The most ancient clocks differed in many respects from those now in use. Clocks of the earlier period had, as we have said, instead of the pendulum now in use, a _balance_, vibrating on the top of the clock, as the regulating medium. The escapement was of the verge construction, a sketch of which will be seen below, which represents a clock of a most ancient character. +----------------------------------------------------------------------+ | [Illustration: Old Balance-Clock.] | +----------------------------------------------------------------------+ Without entering into any very minute detail of the manner in which motion in a clock is successively communicated from one toothed wheel (G or R) or pinion (_e_ or _g_) to another, which, indeed, would only tend to perplex the mind of the general reader, it will be sufficient to state the following. S is a square piece of steel fixed to and forming part of the pinion P. In winding the clock the key is placed upon this square, and being turned round continuously in one direction, the pinion P turns with it. This communicates its motion to the wheel R, which is fixed to the cylinder B, and which in its revolution coils or winds up the cord to which is attached the weight A. While this takes place the wheel G is held in check by another wheel, called the 'ratchet,' and a click (neither of which is seen in the sketch), but when the operation of the winding is completed, and the weight A begins to descend, the cylinder B, together with the wheel G, turn on their common pivots V, V, and the motion is thus communicated from wheel to pinion until it reaches the escapement-wheel I. The teeth of this wheel, in its revolution, act alternately on the pallets _i_, _h_, which project from and form part of the spindle or verge K, M, and thus produce a vibratory or backward and forward motion of the balance L, L. Were it not for this detention, the duration of which is much increased by the swing of the balance, the weight A would descend with gradually accelerated speed, till, in a few moments, the cord would be entirely unwound from the cylinder, and the clock be at rest. +----------------------------------------------------------------------+ | [Illustration: Clock Spring.] | +----------------------------------------------------------------------+