FIG. 93.—Graham’s Dead Beat. ] [Illustration: FIG. 94.—Gravity Escapement (Mudge). ] We will now describe the more elaborate forms of escapement, and we will take first the gravity escapement, as it is called. The principle of its action consists in there being a small impulse given to the pendulum at each oscillation, by means of two small rods hanging, one on each side of it, and tending by their own weight to force the pendulum into a vertical position; these rods are alternately pushed outwards by the escapement before the pendulum in its swing arrives at them, and then they are allowed to press against it on its return towards the vertical, so that the pendulum has a constant force acting on it at each oscillation, unconnected with the clock movement. This is carried out in the escapement invented by Mudge, as shown in Fig. 94. The pendulum rod is supposed to be hanging just in front of the rods hanging from the pivots Y_{1} Y_{2}, and on swinging it presses against the pins at the lower ends of the rods and so lifts the pallets S_{1} S_{2} out of the teeth of the escape wheel. In the position shown the pendulum is moving to the right, having been gently urged from the left by the weight of the pallet rod Y_{2} S_{2}, and the pallet S_{1} has been lifted outwards by the tooth acting on its inclined surface. On the pendulum rod reaching the pin the rod is moved outwards and the end of the pallet S_{1} pushed out of the tooth when the wheel moves on, at the same time pushing outwards the pallet S_{2}. As the pendulum returns towards the left again the rod Y_{1} follows it, giving it a gentle impulse by its own weight until it returns nearly to the vertical or to the corresponding position in which Y_{2} S_{2} is shown. On the pendulum swinging on and releasing T_{2} the pallet S_{1} is again pushed outwards by the inclined plane to the position shown in the diagram. In this escapement there was danger of the pallets being thrown too violently outwards so that the teeth were not caught by the flat surfaces at the ends, and Mr. Bloxam improved on it by letting the pallets be thrown outwards by a small wheel on the axis of the escape wheel so that the action was less rapid; he accomplished this in the following manner. On the end of the axis of the last wheel are a number of arms A A, Fig. 95, say nine, about 1½ inches long, which are prevented from revolving by studs L_{1} L_{2} on the inside of each hanging rod P_{1} P_{2}; then, as each rod is pushed outwards by the pendulum, an arm escapes from a stud and the clock goes on one second. Each rod is pushed outwards by the clock almost sufficiently far for the arm to escape, but not quite, so that the pendulum just releases the arm at the end of its swing in the same manner as in Mudge’s escapement, Fig. 94; but instead of the teeth of the escape wheel pushing the rods outwards there is the small wheel T_{1} T_{2}, having the same number of