152 The Missouri River. — Broadhead. 
ing of boulders, pebbles, coarse and fine sand, the coarser be- 
low. The velocity at St. Joseph at low-water is 2 to 3 miles 
per hour, and in floods as much as 10. 
Bank erosion is constantly going on in the lower river; 
whole farms have been washed away in less than a decade of 
years, and the channel shifts from side to side ; what is des- 
troyed on one side may go to form land upon the other side. 
The general slope of the river averages 0.88 ' to the mile, both 
at high and low water (Suter). 
The actual navigable depth varies from 3 feet at low to 9 at 
high water. Col. Suter's observation at St. Charles gave, for 
sediment carried past for 1879, 5,508,229,008 cubic feet, the 
water discharge for the same time 2,335,143,946,400; and on 
July 1st, 1879, the amount of sediment transported would 
cover one square mile 4 feet, and during the entire 3'ear 197.58 
feet deep ; this not including that directly upon the bottom 
which if counted would increase the amount, even might 
double it. The approximate width from Sioux City to the 
mouth of the Platte is 820 feet. From the mouth of the Platte 
to Kaw river is 960 feet. From the mouth of the Kaw to 
Gasconade it is 1,160 feet. From Gasconade to the mouth of 
the River it is 1,240 feet (Suter). Low water for the same 
would be (Suter) 650 feet, 820 feet, 1,020 feet and 1,100 feet. 
While the Mississippi valley including the Ohio, the upper 
Mississippi and the Missouri valley as far up as near Sioux 
City was dry land during Palseozic times, and during the suc- 
ceeding Mesozoic and Tertiary periods, there lay just west a 
low ridge (or scarcely a ridge being mainly an approximate 
line whence strata dipped rapidly west) passing northward 
through central Kansas into eastern Nebraska and north- 
wardly. This ridge or very flat anticlinal prevented the waters 
of the Laramie seas from flowing eastward!}^ and formed the 
eastern margin of the Laramie brackish water lakes, which 
during a long period of time gradually and slowly settled suf- 
ficiently to receive the lignitic coals and other succeeding beds 
of clay and silt. After the close of the Laramie and during 
later Tertiary times, the fractures incidental to the volcanic 
outflows in the Rocky mountain and Columbia river regions, 
formed the channels for the Columbia, the upper Missouri, 
Yellowstone and other Rocky mountain streams. 
The lower Missouri already had its existence. It dates its 
