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. 
NaptJia 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. 
