VOL. I. PLATE XIV. 



FIG. 69. and 70. Developeraents of pyramidal 

 combinations. 



FIG. 71. Developement of a prismatic combination. 

 FIG. 72. Prismatic combination. 



Pr 1. P 1. ?r. (?r 1)*. 



a bed 



P. P + oo. (Pr + <x) 3 . fr + oo. 



* f g *> 



FIG. 73. and 74. Explanation of the horizontal 

 striae upon the faces of the six-sided 

 prism of rhombohedral Quartz. 



