It is typical of the scientist of the past that he was dependent on phenomena brought about by a highly developed experimental technique for becoming aware of certain properties of the electrical force, whereas for the realistic observer these properties are revealed at once by the most primitive electric phenomena. We remember Eddington's description of the positron as 'negative material', and his subsequent remarks, which show the paradoxical nature of this concept if applied to the hypothetical interior of the atom (Chapter IV). The quite primitive phenomenon of electrical repulsion and attraction shows us the same thing in a manner of which it is not difficult to form a conception.

The discovery of the phenomena we call electromagnetic depended on the possibility of producing continuous electrical processes. This arose with Volta's invention. When it became necessary to find a concept for the process which takes place in an electric conductor between the poles of a galvanic cell, the concept of the 'current', borrowed from hydrodynamics, suggested itself. Ever since then it has been the rule to speak of the existence of a current within an electric circuit; its strength or intensity is measured in terms of a unit named in honour of Ampere.

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.

In our newly developed terminology we may say that magnetism, as a polarity of the second order, represents a field of force both of whose poles are situated within finite space, and that in the macro-telluric mother-field this situation is such that the axis of this field coincides more or less with the axis of the earth's physical body. Thus the magnetic polarization of the earth as a letter in nature's script bids us rank it alongside other phenomena which in their way are an expression of the earth's being polarized in the north-south direction.

There is no friction unless the surfaces of the rubbed bodies have a structure that is in some way interfered with by the rubbing, while at the same time they offer a certain resistance to the disturbance. This resistance is due to a characteristic of matter, commonly called cohesion. Now we know that the inner coherence of a physical body is due to its point-relationship, that is to the gravitational force bound up with it. Indeed, cohesion increases as we pass from the gaseous, through the liquid, to the solid state of matter.

Modern physics itself, with the help of Faraday's field-concept, describes these phenomena as caused by pressure - resulting from the meeting in space of two similar electrical fields - and suction - resulting from the meeting of two dissimilar fields. In the first case the space between the two electrically charged bodies assumes a degree of density, as if it were filled with some elastic material. In the second instance the density of the space where the two fields intermingle is lower than that of its surroundings. Here, clearly, we have a state of negative density which acts on the electrically charged bodies just as a lowering of pressure acts on a gas: in both cases movement occurs in the direction leading from the higher to the lower density. Electricity thus shows itself capable of producing both gravity and levity effects, thereby once more confirming our picture of it.

This concept of the current has had a fate typical of the whole relation of human thought to the facts connected with electricity. Long after it had been coined to cover phenomena which in themselves betray no movement of any kind between the electrical poles, other phenomena which do in fact show such movements became known through Crookes's observations. Just as in the case of atomism, they seemed to prove the validity of the preconceived idea of the current. Soon, however, radiant electricity showed properties which contradicted the picture of something flowing from one pole to the other. The cathode rays, for instance, were found to shoot forth into space perpendicularly from the surface of the cathode, without regard to the position of the anode. At the same time Maxwell's hydrodynamic analogy (as our historical survey has shown) led to a view of the nature of electricity by which this very analogy was put out of court. By predicting certain properties of electricity which come to the fore when its poles alternate rapidly, he seemed to bring electricity into close kinship with light. Mathematical treatment then made it necessary to regard the essential energy process as occurring, not from one pole to the other, but at right angles to a line joining the poles (Poynting's vector). This picture, however, satisfactory though it was in the realm of high frequency, failed as a means of describing so-called direct-current processes.

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.

The Austrian geographer, E. Suess, in his great work The Countenance of the Earth, first drew attention to the fact that an observer approaching the earth from outer space would be struck by the onesided distribution and formation of the earth's continents. He would notice that most of the dry land is in the northern hemisphere, leaving the southern hemisphere covered mainly with water. In terms of the basic elementary qualities, this means that the earth is predominantly 'dry' in its northern half, and 'moist' in its southern.

Whilst a body's cohesion is due to gravity, its spatial extendedness is, as we have seen, due to levity. If we reduce the volume of a piece of physical matter by means of pressure, we therefore release levity-forces previously bound up in it, and these, as always happens in such cases, appear in the form of free heat. Figuratively speaking, we may say that by applying pressure to matter, latent levity is pressed out of it, somewhat like water out of a wet sponge.