206 



GEOLOGY OF THE THIRD DISTRICT. 



The slate at the uplift is not very thick, and shows in the creek and where upturned, two 

 or more layers of the Trenton limestone (3) beneath it. At the junction of these rocks with 

 the wall, a wedge-shaped mass (2) appears, enlarging downwards. Its color is of a dark 

 green when fresh, but becomes earthy or yellowish by exposure. It has the characters and 

 composition of an impure serpentine. It contains some crystals of mica of a third of an inch 

 in diameter, which have been formed in the mass. Between this and the limestone and slate, 

 is the vein of galena first noticed by Mr. Conrad. It is associated with blende and pyrites, 

 and with white and brownish-black lamellar carbonate of lime. 



The dyke, as before mentioned, and the vein, enlarge downwards. It was worked but for 

 a few feet below the entrance, near the level of the creek, yielding no profitable amount of 

 ore in the part excavated. The result is easy to predict, should the ore be derived from the 

 visible upturned rocks, for the quantity would be small, not being of great thickness ; but 

 should the source be independent of these two rocks, proceeding, according to some, from 

 something like the fountains of the great deep, the result is not so easily predicted. It is, 

 however, one of those points theoretically of the highest interest. It is at the junction of dis- 

 similar masses, hence electrical results could take place ; where different exudations by the 

 layers could imite, chemical action would result, and union with the former would produce 

 galvanism : these conditions are requisite for the formation of metallic veins, and may here 

 have all been reaUzed. As matter of science, the investigation of this point is one of interest. 

 It contains ore as a matter of fact. The bottom of the uplifts must extend to the point of 

 fluidity ; therefore ejections from that part may exist in the fissure, though it is more pro- 

 bable that it was filled up by lateral infiltration from the masses between which it exists. 



Along the crest of the junction of the slate and the calciferous are some shallow openings, 

 firom which ochery ore, or hydrate of iron, was thrown out, which evidently was derived from 

 the wall or calciferous group, such exudations being common from this group. 



The calciferous, at the south end of the uplift, appears in the bed of the river. Higher up 

 in the bank, near the ferry house, is the birdseye ; above it, the Trenton limestone ; the 

 Utica slate forming the range in the rear of the river, and appearing in its usual flat or undis- 

 turbed position not only there, but in many points between the ferry and the east end of the 

 uplift of Little-Falls. 



Section of the Gap at Littk-FaUa, on ike south side of the Mohawk. 

 No. 1. Goeiu, Ui« basa rock of the uplift and the district. No. 2. Calciferous sandrock. 



