80 PHYSIOGRAPHY. 



Sulphate of Magnesia 36-66. 



Sulphate of Soda 33-34. 



Protosulphate of Manganese 0-33. 



Muriate of Soda 22-00. 



Water 0-34. 

 with a mechanical admixture of persulphate of iron with 

 excess of base. 



BREISLAKITE. 



This name has been given to a substance from Vesuvius 

 in very delicate capillary crystals, of a reddish-brown or 

 chestnut-brown colour, bent and grouped like wool, on the 

 surface of cavities in a kind of lava, resembling the Grow- 

 stein of WERNER. Its other properties have not been as- 

 certained. It contains a considerable quantity of copper, 

 giving with salt of phosphorus a green globuble in the 

 oxidating flame, which becomes red in the reducing flame 

 of the blowpipe. 



BREWSTERITE. 



KOUPHONE-SPAR. 



Brewsterite. BROOKE. Edin. Phil. Journ. Vol. VI. p. 112. 

 Brewsterite. PHLLL. p. 200. 



Hemi-prismatic. Combination represented Fig. 189. 

 Inclination of the edge between d and d on that 

 between h and h, 93 40' ; d on d = 172. 

 Prisms: h = 176; g = 136; e = 131; 

 c = 121. BROOKE. 



Cleavage, perfect parallel to P, traces parallel to 

 a plane, which replaces the edge between h and h. 

 Fracture uneven. 



Surface of the prisms streaked parallel to their com- 

 mon intersections. 



Lustre vitreous, pearly upon P. Colour white, 



