Mechanics: a machine with pulleys and calibrated dials. Engraving by A. Bell.

Fig. 125 shows George Atwood's apparatus. "Atwood's reputation spread beyond his university [Cambridge], principally because of his design of a pulley machine to demonstrate motions of bodies under constant forces. Built by the London instrument maker George Adams the younger, it consisted of a 6 foot column carrying conical pivots for two pairs of brass wheel-bearings to minimize friction at a brass pulley. On the pulley ran a long silk cord, at each end of which was a stack of weights. Fitted to the column was a pendulum clock, and set behind the cord was a rule with movable stops, one to terminate the weights' fall, the other to remove weights instantaneously from the stack as it fell. Demonstrations showed the proportionality of impressed force and change of motion, the innate passivity of matter, and the behaviour of bodies in collision." (Oxford dictionary of national biography)