When King William died without an heir in 1702, Queen Anne rose to the throne and Halley had his third benefactor within a decade. Since the Glorious Revolution, she had loyally sided with William and her sister Mary.
Anne’s first year as queen saw the War of the Spanish Succession break out. And suddenly Halley’s extensive channel data jumped in significance. The conflict, sometimes referred to as Queen Anne’s War, was fought over Europe’s balance of power and domination of trade. Louis XIV had aspired to control Spanish possessions in northern Europe and America. England, allied again with the United Provinces (now the Netherlands) and the Austria-Hungary Empire (as it had been in the Nine Years’ War against the French), wanted to check the Sun King’s expansionist ambitions.
As the Royal Navy prepared for action, the Paramore was retooled and armed with heavier guns. The sound of unfamiliar footsteps would resound on her deck and in her captain’s quarters. As soon as the war broke out with France, the ship served as a ketch for bombs in
Sir George Rook’s squadron under the captainship of Unton Deering and later Josiah Mighells.
Queen Anne appointed Halley in 1702 and 1703 to diplomatic missions. He visited Vienna and Hanover, adding to his royal contacts. Emperor Leopold and Prince Eugene of Savoy and Istria received him. And in Hanover he dined with England’s electoral prince, later King George II.
After returning to London from Vienna to advise the Emperor on forts along the northern shores of the Adriatic, Halley was charged with overseeing construction of the defenses of the channel he laid out in his survey. The nature of this project lends credence to innuendo that Halley was clearly spying and not merely gathering scientific data on his channel survey. And as further evidence, he was openly paid for his work in Vienna “out of secret service” funds.
Even though the war was still being fought by 1705, Halley’s chart of the English Channel was published in Amsterdam along with a printed explanation in Dutch and French. After a stint in the Mediterranean, the Paramore returned once again to Deptford for repairs. In 1706 she was sold to a Captain John Constable for a mere 122 pounds—less than his wife’s dowry—or roughly 64,000 pounds today.
With three voyages under his belt and service as a government agent, Halley’s name was put forward to fill the prestigious Savilian Chair of Geometry at Oxford. “Dr. Wallis is dead. Mr. Halley expects his place. He now talks, swears, and drinks brandy like a sea captain, so that I much fear his own ill-behavior will deprive him of the vacancy,” was the searing gossip Flamsteed sent to his assistant Abraham Sharpe in December 1703.
But despite Flamsteed’s unsurprising opposition, Halley was unanimously elected, his popularity at a new high. After all, a month earlier he was elected to the council of the Royal Society with more votes than even Newton collected. Newton, naturally, had won the Royal Society presidency that year.
As Halley settled into academic life at Oxford, he built a small observatory atop his own house (which still stands today). The seeing may not have been of the quality that he enjoyed at St. Helena, but at least he could continue his astronomical observations uninterrupted. He also continued to observe on his many visits to London. By 1710, Oxford had added an honorary doctorate to his laurels.
Years before Halley’s voyages, Newton had begun working on the theory of the Moon’s motion. As early as 1694, he had turned to Flamsteed for help. He wanted the royal astronomer to publish his lunar observations for the second edition of the Principia. Initially, Flamsteed supplied some of the desired data, but then their relationship deteriorated. Now a decade later, with his mounting influence, Newton pushed to have Flamsteed’s observations and star catalog (to be titled Historia Coelestis) published once again. After prompting from Newton, Flamsteed secured funding for publishing the observations from Queen Anne’s consort, Prince George of Denmark, who also appointed five Royal Society reviewers to guide the process. More than 100 pages of the estimated 1,450 pages were printed and hundreds more had been reviewed by Flamsteed when the prince suddenly died in 1708. Progress again ceased on the publication.
Likely under pressure in part from Newton, Queen Anne authorized a handful of Royal Society council members to oversee Flamsteed’s activities at the observatory, infuriating Flamsteed. They were to purchase and keep up the facility’s instruments, which were technically Flamsteed’s personal property, and ensure that his results were published annually. Adding insult to injury, the queen appointed Halley—without even consulting Flamsteed—to edit his prized Historia Coelestis.
Halley’s preface, finally published in 1712 as part of his edition of Historia Coelestis, was duly insulting: “Flamsteed had now enjoyed the title of Astronomer Royal for nearly 30 years but still nothing had yet emerged from the observatory to justify all the equipment and expense, so that he seemed, so far, to have worked only for himself or at any rate for a few of his friends, even if it was generally accepted
that all these years had not been wasted and that the Greenwich papers had grown into no small a pile.” While Newton and Halley’s dis-satisfaction with Flamsteed was understandable, their equally egotistical conduct reasonably irked Flamsteed. The friction between these rivals didn’t end there.
THE TREATY OF UTRECHT BROUGHT an end to Queen Anne’s war in 1713. For Britain it was a success. England had gained control of Newfoundland and most of its unusually prolific fishing waters. The newly fashioned peace would permit the monarchy to focus once again on diplomatic means of improving trade.
In 1714, testimony from both Halley and the increasingly irascible Sir Isaac Newton helped pass the Longitude Act, the world’s first scientific legislation. On July 20, Queen Anne gave the nod to the bill, which was encouraged by William Whiston, who had succeeded Newton at Cambridge as Lucasian professor, and a fellow mathematician named Humphrey Dutton. By now even the more conservative members of Parliament had faith that 20,000 pounds could spark native ingenuity into solving a complex problem. The implication was that society needn’t wait passively when confronted with pressing scientific challenges.
Whiston and Dutton aspired to win the prize themselves by stationing ships at steady intervals on trade routes and then having their captains fire star shells at midnight that would all explode at the same height—6,440 feet—above the water. Then the longitude of a passing sailing vessel could be calculated by determining the distance to a fixed signal ship from the time lag between the scheduled explosion (or actual sighting of the fireball if it weren’t overcast) and the time the signal was heard aboard their ship.
Though it would have been expensive and impractical to implement, their approach was no more or less off the wall than the multitude of others out there, ranging from timing the effect of a magic potion released in London on injured dogs that were carried aboard ships to painting longitude meridians in the evening sky. Newton
pompously declared a chronometer—what would prove one of the viable solutions—incapable of solving the longitude conundrum; Halley was wise enough to consider all options and even supported early on the eventual winner, whom almost everyone had doubted: John Harrison and his mechanical marine clock, the H-4. For example, Halley was among the few Royal Society members who advocated for its trial when Harrison completed the timepiece in 1735. In truth, probably the best chance for solving longitude at this point was using several of the methods in combination to cancel out each other’s problems.
Halley’s geomagnetic survey, which proved that there was not much correlation between magnetism and lines of longitude, was also influential in prompting the Longitude Act. Conversely, if his magnetic mission had failed, the resulting lack of confidence in public ventures in science might have undercut Parliament-sanctioned funding of bigger and better endeavors in the future.
The Longitude Act was passed just 12 days before Queen Anne’s death on August 1, 1714, before reaching the age of 50. She left no heir either, bringing a close to the House of Stuart. Her husband, Prince George, had died six years earlier and her only son William, Duke of Gloucester, died at age 11. He was the only child of 17 pregnancies to live past infancy.
Anne had succeeded in strengthening the British domain. Her reign oversaw the 1707 Act of Union, which created Great Britain by truly uniting England and Scotland under the governance of one parliament: For the first time, government of the whole country was centered in London (Wales had been joined to England since the 13th century). In accordance with the Act of Settlement, the elector of Hanover would succeed Anne.
Halley reportedly took an oath of allegiance at Westminster Abbey to the new King George I, who came to the throne on Queen Anne’s death in 1714. His ascension transformed the government from Tory to Whig, which favored Flamsteed once again. And Parliament now held the authority of the oligarchy and would gradually
become the dominant power in England. The royal prerogative was left effectively intact. Anne would be the last British monarch to ever veto an act of Parliament.
Flamsteed died at age 73 some five years after passage of the Longitude Act and the change to the House of Hanover. Halley finally could claim the astronomical throne to which in the minds of many he was long overdue. From his perch as astronomer royal, Flamsteed can be credited for helping spawn the business of scientific instruments and chronometry in England and the resulting improvements in observation and measurement. King George officially named Halley to replace Flamsteed on February 9, 1720.
WHILE PINING FOR THIS POST, Halley had made serious contributions to mathematics. He had published more than half a dozen papers on pure mathematics between 1687 and 1720. They ran the gamut from computing logarithms and trigonometric functions to delimiting the roots of equations. His writings on applied mathematics from his mortality tables to his gunnery trajections were also of note. Yet Halley had been preparing for this next step all his life.
At age 64, Halley had landed the long-sought-after post of astronomer royal. And—always the explorer—with his adventurous spirit still very much alive, he boldly wrote a blueprint for a 19-year-long series of observations of that tidal force and eternal inspiration for poets and scientists: the luminous Moon.
Indeed as England’s second astronomer royal, Halley had joined the ranks of the world’s scientific elite. At this point in his life, only a score or so of men were actually paid as scientists in Europe, including the astronomers at Greenwich, Paris, Berlin, Oxford, Cambridge, and the like; the curators of Padua’s and Leiden’s botanical gardens; and probably a couple of anatomists and chemists at universities and other institutions. Other academics were paid as mathematicians as well.
Flamsteed had believed “that observations of the Moon’s distances from fixed stars were the most proper expedient for the dis-
covery of it [the longitude].” Halley himself was committed to the lunar distance solution to the longitude problem. The method requires that the position of the Moon at any given moment, relative to the Sun or other stars, be predicted accurately.
Halley had conceived of using the cycles of the Moon to determine longitude in 1682, years before Newton had developed his theory outlined in the Principia, which made such a scheme seem possible. (Of course, Nuremberg’s Johann Werner first put forth the method in 1514.) Halley also considered using lunar and solar eclipses as timepieces in the sky.
Meanwhile, the Italian astronomer Cassini in Paris was more partial to using another celestial clock, that of Jupiter’s satellites, to find longitude. Galileo first proposed the idea when he discovered the planet’s four satellites. Like Earth’s moon, Jupiter’s moons are independent of Earth’s rotation. Cassini constructed elaborate tables of the satellites’ motions. Robert Hooke also engaged in making tables of Jupiter’s occultations.
Halley, however, criticized Cassini for rejecting his Danish colleague Olaus Roemer’s theory of light, which explained irregularities in the times of the eclipses. Light, contrary to accepted beliefs, had a finite velocity and did not arrive instantaneously, Roemer explained in a paper later published in the Philosophical Transactions. (Like Cassini and Huygens, Roemer was invited to Paris to join the French academicians, who received pensions from the king.) Halley contended there were big errors in Cassini’s tables because he ignored Roemer’s findings. Halley attempted to correct the tables for London. But the errors even for Jupiter’s first satellite, which was the least affected by the ramifications of the fixed speed of light, were as large as three minutes or 45 degrees of longitude. Halley used components in Newton’s Principia to explain even the smaller anomalies. For example, Halley supposed that the nature of the gravitational attraction of Jupiter’s equatorial bulge could cause minor irregularities in the satellites’ orbits. (In Book III of the Principia, Newton demonstrated that rotating bodies like Earth and Jupiter were spheroids.)
Just the same, when Halley reached the New World on his voy-
age, he made telescopic observations and used Cassini’s tables to attempt to improve his dead-reckoning estimates of longitude while crossing the Atlantic. In places they were more than 400 miles in error. In the absence of a fleshed-out theory of the Moon, Halley recognized that the eclipses of Jupiter’s first satellite were the best-available clock for finding longitude on land. Improvements on Cassini’s tables weren’t made until 1719.
ALMOST POETICALLY, HALLEY HAD started and would culminate his career at the Royal Observatory in Greenwich not far from his place of birth. At that historic site the prime meridian, the arbitrary line of zero degrees longitude, would one day be universally agreed upon. Atop a rolling green hill, the enchanting red-brick building with its observing domes majestically overlooks the Thames and gives a full view of the ingoing and outgoing shipping traffic from London.
Reality would subdue Greenwich’s charm a bit, however, when Halley moved into the observatory and adjoining house in March 1720. Flamsteed’s widow had taken all of her husband’s instruments from the premises, as he’d purchased many of them himself. His instruments not only were valuable but were also symbols of mathematical and professional prowess. Without the proper tools, Halley wouldn’t make his first observation until October 1721. After muddling through with his instruments, Halley secured a 500-pound grant from the government to reequip the observatory in 1724. His first purchase: a mural quadrant, with an eight-foot radius, to measure zenith distances of stars moving toward the meridian in order to determine latitude. Crafted by George Graham, one of the leading instrument makers of the early 18th century, the device consisted of a circular border that forms a 90-degree arc attached to an arm that is pointed at the celestial body. Jonathan Sisson had devised an innovative design that afforded more accuracy than ever before. The model would help spur England’s instrument export business in the coming decades.
With restoration of the observatory under way, Halley concentrated on his scheme to observe the Moon daily over its entire 18-year
cycle or saros. From these data he planned to make empirical tables of the Moon’s motion.
A year later, in 1725, Flamsteed’s widow, abetted by his assistants, published Flamsteed’s own version of Historia Coelestis, which cataloged nearly 3,000 stars, and several years later an accompanying star atlas that displayed his data graphically.
After George’s son succeeded the king in 1727, his wife Queen Catherine visited Greenwich and toured Halley’s observatory there and was favorably impressed. When she heard that the salary of the Astronomer Royal was the same as that when Flamsteed was first appointed more than 50 years previously, she sought a raise for Halley. He, however, declined. “Pray your Majesty do no such thing, for if the salary should be increased it might become the object of emolument to place there some unqualified needy dependent, to ruin the institution.” Catherine went ahead and obtained from her husband King George an annual grant for Halley’s former services in the Royal Navy, half a captain’s salary.
At the age of 82, Halley completed his observations of a full saros. Between 1722 and 1739, he eyed the Moon at meridian passage whenever possible. He bragged to the Royal Society in 1731: “With my own eye without assistant or interruption … 1500 observations of the Moon … more than Tycho, Hevelius, and Flamsteed had taken altogether….”
Ironically, in 1727 Halley, like Flamsteed, had refused to publish his latest observations, so “that he might have more time to finish the theory he designs to build upon them, before others might take advantage of reaping the benefit of his labours.” Flamsteed probably relished that fact from his grave.
PERHAPS HALLEY HAD THE 20,000-POUND longitude prize on his mind. The sum was the equivalent of more than 10 million pounds today. Clearly, his work confirmed the theoretical feasibility of the “method of lunars” as a way to solve the longitude problem. It is unclear whether he, as an ex officio member of the Board of Longitude, would have been eligible. But his detractors were quick to think the worst of
him. Flamsteed had reportedly commented: “Raymer [his unflattering nickname for Halley] sets up for a finder of the longitude.”
By as early as 1731, Halley had acquired enough data to establish the use of lunar observations for determining longitude at sea. Although at the equator the margin of error ranged up to nearly 70 miles, it was an improvement over existing methods. Around this time English astronomer James Bradley, Halley’s eventual successor, discovered another celestial phenomenon that could also skew lunar observations, namely aberration, the ever-so-slight deflection of light through space. And then in 1748, he noticed yet another: nutation, the small oscillation of celestial bodies. He realized all past, present, and future lunar observations needed to be corrected for both.
Getting navigators to use the lunar distance approach was another matter, of course. It was not only tedious but time consuming, and better instruments, such as the Hadley reflecting quadrants, would move things along. With the help of the Nautical Almanac developed by Nevil Masklyne, who would become the fifth astronomer royal, the calculations became less unwieldly. First published in 1767, the Almanac detailed the distance to the Moon from various stars at short intervals from which Greenwich time could be computed.
Throughout the course of the approach’s evolution, Halley’s lunar observations would be heavily criticized for their inaccuracy. Although his Moon work clearly furthered Newtonian dynamics, the criticism must have held much truth for he would be the only royal astronomer whose lunar observations would never be published.
ALTHOUGH THE LUNAR DISTANCE METHOD would never be error-free even if determination of such astronomical benchmarks could be perfected, it would be employed until the early 19th century, when chronometers really came into their own. Or at any rate the lunar tables would be published in the Almanac through 1906, though no longer in use. One sage captain later reported that he had “not fallen in with a dozen men who had themselves taken lunar or had even seen them taken [since 1855]…. They are in fact as dead as Julius Caesar.”