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2g^ 



Outlines of the Mineralogy and Geology 



fcrreywacke at Neponset Falls; it is found at Angler's Corner in 

 Newton, and a strip enters from Maiden, easterly into Chelsea 

 and is lost under the alluvial soiU 



Sienite. 



(Coloured light red.) 



The greatest portions of S 



are on the south 



d south- 



east of Boston. It appears in the harbour of Cohasset, thence 

 passing westerly, through Hingham, Weymouth, Braintree and 



Quincy, it at length forms the Blue H 



radually 



s 



as it proceeds west, till it forms the highest and most western 

 part of this range, near Canton. The direction of this eroun of 



I 



dcd 



is nearly east and west. From the Blue Hill 



the Sienite extends north-west, till 



Greenston 



Ded 



ham, and 



/ 



near the ban 



of Charl 



river. 



Its 



Petrosilex, at Milton. D 



Chester, and Roxbury. It again appears in Needham, and thenci 

 stretches northerly to Weston and the upper part of Waltham 

 where it passes into Greenstone j the eastern part of this last men 

 tioned portion is bounded by Greywacke. An extensive forma 



of Sienite is found on the 



of Boston, bounded on the 



south-west by Greenstone and Porphyry, and on the east by 

 Alluvion ; this extends through Danvers to Beverly, and thei 

 forms the coast to Cape Ann. 



Porphyry. 



(Coloured oratige.) 



This formation extends from Maldei 



tion soulh-west and novtfi.paef • Ha i., 



L 



has a di- 



bound 



Greenstone, and its north eastern is Sienite, into which it passes 



south-westerii bord 



meets Petrosilex and its 



th 



