Watches are made to measure time. If anything is to be measured there must be some standard with which to compare it, for we have seen that measuring is a process of comparing a thing with an appropriate or acknowledged and fixed standard. The only known standard for the measurement of time is the movement of the earth in relation to the stars. It has taken thousands of years for mankind to learn what is now known concerning time. It has also taken hundreds of years to secure the wonderful accuracy in the measuring of time which has now been attained. We have said that nothing has been devised which will equal the accuracy of a "pendulum clock." A story was told of a professor of a theological seminary who was one day on his way to a jeweler's store, carrying in his arms the family clock, which was in need of repairs. He was accosted by one of his students with the question, "Look here, Professor, don't you think it would be much more convenient to carry a watch?" A pendulum clock must of necessity be stationary, but it is now needful that people should be able to have a timepiece whenever and wherever wanted. This need is supplied by the pocket watch.

View of Escapement Making Department.

If Galileo watched the swinging of the big chandelier long enough he found that the distance through which it swung was gradually diminishing, till, at last, it ceased to move; what stopped it? It was one of the great forces of nature, which we call gravitation, and the force which kept it in motion we call momentum. But gravitation overcame momentum.

In order to maintain the constant vibration of a pendulum it is needful to impart to it a slight force, in a manner similar to that given by a boy who gives another boy a slight "push," to maintain his movement in a swing. A suspended pendulum being impossible of application to a pocket watch, a splendid substitute has been devised - in the form of the balance wheel of the watch, commonly called the "balance." The balance is, in its action and adaption, the equivalent of the vibrating, or oscillating, pendulum; and the balance spring (commonly called the hairspring), which accompanies it, is in its action equivalent to the force of gravity in its effect upon a pendulum. For the tendency and (if not neutralized by some other force) the effects of the hairspring upon the watch balance, and of gravitation on the pendulum, are to hold each at a position of rest, and consequent inaction.

Time Train of a Watch.

A- B- Assembled..

Main Wheel and Barel Asseembled..

MAIN WHEEL, A-W-W-Co.

But we have in a pocket watch a "mainspring" to actuate the train of gear wheels which by their ultimate action give the delicate "push" to the balance wheel at distinct intervals, and so keep the balance in continued motion. In the same manner, the "weight" of a clock, acting through the force of gravity, carries the various wheels of the clock train, and gives the slight impulse to the swinging clock pendulum.

Both clocks and watches are "machines" for the measurement of time, and, therefore, it is absolutely imperative that their action must be constant, and, if accurate time is to be indicated, the action must be uniform.

The illustration shows the "time train" of an ordinary pocket watch. The various wheels are here shown in a straight line, so that their successive order may be seen, but for economy and convenience they are arranged in such way as is most convenient when constructing a pocket watch. The large wheel at the left is the "main wheel," called by watchmakers the "barrel." In it is coiled the mainspring - a strip of steel about twenty-three inches long, which is carefully tempered to insure elasticity and "pull." The outer end of the mainspring is attached to the rim of the barrel, and the inner end to the barrel arbor. Bear in mind the fact that the power which is sufficient to run the watch for thirty-six hours or more, is not in the watch itself. It is in yourself, and by the exertion of your thumb and finger, in the act of winding, you transfer that power to the spring, and thereby store the power in the barrel, to be given out at the rate which the governing mechanism of the watch will permit. The group of wheels here shown are known as the "time train," and the second wheel is called the "center," because that, in ordinarily constructed watches, is located in the center of the group, and upon its axis are put the "hour hand" and the "minute hand." On the circumference of the barrel are gear teeth, and those teeth engage corresponding teeth on the arbor of the center. These arbor teeth are in all cases called, not "wheels" but "pinions," and in watch trains the wheels always drive the pinions. Next to the center comes the third pinion and wheel, and then the fourth, which is the last wheel in the train which has regular gear teeth. Now let us look back a little and see that the wheel teeth of the barrel drive the center pinion, and the center wheel drives the third pinion and the third wheel drives the fourth pinion, etc. The speed of revolution of the successive wheels increases rapidly. The center wheel must revolve once in each hour, which is 6 1/2 times faster than the barrel. The third wheel turns eight times faster than the center, and the fourth wheel turns 7 1/2 times faster than the third, or 60 times faster than the center, so that the fourth pinion, which carries the "second hand," will revolve 60 times while the "center," which carries the minute hand, revolves once. If we should put all the wheels and pinions in place, and wind up the main spring, the wheels would begin to turn, each at its relative rate of speed, and we should find that, instead of running thirty-six hours, it would have run less than two minutes. What was needed was some device to serve as an accurate speed governor - and the attainment of this essential device is the one thing on which accurate time measuring depends. Without any mention of the various attempts to produce such a device, let us, as briefly as possible, describe the means used in most watches of American manufacture. While there are several distinct parts of this device, each having its individual function, they may be considered as a whole under the general term of "the escapement." Returning now to the fourth pinion, we see that it also carries a wheel, which engages another little pinion, called the escape pinion. This escape pinion also carries a wheel, but it is radically different in appearance, as well as in action, from any of the previously mentioned wheels. An examination of the "escape wheel" would show that it has a peculiarly shaped piece, which is called the "pallet," the extended arm of which is called the "fork" The fork encloses a sort of half-round stud or pin. This stud projects from the fact and near the edge of a small steel disc. The stud is formed from some hard precious stone and is called the "jewel pin," or "roller pin," and the little steel disc which carries it is called the "roller." In the center or axial hole of the roller fits the "balance staff," which staff also carries the "balance wheel," and the balance spring, commonly called the "hair spring." The ends of the balance staff are made very small so as to form very delicate pivots which turn in jewel bearings. The balance wheel moves very rapidly, and, therefore, its movement must be as free as possible from retarding friction, so its bearing pivots are made very small.