Page - 288 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

Chapter 6288 question of the parallax was now settled to the accuracy of ±0.01″.89 It is known that on December 20, 1771 Hell wrote a letter to Lalande, in which he tried to persuade his French colleague to exclude the observation of Planman entirely from the calculations of the parallax.90 The tone of the letter was perhaps a bit too self-confident, for by March 10, 1772, Lalande had become convinced of the opposite, as is seen in a letter to Boscovich: “What is your opinion of Father Hell, have you seen him observing, is he able, is he well trained? I conclude with the utmost dismay that his observation from Vardøhus is in accordance with no other, and that it has to be discarded.”91 Similarly, he advised his col- league Bernoulli in Berlin, “do not trust the remarks of Father Hell, he is surely wrong, and this will do no honor to your work [i.e., the Receuil pour les Astronomes].”92 Lalande published his rejection of Hell’s data in April 1772, in the Mémoire sur le passage de Vénus devant le disque du Soleil (Memoir on the transit of Ve- nus in front of the disc of the Sun).93 Here, Lalande explained how he had found the mean solar parallax to be 8.50″, by means of virtually every other observation than that of Vardø. As for the competing observation by Planman, Lalande’s conclusion was quite devastating to Hell: “This observation from Cajaneborg has become the most important among all those that were made in Europe, for it has served as confirmation and the element of comparison for all remote observations, with which it is in perfect harmony.”94 Lalande’s memoir was received by the Viennese Jesuit as little short of a declaration of war. In less than three months, he managed to compose—and print—an apology nearly three times the size of Lalande’s work, De parallaxi Solis ex observationibus transitus Veneris anni 1769 (On the parallax of the Sun deduced from observations of the transit of Venus of the year 1769). The mem- oir contains both a detailed calculation of the solar parallax and a furious 89 Hell to Weiss in Trnava, dated Vienna, December 26, 1771, in Pinzger, Hell Miksa, 2:107–9; Hell to Fixlmillner in Kremsmünster, dated Vienna, July 17, 1772, cited in Rabenalt, “As- tronomische Forschung,” 117; Hell, “De parallaxi Solis,” 107–8. 90 Hell, “De parallaxi Solis,” 6. 91 Lalande to Boscovich, dated March 10, 1772, in Varićak, “Drugi ulomak Boškovićeve kore- spondencije,” ccclxxiii–ccclxxvi. 92 Lalande to Bernoulli in Berlin, dated March 18, 1772 (ubb), published in Dumont and Pecker, Mission à Berlin, 86. 93 We had no access to the original but used the extensive summary in the JS (September 1772): 613–23 (“Mémoire sur le passage de Vénus devant le disque du Soleil, observé le 3 Juin 1769, pour servir de suite à l’explication de la carte publiée en 1764 […] Paris”) and other sources. 94 Lalande, Memoire sur le passage de Venus […], 14, cited in kvah (April–June 1772): 191.