Clocks
Marshall McLuhan

It was about 1300 A. D. that the step was taken of momentarily interrupting rotary movement by a crown rod and balance wheel. This function was called "escapement" and was the means of literally translating the continuous force of the wheel into the visual principle of uniform but segmented succession.

Escapement introduced the reciprocal reversing action of the hands in rotating a spindle forward and backward. The meeting in the mechanical clock of this ancient extension of hand movement with the forward rotary motion of the wheel was, in effect, the translation of hands into feet, and feet into hands.

--- Understanding Media