iv PREFACE. 



Yale, but late of Cornell, whose interest made the book possible, 

 these are especially to be made. On particular regions much ad- 

 vice has been obtained from Dr. W. P. Jenney, for which the 

 author is grateful. In the same way Prof. H. A. Wheeler of St. 

 Louis, Prof. R. A. F. Penrose of Chicago, and several other friends 

 have contributed. Dr. R. W. Raymond suggested the method of 

 enumerating the paragraphs. It has the advantages of being elas- 

 tic and of showing at once in what part of the book any paragraph 

 is situated. 



The geologists of the United States Geological Survey, who 

 have been engaged in the study of our great mining regions, es- 

 pecially in the West, have laid the whole scientific world under 

 a debt of gratitude, and in this country have probably been the 

 most potent influences toward right geological conceptions regard- 

 ing ores. Of writers abroad, Von Groddeck has been a means of 

 inspiration to all readers of German who have interested them- 

 selves in this branch of geology. The writer cannot well forbear 

 acknowledging their influence. 



Should errors be noted by any reader, the author will be very 

 appreciative of the kindness if his attention is called to them. 



J. F. KEMP. 



COLUMBIA COLLEGE, 

 IN THE CITY OF NEW YORK. 



