TRANSACTIONS 
OF THE 
AMERICAN PHILOSOPHICAL SOCIETY. 
ARTICLE I. 
ON THE GEOLOGY AND NATURAL HISTORY OF THE UPPER MISSOURI.* 
BY F. Y. HAYDEN, M. D. 
Head July 19th, 1801. 
HISTORICAL INTRODUCTION. 
In presenting a report upon the geological structure of the vast country drained by the 
Missouri river and its tributaries, it is hut just to those who have preceded me that I 
should give a brief statement of the results of different travellers who have passed over 
that region, premising, however, that no detailed account has hitherto been given of its 
geological character. 
The first reliable account of the Upper Missouri country was obtained by those enter¬ 
prising travellers, Captains Lewis and Clarke, and published in their excellent journal ;f 
* Being the substance of a report made to Lieut. G. K. Warren, T. E., U. S. A., by F. V. Hayden, M.D., 
Surgeon and Geologist of the Expedition to the Upper Missouri and Yellowstone, under the command of Lieut. 
Warren. 
f Lewis and Clarke’s Journal of an Expedition to the Sources of the Missouri River, performed during the Years 
1804, ’5 and ’6. 
VOL. XII.—1 
