CHAPTER XC. 



GEOLOGY OF BROWN COUNTY. 



BT H. HKRZER. 



[Note. — The survey of Brown connty was executed in 1871 by Bev. H. Hereer, 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 geologica,! 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 a few 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 th^s 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 county, 

 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 are callpd Gray Linvestone, 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 Trinucleus 



