Louis Antoine de Bougainville's circumnavigation had overtly scientific aims which were:
- to make reliable maps of the Pacific that he voyaged through,
- collect plants,
- try to refine the measurement of longitude on an ocean voyage.
But Bougainville's secret and covert orders were to chart the explored regions for the French colonists which would follow, and
to collect nutmeg and clove plants to grow on Mauritius so that the French could break the Dutch monopoly of the spice supplies. Bougainville's main passion was accurately measuring longitude. An expert astronomer was assigned to the circumnavigation called Pierre Antoine Veron. Veron had the latest scientific equipment and he took many readings with quadrant, octant, and megameter , measuring angles of stars. The French had a right to claim to some measure that their circumnavigation had been based on scientific factors.
Bougainville's flagship was the Boudeuse , a brand new frigate that had twelve inch guns and was a fast warship that carried a large amount of sail. But what Bougainville really needed was a steady work horse like Cook's Endeavour that could carry lots of gear and withstand the force of the ocean's fury. When they hit their first Atlantic storm, the Boudeuse lost her foretop and maintop , took in water and they had to return to Nantes to have the masts shortened and get smaller cannons. Bougainville very cautiously carried out further modifications and sailed for the Falkland Islands, then sailed for Rio de Janeiro and met up with his store ship, the Etoile. He spent five months in Rio de Janeiro fitting out his ships and bringing on board as many provisions as he could fit in the holds.
Bougainville left Rio de Janeiro in November 1767 for Cape Virgins and it took him fifty two days to get through the Magellan Straits to the Pacific. Bougainville was extra cautious going through the straits and always kept within sight of land and anchored frequently. He sailed across the Pacific on a north west course from January to April when he arrived at Tahiti and stayed for two weeks. Bougainville then sailed west , then altered course to the north east in June 1768. Hunger and scurvy was stalking the crew and they were reduced to eating rats. They did not even stop when they reached the Louisiade Archipelago, and Bougainville would not go through Torres strait because he wanted to be sure to reach the spice islands to research the spice trade and collect his plants. He was in a hurry to pick up the monsoons that would take him across the indian ocean to Mauritius.
Bougainville had to sail eastward around the Louisiades and on June 25 rounded Cape Deliverance and altered course to the north towards New Ireland where they safely anchored at the same bay that Carteret had found. They sailed along the north coast of New Guinea and reached the Moluccas on September 1 and sailed into the harbour on the island of Buru. After eight days the Boudeuse and the Etoile left the Spice Islands and on 28 September they reached batavia. He reprovisioned and left as soon as he could on 16 October 1768 and sailed for Port Louis on Ile de France. `The ships finally returned to France and sailed into St Malo harbour in March 1769.