EULER. 



after his return, which was graciously re- 

 warded by the munificence of Catharine 

 the Second, he was seized with a violent 

 disorder, which ended in the total loss of 

 his sight. A cataract formed in his left 

 eye, which had been essentially damaged 

 by the loss of the other eye, and a too 

 close application to study, deprived him 

 entirely of the use of that organ. It was 

 in this distressing situation that he dictat- 

 ed to his servant, a tailor's apprentice, 

 who was absolutely devoid of mathemati- 

 cal knowledge, his elements of algebra, 

 which, by their intrinsic merit in point of 

 perspicuity and method, and the unhappy 

 circumstances in which they were com- 

 posed, have equally excited wonder and 

 applause. This work, though purely ele- 

 mentary, plainly discovers the proofs of 

 an inventive genius; and it is perhaps 

 here alone that we meet with a complete 

 theory of the analysis of Diophantus. 



About this time M. Euler was honoured 

 by the Academy of Sciences at Paris with 

 the place of one of the foreign members 

 of that learned body ; after which the 

 academical prize was adjudged to three 

 of his memoirs, "concerning the inequa- 

 lities in the motions of the planets." The 

 two prize questions proposed by the same 

 academy, for 1770 and 1772, were de- 

 signed to obtain from the labours of astro- 

 nomers amore perfect theory of the moon. 

 M. Euler, assisted by his eldest son, was 

 a competitor for these prizes, and obtain- 

 ed them both. In this last memoir, he 

 reserved for farther consideration several 

 inequalities of the moon's motion, which 

 he would not determine in his first theory, 

 on acccount of the complicated calcula- 

 tions in which the method he then em- 

 ployed had engaged him. He afterward 

 revised his whole theory, with the assist- 

 ance of his son, and Messrs. Krafft and 

 Lexell, and pursued his researches till 

 he had constructed the new tables, which 

 appeared, together with the great work, 

 1772. Instead of confining himself, as be- 

 fore, to the fruitless integration of three 

 differential equations of the second de- 

 gree, which are furnished by mathema- 

 tical principles, he reduced them to the 

 three ordinatcs, which' determine the 

 place of the moon : he divided into classes 

 all the inequalities of that planet, as far 

 as they depend either on the elongation 

 of the sun and moon, or upon the eccen- 

 tricity, or the parallax, or the inclination 

 of the lunar orbit. All these means of in- 

 vestigation, employed with such art and 

 dexterity as would only be expected from 

 a genius of the first order, were attended 



with the greatest success ; and it is im- 

 possible to observe, without admiration, 

 such immense calculations on the one 

 hand, and on the other the ingenious 

 methods employed by this great man to 

 abridge them, and to facilitate their ap- 

 plication to the real motion of the moon. 

 But this admiration will become astonish- 

 ment, when we consider at what period, 

 and in what circumstances, all this was 

 effected. It was when our author was 

 totally blind, and consequently obliged 

 to arrange all his computations by the 

 sole powers of his memory, and of his 

 genius : it was when he was embarrassed 

 in his domestic affairs by a dreadful fire, 

 that had consumed great part of his pro- 

 perty, and forced him to quit a ruined 

 house, every corner of which was known 

 to him by habit, which in some measure 

 supplied the want of sight. It was in 

 these circumstances that Euler composed 

 a work, which alone was sufficient to ren- 

 der his name immortal. 



Some time after this, the famous occu- 

 list Wenzell. by couching the cataract, 

 restored our author to sight ; but the joy 

 produced by this operation was of short 

 duration. Some instances of negligence 

 on the part of his surgeons, and his own 

 impatience to use an organ, whose cure 

 was not completely finished, deprived 

 him a second time, and for ever, of his 

 sight: a relapse which was also accom- 

 panied with tormenting pain. With the 

 assistance of his sons, however, and of 

 Messrs. Krafft and Lexell, he continued 

 his labours : neither the infirmities of old 

 age, nor the loss of his sight, could quell 

 the ardour of his genius. He had engag- 

 ed to furnish the academy of Petersburg!! 

 with as many memoirs as would be suffi- 

 cient to complete its acts for twenty years 

 after his death. In the space of sevea 

 years he transmitted to the academy 

 above seventy memoirs, and above two 

 hundred more, left behind him, were re- 

 vised and completed by a friend. Such 

 of these memoirs as were of ancient date 

 were separated from the rest, and form a 

 collection that was published in the year 

 1783, under the title of "Analytical 

 Works." 



The general knowledge of our author 

 was more extensive than could well be 

 expected in one who had pursued, with 

 such unremitting 1 ardour, mathematics 

 and astronomy as his favourite studies, 

 He had made a very considerable pro- 

 gress in medical, botanical, and chemical 

 science. What was still more extraordi- 

 nary, he was an excellent scholar, and 



