primers upon the most diverse subjects for use in the schools of Belgium, and, in 1782, revised his previous ‘Réflexions sur la Discipline Ecclésiastique,’ in reference to the Belgian church, adding some remarks upon the changes contemplated by the Emperor Joseph II's reforming zeal.
The abbé long suffered from confirmed gout; but from 1779 his health was greatly improved by his use of hemlock and aconite. He was a pioneer of the employment in the Netherlands of these drugs, on the effects of which he wrote a paper in 1784. In this year also he made an extended tour through France, Switzerland, and Germany, acquiring extensive materials for communications to the Royal Academy of Brussels, of which he became a member 7 Feb. 1774 and perpetual secretary and treasurer in 1786.
In 1788 the abbé was elected a fellow of the Royal Society, an honour which he had long coveted. In the next year the French revolution broke in upon Belgium, as he himself said, like ‘a violent sea.’ He was in continual fear of ill-usage until, in 1792, he accompanied his friend Lord Elgin to England. On the re-establishment of the Austrian government in 1793, he returned to Brussels and resumed his functions. In January of the same year he was admitted an honorary member of the Society of Antiquaries. In June 1794 he had to quit Brussels for the last time in company with his friend M. Podevin. The fugitives settled at Lintz and afterwards at Leutmeritz in Bohemia. Thence, however, Mann had to retire at the approach of the French armies as far as Prague, where he received a warm welcome from the Prince-Archbishop de Salm. At Prague he resumed literary production, and for the British Agricultural Society, of which he had been elected a member in 1794, wrote ‘A Memoir on the Agriculture of the Austrian Netherlands’ (1795). This was subsequently printed in Hunter's ‘Georgical Essays’ (vol. v.), together with his ‘Observations on the Wool of the Austrian Netherlands,’ originally communicated to Sir Joseph Banks. In 1804 he compiled ‘by way of recreation’ a most comprehensive ‘Table chronologique de l'Histoire Universelle depuis le commencement de l'année 1700 jusqu'à la conclusion de la paix générale en 1803’ (Dresden, 1803), and continued his communications with learned societies in various parts of Europe until his death at Prague on 23 Feb. 1809. His chief legatee was the sister of his intimate friend, Mlle Podevin.
An extensive collection of Mann's letters written to the Society of Antiquaries and to various private friends, among them Dr. Solander, Magellan, Hartley, and Lord Mulgrave, was published at Brussels in 1845; and a few selected letters are included in Sir Henry Ellis's ‘Original Letters of Eminent Literary Men’ (Camden Society). To the ‘Philosophical Transactions’ he contributed ‘A Treatise on Rivers and Canals’ (1780), ‘A Treatise on Sea Currents and their Effects applied to the Sea and Coasts of the West of Europe, more especially to those which surround the British Islands’ (1789), and a paper ‘On the Formation of great Hailstones and pieces of Ice in great Thunderstorms’ (1798). To the Society of Antiquaries he communicated ‘A Description of what is called a Roman Camp in Westphalia’ (1796), and ‘A short Chronological Account of the Religious Establishments made by English Catholics on the Continent of Europe’ (1797, see Archæologia, xiii. 1 and 251).
The most considerable of Mann's writings in French are: 1. ‘Histoire du règne de Marie-Thérèse,’ Brussels, 1781. 2. ‘Mémoires sur le conservation et le Commerce des Grains,’ Malines, 1784. 3. ‘Abrégé de l'Histoire ecclésiastique, civile et naturelle de la ville de Bruxelles et de ses environs,’ Brussels, 1785. 4. ‘Recueil de Mémoires sur les grandes gelées et leurs effets,’ Gand, 1792. 5. ‘Principes métaphysiques des êtres et des connaissances,’ Vienna, 1807. A fair copy of this work made in Mann's own hand is preserved in the British Museum (Add. MS. 5794).
The abbé also wrote widely on meteorology, philology, political economy, weights and measures, the voyages of Captain Cook and others, on agriculture, religion, and antiquarian matters, devoting (in 1778) an interesting paper to an attempt to refute William Sumner [q. v.] and other English antiquaries, and to prove that Cæsar, when he embarked for Britain, sailed not from Mardyke nor Whitsand, but from Boulogne (Gessoriacum). A great number of his writings take the form of communications to the Brussels Academy; among these will be found a powerful indictment of ‘la grande culture’ (1780) and an interesting ‘Mémoire sur les diverses méthodes inventées jusqu'à présent pour garantir les édifices de l'incendie’ (1778). A volume of his papers, presented by the author to Sir Joseph Banks, is in the British Museum Library.
Finally the abbé compiled numerous catalogues and bibliographical works and many voluminous reports, commanded by the Austrian government, on canalisation, fisheries, agriculture, &c. Several of these papers