17i> 77/' American Geologist. September, 1898 
local origin of the drift seems to indicate that much of it. 
and even, as lie believes, the greater part, was transported be- 
neath the ice. 
Mr. Leverett spoke of the thickness^ of the drift near its 
boundary in Illinois. In general the drift border is attenu- 
ated, but in some places its thickness in the outermost five 
miles attains a maximum of 50 feet ; and several time- as 
much drift is found on that belt as in the adjacent drift-bear- 
ing belt ") to 20 miles back from the boundary. 
Prof. II. F. Reed, referring to his observations of the Muir 
glacier, doubted that basal ice currents could ascend and bear 
drift into the ice-sheet. 
The Succession of Pleistocene formations in the Mississippi 
(i,i</ Nelson river Ixtshis. By Warren Upham. The Lafayette 
formation of loam, sand, and gravel in the southern -tat.-. 
extending in bluffs on each side of the low Mississippi valley 
plain to Cairo, is regarded as a fresh-water deposit laid down 
by rivers when the continent was being raised above its pres- 
ent hight during the epeirogenic uplift ending the Tertiary 
and beginning the Quaternary era, whose culmination was 
attended by the accumulation of the continental ice-sheet. 
Preglacial residual clay and alluvium are supposed to have 
been swept bj r the rivers from the mountain and highland 
regions down to the lower and less rapidly descending broad 
valleys and coastal plains, forming theLafaj-ette beds. But as 
the uplift increased the rivers afterward deeply eroded this 
formation and the underlying strata. The Lafayette forma- 
tion is correlated with the Saskatchewan gravels described by 
McConnell in the vallej-s of the Saskatchewan and Mackenzie 
rivers, interbedded in their upper part with the lowest and 
earliest deposits of the till or glacial drift. Stages of the max- 
imum ice advance and of halts or re-advances interrupting its 
retreat are shown by the till and moraines, and during this 
part of the Glacial period the land was depressed under its 
ice load. The loess and other modified drift were deposited 
when the ice-sheet was rapidly melting and receding, being 
derived from its englacial drift, as were likewise the deltas of 
the glacial lake Agassiz for their greater part. Subsidence of 
the land beneath the ice. and its re-elevation while the ice- 
sheet was melting away, are known by the loess, the north- 
