224 



northerly, and at the quarry near the corner of Dorchester 

 Avenue and Codman Street the inclination in this direction 

 amounts to about 15°. The conglomerate is here conformably 

 overlaid by a distinctly stratified bluish-gray slate. It will be 

 observed that this is north of the anticlinal axis indicated by 

 the amygdaloid belt to the westward. Still farther north, on 

 Washington Street, near Fuller Street, a fault has brought the 

 Shawmut breccia to the surface ; and beyond that, obscurely 

 bedded conglomerate extends to Amadine Street. This is fol- 

 lowed by perhaps one hundred feet of thin-bedded, vertical, 

 greenish-gray slate; and then, after several hundred feet con- 

 cealed, the conglomerate reappears with indistinct pebbles, some 

 of which are pinite, and a northerly dip of 70*^. The slate 

 probably owes its position between the conglomerate masses to 

 a fault having the downthrow on the south. 



Westward, on this line, the conglomerate is found skirting 

 the crystallines as far as Washington Street in West Roxbury, 

 showing at most points where the dip is observable a high in- 

 clination to the north. The ledges are numerous in the vicinity 

 of the New York and New England Railroad, Blue Hill Ave- 

 nue, and Mount Hope and Mount Calvary Cemeteries, At the 

 last-named locality arenaceous and slaty beds are frequently in- 

 cluded. On Back Street, about the middle of Mount Hope 

 Cemetery, the Shawmut breccia has apparently been brought 

 'to the surface again ; though this is one of the points where it 

 is difficult to determine whether the rock is conglomerate or 

 breccia. It is on nearly the same line of strike as the breccia 

 already noticed on Washington Street, one and a half miles to 

 the eastward ; and the conglomerate on the south has in part, 

 at least, a southerly dip, though nearly vertical. This breccia 

 is not indicated on the map. North of the breccia the con- 

 glomerate changes gradually, but rapidly, to a true slate, which 

 is dark colored, homogeneous, obscurely bedded, and vertical. 

 The gradual passage between the conglomerate and slate is par- 

 ticularly evident here. In the cut on the Boston and Provi- 

 dence Railroad, at the crossing of Canterbury Street, and also 



