THE MYSTERY OF RADIOACTIVITY 649 



to understand what has been learnt of Radium and in what 

 respects its behaviour is remarkable. The story is more than 

 fascinating and it is told with remarkable lucidity, often rising 

 to eloquence, by Prof. Soddy — who is one of the most noted 

 workers on the subject of Radioactivity, the new branch of 

 chemistry and physics brought into existence through the 

 discovery of Radium. The present-day interpretation of Radium 

 that it is an element undergoing spontaneous disintegration, was 

 put forward in a series of joint communications to the Philoso- 

 phical Magazine of 1902 and 1903 by Professors Rutherford and 

 Soddy ; moreover, if report speak truly, Prof. Soddy was the 

 first to discover the production of Helium from Radium. In 

 reading the book, therefore, we are drawing inspiration from the 

 fountain head — and the stream is one which runs with quite 

 exceptional clearness and fulness. 



The book consisted originally of the matter of six public 

 lectures delivered at Glasgow early in 1908 ; the present third 

 edition is much enlarged and brings the subject of Radioactivity 

 up to the middle of last year. It should be in the hands of every 

 student of physical science — and in every school library : no 

 person of intelligence should be able to read it without having 

 his imagination fired and a desire awakened in him to know more 

 of the wonders of science. The argument is developed so 

 gradually and so clearly that few will have difficulty in under- 

 standing it. 



As Prof. Soddy says, in discovering Radioactivity " science has 

 broken essentially new ground and has delved one distinct step 

 further down into the foundations of knowledge." But he goes 

 too far in making the statement that it is a new primary science 

 owing allegiance neither to physics nor chemistry as these 

 sciences were understood before its advent, because it is con- 

 cerned with a knowledge of the elementary atoms themselves of 

 a character so fundamental and intimate that the old laws of 

 physics and chemistry, concerned almost wholly with external 

 relationships, do not suffice. 



The fact is, Prof. Soddy is pardonably carried away by his 

 enthusiasm and there are a number of over-statements, if not 

 inaccuracies, in his earlier chapters which he will do well to 

 modify in his next edition. Thus the one outstanding feature in 

 connexion with Radium and the property of Radioactivity which 

 it exhibits to an extraordinary degree, we are told (p. 24), is that 



