826 G. H. SQUIER 
varies greatly. Two measurements obtained not over ten rods 
apart, one on the crest ofa hill, the other on its west slope, gave 
seventeen and thirty-two feet, respectively, with indications that 
at some intermediate point it may reach fifty feet. It is almost 
wholly free from stones and very homogeneous in texture, 
though the deeper parts are somewhat lighter in color and more 
friable, the result apparently of a large admixture of sand. Save 
in the valleys, it usually overlies the residual material derived 
from the disintegration of the underlying rocks, or near the foot 
of the hills, the talus, which being often nearly pure sand well 
shows the abruptness of the transition. In rare cases it rests 
directly on the rock. 
while it is habitually absent from accumulations formed by weathering and by proc- 
esses sequent upon weathering, the balance of evidence seemed to me adverse to the 
glacial hypothesis. At any rate, it seemed best to urge more prolonged and critical 
study before publication. 
In February 1895 Mr. Squier presented similar data more fully worked out 
with reference to ridges of bowldery material accumulated about Trempealeau 
bluff on the Mississippi, in the northern part of the driftless area. The absence 
of limestone cannot be urged here with the same force as at Tomah, since it occurs 
in at least one locality. The absence of glacial scratches on the transported rocks 
as well as the valley sides, and the lack of specific morainic contours leave much 
to be desired here as at Tomah, but these deficiencies are not necessarily fatal 
to the glacial hypothesis. The conception of Mr. Squier, that the glaciers were 
formed by snowdrifts lodged in the valleys, and not by summit accumulations, is 
doubtless the true one if the glacial interpretation be true at all. Examples of such 
snowdrift valley glaciers occur in the extra-glacial belt in Greenland, and might 
reasonably enough be supposed to have occurred in the driftless area. But if these 
deposits are really due to local wind-drift glaciers decisive evidence of the fact should 
be forthcoming on a sufficiently prolonged and critical search. A coarse massive 
mixture of residuary material, however difficult of satisfactory explanation by other 
agencies, cannot safely be taken as in itself proof of glacial origin. It must be 
remembered that as a result of the excessive superficial thawing and freezing incident 
to glacier-border conditions, the facilities for landslides, bodily creeps, and similar 
modes of movement reached an extraordinary degree of development. I have seen 
in Montana a modern landslide that imitated a glacier almost perfectly in the deploy- 
ment of its material. In Yellowstone Park, Mr. Hague showed me several years ago 
an almost perfect imitation of glacial deployment assumed by a talus mass of angular 
blocks of igneous rock. When such formations consist of mixtures of earthy and 
rocky material, their positive differentiation from glacial deposits may not be always 
successfully attained. So long as the constituent material is essentially residuary 
in origin, and there is an absence of any notable quantity of unweathered rock 
