378 NEW YORK STATE MUSEUM 



they are of later age than the gneiss proper, although still Pre- 

 cambric according to the writer's interpretation of the series. The 

 Harrison diorite appears to belong to this general position or 

 perhaps still later. Last of all is the Cortlandt series of gabbros 

 and diorites cutting every formation in the district and including 

 fragments of them so that this last must be Post-Lower Siluric 

 in age. 



