259 



Slate east of Mystic Avenue, and ranging between the two long 

 dykes, has a gentle northerly dip. In the cut on the Boston 

 and Lowell Railroad, on the north side of College Hill, the 

 slate dips south seventy degrees. 



Although unable, as the foregoing resume testifies, to cite 

 evidence of an entirely irrefragable character, I am well satis- 

 fied that, to put the matter concisely, the series of synclinal 

 and anticlinal folds probably characterizing this band of slates 

 in Newton and Watertown is reduced to a single faulted mono- 

 cline in Cambridge and Somerville ; or to a single broken 

 syncline, if we take into account the whole breadth of the 

 formation from the Boston and Albany Railroad to the Mystic. 

 The opinion has long been current among the geologists of 

 this vicinity that the basin of the Charles River, in this part of 

 its course, is a syncline ; and I have simply suggested such a 

 modification of this view as would bring it into more perfect 

 harmony with the facts observed both here and elsewhere in the 

 Boston basin. Before passing on I would call attention to 

 the fact that this great slate syncline, as thus explained, 

 matches, I might almost say exactly parallels, in extent and 

 structure, the broad conglomerate anticline of Roxbuj-y and 

 Brookline. 



North of the Mystic distinct slates are certainly known at only 

 two points, both in Maiden. One-fourth mile south-east of the 

 Maiden Station on the Saugus Branch of the Eastern Railroad, 

 the slate is greatly disturbed by large intrusive masses, and shows 

 high but irregular dips, with a north-easterly strike. One 

 and a half miles to the eastward, on the Newburyport Turnpike 

 and immediately south of the railroad at Maplewood Station, a 

 compact gray slate, seemingly identical with that holding Para- 

 doxides in Braintree, dips at a high angle to the north. 



It is generally supposed that the conglomerate is not exposed 

 north of the ledge in Watertown ; but Mr. L. S. Burbank has 

 recently called my attention to the existence of several out- 

 crops of a distinct conglomerate on the extreme northern limits 

 of the basin. The precise locality is in Medford, north of 



