120 



NEW YORK STATE MUSEUM 



The cracks which ramify everywhere through the lava are, for 

 the most part, soHdly filled with secondary calcite. The amygdules 

 are chiefly of this mineral also. 



Woodworth described coarser grained rock, containing feldspar 

 crystals visible to the eye, from the south end of the knob, and 

 the correctness of the description was verified by Cushing's study 

 of the thin section. But we have been unable to find any rock of 

 this type in our later work. Some rock has been removed from 

 the south end though the original thickness was but slight. None 

 of this coarser material remains and we are left in entire uncer- 

 tainty as to its original amount. 



Fig. II Natural size drawing of a hand specimen of corroded limestone in 



pitchstone 



The inclusions. Inclusions abound throughout the plug, both in 

 the lava balls and in the intervening material. They are all of lime- 

 stone, and limestone of but a single type. Though the knob stands 

 surrounded by black shales, there are no shale inclusions in it. It 

 is possible that there may be inclusions of earlier trap, and the 

 coarser grained rock just mentioned may be an inclusion. But on 

 this point we have no certain evidence. 



The inclusions are of pure limestone, effervescing briskly and 

 immediately with acid. They range in size up to masses a foot 



