No. l. 
GENERAL REPORT 
UPON 
THE GEOLOGICAL COLLECTIONS. 
- 
BY WILLIAM P. BLAKE, 
GEOLOGIST OF THE OFFICE OF THE UNITED STATES PACIFIC RAILROAD EXPLORATIONS AND SURVEYS. 
INTRODUCTORY LETTER. 
WASHINGTON, September 23, 1856. 
Sir: I herewith submit a report on the geology of the route near the thirty-fifth parallel of 
latitude, prepared, agreeably to your instructions, from the collections and notes of Mr. Jules 
Marcou and other sources. 
Very respectfully, your obedient servant, 
W. P. BLAKE, Geologist of the Office. 
Captain A. A. Humpureys, Corps Topographical Engineers, à i 
In charge of the Office of U. S. Pacific Railroad Explorations and Surveys. 
