It is not proposed in the series of articles to follow, to discuss the early history of clocks. Reid and Dennison have written enough to convince the most skeptical that the clock is an old invention. It is not important to us who invented the pendulum, or this or that escapement, but who makes the best pendulum, the best escapement, the most perfect train of wheels and pinions. These are vital points, and we shall endeavor to give them that attention that their importance demands. It is proper to state here that any assertion made, or rule given, has been tested, and is the result merely of our experience, and we do not claim that it is all there is of the subject; for we are aware that the experience of others may have led to results entirely different; but if all clock-makers will avail themselves of the columns of this journal, we shall not only become better acquainted by an exchange of ideas, but better clock-makers. The subject of wheels and pinions is of the greatest importance in clock-making, and the utmost care and skill are required to execute a train which shall not only run with as little friction as possible, but the friction must be equal; for if there is no variation in the train force, the escapement and pendulum will always be actuated by the same amount of power, and the performance of the clock can be relied upon. Clock text-books do not fully impress this subject. We find a great deal upon this or that escapement, and the different pendulums. Dennison has a couple of pages full of abstruse calculations upon a method of shifting an extra weight upon a rod, so that the going of a clock can be varied one second per day; but if his wheels and pinions are not perfect, a large tooth here and there will vary the clock more than that. Reid overawes us with his knowledge of the proper curves of the teeth of wheels; but it must have been only theory, for his practice was to saw his teeth, and his cycloids, epicycloids, and hypocycloids were left to the mercy of the “topping file” in the hands of his “wheel teeth finishers,” instead of shaping up the teeth in the engine, as is done now. We have generally cut the wheels of fine clocks over several times with different cutters before taking them from the engine; the last cutter having but one tooth, which can be made perfect as to cut and shape, and, running with great speed, will leave the teeth the proper shape, very smooth, and as true as the dial of the engine. Escape wheels, especially, require great care in cutting, as the teeth for dead-beat escapements are somewhat long and thin; the least inaccuracy is certain to cause trouble. It is absolutely necessary that the dial plate of the cutting engine should be perfectly true, with clean, round holes, and a perfect fitting index point, with a cutter arbor without end play or lateral motion--these are the essentials of a good cutting engine, without which a good clock cannot be made.