346 



APPENDIX- 



CALCULATION OF THE 



RIGHT RHOMBIC PRISM. 



The required unit is therefore * cos. (^ t 90') 



n R 



For decrements on the lateral edges of the prism, 

 the unit is 1. 



The methods of applying these several units to 

 the determination of the laws of decrement, will be 

 similar to some of those already described. 



Fig. 350. 



- 



If we require the law of decrement producing the 

 plane d e, fig. 350, and we know the angle a d e, 

 which is the inclination of a primary plane on the 

 plane d e, and may be called / 3 , we shall find the 

 ratio of the edges of the defect, 



bd\be :: sin. (/ 3 ^J : sin. (180 7 3 ) :: p : q, 

 which gives the required law of decrement. 



