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, which phenomenon 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 been considered 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 expression _states of matter_ cannot 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 A SHEARING 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 are all 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 adapt the 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 them are 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 his _Grammar 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 as one 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 four number 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. Discontinuous Continuous 2. Limited Unlimited 3. Heterogeneous Homogeneous 4. Atomic Non-atomic 5. Definite structure Structureless 6. Gravitative Gravitationless 7. Frictionable Frictionless 8. aeolotropic Isotropic 9. Chemically selective ---- 10. Harmonically related ---- 11. Energy embodied Energy endowed 12. Energy transformer Non-transformer 13. Elastic Elastic?
14. Density Density?
15. Heatable Unheatable 16. Indestructible? Indestructible 17. Inertiative Inertiative conditionally 18. Magnetic ---- 19. Variable states ---- 20. Subject to shearing stress in solid Shearing stress maintained 21. Has Secondary qualities ---- 22. Sensation depends upon Insensible to nerves
CHAPTER III
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 is not 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 as _heat_; 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 call it 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.
[Illustration: 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 we know, 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 heat is 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.