by Val Ross
This Jean-Dominique Cassini will do — and so will his son, grandson, and great-grandson, making the Cassinis one of the world’s greatest dynasties of mapmaking.
The “corrected Map of France,” by the team under Abbé Jean Picard and J-D Cassini, was drawn by Gabriel de La Hire in 1682. It shocked the French by revealing glaring differences between their ideas about France’s size and the true outline of their country.
When Giovanni Domenico Cassini first arrived in France in 1668 from his native Italy (where he had been astronomer to the Pope), Europe was a mess — at least in mapmaker’s terms. In France, every district, every type of shopkeeper had a different system of measurement. In Paris, an aune — roughly 1 meter (3 feet) — of cotton was shorter than an aune of linen. (Or was it longer? Everyone was confused.) Huge regions of France had never been mapped. Peasants attacked surveyors because they suspected — rightly — that if the extent of their property was formally recorded, they would have to pay more taxes.
MAPPING BY THE SKIES
All over the world, since ancient times, sailors and mapmakers have checked their location by consulting the position of heavenly bodies. The sun shines directly down on the equator twice a year. On the longest day of the year in the northern hemisphere it shines directly down on the Tropic of Cancer (that is, a pole in the ground there casts no shadow). On the shortest day in the northern hemisphere, the sun has moved south, and shines directly down over the Tropic of Capricorn. The stars also move with the seasons. Watching the sun and the position of the stars in the night sky enabled people to tell how far north and south they were — that is, latitude.
Astronomy was also important to surveyors. When they set about to survey France, the Cassinis used large quadrants (a quarter of a circle mounted on a pedestal and fitted with a telescope) and sextants (a sixth of a circle) to measure the angle between the horizon and a star, or other heavenly body. By the end of the 18th century, the devices to measure horizontal and vertical angles were combined to form the theodolite.
Today’s map of the Cassinis’ France.
At university in Bologna Cassini had studied everything from bugs to blood transfusions, but he was best known for his book about the moons of Jupiter, published in 1668. Cassini’s expertise in astronomy made him a real asset in mapmaking. Since Louis XIV was inviting Europe’s top scientists to his court, he asked the Pope if he could borrow his astronomer. On arriving in Paris, Giovanni Domenico Cassini was so delighted to find himself among such men as Jean Picard and the great Dutch scientist Christiaan Huygens, he took out French citizenship and changed his name to Jean-Dominique.
In 1669, the Sun King commanded his scientists to correct the existing maps of France, determining its borders east and west from a brass line set into the floor in the middle of the Royal Observatory in Paris. Led at first by Picard, the mapmakers set out to survey a line running north and south between a tower in the town of Malvoisine near Paris and a clock tower in the town of Sourdon near Amiens. The surveyors sent these new measurements back to headquarters in Paris.
The Vallard Chart of 1547, showing the “Landing of Jacques Cartier” in the New World, is a beautiful thing, but it shows the inaccurate state of French mapmaking before the time of the Cassinis. South is at the top, and the St. Lawrence River flows into a wilderness in which the Great Lakes do not even appear.
Abbé Picard died not long after Louis XIV inspected the first corrected map of France. When Cassini took over the project, he began finding problems with the first survey. A degree of latitude that Picard had measured in the north of France seemed shorter than what Cassini found in the south.
Most people thought the Earth was perfectly round. Cassini proposed that it was not a perfect sphere but was egg-shaped, longer in the middle and shorter at the top. Other scientists, including England’s Isaac Newton, insisted the spin of the Earth made it more like a grapefruit, bulgy in the middle and flattened at the Poles. As he grew older and more respected, Cassini defended his egg theory vigorously. What he was really defending was the accuracy of his first series of observations — in other words, his reputation — and the job that he was planning to pass on to his son Jacques Cassini (known as Cassini II). The debate over Earth’s shape became a question of French versus English approaches to the problem, and a matter of national and family honor.
Cassinis I and II decided to run a new survey from Paris to Dunkirk on the English Channel, and from Paris south to the Spanish border. When the old man died at age eighty-seven in 1712, Cassini II took over the family cause, still insisting that the Earth was an egg, and that lines of latitude got shorter as you went north. By the mid-1700s, even Frenchmen were beginning to doubt this. One young mathematician, Pierre-Louis Moreau de Maupertuis, twenty years younger than Jacques Cassini, made it his personal cause to prove that the royal mapmaker was holding France back from cutting-edge science with his stubbornness.
To resolve the dispute, everyone agreed there should be a new round of measurement and mapmaking. In 1735, Frances new king, Louis XV, agreed to finance two costly expeditions to determine the shape of the Earth. One, under Charles Marie de la Condamine, set off to Peru to measure the length of a degree of latitude at the equator. The other, led by Maupertuis himself, headed for the Arctic Circle in Finland.
After fifteen months, Maupertuis and his team returned with heroic stories of bone-chilling cold, tales of plagues of summer mosquitoes — and measurements that showed the length of a degree of latitude at the Arctic Circle was longer — by about ½ kilometer (⅓ mile) in today’s measurements — than a degree measured in the middle of France. Maupertuis said the Cassinis were wrong.
But Maupertuis had used English instruments to take his measurements, Cassini II pointed out. Surely this must have biased him to accept the English idea about the Earth’s shape. In public, Cassini II played the objective scientist. But Maupertuis complained that in private Cassini raised petty objections to the Finland survey, and would not shut up. Maupertuis fought back by publishing anonymous pamphlets insulting the Cassini family’s scientific abilities.
Nine years after the second team set out, Condamine and his men straggled back from Peru. They had clambered up the Andes Mountains, contracted fevers in the Amazon jungle, and fought so bitterly with one another that they were no longer on speaking terms. But their measurements also confirmed that the Earth was indeed wider in the middle. Voltaire, the great French intellectual, joked, “The expedition flattened both the poles and the Cassinis.”
By this time, Jacques Cassinis son, César-François Cassini (Cassini III), had taken over as royal mapmaker. It was up to him to make peace in 1743 by agreeing that Newton and Maupertuis were right. In any case, there were more important tasks at hand. By the 1740s, the Cassinis had covered France with 400 separate triangulations. No country in the world had ever before been so thoroughly measured.
But many French people hated the whole project. Peasants often tried to steal the surveyors’ equipment. In the 1760s, in one remote mountain town, villagers pulled a surveyor from his ladder and attacked him with their hay-cutting tools. When they finally let the poor man go, he was streaming with blood. The villagers told a local magistrate investigating the attack that the surveyor was “a sorcerer who had come to harm them … and to increase the income tax….”
Another danger was that the king might lose interest in the mapping project. He did. Royal funding was cut in 1756. So Cassini III rounded up private investors and turned his mapmaking into a profitable business, selling charts to the public. He also invited English surveyors to compete with the French in measuring latitude and longitude around the English Channel — mapping was beginning to transcend national boundaries.
THE METRIC SYSTEM
Before the French Revolution, measurements were so chaotic that France’s scientists and shopkeepers alike were clamoring for reform. In 1790 the National Assembly ordered the French Academy of Sciences to come up with “an invariable standard
” — some unit derived from nature, around which could be built a system in divisions and multiples of ten. But how long would the new unit, to be called a meter from the Greek word for measurement, be? The Academy decided it would be one ten-millionth of the distance between the North Pole and the equator. In 1791, under the direction of Cassini IV, two scientists set out to do yet another triangulation of France, to determine that total distance — and then one ten-millionth of it.
The two — Jean Delambre and Pierre Méchain — worked for seven years. The old government was overthrown in the French Revolution, their boss Cassini was imprisoned, and the new regime threatened to call off the entire project. Mobs threw them in jail. They got sick. Worst of all, Méchain fell into a depression and disappeared. When finally tracked down by his long-suffering wife, he said he couldn’t finish the job properly. So Delambre and Madame Méchain did the final calculations. Somehow the meter was defined and, in 1 799, was cast in a rod of pure platinum.
In the 20th century, calculations based on satellite readings of the distance from the North Pole to the equator revealed that the 1799 meter is imperfect — it’s about 0.2 mm (1/140 inch) short. Now the meter is redefined as the distance light travels in a vacuum in 1/299,792,458 of a second. Today 95 percent of countries use the metric system (the U.S. and Liberia are among the holdouts that do not).
Cassini III, the peacemaker, died of smallpox in 1784, and his son Cassini IV (named Jean-Dominique, just like his great-grandfather) became director of France’s Royal Observatory. He was made head of the project to develop the measurement of a single perfect meter, which would form the basis of the new metric system. And he published the Carte de Cassini in 1789.
The Carte de Cassini is drawn to a scale of 1:86,400 and is printed on 184 sheets. Each sheet, folded and delicate, is so detailed, you can see tiny church steeples and windmills. When the maps showing Paris were published for the public in 1793, they became bestsellers.
But 1793 was also a year of revolution. The king lost his head on the guillotine. So did his top scientists, many who were friends of the Cassini family. Mobs searched the Royal Observatory where Cassini IV lived, and terrorized his family. Cassini IV dismissed the mobs as “Don Quixotes,” or crazy dreamers. He did not realize how much France’s poor blamed their miserable lives and heavy taxes on the king and his mapmakers.
Some of the young researchers who worked for Cassini IV at the Observatory did know, however. Alexandre Ruelle had been hired by Cassini IV to work as a guard at the Observatory and to take basic sightings of stars and planets. Astronomical observation is a difficult job calling for a lot of patience, and Ruelle wasn’t very good at it. Cassini IV was probably tough on the young researcher; after all, this Cassini was the fourth generation of the family that had mapped France. In any case, Ruelle hated his boss. One night, he overheard a fellow guardsman come home drunk, yelling, “Cassini the aristocrat must die!” This gave Ruelle an idea.
Ever since the kings execution, revolutionary tribunals were running France. Ruelle went to one and declared that Cassini IV was an old-style aristocrat who exploited his researchers and stole their hard work. The tribunal took the complaints seriously. The members decided to make Cassini pay for his family’s connections to the dead king. First they fired him as director of the Royal Observatory. Then they seized his maps of France, the project for which his family had been responsible for more than a century. When Cassini IV protested, he was thrown in prison.
Giovanni Domenico Cassini is shown in this engraving from 1712 with a telescope in the background, to signify that he was not only a major map-maker, but also an astronomer who discovered four moons of the planet Saturn. The founder of the Cassini dynasty that mapped France for four generations, he is known as Cassini I.
But Ruelle wanted more — the boss’s head. So he pestered the tribunal to bring Cassini IV to trial and the guillotine. At last, others at the Observatory stood up for their master. They told the tribunal that Ruelle was a poor scientist. They said he had made a major error in an observation of the sun and was trying to frame Cassini. Now it was Ruelle’s turn to be thrown in jail.
Cassini IV was lucky. He spent just seven months behind bars, expecting each day to be marched up the guillotine’s wooden stairs and forced to lay his head under its knife. Instead, he was finally set free. But he was still disillusioned, so he left Paris and moved to the country. In a letter to a friend, he wrote that mapmaking and star-watching meant nothing to him any more. The greatest scientists of his age had been killed by the mob, he said, but what saddened him even more was that he had seen scientists “themselves up in arms, divided against one another.”
It was too much. Cassini IV convinced his son that the great map-making dynasty should end. There would never be a Cassini V The son of Cassini IV became a botanist.
THE MAPMAKER’S HANDS
Captain James Cook
THE HORRIFIED MEN and cabin boys of His Majesty’s ships the Resolution and the Discovery, anchored in Hawaii’s Kealakekua Bay, peer into the basket. They see a pair of severed human hands. They know at once whose hands they are.
Large, brown, and callused from years at sea, the hands have a purplish scar running around the right thumb. The men know that these hands have ordered men whipped, but have also fine-timed scientific instruments of delicate precision. They have written journals in a confident, sloping script that looks as orderly as a fleet of ships leaning before a steady wind. They have drawn some of the most accurate maps the world has ever seen. The British sailors would know those hands anywhere. They have been chopped from the body of their captain, the legendary James Cook.
James Cook was born on October 27, 1728, to a poor Scottish farmworker’s family in the north of England. Tall and intelligent, the boy had a magnetic ability to attract attention from people who were willing to help him on his way. He also had a boundless appetite for adventure, and wrote in his journal, “I want to go as far as I think possible for man to go.”
So he went to sea — to the merchant fleet that sailed out of the town of Whitby, hauling coal down the English coast in flat-bottomed boats of the sort known as Whitby cats. But he turned down the chance to become captain of his own cargo ship. He started from the bottom again as an able seaman in the Royal Navy.
In 1758, the ambitious young man was shipped to Canada to fight the French. On his first Atlantic crossing, twenty-six of his crewmates perished from scurvy, a fatal vitamin deficiency. Those who survived spent the winter in Halifax. Unlike his fellow sailors, who mostly drank and fought, Cook spent his time before the final assault on Quebec City learning how to make maps from surveyor Samuel Holland.
To stop the English from sailing up the St. Lawrence River to attack them, the French had removed all the buoys and markers warning sailors of shallow or dangerous waters. All winter, Holland and Cook surveyed the St. Lawrence, taking soundings of the river’s depths and making notes (“good Anchoring here in Soft Clay Ground”). Thanks to their charts, when the British fleet sailed upriver in the spring of 1759, not one ship ran aground.
In this beautiful setting, Hawaii’s Kealakekua Bay, Captain James Cook was killed on February 14, 1779. A small monument has been erected to honor Cook’s memory, and the fact that he mapped the Pacific almost from pole to pole.
After General Wolfe and the British defeated the French outside Quebec City on the Plains of Abraham, Cook sailed home to London. He was thirty-three, and unemployed. But he must have been sure of himself, for he proposed marriage to Miss Elizabeth Batts, a pretty London shop girl. A week after their wedding, in late December 1762, Cook strode into the British Admiralty for new orders.
His way had been smoothed by letters from his commanding officers in Canada that spoke of “Mr. Cooks capacity and genius.” Impressed, the Royal Navy’s admirals made him Master Surveyor and told him to chart the wild 9,600-kilometer (6,000-mile) coast of Newfoundland.
The usual method of surveying a coast at that time was
called a running traverse, and involved triangulating headlands and high points of land from the pitching deck of a moving ship. Master Surveyor Cook decided to combine the running traverse with time-consuming but more accurate surveys from land. Everyday he had to row ashore, measure a base line, fix flags at the end points, and then sight the angles from those points to a third position. The results were so good, his charts were still in use a hundred years later.
Cook’s new career nearly ended August 6,1764, when a powder horn blew up, almost taking his right thumb off. A good surgeon stitched him up — but for the rest of his life, Cooks hand was scarred from thumb to wrist.
Cook spent three years on the Newfoundland survey, his reputation growing with each shipment of beautiful new charts sent home. So the Royal Navy promoted him again. In 1768, he was given his own ship and told to sail to Tahiti in the Pacific to watch the planet Venus cross the sun. There he was to open a secret envelope with further orders from the Royal Navy.
Why send a costly expedition to watch stars? England desperately wanted to make a major scientific discovery to compete with the French, the master mapmakers of the age. Besides, the French, Dutch, and Spanish were already claiming Pacific lands, and the English wanted a share of the action and the profits. They also wanted to solve the mystery of the great southern continent, the one whose existence was predicted by Ptolemy, Mercator, and other geographers. The reliable Cook was just the man to discover it. “The world,” wrote Cook, “will hardly admit of an excuse for a man leaving a coast unexplored he has once discovered.”