March 16, 1894. 
of running water. In a strongly flexed region, for 
instance, the drainage is largely controlled by the attitude 
of the rocks. A country of horizontal strata of moderate 
resistance, such as those of the Ozark plateau, is par- 
ticularly favorable to the development of a swinging 
course. Where soft and hard beds, like shales or lime- 
stones and cherts, alternate, we can readily conceive how 
a stream of comparatively rapid fail may move or expand 
its meanders considerably while cutting only a slight 
depth through underlying resistant beds. Did time and 
space permit it would be interesting to elaborate further 
and to trace the effects of other modifying conditions. 
Without being prepared at present to express final con- 
clusions, it seems to me probable, however, that the 
presence of such streams as the Osage over the Missouri- 
Arkansas plateau can be assigned to local conditions of 
declivity and stratigraphy. : 
“Whichever hypothesis be advanced it is, of course, 
necessary for its acceptance that other facts of the 
geological history of the region be reconcilable with it. 
As I view the question at present, such reconciliation 
seems more readily effected on the hypothesis I have 
advanced, than on Professor Davis’s. The exceptions I 
took to his, that the country had been base-levelled 
in ‘Tertiary times, are not objections against mine. 
But, whether Mr. Davis be right or not as to the 
volume of erosion (leaving out of consideration the 
resultant forms) and as to the earth movements that 
have taken place since Paleozoic time, the explanation 
which I offer stands equally good. 
I do not mean by this, however, to beg the questions 
of the extent of Mesozoic denudation and of the oscil- 
S(CIUEIN CIE, 
19S) 
lations. which have taken place since the Paleozoic 
period. There have undoubtedly been changes of levels: 
such were necessary to bring the Cretaceous and Tertiary 
rocks of the Mississippi embayment to their present alti- 
tudes; but I do not think the differential movements 
within the limits of Missouri 
have been very great. 
While the seas existed in which the post-Paleozoic 
deposits of Kansas and Colorado were laid down, the 
drainage of a part of Missouri probably flowed in that 
direction. With the uplift of the western area, certain 
readjustments of drainage must have taken place over 
Missourit. When I stated in my last letter that the 
sculpturing of the topography must have been uninter- 
ruptedly in progress from the end of the Paleozoic to the 
present time, I meant that Missouri had been essentially 
a land surface since that time. Probably the larger features 
of its drainage system were blocked out at the beginning of 
this period of emergence. ‘Vhis statement is not at all 
opposed to the idea that changes of level or readjustments 
of drainage took place during that period. Just what was 
the exact sequence of events, or the nature of the changes, 
I do not feel prepared to say. More critical field studies, 
better knowledge and more careful consideration of the 
geological history of surrounding areas is necessary before 
anything like the full story can be told. With such 
knowledge as we have, however, I am not inclined to 
accept the hypothesis of a wide base-levelling such as is 
required, if all of the sinuous streams of this region are 
assigned to that cause; and this especially when another 
hypothesis seems adequate to explain the phenomena in 
question. ARTHUR WINSLOW. 
Office State Geological Survey, Jefferson City, Mo., March 5, 1804, 
ba 5, 189 
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