Chapter I: Properties of the Substances Intermediate Between Matter and the Ether
What are the characteristics which allow us to assert that a substance is no longer altogether matter without yet being either, and that it constitutes something intermediate between these two substances.
It is only if we see matter lose one of its irreducible characteristics — that is to say, one of those of which it cannot be deprived by any other means whatever — that we are authorized to say that it has lost its quality of matter.
We have already seen that these irreducible characteristics are not numerous, since up to the present only one has been discovered. All the usual properties of matter — solidity, form, color, etc. — are indestructible. A mass of rock can, by heat, be transformed into vapor. One property alone, the mass measured by the weight, becomes invariable through all the transformations of bodies and allows them to be followed and rediscovered, notwithstanding the frequency of their changes. It is on this invariability of the mass that the sciences of chemistry and mechanics have been built.
Mass, as is well known, is simply the measure of inertia — that is to say, of that property of unknown essence which enables matter to resist motion or the changes of motion. Its magnitude, which can be represented by a weight, is an absolutely invariable quantity for any given body, whatever be the conditions in which it can be placed. We are therefore led to consider a substance of which the inertia, and consequently the mass, can by any means be rendered variable as something very different from matter.
Now, it is just this variability of the mass — that is to say, of the inertia — which is noted in the electric particles emitted by radioactive bodies during their disaggregation. The variability of this fundamental property will allow us to state that the elements resulting from the dissociation of bodies, elements which besides differ so by their general properties from material substances, form a substance intermediate between matter and the ether.
Long before the current theories as to the structure of the electric field, now supposed to be formed by the conjunction of particular atoms, it was noticed that it possessed inertia — that is to say, resistance to motion or to change of motion, but only quite lately has the measurement of this inertia been arrived at. The oscillating discharge of a Leyden jar was one of the first phenomena which revealed the inertia of the electric fluid. This oscillating discharge can be compared to the movements, similarly die to its inertia, which a liquid poured into a U-tube makes before reaching its position of equilibrium. It is likewise through inertia that the phenomena of self-induction are produced.
So long as the inertia of electric particles could not be measured, it was allowable to suppose it to be identical with that of matter; as soon as it was possible to calculate their velocity from the intensity of the magnetic force necessary to deviate them from their trajectory, it became possible to measure their mass. It was then seen to vary with their speed.
The first experiments on this point are due to Kaufmann and Abraham. By observing on a photographic plate the deviation under the influence of two superposed magnetic and electric fields, they noted that the relation of the electric charge e, carried by a radioactive particle, to the mass m of this particle, varied with its velocity. As it cannot be supposed that in this relation the charge changes, it is evident that it is the mass which varies.
The variation of the mass of the particles with their speed is besides in agreement with the electromagnetic theory of light, and had already been pointed out by various authors, Larmor amongst them. The variation of the mass would suffice to prove that substances which exhibit such a property are no longer matter. It is thus that Kaufmann deduces from his observations that the electron, of which certain radioactive emissions are composed, “is nothing but an electric charge distributed over a volume or a surface of very small dimensions”.
By putting Abraham’s equation into the form of a curve, it is easy to see the manner in which the mass of the elements of dissociated matter vary with their speed. Constant at first even for very great velocities, it increases abruptly and quickly tends to become infinite as it approaches the velocity of light.
So long as the mass has not attained a speed equal to 20% of that of light — that is to say, not exceeding 50,000 km/sec, its magnitude, represented by 1 at the beginning, remains about the same (1.012). When the speed reaches half that of light (150,000 km/sec) the mass has still only increased by one-tenth. When the speed equals three-fourths that of light, the increase of mass is still very slight (1.369). When the speed equals nine-tenths that of light, the mass has not quite doubled (1.82); but as soon as the speed reaches 0.999 that of light, the mass increases sixfold (6.678).
We are here very close to the speed of light, and the mass has as yet only increased sixfold; but it is now that the figures deduced from the equation begin to increase singularly. For the mass of the electric atom to become 20 times greater (20,49), its speed will only have to differ from that of light by the fraction of a millimeter. For its mass to become 100 times greater, its velocity would have to differ from that of light by the fraction of a millimeter comprising 58 figures. Finally, if the speed of the electric atom became exactly equal to that of light, its mass would be theoretically infinite.
These last results cannot be verified by any experiment, and are evidently only an extrapolation. We must not, however, consider as a priori absurd the existence of a substance of which the mass would increase in immense proportions, while its already very great speed would only vary by the minute fraction of a millimeter. The considerable increase of an effect under the influence of a very small variation in the cause is observed in many physical laws which can be translated by asymptotic curves. The immense variations in size of the image of an object for a very slight displacement of that object when very close to the principal focus of a lens, furnish an example of this. Suppose an object placed at one-tenth of a millimeter from the focus of a lens with a focus of 10 cm. The general question of lenses shows that its image will be magnified a thousand times. If the object is brought nearer by one-hundredth of a millimeter, its image will, theoretically, be magnified a hundred thousand times, If, lastly, the object is placed in the very focus itself, the image will, theoretically, be infinite. Every time a physical law can be translated by curves to the above, the slightest variation in the variable produces extremely important variations of the function in the neighborhood of the limit (1).
[(1) I must point out, by the way — and this observation will explain many historical events — that it is not only physical, but many social phenomena which can be likewise defined by curves possessing the properties we have just stated, and in which, consequently, very small changes in a cause may produce very great effects. This is owing to the fact that when a cause acts for a length of time in a same direction, its effects increase in geometrical progression, which the cause varies simply in arithmetical progression. Causes are the logarithms of effects.]
Leaving these theoretical considerations and coming back to the results of experiments, we may say this: the particles produced during the dissociation of matter possess a property resembling inertia, and in this they are akin to matter; but this inertia, instead of being constant in magnitude, varies with the speed, and on this point particles of dissociated matter are sharply differentiated from material atoms.
The study of the properties of inertia of these elements leads, as will be seen, to their being considered something which, issuing from matter, possesses properties somewhat similar to, but yet notably different from, those of material atoms. Representing one of the phases of the dematerialization of matter, they are only able to retain a part of the properties of this last. We shall see in another chapter that the electric field likewise possesses properties intermediate between those of matter and those of ether.
Some physicists have supposed — without, however, being able to furnish any proofs — that the inertia of matter is die to the electric particles of which it should be composed, and consequently that all the inertia of material substances is entirely of electromagnetic origin. There is nothing to indicate that material inertia can be identified with that of the particles of dissociated matter. The mass of these last is only, in reality, an apparent mass resulting simply from its condition as an electrified body in motion. They appear, besides, to have a longitudinal mass (that which measures the opposition to acceleration in the direction of the motion), different from the transversal mass (that perpendicular to the direction of the motion). In every way it is evident that the properties of an element of dissociated matter differ considerably from those of a material atom (1).
[(1) The vicious circle of the argument attacked in this paragraph is thus well set forth by Prof. H.A. Wilson: “It is now suggested that all matter is composed of electrons, so that all inertia is electromagnetic. Density, according to this view, is simply the number of electrons per unit volume. Electromagnetic inertia — that is, all inertia — is due to the energy of the magnetic field produced by the moving charges of electricity. The energy of this magnetic field resides in the ether. Accordiing to Maxwell’s dynamical theory, the electromagnetic energy of the ether is due to motion of parts of the ether, these parts possessing motion. But the only kind of inertia which we really know is the inertia of matter, which is due to the electromagnetic action of the electrons of which matter is made up. If inertia is due to electrons, then if we ascribe to parts of the ether the property of inertia, we ought to say that the ether contains so many electrons per unit volume. But the free ether is not supposed to contain any electrons; in fact, if we explain inertia by the energy of the magnetic fields produced by moving charges, then evidently to explain this energy by inertia in the ether is merely to argue in a circle” (Nature, 22 June 1905)]
Of what, then, are constituted these atoms which are supposed to be electric, and are emitted by all bodies during their dissolution? The answer to this question supplies the link required between the ponderable and the imponderable. It is impossible, in the present state of science, to give a definition of a so-called electric particle, but we can at least say this: substances neither solid, liquid, nor gaseous, which pass through obstacles, and have no property common to matter, except a certain inertia, and even then an inertia varying with their speed, are very clearly differentiated from matter. They are likewise differentiated from the ether, of which they do not possess the attributes. They therefore form a transition between the two.
Thus, then, the effluves emanating from spontaneously radioactive bodies, or from bodies capable of becoming so under the influence of the numerous causes we have enumerated, form a link between matter and the ether. And, since we know that these effluves cannot be produced without the definitive loss of matter, we have a right to say that the dissociation of matter realizes indisputably the transformation of the ponderable into the imponderable.
This transformation, so contrary to all the ideas bequeathed to us by science,is yet one of the most frequent phenomena in nature. It is daily produced before our eyes; but as formerly there existed no reagent to show it, it was not seen.
Chapter II: Electricity Considered as a Semi-Material Substance Generated by the Dematerialization of Matter.
(1) Radioactive and Electrical Phenomena
By pursuing our researches on the dissociation of matter, we have been progressively led, by the concatenation of experiments, to recognize that electricity, of which the origin is so entirely unknown, represents one of the most important products of the dissociation of matter, and in consequence can be considered as a manifestation of the intra-atomic energy liberated by the dissociation of atoms.
We have seen in the last chapter that the particles issuing from the radioactive substances constitute a substance derived from matter and possessing properties intermediate between matter and the ether. We shall now see that the products of the dissociation of matter are identical with those disengaged by the electrical machines in our laboratories. This generalization duly established, electricity in its entirety, and not simply in some of its forms, will appear to us as the connecting link between the world of matter and that of the ether.
We know that the products of the dissociation of all bodies are identical, and only differ by the extent of the power of penetration belonging to them and resulting from their difference of speed. We have established that are composed, (1) of positive ions of some volume at all pressures, and always comprising in their structure some material parts; (2) of negative ions formed of electric atoms termed electrons, which can surround themselves in the atmosphere with material neutral particles; (3) of electrons disengaged from all material components, and able, when their speed is sufficient, to create x-rays by their by their impact.
These various elements are generated by all bodies which are dissociated, and especially by spontaneously radioactive substances. They are also found with identical properties in the products obtained from Crookes’ tubes — that is to say, tubes through which, after exhaustion, electric discharges are sent. The only difference which exists between a Crookes’ tube in action and a radioactive body in the course of dissociation is, as we have already seen, that a second produces spontaneously — that is to say, under the influence of actions unknown to us — that which the first produces only under the influence of electric discharges.
Thus, then, electricity under various forms is always met with as the ultimate product of the dissociation of matter, whatever the process employed for its dissociation. It is this experimental fact which induced me to inquire if in a general way the electricity generated by any means — a static machine, for instance — might not be one of the forms of the dissociation of matter.
But, if the analogy between a Crookes’ tube and a radioactive body has at length become so evident that it is no longer disputed, it was less easy to establish an analogy between the phenomena taking place in that tube and electrical discharges in the air at ordinary pressure. Yet they are two identical things, though they differ in aspect. I will now demonstrate this.
When two metal rods connected with the poles of a generator are placed at a short distance from each other, the two electric fluids of contrary signs with which they are charged tend to recombine by virtue of their attractions. As soon as the electric tension becomes sufficiently strong to overcome the resistance of the air, they recombine violently, producing loud sparks.
Air, by reason of its insulating qualities, offers great resistance to the passage of electricity; but if we do away with this resistance by introducing the two electrodes in question into an exhausted receiver, the phenomena will be very different. Yet in reality, nothing has been created in the tube. All that is found there, both ions and electrons, were already in the electricity which has been brought into it. At the most there could have been formed there new electrons arising from the impact of those derived from the source of electricity against the particles of rarified gas still left in the tube.
If the effects obtained by a discharge in a vacuum tube are greatly different from those produced by the same discharge in a tube filled with air, the reason is that in the vacuum the electric particles are not impeded by molecules of air obstructing their course. In a vacuum alone can electrons obtain the speed necessary for the production of x-rays when they strike against the walls of the tube.
In on case, I repeat, are ions and electrons formed in the vacuum tube; they are brought there from outside. They are elements produced by the generator of electricity. It is not in a Crookes’ tube that matter is dissociated; it is taken there already dissociated.
If this be actually so, we ought to be able to meet, in the electric discharges produced in the air by an electric machine, with the various elements — ions and electrons — of which we have noted the existence in the Crookes’ tube, and which we know to be likewise generated by radioactive bodies.
Let us, then, examine the electricity furnished by the little static machines of our laboratories. We might take as a typical generator of electricity the most simple of all, a rod of glass or reason giving out electricity at a tension of from two or three thousand volts, but its use would be inconvenient for many experiments. The majority of electrical machines for laboratory use, however, only differ from this elementary apparatus by the greater surface presented by the body receiving friction, and because it is possible by the help of various artifices to collect separately the positive and negative electricity at two different extremities called poles.
The electricity issuing from a static machine possesses, however a considerable advantage from the point of view which interests us. Its output is very small, but the electricity issues from it at an extremely high tension, which may easily exceed 50,000 volts. It is just this circumstance which will enable us to demonstrate in the electric particles shot forth by the insulated poles of a static machine a strict analogy with the particles emitted by radioactive bodies. The electricity of a battery is evidently identical with that of static machines, but as it is turned out at the tension of a few volts only, it cannot produce the same effects of projection. It is probable also that the friction on which the construction of the static machines is based constitutes one means of dissociation of the atom, and consequently brings intra-atomic energy into play. This, doubtless, does not act on the molecular dissociation of compound bodies on which the battery is based, and this is probably why electricity is produced, but at a very low tension, which in the beast type of battery hardly exceeds two volts. If the output of a static machine could attain that of a small ordinary battery, it would constitute an exceedingly powerful agent capable of producing an enormous amount of industrial work. Suppose an electric machine worked by hand and giving out electricity at a tension of 50 kilovolts had an output of only two amperes — that is to say, the output of the very smallest battery — its yield would represent work to the extent of 100 kilowatts, or 136 hp/sec. Given that a considerable liberation of energy results from the dissociation of a very slight quantity of matter, the creation, in the future, of such a machine — that is to say, of an apparatus giving forth a power extremely superior to that expended in setting it in motion — can be considered possible. It is a problem of which the enunciation would have seemed altogether absurd some ten years ago. To solve it, it would be enough to find the means of placing matter in a state in which it can be easily dissociated. Now, we shall see that a simple ray of sunlight is a model agent of dissociation, it is probable that many others will be discovered.
If the terminal rods forming the poles are very wide apart, there will be seen at their extremities sheaves of tiny sparks named aigrettes (Figures 21 and 22) which are disengaged with a characteristic crackling noise. In the production of these elements dwells the fundamental phenomenon. It is by examining their composition that one notes the analogies which exist between the products of radioactive bodies and Crookes’ tubes, and those of an electrical machine.
The effects obtained with the elements which issue from the poles vary according to the disposition of these poles, and it is important to remember this first of all.
If we connect the two poles by a wire of any length, in the circuit of which we intercalate a galvanometer, the deviation of its magnetic needle will reveal to us the silent and invisible production called an electric current. It is identical with that which traverses our telegraph lines, and is constituted of a fluid formed, according to current ideas, by the conjunction of electric particles called electrons, which the machine constantly generates.
Instead of connecting the poles by a wire, let us bring them a little closer, keeping, however, a certain distance between them. The electric elements of contrary signs attracting one another, the aigrettes we have noticed elongate considerably, and with a fairly powerful machine they can be observed to form in the dark a cloud of luminous particles connecting the two poles (Figure 23).
f we bring the poles still closer to one another, or if, without bringing them closer, we increase the tension of the electricity by means of a condenser, the attractions between the electric particles of contrary signs become much more energetic. These particles now condense over a smaller number of lines or over one line only, and the recombination of the two electric fluids takes place under the form of contracted, noisy and luminous sparks (Figure 24). But they are still constituted of the same elements as before, for the distance between the poles or the elevation of the tension are the only factors we have made to vary.
The various effects we have just described are, naturally, very different from those we observe when the discharge occurs in a globe in which the air has been more or less rarified. The absence of the air produces these differences, but this gas exercises no action on the electric elements disengaged by generators of electricity. Of what do these elements consist?
(2) Composition and Properties of the Elements Emitted by the Poles of an Electric Machine. Their Analogy with the Emissions of Radioactive Bodies
To analyze these elements, they must be studied before the recombination of the electric particles — that is to say, when the poles are far apart and during the production of the aigrettes mentioned above.
We shall meet in them with the fundamental properties of the emissions of radioactive bodies, notably those of rendering air a conductor of electricity and of being themselves deviated by a magnetic field. From the positive pole of the machine start positive ions, and from the magnetic pole start those atoms of pure electricity of defined magnitude termed electrons. But in opposition to what happens in a vacuum, these electrons immediately become the center of attraction for gaseous particles and transform themselves into negative ions identical with those produced by the ionization of gases and in all forms of ionization.
These emissions of ions are accompanied by secondary phenomena, heat, light, etc., which we will examine later on. They are also accompanied by a projection of metallic dust torn from the poles, the speed of which, according to J.J. Thomson, can attain 1800 meters/sec.
The speed of projection of the ions which together form the aigrettes of the poles of a static machine, depends, naturally, on the electric tension. By raising it to several hundred thousand volts with a high frequency resonator, I have succeeded in compelling the electric particles of aigrettes to pass through, visibly (Figures 25 and 26) and without deviation, plates of insulating bodies half a millimeter thick. This is an experiment made some time back with the collaboration of Dr Oudin which I have already publishes with confirmatory photographs. In the experimental part of this book will be found the technical directions necessary for repeating it. Notwithstanding its importance, it made very little impression on physicists, though it was the first time that any one had succeeded in visibly transpiercing matter by electric atoms. By placing a glass plate between the barely separated poles of an induction coil, it can, as has long been known, be easily pierced; but this is a simple mechanical action. The aigrettes in our experiment go through bodies without in any way affecting them, just as does light. The direction of the charge proves that they are composed of positive ions.
The emission by the poles of an electric machine of electrons afterwards transformed into ions is accompanied by various phenomena which are met with in radioactive bodies under hardly different forms. To study them it is preferable to have points at the ends of the poles of the machine. It is then easily verified that what issues from an electrified point is identical with that which issues from a radioactive body.
The only actual difference is that the point does not at ordinary pressure produce x-rays. When it is desired to observe these later, the point must be connected with a conductor allowing the discharge to take place in an exhausted globe. In this case, the production of x-rays is abundant enough, even though only one pole be used, to render the bone sof the hand visible on a screen of barium platinocyanide.
The non-production of x-rays is otherwise in accordance with the theory. The x-rays are only generated by the impact of electrons having a great speed. Now, electrons formed in a gaseous medium at atmospheric pressure immediately change into ions by the addition of a retinue of neutral particles, and in consequence of this surcharge cannot keep up the speed necessary to generate x-rays.
Besides this property of generating x-rays, which, moreover, is not common to all radioactive bodies, the particles which disengage themselves from an electrified point are, I repeat, in every way comparable to those resulting from the dissociation of the atoms of all bodies. They render, in fact, air a conductor of electricity, as Branly showed long since, and are, as J.J. Thomson proved, deviated by a magnetic field.
The projection of particles of dissociated matter — that is to say, of ions — against the air molecules produces what is called the electric wind, by which a lamp can be extinguished and a whirl made to revolve, etc. It is in nowise due, as is constantly stated in all treatises on physics, to the electrification of the particles of the air, for a gas cannot be electrified by any process, save when it is decomposed. It is the kinetic energy of the ions transmitted to the molecules of the air which causes the displacement of these last.
The ions emitted by the points with which we have equipped the poles of an electric machine can produce fluorescent effects very similar to those observed with radium. They allow us to imitate the effects of the spinthariscope, which renders visible the dissociation of matter. One has only, according to M. Leduc, to bring within a few centimeters of a screen of barium platinocyanide in the dark a rod terminating in a very fine point connected with one of the poles — the positive one for choice — of a static machine, the other being earthed. If the screen is then examined with a magnifying glass, exactly the same shower of sparks as is in the spinthariscope will be observed, and the cause is probably identical.
The ions which issue from the poles of a static machine are not, as a rule, very penetrating — no more so, in fact, than the ions which form 99% of the emission of radium. However, I have been able to obtain very clear photographic impressions through a sheet of black paper by raising the electric tension sufficiently (Figure 27)
It is sufficient to place the object to be reproduced — a medal, for instance — over a photographic plate placed on a sheet of metal connected with one of the poles, while above the metal is fixed a road communicating with the other pole. A few small sparks suffice. The reproduction thus obtained cannot be attributed to the ultraviolet light produced by the discharge, seeing that the medal is separated from the pate by a sheet of black paper, and that under these conditions it is evident that no light, visible or invisible, would succeed in producing an impression of the details of the medal. This phenomenon is, however, rather complex, and its thorough discussion would carry us too far. Hence I do not insist on the point.
The ions emitted by electrified points are most often accompanied by the emission of light, a phenomenon likewise observed in certain radioactive bodies. The spectrum of this light is singularly spread out. It varies, in fact, according to my researches, from Hertzian waves not more than two or three millimeters long up to ultraviolet rays, of which the length is under 0.230 microns. If a solar diffraction spectrum is reckoned at one cm length, the spectrum of the electrified points would be on the same scale about 30 meters long. The production of ultraviolet light in the spectrum of electric sparks has long been known and utilized, but it is, I think, M. Leduc who first pointed out its presence in the aigrettes from points.
Yet, there remained in my mind a doubt as to its existence. In the whole region round an electrified point there exists an intense electric field capable of illuminating at some distance a Geissler tube, and perhaps also capable of illuminating fluorescent bodies. It was therefore necessary to eliminate its action.
To separate the action of the ultraviolet light from that which might be due to the electric field, I made use of the large 12-plate machine of Dr Oudin, whose action is so powerful that the aigrettes produced will illuminate a screen of barium platinocyanide or a Geissler tube at a distance of several meters.
The separation of the action of the electric field from that of the ultraviolet light has been realized in the most categorical manner by the following experiment effected with the cooperation of Dr Oudin:
Within a wooden cage enveloped in metallic gauze connected with the earth — so as to obviate all electric action — are placed Geissler tubes and metal plates, on which are traced letters with powdered barium platino-cyanide dissolved in gum Arabic. It is then found that the Geissler tubes, which shine brightly outside the cage, entirely cease to be luminous as soon as they are placed within it; while, on the contrary, the letters placed with the platino-cyanide and enclosed in the metallic cage continue to shine. The illumination of these latter is therefore solely due to the ultraviolet light.
It results, then, from what precedes that the formation of electric aigrettes is accompanied by an enormous production of invisible light. With a high frequency resonator the quantity is so great that illumination of the platino-cynanide can be produced up to a distance of more than 5 meters.
It is not for me to inquire here how ultraviolet light acts on fluorescent bodies. It is admitted, since the days of Stokes, that fluorescence comes from the transformation of invisible ultraviolet waves into larger, and for that reason, visible waves. But I must remark, by the way, that it would perhaps be simpler to suppose that fluorescence is due to the production — under the influence of ultraviolet light, the energetic ionizing action of which is well known — of slight atomic electric discharges from bodies which their structure renders capable of fluorescence.
In order to determine the limits of the ultraviolet produced in the foregoing experiments, I made use of various screens placed on the platino-cyanide screen, having first ascertained their transparency by means of the spectrograph used in former researches. The active part of the ultraviolet — that is to say, that which is capable of producing fluorescence — extends up to about 0.230 microns.
But an electrified point in discharge is not only a source of ultraviolet light; it also emits Hertzian waves, a fact totally unknown before my researches. I have indicated, in the experimental part of this work, the means employed to reveal them. By reason of their slight length, which probably does not exceed two millimeters, they hardly propel themselves farther than 40 to 50 cm (1).
[(1) The Hertzian wave which always accompanies electric sparks is no longer electricity, but it is a phenomenon of vibration of the ether, and only appears to differ from light in length of wave. Though it has gone forth from electricity, it is able to reassume the ordinary electric form whenever it touches any substance. It then communicates to the latter a charge verifiable by the electroscope, and can produce sparks…]
This production of Hertzian waves, visible light and invisible ultraviolet light, the constant companions of all emissions of electric particles, must be borne in mind, for it will furnish us later on with the key to the final process of the transformation of matter into vibrations of the ether when we take up this question in another chapter.
To sum up the foregoing, we may say that a body electrified by any means, notably friction, is simply a body whose atoms have undergone the commencement of dissociation. If the products of this dissociation are emitted in a vacuum, they are identical with those generated by the radioactive substances. If emitted in the air, they possess properties which only differ from those of radioactive emissions, from their speed being less.
Looked at from this point of view, electricity appears to us as one of the most important phases of the dematerialization of matter, and consequently as a form of intra-atomic energy. It constitutes, by reason of its properties, a semi-material substance intermediate between matter and the ether.
Chapter III: Comparison of the Properties of the Electric and the Material Fluids
I have shown that the electric particles and the fluid they form by their conjunction possess an inertia of a special nature differing from that of matter, which, joined to other properties, allows us to consider electricity in all its forms as composing an intermediate world between matter and the ether.
We shall again meet with the properties of this intermediate when we compare the laws of the flow of material fluids with those which regulate the distribution of the electric fluid. The differences between these different fluids are too visible for it to be necessary to indicate them at length. The electric fluid possesses a mobility which allows it to circulate in a metallic wire with the speed of light, which would be impossible for any material substance. It escapes the laws of gravitation while the equilibria of material fluids are governed by these laws alone, etc.
The differences are therefore very great, but the analogies are so likewise. The most remarkable of them is formed by the identity of the laws governing the flow of the material fluids and of the electric fluid. When one knows the former one knows the latter. This identity, which has taken some long time to establish, has now become classic. The most elementary treatises lay stress at every page on the assimilation which can be established between the distribution of electricity and that of liquids. They are careful, nevertheless, to point out that this assimilation is symbolical, and does not apply in every case. On looking a little closer into the matter, it has to be acknowledged, however, that it is in no wise a question of a simple assimilation. In a recent work the learned mathematician Bjerkness has shown that we have only to employ a certain system of electrical units for “the electric and magnetic formulas to become identical with the hydrodynamic formulas” (Les Actions Hydrodynamiques a Distance).
A few examples will at once make evident the resemblance of these laws. To give them more authority , I borrow them from a work of Cornu, published a few years ago (Correlation des Phenomenes d’Electricite Statique et Dynamiique).
It must first be remarked that the fundamental law of electricity, that of Ohm ( i = e/r ) might have been deduced from that movement of liquids in conduit pipes the properties of which have long been known to engineers.
Here is, however, for the most important cases, the comparison of the laws governing these various phenomena. One of the two columns applies to material fluids, the other to the electric fluid:
Material: The outflow of a liquid per unit of time, through a communication tube, is proportional to the difference of level and in inverse ratio to the resistance of the tube.
Electric: The intensity of a current in a given wire is proportional to the difference of potential existing between the two extremities, and in inverse ratio to the resistance.
Material: In the fall of a liquid through a pipe from one given level to another likewise fixed, the work at our disposal is equal to the product of the quantity of liquid by the differences in the levels.
Electric: In the passage of electricity through a wire from one given potential to another likewise fixed, the available work of the electric forces is equal to the product of the quantity of electricity by the difference of potential (fall) of electricity.
Material: The height of the level in a vessel increases in proportion to the quantity of liquid poured into it, and in inverse ratio to the section of the vessel.
Electric: The electric potential of a conductor increases in proportion to the quantity of electricity yielded (charge) and in inverse ratio to the capacity of the conductor.
Material: Two vessels filled with liquid placed in communications with each other are in a state of hydrostatic equilibrium when their levels are the same.
Electric: Two electrified conductors put in connection with each other are in a state of electrostatic equilibrium when their potentials are the same.
Material: The total quantity of liquid is then divided in proportion to the capacities of the vessels.
Electric: The total electric charge is then divided in proportion to the capacities of the conductors.
Cornu, who has carried these analogies much further than I have done here, is careful to remind us that these are assimilations of everyday use in practice, “an electric canalization must be treated like a distribution of water; at every point on the system one must make certain of the pressure necessary for the output”.
All the foregoing phenomena observed with the electric fluid as with the material fluids are the result of the disturbances of equilibrium of a fluid which obeys certain laws in regaining its equilibrium. Disturbances of equilibrium producing electric phenomena manifest themselves whenever by any means — friction, for instance — a separation is made between the two elements positive and negative, of which the electric fluid is supposed to be formed. The re-establishment of the equilibrium is characterized by the recombination of these two elements.
It is only, as I have already said, the phenomena resulting from disturbances of equilibrium which are accessible to us. The neutral electric fluid — the electric fluid which has not undergone any change of equilibrium — is a thing we may assume ot exist, but no reagent reveals it. But it is natural to believe that it has an existence as real as that of water enclosed in different reservoirs, between which there is on alteration of level capable of producing a mechanical effect which would reveal the presence of the liquid. What we call electricity proceeds solely from phenomena resulting from the displacement of the so-called electric fluid or of its elements.
We have just shown that electricity in motion acts like a material fluid, but why should these two substances, evidently so different, obey the same laws? Can the analogy of effects indicate the analogy of cause?
We know that this cannot be, Gravity has no appreciable action on electricity, while it is the sole reason of the laws governing the flow of liquids. If a liquid passes from a higher to a lower level, it is because it obeys gravitation, which is not at all the case with electricity. The potential of a fall of water — the difference in height between its starting point and its destination — is entirely due to gravity; and if water stored at a certain height represents energy, it is because it is attracted towards the center of the earth — an attraction which the walls that imprison it alone prevent its obeying. When, by tapping the reservoir, the water is allowed to flow, its fall produces, by reason of the earth’s attraction, a force corresponding to that used in raising it. Once on the level of the ground, it can no longer produce work.
If the gravitation which governs the flow of liquids is totally foreign to the phenomenon noted in the circulation of the electric fluid, what is the cause of this last? We know that this cause acts exactly like gravitation, but that it differs from it perforce.. Although its inmost nature is unknown to us, we can imagine it, for observation teaches us that the electric fluid, by virtue of the reciprocal repulsion of its molecules, presents a tendency to expansion which is termed tension. His tendency to expansion is also observed in gases, but there it differs from that of the electrical fluid. This last may, in fact, be retained on the surface of any insulated body, while gases diffuse immediately unless confined by the walls of a hermetically sealed vessel. All modes of energy, whether appearing in the form of quantity or of tension, obey the same general laws.
Thus we see continually occurring analogies — sometimes close, sometimes distant — between material things and things no longer material. It is precisely to the nature of these analogies between the ether and matter that are due the differences and the resemblances we have noted.
Chapter IV: The Movements of Electric Particles — The Modern Theory of Electricity
We have just shown the analogies of the electric and material fluids, and have noted that the laws of their distribution are identical.
These analogies become very slight, and even finally disappear when, instead of examining electricity in a fluid state, we study the properties of the elements which appear to form this fluid. We know that, according to current ideas, it is composed of particles called electrons. This conception of a discontinuous — granular — structure of electricity, which goes back to Faraday and Helmholtz, has been greatly strengthened by recent discoveries. Suitably interpreted, it will enable us to bring together in a bird’s-eye view not only the phenomena called radioactivity, but also those previously known in electricity and optics, such as the voltaic current, magnetism, and light. The majority of these phenomena may be produced by simple changes of equilibrium and movement of electric particles — that is to say, by displacements of the same thing. This we shall now demonstrate.
Instead of taking a hypothetical body such as an electric atom or an electron, we will take in its stead, in the majority of cases, a small electrified metal sphere. This simple substitution, which does not modify the theory, has the advantage of making experimental verifications possible.
According to whether this sphere is at rest, or in motion, or stopped when in motion, it will, as we shall see, produce the whole series of electrical and luminous phenomena.
Let us take, then, a little metallic sphere, insulate it by any of the ordinary means, and begin by electrifying it. Nothing can be more simple, since it has only to be placed in contact with a heterogeneous substance. Two different metals separated after contact, remain, as is well known, charged with electricity. Electrification by friction, on which the old machines were based, only represents one particular case of electrification by contact. Friction, in fact, only multiplies and renews the heterogeneous surfaces present.
This settled, let us remove our sphere to a little distance from the body with which it has first been put in contact. We then discover, by various means, that it is bound to this last by lines called lines of force, to which J.J. Thomson attributes a fibrous structure. These lines tend to bring together the bodies between which they exist, and have the property of repelling each other (Figure 6). Faraday compared them to springs stretched between the bodies. It is the extremities of these springs which constitute electric charges.
Let us now remove our sphere to a great distance from the substance which served to electrify it by its contact. The lines of force which connect the two bodies remain attached to each of them and radiate in straight lines into space (Figure 4). It is to them as a whole that the name of electric field is given.
If our sphere thus electrified and surrounded by radiating lines of force be well insulated, it will preserve its electric charge and produce all the phenomena observed in static electricity: attraction of light bodies, production of sparks, etc.
In this state of repose the electrified sphere possesses no magnetic action, as is proved by its absence of effect on a magnetized needle. It can only acquire this property after it has been set in motion. Let us then put it in motion and suppose its speed to be uniform. Our electrified sphere will acquire, form the mere fact of this motion, all the properties of an ordinary voltaic current — the current which circulates along the telegraph wires. It is even supposed, by the present theory, that there can be no other current than that produced by the movement of electrons.
But since our electrified sphere in motion acts in the same manner as a voltaic circuit, it ought to possess all its properties, and consequently its magnetic action. As a fact, it is surrounded, by its very motion, by circular lines of force constituting a magnetic field. These lines envelop the trajectory of the electrified body, composed, as we have said, of radiating straight lines.
This magnetic field which surrounds an electrified body in motion is not at all a merely theoretical view, but an experimental fact revealed by the deviation imparted to a magnetized needle placed near it. The existence of these circular lines of force surrounding a current can be easily shown by passing it through a straight rod of metal piercing, at right angles to its plane, a sheet of cardboard sprinkled with metal filings. These filings, attracted by the magnetic field of the current, arrange themselves in circles round the rod. So that by the mere fact of being set in motion an electrified body acquires the properties of an electric current and of a magnet. This is equivalent to saying that any variation of an electric field produces a magnetic field.
But this is not all. We have supposed the speed of our electrified sphere in motion to be uniform. Let us now vary this motion, either by moderating it or by accelerating it, and new phenomena very different to the above will appear.
The change of speed of the electrified body has for its consequence, by reason of the inertia of the electric particles, the production of the phenomena of induction — the birth of a new electric force which makes itself felt in a direction perpendicular to that of the magnetic lines, and consequently in the direction of the current. The variation of a magnetic field, therefore, has the effect of producing an electric field. It is on this phenomenon that are based many machines for the commercial production of electricity.
Another result of the superposition of this new force on the magnetic field of the electrified body whose movement has been modified, is the apparition in the ether of vibrations which propagate themselves therein with the speed of light. It is waves of this kind that are made use of in wireless telegraphy. In the electromagnetic theory of light accepted by all modern physicists, it is even supposed that these vibrations are the sole cause of light as soon as they are rapid enough to be perceived by the retina.
All through the foregoing we have supposed that the electrified body in motion is displaced in the air or in a gas at ordinary pressure. If it be made to move in a vey rarified medium, still new phenomena of a very different order appear. These are the cathode rays, in which the electric atom seems to be entirely disengaged from all material support, and the x-rays generated by the impact of these electric atoms against an obstacle. Here, evidently we can no longer have recourse to our picture of an electrified sphere of metal. We must consider the electric charge alone, freed from the material sphere which carried it.
Thus, then, as we said at the first, it is sufficient to modify the movement and the equilibrium of certain particles to obtain all the phenomena of electricity and light.
The above theory is verified, in most cases, by experiments. It is even, in reality, only a theoretical translation of experiment. So far as the phenomena of light are concerned, it had, however, prior to the researches of Zeeman, received no experimental confirmation. It was only by hypothesis that it was supposed to be the atoms of electricity, and not matter, which entered into vibration in incandescent bodies. It was thought that a flame contained electrons in motion around a position of equilibrium at a speed sufficient to give birth to electromagnetic waves capable of propagating themselves in the ether, and of producing when rapid enough the sensation of light to the eye.
To justify this hypothesis it was necessary to be able to deviate the electrons of flames by a magnetic field, since an electrified body in motion is deviable by a magnet. It is this deviation that Zeeman in producing by causing a powerful electromagnet to act on a flame. He then noticed that, on examining this flame with the spectroscope, the rays of the spectrum were deviated and doubled. From the distance between the spectrum lines thus separated, Zeeman was able to deduce the ratio e/m existing between the electric charge e of the electron in the flame and its mass m. This ratio was found to be exactly equal to that of the cathode particles in the Crookes tube. This measurement helps to prove the analogy of an ordinary flame with the cathode rays and radioactive bodies.
One here sees the fundamental part played by electrons in current ideas. A great number of physicists consider that they form the sole element of the electric fluid. “A body positively electrified”, says one of them, “is simply a body which has lost part of its electrons. The carrying of electricity from one point to another is realized by the transport of electrons from the place where there is an excess of positive electricity to the pace where there is an excess of negative electricity”. The aptness of elements to enter into chemical compounds should depend on the aptness of their atoms to acquire a charge of electrons. Their instability should result from the loss or excess of their electrons.
The theory of electrons allows us to explain many phenomena in a very simple manner, but it leaves many uncertainties still existing. By what mechanism does the propagation of electrons take place so rapidly in conducting bodies — a telegraph wire, for instance? How is it that electrons pass through metals while these last form an absolute obstacle to the most violent electric sparks? Why is it that electrons which can pass through metals are unable to cross an interval of 1 mm vacuum, as is proved by bringing together the two electrodes if an induction coil in a tube in which a complete vacuum has been made (Hittorf tube)? Even with a coil giving a spark of 50 cm in air, the electricity is powerless to overcome 1mm of vacuum (1).
[(1) By substituting fine needles for the electrodes I have sometimes obtained the passage of the current, but I draw no conclusions from the experiment, not being positive as to whether the vacuum in the tube was complete. But Cooper Hewitt has shown that the electric particles can be compelled to traverse a complete vacuum by first producing between the electrodes a short circuit.]
The electron has become at the present day a sort of fetish for many physicists, by means of which they think to explain all phenomena. There has been transferred to it the properties formerly attributed to the atoms, and many consider it the fundamental element of matter, which would thus be only an aggregation of electrons.
Of its innermost structure we can say nothing. It is not giving a very certain explanation to assure us that it is constituted by a vortex of the ether comparable to a gyrostat. Its dimensions in any case should be extraordinarily small, but can it be considered indivisible, which would imply that it possessed an infinite rigidity? May it not be itself of a structure as complicated as that now attributed to the atom, and may it not, like the latter, form a veritable planetary system? In the infinity of worlds, magnitude and minuteness have only a relative value.
What appears to us most likely in the present state of our knowledge is that under the name of electricity are confused extremely different things, have in the one common quality of finally producing certain electric phenomena. This is an idea I have already dwelt on several times. But we have no more right to call electricity everything which produces electricity than we have to call heat all causes capable of generating heat.