6*4? PHYSIOGRAPHY. CLASS n. 



ture is splintery : in other massive varieties the 

 composition is columnar, commonly thin and pa- 

 rallel. Faces of composition rough. 



OBSERVATIONS. 



1. The species Muriacite of the Wernerian System is sub- 

 divided into five different kinds, pretty easily distin- 

 guishable, but not provided with the best nomenclature. 

 Thus the Cubic Muriactte, also called Cube-spar, compre- 

 hends simple varieties, and easily cleavable compound ones, 

 in which the individuals possess a considerable size. The 

 name of Anhydrite has been given to varieties of a smaller 

 granular composition, and that of Gelcrosstcin or pierre de 

 trippes to the contorted compositions consisting of thin co- 

 lumnar individuals. Compact and fibrous Muriacite were the 

 denominations of compound varieties of very small indi- 

 viduals, the one granular and impalpable, the other co- 

 lumnar. The Vulpinite of Italy, so named from its locali- 

 ty, is composed of granular individuals, a little longer in 

 one direction, of a greyish-white or grey colour, and very 

 much resembling a coarse grained primitive marble. 



2. A cleavable variety from Hall in theTyrol has been 

 found to consist of 



Sulphuric Acid 55*00. 



Lime 41 '75. 



Muriate of Soda 1-00. KLAPROTH. 



Except the muriate of soda, the rest of the varieties have 

 presented nearly the same proportions. The Vulpinite 

 contains a little silica, probably from imbedded crystals of 

 rhombohedral Quartz. The chemical formula for the pure 

 mixture of this mineral is Ca S* 2 , which gives 41-53 of 

 lime, and 58-47 of sulphuric acid. It does not exfoliate be- 

 fore the blowpipe, but is covered with a white friable 

 enamel. 



By a peculiar process, the prismatic Gypsum-haloide at- 

 tracts water, loses its transparency, a portion both of its 

 hardness and specific gravity, and approaches in some of 



