SCIENCE SIFTINGS

New Zealand Tablet, 9 June 1921, Page 46

SCIENCE SIFTINGS

(By “Volt.’)

The Sun Causes Wind. When any part of the earth becomes heated by the sun’s rays the air becomes thinner and rises. As it goes up a current of cooler air takes its place, thus causing the disturbance we call wind. Likewise, damp airwhich is lighter than dry air of the same,degree of heat — also rise and cause a disturbance above and below. It is for this reason that there is usually a breeze from the sea by day and from the land by night, the land being heated faster than the water and the fresh air from the sea coming in to .take its place. At night the process is reversed. The land cools faster than the water and the wind goes out to sea. Because these processes are continually going on all over the globe the wind frequently gathers strength and attains the proportions of a gale. Spiders as Weather Prophets. There is a wealth of weather wisdom to be got from the observation of spiders. These insects cannot spin properly in a high wind. Before a gale they may be observed strengthening their webs. The shape of the web is also a valuable indication. When the frame-lines are short and stout the insect’s instinct has told it that wind and rain are coming, while long and slender frame-lines are a reliable sign of calm and fine weather. If spiders remain active during rain you may be certain it is only a shower and will be over soon. When, at the beginning of rain, they retire into complete indolence, the unsettled weather will almost certainly last for some time. The time of day at which spiders mend their nets is also a good weather sign. If the mending is observed going on during a summer evening there will be no rain that night. When spiders are seen crawling on walls instead of attending to their nets wet weather is imminent. The Magnet Mystery. The exact principle which causes a magnet to take hold of metals and cling to them with a force which overcomes the principle of gravity is, like electricity, one of Nature’s unsolved mysteries. We merely know that a piece of iron which has been electrically treated will attract and hold various other metals. The force it exerts we call “magnetism,” and let it go at that. The most logical explanation would appear to be that an electricallytreated piece - of iron gives off a force analogous to that given off by radium, in that 'it will affect other pieces of metal without materially lessening its own power. The name “magnet” is derived from the mineral “magnetite.” This, in turn, is so called because it was first discovered in Magnesia. Magnetite is a natural magnet, of which loadstone is one of the best-known varieties. Snapshots of the Heart. Recent discoveries have shown that the X-rays can pass through steel and iron, and many engineering firms are using the X-rays to photograph flaws in the castings of important parts of machinery. This new work has been made possible by the wonderful X-ray tube invented by Dr. Coolidge, which gives out immensely powerful rays that can pass through four inches of steel plate. Now another wonderful invention has been described to the Rontgen Society of England. It is a new photographic plate twenty times as sensitive to the X-rays as the plates ordinarily used, and is likely to revolutionise X-ray work, as it will make it possible to take snapshot photographs of the heart, the lungs, or, indeed, any part of the body, and even cinematograph “radiographs” showing the heart beating, or the lungs at work beating.i Only a few years ago it /took half an hour to photograph the thicker parts of the human body-with the X-rays; with the . new invention a small fraction of a second will suffice.