MODERN SCIENCE.

New Zealand Herald, Volume LXI, Issue 18629, 9 February 1924, Page 4 (Supplement)

MODERN SCIENCE.

ITEMS OF INTEREST. THE COLOUR OF THE SEA, ABSOKPTION OF KAYS. The intrinsic colours of the sea and of lakes have been ascribed to two main causes and to accessoryv;features. The chief cause according to some was the high' absorption by the sea water of yellow and red rays; others considered sea water essentially as a turbid medium, the suspended fine particles of which scattered principally blue rays. In a long memoir on the subject, submitted to the Scientific Institution of Moscow, W. Shulykin arrives at the conclusion that these two main causes suggested are both of importance, but that the colour depends chiefly on four factors, viz., selective absorption of light by the water, diffusion of light by very small particles (probably microscopic bubbles of air and occasionally other gases), selective reflection of light by fine dust, plankton and other solid turbidities, and admixture of the reflected light of the sky. Shulykin makes use of many of the spectroscopic measurements which O. von Aufsess had made in Alpine lakes; but he does not interpret them as showing that the scattering has little to do with the blue colour. His study of the influences of

wind waves travelling over the surface is probably novel. By mixing a colloidal .solution of resin in alcohol coloured with rodalin blue and water, he successfully imitated the colour of sea water. He also points out that the intense blue of some mountain lakes is due to their receiving light only from the zenith, the lower portions of the horizon being shut off by mountains. COUNTING ATOMS BY MACHINE. An instrument which counts atoms audibly was shown by Mme. Curie at the Physical Exhibition in the Grand Palais, Paris. It announces by means of a loudspeaking telephone the actual disintegrations of a bit of the rare element polonium and for the first time in history people can thus listen to the transmutation of elements. A tiny silvered plate containing a minute amount of polonium is placed under a tube with its aperture at such a distance that about a dozen alpha particles pass through it each second. Polonium, like radium, is constantly breaking up into alpha particles of helium, which travel a distance of about an inch and a half. It lasts as polonium only 202 days, whereas the life of radium before its disintegration is nearly 2300 years. Each particle on penetrating the tube causes a luminous discharge which acts as a switch, throwing into circuit a minute electric current that actuates the loud speaker of an ordinary wireless valve receiver. One thus hears, the rapid tick-tick caused by the transmutation of polonium into helium. The instrument provides a novel method of counting the alpha particles emitted by radioactive bodies, and, devised as it is by one of the discoverers of radium, it is creating great interest. X-RAYS AND DENTISTRY. A new tube for producing X-rays, the invention of two Dutch scientists, is expected by experts to be likely to help materially the work that is going on in the treatment of disease with the rays. It is now definitely known that in many cases the X-rays treatment can ameliorate cancer and often prove of great value in co-operation with surgery. One of the special benefits of the new tube is the ease ! with which it can be used for dental : work. CULTIVATED PEARLS. There are now three kinds of genuine pearls, according to the Daily Science News Bulletin (Washington). Most valuable arc the " natural " or "normal," .-pearls found by divers the world over. " Blisters." or baroque pearls, not nearly' so beautiful or expensive as the natural article, have been tor years produced simply by inserting a, foreign body in the producing oyster. But. recently a Japanese, Dr. K. Mikimoto, succeeded in developing a patented method for inducing pearl oysters to grow pearls which are spherical and similar externally to fine natural pearls. His process is to remove a pearl oyster from its shell, cut a patch off its outer shell-secreting mantle large enough to enclose, as a sack tied at the neck, a bead of mother-of-pearl or even an inferior pearl. This bead is embedded in another live oyster, which; after proper treatment of the wound, is returned to its native habitat, where in the course of a few years a coating of pearl may be deposited around the inserted bead . ; Tie methods 'of Dr. ;F. E. : Wright, of the U.S. Geophysical Laboratory at Washington, for detecting the presence of such a bead of Tnother-01-pearl depend on. the fact that the layers of, the natural pearl and -| the moth-pearl* nucleus reflect light idifferently. To quote- further:-— ; '' One method of finding the cultivated Eearl, he explained, is to stand with your back to the window, sun, or other strong source of light, and hold the pearl 30 that it is illuminated by the light. When jthe pearl is rotated on a. string, the characteristic sheen of the mother-of-pearl can be clearly seen shining from inside the pearl when the pearl is in certain position*.''