THE LATEST STAGE 243 



matter in aethereal terms. Lord Kelvin's idea of 

 vortex rings in a perfect fluid, Karl Pearson's view 

 that matter might be aether coming into and going 

 out of three dimensions from and to an unknown space 

 of four dimensions, Osborne Reynolds' mechanism of 

 chasms in a medium made of hard spheres packed 

 closely together, Larmor's picture of an electron as a 

 strain knot in the aether all are attempts to explain 

 matter in terms of aether, and thus to bring unity into 

 physical science. 



In spite of the incompleteness of these attempts, 

 few doubted that success was but a question of time. 

 The splendid vision of a conceptual Universe, framed 

 in its physical aspect out of the known properties of 

 one all-pervading medium, led men on. It seemed 

 that the vision might be realized any day, and all 

 science become but the physics of the aether. Materi- 

 alists who wished to be specially forward in the 

 stream of progress began to call themselves aethereal- 

 ists. Whether they were wise time alone can show. 



The difficulties which surround the theory of a stag- 

 nant aether at absolute rest in space have been evaded 

 The Principle by a new principle evolved in different 

 of Relativity. wavs by Einstein and by Minkowski. By 

 reason of the failure of all attempts to measure 

 absolute translatory motion through space by means 

 of reference to the aether, Einstein concludes that 

 it is a principle of nature that such absolute motion 

 can never be detected. The only translatory motion 

 that has meaning for us is the relative motion of 

 one body and another. To use this principle as a 

 basis of deduction, Einstein also assumes that the 



