Longitude

by Dava Sobel

  The Board of Longitude slapped Mudge’s wrist. The commissioners were not overly upset by his indiscretion, and besides, they had a few other matters to oversee, in addition to the Harrison affair. Notable among these was the petition from the Reverend Mr. Maskelyne, who wanted to begin annual publication of the nautical ephemerides for seamen interested in finding longitude by lunars. By incorporating a wealth of prefigured data, he would reduce the number of arithmetical calculations the individual navigator had to make, and thereby dramatically shorten the time required to arrive at a position—from four hours to about thirty minutes. The astronomer royal declared himself more than willing to undertake responsibility for the work. All he needed from the board, as official publisher, was the funding to pay salaries for a pair of human computers who could hash out the mathematics, plus the printer’s fees.

  Maskelyne produced the first volume of the Nautical Almanac and Astronomical Ephemeris in 1766, and went on supervising it until his dying day. Even after his death, in 1811, seamen continued relying on his work for an additional few years, since the 1811 edition contained predictions straight through to 1815. Then others took over the legacy, continuing the publication of the lunar tables until 1907, and of the Almanac itself up to the present time.

  The Almanac represents Maskelyne’s enduring contribution to navigation—and the perfect task for him, too, as it embodied an abundance of excruciating detail: He included twelve full pages of data for each month, abbreviated and in fine print, with the moon’s position calculated every three hours vis-à-vis the sun or the ten guide stars. Everyone agreed, the Almanac and its companion volume, the Tables Requisite, provided the surest way for mariners to fix their positions at sea.

  In April of 1766, after Harrison’s portrait was completed, the board dealt him another blow that might well have changed his mien.

  In order to put to rest all lingering doubts that H-4’s accuracy might be chalked up to chance or luck, the board decided to subject the timekeeper to a new sort of trial, even more rigorous than the two voyages. To this end, the timekeeper was to be moved from the Admiralty to the Royal Observatory, where, for a period of ten months, it would undergo daily tests performed, in his official capacity, by the astronomer royal, Nevil Maskelyne. Also the large longitude machines (the three sea clocks) were to be consigned to Greenwich, and have their going rates compared with that of the big regulator clock at the Observatory.

  Imagine Harrison’s reaction when he learned that his treasure, H-4, having languished many months in a lonely tower at the Admiralty, had been delivered into the hands of his archenemy. Within days of this shock, he heard a knock at his door, and opened it to find Maskelyne, unannounced, carrying a warrant for the arrest of the sea clocks.

  “Mr. John Harrison,” this missive begins, “We the . . . Commissioners appointed by the Acts of Parliament for the discovery of the Longitude at Sea, do hereby require you to deliver up to the Rev. Nevil Maskelyne, Astronomer Royal at Greenwich, the three several Machines or Timekeepers, now remaining in your hands, which are become the property of the public.”

  Cornered, Harrison led Maskelyne into the room where he kept the clocks, which had been his close companions for thirty years. They were all running, each in its own characteristic way, like a gathering of old friends in animated conversation. Little did they care that time had rendered them obsolete. They chattered on among themselves, oblivious to the world at large, lovingly cared for in this cozy place.

  Before parting with his sea clocks, Harrison wanted Maskelyne to grant him one concession—to sign a written statement that the timekeepers were in perfect order when he found them under Harrison’s roof. Maskelyne argued, then acceded that they were by all appearances in perfect order, and affixed his signature. Anger escalated on both sides, so that when Maskelyne asked Harrison how to transport the timekeepers (i.e., should they be moved as is, or partly dismantled), Harrison sulked and intimated that any advice he gave would surely be used against him in the event of some mishap. At length he offered that H-3 might go as it was, but that H-1 and H-2 needed to be taken apart a bit. He could not watch this ignominy, however, and went upstairs to be alone in his private room. From there, he heard the crash on the ground floor. Maskelyne’s workers, while carrying H-1 outside to the waiting cart, dropped it. By accident, of course.

  Although H-4 had traveled on a boat, accompanied by Larcum Kendall, down the Thames to Greenwich for its trial, the three large sea clocks rumbled and bumped their way there through the streets of London in an unsprung cart. We need not imagine Harrison’s response. The enamel paste medallion portrait of him in profile by James Tassie, which dates from about 1770, depicts the aging watchmaker’s thin lips decidedly downturned.

  13.

  The Second Voyage of

  Captain James Cook

  When the greatest of England’s bold voyagers perished,

  ‘Twas the ear of a savage that heard his last groans

  And, far from the land where his memory is cherished,

  On a tropical island are scattered his bones:

  [Un]just was the fate that arrested his motion,

  Who with vigour unequalled, unyielding devotion,

  Surveyed every coast, and explained every ocean,

  In frigid, and torrid, and temperate zones.

  —GEORGE B. AIRY (SIXTH ASTRONOMER ROYAL) “Dolcoath”

  Sauerkraut.

  That was the watchword on Captain James a Cook’s triumphant second voyage, which set sail in 1772. By adding generous portions of the German staple to the diet of his English crew (some of whom foolishly turned up their noses at it), the great circumnavigator kicked scurvy overboard. Not only is sauerkraut’s chief ingredient, cabbage, loaded with vitamin C but the fine-cut cabbage must be salted and allowed to ferment until sour to be worthy of the name. Practically pickled in brine, sauerkraut keeps forever aboard ship—or at least as long as the duration of a voyage around the world. Cook made it his oceangoing vegetable, and sauerkraut went on saving sailors’ lives until lemon juice and, later, limes replaced it in the provisions of the Royal Navy.

  With his men properly nourished, Cook had all hands available to carry out scientific experiments and explorations. He also conducted field tests for the Board of Longitude, comparing the lunar distance method, which Cook was mariner enough to master, with several new sea clocks modeled after John Harrison’s marvelous timekeeper.

  “I must here take note,” Cook wrote in his journal of the Resolution’s voyage, “that indeed our error (in Longitude) can never be great, so long as we have so good a guide as [the] watch.”

  Harrison had wanted Cook to take along the original H-4, not a copy or an imitation. He would gladly have gambled the balance of his reward money and let the win or loss of the second £10,000 ride on the Watch’s performance under Cook’s command. But the Board of Longitude said that H-4 would have to stay at home within the kingdom until its status regarding the remainder of the longitude prize had been decided.

  Remarkably enough, H-4, which had sailed through two sea trials, won plaudits from three captains, and even earned a testimonial to its accuracy from the Board of Longitude, had failed its ten-month trial at the Royal Observatory between May 1766 and March 1767. Its going rate had gone erratic, so that it sometimes gained as many as twenty seconds a day. This may have been the unfortunate result of damage from the dismantling of H-4 during the disclosure proceedings. Some say Nevil Maskelyne’s ill will hexed the Watch, or that he handled it roughly during daily winding. Others avow that he intentionally distorted the trial.

  There is something odd about the logic Maskelyne used to gather his damning statistics. He pretended that the timekeeper was making six voyages to the West Indies, each of six weeks’ duration—harking back to the original terms of the Longitude Act of 1714, which was still in effect. Maskelyne made no allowance for the fact that the Watch seemed to have incurred some damage, which showed in the way it now overreacted mercurial
ly to temperature changes, instead of acclimating smoothly and accurately, as had been its hallmark in the past. Regardless, Maskelyne just tallied up its performance statistics on each “voyage,” while H-4 lay bolted to a window seat in the Observatory. Then he translated its gain in time into degrees of longitude, and from there into a distance expressed in nautical miles at the Equator. On its first mock trip, for example, H-4 gained thirteen minutes and twenty seconds, or 3 degrees, 20 minutes of longitude, and so missed the mark by two hundred nautical miles. It did slightly better on the ensuing sallies, and had its best run on the fifth try, when it shot only eighty-five miles wide of its desired landfall, having gained five minutes and forty-seconds, or 1 degree and 25 minutes of longitude. Thus Maskelyne was forced to conclude, “That Mr. Harrison’s watch cannot be depended upon to keep the Longitude within a degree in a West India voyage of six weeks.”

  Previous records proved, however, that Mr. Harrison’s watch had already kept the longitude to within half a degree or better on two actual voyages to the West Indies.

  Yet Maskelyne was saying the Watch could not be trusted to keep track of a ship’s position on a six-week voyage “nor to keep the longitude within half a degree for more than a few days; and perhaps not so long, if the cold be very intense; nevertheless, that it is a useful and valuable invention, and, in conjunction with the observations of the distance of the moon from the sun and fixed stars, may be of considerable advantage to navigation.”

  With these words of faint praise, Maskelyne tactfully conceded a few major flaws in the lunar distance method. To wit: For about six days of every month, the moon is so close to the sun that it disappears from view, and no lunar distance measurements whatever can be made. At such times, H-4 would indeed “be of considerable advantage to navigation.” A timekeeper would also come in quite handy during the thirteen days per month when the moon lights up the night and lies on the other side of the world from the sun. Unable to measure the huge distance between the two big bodies for these two weeks, navigators plotted the moon against the fixed stars. They checked the times of their night observations on an ordinary watch, which might not be accurate enough to make the game worth the candle. With a timekeeper like H-4 aboard, the lunars could be precisely fixed in time and made more dependable. Thus, in his opinion, the timekeeper might enhance the lunar distance method but never supplant it.

  In sum, Maskelyne airily deemed the Watch to be less constant than the stars.

  Harrison issued a hailstorm of objections in a sixpenny booklet published at his own expense—though doubtless with the help of a ghost writer, since the diatribe is written in clear, plain English. One of his claims attacked the men who were supposed to witness Maskelyne’s daily interactions with the Watch. These individuals resided in the nearby Royal Greenwich Hospital, an institution for seamen no longer fit for active duty. Harrison charged that the ex-sailors were too old and wheezy to climb the steep hill up to the Observatory. Even if they had enough breath and limbs to reach the summit, he argued, they dared not gainsay the astronomer royal in any of his actions but just signed their names in the register, seconding whatever Maskelyne wrote.

  What’s more, Harrison complained, H-4 had been situated in direct sunlight. Secured as it was inside a box with a glass cover, the Watch endured the same stifling heat as in a greenhouse. Meanwhile, the thermometer for measuring the timekeeper’s ambient temperature lay on the other side of the room—in the shade.

  Maskelyne felt no compunction to answer any of these allegations. He never spoke to either of the Harrisons again, nor they to him.

  Harrison expected a reunion with H-4 after it had run Maskelyne’s gauntlet. He asked the Board of Longitude if he could have it back. The Board declined. The seventy-four-year-old Harrison had to proceed with the making of his two new watches on the strength of his past experience and memories of H-4. The board gave him, in the way of further guidance, a couple of copies of the book containing Harrison’s own drawings and description, which Maskelyne had recently published, titled The Principles of Mr. Harrison’s Timekeeper with Plates of the Same. The whole intent of this book, after all, was to enable anyone to reconstruct H-4. (In truth, the description, since Harrison wrote it, utterly defied understanding.)

  Seeking proof positive of H-4’s true reproducibility, the board also hired the watchmaker Larcum Kendall to attempt an exact copy. These efforts evince the board’s ferocious pursuit of the spirit of the law as they interpreted it, for the original Longitude Act never stipulated that the “Practicable and Useful” method must be copied by its inventor or anyone else.

  Kendall, a man known to Harrison and respected by him, had been John Jefferys’s apprentice. He may have lent a hand in the construction of the Jefferys pocket watch and even of H-4. He had also served as one of the expert witnesses at the exhaustive six-day “discovery” of H-4. In short, he was the perfect person to produce the replica. Even Harrison thought so.

  Kendall finished his reproduction after two and a half years’ work. Receiving K-1 in January of 1770, the Board of Longitude reconvened the committee that had scrutinized H-4, for these men would be the best judges of how closely the one resembled the other. Accordingly, John Michell, William Ludlam, Thomas Mudge, William Mathews, and John Bird met to examine K-1. Kendall absented himself this time, as was only fitting. His vacant seat on the panel was filled, naturally enough, by William Harrison. The consensus deemed K-1 a dead ringer for H-4—except that it had an even greater abundance of curlicue flourishes engraved on the backplate where Kendall signed his name.

  William Harrison, lavish with his praise, told the board that in some respects Kendall’s workmanship proved superior to his father’s. He must have wished he could eat those words later, when the Board selected K-1 over H-4 to sail the Pacific with Captain Cook.

  The board’s decision had nothing to do with which was the better watch, for it viewed H-4 and K-1 as identical twins. It was just that the board had grounded H-4. So Cook took the K-1 copy on his world tour, along with three cheaper imitations offered by an upstart chronometer maker named John Arnold.

  Harrison, meanwhile, by 1770—despite his ill treatment, advanced age, failing eyesight, and periodic bouts of gout—had finished building the first of the two watches the board had ordered him to make. This timekeeper, now known as H-5, has all the internal complexity of H-4 but assumes an austere outward appearance. No frills adorn its dial. The small brass starburst in the center of the face seems somewhat ornamental, like a tiny flower with eight petals. Actually, it’s a knurled knob that pierces the glass cover on the dial; turning it sets the hands without lifting that glass, and so helps keep dust out of the movement.

  Harrison perhaps intended the star-flower as a subliminal message. Since it recalls the position and shape of a compass rose, it conjures up that other, more ancient instrument, the magnetic compass, that sailors trusted for so long to find their way.

  The backplate of H-5 looks barren and bland compared to the exuberant frippery scrolled over the same part of H-4. Indeed, H-5 is the work of a sadder but wiser man, compelled to do what he had once done willingly, even joyfully. Still, H-5 is a thing of beauty in its simplicity. It now occupies center stage at the Clockmakers’ Museum in Guildhall, London, literally in the very middle of the room, where it rests on the frayed, red satin cushion inside its original wooden box.

  Having built this watch in three years, Harrison tested and adjusted it for another two. By the time it pleased him, he was seventy-nine. He did not see how he could now start another project of equal proportions. Even if he were able to complete the work, the official trials might extend into the next decade, though his life surely could not. This sense of being backed against the wall, without hope of justice, emboldened him to tell his troubles to the King.

  His Majesty King George III took an active interest in science, and had followed the trials of H-4. He had even granted John and William Harrison an audience when H-4 returned from its first
voyage to Jamaica. More recently, King George had opened a private observatory at Richmond, just in time to view the 1769 transit of Venus.

  In January 1772, William wrote the king a poignant letter covering the history of his father’s hardships with the Board of Longitude and the Royal Observatory. William asked politely, beseechingly, if the new Watch (H-5) might “be lodged for a certain time in the Observatory at Richmond, in order to ascertain and manifest its degree of excellence.”

  The king then interviewed William at length at Windsor Castle. In a later account of this pivotal meeting, written in 1835 by William’s son, John, the king is reported to have muttered under his breath, “These people have been cruelly treated.” Aloud he promised William, “By God, Harrison, I will see you righted!”

  True to his word, George III turned H-5 over to his private science tutor and Observatory director, S. C. T. Demainbray, for a six-week indoor trial, reminiscent of Maskelyne’s modus operandi. As in previous sea and land trials, H-5’s box was locked and three keys distributed among the three principals: one for Dr. Demainbray, one for William, and one for King George. The men met each day at noon in the observatory to check the watch against the regulator clock and then rewind it.

  The watch, despite this reverential treatment, behaved badly at first. It gained and lost with abandon, crushing the Harrisons with embarrassment. Then the King recalled that he’d stored a few lodestones in a closet near the watch station, and he himself rushed to retrieve them. Freed from the stones’ strange attraction to its parts, H-5 regained its composure and lived up to expectations.

  The king extended the period of the trial in anticipation of objections from the Harrisons’ enemies. After ten weeks of daily observations between May and July 1772, he felt proud to defend this new timekeeper, for H-5 had proved accurate to within one-third of one second per day.