THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



NO V EMBER 1890. 



XLI. On Refraction and Dispersion in certain Metals, 

 By H. E. J. G. du Bois and H. Rubens*. 



[Plate XII.] 



§ 1. TNTRODUCTORY.—K method has been worked out 

 by Prof. Kundt, by means of which the laws of 

 propagation of light may be studied in exceedingly thin me- 

 tallic prisms. By this method he has succeeded in obtaining, 

 for a number of metals, the refractive index for light normally 

 transmitted, the approximate value of the dispersion, and the 

 effect of temperature on the former. As his papers f are 

 everywhere easy of access, we shall often refer to them below 

 in order to avoid needless repetition. 



§ 2. Working on the same lines we have now made observa- 

 tions with light obliquely transmitted, in order in the first 

 place to obtain an empirical rule of refraction. We then 

 attempted to determine the dispersion as accurately as pos- 

 sible by using four colours defined by spectral lines. The 

 three metals experimentally examined were ironj cobalt, and 

 nickel ; these were chosen for the following reasons : — 



o 



* Translated by one of the Authors from the Berlin Acad. Sitzungs- 

 berichte, July 24, 1890, p. 955. The principal results were also commu- 

 nicated to Sect. A of the Brit. Assoc, at Leeds, Sept. 4, 1890. 



t Kundt, Berlin Sitzung&berichte, Feb. 1888, p. 255, and Dec. 1888, 

 p. 1387 ; referred to below as (A) and (B) respectively. Reprinted in 

 Wied. Ann. xxxiv. p. 469 (1888), and xxxvi. p. 824 (1889). Transl., Phil. 

 Mag. [5] xxvi. p. 1 ( 1888). 



Phil Mag. S. 5. Vol. 30. No. 186. Nov. 1890. 2 C 



