SCIENCE NOTES.

Otago Witness, Issue 3276, 27 December 1916, Page 59

SCIENCE NOTES.

The Source of Potash.— The German potash fields were once seas. Drained by volcanic activity, they were converted into vast stretches of dry land covered deep with stranded seaweed," which presumably was in the same ratio of size to the present-day kelp as all vegetation of the early periods was to that of to-day. The earth's heat reduced this to ash., and left Germany this rich natural resource. But efforts arc now being made to collect seaweed from the eea on a vast scale, and treat it for potash. One .Steel Car Every Hour.—

In the Pennsylvania Railroad Company's workshops at Alcona an all-steel box car is turned out every 60 minutes. It takes 5100 rivets to put together each of these cars. The plates of steel are cut to size by shears that make a 10ft cut in ain steel plats about as easily'as a tailor snips 3in from a piece of cloth. Curved plates are pressed into shape by a machine that exerts nearly 4-,000,000ib pressure. Rivet holes are punched by a. machine that can make 160 holes through a steel plate at every movement. Each car weighs 60,000Jb, and has a capacity of 100,OG01b. Why You Swing Your Arms.—

If you watch people walk you will note that nearly all of them move their arms. If they walk slowly the movement of their aims is scarcely perceptible; if they walk ropidly their arms generally swing vigorously. Most people believe this swinging of tho arms as they walk is merely a natural swaying motion. It is natural enough; but the evolutionists contend that the nature of it dates back to thoso .unknown days when man was a. quadruped of Darwinian theory. Of course, when man was a four-footed animal he walked with his "arms" as well as his legs, and even to-day, after the thousands upon thousands of generations that have passed since he assumed an upright position, every time he takes a step his arm moves a trifle, involuntarily, as though desirous of taking a step in its turn, just as it did when man, then four-footed, pranced up and down the earth. Light-waves of Many Colours.— Tho light-waves that fill the universe are rot the least of the wonders of the firmament. They are made up of long waves, intermediate v.eves, and short waves, and are therefore of every colour imaginable. In number per second they mount up into the trillions. Were a ricrson to stand on the ocean beach and count tho number of water waves that break upon the strand, it would be found that about six seconds of time are required for each wave — about 10 per minute. Now, since light travels 186.330 miles per second, and each wave of red light has a length of 1-33,000 of an inch, it follows that when the ruddy beams from the star Antaros enter our eves, a shaft of light, 186,330 miles in length, composed of nearly four hundred trillions of waves, piles into the retina in a single sccord! The unit generally used in comparing star distances is known as the "light. year," being the space covered by a light wave, travelling 186.330 miles per second, during; the period of one year. Incomprehensible as is this unit of measurement, nevertheless our nearest star noighbom*, the brightest star in the constellation of the Centaur, is just four of these units distant from our earth. In- other words, it would take us four long years to reach the Centaur wore we to travel on the wings of light, every second of that time speeding 1r6.330l r 6.330 miles outward info space. Possibly a better appreciation of the tremendous distance between our earth and the nearest star may be gained by a few illustrations. A pound of the very finest silk thread, woven from the filmiest portion of the cocoon, will reach, say, completely around the earth at the equator—a girdle of silk 25.000 miles in circumference, and weighing exactly lib. Suppose that we wish to run a single strand of this silk to Alpha of tho Centaur, how much silk would be required?' No less than 500.000 tons! Suppose we had tho power_ to dwindle the heavenly bodies and their respective distances, from each other to such an extent that tho sun and earth, now separated by a chasm 93,000,000 miles across, would be just as far apart as the distance between the two eyes in the human f.iee. How far from the earth, on this same reduced scale, would bo tho nearest "fixed" star? Just Hi miles !