Count de Bourn on on Bardlglione. 361 



which I mentioned at the time in the brief account I gave of this 

 substance in the Journal des M'lnes^ No. 77, is very singular, when 

 we consider the local circumstances of the bardiglione in which it 

 occurred. 



There is another variety of this substance in determinate crystals,' 

 often of considerable bulk, and imbedded in a mass of compact 

 bardiglione of a reddish-brown colour, penetrated with gypsum and 

 sea-salt. In this mass different cavities are perceivable, in which 

 the gypsum, likewise coloured red, is in small crystals ; and some of 

 these also include sea-salt, perfectly pure, and of a red colour. The 

 crystals of bardiglione which are scattered through this mass, while 

 they remain adhering to it, appear themselves reddish, on account 

 of their transparency ; but, when they are detached, their colour is a 

 deep grey. This variety comes from the salt-works of Bex, and is 

 that which I have already mentioned as having its colour destroyed 

 by heat. 



Bardiglione of indeterminate Crystallisation, 



1. Approaching to a determinate form. Among the crystals of 

 this substance there are several in very thin rectangular laminae, 

 which grow thinner by imperceptible degrees towards the two narrow 

 sides of the prism, and this thinning, which varies considerably, is 

 subject to no law. 



At other times, as the edges of the primitive tetrahedral prism, 

 according to the observations hitherto made, may be subjected to six 

 different retrogradations with regard to the placing of the crystalline 

 laminse, the crystals having undergone these six retrogradations in 

 succession, without the crystallization having perceptibly rested at 

 any of them, the faces have assumed a_ curvilinear figure through- 



2 z 



