PREBLE COUNTY. 405 
_ An examination of these altitudes, in connection with the appended 
map of the county, will serve to show that, in a general way, they con- 
mect themselves directly with the geological formations. in other words, 
a geological and a topographical map of Preble county will have many 
points in common. The Cliff Limestone may be said to have an altitude 
of more than five hundred feet above low-water at Cincinnati, and the 
Blue Limestone an altitude of less than five hundred feet. Hlevations 
No. 4 and No. 6, above given, show exceptional altitudes for the Blue 
Limestone, and are to be explained, at least in No. 4, by the presence of 
heavy beds of drift. 
The drainage of the county is principally effected by four streams, 
named in the order of their importance, Twin Creek, Seven Mile Creek, 
®Wour Mile Creek, and Hik Creek. All of these deliver water to the Great 
Miami. On the extreme western boundary, small areas are found, the 
drainage of which is directed to White River. The highest land of the 
county is found on the dividing ridge between these drainage basins, the 
water-shed passing through Israel, Dixon, Jackson, Jefferson, and Mon- 
roe townships. 
Parts of Washington and Jackson townships lie quite flat; but there 
are ne swamps in the county, and no considerable areas from which the 
water runs even sluggishly. The Blue Limestone corner of the county, 
- comprising Twin, Lanier, Gratis, Somers, and Gasper townships, is beauti- 
fully diversified in surface, and constitutes a very attractive as weil as a 
very rich agricultural district. 
GEOLOGICAL SHRIES. 
The geology of the county agrees very closely, as far as its bedded rocks 
are concerned, with that of Montgomery county and Clarke county 
already reported upon. It will not, therefore, need extended treatment 
here. The series comprises three main elements, one of which belongs 
to Lower Silurian time, while the other two are of Upper Silurian age. 
‘The series can be shown in diagram thus: 
| [ Guelph. 
gi | Niagara Group.......-.....3 Springfield stone. 
Upper Silurian........-. g Niagara shaies. 
*, Dayton stone. 
_ Clinton Limestone...-.....--. 
Lower Silurian ........- § Cincinnati Group, Lebanon division. 
The approximate thickness of the divisions can be given as follows: 
FEED. 
INTAV AT AROTOUP te serene arse aise nee aac Sao os OR0 COOH HeObOU Hebn pone (5) 
Clinton Limestone.........--.., py sere Sa aS Ea ee eR PSE UH ee helm Sg bet Spee 15 
SCANCUM MAINA OU Biewenie aw ee seni Se nvsn wc oamee Gabe CNL Ce a 225 
