The upland Loess of Missouri. — Hcrshey. 373 
the Gulf stream in the Atlantic), and this brought a great body 
of silt from far up those valleys to form the broad belts of 
thickened loess which follow the two great rivers and passing 
inland over the uplands, gradually merge with the thinner and 
more uniform sheet of north-central Missouri. This hypothe- 
sis is the only one yet advanced which will explain all the 
observed phenomena of the Missouri Upland loess in accord- 
ance with the recognized processes of nature. 
It is charged against the lacustrine theory, that there ought 
to be observable remnants of beach ridges. I must acknowl- 
edge that their total absence, particularly along the southern 
or landward boundary of this great extra-glacial lake, is a 
puzzle, but it is not as fatal to the theory as is the total absence 
of even a trace of river channels to the fluviatile theory. Rivers 
cannot exist without channels, but a lake may, by frequently 
changing its shore-lines, escape developing any decided beach 
ridges or wave-cut benches. Who has ever observed any 
evidence of a river channel in the upland loess? 
As is well known, the upland loess of Missouri is only a 
part of a very extensive sheet of demonstrably extra-glacial 
lowan silt occupying a large part of central and southern 
Illinois, southern Iowa, northwestern Kansas and eastern Ne- 
braska with a probable yet greater extension up the Ohio, 
Mississippi and Missouri valleys. Although perhaps it is not 
strictly contemporaneous in all parts, it undoubtedly is nearly 
so. The weight of evidence tends to indicate that it is a unit 
and everywhere due to the same body of water. As there is 
not known to have been, during the lowan epoch, any barrief 
on the south to pond the water in the central Mississippi 
region, the existence of this great lake-like body of water can 
only be accounted for as the result of depression of the land. 
This sinking of the land was greater in the north than in the 
south, but may have extended to such a degree as to depress 
the entire upland loess country beneath the sea-level, and 
admit the sea-water through a broad strait on the site of ex- 
treme western Kentucky and southeastern Missouri. 
From the apparent continuity of the upland loess of Mis- 
souri and Ilinois with the loess-like silt of the lower Missis- 
sippi region (which is undoubtedly a marine formation, in 
large part, at least), I think the above depression probable. 
