Lagrange's Memoirs. 109 



His features were moulded after death, and previously while he 

 slumbered, a portrait was made of him that was said to be very 

 correct. 



Sweet, and even timid in conversation, he loved particularly to 

 interrogate, either to show the worth of others, or to add their re- 

 flections to his vast knowledge. When he spoke, it was always in 

 the strain of a doubt, and his first phrase generally began withje ne 

 sais pas. He respected all opinions, and was very far from giving 

 his own as rules. Nor was it easy for him to change them. For 

 he sometimes defended them with a warmth that went on increasing 

 until he perceived some change in himself; then he returned to his 

 usual tranquillity. One day, after a dispute of this sort, Lagrange 

 having gone out, Borda, remaining alone with me, let slip these 

 words ; Je suis fdche d' avoir a le dire d' un komme tel que M. La- 

 grange, mais je n' en connais pas de plus entete. If Borda had gone 

 out first, Lagrange doubtless would have said the same of his brother. 

 a man of sense and much talent. He too, like Lagrange, would 

 not readily change ideas adopted only after a thorough examination. 



Often was remarked in his tone a light and sweet irony, the 

 meaning of which it was possible to mistake, and at which 1 have 

 seen no instance where any one could have felt offended. Thus he 

 said to me one day : " These astronomers are singular ; they will 

 not believe a theory, where it does not agree with their observations." 

 The looks of him who made this reflection, on uttering it, marked 

 sufficiently its real meaning. I did not think myself obliged to de- 

 fend astronomers. 



Among so many master-pieces that are due to his genius, his 

 Mecanique is unquestionably the most grand, remarkable and impor- 

 tant. The fonctions analytique are only secondary, notwithstanding 

 the fruitfulness of the principal idea, and the beauty of the devel- 

 opments. A notation less convenient, calculations more embarrass- 

 ing, although more luminous, will prevent geometers from employing, 

 unless in certain difficult and doubtful cases, his symbols and his 

 demonstrations ; it suffices that he has supported them on the law- 

 fulness of the more expedient methods of the differential and inte- 

 gral calculus. He himself has followed the usual notation in the 

 second edition of his Mecanique. 



This great work is wholly founded on the calculus of which he 

 is the inventor. Every thing in it flows from a single formula, and 

 from a principle known before him, but of which the whole use was 



