Two mechanisms have been devised by clockmakers to enable striking clocks to correctly count out the hours.
The earlier, which appeared in the first striking clocks in the 14th century, is called countwheel striking. This uses a wheel that contains notches on its side, spaced by unequal, increasing arc segments. This wheel governs the rotation of the striking train. In the late seventeenth century, rack striking was invented. Rack striking is so called because it is regulated by a rack and snailmechanism. The distance a rack is allowed to fall is determined by a snail-shaped cam, thereby regulating the number of times the bell is allowed to sound.
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