Dodge.] 396 [February 3, 



So much of this band as lies in Milton, Quincy and Braintree is 

 two and one-half to three miles wide; except east of the Old Colony 

 Railroad, where it is about one and seven-eighths miles wide. That 

 part which lies west of the Neponset River in West Roxbury, Hyde 

 Park and the eastern half of Dedham is about five and one-half 

 miles wide, while the Needham and Newton rocks add almost three 

 miles to this. This diminished width of the sections toward the east 

 (6x : 3x : f x : x), of itself suggests the successive disappearance in 

 each, of the northerly of several parallel axes of elevation ; the most 

 northerly of all ending in Brookline; the second in the isolated brec- 

 cia of Hyde Park ; the third range protracted through Quincy to the 

 Old Colony Railroad; the fourth losing itself at Quincy Point; while 

 the most southerly of all is continued to the coast, showing itself, like 

 the others, at isolated points, or indicating its presence below by its 

 outflows in the manner above suggested (pp. 389, 394, 395), yet not 

 extending so far as the more southern band, the second of the three in 

 order of description above. This idea is consistent with the positions 

 of the geographical valleys and hill ranges which compose these con- 

 tinuous crystalline areas, in spite of the levelling effects of glacial 

 action ; and some of the valleys appear to be also geological, con- 

 taining, as already mentioned, conglomerates in Newton and West 

 Roxbury, slates and conglomerates at Hyde Park, trilobite slates at 

 Quincy Neck and Braintree. Certainly the en echelon arrangements 

 of mountain uplifts (of which this is a modification) is common, and 

 the natural result of forces producing these, as now understood. This 

 probability may, perhaps, be the most that we shall know on the sub- 

 ject, for the stratification of the crystallines has been so obliterated 

 that it is usually impossible to determine their actual geological 

 position originally, although in some cases it seems as if anticlinals, 

 simple or hanging, and faulted monoclinals could be recognised in the 

 hills of the crystalline areas. 



It will be noticed that while the Blue Hill area, as outlined, is 

 more nearly east and west than the other areas, so that, for instance, 

 at Punkapog it is one mile farther from the second of the three bands 

 than at East Braintree, six miles to the eastward, the geographical 

 hills and valleys run obliquely across it in a direction nearly parallel 

 to the second band. 





