IOWA ACADEMY OF SCIENCE 
123 
all the loess was formed in forests, and that on dry prairie hillsides very little 
humus is developed. Furthermore, the possibility of the return of calcareous 
material with the dust from the bars of streams is worthy of consideration. 
Professor Norton further states “that the presence of loess over the prairies 
of southern Iowa shows that neither forest nor hilly country is a necessary con- 
dition to loess accumulation.” He here again assumes that only forests and 
hills can accumulate loess. No such claim has been made by the writer. He 
has simply based certain definite conclusions on the fact that the loess is quite 
uniformly thickest in hilly country near streams, and that in such place the 
forest and other dense vegetation is usually best developed. There is nothing 
to prevent the accumulation of some loess on plant-covered prairie surfaces, but 
this would be in small amounts, and it is noteworthy that where loess does 
occur on the prairies it is in relatively small quantities. Such an accumula- 
tion of loess on the prairies of Iowa has already been noticed 
by Calvin* and by the writer,** and may be observed both on Iowan 
(see Plate XII, fig. 1), and Wisconsin areas. It is also found 
on the Kansan prairies in the southern part of the state, but not in quantities 
comparable with those found along streams, as might be inferred from the state- 
ment quoted. The fact is that the accumulation of loess on the southern prairies 
is very slight; indeed, there is none on large areas. The cut west of Afton 
Junction, Iowa, represented in Plate XII, fig. 2, shows a characteristic veneer of 
loess, overlying a drift clay, which in turn rests on a typical Kansan drift. The 
drift clay has usually been confused with loess, and is evidently the same as the 
drift clay at Sioux City and South Omaha, which is discussed on p. 61 of the 
Proceedings. The delimitation, vertical and horizontal, of the loess of the south- 
ern part of the state in sections remote from larger streams will show that it is 
much less in both volume and area_ than might be inferred from the statement 
quoted. 
After presenting the foregoing objections to the aeolian hypothesis. Profes- 
sor Norton reiterates McGee’s explanation of the presence of isolated masses of 
loess on the paha, the substance of which is contained in the following state- 
ment:*** “The fiuvio-lacustrine theory may be able to explain the insularity of 
the loess tracts by affording ice-barriered water bodies for its deposition and the 
absence of the loess over other tracts by the presence of overlying ice.” And 
in the following additional conclusion:! “In crevasse-like openings in the stag- 
nant ice which covered Bremer county we may entertain the theory that the 
paha received their cap of loess.” As heretofo}’e,t the author quoted here again 
wholly ignores the evidence of the fossils which occur in the loess. Fossilifer- 
ou’s loess is not as abundant on the loess islands within the Iowan area as in 
other parts of the state, but it does occur. Modern mollusks are today less 
abundant in the same territory than in many other sections of the state, probably 
because of the relatively large amount of sandy or poorly drained surrounding 
surface, and the same conditions evidently existed throughout the period of 
deposition of the loess. 
*Iowa Geol. Sur., vol. XIII, 1903, pp. 70 and 329-330. 
*^Proc. Iowa Acad. Sci., vol. IV, 1897, pp. 68-72. 
***Ibid., p. 385. 
tibid., p. 382. 
tSee reports in Iowa Geol. Sur., on the following counties: Linn, vol. VI, 1895: Scott 
vol. IX, 1899; and Cedar, vol. XI, 1901. 
