38 PROFESSOR KELLAND ON THE POLARIZATION OF LIGHT 



CAUCHY,* and NEUMANN,! all of whom have arrived at the opposite conclusion, 

 that light polarized in a certain plane consists of vibrations in that plane. 

 CAUCHY and NEUMANN likewise make the density invariable.^ Mr M'CULLAGH, 

 in some very ingenious papers on crystalline reflexion, has adopted the same 

 view ; and M. NEUMANN || has proceeded to the investigation of the same sub- 

 ject in a most elaborate and valuable memoir. M. SEEBECK^[ has also written 

 on the theoretical expression of the laws of crystalline reflexion. On the other hand 

 Mr GREEN** adopted FRESNEL'S views, and endeavoured to establish his equa- 

 tions by mechanical reasoning founded on LAGRANGE'SJ f equation. His great 

 merit consists in the introduction of a function \\ due to the sudden transition 

 which the vibrations experience from a motion in one direction to a motion in 

 another, at the common surface of two media. The author of this memoir applied 

 the equations of motion of a system of unconnected particles to the solution of the 

 same problem. $$ In that memoir he availed himself of Mr GREEN'S hypothesis, 

 that a function is destroyed by the effect of the surface. M. CAUCHY, although 

 he held different views in 1830, adopted nearly all of FRESNEL'S hypothesis in 

 1836. || || Then and subsequently he held that common light may be conceived to 

 consist of two rays polarized in planes at right angles to each other ;^[ and that 

 the vibrations which constitute light polarized in a certain plane, are at right 

 angles to that plane.*** Until very lately, he appears to have supposed that no 

 motion is destroyed at the common surface, as well as that all the motion is of 

 the same kind.f f f His present views appear to differ considerably from those just 

 stated. In various recent memoirs he has proceeded on a new principle. \ \ \ In one 

 of these, $f he lays down the law which regulates the changes of motion at the 

 common surface of two media, in terms which differ little from Mr GREEN'S. This 

 law (cette loi remarquablfi) || || || he applies to uncrystallized media, ^[^[ and proposes 

 to continue his investigations. He has also given a theory of metallic reflexion,**** 



* Mem. de I'Acad. des Sci. vol. x. p. 304. 



t Annalen der Physik, vol. xxv. p. 418, &c. See also Navier, Mem. de I'Acad. 1824. 



| Memoirs quoted, and Bulletin des Sci. Matth. Juillet, 1830. Compare Comptes Rendus, 

 Av. 4. 1836. 



Philos. Mag. vol. vii. p. 295 ; vol. viii. p. 103 ; vol. x. p. 43. L'Institut. vol. v. p. 223. Trans. 

 of the Royal Irish Ac. vol. xiii. p. 11, for 1837. 



[| Abhandlungen der Akad. zu Berlin, vol. xxii. p. 1, fur 1835. If Annalen der Physik. 



** Transactions of the Cambridge Ph, Soc., vol. vii. pp. 1 and 113. 



tt Mlcan. Anal. Dyn, Sect., 2. Art, 5. }{ Trans. Camb. Phil. Soc., vol. vii. p. 20. 



Trans, of the Royal Society of Edinburgh, vol. xiii. p. 393. 



HI Comptes Rendus, Avril 1836. See also Nouveaux Exercises de Mathematiques, 7e livraison. 



1ffl Ibid. vol. viii. pp. 10 and 115. *** Ibid. p. 116. 



ttt Ibid. vol. ix. p. 676, Dec. 1838. See also vol. viii. pp. 40, 43. 



Itt Ibid. pp. 374, 432, 459; March 1839, &c. Ibid. vol. x. p. 273, Feb. 1840. 



{Hill Cauchy, Comptes Rendus, vol. x. p. 273, for February 1840. 



Ib. vol. x. pp. 350, 359 ; 2d May 1840. *** Ib. vol. viii. p. 553. 



