VOL.8, NO. 9
SCIENTIFIC METHOD I N PRACTICE
1823
and then classification, "consecutiveness, and continuity" become of major importance. The course in general chemistry a t the University of Virginia is based upon the laboratory work. Lectures supplement and are parallel to the laboratory. In both, as especially brought out in the laboratory manual, the material is logically arranged to encourage thinking as much as possible and to minimize memory. The Battle of the Rags. Modern physics may he said t o have begun in 1895 when Professor Wilhelm Konrad Rdntgen (1845-1923) accidentally discovered X-rays. In the thirty-five years t h a t have elapsed, scientists, traveling the uncharted seas of radiation and radioactivity, have revealed a new world. Explorations into this scientific wilderness have hardly started and every day brings new discoveries. A list of the more understandable ones reported during the month of October, 1930, gives evidence of the fruitful activity that prevails: 1. Using gamma rays emitted by radium, scientists workins in the U. S. Naval Rescarch Laboratory have "looked" through steel girders and plates to determine the presence of weaknesses and defects. With a bit of radium hardly larger than the size of a bean, it has been possible t o sensitize a photographic plate on the opposite side of a battleship's hull, a feat impossible with generally available X-ray equipment. This gamma-light photography, requiring nothing like the cumbersome equipment necessary in X-ray photography, will reveal defects in a metal as small as two per cent of its thickness. 2. Almost simultaneously with the demonstration of the usefulness of gamma-ray photography came the production of a giant X-ray tube a t the California Institute of Technology, utilizing 600,000 volts, or more than double the voltage used in present "available X-ray equipment." Giant tubes such as this one may emit rays that have the therapeutic value of radium rays, and t h a t will penetrate two inches of lead and two feet of concrete. Gamma-ray photography may not be so superior after all. 3. Professor Robert A. Millikan working far up in the invisible spectrum from the comparative long-wave gamma and X-rays, has been stalking the more elusive cosmic rays. His recent investigations indicate t h a t they are not high-speed electrons but ether waves of exceedingly high frequency. If they were electrons, the rays' reception on earth would be influenced by the magnetic polar regions. To test this, Dr. Millikan took the electroscope with which he measures the rays to Churchhill, Canada, only 876 miles from the North Magnetic Pole. He made observations every day and night for a week, found the intensity of the waves the same in Churchhill as it was in his home in Pasadena, and concluded that cosmic rays bombard the whole earth equally. He also suggtited that, since cosmic rays are affected by small changes of density in the air, the cosmic ray electroscope muld be used to supplement the barometer in collecting information about the weather. These three developments in the course of a month represent hut a fraction of the discoveries in modern physics t h a t are revealing the unseen activity of the universe. Sir J. H. Jeans, in discussing Millikan's cosmic rays, has speculated thusly on what it all may mean: "In a sense this radiation is the most fundamental physical phenomenon of the whole universe, most regions containing more of i t than visible light and heat. Our l ~ ~ l i ac ns travrrsrd by it n i v h t and dav. . . i t Irmks up scwral rnillicm atoms in rach uf uur t w d i e ~wry cccund It mtv be rsirntinl t o our hfcor it may be killmy i t s . ' ' The Technology Re&"
