On the Michel son- Mori ei/ Mther Experiment , 343 



A. Gruxwald. Dr. H. Kayser und meine matliematisclie Spectral- 

 analyse. Chemiker Zeitung, xiv. No. 20. 



A. Kayskr. Ueber Griinwald's mathematische Spectralanalyse. 

 Chemiker Zeitung, xiv. No. 81. 



H. Kayskr. Ibid. Chemiker Zeitung, xiii. No. 100 u. 102. 



II. Kayskr. The Hydrogen Spectrum. Astrophysics! Journ. v. 

 p. 243 ( L897). 



E. U. Pickering. The New Series in the Hydrogen Spectrum, 

 Astrophysical Journ. v. p. 03 (1897). 



W. W. Randall. The Permeation of Hot Platinum by Gases. 

 Amor. Chem. Journ. xix. p. 682 ( 1897). 



J. 1\. Rydbkrg. The New Series in the Hydrogen Spectrum. 

 Astrophys. Journ. vi. pp. 233-238 (1897). 



V. Schumann. The Hydrogen Line II /3 in Spectra of the New Stars 

 in Auriga and in Spectra of Vacuum Tubes. Astron. & Astro- 

 phys. xii. pp. 159-166 (1893). 



V. Schumann. Yoni Wasserstoffapectrum. Jahr. f. Photog. u. 

 lieprod.-techn. viii. p. -59; Wied. Beibl. xviii. p. 702. 



L. Thomas et Ch. Trepied. Sur l'application des hautes tempera- 

 tures a l'observation du Spectre de I'Hydrogene. Comptes Rendus, 

 cix. pp. o2±-o2o (1889). 



J. Trowbridge & Th. W. Richards. Multiple Spectra of Gases. 

 Phil. Mag. [5] xliii. pp. 135-139. 



XXXII. Note on Mr. Sutherland's Objection to the Conclusive- 

 ness of the Miclielson-Morley JEther Experiment. 



To the Editors of the Philosophical Magazine, 



Gentlemen, 



I HAVE just seen a paper by Mr. W. Sutherland in 

 your number for Janu ary this year, where he suggests 

 reasons for doubting the trustworthy character of the negative 

 result of Michelson and Morley's great experiment. It might, 

 for instance, be attributed to the possible second-order influ- 

 ence of a hitherto neglected first-order tilting or shifting of 

 the wave-fronts brought about by the undiscovered drift of 

 the aether past the earth. (I am not sure that Mr. Sutherland 

 means exactly this; but if not his meaning is unintelligible, 

 having regard to the way in which the experiment was actually 

 performed, viz. by revolving a floating stone and observing in 

 all azimuths. A criticism by Mr. Sutherland is, however, 

 always of importance.) 



But in my memoir on Aberration (Phil. Trans. A. 1893, 

 pp. 739, 748, & 790) 1 have shown that though motion of the 

 entire medium can readily affect ivaves, it has no first-order 

 effect upon rays, neither upon their path nor their time of 

 journey; and inasmuch as it is either ray-path or time of journey 

 which is observed in any optical experiment, I am unable to per- 

 ceive any flaw in the Michelson-Morley result, that the expected 

 second-order effect is also nil. It might be thought that the 

 varying inclination of the ray to the mirror at different 



Y V 



