Modern Magic: A Practical Treatise on the Art of Conjuring

Fig. 289 shows the action of the second or middle group of levers, serving to produce the opening of the mouth. The chin of the figure consists of a solid block of wood i, working on a pivot j in each cheek, and so counterweighted that its normal position is as in Fig. 289, thus keeping the mouth closed. When, however, the shaft k is raised by pressure from below, the lever l rises with it, and proportionately depresses the opposite end of the block i, thereby opening the mouth. As soon as the pressure is removed, the block falls back into its original position, and the mouth closes.