ESSEX COUNTY. 
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ten feet, and their ends also bent as in the cut. This we may, without doubt, consider as 
having been produced at the time of the preceding uplift, communicating in this direction a 
wave-like motion to the rocks. 
Near the plane of junction of the southern fracture, there is a trap dyke in the face of the 
cliff, about two feet wide, which may be traced a mile in a northwest direction. Whether 
the force required to inject this mass of volcanic matter fractured the rocks as has been 
described, cannot be determined, I have supposed that the trenton, and the slates and shales 
of the Hudson river, were borne upwards upon the chazy limestone. We do not, however, 
find a vestige of either mass remaining, though the chazy limestone may be traced west two 
or three miles, and we find the other rocks on either hand as has been stated. It is not difficult 
to reach the cause of this ; for there can be no doubt that the whole of that portion of these 
masses thus elevated has been swept away entirely down to the hard and firm rock called the 
chazy limestone, at least so as to form a tolerably level surface. This mass is, however, 
some fifty feet higher than those on either side, though the latter are geologically three or 
four hundred feet higher than the former. At this locality, then, we have two very distinct 
kinds of changes, which have taken place since the deposition of the Hudson river shales: 
first, an elevation of the strata in mass; and secondly, a change by denudation, by which the 
height of the surface is diminished and reduced nearly to its former level. The scale, it is 
true, upon which these changes have taken place, is small, and confined really to a limited 
area; yet it is a fine illustration of the changes which have taken place since the creation of 
organic beings, and it is the more interesting as the whole effect is within, the sphere of our 
observation. 
On the south side of the uplift which has been described, there are phenomena differing 
somewhat in character from those upon the north, but resembling them in some particulars. 
Several dykes, in the first place, appear in the face of the cliff, traversing the slate of the 
Hudson river series. Some of them are in a soft decomposing state, and unlike the one 
already mentioned in the chazy limestone a few feet farther north; they are both curved or 
contorted, and apparently insulated or surrounded by the slate. This is probably not the 
case, but their position may be explained on the supposition, either that a portion of the slate 
is broken down and washed away, which contained the part which connects whatever now 
remains in the cliff with the mass below; or else, the connecting part is still contained deeper 
in the slate, and may yet be exposed as the cliff 4s broken down. Numerous veins of calca¬ 
reous spar, too, appear in the cliff in parallel lines. But what is still more interesting, is 
the shift which the strata have suffered, not, as may appear to some, by the filling of the 
vertical veins of spar, but probably by the movement communicated to the strata at the time 
the chazy limestone was thrust through the adjacent mass of slate. The annexed cut will 
illustrate what has taken place, and the shifts the strata have suffered: 
