202 Pro p . L. T, More on the 



recent discussion^, while clearing away crude conceptions, 

 have invariably tended to the strengthening of that hypo- 

 thesis. The mode in which the ordinary forces of colies-ion 

 could be included in such a view is still quite undeveloped." 

 He thus rather leaves this question in the air by concluding 

 that a complete theory is not necessary. But the history of 

 science shows that we shall soon hypothecate two aethers or 

 try to give properties to one which will include electrical, 

 chemical, and material forces ; indeed this latter is already 

 being attempted. Evidently he fears the tendency of 

 explaining things too exactly by mechanical analogies, for 

 he believes * "all that is known (or perhaps need be known) 

 of the aether itself may be formulated as a scheme of 

 differential equations defining the properties of a continuum 

 in space, which it would be gratuitous to further explain by 

 any complication of structure ; though we can with great 

 advantage employ our stock of ordinary dynamical concepts 

 in describing the succession of different states thereby 

 defined. " Yet it seems that a more complicated structure 

 than the modern molecule, composed of an interminable series 

 of electrical getherial strains, could hardly be conceived. 



If the conception of an elastic-solid aether was admittedly 

 a fiction of the mind, and one impossible to align with any 

 known kind of matter, the electromagnetic aether is so 

 esoteric, so subtilized from all substance, that it merely 

 provides a nomenclature for a set of equations expressing 

 the propagation of radiant energy. Both Sir J. Larmor 

 and Professor Lorentz give the impression in their writings 

 that the least said of the properties of such an aether the 

 better, since the final verdict will be that the process of 

 radiant energy, in transit through space, is best expressed as 

 an equation containing unknowable qualitative coefficients. 

 We may well go still further, for I believe the time is 

 rapidly approaching when all scientific discussion of the 

 nature of the gether will be considered futile. But Sir J. 

 Larmor does lay down in his treatise certain attributes, 

 mostly negative, which he accepts. Thus, the aether is a 

 continuous and quiescent plenum, absolutely unaffected by 

 mechanical energy. Existing in it, are countless places of 

 discontinuity, or electrical strains, which constitute the 

 elements of matter. Its only positive properties are the 

 ability to maintain such strains and to transmit any electro- 

 magnetic disturbance with the velocity of light. All 

 chemical and mechanical forces must therefore be attributes 

 of electricity, or else referable to seme other distinct cause. 



* L. c, p. 78. 



