yr. 
2 
Melaph 
Melaphyr. 
Conglomerate. 
SCALE, 
The Horizontal dotted line marks the low-tide lez 
SECTION ACROSS Lonc BEACH Rock. 
I. 
FiG. 
vel. 
46 
Melaphyr and Tuff The Long 
Beach Rock sediments are overlain 
conformably by a compact green 
melaphyr. The contact of the mel- 
aphyr and slate is exposed for about 
one hundred feet along the strike ; 
and at several points there are fine 
transverse sections of the contact, 
which is accessible only at low tide. 
Fig. lis a general section of both 
the conglomerate and  melaphyr. 
The irregularities of the actual con- 
tact, and especially the bending of 
the subjacent lamin of slate, as well 
as the intense induration of this rock, 
which has been baked to a good semi- 
porcelainite, indicate that it was but 
imperfectly consolidated, if not en- 
tirely plastic, when the melaphyr 
flowed over it. Sut, on the other 
hand, the exquisitely beautiful brec- 
ciation and miniature faulting ex- 
hibited on some of the wave-washed 
surfaces show that before the dis- 
turbance ceased the clay had be- 
come brittle enough to break. “This 
fascinating exposure is the gem 
of Nantasket geology; and it is 
hoped that it may long remain un- 
mutilated, to delight and instruct 
future students. That the eruption 
was submarine, or at least essentially 
contemporaneous with the deposition 
of the sediments, is beyond reasona- 
ble doubt; although it is probable 
that the thin layer of green slate on 
which the melaphyr immediately 
