Professor Heim takes up the same hypothesis as others before him, and Dr. Granville among the rest, that the caloric of mineral waters is of a _specific_ kind, analogous to the vital heat of the body. “It is a heat incorporated with the water by a chemico-vital process.” “And as no external warmth can supply the body with _vital_ heat, so no artificially created temperature can be a real substitute for the natural heat of thermal springs.” The temperature, then, of the Wildbad waters being that of the human blood, immersion in them produces but a slight sensation of heat, the surface of our bodies being below that of our blood in temperature. The sensation is that of _comfort_—a word not to be more nearly translated into French than by the term “_bien-être_.” Here Professor Heim quotes, of course, Dr. Granville’s description of the “ecstatic” feelings which he experienced in these waters. He adds:—“But another circumstance which, more than all the rest, conduces to this favourable impression, is the _dynamic combination_ (le lien dynamique) of the solid and gaseous elements—the spirit of the water—received from the hand of Nature, in the bowels of the earth. It is this general impression on the whole human organism, which effects the cure of divers sufferings and maladies, by awakening and reviving the vital powers enfeebled or prostrated—and thus restoring activity to the circulation and to the nervous system, through which a reaction and energy is communicated to all the functions of the body.” These effects, Prof. Heim acknowledges, cannot be accounted for by the chemical composition of the water. The cosmetic qualities of Wildbad and Schlangenbad, he thinks, may be _partly_ owing to the soda contained in them, which forms a kind of oily soap on the surface, and gives it that feeling of lubricity and softness, so much vaunted: but he believes it to be _principally_ owing to the peculiar power of the bath to invigorate the functions of the skin as well as of the internal organs—a power greater, he maintains, in the waters of Wildbad than of Schlangenbad. Although these waters generally produce an exciting or exhilarating effect, yet in a certain number of instances, they cause a sense of lassitude and heaviness in the extremities, with an inclination to sleep, especially after leaving the bath. These effects are commonly attributable to improper use of the baths, or staying too long in them, in consequence of the pleasant feelings derived from them. Dr. H. recommends all persons to stay but 10 or 15 minutes in the bath at first, gradually increasing the time to half or three-quarters of an hour. In some, the head is affected with vertigo—in others, there is oppression on the chest—all which soon go off, after five or six baths.