GREENE COUNTY. 667 



they were in the earlier history of the county. It serves a very fair pur- 

 pose as a building stone, but occurring, as it so generally does, in close 

 proximity to the Niagara series, which yields' some of the finest building 

 rock of Ohio, it comes to be but little thought of when quarries of the 

 latter are made accessible. In earlier times, however, the higher degree 

 of accessibility of the Clinton beds caused them to be largely drawn upon. 



In like manner the manufacture of quick-lime from the Clinton forma- 

 tion has been wholly abandoned. For many years the outcrops of this 

 stratum on Reed's Hill supplied the Mad River valley and the western 

 side" of the county quite largely with lime. Lime was also burned from 

 this horizon in Xenia -township twenty years ago. It has, however, 

 been fully established that in the manufacture of quick-lime none of the 

 numerous varieties of calcareous rocks in south-western Ohio can enter 

 into successful competition with the Guelph or Cedarville beds of the 

 Niagara series, where the latter occur. The economy with which lime 

 can be produced from this formation, and the manifest and decided supe- 

 riority of the product, have ruled out all other sources. 



In the vertical scale of the rocks of the county a thickness of fifty feet 

 was assigned to the Clinton limestone. This measure is to be obtained 

 in the first section described, namely, that from Goe's Station to Yellow 

 Springs. It is, however, to be remarked that it is an exceptional thick- 

 ness, and that the formation rapidly thins out to the southward, being 

 reduced in Spring Valley township to less than half this measurement. 



3. The last element in the geological scale of the county is now 

 reached, viz., the Niagara series. It takes precedence among the forma- 

 tions of the county on several grounds. It occupies a somewhat greater 

 area than the Cincinnati group, and it impresses much more distinct 

 features upon the district in which it occurs than does the latter forma- 

 tion. Several of the more noticeable facts in the topography of the 

 county are referable, as has been already intimated, to the presence and 

 characteristics of the cliff limestone, of which the Niagara is the leading 

 element. Its outcrop is a rocky wall, very often uncovered, and gener- 

 ally reached by quite an abrupt ascent at least one hundred feet above 

 the level of the adjacent county. The picturesque gorges of the Little 

 Miami and its tributaries are due to the order of stratification of the 

 Niagara beds, and to the same order must be referred the water-supply of. 

 a considerable part of the county. The building stone and quick-lime of 

 the county are almost wholly obtained from the Niagara beds; and, in ad- 

 dition to these home supplies, large amounts of each are exported to sur- 

 rounding cities and towns. 



The divisions of the Niagara group are well marked, and several of the 



