Читать книгу Captains of Industry; or, Men of Business Who Did Something Besides Making Money - James Parton - Страница 17

It is supposed that the oldest clock in existence is one in the ancient castle of Dover, on the southern coast of England, bearing the date, 1348. It has been running, therefore, five hundred and thirty-six years. Other clocks of the same century exist in various parts of Europe, the works of which have but one hand, which points the hour, and require winding every twenty-four hours. From the fact of so many large clocks of that period having been preserved in whole or in part, it is highly probable that the clock was then an old invention.

But how did people measure time during the countless ages that rolled away before the invention of the clock? The first time-measurer was probably a post stuck in the ground, the shadow of which, varying in length and direction, indicated the time of day, whenever the sun was not obscured by clouds. The sun-dial, which was an improvement upon this, was known to the ancient Jews and Greeks. The ancient Chinese and Egyptians possessed an instrument called the Clepsydra (water-stealer), which was merely a vessel full of water with a small hole in the bottom by which the water slowly escaped. There were marks in the inside of the vessel which showed the hour. An improvement upon this was made about two hundred and thirty-five years before Christ by an Egyptian, who caused the escaping water to turn a system of wheels; and the motion was communicated to a rod which pointed to the hours upon a circle resembling a clock-face. Similar clocks were made in which sand was used instead of water. The hour-glass was a time-measurer for many centuries in Europe, and all the ancient literatures abound in allusions to the rapid, unobserved, running away of its sands.

The next advance was the invention of the wheel-and-weight-clock, such as has been in use ever since. The first instrument of this kind may have been made by the ancients; but no clear allusion to its existence has been discovered earlier than 996, when Pope Sylvester II. is known to have had one constructed. It was Christian Huygens, the famous Dutch philosopher, who applied, in 1658, the pendulum to the clock, and thus led directly to those more refined and subtle improvements, which render our present clocks and watches among the least imperfect of all human contrivances.

George Graham, the great London clock-maker of Queen Anne's and George the First's time, and one of the most noted improvers of the clock, was born in 1675. After spending the first thirteen years of his life in a village in the North of England, he made his way to London, an intelligent and well-bred Quaker boy; and there he was so fortunate as to be taken as an apprentice by Tompion, then the most celebrated clock-maker in England, whose name is still to be seen upon ancient watches and clocks. Tompion was a most exquisite mechanic, proud of his work and jealous of his name. He is the Tompion who figured in Farquhar's play of "The Inconstant;" and Prior mentions him in his "Essay on Learning," where he says that Tompion on a watch or clock was proof positive of its excellence. A person once brought him a watch to repair, upon which his name had been fraudulently engraved. He took up a hammer and smashed it, and then selecting one of his own watches, gave it to the astonished customer, saying: "Sir, here is a watch of my making."

Graham was worthy to be the apprentice of such a master, for he not only showed intelligence, skill, and fidelity, but a happy turn for invention. Tompion became warmly attached to him, treated him as a son, gave him the full benefit of his skill and knowledge, took him into partnership, and finally left him sole possessor of the business. For nearly half a century George Graham, Clock-maker, was one of the best known signs in Fleet Street, and the instruments made in his shop were valued in all the principal countries of Europe. The great clock at Greenwich Observatory, made by him one hundred and fifty years ago, is still in use and could hardly now be surpassed in substantial excellence. The mural arch in the same establishment, used for the testing of quadrants and other marine instruments, was also his work. When the French government sent Maupertuis within the polar circle, to ascertain the exact figure of the earth, it was George Graham, Clock-maker of Fleet Street, who supplied the requisite instruments.

But it was not his excellence as a mechanic that causes his name to be remembered at the present time. He made two capital inventions in clock-machinery which are still universally used, and will probably never be superseded. It was a common complaint among clock-makers, when he was a young man, that the pendulum varied in length according to the temperature, and consequently caused the clock to go too slowly in hot weather, and too fast in cold. Thus, if a clock went correctly at a temperature of sixty degrees, it would lose three seconds a day if the temperature rose to seventy, and three more seconds a day for every additional ten degrees of heat. Graham first endeavored to rectify this inconvenience by making the pendulum of several different kinds of metal, which was a partial remedy. But the invention by which he overcame the difficulty completely, consisted in employing a column of mercury as the "bob" of the pendulum. The hot weather, which lengthened the steel rods, raised the column of mercury, and so brought the centre of oscillation higher. If the column of mercury was of the right length, the lengthening or the shortening of the pendulum was exactly counterbalanced, and the variation of the clock, through changes of the temperature, almost annihilated.

This was a truly exquisite invention. The clock he himself made on this plan for Greenwich, after being in use a century and a half, requires attention not oftener than once in fifteen months. Some important discoveries in astronomy are due to the exactness with which Graham's clock measures time. He also invented what is called the "dead escapement," still used, I believe, in all clocks and watches, from the commonest five-dollar watch to the most elaborate and costly regulator. Another pretty invention of his was a machine for showing the position and motions of the heavenly bodies, which was exceedingly admired by our grandfathers. Lord Orrery having amused himself by copying this machine, a French traveler who saw it complimented the maker by naming it an Orrery, which has led many to suppose it to have been an invention of that lord. It now appears, however, that the true inventor was the Fleet Street clock-maker.

The merits of this admirable mechanic procured for him, while he was still little more than a young man, the honor of being elected a member of the Royal Society, the most illustrious scientific body in the world. And a very worthy member he proved. If the reader will turn to the Transactions of that learned society, he may find in them twenty-one papers contributed by George Graham. He was, however, far from regarding himself as a philosopher, but to the end of his days always styled himself a clock-maker.

They still relate an anecdote showing the confidence he had in his work. A gentleman who bought a watch of him just before departing for India, asked him how far he could depend on its keeping the correct time.

"Sir," replied Graham, "it is a watch which I have made and regulated myself; take it with you wherever you please. If after seven years you come back to see me, and can tell me there has been a difference of five minutes, I will return you your money."

Seven years passed, and the gentleman returned.

"Sir," said he, "I bring you back your watch."

"I remember," said Graham, "our conditions. Let me see the watch. Well, what do you complain of?"

"Why," was the reply, "I have had it seven years, and there is a difference of more than five minutes."

"Indeed!" said Graham. "In that case I return you your money."

"I would not part with my watch," said the gentleman, "for ten times the sum I paid for it."

"And I," rejoined Graham, "would not break my word for any consideration."

He insisted on taking back the watch, which ever after he used as a regulator.

This is a very good story, and is doubtless substantially true; but no watch was ever yet made which has varied as little as five minutes in seven years. Readers may remember that the British government once offered a reward of twenty thousand pounds sterling for the best chronometer, and the prize was awarded to Harrison for a chronometer which varied two minutes in a sailing voyage from England to Jamaica and back.

George Graham died in 1751, aged seventy-six years, universally esteemed as an ornament of his age and country. In Westminster Abbey, among the tombs of poets, philosophers, and statesmen, may be seen the graves of the two clock-makers, master and apprentice, Tompion and Graham.