196 nutting: the ether 



there is no material connecting link, such as a wire or pulsating 

 fluid, between them, it has always been customary to put the bur- 

 den upon an immaterial medium. Gravitational attraction, elec- 

 trical and magnetic attraction and repulsion are of this nature. 

 Chemical affinity should probably be included but some hold that 

 a material link actually holds tile atoms together. 



In my opinion not much weight can be attached to action at 

 a distance as evidence for the existence of an ether. The assump- 

 tion of an ether is doubtless the simplest explanation of the facts, 

 but it is certainly not the only possible explanation. It is easy 

 to imagine an intervening medium pulled by one body and itself 

 pulling a second body. However, in imagining such a medium, 

 we are endowing it with mechanical properties and with such 

 extreme properties as no known material possesses. In discard- 

 ing the mechanical assumption we may either assume a non- 

 mechanical ether or else assume that these forces really belong 

 to some higher mechanical system in which the apparent action 

 at a distance is in reality contact action. Perhaps there are still 

 other alternatives. I merely cite these two to show how far we 

 are from a final disposition of the problem. 



2. The propagation of electromagnetic energy from one body to 

 another. Radiation is emitted by one body and received after 

 an interval of time by another. Where and what was this energy 

 during that interval of time? Until recently, these questions were 

 readily answered; radiation travels as wave energy, where waves 

 are there is motion, where motion is there is something that moves, 

 namely, the ether. At present with an ether devoid of mechani- 

 cal properties, there are wide differences of opinion as to just how 

 electromagnetic energy travels through space, but if we knew how 

 it is propagated through any material di-electric, we could very 

 probably give at least a tentative explanation of how it travels 

 from one body to another. 



So far as we now know, such energy could be propagated through 

 void space only in corpuscular form. If we assume corpuscular 

 light, we have to contend with a solid array of firmly established 

 facts. Further, electromagnetic theory itself shows that energy 

 thus propagated is essentially alternating in character and in 

 definite relations to the direction of propagation. To my mind, 



