56 NEW YOPwK STATE MUSEUM 



sion of an eye, around which the dark minerals are ranged like 

 eyelashes and eyebrows. For this reason it is customary to des- 

 cribe the labradorites as ' Augen ' using the German word for 

 eyes. They indicate relationships with the anorthosites, the next 

 group of rocks. 



The obscure geologic questions that arise in connection with 

 the gneisses are those which deal with their original condi- 

 tion and the changes through which they have passed to reach 

 their present condition. The gneisses are essentially ^ meta- 

 morphic ' rocks, and the term means that by recrystallization 

 or by compression, crushing and consequent internal move- 

 ments, or by both combined, they have been produced from 

 sediments or from igneous rocks. It was formerly believed 

 that the foliation represented the bedding of sediments, but it 

 seems now more reasonable to regard it as the result of pressure 

 and of a movement analogous to a viscous flow, that has strung 

 out the minerals in lines. It is quite probable that some of the 

 gneisses and specially those associated with the limestones and 

 quartzites are altered sediments, and it is also probable that 

 those with the labradorite augen are squeezed igneous rocks, but 

 our investigations do not yet admit of their separation in map- 

 ping. 



The gneisses are colored brown on the map, by reference to 

 which it will be seen that they bound Lake Placid on the east 

 and appear to some extent in the islands on the east side. Excel- 

 lent exposures with pronounced foliation will be found in the 

 cliffs of Pulpit mountain, on Eagle Eyrie and in Sunrise Notch. 

 Along the West Branch they are the country rock. Pitchoff 

 mountain and the southwest portions of Sentinel are composed 

 of them and the ledges on the East Branch in Jay and northern 

 Keene are the same. The boundaries between them and the anor- 

 thosites are not sharp and passage forms are met so that the 

 areal distribution on the contacts is approximate. Kepeated ex- 

 perience has, however, indicated both to the writer in Essex 

 county, and to H. P. Gushing in Franklin county that dark 

 gneisses with labradorite augen, often surround areas of anor- 



