REPORT OF A. C. PEALE, M. D., GEOLOGIST OF THE GRAND 

 RIVER DIVISION, 1876. 



LETTER OF TRANSMITTAL. 



Washington, D. 0., December 28, 1877. 



Sir: I have the honor herewith to hand you my report as geologist 

 of the Grand River division for the season of 1876. 



The division was in the field just two months, of which thirty-two 

 days were occupied in the work. During this time the area actually ex- 

 amined so that its general geology can be mapped is about 4,000 square 

 miles. 



The district assigned us consists of two widely separated areas, par- 

 tially reported on in previous reports. Both are remote from settle- 

 ments, and hence almost half the time the i ivision was in the field was 

 necessarily occupied in marching to and from the areas. 



In the geological investigation of these detached areas (which in the 

 report are designated as areas A and B) difficulty was experienced from 

 the limited amount of time, owing to the lateness of the season. Owing 

 to this cause also another difficulty was met with, the lack of water. 

 Both areas are desert-like, even at the best, and it is utterly impossible 

 to study them in detail unless the work be undertaken in the spring and 

 early summer, when the streams contain water. 



Fortunately, however, the geological structure was found to be com- 

 paratively simple, as the sketches accompanying the report show. Had 

 it been otherwise, the character of the country, and the rapidity with 

 which we were obliged to travel over it would have precluded the pos- 

 sibility of coloring the map. 



In the report I have followed my usual plan, considering first the 

 general features, and afterward the special geological facts relating to 

 the district. The geological map and general sections for the Atlas of 

 Colorado have been prepared. 



For the illustrations accompanying the report I am indebted to Mr. 

 W. H. Holmes and Mr. F. D. Owen. The profiles of the sections are 

 based on the topographical work of Mr. Henry Gannett, to whom also 

 I am indebted for the accompanying maps. 



With great respect, 1 have the honor to remain your obedient servant, 



A. C. PEALE. 



Dr. F. V. Hayden, 



United States Geologist, in charge. 



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