52 
GEOLOGY OF THE SECOND DISTRICT. 
The locality from which this sketch No. 15 was taken, is on the south side of the road, 
nearly half a mile from the landing, in the field where limestone forms a part of the surface 
rock. At this locality, the alternating rocks of hornblende, sienite, gneiss, and limestone, are 
well contrasted; the former exhibiting very clearly what is termed stratification, while the 
limestone is a mass incapable of division in any one direction more than another. The figure 
is a ground plan, and exhibits one feature worthy of notice : it is the sudden stop which is put 
to the extension of the limestone in one direction. I leave it to others to offer a rationale of 
such a remarkable feature in the rock at this place. 
At this locality, as well as that near the landing, all the phenomena bear favorably upon the 
igneous origin of limestone. Though in the midst of stratified rocks, it presents no traces 
of stratification itself, but traverses them in a mode perfectly analogous to granite, trap, 
or some varieties of greenstone. It furnishes numerous imperfect crystals of pyroxene, 
mica, and hornblende. The west side of the mass is mixed with green serpentine, passing 
from light to dark. In some parts it is about equally mixed, the serpentine appearing in 
masses uniformly about the size of a pea ; in others, they are of the size of a peck measure, 
of pure green color and translucent, forming what is usually called nohle serpentine. Beau¬ 
tiful asbestus occurs also in seams of a fine silky lustre. 
16 . 
The diagram No. 16 differs somewhat in character from those which have preceded it. 
The rocks associated with the limestone are still those called stratified, as gneiss, steatite, or 
soapstone. Upon the left is a thick bed of limestone, which is as well exposed as those upon 
the right; yet I was unable to discover its stratification. It occurs here in a bed, in a mode 
quite similar to granite, and like a mass which has been projected up subsequent to the forma¬ 
tion of those upon the right; of which, were it granite, we should not hesitate to say that it 
had effected all the disturbance which appears at this locality.* 
A very similar arrangement appears at Theresa falls, where the limestone appears in the 
cliffs composed partly of serpentine, limestone and gneiss ; and whicli, was the stratification 
at all distinct, would be a fine opportunity for its exhibition if it existed. I conceive this 
last to be one of those instances in which limestone seems to be inter stratified with gneiss, 
a term which appears to be inapplicable where only one of the masses is stratified. It is 
undoubtedly the case, that in those places where this rock appears to be stratified, the planes 
are merely an irregular jointed structure. I say, irregular; for those planes are never paral¬ 
lel to each other, as a general rule or fact. 
Falls in the Oswegatchie, in Dekalb. 
