Earth and Space

Le Gentil’s journey

Stories from Physics for 11-14 14-16 IOP RESOURCES

A strong candidate for the title of ‘most unfortunate astronomer’ is the extravagantly named Frenchman Guillaume Joseph Hyacinthe Jean Baptiste Le Gentil de la Galaisière. Le Gentil believed that Halley’s calculations for the transit of Venus were inaccurate and he was sent by the French government to observe the 1761 transit in Pondicherry in India, then under French control.

However, three months into his voyage, whilst breaking his journey at Mauritius, Le Gentil learned that the Indian Ocean was under the control of the British Navy. Undeterred, he continued his journey only to discover, whilst off the Indian coast, that Pondicherry had fallen to the British. The transit occurred whilst he was returning to Mauritius and heavy seas and poor visibility interfered with his measurements.

Le Gentil chose to stay in Mauritius to study the islands and made plans to travel to Manila for the next transit in 1769. However, on arriving in Manila after three months at sea, he learned that the governor would not allow the establishment of an observatory. He again set sail for Pondicherry, which had since been re-established under French control. But having finally reached Pondicherry and set up his observatory, the day of the transit proved to be overcast.

Devastated, Le Gentil planned to leave by the next available ship but contracted a serious illness and did not leave till the following year. On his journey home, his ship was nearly sunk by a storm and he was forced to return to Mauritius where he boarded a returning Spanish warship and travelled over land from Spain. On his arrival in France, 11 years after setting out, he discovered that he had been declared dead, his estate divided up and his chair at the academy taken by another scientist.

Nonetheless, his story has a happy ending: Le Gentil published the story of his adventures which became a financial success. He went on to marry a wealthy heiress and regained his academic chair


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