Geological Papers. 101 



a peculiar deposit of very fine, even-grained and usually un- 

 stratified material, remarkable for forming by river-erosion 

 perpendicular walls — although soft enough to be easily spaded. 

 It is usually destitute of organic remains, but when these are 

 found they consist of fresh-water shells and especially land 

 shells. When fresh-water shells are found, the material is 

 usually obscurely stratified. Similar bluff -materials are found 

 bordering nearly all European rivers, such as the Rhine and 

 Danube, and is there called loess, and referred to the Cham- 

 plain epoch. 



A somewhat similar material, however, is found also spread 

 over wide areas in many countries, especially in arid regions. 

 These have no obvious connection with any rivers. Such is 

 the case in northern China and also in the Basin and Rocky 

 Mountain regions. 



The loess of the Mississippi and its tributaries, as also of 

 the European rivers, was probably deposited in flooded lakes 

 and in the slackened water regions of flooded rivers of the 

 latter Glacial and Champlain epochs. It is poor in fossils, 

 because the waters were ice-cold. It is unstratified, because 

 the waters were overloaded with the very finely triturated ma- 

 terial left by the retreating ice-sheet. 



The loess of northern China is seolian in formation, ac- 

 cording to Richthofen. The unstratified superficial soil of the 

 basin region, Russell thinks, is due partly to wind-borne dust, 

 but mainly to rain-wash. The unstratified soil covering the 

 hilly country at the base of the Alps is attributed by Sacco to 

 rain-wash of the base-soil recently left by the retreating ice. 



In writing concerning the loess, Mr. Chamberlin says, in 

 substance:' While the larger part of the loess found in the 

 glaciated region of North America is believed to be the prod- 

 uct of glacial waters, it still remains, in my view, that certain 

 parts of it were produced by winds. This part in general is 

 believed to have been derived from the water-deposited por- 

 tion, but perhaps this is not universally true. For instance, 

 the loess collected along the leeward side of the Mississippi 

 river seems to have been derived by wind from the flooded 

 flats of the river below. While coinciding with what seems 

 to be the majority opinion of American geologists, that the 

 loess deposits of the glaciated region are chiefly water-lain, 

 it appears to me prudent, if not important, to recognize the 



8. Journal of Geology, vol. 2, p. 537. 



