26 PHYSIOGRAPHY. CLASS i. 



of this substance has been inferred from Dr BREWSTER'S 

 optical observations. 



2. According to Professor STROMEYEH, the prismatic 

 Boracic-acid from Volcano, one of the Lipari islands, is 

 perfectly pure Boracic Acid, with an accidental admixture 

 of sulphur. If pure, it consists of 



Boron 25-83. 



Oxygen 74-1 7 BERZELIUS. 



The crystallised variety contains 45 per cent, of water. It is 

 fusible at the flame of a candle, and yields a glassy globule, 

 which acquires resinous electricity by friction, even without 

 being isolated. 



3. It is deposited from the hot springs near Sasso, and 

 from the lag&ni in Tuscany. Another locality is Volcano, 

 one of the Lipari Islands. 



GENUS V. ARSENIC-ACID. 

 1. OCTAHEDRAL ARSENIC-ACID. 



Oxide of Arsenic. JAM. System. Vol. III. p. 552. Oc- 

 tahedral Arsenic Acid. Man. p. 5. Arsenikbliithe. 

 HAUSM. III. S. 805. Arsenikbluthe. LEONH. S. 170. 

 Arsenic oxyde'. H AU Y. Traite', T. IV. p. 225. Tabl. comp. 

 p. 108. Traite', 2de. Ed. T. IV. p. 241. 



Fundamental form, Hexahedron, Vol. I. Fig. 1. 



Simple forms. O, Vol. I. Fig. 2., commonly elon- 

 gated in one or another direction. 



Cleavage octahedron, perfect. Fracture conchoidal. 



Colour white, often inclining to yellow. Streak 

 white. Lustre vitreous, inclining to adamantine. 

 Semi-transparent ... opake. 



Sp. Gr. = 3-698. ROGER and DUMAS. Taste 

 sweetish astringent. 



