Continuity 49 



reference to the ether alone has ever yet 

 been observed: there are always curious 

 compensating effects which just cancel 

 out the movement-terms and destroy or 

 effectively mask any phenomenon that 

 might otherwise be expected. When 

 matter moves past matter observation 

 can be made; but, even so, no consequent 

 locomotion of ether, outside the actually 

 moving particles, can be detected. 



(It is sometimes urged that rotation 

 is a kind of absolute motion that can be 

 detected, even in isolation. It can so be 

 detected, as Newton pointed out; but 

 in cases of rotation matter on one side 

 the axis is moving in the opposite direc- 

 tion to matter on the other side of the 

 axis; hence rotation involves relative 

 material motion, and therefore can be 

 observed.) 



To detect motion through ether we 

 must use an etherial process. We may 

 use radiation, and try to compare 

 the speeds of light along or across the 

 motion; or we might try to measure the 

 speed, first with the motion and then 



