THE ACTION OF LIGHT UPON SPIRITUAL MANIFESTATIONS. THERE are certain spiritual manifestations which can be obtained only in darkness, such, for instance, as the ordinary spirit voices; and subdued light is a favour able condition for nearly all the phenomena, trance speaking included. What is this “ light ” which exer cises so much influence upon the manifestations According to modern philosophers it is the wave-motion of an infinitely elastic fluid known as the “ interstellar ether," which fills all space, stretches from star to star and bathes the vibrating atoms of all solid bodies. The vibrating atoms of luminous bodies ’throw the ether into waves, and these waves beat against the retina of the human eye, just as the waves of the ocean break upon the sea-shore. But the eye is so far an imperfect instrument that it is insensitive to the shortest of the ether waves, and cannot see them, neither can it see the longest waves. The longest waves emanating from the sun, which warm our backs and melt the mountain snows, are nearly all invisible to the eye. The invi sible waves contain about cight times more heat than the visible waves. A few days ago, Professor Tyndal at the Royal Institution filtered away the visible waves from the electric light, by means of a glass vessel filled with a solution of iodine in bisulphide of carbon ; the invisible waves passed freely through this opaque liquid and were made to set fire to paper at a distance of several yards from the electric lamp. The red waves are the longest which can be seen by the eye, and the violet and blue waves are the shortest ; in fact, the sensation of colour is due simply to variations in wave length. The spirits who speak at Mrs. Mary Marshall’s séances, on being questioned upon the subject said that there was so much motion in light that it “ burnt up the atmospheres they used to produce the voices.” By “ atmospheres” they perhaps meant the emanation from the medium. Accordingly some experiments were once tried, by giving them a cool light, containing very much less wave motion than ordinary white light. It was produced by passing the rays from a paraffin flame, first through a glass trough filled with a solutior of alum, and, secondly, through another glass trough filled with a solution of ammonio-sulphate of copper. A cold blue light, of feeble intensity, was thus em ployed to illuminate the room. It was a failure so far as seeing the tubes was concerned, as the voices could only be produced in those parts of the room where the darkness was too deep for the eyes of the witnesses to penetrate. There are other ways by which the diffi culty may perhaps be overcome, and further experi ments will be made. Mr. Mumler is as busy as ever producing spirit pho tographs, and defying all the photographers in New York to detect imposture. As Judge Edmonds and Mr. Livermore, the banker, pronounce Mr. Mumler to accurate portraits of their departed have produced friends, we presume them to be right in considering it a case of genuine mediumship. Assuming the pictures to be genuine spirit photographs, the question arises How do the spirits produce them? Short waves of ether, too short to be visible to the eye, act upon pho tographic films, it being therefore possible for photo graphs to be taken very slowly indeed, in a peculiar kind of pitch darkness, which the philosopher knows how to produce. The editor of the British Journal of Photography once suggested that perhaps the bodies of spirits can be materialised sufficiently to reflect these short invisible waves, by which means a photograph could be taken. But the fact is that in Mr. Mumler's pictures, the spirit forms produce more photographic action on the plates than the human forms in the same space of time, whieh could not be the ease if the spirit bodies set up an action upon the sensitive film by means of the extra-violet rays, since these rays act very feebly. In short, the way in which these pictures are produeed, is as great a mystery as ever.