The Day the World Discovered the Sun (11 page)

For France, 1763 was a cruel year. In February the Treaty of Paris effected one of the largest and richest territorial surrenders of the century. Along with Louis XV handing over Caribbean and Indian possessions to his rival across the channel, French Canada and French Louisiana east of the Mississippi had, with the flourish of an English quill, become British possessions.
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But Jean-Baptiste Chappe d'Auteroche had more immediate concerns on his mind. In 1763 alone, French ships had barely averted three disasters—all of which sprang from the lack of reliable longitudes at sea. Chappe reviewed these near misses for his colleagues at the Royal Academy of Sciences in Paris. One boat traveling to the city of Cayenne in South America had overshot its destination by 150 miles. It was only spared because its surprise landfall came in broad daylight, in fair weather. Another vessel traveling to the Bermudas nearly wrecked when its longitude estimates proved wrong by 100 miles. Tall island landmarks that enabled quick course correction proved its salvation. And a third voyage, with one of the finest navigators in France at the helm, flirted with cataclysm when he calculated his ship's position 179 miles off its true course. Hundreds of lives would have been doomed were it not for the fact that the navigator had this time underestimated the distance to port. Where they expected land, they found open ocean. Worse fates have befallen.

To drive his point home, Chappe recalled seven other recent cases of faulty longitudes at sea that resulted in unexpected coastlines committing wholesale slaughter. “Few discoveries, in fact, have more interested mankind,” Chappe said. “The discovery of longitudes would preserve for the nation the multitude of citizens who are [instead] buried in the waves.”
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Contrary to his esteemed colleague, Lalande, newly returned from England, Chappe played no favorites in the longitude war. Indeed, he was eager to contribute to breakthroughs in marine chronometers.

The watchmaker who had returned with Lalande from an only partly successful British spy mission, Ferdinand Berthoud, spent 1764 applying the intelligence he gained to new marine chronometer designs. Berthoud tapped Chappe to join a team that would put the “Montre Marine No. 3” to a sea trial.
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For once in the bitter race between competing longitude techniques, the chronometer and the astronomer were cooperating.

Chappe and the naval architect Henri-Louis Duhamel du Monceau arrived at the French Atlantic coastal town of Brest—one of the navy's key port cities—in early October 1764. The visitors discovered a shipyard that an uninformed observer might think was in the midst of all-out war. Seventy-four gunships of the line lay in dry dock. Shipwrights, carpenters, and apprentices scurried through the yard refurbishing the gunboats' long hulls and refitting new cannon to their three towering gun decks.
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Saw pits filled the air with piney scents of fir trees, while the yard's anthill-like activity belied the new peace its nation allegedly enjoyed.

For the first week, Chappe joined two other astronomers at the Naval Observatory in Brest to test the clock's baseline performance on shore—its “ground state,” as Chappe termed it. They'd discovered less than Harrison-like performance. One day the clock gained two seconds over a twenty-four-hour period; two days later it gained five seconds.
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On Sunday, October 14, the team loaded the Montre Marine 3 onto the
sixteen-gun corvette
L'Hirondell
. There they set up a glass cabinet housing the chronometer. The timepiece, Chappe reported to the Royal Academy, “is about the size of a coach watch. It . . . can be placed in all parts of the vessel without causing the least embarrassment. Its volume is not [even] a square foot [
sic
].”
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Chappe stayed ashore to synchronize the observatory's pendulum clock every day with the exact solar time—while the rest of the team sailed with the the Montre Marine through the coastal waters near Brest.
L'Hirondell
returned after three days. Now, they found, the watch had lost four seconds every twenty-four hours. Next, Chappe joined the crew on a five-night sea voyage. Berthoud's machine this time lost nine seconds every twenty-four hours.
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Berthoud's timekeeper performed well, but not stunningly so. Close inspection of the watch's movements revealed that at least its slippage in time was independent of a boat's swaying and jostling. The watch's performance over longer journeys and over greater ranges of temperatures still needed testing.

“Berthoud is certain of the cause that produced these anomalies,” Chappe reported to the Royal Academy in Paris in November. Berthoud would be perfecting his design and making his revised Montre Marine 3 available for another sea trial soon, Chappe said. “There is every reason to hope that a second test will leave nothing but elation over the perfection of that clever artist's machines,” Chappe added.
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All the while, the celestial clock was advancing too. The coming year would see the first plans being laid for 1769 Venus transit expeditions. Here is when Chappe's interest in Berthoud's handiwork stopped. The vicissitude of longitude was a worthy problem of its day—fit for natural philosophers and mechanical craftsmen alike. But the heavens' architecture would only be uncovered once.

And with war now—at least officially—concluded, a true international collaboration like nothing else in human history was getting into gear. Learned men looked now toward a new dawn: June 3, 1769. Astronomers
had already forecast that the prime location to view this Venus transit in fact had very little known terra firma from which to view it.

The mysterious and largely uncharted Pacific Ocean would be the new playground for a new kind of player.

William Wales and Mary Green were married on Thursday, September 5, 1765, in Greenwich. The bride was the daughter of the late Joshua Green, of the South Yorkshire village of Swinton, and the youngest sister of the astronomer Charles Green. The bridegroom, 30, also hailed from Yorkshire (Warmfield) and worked as a “computer” for the new Astronomer Royal of England, Nevil Maskelyne. Wales regularly contributed mathematical problems and solutions to the “New Queries, Paradoxical-Problems, Rebuses, and Flowers to Be Answered in the Next Year's Diary” section of the annual
Ladies' Diary: or, The Woman's Almanack Containing New Improvements in Arts and Sciences and Many Entertaining Particulars Designed for the Use and Diversion of the Fair-Sex
.

The newlywed Wales and fellow computer John Mapson had a busy season ahead. Since June, they'd been predicting the moon's position in the sky months in advance courtesy of the formulas that Astronomer Royal Maskelyne (appointed to the job in February) had proved in his sea voyages to St. Helena and Barbados. Their job was straightforward,
although still difficult. They were preparing the first two editions of a book of tables that would be titled
The Nautical Almanac
. For every day in 1768, they had to forecast where exactly the moon would be at noon and at midnight, Greenwich time. Performing even one such calculation involved hours of mathematical gear grinding, keeping track of coefficients such as the “lunar mean anomaly,” “solar mean anomaly,” and “the lunar anomaly corrected by the minor equations.”
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Theirs was a classic cottage industry—albeit one whose product was computations and whose computers were humans. Wales and Mapson—along with Israel Lyons and George Witchell, the lunar forecasters for 1767—worked from their homes, receiving regular mailings from Maskelyne updating them on their assignments.

By July, the Board of Longitude had also hired the Cambridge-based mathematician and astronomer Richard Dunthorne for the job of “Comparer of the Ephemeris and Corrector of the Proofs.” Wales, Mapson, Lyons, and Witchell would each individually work out their lunar predictions for the month at hand, either serving as what was then called a human “computer” (calculating each day's lunar position at noon Greenwich time) or “anticomputer” (calculating lunar positions every midnight). Each would post his results to Greenwich, where Maskelyne would examine the pages for obvious errors and then forward the predictions to Cambridge, where Dunthorne considered each prediction in greater detail. If the computer and anticomputer for a given series of days had forecast lunar motions that wobbled or zigzagged (motions the moon does not make), Dunthorne would then sort out where the error originated. And back would go the calculations to the computers and anticomputers to run the numbers again. Once Dunthorne had established the accuracy of the first set of lunar predictions, he then returned the month's framework table to his computers and anticomputers so they could then mathematically interpolate the moon's position at three, six, and nine o'clock, both
AM
and
PM
, Greenwich time.

It was painstaking work, but it yielded unprecedentedly precise results.

The
Nautical Almanac
produced longitudes that were an order of magnitude more accurate than its competitors—sometimes down to just 0.017 degrees (1 arc minute) of longitude accuracy for the
Almanac
compared, say, to more than 0.17 degrees (10 or more arc minutes) accuracy for the French
Éphémérides des mouvemens célestes.
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On April 3, 1767, for instance, the
Almanac's
computers predicted the moon's center would be 65 degrees, 39 arc minutes, and 18 arc seconds away from the nearest edge of the sun as of noon Greenwich time. By 6:00
PM
Greenwich time, that angular separation had increased—the
Nautical Almanac
predicted—to 68 degrees, 37 arc minutes, and 14 arc seconds. Then, as the moon waxed closer to full (when it would only be visible in the nighttime sky), the
Nautical Almanac
predicted that, for instance, on April 15, 1767, the moon's center would lie 25 degrees, 4 arc minutes, and 34 arc seconds from the star Spica at noon in Greenwich. But by 6:00
PM
Greenwich time, the moon separated farther from Spica to 28 degrees, 14 arc minutes, and 26 arc seconds.

The end result was a table that mariners across the world would use to transform the moon into a universal timekeeper. Measuring the angular separation between the moon and sun or reference star gave them, courtesy of the
Nautical Almanac
, Greenwich time. Comparing that to the local (solar) time yielded a quantity—measured in hours, minutes, and seconds—that represented their east-west separation from Greenwich.
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Although Maskelyne never received any reward money from the Board of Longitude (while the clock maker John Harrison ultimately won £20,000), the Astronomer Royal's brainchild effectively solved the greatest maritime problem for most ships for at least the remainder of the century. Improvements to Harrison's marine watch would still take decades to render affordable and practicable for the vast fleet of English vessels navigating the planet. But with its January 1767 first edition, Maskelyne's
Nautical Almanac
opened a new and better era of navigation at sea. Any captain or ship's master possessing an £8 Hadley quadrant
(or, better still, a £15 brass sextant) could with an additional five shillings buy Maskelyne's two books of tables that saved countless lives and ships from longitude's maw.
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Publication of the first
Nautical Almanac
—an annual tradition that began in 1767 and has never missed a year since—marked a historical watershed moment. “What may be termed the pre-scientific age of navigation was brought to a close,” historian Eva Taylor wrote. “Landmark or no landmark, the sailor [now] knew precisely where he was—or had the means to know. He did indeed at long last possess the Haven-finding Art.”
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Human statuettes, animated by clockwork, struck bells over their heads, signifying every fifteen-minute increment on the hour. The west London church whose third-story portico broadcast this clamor, St. Dunstan-in-the-West, vied for pedestrians' attention with nearby Temple Bar. From Fleet Street, whose traffic rushed beneath Temple Bar's archway, a Londoner might admire the Bar's classically inspired lines and curves—or wonder at the two decomposing human heads (examples of the city's rough justice) impaled on spikes above it.
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Just up the street from these conspicuous west London landmarks, a lamp hung at the entrance to a darkened cul-de-sac, Crane Court. On November 19, 1767, Nevil Maskelyne walked down the lamp-lit alley and into the small quarters of the Royal Society. The Council of the Royal Society, the scientific body's decision-making board, was now in session. Inside the same Crane Court walls a half century before, Astronomer Royal Edmund Halley had championed Venus transits as “the noblest [sight] astronomy affords.”
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Now newly christened Astronomer Royal Maskelyne endeavored to make his predecessor's vision a reality.

Maskelyne joined the physician and astronomer John Bevis and the instrument makers James Ferguson and James Short to argue, astonishingly, in favor of a glorified crapshoot.

Calculations performed the previous year by Oxford astronomer Thomas Hornsby projected the best locations on the planet to send Venus transit missions. As with 1761, comparing the longest and shortest transit times—combined with a parallel method that compared arctic and tropical Venus transit observations—would yield the most accurate solar parallaxes and, Hornsby said, “consequently the dimensions of the whole solar system.”
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