360 The American Geologist. December, 1903. 
3. r| jiat the valleys were filled with loess and subsequently 
eroded, so that the loess now represents only a remnant which 
remained after extensive erosion. 
4. That the loess was deposited wholly (or at least in 
greater part) during the Iowan stage of glaciation. 
5. Since the evidence of aeolian origin cannot be wholly 
set aside, it is assumed that there is an "upland loess" of aeol- 
ian origin, but that a "valley loess" owes its origin to fluviatile 
agencies. 
6. Professor Winchell, (1. c.) especially maintains that 
there is no satisfactory distinction between the loess and the 
drift. 
The first of these assumptions has been made repeatedly 
simply to meet an emergency. There is no direct evidence that 
such movements have taken place in more recent time. There 
is evidence in other parts of the world that slight movements 
do take place, but nothing has thus far been produced in the 
area under discussion, other than the assumption which is es- 
sential to a theory of the formation of the loess. Such de- 
pression would result in the formation of large bodies of water. 
Where are the shore-lines or other evidences of the existence 
of such bodies of water? 
The second assumption is based on McGee's explanation 
of the formation of the river-valleys along the highest ridges, 
which, while applying to the underlying drift cannot be ex- 
tended to the loess. The ice-walled channels would call for 
climatic conditions which are impossible in view of the fossil 
fauna of the loess, and the vegetation which was necessary to 
maintain it. To show the possibility of the existence of plants, 
etc., even in close proximity to perennial ice, attention has been 
called to the fact that in alpine regions trees 'and other plants 
sometimes grow on masses of earth which were carried over 
glaciers by land slide. The conditions in the glacier-covered 
Mississippi valley, however, must have been entirely different. 
If the glacial mass was so thin and in a climate so warm that 
it melted away during each season to expose the necessary land 
surfaces, then there could have been no steady advance of the 
ice-mass by which enormous quantities of material were car- 
ried hundreds of miles from the northern ledges of rock to 
which thev can be traced. If on the other hand the greater 
