106 E. W. Aiigard—The Less of the Mississippi Valley. 
“The straightening of a wire under the influence of a current,” 
Walker’s Hlectric Magazine, 1846. The magazine in question 
bas not been found in any of the libraries consulted ; it is there- 
fore a matter of uncertainty how far M. Guillemin has antici- 
pated the results here given. ] 
Art. XVIL—The Less of the Mississippi Valley, and the Aolian 
Hypothesis ; by EK. W. Hiuearp, University of California. 
[Read before the National Academy of Sciences, April 16, 1879.] 
In a highly interesting paper read before this body a year 
ago, and published in the February number of this Journal, 
Prof. Pumpelly, speaking of the loess formation, sums up his 
views on the subject of the origin of these peculiar deposits in 
the statement that, rejecting his own previously expressed ex- 
planation, he is led to “believe with Richthofen that the true 
cess, wherever it occurs, is a subaérial deposit, formed in a dr 
central region, and that it owes its structure to the formative 
to render the zolian hypothesis untenable s 
to the troughs of large river courses. 
The latter fact scarcely needs more than a cursory reference, 
if only to the circumstance that western geologists have habit- 
ually brought the loess under the general designation of “ bluff 
formation.” The loess of the Rhine, and of the Danube, are 
familiar to us in the same connection. It can hardly be that 
oe is not willing to consider these prototypes as “true > 
cess.” 
Now, what are the points in which the typical leess differs so 
far from other aqueous deposits, that in spite of this obvious 
correlation we hesitate to class it as such? Aside from Richt- 
hofen’s objections based upon the hypsometrical relations of 
the Chinese deposit (concerning the cogency of which I am 
unable to judge, not having seen his original publication), 
there are two principal ones, viz: Se 
