the same manner, the problem of the action of matter upon mind should be rendered as little complicate as possible; and thus, in considering sensation, it is desirable to bring into one comprehensive view its chief conditions, to the exclusion of such contingencies as merely arise from the modifying influence of particular circumstances. Now we have seen that the external and mechanical portions of our senses are not indispensably and fundamentally connected with sensation, but rather are adaptations to the exigencies of this our temporary existence. The two absolute essentials of sensation, without which it could not take place under any circumstances, in which it bears coincident relation to real external objects, are a medium and a system capable of responding to that medium. Now the question is, whether there be any fact which renders impossible, during the mesmeric sleep, the co-existence of the two essential conditions of sensation. One of them that is, motion of the nervous system has been shown to be by no means of necessity abrogated during mesmeric sleepwaking; but the other, that is the correlative motion of a medium, does, on a cursory view, seem forbidden in cases where the patient sees through obstacles which intercept the light, and, to our common apprehensions, break up the continuity of visual impulsions. On maturer consideration, however, we must own that the great principle of sensation - namely, motion communicated by media - may not only subsist in its

integrity during the mesmeric vision, but subsist also analogically to all we know or can discover of nature's constitution.

It is true that, in the endeavour to reconcile mesmeric sensation with established laws, we are in a manner forced into hypothesis. But is this a fault? A great metaphysician has pronounced that " an hypothesis, in the first stage of inquiry, far from being inconsistent with sound philosophy, may be said to be essential to it." Now the case of mesmerism is one in which we are absolutely obliged from given data to draw deductions, and to reconcile two facts by the interposition of a third. With regard to mesmeric vision, for instance, we have a phenomenon, accurately determined by rigorous experiment, which involves two things, a perceiving mind, and an object perceived; and these we are forced, through reason, to connect by a third, namely, a medium, for we never knew mind to perceive but through an intermediary, and we have reason to think that none but the Almighty mind can immediately perceive objects. Yet more,-the sleepwaker has a nervous system, which, though externally inert, is manifestly in internal activity; and there is no ground whatever to suppose that the established language of sensation, namely, motion of a nerve, is, in mesmerism, abolished, though it be produced in an unusual way. If then there be motion of a nerve correlative with an external object, it is plain that this motion must be brought about by means, and by material means. What these means are we

do not indeed exactly know, and we are therefore compelled, in a degree, to form conjectures about them. Certainly the less of this the better, but at any rate we cannot but imagine such a medium as shall meet the necessities of the case; herein, at least, we have a sure guide. If, taking the facts, we proceed, step by step, to deduce from them the characteristics of our medium, fitting always the supposition to the reality, and not the reality to the supposition, it seems as if we could not greatly err.

The first thing of which we may be sure is, that the medium which connects mesmeric persons with external objects is not any of those which we believe to be efficient in ordinary sensation. The mechanism of the senses being null, the media especially adapted to that mechanism must also be useless in conveying information. The ear was made for air, and the eye for light; but, in this case, the ear is closed, and the eye is an abolished organ. That, however, there should be no communication between the sleepwaker and external objects does by no means follow. We have seen that real information respecting the material world can be conveyed through other inlets of the body than the ordinary. In the same manner, may be affirmed that even our common experience may show us sensation taking place through other external media than the ordinary. Let us adhere to our principle, that similar motions of the nerves may be produced in various ways, and different causes end in the same result; and here also it will not fail us.

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The deaf, who hear and enjoy music by means of a staff connecting their teeth, or their chest, with a musical instrument, do really use another medium than the air for the conveyance of acoustic impulses. In the same way, we have instances to show that real information respecting external actions of matter may reach from great distances by other than the usual media. Water is even a better conductor of sound than air. According to the experiments of M. Colladon the sound of a bell was conveyed under water, through the Lake of Geneva, to the distance of about nine miles." Yet again: "The velocity of sound, in passing through solids, is in proportion to their hardness, and is much greater than in air or water. A sound, which takes some time in travelling through the air, passes almost instantaneously along a wire 600 feet long; consequently it is heard twice; first, as communicated by the wire, and afterwards through the medium of the air. The facility with which the vibrations of sound are transmitted along the grain of a log of wood is well known. Indeed, they pass through iron, glass, and some kinds of wood, at the rate of 18,530 feet in a second."

Does any thing similar take place with regard to light? There does; and even in a more remarkable manner. The electic medium is a far more swift and subtle messenger of vision than is the luminous ether. "A wheel revolving with celerity sufficient to render its spokes invisible, when illuminated by a flash of lightning, is seen, for an instant, with all its

spokes distinct, as if it were in a state of absolute repose; because, however rapid the motion may be, the light has come and already ceased, before the wheel. has had time to turn through a sensible space." Again, some ingenious experiments, by Professor Wheatstone, demonstrate to a certainty that the speed of the electric fluid much surpasses the velocity of light. It is therefore a different medium - yet can it serve for all the purposes of vision, and even in a superior manner. After hearing these things, shall we start at the notion of mesmeric sensation being conveyed through another medium than that in ordinary action? Even should the sleepwaker perceive the most distant objects (as some are said to have done), can we, from the moment a means of communication is hinted to us, be so much amazed? If his perception be more vivid, there seems to be an efficient cause in his abjuring the grosser media for such are more swift and subtle.

But the mesmerised person perceives objects not only at a distance, but through obstacles which are complete impediments to ordinary vision. Let us keep in view our principle. Motions of the nerves, and something to produce those motions, in correspondence with an external cause, are the required conditions which we seek to unite. If a mesmerised person seems to behold an object through an obstacle which commonly bars vision, let us not take so vulgar a view of this apparent miracle as to suppose that the sleepwaker's sight pierces through opaque bodies. It is not, in any case, the eye, but