184 BRINE AND NAPTHA SPRINGS. 



already seen that many sandstones, which were 

 doubtless the sedimentary strata of ancient waters, 

 are bound together and coloured red by iron ; and 

 among such rocks we often meet with carbonate 

 and sulphuret of iron, as we now find the same 

 metal existing in the form of a carbonate or a sul- 

 phate in chalybeate springs. Dr. James found, in 

 his expedition to the Rocky Mountains, that the 

 thermal springs of the Washita deposite a very copi- 

 ous sediment, composed of silex, lime, and iron. 

 There are numerous springs in this country which 

 deposite both calcareous as well as silicious matter. 



Brine Springs, — There are some springs which 

 yield so large a quantity of muriate of soda (table- 

 salt), that one fourth the weight of water may be 

 extracted by evaporation. Together with these, 

 there are usually intermixed more or less carbonate 

 and sulphate of lime, magnesia, and other mineral 

 ingredients. The salt-springs of Cheshire (Eng- 

 land) rise up through strata of sandstone and red 

 marl, which contain large beds of rock-salt; and 

 they are known to have flowed more than 1000 

 years. Brine springs are supposed to owe their 

 origin to beds of fossil salt. The waters of the 

 Dead Sea contain large quantities of muriatic salts, 

 which Dr. Daubeny thinks lends countenance to 

 the volcanic origin of the surrounding country, as 

 such salts are the frequent products of volcanic 

 eruptions. There are numerous salt-springs in 

 the United States, which will be described particu- 

 larly when we come to treat of descriptive geol- 

 ogy. 



Naptha and Asphaltum Springs. — We find springs 

 in various parts of the world impregnated with pe- 

 troleum and other substances allied to it, such as 

 bitumen, naptha, asphaltum, and pitch; which, in 

 many cases, it is presumed, owe their origin to sub- 

 terranean fires, which raise or sublime the more sub- 

 tle parts of the bituminous matter contained in rocks, 



