20 SCIENCE AND LIFE 



which ideas are arranged, is too well and truly laid 

 to fear demolition. Even when, as in the present 

 day, the foundations of science are shifted to an 

 ever deeper and more fundamental plane the ex- 

 perimental basis of fact is unthreatened. The idea 

 that the whole edifice of chemical science was totter- 

 ing to its fall as the result of the discovery of the 

 intra-atomic changes of the radio-elements, is one 

 that has always been too absurd to call for reply. 

 But for that science and its clear-cut conception of 

 the chemical elements, the result of more than three 

 centuries of continuous experimental labour, the facts 

 of radioactivity might still have been as arresting 

 and magnificent as any discoveries ever were. But 

 without the older knowledge, exquisitely and finely 

 wrought, for the newer knowledge to dovetail into 

 and complete, the chief human significance of the 

 new science and its power to interpret the physical 

 side of the drama of life could scarcely have been 

 so early perceived. 



Radium, no longer a mystery, one of the chemical 

 elements doing what more than a score are doing 

 at their own characteristic rates, owes its peculiar 

 position to the fact that it is changing neither too 

 slowly nor too quickly in reference to the allotted 

 span of threescore years and ten. Energy of the 

 order of a million times that evolved in the combus- 

 tion of the same weight of coal, instead of being, 

 as in the case of radium, evolved in the average 

 period of 2500 years, is in the case of uranium and 

 thorium spread over a term of thousands of millions 

 of years. The effects are small but enduring, and, 

 almost imperceptible in themselves, come to maturity 

 in due time in the cosmical calendar. Small as is 

 the proportion of uranium and thorium in the rocks 

 of the earth, the energy they evolve is estimated 

 to be far more than the earth loses to outer space, 



