Geology of Lincoln Co., S. D. — Bcndrat. 93 
rising about 220 feet above the level of the Big Sioux, fairly 
corrospoiuls with the levels reported from the upper bowldery 
terraces along the Sioux (175, 200, 220, 180 feet). The lower 
one, east of the former, about 120 feet above the river, within 
the limits of the lower bowldery terraces (80, 90, 125, 80). 
But while terraces were forming along the banks of the big 
channel which is now occupied by the Big Sioux river, other 
valleys, more or less distant, but connected with the main chan- 
nel, were submitted to the same agency, and although the ter- 
races thus formed along the tributaries of the Big Sioux have 
become obliterated to a greater or less extent, they have been 
found by the writer fairly preserved at other places, for instance 
in the sides of the valley of the most northern tributary of 
Pattee creek, where two terraces were observed, one about 20 
feet above the other, the higher rising about 175 feet above 
the level of the Sioux. 
There liave been no terraces found of any kind along the 
Vermilion. 
f : The Alluvial Bottoms of the Sioux and the Vermilion Rivers. 
After having cut down the deposits accumulated in its chan- 
nel to a depth of approximately 180 feet below the average level 
of the highlands on the Iowa side, the Sioux river ceased cut- 
ting and, meandering from one side to the other, it began to 
widen its valley. This resulted in the formation of two bot- 
toms, besides the present one. As a rule they are found wher- 
ever the banks of the river are developed to high blufifs, but 
on the other side of the stream. Thus within R.48\V. and 
T.iooN., T.ioiN. : where the banks rise to over 100 feet on the 
western side, the bottom lands are on the eastern side, about 
one mile in width. Farther south, from about Klondike to 
Canton, they are better developed on the western side, while to 
the east the highlands of Lyon county, Iowa, rise abruptly to a 
hight of 1420 feet above sea level. South of Beloit the bottoms 
reoccupy the eastern side, their development ;vest of the stream 
being hindered by the bluffs of the Sioux, which rise here in 
more or less bold relief to a hight of 1500 feet above sea level ; 
in the southeast corner of the area they are exceptionally found 
on both sides of the river, flanked on the west by the lower 
terrace mentioned above. These bottoms are fairly rich and 
relativelv well settled. 
