Our picture of the process which is commonly called an electric current is now sufficiently complete to allow us to make a positive statement concerning the direction in which it takes place. Let us once more sum up: In order that this process may occur, there must be present in an electrically excited part of space a body which does not suffer the particular polarization of space bound up with such a field. As a result, the electrical field disappears, and in place of it appear a thermal field and a magnetic field, both having as their axis the line connecting the two poles. Each of them spreads out in a direction at right angles to this fine. Obviously, therefore, it is in this radial direction that the transformation of the electrical into the thermo-magnetic condition of space must take place.
This picture of the electro-thermo-magnetic happening, as regards its direction, is in complete accord with the result obtained (as indicated earlier) by the mathematical treatment of high-frequency phenomena. Once more we see that quite primitive observations, when properly read, lead to findings for which scientific thought had to wait until they were forced on it by the progress of experimental technique - as even then science was left without a uniformly valid picture of the dynamic behaviour of electricity.
Further, we can now see that when we apply electricity to practical purposes, we are in fact seldom using electricity itself, but other forces (that is, other combinations of gravity and levity) which we make effective by making electricity disappear. The same is true of most of the methods of measuring electricity. As a rule, the force which sets the instrument in motion is not electricity but another force (magnetism, heat, etc.) which appears in the place of the vanishing electricity. Thus the so-called intensity of an electric current is actually the intensity with which the electricity in question disappears! Electricity serves us in our machines in the same way that food serves a living organism: it gets itself digested, and what matters is the resulting secondary product.
Just as alterations in the electrical condition of space give rise to the appearance of a magnetic field, any alteration of the magnetic state of space gives rise to the appearance of an electrical field. This process is called electromagnetic induction. With its discovery, the generation of electricity through friction and in the galvanic way was supplemented by a third way. By this means the practical use of electricity on a large scale became possible for the first time. If our picture of the two earlier processes of generating electricity is correct, then this third way must also fit into the picture, although in this case we have no longer to do with any direct atomization of physical matter. Our picture of magnetism will indeed enable us to recognize in electromagnetic induction the same principle on which we found the two other processes to rest.
Magnetism is polarized gravity. Hence it has the same characteristic of tending always to maintain an existent condition. In bodies subject to gravity, this tendency reveals itself as their inertia. It is the inertia inherent in magnetism which we employ when using it to generate electricity. The simplest example is when, by interrupting a 'primary current', we induce a 'secondary current' in a neighbouring circuit. By the sudden alteration of the electric condition on the primary side, the magnetic condition of the surrounding space is exposed to a sudden corresponding change. Against this the magnetic field 'puts up' a resistance by calling forth, on the secondary side, an electrical process of such direction and strength that the entire magnetic condition remains first unaltered and then, instead of changing suddenly, undergoes a gradual transformation which ideally needs an infinite time for its accomplishment (asymptotic course of the exponential curve). This principle rules every process of electromagnetic induction, whatever the cause and direction of the change of the magnetic field.
We know that electromagnetic induction takes place also when a conductor is moved across a magnetic field in such a way that, as the technical term goes, it 'cuts' the field's lines of force. Whereas the process discussed above is employed in the transformer, this latter process is used in generation of electricity by dynamo. We have seen that a magnetic field imparts to the relevant part of space qualities of density which otherwise prevail only in the interior of solid masses. We remember further that the appearance of electricity, in the two other modes of generating it, is caused by the loosening of the coherence of the material substance. A similar loosening of the coherence of the magnetic field takes place when its field-lines are cut by the movement of the conductor across it. Just as heat occurs when we move a solid object through a liquid, electricity occurs when we move a conductor across a magnetic field. In each case we interfere with an existing levity-gravity relationship.
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Having established thus far the picture of both electricity and magnetism which shows each as an outcome of certain levity-gravity interactions, we now ask how, in particular, negative and positive electricity on the one hand and north and south magnetism on the other are determined by these interactions. Let us again begin with electricity.
We remember that Galvani was led to his observations by the results of Walsh's study of the electric fishes. While Galvani clung to the view that in his own experiments the source of the electrical force lay within the animal bodies, Volta saw the fallacy of that. He then conceived the idea of imitating with purely inorganic substances the set-up which Galvani had come upon by accident. The paradoxical result - as he himself noticed with surprise - was that his apparatus turned out to be a close replica of the peculiar organ with which the electric fishes are endowed by nature. We must now take a closer view of this organ.
The electric organ of such a fish consists of many thousands of little piles, each made up of a very great number of plates of two different kinds, arranged in alternating layers. The two kinds differ in substance: in one case the plate is made from a material similar to that present in the nervous system of animals; in the other the resemblance is to a substance present in the muscular system, though only when the muscles are in a state of decay. In this way the two opposing systems of the animal body' seem to be brought here into direct contact, repeated many thousands of times.