10 



DEFINITIONS, 



Fig. 19. 



A right rhombic prism, or right prism whose base is 

 a rhomb, fig. 19, and whose lateral planes a, b, are 

 equal These planes may be either square or rectan- 

 gular. 



Fig. 20. 



A right oblique-angled prism, or right prism whose 

 base is an oblique-angled parallelogram, fig. 20, and 

 whose adjacent lateral planes a, b, are unequal. One 

 of these planes must be rectangular, the other may 

 be either a square or a rectangle. 



Fig. 21. 



An oblique rhombic prism, or oblique prism whose 

 base is a rhomb, fig. 21, and whose lateral planes d, e, 

 are equal oblique-angled parallelograms if they were 

 equal rhombs the solid would be a rhomboid. 



