PRIMARY SYSTEM. 21 



bright, the rock showing the hke color for some inches from the surface of the joints, the pro- 

 toxide of iron of the feldspar having been changed to the peroxide. These appearances 

 are of interest ; for heated air must have been the agent of conversion, the coating must 

 have been an exudation, and therefore yellow, and such would also be the color of the altered 

 part of the rock, if it were the result of ordinary causes of change. 



The third locahty where it forms the base of an uplift, is at Middleville, just above the dam, 

 on the west side of the creek, and also in the bed of the creek. It shows but about ten 

 feet of height, being covered with alluvial under which it disappears. 



The fourth and last place noticed, where disconnected as to surface with the central mass, 

 was in the road from Lasselsville to St. Johnsville. It rises but a few feet above the surface, 

 and is evidently encircled by the calciferous sandrock. 



