relation, by holding cords or jointed rods; and among them moved slowly and mysteriously Mesmer himself, affecting one by a touch, another by a look, a third by continued stroking with the hand, a fourth by pointing at him with a rod. What followed is easily conceivable from the scenes referred to in my last letter, which are witnessed at religious revivals. One person became hysterical, then another; one was seized with catalepsy, then others; some with convulsions; some with palpitations of the heart, perspirations, and other bodily disturbances. These effects, however various and different, went all by the name of "salutary crises." The method was supposed to produce, in the sick person, exactly the kind of action propitious to his recovery. And it may easily be imagined that many patients found themselves better after a course of this rude empiricism; and that the impression made by these events, passing daily in Paris, must have been very considerable. To the ignorant the scene was full of wonderment. To ourselves, regarding it from our present vantage-ground, it contains absolutely nothing of the marvellous. We discern the means which were in operation, and which are theoretically sufficient to produce the result. Those means consisted in,--first, high-wrought expectation and excited fancy, enough alone to set some of the most excitable into fits;--secondly, the contagious power of nervous disorder to cause the like disorder in others, a power augmenting with the number of persons infected;--thirdly, the physical influence upon the body of the _Od force_ discovered by Von Reichenbach, which is produced in abundance by chemical decomposition, which can be communicated to, and conveyed by inanimate conductors, and which finally emanates with great vivacity from the subtle chemistry of the living human frame itself. The reality of this third cause you must allow me to take for granted without farther explanation. Von Reichenbach's papers, the credit of which is guaranteed by their publication in Liebig and Woehler's Annals of Chemistry, have been now some time translated into English, and are in the hands of most English readers. It is remarkable that Jussieu, the most competent judge in the commission which, in 1784 condemned mesmerism as a scientific imposition, was so much struck with the effects he witnessed, that he recommended the subject, nevertheless, to the farther investigation of medical men. His objections were to the theory. He laid it down, in the separate report which he made, that the only physical cause in operation was animal heat; curiously overlooking the point, that common heat was not capable of doing the same things, and that, therefore, the effects _must be owing to the agency of that something else_ which animal heat contained in addition to common heat.