ANALYTICAL ABSTRACTS. 533 



gneiss was found in two localities, and was indicated in several others ; there 

 is no evidence of irruptive contacts between the gneiss and limestone ; the 

 gneiss shows no evidence of sedimentary origin ; therefore, the simplest 

 hypothesis, but requiring more proof, is that the gneiss is an- eroded meta- 

 morphosed plutonic rock, upon which the limestone was deposited. The 

 marble is coarsely crystalline, and in age is next to the gneiss. Near the 

 base of the limestone, and interbedded with it, are peculiar schistose rocks, 

 which, while completely crystalline and resembling igneous rocks in composi- 

 tion, are indicated by their field relations to be of sedimentary origin. Near 

 Gouverneur an outcrop of limestone contains abundant fragments of black 

 schist, scattered through the limestone in a most irregular manner, and 

 making up, perhaps, one-third of the rock. This and other outcrops show 

 that the schist fragments are remains of once continuous schist layers, which 

 have been completely shattered in the course of metamorphism, since between 

 the continuous belts of schist and the Gouverneur locality there is every 

 possible gradation. While the schists show the effects of foldings, contor- 

 tions, stretchings and shattering, the limestone shows no traces of it, it 

 appearing to have been a plastic mass in which the schists moved with con- 

 siderable freedom. The conspicuous result of metamorphism in the lime- 

 stone is crystallization. In the limestones are also pegmatitic veins, which 

 have been much shattered by the dynamic action, reducing them to small 

 lumps of quartz and feldspar, scattered through the limestone. So far as 

 observed the pegmatite yields to strain only by fracturing, not showing pre- 

 liminary contortions, so general in the schistose layers. 



In the southern part of the area examined is a granite, not grading into 

 gneiss, and which breaks through the limestone, causing great disturbance in 

 strike and dip, enclosing masses of the rock many feet in diameter, and 

 metamorphosing this rock to some extent. The sandstone at Gouverneur was 

 found in direct contact with the limestone. Here it appears that the lime- 

 stone surface has been subjected to erosion before the sandstone was deposited 

 upon it. In confirmation of this are seen narrow irregular cracks extending 

 several feet into the limestone, which have been filled with sandstone. The 

 limestone was evidently completely lithified when the sandstone was deposited 

 and sifted into it, and this implies discordance. This unconformity proves 

 that the limestone is older than the upper Cambrian, the data being wanting 

 for any more definite determination of its age. The metamorphism of the 

 rocks of the limestone -bearing series occurred before upper Cambrian time, 

 but the sandstone is metamorphosed, and this metamorphism must therefore 

 belong to post-Potsdam time. 



Comments. — The inquiry rises whether the second metamorphism spoken 

 of, that of the sandstone, is produced merely by interstitial cementation, or is 

 dynamic metamorphism. If the first is found to be the explanation, so far as 



