276 



TRANSACTIONS OF THE 



To the east and west of Fredericksburg, for several 

 miles, the Rappahannoc cuts through thick beds of hori- 

 zontal sedimentary rocks, which overspread the almost 

 vertically disposed and stratified primitive rocks.* 



An examination of the character of these interesting 

 deposits, in connection with those occurring along a sec- 

 tional line passing through the gold region, in a north 

 west direction, over a space of upvvards of 70 miles, will 

 form the subject of a future communication by Mr Clem- 

 son. 



Some deposits of sedimentary character and mechanical 

 origin, somewhat like those of Fredericksburg, are par- 

 tially exhibited at Richmond on the banks of James 

 river ; both positions being probably nearly on the same 

 level, at the head of tide water and of sloop navigation. 



Feldspathic granite, containing large crystals of trans- 

 lucent feldspar, is laid bare by the waters of the Chick- 

 ahominy ; and granite rocks, highly inclined, occur in 

 the vicinity of Richmond, forming rapids where they 

 cross the James river. 



Slaty hornblende rock is cut through by the Mas- 

 sapponoe river, at eight miles south of Fredericksburg. 



A thick alluvial deposit, consisting of transported frag- 

 ments, many of them of considerable magnitude, and 

 much decomposed, derived from granitic, quartz and va- 

 rious primitive rocks, lines the sides of the James^ river 

 at Richmond, covering the argillaceous and gritty hori- 

 zontal beds to which we have alluded. 



A considerable thickness of similar detritus covers the 

 granite in a westerly direction. 



Sienitic rocks rise to the surface about ten miles west 

 of Richmond, ranging about north east. 



Then succeeds granite with large feldspar crystals ; 

 and within an extensive depression or trough of this rocli 



* Vide Section from Fredericksburg to Winchester. PI. 17, fig. 2. 



