April 1, 1904.] 



SCIENCE. 



533 



Evidence of the Agency of Water in the 

 Distribution of the Loess in the Missouri 

 Valley: George Fredekick "Wright. 

 The papei- is the result of field work con- 

 ducted during the past year in the vicinity 

 of the Missouri between St. Joseph and St. 

 Louis. The direct evidence of the agency 

 of water in distributing the loess is found : 

 (1) in the relations of the loess to the 

 main valleys of the Missouri and its larger 

 tributaries; (2) the existence of distinct 

 laminte, at a height of 180 feet above the 

 river at St. Joseph, which are very clearly 

 of water origin; (3) the new light shed 

 upon the glacial occupation of the region 

 by the discovery of northern drift on the 

 south side of the Missouri River forty 

 miles beyond the boundary which has here- 

 tofore been assigned to it; (4) considera- 

 tions which show the doubtful character of 

 the conclusions drawn from the fossil 

 shells found in the loess; (5) calculations 

 showing the reasonableness of the supposi- 

 tion that at the close of the lowan stage 

 of the glacial period there were periodical 

 floods each summer sufficient to cover the 

 whole i-egion occupied by the great body of 

 the loess, and the presentation of a theory 

 that would seem to harmonize all the facts. 



The Loess at St. Joseph. (Illustrated by 



lantern slides.) Read by Professor G. 



Frederick Wright for Luella Agnes 



Owen. 



Exposures of undisturbed loess in cuts 

 at a variety of elevations are described. 

 Several of the highest are distinctly strati- 

 fied and the horizontal strata, in places, 

 regularly banded with iron stain. Fossil 

 snail shells of the two forms common to the 

 loess are abundantly distributed through- 

 out these high-level laminations. The iron 

 bands can be accounted for by aqueous 

 deposition, but the seolian theory does not 

 so readily offer a solution of their presence 

 and regularity. Objection to the glacial 



origin of loess has depended largely for 

 support on the absence of an adequate bar- 

 rier on the south and west to have retained 

 a body of water of sufficient depth for the 

 deposition of the higher portions of the 

 bluffs. Such a barrier, however, can be 

 shown to have existed and to still remain, 

 by giving attention to the elevations of the 

 tributary water-sheds in those directions 

 and to the known conditions during the 

 flood period in May of 1903. Authority 

 is quoted to the effect that snails can not 

 be identified by the shells alone, as the same 

 kind may be common to forms of radically 

 different organization ; and the shell, there- 

 fore, is entirely subordinate to differences 

 in structure of the animal. If this is true, 

 the ffiolian theory suffers the loss of its best 

 support. 



Fresh-water Shells in the Loess: B. Shi- 



MEK. 



1. A review of the available literature in 

 which reference is made to the occurrence 

 of fresh-water shells in the American loess, 

 with a discxission of the significance and 

 weight of such testimony, showing that 

 as yet no well-authenticated cases of the 

 occurrence of fluviatile shells, at least in 

 original loess, are known. 



2. A statement of the author's own ex- 

 perience in the study of loess mollusks, 

 which shows that land shells greatly pre- 

 dominate, and that only such fresh-water 

 forms as inhabit temporary small ponds 

 and streamlets occur in the loess, and these 

 in relatively small numbers. 



Comparison of the Stratigraphy of Black 

 Hills, Big Horn Mountains, and Rocky 

 Mountains, Front Range: N. H. Darton. 

 (Read by title.) 



George B. Shattuck, 

 Secretary. 

 .Johns Hopkins University, 



