PREFACE 



remaining figures, namely Figures 48, 50, 63- 

 69, 71, 76, 78-80, 84-96 were copied with little 

 or no modification from various papers, photo- 

 graphs and books, the original source being 

 given in each case. The writer wishes to ex- 

 press his obligation to all authors and publish- 

 ers upon whose works he has drawn, and he 

 thanks especially the Columbia University 

 Press for permission to use Figures 48 and 50, 

 and the Open Court Publishing Company for 

 Figures 84-87. 



I take this opportunity of thanking Dr. W. 

 E. Castle and Dr. J. H. McGregor for the 

 use of photographs which are reproduced in 

 Figures 81, 82 and 96; and I wish especially to 

 thank my assistant, Marguerite Ruddiman, 

 for her aid in preparing figures and manu- 

 script for publication. 



Princeton,. December, 1914 



viii 



