SCIENTIFIC TREATS AT CHRISTMAS.

Waimate Daily Advertiser, Volume XXIV, 24 March 1924, Page 2

SCIENTIFIC TREATS AT CHRISTMAS.

There is a Xmas treat for children whicx. many grown-ups envy them —tnlectures given every year at the Koya, institution. Given l>y the masters of their subject from Faraday on they are of a delightful nature and such as only real masters can give. Sir William Bragg, who long laboured south the line at Adelaide University and is with Sir Ernest Rutherford in the first rank of physicists, is now lecturer. In 1909 he returned to England to take up the position of Cavendisli Professor in Leeds University. Since 1915 he has been Quain Professor of Physics in the University of London. He is especially known for his investigations into crystal structure by the aid of X-rays and in 1915 this work won him the Nobel Prize jointly with his son, who is Langivorthy Professor of Physics in the Victoria University of Manchester. He is now Fullerean Professor of Chemistry at the Royal Institution, having been appointed in succession to the late Professor Dewar. His Xmas course for the youngsters—privileged young things -they are—for the tickets are issued to members only who have the right to distribute them. Half the seating in the theatre is reserved for juveniles, but the demand for space for adults is usually much more in excess of accommodation than that for the

■ youngsters privileged to attend. Sir William is devoting his course to one “Concerning the nature of things,” 1 and beginning as he did on the atoms of which things are made, he gave us a thrilI ling and picturesque description of these j creatures. , His title is the same as that of the great poem of Lucretius, aad he started by reminding us that modern science supports the main principle of Lucretius—that matter consists of assemblages of very small particles which he called “atoms.” Lucretius did not, however, reach the conceptions of modern chemistry. He knew nothing of the existence of about ninety kinds of atoms, all atoms of the one kind being practically alike. This doctrine had been held for more than a century, and was the basis on which the science of chemistry was built. Everything in the universe, so far as we knew, was, built of these ninety kinds of atoms,—they were not only the bricks, but the cement and the tools and

Before radium was discovered he said we knew roughly the number of atoms u. a body ot given size and therefore, approximately, the volume of each. brom radium we have learnt that each atom, tiio.gli occupying a space such as we had supposed, was quite penetrable by other atoms approaching it with sufficient speed. The atom was now imagined as resembling a minute solar system with a central sun and surrounding planets. The central sun was called tne nucleus and the p.anets the electrons. He discussed illuminatingly how each atom, though so small as to be invisible to the nak.nl eye, was quite penetrable by other atoms approaching it with sufficient speed. We saw atoms of helium on the screen lly off from an atom oi radium and go uatlung through the air at the rate of 100,01)0 miles a second, smashing millions of other atoms on the way, and suddenly pegging out after a thrilling run. But ror that they’d have reached the menu in 24 seconds! The Professor demonstrated this on a billiard tabel covered with balls through which he tried to impel a ball in a straight line. Nor could the helium atom keep on a line which was on the wlio.e straight, although it had to twist and turn in’order to get through the atoms in the air. To suppose that that was possible would be equivalent to endowing helium with intelligence such as a boy would display if given a sixpence and directed to a cake shop on the other side of a crowded street.

There is no answer to the problem except one—that the atoms pass through one another when they move relatively to each other with sufficient speed. It is this which convinces us, said Sir William, of the emptiness of the atomic structure; and, taken in conjunction with other facts, makes us think of the atoms as solar systems in miniature. The helium atom going through an oxygen atom of the an may pass through without serious injury to either, just as one solar system might flash through another, and the faster it went the less the possible injury. Professor Bragg followed this up by other lectures on the nature of gases and of liquids and has devoted two to crystals, the subject on which he is the greatest living authority. He showed several models which represented the exact way in which the atoms of oxygen and hydrogen fitted together in an ice cyrstal. Twenty years ago, he said, such models would have been guess-work, but now that we had the help of X-rays we were able to look 10,000 times deeper into the secrets of nature than we could do before they were discovered. He showed fascinating pictures of snowcrystals and one especially of a shape that might be called a fairy tea table. Myriads of these little tables falling slowly through the air cause the haloes and mock suns that are to be seen ■ in the Arctic and Antarctic regions.