(_t_) These arrangements being made, the spirits were invoked to show their power, when repeatedly the spring-balance indicated an augmentation of weight equal to three pounds. The relative distances of the vase and balance from the fulcrum being as 6 to 36, the force exerted must have been 3 × 6 = 18 pounds; yet the medium did not appear to be subjected to any reaction, and declared that he experienced none. (_u_) It was on stating this result to the Association for the Advancement of Science, that I met with much the same reception as the King of Ava gave to the Dutch ambassador, who alleged water to be at times solidified in his country, by cold, so as to be walked upon. (_v_) The belief in spiritual agency was treated as a mental disease, with which I, of course, had been infected; those who made this charge being perfectly unconscious that their education has associated morbid incredulity with bigoted and fanatical credence. [Illustration: PLATE IV.] PLATE IV. (_x_) The apparatus of which the opposite cuts afford a representation are spiritoscopes, under modifications to which I resorted subsequently to the contrivance in which Pease’s dial is employed. For Pease’s “dial,” disks are substituted, resembling those originally employed by me, as represented in Plates I. and II. These last mentioned, however, were made to revolve under the index; while in Pease’s apparatus the index revolves, the disk remaining at rest. The advantage of having the disk to revolve is, that the letter is always to be looked for, within the same space; whereas in operating with the other the eye has to follow the index through all its rapid movements. (_y_) The convenience and economy of casting the disks of iron was deemed a sufficient motive for resorting to the rotation of the index; as when made of that metal the disk becomes too heavy to be rotated with ease, first one way and then another. (_z_) In FIG. 1 the vibrating lever is resorted to, and the process is precisely the same as that already described, in which Pease’s dial is associated with the same mechanism. (_aa_) The words on the dial faces in Figures 1 and 2 are somewhat abbreviated.[2] (_bb_) The rod _R_ slides in staples, so as to be made to extend farther or nearer from the fulcrum. The legs on which the disk is supported, which are a part of the casing, terminate below in a socket which fits upon a plug screwed into the base-board; upon this plug it may be fastened by the set screw (_s_). By sliding the rod (_r_) inward, the disk may be turned half round upon the plug, so as to place the lettered surface out of the sight of the medium, whose power to influence the communications is thus nullified. This is one mode of attaining test conditions; in other words, those conditions which make it impossible that the communications received should be due to any mortal, (151 to 166,) unless, as gratuitously and erroneously, as I believe, alleged, the medium by clairvoyancy sees the letters.