IOWA ACADEMY OF SCIENCE 
249 
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Kansan. That portion within the Illinoian lobe was removed by 
the ice, but outside of the lobe only such effect as has been noted 
could have been produced. In Scott county, Iowa, north of Daven- 
port, several exposures show two loesses, the interval between 
which evidently marks the time of the presence of the Illinoian 
ice near by. Similarly two loesses occur just outside the Iowan 
lobe at Decorah, near Iowa City and at Carroll, Iowa, the interval 
between which marks the presence of the Iowan ice. That this 
view is correct is further attested by the presence of a drift (the 
Iowan) in the interval, as in the northern part of Johnson county, 
or by a drift (the Wisconsin) capping the loess as at Des Moines 
and Carroll. 
Thus the presence of several loesses does not weaken the aeolian 
hypothesis. On the contrary it strengthens it, for each ice-sheet 
produced new conditions and brought new materials, which during 
the inter-glacial periods were built up into loess under conditions 
which produced an abundance of plants and land-snails, a fact 
which precludes the presence of floods. 
Professor Todd again refers to the “interloessial till” found by 
Dr. Bain and himself at Sioux City. It is worthy of note that the 
numerous observers who have studied the loess along the Missouri 
and elsewhere have failed to discover any other “interloessial till.” 
If the conditions assumed by the advocates of the fluviatile hy- 
pothesis once existed, such examples should be frequent. It may 
further be said that the particular exposure in question has not 
been so carefully studied that its character could be considered as 
absolutely established for broad conclusions.* It is also a fact that 
on both sides of the Missouri river the drift frequently rises to 
form huge cores of the loess-covered ridges, and that it rises much 
above some of the loess exposures which appear on the slopes, thus 
making it locally possible to have drift carried over loess during 
heavy rains. 
So long as all this is true, and until Professor Todd brings to 
light other and later evidences than he has thus far produced, the 
writer’s objection (which he designates as “strictures”) to gen- 
eral conclusions which are based upon such insufficient evidence, 
must stand. 
*In the interval between the presentation and the printing of this paper the writer made 
a careful examination of numerous sections near Sioux City, among them the sections 
showing the ‘ ‘ interloessial till , ” and found that the member below this till is not loess , but 
a heavy joint clay which is evidently glacial and pre-loessial. This removes one of Professor 
Todd’s strongest props, and explains what heretofore has been a puzzle to students of the 
loess. A more complete account of this and related deposits is in preparation. 
