Manchu as a tool language for European missionaries
Like some of the other missionaries at the Qing court in the early 18th century, the French Jesuit Joseph-Anne-Marie de Moyriac de Mailla (1669-1748) studied both Chinese and Manchu. He is said to have started studying Manchu rather late in life, at the age of fifty. Soon after, he started translating into French large parts of the Han-i araha tung giyan g’ang mu bithe, a Manchu-language translation and revision of the Tongjian gangmu 通鉴纲目 (“Outline and detail of the Comprehensive Mirror“), commissioned by the emperor in 1691. The original work (first published in 1172), credited to Zhu Xi, was a thoroughgoing revision of Sima Guang’s Zizhi tongjian (“Comprehensive mirror to aid in government”), restructured according to Neo-Confucian principles of history. The Chinese and Manchu versions together constituted a principal source for de Mailla’s thirteen-volume Histoire générale de la Chine, itself a seminal achievement in European sinology; its idealized view of the Chinese past influenced much Enlightenment thinking, even if (as Cordier notes), some of de Mailla’s Jesuit colleagues recognized it was probably completed in too much of a hurry.
It is clear that de Mailla made reference to the Manchu translation of the Tongjian gangmu as he worked on his French translation. At the Archives jésuites de la Province de France (at Vanves), a letter is preserved in which de Mailla raises a number of issues concerning the use of astronomical data recorded in ancient Chinese texts for establishing Western historiographies of China. In the course of doing so, he criticizes the ‘rather rigid’ translations of Martino Martini (1614-1661) and Jean Couplet (1623–1693), and of one sentence in particular, relating the decision by Zhuanxu 颛顼 (one of the legendary five emperors) to let the first day of the year coincide with the first day of spring. The Manchu translation of the Chinese text is then quoted alongside the Chinese in support of his argument.
Father de Mailla writes:
Les R.P. Martini et Couplet ont à mon avis expliqué cet endroit de l’histoire chinoise trop rigidement lors qu’ils disent qu’il y eut une conjonction des 5 planètes le même jour qu’il y en avoit une du soleil et de la lune […]. C’est ainsi que s’explique le P. Couplet, or le chinois ne parle point de conjonction de planètes, mais d’assemblée de planètes , et se sert du caractère hoei qui ne signifie nullement conjonction mais seulement ‘assembler, s’assembler’. Le texte même donne assez à entendre qu’il ne s’agit point icy de conjonction, puisqu’il ne détermine aucune étoile en particulier où c’est faire cette assemblée, mais se contente d’une expression générale, au-delà de la constellation Che […]. Cela pose voici le sens que je donne au passage de l’histoire chinoise. Je mets le texte à la marge en Chinois, tel qu’il est rapporté dans les plus anciens livres; et en Tartare, tel qu’il a été traduit par les plus habiles gens de l’empire sous les ordres et la direction du grand empereur Kanghi. 
(I think that Fathers Martini and Couplet have too rigidly explained this part of Chinese history when they say there was a conjunction of 5 planets on the same day that there was one of the sun and the moon […]. This is how father Couplet explains it, but the Chinese text does not mention a conjunction of planets, but rather a gathering of planets. The character hui is used, signifying not a conjunction, but merely ‘to gather’. The text even gives us enough information to understand that it does not describe a conjunction: it does not point to one particular star where the gathering [of stars] took place, but contents itself with a general expression: ‘on the far side of the Che-constellation’ […] This is how I understand this passage in Chinese history. I will put the Chinese text in the margin, the way it is found in the most ancient of books; and in Manchu [litt: ‘the Tartar language’], the way is has been translated by the most able persons in the Empire, in accordance with the orders and directions of the great Emperor Kangxi.)
In the margin of the letter, de Mailla has written in the Manchu text, along with its reading and basic meaning in Latin:
Ere aniya aniya biya ice inenggi niyengniyeri dosika sunja usiha abka de acafi ing Ši usiha ba duleke .
(This year’s first day of the first lunar month, the arrival of spring, five stars came together (lit., ‘met’) in the skies and passed the Shi-constellation.)
(This year, on the first day of the first lunar month, the arrival of spring, five stars gathered in the skies beyond the Shi-constellation.)
Thus, in his letter, de Mailla clearly shows us one of the ways in which Manchu was used by missionaries at the Qing court, namely as a tool language for the correct understanding of Chinese texts, a cross-reference for their own translations of writings whose meanings were often obscure to them and which others before them may have misunderstood.
 According to an entry in the Catholic Encyclopedia (1913) by Henri Cordier. http://en.wikisource.org/wiki/Catholic_Encyclopedia_%281913%29/Joseph-Anna-Marie_de_Moyria_de_Mailla (last visited 2/5/2013)
 Histoire générale de la Chine, ou Annales de cet Empire, traduites du Tong-kien-kang-mou, Vol. 1, Paris: Pierres et Clousier, 1777-1785, pp. lxvj-lxvij.
 Fonds Brotier, Vol. 123, ff. 22-29. Letter written in Beijing on October 1st 1723. The letter was most likely addressed to Étienne Souciet.
 In modern astronomy, a conjunction usually refers to a perfect alignment in the skies of a number of celestial bodies. ‘Assemblée’, on the other hand, seems to be used here for what I freely translate as a ‘gathering’ of planets, in the sense that they are positioned closely together in the skies, but that there’s no perfect conjunction or alignment. It remains unclear, however, what exactly de Mailla meant when he wrote about a ‘conjonction’.
 Emphasis added.