TRAPPEAN DIVISION. 
279 
above by the action of the weather and the frost. On the western and southern sides of this 
range, the trap rock generally slopes oif more gradually, but in a few places it is precipitous. 
It can scarcely be considered otherwise than an enormous projecting trap dyke. Dykes were 
observed in several places cutting through the sandstone, some of which were very large. 
Occasionally it was seen spreading laterally from the dykes between the strata of sandstone. 
There are several places where valleys pass through the trap range above described, but it 
is believed there are none where this rock is discontinued. The valley west of Nyack, and 
that at Tappan, are perhaps the lowest, but even here the trap is seen at the bottom of the 
valleys. 
The trap rocks at Rockland and Richmond counties vary in mineralogical character, from 
coarse crystalline to a perfectly compact greenstone, and from a slaty clinkstone to a coarse 
amygdaloid. The steep escarpments along the shore of the Hudson present a rude columnar 
aspect, without having any regular columnar forms. These cliffs have long been called the 
Palisades, a name which most persons will acknowledge is appropriate. 
On the west bank of the Hudson, the general aspect is extremely forbidding to the agri¬ 
culturalist ; being naked precipitous rocks, with a stinted growth of forest trees on the thin 
soil on the summit, and among the broken debris that form a steep slope at the base of the 
cliffs. Where the slopes are gentle, the soil is rich and productive. On the western and 
southern side of the trappean range, the slope is not precipitous as it is on the east and north, 
but generally slopes off by a gentle descent. In the southeastern part of Rockland county, 
Tappan creek flows through a gorge, or clove, as it is called, in the trappean range; and this 
is the only place a stream crosses this range, except a branch of the Sampsondale creek flow¬ 
ing north and entering the Hudson at Grassy point. 
The sandstone was not observed by Mr. Cassels, who examined along the gorge of the 
Tappan creek, but the trap rock shows itself down to near the level of tide water. At Lord 
and Blauvelt’s quarry, two and a half miles north of that gorge, Mr. Cassels observed some 
“ crystals of carbonate of lime of a deep red color,” in a reddish grey sandstone, “ that seems 
to have been subjected to a high heat ” by the influence of trap rocks. From Tappan creek, 
the trap range does not present a mural castellated front like the Palisades betw'een that point 
and Hoboken; but it forms a more gentle swell, in some places steep, but generally with a 
moderate acclivity, extending back one to two miles from the shore, with the red sandstone 
exposed in numerous quarries and in the small ravines, to about two miles north of Nyack, 
where the trap ranges to the northeast to Verdrietige hook.* 
The trappean range on the Hudson gradually increases in height above tide-water level, 
from Bergen point, to the northern termination of Closter mountain, in the southeast cor¬ 
ner of Rockland county, where, on the line between New-York and New-Jersey, the height 
