339 



Leverett accepts this, hypothesis, or at least he quotes it and offers 

 no objections. (64:461-2.)^ 



The question of the preglacial course below Clinton, Iowa, is not yet 

 fully settled. Leverett discusses the problem fully in his writings (58, 60, 

 ('2, 63, 64), and lately Carmen has spent some time in the Clinton region, 

 but his paper is not yet published (16). The number of wide channels be- 

 tween Clinton and Muscatine, and the depth of drift renders the problem 

 very complex. 



A quotation from Leverett (Monograph 38, pp. 466-7,) will give a 

 fair idea of the location of the preglacial course below Clinton : "Udden's 

 special investigation has led him to the conclusion that the praeglacial line 

 must have been along one of two courses, either southeastward througli the 

 Meredosia slough and Green river basin to the Illinois at the bend near 

 Hennepin, or directly westward through tlie Wapsipinnicon basin to the 

 mouth of Mud creek, and thence southwest^vard along the Mud creelv sag 

 to the Cedar ; thence the course may have been by way of the present 

 Cedar and lower Iowa, or more directly southward to the Mississippi just 

 west of the meridian of Muscatine. Udden has collected well data along 

 the Mud creek sag showing that a buried channel occurs there whose rock 

 floor is more than 100 feet below the level of the Mississippi river at Clin- 

 ton, and perhaps sufficiently low to have carried the drainage of the pre- 

 glacial stream whose valley has been traced southward to Clinton. The 

 data are scarcely sufficient to fully establisli the connection of this channel 

 across the Wapsipinnicon basin, for there are very few deep wells in the 

 basin. Another feature which throws some doubt upon this connection is 

 the narrowness of tlie deep portion of the channel along the Mud crecK 

 sag. 



"Turning to the southeastward course, one finds a broad depression or 

 lowland tract leading from Clinton through to the Illinois river. This low- 

 land, except at the outer moraine of the Wisconsin drift in Bureau 

 County, stands only a few feet above the level of the Mississippi, and yet 

 apparently carries a lieavy accumulation of drift. Tlie drift is largely 

 sand and there has been no necessity for sinking wells entirely through it. 



1 It may be woll to sny hero that such constrictions in tlic valley of tho Mis- 

 sissippi occur whfrovcr tho rlvor crossps resisting strata of rock, such as the Lower 

 Magnesian. and the Galena, Trenton and Ningara limestones, and It may be possible 

 that the river has always been running south, being unable to cut its valley so wide 

 in the more J"esistauj; beds, Ilershey's theory is interesting but not well established. 



