July 26, 1883] 



NA TURE 



2 95 



posing and quiescent, and internally passive, neutral, and in- 

 different to all surrounding material universes, yet I am disposed 

 to concur with Prof. Morris in his emphatic enunciation and very 

 appropriate and varied illustrations of this law, because the 

 idea of es'ablished boundaries, prescribing fixed terms and limits 

 to motor-vigour's local actions, has, in an investigation of the 

 principles of thermodynamics which lately occupied me, already 

 presented itself tome as an indispensable foundation for a theory 

 of heat, in which temperature was identified with motor-couple's 

 . dual power of dispensing motor-vigour between ordinary and 

 ether masses, partly by opposing undulatory, and partly by con- 

 tending diffusive motions of ether's and gro-s-matter's aerilian 

 parts. 



Easily as that theory lent itself in olher respects to a deductive 

 establishment of the laws of heat, it yet stumbled abruptly upon 

 this blank presumption, or frowning precipice, of how boundaries 

 of the kind (to such forms of aerilian action) come to be esta- 

 blished and imposed between ether and gross matter, as well as 

 between material bodies generally, wherever superficial contact 

 between their substances takes place ? 



Granting indeed, provisionally, that we may freely accept 

 Prof. Morris's somewhat too simple, and in fitness for its purpose 

 mucn too meagre and unassuming supposition (which I should 

 also say that he errs in describing me at the beginning of his 

 letter as being just as n tiling and contented to accept and conform 

 to as he is himself), that " particles of ponderable matter consist 

 of aggregations of ethereal substance," or that "ether is a srb- 

 stance whose condensation yields particled matter," it would ihen 

 be making a step of inference which would neither be a uositively 

 ungrounded one, nor (supposing that nature's system were really 

 such a simple one as this hypothesis assumes) at all a likely one 

 to conduct us to any embarrassing or perplexing consequences, to 

 describe the "excessively disintegrated matter" which in his 

 apercit of the retinues of space "replaces ether," as ordinary 

 matter in a "fourth state" of attenuation ; because we would 

 immediately reflect that the boundaries between the solid, liquid, 

 and vaporous forms of such a multistructured substance as ethro- 

 genous matter would then be, are themselves well known to be 

 the seats of a certain diffusive and undulatory struggle and ba- 

 lanced equipoise, the real nature of which, beyond what is known 

 of its laws of relation to pressure, heat, and temperature, cannot 

 be accurately described. The fact that temperature and tension 

 regulate it does, indeed, assimilate it to the similar dual balance 

 of motor-couple's diffusive and undulatory actions at the borders 

 between ether and ordinary matter which 1 found to be indis- 

 pensable as a first starling-ground for basing a mechanical theory 

 of temperature, heat, and entropy on mathematical properties of 

 motor-couples ; and our ignorance of how the boundaries are 

 established in each case is not only no greater, but it actually 

 appears to be of precisely the same nature and description in one 

 of these cases as in another. 



The parts which collision and vibration play in distributing 

 motor-vigour in solids, liquids, gases, and in ether, are abund- 

 antly well-instanced and described in Prof. Morris's letter ; and 

 it again affords me extreme gratification to 1 ote the exact paral- 

 lelism which his views present with those furnished by a systematic 

 and not perhaps altogether unmathematical treatment of the sub- 

 ject which I have pursued, if, as I surmise, undulation and diffu- 

 sion are kinds of motor-action (both active in a motor-couple) of 

 such primitive simplicity of construction in their agitational or 

 motor-type, that, in virtue of their elementary mathematical cha- 

 racter, one single mechanical explanation really suffices for and 

 applies with equal exactitude to all those instances of material 

 conflict just considered, which occur at the boundaries between 

 the seveial gross and ethereal states of matter. 



But both physical and mathematical considerations have be- 

 sides this led me to supposr, as 1 trust that they may also in 

 the end influence Prof. Morris's decision, that the title of the 

 " fourth state " of matter which we might thus quite fairly at 

 first sight and provisionally apply to ether, is in the all-essential 

 meaning of the words an undeniable misnomer ; because mutual 

 conversion of the two substances composing the first three and 

 the last of the forms in question one into the other is bond fide 

 shown by the clearest evidence of experience, and equally by 

 theoretical proofs based on the two substances' motor relations, 

 to be, even more certainly than making gold out of copper, an 

 impossible physical proceeding. With such plain reasons as I 

 will try briefly to produce for pronouncing ether and ordinary 

 matter to be perfectly distinct and totally untransmutable fellow- 

 occupants of space, it is really more consistent with simple fact, 



and a more precise and correct use of language, to speak of 

 ether as " matter of the second class " or of the second grade or 

 order, than it would be to call it either dubiously matter "in a 

 fourth form," or to give it the still more erroneous title of a 

 "fourth state of ordinary matter." 



While, in fact, we know innumerable chemical and physical 

 forces capable of altering to any give-and-take extent the boun- 

 daries between liquids and their vapours, between similar ard 

 dissimilar solids and liquids, and like and unlike gases and 

 molecules, so as to change entirely all their physical and chemi- 

 cal states, or groupings, yet no force of art or nature can make 

 any portion of gross matter change its weight by condensation 

 or escape of ether. Even chemistry, to whose reactions Prof. 

 Morris assigns the greatest power of altering molecular group- 

 ings, although tested in this direction with the delicacy of a 

 vacuum-balance in Mr. Crookes' researches, has been found to 

 be powerless to do so. It is true that its reactions only employ 

 the sedatory tendency of motion in order to produce new group- 

 ings, and the electric current, which first disclosed the existence 

 of the elements sodium and potassium, and whose arc of light 

 gives us glimpses of chemical dissociations scarcely less com- 

 plete than those detected by the spectroscope in the sun, over- 

 comes and reverses the power of chemical affinity to form com- 

 binations in this w ay more effectually than any other force, and 

 breaks up all chemistry's compound productions more completely 

 than any other force can do. Yet, while no dissipation of weight 

 of ordinary materials by electric currents has yet been detected, 

 it is just as certain that ponderable matter has never yet to our 

 knowledge gained or increased in weight in virtue of the exer- 

 tion of any possible chemical affinity which it may have tor 

 ether, although this affinity, if it exists, must yet be of extra- 

 ordinary strength, since it can successfully resist every effort that 

 has yet been made to loosen it ! Either imponderability of ether 

 or immutability of its boundaries of junction with gross matter, 

 or both of these together, must therefore be assumed to account 

 for the sum of this experience ; and whichever of the alterna- 

 tives we are led to choose, distinctly differentiates the two sub- 

 stances from each other as regards this particular character of 

 mutual convertibility of substance, for no known ordinary matter 

 arising from ether's condensation is imponderable, or, on the 

 other hand, if ether has weight, experience still shows that no 

 condensation of it into ponderable ordinary matter is possible. 



Ano'her conspicuous peculiarity of ether consists in a special 

 independence between its motor-vigour and that of ordinary 

 matter, of which instances of the plainest proof are afforded by 

 Doppler's theory and by the theory of the aberration of light. 

 The motions of ether in an ether-replenished field are not in the 

 least degree affected by the directed motion across it of a mass 

 of ordinary matter, just as a perfectly smooth anchor would 

 leave no permanent agitation whatever behind it in water or 

 liquid inwardly and outwardly as smooth as itself, through 

 which it takes its way. It is only by such a passing body's 

 aerilian or undirected motions that ether can be disturbed, and 

 with those it harmonises or collides, mutually receiving from 

 and imparting to the body it so touches motor vigour (which 

 may either take the form of actual heat or of stresses in the 

 ponderable body) by the primitive aerilian processes of wave- 

 impact and diffusion-blows of the two substances at the boundary 

 between them. With the absence of these (if we could imagine 

 the privation to exist) the bodily or directed motion of the two 

 substances, like those of a smooth anchor swinging in a stream of 

 frictionless water, would all the while be wholly unaffected by, 

 indifferent to, and independent of each other. The ether there- 

 fore stands in such motor-relations to gross matter that the two 

 can only exchange motor- vigour with each other by means of the 

 aerilian impulses of their touching parts. 



Now this theory of ethereal action, suggested to me by an 

 accidental consideration of the well known mathematical equa- 

 tion of stationary motion, which was at once seen to furnish, on 

 closer examination, a very consistent interpretation of the second 

 law of thermodynamics, and of its several thermal quantities, 

 led me to describe in my formerletter (Nature, vol. xxvii. pp. 

 458 and 504) some of the necessary postulates or maxims of 

 the new theory in its integrity of fitting enunciation for such 

 applications. 



If the mutual motor-relations between ether and gross matter 

 are indeed (as I have very full grounds for confident assurance) 

 of the extraordinary nature and description there set forth, there 

 seems to be no room to pause or to waver and hesitate over nicely 

 raised but unavailing protests of prejudice and predilection in 



