680 GEOLOGY OF OHIO. 



unstratified maps, thickly set with pebbles and bowlders of small size, 

 many of which have rubbed or striated faces, like that of the rock on 

 which they rent. In its original state it is a very compact formation, as 

 is shown in the deeper sections of it ; but where the deposit is shallow it 

 has been considerably transformed by atmospheric agencies. The par- 

 tial or complete solution of the limestone pebbles that make so prom- 

 inent an element in it renders the whole bed more porous and permeable 

 than the unaltered deposits are. With this transformation of texture a 

 change of color is also connected, the lower oxides of iron in the bowlder 

 clay being converted into peroxides b'y the presence of air and water, 

 and' the bed becoming a yellow clay instead of blue clay. 



The unaltered blue clay is often struck in wells, and is also shown in 

 the banks of streams where the weathered materials are removed as fast 

 as formed. 



As elsewhere, seams of sand and gravel are intermingled with the 

 bowlder clay. 



3. A third phase of the Drift formations is also abundantly shown in 

 Greene county, in the beds of clean sand and gravel, which occur every 

 where throughout its area, and especially on the highest lands of the 

 county. These beds are distinctly stratified, oftentimes with conspicuous 

 lines of false or uneven bedding, differing in composition from the bowl- 

 der clay in this respect, viz., that they contain water-washed instead of 

 striated pebbles, and that they present unmistakable indications of hav- 

 ing been sifted and arranged under water. Examples of these high- 

 level grades can be seen at various points, but at none more clearly than 

 in Miami township ; as, for example, at the Yellow Springs gravel bank, 

 at the banks of W. C. Neff, Daniel Jobe, and J. H. Little ; and also in the 

 Hamma neighborhood, along the Yellow Springs and Fairfield pike. All 

 of these points belong to the high grounds of the county, and some of 

 them constitute its summit levels. From some peculiarities in its struo 

 tnre, the Yellows Springs bank deserves a somewhat more extended 

 notice. 



It ie located to the south of the village, about half a mile from the 

 railroad track. It rises forty feet in height above a very flat-lying area, 

 and thus makes a conspicuous feature in the topography. Its summit is 

 not far from ten hundred and sixty feet above the sea. It embraces an 

 area of somewhat more than two acres. It is composed of sand and 

 gravel, with considerable quantities of clay, the three orders of materials 

 being, however, quite well separated from each other. Some bowlders 

 are met with, the largest one now exposed measuring seven feet in 

 length. Like almost all of the largest sized bowlders of southern Ohio, 



