. 309 
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, 
62, 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 388, pp. 466-7,) will give a 
air 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 through the 
Meredosia slough and Green river basin to the Illinois at the bend near 
Hennepin, or directly westward through the Wapsipinnicon basin to the 
mouth of Mud creek, and thence scuthwestward along the Mud creek sag 
to the Cedar; thence the course may have been by way of the present 
Cedar and lower Towa, 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 establish 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 the deep portion of the channel along the Mud crecs 
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 heavy accumulation of drift. The drift is largely 
sand and there has been no necessity for sinking wells entirely through it. 
1Tt may be well to say here that such constrictions in the valley of the Mis- 
sissipp! occur wherever the river crosses resisting strata of rock, such as the Lower 
Magnesian, and the Galena, Trenton and Niagara 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 resistant beds. Hershey’s theory is interesting but not well established. 
