Seite - 282 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

Chapter 6282 Mister Borgrewing [sic] match my own accurately, if a solar parallax of 8.3 arc seconds is supposed. That satisfies me.”71 Our next interlocutor, Anders Johan Lexell,72 was born and raised in Åbo, where he attended university and was noticed for his brilliance in mathemat- ics. No positions were vacant in Swedish universities, however, and it may be that he had higher ambitions as well. Be that as it may, in 1768, he sent two treatises of mathematics to the Imperial Academy in St. Petersburg. Leonhard Euler (1707–83) examined them and made sure that Lexell obtained a position as his adjunctus (assistant) at the academy. One of Lexell’s first tasks was to observe the transit of Venus from the academy building. He did so along with the secretary of the academy Euler and the two Jesuit visitors, Mayer and his assistant Gottfried Stahl (dates unknown).73 Having gained access to the ob- servations from St. Petersburg, Planman commented in a letter to Euler that the observations of Lexell were the closest match to his own, under the precon- dition that the solar parallax was 8.3 arc seconds.74 Unlike Planman, however, Lexell was not convinced of the accuracy of his own observation—or of a solar parallax of 8.3 arc seconds for that matter. He was soon entrusted the task of calculating the solar parallax on the basis of the observations of 1769. In this process, Lexell declined all temptation to accord the St. Petersburg observations any special reliability. Quite the contrary, in a letter to Planman dated June 25, 1770, Lexell said that as far as Father Hell’s observations of both last contacts [of Venus with the limb of the Sun] are concerned, I do not know what to say. He may perhaps have tried to fabricate them according to the Petropolitan 71 Planman to Wargentin in Stockholm, dated Åbo, June 22, 1770 (cvh). 72 On Lexell, see Johan C.-E. Stén, A Comet of the Enlightenment: Anders Johann Lexell’s Life and Discoveries (Cham: Springer, 2014); his role in the Venus transit observations is dis- cussed in Chapter 5. 73 Stahl and Lexell used comparatively small telescopes, while the two largest and best were used by Euler and Mayer. Cf. Christian Mayer, “Expositio utriusque observationis et Ven- eris et eclipsis Solaris factae Petropoli in Specula Astronomica,” NcASIP 13 (1769): 541–60. 74 Planman to Johann Albert Euler in St. Petersburg, dated Åbo, September 26, 1769 (copy in Planman’s handwriting, cvh): “In order to be able to compare my observation with yours from St. Petersburg, it was necessary to calculate the effect of parallax with regard to these places. Assuming a solar parallax of 8.3 arc seconds, which I obtained from the observa- tions of the transit in 1761, I found that, after calculation, the total emersion should have taken place twenty-two seconds earlier in Cajaneborg than in St. Petersburg […]. Thus, my observation is closest to that of Lexell and least in harmony with that of [Christian] Mayer.”