Chaplain on board the La Boussole, one of the ships on the French expedition led by Jean-François de Galaup La Pérouse. Abbé Mongès is listed in Voyage de La Pérouse autour du monde, Vol. 1, p. 5 as "Chanoine régulier de la congregation de France, physicien, et faisant les fonctions d'aumônier" (Canon Regular of the Congregation of France, doctor, acting as chaplain).

Abbé Mongès is believed to have conducted the funeral of his fellow chaplain (on the Astrolabe, the other ship in the expedition), Abbé Le Receveur, at Botany Bay in February 1788. This funeral is considered to have constituted the first Catholic religious ceremony held in Australia.

The La Pérouse expedition left Botany Bay on 10 March 1788, and was never heard from again. It was not until 1828 that the expedition was found to have been wrecked at Vanikoro, Santa Cruz, north of the New Hebrides.

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Michaud, Biographie universelle ancienne et moderne, 1843, vol 28, p 622:

Mongez (Jean-André), né à Lyon en 1751, entra chez les chanoines réguliers de Ste-Geneviève, et s'adonna à l'étude des sciences. Ses connaissances en physique l'avaient fait agréger à plusieurs sociétés savantes, et déjà il avait obtenu quelques voix pour entrer à l'Académie des sciences, lorsqu'il partit en 1785 avec la Pérouse en qualité de physicien et avec les fonctions d'aumônier. Les dernières nouvelles qu'on ait reçues de la Pérouse étaient datées de Botany-Bay, où l'expédition avait relâché dans l'espoir, qui fut trompé, de rafraîchir ses provisions. Il est donc à croire que Mongez a partagé le sort de l'infortuné voyageur qu'il accompagnait (voy. Pérouse). On a de lui: 1º Description, usages et avantages de la machine pour la fracture des jambes d'Albert Pieropan, 1782, in-8°; 2° Manuel du minéralogiste, etc., traduit de Bergmann et augmenté de Notes (voy. Bergmann). Il avait eu une grande part aux premiers volumes du Cours d'agriculture de l'abbé Rozier, et avait, depuis 1779, rédigé le Journal de physique, commencé par cet abbé. Il y avait précédemment fait insérer plusieurs morceaux, et, entre autres, un sur les Ombres colorées du matin, et (mars 1777) un sur les Causes principales qui font fumer les cheminées, sujet proposé quelques années auparavant par l'académie de Bordeaux. On a presque toujours confondu J.-A. Mongez le jeune avec son frère Antoine Mongez, membre de l'Institut (voy. l'art. précédent). А. Вeuchot.

Mongez (Jean-André), born at Lyons in 1751, entered the Canons Regular of St Genevieve, and devoted himself to the study of science. His knowledge of physics gained him entry into several scientific societies, and he had already obtained several votes to enter the Academy of Science when he left in 1785 with La Perouse in the capacity of physicist and with the role of chaplain. The last reports received from La Perouse were dated from Botany Bay, where the expedition had dropped anchor in the hope (which was disappointed) of renewing its provisions. This leads one to conclude that Mongez shared the fate of the unfortunate explorer whom he was accompanying (see La Perouse). His publications comprise: 1. Description, uses and advantages of Albert Pieropan’s machine for leg fractures, 1782, octavo; 2. Manual of mineralogy, etc., translated from Bergmann and augmented with notes (see Bergmann). He had played a large part in the first volumes of A Course on Agriculture by Abbé Rozier, and since 1779 had been editor of the Journal of Physics, commenced by Rozier. He had previously published several articles in it, amongst which, one on The Coloured Shadows of the Morning and (in March 1777) The Principal Causes of Smoky Chimneys, a subject proposed a few years before by the Academy of Bordeaux. J.-A. Mongez the Younger has almost always been confused with his brother Antoine Mongez, a member of the Institute of France (see preceding article). A. Beuchot. (Translation Patrick N. O’Neill, 2025).