Once the latitudes of the starting and finishing points had been determined by astronomical observation, the size of the Earth itself would be known. A universal standard measurement would exist for the first time in history. This holy grail of the Age of Reason would be France's gift to the world: a single unit of measure which, as Condorcet said, would be 'for all men, for all time'. The metre would measure exactly one ten-millionth of the distance from the North Pole to the Equator. The 'king's foot' and all the other cranky measures that varied from one village to the next would be swept away forever. The free world and all its wares and produce would be measured only by the eternal laws of Nature, not by the length of a man's arm, the appetite of a cow or the arbitrary decision of a despot. Louis XVI gave his blessing to the project and went back to preparing his escape...The biggest obstacle was the fact that few people understood the fraternal and egalitarian nature of the project. At Montjay, Delambre's observation platform was torn down by citizens exercising their new democratic right to destroy anything new. In the Orléans forest, he was able to build his platform only because the local people were busy elsewhere in the forest, demolishing 'a stone pyramid called the Meridian which was built by the former seigneurs as a sign of their greatness'. (It was an obelisk commemorating Cassini's survey of 1740.) Delambre was forced to give impromptu public talks to explain his mission: he was not a Prussian, his spyglass was not for spying and the letters of accreditation bearing the royal seal were not secret messages from Citizen Capet (formerly known as Louis XVI). At Saint-Denis, where the kings of France were buried, a crowd broke into his carriage and discovered the most suspicious-looking collection of objects they had ever seen.
The instruments were laid out on the square, and I was forced to recommence my lecture on geodesy . . . The light was failing and it was almost impossible to see. The audience was very large. The front rows heard without understanding; the others, further back, heard less and saw nothing. Impatience was spreading and there were murmurs from the crowd. A few voices proposed one of those expeditious means, so commonly used in those days, which cut through all difficulties and put an end to all doubts.
...Some old people remembered seeing Cassini pass through their village many years before, but the platforms and wooden pyramids he had built as triangulation points had been dismantled for the wood or destroyed as enemy signalling devices. The plains around Bourges had been shorn of every eminence: Delambre was told that a representative of the people had 'demolished all those steeples that elevated themselves arrogantly above the humble dwellings of the sans-culottes'. The Temple of Reason at Rodez - formerly known as the cathedral - was the only original triangulation point that remained in the Aveyron. The more remote the area, the more tenuous the connection with scientific truth. At Bort-les-Orgues, Delambre's signal, placed on the bizarre organ-pipe escarpment above the town, was said to have caused a landslide that sank the streets waist-deep in mud. This happened almost every year, but, for once, the cause was obvious. On the fog-bound summit of Puy Violent above Salers, the wizard's straw-covered house made from three twenty-three-foot tree trunks was blamed for the death of several cows and a spate of minor accidents.
Seven years and thousands of miles later, after suffering atrocious weather, impassable roads and impossible peasants, illness, flimsy platforms that wavered in the wind because the carpenters had skimped on materials, the mental breakdown of Méchain and an attack of wild dogs who scattered the rulers that had been carefully laid along the baseline near Perpignan, Delambre submitted his results at the world's first international scientific conference, held in Paris on 2 February 1799. A metre-long bar of pure platinum was presented to the National Assembly in April. This was to be the permanent standard metre 'for all people, for all time', though it would take another century to persuade the whole country to adopt the decimal system.
In some places, the arrival of a stranger with fantastic tools and an inexplicable plan was a major historical event. In gazetteers and guidebooks published decades later, the only thing worth mentioning in some places was the 'ruins of a pyramid erected by Cassini'. The novelty was too much for some small villages. In 1773, in the heart of the Tarn, a young surveyor from Issoudun was pulled down from the tower of the ruined church of Saint-Martin-de-Carnac near the village of Cuq. Epidemics had passed through the region and left the local people fearful and resentful. His attackers set about him with clubs and knives. Somehow, he escaped. Later that day, a man with bleeding hands and a broken skull was seen staggering along the road from Castres to Lavaur, a mile south of Cuq. No one dared help the fleeing sorcerer. At last, he reached a roadside inn run by 'the Widow Julia', who sent for a doctor and a surgeon. The surveyor survived but was forced to retire with a pension.
The Cassini map shows the route as two shaded lines with dots on either side. This was the symbol for a surfaced, tree-lined road. The Emperor's valet remembered the journey for years to come:
In the Ardennes, we ran into danger. The Emperor had planned the route we were to take. Unfortunately, the road existed only on the map. It became so bad that, on a very steep descent, we were forced to restrain the carriages with ropes. In fright, Joséphine decided to decided to abandon the coach, despite the rain and the mud. . . . The carriage in which the first lady-in-waiting Mme Saint-Hilaire was travelling tipped over. She reached Liège a day after the rest of the party. Riders of the escort were sent out to see what was causing the delay and to offer protection, but these attentions appeared insufficient to Mme Saint- Hilaire, who was most offended that the entire court was not thrown into confusion by her absence.
A representative tableau of France in 1804 might show Napoleon at Notre-Dame in Paris, taking his crown from the hands of Pope Pius VII, or the hundred thousand soldiers of the Grande Armée waiting on the coast at Boulogne for the order to invade England, but it would be just as representative if it showed the imperial party wading through a quagmire somewhere north of Sedan. Long after the country had been mapped, getting lost or stranded in the heart of the French empire was a common experience. Dozens of nightmare journeys can be recreated by comparing Cassini's charts to contemporary accounts. A young army officer called Paul Thie´bault, who was in the crowd that stormed the Tuileries in 1792, was travelling from Paris to Millau with two fellow officers in 1795. At this point in his account, they had reached a part where the map showed a 'metalled, tree-lined road':
Having no paths to follow but the beds of torrents, and finding no habitation, we became lost after passing the spot where our guide informed us that the Beast of the Gévaudan had been killed.27 Meanwhile, the light was failing and we were beginning to wonder how we would spend the night among these arid hills when we spotted a house on the far side of a deep gorge.
The house was called La Bastide. It appears on the Cassini map, on an isolated stretch of road, as a little square building marked 'la Bastide - cabaret'. Though the roof was blown off by gales in 2004, the sunken stone vaults of the original ground floor can still be seen. It was here that Thiébault and his comrades spent the night. The inn was deserted apart from two shifty-looking women. After discovering a trapdoor in the floor of their bedroom, the officers barricaded themselves in and slept in their clothes. At daybreak, they asked for the bill and were charged one louis (twenty-four francs) for bed and a stingy omelette. (Twenty-four francs would have bought a cow's milk for a year.)
. . . As we were leaving through the courtyard gate, we found ourselves face to face with two armed men coming along the route we had taken the day before. Behind them, at a thousand paces, were several other men, also armed. . . . We spurred our horses and set off at a full trot. The walls of the house covered our departure and we were out of range before they could decide what to do.
...People travelling from Toulouse to Bordeaux must have wondered what had happened to the (fictitious) bridges at Verdun and Tonneins, and some travellers in the Alps must have been disappointed when they found that the only way to continue on the road marked 'Grand Chemin de France au Piémont' was to have the carriage dismantled and loaded onto the back of a mule.
...Typically, the 'eye' had seen very little of what was shown on the map. Until Cassini, much of what appeared to be known about the provinces was based on second-hand reports. Even the government inspector of historic monuments, Prosper Mérimée, was partly dependent on hearsay when planning his tours of inspection in the 1830s:
I have often heard tell of a very ancient monument that lies somewhere in the mountains to the south-west of Perpignan. Some say that it is a mosque, others that it is a church of the Knights Templar. I have also been told that it's a hovel in such a ruinous state that no one can tell when it was built. Whatever the case, it must be worth an excursion of three or four days on horseback.
Thanks to Cassini, Mérimée could at least confirm the existence and check the location of this mysterious temple. (It was the star-shaped eleventh-century church at Plane`s, known locally as 'the Mosque'.)