GRANITE ON BRISTOL NECK. 263 



coal was said to be of excellent quality. 1 Granite is exposed at the north 

 end of Walkers Cove. Thence it occurs along all the more elevated streets 

 of the town. North of Bristol the outcrops extend for about a mile a little 

 east of north, and then eastward for another mile. The nature of the rock 

 which underlies the area along the shore east of the very large quartz 

 veins on the east side of Mount Hope, and thence northward at least for a 

 mile, is unknown, since there are no exposures. At Walkers Cove, and 

 numerous other points in the granite area, the granite is coarsely porphyritic, 

 containing phenocrysts of feldspar an inch and more in diameter. Still 

 more frequently it does not contain the feldspar phenocrysts. Gneissoid 

 structure, in consequence of shearing, is very common, the shearing having 

 been as a rule in the direction N. 30° to 40° W. This agrees fairly well with 

 the direction of shearing in some of the exposures south of Common Fence 

 Point, north of the railroad, on Aquidneck Island. A very fine-grained 

 pinkish rock occurs in places, especially in the valley northwest of Mount 

 Hope. This is believed to be an aplitic rock. The western side of Mount 

 Hope is formed by granite. The summit and precipitous eastern side are 

 formed by quartz veins of gigantic proportions, varying from 40 to 80 feet 

 in width. Granite abuts against these veins on the west, but no exposures 

 occur on the east. On the shore northwest of Mount Hope Point a black 

 schistose rock is included in the granite. Its structure is probably the 

 result of shearing in the granite. 



This granite may have formed an island in the Carboniferous sea, but 

 no arkose is known to occur at any point on Warwick Neck, and no 

 contacts are exposed between the granite and any clastic rock. Moreover, 

 the Carboniferous shales nearest the granite area do not show either strike 

 or dip, and the cleavage is also discordant with the outline of the granite 

 area, There is, therefore, no evidence of the existence of the granite area 

 as an island in Carboniferous time, although, judging from the history of a 

 similar granite on Conanicut, south of Jamestown, it is extremely probable 

 that it did so exist. Moreover, the granite of the Bristol Neck area and the 

 pre-Cai-boniferous granite along the east side of Taunton and Sakonnet 

 rivers show features so similar as to make it very probable that they 

 together constitute a geological unit. 



1 This mine has been filled up. Specimens of coal shown me were of the same nature as that 

 from the Portsmouth mine.— N. S. S. 



