.116. 



OF THE CONNEXION OF FORMS. 



The values of the cosines, and ihe angles of the trans- 

 verse sections of the limits, relative to the above-mentioned 

 series occurring in nature, are the following : 



Few ,of these prisms have as ye been observed in na- 

 ture. Those which have been observed are (P + co) B and 

 (P + co) 3 in rhombohedral Fluor-haloide, (P -f cs) 3 in 

 rhombohedral Lime-haloide and in rhombohedral Tour- 

 maline, (P + co) 5 in rhombohedral Quartz, (P -f co) 5 in 

 rhombohedral Corundum. The angles of other prisms have 

 not been exactly ascertained. 



The angles of the first and sixth of the preceding prisms, 

 those of the second and fifth, and those of the third and 

 fourth, are inversely equal to each other. In general, 

 the number of derivation which produces the one, may be 

 found from that which produces the other, by the formula : 



3 (m' 1) 

 . 116. SUBORDINATE SERIES. 



To the series of rhombohedrons, . 110., belong 

 several subordinate series, in reference to winch 

 tl>e former is termed the principal series. 



