226 DESCRIPTIONS OF MINERALS. 



The Dead and Caspian Seas, and the lakes of Khoordistan, 

 are salt. From 20-26 per cent, of the weight of the water 

 from the Dead Sea are solid salts, of which 10 per cent, are 

 common salt. Over the pampas of La Plata and Patagonia 

 there are many ponds and lakes of salt water. 



The greater part of the salt made in this country is ob- 

 tained by evaporation from salt springs. Those of Salina and 

 Syracuse are well known ; and many nearly as valuable are 

 worked in Ohio and other Western States. At the best New 

 York springs a bushel of salt is obtained from every 40 gal- 

 lons. But the discovery of rock salt at Wyoming, west of 

 Syracuse, may lead to further discoveries, which will make 

 the brines of New York of comparatively little value. To 

 obtain the brine, wells from 50 to 150 feet deep are sunk by 

 boring. It is then raised by machinery. 



The process of evaporation under the heat of the sun is 

 extensively employed in hot climates for making salt from 

 sea water, Avhich affords a bushel for every 300 or 350 gal- 

 lons. For this purpose a number of large shallow basins 

 are made adjoining the sea ; they have a smooth bottom of 

 clay, and all communicate with one another. The water is 

 let in at high tide and then shut off for the evaporation to 

 go on. This is the simplest mode, and is used even in un- 

 civilized countries, as among the Pacific Islands. 



Mirabilite. — Glauber Salt. Hydrous Sodium Sulphate. 



Monoclinic. Occurs in efflorescent crusts of a white or 

 yellowish- white color ; also in many mineral waters. Taste 

 cool, then feebly saline and bitter. 



Composition. Xa* 4 S 4- lOaq = Sulphur trioxide 2-4*8, 

 soda 19-3, water 55*9 = 100. 



Diff. It is distinguished from Epsom salt, for which it 

 is sometimes mistaken, by its coarse crystals, and the yel- 

 low color it gives to the blowpipe flame. 



It is made in enormous amounts from common salt, its 

 production being one stage in the manufacture of sodium 

 carbonate. It is used in medicine, and is known by the 

 familiar name of "salts." 



Obs. On Hawaii, one of the Sandwich Islands, in a cave 

 at Kailua, Glauber salt is abundant, and is constantly form- 

 ing. It is obtained by the natives and used as medicine. 

 Glauber salt occurs in "efflorescences on the limestone below 



