Hilgard on Drift in the Western and Southern States. $45 
As for the drift of Illinois, I am unable to refer to the Reports 
of that State; but my own early recollections of it such as it 
exists in St. Clair county, place it in precisely the same category 
with the drift of lowaand Missouri. Only I remember distinetly 
the occurrence in it, of angular boulders of syenite, greenstone 
and quartzite. 
delta south of it. And even as far south as Vicksburg, the ac- 
tion of waier alone is inadequate to account for the transportation 
of the boulders found in these beds. 
Dana's remark (Manual, p. 554) that “ while the glaciers were 
disappearing, many a stream or lake would have existed to strat- 
ify the drift, and cause denudation in elevated places,” points no 
doubt to the true explanation of these phenomena: but it does 
not go far enough to satisfy existing facts. Agassiz has obser- 
ved that “the melting snows of the declining glacier epoch” may 
have been instrumental in the formation of the river terraces ; 
but Tuomey was, I believe, the first to point out, that the South. . 
‘ern drift may have been formed in consequence of the sudden 
melting of the northern glaciers (Second Report on the Geology 
of Alabama, ed. Mallet, p. 146); such as would have resulted 
from a first, rapid depression of so huge a mass of ice below the 
snow line. 
The assumption of a pretty rapid depression seems necessary 
to account for the immense volumes of water required to produce 
with ice-cold water by the enormous influx rom the glacier re- 
a state of violent flow. ; 
That the action must at first have been extremely violent, is 
Proved by the deep erosion of the un:erlying formations, ant 
the transportation and subsequent redeposition in mass, of their 
Materials, more or less altered; which 1s exhibited on so exten- 
Sive a scale in Mississippi. But for the fact that wherever the 
