GEOLOGICAL AND MINERALOGICAL NOTES. 123 



commencing on Briscoe hill in the centre of the village the 

 ]ine of contact with the hornblende-granitite of Powder 

 hoiise hill is seen on Essex street, by the roadside ncar 

 the cemetery, the contact at this point being qiiite phiin 

 in a northeasterly direction. From here numerous outcrops 

 can be traced to Coy's pond, East Wenham and the Che- 

 bacco lakes, whence a long tongue extends in a north- 

 westerly direction across Hamilton nearly to Vineyard 

 hill. It occupies the entire area from Cutler's pond in 

 Hamilton to Powder house hill in Essex, Conomo point, 

 Gross' Island, Thompson ville, Essex, to West Gloucester, 

 the Southwest side of Annisquam and Bay View to the 

 outcrop opposite Young avenue, Lanesviile, thus forming 

 a circle nearly around Cape Ann. The largest area oc- 

 cupied by these augite-syenite rocks is in Salem, Beverly, 

 Essex and Manchester ; an area eight niiles in length by 

 six miles in width besides an area nearly equal in extent, 

 in Gloucester, including Eastern point and West Glouces- 

 ter. The outcrops at Bay View and Lanesviile are proba- 

 bly connected with the larger mass in the city of Gloucester, 

 under a drift covered Valley, w^hich is quite extensive and 

 well marked to the east of Riverdale and which extends 

 nearly to some of the outcrops at Bay View and Lanes- 

 viile. It is clear that the drift covered Valley occupied 

 by the Boston and Maine railroad between Gloucester and 

 Eockport may cover a narrow vein of the syenite coiniect- 

 Ing those at the Rockport Granite Company's quarry (the 

 so-called black granite) and the dry salvages with the main 

 mass at Gloucester. It will be seen, therefore, that the 

 augite-syenites form the principal rock mass of Cape Ann 

 and that the hornblende-granitites occupy a secondary place 

 in this large area of granitic rocks. I include as Cape Ann 

 all of the area given in the state atlas covering parts of 

 Beverly, Essex and Manchester together with Gloucester 

 aud Rockport. 



