Wfiite Clays of the Ohio Region. — Leverett. 21 
Not only jire the clays of these two localities similar in macro- 
scopic and microscopic aspect, but they form a practicalh' con- 
tinuous sheet extending from the Beech Flats and adjoining low- 
lands outside Wright's glacial boundary westward onto the glacia- 
ted districts of southwestern Ohio, northern Kentucky and south- 
eastern Indiana, occupying the site of the hypothetical Cincinnati 
ice-dam and showing as strong development below (west of) the 
site of the supposed dam as they do above it. The fact that these 
clays cover a pari of the glaciated district proA'es that their dep- 
osition occurred subsequent to the time of maximum glaciation, 
and their distribution shows that the ice-sheet nowhere reached 
the Ohio river while they were l>eing deposited. It is evident, 
therefore, that their deposition cannot be attributed to an ice-dam 
on the Ohio at Cincinnati or at any point below. 
A feature of much importance in connection with these white 
clays is a black soil with leached and highly oxidized subsoil 
which immediately underlies them. The structure of this soil 
corresponds with that of the underlying drift sheet and as a rule 
it appears to be inseparable from it, though the weathering and 
the addition of humus has given it an aspect somewhat different 
from the unweathered portion of the drift. It is of A'er}' com- 
mon occurrence and indicates the lapse of a considerable interval 
between the retreat of the ice-sheet and the deposition of the cla3's 
Its presence etfectually disproves the curi-ent theory that the white 
clay was derived through organic agencies, from the underlying 
sheet of glacial drift. 
It has been suggested that the presence of the white clays if 
not explicable on the foregoing hypotheses, might be explained on 
a theory of general submergence due to a depression of the region 
to sea-level, the main objection urged against this theory having 
been that it involves a great change in altitude. The facts now 
ascertained, however, remove this ol)jection by indicating the 
occurrence of a depression of several hundred feet, but at the 
same time raise other and more serious objections to the theory 
of general submergence. It is scarcely probable that a body of 
water of the magnitude indicated, involving as it must have done 
considerable time in its incursion and withdrawal, would leave 
no shore lines sufficiently marked to have attracted notice. l)ut so 
far as I am aware none have ])e(^n reported. Furthermore presi- 
dent Chamberlin informs me that he has personally examined 
