194 
IOWA ACADEMY OF SCIENCES 
of shells should show some trace of the large roots of trees if any were 
ever there. The writer has searched in vain for any not easily referred 
to the present surface, nor to his knowledge has any other observer 
reported any. If therefore the former existence of trees must be dis- 
credited, then also the great age of the shells may be, unless the expla- 
nation offered for their recent introduction given on a previous page 
is disproved. 
But time forbids further discussion at present. Possibly a word of 
forecast concerning probable untimate conclusions may be of interest 
and of possible help to direct observation. Imagination is often a 
serviceable scout in the advance of • Science, even if she may sometimes 
err in her vision. 
CONCLUSIOISr. 
It seems not improbable that the mass of the Missouri River loess 
wull remain credited to aqueous forces. The absence of fresh-water 
molluscan remains may be explained by the coldness of waters from the 
north, and the muddineses of the same as also of those from the west. 
Perhaps those existing in some remote pools or streams were destroyed 
in transportation or were too heavy to be carried to higher or distant 
localities. 
Very considerable portions of the loess will be proved to be the 
work of wind; the pinnacles along the eastern verge of the trough of 
the Missouri in Iowa including possibly Council Bluffs in part, and the 
higher ridges south of the Missouri in northern Nebraska, also in less 
degree south of the Platte, the extensive blanket covering the broad 
divides especially those between larger streams, may be placed under 
this head. The aqueous loess in its early bare condition afforded abun- 
dant source for comparatively rapid accumulation. Nor Should the dif- 
ficulty of distinguishing the aqueous from the aelian form be an objec- 
tion to this view. We all know how difficult it is to distinguish sand 
deposits laid down by these two agencies, particularly if they have been 
subject to surface, action. How much less then should we expect to see 
differences when the material is finer grained and more homogeneous. 
