50 Presidential Address 



against it. But how are we to make the 

 comparison? If the time of emission 

 from a distant source is given by a dis- 

 tant clock, that clock must be observed 

 through a telescope, that is by a beam of 

 light; which is plainly a compensating 

 process. Or the light from a neighbouring 

 source can be sent back to us by a distant 

 mirror ; when again there will be compen- 

 sation. Or the starting of light from a 

 distant terrestrial source may be tele- 

 graphed to us, either with a wire or with- 

 out; but it is the ether that conveys the 

 message in either case, so again there 

 will be compensation. Electricity, Mag- 

 netism, and Light, are all effects of the 

 ether. 



Use Cohesion, then; have a rod stretch- 

 ing from one place to another, and 

 measure that. But cohesion is trans- 

 mitted by the ether too, if, as believed, 

 it is the universal binding medium. 

 Compensation is likely; compensation 

 can, on the electrical theory of matter, 

 be predicted. 



Use some action not dependent on 



