352 



he was called upon, with all other public functionaries, to take the 

 oath of allesiance to Louis Napoleon, as President of the Republic ; 

 this his antecedents and his convictions would not allow him to do, 

 and he resolved, rather than put this constraint on liis conscience, 

 to abandon the establishment with which his name had been so 

 gloriously identified. Happily, he was spared this wrong ; the 

 Prince President authorized his Minister to inform him, that he 

 made " a special exception in favour of a philosopher whose labours 

 had rendered France illustrious, and whose existence the Govern- 

 ment would be loath to sadden." Arago did not long survive this 

 event ; a comphcation of disorders was carrying him to the grave ; 

 he returned, after a painful journey to his native place, seriously 

 indisposed, and died at the Observatory, on the 2nd of October in 

 the present year. His funeral took place on the 5th, at the cemetery 

 of Pere la Chaise: a brigade of infantn,- marched with the procession, 

 and the Emperor was represented at the ceremony by Marshal 

 A'aillant, Grand ^larshal of the palace. Though it rained inces- 

 santly, above 3000 persons attended the funeral cortege. 



Arago was but once married, and had the misfortune to lose his 

 wife, a lady of gi-eat accomplishments, in 1S29. He has left two 

 sons : Emanuel, a member of the Parisian bar, and formerly repre- 

 sentative with his father for the Oriental Pyrenees ; and Alfred, a 

 painter of distinguished reputation. 



It now remains to give a short retrospect of the most prominent 

 original investigations in physical science made by this indefatigable 

 philosopher during the intervals of a busy and sometimes agitated hfe. 



The important discoveries of Mains relating to polarized light 

 attracted the attention of Arago strongly to this new and fertile field 

 of physical research, and on the 11th of August, ISll, he read to 

 the Academy a memoir abounding witii new and beautiful facts, each 

 forming a starting-point for subsequent investigarions which have 

 extended in no mean degree our knowledge of the laws of Hght. In 

 this valuable communication, M. Arago examined, for the first time, 

 the changes in the properties of polarized rays when they pass 

 through plates of mica, sulphate of lime, and other crystals ; he 

 showed that they acquire the property of being diwided by a bi- 

 refringent prism into' two complementary coloured pencils ; and he 

 examined the changes of colour and intensity dependent on the 

 thickness of the plate, its inclination to the ray, its rotation in its 

 ov,-n plane, and the rotation of the analysii^g prism ; he also ascer- 

 tained that when the emergent hght v/as renectedfrom a glass plate 

 at the polarizing angle, only a single-coloured image appeared, which 

 changed to the complementary colour when the mirror was turned 

 round 90', the angles of incidence and refiexion remaining constant. 

 He also discovered the different remarkable modifications which a 

 polarized ray undergoes when transn^itted through a thick plate of 

 rock crystal cut perpendicular to its axis, viz. that it is analysed 

 by a bi-refringent prism into tvro complrmentan,-rays which remain 

 the same, however the plate is turned in its own plane, and pass 

 through all changes of colour in successive order, when the analysing 



