278) «=. C. Russell—Triassic Trap Sheets of New Jersey. 
the rare occurrence of the exposure of the junction of the trap 
rocks with the stratified rocks that overlie them—owing to the 
removal of the latter by denudation, and to the line of contact 
‘being covered with drift or overgrown by vegetation—have led 
to the supposition that the sheets of trap were not intrusive, but 
were formed cotemporaneously with the shales and sandstones 
as a bed or stratum of igneous rock, which was spread out in a 
molten condition at the bottom of the shallow sea in which the 
strati rocks were being deposited. The question in hand, 
then, is to determine (1) whether the plutonic rocks of the 
Triassic were spread out as a sheet of molten matter and allowed 
to cool and consolidate before the rocks that rest upon them 
were deposited, both, therefore, belonging to the same geolog- 
ical period; or (2) were the trap rocks forced out in a fused state 
among the sedimentary strata after their consolidation, which, 
consequently, would make them more recent than either the 
rocks above or below them. 
ewark Mountain, for some twenty miles of its course in the 
neighborhood of Plainfield, New Jersey. We hoped by making 
t. 
2d. To determine, if possible, if the trap sheets seem in all 
eases to be conformable in bedding with the stratified rocks 
with which they are associated. 
_ It is not difficult to find the junction of these igneous rocks 
with the shales and sandstones that underlie them. In all such 
of places in the shales and sandstones beneath the trap rocks in 
eo Plainfield, New Jerse : 
ese 0 indi 
