103 



crystal-plate parallel to (0001) will show a ternary axis and three 

 symmetry-planes perpendicular to the plane of the photographic 

 plate; with a crystal-plate parallel to (1010) a single vertical plane 



Fig. 97 a c. 



Stereographical Projection of the Rontgen-patterns of quartz, turmaline 

 and calcite. Plates parallel to 0001$. 



of symmetry perpendicular to the photographic plate; and with 



Fig. 98 a c. 



Stereographical Projection of the Rontgen-patterns of quartz, turmaline, 

 and calcite. Plates parallel to 



a crystal-plate parallel to (1210) it will show a single binary axis 

 perpendicular to the photographic plate. *) 



In fact, our experiments completely confirm the conclusions drawn 

 here. In fig. 97 a c, 98 a c, and pp a c the Stereographical pro- 

 jections of the Rontgen-patterns are reproduced, as they were 



*) A binary axis perpendicular to the photographic plate, manifests itself 

 in the photographs as a centre of symmetry of them ; a centre of symmetry in 

 the crystal is not manifested in the patterns itself, 



