COMPOUNDS OF POTASSIUM AND SODIUM. 225 



enough salt remaining to supply the whole world for many 

 centuries. Its deep subterranean regions are excavated into 

 houses, chapels and other ornamental forms, the roof being 

 supported by pillars of salt ; and when illuminated by lamps 

 and torches, they are objects of great splendor. 



The salt is often impure with clay, and is purified by dis- 

 solving it in large chambers, drawing it oif after it has 

 settled, and evaporating it again. The salt of Norwich (in 

 Cheshire) is in masses 5 to 8 feet in diameter, which are 

 nearly pure, and it is prepared for use by crashing it be- 

 tween rollers. 



In North America, beds of rock salt exist at Goderich in 

 Canada ; at Wyoming in Western New York (reached by 

 boring to a depth of 1,279 feet) ; in Washington County, in 

 Virginia; and extensively at Petite Anse in Louisiana, where 

 it underlies 144 acres ; in Nevada, at several localities ; in 

 the Salmon River Mountains, Oregon. 



Brine springs also proceed from rocks of various ages ; 

 and often they are indications of deep-seated beds of rock 

 salt. 



The salt of Western New York, and Goderich, Canada, 

 is of the Salina period of the Upper Silurian ; the brine 

 S£>rings of Michigan, from shales and marlytes of the Sub- 

 carboniferous period ; those of the salt beds of Norwich, 

 England, in magnesian limestone of the Permian ; those of 

 the Vosges and of Saltzburg, Ischl, and the neighboring 

 regions, in marly sandstone of the Triassic ; those of Bex, 

 in Switzerland, in the Lias formation ; that of Wieliczka, 

 Poland, and the Pyrenees, in the Cretaceous or chalk forma- 

 tion; that of Catalonia, in the Tertiary ; that of Louisiana, 

 in the Quaternary, and large deposits are still more recent ; 

 and besides there are lakes that are now evaporating and 

 producing salt depositions. 



Vast lakes of salt water exist in many parts of the world. 

 The Great Salt Lake of Utah has an area of 2,000 square 

 miles, and is remarkable for its extent, considering that it 

 is situated toward the summit of the Rocky Mountains, at 

 an elevation of 4,200 feet above the sea. Its waters contain 

 20 per cent, of sodium chloride (common salt). The dry 

 regions of these mountains and of Southwestern California 

 are noted for salt licks and lakes. In Northern Africa 

 large lakes as well as hills of salt abound, and the deserts 

 of this region and Arabia abound in saline efflorescences. 



