ACKNOWLEDGMENT 



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

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

 (of London), Harpers 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. 



