Time Telling through the Ages. Harry Brearley

Чтение книги онлайн.

СКАЧАТЬ although this story may not be true, the things that he is known to have done are extraordinary.

      Archimedes and his knowledge had long passed away when the monastery clocks of the eleventh century began to sound the hour. These were the fruit of a crude new civilization just struggling for expression, and represented the general period when William the Conqueror led his Norman army into England.

      CHAPTER SEVEN

      The Modern Clock and Its Creators

      We learn that toward the close of the thirteenth century a clock was set up in St. Paul's Cathedral in London (1286); one in Westminster, by 1288; and one in Canterbury Cathedral, by 1292. The Westminster clock and the chime of bells were put up from funds raised by a fine imposed on a chief justice who had offended the government. The clock bore as an inscription the words of Virgil: "Discite justitiam moniti," "Learn justice from my advice," and the bells were gambled away by Henry VIII! In the same century, Dante, whose wonderful poem the Commedia, (the Inferno, Purgatory and Paradise) is sometimes called the "Swan Song of the Middle Ages," since it marks the passing of the medieval times, spoke of "wheels that wound their circle in an orloge."

      Chaucer speaks of a cock crowing as regularly "as a clock in an abbey orloge." And this shows, curiously, the early meaning of the word, for by the word "clock," Chaucer evidently meant the bell which struck the hour, and, very obviously, he used the word "orloge" to indicate the clock itself.

      Many of these "clocks" had neither dials nor hands. They told time only by striking the hour. Sometimes in the great tower clocks there were placed automatic figures representing men in armor or even mere grotesque figures which, at the right moment, beat upon the bell. These figures were called "jacks o' the clock" or "jacquemarts" and curious specimens of them are still in existence.

      The early abbey clocks did not even strike the hour but rang an alarm to awaken the monks for prayers. Here again, the alarm principle precedes the visible measurement of time; even now, as already noted, we speak of a "clock" by the old word for "bell."

      In the course of the following century – the fourteenth – clocks began to appear which were really worthy of the name, and of these we have authentic details. They were to be found in many lands. One of them was built, in 1344, by Giacomo Dondi at Padua, Italy. Another was constructed in England, in 1340, by Peter Lightfoot, a monk of Glastonbury. And in 1364, Henry de Wieck, De Wyck, or de Vick, of Wurtemburg, was sent for by Charles V, King of France, to come to Paris and build a clock for the tower of the royal palace, which is now the Palais de Justice. It was finished and set up in February 1379, and there it still remains after lapse of five and a half centuries, although its present architectural surroundings were not finished until a much later date.

      This venerable timepiece termed by some chroniclers "the parent of modern timekeepers," was still performing its duty as late as 1850. And so it is a matter of interesting record that its mechanism, which served to measure the passage of time in the days when the earth was generally believed to be flat and when the Eastern Division of the Roman Empire was still ruled from Byzantium, now Constantinople, has served the same purpose within the possible memory of men now living. Its bell has one grim association – it gave the signal for that frightful piece of Medicean treachery, the Massacre of St. Bartholomew, planned by Catherine de Medici, the mother of the King Charles IX, when the armed retainers of the crown of France flung themselves upon the unsuspecting Huguenots and caused the streets to run red with the blood of men, women and children – a ghastly butchery of thousands of people.

      As we have seen, de Vick's clock was neither the earliest made, nor among the earliest; nor, probably, did it embody any at that time new mechanical invention. It does, however, fairly and clearly typify the oldest style of clock of which we to-day have any accurate knowledge. Compare its description, then, with the clock upon your shelf.

      We think of the tall-cased "grandfather's clocks" as antique; but this tower-clock of de Vick's outdoes them in antiquity by some four hundred years. And its most interesting feature is its curious likeness in mechanical principle to the clocks of modern times. Like most early clocks, it has only one hand – the hour-hand. Its ponderous movement is of iron, laboriously hand-wrought; the teeth of its wheels and pinions were cut out one by one. It was driven by a weight of five hundred pounds, the cord of which was wound round a drum, or barrel. This barrel carried, at one end, a pinion, meshing with the hour-wheel, which drove the hands; the flange at the other end of the barrel formed the great wheel, or first wheel of the train. This meshed with a pinion on the shaft of the second wheel, and this in turn with a lantern-pinion upon the shaft of the escape-wheel. All of this is, of course, essentially the modern train of gears, only with fewer wheels.

      The escapement is the most important part of the whole mechanism, because it is the part which makes the clock keep time. It is an interrupter, checking the movement almost as soon as, under the urge of the mainspring, it starts forward. The frequency and duration of these interruptions determines the rate of running. Without this, the movement would run down swiftly; with it, the operation stretches over thirty hours, involving 432,000 interruptions.

      De Vick's escapement is shown in the illustration. The escape-wheel was bent into the shape of a shallow pan, so that its toothed edge was at a right angle to the flat part of the wheel. Near it was placed a verge, or rotating shaft, so called from a Latin word meaning "turning around." On this verge were fastened two flat projections called pallets, diverging from each other at about an angle of one hundred degrees. The width between the pallets, from center to center of each, was equal to the diameter of the wheel, so that one would mesh with the teeth at the top of the escape-wheel and the other with the teeth at the bottom.

      de Vick's Clock

      Now, if the upper pallet were between the teeth at the top of the wheel, the pressure of the wheel trying to turn would push it away until the teeth were set free. But, in so doing, it would cause the verge to turn and bring the lower pallet between the teeth at the bottom of the wheel. And since the bottom of the wheel was, of course, traveling in the opposite direction from the top, the action would be reversed, and the lower pallet would be pushed away, bringing the upper one back between the teeth of the wheel again; and so on, "tick-tock," the wheel moving a little way each time, and the pallets alternately catching and holding it from going too far.

      The device was kept running slowly by means of a cross-bar called a "foliot," fastened across the top of the verge in the shape of a T, and having weights on its two ends. When this weighted bar was set turning in one direction, it would, of course, resist being suddenly stopped and started turning the other way, as it was constantly made to do. And this furnished the regulating action which retarded the motion of the works and kept them from running down.

      This involves the principle of the modern balance-wheel in both watches and clocks, which is that of inertia; the rim of the balance-wheel represents the weights on the bar that resist the pull of the pallets. A vital improvement, however, is the interception of the hair spring which gives elasticity to the pull and thus supplies the elements of precision and refinement. The inertia of the balance-wheel is gauged by the weight of the rim and its distance from the center; and the last refinement of regulation of the mechanism is produced by moving the tiny screws on the periphery of this wheel outward or inward.

      We shall see later how this old escapement was in principle much like the improved forms in use to-day. It was as quaint and clumsy an affair as the first automobile or the first steam-engine. But, like them, it was a great invention, destined to achieve great results. For it was the means of making a machine keep time. And every clock and watch in use to-day depends for its usefulness upon a similar device. The tick is the first thing we think of in connection with a clock; and it is the most essential thing also, because it is the escapement which does the ticking.

СКАЧАТЬ