118 
it begins abruptly and with its full width on the northern 
escarpment of the plateau, not a trace of it or of 33, which is 
probably a branch of 31, appearing on the bare ledges of the 
hill. It crosses the composite N.-S. dike (66) without per- 
ceptible displacement, slips the dikes of the first system оп East 
Porphyrite Hill and is itself thrown abruptly to the south about 
25 feet at the eastern base of the hill. It crosses the bay with- 
out further important displacement and is readily recognized on 
both sides of the railroad by its width and hade. It can be 
followed by frequent outcrops across Melaphyr Plateau, gradu- 
ally approaching and appearing to unite with 29. But they 
are widely separated in the conglomerate ledges beyond, 31, on 
account of its greater hade, suffering a greater lateral displace- 
ment in crossing the fault between Melaphyr and Conglomerate 
Plateaus. In the ledges west of Hull Street some interesting 
inclusions of conglomerate are clearly exposed. The last ap- 
FIG. 15.— NATURAL SECTION OF THE INCLINED DOUBLE 
DIKE (34) ON THE WESTERN SHORE OF Rocky NECK. 
SCALE, T INCH =O) FEET, 
