The Geology of H Ingham. 47 



sedimentary rocks has been passed, as granite now appears. This 

 extends 30 feet and is followed by an exposure of trap. Beyond 

 this trap, which here crosses the street, the rocks are all granite. 



On the left side of the street, ascending the hill from South 

 Street and about 310 feet from it, there is an exposure of rocks 

 which present themselves in the following order: conglomerate 

 nine feet, slate six feet, sandstone twenty feet, slate again twelve 

 feet, this last being succeeded by a dike of trap about nine feet in 

 width. Beyond this trap there is no exposure for about 60 feet, 

 at which distance another ledge appears, the first part of which 

 shows blue and red slate six feet, the rest of it being conglom- 

 erate, which extends 36 feet. Another space, of 72 feet, without 

 rock follows the conglomerate, when this rock reappears in 

 another ledge, — composing the first part of it for six feet, the 

 rest of it, 45 feet, being blue and red slate. Still another space 

 of about 80 feet occurs without rock, when sandstone appears 

 along the road for the very considerable distance of 110 feet. 

 Trap, partially covered with soil, succeeds the sandstone for about 

 40 feet, then conglomerate with an exposure of six feet. Beyond 

 this conglomerate, which is the last seen on the road of the sedi- 

 mentary strata, no other rocks appear on the left side of it for 650 

 feet. Then appears a considerable elevation of trap rock, which 

 extends along the street about 30 feet and back upon the adjoin- 

 ing fields towards Elm Street. As stated above, when mention- 

 ing the portion of this dike exposed on the right side of the road, 

 there are no other rocks beyond it excepting granite. 



Rocky Neck. 



East of Planter's Hill, and partially separated from it by a 

 depression of the surface, is an elevation of land forming a prom- 

 ontorv, which is bordered bv Weir River on its north and east- 

 erly shores. The rocks here, finely exposed as they are along the 

 water's edge, and exhibiting well their relation to each other, 

 afford one of the localities the best worth visiting of any within 

 the town. The map of course shows the development over and 

 beneath the surface of the land as made known by the rock expos- 

 ures ; but a statement of what may be readily observed in a walk 

 along the margin of the water will perhaps help visitors to 

 understand what they pass, and thus make such a trip the more 

 interesting. 



At low water on the river front of the meadow that lies south 

 of Rockv Neck, mav be seen close to the water's eds;e a small 

 ridge of rocks which the student should especially notice, as they 

 are composed of the basic rock Porphyrite, and no other exposure 

 of this rock is known in Hingham. Following the shore north of 

 the porphyrite and just where the land rises from low and marshy 

 ground, the first rocks which appear above the surface and rest- 



