REPORT OF THE DIRECTOR 1916 29 



and which seem to be sills. This type of occurrence is unusual 

 in northern New York, in which the igneous rocks occur usually 

 in batholiths, stocks and dikes, and I have met with it only in this 

 immediate region. When the mapping shall have been extended 

 over the southeast part of the quadrangle it may prove that these 

 sills are merely outlying members of a batholite of granite or 

 syenite which occurs there. If not that then, in all probability, 

 they indicate the presence of a batholite at no great depth below 

 the present surface. Evidence has been forthcoming in the 

 Thousand Islands region, in the case of the Picton granite, that 

 the present surface exposures of the batholite are of its very roof. 

 The occurrence of these granite sills on the Gouverneur quad- 

 rangle, and on the Ogdensburg and Lake Bonaparte quadrangles 

 just north and south also, sills which have with little doubt been 

 given off from a larger mass of probable batholic nature, is addi- 

 tional evidence that in this northwestern region erosion has not 

 cut deeply into the Precambrian rocks ; and the large amount of 

 the Grenville series which still remains, in contrast to the region 

 farther east, is indicative of the same thing. It is becoming quite 

 clear that there is a sharp contrast between this region and the 

 general Adirondack region in this respect; that the general altitude 

 of the former has been less than that of the latter, as it is today ; 

 that it has been less subject to considerable uplift; and that as a 

 result erosion has bitten far less deeply into the Precambrian rocks 

 of the Gouverneur region than into those which lie more to the 

 east. 



Lake Placid quadrangle. Professor Miller, who is completing 

 the survey of this region for a joint report thereon by Professor 

 Ruedemann and himself, makes the following statement : 



A prominent belt of coarse, often porphyritic, granite extends 

 across the northern portion, and extensive areas of the Whiteface 

 type of anorthosite lie just south of the granite. Two consider- 

 able areas of Grenville gneisses with some limestone occur, one 

 near Franklin falls and the other between Catamount and Wil- 

 mington mountains. 



Between I and 2 miles west of East Kilns a large mass of rock 

 was discovered which quite certainly has resulted from the 

 assimilation of anorthosite by syenite (and possibly granite) 

 magma, the evidence for this mode of origin being well shown in 

 good outcrops. 



A feature of particular importance is the occurrence of parallel, 

 narrow dikes of basic rock cutting the coarse granite on Cata- 



