"9 
id 
embracing the isolated ledges of granite in the marsh and the 
southern slope of Great Hill, is essentially similar in every re- 
spect, including the outliers of conglomerate ; but the interven- 
ing marsh is probably underlain wholly by conglomerate, which 
Great Hill, where it is seen almost in contact with but not di- 
rectly upon the granite, dipping away from the latter or south- 
east 5° to 10°. The outlying mass near the bank of the river 
is almost certainly 7» situ, and indicates that a considerable 
body of conglomerate is concealed here. Traces of conglomer- 
ate have been observed on the outlying ledge of granite in Weir 
River Bay ; and the preceding description might be repeated for 
Granite Point, although it is separated from the plateau by the 
boundary fault, which, with the downthrow to the north, marks 
the northern limit of the granite at most points. 
Granite Point is a knob of granite capped with conglomerate 
dipping slightly to the east and northeast, the beginning of an 
important bed extending into Cliff Plateau. The relations of 
the granite and conglomerate are especially clear on the south 
side of the point (Fig 9). A large and irregular hollow or 
raviné in the granite is filled with conglomerate largely composed 
of granite débris and including several large bowlders of gran- 
ite, each of which is precisely similar in character to the nearest 
part of the enclosing granite. This conglomerate is from one- 
half to two-thirds melaphyr, often in large and angular frag- 
ments. Although this is so clearly not the basal conglomerate 
of the Boston Basin, it will appear in the sequel that it is prob- 
ably the lowest bed now exposed in any of the Nantasket sec- 
tions ; and it will, for convenience, be designated hereafter the 
first or basal conglomerate. It is interesting mineralogically 
on account of the numerous segregations of bright red jasper 
which occur in it. “These are exceedingly irregular in outline, 
apparently replacing the paste of the conglomerate. The origin 
of the jasper is, doubtless, to be found in the alteration of the 
melaphyr ; and attention has already been called to the prob- 
has been depressed by faulting. The principal exposures of 
conglomerate are on the borders of the marsh, directly south of 
