1877.] 225 [Wadsworth. 



18. Wigglesworth St., opposite Everett Avenue, a " trap " dike 

 faults a large " greenstone " one, and occasions in the contiguous 

 argillite a prismatic jointing, perpendicular to the walls of the dike, 

 similar to the usual jointing of dikes. 



19. On Wigglesworth St., near Bonair St., a "porphyry" dike 

 occurs, which was traced to quite a distance when the cellars were 

 excavated along Bonair St. 



20. Near Walnut St., between Bonair St. and Broadway, three 

 " trap " dikes and several of " porphyry" or altered "greenstone" 

 are seen. 



21. Corner of Crescent and Washington Streets " greenstone," 

 which here well shows its junction with the indurated argillite and 

 sandstone. The " greenstone," through alteration, is sometimes 

 amygdaloidal in appearance, and, further, contains much epidotic 

 matter, which is to be found in many of the " greenstones " and 

 other rocks to the northward of Boston. 



LOCALITIES IN MALDEN. 



1. In the space included by Ferry, Upham, Franklin and Haskins 

 Streets, three outcrops of the " greenstone " occur, one near Upham 

 St., the second to the eastward, and the third to the northward of 

 the first. 



2. Near the " Old Cemetery " on Tufts Avenue and Green St.,— 

 " diorite." 



LOCALITIES IN MEDFGRD. 



1. West side of Forest St., corner of High St., — a series of 

 quarries in the " diorite." 



2. Corner of Main and Dexter Streets, — a dike of " green- 

 stone," one of " porphyry," and one of " trap." 



3. On the Medford Turnpike or Mystic Avenue an outcrop of 

 "greenstone" is to be seen, which is very much altered, and resembles 

 closely an impure decomposing felsite on its surface. It can be traced 

 for about half a mile into Somerville. It is one of the widest of 

 the " greenstone " dikes, and at one time formed a high bluff", whose 

 foot was washed by the Mystic. 



BRIGHTON. 



1. On Cambridge St., between Union Square and Warren St., by 

 the Brighton Water-works, there are four " trap " dikes in the 

 " amygdaloid," one of which ends quite abruptly in it. 



