M. la Grange took possession of his situation on the 6th of November 1766. He was well received by the king; but soon perceived that the Germans do not like to see foreigners occupy situations in their country. lie applied to the study of their language. He devoted himself en tirely to mathematics, and did not find himself in the way of any person, because he demanded nothing, and he soon obliged the Germans to give him their esteem. The king," said he himself, " treated me well ; 1 thought that he preferred me to Euler, who was something of a devotee, while I took no part in the disputes about worship, and did not contradict the opinion of any one." This prudent reserve, if it deprived him of the advantages of an honour able'familiarity, which would have been attended with some inconveniences, left him the whole of his time for mathe matical labours, which hitherto had brought him nothing but compliments the most flattering and the most unani mous. This concert of praises was only once interrupted during the whole of his life.
A French mathematician, who to much sagacity united a still greater degree of selfishness, and scarcely gave himself the trouble to study the works of others, accused M. la Grange of having gone astray in the new route that lie had traced, from not having well understood the theory of it. He reproached him with having deceived himself in his assertions and calculations. La Grange in reply ex presses some astonishment at these harsh expressions, to which he was so little accustomed. He expected at least to have seen them founded on some reasons either good or bad; but he discovered nothing of the kind. Ile skews that the solution proposed by Fontaine was incomplete and illusory in certain respects. Fontaine had boasted that he had taught mathematicians the conditions which render possible the integration of differential equations with three variables. La Grange shelved him, by several cita tions, that these conditions were known to mathematicians long before Fontaine was capable of teaching them. lie does not deny that Fontaine discovered these theorems himself; 64 at least I am persuaded," says he, "that he was as capable of finding them as any person what ever." It was with this delicacy and moderation that he answer ed the aggressor. Condorcet, in his eloge of Fontaine, is obliged to avow that, on this occasion, his friend deviated from that politeness which ought never to be dispensed with, but which perhaps he thought less necessary with illustrious adversaries, whose glory did not stand in need of these little delicacies. Every one can estimate the value of that apology, especially when applied to a man who, by his own acknowledgment, studied the vanity of others, that he might have an opportunity of wounding it. \Ve must at least acknowledge, that he, who saw him self attacked in that manner when he was in the right, and who knew how to maintain politeness with an adver sary who had himself dispensed with it, acquired a dou ble advantage over him, besides victoriously repelling his imprudent attack.
It will not be expected that we should follow M. la Grange in the important researches with which he filled the Berlin Memoirs; and even some volumes of the Me moirs of the Turin Academy, which was indebted to him for its existence. All the space that can be devoted to this biographical account would not be sufficient even to convey an imperfect idea of the immense series of his labours, which have given so much value to the Memoirs of the Berlin Academy, while it had the inestimable ad vantage of being directed by M. la Grange. Some of these Memoirs are of such extent and importance, that they might pass for a great separate work, yet they constitute a part only of what these twenty years enabled him to produce. He had composed his Mecanique but he wanted to have it printed at Paris, where he ex pected that his formulx would be given with more care and fidelity. On the other hand, it was running too great a risk to intrust the manuscript into the hands of a travel ler, who might not be aware of the whole of its value. M. la Grange made a copy of it, which M. Duchatelet undertook to deliver to the Abbe Marie, with whom he was intimately connected. Marie fulfilled with honour the confidence pla6ed in him. His first care was to find a bookseller who would undertake to publish it ; and, what it will be difficult to believe at this time, he could not find one. The newer the methods in it were, and the more sublime the theory, the fewer readers would be found capable of appreciating it ; hence, without enter taining any doubts of the merit of the work, the booksel lers were excusable in hesitating to print a book, the sale •of which would probably be confined to a small number mathematicians, disseminated through Europe. De sam,. who was the most enterprising of all those to whom appljcation was made, would not undertake to publish it, till Marie entered into a formal engagement to take all the copies of the edition which were not sold by a given time. To this first service, Marie added another, of which M. la Grange was not less sensible; he procured him an editor worthy of superintending the publication of such a work. M. endre devoted the whole of his time to the trou blesome task of correcting the press, and was repaid by the sentiment of veneration for the author with which he was penetrated; and by the thanks which he received from him in a letter which I have had in my possession, and which M. la Grange had filled with expressions of his es teem and his gratitude.