56 BELL SYSTEM TECHNICAL JOURNAL 



literature of these times to disappear all but a few scraps, posterity 

 could date them by the appearance of that word, as Latin manuscripts 

 are dated through containing some word or some trick of style that 

 came into use at a definite moment of history. A word must bear 

 almost magical connotations, to enter so thoroughly into popular 

 usage; and the phenomena of radioactivity endowed it with these in 

 abundance, with suggestions of rays piercing all matter, and inexhaust- 

 ible stores of energy, and transmutation of elements, and influences 

 having power even over life and death. Wonderful to relate, the 

 suggestions for once were justified by the truth. 



From 1898 onward there was a tremendous rush of investigators 

 into the new field, and in a few years there were explorers of almost 

 every conceivable aspect of radioactivity — chemists ascertaining the 

 chemical properties of the radioactive elements, physicists observing 

 their physical properties, and a great host of students investigating 

 the numerous and striking effects of the rays. The subject presently 

 became so wide that books on radioactivity written before and during 

 the War resemble treatises on the contemporary physics of their dates 

 of publication; for the new rays seemed to be able to invade all the 

 provinces of physics as easily as they could penetrate matter in all its 

 forms. 



Eventually, however, it became clear that many of the topics classed 

 at first with radioactivity should be removed into other fields of science. 

 The radioactive elements all have their places in the Periodic Table, 

 and their chemical properties are what should be expected from ele- 

 ments thus placed; peculiar as radium is in its one famous feature, 

 there is nothing abnormal about its chemical reactions, and they may 

 justly be relegated to the handbooks of chemistry and to the manuals 

 written for those who wish to prepare or purify the element. The same 

 thing is true of the physical properties of radium; nothing in its optical 

 spectrum suggests that it is other than an ordinary member of the 

 second column of the Periodic Table, nothing in its X-ray spectrum 

 intimates that it is more than just the 88th member of the Procession 

 of the Elements. None of these needs to be taken into account in the 

 study of radioactivity. 



The various effects of the rays which the radioelements emit are like- 

 wise quite irrelevant. At the beginning it was natural and proper for 

 every writer to describe all that was known of the actions of the alpha- 

 rays, the beta-rays and the gamma-rays, after having said that these 

 are the three kinds of rays which radioactive substances emit. Indeed 

 it was essential, for at first there was no way of defining the rays, much 

 less of ascertaining their real nature, except by considering en bloc 



