133 



petrologic relations. Taken as a whole this granite is decidedly 

 not of a uniform character, and yet a fine-grained, little mica- 

 ceous, variety appears to prevail. In Fall River it is fine, 

 contains some hornblende, and the quartz is opalescent. When 

 of this character it bears some resemblance to the Huronian 

 granite ; but in the next towns to the south-west, Tiverton and 

 Saugkonnet, granite which, though coarser and more micaceous, 

 is unquestionably the same as that in Fall River is so intimately 

 associated with the typical Montalban gneiss occurring there, 

 being sometimes interstratified with it, that the age and true 

 relations of this end of the granite belt, at least, can no longer 

 be regarded as an open question. In the interstratification of 

 portions of the granite with distinct gneisses we have an indica- 

 tion that much of the granite of this range is probably indige- 

 nous. On the Centennial Geological Map of Massachusetts I 

 have represented this granitic belt as extending from the south- 

 ern part of Middleborough easterly through Plymouth, south 

 of Manomet Hill, to the shore ; instead of spreading northward 

 through Carver, Plympton, and Kingston into Duxbury, as 

 has been done on previous maps. The reasons for this course 

 have already been given in part (p. 29), but a further reason 

 is found in the following quotation from Prof. Hitchcock's 

 Final Report, p. 682 : — 



" On my former map I colored a deposit of granite, con- 

 nected on the north with that just described, and extending to 

 Brewster on Cape Cod. I did this because a ridge of consider- 

 able elevation extends down the Cape to Brewster, and many 

 boulders of granite are found of great size upon the hills. But 

 re-examination renders it probable that the largest and most 

 abundant of these boulders are granitic gneiss, approaching so 

 near to real granite as easily to be mistaken for it." 



Now, if we regard the granite in question as mainly in- 

 digenous, and this is certainly the most probable view, and 

 consider that from Tiverton to Middleborough at least it un- 

 doubtedly lies parallel with the strike of the gneisses on the 

 south, and that these gneisses have throughout this region a 



