The Moon's gravitational torque on the ocean tide has been computed on the basis of Dietrich's cotidal charts. The result is -4.5 × 1023 dynes cm as compared to Heiskanen's (1921) value of -2.9 × 1023 dynes cm based on Sterneck's (1920) charts. Both values are subject to great uncertainty. The observed deceleration of the Moon implies a torque of (-3.9 ± 1.0) × 1023 dyne cm, which is consistent with both foregoing calculations. It is concluded that the deceleration of the Moon's orbital motion and the associated deceleration of the Earth's rotation may be due to oceanic tidal dissipation....