DiirliK/ tlw Glacial I'rrlod. — Chamlx j-Iin. 269 
face at the time of its formation, if 1 interpret the phenomena 
correctl3\ The drift does not terminate in any well-defined 
morainic ridge, such as the ancient glaciers formed at several 
later stages. On the contrary, the termination is found in a 
gradual thinning out of the drift unattended ))y marks of forci- 
ble action on the part of the ice. The inference is therefore 
drawn that the ice crept out slowly upon a low slope, the gentle- 
ness of which accounts for the lack of vigorous action or forcible 
heaping of material. 
This inference, which by itself might have but slight value, is 
supported l)y the fact that the sheets of till in this border region 
to a large extent graduate upwards into pebbleless clays and 
thence into loess-loams, or true loess, making it appear certain 
that slack drainage was a prevailing phenomenon. 
This is further supported bv the absence, in general, of coarse wash 
from the edge of these outermost drift sheets. At some points 
near the edge, but more commonly at points remote frf)m it. there 
are beds of gravel, often taking a lenticular form, but these may 
be attributed to waters acting in channels in the ice or l)eneath it. 
where b}' confinement and by the peculiar conditions of glacial 
drainage they were forced to a vigorous action \\hicli they lacked 
when once they had issued from the border of the ice. 
As a summary statement, it may be asserted that the phenomena 
of tlie border drift in the Mississipiji valley })resent everj'where 
evidences of slack or slow drainage, with only such exceptions as 
may Ite rationally referred to enforced vigor through the immediate 
agency of the ice: and that there is nowhere evidence of i)owerful 
or specially rapid currents of water such as must inevitably have 
is.sned from the glacial border, in the axis of the great Mississippi 
basin, had the slope of the surface been at all considerable. Tt 
is therefore a firm and safe inference that at the time of the form- 
ation of the drift sheets that reach farthest southward there was 
no considerable slope of tlic surface; not even so much as now 
exists. 
///. Tlic Sinootlt (oil ('HI IS mid Silt A/nous of tin Ohhr 
Moraines. In the axis of the Mississippi basin on account of the 
planeness of the surface and the great extent to which the ice 
stretched forward, the successive glacial stages are better deploj-ed 
than in most regions east or west where later invasions overrode 
the territory of earlier ones and ol)scured the phenomena. Tlie 
