652 GEOLOGY OF OHIO. 
place with the regions to the southward over which the northern ice 
never advanced. This boundary is perfectly distinct in several. town- 
ships, while in others it is less sharply defined. 
Bevinning on the eastern side of the county, it passes through the 
_northern half of Colerain township in a south-westerly direction, not far 
south of the line of the Adelphi and Chillicothe pike. It leaves almost 
all of Green township to the northward. West of the river it coincides, in 
a general way, with the Chillicothe and Greenfield pike, passing, how- 
ever, two or three miles below it on the west side of Buckskin township. 
There are, within the area to the northward, and especially along its 
more southerly extension, occasional summits that stood above the gla- 
clers, but the clay and bowlders that mark the Drift overlie all of the 
ordinary high land of the country, as is well shown along the road 
above named in the vicinity of Lattaville. 3 
This boundary is shown with great distinctness in Colerain township. 
A very instructive view can be obtained by following the eastern road 
leading from Mooresville to Adelphi. Ascending a branch of Walnut | 
Creek, the native rocks are shown in more or less extensive sections on 
every hand, and the soils are seen by all of their characteristics to have 
been formed, where they now lie, by the weathering and disintegration 
of these rocks. The banks of the stream approach each other more and 
more closely, until at last the road is shut within a narrow valley, above 
which rise, on either side, steep hills of sandstone and shale. The gorge 
proves to ba a pass, and after a rapid ascent, an open country is reached 
which differs, in a very marked degree, from that left behind. A broad 
valley, filled with gravel and clay, and dotted with bowlders, is found at 
a high level; the native rocks are so well covered that no clue to their 
composition is furnished, and rounded outlines prevail in all of the 
scenery, instead of the angular contour observed before. The gravel and 
clay contain a considerable quantity of limestone pebbles and bow!ders, 
and thus the land comes to be known as limestone land. Its natural 
vegetation and its agricultural capacities are as sharply distingushed 
from those of the lands on the other sides of the hills as is the scenery. 
A great improvement is at once visible in the farm buildings, the quality 
of which is, in a general way, determined by the degree of fertility of 
the soil. On looking back, after passing a mile or two to the northward, 
the explanation comes clearly to view. The Drift-storm was stopped by 
this :anze of hills, against the northern slopes of which these heavy 
beds of clay and gravel are piled. In other words, these hills form in 
their sinuous outlines the boundaries of the true glacial Drift. Sugar 
Loaf Mountain, already referred to in another connection, forms the 
