68 The American Geologist. February, i904. 
speak, one at a general level of 1400 feet above the sea bounded 
by the southern slope of the Canton ridge and by minor western 
tributaries of the Big Sioux on the other side and traversed 
by the broad valleys of the two Brule creeks — the other ter- 
race less significant about 100 feet below the level of the form- 
er and trending N.-S. along its eastern slope and bounded on 
the east by Pattee creek and the bottom land of the Big Sioux, 
above the level of which it abruptly rises to a relative hight of 
about 140 feet. 
Only the upper course of Pattee creek which is the western 
tributary of the Big Sioux is here concerned. It falls at first 
to the E.N.E. at a rate of 26 feet per mile, which course it 
changes after a mile and a half into a northeastern one, turn- 
ing after one mile's run to the S.E., thus forming a semi- 
circle the diameter of which runs due W. and E. It then fol- 
lows a southeastern direction, while bends and loops appear 
more frequently in its course and its grade is less rapid, i.e. a 
little less than 14 feet per mile. 
East Brule creek maintains in its upper course a direction 
E.S.E. slowly sweeping around to the S.S.E. and forming in 
section 12 of Norway township a sudden bend to the S.S.W., 
which course it follows, until it receives its western fork. From 
this point on it turns more and more to the S.E., only occasion- 
ally showing bends, which are in the upper course more fre- 
quent. It descends at a rate of 22.4 feet per mile upon the up- 
per terrace before alluded to, while its fall farther down is not 
by far as rapid, amounting to about 7 feet per mile and 4.4 feet 
per mile near the southern boundary of the area under con- 
sideration. 
With West Brule creek about the same conditions hold good 
as with its neighbor. Both of them flow in valleys which are 
at first deep and narrow, but then rapidly widen out and unite 
with each other some distance beyond the southern limits of the 
area in order to form a broad flat-bottomed valley with gentle 
slopes. 
From its head waters down to the southern boundary of 
Lincoln county West Brule creek entertains a course almost 
parallel to the west fork of East Brule creek, showing also 
about the same grade. In its middle course, however, the me- 
andering character is more pronounced. It receives its waters 
