224 Pogue, Jr. — Geology and Structure of Volcanic Rocks. 



original nature and may be recognized as fine and coarse- 

 grained acid tuffs. Eveiy gradation can be found from such 

 comparatively massive occurrences into the sericite schists ; 

 these are consequently considered to have been derived through 

 dynamic metamorphism from the acid tuffs. 



Those outcrops of the coarse tuff which have undergone a 

 moderate amount of compression assume a peculiar and inter- 

 esting contour upon weathering. The rock stands up in huge 

 almond-shaped masses, many of which are 20 feet long, 10 



Fig. 2. 



Fig. 2. — Huge almond-shaped outcrops of the mashed acid coarse tuff. 



feet high, and 5 feet thick at the base. These are abundantly dis- 

 tributed in troops, as it were ; and often scores may be seen, 

 all in alignment, following the trend of a tuffaceous belt. 

 Similar outcrops have been aptly described as resembling 

 enormous military or cockade hats.* These probably represent 

 slightly more massive phases of the surrounding rock, which 

 stand up by virtue of this characteristic : enormous kernels or 

 "augen," which, fortuitously escaping an extreme of mashing, 

 were subsequently stripped by the forces of weathering of con- 

 centric coatings of more schistose rock, until the present elon- 

 gated cores alone remained. 



* Emmons, Ebenezer, Geological Eeport on the Midland Counties of North 

 Carolina, p. 52. 



