705 On the Former Extent of the Triassic Formation (October, 
usually bent eastward so as to give them a “canoe-shape.” In 
New Jersey the sheets of trap are inclined to the westward at an 
average angle of about fifteen degrees, and present their mural 
faces to the eastward, as in the Palisades along the Hudson. The 
trap ridges in New Jersey are also canoe-shaped, but have the 
ends bent to the westward. 
From the study of these trap sheets we may derive important 
conclusions in reference to the former thickness and extent of the 
sedimentary rocks with which they are associated. We have 
previously shown that the long mountain-like ridges giving vari- 
ety to the landscape in the Triassic areas of New Jersey and the 
Connecticut valley, are the outcropping edges of sheets of trap 
that have altered and metamorphosed the stratified rocks both 
above and below them? From the slope which these outcropping 
sheets still show—to the westward in New Jersey and eastward in 
the New England area—it is evident that they were at one time 
inclosed in sedimentary strata, which have since been eroded 
away. ‘That these sheets of trap did not reach the surface of the 
sedimentary beds is also evident from the fact that the molten 
material did not overflow and form table-lands, like those so com- 
mon in New Mexico and other portions of the far West. On the 
First mountain, at Plainfield, New Jersey, as exposed along the 
Johnston drive, the baked and altered shale is still to be seen on 
the top of the trap ridge, three hundred feet above the general 
level of the surrounding plain; here we know that the trap ridge 
was entirely inclosed in beds of shale and sandstone, and at the 
very least three hundred feet of* sedimentary beds have been 
removed by denudation. Extending the same reasoning to the 
Palisade range, we find that it too is a sheet of trap that cooled 
between strata of shale and sandstone; this conclusion is also 
borne out by the nature of the trap forming the Palisade range, 
which is dense and compact, showing that it cooled under pres- 
sure. This ridge of trap presents a continuous outcrop from 
Bergen Point, where it is but a few feet above tide water, north- : 
ward to Haverstraw, when it attains an elevation of over a thou- — 
sand feet. Are we not safe in concluding from this evidence that 
the sedimentary beds were once more than a thousand feet thick 
along the western bank of the Hudson, and that these same _ 
10n the Intrusive Nature of the Triassic Trap sheets of New Jersey. Amer © 
Jour. Sci., Vol. xv, April, 1878, 
