The Ship Within its Historical Context

A civilian pleasure craft, l'Aurore was built for the Marquess de Courtanvaux in 1766 for scientific purposes inspired by the Academy of Sciences: to develop marine chronometers accurate enough to permit a reliable determination of longitude. In 1707 a British fleet commanded by Sir Clowdisley Shovell lost 5 ships out of 20 and several hundred men in a wreck near the Scilly Isles because of a navigational error in foggy weather. As a result, the scientific community in that country concentrated their effort toward a solution to the problem: William Whiston even suggested to place ships at various locations on the main maritime routes to fire guns at regular intervals so that ships would be able to ascertain their position!

In 1714, the British Parliament created the Board of Longitude and offered a prize of 20,000 pounds to whoever solved the problem. At that time, the determination of the position of a star was made with two mirrors, a fixed one aimed on the horizon and the other movable one on the star. In parallel with this research, efforts were made to publish a table of the moon's motion. The main participants in this effort were the British astronomer Edmond Halley, the Frenchmen Lemonnier and the abbot de la Caille, the American Godfrey and the Swiss Euler.

In the years 1760, the determination of longitude using lunar distance was relatively accurate, but not adequate to satisfy one of the requirements of the Board of Longitude: a maximum error of 3 seconds per day, corresponding to a difference of .5 degree in a round trip to America.

In this context, numerous attempts were made to improve clocks operating with spring and escapement mechanism: the Englishman John Harrison managed an accuracy of 54 seconds in a 156-day trip to Barbados. The Frenchmen Pierre Leroy and Ferdinand Berthoud on their side, presented their model in 1766 for the former and 1768 for the latter who was subsequently named the King's and the Navy's Clockmaker and became exclusive supplier of marine chronometers for French naval vessels.

The Royal Academy of Sciences delayed the prize to 1769 but doubled its amount. It is while attempting to find a vessel for the French scientists that the Marquess de Courtanvaux, himself a member of this respectable institution since 1764, offered to finance this voyage intended to test Leroy's marine chronometers. He then decided to build a fairly fast small vessel capable of laying over fairly frequently to verify the accuracy of the scientific instruments aboard. The destination to be northerly towards Amsterdam via the Zuiderzee.