PREFATORY NOTE. xill 



E. E. Howell, whose elaborate notes were placed in the hands of Captain 

 Dutton, and from time to time he has in his volume given Mr. Howell 

 credit for the material which he has used. It was unfortunate for Mr. 

 Howell that his labor was suspended prematurely, and that he was not 

 able to elaborate a report upon the country studied by him. 



The geography of the district, as exhibited in the atlas accompanying 

 this volume, was the study of Prof. A. H. Thompson, who was my assistant 

 in charge of that branch of the work during the earlier years of explora- 

 tion and survey. Through his skill and industry the geography has been 

 represented with all the accuracy and detail that the adopted scale will 

 permit. 



I am especially indebted to Brig. Gren. S. V. Ben^t, chief of the Ord- 

 nance Bureau, for the interest he has taken in the geologic and geographic 

 researches prosecuted by the survey under my direction. Through the 

 wise policy of administration adopted b}^ him, Captain Dutton has been 

 enabled to carry on his labors as a geologist outside of the general oper- 

 ations of the Ordnance Bureau. The contribution to science which he here 

 presents will abundant^ justify the course pursued hy his distinguished 

 chief. 



To the Secretary of War and the General of the Army, the survey is 



indebted for assistance rendered in various ways — especially in furnishing 



subsistance to field parties from the commissariat of the Army, but chiefly 



in the opportunity given Captain Dutton to prosecute his researches. 



J. W. POWELL. 

 Apeil 1880. 



