The promontory, on the east-northeast entrance of the bay, was named after the Benedictine chaplain and mathematics professor Ambroise Pierson (1765-94), who served as astronomer, first on L’Espérance and later in the voyage, from 21 August 1793, on La Recherche.

To measure longitude and latitude, Pierson was using a marine chronometer made by the instrument maker Lenoir, with the registration number 10. He was continually testing the steadiness and accuracy of the chronometer’s motion. To carry out his observations, he also used a reflecting circle, a graduated circular instrument like a theodolite used to take angles and duplicate their measurements, thus enabling them to be checked, a tilt compass, and a telescope.

During the expedition’s two stopovers in the D’Entrecasteaux Channel, Pierson organised the moving of the astronomical and surveying instruments to the shore where an observatory was set up for astronomical observations to calculate latitudes and longitudes from the angles between the sun and specific stars, or the sun and the moon. His results were compared to those calculated at the nearby observatory set up by L’Espérance’s consort, La Recherche, to allow for comparison and corrections.

Pierson may have sworn allegiance to the Civil Constitution of the Clergy during the French Revolution, but it has been reported that, thanks to his “gentleness”, he had good relationships with every member of the crew from all sides of the political spectrum. One officer also noted that he was “a big man with a beautiful face” (La Motte du Portail’s sea journal, Archives nationales de France, MAR/5JJ/13/A, 10th letter; also quoted in Duyker, p. 71). He died, probably of dysentery, while the expedition was in Java, as the crew waited for the Dutch to grant them permission to depart from Batavia.