General Introduction 



tions of science may be, it is not in these so much 

 as in its broadening and correction of human 

 thought that this age will be memorable for all 

 time. Upon men not yet old, new heavens and 

 a new earth have dawned in the successive 

 decades of their lives. A generation or so ago 

 the word "universe" had a significance faulty 

 and meagre in comparison with its meaning to- 

 day. To be sure, the visible contents of space 

 were regarded as one, but that there was an equal 

 unity of law, of sequence in nature, was not under- 

 stood. Then, current theories of the universe 

 were theories of creations, annihilations, sus- 

 pensions of natural law. Year by year has 

 science advanced until order has at last dislodged 

 magic from every stronghold of her ancient terri- 

 tory; the universe has been discovered to be in 

 agreement with itself. 



In an important point of view the history of 

 modern knowledge is the history of identification, 

 of tracing the many in the one, or reducing what 

 seemed antagonism to concord, difference to 

 unity. It was in physics that this process of 

 identification first took place. Fifty years ago 

 electricity was imagined a fluid. Chemical 

 affinity was deemed essentially different from 

 either heat or mechanical motion. Observers 

 and experimenters have in our day established 

 that every phase of physical force is in its last 

 analysis motion, and is therefore identical with 

 every other; that throughout all its maze of 

 transformation, its quantity remains ever the 

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