DIKE EOCKS OF THE BASIN. 29 



pegmatites, but rather lead to the supposition that these last-named deposits 

 have been derived from some large granitic mass intruded into the basement 

 rocks of the section, though at no point exposed on the surface. 



The facies of the beds in the region about North Attleboro makes it 

 appear not unlikely that volcanic action may have taken place in this por- 

 tion of the field. 



