PHYSICS 335 



a-, /?- and y-rays all have the power of wrenching electrons free 

 from substances which absorb them. By this power to ionize gases a 

 wholly new method of chemical analysis has sprung up — the method 

 of analyzing by the electroscope. So marvelously delicate is this new 

 radio-analysis that one part of radium in one hundred-million-million 

 parts of uranium can not escape detection. The electrometer test for 

 differentiating the various radio-active substances is the time required 

 for the fresh product gained by chemical manipulation to lose half its 

 ionizing power. This important characteristic of each substance is 

 disparagingly called its mte of decay. 



By the aid of the new analysis, Eutherford and others have found 

 that radium is slowly disintegrating into radium emanation, which in 

 turn changes into a distinct substance called radium A, and so on by 

 successive steps down the alphabet to radium F, which is possibly a 

 parent of lead. Helium appears also as a by-product of radium dis- 

 integration. From radium downward each of the seven substances 

 has a characteristic rate of decay ranging from 1,300 years for radium, 

 to three minutes for radium A. Badium emanation is a gas which 

 liquefies at — 150° C. Some of the later products seem to be solids. 



Is it not amazing that any of the properties of these six derivative 

 products should be known at all, when never yet has one of them been 

 seen, nor weighed, nor caught for direct examination? 



Not only has radium offspring down to the sixth and seventh gen- 

 eration, but it apparently has ancestors as well. It is only a link in a 

 genealogical chain. The probable discovery of radium's immediate 

 parent was published less than a month ago by Boltwood. Uranium 

 is thought a remoter ancestor, possibly a great-grandparent. 



Accompanying the atomic disintegration of radio-active substances, 

 large quantities of heat are evolved showing vast stores of energy hith- 

 erto unknown inside the atom. 



The most reasonable explanation yet offered of the observed radio- 

 active phenomena indicates that the complex system of electrons re- 

 volving at enormous speeds within the atom gradually loses energy until 

 the configuration becomes unstable. A sudden readjustment takes 

 place — a kind of internal explosion by which electrons or a particles, 

 or both, are hurled out. The atomic structure thus relieved starts life 

 as a new substance with a lower atomic weight. Later the new sub- 

 stance for a like reason again becomes unstable, another explosion 

 occurs, and an atom of yet another substance is born. 



If this interpretation of the evidence be accepted a conclusion of 

 vast importance may be drawn. We have, we can not say going on 

 before our eyes, but we may say in a sense going on under our hands, 

 a slow evolution or transmutation of matter. This conclusion is not 

 accepted as yet without reserve, for it strikes too deep at one of the 

 assumptions of our older knowledge. Material atoms have long been 



