SCIENCE NOTES.

New Zealand Times, Volume LXXVI, Issue 5288, 28 May 1904, Page 13

SCIENCE NOTES.

WHAT IS A CENTRIFUGAL FORCE? A writer in ‘'The Science and Art of Mining” says the key to the definition of the term “centrifugal force” may he found by first understanding Jiow the word centrifugal is built up. First take “centri,” meaning “centre”; then fugal,” 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 anotiier body tends to fly away from the axis of its motion. Manifestations of centrifugal force are made >n many ways, via., by tho.motion of the earth, the motion of tho governor balls of an engine, the throwing of a stone from a sling, or by the whirling round in a circle of a can of water, the centre of which circle is the shoulder. If by 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 pcu.plicry of tho wheel. Tho air thrown eff from the circumference of a revolving fan is thrown off by centrifugal force, as when the blades of tho fan come into contact with the air the air. strives to reach the fan-tip in os nncircuitous a route aspossible; and it is in this fact that lie® the important part that centrifugal force plays in mine ventilation. Tho immense volume of air thrown off by a fan is all caused by the centrifugal Joroo of the fan, and such being the case tho 'importance of centrifugal force will readily be seen. CURIOUS TREES. Tho most curious specimens of vegetable or plant life in existence are the so-called: “living stones” of the Falkland Islands. Those islands arc among the most cheerless spots in the world, being constantly subjected to a strong Polar wind. In such a climate it is impossible for trees to grow erect as they do m other countries; but Nature has made amends by furnishing a supply of wood in the most curious shape imaginable. The visitors to the Falklands, says an American writer, sees scattered here and there singuiay-shaped blocks of what appear to bo weather-beaten and mosscovered boulders in various sizes. Attempt to turn one of these boulders over and 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 cue of the native trees. No other country in tho world has such a peculiar “forest” growth, and it is said to be next to impossible to work tho ddd-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. Few realise how I'tfclc can sustain the 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 other hand are paddling towards .shore. One need not know how to swim to keep from drowning. Faith in the buoyancy of water is all you need, and children and all others should practice to gain it; it will serve better in most emergencies than even expertnags as a swimmer. When pleasureboats capsize everybody wants to get on top of the overturned or half-filled boat; but it is generally not large enough to keep all entirely above water, and 'nearly all are drowned'. If they would trust the water to boar ninetynine hundredths of their weight, and the wrecked boat the other one-hun-dredth. they niight all be saved. An upset boat will keep Tho head above water of as many people as can get their hands on the gunwale, though it would carry very few. Some day these simple facts may save your life. ' TEMPERATURE OF INSECTS. A Russian naturalist has made a series of measurements, by a thermoeleetrio method, of the temperature of insects. A few of hlis results are noticed below. The temperature of the human body, 1 it will bo remembered, is essentially the same in the Tropics and in the Polar Zones. Insects at rest have a temperature o.mentia I !y the same as that of the air in ordinary conditions of heat and of humlidity. ■When' the insect begins to move, its temperature rises and continues to rise until the motion ceases. This rise of temperature''-continues till at about s degrees 0. (102.2 degrees Fahr.) a heat paralysis sets in. The paralysis is only temporary ; it ceases as .the temperature falls once more. Below—o.s degrees C. (31 degrees Fahr.) insects ly without, motion. The • temperature must, in general, be raised to 12 degrees O. (53.6 degrees Fahr.) before the wings are moved. ELECTRIC POWER WITHOUT FIRES. In an editorial note, "Tho 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 \surfaoe -t 100,000,000 volts, houses being provided with a roof terminal for receiving tho waves. The power transmitted could then bo used for lighting vacuum tubes inside the house! or for driving small motors. The scheme, if practically developed, will revolutionise present methods of supplying electrical energy. CAPTIVE AIRSHIPS. Sir Hiram Maxim proposes to put up two large machines, one at Bari’s Court and the other at tho Crystal Palace. They are to he called captive flying machines. Their combined cost will ba about £12,000. In his grounds at Thurlow Park he has built up one of these machines. , The transmission of power from the motor of the tall steel shaft has been so arranged that* all speeds up to 65 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 he performed. ,• RAIN AND HEALTH. It has often been mode the subject of remark that a very wet year is not ne(cssarily represented by a year of high general' mortality. ?>, far indeed, is this from being the case, writes Dr 4ndr»w Wilson in the ‘'lllustrated London News.” that as regards 1903 it can he asserted that it was a year in which the deaih-rate from infections diseases at large was practically under the average. Tt m* ef course, be held that other conditions than rainfall contributed to this result, but at leas* that cannot b“ regarded as an unreasonable argument which considers the excessive fall of 1903 as a prominent factor "n inducing whatever results are to he recorded during that period in the matter of the public health. Nor are we without certain definite support of the view that an intimate connection exists betwixt rain and health. As has been frequently pointed cut, heavy rainfall washes and purifies the air of • much of its floating dust, among which falls to be reckoned a cer-

tain proportion of disease germs. This dust is washed into the sewers, and passed on to the rivers and seas, ana so may be said temporarily to be lessened, wjtu tho result of diminishing the risks of infection to which we are exposed. Again, heavy rainfalls snisn the sewers, ami remove quickly and effectively the refuse and debris which iu civilised lifo represent sources of illness, especially wnen they are allowed to accumulate near the anodes of mankind. RADIO-ACTIVITY OF THE AIR AND SOIL. An exceedingly interesting summary of the recent work of Professors Lister and (Soitel on the radio-activity of the air and the soil is contained in a recent number of the Geneva “Archives des Sciences/' In order to test whether the rauio-activity of the air was inherent or induced from outside, „a steel boiler of 23 cubic metros capacity was kept closed during six weeks, and an aluminium wire was then introduced and negatively charged to a potential of 2000 volts; no radio-activity was induced on the wire, and the air. isolated in this way from the rest of the atmosphere, was completely inactive. The radio-activity is attributed to an emanation produced by some radio-active substance in the soil which finds its way. into tho included air, and thence into the free atmosphere as well as into the water of mineral springs. An attempt was made to isolate the radioactivity constituent of a specially active earth from the Italian Alps, and the results obtained were in accordance with the view that the soil contained a trace of radium; the hydrochloric acid extract yielded a barium sulphate precipitate as active as potassium uranyi sulphate, and a platinum kathode immersed in the solution became permanently t?) radio-active. Further support of this view is found in the fact that the induced activity separated from the air decays at the same rate as that induced by radium salts.—'‘Nature." GAS LIGHTING^ A novel, but exceedingly useful, suggestion was made by Mr JF. A. 'Sinnatt in an address to the Manchester and District Junior Gas Association, He remarked that while gas engineers very efficiently performed their work os regarded the manufacture of gas they seemed to forget that there were two ends to the gaspipe, and did not pay enough attention to the "flame end." He thought the lighting of houses and other buildings should be supervised by tho gas engineer, in the same way as gas-stoves and the like, and he urged that what was really needed was a perfect Incandescent mantle which should last a year with ordinary usage, cost not more than sixpence, and give a high candle-power. A practically non-luminous gas, of 10 can-dle-power at tho most, with high calorific power, and not to cost more than 2s per thousand could bo burned with these mantles and everybody, he suggested, should be compelled to use the incandescent burners if they wished to use gas. THE WOUNDED' IN BATTLE. A man's life may depend when wounded in battle on the measures adopted when lifting him from the spot where he has fallen and carrying him to the nearest hospital ifcent. There may not be a sufficient number of bearers’ handy, as the "Lancet" has pointed out. Therefore, every combatant soldier should be taught stretcher-bearing. * All appliances for emergency use has already been employed by our Colonial forces. It consists of a 10 or 12ft. bamboo rod—capable of supporting a weight of 3301bs —and a piece of canvas and some fin*. but strong, cord. This makes an’ admirable stretcher, the soldier being wrapped In the canvas and bound up with the cords, through which tho polo Is pushed. A largo number of such stretchers could be carried in an empty regulation stretcher to the fighting line. DEEPEST GOLD MINING SHAFT. „ A correspondent of fe The Science and Art of Mining," resident in. the Transvaal, says that Jupiter Q. M. Co.'s ‘Gatlin'' shaft is the deepest of any gold mine in the world. The present depth is 3913 feet, and this is being continued down to the reef, which will be encountered 1 at a depth of nearly 4200 feet. In the near future the "Gatlin" will hold only a secondary place amcftxg the deepest gold mining shaffi. as there are bore-holes on oth**r properties which have reached a depth of almost 5000 feet before entering auriferous strata. Among these may be mentioned the two bore-holes of the Turf Mines which have encountered the Keef. Series at a depth of 4802 feet and 4742 feet respectively. The above company are only awaiting a suppply of labour to commence sinking operations, - OCEAN TEMPERATURES. It is always cold at the bottom of the sea; the influence of the warm surface currents does not extend below 100 fathoms. In the great depths the temperature is for ever close to the freezing point. In the tropics ‘•he difference between surface and bottom temperatures is frequently over 45 decrees. From 100 fathoms down, or throughout the waters beyond the influence of the! sun. temperatures remain practically 'constant. At tho surface the. lines of equal temperatures are parallel with the equator although subject to deflections by currents; at the bottom they follow the general trend of the continents. The coldness at the bottom of the sea is due to <*he water in polar regions sinking and gradually spreading itself over the ocean floor. ‘A BRILLIANT LIGHT. There are reports of a new incandescent lamp tho invention of Professor Drehschmidt. It burns petroleum, and gives a light equal to 2200 standard candles. It has no wick. The light is started by the ignition of a small quantity of methylated spirit.and actuating a small air-pump worked ' by hand. When the lamp is warmed up sufficiently it appears to require no more A pressure-gauge indicates any variation, and a filing off in the light may be remedied by means of tbe air-pump. Portraits, it is said, have been taken by its -light in from five to seven seconds, and collodio-ohloride prints hav> been made in 35 minutes. The mantles cost eighteen pence, and last for 100 hours. The cost of the petroleum is about Id per hour. THE SENSE OF TASTE. The tongue is not the only organ used in the enjoyment of this sense, and alone it is scarcely capable of annraciating delicate flavours. The difference .between sail and sugar when placed on the tongue is hardly perceptible, provided the tonoue is pet allowed to touch th- roof of the mouth and the lips. Indeed, the act of getting the full enjoyment of a flavour, commonly called smacking the lips, consists in bringing the tongue into contact with the roof of the mouth and the lips. By this act the' substance to be tasted is spread over the surfaces of these parts, parHcularlv of the tongue, and mixed ■with the saliva. Hew this act produces taste is not exactly known. ‘ TTCK-TOCK.” The "fick-tock” that is nnivorwlTv re-' garded as the seumi ef both pe-dnlnm end soring clucks has been inve.t-'ge+ed h- Dr ■Ree-nhecll a TWlin nsveholom'ct H» finds that tdm "tick" results when the right arm of the escanement anchor strikes a cog the wheel moving upward, while the Ueck” is produced when the other arm strikes a cog moving downward. The different conditions give different acoustic effects. STIMULATING THE INVENTIVE FACULTY. The Ncwhurg. N.Y.. Board of Education has decided to make an effort to cultivate the inventive genius of pup..s in the public schools. I he J)lan adoptid

for tho manual training schools is ns follows:—-Six prizes are offered for tho Inst original suggestion or invention that may bo presumed during tho coming school year. The prizes aro lo ho lOdol. for tho first prize, odol. for the second, 3d„l. each for tho titled and fourth, and gild. each for the fifth and sixth. Tho suggestion or invention must be now, and the sole production of the one who presents it. CURIOUS BYES OP ANIMALS. Many animals possess more than two eyes which do not act together. A leech, for example, has 10 eyes on the top of its head which do not work in concert, and a kind of marine worm has two eyes on tho head and a row down each side of the body. Some lizards have an extra eye on the top of the head which does not act with the other two. A bee or wasp has two largo compound eyes, which possibly help each other, and aro used for near vision, and also throe little simple eyes on the lop of. the head which are employed for seeing things a long way off. TO FIND THE HEIGHT OF HIGH EOOirS. A simple method of finding the height of high interiors is to use«a toy balloon attached to a thread. When the balloon touches the roof or coiling, the floor lino is indicated on the thread by a knot, and the length measured along n convenient horizontal plane. This method was successfully used iu the measurement of tho height of cavern roofs in the Mammoth. Cave, Kentucky, THORIUM. At a meeting of the Society of Chemical Industry held in New York Mr Lieber is reported by the "World" to have stated that thorium gives off emanations which, like those of radium, possess the ability to render all matters radio-active with which they came in contact.