PREFACE. vii 



tnitions were ever more conscieiitioutily prepared, ami I have met with none 

 which seem to represent microsoo])ical effects more exactly. 



Special thanks are due from me to Dr. Barus and to Mr. ,1. I*. Iddings 

 (assistant geologist on Mr. Arnold Hague's staff), with whom I have 

 repeatedly consulted on the subjects treated in Chapters 1\'. and III., 

 respectively. But for the stimulus of their criticisms the proofs offered 

 would be less satistactory ; and in enal:)ling me to meet the objections 

 which occurred to them, they have placed me more in their debt than if 

 tiiey had made positive additions to the discussions of lithology and faultiny-. 



The office work has been done at the American Museum of Natural 

 History, New York, that institution having courteously |)laced some of its 

 admirable working rooms at the disposal of the Survey. 



G. F. B. 



New York, May 6, 1882. 



Oct. 16. — Mr. Albert Williams, jr.. Statistician of the Survey, has 

 kindly given me the benetit of his extremely efficient assistance in the 

 proof correction of the volume 



G. F. B. 



