110 
tively, with 3 feet of separating melaphyr. The dike is thus 
widening eastward, and it undoubtedly begins оп Centre Hill 
near where it is first observed. In the third or eastern outcrop 
it is very plainly cut by a dike of the second system (11), this 
intersection (Fig. 14) being the one chiefly relied upon to 
determine the relative ages of the two systems 
We pass now to the dikes of the second system, commencing 
with the three typical examples crossing Long Beach Rock. 
The most northerly of these (10) is about 50 feet from the 
north end of the ledge at low tide. It crosses the strike of the 
conglomerate, but the intersection is under water. About 60 
feet of the melaphyr separate this from the large dike (9), 
which crosses the eastern end of the conglomerate, and is there 
seen to be attended by slight faulting, the contact between the 
conglomerate and melaphyr being displaced in such a way as 
to show a downthrow to the north of about 5 feet. The third 
dike (8) is 120 feet south of this and crosses the conglomerate 
contact without apparent faulting. It is, perhaps, the most 
distinctly cross-jointed of all the east-west dikes. These three 
dikes appear to cross the low-tide ledge north of Valley Beach ; 
and 10 appears again on the south side of Gun Rock, but with 
a northerly hade of 15°. In the place of 9 we find on the shore 
south of Gun Rock a series of six small parallel dikes, with an 
aggregate thickness of 9 feet, which appear to be the equiva- 
lent and continuation of it. But 8, if it extends this far, 
must pass under the beach. 
The shore along the northern base of Atlantic and Centre 
Hills appears to be determined immediately by the great dike 
(7), which must also pass under the beach south of Gun 
Rock. It shows several small faults or lateral shifts of from 3 
to 8 feet at the base of Atlantic Hill, and suffers a displace- 
ment of perhaps 10 feet in crossing Valley Beach, passing 
beneath the foot-bridge in front of the Waverly House. The 
smaller dike (6) parallel with this is well exposed in front of 
the Pacific House, but cannot be traced more than half-way to 
