(_l_) In the employment of the apparatus (Plate I.) it has been suggested that through clairvoyance the medium might see the letters, despite of the screen, or might learn them from the mind of the observer; but in this case the medium sees the letters without the aid of clairvoyancy; but this power does not account for the regulation of the manifestations; since, even seeing the letters, they cannot control the movements so as to give to the intuitive power thus exercised any efficacy. (_m_) On the surface of the table, on the right, may be seen a board upon castors. This was contrived as a substitute for the plate on balls. The castors, of course, perform the same office as the balls in allowing a solid material communication between the hands of the medium and the table, without giving the power to induce or control the movement. Evidently, though by any horizontal impulse the medium might cause the castors to turn and the board to move in consequence, the force necessary to effect this must fall short of that requisite to move the table. (_n_) In point of fact, the board, when under the plate, balls, and hands of the medium, was often moved rapidly to and fro, without moving the table. To move this under such conditions without moving the board or tray, required a distinct spiritual process, of much greater difficulty, and which some spirits were either _unwilling_ or _unable_ to employ successfully. See “Mediumship” in this work. See also 164, 166. [Illustration: PLATE III.] PLATE III. (_o_) On the opposite page is a representation of an experiment, in which the medium was prevented from having any other communication with the apparatus, actuated under his mediumship, excepting through water. Yet under these circumstances the spring balance indicated the exertion of a force equal to 18 pounds. (_p_) A board is supported on a rod so as to make it serve as a fulcrum, as in a see-saw, excepting that the fulcrum is at the distance of only a foot from one end, while it is three feet from the other. This end is supported by a spring-balance which indicates pounds and ounces by a rotary index. (_q_) Upon the board, at about six inches from the fulcrum, there is a hole into which the knob of an inverted glass vase, nine inches in diameter, is inserted. (_r_) Upon two iron rods proceeding vertically from a board resting on the floor, so as to have one on each side of the vase, a cage of wire, such as is used to defend food from flies, of about five inches diameter, is upheld [inverted] by the rod within the vase concentrically, so as to leave between it and the sides of the vase an interstice of an inch nearly, and an interval of an inch and a half between it and the bottom of the vase. (_s_) The vase being filled with water until within an inch of the brim, the medium’s hands were introduced into the cage and thus secured from touching the vase.