DELAWARE COUNTY. BS 
with its Phaiatamien constitutes an important system of drainage. The 
whole limestone district, which embraces all that part of the county 
west of the Olentangy River, except that underlain by the Waterlime, 
is moderately undulating, the surface being worn by erosion into shal- 
low depressions, which, near their junction with larger streams, be- 
come ravines bounded by steep blufis. The district of the Waterlime is 
flat, especially in the townships of Radnor, Thompson, and Scioto. The 
deeply eroded valleys of the Scioto and Olentangy constitute the most 
marked topographical features of the county. In the southern part of 
the county these valleys are deeply cut in the underlying rock. The 
divide between them at a point west of Powell is one hundred and 
twenty-five feet above the Scioto. That interval is made up mostly of 
the beds of the underlying limestone, the Drift notehaving an average 
thickness of over twenty-five feet. The descent to the Olentangy is 
usually very gentle, occupying sometimes the space of a mile or more on 
either side; while the valley of the Scioto is narrower, and its banks 
more frequently rocky and precipitous. The valley of the Olentangy is 
excavated for the most part in the black slate or the underlying shale, 
but that of the Scioto is cut in solid limestone strata. This fact may 
account for the greater breadth of the former. 
In the north-western part of the county the valley of the Scioto 3 is 
strikingly different from the southern part. It has here the features 
that the same valley presents in Marion and Hardin counties. The 
bluffs are never rocky. The general level of the country is but little 
above the level of the water in the river. The stream has not yet cut 
. its channel throughout this part of its course through the Drift, and in 
traveling along its valley one is forcibly reminded of the strong resem- 
blance of the face of the country to the Black Swamp region of north- 
western Ohio. It is a natural and reasonable inference that this portion 
of the country has had a very different superficial history from the south- 
ern and eastern parts, and one that allies it more to the Lake Erie val- 
ley than to the Ohio slope. These Black Swamp features prevail in the 
townships of Radnor and Thompson, and in the north-western part of 
Scioto. 
RAILROAD ELEVATIONS. 
Above Lake Erie. Above the Ocean. 
Morrow county line (C. C. C.’& I. R. RB.) ............ 405 feet. 970 feet. 
Ashley (C. C. C. . PRB VaEe Ree ane eer ee: ALD SS Oa. & 
POTOWE SD jioittigh cogs hue ' fo Sa] Gt Te RS He eee 405“ 970 “ 
Delaware STEREO ace ee AR as 5d ce aie 943 
Berlin. aM TSM RRR retusa CEES 0 Seal tall 946 
Pe wish Cemtersmnuccanmne note teres cote ss ssnceeoscue Soy), 952° S$ 
18 
