THE LOESS AND THE LANSING MAN. 343 



show that the loess was not deposited by ice. If it is main- 

 tained that the loess was deposited by flooded streams after 

 the ice receded, then it devolves upon the advocates of this 

 theory to explain the following phenomena: 



a. The region immediately adjacent to the larger streams 

 in onr loess-covered sections is the highest, as a rule, and has 

 the thickest deposit of loess. There are no bluffs or eleva- 

 tions lying beyond, which could have formed the banks of 

 the swollen streams. If there were great barriers southward 

 which retained the vast volumes of water postulated by this 

 supposition where are traces of them? 



b. The loess is fine and comparatively homogeneous. The 

 movement of such enormous volumes of water, would certain- 

 ly have resulted in the transportation of more coarse material. 



c. The loess is usually of approximately uniform thick- 

 ness on tops and slopes of hills, and is often laminated paral- 

 lel to the surface. Under what conditions could flooded 

 streams have produced this result. If it is assumed that the 

 loess was deposited in enormous lakes, where are their shore- 

 lines, and where were the land areas which produced the ter- 

 restrial molluscs? 



d. The loess is more or less fossiliferous, especially where 

 it is thickest, and where therefore the floods should have had 

 greatest influence. The shells are, with slight exceptions, 

 those of land snails which are not found, at least in large 

 part, upon alluvial low lands adjacent to streams. Great 

 floods covering such areas would render them wholly unfit 

 for such plant life as these snails require. Presumably these 

 floods would come in late spring and summer. How much 

 advancement of plant and snail growth could be expected in 

 the fall, winter and early spring ? 



In his recent article* Upham makes the remarkable state- 

 ment that in "the summers of each year the floods pouring 

 along the valleys from the ice melting and rains added little 



*Am. Geol., 1. c. p. 29. 



