IGNEOUS ORIGIN Of LIMESTONE. 



51 



^^iiiiSiifi^^ 



Limestone. 



A. Gnciss- 



where the limestone has the appearance of having 

 been protruded between the layers of gneiss, 

 which it has disturbed. The limestone is gra- 

 nular, and what is particularly worthy of notice, 

 is its mixture with serpentine ; an association so 

 constant, that there is scarcely an exception in 

 the northern counties. Its presence serves to keep 

 up the analogy between those beds which occur in granite ; while the presence of serpentine,, 

 which is an acknowledged igneous rock, goes far in itself to support the theory of the 

 igneous origin of the Umestonc. 



In 13 the limestone not only appears to have protruded upward, and disturbed the beds of 

 gneiss, but also to have produced an important change in the adjacent portion in immediate 

 contact with the limestone. It appears like a band of trappean matter, of a darker color and 

 more compact than llie gneiss. It is possible to be deceived as to the cause of this change in 

 the proximity with this mass of hmestone ; but that it is some way connected with the in- 

 fluence of this rock, seems higlily probable. It is to be observed, that the limestone of this 

 locality is not a pure white crystalline rock : it is brown or grey, mixed in part with quartz and 

 hornblende, and in incoherent masses or grains. It is obscure, and does not form a prominent 

 mass in the rock, and might therefore pass unnoticed,, unless the attention was directed to it. 



a. Homljlende. b. Limestone, c. Sienite. d. Granite. 



The next mass of limestone associated with the schistose rocks, and to which I would 

 direct the attention of geologists, is at Port Henry in Essex county. It is that mass, too, 

 which has already been pronounced upon as one which exliibits evidence of the metamorphic 

 theory. This bed of limestone is extensive, and occurs near the lake ; it projects out of the 

 side liill in a very prominent manner, and forms a conspicuous object from several points of 

 view. There are several points of interest which may be examined with profit in this vici- 

 nity ; but I would particularly refer the geologist to this bed of limestone, as one well worthy 

 his examination, occurring as it does in a situation quite accessible, and associated with horn- 

 blende, gneiss, etc. 



