98 TRANSACTIONS OF THE [FeB. 23 



The same trend is shown in the lakes north of the Oswegatchie, 

 notably in Yellow and Black lakes, the former lying close to the 

 river and exactly parallel to it. As would be expected, the 

 glacial scorings have the same direction, and it is possible that 

 the ice has been a considerable factor in cutting the valleys ; 

 but of this no proof is at hand. 



Rock Formation. — The rocks of the district are chiefly gneiss, 

 limestone, sandstone, and granite ; with which are associated 

 limited amounts of iron ores, serpentine, pyroxenic schists, 

 and hornblendic rocks. 



The areas occupied by the four important formations are 

 roughly outlined upon the accompanying map, which, though , 

 including only a small portion of the region examined, shows 

 the most interesting localities. 



{jneiss. — The gneiss forms the more elevated portions of the 

 region and is the oldest of the rocks, underlying the other 

 members of the series. It has no characteristics which distinguish 

 it from the gneiss of the southern and western portions of the 

 Adirondack region, unless it be a larger proportion of biotite, as 

 compared with hornblende. The usual color is gray or red, but 

 dark colored basic layers are not uncommon. Veins of quartz 

 and of jjegmatite are abundant, cutting the gneiss in all direc- 

 tions. Jointing is pronounced at many points. The hillside 

 south of Gouverneur village shows a marked step-like structure, 

 due to jointing. North of the village, at E 4, the gneiss shows 

 a large number of small parallel joints, running at right angles 

 to strike and dip, and separating the rock into thin layers. 

 Along some of these joints slipping has occurred, causing 

 miniature faults, with a maximum throw of two feet. These are 

 exhibited with diagramatic perfection, as they displace a black 

 hornblendic layer about one foot wide, enclosed in red gneiss. 



The gneiss shows no very pronounced effects of weathering. 

 The surface is often roughened by solution of the feldspar, the 

 quartz remaining intact. Oxidation of iron sometimes gives a 

 red or yellow tint, extending to no great depth. Where the 

 rock is coated with moss, the surface layer of perhaps 5mm. 

 thickness is commonly bleached to pure white by decomposing 

 organic matter derived from the moss. 



The banding and foliation of the gneiss are quite variable, 

 being sometimes very pronounced, and again nearly or quite 

 lacking. As they decrease the gneiss approaches, and some- 

 times passes into true granite. A particularly good example of 



