…continuedThe Transit of Venus: Tales from the 18th and 19th Centuries
Travelers' Tales: 1761
The French had similar troubles. For example, there was the epic journey of Guillaume-Joseph-Hyacinthe-Jean-Baptiste Le Gentil de la Galaisière He arrived in Mauritius a year in advance of the transit but could not continue because the British were besieging his final destination the coastal fort of Pondicherry, India. While waiting for the blockade to be lifted Le Gentil fell ill, recovered, and finally joined a French warship bound for India to relieve the French colony. Despite being blown off course by a monsoon they reached the Indian coast, but passing ships notified them that Pondicherry had fallen. Le Gentil's vessel turned back toward Mauritius. June 6th was a beautiful day in the Indian Ocean, and Le Gentil saw the entire transit, but from the deck of his pitching ship he could make no scientifically useful observations.
All in all, the 1761 observations were a sharp disappointment. The black-drop effect caused significant variations in the recorded times of contacts, even among observers at the same site, and seriously undermined attempts to refine the Earth-Sun distance.
Travelers' Tales: 1769
If nothing else, 1761 provided a dress rehearsal for the next (and last) transit of the 18th century: June 34, 1769. By then peace reigned across Europe, and Britain enjoyed a far reach over the surface of the Earth. With colonial possessions so vast that the Sun never set on their empire, the British organized two expeditions to, literally, the opposite ends of the planet.
Meanwhile, the French remained active; new expeditions were mounted while one simply continued on. Le Gentil decided to remain south of the equator so as not to be deprived of a chance to observe the last transit of his lifetime. He hoped to observe the transit from Manila, but after arriving in the Philippines he was ordered to Pondicherry once more a French possession where he experienced the most devastating experience of any traveling astronomer: he was clouded out.