CHAPTER XC. 
GEOLOGY OF BROWN COUNTY. 
BY H. HERZER. 
| Norr.—The survey of Brown county was executed in 1871 by Rev. H, Herzer, and 
some of the facts transmitted by him are embodied in the present report.—E. O.] 
Brown county is bounded on the north by Clinton and Highland coun- 
ties, on the east by Highland and Adams, on the south by the Ohio 
Riyer, and on the west by Clermont county. 
Its geology agrees almost exactly with that of the last named county. 
All the general statements made in regard to Clermont county can be 
applied, without change, to Brown. Both of them agree in containing, 
beside the deposits of the Drift period, but a single geological formation, 
viz., the Cincinnati Group. In range they vary slightly, the very sum- 
mit of the series being attained in Eagle township, Brown county, in the 
north-eastern corner. At afew points in this township, there is evidence 
of the former presence of the cliff limestone, in the characteristic red 
clays that result from its decomposition. It is possible that the cliff 
limestone (Upper Silurian) will yet be found in place in the highest 
lands east of Fincastle. The ground is certainly very nearly high 
enough to catch it. It is found in force as soon as the Adams county 
line is reached, but thus far no bedded rocks have been discovered of 
Upper Silurian age in Brown. , 
The upper beds of the Cincinnati Group, on the east side of the sonia 
are distinguished from the middle and lower portions of the series by a 
change of name. Instead of being counted with them as Blue Limestone, 
they aré called Gray Limestone, their color being decidedly lighter than 
that of the typical beds. There is no doubt that with this change of 
color appreciable changes of chemical constitution are associated. It is 
held by some that the soils of the Gray Limestone lands are somewhat 
more productive than those derived from the lower portions of the series. 
The upper limit of the rocks of the county has been found, in the base 
of the Upper Silurian formation.. The lower limit almost exactly coin- 
cides with the geological horizon of Cincinnati. The trilobite Trenucleus 
