Wohlgemuth, Adolf, b. 1868 · Cambridge, University Press · leaf 104
ving six pairs of white and grey sectors, was fixed in a circular frame. This frame ran on a peripheral ball bearing in a wooden board 40 cm. square. Thus the disc required no axle, and was driven by means of an endless band from a motor, the endless band moving round the frame of the disc, which… … Fig. 12. clockwork at so fast a rate that the observer had difficulty in adding the numbers together as the}' passed behind the window (Fig. 12). Experiments were made both with the attention of the observer occupied by the addition of the numbers and with the attention concentrated on the movement…
