288 
GEOLOGY OF THE SECOND DISTRICT. 
related to rocks, if they are not really to be considered truly rocks and constituent parts of 
the earth. It exists again in veins clearly so, but these are found in gneiss. We may notice, 
in some of them, a disposition to pass into a state of peroxidation. 
Primary limestone occupies an important place in the geology of Essex county. I have 
regarded this rock as analogous to granite : the w^ide heavy masses as similar to the wide and 
extended beds of the ordinary granite, and the narrow vein-like masses as similar to veins of 
granite in gneiss. The wide beds in both cases are poor in minerals, and the narrow in both 
cases abound with them. In some instances, the narrow veins of limestone contain the same 
mineral species which have been ejected from volcanoes : thus, the pyroxenes and amphiboles, 
scapolite and phosphate of lime, idocrase, etc. are more common to thin limestones which 
occur in a mode similar to that at Long pond, than in the wide and extended masses. 
The sedimentary rocks occupy only an extremely narrow belt along the shore of Lake 
Champlain; they exhibit some important facts. They are evidently broken from those rocks 
which are of the same kind, upon the east side of the lake. The lake lies in a deep rent in 
the rocks, which has been widened by the action of agents of a different kind. In support 
of this hypothesis, we find long narrow fissures in the hardest of the rocks, the potsdam sand¬ 
stone, for example. The fracture of the rocks themselves, and their dip from the lake or 
fissures, is proof more positive. 
Tlie tertiary is another remarkable formation. All the facts connected therewith go to prove 
that it is very recent. Its beds are sometimes slightly disturbed ; but whether from a general 
uplift, or from having been partially undermined, and a portion in consequence fallen down, 
cannot be distinctly shown. Hence, it is difficult to determine the question whether a material 
change has taken place in particular points since its deposition, or not. The general uplift 
of the country, since its deposition, must of course^be admitted. There is no other rational 
mode of accounting for the drainage, and the displacement of the ocean, in waters in which 
this sediment was deposited. 
The igneous or trap rocks never, correctly speaking, form extended masses over the surface 
of the county, except in one instance, namely, that of the porphyry at Canon’s point; and 
this is comparatively limited. The trap dykes are far more numerous at the extreme points of 
the mountain chain, where they terminate upon or near the lake shore, as at Trembleau point, 
Port Henry, and Split-rock. 
