Chemical Equilibrium of Solids. 29 



question, and the explanation of magnetic hyteresis, as given 

 in the present and preceding paragraphs, mutually sustain 

 each other. 



28. Whether viscosity and dissociation in solids are to be 

 explained with reference to a single mechanism, or whether 

 we are to conceive of two mechanisms (molecular and atomic 

 frameworks), one, as it were, within the other, is at the present 

 stage of research a mere question of special convenience. The 

 remarkably low viscosity at the yield-points of metals, as well 

 as the similarly low viscosity near the Gore-Barrett phe- 

 nomena, are both in conformity with the sudden passage from 

 a first molecular state to a second, through an instability. 



29. It follows from Tables I. to VIII., that in an reolotro- 

 pically strained transparent solid like glass, electric conduction 

 is different in different directions, the difference depending 

 on the intensity of strain. Suppose this be considered in 

 connexion with the doubly refracting property of such a 

 solid, and again with Warburg and Tegetmeier's* researches on 

 the electric conduction of quartz along its optic axis, with 

 non-conduction at right angles to it. Then the inference is 

 tenable, that the strain artificially sustained in one case is 

 naturally sustained in the other. Tegetmeier's conducting 

 sodic silicate, ingrained in the crystalline structure of quartz, 

 and possessing larger molecular conductivity in quartz than 



of the magnetic field, could be made to replace the usual conception of 

 molecular currents circulating in a molecule without resistance. From 

 this point of view magnetic and electric fields merely differ in the 

 rotational character of the former as compared with the non-rotational 

 character of the latter. Whereas in an electrolyte the ion-dissociation 

 takes place as the result of chemical relations and heat, it takes place in 

 a metal under the mere influence of heat. The immediate action of both 

 fields is directional ; and by taking advantage of the positions of labile 

 equilibrium of the ion, they act in a way analogous to Clerk-Maxwell's 

 demons ('Heat/ chap. xxii. § 10), producing marked effects at the ex- 

 penditure of a relatively small amount of work. 



The advantage which I seek for in this tentative suggestion has direct 

 reference to my own line of work. I can picture to myself the role 

 played by the foreign ingredient chemically present in iron, in modifying 

 the retentiveness and the magnetic stability of the metal. Thus I con- 

 ceive the carbon atoms in hard steel to be so placed that after mag- 

 netization they block out definite closed helical paths in the metal, along 

 which the transfer of charges must thereafter take place. Hence an 

 increase of magnetic stability as contrasted with pure iron, where from 

 any point four or more such paths may be open. Again, other substances 

 (manganese, say) may be conceived to unite with the iron in such a way 

 as to shut out the possibility of closed helical paths altogether. The fact 

 that my permanent magnet is essentially a self-exhausting engine does not 

 seem to be a serious objection. 



* Warburg and Tegetmeier, Wied. Ann. xxxv. p. 455 (1888) ; xli. 

 p. 18 (1890). 



