ACKNOWLEDGMENT 



The substance of several of the essays, or of parts of 

 them, that follow, has been printed heretofore in The Field 

 (of London), Harper'' s Magazine, The Popular Science 

 Monthly, The Evening Post (of New York), or Frank Leslie''s 

 Popular Monthly. The author desires to credit these publi- 

 cations with this priority, and to thank them for permitting 

 him to make this new and revised use of the material. 



