Page - 268 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

Chapter 6268 began. By the time the moments of egress were observed, the sky had again become perfectly clear.33 The interior contact of egress is described by Hell somewhat differently from that of interior contact of ingress. Here, Hell speaks of the gutta nigra (black drop), which starts forming some eleven seconds before it “in an instant disappears, and so-to-speak bursts, and the limbs of the Sun and Venus flow together as one.”34 Hell and Sajnovics had, according to Hell’s account, deter- mined this moment only a single second apart—at 3:26:17 and 3:26:18 a.m., re- spectively, according to the Viennese clock—whereas Borchgrevink noted what he simply called “the interior contact” (contactus interior) at 3:26:10 a.m.35 The moment of total egress was, according to the same account, encumbered with some uncertainty. However, it was observed by Hell, Sajnovics, and Borch- grevink within a range of seven seconds, the moment expressly stated as egres- sus certus (certain egress) being recorded by Sajnovics and Hell only a second apart—at 3:44:26 and 3:44:27 a.m., by the Viennese clock.36 The above extract is based upon the printed report alone. Moreover, it does not render justice to the intricate theoretical deliberations accompanying the data. The account of the observation itself is found very near the end of the eighty-two-page report, after an elaborate account of instruments used, proce- dures followed in the testing of the clocks, definitions of “true” and “optical” contacts, the black drop effect, and so forth. This feature of Hell’s report is—to the best of our knowledge—unparalleled in all other Venus transit reports of the year 1769: no other observer produced a first edition of his observation that included such long and intricate theoretical discussions. But where theory and detail might be an advantage in a report of such momentum, the time con- sumed in writing and publishing it was not. As explained previously, Hell took his time when traveling back to Copenhagen, which they did not reach until October 17 (covering nearly the same period of the year, and following roughly the same route, as on their outward journey in 1768). Here, during three ses- sions at the Royal Society—November 24, and December 1 and 8, 1769—Hell presented his report on the Venus transit observation from Vardø.37 He also had an audience with King Christian vii on November 29, during which he obtained permission to dedicate the printed version of the report to His 33 Hell, Observatio transitus Veneris […] 1769, 74–75. 34 Hell, Observatio transitus Veneris […] 1769, 75–76, here 76. 35 Hell, Observatio transitus Veneris […] 1769, 76. 36 Hell, Observatio transitus Veneris […] 1769, 76. 37 Sajnovics’s travel diary 1768–70 (wus), entries on November 24 and December 1 and 8, 1769; the protocol of the Royal Danish Society of Sciences (dkdvs), entries November 24 and December 1 and 8, 1769.