On the 20th of April, at the time of applying the leeches, Nicolai's room was full of figures moving about among each other. They first began to have a less lively motion; shortly afterwards their colours became paler--in another half hour fainter still, though the forms still remained. About seven o'clock in the evening, the figures had became colourless, and they moved scarcely at all, but their outline was still tolerably perfect. Gradually that became less and less defined. At last they disappeared, breaking into air, fragments only remaining, which at last all vanished. By eight o'clock all were gone, and Nicolai subsequently saw no more of them. Other cases are on record in which there was still greater facility of ghost-production than Nicolai evinced. One patient could, for instance, by thinking of a person, summon his apparition to join the others. He could not, however, having done this, subsequently banish him. The sight is the sense most easily and frequently tricked; next, the hearing. In some extraordinary cases the touch, also, has participated in the delusion. Herr von Baczko, already subject to visual hallucinations, of a diseased nervous system, his right side weak with palsy, his right eye blind, and the vision of the left imperfect, was engaged one evening, shortly after the battle of Jena, as he tells us in his autobiography, in translating a brochure into Polish, when he felt a poke in his loins. He looked round, and found that it proceeded from a Negro or Egyptian boy, seemingly about twelve years of age. Although he was persuaded the whole was an illusion, he thought it best to knock the apparition down, when he felt that it offered a sensible resistance. The Negro then attacked him on the other side, and gave his left arm a particularly disagreeable twist, when Baczko pushed him off again. The Negro continued to visit him constantly during four months, preserving the same appearance, and remaining tangible; then he came seldomer; and, after finally appearing as a brown-coloured apparition with an owl's head, he took his leave. The illusion and its principle having been thus elucidated, it is hardly worth while to look into its operation in tales of vulgar terror. But it is highly interesting to trace its effects on minds of a high order, when its suggestions have been received and interpreted as the visits and communications of superior beings. You have heard, I dare say, my dear Archy, of the mysticism of Schwedenborg. Now that they are explained, the details of his hallucinations are highly gratifying to one's curiosity.