vi Preface 



The additional figures are nearly all taken 

 from well-known works to which, in each case, 

 acknowledgment is made. 



The writer is again indebted to Professor 

 Minot and to his publishers, Messrs. P. Blak- 

 iston's Son & Co., and to the Macmillan 

 Company for use of numerous electros. 



A. M. R. 



WEST VIRGINIA UNIVERSITY, 

 August 



