i 
GREENE COUNTY. 661 
already described. Its upper reaches occupy slight depressions in the 
Drift beds that cover so deep the eastern side of the county, and while 
at the western margin of the cliff limestone it is bedded in rock, it has 
wrought out no deep channel for itself. 
Aside from these principal depressions the general surface of the county - 
is a plain, having an average elevation above the sea of one thousand feet. 
Throughout the six eastern townships, and in Miami township on the 
north, the surface is quite uniform—one hundred feet, or one hundred 
and fifty feet at most, comprising the extreme range of variation in level. 
The remainder of the county lies, it is true, at a somewhat lower average 
elevation, but there are insulated summits all through it holding the 
general level above given. 
By reference to the appended geological map it will be seen that these 
divisions agree exactly with the great geological divisions of the county, 
its northern and eastern portions being underlain with the Upper Silu- 
rian, or cliff limestones; while from the western half, though originally 
present, this formation has been carried away by long-continued erosion, 
only insulated patches of it now remaining to attest its former extent. 
It is to be remarked that the occasional summits, already spoken of, in 
the western half of the counvy, that are one thousand feet or more above 
the sea, are in all cases these outliers ci cliff limestone, to which atten- 
tion is now called. 
By the removal of the protecting sheet of the cliff limstone, the softer 
beds of the Cincinnati series have been uncovered, and the wear and 
waste in them have been much more rapid than in the higher rocks. 
The deposits of the Drift have been spread over all of the county, re- 
ducing the asperities of the surface and hiding many ancient channels, 
but after all only modifying and not essentially changing the great fea- 
tures determined by the underlying geological structure. So that here, 
as in other counties reported upon, a geological map becomes in great 
‘degree a topographical map, the areas of the cliff limestone comprising 
those districts of the county that have an elevation of a thousand or 
more feet above tide water, while all other areas belong to the Lower 
Silurian, or Cincinnati series. 
The lowest land of the county is found on its southern boundary, in 
the valley of the Little Miami, and ranges between two hundred and 
seventy-five feet and three hundred feet above low water at Cincinnati, 
or between seven hundred feet and seven hundred and twenty-five feet 
above the sea. The highest land is found in Cedarville and Miami town- 
ships, along the water-sheds between the Little Miami and Massie’s 
Creek, and the Little Miami and Mad River respectively. It may be 
