Maximilianus Hell (1720-1792) - Munin

the official observatory of that academy. Lalande also kept an assiduous correspondence with
fellow astronomers in Sweden and England in this period.
Not surprisingly, Lalande received news from all over the world in the weeks and months
after 3 June 1769. Thus, thanks to his close contacts with astronomers on the other side of the
Channel, Lalande received all British observations and summarised them in the Journal des
Sçavans long before they were printed in the Philosophical Transactions. 86 Similarly, the
Imperial Russian Academy extracted the Venus-transit observations from the expedition
diaries of its observers, printed them immediately, and sent them to Lalande. And by mutual
agreement, its secretary – Johann Albrecht (Jean Albert) Euler – received news of French and
British observations from Lalande in return. 87 Furthermore, Wargentin in Stockholm
summarised all Swedish (including Finnish) observations in letters to Lalande soon after the
transit had taken place. 88
No comparable agreement existed between Lalande and the Royal Society of Sciences in
Copenhagen – quite the contrary, in fact. Hell’s refusal to share his observations with anyone
else, as explained in his letter to Wargentin quoted above, evidently included the
academicians of Paris. Despite Hell’s status as a corresponding member of the Académie
Royale des Sciences, with none other than Lalande as his personal contact, no details
whatsoever were revealed to Lalande or his confrères until a copy of Hell’s Observatio
Transitus Veneris ... Wardoëhusii … facta finally reached Paris 4 March 1770, exactly nine
months after the transit had taken place. 89 By that time, Lalande had received reports from all
over Europe, and even from Hudson’s Bay in present-day Canada. The only crucial
observations he lacked were a couple of Siberian observations by Lowitz and Islen’ev
(published in French in May/June 1770), 90 the observations of Chappe and his companions in
86 See Journal des Sçavans, Septembre 1769, pp. 644-645; Décembre 1769, pp 835-836; Avril 1770, pp. 227-
228 & Décembre 1771, pp. 825-826 (the last being a ‘letter to the editors’ dated 13 September 1771, in which he
explains that he had received the Tahiti observations of Cook’s team two days earlier). For a recent analysis of
Lalande’s contacts with British astronomers, see Fauque 2010.
87 J.A. Euler to Lalande in Paris, dated St. Petersburg 14 / 26 May 1769 & 8 / 19 September 1769 (RAN St.
Petersburg); Lalande to J.A. Euler in St. Petersburg, dated Bourg-en-Breste 26 July 1769 & Paris 12 January
1770 (RAN St. Petersburg).
88 Wargentin is known to have sent letters to Lalande in Paris, dated 9 June & 11 July 1769 (see the list of
outgoing correspondence in Nordenmark 1939, pp. 399-424, here p. 406). It is probably the contents of these
letters that appeared in Lalande’s “Lettre sur le passage de Vénus; adressée à Messieurs les Auteurs du Journal
des Sçavans”, published September 1769, p. 645.
89 According to Hell, De Parallaxi Solis ex Observationibus Transitus Veneris A. 1769 1772, p. 92.
90 On 19 June 1770, J. A. Euler sent to Hielmstierne (secretary of the Royal Society of Sciences in Copenhagen)
the two reports, “qui viennent d’être publié tout nouvellement” = “which were published quite recently” (KDVS
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