We have a larger experience of such phenomena now, and we can define with some accuracy what it was that happened at Hydesville in the year 1848. We know that these matters are governed by law and by conditions as much as any other phenomena of the universe, though at the moment it seemed to the public to be an isolated and irregular outburst. On the one hand, you had a material, earth-bound spirit of a low order of development which needed a physical medium in order to be able to indicate its presence. On the other, you had that rare thing, a good physical medium. The result followed as surely as the flash follows when the electric battery and wire are both properly adjusted. Corresponding experiments, where effect, and cause duly follow, are being worked out at the present moment by Professor Crawford, of Belfast, as detailed in his two recent books, where he shows that there is an actual loss of weight of the medium in exact proportion to the physical phenomenon produced.[1] The whole secret of mediumship on this material side appears to lie in the power, quite independent of oneself, of passively giving up some portion of one's bodily substance for the use of outside influences. Why should some have this power and some not? We do not know--nor do we know why one should have the ear for music and another not. Each is born in us, and each has little connection with our moral natures. At first it was only physical mediumship which was known, and public attention centred upon moving tables, automatic musical instruments, and other crude but obvious examples of outside influence, which were unhappily very easily imitated by rogues. Since then we have learned that there are many forms of mediumship, so different from each other that an expert at one may have no powers at all at the other. The automatic writer, the clairvoyant, the crystal-seer, the trance speaker, the photographic medium, the direct voice medium, and others, are all, when genuine, the manifestations of one force, which runs through varied channels as it did in the gifts ascribed to the disciples. The unhappy outburst of roguery was helped, no doubt, by the need for darkness claimed by the early experimenters--a claim which is by no means essential, since the greatest of all mediums, D. D. Home, was able by the exceptional strength of his powers to dispense with it. At the same time the fact that darkness rather than light, and dryness rather than moisture, are helpful to good results has been abundantly manifested, and points to the physical laws which underlie the phenomena. The observation made long afterwards that wireless telegraphy, another etheric force, acts twice as well by night as by day, may, corroborate the general conclusions of the early Spiritualists, while their assertion that the least harmful light is red light has a suggestive analogy in the experience of the photographer.