446 NATURAL HISTORY. 



boring into them often to a depth of from fifty to one 

 hundred and fifty feet, and having the brine raised by 

 machinery. It is then conducted by troughs into boilers, 

 and there evaporated by heat. The water thus impreg- 

 nated by salt, is in Germany called Salsola ; is made 

 into salt by condensation. Salt is every where consid- 

 ered indispensable in the wants of man ; not only is it 

 valuable as a seasoning and preservative for his food, but 

 is of infinite use in the arts, manufacture of glass, soda, 

 etc., and in the forms of Epsom and Glauber salts well- 

 known in medicine. 



Soda. Nit rum of the ancients Saltpetre, or Nitrate 

 of Potash, of the present day occurs in minute, needle- 

 formed crystals, or is obtained from compact masses of 

 earth containing it lixiviated. It is also often found in a 

 state of efflorescence on stones, walls, etc. Luster vit- 

 reous ; colorless, else green or yellow ; deliquesces 

 slightly ; taste sharp and cooling. Fracture conchoidal ; 

 effloresces on exposure to the air. H. = 1.0 to 1.5. 

 G. = 1.4 to 1.5. 



Natron, a native carbonate of Soda, is formed from 

 the condensation of the waters of a small lake (Natron 

 Sea") in Egypt. Occurs also in other soda lakes, in 

 Hungary, Persia, Italy, Mexico, and is particularly 

 abundant in Chili. Natron accidentally led to the in- 

 vention of glass making ; the Phoenicians, having landed 

 in Egypt, and obtained a quantity of soda, placed their 

 kettle on some soda blocks which they fixed in a little 

 hollow they scooped out of the sand. When the water 

 in the kettle boiled, it ran over the top among the sand, 

 and the soda melting with it, the two combined formed 

 glass. Soda is of infinite importance, and is much used 

 in soap making, by glass manufacturers, and also as 



