that in 400 million years the sun has journeyed so far that its light will take 23,000 years to retrace the path. In other words, in 400 million years tho sun has travelled 25,000 light years. OIL FROM WASTE POTATOES. The thin oil extracted by a simple Australian process from spoiled potatoes is claimed to bo of special value in lubricating delicate mechanisms, such as certain scientific instruments. Having a low •.freezing point it may be used for the engines and instruments of airplanes. A HIGH-SPEED HAND-SAW. A new electric hand-saw, pushed like a carpenter's plane by two handles, is claimed to trim tho roofs of freight, cars at the rato of 15ft. a minuto and to bo adapted for inlay work on doors, laying of floors, and a great variety of other purposes. Tho motor, connected to a lighting circuit, is mounted in the frame, ■with the circular .saw at ono end of tho motor-shaft. Saws of various sizes may bo used, and an adjustment may bo made to cut at any mitre. FREEZING A FIRE TO DEATH. A new kind of fire extinguisher has been invented for use in petrol storehouses, oil tankers, and other structures containing inflammable substances. When directed on a blaze these devices actually freeze the flames to death. A very cold and denso carbon dioxide gas is released so that all oxygen is blocked, and the fire, with no oxygen to feed on, immediately dies out no matter how combustible tho material burning may be. Tests havo proved this extinguisher to be very efficient, and even burning oil can bo put out by its use. NEW USE FOR X-RAYS. A French doctor has invented a means of preventing forgeries of modern paintings from being passed off as tho genuine work of tho original art,ist. His method consists o!: a new application of X-rays. Before leaving the studio the painting will be radiographed, so that the film will reveal every detail of tho material on which the picture is painted; every fibre of tho canvas and every knot or stain in tho wood, if the painting is on a panel. A positivo filim will supply proof of identification of the painting and secure the purchaser against fraud. THE DECAY OF STONE. Jlecrystallation of substances dissolved from tho stone or mortar arid deposited just under the, surface of tho stone is a cause of the decay of walls found by the United States Bureau of Standards in several buildings among the 200 examined. The effect—most noticeablo in walls of sandstone—is the same as that produced by the freezing of water in porous iitone. It has been reproduced in tho laboratory by immersing pieces of sandstone in a weak solution of sodium sulphate, and causing the salt to crystallise by evaporating its water. A BIG ELECTRIC FREEZER. The 700-ton refrigerating machine lately installed in Lis Angeles, the largest machine of its kind, uses the power of an 800 horse power 2200-volt three-phase 50 cycle motor. The two-stage compressor has a low pressure cylinder 26 inches in diameter with a 30-inch stroke, and a high-pressure cylinder 16J inches in diameter with a 30-inch stroke. Driven at .150 revolutions per minute and operating at a pressure of 20 pounds suction and a condensing pressure of 170 pounds, the machine has a refrigerating power equal to the melting of 700 tons of ice every 24 hours. The floor space occupied is only 400 square feet. MEASURING OCEAN TIDES. An artificial island, consisting of a buoy bo anchored as to be kept a fow feet below the surface, is suggested by Prof. 11. W. Wood, of Johns Hopkins University, as a method by which bydrographers could obtain the much-desired measurement of the tides in mid-ocean. A special self-record-ing barograph would be operated by tho pressure of the water above the buoy. Winds, waves, and ocean currents would irregularly affect the height of the buoy above sea bottom and the depth of water over it, but il is believed that analysis of the curve drawn on the revolving drum fit' the barograph would show the regular variations due to the periodic rise and fall of the tide. COMBATTING MINE GASES. Danger of mine deaths through smothering by poisonous gases is being reduced in the Illinois coalfields by equipping the . workers with "self rescuers," tested and approved by the American Bureau of Mines. They are designed to give tho wearer half an hour or more after the gas surrounds him before he is overcome, and consist of a pinch clamp for the nostrils, attached to a small can with a mouthpiece. The device is worn in the pocket or on the belt, and is enclosed in a soft brass c.ise that may be ripped open by hand. When the fumes rise, the breathing apparatus is quickly adjusted, and, by inhaling and exhaling through tho mouth into the can, the miner is protected from the poison for at least half an hour, and has a chance to eeek escape. j