680 GEOLOGY OF OHIO. 
unstratified mass, 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 rest. 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 by 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 hay- 
ing been sifted and arranged under water. Hxamples 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 struc- 
tnre, the Yellows Springs bank deserves a somewhat more extended 
notice. i 
It is 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 teh 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, 
