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Preston, Samuel Tolver (1878), = =E2=80=9CThe=20 Bearing of the Kinetic Theory of Gravitation on the Phenomena of=20 "Cohesion" and "Chemical Action," together with the important = connected=20 Inferences regarding the existence of Stores of Motion in Space, = No. IV=E2=80=9D,=20 Philosophical Magazine 5: 297-311 |
No. IV[1]
1. IT would be natural to expect that any theory competent to explain = the=20 effects of gravity ought to be able to throw some light upon the = subsidiary=20 effects of molecules exhibited in "cohesion," "chemical action," &c. = Before=20 proceeding to consider this question, and in order to have a clear = conception of=20 the point we have to deal with, we will recapitulate in a few words the = physical=20 conditions involved in the case of gravity as already dealt with. It has = been=20 our object to point out that the molecules of a gas within the range = of free=20 path are moving in precisely the right way to produce [298] gravity = in two=20 masses immersed in the gas within the range of free path. For since it = has been=20 proved from the kinetic theory that the particles of a gas adjust their = motions=20 so as to move uniformly or equally in all directions, and since = the=20 particles within the range of free path are moving in unbroken streams, = it=20 follows that two masses immersed in the gas at a distance apart within = this=20 range will (owing to the one sheltering the other) be struck with more = particles=20 on their remote (unsheltered) sides than on their adjacent (sheltered) = sides, so=20 that the two masses will be urged together. This, therefore, fulfils Le = Sage's=20 fundamental idea without the necessity for accepting any of his = postulates. We=20 need not accept the scarcely realizable postulates of streams of = particles=20 coming from indefinite distances in space (at uniform angles), each = stream=20 moving continuously in one direction; but we can substitute for this the = natural=20 conception of the normal motion of the particles of a gas within the = range of=20 free path, where, although each particle is continually changing = the=20 direction of its motion, yet the general character of the motion = of the=20 system as a whole remains unchanged; or the system of particles = automatically=20 correct their motions so as to continue to move uniformly or equally = in all=20 directions, as demonstrated in connexion with the kinetic theory of = gases.=20 This movement of the particles equally in all directions is the = condition=20 required to produce equal gravific effect in all directions. Thus all we = require=20 to admit in order to produce all the effects of gravity as = necessary=20 results, is the existence of a gas in space. This gas differs from an = ordinary=20 gas only as to scale, i. e. in the proximity, velocity, and extreme=20 minuteness of its particles, whereby a length of free path = commensurate=20 with the greatest observed range of gravity is insured, the extreme = minuteness=20 of the particles being at the same time adapted to that high velocity = which the=20 effects of gravity require, and which also necessarily renders the = medium itself=20 impalpable or concealed from the senses. The range of free path, though = great in=20 one sense, may be considered small and suitable for a gas that pervades = the vast=20 range of the visible universe.
2. In applying these principles to cohesion, or the approach of = molecules in=20 chemical reactions, it is so far easy to see that when two molecules of = matter=20 come very close together, or if we suppose them actually to come into = contact,=20 then they will cut off the entire stream of particles of the gravific = medium=20 from between the parts in contact; and therefore, as the gravific = particles now only strike against the remote sides of the two molecules, = the=20 latter will be urged together with very great [299] force, thus = explaining=20 "cohesion".[2]=20 But then a difficulty at once presents itself here. When two masses (or=20 molecules) are gradually approached towards each other, instead of the = tendency=20 to approach gradually increasing up to a maximum ( as we should expect = from the=20 theory), they begin to repel at a certain distance, and very = considerable force=20 is in general required to overcome this first repulsion, when the masses = then=20 unite into one. Thus two freshly cut pieces of lead may be made to unite = with=20 some pressure, also glass, or various metals, with more or less = pressure. There=20 is therefore a neutral point which has to be passed, when the = tendency to=20 recede changes into a tendency to approach. The same thing is exhibited = (=20 conversely) when a substance is broken into two parts by tension. If = pulled=20 (nearly) up to the neutral point, the two parts recoil or return into = their old=20 positions. If pulled beyond the neutral point, the parts repel and will = not=20 return into their old positions, i. e. they separate permanently. The = thing,=20 therefore, to be explained is the existence of this neutral point, or, = in other=20 words, the repulsion that exists at a certain distance from the = surfaces.
3. The explanation we have to offer here depends upon quite recent=20 investigations. It must be observed first that facts prove the existence = of a=20 second medium in space besides the gravific medium, viz. the heat- or=20 light-conveying medium (the aether). If we admit the existence of = one=20 medium in space constituted according to the kinetic theory (the = gravific=20 medium), it would be natural to conclude that the second medium (or = aether) was=20 constituted in an analogous manner. We shall give independent reasons = afterwards=20 that lead to infer this constitution, and endeavour to answer possible=20 objections; but in the mean time it is only necessary to suppose it to = be so=20 constituted (in the absence of proof to the contrary); and if this = supposition=20 serves to explain in general principle a number of facts, this will be = one=20 argument for its truth. On account of the extreme shortness of the waves = of=20 light and heat, it would be reasonable to suppose that the length of = free [300]=20 path of the aether particles was contained within compact limits, or = was, at any=20 rate, shorter than the length of the wave itself. It has been proved = recently,=20 in investigations by Mr. Johnstone Stoney in connexion with the = radiometer,[3]=20 that a medium constituted according to the kinetic theory has a special = power of=20 propagating a pressure unequal in various directions, or that, when a = layer of=20 the medium (such as a layer of air) is intercepted between two surfaces = whose=20 distance apart is a small multiple of the length of free path of = the=20 particles of air, the layer can then transmit a pressure in the line=20 perpendicular to the surfaces which is in excess of the = transverse=20 pressure; and thus a repulsion is produced, accounting for the = spheroidal state,=20 the motion of the radiometer, &c. In fact it is evident (as pointed = out)=20 that, since in a medium constituted according to the kinetic theory the=20 particles move in straight lines, the particles (when the distance of = the=20 opposed surfaces approximates to the range of free path) get reflected = backwards=20 and forwards repeatedly between the opposed surfaces, the increments of = energy=20 received by the particles accumulating by successive reflections, so = that the=20 particles produce a bombardment tending to separate the two opposed = surfaces The=20 increments of velocity imparted by the heated[4]=20 [301] surfaces are also mainly received in the line joining the surfaces = (not so=20 much transversely); so that this conduces to the pressure on the = surfaces, or=20 repulsion.
4. This is precisely what we have to put forward, in its = application to=20 the aether, as an explanation of the repulsion in the cases referred = to,=20 such as for example the repulsion of two lenses or glass surfaces placed = together in such proximity as to exhibit "Newton's rings," the repulsion = of two=20 molecules &c.; for if the tether be constituted according to the = kinetic=20 theory, we shall inevitably have the same phenomena here, though on an=20 infinitely more energetic scale; for the particles of tether come into = direct=20 contact with the vibrating molecules of matter, whose energy of = vibration is=20 known to be enormous at normal temperature; and the layer of aether is = very=20 thin, and the motion of the aether particles very rapid,[5]=20 so that the successive increments of velocity imparted by the vibrating=20 molecules accumulate by successive reflections (backwards and forwards) = between=20 the opposed surfaces, producing a forcible repulsion. These results have = been=20 theoretically demonstrated to follow on the basis of the kinetic = theory,=20 and have been established by experimental facts. It is a point of great=20 importance to observe that it is specially the kinetic theory = that=20 explains this otherwise most curious fact of an excess of = pressure in a=20 medium in one direction (producing a repulsion), with normal pressure = existing=20 in transverse directions, which otherwise it would be so difficult to = explain,=20 and which must be explained in order to account in a realizable manner = for the=20 phenomena observed. It is difficult to conceive how any other means of=20 explaining this curious fact could be afforded than that supplied by the = kinetic=20 theory. Moreover it is generally admitted that heat has the = property of=20 producing repulsion. The "heat" of the molecules in the cases mentioned = is known=20 to consist in their vibrations, by which they generate waves of = heat in=20 the aether. We have therefore to explain under what particular = constitution of a=20 medium vibrations can (within certain limits) produce repulsion. = The=20 kinetic theory of the constitution of the medium solves = completely this=20 peculiarly difficult problem. [302]
5. When the two surfaces (or two molecules) are pushed up closer to = each=20 other, then the energy of the gravific medium directed against the = remote sides=20 of the molecules prevails more and more, since the mutual = sheltering-power of=20 the molecules increases in an enormously rapid ratio as contact is = neared, and=20 so the unbalanced energy of the gravific medium directed with full force = against=20 the remote sides of the opposed molecules at length outweighs the action = of the=20 intercepted aether particles, and the two molecules are propelled = together ( or=20 unite).
6. We may allude to a few examples serving to illustrate the = application of=20 the above principles. Supposing we take the common case of the ignition = of a gas=20 jet. Then when the gas is turned on, the molecules of gas and air mingle = with=20 each other and are known to be exchanging motion and rebounding from = each other,=20 and yet they do not unite. According to the above principles the = molecules, as=20 they approach each other in their encounters, are kept apart by the = forcible=20 vibrations (which the molecules are known to possess[6])=20 which, through the increments of velocity imparted to the particles of = the=20 intervening aether, produce a repulsion in the manner described, as soon = as the=20 molecules in their encounters have approached nearly within range of the = mean=20 path of the aether particles. When a flame is applied to the jet, = the=20 rapidly moving gaseous molecules of which the flame consists naturally = produce a=20 disturbance, jostling some of the molecules of the mixture of gas and = air=20 against each other, so that, the neutral point is passed, whereby the = molecules=20 are brought into such proximity that their mutual sheltering action = causes the=20 gravific medium to impinge with full energy upon their remote sides, = thus urging=20 the molecules together (producing combination). The molecules are thrown = into=20 forcible vibration by the shock of approach, and become luminous through = the=20 energy of the waves thus generated by them in the surrounding aether. = These=20 vibrations of the compound molecules after combination naturally cause = the=20 forcible rebound of any other molecules that happen to be in their = proximity,=20 the disturbance thus set up sufficing to effect the successive ( = practically=20 instantaneous) combination of the entire jet of gas. The same = considerations of=20 course apply to the practically instantaneous combination (explosion) of = a=20 mixture (in definite proportions) of gas and air, by an initial = disturbance=20 [303] produced by a flame. In the case of solid bodies, where the = molecules are=20 fixed or under control, a forcible pressure or concussion may serve to = bring the=20 molecules over the neutral point (and thus effect combination), as = illustrated=20 by the effect of the blow struck in "percussion" powders. It would not = appear=20 that matter in the gaseous state could ever be exploded by pressure (so = long as=20 the gaseous state was retained); for the molecules of gases cannot be = pressed=20 against each other by any amount of pressure, since, the molecules being = in free=20 translatory motion among themselves, the only effect of pressure would = evidently=20 be to put a greater number of molecules into unit of volume, without = thereby=20 causing the molecules in their encounters to approach nearer to each = other than=20 before. The degree of approach of the molecules (in their encounters) = depends=20 evidently on their momentum or velocity; and this remains the same = whatever the=20 pressure.
7. Heat could not apparently be said to augment the energy of = chemical=20 combination, since, in general, heat is known to possess the exactly = opposite=20 effect, or to disintegrate matter. The part played by heat in effecting = chemical=20 combination would seem to consist simply in producing a molecular=20 disturbance, whereby unavoidably some molecules are urged towards = each=20 other so as to pass the outer neutral point, which is the necessary = preliminary=20 to combination. No doubt, when heated elements combine, the original = heat adds=20 itself to the work thus to be derived, as the heat cannot be destroyed, = though=20 it cannot increase the work of combination. Heat may (as is known) = entirely=20 prevent chemical combination, and oven dissociate combined elements. The = action=20 of heat in preventing chemical combination and producing dissociation = would on=20 the above principles consist in the fact that, when the vibratory motion = of the=20 molecules becomes excessive, this vibratory motion generates such a = pressure in=20 the intervening layer of aether on the approach of the molecules as to = prevent=20 them from passing the neutral point: or, indeed, no neutral point may = exist,=20 provided the pressure or repulsion thus generated be such as to outweigh = the=20 action of the gravific medium, as appears actually to take place in the=20 dissociation of matter by excessive heat. Thus it would appear probable = from=20 this, that when combination ensues in the case of a mixture of gases = previously=20 considerably heated (but not so much so as to produce dissociation), the = molecules on combination do not at once settle clown into that full = proximity=20 (which belongs to a lower temperature), but they do so gradually as the=20 temperature falls. Thus the work of combination is prolonged over the = falling=20 temperature, and the cooling thereby [304] somewhat retarded. Precisely = the same=20 thing is illustrated in the aggregation of groups of molecules (to form = masses),=20 as in the aggregation of single molecules to form compound molecules. = Thus when=20 a bar of iron is welded by heat, the molecules (though aggregated or = combined)=20 do not settle down into their final positions of proximity until the bar = cools,=20 the bar being observed to contract on cooling. In this instance also the = cooling=20 of the bar is somewhat retarded by the approach of the molecules in the = act of=20 cooling.
8. In the case of the ignition of a solid body, the same = considerations no=20 doubt apply as in the case of a gas. Thus, for example, the molecules of = oxygen=20 are impinging against the surface of a piece of coal, but do not produce = ignition. To effect this a certain number of the molecules must be = impelled with=20 sufficient energy against the coal so as to carry them over the neutral = point=20 (i. e. beyond the initial repulsion). The application of a flame, which = consists=20 of matter in a state of violent agitation, suffices to effect this, and, = no=20 doubt by loosening some of the molecules of carbon (of the coal) and = giving them=20 translatory motion and mixing them with the air, facilitates the = process.
9. As a further illustration of the exact similarity of behaviour of=20 single molecules and groups of molecules (masses) as regards the=20 existence of the above-mentioned neutral point, we may take the case of = the=20 substance iodine. This substance gives off a visible vapour at normal=20 temperatures. The single molecules of iodine composing the vapour = rebound from=20 each other without uniting; and this can only be due to the existence of = the=20 above-mentioned neutral point, outside which there is a repulsion. If = the=20 colliding molecules were to approach within the neutral point, they = would unite=20 and form solid iodine. No doubt some of the molecules of the = vapour (as=20 their velocities are known to be very diverse) do pass beyond the = neutral point;=20 and thus molecules of vapour striking against the fragments of solid = iodine in=20 the bottle, will sometimes unite with the solid iodine and form part of = it,=20 while, on the other hand, other molecules of the solid which happen to = possess=20 excessive vibrating energy are thrown off, this being the known way in = which the=20 balance in evaporation is maintained. The masses of iodine have the same = neutral=20 point as the single molecules, since two masses of the substance when = pressed=20 together will not readily unite; i. e. the neutral point, where the = outer=20 repulsion terminates, must be passed first.[7]=20 [305]
10. Just as increase of vibrating energy (temperature) tends, by the = increase=20 of pressure thus produced in the intervening film of the medium, to = dissociate=20 molecules, so reduction of vibrating energy (attendant on reduction of=20 temperature) tends to facilitate the approach of molecules, on account = of the=20 reduction of the pressure or repulsive action of the intervening film. = Thus the=20 molecules of a vapour when their vibrating energy is reduced (by a fall = of=20 temperature) may by the simple momentum of their own encounters, carry=20 themselves over the neutral point, and thus effect the condensation of = the=20 vapour. Numerous other cases might be cited illustrative of the = application of=20 the above principles, as, indeed, the molecular effects are very similar = in=20 their fundamental aspects. The molecular phenomena, however diverse, may = be all=20 correlated in one fundamental respect, viz. as consisting in phenomena = of=20 approach and recession. The fundamental conditions to be=20 explained, therefore, are the conditions capable of producing the=20 approach and recession of molecules. Whatever may be said = of the=20 above deductions, it is at least so far certain that the conditions=20 investigated, and based upon experimental facts, are competent to = produce these=20 fundamental movements of approach and recession in the case of = molecules, and to=20 do so in the simplest manner, the constitution of media according = to the=20 kinetic theory being admittedly the simplest conceivable. To look = therefore to other conditions than the simplest would be to imply that = the same=20 results are brought about by a superfluity of mechanism. This = superfluity is=20 known not to be the characteristic of nature; and all the = teaching of=20 mechanism points to the fact that superfluity or unnecessary = complication=20 entirely prevents the attainment of precision and certainty in the = mechanical=20 effects. The great precision and unfailing certainty of the molecular = effects=20 would therefore render it necessary to infer that the regulating=20 mechanism was simple, or that there was no unnecessary superfluity.
11. The fundamental conclusion above drawn regarding the mechanism = concerned=20 in the approach of molecules is grounded upon the only = explanation of the=20 mechanism of gravity that has withstood criticism and received support = by=20 competent judges, viz. the kinetic theory of gravity, of which Le Sage's = ingenious idea forms the fundamental basis, and is at once the simplest=20 explanation of gravity conceivable. The [306] application of this theory = to=20 molecules in close contact ("cohesion" &c.), is necessary and = inevitable, and it serves to correlate the molecular effects generally = under=20 one cause. The explanation of the fundamental condition capable = of=20 producing the recession of molecules, as above given, rests upon=20 experimental facts recently established, and upon a basis for the = constitution=20 of the aether which is the simplest conceivable.
12. We now propose to show some independent reasons in support = of this=20 constitution for the aether, in addition to the argument afforded by the = numerous molecular effects which this constitution, in principle, serves = to=20 explain. First, if the subject be reflected on, it will be apparent = that, in=20 principle, u. movement of the component particles of the medium in = straight=20 lines is the only possible constitution for the ultimate = medium in=20 space. For a particle of matter cannot move in a curved line unless it = have a=20 medium about it to control its motion. Thus a planet can move in a curve = because=20 it has a medium about it (the gravific medium) to cause it to move in a = curve.=20 It is a known principle that a particle of matter cannot of itself = change the=20 direction of its motion. The particles of the ultimate medium in = space must=20 therefore move in straight lines. This deduction is surely of = great=20 importance in the inquiry as to the constitution of the physical media = in space.=20 Also in addition to this, the observed facts of gravity prove that the = particles=20 of the gravific medium move in straight lines, since no other = motion than=20 this can harmonize with the observed effects of gravity. It would = therefore=20 surely be a strange thing if the particles of the aether, as a second = medium=20 immersed in the gravific medium, did not move in straight lines. To = suppose this=20 would be very like supposing that when the particles of a second gas are = immersed among those of another, the particles of the first gas acted = upon those=20 of the second to make them move otherwise than in straight lines, which = is known=20 to be impossible. Moreover the fact of the kinetic theory representing = the=20 simplest conceivable constitution for a medium would by itself be = a=20 strong argument for this constitution in the case of the aether. The = very fact=20 of the great precision and delicacy of the operations performed by the = author as=20 the mechanism for the transmission of the varied phenomena of colour = &c.=20 would point to a simple constitution; just as the complex effects of = sound with=20 all its intricate and varied gradations of tone are known to be = transmitted by a=20 medium (the air) of the simplest conceivable constitution, viz. = that=20 represented by the beautiful kinetic theory of gases.[8]=20 The more intricate the functions of a mechanism, [307] the more is = simplicity=20 indispensable, and superfluity incompatible with precision and certainty = in the=20 results. To assume a constitution for the aether that could not be = realized or=20 clearly explained would surely be futile, since the explanation or clear = conception forms the logical support of any theory, without which the = theory=20 resembles a mere dogmatic statement incapable of being sustained by = reason.
13. There is one other point which we would notice in connexion with = this=20 subject. The idea would appear to be to a certain extent prevalent that = the=20 aether must have a constitution essentially different from the air, = because the=20 vibrations producing light are transverse, while those producing sound = are=20 longitudinal. It seems to be sometimes inferred from this that the = vibrations of=20 the Bather are only transverse, and those of the air only=20 longitudinal. There would be no warrant for this conclusion; and we = think that=20 it has done harm and greatly hindered any rational idea from being = formed of the=20 nature of the aether. According to the kinetic theory, which is known to = represent the constitution of the air, the vibrations of the particles = of air=20 disturbed by a vibrating body and propagated in the form of waves, are = not=20 only longitudinal; for since according to the kinetic theory the=20 particles of air in their normal state are moving equally in all=20 directions, it follows that these particles are accelerated and retarded = both in=20 transverse and in longitudinal directions at the passage of waves. It is = true=20 that the transverse component of the motion probably may not = affect the=20 ear, on account of its special structure. It would be wrong, however, to = infer=20 from this that the transverse component of the motion did not = exist. So=20 in the case of the aether, it would be unwarranted to infer that the=20 longitudinal component of the motion did not exist, because this = component was=20 incapable of affecting the eye. The eye and the ear may be very = differently=20 constituted; and a motion that affects the one might not affect the = other. Sir=20 John Herschel says regarding this point in his essay "On Light" (' = Popular=20 Lectures on Scientific Subjects,' page 358): =E2=80=94 "According to any = conception we=20 can form of an elastic medium, its particles must be conceived free to = move (=20 within certain limits greater or less according to the coercive forces = which=20 restrain them) in every direction." He then goes on to explain how the = efficacy=20 of the transverse component of the movement in the case of light, and = the=20 longitudinal component of the movement in the case of sound, may be = accounted=20 for by the diverse structure of the eye and ear. Any inference which is = not=20 valid, invariably does some harm; and this idea of a forward movement = being=20 propagated in a medium by only transverse vibrations, being = almost=20 inconceivable, has [308] naturally led to some incongruous ideas = regarding the=20 structure of the aether, in the effort to explain it. Thus some have = supposed=20 the aether to resemble a solid, which is in direct opposition to the = teaching of=20 the senses; for we move about so freely in this "solid" as to be = unconscious of=20 its existence. Another supposition has been that "lines of tension," = behaving=20 somewhat in analogy to stretched chords, exist in the aether. Such a = mechanism=20 would be, to say the least, somewhat deranged by the passage of a planet = through=20 the aether. Indeed it is sufficiently evident that these are the = hopeless=20 attempts made to surmount an impossible condition, or a difficulty for = whose=20 existence there is really no warrant. If the aether be not a solid, or a = liquid=20 (for liquids oppose enormous resistances to the passage of bodies = through them=20 at high speeds), then what other resource have we than to conclude that = it is a=20 gas?
14. A gaseous constitution of the aether according to the kinetic = theory=20 would perfectly satisfy the two fundamental conditions of a medium = highly=20 elastic in all directions, and opposing no appreciable resistance to the = free=20 movement of bodies (the planets &c.) through its substance. For it = is a=20 known fact that the resistance opposed by a medium constituted according = to the=20 kinetic theory to the passage of bodies through it diminishes as = the=20 normal velocity of the particles of the medium increases. The high = normal=20 velocity of the particles of the aether, proved by the velocity of = light,=20 therefore necessarily renders the resistance inappreciable, and the = medium=20 itself impalpable and undetected by the senses.
15. A difficulty has been raised in the way of the aether being = constituted=20 as a gas on the following grounds, which, being only anxious for truth, = we are=20 bound to consider.[9]=20 It has been argued that if the aether be constituted as a gas, the = specific heat=20 of unit of volume of the aether would be the same as that of any = ordinary gas at=20 the same pressure, and that therefore it would appear that the presence = of the=20 aether could not fail to be detected in the experiments on the specific = heat of=20 ordinary gases. We have to offer the following as a means of meeting = this=20 difficulty. It will be admitted that the detection of the aether in the=20 experiments on specific heat will depend, not on the specific capacity = for heat=20 possessed bv the aether, but on the rate at which the heat passes from = the gas=20 experimented on to the aether. The molecules of the gas are moving = through the=20 aether with their normal translatory motion, this motion of the = molecules=20 representing the "heat" of the gas. It will be evident that the rate at = which=20 the [309] motion ("heat") of the molecules of the gas passes to the = aether will=20 depend on the resistance the aether offers to the passage of = these=20 molecules through it. But we have shown that this resistance may (on = account of=20 the high normal velocity of the aether particles) be inappreciable. = Hence the=20 rate of passage of the heat from the gas to the tether will be = inappreciable.=20 This, we submit, removes the difficulty in question. It is clear that, = if the=20 aether opposes no appreciable resistance to the passage of a planet = through it=20 (moving at several miles per second), it cannot be affected by the = passage of a=20 molecule of a gas through it, which in its relatively slow rate of = translatory=20 motion may be considered at rest compared with the aether = particles. The=20 high normal velocity of the aether particles is only appropriate to = their=20 minute mass.
16. It must be apparent to any reflecting observer, that in physical = science=20 we have a vast array of facts accumulated through years of = experiment,=20 but a great paucity of causes; or the number of facts known is = quite out=20 of all proportion to the number of causes known, these latter being = replaced by=20 more or less vague and unsubstantial theories. As, therefore, we have no = paucity=20 of facts as a basis to reason upon, it surely cannot be too soon to make = an=20 effort to correct this anomalous state of things, and to replace the = above=20 unsubstantial theories by rational conceptions of the processes of = nature,=20 Clearness of conception is the test of truth, and constitutes its real = dignity;=20 and theories, however elaborated, if vague, have no real dignity.[10]=20 Since there is nothing occult about the physical media in space, in so = far as=20 they differ in no way from ordinary matter excepting in the mere scale = or=20 dimensions of their parts, and since it is obviously just as easy to = reason of=20 matter of one dimension as of another, any hesitation in entering upon = this=20 course of study would be wholly uncalled for; indeed, surely there is = reason for=20 a rational interest in realizing the admirable adaptation of these media = in a=20 mechanical point of view for their special functions; and the question = as to the=20 utilization of the stores of motion enclosed by them to the best = advantage may=20 present a problem of the highest practical interest and importance.[11]=20 It should be observed that these stores of [310] motion simply consist = in small=20 particles of matter in a state of rapid motion; or there is nothing = occult about=20 the subject at all, as indeed obviously principles of reasoning are = independent=20 of size. The minute size (and consequent invisibility) of the particles = is=20 necessary to the efficiency of the media as powerful motive = agents, since=20 minuteness of size is necessary to render a high velocity possible for = the=20 particles, without producing disturbing effects among the matter = immersed in=20 these media. There is one very noteworthy point that cannot be too = distinctly=20 kept in view in connexion with this subject. It is the fact that the = high=20 intensity of the stores of motion possessed by these media, and which = renders=20 them so important, serves to conceal their existence from the senses. = Thus the=20 higher the intensity of the store of motion enclosed by these media, and = consequently the greater their capacity for practical utility, the more = likely=20 (if the mere evidence of the senses were relied on) is their existence = to be=20 forgotten. For it may be proved beforehand, by the kinetic theory of = gases, that=20 the greater the velocity of the component particles of a medium, and=20 consequently the greater the value of the store of energy = enclosed (which=20 may even reach an explosive intensity), the more does the presence of = the medium=20 elude detection, because the resistance opposed by the medium to the = passage of=20 bodies through it diminishes as the velocity of the particles = increases.=20 The less indication the mere senses (unaided by reason) afford of the = existence=20 of such media, the higher, therefore, should we be warranted in = inferring their=20 importance to be. Even independently of all question of the existence of = these=20 media, it may be proved beforehand that, if media did = exist and=20 enclose stores of motion to an enormous intensity, they would be=20 concealed. This is, no doubt, a remarkable fact, and contrary to=20 preconceived ideas, as it would doubtless appear on the first thought = that the=20 higher the intensity of a store of energy existing in space, the more = likely=20 would it be to make itself apparent to the senses, whereas precisely the = contrary is found to be the fact. This forms a notable instance of one = of those=20 cases where analysis completely reverses preconceived ideas. It is = possibly the=20 absence of appreciation of this fact that may in some way account for = the=20 failure of the most striking proof's of nature to carry their practical=20 teaching, as for example, the sudden setting free of concealed motion in = the=20 explosion of a mass of gunpowder. Here to the mere bodily senses, we = have=20 apparently an actual creation of motion. Something [311] more, = however,=20 than the evidence of the mere bodily senses may be required, to = appreciate the=20 truths of nature, as it is a notorious fact that the most important = truths=20 generally lie below the surface. It should be noted that these media = would not=20 be efficient as working agents unless they were concealed; for=20 concealment (as observed) is the necessary condition to the = enclosure of=20 a store of motion to a high intensity. Possibly the absence of = realization of=20 this fact, and perhaps that prejudice which besets every new path, may = in some=20 degree account for what must otherwise appear an extraordinary = indifference and=20 absence of inquiry in a subject of great mechanical interest and = involving=20 possibly issues of the highest importance and practical utility. When = this, like=20 every other illogical prejudice to change, comes to be broken down by = the light=20 of reason and reflection, there may be just ground for surprise at the = previous=20 delay, and at the shallow and unsubstantial character of the theories = which so=20 long supplanted rational conceptions of the processes of nature.
London, March 13, 1878.
This=20
work is in the public =
domain in=20
the United States because it was published before January =
1, 1923.=20
The author died in 1917, so this work is also in the public=20 domain in countries and areas where the copyright=20 term is the author's life plus 80 years or less. This = work may=20 also be in the public domain in countries and areas with = longer=20 native copyright terms that apply the rule of = the=20 shorter term to foreign = works. |