3. Chalybeate or ferruginous: those in which iron is a leading constituent; and—
4. Sulphurous: those that contain sulphureted hydrogen.
Of the latter class there are two instances.
Almost without exception the rest of the waters of this locality possess some of the properties of those belonging to the first three classes, being a combination of gaseous, saline, and ferruginous principles, their difference, as you will observe, being more one of quantity than of quality. As a matter of convenience they are designated as cathartic, alkaline, iron, and sulphur waters, according to the degree in which these characteristics present themselves.
Mineral waters were known at an early day, their use being held in high repute by the ancient Greeks and Romans, as well as by their less illustrious successors. Their physiological action and therapy are not, however, perfectly understood. With the exception of the chalybeate, the persistent use of the cathartic, alkaline, and sulphur waters favors retrograde metamorphic action, the ferruginous alone producing an opposite effect and increasing the number of the red blood-corpuscles.
From the diversified character of their constituents their application as therapeutic agents must necessarily have a wide range. Probably the best results from their use are obtained in those functional diseases that are connected with derangement of the portal circulation, and in certain rheumatic and arthritic affections. In some forms of indigestion their use is attended by very gratifying results, as well as in certain types of renal difficulties. In anæmia, uncomplicated with organic lesions, the iron waters are of decided benefit. That many persons injure themselves from the injudicious use of the waters is a matter of common observation. They are medicinal, and should be so regarded and used accordingly. The late Dr. Steele, in referring to this subject, remarked that "there are numerous persons who flock about the Springs during the drinking-season, without any knowledge of the composition of the waters, and little or none of their effects, who continue to dispose of their directions to the ignorant and unwary, with no other effect than to injure the reputation of the water and destroy the prospects of the diseased."
THE Royal Society has already done me the honor of publishing a long series of memoirs on the interaction of radiant heat and gaseous matter. These memoirs did not escape criticism. Distinguished men, among whom the late Professor Magnus and the late Professor