228 



series on tlie west conceals for the entire distance all but the 

 highest bed of conglomerate, and this also is cut out or, rather, 

 concealed for a part at least of the distance between the cove 

 and Lincoln Street, the slate lying here directly against the 

 nielaphyr. The area crossed by the western portions of Beal 

 and Lincoln Streets is an unbroken 8and})lain, and the broad 

 expanse of slate represented here is unsupported by a single 

 outcrop. The map finds abundant justification, however, in 

 the topography and in the extensive outcrops of slate on the 

 shores of Huit's Cove, since, if continued, and we have no 

 reason to suppose the contrary, these beds must cross this area. 

 The tongue of melaphyr can not be traced south of a point 500 

 feet north of Beal Street ; and whether the bounding faults 

 actually meet, as mapped, and, if so, whether the united fault 

 extends farther to the southwest, it is impossible to determine. 

 The general interpretation of the geologic structure here pro- 

 posed makes it unnecessary to suppose that any of the Hingham 

 strata extend far into Weymouth. All of which tends to 

 emphasize the importance of Weymouth Back River as a 

 geologic boundary ; and we may reasonably assume that this 

 valley follows a fault comparable in magnitude and structui-al 

 importance with that along the east side of Hingham Harbor, 

 senaratinjx areas which are stronj^lv contrasted in their <2colooic 

 features. 



The Lincoln Street and Broad Cove Area. 



This area is represented by the southern part of the third 

 special map (Plate 9), or all that part southeast of the melaphyr 

 and south of the great dike. It embraces but few ledges, 

 being covered almost continuously by the Squirrel Hill and 

 Bradley Hill drumlins and the low sandplain and broad 

 meadows into which they sink. 



Tiie monocline northwest of Squirrel Hill can be readily 

 traced to the northeast across Lincoln Street, as the map 

 shows, as far as Unit's Cove Lane. All the beds, so far as 



