122 GEOLOGICAL AND MINERALOGICAL NOTES. 



paper (Geological and Mineralogical Notes No. 5), I con- 

 sidered part of this formation to be a granophyre. In the 

 microscopical investigation made of loose grains of all 

 these augite-syenites, the specific gravity of the feldspars 

 iu the crushed rock, as passed through the 90 sieve and 

 separated in the Thoulet solution, has been obtained of all 

 the specimens from which these microscopic sections have 

 been prepared, giving the same general result, as deter- 

 mined by the Westphal balance, 2.65 for the quartz and 

 some albite, 2.57 for the microcline and orthoclase ; lighter 

 minerals ranging between 2.55 for uepheline and 2.28 

 for sodalite have been found. 



IV. THE EXTENT AND TREND OF THE WHOLE SERIES 

 OF THESE SYENITES. 



The trend of these syenites in Essex County, Mass., is 

 from southwest to northeast. The most distant south- 

 western outcrop observed is in Lynnfield Centre, near 

 Filling's pond, in an old railroad quarry. From this point, 

 across Peabody to Salem and Marblehead, and, extending 

 across f Salem harbor, it is seen on the shore line, in con- 

 nection with the elaBolite-zircon-syenite, from Beverly to 

 the Singing beach and Eagle head in Manchester. From 

 here to the railroad cutting at Magnolia it is continuous and 

 crossing the great Magnolia swamp it is seen again at West 

 Gloucester, in the city of Gloucester, at Eastern point and 

 the islands and rocks known as Bemo ledge, Salt island, 

 Milk and Thatcher's islands and the Salvages outside of 

 Pigeon Cove, Rockport. It also occupies part of the main 

 land, one outcrop being the so-called black granite of 

 the Rockport Granite Company's quarries, and numerous 

 tongues are seen extending into the hornblende-granitite at 

 Gap head and on Emerson's point. The west and north- 

 west line of contact across Beverly is extremely irregular, 



