Igi4,] ^^' Mains. 243 



received from her to his very last moments the most tender and 

 hero'c attention. She constituted the wliole ot _ h.s happiness, and 

 ir'notlble to survive l.im. (She fell a victim to t'- hmgucs 

 which had been occasioned by her care ot hm,, and d>cd on t e 

 imrl, of Anyust 1813.) It was at the commencement ot this 

 ial utitf ?/at M. Mains made himself known to the French 

 ItSte, bv a work in which he treated, in the most general and 

 ;lus manne^^^ all the questions in optics that fpend upon 

 geometry alone. He there explained ^-"d/,^'^»l=f ^^ all the phc . 

 n.,.nena of reflection and refraction, and followed through ail its 

 chin.^es the motion of the rays of light. This production drew tne 

 attemion of philosophers to a phenomenon which had occup.ed 

 isjewton and Huvgens, I mean double refraction. The Institute 

 conceived the hope of seeing this remarkable phenomenon, which 

 had employed the greatest geniuses without a satisfactory explana- 

 tion, better understood. It was made the sid)ject ot a prize. I his 

 prize was gained by M. Mains, who showed. that, besides mathe- 

 matical knowledge, which he had displayed in his first work, he* . 

 possessed the pat^ience, the address, and the sagacity, which consti- 

 tute a groat philosopher. By delicate experiments be discovered m 

 light remarkable properties either wholly unknown belore, or which 

 Imd not been exhibited in so clear a point ot vle^^^ He discovered 

 that resemblance of the molecules of light to the magnet which 

 jrives them poles and a determinate direction. ^ i t •. . 



This success caused him to be elected a member of the Institute. 

 He succeeded a philosopher whose name has been immortahzed by 

 a brilliant discovery (iMontgolfier). In 1804 he was made a member 

 of the Legion of Honour, and subdirector of the lortincations of 

 Antwerp. In 1809 he was made subdirector of barracks in the 

 department of the Seine: in 1810, member of the Committee ot 

 Fortifications, and major of genms. In 18 J 1 he was second com- 

 mander and director of the studi^.s of the Polytechnic School, in 

 which for some years he had fultilled, to the satisfaction ot the 

 superiors and of the pupils, the severe duties of examiner. His 

 ditferent occupations did not prevent him from continuing those hne 

 fxneriments upon which his reputation is founded, and tor wliiclx he 

 lia'l received the gold medal given every other year by the Koya 

 Society of London to the philosopher who has made the most 

 striking discovery respecting light or heat. , . , , • ^^ 



'Jh- activity of Malus cnalilcd him to discharge his duty m all 

 these ditferent employments. 'I'hough he still curried about him 

 the seeds of that cruel disease which was so soon to deprive the 

 seientific world of his assistance, he scarcely permitted a month, or 

 even a week, to pass without laying before the Institute the new 

 fruits of his researches. When his health no l<Migcr permitted hiin 

 lo attend the meetings of that Iiody, one ol his friends still conti- 

 nued to relate the result of his labours : but his disease maue such 

 r.ipid progress that scared v was his illness known before U became 

 .ertain that he could not recover. He wa. afflicted N\uh contimial 



