1 882.] The Loess of North America. 



The composition of the concretions is essentially the sa 

 that of the loess proper, though some of the elements d 

 appear therein. After treatment of ioo grains of the ir 

 with strong muriatic acid, there remained, after thorough 



ing and drying, thirty-one gra 



ins of insoluble re 



sidue, or nearly 



one-third, which was plainly sil 



ica. Dr. Litton's ; 



malyses of con- 



cretions from the loess of Mis 



souri, the only one 



;s, I believe, on 



record in America, gave him : 







Carbonate of lime 58.33 



Carbonate of magnesia 0.77 



The absence of a greater amount of carbonaceous material in 

 the loess soil proper is matter of common remark. It may be 

 accounted for, perhaps, by the fact that carbon in the soil tends 

 generally to oxidize and disappear, save where there is an accu- 

 mulation of water and a cool climate. 1 Its presence in the shape 

 of " organic remains " seems to have been noticed, in chemical 

 manipulations, only by Aughey and Emery, as noted in the 

 table. 



Method of Deposition. — The older geologists, without excep- 

 tion, seem to have agreed either upon the fluviatile or lacustrine 

 origin of these famous deposits. Nor does this decision appear 

 to have been questioned until the publication of Von Richtho- 

 fen's China, in which that celebrated geologist elaborated his 

 views, based upon extensive and painstaking study of the loess of 

 that country. His views are radically distinct from those of his 

 predecessors in the same field of investigation. They are based 

 upon a study of the Chinese loess extending over a period of five 

 or six years, while engaged in certain other investigations under 

 the auspices of the Prussian Government. His observations were 

 published at length in the work to which allusion has been 

 made, in 1877, but not having access to the original containing 

 them, I am obliged to formulate a resume of his theory from 

 reviews which have appeared in the several scientific journals. 

 This is deemed necessary for the reason that though based upon 

 the Chinese loess, Richthofen expressly states that in his judg- 

 ment the theory of that deposit is applicable to the loess where- 

 ever on the globe it may be found. 



