lO NEW YORK STATE MUSEUM 



lighter colored gneisses ; by a process of elimination the conclusion 

 is reached that these represent true xenoliths in an intrusive acid 

 magma, disrupted, however, and thoroughly metamorphosed by the 

 invading granite in which they are inclosed. Similarly, certain of 

 the amphibolite rocks of wide distribution in this region were 

 correlated with intrusions of gabbro and shown to be their meta- 

 morphic equivalents. Thus the origin of one of the most funda- 

 mentally important rock types was definitely ascertained. Others, 

 moreover, were shown to be sedimentary, but the true elastics were 

 found to possess a far smaller areal extent than had previously 

 been assigned to them. 



In spite of such advances, the interpretation and mapping of 

 many of the gneisses in adjoining areas presented apparently insur- 

 mountable difficulties. Thus, in the northern Adirondack region 

 Gushing (1905, pages 294-95), after unraveling the relations over 

 most of the area examined, expresses himself upon the apparently 

 hopeless confusion existing over certain, often extended, areas. 

 Again two years later in the bulletin on the Long Lake quadrangle, 

 (1907, pages 463-70), vre find the same author, in spite of abimdant 

 relations definitely ascertained, pointing out the uncertainty which 

 exists with respect to the relations of several of the widespread 

 gneisses of the district. 



Such instances, though briefi.y cited, may be taken as typifying the 

 circumstances surrounding the mapping and interpretation of the 

 geolog}- of the northwestern Adirondacks. ^lany of the hardest 

 problems have yielded to the patient and painstaking researches of 

 Professors Smyth and Gushing during the last twenty years. At 

 the same time, the field is so broad and investigators so few that it 

 is hardly a matter of surprise that numerous problems of genesis 

 and distribution are still far from being solved. 



Realizing to a certain extent the difficulties involved in the study 

 of such a region, and appreciating the inherent complexities of the 

 Precambrian basement, it was with some hesitation that the present 

 writer undertook a rather detailed examination of a small part of 

 this outlying section of the Adirondacks. It was thought probable 

 that a careful study of a restricted district, going over it outcrop by 

 outcrop if necessary, might yield results which would aid in under- 

 standing certain phases of the history of the northwestern flank of 

 these mountains. The availability of a topographic base map, the 

 openness and low relief of the countr}-. the abundance of outcrops. 

 especiallv in the southern part, coupled with the fact that the area 



