40i) The American GeoUxfisf. December, iso7 
extensive luas? of red clay, chert and sandstone blocks mixed 
together. A half mile farther anotlier cut enters first through 
Saint Peter sandstone, then 100 yards through clay with chert 
fragments and sandstone blocks. This mass rests upon an ir- 
regular sandstone surface and is about six feet thick, covered 
by a six-foot mantle of undisturbed loess loam. T'he base of 
the exposure is fifteen feet above the flood plain of the river. 
At the southern end of the cut the chert and clay drift dips 
below the grade and probably extends a considerable distance 
down the valle}''. 
The three described masses of clay and chert are explicable 
only as the successive moraines of a glacier, that descended 
the valley from' its head, five to six miles distant. How much 
farther the glacier may have ]ireviously extended I can not 
tell, but possibly to the limits of the "driftless area." I ex- 
amined many exposures of residuary cla}'- farther down the 
valley but came upon no accumulations^ like those described. 
One is everywhere reminded that no accumulation of clay^and 
chert would have remained intact. The residuary clay upon 
the appertaining formations is uniformly thin and alike thin 
i^whether the latter are little or much reduced in thickness. 
Seemingly conditions had been such that the clay was swept 
off gradual 1}^ following closely its growth from beneath, and 
in such a manner that it did not creeo down the slopes onto 
the sandstone, nor remain accumulated. Moraines of loose 
clay would probably hiave been obliterated, leaving onlj^ their 
contained quartz f ragments^ which same are not safely inter- 
preted as moraines because such heaps may be due to unequal 
distribution of the chert in the decomposed strata. Thus, too, 
the polished surfaces of the same fragments are not safely 
attributed to glaciation because the chert and other pieces in 
the residuary clay are more or less etqhed and are rough pol- 
ished anyway. 
'J'he transportation of chert fragmejits from lower to high- 
er level might prove the existence of glaciers, but a place was 
sought in vain where a glacier must necessarily have ascend- 
ed. The "Freeport gravel"* was found however on low hills 
but still far above the flood plain of the river. This brown 
gravel if truly an ancient deep-lying river gravel, as liershey 
*Hershey (1897): Am. Geologist, vol. xix, p. 207. 
