INTRODUCTION 



When the scientific worker does his miracle, how- 

 ever, he publishes his method, and another worker 

 may follow him and duplicate his results. There are 

 no esoteric methods, no secret processes, in the world 

 of inductive science. Nor is there much that may 

 not be interpreted in untechnical language and made 

 of interest to the general reader without sacrifice of 

 accuracy. Such an interpretation I shall endeavor to 

 present in the ensuing pages, which will in effect take 

 up the record where my Story of Nineteenth Century 

 Science left it, and describe the progress of the past 

 decade. 



Every period of history is a transition period. The 

 happenings of to-day grow out of the events of yester- 

 day, and lead on to the developments of to-morrow. 

 Arbitrary dividing lines, to mark off periods and 

 epochs, are largely of man's creation. 



Yet as we look back on the history of human prog- 

 ress, we see that great events tend to cluster. Cer- 

 tain generations seem to have been times of stasis; 

 while other generations seem to vibrate with the 

 energy of creative effort. Here and there a decade 

 stands out as marking a turning point in human 

 thought. 



Such a vital, germinative epoch, I believe, is that 

 with which we are here concerned. The first decade 

 of the twentieth century will always be memorable as 

 a time of great activity in the wide field of natural 

 sciences, theoretical and applied. When the achieve- 

 ments of divers workers in this domain have been, 

 passed in review, it will be clear, I think, that the 

 present epoch must take rank with the half dozen 



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