61 



mountain, recently said to have been made, derives peculiar interest 

 from the fact of the existence, in the same vicinity, of hematite and 

 magnetic iron ores in great abundance. 



SANDSTONES OVERLYING THE PRIMARY ROCKS ALONG THEIR EASTERN 



BOUNDARY. 



Sandstones of various degrees of coarseness are found in many 

 places along the eastern outcrop of the primary rocks, and extending 

 for some distance below the head of tide. On the Rappahannock, in 

 the vicinity of Fredericksburg, considerable exposures of these rocks 

 are seen, the strata lying nearly in a horizontal direction upon the 

 edges of the primary rocks beneath. At Falmouth, the two are seen 

 in contact ; the latter forming the bed of the river, and the former 

 resting horizontally upon them. At the head of the Pamunkey, the 

 same rocks appear, dipping with some steepness to the east ; they 

 are again met with, gently inclining in the same direction, a short 

 distance below Richmond, and also in the neighbourhood of Peters- 

 burg, and at several points in Chesterfield county. Further south, 

 they occur in the upper part of Greensville, and over a considerable 

 portion of the county of Brunswick, and, as is believed, in portions of 

 the adjoining counties. 



In composition they are merely a mixture of quartz and felspar, 

 in rather loose cohesion — the felspar often decaying rapidly on ex- 

 posure. In some varieties, the rounded pebbles are not larger than 

 birdshot ; in others, they attain a diameter of many inches. In cer- 

 tain localities, the sandstone has a fine close texture, suiting it for 

 various useful purposes, and is employed to a considerable extent in 

 building. The quarries in the neighbourhood of Fredericksburg and 

 Acquia creek, present beds of great thickness of a homogeneous 

 rock of this description, of which extensive use has been made in 

 some of the public edifices in Washington, Richmond, and else- 

 where. In the superior portion of these beds, Lignites, silicified 

 wood, and vegetable impressions, are frequently to be seen — all of 

 which contribute to render the examination of these deposites a sub- 

 ject of much curious interest to science. Whether these sandstones 

 be in reality contemporaries of the analogous, though somewhat differ- 

 ing rocks of the coal measures of eastern Virginia, impressed with 

 peculiarities as to texture, and included fossils by some circum- 

 stance of position and exposure in the progress of their deposition 



