3G 



rally to be found at no remote distance to the northwest. An in- 

 spection of these pebbles is sufficient to show, that in many, if not 

 nearly all cases, they are derived from the grits and sandstones 

 with which the bituminous coal of eastern Virginia is associated, 

 while from the similar nature of the sand and gravel in which they 

 are embedded, we are entitled to conclude, that at least in part) 

 they also refer themselves to the same region for their origin. In 

 the hills at and below Richmond, and in many other places these 

 beds of gravel have considerable depth, and present a structure at 

 once curious and instructive. A series of strata at these places, in 

 some of which the pebbles are disposed in horizontal lines ; in 

 others, in lines oblique, but still generally parallel, inclining down- 

 wards to various points in the different layers, give striking evidence 

 of the agency of those diluvial and oceanic currents, of which 

 geologists have discovered so many memorials in other regions, and 

 may serve when minutely studied, to throw much light on the 

 physical changes to which this portion of the continent must for- 

 merly have been subjected. 



Beneath these beds of gravel, in many places strata of clay 

 occur ; but whether referable to the same epoch of deposition, can- 

 not as yet be clearly ascertained. Many beds of very argillaceous 

 clay, suited for the potter and brickmaker, and occasional layers of 

 a pure beautiful yellow ochre, may be placed in this portion of the 

 series. 



Other strata of clay and sand of a peculiar character present 

 themselves in many localities beneath the superficial beds. These 

 contain a record of their origin legible to the geologist, in the im- 

 pressions of shells and Zoophytes with which they are generally 

 filled. On comparing these casts, which in most cases can be 

 easily recognised even in their more delicate markings, with the 

 fossils of our Miocene marl strata, their identity is established, and 

 thus the strata in question at once take their places in the scries of 

 Miocene Tertiary deposites. In many parts of Hanover, King 

 William, Henrico, and other counties in this range, these beds 

 of clay are found, usually characterised by a dark greenish gray or 

 brown colour, a sulphureous odour, and an astringent taste. On 

 Governor's hill in Richmond, a stratum of the same kind is exposed; 

 and at this spot, the fossil impressions and other characters above 

 noticed, may be distinctly seen. Like the clays and sands for- 

 merly described as associated with the Miocene, these contain sul- 



