THE STORY OF NINETEENTH-CENTURY SCIENCE 



with Thomson as the great developers of thermo-dynam- 

 ics, were both far advanced with their novel studies 

 before they were thirty. We may well agree with the 

 father of inductive science that " the man who is young 

 in years may be old in hours." 



Yet we must not forget that the shield has a reverse 

 side. For was not the greatest of observing astrono- 

 mers, Herschel, past thirty-five before he ever saw a 

 telescope, and past fifty before he discovered the heat 

 rays of the spectrum? And had not Faraday reached 

 middle life before he turned his attention especially to 

 electricity ? Clearly, then, to make his phrase complete, 

 Bacon must have added that "the man who is old in 

 years may be young in imagination." Here, however, 

 even more appropriate than in the other case more's 

 the pity would have been the application of his quali- 

 fying clause: " but that happeneth rarely." 



There are only a few great generalizations as yet 

 thought out in any single field of science. Naturally, 

 then, after a great generalization has found definitive 

 expression, there is a period of lull before another for- 

 ward move. In the case of the doctrines of energy, the 

 lull has lasted half a century. Throughout this period, 

 it is true, a multitude of workers have been delving in 

 the field, and to the casual observer it might seem as if 

 their activity had been boundless, while the practical 

 applications of their ideas as exemplified, for example, 

 in the telephone, phonograph, electric light, and so on 

 have been little less than revolutionary. Yet the most 

 competent of living authorities, Lord Kelvin, could as- 



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