REPORT OF A. C. PEALE, M. D., GEOLOGIST OF THE MIDDLE DIVISION. 



Washington, D. C, May 15, 1875. 



Sir : I have the honor herewith to submit my report as geologist of 

 the middle division of the United States Geological and Geographical 

 Survey of the Territories for the season of 1874. 



The report of Mr. Henry Gannett, who was in charge of the division, 

 will supplement this report, and to it I refer for more detailed informa- 

 tion in regard to the routes followed, elevation, and topographical fea- 

 tures of the district assigned us. We left Denver on the 21st of July, 

 and by the 5th of August had commenced work near the head of the 

 Eagle River. 



On the 1st of November work was suspended and we started for Den- 

 ver, reaching that city about the middle of the month. During the 

 three months we were in the field at work 5,300 square miles were sur- 

 veyed. 



My plan of working was in general the same as during the season of 

 1873. 



Accompanying the topographer in charge to almost all the high sta- 

 tions, I made sketches of the surrounding country, on which I defined 

 in colors the boundaries of the various formations. Whenever time 

 permitted I made detailed sections of the strata. 



This report is divided into nine chapters, the first three of which are 

 devoted to the general geological and topographical features respect- 

 ively of the valleys of Eagle, Grand, and Gunnison Rivers. The suc- 

 ceeding chapters give the special and detailed features of the various 

 formations, and the economical geology of the district. Catalogues of 

 the minerals and rocks are appended. 



The report is accompanied by maps and sections, for which I am 

 largely indebted to Mr. William H. Holmes and Mr. Henry Gannett. I 

 have colored the geological formations on a provisional map, reduced by 

 photography from the original drawing of Mr. Gannett's map of the 

 district. 



The rapidity of preparation and necessary absence during publication 

 of the report must be my excuse lor any errors that may appear. 



In conclusion I wish to express my thanks for the cordial co-opera- 

 tion of all the members of the party. 



With great respect, I remain your obedient servant, 



A. 0. PEALE. 



Dr. F. V. Hayden, 



United States Gologist. 



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