Exactly: How Precision Engineers Created the Modern World. Simon Winchester

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СКАЧАТЬ of heroic work on five timekeeper designs, would claim the bulk of the prize.

      Harrison’s legacy is much treasured. The curator of the Greenwich Royal Observatory, high on its all-seeing hill above the Maritime Museum to the east of London, comes in each dawn to wind the three great clocks that he and his staff are disposed simply to call “the Harrisons.” He stands on much ceremony to wind them, well aware of the immense historical importance invested in the three timepieces and their one unwound sibling. Each was a prototype of the modern marine chronometer, which, in allowing ships to fix their positions at sea with accuracy, has since saved countless sailors’ lives. (Before the existence of the marine chronometer, before ships’ masters had the ability to determine exactly where they were, vessels tended to collide with importunate frequency into islands and headlands that loomed up unexpectedly before their bows. Indeed, it was the catastrophic collision off the Cornish coast of Admiral Sir Cloudesley Shovell’s squadron of warships in 1707 [which drowned him and two thousand of his sailors] that compelled the British government to think seriously about the means of figuring out longitude—setting up a Board of Longitude and offering prize money—which led, ultimately, to the making of the small family of clocks that are wound each dawn at Greenwich.)

      There were other reasons for the vast importance of the Harrisons. By allowing ships to know their positions and plot their voyages with efficiency, accuracy, and precision, these clocks and their successors enabled the making of untold trading fortunes. And though it may no longer be wholly respectable to say so, the fact that the Harrison clocks were British-invented and their successor clocks firstly British-made allowed Britain in the heyday of her empire to become for more than a century the undisputed ruler of all the world’s oceans and seas. Precise-running clockwork made for precise navigation; precise navigation made for maritime knowledge, control, and power.

      And so the curator pulls on his white curatorial gloves and, using in each case a unique double set of brass keys, unlocks the tall glass-sided cabinets in which the great timekeepers stand. Each of the three is on near-permanent loan from Britain’s Ministry of Defence. The earliest made, finished in 1735 and known these days as H1, the curator can wind with a single strong downward pull on a chain made of brass links. The later pair, the midcentury H2 and H3, require simply a swift turn of a key.

      The final device, the magnificent H4 “sea watch” with which Harrison eventually won his prize money, remains unwound and silent. Housed in a five-inch-diameter silver case that makes it look rather like an enlarged and biscuit-thick version of grandfather’s pocket watch, it requires lubrication and, if it runs, will become less precise with time as the oil thickens; it will lose rate, as horologists say. Moreover, if H4 were kept running, only its second hand would be seen to be moving, and so, as spectacle, it would be somewhat uninteresting—and as a trade-off for the inevitable wear and tear of the movement beneath, the sight of a moving second hand made no sense. So the decision of the observatory principals over the years has been to keep this one masterpiece in its quasi-virgin state, much like the unplayed Stradivarius violin at the Ashmolean Museum in Oxford,^* as an untouched testament to its maker’s art.

      And what sublime pieces of mechanical art John Harrison made! By the time he decided to throw his hat in the ring for the longitude prize, he had already constructed a number of fine and highly accurate timekeepers—most of them pendulum clocks for use on land, many of them long-case clocks, each one more refined than the last. Harrison’s skills lay in the imaginative improvement of his timekeepers, rather than in the decorative embellishment that many of his eighteenth-century contemporaries were known for.

      He was fascinated, for instance, with the problem of friction, and in a radical departure from the norm, he made all his early clocks with wooden gearwheels, which needed none of the lubricant oils of the day, oils that became notoriously more viscous with age and had the trying effect of slowing down most clockwork movements. To solve this problem, he made all his gear trains first of boxwood and then of the dense, nonfloating Caribbean hardwood Lignum vitae, combined in both cases with pivots made of brass. He also designed an extraordinary escapement mechanism, the ticking heart of the clock, that had no sliding parts (and hence no friction, either) and that is still known as a grasshopper escapement because one of the components jumps out of engagement with the escape wheel, just as a grasshopper jumps suddenly out of the grass.

      A portable precision clock designed for use on a rolling ship cannot easily use a long gravity-driven pendulum, however, and the first three timepieces Harrison designed for the contest were powered by systems of weights that look very different from the heavy plumb bobs that hang in a conventional long-case clock. They are instead brass bar balances that look like a pair of dumbbells, both placed vertically on the outer edges of the mechanism and its wheel trains, and connected at their tops and bottoms by pairs of springs, which provide the mechanism with a form of artificial gravity, as Harrison wrote. These springs allow the two balance beams to swing back and forth, back and forth, nodding toward and away from each other endlessly (provided that the white-gloved curator, successor on land to the ship’s master at sea, winds the mechanism daily) as the clock ticks on.

      H1, H2, and H3, each clock a subtle improvement upon its predecessor, each the work of years of patient experimentation—H3 took Harrison fully nineteen years to build—employ essentially the same bar balance principle, and when they are working, they are machines of an astonishing, hypnotic beauty and seemingly bewildering complexity. Many of the improvements that this former carpenter and viola player, bell tuner and choirmaster—for eighteenth-century polymaths were polymaths indeed—included in each have gone on to become essential components of modern precision machinery: Harrison created the encaged roller bearing, for example, which became the predecessor to the ball bearing and led to the founding of huge modern corporations such as Timken and SKF. And the bimetallic strip, invented solely by Harrison in an attempt to compensate for changes in temperature in his H3 timekeeper, is still employed in scores of mundane essentials: in thermostats, toasters, electric kettles, and their like.

      As it happened, none of these three fantastical contraptions, however beautiful in appearance and revolutionary in design they may have been, turned out to be a success. Each was taken to a ship and used by the crew as timekeeper, and each time, though the timekeeper offered an improvement on surmising the ships’ various positions, the accuracy of the vessel’s clock-derived longitude was wildly at variance from what the Board of Longitude demanded—and so no prize was awarded. Harrison’s genius and determination were recognized, though, and hefty grants continued to come his way in the hope that he would, in time, make a horological breakthrough. And this he did, at last, when between the four years from 1755 until 1759 he made not another clock, but a watch, a watch that has been known, since it was cleaned and restored in the 1930s, simply as H4.^*

      The watch was a technical triumph in every sense. After thirty-one years of near-obsessive work, Harrison managed to squeeze almost all the improvements he had engineered in his large pendulum clocks into this single five-inch silver case, and add some others, to make certain that his timekeeper was as close to chronological infallibility as was humanly possible.

      In place of the oscillating beam balances that made the magic madness of his large clocks so spectacular to see, he substituted a temperature-controlled spiral mainspring, together with a fast-beating balance wheel that spun back and forth at the hitherto unprecedented rate of some eighteen thousand times an hour. He also had an automatic remontoir, so-called, which rewound the mainspring eight times a minute, keeping the tension constant, the beats unvarying. There was a downside, though: this watch needed oiling, and so, in an effort to reduce friction and keep the needed application of oil to a minimum, Harrison introduced, where possible, bearings made of diamond, one of the early instances of a jeweled escapement.

      It remains a mystery just how, without the use of precision machine tools—the development of which will be central to the story that follows—Harrison was able to accomplish all this. Certainly, all those who have made copies of H4 and its successor, K1 (which was used on all Captain James Cook’s voyages), СКАЧАТЬ