The Paramore pushed toward the Antarctic, well beyond Magellan’s path through Tierra del Fuego. Outside the protection of this enchanting island cluster off the southernmost tip of South America, the cleavage of South Atlantic and South Pacific often produced tricky winds and agitated currents. But the ship passed without incident. The novelty of sea creatures and terrain unfolding before them probably only stoked the crew’s wildest imaginations.

On January 31 the Paramore reached the farthest point south ever recorded by an expedition at the time, latitude 52 degrees, 24 minutes south, but for the first time Halley distrusted his measurements. Another bed of weeds—often a sign that land or shallow waters were near—floated by the ship. How unnerving it must have been for a meticulous scientist like Halley. A commander does not generally like more than the usual uncertainty.

On the horizon, an unusual, massive form emerged. Captain Halley wrote in his journal, despite his stiff, cold hands, “flat on top

and covered with snow. Milk white with perpendicular cliffs all around.” Three of them—monstrous, barren forms. None appeared on any of the charts in his collection. Did any lips dare to murmur it? Were they witnessing the first glimpse of mystical terra incognita? They seemed otherworldly. Halley held any speculations in check. “The great height of them made us conclude them land, but there was no appearance of any tree or green thing on them.” But the crew quickly tried to introduce some familiarity. “Our people called [the first island] by the name of Beachy Head, which it resembled in form and colour. And the [second] island, in all respects was very [much] like the land of the North Foreland in Kent.” Halley sketched the three masses and their positions in his journal, labeling the nebulous blobs A, B, and C. Undoubtedly by now, slick layers of ice had coated the Paramore’s masts and rigging, rendering the sheets hard to grip and to maneuver.

Halley estimated the height of the first island to be close to that of the real Beachy Head in Eastbourne Downland. At 530 feet it is England’s highest chalk sea cliff. The second island was about 200 feet high, roughly the height of the real North Foreland lighthouse, which was established in 1499 and marks the southerly entrance to the River Thames. And according to Halley’s journal, the second was “not less than five miles in front.”

“The cliffs of it were full of blackish streaks,” Halley described, “which seemed like a fleet of ships standing out to us. Wind blowing fresh, and night in hand, and because our vessel is very leewardly, I feared to engage with the land or ice that night, and having [stood] in as far as I durst, I resolved to stand off and on till day, when weather permitting I would send my boat to see what it was.”

As if the crew was not already facing enough of a mystery, the night before them quickly turned foggy. Not until the next day at quarter past noon did the thick curtain lift. To Halley’s eyes the landscape had rearranged itself. The islands were not as they had been at last sight. The first island now glared before them. “We saw the island

we called Beachy Head very distinctly to be nothing else but one body of ice of an incredible height.”

The voyagers had ventured farther south than any previous explorer in recorded history—to nearly 53 degrees latitude but to little avail. The strange masses proved not to be an ice-enshrouded terra incognita, but naturally occurring formations unfamiliar to experienced seafarers in 1700. By the time Halley realized the so-called islands were colossal floating icebergs, his Paramore was in harm’s way. Once again, the world had proven not to be as it seemed—even the visible world of their common senses betrayed the crew and their elite navigator and diligent scientist.

“We were in imminent danger of losing our ship among the ice,” Halley scribbled soon after in his journal, “for the fog was all the morning so thick that we could not see for long about us.”

He immediately swung the Paramore northward, narrowly escaping, at least for the moment, wrecking in the fatally frigid water. He noted in his journal entry on February 1: “True course to this day noon is S 44 E 25 miles. Difference of longitude 29 minutes East; Longitude from London 35 degrees 13 minutes.” Until that day the Paramore had never abandoned its course. The ship ventured within 13 degrees latitude of the Antarctic Circle and approached the northernmost tip of the Antarctic continent, just north of South Georgia Island, which was then undiscovered. They undoubtedly reached the Antarctic convergence, which surrounds the continent. In this region cold surface water moving away from Antarctica meets warmer, southerly moving surface water. Where the water masses collide, the colder water sinks below the warmer water. The net effect is a sudden drop in water temperature and salinity. Halley had just missed discovering a continent.

February 2. Fog set in again. Visibility was less than a mere furlong. Sometime after 11 a.m., the ghostly outline of another iceberg emerged on the Paramore’s leeward bow. Halley shifted his pink to avert collision. But now the Paramore found itself cruising on a path

toward an even larger mass. Halley attempted to tack again, but the ship failed to move into the wind’s eye. The poor draw of her square rigging disappointed her crew once again. Her captain knew full well that the icy mounds above the water were only an intimation of what loomed beneath the surface. Seven-eighths of each ice mass was submerged, an invisible threat to the most experienced seafarer.

“But the sea being smooth and the gale fresh got us clear: God be praised. This danger made my men reflect on the hazards we run, in being alone without a consort [that is, a companion or escort ship], and of the inevitable loss of us all, in case we staved our Shipp which might so easily happen amongst these mountains of ice in the fogs, which are so thick and frequent here.”

Thanks to a sudden favorable gale that seemed to swirl in from nowhere, the explorers retreated unscathed to warmer waters. Halley felt he had done his best to satisfy the queen’s desire to find terra incognita. Any further exploration might jeopardize both his crew and his primary mission.

Ultimately, Halley failed to claim Australia or Antarctica for the British monarchy. Terra incognita would remain elusive, although later explorers would know where not to venture at this time of year in the Southern Hemisphere. England would receive no bonus of doubling in size or of miraculous new elixirs from Halley’s expedition. It would be nearly 70 years before another explorer would pass this way again to stare down the floating white beasts that guarded the passage to the seeming bottom of the globe.

Halley headed north toward his old stomping grounds of St. Helena, where he’d spent that seminal year as a student, and made for Tristan da Cunha, a remote, uninhabited cluster of islands of volcanic origin midway between South America and South Africa. The largest, nearly circular in shape, was reputed to harbor a towering fall of fresh water and exotic species of plants unique in all the world.

The fog, cloud cover, and chilly temperatures persisted. “The weather being commonly foggy with so penetrating a moisture that our linen, our clothes, our papers, etc. feel wet with it even in our

cabins,” he wrote in his journal. But at last February 8 brought “pretty clear sunshine.”

After another week of sailing, an uncountable swarm of birds and albatrosses about the ship signaled the Paramore’s proximity to Tristan da Cunha. Its Portuguese discoverer had never set foot on the shore because he was unable to find a suitable landing place. Halley would not have any more luck.

They had been at sea for six weeks, the longest stretch of the voyage. Until now, Rio de Janeiro was the last land they’d glimpsed. Meanwhile, pitch-black clouds shrouded the main island’s 1,800-foot peak, and thick fog and hazy air obfuscated the basaltic cliffs along its coastline. Often the dangers for seamen were just as great as at sea when a ship anchored close to shore. For one thing, maneuvering in a small boat in churning surf or along a rocky coastline could be perilous. Ever cautious, Halley decided not to attempt watering there and headed for the Cape of Good Hope.

While en route in the chill Benguela current, a violent squall erupted on February 26 that “threw us so that we had liked to have overset, but please God. She righted again.”

Although leaks, perhaps aggravated by cold waters, had spoiled six dozen loaves of bread and 30 pounds of flour and cheese, Halley refused to return directly to England “fearing to go home in the winter, which would expose my weak ship’s company to great hardships.”

On March 11 they made St. Helena. From there Halley penned a letter to the secretary of the Admiralty, Josiah Burchett, informing him of their confrontation with the icebergs and his continued optimism for the mission: “In this whole course, I have found no reason to doubt of an exact conformity to the variations of the compass to a general Theory, which I am in great hopes to settle effectually.”

The island was a refuge for Halley in several ways. Besides being a haven for some rest and relaxation after a long stretch at sea, it came to be considered “one of the most healthful places in the world,” and sailors “when carried ashore here, recover to a miracle, rarely any dy-

ing though never so ill when brought ashore,” according to an 18th-century ship’s log. The East India Company had even made medical services available on St. Helena to passing seamen.

And here in 1677 Halley became the first person in the Southern Hemisphere to observe the transit of Mercury across the disc of the Sun. And here he likely developed the idea, which he first suggested in 1679, that the distance from Earth to the Sun (now known as an astronomical unit or AU) could potentially be calculated with a high degree of precision by observing the analogous transit of Venus across the Sun since it is the closest planet to Earth between it and the Sun. Because Earth and Venus orbit in different planes, this celestial alignment occurs only at intervals of 8, 121.5, 8, and 105.5 years. Not only could humankind have a better idea of the scale of our solar system, but also with such knowledge could improve star charts for navigation at sea.

In a 1691 paper Halley presented his idea to the Royal Society on using transit timings from several distant locations on Earth to accurately calculate the Earth to Sun distance. Readings from different sites would help astronomers pinpoint the timing of the end and the start of the egress, the period when Venus moves inside the limb of the Sun. By observing the transit at different locations that are known distances apart, the Earth to Sun distance could then be determined by triangulation. Because the Sun appears to have a diameter 30 times that of Venus, the silhouette of Venus seen from different vantage points on Earth appears against different points on the Sun due to parallax. The greater the number of simultaneous observations, the more accurate the calculation would be.

More than 60 years before Halley’s presentation, Johannes Kepler had determined relative distances between known planets. For example, scientists knew that the distance from the Sun to Mars was slightly more than 1.5 times the distance between the Sun and Earth. But absolute distances between celestial bodies were still unknown. Kepler estimated the distance between Earth and the Sun to be 24 million miles, which was off by a factor of almost four.

Halley reasoned that the differences in the apparent paths to Venus’s transit could be used to determine the distance between Earth and Venus. From this information, basic trigonometry would solve the distance between Earth and the Sun.

Actually, Scottish mathematician James Gregory had suggested the idea in passing several years before Halley. But it was Halley who advanced the idea and promoted sea expeditions to observe the transit of Venus across the visage of the Sun from distant sites around the world. A pair of English astronomers, Jeremiah Horrocks and William Crabtree, made the first known observations of a Venus transit in 1639, predicted by Kepler. It appeared as a black spot roughly one-thirtieth the diameter of the Sun. Though visible to the naked eye, they viewed it indirectly using small telescopes that projected the image onto paper. But the Englishmen lived only 30 miles from each other, Horrocks in Lancashire and Crabtree in Salford. Many more measurements would be needed to determine the distance from Earth to the Sun. But another transit wasn’t due to occur until 1761.

Because of the rarity of the event (at least measured in the human life span), the transit wouldn’t be sufficiently observed until 1769, almost a century after Halley’s writings and decades after his death. A Royal Society commission secured King George III’s approval for an expedition to Tahiti to do exactly that. Based in large part on Halley’s proposals, the mission was led by Lieutenant James Cook aboard the Endeavour. According to Cook’s journal, the day that he measured the transit from the French Polynesian island “proved as favorable to our purpose as we could wish, not a cloud was to be seen all day and the air was perfectly clear.”

Cook’s transit data in combination with observations from 63 other locations around the globe enabled astronomers to calculate the distance from Earth to the Sun more precisely than ever before. They carefully deduced a distance of 95 million miles. The figure came within a few percentage points of the value accepted today: about 93 million miles. (The number wasn’t officially agreed upon internationally until 1942.)

Cook also continued southward where Halley left off and made the east coast of Australia—that southern land of intrigue, nearly 70 years after Halley almost met his demise amid the icebergs. More than a century would pass before Antarctica would be discovered.

The goliath intellects of Copernicus, Kepler, Galileo, and Descartes chiseled the physical science foundation of Halley’s day. Halley’s accomplishments as an astronomer were shaped not only by the resulting contemporary world view but also by the instruments available to him.

At the time of Halley’s birth in about 1656, the Copernican revolution in astronomy was at least a century old and nearing acceptance in mainstream thought. About this time at the French Academie, the Dutch vanguard Christiaan Huygens built the first efficient pendulum clock, key for measuring time at night at remote locations. By the time Halley began studying astronomy, it was well established theoretically that the Sun—not Earth—was the center of our solar system. By then, viewing sights had also been introduced to telescopes, but not without controversy. Although the old observing guard clung to their established methods using open sights, telescopic sights would soon prove superior. They afforded a 40-fold enhancement in precision over the instruments used, for example, by Tycho Brahe, the most accurate observer of the 16th century. The first telescopes, made in the Netherlands, didn’t come into use until about 1609. Galileo Galilei in Venice was among the first astronomers to point one at the heavens. Halley himself would be active in improving the observing technologies of his era in several ways. Nonetheless, the technology on hand in Halley’s day was good enough that he was able to advance stellar astronomy.

Although questions about the size of the universe and the population of its stars intrigued Halley, his discovery of stellar motion was probably his most important accomplishment in that field. Always attune to history, Halley decided to take a look at Ptolemy’s observations from the 2nd century A.D. Since before Ptolemy’s time, stars had been looked on as stationary with respect to each other, though

they moved in a circular fashion around the North Star. But when Halley scrutinized Ptolemy’s star catalog, he noticed some irregularities. Even after compensating for errors, Halley realized that the flagrant discrepancies between Ptolemy’s charts and ones put together some 1,500 years later meant the stars must have moved in relation to each other or independently. He was able to determine the individual or “proper motion” of three very bright stars: Arcturus, Procyon, and Sirius. Halley surmised that the motion of brighter stars would be easier to detect because they were closer to Earth. Conversely, the farther away the star, the harder it would be to detect its proper motion. The technology to expand on his premise wouldn’t be developed for another 150 years.

The limitations of the precision of the instruments then available also prevented the successful measurement of a single accurate stellar distance in Halley’s lifetime, though that didn’t stop Cassini and others from making triumphant claims that they had made accurate determinations of such distances.

UNTIL CONSTRUCTION OF THE GREAT observatories in London and Paris in the 1670s made English and French astronomers famous, Johannes Hevelius, a city councillor and Consul of Danzig, was the most renowned astronomer in all of Europe. Besides being among the first to observe transits of Mercury and Venus, he discovered several comets and the first known variable star. He mapped the Moon’s surface and proposed that comets follow parabolic orbits.

The son of a prosperous brewer, Hevelius built an observatory on his family’s property that was probably the grandest and best equipped of any at the time. Curiously, he made most of his observations from the roof of his townhouse. He corresponded with other leading astronomers, including Flamsteed the astronomer royal and Cassini in Paris, and was made a fellow of the Royal Society.

When a dispute erupted in the 1670s between Robert Hooke and the then-elderly Hevelius over the question of open sights versus telescopic ones, the Royal Society called on Halley to settle it. With his

recent experience at St. Helena and his penchant for diplomacy between some of the high-strung egos in science, he was an ideal choice.

Rightly proud of his achievements and reputation as an observer, Hevelius refused to adopt the emerging advances in instrumentation. He preferred to use his proven sights: pinnules or metal plates with small holes in them that were attached to his quadrant. Stubbornly, he dismissed out of hand the improvements in precision afforded by telescopic sights, which had yet to yield comparable results.

At first glance, Halley might hardly be considered impartial. After all, telescopic sights were behind the success of his original catalog of 300 stars completed on his St. Helena trip during his Oxford student days. In fact, Halley was among the first to use the new methods in the field. (Of course, Flamsteed and Cassini from their perches at the world’s leading observatories had little incentive to survey the heavens from the field at all.)

In late May of 1679, fresh from his early triumph at St. Helena, Halley visited the like-minded Hevelius at his invitation. They began observing on the first night of his arrival in the magnificent Baltic city. Hevelius would describe Halley as “a very pleasant guest, a most honest and sincere lover of truth.”

Although Halley stayed for two months, he was satisfied—nay, dumbfounded—with the accuracy achievable with Hevelius’s instruments. He reported his findings to the Royal Society within the first 10 days of his visit: “As to the exactness of the … distances measured by the sextants, I assure you I was surprised to see so near an agreement in them, and had I not seen, I could scarce have credited the relation of any; verily I have seen the same distance repeated several times without any fallacy agree to 10 seconds,” or 1/360 of a degree.

In fact, on some observations Halley and Hevelius, working to find star positions in tandem on a six-foot sextant with both a movable and a fixed sight, attained an accuracy within five seconds, or twice as accurate as Flamsteed claimed with his telescopic sights. In Halley’s absence, Hevelius often observed the night sky with his second wife, Catherine Elisabeth, a reputed beauty 36 years his junior.

In this period, women were rarely engaged in science. For a start, even the brightest women were denied access to any sort of formal or disciplined education. But there were some exceptions. Flamsteed’s wife Margaret Cooke, whom he married later in his career in 1692, also assisted him with compiling astronomical data and mathematical calculations.

The use of two observers likely increased the open-sighted sextant’s accuracy, as did Hevelius’s customization of the graduation of his instruments. The Danzig astronomer and Halley also observed with telescopic sights that Halley had brought. The best they achieved was an accuracy within 10 seconds. Hevelius believed this added additional support to his argument, but the shortfall was likely due to the fact that Halley’s instruments, being portable, couldn’t be expected to generate the same accuracy as the best larger scopes permanently stationed at a big observatory, which remained still and in calibration. Hevelius’s largest scope was 150 feet long. While important for power, length, of course, did not necessarily govern accuracy. Flatter-profiled lenses could potentially achieve better clarity.

Halley was impressed enough that with prompting from Hevelius he wrote a testimonial. “I offer myself voluntarily as a witness of the scarcely credible certainty of your instruments, against anyone who shall hereafter call the truth of your observations into question,” Halley wrote. Hevelius’s observations may have been more accurate at that time and place, but telescopic sights would soon be shown to unequivocally afford finer resolution and greater accuracy than the unassisted human eye.

But Halley’s kind letters did little to persuade Hevelius’s persistent adversaries: Flamsteed, Hooke, and others. The controversy thundered on, forcing Hevelius on the defensive. Hevelius charged that Halley’s visit was more about espionage than diplomacy. He was dispatched “for no other purpose but to rigidly examine [my] instruments.”

Back in London, the usually reserved Halley apparently took offense at that charge and responded less moderately: “I am very un-

willing to let my indignation loose upon him … for I would not hasten his departure by exposing him and his observations as I could do and truly as I think he deserves I should.”

Then a devastating tragedy would leave the squabble forever unresolved in Hevelius’s mind. A mere two months after Halley left the hospitality of his host, Hevelius’s observatory went up in flames, destroying most of his instruments and observations along with the facility. The fire was allegedly started by a careless servant whom Hevelius later called “the most perverse animal on two legs.”

News arrived in London that the fire had claimed Hevelius’s life. In a 1681 letter to Catherine Elisabeth, Halley expressed his sorrow and offered to make good on a request to buy her a fashionable dress hand-tailored in London from 10 yards of the highest-quality silk. “We cherish ardent hopes that Mr. Hevelius may still survive and that rumour has shown herself false in this particular, though it is but rarely that she deceives us in unhappy things. I quite realize that his heartbroken spouse must be wearing sad-coloured apparel, yet for several reasons I have thought well to send the gown procured for her,” Halley wrote. “Anyhow she will be able to preserve it until her period of mourning is past.”

All of London learned several months later that Hevelius had survived the fire, but the catastrophe did not stop proponents of telescopic sights from raging on with their technology crusade, nor did it stop Flamsteed, when it would suit his political agenda, from later using the silk dress as evidence of some sort of indiscretion on Halley’s part. His insinuations seemed plausible enough. After all, Hevelius’s wife was only 10 years Halley’s senior. Hevelius might have been her grandfather.

Although Halley remained in Hevelius’s good graces thanks in part to his work at St. Helena, Hevelius continued his personal attack on Hooke: “That he makes it his own business to persuade him and all the world, that his own way is the best, safest, and most exquisite, which ever can be invented by any; reproaching this author all along

for not obeying him and following his dictates (as if this author were one under his command) bragging only of what he can do, but doth nothing,” Hevelius ranted in an issue of the Philosophical Transactions. Hooke’s rivals in the Royal Society, including John Wallis, relished whatever collateral damage might result from such invective. Meanwhile, Halley cleverly let the proverbial chips fall as they may. And there was political mileage to be gained.

The Royal Society secretaries, Francis Aston and Tancred Robinson, who allowed Hevelius’s harangue to be published, were forced to resign. Installed in their place within the next couple of months were John Hoskins and Thomas Gale, two friends of both Hooke and Halley. In turn, a salaried post of clerk was set up to which Halley was easily elected. Oversight of the publication of Philosophical Transactions fell on Halley’s plate. While Hooke’s reputation suffered somewhat in the process, Halley’s prominence rose.

The sight controversy ended with Hevelius’s natural demise in 1687. In death Halley still considered him a friend. A new era in observation was dawning, and Halley was in the thick of it. For Hooke it was just another instance where his contributions were key but where others who were better political navigators would reap greater rewards. In his diary Hooke expressed envy of Halley and his contemporaries’ daring travels. Six months before Halley sailed to St. Helena, Charles Boucher had voyaged to Jamaica, enduring raging seas and shipwreck. Boucher lost his precious instruments and books, but he brought back hot new data from his observations afforded by the good seeing on the island. In 1687, Sloane would also travel to Jamaica, where he’d be introduced to cocoa, to serve for a time as physician to its new governor, the second Duke of Albermarle. And soon enough Halley, the risk taker, would again be “a sayling,” as Hooke described it, and Hooke once more was left ashore.

AFTER THREE WEEKS OF REST on St. Helena, Halley set a course for his Paramore back across the Atlantic on March 30, 1700. The drinking

water they had obtained on St. Helena was rather brackish because it rained heavily during their stay. So he set his sights on the island of Trinidad, roughly 900 miles off the Brazilian coast.

On the sail, Halley recorded latitude daily and measured the variation almost every day. He used his telescopic sights—no offense intended to Hevelius—to observe the Moon on April 11. He calculated the relative position in latitude between St. Helena and Trinidad to be 21 degrees 20 seconds.

Sure enough, three days later they glimpsed the rocky outline of the three isles of Martin Vaz and on the 15th reached Trinidada, which Halley called both Troindada and Trinidad in his log. “The island being about 1.5 leagues in length, lying nearest NW and SE. The North and West part is nothing but steep rocks scarce accessible.”

Pleasantly surprised with the unpopulated piece of real estate once ashore, he thought the island, with its bountiful water supply, would be a valuable resupply point for English ships. Halley rowed around the island in the pinnace, and he and his crew took all of five days to map it. He measured the variation to be 6 degrees 30 seconds east. He planted a Union flag with its hallmark crosses and claimed the small oasis for the king of England (though the Portuguese discovered it in 1502). And the crew released a breeding stock of goats, hogs, and guinea fowl on the island.

The tiny island was hardly terra incognita. But for the Crown, it would have to suffice for now.