* 228 



there is ground, in these facts, for the opinion that several con- 

 siderable beds of slate are intercalated in the conglomerate, and 

 pass with it beneath the main band of slate ; yet to my mind 

 the conclusion is more reasonable, more in harmony with the 

 facts observed elsewhere, that these different beds of slate are 

 detached portions of the great mass of that rock ; and that this 

 section is broken by one, possibly two, faults. The probable 

 position of one fault is shown in PL 5, fig. 3. According to 

 this view the gradual passage between the conglomerate and 

 slate is repeated several times on the surface. 



One-half mile east, on and near Blue Hill Avenue, the section, 

 though not so well exposed as on Morton Street, appears to 

 be very similar. Just south of Williams Street, and also near 

 the crossing of Washington Street and the New York and New 

 England Railroad in Dorchester, there is conglomerate with 

 sandy beds passing to slate, and showing a high dip to the 

 south. On Canterbury Street, near the avenue, is a ledge of 

 slate and sandstone, with a nearly vertical southerly dip ; and 

 conglomerate at the corner of Back Street is on a line with, 

 similar to, and probably represents that on Morton Street, south 

 of Canterbury. At Field's Corner Station, on the Shawmut 

 Branch of the Old Colony Railroad, the conglomerate is small- 

 grained and evidently changing to sandstone ; the dip is 80° or 

 more to the south. According to Mr. Dodge, erratics of sand- 

 stone from this belt occur on Commercial Point. 



Following this faulted belt west from Morton Street we find 

 the escarpment well marked in Forest Hills Cemetery, dividing 

 the cemetery into two nearly equal parts, which are strongly 

 contrasted ; that on the north being characterized by numerous 

 bold ledges of conglomerate, while south of the escarpment the 

 land is level, with a few obscure croppings of conglomerate, 

 but no slate so far as I have observed. Conglomerate occurs 

 at two points on Walk Hill Street, and beyond this there are 

 no exposures for nearly a mile. Bussey Street, where it runs 

 east-west, is on the northern border of the belt, the conglom- 

 erate ridge being well marked in Bussey Woods. The uplift is 



