Geology of Lincoln Co., S. D. — Bendrat. 
67 
into the body of the divide, the two other head beyond the Hm- 
its of the aiea in the slope of the ridge. All three run for the 
upper and middle parts of their courses in more or less wide 
and comparatively shallow valleys. 
As the general characteristic of all the waters traversing the 
area under discussion, the Big Sioux and the Vermillion rivers 
not being excepted, is to be mentioned their meandering course 
which is so commonly met with in regions of Quaternary phys- 
iography. 
EXPLANATION. 
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The drainage system of the southern watershed which we 
may name for convenience sake "Canton ridge" comprises two 
classes of streams, those which issue from its northwestern side 
and those Av'hich head in its more hilly southeastern slope. But 
while those of the former class are only feebly developed, the 
second class of streams cut deeply into the deposits, thus form- 
ing a system of ravines and gullies and of spurs and elongated 
hills which is remarkable for its complex nature. 
All of them head at about the same hight, i.e. about 1500 
feet above sea level. All of them flow in deep channels widen- 
ing rapidly as they proceed down the slope of the divide and 
enter upon the plain south of it. All of them receive a number 
of creeklets and brooks along their courses and thus cut up 
the country to the S. E. into two prominent terraces, so to 
