190 



sections of special geological' interest, exclusive of Rocky Neck ; 

 and, territorially, they are continuous from Crow Point via 

 Huit's Cove, Beal's Cove, and West Hingham to the southern 

 end of the harbor. 



THE GRANITIC ROCKS OF HINGHAM. 



On account of the more continuous development of the sand- 

 plains, the outcrops of the granitic rocks over the greater part 

 of Hingham are less frequent than in Cohasset ; and nowhere 

 in Hingham do we find any section of these rocks comparable 

 in clearness and continuity with that along the Cohasset shore. 

 There can be no question, however, that the granitic rocks of 

 Hingham are essentially similar in most respects to those of 

 Cohasset. They embrace in the same general proportions the 

 three principal types — granite, diorite, and felsite. The diorite 

 is, in every case, clearly the oldest rock, its relations to the 

 granite being the same as in Cohasset. Consideralde attention 

 has been given, especially by Mr. Bouve, to tracing the 

 distribution of the diorite, with the object, originally, of repre- 

 senting it by a separate color on the map ; but tiiis has been 

 found wholly impracticable. Its relations to the granite are so 

 intimate and intricate that, in the absence of perfect and con- 

 tinuous exposures and a map on an inconveniently large scale, 

 no lines could be drawn which would not include considerable 

 granite or exclude a large part of the diorite. We have learned, 

 however, as the result of this attempt to map the diorite, that, 

 while occasional inclusions of diorite (often very small inclusions, 

 it is true), may be observed in almost every good exposure of 

 granite in Hingham, this rock occurs abundantly only in a fairly 

 well-defined east-west belt near the northern edfje of the ofranite. 

 The limits of this belt are roughly indicated by the distril)ution 

 of the V-shaped characters on the general map.^ Commencing 



1 Tlie diorite of Coliasset is similarly represented; hut this feature of the map had 

 not been adopted when the Cohasset text was printed. 



