A short time afterwards, he published his Melanges de Philosophie, fli.vtoire it de Literature ; his Memoirs of Christina, queen of Sweden ; Essay on the Inter course of Men of Letters with Persons of Rank and Of fice ; and his Traduction de Diverse Morceaux de Tacit', works which arc adorned with the most generous and exalted sentiments, and ‘, hi( 6, by raising nis fame, in creased the number and the malignity of his enemies. The next work published by D'Alembert was the /?c, rherches sur different's impQrtants du Systemic du it r) n e, in 1754, and 1756, in which he improved the so lution of the problem of three bodies. The honour of resolving this important problem belongs equally to Euler, Clairaut, and D'Alembert, who, without the least communication, gave a more accurate determination ()I' the lunar inequalities, as considered by New tun, confirm ed some which he had merely learned from observa tion, and discovered others which had hitherto been un known. Clairaut had the honour of being the first who applied his solution to the motion of comets ; and in 1758, he announced to the academy, that the comet of 1682 would appear in the beginning of 1759. The cu riosity of the public was exciled by this notice, and the name of Clairaut was every where mentioned with ap plause. In opposition to the claims of Halley, he was regarded as the sole author of the prediction ; and some of his pupils were imprudent enough to maintain, that the solution of Clairaut was more applicable to the mo tion of comets, than those of Euler and D'Alembert. This claim of superiority Clairaut was supposed to have arrogated in private. Euler was in no respect affected with the injustice that had been clone to him ; but D'Alembert, whose temper was more keen, and who then lived in Paris, where these erroneous opinions were cherished, could not remain a silent spectator. He at tacked the solution given by Clairaut as inaccurate and defective, and resolved the problem of comets in a way which was at once simple and complete. Thus were two of the first mathematicians in Europe opposed to each other in open war ; and thotigh the subject of dis pute was intelligible only to a few, yet every literary circle in Paris was ranged on the side of its favourite philosopher. Clairaut had the happiness of enjoying universal esteem. The gentleness of his dispositions, the urbanity of his manners, and his extreme tenderness for the feelings of others, could not fail to fix the af fections of all who knew him ; while his ambition of fame led him to pursuits which could be generally ap preciatcd, and which were therefore more likely to ex cite public applause. The character of D'Alembert, on the contrary. was distinguished by that stern honesty of mind which cannot stoop to the arts by which fame is generally acquired. Accustomed to speak what he thought, and es en to indulge his wit and raillery beyond the limits which prudence would have prescribed, he was more apt to make enemies than to acquire friends. He disdained that species of applause which is propaga ted merely by the lips of the vulgar ; and therefore he dismissed, without ceremony, the numerous visitors who came to court and to flatter him. From these causes, Clairaut enjoyed, during his life, a much higher repu tation than D'Alembert ; but as he did not equal him in genius, posterity have corrected this unequal distribu tion of praise.
ita 1756, D'Alembert received from the academy the title of Supernumerary Pension&ry ; a distinction which was contrary to the usage of the academy', and therefore a more flattering proof of the estimation in which he was held by his colleagues. In 1759, he published his ":'Element-,of Philosophy," a work of remarkable acute ness. and containing, as it were, the metaphysics of the 1,71enct.s.
of D'Alembert was now disturbed by new persecution... The freedom of thought which ventm.red to indulge in some or his papers in the Ency elop.edia, involved him in a contest which was long and keenly maintained. In the article on Geneva, he hap pened to censure the bigotry and intolerance which for merly reigned in that city, to throw a suspicion upon the orthodoxy of the Genevese clergy, and to regret that the proscription pronounced by Calvin against the thea tre and other public amusements, was still enforced by the ministers of religion. The zeal of D'Alembert
for the liberty of his fellow creatures, could not brook the idea that such an authority should be usurped over the consciences of men, and might have justified him in speaking with greater severity of any despotic enactrmnt, which prohibited the enjoyment of rational pleasure. His language, however, is as temperate as his arguments are clear. He shows the effects of a well regulated stage upon the taste and manners of the citi zens, and suggests the means of preventing it from being an instrument of immorality. The reasoning of D'Alem bert was keenly and eloquently controverted by Rous seau ; and the arguments of an author, who had himself written a comedy and an opera, had a surprising effect upon the public opinion. D'Alembert replied to the Letter of Rousseau ; but his answer did not meet with the same approbation and success. Voltaire, who was then residing at Geneva, brought to the assistance of his friend the weapons of wit and ridicule, which he never wielded without effect ; but he felt little concern in the issue of time contest, and D'Alembert alone was exposed to the assaults of the enemy.
In the midst of this literary war, the king of Prussia, after the peace of 1763, invited D'Alembert to his capi tal, to fill the office of president of the academy of Ber lin, which was newly vacant by the death of Mauper tuis.' The French geometer refused this high and honourable situation, and preferred a life of poverty in his own country to the most splendid situation in another. Ile cherished, however, the liveliest gratitude to Frede rick for his proffered kindness, and spent several months at the Prussian court. A short time before. D'Alembert had been solicited by the empress of Rus sia to superintend the education of her family ; but neither the offer of titles or fortune could induce him to comply.
In 1772, D'Alembert was appointed perpetual secre tary to the French academy; and no sooner was this honour conferred upon him, than he formed the design of writing the lives of all the academicians from 1700 to 1772. In three years, he executed this grand design. by composing no less than 70 elopes.
Besides the works which have been already mentioned. D'Alembe•t published a treatise, entitled, De hi Dr struction des Jesuites ; a collection of memoirs and treatises under the title of Gfiuseules Mathematiyues ; and an immense variety of papers in the Memoirs of the academies of Paris, Berlin, and Turin.
Hitherto D'Alembert has appeared chiefly as a phi losopher, passionately devoted to literature and science ; but an event now occurred which unfolded new features of his character, and shows what a feeble resistance phi losophy can make to time most outrageous of our pas sions, even when age has circumscribed its extravagance, and experience pointed out the littleness of what we pursue.
In the literary circles which D'Alembert frequented at Paris, he met with the marchioness du D6fant, an old lady, whose capricious and splenetic disposition was rendered tolerable only by her wit and genius. Charmed with each other's talents, D'Alembert was a daily visi ter at the convent to which the narrow fortune of the Marchioness had compelled her to retire ; and the pleasure of these visits was considerably heightened by the presence of Mademoiselle L'Espinasse, whom Ma dame du Defant had selected as the companion ()I' her solitude.* This young lady, always attractive by the elegance of her accomplishments, was peculiarly en cleared to D'Alembert by the similarity of their misfor tunes, and every interview gave additional ardour to the flame which was already lighted in their breasts. In consequence of a difference between the two ladies, D'Alembert was arrogantly commanded by the mar chioness, either to renounce her friendship, or the socie ty of Mademoiselle L'Espinasse. The alternative was not painful, nor the choice difficult to make : The attraction of wit and high birth sunk before the enchantments of youth and beauty.