THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOUENAL OF SCIENCE. 



[FIFTH SERIES.] 



FEBRUARY 1889. 



XII. On the Polarization of Sky Light. By James C. 

 McCoNNEL, M.A., Fellow of Clare College, Cambridge*. 



[Plate VII.] 



THIS " mysterious and beautiful phenomenon," as it was 

 called by Sir John Herschel, must be now admitted to 

 have been satisfactorily explained. It has been shown by 

 Briicke (Pogg. ^ww. vol. Ixxxviii.), Tyndall (Proc, Roy. Soc. 

 Jan. 1869), and others, that an artificial blue sky may bo 

 produced in water or air by the introduction of myriads of 

 very minute particles of some denser substance, and that the 

 light scattered by these particles in a direction perpendicular 

 to the incident beam is completely polarized in the plane of 

 incidence. Lord Rayleigh has placed the matter on a more 

 satisfactory basis by deducing the same results from the elec- 

 tromagnetic theory of light f. He further defined accurately 

 the colour of the scattered light, showing that the amount 

 scattered of different kinds of homogeneous light varied 

 inversely as the fourth power of the wave-length. With 

 regard to the intensity and polarization of light scattered in 

 different directions he obtained the following results. To 

 find the nature of the light deflected in any given plane, 



* Communicated by the Author, 



t He first employed a form of the " elastic solid " theory in which the 

 density of the aether is supposed to vary in different media (Phil. Mag, 

 Feb., April, June, 1871). In a later paper (Phil. Mag. Aug. 1881) he 

 showed that the electromagnetic theory led to the same equations. 



Phil. Mag. S. 5. Vol. 27. No. 165. Feh. 1889. G 



