132 



disconnected, yet covering in the aggregate a considerable 

 area. This region is largely drift-covered and the relations of 

 the granite to the enclosing gneiss are difficult to determine. 

 In Andover Village the granite appears to be inters tratified 

 with the gneiss ; but to the eastward, so far as I have observed, 

 it exhibits no trace of bedding; while at some points, especially 

 east of Frye Tillage, near the Shawsheen River, its relations 

 to the gneiss are plainly those of an exotic. This granite is 

 for the most part very coarse, contains much muscovite, and, 

 in these respects, at least, bears a striking resemblance to the 

 endogenous granite of this formation. According to Prof. 

 Hitchcock, 1 granite similar to that in Andover occurs in Bil- 

 lerica, Stow, and other towns in this Middlesex County range 

 of gneiss. There can be but little doubt that the major part of 

 this is indigenous. And the band of granite represented as 

 bordering the Middlesex gneiss on the south-east, on the earlier 

 of the several geological maps of Massachusetts prepared by 

 Prof. Hitchcock, simply expressed the undoubted fact that 

 there is through that region, along with some fine-grained 

 gneiss and intercalated mica schist, much coarse, granitoid 

 gneiss, or indigenous granite. The granite quarried in Con- 

 cord, and also that just mentioned in Stow, belong here. Im- 

 mediately north of the Huronian boundary in the western part 

 of Newburyport, and in West Newbury, there is considerable 

 coarse, feldspathic granite, very coarsely porphyritic with feld- 

 spar crystals ; crystals of orthoclase five inches long having 

 been observed. Succeeding this rock on the north are fine- 

 grained, gneissic schists. The extended and little-known area 

 of granite lying north of the gneiss in Plymouth and Bristol 

 Counties is referred to this age on account of its intimate rela- 

 tions to the gneiss, and its general unlikeness to the Huronian 

 granite. The greater part of this belt, especially toward the 

 north-east, is deeply buried by the drift mantling this region ; 

 and, consequently, little is known concerning its limits and 



1 Final Report on the Geology of Massachusetts, p. 681. 



