GEOLOGICAL SOCIETY OF PENNSYLVANIA. 313 



sions of plants; another thin layer of entirely diiferent 

 composition overlies this ; it is red, and contains much 

 mica. This last seam appears to be free from organic 

 remains. These interesting rocks are covered with 

 rolled pebbles. In the environs of Richmond a thin 

 horizontal bed occurs, but so masked by the alluvium, 

 that occupies a great thickness., as to prevent a minute 

 examination. At Falmouth, two railes up the river 

 Rappahannockj above the spot where the conglomerates 

 disappear under the bed of the stream, granitic rocks 

 show themselves, forming the rugged beds of the river. 

 These granitic rocks are overlaid by the horizontal for- 

 mations, which do not show the slightest evidence ulterior 

 to their deposition ; hence we learn that these beds were 

 deposited after that great event which upheaved those 

 mountains and metalliferous rocks which so uniformly tra- 

 verse our continent in a north east direction, and which 

 have been detailed in the foregoing pages. 



I. — 2 p 



