Glacial Dejjo-sils in Dyiftless Area. — Sardesou. £97 
compared to the pre-AVisconsin loess is no doubt inconsider- 
able in amount. Tlie relatively modern and inconsiderable 
deposits of loess and loess sand, nevertheless, are of very 
great interest since they may be a true indication of what the 
great loess periods were. The Wisconsin glaciers obliterated 
part of the great loess deposits; did it first overrun large 
associated deposits of wind-driven sands to the northw^ardV 
It may be that the Wisconsin drift lies here and thereupon 
old lake beds and swamps, and that just preceding theglacia- 
tion the climate was not that of a desert. There may have 
been such a period of erosion and non-deposition of the loess 
formation. But if we consider the period of loess ueeuraula- 
tion itself, who can say that a desert did not exist then on a 
large scale? In Fillmore county, southeastern Minnesota, I 
have noticed beds of finely polished pebbles on the top of the 
lowan drift. They are on high land, 1200 feet elevation ; the^^ 
are not waterworn pebbles, they are not rough-etched like 
the cliert in residuar}' cla}^ but are very smooth like the wind- 
sand polished surfaces found on exposed quartzite rock of 
southwestern Minnesota. It is not now possible for me to 
tell whether abundance of such materials existed, but possibly 
they did and evidence of it ma}'^ be looked for. 
T'urning again to the explanation of the desert sand of An- 
oka county, as sand gathered by the wind from the modified 
drift at a time following the retreat of the glacier, and add- 
ing that as sand was driven so fine dust was at the same time 
transported to higher and more remote hills, we have one of 
the accepted theories regarding the loess deposits exemplified. 
If following the lowan drift period, an arid region prevailed 
through which retreating glaciers poured flooded rivers there 
was an ideal condition for the driving of dust onto the hills 
and the formation of loess. The Wisconsin glaciers could 
have again obliterated the sand plains and its rivers worked 
over the valley deposits so that little except the loess could 
remain. 
Chamberlin and Salisbury (op. cit, p. 286) have discussed 
the origin of the loess around the "driftless area," and have 
presented as an objection to the aeolian hj'pothesis the ver^ 
phenomenon which I would else have presented as evidence of 
it, viz., "the predominant distribution of loess along thegreat 
