1/6 Tlic American Geologist. September, ibSK 
A discrimination between the extreme southern tract of the 
drift, in the Mississippi basin* and the more definite morainal 
belt of a later ice invasion was made by professor Chamberlin 
in 1882. A similar discrimination in Pennsylvania and New 
Jersey was made by R. D. Salisbury in 1891. 
Against the great debt which American glaciology owes to 
European investigation there is something on the credit side. 
The skill accjuired in the study of American moraines enabled 
two American geologists to find similar phenomena in Eur- 
ope. H. Carvill Lewis, in 1886, traced terminal moraines in 
Great Britain and Ireland, and one year later R. D. Salisbury 
did the same thing in Germany, these being the first discovery 
of open-country moraines of the massive order of the Euro- 
pean ice sheets. These discoveries of European peripheral 
moraines were of great importance, as they laid the foundation 
for further location of morainal belts and so made possible a 
comparison of the marginal oscillations of the ice sheets of 
the two continents, by help of which the geologic equivalency 
of the successive glacial and interglacial deposits of Europe 
and America has been determined. 
A peculiarity of the American deposits is the peripheral 
moraines common to, and produced by, two opposing or ad- 
jacent ice lobes and termed "interlobate" by professor Cham- 
berlin. 
The correlation of moraines of recession with glacial lake 
shorelines will be noted below. In the study of the successive 
moraine belts between Cincinnati and Mackinac, F. B. Taylor 
has reached the conclusion that these moraines were produced 
by periodic oscillations of climate, so slow as to be referable 
only to some astronomical cause, probably the precession of 
the equinoxes. But Croll's hypothesis is not believed to fur- 
nish alone a satisfactory explanation. 
As regards the precise manner of morainal accumulation, 
especially of the taller hills, there is not entire concordance of 
opinion. In several writings Mr. Upham has argued that the 
moraines were formed from englacial drift during episodes 
of equality of advance and melting, following stages of greater 
ablation and concentration of superglacial drift ; and that these 
conditions were possible only during the warm Champlain 
epoch. Other writers deny the existence of any large amount 
