Fig. 1. X 25. 



Fig. 2. x 25. 



Continuity of cracks in quartz and matrix. 

 Faulting of flow-structure by cracks ; 

 trichites in brown glass (I 927). 



Fig. 3. x 25. 



Concentric and radial cracks in 

 quartz (I 926a). 



Fig. 4. X 25. 



Concentric cracks in quartz ; flow- 

 structure in matrix (I 860). 



Cracks of perlitic type in quartz ; 

 perlite in glass inclusion (I 860). 



Fig. 6. x 25. 



Quartz at centre of perlite, which is 

 completed in matrix (I 927). 



Quartz at centre of perlitic crack, which 

 traverses matrix and neighbouring 

 quartz (1 927). 



