hung with mirrors, was dimly lighted. A profound silence was observed, broken only by strains of music, which occasionally floated through the rooms. The patients were seated round a sort of vat, which contained a heterogeneous mixture of chemical ingredients. With this, and with each other, they were placed in relation by means of cords, or jointed rods, or by holding hands; and among them slowly and mysteriously moved Mesmer himself, affecting one by a touch, another by a look, a third by passes with his hand, a fourth by pointing with a rod. What followed is easily conceivable from the scenes referred to in my last letter as witnessed at religious revivals. One person became hysterical, then another; one was seized with catalepsy; others 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 crisis.” The method was supposed to provoke in the sick person exactly the kind of action propitious to his recovery. And it may easily be imagined that many a patient found himself the better after a course of this rude empiricism, and that the effect 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 presents no marvellous characters. The phenomena were the same which we have been recently contemplating—a group of disorders of the nervous system. The causes which were present are not less familiar to us, nor their capability of producing such effects; they were—mental excitement, here consisting in raised expectation and fear; the contagiousness of hysteria, convulsions, and trance, its force increased by the numbers and close-packing of the patients; the Od force, developed by the chemical action in the charged caldron, developed by each of the excited bodies around, its action first favoured by the absolute stillness observed, then by the increasing sensibility of the patients as their nerves became more and more shaken. It is remarkable that Jussieu—the most competent judge in the commission of inquiry into the truth of mesmerism, set on foot at Paris in 1784, of which Franklin was a member, and which condemned mesmerism as an imposture—was so struck with what he saw, that he strongly recommended the subject to the attention and study of physicians. His objections were against the theory alone. He laid it down in the separate report which he gave in, that no physical cause had been proved to be in operation beyond animal heat! curiously overlooking the fact that common heat would not produce the effects observed; and, therefore, that the latter must have been owing to that something which animal heat, or the radiating warmth of a living body, contains, in addition to common heat. That something we now know, but only since 1845, to be the Od force.