602 SAMUEL CALVIN 



The Missouri River loess and all other loess deposits which have 

 evidently been derived from the broad flood plains of near-by 

 rivers, have a similar distribution relative to their source ; they are 

 thickest and coarsest near the gathering-ground and become 

 thinner as the distance from the base of supply increases. All 

 the facts connected with the origin, composition, and distribution 

 of the loess are perfectly explicable without resorting to the 

 hypothesis that "a considerable part' was derived from the great 

 plains east of the Rocky Mountains." Studies in the field afford 

 overwhelming evidence that, genetically and geographically, the 

 Iowan drift has very intimate relations to certain bodies of loess. 



The Iowan Drift Is Not Related to the Illinoian 



It is scarcely necessary to discuss the suggestion that the Iowan 

 may be correlated with the Illinoian. Parenthetically it may be 

 said that if the Iowan and the Illinoian represent the same stage 

 of glaciation, the name Illinoian becomes a synonym for Iowan, and 

 we shall be reduced to the painful necessity of referring to one of 

 our most beloved drift sheets as the "so-called Illinoian." But 

 no such calamity awaits the Illinoian. The Iowan is much the 

 younger of the two. As indicated by the structural and genetic 

 relations above noted, the Iowan — a little later probably than its 

 maximum stage — is practically contemporaneous with the loess; 

 and as the Berlin paper, with noteworthy lucidity, correctly states 

 on p. 299; "the Sangamon interval separates the loess from the 

 Illinoian stage of glaciation so widely that there would seem to be 

 no relation between loess deposition and Illinoian outwash." The 

 same long interval, the same wide separation, exists between the 

 Iowan and the Illinoian stages of glaciation. The two drifts are 

 not related in time or in any other way. All the facts which may be 

 gathered from the most thorough investigations in the field, support 

 this last proposition: 



The Iowan drift is not related to the Illinoian. 



