THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



SEPTEMBER 1919. 



XXV. On the Molecular Theory of Refraction, Reflexion, and 

 Extinction. By Ladislas Natanson, Ph.D., Professor of 

 Natural Philosophy in the University of Cracow* . 



IN two communications brought under the notice of the 

 Cracow Academy o£ Sciences in January and in June 

 1914f, I have been concerned with following out the circum- 

 stances of the mutual action which must be supposed to take 

 place between an advancing wave of light and the ultimate 

 fragments of matter lying in its path. The leading assump- 

 tions adopted in this investigation appeared conducive to 

 clearness and consistency, and 1 believe they may possibly 

 still commend themselves to the theorist's attention. In the 

 meantime, however, Science has progressed. Owing to 

 excellent researches J the treatment of the subject has been 

 notably extended and deepened, so that the interest of the 

 papers published in 1914 may now perhaps be regarded 

 as having passed away. Acceding, nevertheless, to friendly 

 advice 1 venture to lay before the readers of the Philosophical 

 Magazine the present essay which contains the substance of 

 the papers to which I allude. Having found advantage 



* Communicated by the Author. 



f Bulletin Int. de VAcad. d. Sc. de Cracom'e, CI. d. Sc. Math, et Nat. r 

 Series A, 1914, pp. 1-29 £ 335-352. 



% C. W. Oseen, Annalen der Physik, vol, xlviii. pp. 1-56 (1915). 

 P. P. Ewald, Annalen der Physik, vol. xlix. pp. 1-38 & 117-143 (1916). 

 Fr. Reiche, Annalen der Physik, vol. 1. pp. 1-52 & 121-162 (1916). 

 Ragnar Lundblad, Annalen der Physik, vol. lvii. pp. 183-202 (1918). 



Phil. Mag. S. 6. Vol. 38. No. 225. Sept 1919. II 



