Crosby.] 
510 
[May 18, 
now exposed to our observation. The slate forming the, shores 
of Unit’s Cove and extending around the northern end of the 
melaphyr must be, in its normal position, separated from the 
melaphyr by more than a thousand feet in thickness of the con- 
glomerate series. During the three years since the map of this 
district was drawn, the discovery of additional outcrops of slate 
along the east shore of Huit’s Cove has led me to a somewhat dif- 
ferent view of the relations of the slate to the associated conglom- 
erate from that expressed on the map, the conglomerate ap- 
pearing now as a limited bed in the slate. A more accurate map 
of this interesting shore will accompany the complete mono- 
graph in the Occasional Papers. A portion of the conglomerate 
on this shore is very coarse and irregular ; and on account of its 
relations to the slate, the composition of the conglomerate pos- 
sesses unusual interest. The conglomerate is overlain by fully 
a thousand feet of slate, and is also clearly underlain by slate. 
It is evident that in the absence of fossils in the slate, the key to its 
geological age is to be sought in this intercalated conglomerate. 
We are able to prove by the conglomerate that the slate is newer 
than the most, at least, of the granites and felsites, as well as 
some of the melaphyrs and porphyrites. The pebbles of the con- 
glomerate also prove the existence in this region of an older slate 
formation, and of special interest in this connection are the un- 
doubted pebbles of limestone. The limestone is dull gray, finely 
crystalline, and evidently impure, but not visibly fossiliferous. 
AGE OF THE HINGHAM STRATA. 
The principal facts bearing upon this problem have been pre- 
sented in the preceding pages and it remains now simply to mar- 
shal the scanty evidence and note its collective value. Paleon- 
tological evidence is, at present, wholly wanting ; although we 
may reasonably entertain the hope that fossils will yet be found 
in the slates or sandstones of Hingham. The lithological evi- 
dence, although it might be said to point to the correlation of the 
Hingham slates with those of ^Weymouth and Braintree, is cer- 
tainly very unreliable in a case like this ; and, furthermore, it is 
entirely at variance with the plain indications of stratigraphy. 
But the stratigraphic evidence, again, is far from direct or satis- 
factory, since the deposits of Hingham are completely isolated by 
