354 



APPENDIX- 



IALCULATION OF THE 



OBLIQUE RHOMBIC PRISM. 



of a b' to a e, when that angle is acute ; a #, or a b 1 

 being perpendicular on the edge g d, and a e perpen- 

 dicular on the edge e c. 



This ratio may be thus deduced. 



i 90") 



The unit is equal to 1, in relation to decrements 

 producing the planes i and /. 



The units for determining the several laws of de- 

 crement producing the planes of classes b and d, and 

 such of class e as are not represented by the symbol 



E, are the ratios of the primary edges ; and the methods 

 of determining the laws of decrement producing any 

 modification of this form, will be analogous to some 

 of those already described. 



