ESSEX COUNTY. 273 



The upper surface of lliis 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 ; tlie 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 linguls : 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 Orlhis 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 Wcstport. But not having examined this place with sufficient care to speak 

 confidently of its characters and relations, I 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 ffiid 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 

 firequently 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 



