26 THE GEOLOGY OF THE SECTION. 



thoroughly mixed at one part of the outcrop at Wood- 

 bury's point. The granites of this region are of the same 

 kind as those of Peabody, and having a strike from the 

 southwest to the northeast underlie the towns in Essex 

 county, as follows : commencing at North Saugus, cross- 

 ing Lynnfield, Lynn northwest of Dungeon rock, through 

 Peabody, Ryall Side, Beverly, East Wenham, Essex, 

 West Gloucester, Aunisquam to Halibut Point and out 

 into the Atlantic ocean. All the granites of this region 

 are classed as hornblendic granite, but there is a difference 

 in the kind of feldspar in the various quarries ; this Pea- 

 body, Beverly and Cape Ann granite is composed of 

 quartz, hornblend and oligoclase feldspar, whereas the 

 granite which outcrops at Briscoe Hill, if we follow it 

 across the cove to Miugo's Beach and Manchester to Glou- 

 cester and to the Rockport Granite Company's quarry, run- 

 ning exactly parallel to the other, we find it is composed 

 of smoky quartz, hornblend and orthoclase feldspar. 

 These granites at Moutserrat, Beverly and Rockport are 

 substantially the same as those of the Quincy quarries, the 

 general points of difference being in color and crystalline 

 texture ; and this is due in a great measure to the rock 

 as quarried in Beverly and vicinity being taken only from 

 the surface or the outer joint plains, whereas, if the works 

 were carried to a greater depth, lighter colored and better 

 material, probably as good as the Rockport granite, would 

 be found, and could be quarried at a much less expense. 

 Mr. Sears said that he had found a number of species of 

 minerals new to the county collections ; and in regard to 

 the dike formations, that, instead of their being formed of 

 only two different rock structures, as usually understood, 

 dolorite dikes and diabase, he found sixteen different 

 rock formations in them. 



Mr. Sears then went on to speak of the plants col- 



