SCIENCE NOTES.

New Zealand Mail, Issue 1682, 25 May 1904, Page 63

SCIENCE NOTES.

iWHAX'IS A CENTRIFUGALFORCE ?

A miter ill.‘‘The Science and Art of Mining’’ says the key to the definition of: the. term “centrifuga-l force” may be found- by first understanding how the word centrifugal is built up. First take, “centri,” meaning “centre” : then fu- >. gal,” meaning “fugitive” ; and from this we see that centrifugal force must be a force which is a fugitive from a centre, or the force by which one body rotating round' another body tends to fly away from the axis of its motion. Manifestations of centrifugal force are made m many ways, adz., by "the motion of the earth, the motion of the governor balls of an engine, the throwing of a stone from ia ; . sling, or by the whirling round in a circle of a can of water, the centre of which circle is the shoulder. If by r means of a' flaw the rim of a fly-wheel were to break the broken piece would fly off, through, the agency of centrifugal force, at a.tangent to. the periphery of the. wheel. The. air thrown.,off" from the circumference of a revolving fan is thrown off by centrifugal force, as when the blades of the fan come into contact with the air the air strives to reach the fan-tip. in. as uncircuitou® a route: as passible; and it. is in this fact that lies the important part that. centrifugal v force plays in mine, ventilation. The. immense volume of air thrown off by a. fan is all caused by the centrifugal force, of the fan, and such being the case the ’importance of centrifugal force will readily be seen. CURIOUS TREES. The most; curious- specimens of vegetable or .plant.,life” in existence are- the so-called “living’stones” of the Falkland Islands. Those-island's are .among the most 'cheerless spots in the world; being „ constantly’Subjected to a strong Polar wind; -In such a cllimate it: is impossible’ for trees- to grow erect as they. do. in * other-,countries; but Nature has made amends by furnishing a supply of - wood' • in the-most curious'-shape imaginable. The visitor's to the Falklandsy says an American' writer, sees scattered. ■ here and there singular-shaped blocks of what appear, to,, be weather-beaten, and mosscovered boulders in various size®. At-tempt:-to turn . .one. of these boulders over aud you will met with an actual surprise/ because the stone is actually anchored by roots of great strength; in fact, you will find- that you are. fooling with one of .the native 1 tree®. No other country in the world has such a peculiar , - “forest” growth, audit is said to be next to impossible-to work the odd-shaped blocks into fuel, because the wood is perfectly, devoid of grain, and' appears to be a twisted mass of woody fibres. WORTH TRYING TO REMEMBER. 1 Few realise bow l ; ttle can sustain tbe body in water. One finger: on a campchair or small box or board will; easily keep the head above water, while the feet and the ot-lier hand are paddling towards shore. One need not know bow to swim to keep from drowning. Faith in the buoyancy of. water is l all you heed, and children and all’others: should practice to gain it; it will serve better . in* most emergencies than even expertness as a swimmer. When pleasureboats capsize everybody wants to get on top of the overturned or half-filled boat; but it is generally net large enough to.keep all entirely above water, and nearly all are drowned. If they would trust tlie water to bear ninetynine hundredths of their weight, and the wrecked boat the other one-hun-dredth, they might all he saved. Anupset boat will keep the head above water, of as many people as can get then* hands on the gunwale, though it would carry very few. Some day these simple facts may save your life l . . ' TEMPER ATTIRE OF INSECTS. A Russian naturalist has made a series of measurements, by a thermoelectric; method, of the temperature: of bisects. A few of-Ms results are noticed, below. The temperature of the human body, it will be remembered, is essentially the same in the Tropics and in the Polar Zones. Insects at rest have a temperature essentially the same as that of the surrounding air in ordinary conditions of heat a-ncl of humidity. When the insect begins to move, its tem.pei*ature- rises and continue® to rise until the motion'ceases. This rise of temperature continues till at about -S degrees G. : (102.2. decrees Faihr.) a heat paralysis sets in. The paralysis is only temporary; it cease® a® the temperature falls once more. Below- —0.5 degrees C. (31 degrees Falir.) insects are perfect]y" without motion. ~ T!ho temperature must in general, he raised to 12 degree® C. (53.6 degrees Fahr.) before the wings are- moved. s i the mosquito crusade. . - In' 1902 Major Ross, at the invitation off the Suez Canal Company,, proceeded to Ism ail i a in order to advise upon a method to rid the town of mosquitoes, and as the result of his- advice .a series of: measures was instituted to accomplish this.' These consisted in filling in ~ ntarsh land/:a weekly flushing and cleansing of drainage channels, and,

about the houses, petroleum treatment of drains and waste water- that does not soak away. Professor Boyce has recently made a 'tour of Inspection, and! reports that as a result of this anti-mos-quito campaign, the mosquitoes in Ismailia are no more abundant than in Paris. Malaria also has much diminished, from 1555 cases in 1902 to only 209 cases in. 1903. The expenditure to accomplish such results has not been great, £4400 in the initial cleansing operations, and an annual outlay of £720. PHYSIQUE OF THE- JAPS. Although small in stature, the Japanese are physically and mentally a wellendowed race. This is attributed to their mode of living. They go ; in strongly for gymnastics, and are extremely frugal in their diet. The Japanese soldier has muscles like whip-corch and has an excellent memory. One of the secrets of their high standard l is the copious- use of water, both internally and externally. They often drink a gallon a day, and are very fond) of exceedingly hot baths followed by cold douches. It is said that such, a disease a® rheumatism is unheard of in Japan. They are exterm-ely fond of fresh air, and in the matter of alcohol and to-

bacco are extremely moderate. Truly a splendid example for many Western nations. ELECTRIC POWER WITHOUT FIRES. In an editorial note, “Tlie Electrical Magazine” comments upon the work of Mr Nikola Tesla, the great- American electrician, who promises commercial schemes for wireless electric power transmission. A-tower will be erected at some suitable spot, and energy delivered over the earth's surface it 100,000,090 volte, house®-being;provided with a roof terminal for receiving the waves. The power transmitted could then ho used for lighting vacuum tubes inside the house, or for driving small motor®. The scheme, if. practically developed, will revolutionise present methods of .supplying electrical energy. CAPTIVE AIRSHIPS. Sir Hiram Maxim propose®, to put up two large machines, one at Earl’s. Court and the other at the Crystal Palace. They are to be called captive flying machines. Their combined cost will be about £12,000. In his grounds at Thurlow Park he has built up one of these machines. Tli© transmission of power

from the motor of the tall steel shaft lias been so arranged that all speeds up to Go miles an hour may be obtained. Each car will hold about six people, and with the speed sufficient- to make the aeroplanes effective, curious evolutions in the air may be performed.