The Day the World Discovered the Sun

by Mark Anderson

  The governor’s eldest daughter approached Chappe and kissed his hand. Unsure how to respond, Chappe learned by the time the third daughter took his hand that he was expected to mirror her gestures and make the same kissing motions simultaneously. The governor told Chappe, through the interpreter, that he’d begun to worry that the team would not make it before the spring thaw, when travel slowed or ceased entirely.

  But worries could now rest, Chappe explained. The best observers—and instruments—this region had seen had now arrived. And all that remained was to find a suitable location for an observatory. Then, with an enlisted crew of local laborers at hand, the Frenchman only needed to build.

  Chappe located a hilltop three-quarters of a mile from Tobolsk and, with just twenty-six days till the transit, set out to create the site where he hoped to make history. No one suffered for daylight in this northern latitude. In early May, the sun rose at 5:30 AM and set at 9:30 PM. By transit day, June 6, daylight would trim the night by another hour on either end. Chappe unpacked and tested his equipment: the quadrant for measuring angles on the sky, his telescopes and the elaborate mechanical mounting that kept them trained on the same star or planet even as the earth’s rotation made it “move” through the sky throughout the night.

  Chappe supervised construction during long stretches of the day while fixing his instruments after their 3,400-mile marathon of gear-grinding and lens-scratching shocks and bumps. Chappe also had plenty of business to attend to in the build-up to the Venus transit. The astronomer had set up his clocks in the observatory building and tuned their accuracy down to the second. He further tested that his telescopes and quadrants could detect and precisely track a small shadow crossing the sun’s surface.

  Chappe also needed an exact fix on his observatory’s latitude and longitude. To find Tobolsk’s latitude (the number of degrees from the equator), Chappe measured the angle between the horizon and the sun at its highest position in the sky: noon.18 He performed similar “altitude” measurements for the well-known stars Mizar and Caph when they crossed the same meridian line at night.

  Measuring such angular distances involved using an instrument as commonplace as the compass on a ship: the quadrant. Named after the portion of a full circle that it subtends (one-fourth of a circle or 90 degrees), the quadrant was like a protractor for the sky. Measuring altitudes with a quadrant—or its cousin, the sextant, which using a clever set of mirrors enabled measuring distances up to 120 degrees—involved first pointing the viewfinder at the horizon. Then holding the right side of the instrument in place (typically using a stand), one swung the viewfinder up to find the sun or star being sited. An arm extending down from the viewfinder pointed to a semicircle hanging beneath the finder containing hash marks that read out exactly how many degrees separated the two. (Like an hour, each degree is subdivided into 60 minutes of arc, or “arc minutes,” each of which is divided into a further 60 arc seconds.)

  So, for instance, Chappe observed with his quadrant on May 27 that Mizar—the second star from the end of the Big Dipper—was 87 degrees, 57 arc minutes, 15 3/4 arc seconds from the horizon. His star charts told him (with some additional calculations) what Mizar’s altitude would be if he were at the equator. His latitude was then the additional degrees, minutes, and seconds between Mizar at the equator and Mizar’s altitude in Tobolsk.19 The Mizar and Caph measurements both told him his Tobolsk observatory’s latitude was 58 degrees, 12 arc minutes, and 22 arc seconds, give or take an arc second. According to his solar measurement, his latitude was 58 degrees, 12 arc minutes, and 13 arc seconds. Either way he was close but not quite spot-on, 39 arc seconds or about three-quarters of a mile off the actual latitude of Chappe’s observatory site.20

  Calculating longitude, though, was the real trick. French astronomers typically relied on careful timing of the motions of the planet Jupiter’s moons to find longitude. Noting the exact moment (local time) when any of the four prominent Jovian moons passed behind or emerged from the planet provided an ersatz celestial clock. Nautical almanacs like the Parisian Conaissance des Temps contained predictions of when (Paris time) the Jovian eclipses would take place. An astronomer in the field could then, ideally, look up when (Paris time) the Jovian moon was predicted to disappear and reappear from behind Jupiter. The difference between local time and Paris time for any given Jovian eclipse, then, represented the longitude difference between Paris and the observer’s location.

  However, Chappe also happened into an even better longitude trick: a partial eclipse of the sun passed through the region on June 3. Chappe took down exactly when it began and ended. Ultimately he could use this number to calculate Tobolsk’s longitude down to at least a few arc minutes.

  None of his technical accomplishments meant a whit to anyone around him. Other than the governor and a few of his aides, practically no one in Tobolsk knew what the newcomers were doing on the hilltop near town. None of the hired hands knew what mysterious deeds lie concealed behind the intricate machinery that the strange man from afar so carefully attended to. All the locals had to judge by was the stranger’s peculiar behavior.

  A contemporary engraving based on a sketch by Chappe’s artistic collaborator Jean-Baptiste Le Prince depicts what was probably a familiar sight at the observatory. In the image, the observatory’s tall wooden front door was swung wide open with a rapturous Chappe peering through the sights of his astronomical quadrant, set squarely in the middle of the barn-like structure’s opening. Through his instrument the Frenchman viewed lightning discharges during a thunderstorm. Meanwhile, local officials and assistants were huddled around the door frame’s edge, as if taking shelter from the possible wrath of God that could be unleashed by such a close and inquisitive inspection of nature’s wonders.21

  Chappe did most of his instrument calibration during brief stretches at night, training his telescopes on the moon and prominent stars. His living quarters, though, were in town. Some mornings Chappe returned to his bunk in town as the 5:00 AM sunrise colored the awakening city in pink and orange. The philosophe paid little attention to clothes or grooming, not even presenting token efforts to match the ostentatious rank his royal post had given him. Already every bit the foreigner in a foreign town, Chappe recognized the suspicious glances his grizzled appearance cultivated. To everyone but the lofty folks on the hill, Chappe was persona non grata.

  From his group’s translator, he learned that some in town had thought Chappe was a wizard preparing to commune with the skies or some spiritual realm. Some who’d heard about the purpose of Chappe’s observations whispered that the wizard was preparing for the end of the world—which, naturally, would arrive when Venus crossed the solar disk on June 6.

  The storm clouds of spring gathered as the already overflowing Irtysh River hugged Tobolsk. On one fateful spring day, drenching rains and thunder rumbling through the hills gave the French visitors a second welcome. Timber crashed to the ground as the Irtysh breached its banks and drowned sections of Tobolsk in floodwater. Refugees seeking higher ground brought reports of townsfolk drowning in the flood.

  Some superstitious locals didn’t wait for the rains to abate to begin pointing fingers at the strange man from out of town. As if to punctuate the fury from above, mudslides broke off chunks of Chappe’s mountain, sending clumps of hilltop booming into the plains below.

  The rains eventually receded but the Irtysh did not. From the observatory, Chappe wrote, the flooded regions of Tobolsk looked like “a number of islands scattered on [a] watery surface and extending as far as the sight.” Standing on the muddy grounds of his now completed observatory, Chappe gazed at the unfortunate town below. Tobolsk’s governor had already assigned a second sergeant and three grenadiers to Chappe’s entourage.

  The guard now tailed Chappe wherever he went—which, by consensus, would be the hilltop and the hilltop only. Chappe started sleeping at the observatory, fearing his presence in town might incite an angry mob. For this reason, some on the hill advised Chappe
not to visit the observatory without his armed guard to protect him. The locals, Chappe said, “imagined they should see no end to their misfortunes till I was gone from Tobolsk.”22

  Chapter 2

  THE CHOICEST WONDERS

  OFFSHORE OF SALCOMBE, ENGLAND

  February 14, 1760

  Sharp winds and stinging rain greeted all hands on His Majesty’s warship the Ramillies,1 who had lost her course and fallen away from a military blockade of the French coastline somewhere in the English Channel. A ninety-gun ship of the line, Ramillies had seen action in seven naval battles over five wars. But now the seas were battling her. The storm had sprung gushing leaks in her hull.

  Her navigator recognized a welcoming headland on the nearby Devon coastline. Captain William Whitrong Taylor ordered Ramillies hoved-to for repairs, assured by the promise of a sheltering bay. But as she drifted closer to land, the winds and surf only battered harder. Rocky coastline stretched well beyond where the bay’s inlet should have been. The inlet was actually far west—one-third of a degree longitude west—from where Captain Taylor thought it was. In fact, the Ramillies had drifted into perhaps the most deadly length of shore in the entire channel. Before long, the captain realized this too. He shouted contravening orders to his commanders on deck. But the emergency course correction snapped the mainmast and mizzenmasts and shredded the remaining sails to ribbons.

  Dropping two anchors seemed to rescue the moment, but the panicked crew failed to notice the dual anchor lines twisting around each other. Tension built until a snap unmoored the ship and sent it hurtling stern first into a cliff side. Seven hundred men died gruesome deaths that night. And the next morning, the Devon locals onshore ignored the bloated bodies bobbing in the surf to rescue hardtack for their pantries and stray shards of hull for their lumber piles.

  Ramillies was just the latest sacrificial offering on the altar of longitude. In 1707, more than 1,400 sailors died when four British naval ships sank off the Isles of Scilly. The fleet’s navigators had mistaken the craggy English archipelago for Ushant—an island that marks the southwestern entrance to the English Channel. To commemorate the Scilly disaster, Parliament ultimately passed the Longitude Act of 1714—legislation that established a princely prize (up to £20,000) for a practical method to reliably find longitude at sea.

  In the generations since, no one had claimed it, though many had tried. The bureaucratic body set up to administer the prize, the Board of Longitude, had considered some bizarre proposals over the years. One, for instance, would have set up a network of anchored gunships throughout the Atlantic that fired clock-synchronizing exploding projectiles into the sky every midnight.

  The board’s most promising prospect involved comparing the moon’s position in the sky to its predicted position from navigational tables printed months in advance. One of the prodigies working on these very tables was a West Country boy whose name would one day divide a nation.

  OFFSHORE OF SALCOMBE, ENGLAND

  January 9, 1761

  Charles Mason squinted through the early morning light to make out the cove where the Ramillies had crashed ashore just eleven months before. Mason’s ship, the HMS Seahorse, creaked the easy groan of a frigate cutting a line through the English Channel.

  The Seahorse hadn’t even been under sail for twenty-four hours. But disquieting recollections of a treacherous coastline to starboard begged the question: How soon till we set a course toward the open Atlantic? The coming day would in fact be the last day Mason could lay eyes on English land for more than a year.

  Mason and his assistant, Jeremiah Dixon, were making hasty passage to Bencoolen, Sumatra (today Bengkulu, Indonesia) to observe the June 6, 1761, Venus transit.

  Mason, 32, had made a reputation among Gloucestershire schoolmasters and tutors as a mathematical wunderkind. England’s Astronomer Royal, James Bradley, hailed from the same county and through local connections learned about Mason’s prowess. Bradley hired Mason in 1756 as an assistant at the Royal Observatory in Greenwich.

  Dixon, 27, was the son of a wealthy coal mine owner near Newcastle-upon-Tyne who began his career as a surveyor but showed remarkable talent at both math and astronomy. Dixon’s skills impressed a family friend, one of Bradley’s top instrument makers, enough to recommend the surveyor when the Royal Society began casting about for someone to assist Mason on his 1761 Venus transit voyage.

  The East India Company operated a factory in Bencoolen that, as one contemporary visitor put it, “produces some drugs, but chiefly pepper.”2 The factory town was going to be their new home and site of an astronomical observatory of their making. The company had promised to cover Mason and Dixon’s “diet and apartments” in Bencoolen and “whatever else the service they are employed upon may require.” Plus the company would cover all expenses for the observers’ passage home. All their services expressed, as a company memo to the Royal Society put it, that this profit-oriented corporation was “extremely desirous of contributing every thing in their power for facilitating the making of observations upon the transit of Venus.”3

  Mason and Dixon, who had never met before the Royal Society paired them up for this voyage, were promised £200 each ($50,000 in today’s money) to venture 14,000 miles around Cape Horn and through the Indian Ocean to their Pacific destination. Neither had traveled more than three hundred overland miles from home before. And home, for both of them, meant some heavy freight to be left behind. Mason was a recent widower, with two sons whose care he had to arrange for in his absence. Dixon was a tippler—having been kicked out of his Quaker congregation for excessive drinking just three months before.

  As seamen manned the first night watch, Seahorse sailed through the icy waters of the channel toward a rare alignment of the moon and planets. Within 40 degrees of one another in the southwestern sky lay Venus, Mars, Jupiter, Saturn, and a sliver of a crescent moon. Both Mason and Dixon had earned their place on this voyage as meticulous watchers of the night sky. Mars shined near the horizon, south by south-west, separated from Venus by 10 degrees and 29 arc minutes. Jupiter practically sat atop Venus, a mere 3 degrees and 6 arc minutes distant in the sky. Both hugged the upper edges of the moon’s crescent.4

  The Astronomer Royal’s instructions for observing the Venus transit once they’d landed at Bencoolen called for both timing the duration of the transit and making angular separation measurements with their quadrant. “Observe the first and second contacts of Venus with the limb of the sun,” Mason’s boss, James Bradley, instructed. “Then measure the distance of Venus from the limb of the sun to ascertain the nearest approach of Venus to the center of the sun’s disk. Measure the diameter of Venus.”5

  More instructions followed about setting up and calibrating their pendulum clock with the varying day and night temperatures in Sumatra and the sun’s slowly changing passage through the sky. More nights ahead would surely find Mason and Dixon getting to know each other’s quirks and points of personal style in the telescope and quadrant measurements they’d need to keep.

  8.5 LEAGUES NORTH OF USHANT ISLAND, FRANCE

  January 10, 1761

  The cry from high on the mainmast, at least as far as international agreements were concerned, represented no threat whatsoever: “Enemy sail bearing down hard to windward!” The Seahorse carried a scientific mission that both French and English courts heartily supported. Her captain, James Smith, had every military permission, domestic and foreign, to sail under a white flag—a universally accepted protocol for warships undertaking nonhostile expeditions.6 Of course, white flags were also run up at times of surrender, and Smith captained a military vessel full of English seamen who knew from six years of fighting that the tide of war was now turning in their favor. As the leeward ship, the Seahorse had poor maneuverability and was thus the more vulnerable vessel as it rode toward the enemy.

  The Seahorse was a “sixth rate” frigate, carrying a modest 24 nine-pound guns and 160 men—carpenters, sail makers, quarter gunners, and yeomen
of the powder room—to make this small fortress function. Considered too weak for the battle line, sixth rates were typically, as a Royal Marines handbook of the time put it, “destined to lead the convoys of merchant ships, to protect the commerce in the colonies, to cruize in different stations, to accompany squadrons, or to be sent express with necessary intelligence and orders.”7

  As the French ship held its tack, it came into viewing range of the captain’s nautical spyglass. A bigger and more intimidating warship came into focus. The thirty-four-gun frigate L’Grand was clearly not interested in discussing cosmographical matters with the astronomers onboard. “Monsieur,” the snide nickname English sailors gave to French ships, had its big guns ready. Captain Smith wouldn’t deny the enemy its due.

  Mason and Dixon, men of philosophy and “mathematicks,” had no place on deck once L’Grand came within firing range. Perhaps sequestered away in one of the officer’s quarters or their own lodgings, the two said their prayers. Thumps from afar and loud cracks from the gun deck made every moment of the eleven o’clock hour a God-fearing one. Marines boarded the L’Grand in punctuated waves of assaults, while their French counterparts shouted “Allez à l’abordage!” and crossed a plank onto the Seahorse for tense minutes of close-quarters musket shots and bayonetting. Heard from behind closed doors, the din of screaming, shouting, moaning, vomiting, exploding, and crashing only heightened these men’s focus on their delicate telescopes. With the June transit date fast approaching, and no time or place on their itinerary that allowed for replacements or repairs, Mason and Dixon could be severely injured or maimed without necessarily jeopardizing the mission. Not so their precious instruments.

  Mason and Dixon’s shipmates worked feverishly to better the volleys of French cannonballs bashing Seahorse’s timbers. However, for the instruments under Mason and Dixon’s charge, this was exactly the problem. Unless an unlucky French cannonball actually pierced the boards protecting Mason and Dixon’s cabin—in which case both instruments and instrument tenders were probably done for—enemy fire posed less of a threat to delicate casings of glass, wood, and metal than did the Seahorse’s own cannon. With every English broadside came a fusillade of case-rattling tremors and quakes. With every English broadside, Mason and Dixon had the work of ten hands spread out among four.