SPECULATIONS ON THE NATURE OF MATTER. 793 



pose, the establishment of the ether with any demonstrated properties 

 might aid our conceptions of matter, and be concatenated with it as 

 one of its higher forms. Maxwell has pointed out (" Encyclopae- 

 dia Britannica," ninth edition, article "Ether") that, though many 

 ethers have been proposed for various purposes, none have survived 

 except that which was invented by Huygens to explain the propaga- 

 tion of light. Evidence accumulates for this hypothesis, in some form, 

 for we have no other way of accounting for the facts, but the mechan- 

 ism is still a mystery. 



The very property of the supposititious ethers which is so fatal to 

 all explanation of a static stress, like gravity, namely, the requirement 

 of time for their functions, qualifies them so far as a vehicle of radiant 

 manifestations. Were it not for the transmission of radiant energy in 

 specific time, doubtless it would be far simpler and more satisfactory 

 to explain the whole effect as actio in distans, under the necessary law 

 of conservation, or on the Cartesian principle of contact. The phe- 

 nomenon of electro-magnetic induction which is believed to occur be- 

 tween the earth and sun, as a real material effect manifest in converted 

 energy, and yet acting in lines transverse to the lines of transmission, 

 and apparently simultaneous even now outstands as unexplainable in 

 any other way, for its mechanism certainly can not at present be com- 

 prehended. Nor is the mechanism for the transmission of the radiant 

 forms of energy yet clearly made out, though some postulates about 

 it having consistency and probability have been laid down. The fact 

 that something supra-material is necessary and probable on other 

 grounds gives encouragement to the idea that a basis for the atom can 

 eventually be found. 



The ether has been conceived under four principal modes of struc- 

 ture, all fashioned out of our concepts of matter. Two of these are 

 static, and two kinetic. The first is the pseudo-concept of a continuous, 

 colloidal plenum. This is a metaphysical, not a physical, concept ; de- 

 rived from an idealization of a false observation of matter which can 

 not be realized consistently in thought with what is postulated of it 

 afterward. As Maxwell happily remarks about the notion of homo- 

 geneous and continuous matter (" Encyclopaedia Britannica," ninth 

 edition, article " Atom "), " it is in its extreme form a theory incapable 

 of development." 



The second concept is that of a solid. This has been assumed as a 

 conceivable way of accounting for the very high co-efficient of elas- 

 ticity required by the undulatory theory, and also for the transverse 

 mode of transmitting vibrations exhibited. The word " solid," how- 

 ever, can not have any meaning such as we ordinarily attach to it ; 

 and under any signification it is admitted that the theory is encum- 

 bered with several difficulties, some of which have been set forth by 

 Professor G. G. Stokes, in his " Report on Double Refraction " (" Brit- 

 ish Association Report," 18G2, p. 253). 



