SUPPLE MENTE eeyY POTHESIS. RESPECTING, THE 
ORIGINSOPS THE, LOESS OF THE sMISSISSIPE! 
VALELENE: 
Tue loess problem still remains obstinate. While it has 
yielded somewhat to progressive research, there is, I think, a 
nearly universal feeling of dissatisfaction with all theories thus 
far advanced. The eolian hypothesis appears to be the better 
supported so far as concerns the chief deposits of China and 
perhaps some of those of western America, while the aqueous 
hypothesis seems best supported so far as concerns the deposits 
of the Mississippi valley and western Europe. It is the judg- 
ment of some students that the ultimate solution will lie in the 
recognition of both hypotheses, but the means of discriminating 
between the two and of applying the criteria are as yet wanting. 
The present paper is intended to be a contribution in this direc- 
tion. It is confined to the loess deposits of the Mississippi 
valley, but is probably applicable to the loess of western Europe. 
The distribution of the loess in the Mississippi valley seems 
to be very significant inits peculiarities. These may be summed 
up in two great features. 
1. The loess is distributed along the leading valleys. These 
embrace not only the great valleys, the Missouri and the Mis- 
sissippi, but some of the subordinate valleys, as the Illinois, the 
Wabash, and others. The loess is found along the Missouri 
River from southern Dakota to its mouth; along the Mississippi 
River from Minnesota to southern Mississippi ; along the illinois 
and the Wabash from the points of their emergence from the 
territory of the later glacial sheets to their mouths. Along 
these valleys the loess is thickest, coarsest and most typical in 
the bluffs bordering the rivers and grades away into thinness, 
fineness and non-typical nature as the distance from the rivers 
tRead before Section E, Am. Asso. Adv. Sci. Aug. 12, 1897. 
795 
