304 C. A. White on Drift phenomena in S.W. Iowa. 
in the southern tier of counties, there are evidences that the 
drift deposit reaches a thickness of more than a hundred and 
fifty feet. Westward from that region a sensible diminution of 
its thickness is seen, and, reaching the region of the Bluff forma- 
tion along the Missouri river, the drift material is found in 
eases comparatively thin, being thinnest where the bluff mate- 
rial is thickest. 
At the localities where the scratches were observed, the drift 
material showed evidences of unusual violence of glacial action, 
being, as before remarked, only a few feet in thickness; and in 
some places in the same neighborhood it was entirely wanting, 
the bluff material resting directly upon the Coal-measure lime- 
stone. 
An explanation of these facts is naturally sought for. The 
glacial action extended more 
deeply beneath the general surface here than elsewhere, and 
that the direction and character of the currents were such that 
tain in relation to the general direction of ancient glacial cur- 
middle of the state, as far northward as the fourth tier of coun- 
ties and probably much farther, are boulders and fragments © 
reddish colored i 
by Dr. Hayden of the rock which encloses the pipestone of 
meee 
reached their present locations with glacial currents in the direc- 
tion of the drainage of the western watershed, particularly if 
they are of the age to which Dr. Hayden has referred the rocks 
of that famous locality; for in that case they cannot be pre- 
sumed to have ever existed much farther to the eastwar 
me om z: V. Hayden on the Geology of Northeastern Dakota; this Journal, Jan- 
