Page:Popular Science Monthly Volume 21.djvu/845

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827
THE FORMATION OF SALINE MINERAL WATERS.

waters, with the immense variety of labors of which they have been the object, the fundamental questions relating to them still remain enveloped in profound darkness. An examination of the most recent and most authoritative publications suffices to show us that, with regard to the most capital point, the origin and mode of formation of these waters, we, at the end of fifteen centuries, are not much further advanced than were the Romans. Modern science, it is true, has put the ancient nymph to flight, and driven from his sanctuary the little beneficent god that presided at each fountain; but it has not yet succeeded in raising the statue of the truth upon the vacant altar.

Mineral waters take up the substances which give them their peculiar composition, and acquire all their medical value, at greater or less distances within the globe. It is, then, for geology, the science which deals with the formation of the globe, to seek the solution of the questions of their origin.

The number of mineral springs is immense, and the variations among them seem infinite; but there exist among them certain groups which distinguish and separate themselves at the first glance. Among these we place in the first rank the saline waters, or those of which the sea is the type. This is the division which I propose to consider, and of which I shall endeavor to set forth the origin and method of formation.

It is a fact, which I may state as uncontested at the present time, that all spring-waters, whether mineralized or not, are of exterior origin—that is, are waters of infiltration derived from the atmosphere. When these waters return to the light without having met, in the strata they have traversed, either soluble minerals or gases other than those of the atmosphere, they constitute ordinary waters. If, on the contrary, they have met soluble substances or gases different from those of the atmosphere, they will return more or less charged with those substances, and will then be mineral waters. In studying them we need not, therefore, inquire about the origin of the water itself, for it comes from the atmosphere, but only about that of the saline substances which it has encountered in its course.

It has been known from the most remote antiquity that considerable masses of saline substances, generally composed of gypsum, more rarely of rock-salt, exist at numerous points of our globe. The two salts we have named are the ones that have hitherto attracted the attention of commercial and scientific men; but the saline beds are in reality of a more complex composition than is superficially indicated by the predominance of those compounds.

The hypotheses which have been proposed to account for the origin of these salts, though many, may be grouped around three principal heads: 1. Free sulphuric acid, coming up from the depths of the globe, has acted upon carbonate of lime already formed and produced gypsum. 2. Hydro-sulphuric acid, coming in like manner from the