144 



Mr HAIDINGER on the Natural-Historical 



by the highest authorities. Among all the proofs for the pecu- 

 liarity of a species, there is none more evident than that found- 

 ed upon the existence of crystalline varieties. It seems that the 

 rarity of crystals of Serpentine, has been the reason of their not 

 sooner having been noticed by mineralogists ; although, perhaps, 

 they have long ago been observed, but not sufficiently distin- 

 guished from other substances. 



The forms of Serpentine are combinations of the Prismatic 

 System of MOHS. One of its most common 

 varieties is that represented in the annexed 

 figure. According to the method of desig- 

 nation of Professor MOHS, its crystallogra- 

 phic sign is, 



P*. P. (Pr+oo) 3 . Pr+oo. Pf + oo. 

 o P d b s 



The measures of the angles of P, the fundamental pyramid, are : 

 189 34', in the place of its more obtuse terminal edges ; 105 26' 

 in that of the more acute ones, replaced in the represented variety 

 by the planes o of the horizontal prism Pr ; 88 26' at the basis. 

 The ratio of the axis, and the diagonals : b : c is 1 : V 4.3 : V 1 .4, 

 which, however, must not be taken for any thing more than an ap- 

 proximation, the dulness of the faces being prejudicial to the em- 

 ployment of the reflecting goniometer. The angles of the prisms 

 are the following: Przz 128 31', the angle contiguous to the ter- 

 minal edge ; (Pr + oo) 3 = 97 33' in the place of b, 82 27' in 

 that of s, the faces b and * forming truncations upon the respec- 

 tive obtuse and acute lateral edges of the prism d. Several of 

 these crystals have one-fourth of an inch, or even more, in their 

 greatest extension : they adhere to the sides of small cavities in 

 the interior of a massive Serpentine, which moreover contains 

 particles of Calcareous-spar. 



