JEAN-JACQUES D'ORTOUS DE, descended from a noble family at Beziers, was born in that city in 1678, and died at Paris of a fluxion on the lungs on the 20th of February 1771, at the age of 93. He was one of the most illustrious members of the Academy of Sciences and of the French Academy. Being early connected with the former society, he, in the year 1741, succeeded Fontenelle in the office of secretary. This station he filled with the most distinguished success till the year 1744; and, like his predecessor, possessed the faculty of placing the most abstract subjects in the clearest light; a talent which is very rare, but which appears conspicuous in all his works. The chief of them are, 1. Differation sur la Glace, the last edition of which was printed in 1749, 12mo. This excellent little tract has been translated into German and Italian. 2. Differation sur la cause de la lumiere des Phosphores, 1717, 12mo. 3. Traité historique et physique de l'Aurore Boreale, first published in 12mo, 1733, and afterwards much enlarged and printed in 4to in 1754. The system embraced by the author is liable to be controverted; but the book displays great taste and erudition. 4. Lettre au Pere Parennin, contenant diverses questions sur la Chine, 12mo. This is a very curious work, and is full of that philosophical spirit which characterizes the author's other publications. 5. A great number of papers in the memoirs of the Academy of Sciences (since 1719), of which he published some volumes. 6. Several dissertations on particular subjects, which form only small pamphlets. 7. The Eloges of the Academicians of the Academy of Sciences, who died in 1741, 1742, 1743, in 12mo, 1747. Without imitating Fontenelle, the author attained almost equal excellence by his talent of discriminating characters, appreciating their worth, and giving them their due share of praise, without at the same time concealing their defects.

Mairan's reputation extended itself into foreign countries. He was a member of the Imperial Academy at Peterburgh, of the Royal Academy of London, of the institution at Bologna, of the royal societies of Edinburgh and Upsal, &c. The gentleness and sweetness of his manners made him be considered as a perfect model of the social virtues. He possessed that amiable politeness, that agreeable gaiety, and that steady firmness, which never fail to procure love and esteem. But we must add, says M. Saverien, that everything had a reference to himself; self-love and a regard to his own reputation were the motives of all his actions. He was deeply affected with censure or applause, and yet he had many friends. Uniting much gentleness of disposition to an ingenious and agreeable expression of countenance, he possessed the art of infusing himself into the good graces of others, so as to pave the way to elevation and success. He was honoured with protection and particular marks of regard by the duke of Orleans the regent, who bequeathed to him his watch in his will. The prince of Conti loaded him with favours; and the chancellor Dagueleau, observing in him great originality and ingenuity of thought, appointed him president of the Journal des Savans: a station which he filled very much to the satisfaction of the public and of the learned. The private and selfish views imputed to him by M. Saverien never made him deficient in what was due to the strictest probity. An expression of his is remembered, which could have proceeded only from sentiment; "An honest man (said he) is one whose blood is refreshed with the recital of a good action." He was ready at repartee. One day he happened to be in company with a gentleman of the gown, and to differ with him in opinion upon some point which had no more connexion with jurisprudence than with geometry. "Sir (said the magistrate, who supposed that a learned man was a perfect idiot out of his own sphere), we are not now talking of Euclid or Archimedes."—"No, nor of Cujas nor Barthole!" replied the academician.