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 off 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 crushing 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 
springs 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 Pyrences, in the Cretaccous 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. 
