28 NEW YORK STATE MUSEUM 



though with the candid admission that certainty is unattainable in 

 the matter. 



The only representative within the quadrangle of the old granite 

 gneiss which I correlate with the Laurentian granite of Canada is 

 the oval mass or stock, comprising some 7 square miles in areal 

 extent, which lies directly north of the village of Gouverneur. In 

 its thorough conversion to orthogneiss with evenly granular tex- 

 ture and its abundant inclusions which are invariably of amphibo- 

 lite, it conforms wholly to the type of this earliest granite and is 

 quite distinct from the remainder of the granite of the quadrangle. 

 Though the mass is small it lies only a short distance from, and 

 is really the northeast prolongation of, a large mass of this granite 

 which the railroad cuts across all the way from Keene to Phila- 

 delphia and which forms what I have called the Antwerp batholith 

 in reporting upon the Theresa quadrangle. This stock at Gouver- 

 neur is entirely surrounded by limestone, into which it sends dikes ; 

 hence it is impossible to determine its time relations with the 

 gabbro and the other granite. 



The younger granite of the quadrangle is a porphyritic granite 

 which is precisely like the porphyritic granite which in many 

 localities in northern New York occurs as a border phase of the 

 augite syenite of the region, so that I have no hesitation in corre- 

 lating it with that rock. It shows many phases, sometim.es being 

 very coarsely porphyritic, sometimes being fine grained and with 

 little trace of porphyritic texture. The smaller bodies of the rock 

 are most apt to be fine grained, and the larger masses are often of 

 similar grain marginally ; but there is much variation in the differ- 

 ent masses, and from place to place in the same mass. Where the 

 granite cuts gabbros broad zones of mixed rock are often pro- 

 duced, in the manner just described, injection gneisses, soaked 

 zones, and a host of pegmatite and quartz veins. Where Grenville 

 rocks are cut the granite sends occasional dikes into them and 

 holds occasional inclusions of them, but the Grenville rocks are 

 little affected by the intrusion except locally. Some very large 

 Grenville inclusions are found in these granites, often large enough 

 to be mapped, and several of these are of limestone. In this 

 respect this granite contrasts strongly with the older granite in 

 which the inclusions are always of amphibolite. 



The most unusual feature attaching to the porphyritic granite 

 is its manner of occurrence, in a series of subparallel, long, narrow 

 tongues, which conform to the bedding of the adjacent sediments 



