From the evidence adduced respecting the origin and inventors of the clock it is not unreasonable to conclude with Ferdinand Berthoud (a Frenchman who wrote much and was a great authority upon the subject) that such a clock as that which was constructed by Henry de Wyck for Charles the Wise of France, was not the invention of one man, but was the result of a series of inventions made at different times by various persons, each of which is worthy to be considered a separate invention. It was the simple employment of the natural force of gravity as to the fall of bodies in free space, that paved the way to the extreme accuracy and constancy of rate which belong to the clocks of modern times, and the conclusion to which Mons. Berthoud arrived respecting the progression of the essential improvements is thus stated:-- 1. Toothed wheel-work was known in ancient times, and particularly to Archimedes, whose instrument was provided with a maintaining power, but had no regulator or controlling mechanism. 2. The weight applied as a maintainer at first had a fly, most probably similar to that of a kitchen-jack. 3. The ratchet-wheel and click for winding up the weight, without detaching the teeth of the great wheel. 4. The regulation of the fly depending upon the state of the air, it was abandoned, and a balance substituted. 5. An escapement next became indispensable, as constituting with the balance a more regular check than a fly upon the tendency which a falling weight has to accelerate its velocity. 6. The application of a dial-plate and hand to indicate the hours was a consequence of the regularity introduced into the going part. 7. The striking portion, to proclaim at a distance, without the aid of a watcher, the hour that was indicated: and this was followed by the alarum. 8. The reduction and accommodation of all this bulky machinery to a portable and compact size, as in watches.