1. It is shown, by the testimony adduced, that whereas in the hands of most persons the divining rod remains motionless, in the hands of some it moves promptly and briskly when the requisite conditions are observed. 2. It is no less certain that the motion of the divining rod has appeared, to various intelligent and honest persons, who have succeeded in producing it, to be entirely spontaneous; or that the said persons were not conscious of having excited or promoted the motion by the slightest help of their own. 3. It appears that in the ordinary use of the divining rod by competent persons, its motion only manifests itself in certain localities. 4. It being assumed that the operator does not, however unconsciously, by the muscular action of his hands and wrists produce the motion of the divining rod, the likeliest way of accounting for the phenomenon is to suppose that the divining rod may become the conductor of some fluid or force, emanating from or disturbed in the body by a terrestrial agency. But here a difficulty arises: How can it happen that the hypothetical force makes so long and round-about a course? Why, communicated to the body through the legs, does not the supposed fluid complete a circuit at once in the lower part of the trunk? Such, at all events, would be the course an electric current so circumstanced would take. The difficulty raised admits of being removed by aid derived from a novel and unexpected source. I allude to the discovery, by Von Reichenbach, of a new force or principle in the physical world, which, whether or not it is identical with that which gives motion to the divining rod, exhibits, at all events, the very property which the hypothetical principle should possess to explain the phenomena which we have been considering. No attempts have indeed been made to identify the two as one; and my conjecture that they may prove so, should it even appear plausible, is so vague, that I should have contented myself with referring to Von Reichenbach’s new principle as to an established truth, and have introduced no account of it into this Letter, had I not a second motive for insuring your cognisance of the curious facts which the Viennese philosopher has brought to light. It is less with the view of furnishing a leg to the theory of the divining rod, than in order to provide the means of elucidating more interesting problems, that I now proceed briefly to sketch the leading experiments made by Von Reichenbach, and their results.