324 The American Geologist. * May,i899 
The abundant intraglacial drift that was being transported 
very slowly at hights not far above the ground appears, during 
the glacial recession, to have been at last carried downward be- 
neath the outer part of the ice-sheet, probably in some degree 
on account of basal melting of the ice, being then amassed in 
the usually flat or moderately undulating ground moraine. Un- 
der certain peculiar conditions, due to climatic influences, I 
suppose that great quantities of the ice-held drift, having once 
become superglacial, were again covered by onflowing ice and 
heaped by its convergent descending currents in the high oval 
hills of till called drumlins. When the North American ice- 
sheet attained its greatest extent, erosion probably was in pro- 
gress on all the ice-covered country, excepting near its limits, 
being most rapid within some such distances as from 100 miles 
to 200 or 300 miles back from the boundary. Deposition pre- 
vailed, we may infer, on a submarginal belt, and the disappear- 
ance of the ice-sheet, during the Champlain epoch, was attend- 
ed by the recession of this belt, estimated to have been 20 to 50 
miles wide, across all the previously eroded country. The in- 
traglacial drift suplied by the wide and long continued erosion 
was then laid down, according to the view here presented, in 
great part and apparently more than half of it all, as the 
ground moraine of subglacial till; and the remainder formed 
the upper till, retreatal moraines, and all the superficial modi- 
fied drift, including kames, eskers, paha, and plateau, plain, 
and valley drift in their A^arieties of gravel, sand, clay, and 
loess. 
REVIEW OF RECENT GEOLOGICAL 
■ LITERATURE. 
Mineralogical Notes: Analyses of Tysonite, Bastnasite, Prosopite, 
Jeffersonite, Covellite, etc. By W. F. Hillebrand. Am. J. Sci., 157, 
51-57- 
The analyses of the following minerals were made in the laboratory 
of the U. S. Geological Survey, i. Tysonite and bastnasite. Analy- 
ses of fine specimens from Cheyenne Mt., near Pikes Peak. Col., agreed 
essentially with those of Allen and Com.stock. The formulas R"'F '., for 
tysonite and R"' (F', CO3") for bastnasite.. which in the absence of 
