— — 
the bay and along Rockland Street and Jerusalem Road. The 
dikes of this section may be regarded as forming a fourth east- 
west belt, and it is noteworthy that, for the first time, the 
older system predominates. The outcrops are so imperfect 
that no attempt will be made to deseribe these dikes in detail. 
North-South Dikes. 
Width 
No. 'Trend. Hade. in Remarks. 
feet. 
62 | N.-S. W. 389-5 75-1.75] Cuts 18, 14, and 15. 
63 | N.-S. Imperfect exposure. 
64 | N.-S. W. 10' 1.5 Irregular and. interrupted. 
65 | N.-S. Imperfect exposure. 
66 | N.--S. Vertical t0 Composite, six paralel dikes. 
67 | N.-8. Vertical 8 Probably ends against fault on 
the south. 
08 | N.-8. E. 8° 2.—2.25 
69 | N.-S. Vertical 1-1.5 
TORN UA W. 5°-105 2.5 In granite south of Weir River 
Bay. 
The dikes of the third or newest system, with the normal 
trend N.—S., have their best development in the central and 
western areas, only one having been observed in the coastal area 
and none on Rocky Neck. Unfortunately, the only clear. and 
satisfactory intersections with the east-west dikes are those 
afforded by the small dike in the Green Hill ledge; but that 
the dikes of this system are all of about the same age, and newer 
than the east-west dikes, there can, I think, be no reasonable 
doubt. They are, as previously explained, darker colored 
(less chloritic and epidotie ) than the older dikes, more prone 
to weather brownish and to disintegrate on exposure, and 
more generally characterized by transverse or columnar jointing. 
The single small example of this system in the coastal area 
(62) breaks through the Green Hill conglomerate and cuts all 
the east-west dikes (18, 14, 15) in this ledge, without sensibly 
displacing them. But it is itself slipped or jogged to the west 
4 feet near its intersection with 14; and north of 15 it is 
