At this point in our discussion it is possible to raise, without risk of confusing the issue, the question of the distribution of the two electric forces over the pairs of substances concerned in the generation of electricity both by friction and in the galvanic way. This distribution seems to contradict the picture to which the foregoing observations have led us, for in both instances the 'sulphurous' substances (resin in one, the nobler metals in the other) become bearers of negative electricity; while the 'saline' substances (glass and the corrosive metals) carry positive electricity. Such a criss-crossing of the poles-surprising as it seems at first sight - is not new to us. We have met it in the distribution of function of the plant's organs of propagation, and we shall meet a further instance of it when studying the function of the human eye. Future investigation will have to find the principle common to all instances in nature where such an interchange of the poles prevails. While the electric field arising round an electrified piece of matter does not allow any recognition of the absolute characteristics of the two opposing electrical forces, we do find them revealed by the distribution of electricity in the human body. Something similar holds good for magnetism. Only, to find the phenomena from which to read the absolute characteristics of the two sides of the magnetic polarity, we must not turn to the body of man but to that of the earth, one of whose characteristics it is to be as much the bearer of a magnetic field as of gravitational and levitational fields. There is significance in the fact that even to-day, when the tendency prevails to look for causes of natural phenomena not in the macrocosmic expanse, but in the microscopic confines of space, the two poles of magnetism are named after the magnetic poles of the earth. It indicates the degree to which man's feeling instinctively relates magnetism to the earth as a whole. 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.