FEANKLIN BUTTES. 493 



Included in the granite-porphyries of the middle butte is a bed or dike 

 of diabase, a heavy dark-green, amorphous rock, in which no cr3^stalline 

 ingredients are visible to the unaided eye : its association and physical 

 habit suggest, however, the mineralogical character, which is confirmed by 

 the microscope, of an older eruptive rock, consisting mainly of plagioclase 

 and augite. 



