

Notes on JEther and Electrons. 693 



elastic properties of the overstrained material are restored by 

 immersion for a short time in boiling-water. (c) That 

 recovery is not aided by repeated impact from a light 

 hammer. (d) Materials overstrained in either tension or 

 compression lose their elasticity for stress of the opposite 

 kind, but the elasticity is restored by rest, (e) The carbon- 

 steel seems to recover more quickly than the nickel-steel. 

 This, however, has not been shown conclusively by these tests, 

 but all evidence goes to show that it is true. 



The writer wishes to acknowledge the efficient help of the 

 following senior students who assisted in carrying out the 

 testing work : — Mr. Henrv Jacobson and Mr. Harry W. 

 Steindorf, of the class of 1906 ; Mr. Clinton G. Reed, Mr. 

 Lawson Stone, Mr. F. 0. Blair, and Mr. Charles E. Shearer, 

 of the class of 1905. 



LXI. Notes on JEther and Electrons. 

 Bij C. V. Bukton, D.Sc* 



1 t /4PHEXOMEXAL Processes defined. — There are some 

 processes whose type is such that an observer with 

 his surroundings may be the seat of them without any 

 resulting phenomena being manifested to him; that is to say, 

 the processes in question are without influence on the senses 

 of the observer, or upon any instrumental test or measure- 

 ment which he can make. We may exclude from present 

 consideration such motions and other effects as remain un- 

 detected solely by reason of their minuteness, defining as 

 aplienomenal those processes which elude observation through 

 the absence of any standard of permanence by comparison 

 with which they may be judged. 



Thus absolute velocity in space, if admissible at all as a 

 physical conception, appears to be rigorously aphenomenal. 



2. Absolute Acceleration. — As a further example, consider 

 a mass of perfectly incompressible substance of uniform 

 density, completely filling an absolutely rigid envelope. We 

 may suppose the incompressible substance to be a deformable 

 solid, or a liquid either possessing viscosity or perfectly 

 frictionless. Let the deformable substance be in motion in 

 any definite manner, subject only to the limitations imposed 

 by its incompressibilit}' and by the rigid containing boundary. 

 At any subsequent time, provided the- envelope is without 

 rotation, the relative motions affecting the deformable sub- 

 stance are completely determinate, and independent of any 



* Communicated bv the Author. 



