714 SCIENCE AND HYPOTHESIS 



To-day, what do we see ? In the first place, a step in advance im- 

 mense progress. The relations between light and electricity are now 

 known; the three domains of light, electricity, and magnetism, for- 

 merly separated, are now one ; and this annexation seems definitive. 



Nevertheless the conquest has caused us some sacrifices. Optical 

 phenomena become particular cases in electric phenomena; as long as 

 the former remained isolated, it was easy to explain them by move- 

 ments which were thought to be known in all their details. That 

 was easy enough; but any explanation to be accepted must now cover 

 the whole domain of electricity. This cannot be done without diffi- 

 culty. 



The most satisfactory theory is that of Lorentz ; it is unquestionably 

 the theory that best explains the known facts, the one that throws into 

 relief the greatest number of known relations, the one in which we 

 find most traces of definitive construction. That it still possesses a 

 serious fault I have shown above. It is in contradiction with New- 

 ton's law that action and re-action are equal and opposite or rather, 

 this principle according to Lorentz cannot be applicable to matter 

 alone; if it be true, it must take into account the action of the ether 

 on matter, and the re-action of the matter on the ether. Now, in the 

 new order, it is very likely that things do not happen in this way. 



However this may be, it is due to Lorentz that the results of 

 Fizeau on the optics of moving bodies, the laws of normal and abnor- 

 mal dispersion and of absorption are connected with each other and 

 with the other properties of the ether, by bonds which no doubt will 

 not be readily severed. Look at the ease with which the new Zeeman 

 phenomenon found its place, and even aided the classification of 

 Faraday's magnetic rotation, which had defied all Maxwell's efforts. 

 This facility proves that Lorentz's theory is not a mere artificial com- 

 bination which must eventually find its solvent. It will probably have 

 to be modified, but not destroyed. 



The only object of Lorentz was to include in a single whole all 

 the optics and electro-dynamics of moving bodies; he did not claim 

 to give a mechanical explanation. Larmor goes further; keeping the 

 essential part of Lorentz's theory, he grafts upon it, so to speak, Mac- 

 Cullagh's ideas on the direction of the movement of the 

 ether. MacCullagh held that the velocity of the ether is the 

 same in magnitude and direction as the magnetic force. Ingenious 

 as is this attempt, the fault in Lorentz's theory remains, and is even 

 aggravated. According to Lorentz, we do not know what the move- 

 ments of the ether are; and because we do not know this, we may 

 suppose them to be movements compensating those of matter, and re- 

 affirming that action and re-action are equal and opposite. According 

 to Larmor we know the movements of the ether, and we can prove 

 that the compensation does not take place. 



