All time measurements, whether by differential or integrative methods, originally required the attention of a watchman. The need for such attention only ceased when, besides automatic means of maintaining any artificial process involved in the measurement itself, automatic means of differentiation and/or integration had been developed. Automatic time measurement by a method combining differentiation and integration of time in a single mechanism was employed in early Chinese waterwheel clocks. Other methods of automatic differentiation were those of the Chinese and Arab water clocks in which an anaphoric-dial mechanism of the Greek type was made, by an axle-and-string arrangement, periodically to operate visible time signals and to release metal balls to operate audible signals. Automatic integration followed in some Chinese examples in which the metal balls also operated carousel jackwork. The Chinese waterwheel clocks also provided continuous integration of time over intervals longer than that required for a single rotation of the water wheel, by toothed wheelwork. With the development of weight-driven mechanical clocks, such wheelwork gradually came into general European use, but it is now being superceded by digital electronic integration in electronic clocks.