330 COMSTOCK— THE MODERN THEORY [April 22, 



system, used in this sense, includes, of course, all radiant energy, 

 for it will be remembered that this type of energy is also electro- 

 magnetic. 



Thus, on grounds of well-established electromagnetic theory and 

 without any new fundamental conceptions whatever, we can make 

 a general statement that any electromagnetic system, zvhen set in 

 motion, tends to assume a nezc state of equilibrium, and if this 

 change be allozced to take place, then all effects, electric and optical, 

 take place in the changed system in a manner exactly corresponding 

 to the cC'flv they did take place before the syston zvas set in motion. 



A moment's thought will make it evident that we are here ap- 

 parently in the presence of a fundamental lack of harmony between 

 electromagnetic phenomena and the phenomena connected with 

 matter in general ; for, from the ordinary point of view, the parts of 

 a " rigid body " maintain their mutual relations unaltered whether 

 or not it is set in motion, while, as we have seen, this is not true of 

 electromagnetic systems. 



Now, we have no choice but to consider a real body as a com- 

 bination made up of the two kinds of systems if there are two, the 

 electromagnetic type and the " rigid body " type ; hence it is clear 

 that, wdien such a mixed system is set in motion, there will be a 

 considerable amount of what we might term internal discord, owing 

 to the conflicting tendency of the two types. It would be very easy 

 to distinguish such a mixed moving system from the same system 

 at rest, because its parts would bear quite different relations to each 

 other than they did before. Setting a real system in motion would 

 be like heating an object made up of two substances having different 

 coefficients of expansion. The parts of such a system would then 

 bear totally dift'erent relations to each other than when the whole 

 thing was at rest, and the internal dissension would increase with 

 the velocity and would depend on its direction. 



Now as a matter of fact, we all live on such a moving mixed 

 system, a system which is going around the sun with a velocity of 

 nearly twenty miles a second; and yet, although many carefully 

 planned and executed experiments have been carried out to detect 

 dift'erences in the actions of various electrical and optical systems, 

 according as thev are made to face with the earth's velocity or 



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