Matter.
II.
The activity displayed by matter in the production of natural phenomena is twofold, viz., attractive and repulsive; and the question has been raised whether these two kinds of activity can reside in one and the same subject, or, owing to their opposite nature, require separate subjects. With regard to molecules, it is quite certain, though some have thought otherwise, that in all ponderable bodies each molecule is in possession of both powers; but with regard to the primitive elements which enter into the constitution of a molecule, the question needs a special treatment, as no direct evidence is supplied by experimental science for an affirmative more than for a negative solution, and different views have been advanced which it is important to examine in the light of philosophical principles, that we may ascertain which of them has the best claim to adoption both in philosophy and in molecular mechanics.
Attractive and repulsive powers.
Since it is well known that all the phenomena of the material order, whether physical or chemical, ultimately depend on attractions and repulsions, we are compelled to admit the existence in nature of attractive and repulsive powers. Neither attractive powers alone nor repulsive powers alone would afford us a rational explanation of natural facts. If the primitive elements of matter were all repulsive, and nothing but repulsive, then neither the cohesion of material particles nor the gravitation of bodies would be possible; no solid and no liquid would exist; and all matter from the very beginning of its existence would have vanished in a state of extreme attenuation through the immensity of space. If, on the contrary, the primitive elements of matter were all attractive, and nothing [pg 722] but attractive, no expansive power would be found in nature; for the expansion of bodies evidently depends on a repulsion prevailing between their molecules. All solid and liquid bodies likewise proclaim the existence of repulsive powers by the resistance they oppose to compression. This resistance shows that their molecules are endowed with powers whose exertion impedes their mutual approach as soon as they have reached a certain limit of distance. It is plain that the power which impedes the approach under pressure must be a repulsive one. Thus both attractive and repulsive powers exist in nature.
But do they exist together in the same primitive element of matter? Boscovich answers in the affirmative; but his answer is not supported by any cogent reason. Having found no other means of accounting for the impenetrability of bodies, he assumed that every element of matter is so constituted as to be attractive at all great distances, according to the law of universal attraction, but that each element, at molecular distances, becomes repulsive in order to resist pressure, and again attractive in order to exercise chemical affinity, and then repulsive again, these alternations going on a certain number of times, till at last repulsivity alone prevails, which indefinitely increases when the distance of two elements indefinitely diminishes.
Yet this theory is by no means needed to account either for the impenetrability of bodies or for any other phenomenon; as what Boscovich ascribes to elements may be, and is in fact, a property of molecules—that is, of a compound system of elements. On the other hand, the theory is unnaturally complex, and the alternation of the attractive and repulsive exertions looks as unscientific as the epicycles of the old astronomers and other hypotheses once admitted as plausible, and now superseded by a fuller knowledge of natural laws. To a mind which examines the question of attractive and repulsive powers in the light of philosophy, it must be evident that each primitive element of matter cannot possess them both. If an element is attractive at any distance, it must be attractive at all distances, whether enormously great or indefinitely small; likewise, if an element is repulsive at any distance, it must be repulsive at all distances.
This proposition can be proved as follows: Opposite actions cannot originate from one and the same simple principle when such a principle has no control over itself, but acts by inherent necessity. But in each primitive element of matter there is but one simple principle of activity, which has no control over itself, as it acts by inherent necessity. And therefore no primitive element can be both attractive and repulsive, but is either attractive at all distances or at all distances repulsive.
In this syllogism the major is evident. An active principle which, like the human soul, can, by immanent operations, assume at pleasure different attitudes towards the term of its action, and which masters the conditions and controls the intensity of its exertions, may perhaps be considered competent to originate actions of opposite kinds.[159] But a being which is destitute [pg 723] of immanent operations, and acts by an inherent necessity of its nature, has no power to modify itself or to alter its intrinsic determination; and its action is so ruled by its intrinsic determination that there is no chance of its being either transmuted into its opposite, or even partially suspended. Now, in a primitive being the principle of activity is nothing else than the simple act which formally determines its nature; and it is plain that wherever there is one simple formal act, there can be only one formal determination to act. And consequently a simple principle of activity which has no immanent operations cannot be the source of two opposite kinds of actions. Bodies and their molecules, on account of their physical composition, contain as many distinct principles of activity as they contain physical components or elements; hence we can easily account for their capability of originating opposite actions by admitting that among those elements some are attractive and others repulsive. But in a primitive element it is impossible to admit of two opposite active principles; for a primitive element is a being entitatively one, having only one essential act, and consequently only one active principle and one intrinsic determination to act. It would therefore be absurd to expect from such an element actions of such an opposite nature as are attraction and repulsion. For evidently, to enable the element to display two opposite powers, two opposite determinations would be necessary. Hence, if the intrinsic determination enables the primitive element to attract, such an element will always attract, and never repel; and if, on the contrary, the intrinsic determination enables the primitive element to repel, such an element will always repel, and never attract. In other terms, the attractive and the repulsive power cannot coexist in the same primitive element.
This conclusion, which affords the only possible basis for the speculations of molecular mechanics, is one of those which mere scientists cannot reach through their empirical and inductive method; but its truth is not less certain for that; it is rather all the more certain, as it is not founded on accidental facts, but on the unchangeable nature of things and the transcendental relation of the principles involved in the constitution of real beings.
Our proposition may be confirmed by reflecting that the change of attraction into repulsion, according to Boscovich, would depend on the diminution of the distance between the agent and the patient. Now, this view is inadmissible. For a change of distance, though necessarily accompanied by a change in the intensity of the action, cannot exercise any influence on the specific nature of the action. The intensity of the action is an accidental thing, and can change without in the [pg 724] least interfering with the nature of the agent; and for this reason it can, and must, depend on distance as a condition implied in the exercise of the active power. But the nature of the action always follows the nature of the substance from which it proceeds. Now, a change of distance does not change the nature of the substance. And accordingly the nature of the action must remain the same, even though the distance be indefinitely diminished.
Moreover, if there were any distance at which the action of a primitive element could change from attractive to repulsive, evidently the element, at such a distance, would be unable to exercise either attraction or repulsion, as Boscovich concedes; and therefore, at such a distance, the material element would have no activity. We may, then, ask: Whence does the attractive power emanate which is to have uncontrolled sway at all greater distances? Does it emanate from any point of space outside the element? Then it would not be the active power of the element, as it would have nothing to do with it. On the other hand, it is obvious that if it emanates from the element, it does not end at a distance from it. For, since the active power is really identical with the formal principle from which the primitive element receives its nature, it is as necessary for the elementary power to reach the very centre of the element as it is for the form to be intrinsically terminated to its matter. Whence it follows that the elementary power of attraction, which prevails at all great distances, must emanate from the very centre of the element. But if so, why shall it not prevail up to that very centre? Is it, forsooth, because in the neighborhood of the centre an opposite principle prevails? Were this the case, the same primitive being would have two formal acts, and it would be two beings and two natures; which is an evident contradiction. As long, therefore, as we adhere to the fundamental doctrine that a primitive being cannot have more than one simple principle of activity, we must admit that a primitive element, if attractive at any distance, is attractive at all molecular distances, and, if repulsive at molecular distances, is repulsive at all distances.
Against the existence of attractive and repulsive powers in distinct primitive elements some objections now and then have been made. It has been said, first, that what we call repulsion is only a result of certain vortical movements of the ether all around the molecules of ponderable bodies. This objection is based on a false supposition. We have already shown that the arbitrary theory of the vortices fails altogether to explain the great phenomenon of universal attraction; and we may easily show that it fails as completely in regard to molecular repulsion. In fact, the centrifugal forces which are developed by vortical movements, and which in this theory are assumed as the cause of the phenomena of molecular resistances, are not active powers. They are components of the vortical movements, and nothing more; that is to say, they do not efficiently produce movements, but are the formal principles of movements already produced. To ascribe to them the molecular resistances and the impenetrability of bodies is, therefore, to admit the effect without the cause.
Secondly, some authors object that the resistance called into play by pressure is not a real action, and [pg 725] requires no efficient repulsive powers. They consider it, according to the vulgar prejudice, as a merely passive resistance; for they imagine that a body, when pressed or impinged on, resists the progress of the obtruding body by its own inert matter, which with its materiality obstructs the way onward. This old explanation is still popular with the great mass of the uninstructed, but is scientifically and philosophically worthless. For whatever causes a real change really acts; now, a body resisting the advance of another body causes a real change in the rate of its movement; therefore a body resisting the advance of another body really acts. Its resistance is therefore active, and not passive; that is, it consists in an exertion of repulsive power, and not in a material obstruction of the path.
Hence what physicists call “force of inertia” is not a passive resistance proceeding from the inertia of matter, but an active exertion of the molecular powers, and has been so called only because, all other things being equal, its intensity is proportional to the mass of the inert body.[160] Evidently, inertia itself cannot resist or check the advance of an impinging body. Nothing but a positive action can do it; for nothing but a positive action can communicate to the advancing body that impetus in the opposite direction which alone is competent to neutralize the impetus of the advance. Physicists know this very well, though many of them, owing to the difficulty of analyzing and expressing certain things with philosophical accuracy, do not always use, in this particular, a very correct language—a thing which, after all, must not surprise us, as one can be well read in physics without necessarily being a profound philosopher.
The third objection is aimed at our argument against Boscovich's theory, in which we have said that attraction and repulsion are actions of opposite kinds. Boscovich, on the contrary, maintains that attraction and repulsion differ only as the greater from the less, and therefore cannot be considered as actions of a different kind. He says: “Both actions are of the same kind; for the one, as compared with the other, is negative; and negative things do not differ in kind from positive ones. That the one, as compared with the other, is negative, is evident from this: that they differ only in direction. That the negative and the positive belong to the same kind is evident from the principle, More and less do not differ in kind. In fact, from the positive, by a continued subtraction or diminution, we obtain first some smaller positive quantities, then zero, and lastly, if we still go on in our subtraction, negative quantities.”[161]
This argument, notwithstanding its speciousness, is not difficult to upset. It is not true, in the first place, that attraction and repulsion differ only in direction; on the contrary, they differ in everything except in direction. Two points A and B being given, there is only one direction from A to B, whether A be attractive or repulsive. If A is attractive, its attraction is directed from A to B; and if A is repulsive, its repulsion is no less directed from A to B. This is quite evident, as the action must in all cases proceed from the agent to [pg 726] the patient. It is evident, therefore, that the two actions must have the same direction. The movements of B will indeed have opposite directions, according as B is attracted or repelled; but this does not show that the actions themselves have opposite directions; it shows, on the contrary, that those actions, though directed in the same manner from A to B, are of a different nature, and proceed from opposite principles. And this conclusion may be confirmed by remarking that the direction is always from a point to a point, or from matter to matter; and consequently it is not the active power or the action, but only the position of the material centres, that can determine any direction. Accordingly, so long as such a position is not inverted, it is impossible to conceive two opposite directions from A to B. It is therefore evidently false that attraction and repulsion differ in direction.
It is not true, in the second place, that attraction and repulsion differ only as the positive differs from the negative, or the greater from the less. In the mathematical expression of mechanical relations, if we consider a movement as positive, the movement which points to an opposite direction must, of course, be affected by the negative sign. The same we must do with regard to forces and actions; for we estimate the actions by the movements which they produce, and we express them only in terms of movement—that is, by their effects. But this does not mean that there is either any movement or any action absolutely negative; for a negative movement would be no movement, and a negative action no action. It is in a relative and conventional sense only that movements are considered as positive or negative; and, moreover, either of the two opposite movements can be assumed as positive or as negative, at will; which shows very clearly that the negative and the positive do not differ in this case as the greater differs from the less, as Boscovich assumes; for either of the two can, at pleasure, be taken as positive, whereas it would be absurd to pretend that either of the two can, at pleasure, be pronounced to be the greater. Thus, when a stone is thrown up vertically, and abandoned to itself, if its ascent is taken as positive, its descent will be considered as negative. Now, according to Boscovich's reasoning, we should infer that the ascent is greater than the descent, though they are evidently equal. And in the same manner, if the ascent is taken as negative (which nothing forbids), the descent must be taken as positive; whence, according to Boscovich, we ought to infer also that the descent is greater than the ascent. Any argument which leads to such glaring contradictions must be radically false. And therefore it is false that attraction and repulsion differ from one another as the greater from the less.
It might be urged, as a fourth objection, that if an attractive and a repulsive power differ in kind, then a repulsive element and an attractive element will be two kinds of material substance; which is inadmissible. For we cannot admit two kinds of primitive material beings essentially different, as the essence of matter must be the same in all the elements.
To this we answer that although there are two kinds of elements, there are not two kinds of matter. In other terms, an attractive element differs from a repulsive one as [pg 727] to the principle of action, but not as to the matter itself. In fact, the essence of a material being as such requires nothing more than a form giving existence to matter; hence, wherever there is a form giving existence to matter, there also is the essence of matter. Now, matter is as much and as completely actuated by a form or act which is a principle of attraction as by a form or act which is a principle of repulsion. For the actuation of the matter by its form is not efficient, but formal; and its result is not to approach by attraction or to recede by repulsion, but to be simply and absolutely; so that neither attractivity nor repulsivity has any bearing on the essential constitution of a material element as such—that is, inasmuch as it is material. Accordingly, two elements of opposite natures differ in kind as agents, but not as material beings; and thus the essence of matter as such remains one and the same in all the elements. Matter, as we have already shown, is the centre of a sphere of activity; and it is evident that, by this activity of an attractive or of a repulsive nature, the centre remains a centre, and the sphere a sphere, without the least alteration. Gold and ivory differ in kind; but a sphere of ivory and a sphere of gold do not differ in kind as spheres, and their centres do not differ in kind as centres. In a like manner the sphere of activity of an attractive element does not differ from the sphere of activity of a repulsive element, nor the centre of the one from the centre of the other. And therefore two elements, however different in their nature as agents, do not cease to be of the same kind as material. Their form is different, but informs equally, and their matter is exactly the same.
We have stated that Boscovich was led to admit two opposite powers in the same element, because he thought this to be the only means of accounting for the impenetrability of bodies. We observe that, although the impenetrability of bodies peremptorily proves the existence of repulsive powers, it by no means proves that the repulsive power coexists with the attractive in the same primitive element. Hence Boscovich's inference is not legitimate. Molecules, as we have already remarked, may possess both powers, as their composition involves a great number of elements, which can be of different natures. And this suffices to explain the impenetrability of bodies, and all other properties dependent on molecular actions, without need of arbitrary hypotheses.
A last objection against the doctrine we have established might be drawn from the difficulty of reconciling the existence of repulsive elements with universal attraction; for if we admit that repulsion can be exercised at astronomical distances, it will be difficult to see how the celestial bodies can attract one another in the direct ratio of their masses, as the law of attraction requires.
The answer is obvious. If all matter were repulsive, universal repulsion would be the consequence. But if bodies are made up partly of attractive and partly of repulsive elements, then will either universal repulsion or universal attraction prevail, according as the number and power of the repulsive elements is greater or smaller than that of the attractive ones. Hence, from the fact that in the solar system and elsewhere attraction prevails, it follows, indeed, that the attractive powers are the stronger, but it [pg 728] does not follow that they are the whole stuff of which bodies are compounded.
As to the law of attraction in the direct ratio of the masses, a distinction is to be made. The law is certainly true if by masses we mean the masses acted on; not so, however, if for the masses acted on we substitute the masses of the attracting bodies. The fact of universal attraction shows that two planets, all other things being equal, must be attracted by the sun in the direct ratio of their masses. This is an established truth. But to say that, all other things being equal, the sun and the earth would attract the moon in the direct ratio of their absolute masses, is to assume what no fact whatever gives us the right to assert. Physicists very commonly admit this second assumption, and consider it a part of the law of attraction; but they would be not a little embarrassed were they required to undertake its demonstration. They take for granted that all the particles of matter are equally and uniformly attractive. Now, this assumption has never been established by facts; it simply arises from an unlawful generalization—that is, from the extension of the law of kinetic forces to dynamical actions. The momenta of two bodies animated by equal velocities are proportional to the masses of the same bodies; but nothing justifies the inference that therefore the attractive powers must be proportional to the masses. Indeed, it is scarcely possible to believe that equal masses of lead, iron, and zinc possess equal powers. Their properties are, in fact, so different that we cannot assume their constitution to be the result of an assemblage of equal powers. Hence we maintain that, unless two bodies have the same molecular constitution, their attractions cannot be proportional to their masses.[162]
Universal attraction being also proportional to the inverse squares of the distances, as we are going to show, we may add that the existence of repulsive elements in the sun and in the planets by no means interferes with this law. In fact, the total action of one celestial body on another, on account of the great distance at which the law of universal attraction is applied, equals the algebraic sum of all the actions by which one body makes an impression upon the other. Hence, if all the elements of which the body consists, whether they be attractive or repulsive, act proportionally to the inverse square of the distance, it is evident that the resultant of all such actions will also be proportional to the inverse square of the distance, whenever the form of the body is spherical, or nearly so, as is the case with the celestial bodies. And thus it is plain that no valid objection can be drawn from universal attraction against the existence of repulsive elements.
Law of elementary actions.
We have now to establish the general law of elementary attraction and repulsion. We hold that the actions of every primitive element are always inversely proportional to the squares of the distances, no matter whether such distances be great or small, astronomical or molecular.
This proposition can be briefly proved in the following manner: Astronomy teaches us that the Newtonian law, according to which the actions are inversely proportional to the squares of the distances, is true for all the celestial bodies. Now, the total action of one celestial body upon another is a resultant of elementary actions, and arises from the algebraic sum of them all. Hence it follows that every element of matter, when acting from certain distances, obeys the Newtonian law; for it is evident, from the theory of the composition of forces, that the sum of the elementary actions cannot follow the Newtonian law unless these actions themselves follow it. But if the law is true in the case of astronomical distances, it must be true also in the case of microscopical and molecular distances. For as a primitive element cannot have two laws of action, so neither can it follow at molecular distances any other law than that which it follows at all other distances.
That a primitive element cannot have two different laws of action will be manifest by considering that the law which an element obeys in its actions results from the intrinsic determination of its nature—that is, from its formal constitution—inasmuch as the principle of action is, in every primitive substance, the formal principle of its very being: Principium essendi est principium operandi. Now, a primitive element has but one formal principle of being; for it is entitatively one, and therefore it has but one formal determination to act, which, as resulting from its essential constitution, is unchangeable and inviolable. But it is evident that from one formal determination to act only one law of action can possibly result. Two laws would be two formal results, and would require two formal principles giving two different determinations. Accordingly, since each primitive element has but one formal principle, it cannot have two laws of action. And therefore the Newtonian law, which primitive elements follow at astronomical distances, must prevail also at all other distances.
Let the reader observe that this conclusion regards the action of primitive elements, not the action of molecules. That molecular actions at molecular distances are not inversely proportional to the square of the distance is a known fact. Molecular cohesion, for instance, is immensely greater than it could possibly be by the Newtonian law; so also molecular repulsion. This is what prevented physicists from recognizing the applicability of the Newtonian law at molecular distances. As long as the primitive elements were confounded, under the name of atoms, with the molecules of the so-called primitive bodies, hydrogen, oxygen, carbon, etc., it was impossible to recognize in the molecular actions any trace of the Newtonian law; hence came the division of attraction into universal and molecular, the first following a known law, the second following some other law or laws which physicists could never discover. Their embarrassment was a necessary consequence of an incomplete analysis of the material [pg 730] compound. The molecule of a given substance, though often called an atom, is a system of primitive elements; and elements acting according to the Newtonian law can give rise to molecular systems which, at very small distances, will act according to any other law that may be indicated by molecular phenomena. This other law depends entirely on the number, kind, strength, and geometrical arrangement of the primitive elements which enter into the constitution of the molecule; and since molecules of different primitive substances are very differently constituted, every kind of molecule must have its own peculiar law of acting at molecular distances—a fact on which the scientific explanation of the different physical and chemical properties of different substances entirely depends. Hence it is clear that all the attempts at finding a general law of molecular attraction were, from the very nature of the case, destined to fail. The only general law of action which all matter obeys is the Newtonian law; and what was once considered to form an exception to it is now acknowledged to be the result of its application to a complex system of attractive and repulsive elements.
From the fact that the actions of all elements are proportional to the inverse squares of the distances, it follows that the sphere of activity of material elements extends beyond any assignable limit. The intensity of the action cannot, in fact, become = 0 unless the distance becomes infinite. The objections to which this corollary of the Newtonian law may give rise will be answered in our next article, where all the difficulties concerning the actio in distans will be solved.
Mode of action.
A last question remains here to be examined respecting the action of primitive material elements—viz., whether such an action needs a medium through which it may be transmitted and communicated to distant bodies, or whether, on the contrary, it is exerted upon them directly without dependence on any material medium.
In answering this question we must be careful not to confound action with movement. Movement, though not properly transmitted, is propagated, as we shall explain; and this cannot take place where there is no movable matter. Those who are wont to identify movement with force, and force with action, as is unfortunately the fashion even in scientific treatises, will no doubt imagine that actions must be transmitted or propagated through a material medium, just as sound through air, or as light through luminiferous ether. But action is not movement; and therefore the question how elementary actions—that is, how attractions or repulsions—reach distant bodies has to be resolved on its own merit, as one altogether distinct from the question about the propagation of movement. This premised, we are going to show that the elementary actions are independent of all material medium of communication.
In the first place, there is no reason why we should assume that the elementary action (attraction or repulsion) depends on a medium of communication, except inasmuch as we may apprehend that the action itself, or the active power whence it proceeds, is in need of being transmitted to some matter located at a certain distance. But neither the elementary power nor the elementary action can be [pg 731] transmitted to the distant matter. And therefore neither the power nor the action can be dependent on a medium of communication.
In this syllogism the major is evident; and the minor can be proved in two manners: First, because the power and the action are, of their own nature, intransmissible. Secondly, because, prescinding from their intransmissibility, no medium can be assigned which would be capable of transmitting them. And as to the first, we know that nothing can be transmitted to a distant place except by local movement; but neither the active power nor the elementary action is capable of receiving local movement; for there is no other subject capable of local movement than matter alone, on account of its passive potentiality. Hence neither power nor action can be transmitted. And in the second place, even were they transmissible, what medium could be found for their transmission? If any such medium could be found, it would consist of some matter like ether or air, this being the view of those who admit the necessity of such a medium. On the other hand, a material substance is not a suitable medium for transmitting action or power. For whenever an active power is exerted upon matter, the result of the exertion is nothing but a determination to a change of place; as it is well known that matter cannot receive any other determination. And therefore it is not the power that is received in the matter acted on, but only the act produced by its exertion, which act is otherwise called a momentum either statical or dynamical. Strictly speaking, not even the action itself is received in the matter, although we are wont to tolerate such an expression; for the action properly so called is the production of an act, and the matter receives, indeed, the act produced, but not its production. And thus the action, properly speaking, is terminated to the matter, and not received in it. Hence we see that neither the power of the agent nor its exertion is received in the matter acted on; it is merely the produced accidental act, or, in other terms, the momentum, that is received. But evidently matter cannot transmit what it does not receive. And therefore matter cannot be a medium for transmitting either power or action. Whether it can transmit movement we shall examine at the end of the present question.
This argument would suffice to show that elementary actions are quite independent of a material medium. Yet as the prejudice against which we are fighting is ancient, popular, and deeply rooted, we think it will not be superfluous to confirm our proof by a few other considerations.
Those who maintain the transmission of forces admit a material medium, in which, by successive contact of particles with particles, the transmission of the force to a distant body is supposed to be carried on. By the word “force” they understand action as well as movement. Now, let us ask them whether the particles of their material medium come into mathematical contact or not. If they do not come into mathematical contact, then the action is not transmitted by the medium from one particle to another, for there will be a vacuum between them; and vacuum is not a material medium. If, on the contrary, the particles come into mathematical contact with their own matter, then, as we have already shown in our past article, [pg 732] they cannot by such a contact communicate any movement to each other; and since the transmission in question should be carried on by successive communications of movement, it is plain that no such transmission will be possible. And accordingly the theory of the transmission of actions through a medium must be rejected.
Moreover, elementary actions are either attractive or repulsive, and neither of them can be conceived without intensity and direction. Now, no direction is possible unless there be two points distinctly ubicated in space. And therefore the action, no matter whether attractive or repulsive, cannot reach any material point which is not distant from the matter of the agent. But if so, the action is independent of a medium of communication; for the material medium, if it were needed, should lie between the agent and the patient in such a manner as to link them together, and fill by its material continuity the gap by which they are separated; and if this were the case, the medium could not be set in motion, as its contact with the agent would exclude distance, and consequently the possibility of any direction from the agent to the medium itself.
Some will say that this argument proves nothing, as the direction of the action can be sufficiently accounted for by the direction of the impulse. But this conclusion is evidently wrong. For what impulse can they imagine to proceed from the sun to the moon? Uncultivated minds are easily deluded by unlawful generalizations. They apply to all actions what they imagine to agree with some special phenomenon; and because they see that in the case of impact there is an impulse in a certain direction, they hastily conclude that the direction of every action depends on the direction of some impulse. We may remark that, even in the case of impact, it is not safe to conclude that the direction of the movement will follow the direction of the impulse, unless the impulse be central, and the body impinged upon homogeneous. But leaving aside the theory of impact, which has nothing to do with the present question, what impulse can explain the continuous resistance of a body to statical forces? What impulse can account for the expansive tendency of gases, and for their continuous pressure against the recipients in which they are contained? What impulse, above all, can account for universal attraction?
We have mentioned this objection, not because it needed any scientific or philosophical discussion, but simply because it is one of those notions to which the prejudices of our infancy give easy admittance into our minds when we allow ourselves to be guided, as is often the case, by our senses and imagination, in matters pertaining in great part to the intellectual order. Our mistakes in the appreciation of the character and conditions of natural facts most ordinarily originate in the unwarranted assumption that, since the facts are sensible, our knowledge of them must wholly depend on our senses; whilst the truth is that our senses perceive the movements, but not the actions which cause them, and therefore do not see the entirety of the natural facts, but that portion only which is most superficial. “A fundamental fact, like an elementary principle, never fails us,” says M. Faraday, speaking of natural philosophy; “its evidence is always true; but, on the other hand, we frequently have to ask, What is the [pg 733] fact? often fail in distinguishing it—often fail in the very statement of it—and mostly overpass or come short of its true recognition. If we are subject to mistake in the interpretation of our mere sense impressions, we are much more liable to error when we proceed to deduce from these impressions (as supplied to us by our ordinary experience) the relation of cause and effect; and the accuracy of our judgment, consequently, is more endangered.”[163]
And now, let no one imagine that we have any intention of denying the existence of a material medium between the celestial bodies. We only deny that there is a medium for transmitting actions. Again, we do not deny that when the earth, for instance, acts upon the moon, the elements of matter lying between the earth and the moon exert their activity on one another. But we maintain that their actions are their own, and proceed from their own intrinsic and permanent power, and not from any extrinsic agent, and that such actions are not travelling from element to element till they reach the moon. Neither do we deny that the elements located between the earth and the moon are also acted on, for it is clear that gravity must tend to alter their position in space; but we hold that the whole possible effect of gravity on all such elements is movement, and that movement is a mere change of place, and not a transmission of the action by which it is produced. How the movements themselves are communicated from element to element we shall explain presently.
Meanwhile, from the fact that the elementary actions are independent of all material medium of communication, we infer that bodies, in attracting and in repelling, act with equal promptitude, and without loss of time, whether the distance of the body acted on be great or small. Time, in fact, follows movement; for without movement there is no succession. Now, the action of a body does not reach the distant body through movement—that is, through successive transmission; on the contrary, each element is, of its own nature, determined to act directly and immediately on every other element existing in the indefinite sphere of its activity. Hence a body will indeed act with a greater intensity at a less distance, but will not act sooner than at a greater distance. There have been scientists who surmised that the solar attraction may perhaps need time for reaching the earth and the planets, and therefore that the attraction may reach Mercury in a shorter time than Jupiter or Neptune. From what precedes it is manifest that the surmise is wholly without foundation. Light needs time for its propagation, because it consists in a kind of movement; but attraction, as we have just remarked, is not movement, and therefore is not dependent on time.
Propagation of movements.
We have shown that there is no material medium for the transmission of forces, if the word “forces” is taken to mean “actions”; but if the word is intended to express “movements,” then the material medium is quite indispensable. We read very frequently in scientific books that actions are transmitted; but as this is not true of the actions themselves, we must suppose that the phrase is intended to express only the fact of a progressive development of the effects resulting from those actions. In the same way, when we read that [pg 734] actions are conveyed through a material medium, we interpret this expression as meaning that a material medium is strictly required for the progressive development of the series of effects due to such actions. We will explain the fact by an example.
If, a mass of air being at rest, a string is stretched in order to elicit sound, the vibrations of the string will be communicated to the neighboring molecules of air by the action (not by the movement) of the string itself; these first molecules, being thrust out of their position of equilibrium, will, by their action (that is, by the exertion of a power residing in each of their component elements, not of a power coming from the string, nor by their movement, nor by transmitted action), put in movement a following set of molecules, and so on indefinitely; so that, in the whole series of molecular vibrations, each preceding molecule causes the motion of the following one, and causes it by the exertion of its own powers, not of any power transmitted. It is evident that the string cannot give activity to the molecules of air. These molecules, whether the string vibrates or not, have already their own activity and their own mutual action; only their actions balance each other as long as the mass of air is at rest. But when the string begins to vibrate, the equilibrium being broken near it, those molecules of air which first cease to be in equilibrium begin to act on the following molecules with a different intensity, according to the change of the molecular distance. Thus the movement by which the distance is altered is not the cause, but the condition, of the phenomenon.
What we say of air and sound applies to any other medium, as ether with its vibrations, whether luminous or calorific. The molecules of ether have their own powers, and exert them continually, whether there exists a flame determining a series of vibrations or not; but with the flame the first molecules of ether which are displaced from their position of equilibrium will acquire a new local relation with regard to the following, and their actions will be of a new intensity, sufficient to cause the displacement of the next set of molecules, and so on. The flame, then, causes the displacement of the first set of molecules; the first set displaced causes the displacement of the second; the second displaced causes the displacement of the third, etc.; each set producing its own effect by its own inherent powers, not by the exertion of any power communicated to them by the flame, and their displacement being not a cause, but only a condition, on which the intensity of the exertion depends.
Hence it appears that in phenomena of this description it is not the action, and much less the power, that is transmitted, but only the movement, or the formal perturbation of the equilibrium; and even the movement is not properly transmitted, but only propagated; because the movement of each following molecule is not the identical movement of each preceding one, but is a movement really produced in the very impact of the one on the other, as our reader must have easily gathered from our preceding discussion. And therefore one movement succeeds another indefinitely, the one being a condition for the existence of the other; which constitutes propagation, not properly transmission.
To Be Continued.
Antar And Zara; Or, “The Only True Lovers.” V.
An Eastern Romance Narrated In Songs.
By Aubrey De Vere.
Part V.
They Sang.
I.
Sudden, in golden arms he came:
I stood begirt with maiden bands:
Sudden he came, all bright like flame;
Upon my head he laid his hands.
“This day past victories I disown:
This day I seek the battle-field
A stranger chief, a knight unknown,
Without a blazon on my shield.”
“Not man, but He the worlds who made,
My hope shall frustrate or approve”—
I only bent my knee, and said,
“Victor or vanquished, thee I love.”
II.
They set me on a milk-white horse;
Our household tribe around me trod;
Like rivers down a rocky course,
On rushed the warriors vowed to God.
I rode, the victor's destined prize,
Last stake when hope was all but gone:
The flashes from a virgin's eyes
Like music swept the warriors on!
'Twas theirs their maid elect to guard,
The direful battle's gentle guest:
'Twas mine to watch, inspire, reward;
To honor all—to crown the best.
But who that stranger chief from far
That like some brave ship tempest-tossed
Bore on o'er all the waves of war;
Redeemed a battle all but lost?
I knew. The victor's crown I dropp'd
Upon thy brows, my future lord:
That night thou satt'st—O boon unhoped—
The first time by my father's board!
III.
The victory ours, the feasting o'er,
The nameless victor gazed around;
“Emir! I claim the prize of war,
Thy daughter's hand.” My father frowned.
“Uplift her in thine arms,” he said;
“Then scale yon hillside smooth and dry:
This done, my daughter thou shalt wed:
To halt—forget not—is to die.”
I stood: my beating heart cried out,
“Thou canst not fail!” That cry he heard:
He raised me 'mid the warriors' shout;
Forward he rushed without a word.
His breath came quick: his brows grew dark:
“My brother, lover, friend,” I cried:
He reeled: his eyes were stiff and stark:
I wept, “This day thou winn'st thy bride!”
He fell—but on the summit won,
Amid the vast and wide acclaim:
He lay, a dead man, in the sun:
I kissed his lips, and felt no shame.
Round him the warriors stood amazed;
His love—'twas that brought back his life:
Down on him long my father gazed,
Then spake, “My son, behold thy wife!”
IV.
On carpets heaped my mother sate:
I sate, I nestled on her knee;
We heard a murmur round the gate:
My mantle, purple as the sea,
I drew about my little feet,
And nearer sought my mother's breast:
He came; she spake, not slow to greet
With courteous words the victor-guest.
Slowly my veil my mother's hands
Lifted, to boast the battle's prize;—
“Prince! thou would'st give thy life and lands,
If I but raised it to her eyes!”
V.
I knew thee well when first we met;
I knew thee well when seldom seen;
When we had parted, plainlier yet
I read thy nature—nay, thy mien.
Thine earliest glance my tremors stayed;
Then softly, and by slow degrees,
With thee my confidence I made,
And, pleased, discovered I could please.
But now that we are drawn so near,
I lose thee in thine own fair light;
Vanish the outlines once so clear:—
I know thee more by faith than sight.
VI.
Upon my shoulder, lightly as a bird,
Her white hand lit: then back she fled, afraid;
Beside my seat once more she stood, nor stirred,
But loosed her hair, and round me dropped its shade.
Down to my feet it fell—a sudden night:
She spake, “Thy darkness and eclipse am I;
But thou my sunrise art, and all my light;
Still to weak things love grants the victory.”
More dulcet than the viol rang her laugh;
Low laughed her mother; laughed her nurse full loud:
“Not thee I fear,” she cried, indignant half,
And kissed, methought, the head o'er which she bowed.
VII.
My Lyre reproved my childish mirth:
My Lute, remembering sad, old years,
Complained, “Thy feet are yet on earth;
Thou caroll'st in the vale of tears.”
I hung my head: ashamed I moved;
I answered soft with whispering voice,
“O Love! 'tis thou that stand'st reproved;
The fault is thine, if I rejoice;
“Not less this covenant have I made:
I will not fold my hands in sleep
Till aid to those who cry for aid
I stretch—have wept with them that weep.”
VIII.
He sang, “I dreamed. Of thee, all night, one thought
Shone like a white flower on a darkling mere
Or like one star that flashes, rapture-fraught,
Through one blue gulf of heaven serene, and clear.”
She sang, “I dreamed not: happiest sleep is deep:
I woke as wakes the young bird in the woods;—
Thy spirit must have hung above my sleep,
A bower balm-breathing from a thousand buds.”
We strove in song; we sang, my love and I,
Where laughed the streams, and where the rock's broad breast
Echoed the untaught, ecstatic harmony:
We warred in happy songs; but hers was best.
IX.
Thou art not mine as I am thine:
As great, or greater, is thy love;
But loftier thoughts above thee shine,
And lordlier aims before thee move.
The hand now clasping mine—that hand
Let drop this hand to grasp the sword;
It hurled in ruin from our land
The impostor Prophet's sons abhorred.
Manhood fell on thee with my tears
At parting. With a woman's joy
I loved the warrior 'mid his peers—
'Twas girlish fancy loved the boy!
X.
Mother of him I loved and love,
My mother too, ere long, to be!
With loving words his choice approve,
And take thy daughter to thy knee:
So shall mine eyes, up-gazing still,
Thine eyes in filial reverence watch;
My hand be subject to thy will;
My heart from thine its greatness catch.
The young can learn, and I am young
And labor to be good and true—
Tell her, O thou that know'st! I long
To give her age its honors due.
XI.
He sang, “Upon the myrtle's silver stem
Thy name I carved. Henceforth that tree is mine!”
Low-laughing 'neath her vine-wrought anadem
She sang, “Thy name I graved upon the pine!
“The slenderer hand the stronger bark subdued—
Say, is it lordlier, bound and tamed to lead
The forest-monarch from his sunburnt wood,
Or snare some little bird that took no heed?”
We sang in valleys where the spring flowers sprang
To passionate life: the eagle o'er us sailed:
Down plunged the torrents, and the gray cliffs rang:
We clashed our songs in war; but hers prevailed.
XII.
Methought to thine my angel spake:—
Near us he seemed, and yet above—
“Two children these! their sport they take;
They teach each other how to love.”
Thine angel answered thus to mine:
“When Virtue, perfected by pain,
Has changed earth-love to love divine,
Then, stooping, we will lift these twain
“From this dull cave of mortal life
Low-roofed, and dimly lit with spars,
To realms with love's whole glories rife,
And over-vaulted by the stars,
“Where souls that love their God are one;
Where He who made them is their joy:
Play on—too young for love—play on!
Your sports are sport of girl and boy!”
XIII.
Two hands—they meet; they part—'tis better so;
Parted, they meet to shape one coronal:
Two feet—they meet; they part, now swift, now slow
They pace to music through one palace hall.
Two eyes—they move in concord: wanderers long,
At last they rest on one unmoving star:
Two mouths, in kisses met, dispart in song—
Sweet are our meetings; sweet our partings are.
XIV.
I come, I go; yet neither shall repine:
Sad is the parting; the return is sweet:
Once more the battle with a voice divine
Decrees our severance. Soon once more we meet.
We part not, save in seeming. We are one,
In spirit one; in spirit we rejoice;
Two voices are we, blent in unison,
Two echoes of one mountain-thrilling voice.
Nearer we are than words, than thought, can reach;
Nearer we shall be; nearest, met on high;
Nearest as not belonging each to each,
But both to Him—that Love Who cannot die.