Page:Popular Science Monthly Volume 40.djvu/767

 wooden frame, holding a heavy plate glass, fifteen inches square, and mounted on three brass legs, with screw adjustments by means of which the plate may be brought into exact level. Upon the plate glass are placed in the form of a triangle three very perfectly turned and polished brass balls, and upon the balls rests a thin crystal plate glass fourteen inches square, set in a light wooden frame. Covering the upper glass is a sheet of paper, and upon the paper the subject lightly rests the finger-tips of one hand. When all is properly adjusted, and glass and balls are rubbed smooth with oil, it is quite impossible to hold the apparatus still for more than a few seconds; the slightest unsteadiness or movement of the hand at once sets the apparatus going. If one closes his eyes and thinks intently of something, one readily forms the conviction that the glass remains quiet, but a bystander is equally convinced of the opposite. The rest of the apparatus is designed to give a permanent record of these movements. Fastened to the light frame containing the upper glass is a slender rod some ten inches long, bearing at its end a cork, and piercing the cork is a small glass tube that serves to hold a snugly fitting glass rod. The rod is drawn to a smooth rounded point, and when in position rests upon a piece of glazed paper that has been blackened over an oil-flame, and is smoothly stretched over a small glass plate. The point of the rod thus records easily and accurately every movement of the hand that is imparted to the upper plate, and by the manner of its adjustment accommodates itself to all irregularities of movement or surface. Inasmuch as the main purpose of the apparatus is to write involuntary movements, it may not be amiss to name it the "automatograph," and speak of the record it yields as an "automatogram."



Various means may be employed to hold the attention of the subject in a definite direction, and in all he is instructed to think as little as possible of his hand, making an effort, if he chooses, to