16 



DEFINITIONS. 



Fig. 35. 



The doubly oblique prism has four unequal axes 

 passing through the pairs of opposite solid angles, 

 a by &c. fig. 35 ; it has also the prismatic axis i A*. 



Fig. 36. 



The line a b, fig. 36, which passes through the 

 summits of the rhomboid, may be called the perpen- 

 dicular axis, and those lines, c d, e /, g h, which 

 pasa through the opposite pairs of lateral solid angles 

 may be termed the transverse axes. But the lines 

 a by and c d, are sometimes called the greater and 

 lesser axes of the rhomboid. 



Fig. 37. 



The line a b, fig. 37, passing through the opposite 

 solid angles of the hexagonal prism, may be termed 

 an axis ; but the prismatic axis, c d of this form, is 

 that which is most generally regarded as its axis. 



