It could not have been long after man first became cognizant of his reasoning faculties that he began to take more or less notice of the flight of time. The motion of the sun by day and of the moon and stars by night served to warn him of the recurring periods of light and darkness. By noting the position of these stellar bodies during his lonely vigils, he soon became proficient in roughly dividing up the cycle into sections, which he denominated the hours of the day and of the night. Primitive at first, his methods were simple, his needs few and his time abundant. Increase in numbers, multiplicity of duties, and division of occupation began to make it imperative that a more systematic following of these occupations should be instituted, and with this end in view he contrived, by means of burning lights or by restricting the flowing of water or the falling of weights, to subdivide into convenient intervals and in a tolerably satisfactory manner the periods of light.
These modest means then were the first steps toward the exact subdivisions of time which we now enjoy. Unrest, progress, discontent with things that be, we must acknowledge, have, from the appearance of the first clock to the present hour, been the powers which have driven on the inventive genius of watch and clockmakers to designate some new and more acceptable system for regulating the course of the movement. In consequence of this restless search after the best, a very considerable number of escapements have been invented and made up, both for clocks and watches. Only a few, however, of the almost numberless systems have survived the test of time and been adopted in the manufacture of the timepiece as we know it now. Indeed, many such inventions never passed the experimental stage, and yet it would be very interesting to the professional horologist, the apprentice and even the layman to become more intimately acquainted with the vast variety of inventions made upon this domain since the inception of horological science. Undoubtedly, a complete collection of all the escapements invented would constitute a most instructive work for the progressive watchmaker, and while we are waiting for a competent author to take such an exhaustive work upon his hands, we shall endeavor to open the way and trust that a number of voluntary collaborators will come forward and assist us to the extent of their ability in filling up the chinks.
WATCHES PROBLEMS TO BE SOLVED
The problem to be solved by means of the escapement has always been to govern, within limits precise and perfectly regular, if it be possible, the flow of the motive force; that means the procession of the wheel-work and, as a consequence, of the hands thereto attached. At first blush it seems as if a continually-moving governor, such as is in use on steam engines, for example, ought to fulfil the conditions, and attempts have accordingly been made upon this line with results which have proven entirely unsatisfactory.
Having thoroughly sifted the many varieties at hand, it has been finally determined that the only means known to provide the most regular flow of power consists in intermittently interrupting the procession of the wheel-work, and thereby gaining a periodically uniform movement. Whatever may be the system or kind of escapement employed, the functioning of the mechanism is characterized by the suspension, at regular intervals, of the rotation of the last wheel of the train and in transmitting to a regulator, be it a balance or a pendulum, the power sent into that wheel.
ESCAPEMENT THE MOST ESSENTIAL WATCHES PART
Of all the parts of the timepiece the escapement is then the most essential; it is the part which assures regularity in the running of the watch or clock, and that part of parts that endows the piece with real value. The most perfect escapement would be that one which should perform its duty with the least influence upon the time of oscillation or vibration of the regulating organ. The stoppage of the train by the escapement is brought about in different ways, which may be gathered under three heads or categories. In the two which we shall mention first, the stop is effected directly upon the axis of the regulator, or against a piece which forms a part of that axis; the tooth of the escape wheel at the moment of its disengagement remains supported upon or against that stop.
In the first escapement invented and, indeed, in some actually employed to-day for certain kinds of timekeepers, we notice during the locking a retrograde movement of the escape wheel; to this kind of movement has been given the name of recoil escapement. It was recognized by the fraternity that this recoil was prejudicial to the regularity of the running of the mechanism and, after the invention of the pendulum and the spiral, inventive makers succeeded in replacing this sort of escapement with one which we now call the dead-beat escapement. In this latter the wheel, stopped by the axis of the regulator, remains immovable up to the instant of its disengagement or unlocking.
In the third category have been collected all those forms of escapement wherein the escape wheel is locked by an intermediate piece, independent of the regulating organ. This latter performs its vibrations of oscillation quite without interference, and it is only in contact with the train during the very brief moment of impulse which is needful to keep the regulating organ in motion. This category constitutes what is known as the detached escapement class.
Of the recoil escapement the principal types are: the verge escapement or crown-wheel escapement for both watches and clocks, and the recoil anchor escapement for clocks. The cylinder and duplex escapements for watches and the Graham anchor escapement for clocks are styles of the dead-beat escapement most often employed. Among the detached escapements we have the lever and detent or chronometer escapements for watches; for clocks there is no fixed type of detached lever and it finds no application to-day.