Crosby and Barton.] 326 [Oct. 6, 



occupies a well-established position in the carboniferous series of 

 Narragansett Bay, and there is essentially no difference of opinion 

 concerning either its nature or its strati graphic relations. It forms 

 the two westernmost ridges of Paradise (ridges I and II of Dale's 

 map), and its structure here, as explained by Dale, is synclinal. 

 Ridge I is a northern extension of the cliffs at Purgatory, and 

 along this entire line the conglomerate dips eastward about 70°, 

 being underlaid conformably on the west, as Dale has so clearly 

 shown, by the gray slate of Easton's Point, which forms a well- 

 marked anticlinal axis here. This slate outcrops again under the 

 conglomerate along the western border of Paradise. In ridge II 

 the dip of the conglomerate changes to westerly at a high angle. 

 The conglomerate also forms the two easternmost ridges of Para- 

 dise (VI and VII), Hanging Rocks and the low, ill-defined ridge 

 or line of ledges along its eastern base. The dip in these two 

 ridges, at all points examined by us, is toward the west at high 

 angles, 70° to y0°. Mr. Dale's determinations of the dip in the 

 Paradise district appear to be generally correct, although the an- 

 gles seem in many cases to be steeper than he has recorded ; but 

 we are entirely unable to agree with him that the conglomerate in 

 ridge VII dips to the east ; and we find that the gray slate exposed 

 on the east of the conglomerate has the same steep westerly dip, 

 appearing to underlie the conglomerate conformably, as on East- 

 on's Point and along the west side of Paradise. 



(2). Passing toward the central ridges of Paradise, we find the 

 conglomerate upon either side succeeded by slate. President 

 Hitchcock described it as a hard graywacke slate ; and we regard 

 it simply as a gray or greenish-gray clay slate, indistinguishable 

 from that underlying the conglomerate on Easton's Point and on 

 the east and west sides of Paradise. Mr. Dale, on the other hand, 

 describes it throughout as a mica schist, assigning it a stratigraphic 

 position far below the carboniferous. Portions of the slate are 

 somewhat micaceous, but so are nearly all the carboniferous rocks 

 of Narragansett Bay, this character being a necessary consequence 

 of their derivation from the highly micaceous gneisses and schists 

 surrounding and probably underlying this geological basin. Some 

 of the mica in the slate may be indigenous, but we can find no evi- 

 dence that it is mainly so. Much of the rock is no more mica- 

 ceous than the slate of Easton's Point ; and like that it contains 

 numerous minute crystals of magnetite. This slate forms nearly 



