498 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



uniform with that below in its maturity, and it would be unlikely 

 that either the very short stream postulated as rising on the eastern 

 slope of the divide near Herring and flowing eastward past Wall 

 Lake, or even the much longer one rising on the western side and 

 flowing southwest, should, during the brief time allotted, have cut 

 out such a wide valley and developed such a mature flood plain as 

 now exist, both in the unoccupied sag valley near Wall Lake and 

 in Boyer valley near Herring and in increasing measure to the south- 

 west. 



Professor Todd" has recently argued that Niobrara river of north- 

 ern Nebraska, during pre-Pleistocene time "followed the courses of 

 James and Missouri rivers as far as Onawa, Iowa, thence east and 

 northeast through Ida and S'ac counties past A\'all Lake and thence 

 southeast along the Raccoon river. This conclusion rests on a few 

 apparently reliable reports from wells which show that the pre- 

 glacial surface indicates a valley whose bottom is less tlian 900 A. 

 T., in some cases less than 850." "The fact that Wall lake, lying on 

 the summit, formerly drained into Boyer river and now into the 

 Raccoon, and another fact that the Boyer rises east of the crest of 

 the divide, has first a course east of south and at this point turns 

 southwest" are considered to be explained by this theory. Such 

 well records as are available to the writer do not indicate such a 

 valley as Professor Todd postulates and while Wall lake and the 

 sag valley doubtless partly suggested the theory it must be remem- 

 bered that the lake is pf late Wisconsin age while the valley is 

 doubtless to be dated at the close of the Kansan. These facts seem 

 to invalidate the whole argument since Professor Todd is discussing 

 a preglacial stream. 



Professor Todd further states that : "There was a fall of 350 

 feet from Sioux City to Wall lake." But at present the elevation 

 of low water in Missouri river at Sioux City is 1,076 feet, whil« 

 the elevation of Wall lake is about 1,225 feet. There is no indica- 

 tion of such a warping as would be necessary to equalize the dis^ 

 crepancy between these figures and the grade indicated by Todd. 

 In fact, the evidence seems to point to uplift in northwestern Iowa 

 during glacial times rather than to the depression which seems to be 

 necessitated by Professor Todd's hypothesis. 



Doctor Carman* has recently restated the theory of an eastward 

 flowing Boyer in his report on the Pleistocene Geology of North- 

 western Iowa. Carman emphasizes the facts that the Mississippi- 



^Todd, J. E., The Pleistocene History of the Missouri River: Science: N. K., 

 Vol. XXXIX, F&b. 20, 1914, pp. 263-274. 



••Iowa Geological Survey, Vol. XXVl, pp. 318-320, 1915, 



