216 



being so much greater than that on the south as, in conjunction 

 with a horizontal or pHcating stress, to overturn tlie beds. Or it 

 may be otherwise described as an inverted syncHne deeply 

 folded down in the granite and the northern half" carried away 

 by the fault which elevated the granitic axis on the north. 

 The map shows two areas of slate along the northern border of 

 the conglomerate series. These are not based upon any out- 

 crops ; l)ut the topography is favorable to the occurrence of 

 slate here, and they are introduced in accordance with the 

 foregoing explanation of the structure. The same is the case 

 also with the conglomerate shown south of the melaphyr, east 

 of the railroad ; but the conglomerate which is re[)resented in 

 the section as lying upon the granite is the basal conglouierate 

 already described south of the melapiiyr, near Hockley Lane. 



The Ideal's Cove Area. 



This is tlie area indicated by the second s[)ecial nnq) 

 (Plate 8) . It is crossed diagonally by Beal Street and euibraces 

 all tlie ledges between Beal's Cove and Lincoln Street. 

 Topographically it belongs chiefly to the broad lower or lowest 

 sandplain, but iucludes Tucker's Swamp and the western 

 slopes of Baker's and Squirrel Hills. This area has been 

 already described as affording, between the granite on Beal 

 Street and Beal's Cove, the most complete and normal section 

 of the Hingham strata. 



The western extremity of the granite axis is, fortunately, 

 well defined, as the map shows, by numerous outcrops north 

 of and in the street and the obscure but reliable outcrops 

 between the houses south of the street. The granite is over- 

 lain at this point, as already described, by several irregular 

 patches of effusive felsite, including the mass wrongly marked 

 as an outlier of conglomerate. One proof that not only this 

 felsite but also that farther east, in the vicinity of Thaxter and 

 Lincoln Streets, are part of a surface flow or truly effusive has 

 not been stated; viz., that it occurs only near the junction of 



