66 EXPLORATION OF THE COUNTRY BETWEEN 
differs from that already described only in containing a little dusk, and — 
a very little organic matter—particles of the roots and grasses—which 
It is wonderful that even the seat v vegetation you describe should 2 a 
exist on such a barren foundation 
Respectfully and truly, yours, 
BLAK 
eeagiet of the office of ihe Tiited States 
Pacific Ltailr oad Laplorations and Surveys. 
Lieut. G. K. Warren 
United States Topographical Engineers. 
Wasutneton, D. C., 
“March 15, 1856. 
Sir: I herewith present a brief f sketch of the ponte and payee 
al features of the re egion of the e upper Missouri, with some noten On, on its 
soil, vegetation, ean life; &c. <7 
vege ai is ; ee: Beet 
Very cnmieanes vg yu pieretiens servant, eis 
Lieut. G. K. W. “ 
5g HAYDEN. 
United. States ee, Engineers. 
—- hy offent of country drained by the great hy croanbicn! 
of the Missouri, may be characterized as one principal syst 
of aise the Missouri river and its larger tributaries as isbn: 
The Missouri river or principal. system rises in the main chain of the 
Rocky mountains, RUDGE, east or ‘slightly northeast course to the 
confluence ¢ ite h river. pear the 49th parallel, the —_ 
northern point te iver: ; then changing its course it flows in a , 
southeasterly direction to its confluence with the Mississippi, in mee 
tude 38° 50’ 50”. Its topography is quite well understood ag far as 
Fort Benton, and in the vicinity of the mountain passes, but of its 
sources very little as yet is definitely known 
1en come the principal tributaries of the Missouri river, whit ich T 
have called sub-systems, or subsidiary hydrographical . por- © 
at in ascending the Missouri, we have— 
i. The sub-system, of the Platte river, an important arte draining 
an immense area, which also rises in ‘the main chain of the Rocky 
pare Ae Leto in latitude 41° + 24”. 
stem of t u qui Court, or Running zag which 
its rise in the eastern portion of the Black Hills, drains an area 
‘y about three bu dred miles i in anette and per in breadth, 
18 Meeperiee ata eous and | a iapeaations . This has. 
White nr, hick al iin th er 
tion of which I will mention as illustrative of this paper. Commenc- { 
