GEOLOGY OF FRANKLIN COUNTY 119 



As nearly all the dikes have prophyritic feldspar, or augite or 

 both, they are strictly diabase porphyrites, and this is to be under- 

 stood in the table which immediately follows. In the large dikes 

 the porphyritic structure fades out in the center, with increasing 

 size of the ground mass constituents, the structure becoming 

 either ophitic or gabbroic. All the dikes show intersertal, or even 

 vitrophyric structure near the borders, according to the amount 

 of glass present. 



Where the dikes have porphyritic structure, olivine is of the 

 first generation only, and is so to be understood in all olivine 

 diabase in the table. 



