of Crystalline Combinations. 407 
RHOMBOHEDRAL SYSTEM. 
Relations of Edges, &c. 
A horizontal face, which is a regular hexagon. 
E. C. horizontal. 
A regular six-sided prism terminated by a rhombohedron. 
Faces of prism replace lateral edges of rhombohedron. 
E. C, are parallel to each other, and to lateral edges of rhombohedron. 
Faces of prism are rhombs with two sides vertical. 
The lateral angles of the pyramid are truncated by the faces of a prism. 
E. ©. are parallel to each other. 
Faces of prism are rhombs with a diagonal vertical. 
An equiangular twelve-sided prism. 
Forms are co-ordinate six-sided pyramids. 
Lateral edges of obtuse pyramid replaced by faces of acute pyramid. 
E. C. are parallel to lateral edges of both pyramids (B). 
E. C. are horizontal (A). 
Two pyramids meeting in a plane perpendicular to the axis. 
Face perpendicular to axis is a hexagon with alternate angles equal. 
E. C. horizontal. 
A twelve-sided prism, terminated by a six-sided pyramid. 
E. C. of pyramid with alternate pairs of faces of prism, are horizontal. 
The pairs of faces with which this is the case, are alternate at the two apices. 
The remaining edges of combination are inclined. 
Vol. 1. Part Il. 3G 
