ESSEX COUNTY. 
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The upper surface of this rock is plated with a layer of chert, one or two inches thick, which 
is spread very evenly over almost the whole exposure of the rock on the point. This layer 
is smoothed and polished by drift, which has been forced over it. The scratches or scorings 
sweep round to the west, and pass in the direction of Bulwagga bay; the inclined plane up 
which the boulders were carried being deflected both to the right and left, by the ridge of 
rock which extended some distance north into the lake. 
The dip of the rocks on the point is northwest. As none of them rise more than twenty 
or thirty feet above the lake, their thickness is not easily determined. Following the shore 
along the bay, I found a stratum about one foot thick filled with lingulas : they were confined 
wholly to this layer; and thousands of them could be obtained, though from the thinness of 
the shell, it is difficult to obtain them in a perfect state. That part of the rock which has been 
employed for the fortification, is the trenton limestone. As in the walls, the shaly part of 
the stone frequently contains the Trinucleus tessellatus and Orthis testudinaria ; but the greater 
part, if not all of this mass, has been raised and put into the walls of the fort. 
Proceeding north along the lake shore, the next place at which this rock appears is two 
miles south of Westport. But not having examined this place with sufficient care to speak 
confidently of its characters and relations, T proceed to Essex, where, in the neighborhood of 
the village, it is remarkably well developed, and is especially worthy of a careful examination. 
The rock, partly within the village, and extending south and west, is principally the chazy 
limestone. It forms a bold bluff, rising one hundred and fifty to two hundred feet above the 
lake. Its color is nearly black ; it is generally thick-bedded, and without shaly layers ; and 
it is a fine, substantial and durable rock for building. The dip of this mass is west, or a 
few degrees north of west, or in a direction from the lake ; and so far as I have been able to 
observe, the whole mass is the chazy limestone. 
At this place, we first find an abundance of the maclurea, a fossil first named maclurite 
by Lesueur, and which I have changed to maclurea. They are large coils, some of which 
are seven or eight inches in diameter. It truly belongs to the genus Euomphalus. 
The immediate vicinity of Essex furnishes an instance in the arrangement of the rock, well 
calculated to deceive when only a cursory examination is made. Near the central part of 
the village, where the church stands, we find the trenton limestone very distinctly revealed, 
bearing its most common fossils, the Orthis testudinaria, Calymene senaria, and several others, 
in a shaly mass. Proceeding less than forty rods south, we pass on to this dark-colored lime¬ 
stone, elevated at least fifty feet above the trenton; which limestone being of a dark color, 
and resembling lithologically some varieties of the trenton, might thus be considered, only we 
frequently find in it the maclurea, which never appears in the trenton. On looking about, 
however, we shall find, that in going south from the church, we pass a slight depression; 
and upon a close examination, this will be found to mark the line of separation between the 
trenton and chazy limestone. This depression is directed towards the northwest, and may be 
traced some distance : on the right is the trenton, and upon the left the chazy. This depres¬ 
sion extends down to the lake shore, and both masses being elevated somewhat above the 
Geol. 2d Dist. 
35 
