97 
Hill, but beyond these we encounter, in Hingham Harbor and 
northern Hingham, structural features. of a radically distinct 
type. 
The eastern base of Planter’s Hill is the typical, coarse, and 
somewhat reddish granite, which extends eastward in numerous 
ledges to Weir River Bay. Advancing north along the west 
shore of Rocky Neck, we find the granite, near dikes 22 and 
23, overlain by the basal conglomerate. It is largely com- 
posed, as on the Nantasket side, of the more or less angular de- 
bris of granite and felsite, including, however, few large frag- 
ments, and it has, in consequence, a prevailing reddish tint. 
Erosion has evidently again cut just to the base of the con- 
glomerate over a considerable area; and, as on Granite Plateau, 
several thin patehes have been isolated by unequal erosion. 
These outliers show that the conglomerate conforms in the 
usual manner to the fissures and other inequalities of the origi- 
nal granite floor. The dip is S. E. 0°-10°. The granite rises 
from beneath the conglomerate on the northwest, forming 
Granite Head ; while on the south the conglomerate is certainly 
cut off by an oblique fault with a decided upthrow on the 
south. Hence the conglomerate is naturally thickest toward the 
east, where the ledges overlook the little valley running north- 
west to the bay north of Granite Head. In this natural section 
the conglomerate encloses considerable layers of sandstone and 
even slate, and the bedding is very distinct. The fault just 
referred to divides the basal conglomerate into two principal 
areas; and in going castward the conglomerate again appears, 
first in small outliers capping the granite ledges, and then, ар- 
parently, in a continuous bed reaching to the shore. This is a 
drift slope, however ; and the outerops are, perhaps, insufficient 
to make this inference entirely safe. 
These masses of granite and overlying conglomerate must 
be bounded on the north by a fault transverse to the strike 
of the conglomerate and reaehing from Granite Head to the 
o 
” 
7 
OCCAS. PAPERS B. S. N. H. IV. 
