378 APPENDIX - CALCULATION OF THE 



and the inclination of either of the new planes 

 on the adjacent primary plane would be 

 = 225 f /. 



2. Let the lateral edges of the right or oblique 

 rhombic prism, or any edge of the rhomboid 

 be modified by 2 similar planes, and let the 

 inclination of the primary planes to each other 

 zr /, and that of the secondary planes to each 

 other 1 '. 



Then = sn - - 



q sin. (I /'-i /) 



And the inclination of either of the new planes 

 on the adjacent primary planes would be 



\r. 



The following application to a particular case of 

 the proposed methods of calculation, will probably 

 be sufficient to illustrate their general use. 



It will be found convenient, if we have to deter- 

 mine the laws of decrement producing secondary 

 planes upon any primary form, to determine in 

 the first place the particular values of such of the 

 elements of that form as we may require for ascer- 

 taining those laws of decrement; and the values 

 so determined may be reserved for any future occa- 

 sion. 



Let it be required to determine the elements of 

 the rhomboid of carbonate of lime : 



