I08 NEW YORK STATE MUSEUM 



later than, the de^'elopment of the isocnnal folding. \\'est of the 

 Harrison Creek-Grass River valley, the granite is probably to be 

 considered as a huge sill, with a maximum surface breadth of over 

 4 miles. Its eastern margin holds a fairly uniform northeasterly 

 course, and the western margin for most of its course is approxi- 

 mately parallel to it, but describes a sinuous cur^'e on passing 

 through Eddy. 



East of Pyrites, there is a large subtriangular isolated body of 

 granite,, which for lack of a better name has been called a boss. 

 Of abbreviated or bluntly lenticular form, it has intruded itself be- 

 tween two contiguous horizons in the Grenville, garnet gneiss below 

 and limestone above, and has pushed them apart in the same abrupt 

 manner as was observed in the case of the elliptical granite sill or 

 lens west of Canton. From the nortliAvesternmost point the Pyrites 

 boss has sent toward Pyrites ^ long slender apophysis which has 

 likewise intruded itself between garnet gneiss and limestone. 



Although it is uncertain what is the actual topography of the 

 underground surface of the granite gneiss, it is improbable that any 

 of the masses are batholiths in the sense in which the circular bodies 

 described by Adams and Barlow (1910, pages 11-18) are batho- 

 liths. The rounded area of granite occurring here is not surrounded 

 by gneisses having a quaquaversal dip. On one side, to be sure^ 

 gneisses or limestones overlie the granite, but on the other, they 

 underlie it. There can scarcely be any doubt, however, that all the 

 masses of granite are connected at no great depth, and that the 

 Grenville sediments are to be thought of as lying upon the irregular 

 surface of a granite batholith of huge or regional dimensions, and 

 are in the process of disruption and disintegration and perhaps of 

 assimilation bv it. 



