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4 
Physics and Hydraulics of the Mississippi River. 185 
Missouri Basin.—This is much the largest of any of the trib- 
utary basins of the Mississippi, and differs from all the rest in 
containing a large area covered by lofty mountain chains. The 
river issues from the Rocky mountains in many branches, which 
form a series of large rivers that flow through the great unculti- 
vated plains, Comparatively little rain falls upon the mountains 
and the plains, and hence the size of the main river is dispro- 
ttionately small, when the drainage area alone is considered. 
ts annual discharge is only about three-quarters of that of the 
Ohio, although its basin is nearly two and a half times as large. 
After passing the 98th meridian, the banks of the river become 
more and more fertile, and the region through which it passes 
gradually changes from an uncultivated waste to a populous 
above its mouth, the former again divides into two nearly equal 
branches, the Big Horn and the Upper Yellowstone. The Up- 
per Missouri remains a single stream to within about 100 miles 
of its sources, where it divid 
to the year 1859. At this date, a party under Capt. W. 
F. Raynolds U. S. Topl. Engrs., was organized by the War De- 
Partment, to explore the region. : ms 
the Yellowstons from its soul to the point where it issues 
"specting the Gallatin fork and the Upper Yellowstone. The 
has not yet been published, but throu the kindness of 
a we Raynolds, wile the sanction of the War Department, the 
- facts have been communicated : 
In lat. 48° 30’ and long. 110° 00’ a mountain Tises to some 
Fr 
Au. Jour. Scr—Szconp Suntms, Vor. XXXII, No. 98.—Mance, 1862. 
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