206 



north-west side of Baker's Hill the granite extends about one- 

 eighth of a mile farther than it is indicated on the map , and the 

 belt of amygdaloid skirting the granite is continued south- 

 westerly, probably to Beal Street. So that from Baker's Hill, 

 north-westerly, the following succession can be made out ; (a.) 

 granite; (6.) amygdaloid; (c.) conglomerate; (c?.) slate, 

 forming centre of synclinal; (c.) conglomerate; (b.) amyg- 

 daloid. PL 4, fig. 3, represents a section across this synclinal. 

 The dip, wherever observable, is vertical, or nearly so. The 

 volume of the conglomerate appears to exceed that of the slate ; 

 and the latter rock is very similar to that in the Downer Land- 

 ing synclinal, the two varieties, brown and gray, being repre- 

 sented. The disposition of the amygdaloid and conglomerate 

 along the railroad, near West Hingham Station, appears to be 

 about as mapped. This is probably a small synclinal, too shal- 

 low and narrow to hold any slate. Between this and Weymouth 

 Back River the boundary between the granite and conglomerate 

 is located very exactly at several points, and the amygdaloid 

 seems to be wanting here. 



In North Weymouth there are no outcrops, except in the 

 vicinity of Mill Cove, and, according to Mr. W. W. Dodge, 

 between Rowe's and Great Hills on Eastward Neck ; the for- 

 mer are described on p. 192, and the latter I have not seen; 

 but Mr. Dodge 1 describes the rock as slate, " black, thin and 

 contorted." In the Mill Cove slate there are evident indications 

 of a passage to conglomerate toward the north ; and it seems 

 probable that the anticlinal crossing Beal Street, in Hingham, is 

 continued through North Weymouth ; the strike shifting to E.-W. 

 The slates of the two localities are very similar. The Paradox- 

 ides bed is apparently on the south side of this line. The 

 absence, so far as known, of conglomerate between the granite 

 and slate in North Weymouth might be explained by a fault ; 

 for the slate beds are here either cut off on the south by a wall 

 of granite, or they are folded in a sharp synclinal, and the 

 former view is most probable. The occurrence of calcareous 



^roc. Bost. Soc. Nat. Hist., xvn., 404. 



