ROSS COUNTY. 643 
Oreek flows in an old and deeply excavated valley. These constitute the 
leading cases of erosion and material modification of the surface. Still 
other examples are furnished by Deer Creek and Kinne-Kinnick, on the 
northern side, and by Indian and Walnut creeks on the south. 
The high table-lands that make so prominent a feature in the topog- 
raphy of Pike county are wanting here, except in the southern tier of 
townships, and in several of these there are but few examples. | 
Paint Creek is flowing, for a short portion of its course, in a new val- 
ley, the origin of which can easily be understood in the light of recent 
geological history. There are numerous cases of this kind in south-west- 
ern Ohio, an interesting one of which is given in the report on the 
geology of Clarke county, in the first volume. The facts connected 
with the present instance, however, are more remarkable than any 
yet recorded in this geological district. As the origin of this new val- 
ley is unmistakably connected with the history of the Drift period in 
the county, a full account of the case will be deferred until that part of 
the report is reached in which the formations of the Drift shall be 
taken up. 
Ii. GEOLOGICAL SERIES. 
1. There are several facts which render the limestones of Ross county 
much more interesting and important than those of Pike county. In 
the first place, the county stretches several miles further to the west- 
ward, and thus takes in a larger area of these rocks. In the second 
place, and chiefly, they have been laid bare in the deep valley of Paint 
Creek and its tributaries through all of the western border of the county, 
so that not only is a large area exposed, but the valley has been cut en- 
tirely through the Helderberg series deep into the Niagara group. The 
section thus exposes two Silurian limestones instead of one, as in the 
district beyond. In addition to these points, it may be remarked that 
the deep gorge of Paint Creek furnishes some of the most picturesque 
scenery of southern Ohio. Ns 
On the west line of Buckskin township, for two miles above and two 
miles below the Marietta and Cincinnati Railroad, the valley of Paint 
Creek is hewn out of the heaviest section of limestones of the Helder- 
berg division known in this part of the State. There are not less than 
forty feet shown in vertical section in the Rucker quarries, opposite 
Greenfield. It is probable that this forty feet exhausts the Helderberg 
series in its downward reach, or, in other words, that the courses imme- 
diately beneath belong to the Niagara group. The character and value 
of the stone and the extent of the quarries have been described at length 
