A Few Cosmic Riddles

Science for You. By J. G. Crurv her. (Routledge. 5s.)

New Worlds for Old. By R.. G. Lunnon.. (Methuen. 2s. 6d.) Science for You is a brilliant collection of essays on some of the most interesting developments now engaging the scien- tific world. They are -written in good plain English, free from technicalities, and cover a large range of subjects-. They are, of course, for the layman, not the expert, and rketend to 'nothing except being informative: " The Moon our Saviour" is an amount of the part -taken by the Moon in assisting the Earth to recover its health after one of its periodic ailments. We are told that radio-activity tends to heat up- the Earth faster than it can get rid of the heat. That part of the Earth's crust which overlies the oceans gets adequately cooled on the same principle as the car engine gets cooled by the radiator ;- but the large continental masses cannot get rid of the heat fast enough

and so the lava in which their roots are embedded gets slowly melted. These granitic roots extend down into the lava about eight times as far as the portions we see extruding. When the lava is fluid enough, the continents have lost their anchors, and the Moon with its gravitational pull is able to start moving them to westwards. This exposes a fresh portion of the molten lava -to the cooling action of the oceans and so gets rid of the excessive heat.

The Moon, therefore, -acts like the dentist who removes inflammation by pulling out teeth.- It is a clumsy dentist, and sometimes some of the gums come away in the process. The rent so caused in the Earth crust may be an additional means whereby heat escapes. After these cooling processes, which last for about five million years, the Earth has a spell of arctic conditions. We have just finished one of -these glacial epochs and are now due for a long spell of increasing warmth in which the world will be safe for democracy.

Another interesting essay relates to cosmic rays, a mys- terious emanation which it is now known reaches us from the outer Universe. These rays are akin to radium but are four times as powerful.

• They were discovered by taking up in a balloon an electro- scope similar to that used for measuring the rays from radium.

• The higher the balloon went, the greater grew the readings, but since the radium rays were steadily growing weaker, this must have been caused by the cosmic rays, which were growing stronger owing to the lessened absorption by the • terrestrial atmosphere.

- By lowering the electroscope into Muir Lake and Arrow '•• Head Lake (both mountain lakes in North _America whose ' waters are fed by melting snow and so are not radio-active) it was proved that the cosmic rays were independent of the ;rotation of the Earth. They cannot, therefore, come from any particular sun, or star, or comet, but must be some general manifestation, literally from the back of Beyond.

- Professor Milligan suggests that these rays are the outcome of some new kind of nuclear condensation of rays into atomic.

matter, that is, that the countless streams of rays from all • the suns and stars meet somewhere in the celestial concave, -and there re-create the matter out of which they themselves originated ; and that the product is manifested to us in these cosmic rays. Were there not some such process at work the Universe would be running down towards zero and towards a • final futility repugnant to religious faith. The truth emerges

but slowly, but every fresh discovery of science reveals an immutable- fixity of purpose which confirms our belief in the

future.

In "The Health of Miners" we read of researches on the action of salt added to the miners' drinking water. In some deep collieries the miners lose as much as 18 lb. of water and one ounce of salt from their bodies per working shift.

The experiment was tried of adding salt to the water the miners drink. It was found that this relieved cramp and reduced the after-effects of fatigue so much that in some cases

"their wives reported that their husbands had become easier to live with. This capital discovery is of the utmost importance to the future of mining, when most pits will have temperatures of upwards of 100°F., and also sheds light on the popularity of salt in the tropics, and at Shanghai, the large consumption of salted ham and salted beer in mining districts, and the passion for salted herrings amongst Cornish tin miners."

Other interesting chapters deal with earthquakes, hurricanes, thunderstorms, heating of houses, ultra-violet rays, and ultra-sounds as used for detecting submarines in the late War. With regard to the latter the present writer was associated with the original researches carried out during the War, and has seen fish killed by these very powerful but quite inaudible vibrations. The principle is this : a plate cut from certain

varieties of quartz alters its volume when subjected to elec. Ideal forces; and therefore communicates a Pressure wave to the air or water in which it is immersed. If these pressure waves follow each other at more than twenty thousand waves

.-eCond, the "sound "'is above the audible limit, but can still

manifest itself in other ways, as for instance, by disrupting a wooden object so that it bursts into flame, or by killing fish, or by acting on a suitable receiver. The waves are also re-

flected from objects like submarines and give rise to an echo. Now by taking the time between the starting of the wave and the return of the echo in the receiver above-mentioned, it is possible to deduce the distance of the submarine, and two such observations from different positions will • give its location by triangulation.

Mr. Crowther -combines the scientific method with a rare capacity for exposition. He is so thoroughly master of his subject that he can make himself plain to the reader without the obfuscations of the second-rate writer, who so often designs, not to elucidate any depth of thought, but rather to hide its shallowness.

Professor Lunnon's excursion into the realm of modem physics is mild in comparison with the foregoing, but the book is both sound and simple.

He treats of the atom with its satellite protons and electrons without perhaps the verve of an Andrade, - but well enough. He tells us of radium, of gravitation and Einstein's theory, and of the nature of crystals. The table of the elements with which he concludes makes us wish Professor Lunnon had given us another chapter on the atomic theory and the two elements not yet discovered, but we should be grateful for what we have.