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. [Illustration: A DEVICE FOR THE GOVERNING OF SPEED IS THE ONE THING ON WHICH ACCURATE TIME MEASURING DEPENDS] [Illustration: _WALTHAM TAPER SHOULDER DETACHABLE BALANCE STAFF._]