54 PHYSIOGRAPHY. CLASS i. 



This composition corresponds to the formula Na 15 8 + 24 Aq. 

 The preceding general description, however, refers to the 

 artificial salt, which is expressed by Na B 2 + 10 Aq, and 

 consists of 31-97 Soda, 22-06 Boracic acid, and 45-97 water. 

 It is soluble in water ; the solution changes the blue colour 

 of litmus into green. It intumesces before the blowpipe, 

 and then melts into a transparent globule. 



2. The natural salt, the natural-historical properties of 

 which are as yet unknown, occurs in different districts of 

 Persia and Thibet, where it is found on the surface of the 

 soil, in the vicinity, and sometimes at the bottom, of several 

 lakes, and in a state of solution in the waters of mineral 

 wells. It is said also to have been met with in Ceylon, 

 and in considerable quantity in Potosi. 



3. The natural salt is employed in manufacturing the 

 artificial one by the addition of a greater quantity of soda. 

 The artificial salt is made use of as a flux, in the produc- 

 tion of imitation gems, and in the process of soldering. 



GENUS X. BRITHYNE*-SALT. 

 1. PRISMATIC BRITHYNE-SALT. 



Glauberite. JAM. Syst. II. p. 613. Prismatic Glauberite. 

 Man. p. 19. Glauberite. PHILL. 198. Glauberit. 

 HAUSM. III. S. 839. Brongniartin. LEONH. S. 618, 

 Glaube'rite. HAUY. Tabl. comp. p. 23. Traite', 2de 

 Ed. T. II. p. 215. 



Fundamental form. Scalene four-sided pyramid. 



P = { }J Jf, }, 128 0' ; 90 0'. Inclina- 



tion = & 49' in the plane of the long diagonal. 

 Vol. I. Fig. 41. HAUY. 



a : b : c : d = 2-3717 : 4 : 3-0984 : 1. 

 * From fyii>; dense (heavy). 



