534 F. V. EMERSON 
two belts correspond in having the thickest loess near the Mississippi 
lowlands. 
Here, as in most places elsewhere, the loess shows the charac- 
teristic uniformity in size of particles. There are no available 
mechanical analyses of the lower part of the loess, but several 
analyses of lower subsoils show that about 70 per cent ranges in 
size from +25 to;}5 mm. in diameter and about 20 per cent is below 
this diameter. The remainder is composed of particles but slightly 
larger than ;3 mm. in diameter. In general the loess particles of 
Louisiana seem to be more rounded than those farther north, so 
far as the writer can judge from the examination of half a dozen 
samples from Iowa and Illinois. This difference is doubtless to be 
explained by the fact that the southern loess particles have been 
subjected to long transportation by the Mississippi. In the main 
body of the loess an examination of perhaps 500 exposures shows 
little if any stratification, although here and there there are faint 
indications of such structure. For example, the snail shells which — 
are abundant locally show in a few places a rude horizontal align- 
ment and lie in thin dark streaks suggesting buried soils. In a few 
places dark bands never more than a few inches long and probably 
due to iron and manganese coatings suggest that these substances 
have accumulated along bedding planes. A sharp contact between 
the loess and the underlying materials has never been observed, but 
rather there is a transition zone 3 to 20 inches in thickness. The 
transition is most indefinite between the loess and underlying clays, 
for there is more or less similarity in texture and in some cases in 
color. Where Lafayette and Columbia sandy materials underlie 
the loess, there is in places a “‘feathering”’ of the one into the other 
and in places very faint stratification. 
THE ORIGIN 
Two problems are involved, (1) the source of the loess materials, 
a problem with which this paper does not deal directly, and (2) the 
secondary or the depositing agents. Since the loess belts follow 
only the Mississippi lowlands and do not extend up the tributaries, 
it is clear that there is a genetic relation between the river from 
Cairo southward and the loess. The Mississippi doubtless carried 
