23 



be seen penetrating the Huronian diorite. It is undoubtedly 

 safe to regard this as an outlier of the series in question. In 

 what precedes I have described all the areas of the Naugus Head 

 series marked on the map ; but recent observations have con- 

 vinced me that others exist. The hills immediately north of 

 Wadsworth's Station on the New York and New England Rail- 

 road, in Franklin, appear to be entirely composed of a rock very 

 similar to the prevailing type on Salem Neck, — quite destitute 

 of quartz, and consisting chiefly of a coarse, triclinic feldspar, of 

 bluish and grayish colors, with some mica, dark-colored, and 

 often bronze-like, a green mineral that may be hypersthene, and a 

 very little hornblende or pyroxene. No stratification is visible ; 

 and the boundaries of this area are entirely unknown, save that 

 it does not appear to extend much, if any, south of the railroad. 

 The high hills in Sharon, near Sharon Centre, and on either 

 side of the Boston and Providence Railroad, appear to afford 

 another area of these rocks. These hills are near the centre of 

 the large area marked on the map as Huronian diorite ; and some 

 observations made by Mr. F. W. Very, in Foxboro', in connec- 

 tion with my own, lead me to suspect that, on the geological 

 map of the future, the Naugus Head series will demand a con- 

 siderable portion of the territory here assigned to a newer for- 

 mation. Among the rocks occurring here I have recognized the 

 most of those found in the Salem and Beverly areas. They are 

 of all textures, and some varieties hold abundant grains of 

 magnetite or menaccanite. In passing over the road leading 

 north-easterly from Reading Village, and about one mile from 

 the Boston and Maine Railroad, I have observed several ledges 

 of a coarse, apparently exotic, dioritic rock, the chief constitu- 

 ent of which is a coarsely crystalline plagioclase, which I am 

 strongly inclined to believe is labradorite ; the rock, in that 

 event, probably being a norite. It is in a region where out- 

 crops are few and far between, and I could learn nothing of 

 its extent. 



