17. MATTER HAS INERTIA.The resistance that a mass of matter opposes to a change in its position or rate and direction of movement, is called inertia. That it should actively oppose anything has been already pointed out as reason for denying that matter is inert, but inertia is the measure of the reaction of a body when it is acted upon by pressure from any source tending to disturb its condition of either rest or motion. It is the equivalent of mass, or the amount of matter as measured by gravity, and is a fixed quantity; for inertia is as inherent as any other quality, and belongs to the ultimate atoms and every combination of them. It implies the ability to absorb energy, for it requires as much energy to bring a moving body to a standstill as was required to give it its forward motion.Both rotary and vibratory movements are opposed by the same property. A grindstone, a tuning-fork, and an atom of hydrogen require, to move them in their appropriate ways, an amount of energy proportionate to their mass or inertia, which energy is again transformed through friction into heat and radiated away.One may say that inertia is the measure of the ability of a body to transfer or transform mechanical energy. The meteorite that falls uponthe earth to-day gives, on its impact, the same amount of energy it would have given if it had struck the earth ten thousand years ago. The inertia of the meteor has persisted, not as energy, but as a factor of energy. We commonly express the energy of a mass of matter bymv2/2, wheremstands for the mass andvfor its velocity. We might as well, if it were as convenient, substitute inertia for mass, and write the expressioniv2/2, for the mass, being measured by its inertia, is only the more common and less definitive word for the same thing. The energy of a mass of matter is, then, proportional to its inertia, because inertia is one of its factors. Energy has often been treated as if it were an objective thing, an entity and a unity; but such a conception is evidently wrong, for, as has been said before, it is a product of two factors, either of which may be changed in any degree if the other be changed inversely in the same degree. A cannon ball weighing 1000 pounds, and moving 100 feet per second, will have 156,000 foot-pounds of energy, but a musket ball weighing an ounce will have the same amount when its velocity is 12,600 feet per second. Nevertheless, another body acting upon either bullet or cannon ball, tending to move either in some newdirection, will be as efficient while those bodies are moving at any assignable rate as when they are quiescent, for the change in direction will depend upon the inertia of the bodies, and that is constant.The common theory of an inert body is one that is wholly passive, having no power of itself to move or do anything, except as some agency outside itself compels it to move in one way or another, and thus endows it with energy. Thus a stone or an iron nail are thought to be inert bodies in that sense, and it is true that either of them will remain still in one place for an indefinite time and move from it only when some external agency gives them impulse and direction. Still it is known that such bodies will roll down hill if they will not roll up, and each of them has itself as much to do with the down-hill movement as the earth has; that is, it attracts the earth as much as the earth attracts it. If one could magnify the structure of a body until the molecules became individually visible, every one of them would be seen to be in intense activity, changing its form and relative position an enormous number of times per second in undirected ways. No two such molecules move in the same way at the same time, and as all the molecules cohere together, their motions in different directions balance each other, so that the body as a whole does not change its position,not because there is no moving agency in itself, but because the individual movements are scattering, and not in a common direction. An army may remain in one place for a long time. To one at a distance it is quiescent, inert. To one in the camp there is abundant sign of activity, but the movements are individual movements, some in one direction and some in another, and often changing. The same army on the march has the same energy, the same rate of individual movement; but all have a common direction, it moves as a whole body into new territory. So with the molecules of matter. In large masses they appear to be inert, and to do nothing, and to be capable of doing nothing. That is only due to the fact that their energy is undirected, not that they can do nothing. The inference that if quiescent bodies do not act in particular ways they are inert, and cannot act in any kind of a way, is a wrong inference. An illustration may perhaps make this point plainer. A lump of coal will be still as long as anything if it be undisturbed. Indeed, it has thus lain in a coal-bed for millions of years probably, but if coal be placed where it can combine with oxygen, it forthwith does so, and during the process yields a large amount of energy in the shape of heat. One pound of coal in this way gives out 14,000 heat units, which is the equivalent of 11,000,000 foot-poundsof work, and if it could be all utilized would furnish a horse-power for five and a half hours. Can any inert body weighing a pound furnish a horse-power for half a day? And can a body give out what it has not got? Are gunpowder and nitro-glycerine inert? Are bread and butter and foods in general inert because they will not push and pull as a man or a horse may? All have energy, which is available in certain ways and not in others, and whatever possesses energy available in any way is not an ideally inert body. Lastly, how many inert bodies together will it take to make an active body? If the question be absurd, then all the phenomena witnessed in bodies, large or small, are due to the fact that the atoms are not inert, but are immensely energetic, and their inertia is the measure of their rates of exchanging energy.THE ETHER IS CONDITIONALLY POSSESSED OF INERTIA.A moving mass of matter is brought to rest by friction, because it imparts its motion at some rate to the body it is in contact with. Generally the energy is transformed into heat, but sometimes it appears as electrification. Friction is only possible because one or both of the bodies possess inertia. That a body may move in the ether for an indefinite time without losing its velocity has beenstated as a reason for believing the ether to be frictionless. If it be frictionless, then it is without inertia, else the energy of the earth and of a ray of light would be frittered away. A ray of light can only be transformed when it falls upon molecules which may be heated by it. As the ether cannot be heated and cannot transform translational energy, it is without inertia forsucha form of motion and its embodied energy.It is not thus with other forms of energy than the translational. Atomic and molecular vibrations are so related to the ether that they are transformed into waves, which are conducted away at a definite rate. This shows that such property of inertia as is possessed by the ether is selective and not like that of matter, which is equally “inertiative” under all conditions. Similarly with electric and magnetic phenomena, it is capable of transforming the energy which may reside as stress in the ether, and other bodies moving in the space so affected meet with frictional resistance, for they become heated if the motion be maintained. On the other hand, there is no evidence that the body which produced the electric or magnetic stress suffers any degree of friction on moving in precisely the same space. A bar magnet rotating on its longitudinal axis does not disturb its own field, but a pieceof iron revolving near the magnet will not only become heated, but will heat the stationary magnet. Much experimental work has been done to discover, if possible, the relation of a magnet to its ether field. As the latter is not disturbed by the rotation of the magnet, it has been concluded that the field does not rotate; but as every molecule in the magnet has its own field independent of all the rest, it is mechanically probable that each such field does vary in the rotation, but among the thousands of millions of such fields the average strength of the field does not vary within measurable limits. Another consideration is that the magnetic field itself, when moved in space, suffers no frictional resistance. There is no magnetic energy wasted through ether inertia. These phenomena show that whether the ether exhibits the quality called inertia depends upon the kind of motion it has.18. MATTER IS MAGNETIC.The ordinary phenomenon of magnetism is shown by bringing a piece of iron into the neighbourhood of a so-called magnet, where it is attracted by the latter, and if free to move will go to and cling to the magnet. A delicately suspended magnetic needle will be affected appreciably by a strong magnet at the distance of several hundredfeet. As the strength of such action varies inversely as the square of the distance from the magnet, it is evident there can be no absolute boundary to it. At a distance from an ordinary magnet it becomes too weak to be detected by our methods, not that there is a limit to it. It is customary to think of iron as being peculiarly endowed with magnetic quality, but all kinds of matter possess it in some degree. Wood, stone, paper, oats, sulphur, and all the rest, are attracted by a magnet, and will stick to it if the magnet be a strong one. Whether a piece of iron itself exhibits the property depends upon its temperature, for near 700 degrees it becomes as magnetically indifferent as a piece of copper at ordinary temperature. Oxygen, too, at 200 degrees below the zero of Centigrade adheres to a magnet like iron.In this as in so many other particulars, how a piece of matter behaves depends upon its temperature, not that the essential qualities are modified in any degree, but temperature interferes with atomic arrangement and aggregation, and so disguises their phenomena.As every kind of matter is thus affected by a magnet, the manifestations differing but in degree, it follows that all kinds of atoms—all the elements—are magnetic. An inherent property in them, as much so as gravitation or inertia; apparently aquality depending upon the structure of the atoms themselves, in the same sense as gravitation is thus dependent, as it is not a quality of the ether.An atom must, then, be thought of as having polarity, different qualities on the two sides, and possessing a magnetic field as extensive as space itself. The magnetic field is the stress or pressure in the ether produced by the magnetic body. This ether pressure produced by a magnet may be as great as a ton per square inch. It is this pressure that holds an armature to the magnet. As heat is a molecular condition of vibration, and radiant energy the result of it, so is magnetism a property of molecules, and the magnetic field the temporary condition in the ether, which depends upon the presence of a magnetic body. We no longer speak of the wave-motion in the ether which results from heat, as heat, but call it radiation, or ether waves, and for a like reason the magnetic field ought not to be called magnetism.THE ETHER IS NON-MAGNETIC.A magnetic field manifests itself in a way that implies that the ether structure, if it may be said to have any, is deformed—deformed in such a sense that another magnet in it tends to set itself in the plane of the stress; that is, the magnet is twisted into a new position to accommodate itself to the conditionof the medium about it. The new position is the result of the reaction of the ether upon the magnet and ether pressure acting at right angles to the body that produced the stress. Such an action is so anomalous as to suggest the propriety of modifying the so-called third law of motion, viz., action and reaction are equal and opposite, adding that sometimes action and reaction are at right angles.There is no condition or property exhibited by the ether itself which shows it to have any such characteristic as attraction, repulsion, or differences in stress, except where its condition is modified by the activities of matter in some way. The ether itself is not attracted or repelled by a magnet; that is, it is not a magnetic body in any such sense as matter in any of its forms is, and therefore cannot properly be called magnetic.It has been a mechanical puzzle to understand how the vibratory motions called heat could set up light waves in the ether seeing that there is an absence of friction in the latter. In the endeavour to conceive it, the origin of sound-waves has been in mind, where longitudinal air-waves are produced by the vibrations of a sounding body, and molecular impact is the antecedent of the waves. The analogy does not apply. The following exposition may be helpful in grasping the idea of such transformation and change of energy from matter to the ether.Consider a straight bar permanent magnet to be held in the hand. It has its north and south poles and its field, the latter extending in every direction to an indefinite distance. The field is to be considered as ether stress of such a sort as to tend to set other magnets in it in new positions. If at a distance of ten feet there were a delicately-poised magnet needle, every change in the position of the magnet held in the hand would bring about a change in the position of the needle. If the position of the hand magnet were completely reversed, so the south pole faced where the north pole faced before, the field would have been completely reversed, and the poised needle would have been pushed by the field into an opposite position. If the needle were a hundred feet away, the change would have been the same except in amount. The same might be said if the two were a mile apart, or the distance of the moon or any other distance, for there is no limit to an ether magnetic field. Suppose the hand magnet to have its direction completely reversed once in a second. The whole field, and the direction of the stress, would necessarily be reversed as often. But this kind of change in stress is known by experiment to travel with the speed of light, 186,000 miles a second; the disturbance due to the change of position of the magnet will therefore be felt in some degreethroughout space. In a second and a third of a second it will have reached the moon, and a magnet there will be in some measure affected by it. If there were an observer there with a delicate-enough magnet, he could be witness to its changes once a second for the same reason one in the room could. The only difference would be one of amount of swing. It is therefore theoretically possible to signal to the moon with a swinging magnet. Suppose again that the magnet should be swung twice a second, there would be formed two waves, each one half as long as the first. If it should swing ten times a second, then the waves would be one-tenth of 186,000 miles long. If in some mechanical way it could be rotated 186,000 times a second, the wave would be but one mile long. Artificial ways have been invented for changing this magnet field as many as 100 million times a second, and the corresponding wave is less than a foot long. The shape of a magnet does not necessarily make it weaker or stronger as a magnet, but if the poles are near together the magnetic field is denser between them than when they are separated. The ether stress is differently distributed for every change in the relative positions of the poles.A commonU-magnet, if struck, will vibrate like a tuning-fork, and gives out a definite pitch. Itspoles swing towards and away from each other at uniform rates, and the pitch of the magnet will depend upon its size, thickness, and the material it is made of.Let ten or fifteen ohms of any convenient-sized wire be wound upon the bend of a commercialU-magnet. Let this wire be connected to a telephone in its circuit. When the magnet is made to sound like a tuning-fork, the pitch will be reproduced in the telephone very loudly. If another magnet with a different pitch be allowed to vibrate near the former, the pitch of the vibrating body will be heard in the telephone, and these show that the changing magnetic field reacts upon the quiescent magnet, and compels the latter to vibrate at the same rate. The action is an ether action, the waves are ether waves, but they are relatively very long. If the magnet makes 500 vibrations a second, the waves will be 372 miles long, the number of times 500 is contained in 186,000 miles. Imagine the magnet to become smaller and smaller until it was the size of an atom, the one-fifty-millionth of an inch. Its vibratory rate would be proportionally increased, and changes in its form will still bring about changes in its magnetic field. But its magnetic field is practically limitless, and the number of vibrations per second is to be reckoned as millions of millions; the waves arecorrespondingly short, small fractions of an inch. When they are as short as the one-thirty-seven-thousandth of an inch, they are capable of affecting the retina of the eye, and then are said to be visible as red light. If the vibratory rate be still higher, and the corresponding waves be no more than one-sixty-thousandth of an inch long, they affect the retina as violet light, and between these limits there are all the waves that produce a complete spectrum. The atoms, then, shake the ether in this way because they all have a magnetic hold upon the ether, so that any disturbance of their own magnetism, such as necessarily comes when they collide, reacts upon the ether for the same reason that a large magnet acts thus upon it when its poles approach and recede from each other. It is not a phenomenon of mechanical impact or frictional resistance, since neither are possible in the ether.19. MATTER EXISTS IN SEVERAL STATES.Molecular cohesion exists between very wide ranges. When strong, so if one part of a body is moved the whole is moved in the same way, without breaking continuity or the relative positions of the molecules, we call the body a solid. In a liquid, cohesion is greatly reduced, and any part of it may be deformed without materially changingthe form of the rest. The molecules are free to move about each other, and there is no definite position which any need assume or keep. With gases, the molecules are without any cohesion, each one is independent of every other one, collides with and bounds away from others as free elastic particles do. Between impacts it moves in what is called its free path, which may be long or short as the density of the gas be less or greater.These differing degrees of cohesion depend upon temperature, for if the densest and hardest substances are sufficiently heated they will become gaseous. This is only another way of saying that the states of matter depend upon the amount of molecular energy present. Solid ice becomes water by the application of heat. More heat reduces it to steam; still more decomposes the steam molecules into oxygen and hydrogen molecules; and lastly, still more heat will decompose these molecules into their atomic state, complete dissociation. On cooling, the process of reduction will be reversed until ice has been formed again.Cohesive strength in solids is increased by reduction of temperature, and metallic rods become stronger the colder they are.No distinction is now made between cohesion and chemical affinity, and yet at low temperatures chemical action will not take place, whichphenomenon shows there is a distinction between molecular cohesion and molecular structure. In molecular structure, as determined by chemical activity, the molecules and atoms are arranged in definite ways which depend upon the rate of vibrations of the components. The atoms are set in definite positions to constitute a given molecule. But atoms or molecules may cohere for other reasons, gravitative or magnetic, and relative positions would be immaterial. In the absence of temperature, a solid body would be solider and stronger than ever, while a gaseous mass would probably fall by gravity to the floor of the containing vessel like so much dust. The molecular structure might not be changed, for there would be no agency to act upon it in a disturbing way.THE ETHER HAS NO CORRESPONDING STATES.Degrees of density have already been excluded, and the homogeneity and continuity of the ether would also exclude the possibility of different states at all comparable with such as belong to matter. As for cohesion, it is doubtful if the term ought to be applied to such a substance. The word itself seems to imply possible separateness, and if the ether be a single indivisible substance, its cohesion must be infinite and is therefore not a matter of degree. The ether has sometimes beenconsidered as an elastic solid, but such solidity is comparable with nothing we call solid in matter, and the word has to be defined in a special sense in order that its use may be tolerated at all. In addition to this, some of the phenomena exhibited by it, such as diffraction and double refraction, are quite incompatible with the theory that the ether is an elastic solid. The reasons why it cannot be considered as a liquid or gas have been considered previously.The expressionstates of mattercannot be applied to the ether in any such sense as it is applied to matter, but there is one sense when possibly it may be considered applicable. Let it be granted that an atom is a vortex-ring of ether in the ether, then the state of being in ring rotation would suffice to differentiate that part of the ether from the rest, and give to it a degree of individuality not possessed by the rest; and such an atom might be called a state of ether. In like manner, if other forms of motion, such as transverse waves, circular and elliptical spirals, or others, exist in the ether, then such movements give special character to the part thus active, and it would be proper to speak of such states of the ether, but even thus the word would not be used in the same sense as it is used when one speaks of the states of matter as being solid, liquid, and gaseous.20. SOLID MATTER CAN EXPERIENCE ASHEARING STRESS, LIQUIDS AND GASES CANNOT.A sliding stress applied to a solid deforms it to a degree which depends upon the stress and the degree of rigidity preserved by the body. Thus if the hand be placed upon a closed book lying on the table, and pressure be so applied as to move the upper side of the book but not the lower, the book is said to be subject to a shearing stress. If the pressing hand has a twisting motion, the book will be warped. Any solid may be thus sheared or warped, but neither liquids nor gases can be so affected. Molecular cohesion makes it possible in the one, and the lack of it, impossible in the others. The solid can maintain such a deformation indefinitely long, if the pressure does not rupture its molecular structure.THE ETHER CAN MAINTAIN A SHEARING STRESS.The phenomena in a magnetic field show that the stress is of such a sort as to twist into a new directional position the body upon which it acts as exhibited by a magnetic needle, also as indicated by the transverse vibrations of the ether waves, and again by the twist given to plane polarized light when moving through a magnetic field. These areall interpreted as indicative of the direction of ether stress, as being similar to a shearing stress in solid matter. The fact has been adduced to show the ether to be a solid, but such a phenomenon is certainly incompatible with a liquid or gaseous ether. This kind of stress is maintained indefinitely about a permanent magnet, and the mechanical pressure which may result from it is a measure of the strength of the magnetic field, and may exceed a thousand pounds per square inch.21. OTHER PROPERTIES OF MATTER.There are many secondary qualities exhibited by matter in some of its forms, such as hardness, brittleness, malleability, colour, etc., and the same ultimate element may exhibit itself in the most diverse ways, as is the case with carbon, which exists as lamp-black, charcoal, graphite, jet, anthracite and diamond, ranging from the softest to the hardest of known bodies. Then it may be black or colourless. Gold is yellow, copper red, silver white, chlorine green, iodine purple. The only significance any or all of such qualities have for us here is that the ether exhibits none of them. There is neither hardness nor brittleness, nor colour, nor any approach to any of the characteristics for the identification of elementary matter.22. SENSATION DEPENDS UPON MATTER.However great the mystery of the relation of body to mind, it is quite true that the nervous system is the mechanism by and through which all sensation comes, and that in our experience in the absence of nerves there is neither sensation nor consciousness. The nerves themselves are but complex chemical structures; their molecular constitution is said to embrace as many as 20,000 atoms, chiefly carbon, hydrogen, oxygen, and nitrogen. There must be continuity of this structure too, for to sever a nerve is to paralyze all beyond. If all knowledge comes through experience, and all experience comes through the nervous system, the possibilities depend upon the mechanism each one is provided with for absorbing from his environment, what energies there are that can act upon the nerves. Touch, taste, and smell imply contact, sound has greater range, and sight has the immensity of the universe for its field. The most distant but visible star acts through the optic nerve to present itself to consciousness. It is not the ego that looks out through the eyes, but it is the universe that pours in upon the ego.Again, all the known agencies that act upon the nerves, whether for touch or sound or sight, imply matter in some of its forms and activities, to adaptthe energy to the nervous system. The mechanism for the perception of light is complicated. The light acts upon a sensitive surface where molecular structure is broken up, and this disturbance is in the presence of nerve terminals, and the sensation is not in the eye but in the sensorium. In like manner for all the rest; so one may fairly say that matter is the condition for sensation, and in its absence there would be nothing we call sensation.THE ETHER IS INSENSIBLE TO NERVES.The ether is in great contrast with matter in this particular. There is no evidence that in any direct way it acts upon any part of the nervous system, or upon the mind. It is probable that this lack of relation between the ether and the nervous system was the chief reason why its discovery was so long delayed, as the mechanical necessities for it even now are felt only by such as recognize continuity as a condition for the transmission of energy of whatever kind it may be. Action at a distance contradicts all experience, is philosophically incredible, and is repudiated by every one who once perceives that energy has two factors—substance and motion.The table given below presents a list of twenty-two of the known properties of matter contrasted with those exhibited by the ether. In none of themare the properties of the two identical, and in most of them what is true for one is not true for the other. They are not simply different, they are incomparable.From the necessities of the case, as knowledge has been acquired and terminology became essential for making distinctions, the ether has been described in terms applicable to matter, hence such terms as mass, solidity, elasticity, density, rigidity, etc., which have a definite meaning and convey definite mechanical conceptions when applied to matter, but have no corresponding meaning and convey no such mechanical conceptions when applied to the ether. It is certain that they are inappropriate, and that the ether and its properties cannot be described in terms applicable to matter. Mathematical considerations derived from the study of matter have no advantage, and are not likely to lead us to a knowledge of the ether.Only a few have perceived the inconsistency of thinking of the two in the same terms. In hisGrammar of Science, Prof. Karl Pearson says, “We find that our sense-impressions of hardness, weight, colour, temperature, cohesion, and chemical constitution, may all be described by the aid of the motions of a single medium, which itself is conceived to have no hardness, weight, colour, temperature, nor indeed elasticity of the ordinary conceptual type.”None of the properties of the ether are such asone would or could have predicted if he had had all the knowledge possessed by mankind. Every phenomenon in it is a surprise to us, because it does not follow the laws which experience has enabled us to formulate for matter. A substance which has none of the phenomenal properties of matter, and is not subject to the known laws of matter, ought not to be called matter. Ether phenomena and matter phenomena belong to different categories, and the ends of science will not be conserved by confusing them, as is done when the same terminology is employed for both.There are other properties belonging to the ether more wonderful, if possible, than those already mentioned. Its ability to maintain enormous stresses of various kinds without the slightest evidence of interference. There is the gravitational stress, a direct pull between two masses of matter. Between two molecules it is immeasurably small even when close together, but the prodigious number of them in a bullet brings the action into the field of observation, while between such bodies as the earth and moon or sun, the quantity reaches an astonishing figure. Thus if the gravitative tension due to the gravitative attraction of the earth and moon were to be replaced by steel wires connecting the two bodies to prevent the moon from leaving its orbit, there would be needed fournumber ten steel wires to every square inch upon the earth, and these would be strained nearly to the breaking point. Yet this stress is not only endured continually by this pliant, impalpable, transparent medium, but other bodies can move through the same space apparently as freely as if it were entirely free. In addition to this, the stress from the sun and the more variable stresses from the planets are all endured by the same medium in the same space and apparently a thousand or a million times more would not make the slightest difference. Rupture is impossible.Electric and magnetic stresses, acting parallel or at right angles to the other, exist in the same space and to indefinite degrees, neither modifying the direction nor amount of either of the others.These various stresses have been computed to represent energy, which if it could be utilized, each cubic inch of space would yield five hundred horse-power. It shows what a store-house of energy the ether is. If every particle of matter were to be instantly annihilated, the universe of ether would still have an inexpressible amount of energy left. To draw at will directly from this inexhaustible supply, and utilize it for the needs of mankind, is not a forlorn hope.The accompanying table presents these contrasting properties for convenient inspection.CONTRASTED PROPERTIES OF MATTER AND THE ETHER.MATTER.ETHER.1.DiscontinuousContinuous2.LimitedUnlimited3.HeterogeneousHomogeneous4.AtomicNon-atomic5.Definite structureStructureless6.GravitativeGravitationless7.FrictionableFrictionless8.ÆolotropicIsotropic9.Chemically selective10.Harmonically related11.Energy embodiedEnergy endowed12.Energy transformerNon-transformer13.ElasticElastic?14.DensityDensity?15.HeatableUnheatable16.Indestructible?Indestructible17.InertiativeInertiative conditionally18.Magnetic19.Variable states20.Subject to shearing stress in solidShearing stress maintained21.Has Secondary qualities22.Sensation depends uponInsensible to nerves[1]Vortex-rings for illustration may be made by having a wooden box about a foot on a side, with a round orifice in the middle of one side, and the side opposite covered with stout cloth stretched tight over a framework. A saucer containing strong ammonia water, and another containing strong hydrochloric acid, will cause dense fumes in the box, and a tap with the hand upon the cloth back will force out a ring from the orifice. These may be made to follow and strike each other, rebounding and vibrating, apparently attracting each other and being attracted by neighbouring bodies.By filling the mouth with smoke, and pursing the lips as if to make the soundo, one may make fifteen or twenty small rings by snapping the cheek with the finger.CHAPTER IIIAntecedents of Electricity—Nature of what is transformed—Series of transformations for the production of light—Positive and negative Electricity—Positive and negative twists—Rotations about a wire—Rotation of an arc—Ether a non-conductor—Electro-magnetic waves—Induction and inductive action—Ether stress and atomic position—Nature of an electric current—Electricity a condition, not an entity.So far as we have knowledge to-day, the only factors we have to consider in explaining physical phenomena are: (1) Ordinary matter, such as constitutes the substance of the earth, and the heavenly bodies; (2) the ether, which is omnipresent; and (3) the various forms of motion, which are mutually transformable in matter, and some of which, but not all, are transformable into ether forms. For instance, the translatory motion of a mass of matter can be imparted to another mass by simple impact, but translatory motion cannot be imparted to the ether, and, for that reason, a body moving in it isnot subject to friction, and continues to move on with velocity undiminished for an indefinite time; but the vibratory motion which constitutes heat is transformable into wave-motion in the ether, and is transmitted away with the speed of light. The kind of motion which is thus transformed is not even a to-and-fro swing of an atom, or molecule, like the swing of a pendulum bob, but that due to a change of form of the atoms within the molecule, otherwise there could be no such thing as spectrum analysis. Vibratory motion of the matter becomes undulatory motion in the ether. The vibratory motion we call heat; the wave-motion we call sometimes radiant energy, sometimes light. Neither of these terms is a good one, but we now have no others.It is conceded that it is not proper to speak of the wave-motion in the ether asheat; it is also admitted that the ether is not heated by the presence of the wave—or, in other words, the temperature of the ether is absolute zero. Matter only can be heated. But the ether waves can heat other matter they may fall on; so there are three steps in the process and two transformations—(1) vibrating matter; (2) waves in the ether; (3) vibration in other matter. Energy has been transferred indirectly. What is important to bear in mind is, that when a form of energy in matter is transformed in any manner so as to lose its characteristics, it is not proper to callit by the same name after as before, and this we do in all cases when the transformation is from one kind in matter to another kind in matter. Thus, when a bullet is shot against a target, before it strikes it has what we call mechanical energy, and we measure that in foot-pounds; after it has struck the target, the transformation is into heat, and this has its mechanical equivalent, but is not called mechanical energy, nor are the motions which embody it similar. The mechanical ideas in these phenomena are easy to grasp. They apply to the phenomena of the mechanics of large and small bodies, to sound, to heat, and to light, as ordinarily considered, but they have not been applied to electric phenomena, as they evidently should be, unless it be held that such phenomena are not related to ordinary phenomena, as the latter are to one another.When we would give a complete explanation of the phenomena exhibited by, say, a heated body, we need to inquire as to the antecedents of the manifestation, and also its consequents. Where and how did it get its heat? Where and how did it lose it? When we know every step of those processes, we know all there is to learn about them. Let us undertake the same thing for some electrical phenomena.First, under what circumstances do electrical phenomena arise?(1)Mechanical, as when two different kinds of matter are subject to friction.(2)Thermal, as when two substances in molecular contact are heated at the junction.(3)Magnetic, as when any conductor is in a changing magnetic field.(4)Chemical, as when a metal is being dissolved in any solution.(5)Physiological, as when a muscle contracts.Fig. 5.—Frictional electrical machine.Each of these has several varieties, and changes may be rung on combinations of them, as when mechanical and magnetic conditions interact.(1) In the first case, ordinary mechanical or translational energy is spent as friction, an amount measurable in foot-pounds, and the factors weknow, a pressure into a distance. If the surface be of the same kind of molecules, the whole energy is spent as heat, and is presently radiated away. If the surfaces are of unlike molecules, the product is a compound one, part heat, part electrical. What we have turned into the machine we know to be a particular mode of motion. We have not changed the amount of matter involved; indeed, we assume, without specifying and without controversy, that matter is itself indestructible, and the product, whether it be of one kind or another, can only be some form of motion. Whether we can describe it or not is immaterial; but if we agree that heatis vibratory molecular motion, and there be any other kind of a product than heat, it too must also be some other form of motion. So if one is to form a conception of the mechanical origin of electricity, this is the only one he can have—transformed motion.Fig. 6.—Thermo-pile.Fig. 5.—Dynamo.(2) When heat is the antecedent of electricity, as in the thermo-pile, that which is turned into the pile we know to be molecular motion of a definite kind. That which comes out of it must be some equivalentmotion, and if all that went in were transformed, then all that came out would be transformed, call it by what name we will and let its amount be what it may.(3) When a conductor is moved in a magnetic field, the energy spent is measurable in foot-pounds, as before, a pressure into a distance. The energy appears in a new form, but the quantity of matter being unchanged, the only changeable factor is the kind of motion, and that the motion is molecular is evident, for the molecules are heated. Mechanical or mass motion is the antecedent, molecular heat motion is the consequent, and the way we know there has been some intermediate form is, that heat is not conducted at the rate which is observed in such a case. Call it by what name one will, some form of motion has been intermediate between the antecedent and the consequent, else we have some other factor of energy to reckon with than ether, matter and motion.(4) In a galvanic battery, the source of electricity is chemical action; but what is chemical action? Simply an exchange of the constituents of molecules—a change which involves exchange of energy. Molecules capable of doing chemical work are loaded with energy. The chemical products of battery action are molecules of different constitution, with smaller amounts of energy asmeasured in calorics or heat units. If the results of the chemical reaction be prevented from escaping, by confining them to the cell itself, the whole energy appears as heat and raises the temperature of the cell. If a so-called circuit be provided, the energy is distributed through it, and less heat is spent in the cell, but whether it be in one place or another, the mass of matter involved is not changed, and the variable factor is the motion, the same as in the other cases. The mechanical conceptions appropriate are the transformation of one kind of motion into another kind by the mechanical conditions provided.
The resistance that a mass of matter opposes to a change in its position or rate and direction of movement, is called inertia. That it should actively oppose anything has been already pointed out as reason for denying that matter is inert, but inertia is the measure of the reaction of a body when it is acted upon by pressure from any source tending to disturb its condition of either rest or motion. It is the equivalent of mass, or the amount of matter as measured by gravity, and is a fixed quantity; for inertia is as inherent as any other quality, and belongs to the ultimate atoms and every combination of them. It implies the ability to absorb energy, for it requires as much energy to bring a moving body to a standstill as was required to give it its forward motion.
Both rotary and vibratory movements are opposed by the same property. A grindstone, a tuning-fork, and an atom of hydrogen require, to move them in their appropriate ways, an amount of energy proportionate to their mass or inertia, which energy is again transformed through friction into heat and radiated away.
One may say that inertia is the measure of the ability of a body to transfer or transform mechanical energy. The meteorite that falls uponthe earth to-day gives, on its impact, the same amount of energy it would have given if it had struck the earth ten thousand years ago. The inertia of the meteor has persisted, not as energy, but as a factor of energy. We commonly express the energy of a mass of matter bymv2/2, wheremstands for the mass andvfor its velocity. We might as well, if it were as convenient, substitute inertia for mass, and write the expressioniv2/2, for the mass, being measured by its inertia, is only the more common and less definitive word for the same thing. The energy of a mass of matter is, then, proportional to its inertia, because inertia is one of its factors. Energy has often been treated as if it were an objective thing, an entity and a unity; but such a conception is evidently wrong, for, as has been said before, it is a product of two factors, either of which may be changed in any degree if the other be changed inversely in the same degree. A cannon ball weighing 1000 pounds, and moving 100 feet per second, will have 156,000 foot-pounds of energy, but a musket ball weighing an ounce will have the same amount when its velocity is 12,600 feet per second. Nevertheless, another body acting upon either bullet or cannon ball, tending to move either in some newdirection, will be as efficient while those bodies are moving at any assignable rate as when they are quiescent, for the change in direction will depend upon the inertia of the bodies, and that is constant.
The common theory of an inert body is one that is wholly passive, having no power of itself to move or do anything, except as some agency outside itself compels it to move in one way or another, and thus endows it with energy. Thus a stone or an iron nail are thought to be inert bodies in that sense, and it is true that either of them will remain still in one place for an indefinite time and move from it only when some external agency gives them impulse and direction. Still it is known that such bodies will roll down hill if they will not roll up, and each of them has itself as much to do with the down-hill movement as the earth has; that is, it attracts the earth as much as the earth attracts it. If one could magnify the structure of a body until the molecules became individually visible, every one of them would be seen to be in intense activity, changing its form and relative position an enormous number of times per second in undirected ways. No two such molecules move in the same way at the same time, and as all the molecules cohere together, their motions in different directions balance each other, so that the body as a whole does not change its position,not because there is no moving agency in itself, but because the individual movements are scattering, and not in a common direction. An army may remain in one place for a long time. To one at a distance it is quiescent, inert. To one in the camp there is abundant sign of activity, but the movements are individual movements, some in one direction and some in another, and often changing. The same army on the march has the same energy, the same rate of individual movement; but all have a common direction, it moves as a whole body into new territory. So with the molecules of matter. In large masses they appear to be inert, and to do nothing, and to be capable of doing nothing. That is only due to the fact that their energy is undirected, not that they can do nothing. The inference that if quiescent bodies do not act in particular ways they are inert, and cannot act in any kind of a way, is a wrong inference. An illustration may perhaps make this point plainer. A lump of coal will be still as long as anything if it be undisturbed. Indeed, it has thus lain in a coal-bed for millions of years probably, but if coal be placed where it can combine with oxygen, it forthwith does so, and during the process yields a large amount of energy in the shape of heat. One pound of coal in this way gives out 14,000 heat units, which is the equivalent of 11,000,000 foot-poundsof work, and if it could be all utilized would furnish a horse-power for five and a half hours. Can any inert body weighing a pound furnish a horse-power for half a day? And can a body give out what it has not got? Are gunpowder and nitro-glycerine inert? Are bread and butter and foods in general inert because they will not push and pull as a man or a horse may? All have energy, which is available in certain ways and not in others, and whatever possesses energy available in any way is not an ideally inert body. Lastly, how many inert bodies together will it take to make an active body? If the question be absurd, then all the phenomena witnessed in bodies, large or small, are due to the fact that the atoms are not inert, but are immensely energetic, and their inertia is the measure of their rates of exchanging energy.
A moving mass of matter is brought to rest by friction, because it imparts its motion at some rate to the body it is in contact with. Generally the energy is transformed into heat, but sometimes it appears as electrification. Friction is only possible because one or both of the bodies possess inertia. That a body may move in the ether for an indefinite time without losing its velocity has beenstated as a reason for believing the ether to be frictionless. If it be frictionless, then it is without inertia, else the energy of the earth and of a ray of light would be frittered away. A ray of light can only be transformed when it falls upon molecules which may be heated by it. As the ether cannot be heated and cannot transform translational energy, it is without inertia forsucha form of motion and its embodied energy.
It is not thus with other forms of energy than the translational. Atomic and molecular vibrations are so related to the ether that they are transformed into waves, which are conducted away at a definite rate. This shows that such property of inertia as is possessed by the ether is selective and not like that of matter, which is equally “inertiative” under all conditions. Similarly with electric and magnetic phenomena, it is capable of transforming the energy which may reside as stress in the ether, and other bodies moving in the space so affected meet with frictional resistance, for they become heated if the motion be maintained. On the other hand, there is no evidence that the body which produced the electric or magnetic stress suffers any degree of friction on moving in precisely the same space. A bar magnet rotating on its longitudinal axis does not disturb its own field, but a pieceof iron revolving near the magnet will not only become heated, but will heat the stationary magnet. Much experimental work has been done to discover, if possible, the relation of a magnet to its ether field. As the latter is not disturbed by the rotation of the magnet, it has been concluded that the field does not rotate; but as every molecule in the magnet has its own field independent of all the rest, it is mechanically probable that each such field does vary in the rotation, but among the thousands of millions of such fields the average strength of the field does not vary within measurable limits. Another consideration is that the magnetic field itself, when moved in space, suffers no frictional resistance. There is no magnetic energy wasted through ether inertia. These phenomena show that whether the ether exhibits the quality called inertia depends upon the kind of motion it has.
The ordinary phenomenon of magnetism is shown by bringing a piece of iron into the neighbourhood of a so-called magnet, where it is attracted by the latter, and if free to move will go to and cling to the magnet. A delicately suspended magnetic needle will be affected appreciably by a strong magnet at the distance of several hundredfeet. As the strength of such action varies inversely as the square of the distance from the magnet, it is evident there can be no absolute boundary to it. At a distance from an ordinary magnet it becomes too weak to be detected by our methods, not that there is a limit to it. It is customary to think of iron as being peculiarly endowed with magnetic quality, but all kinds of matter possess it in some degree. Wood, stone, paper, oats, sulphur, and all the rest, are attracted by a magnet, and will stick to it if the magnet be a strong one. Whether a piece of iron itself exhibits the property depends upon its temperature, for near 700 degrees it becomes as magnetically indifferent as a piece of copper at ordinary temperature. Oxygen, too, at 200 degrees below the zero of Centigrade adheres to a magnet like iron.
In this as in so many other particulars, how a piece of matter behaves depends upon its temperature, not that the essential qualities are modified in any degree, but temperature interferes with atomic arrangement and aggregation, and so disguises their phenomena.
As every kind of matter is thus affected by a magnet, the manifestations differing but in degree, it follows that all kinds of atoms—all the elements—are magnetic. An inherent property in them, as much so as gravitation or inertia; apparently aquality depending upon the structure of the atoms themselves, in the same sense as gravitation is thus dependent, as it is not a quality of the ether.
An atom must, then, be thought of as having polarity, different qualities on the two sides, and possessing a magnetic field as extensive as space itself. The magnetic field is the stress or pressure in the ether produced by the magnetic body. This ether pressure produced by a magnet may be as great as a ton per square inch. It is this pressure that holds an armature to the magnet. As heat is a molecular condition of vibration, and radiant energy the result of it, so is magnetism a property of molecules, and the magnetic field the temporary condition in the ether, which depends upon the presence of a magnetic body. We no longer speak of the wave-motion in the ether which results from heat, as heat, but call it radiation, or ether waves, and for a like reason the magnetic field ought not to be called magnetism.
A magnetic field manifests itself in a way that implies that the ether structure, if it may be said to have any, is deformed—deformed in such a sense that another magnet in it tends to set itself in the plane of the stress; that is, the magnet is twisted into a new position to accommodate itself to the conditionof the medium about it. The new position is the result of the reaction of the ether upon the magnet and ether pressure acting at right angles to the body that produced the stress. Such an action is so anomalous as to suggest the propriety of modifying the so-called third law of motion, viz., action and reaction are equal and opposite, adding that sometimes action and reaction are at right angles.
There is no condition or property exhibited by the ether itself which shows it to have any such characteristic as attraction, repulsion, or differences in stress, except where its condition is modified by the activities of matter in some way. The ether itself is not attracted or repelled by a magnet; that is, it is not a magnetic body in any such sense as matter in any of its forms is, and therefore cannot properly be called magnetic.
It has been a mechanical puzzle to understand how the vibratory motions called heat could set up light waves in the ether seeing that there is an absence of friction in the latter. In the endeavour to conceive it, the origin of sound-waves has been in mind, where longitudinal air-waves are produced by the vibrations of a sounding body, and molecular impact is the antecedent of the waves. The analogy does not apply. The following exposition may be helpful in grasping the idea of such transformation and change of energy from matter to the ether.
Consider a straight bar permanent magnet to be held in the hand. It has its north and south poles and its field, the latter extending in every direction to an indefinite distance. The field is to be considered as ether stress of such a sort as to tend to set other magnets in it in new positions. If at a distance of ten feet there were a delicately-poised magnet needle, every change in the position of the magnet held in the hand would bring about a change in the position of the needle. If the position of the hand magnet were completely reversed, so the south pole faced where the north pole faced before, the field would have been completely reversed, and the poised needle would have been pushed by the field into an opposite position. If the needle were a hundred feet away, the change would have been the same except in amount. The same might be said if the two were a mile apart, or the distance of the moon or any other distance, for there is no limit to an ether magnetic field. Suppose the hand magnet to have its direction completely reversed once in a second. The whole field, and the direction of the stress, would necessarily be reversed as often. But this kind of change in stress is known by experiment to travel with the speed of light, 186,000 miles a second; the disturbance due to the change of position of the magnet will therefore be felt in some degreethroughout space. In a second and a third of a second it will have reached the moon, and a magnet there will be in some measure affected by it. If there were an observer there with a delicate-enough magnet, he could be witness to its changes once a second for the same reason one in the room could. The only difference would be one of amount of swing. It is therefore theoretically possible to signal to the moon with a swinging magnet. Suppose again that the magnet should be swung twice a second, there would be formed two waves, each one half as long as the first. If it should swing ten times a second, then the waves would be one-tenth of 186,000 miles long. If in some mechanical way it could be rotated 186,000 times a second, the wave would be but one mile long. Artificial ways have been invented for changing this magnet field as many as 100 million times a second, and the corresponding wave is less than a foot long. The shape of a magnet does not necessarily make it weaker or stronger as a magnet, but if the poles are near together the magnetic field is denser between them than when they are separated. The ether stress is differently distributed for every change in the relative positions of the poles.
A commonU-magnet, if struck, will vibrate like a tuning-fork, and gives out a definite pitch. Itspoles swing towards and away from each other at uniform rates, and the pitch of the magnet will depend upon its size, thickness, and the material it is made of.
Let ten or fifteen ohms of any convenient-sized wire be wound upon the bend of a commercialU-magnet. Let this wire be connected to a telephone in its circuit. When the magnet is made to sound like a tuning-fork, the pitch will be reproduced in the telephone very loudly. If another magnet with a different pitch be allowed to vibrate near the former, the pitch of the vibrating body will be heard in the telephone, and these show that the changing magnetic field reacts upon the quiescent magnet, and compels the latter to vibrate at the same rate. The action is an ether action, the waves are ether waves, but they are relatively very long. If the magnet makes 500 vibrations a second, the waves will be 372 miles long, the number of times 500 is contained in 186,000 miles. Imagine the magnet to become smaller and smaller until it was the size of an atom, the one-fifty-millionth of an inch. Its vibratory rate would be proportionally increased, and changes in its form will still bring about changes in its magnetic field. But its magnetic field is practically limitless, and the number of vibrations per second is to be reckoned as millions of millions; the waves arecorrespondingly short, small fractions of an inch. When they are as short as the one-thirty-seven-thousandth of an inch, they are capable of affecting the retina of the eye, and then are said to be visible as red light. If the vibratory rate be still higher, and the corresponding waves be no more than one-sixty-thousandth of an inch long, they affect the retina as violet light, and between these limits there are all the waves that produce a complete spectrum. The atoms, then, shake the ether in this way because they all have a magnetic hold upon the ether, so that any disturbance of their own magnetism, such as necessarily comes when they collide, reacts upon the ether for the same reason that a large magnet acts thus upon it when its poles approach and recede from each other. It is not a phenomenon of mechanical impact or frictional resistance, since neither are possible in the ether.
Molecular cohesion exists between very wide ranges. When strong, so if one part of a body is moved the whole is moved in the same way, without breaking continuity or the relative positions of the molecules, we call the body a solid. In a liquid, cohesion is greatly reduced, and any part of it may be deformed without materially changingthe form of the rest. The molecules are free to move about each other, and there is no definite position which any need assume or keep. With gases, the molecules are without any cohesion, each one is independent of every other one, collides with and bounds away from others as free elastic particles do. Between impacts it moves in what is called its free path, which may be long or short as the density of the gas be less or greater.
These differing degrees of cohesion depend upon temperature, for if the densest and hardest substances are sufficiently heated they will become gaseous. This is only another way of saying that the states of matter depend upon the amount of molecular energy present. Solid ice becomes water by the application of heat. More heat reduces it to steam; still more decomposes the steam molecules into oxygen and hydrogen molecules; and lastly, still more heat will decompose these molecules into their atomic state, complete dissociation. On cooling, the process of reduction will be reversed until ice has been formed again.
Cohesive strength in solids is increased by reduction of temperature, and metallic rods become stronger the colder they are.
No distinction is now made between cohesion and chemical affinity, and yet at low temperatures chemical action will not take place, whichphenomenon shows there is a distinction between molecular cohesion and molecular structure. In molecular structure, as determined by chemical activity, the molecules and atoms are arranged in definite ways which depend upon the rate of vibrations of the components. The atoms are set in definite positions to constitute a given molecule. But atoms or molecules may cohere for other reasons, gravitative or magnetic, and relative positions would be immaterial. In the absence of temperature, a solid body would be solider and stronger than ever, while a gaseous mass would probably fall by gravity to the floor of the containing vessel like so much dust. The molecular structure might not be changed, for there would be no agency to act upon it in a disturbing way.
Degrees of density have already been excluded, and the homogeneity and continuity of the ether would also exclude the possibility of different states at all comparable with such as belong to matter. As for cohesion, it is doubtful if the term ought to be applied to such a substance. The word itself seems to imply possible separateness, and if the ether be a single indivisible substance, its cohesion must be infinite and is therefore not a matter of degree. The ether has sometimes beenconsidered as an elastic solid, but such solidity is comparable with nothing we call solid in matter, and the word has to be defined in a special sense in order that its use may be tolerated at all. In addition to this, some of the phenomena exhibited by it, such as diffraction and double refraction, are quite incompatible with the theory that the ether is an elastic solid. The reasons why it cannot be considered as a liquid or gas have been considered previously.
The expressionstates of mattercannot be applied to the ether in any such sense as it is applied to matter, but there is one sense when possibly it may be considered applicable. Let it be granted that an atom is a vortex-ring of ether in the ether, then the state of being in ring rotation would suffice to differentiate that part of the ether from the rest, and give to it a degree of individuality not possessed by the rest; and such an atom might be called a state of ether. In like manner, if other forms of motion, such as transverse waves, circular and elliptical spirals, or others, exist in the ether, then such movements give special character to the part thus active, and it would be proper to speak of such states of the ether, but even thus the word would not be used in the same sense as it is used when one speaks of the states of matter as being solid, liquid, and gaseous.
A sliding stress applied to a solid deforms it to a degree which depends upon the stress and the degree of rigidity preserved by the body. Thus if the hand be placed upon a closed book lying on the table, and pressure be so applied as to move the upper side of the book but not the lower, the book is said to be subject to a shearing stress. If the pressing hand has a twisting motion, the book will be warped. Any solid may be thus sheared or warped, but neither liquids nor gases can be so affected. Molecular cohesion makes it possible in the one, and the lack of it, impossible in the others. The solid can maintain such a deformation indefinitely long, if the pressure does not rupture its molecular structure.
The phenomena in a magnetic field show that the stress is of such a sort as to twist into a new directional position the body upon which it acts as exhibited by a magnetic needle, also as indicated by the transverse vibrations of the ether waves, and again by the twist given to plane polarized light when moving through a magnetic field. These areall interpreted as indicative of the direction of ether stress, as being similar to a shearing stress in solid matter. The fact has been adduced to show the ether to be a solid, but such a phenomenon is certainly incompatible with a liquid or gaseous ether. This kind of stress is maintained indefinitely about a permanent magnet, and the mechanical pressure which may result from it is a measure of the strength of the magnetic field, and may exceed a thousand pounds per square inch.
There are many secondary qualities exhibited by matter in some of its forms, such as hardness, brittleness, malleability, colour, etc., and the same ultimate element may exhibit itself in the most diverse ways, as is the case with carbon, which exists as lamp-black, charcoal, graphite, jet, anthracite and diamond, ranging from the softest to the hardest of known bodies. Then it may be black or colourless. Gold is yellow, copper red, silver white, chlorine green, iodine purple. The only significance any or all of such qualities have for us here is that the ether exhibits none of them. There is neither hardness nor brittleness, nor colour, nor any approach to any of the characteristics for the identification of elementary matter.
However great the mystery of the relation of body to mind, it is quite true that the nervous system is the mechanism by and through which all sensation comes, and that in our experience in the absence of nerves there is neither sensation nor consciousness. The nerves themselves are but complex chemical structures; their molecular constitution is said to embrace as many as 20,000 atoms, chiefly carbon, hydrogen, oxygen, and nitrogen. There must be continuity of this structure too, for to sever a nerve is to paralyze all beyond. If all knowledge comes through experience, and all experience comes through the nervous system, the possibilities depend upon the mechanism each one is provided with for absorbing from his environment, what energies there are that can act upon the nerves. Touch, taste, and smell imply contact, sound has greater range, and sight has the immensity of the universe for its field. The most distant but visible star acts through the optic nerve to present itself to consciousness. It is not the ego that looks out through the eyes, but it is the universe that pours in upon the ego.
Again, all the known agencies that act upon the nerves, whether for touch or sound or sight, imply matter in some of its forms and activities, to adaptthe energy to the nervous system. The mechanism for the perception of light is complicated. The light acts upon a sensitive surface where molecular structure is broken up, and this disturbance is in the presence of nerve terminals, and the sensation is not in the eye but in the sensorium. In like manner for all the rest; so one may fairly say that matter is the condition for sensation, and in its absence there would be nothing we call sensation.
The ether is in great contrast with matter in this particular. There is no evidence that in any direct way it acts upon any part of the nervous system, or upon the mind. It is probable that this lack of relation between the ether and the nervous system was the chief reason why its discovery was so long delayed, as the mechanical necessities for it even now are felt only by such as recognize continuity as a condition for the transmission of energy of whatever kind it may be. Action at a distance contradicts all experience, is philosophically incredible, and is repudiated by every one who once perceives that energy has two factors—substance and motion.
The table given below presents a list of twenty-two of the known properties of matter contrasted with those exhibited by the ether. In none of themare the properties of the two identical, and in most of them what is true for one is not true for the other. They are not simply different, they are incomparable.
From the necessities of the case, as knowledge has been acquired and terminology became essential for making distinctions, the ether has been described in terms applicable to matter, hence such terms as mass, solidity, elasticity, density, rigidity, etc., which have a definite meaning and convey definite mechanical conceptions when applied to matter, but have no corresponding meaning and convey no such mechanical conceptions when applied to the ether. It is certain that they are inappropriate, and that the ether and its properties cannot be described in terms applicable to matter. Mathematical considerations derived from the study of matter have no advantage, and are not likely to lead us to a knowledge of the ether.
Only a few have perceived the inconsistency of thinking of the two in the same terms. In hisGrammar of Science, Prof. Karl Pearson says, “We find that our sense-impressions of hardness, weight, colour, temperature, cohesion, and chemical constitution, may all be described by the aid of the motions of a single medium, which itself is conceived to have no hardness, weight, colour, temperature, nor indeed elasticity of the ordinary conceptual type.”
None of the properties of the ether are such asone would or could have predicted if he had had all the knowledge possessed by mankind. Every phenomenon in it is a surprise to us, because it does not follow the laws which experience has enabled us to formulate for matter. A substance which has none of the phenomenal properties of matter, and is not subject to the known laws of matter, ought not to be called matter. Ether phenomena and matter phenomena belong to different categories, and the ends of science will not be conserved by confusing them, as is done when the same terminology is employed for both.
There are other properties belonging to the ether more wonderful, if possible, than those already mentioned. Its ability to maintain enormous stresses of various kinds without the slightest evidence of interference. There is the gravitational stress, a direct pull between two masses of matter. Between two molecules it is immeasurably small even when close together, but the prodigious number of them in a bullet brings the action into the field of observation, while between such bodies as the earth and moon or sun, the quantity reaches an astonishing figure. Thus if the gravitative tension due to the gravitative attraction of the earth and moon were to be replaced by steel wires connecting the two bodies to prevent the moon from leaving its orbit, there would be needed fournumber ten steel wires to every square inch upon the earth, and these would be strained nearly to the breaking point. Yet this stress is not only endured continually by this pliant, impalpable, transparent medium, but other bodies can move through the same space apparently as freely as if it were entirely free. In addition to this, the stress from the sun and the more variable stresses from the planets are all endured by the same medium in the same space and apparently a thousand or a million times more would not make the slightest difference. Rupture is impossible.
Electric and magnetic stresses, acting parallel or at right angles to the other, exist in the same space and to indefinite degrees, neither modifying the direction nor amount of either of the others.
These various stresses have been computed to represent energy, which if it could be utilized, each cubic inch of space would yield five hundred horse-power. It shows what a store-house of energy the ether is. If every particle of matter were to be instantly annihilated, the universe of ether would still have an inexpressible amount of energy left. To draw at will directly from this inexhaustible supply, and utilize it for the needs of mankind, is not a forlorn hope.
The accompanying table presents these contrasting properties for convenient inspection.
MATTER.ETHER.1.DiscontinuousContinuous2.LimitedUnlimited3.HeterogeneousHomogeneous4.AtomicNon-atomic5.Definite structureStructureless6.GravitativeGravitationless7.FrictionableFrictionless8.ÆolotropicIsotropic9.Chemically selective10.Harmonically related11.Energy embodiedEnergy endowed12.Energy transformerNon-transformer13.ElasticElastic?14.DensityDensity?15.HeatableUnheatable16.Indestructible?Indestructible17.InertiativeInertiative conditionally18.Magnetic19.Variable states20.Subject to shearing stress in solidShearing stress maintained21.Has Secondary qualities22.Sensation depends uponInsensible to nerves
[1]Vortex-rings for illustration may be made by having a wooden box about a foot on a side, with a round orifice in the middle of one side, and the side opposite covered with stout cloth stretched tight over a framework. A saucer containing strong ammonia water, and another containing strong hydrochloric acid, will cause dense fumes in the box, and a tap with the hand upon the cloth back will force out a ring from the orifice. These may be made to follow and strike each other, rebounding and vibrating, apparently attracting each other and being attracted by neighbouring bodies.By filling the mouth with smoke, and pursing the lips as if to make the soundo, one may make fifteen or twenty small rings by snapping the cheek with the finger.
[1]Vortex-rings for illustration may be made by having a wooden box about a foot on a side, with a round orifice in the middle of one side, and the side opposite covered with stout cloth stretched tight over a framework. A saucer containing strong ammonia water, and another containing strong hydrochloric acid, will cause dense fumes in the box, and a tap with the hand upon the cloth back will force out a ring from the orifice. These may be made to follow and strike each other, rebounding and vibrating, apparently attracting each other and being attracted by neighbouring bodies.
By filling the mouth with smoke, and pursing the lips as if to make the soundo, one may make fifteen or twenty small rings by snapping the cheek with the finger.
Antecedents of Electricity—Nature of what is transformed—Series of transformations for the production of light—Positive and negative Electricity—Positive and negative twists—Rotations about a wire—Rotation of an arc—Ether a non-conductor—Electro-magnetic waves—Induction and inductive action—Ether stress and atomic position—Nature of an electric current—Electricity a condition, not an entity.
So far as we have knowledge to-day, the only factors we have to consider in explaining physical phenomena are: (1) Ordinary matter, such as constitutes the substance of the earth, and the heavenly bodies; (2) the ether, which is omnipresent; and (3) the various forms of motion, which are mutually transformable in matter, and some of which, but not all, are transformable into ether forms. For instance, the translatory motion of a mass of matter can be imparted to another mass by simple impact, but translatory motion cannot be imparted to the ether, and, for that reason, a body moving in it isnot subject to friction, and continues to move on with velocity undiminished for an indefinite time; but the vibratory motion which constitutes heat is transformable into wave-motion in the ether, and is transmitted away with the speed of light. The kind of motion which is thus transformed is not even a to-and-fro swing of an atom, or molecule, like the swing of a pendulum bob, but that due to a change of form of the atoms within the molecule, otherwise there could be no such thing as spectrum analysis. Vibratory motion of the matter becomes undulatory motion in the ether. The vibratory motion we call heat; the wave-motion we call sometimes radiant energy, sometimes light. Neither of these terms is a good one, but we now have no others.
It is conceded that it is not proper to speak of the wave-motion in the ether asheat; it is also admitted that the ether is not heated by the presence of the wave—or, in other words, the temperature of the ether is absolute zero. Matter only can be heated. But the ether waves can heat other matter they may fall on; so there are three steps in the process and two transformations—(1) vibrating matter; (2) waves in the ether; (3) vibration in other matter. Energy has been transferred indirectly. What is important to bear in mind is, that when a form of energy in matter is transformed in any manner so as to lose its characteristics, it is not proper to callit by the same name after as before, and this we do in all cases when the transformation is from one kind in matter to another kind in matter. Thus, when a bullet is shot against a target, before it strikes it has what we call mechanical energy, and we measure that in foot-pounds; after it has struck the target, the transformation is into heat, and this has its mechanical equivalent, but is not called mechanical energy, nor are the motions which embody it similar. The mechanical ideas in these phenomena are easy to grasp. They apply to the phenomena of the mechanics of large and small bodies, to sound, to heat, and to light, as ordinarily considered, but they have not been applied to electric phenomena, as they evidently should be, unless it be held that such phenomena are not related to ordinary phenomena, as the latter are to one another.
When we would give a complete explanation of the phenomena exhibited by, say, a heated body, we need to inquire as to the antecedents of the manifestation, and also its consequents. Where and how did it get its heat? Where and how did it lose it? When we know every step of those processes, we know all there is to learn about them. Let us undertake the same thing for some electrical phenomena.
First, under what circumstances do electrical phenomena arise?
(1)Mechanical, as when two different kinds of matter are subject to friction.
(2)Thermal, as when two substances in molecular contact are heated at the junction.
(3)Magnetic, as when any conductor is in a changing magnetic field.
(4)Chemical, as when a metal is being dissolved in any solution.
(5)Physiological, as when a muscle contracts.
Fig. 5.—Frictional electrical machine.
Each of these has several varieties, and changes may be rung on combinations of them, as when mechanical and magnetic conditions interact.
(1) In the first case, ordinary mechanical or translational energy is spent as friction, an amount measurable in foot-pounds, and the factors weknow, a pressure into a distance. If the surface be of the same kind of molecules, the whole energy is spent as heat, and is presently radiated away. If the surfaces are of unlike molecules, the product is a compound one, part heat, part electrical. What we have turned into the machine we know to be a particular mode of motion. We have not changed the amount of matter involved; indeed, we assume, without specifying and without controversy, that matter is itself indestructible, and the product, whether it be of one kind or another, can only be some form of motion. Whether we can describe it or not is immaterial; but if we agree that heatis vibratory molecular motion, and there be any other kind of a product than heat, it too must also be some other form of motion. So if one is to form a conception of the mechanical origin of electricity, this is the only one he can have—transformed motion.
Fig. 6.—Thermo-pile.
Fig. 5.—Dynamo.
(2) When heat is the antecedent of electricity, as in the thermo-pile, that which is turned into the pile we know to be molecular motion of a definite kind. That which comes out of it must be some equivalentmotion, and if all that went in were transformed, then all that came out would be transformed, call it by what name we will and let its amount be what it may.
(3) When a conductor is moved in a magnetic field, the energy spent is measurable in foot-pounds, as before, a pressure into a distance. The energy appears in a new form, but the quantity of matter being unchanged, the only changeable factor is the kind of motion, and that the motion is molecular is evident, for the molecules are heated. Mechanical or mass motion is the antecedent, molecular heat motion is the consequent, and the way we know there has been some intermediate form is, that heat is not conducted at the rate which is observed in such a case. Call it by what name one will, some form of motion has been intermediate between the antecedent and the consequent, else we have some other factor of energy to reckon with than ether, matter and motion.
(4) In a galvanic battery, the source of electricity is chemical action; but what is chemical action? Simply an exchange of the constituents of molecules—a change which involves exchange of energy. Molecules capable of doing chemical work are loaded with energy. The chemical products of battery action are molecules of different constitution, with smaller amounts of energy asmeasured in calorics or heat units. If the results of the chemical reaction be prevented from escaping, by confining them to the cell itself, the whole energy appears as heat and raises the temperature of the cell. If a so-called circuit be provided, the energy is distributed through it, and less heat is spent in the cell, but whether it be in one place or another, the mass of matter involved is not changed, and the variable factor is the motion, the same as in the other cases. The mechanical conceptions appropriate are the transformation of one kind of motion into another kind by the mechanical conditions provided.