252 THE HISTORY OF SCIENCE 



Even a glance at this long list of new elements 

 reveals certain analogies between one series of trans- 

 formations and another. Each series contains an ema- 

 nation, or gas, which through the loss of a particles 

 is transformed into the next following member of the 

 series. Continuing the comparison in either direction, 

 up or down the lists, one could readily detect other 

 analogies. 



There is some ground for thinking that lead is the 

 end product of the Uranium series. To reverse the 

 process of the transformation and produce radium from 

 the base metal lead would be an achievement greater 

 than the vaunted transmutations of the alchemists. 

 Although that seems beyond the reach of possibility, 

 the idea has stirred the imagination of more than one 

 scientist. "The philosopher's stone," writes Soddy, 

 " was accredited the power not only of transmuting 

 the metals, but of acting as the elixir of life. Now, 

 whatever the origin of this apparently meaningless 

 jumble of ideas may have been, it is really a perfect 

 and but very slightly allegorical expression of the 

 actual present views we hold to-day." Again, it is 

 conjectured that bismuth is the end-product of the 

 thorium series. The presence of the results of atomic 

 disintegration (like lead and helium) has proved of 

 interest to geology and other sciences as affording a 

 clue to the age of the rocks in which they are found 

 deposited. 



Before Rutherford, Mme. Curie, and others espe- 

 cially interested in radioactive substances, assumed 

 that atoms are far different from the massy, hard, im- 

 penetrable particles that Newton took for granted, 

 Sir J. J. Thomson and his school were studying the 



