236 GEOLOGY OF THE NARRAGANSETT BASIN. 



along the northern margin of the island black shales and fine-grained sand- 

 stones underlie the sandstone, dipping northeastward. Farther west, extend- 

 ing from the northwest angle of the island to the indentation northwest of 

 the dwelling house, is more white quartzitic sandstone, dipping under the 

 black shales at a low angle to the northeast. Near the southern end of 

 this part of the shore a black shale layer is seen to underlie the sandstone. 



South of the fault line, on the west shore, are found in succession the 

 following rocks, numbered downward in the section : 



(1) Black shaly rock, strike N. 30° E., dip 80° E., the strike continu- 

 ing far southward. 



(2) Conglomerate with small pebbles and with flakes of black shales 

 in the lower courses. 



(3) Black shale. 



(4) A considerable thickness of sandstone, becoming conglomeratic 

 southward along the strike; dip about vertical, becoming 60° W., then 45° 

 W., then more nearly vertical, and finally, on going southward, 70° E. 

 again. 



(5) Black shales adjoin the sandstone on the west. This black shale 

 layer makes its appearance in the projection southeast of Gooseberry Island 

 and continues to be exposed or otherwise indicated for a distance of 1,000 

 feet. The strike is parallel to the shore, and the dip is 70° to 60° E. 



(6) West of this black shale layer occurs sandstone, more black shale, 

 and again sandstone on the shore southeast of Seal Rocks. 



(7) East of this long black shale layer occurs a great mass of sand- 

 stone as far as the south end of the island, becoming conglomeratic along 

 the eastern side of the island, being there often a rapid alternation of sand- 

 stone and conglomerate layers. Along the eastern side of Hope Island the 

 dips are low eastward, usually 30° to 45°. 



The sandstones of Hope Island are very white and quartzitic, but abun- 

 dantly specked by some small black micaceous mineral, probably biotite. 

 The blue and gray color ot the standstones, so characteristic in less meta- 

 morphosed regions, has disappeared. Pebbles are present to a certain meas- 

 ure in all the sandstone layers, but on the western side of the island the 

 sandstone predominates greatly, while along the eastern shore almost half 

 of the rock is conglomeratic. The black shaly and evidently Carboniferous 

 beds are found only along the western and northern shore, and evidently form 



