THE DISTRIBUTION OF ANCIENT VOLCANIC ROCKS. 29 



of an argillaceous or chloritic base, containing angular chert frag- 

 ments of all sizes up to two feet. He mentions many localities 



Fig. 2. 

 Fig. 2. Sketch map of parts of Chatham and Orange counties, N. C, showing locali- 

 ties for ancient volcanic rocks. 



for these rocks, most of which are near the Yadkin river in 

 Davidson, Rowan and Montgomery counties. 



I am informed by Mr. Arthur Keith that he discovered a 



