PEEBLE COUNTY. 411 



Sellers's Run, near the head of which these quarries are found, fur- 

 nishes in its bed and banks an excellent section of the upper rocks of the 

 county. Beginning with a fine show of the Clinton limestone, rich in 

 its characteristic fossils, which is shown near Turner's distillery, the suc- 

 ceeding beds of the Niagara series to the Cedarville division, inclusive, 

 are traversed and disclosed within the course of a mile. 



DRIFT. 



The Drift beds of the county, which may be said to cover its entire 

 area, remain to be briefly described. In all of their general characters 

 they agree perfectly with the same order of deposits in adjacent regions. 



The bowlder clay, or unmodified Drift, is shown in very numerous sec- 

 tions, and is reached in the digging of many wells. In the northern 

 half of the county this deposit is uniformly deep — so deep, at least, as 

 never to be reached in ordinary sections or excavations. Its surface is 

 often covered with the deposits of saad, gravel, and stratified clay which 

 compose the modified Drift of this region, and when so covered it consti. 

 tutes the water bearer for the area which it occupies. When the bowl- 

 der clay itself makes the surface, the water supply is found at easily 

 accessible depths within it, in some of the seams of sand and gravel that 

 are scattered at irregular intervals through its substance. 



In the central regions of the county the bowlder clay rests directly 

 upon the polished surface of the Niagara limestone, and in the southern 

 regions it is not seen as distinctly or as often, its best exposures being 

 confined principally to the deeper valleys. 



The bowlder clay gives every indication of having been formed under 

 the great glacial sheet which has been demonstrated to have covered the 

 northern portions of the continent in the period preceding the present. 

 It is filled with scratched and polished fragments of limestone and northr 

 ern rocks, compactly laid in the dark blue clay which characterizes the 

 formations of this age in every part of the world where they occur. The 

 seams of sand and gravel interpolated in the clay, doubtless, result from 

 partial meltings of the glacial sheet in some of the milder periods of its 

 history. The ice-sheef in its southward advance must have found the 

 face of the continent covered with a forest growth and other forms of 

 vegetation. It seems certain that some remnants of this pre-glacial 

 growth are preserved in the bowlder clay. Worn fragments of wood, at 

 least, are often found deep in the clay, which it seems impossible to refer 

 to any other source. 



This pre-glacial vegetation must not, however, be confounded with the 

 interglacial growths to which attention has often been called in the 



