58 



NEW YORK STATE MUSEUM 



become a coaly black glass from the effects of chill, and always the 

 borders are denser than the centers. One very interesting case has 



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Fig. 9 Step-faulted dike in Walker brook, North Hudson 



been found of one dike penetrating another and chilled by it. 

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Fig. 



Basaltic dike in an irregular and jagged crack on Slide brook. The dike strikes 

 ' e. and dips io° east. The wall rock is gabbro of the Split Rock Falls type. 



