Page - 260 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

Chapter 6260 The third part of the third volume, on measurements of the declination of the magnetic needle, has survived in manuscript but was not published until 2005.4 The fourth part is not extant, either in manuscript or in any printed ver- sion. By means of barometrical observations, Hell argued, it should be possible to determine the curvature of the Earth’s surface far more accurately than Maupertuis had done some decades earlier.5 Hell never published this part— perhaps fortunately for him, as this marvelous idea was surely a dead end. Highest among Hell’s priorities, obviously, was publication of his Venus transit report from Vardø, followed shortly afterward by calculations of the so- lar parallax. However, whereas his plans involved a straightforward process of summarizing, calculating, and publishing a definite result, he was soon pro- voked into an all-out attack on real and perceived enemies. These included colleagues across Europe that he had earlier considered as friends and collaborators. 1 Mission Accomplished To begin with, the determination of the exact coordinates of all observational sites was of crucial importance to the Venus transit project. Hell planned to determine the longitude of Vardø by various means. In addition to a solar eclipse that was expected around midday on June 4, 1769, he intended to make use of occultations of satellites of Jupiter; a lunar eclipse that was to take place on December 23, 1768; occultations of fixed stars by the moon; and transits of the moon through the meridian compared to the positions of stars. Accord- ingly, he contacted Wargentin beforehand, asking him to provide correspond- ing datasets from Sweden.6 In Vardø, however, all these attempts failed, partly 4 Lynne Hansen and Aspaas, Maximilian Hell’s Geomagnetic Observations; Aspaas and Lynne Hansen, “Geomagnetism by the North Pole.” Cf. Lajos Bartha, “Magyar tudósok mágneses megfigyelései a sarkkörön túl 1769-ben,” Földrajzi Múzeumi Tanulmányok 13 (2004): 49–55. 5 A particularly valuable source not appreciated on this account is Christian Mayer’s lengthy treatise on the 1769 transit of Venus. Mayer elaborates on the potentials of using barometric observations from various places as a means to settle several questions, among them the figure of the Earth: “For this reason, Honorable Father Hell, that famous astronomer of Vi- enna, has distributed more than twenty diligently calibrated barometers, which he had brought with him from Vienna, to curious and able observers at various places along his journey, so that he thereafter, upon his return from Vardøhus may receive their observations.” Mayer, Ad Augustissimam Russiarum omnium Catharinam ii Alexiewnam Imperatricem expo- sitio de transitu Veneris, 314–23, here 317. 6 Hell to Wargentin, dated Copenhagen, June 30, 1768 (cvh): “I would like to ask You to make known to your colleagues and correspondents this proposal of mine: that they care to obtain astronomical observations, especially such that pertain to the determination of the