IOWA ACADEMY OF SCIENCES 
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TESTIMONY OF RIVER BLUFFS. 
One of these is that if the Missouri loess is supposed to be mainly 
derived by the winds from the sand bars of the Missouri River as Shi- 
mek states, (Bulletin, Lab. of Nat. Hist, of Univ. of Iowa. Vol. V. No. 
4, pp. 318 and 373) there should be a marked excess of loess on the 
east side, for the same reasons that sand dunes, which are surely 
aeolian are found best developed to the east and south of wide stretches 
of large river valleys. (Bui. 158, U. S. G. S., p. 64.) This is because 
northwest winds are most efficient in this work in this region, though we 
may admit that winds from other directions have some effect. In this 
latitude westerly winds are prevalent the northwest in winter and the 
southwest in summer. Hence if the loess is from the river bars there 
should be a very perceptible preponderance of it east of the Missouri. The 
slight excess claimed by Shimek and admitted by advocates of the 
aqueous theory seems fairly explained in this way, but this leaves the 
great mass of loess very imperfectly accounted for, and its nearly equal 
development east and west sadly out of proportion to the directions and 
relative strengths of winds, as Prof. Wright well claims. (Amer. Geolo- 
gist, XXXV. p. 236.) 
If the aeolian hypothesis is ever to explain the mass of Missouri 
loess, the origin should be sought rather on the arid plains further west, 
yet in that case there is met the difficulty of accounting for so much 
greater depth near the river. Moreover, there should be a steady 
increase in claj^ey character toward the east. 
TESTIMONY OF ROOT MARKS. 
Again, there is an evidence which Richthofen, the first advocate of 
the aeolian theory, made much of, but which later advocates, for some 
reason, seldom mention. It is this, minute rootmarks very generally fill 
the loess from top to bottom to which fact perhaps the vertical cleavage 
is partly due. He ascribed these to grasses growing a few feet above 
and therefore found in them evidence that the surface had gradually 
risen by dust accretion. This was shown by the writer to have little 
if any significance in that direction so far as American loess was con- 
cerned, because grasses and other prairie plants were shown to send 
down roots 15, 25, even in some cases 60 feet. (Proc. A. A. A. S., 1878, 
pp. 236-7.) But they do furnish testimony opposed to Prof. Shimek’s 
plea for the aeolian theory. He postulates timber-clad hills for the 
habitat of his land shells. (Proc. I. A. S., VI. p. 108.) And he explains 
the disappearance of tree trunks and other marks of vegetation by pos- 
tulating the .very slow accumulation of the dust. (Bull. Lab. Nat. Hist. 
5. U. I., V. No. 4, p. 320.) But if this were the case, how can the 
absence of large tree root-marks be accounted for? Wood and leaves 
may decay and the processes of the surface obliterate every trace but 
we cannot believe that of the rootmarks when we find the minute ones 
so perfectly preserved. May it be that they have been overlooked? 
Take the Council Bluffs localities; certainly that remarkable stratum 
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