THE LOESS OF NATCHEZ, MISS. 317 



such species as inhabit the warmer parts of our country today, 

 and there is nothing in the molluscan fauna of this loess 

 which would suggest even the remotest possibility of a glacial 

 climate. 



It appears that the aeolian theory offers the best explana- 

 tion of the origin of the loess not only of Natchez, but of all 

 the Mississippi drainage. The writer's first paper in which a 

 modified form of the aeolian theory was presented,* was based 

 almost wholly on the study of fossils, and subsequent inves- 

 tigations, geological, paleontological and botanical (for the 

 loess presents an interesting problem to the plant ecologist, 

 and the influence of plants on the formation of the deposit 

 seems to be great), have only served to emphasize in the main 

 the conclusions therein presented, though perhaps modifying 

 them in some details. The chief purpose of the subsequent 

 papersf was rather the demonstration of the impracticability 

 and impossibility of the generally accepted theories which 

 postulated aquatic and glacial conditions. 



While it is not purposed here to enter upon a detailed dis- 

 cussion of the positive evidence in favor of the aeolian theory, 

 this being reserved for a more extended paper on that subject, 

 certain considerations which have a direct bearing upon loess 

 in general, and upon that of the southern Mississippi valley 

 in particular, are here presented together with the writer's 

 conception of the origin of the loess. 



To make the formation of such a deposit as the loess pos- 

 sible it is necessary to have: 1) A source of supply of material 

 at hand; 2) an agency capable of transporting the material; 

 and 3) a lodging place upon which it may be safely anchored. 

 Where any of these conditions fail there can be no deposition 



*A Theory of the Loess. — Proe. la. Acad. Sci., vol. Ill, pp. 82-80. 

 — 1896. 



tProc. la. Acad. Sci., vol. V, pp. 32-45, 1898; vol. VI, pp. 98-113, 

 1899; vol. VII, pp. 47-59, 1900. 



Journal of Geology, vol. VII, Mch. , 1899. 



Bull. Lab. Nat. Hist. St. Univ. of Iowa, vol. V, pp. 195-212, May, 1901. 



