GEOLOGICAL SKETCH. a 
was presented by him to the geological section of the American Association 
at its meeting at Buffalo, in 1886, and was subsequently published in the 
American Journal of Science for November of that year. This theory sup- 
poses that the Triassic rocks were once deposited horizontally, or nearly so ; 
that the trap sheets were overflows and not intrusive, and that all were 
broken and inclined by a series of faults, the result of lateral pressure; this 
pressure affecting primarily the underlying crystalline rocks, which, stand- 
ing nearly vertical, slipped on each other, causing a series of fractures and 
uplifts along their lines of strike. Professor Davis has worked out this theory 
with much ingenuity and ability, and, if it shall be found upon further ex- 
amination that the series of faults which he depicts do really traverse the 
Triassic rocks, we shall be indebted to him for the solution of what has been 
one of the most difficult problems in American geology. But there are some 
facts which are apparently incompatible with its universal application. No 
such faults as Professor Davis supposes to exist are discoverable in the 
localities I have had an opportunity of examining since the promulgation 
of his views, viz: along the Palisades, and at East Rock and West Rock, 
New Haven; and some of the trap sheets are certainly intrusive, having 
baked the beds on both sides of them. 
The materials of which the Triassic beds are composed are all pre- 
sumably, and in part at least demonstrably, derived from the adjacent 
highlands. In New Jersey the conglomerates are made up of rolled frag- 
ments of the granitoid rocks of the neighboring hills, and the sandstone, 
arkose, and shale apparently represent the different stages of mechanical 
decomposition of the quartz and feldspar of the granite. The New Jersey 
highlands, as well as other portions of the Blue Ridge belt, are known to 
contain great quantities of iron ore, and the erosion of the eneiss which 
forms this beit must necessarily result in the distribution of a large amount 
ofiron Hence it is not surprising that the shales and sandstones all con- 
tain enough of this element to give them a red or reddish color whenever it 
is in the form of the anhydrous peroxide. The fact that it is generally in 
this condition, and therefore that the rock is red, proves that it contained 
little or no organic matter when deposited ;. for whenever decaying organic 
matter is present in any cousiderable quantity it reduces the peroxide of 
