Science Siftings

New Zealand Tablet, 6 September 1906, Page 35

Science Siftings

By «VoIt»

A Door-Key Alarm. A novel burglar alarm made in Berlin consists of a small box containing a dry battery with „an electric -bell on top. The apparatus is .fastened - on the door above the' key, and contacts are so arranged that any attempt to turn the key or, -open - the door rings the bell. If- desired, the bell . can be placed at a distance; as in the usual form of .alarm. - - - - Destroying Disease Germs. Once- again it_ is contended that the acids'' oflemons, apples, and other "fruit— citric acid "malic" acid-are capable of destroying all kinds of > disease " germs. Cholera germs are killed by lemon juice or ' apple juice, and typhoid fever germs are killed in half an h o ur~ by .th«se acids, even when considerably diluted. If you- squeeze a ' lemon ' into a glass of water, containing cholera germs, and let it stand fifteen or twenty minules, you may drink the water~ with impunity, as the germs will be dead. These juices will kill other, disease germs. ' Novel Telephone; - - 0 The laltest use of the "telephone, is in locating shoals of fish. The electiic apparatus is a German patent. A microphone, enclosed in a watertight case connected with an electric battery and telephone, is lowered mifa the water. So long as -the telephone hangs free no sound is heard, but on its coming into contact with a Phoal of fish the constant tapping of the fish ajrainst the microphone case produces a series of sounds which at once -betray their presence " The cord attached to the microphone is marked so that the exact depth of the shoal is designated. Electric Plants in Switzerland. The hydraulic power now used in .Switzerland for running electric plants is estimated at more than 225,000 horse-power, of which 40 per cent is employed for electric lighting, 13 per cent, for traction, 23 per cent, for electrolytic work, and 24 per cent, for motors. Even" with- this work - done by water, the imports of foreign coal amount" to,' nearly £400,0.00 annually. Continued increase in electric ' plants is thus assured, and a projected one in the Bernese Oberland promises 40,000 horse-power, whileothers are expected .to follow to supply the 150 000 horse-power needed by the railroads. A iiydro-elec-tric plant on the Rhine near Numpf is to have a 230-foot head of water, with a canal 15 miles long to lead the water from the, dam to" the turbine station. Windmill Electricity. ' *_„ The use of windmills for generating electric current has igiven favorable" results in _the tests for the Danish Government made at Askow by Prof. La Cour, .The - four-wing wheel proves (to "be the best form. With such a wheel having 15 square yards "of surface, he obtained two horse-power " from a wind of 20 feet per second, and ten horse-power from a wind of 35 feet per second. As reserve power when there is no wind, a small -petrol, motor has been more satisfactory and less expensive than a storage battery. 'The JAskow plant cost £1200, including-; land, and the- annual expense of operation is £35. It feeds 350 incandescent lamps, and some arc slamps and motors. A- similar .outfit, costing a'hout £300 r . is recommended for farm purposes and a numiijer of these windmill electric plants are - already running in Denmark. " - The Brightness, of the Sky. . The brigjhtlness of , the sky on a clear, moonless night is one of the mysteries astronomers are trying to explain. The stars appear to shine - from a slightly luminous background, and. ' in a recent paper G. J. Burns, a British astronomer, consid- \ ered that 'the* total light may be roughly taken as eoflial to t>hat of 1000' first-magnitude stars, while J the" lfgfh-fc of all stars visible at one time has leperi j estimated as equal only- fco that of 70- first-magni--tude stars. A common theory is that the light ol the sky is due to telescopic stars. If this were the sole cause, however, the luminosity should "di-minish-near the- horizon, but "instead an increase in ■brightness is plainly perceptible. This and a variability in ..the brightness observed, at different times might bfc explained by assuming -that the> sky's luminosity is partly due to a stratum of luminous " particles at a moderate distance from the earth.