PKE OAEBONIFEEOUS ROOKS OF PARADISE. 301 



The igneous rock has evidently penetrated a great mass of quartzitic 

 schists similar to those found west of East Greenwich, north of Tiverton, 

 south of Common Fence Point, and elsewhere, and to a somewhat less 

 degree like the quartzitic schists or shales east of Browns Point. These 

 schists may be fotmd well exposed in the area between the two main ranges 

 of the igneous rock east of the pond and on the promontory between the 

 middle and east creeks north of the reservoir. They were formerly also 

 well exposed on an island in the southeastern comer, now covered by the 

 reservoir. They occur also as fragments inclosed in the larger ridges of the 

 igneous rock and in the smaller exposures of the same material. Curiously 

 the strike and dip of the included fragments and of the larger masses of 

 the quax^tzitic schist penetrated by the trap dikes are so constant that a gen- 

 eral strike of N. 20*^ E. and a dip of 50^ to 60°, sometimes 70^, W. will 

 sufficiently explain their general relations to one another. On the promon- 

 tory of trap rock north of the pond, however, it may be seen that this strike 

 is chiefly the direction of the plane of schistosity, the bedding being appar- 

 ently, at least in places, at variance with the same. 



The igneous rock above referred to as cutting the pre-Carboniferous 

 whitish quartzitic rocks in the Paradise-Hanging Rock region shows, even 

 macroscopically, the presence of a crystalline structure. The rock is 

 composed chiefly of plagioclase and hornblende, both in a very advanced 

 state of decomposition. This combination would place the rock under the 

 heading of diorite, and here it is placed by Mr. Greorge P. Merrill, who 

 first made a microscopical examination of these dike rocks. He makes, 

 however, the qualification that ^4t is, of course, possible that this horn- 

 blende may itself be secondary and that the perfectly fresh rock would 

 show augite; but this does not seem probable." If hornblende replaced 

 original augite, the trap rock would then be an altered diabase. 



^With this determination of the igneous character of the trap rocks of 

 the Paradise-Hanging Rock region in band, Professors Crosby and Barton^ 

 were the first to make a careful study of these dikes, and they state that in 

 no instance did they '' discover the slightest indication of a passage from 

 the dike rock to the [quartzitic] slate, but the two are always separated by 

 a perfectly sharp and definite line." 



The trap occurs in parallel ridges running in the same direction as the 



Proc Boston Soc Nat Hist , Vol XXIII, 1886, p. 325 et seq 



