216 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



road already mentioned. To the north of this hne the whole series of the 

 schists is moved horizontally to the west for a considerable distance, 

 dragging upon the fault so that the strata bend around from the normal 

 north-south direction to a direction due east at the fault. The series main- 

 tains, however, the inverted position and constant westerly strikes of the 

 2)ortion south of this fault. 



The explanation of this complex system of faults seems to be that the 

 great Pelham gneiss mass on the west ends just where the first of these 

 tranverse faults appears, while to the east of the great north-south fault an 

 equally high gneiss area extends north across the whole town of Warwick. 

 When the east- west compression acted on these beds they were on the south 

 of the first transverse fault, supported by the north end of the Pelham gneiss 

 in Brush Mountain, wdiile on the north, finding firm su])port oidy at a lower 

 level, they were tlu-ust westward and overturned. 



PEGMATITE DIKES AND MINERALS. 



A curious point of resemblance between the Conway schists of the 

 west side of the county and the same schists in this section — the upper beds 

 (/) of the seines — is the apj)earance of large granite dikes carrying 

 spodumene, cleavelandite, tourmaline, columbite, and beryl. One great 

 dike of this character appears in the yard of M. A. Brown, on the Win- 

 chester road and just over the town line in Vermont, and is there filled 

 with poor cry.stals of spodumene. On the top of Strowbridge Hill, a half 

 mile south, I found the same dike, or its successor on the line of strike, 

 filled with cleavelandite and a little tourmaline; and the same distance again 

 to the south along the line of strike is the fine columbite locality discovered 

 by Mr. M. A. Brown. This may be reached by following the lane back of 

 L. A. Moody's house, east through the woods nearly to the Warwick road. 

 Farther south, on the Minot section, the same coarse granites carry immense 

 beryls, and just where the beds cross the town line to the south the granite 

 abounds in spodumene. 



This is one of those curious and inexplicable matters of paragenesis, 

 and it derives its problematical character from the fact that the pegmatites 

 cutting all the other beds are wholly wanting in those minerals containing 

 rare elements, except those penetrating tlie comparatively recent Conway 

 schist, which at distant localities on botli sides of the Connecticut River 

 carries them abuiidantly. 



