306 



TRANSACTIONS OF THE 



alluded to, still continue from time to time, and are seen 

 nine miles west of the village last named. You then 

 come npon soft shaly beds of the nature of talcose chlo- 

 rites and argillaceous schists. The dip of these beds is 

 from 5 to 10° from verticality, south east. 



Near about the distance of seven miles east from War- 

 renton, a trap dyke or vein of a few feet in breadth is 

 crossed. This is a conspicuous feature in this locality ; 

 it pursues a direction parallel with the prevailing strati- 

 fication. Modified and amphibolic rocks occur for the 

 distance of one and a half miles. A band of sienite, 

 nearly a mile in bread th^ is then crossed. It is seen on 

 the river Rappahannock at Wheatley's mills, below Nor- 

 way ford. This rock is almost entirely composed of 

 amphibole, which exists in crystals of different sizes, 

 almost black, and traversing the mass in almost every 

 possible direction, leaving here and there a spot of the 

 white base exposed to view. On the banks of the river 

 near the above named mill, numerous boulders or round- 

 ed blocks of this same rock, with other rocks rounded by 

 attrition, lie on the shores and in the bed of the stream. 

 The gradations from one rock to the other, and the great 

 variety of distinct rocks that are to be seen at this local- 

 ity, make it particularly interesting to the student of 

 mineralogical geology. 



To the sienites succeed beds of blue chlorite slates, 

 and blue schistose contorted limestone, traversed by 

 veins of white carbonate of lime. These beds of lime- 

 stone slates appear to have been twisted and turned in 

 every possible manner. This limestone has been burned 

 for lime in the vicinity of Marsh run. 



In succession, a bed of chlorite schist crosses the river 

 at Kelly's mill, below which another series of amphibolic 

 rocks occur, which pass into a fine-grained sienite, ap- 

 parently alternating with a rock that has the character 

 of an amygdaloid. The base of this rock is purple or 



