23 Fifth Avenue, New York, 



January^ 1877. 



Sir: We have the honor to present herewith our report upon the 

 Desciiptive Geology of the region examined during the years 1867 to 1873. 



The material has been treated under five general chapters, corre- 

 sponding to the five geological maps of the Atlas, and proceeding, like 

 them, from east to west. We each have written upon those regions with 

 which we were most familiar, but, as our field-observations have not always 

 been entirely independent, we have at times been obliged to use each 

 other's notes, while always availing ourselves freely of your own field- 

 notes and suggestions. 



It will be readily understood by the reader, from the very title of the 

 work, that this does not claim to be a systematic survey like those of 

 Europe, based on accurate maps, but is rather a geological reconnaissance 

 in an unknown and often unexplored region, where geology and topography 

 had to go hand in hand, and that therefore, while details were often, from 

 tlie necessities of the case, somewhat neglected, it was the general bearing 

 of the leading geological facts that was most constantly in our minds. 



In closing thus an official connection of ten years' duration, we cannot 



refrain from expressing our many obligations to you, not only for your 



advice and assistance in our earl}^ work, and your general supervision, but 



more especially for the unwearying kindness and consideration which have 



characterized your intercourse with us, often under circumstances rendered 



peculiarly trying to the patience by the obstacles which nature opposed to 



the successful accomplishment of the work you had so boldly planned. 



Sincerely yours, 



S. F. EMMONS. 



ARNOLD HAGUE. 



Clarence King, 



Geologist-in-^CJmrge. 



XJII 



