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 wortliy of notice : it is the sudden stop wliich is put 

 to the extension of the limestone in one direction. I leave it to others to ofi'er a rationale of 

 such a remarkable feature in the rock at this place. 



At this locality, as well as that near the landing, all tlie 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 pwoxene, 

 mica, and hornblende. The west side of the mass is mixed with gi-een 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 tlie size of a peck measure, 

 of pure green color and translucent, forming what is usually called nohJe serpentine. Beau- 

 tifid asbestus occurs also in seams of a fine silky lustre. 



IS. 



a. Gneiss. 6. Limestone, c. Steatite. 



The diagram No. 16 differs somewhat in character from those whicli 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 jierc in a Ixxl, 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, wc should not hesitate to say that it 

 had effected all tlic disturbance which appears at this locality.* 



A very similar arrangemont appears at Theresa falls, where the limestone appears in the 

 cliffs composed partly of serpentine, limestone and gneiss ; and which, was the stratification 

 at all distinct, would be a fine ojiijortunity for its exhibition if it existed. I conceive this 

 last to be one of those instances in which limestone seems to be interstratified with gneiss, 

 a term which appears to be inapplicable where only one of tjie 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. 



♦ Fiills in the Oswegntchie, in Dckalli. 



