2IO TIic American Geologist. Apni, i904. 
tainly it is as easy to conceive of the deposit's taking place in 
this way as of its being left by the wind in the manner sup- 
josed. The extensive level areas of loess referred to probably 
accumulated over rock shelves or expanses which were already 
approximately level. 
Such being the case, it could represent a deposition either 
from moving water or moving air of given velocities upon a 
diminution of the currents. As I have elsewhere maintained,*" 
there can be no question that large bodies of typical loess in 
eastern Mongolia and northern China are wind deposits. In 
numerous places over those regions typical loess is drifted in 
on the lee side of the mountain 5000 feet high as snow is drift- 
ed on the lee side of fences; so that, in accounting for the 
ultimate origin of the Chinese loess, I could see no better ex- 
planation than that of Richthofen, that it has been brought in 
from the arid regions of central Mongolia by the strong pre- 
vailing westerly winds, and accumulated along the mountain- 
ous border which marks the boundary between Mongolia and 
China proper. From these centers of accumulation it is now 
in process of rapid erosion, being carried by the streams to 
lower levels along the coast of China. In similar manner it 
may be plausibly maintained that the ultimate origin of the 
loess of the Mississippi valley may be found in the arid plains 
west of the Missouri over which winds of a definite velocity 
have been sweeping the material eastward during long pre-Gla- 
cial times, permitting it to accumulate over the area subse- 
quently covered by ice. But that it was immediately distributed 
into its present position largely by ice and the floods of water 
ensuing upon its departure can now be maintained with great- 
er confidence than formerly by reason of a remarkable discov- 
ery announced by professor Buckley, of the Missouri Geolog- 
ical Survey, at the meeting of the Geological Society of Amer- 
ica at Washington, in January, 1903. This announcement was 
that granite boulders of considerable size had been found as far 
south as Tuscumbia. This startling announcement really opens 
up a new chapter in the Glacial history of this region, and pre- 
pares the way for a very satisfactory explanation of the loess 
deposits in the valley of the Missouri above the Osage ; for the 
*"Origin and Distribution of tlae Loess in Norttiern Cliina and Central 
Asia." Bull. Geol. Soc. of Am., vol. xiii. p. 1.S8. 1902. 
