108 =. W. Hilgard—The Leess of the Mississippi Valley. 
valleys between sharp-backed ridges.* But wherever vertical 
cuts have been made, they stand like stone walls, unaffected 
ut if it must be admitted that the loess of the Lower Missis- 
sippi is a true, typical loess, exhibiting all the lithological and 
structural characteristics by which that deposit is recogniz 
elsewhere; and that hypsometrical and stratigraphical data 
compel us to assume that it has here been formed under water: 
then the mainstay of the xolian hypothesis falls at once, for 
what has happened here can have happened elsewhere. Nor 
should it be forgotten that, if the loess does not exhibit the 
and the leeward regions. At least no such differences are re- 
ported in the United States; nor are they mentioned in the 
resumés of Richthofen’s views that have been published. 
As to the absence of almost all but terrestrial fossils, save 
locally where the materia] generally is more clayey, I cannot 
elp suspecting some connection between this fact and the so- 
lution and re-deposition of carbonate of lime, so constantly and 
rapidly going on in these deposits. The adherents of the zeolian 
hypothesis find no difficulty in accounting for the absence of 
every vestige of the vegetation which they consider as a more 
or less essential agent of its formation. According to them, 
this vegetation has left no mark but the tubes originally coat- 
* See Rep. on the Geology and Agriculture of Mississippi, 1860, pp. 194, 313, ff. 
