242 



case, Crow Point and the extreme northern part of Hingham 

 Harbor are probably underlain by the conglomerate series. 

 While in the absence of strike-faults this concealed area may 

 be regarded, with much probability, as melaphyr, an oblong 

 and approximately horizontal block with the conglomerate 

 series dipping gently away from it on the south and west. 

 It is important to notice, however, that if the very low dip 

 west of Walton's Cove be regarded as normal, the conglom- 

 erate series would naturally reach across Crow Point and 

 cover the melaphyr ; and since this view is most distinctly 

 indicated by the actual observations, it has l)een followed in the 

 construction of the map and sections. The eastward extension 

 of the beds of Langlee and Sarah Islands would carry them 

 beneath Pine and Planter's Hills ; and in the absence of 

 evidence to the contrary the conglomerate series is represented 

 on the general map as ending in this direction against the 

 great faidt separating the Hingham and Nantasket areas. 



The Hint's Cove Ai^ea. 



This area embraces all that remains of the third special map 

 (Plate *J), including the lai-ge quadrangular body of melaphyr 

 east of Huit's Cove and the sedimentary rocks which border 

 the melaphyr on the north and west and form the immediate 

 shores of the cove. It is a moderately elevated and ledgy 

 tract, with comparatively little swampy ground. The east and 

 southeast borders of the melaphyr, as previously noticed, are 

 not ex[)Osed at any point ; and it is possible to determine 

 neither the exact position nor the nature of the contact with 

 the sedimentary rocks. But on the north and west the con- 

 ditions are nmch more favorable, and the boundary is drawn 

 with substantial accuracy at most points. This melaphyr is, 

 for the most part, a compact to imperfectly crystalline dark 

 gray rock. The color varies, according to the condition of the 

 iron oxide, from grav or greenish to reddish or purplish tints. 



