Cir. XVII.] 



MINERAL SPRINGS. 



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sphere by the sun ; but it is also true that mineral springs are 

 powerful instruments in rendering the surface subservient to 

 the support of animal and vegetable life. Their heat is 

 believed to promote the development of the aquatic tribes in 

 many parts of the ocean, and the substances which they carry 

 up from the bowels of the earth to the habitable surface, are 

 of a nature and in a form which adapts them peculiarly for 

 the nutrition of animals and plants. 



As these springs derive their chief importance to the geolo- 

 gist from the quantity and quality of the earthy materials 

 which, like volcanos, they convey from below upwards, they 

 may properly be considered in reference to the ingredients 

 which they hold in solution. These consist of a great variety 

 of substances ; but chiefly salts with bases of lime, magnesia, 

 alumine, and iron, combined with carbonic, sulphuric, and 

 muriatic acids. Muriate of soda, silica, and free carbonic 

 acid, as well as nitrogen, are commonly present ; there are 

 also springs of petroleum or liquid bitumen, and of naphtha. 



The ingredients of mineral springs, such as common salt, 

 chloride of magnesia and others, so often agree with the con- 

 stituents of sea- water, that the theory of their marine origin 

 has been naturally suggested. Such materials are, no doubt, 

 often to be obtained from those strata through which the 

 descending rain-water flows ; but in many cases they may 

 come from the sea even where the substances are not found 

 in the same relative proportions as in sea- water ; for where 

 hot springs charged with gaseous matter penetrate through 



masses 



decomposition 



minerals must 



often be going on, and where new chemical combinations 

 take place, some of the gaseous, earthy, or metallic ingredients 

 of springs may be intercepted in their upward course. 



from 



from 

 This 



gas may be derived, says Dr. Daubeny, from atmospheric air, 

 which is always dissolved in rain-water, and which, when this 

 water penetrates the earth's crust, must be carried down to 

 great depths, so as to reach the heated interior. When 

 there, it may be subjected to deoxidating processes, so that the 

 nitrogen, being left in a free state, may be driven upwards 



