Absence of Mechanical Connection between Ether and Matter. 31 



IV. "Luminosity and Photometry." By John Berey Haycjraft,. 

 M.D., University College, Cardiff. Communicated by Pro- 

 fessor SCHAPER, F.R.S. 



" Experiments on the Absence of Mechanical Connection 

 between Ether and Matter." By Oliver Lodge, D.Sc.,. 

 F.R.S., Professor of Physics, University College, Liverpool. 

 Received January 19, — Read March 4, 1897. 



(Abstract.) 



The author gives an abbreviated account of a long series of experi- 

 ments conducted by himself and his assistant, Mr. Davies, in con- 

 tinuation of those related in 'Phil. Trans.,' A, 1893 (Aberration 

 Problems, &c). The method consists in bifurcating a beam of light,, 

 and sending each half in opposite directions round a closed periphery 

 very near a rapidly rotating mass of matter, and then observing by 

 means of interference fringes whether the velocity of light is affected 

 in the slightest degree by this neighbourhood of moving matter. 

 The steel disks have been now whirled to higher speeds, chiefly at 

 3000 revolutions a minute ; the steadiness of the machine and the 

 definition of the bands have been improved, other minor improve- 

 ments have been made, and a long series of micrometric readings 

 have been taken, both at increasing and at decreasing speeds. 



Further, the steel disks have been replaced by a much more 

 massive lump of iron, weighing J ton, with a narrower channel for 

 the light to travel in ; and the bands have been observed close up to 

 the moving surface, and even when reflected in it. The rotation was 

 also continued for some hours to see if by chance time had any 

 influence. 



Moreover, the iron mass was strongly magnetised by a steady 

 current, so that the light travelled across a moving magnetic field ; 

 and lastly the steel disks. were replaced, with an insulated third disk 

 between them, and strongly electrified, so that the beam of light 

 travelled across a moving electrostatic field. After a number of 

 spurious disturbances had been gradually eliminated, the author 

 finds that in none of these ways is the velocity of light at all appre- 

 ciably affected, and accordingly concludes that there is no viscous 

 connexion between the ether and matter of observable magnitude ; i.e., 

 that whatever motion moving matter may confer upon the ether must 

 be of an irrotational kind. It was demonstrated theoretically in the 

 previous memoir that no optical experiments could be competent to 

 detect motion of this latter character, and accordingly no attempt has 



