on the Propagation of Waves in a Resisted Fluid. 521 



The leaden tube did not appear to be acted upon, neither could 

 any trace of lead be detected in the product, which gradually 

 deposits in crystalline scales, very similar in appearance to 

 those of icjdide of lead. Fluoride of bromine was prepared 

 in a similar manner, but did not yield a crystalline deposit, 

 being very soluble in water. The latter answers extremely 

 well for the Daguerreotype, giving instantaneous pictures, but 

 I cannot at present decide that it is superior to bromine alone. 

 I hope when the Society reassembles to furnish them with 

 a more detailed account of these compounds. 



LXXXIV. On the Propagation of Waves in a Resisted Fluid ; 

 iioith a new Explanation of the Dispersion and Absorption of 

 highly and other Optical Phenomena. Bij the Rev. M, 

 O'BuiEN, Professor of Natural Philosophy and- Astronomy 

 in King^s College^ London, and late Fellow qfCaius College, 

 Cambridge. 



[The subject resumed from p. 334,] 



To the Editors of the Philosophical Magazijie and Journal. 

 Gentlemen, 

 17. TN a paper which you did me the honour to print in 

 your Magazine for November, I attempted to show 

 that the general facts of the dispersion and absorption of 

 light may be accounted for by supposing that the vibrations 

 of the ffithereal fluid are resisted by the particles of matter, the 

 forces of resistance brought into play being of the same nature 

 as those which act upon a particle moving in an ordinary re- 

 sisting medium. I made no hypothesis whatever respecting 

 the law of the resistance experienced by the aethereal fluid, as- 

 suming nothing more than simply the existence of that resist- 

 ance; and I showed that, in the important and really general 

 case of circularly polarized light (for all kinds of polarized 

 light may be formed by compounding circularly polarized 

 rays), the equations of motion may be completely integrated 

 without our knowing anything respecting the law of resistance, 

 and that thus the following formulae may be obtained, namely, 

 ^ = ae~^^ cos, {nt — kz), ri = ae~^^ am^nt—kz), . (1.) 

 where h and k are given by the equations 



Phil. Mag. S. 3. No. 169. Suppl. Vol. 25. 2 M 



(2.) 



