In an age following van Helmont's discovery of the gaseous state of matter and the statement of the Contra Levitatem maxim, men were bound to think that the circulation of atmospheric moisture was limited to the three stages of liquid, vaporous (peculiar to the clouds, etc.) and the invisible aeriform condition. Yet the role played by clouds in the myths of early peoples shows that they were once given a quite different status, between the 'created' and 'uncreated' worlds. Our observations lead to a corresponding conception, but along the path of knowledge, guided by sense-perception, as befits our own age.

As we know of mass through a definite sense-perception, so we know of heat. In the latter case we rely on the sense of warmth. In Chapter VIII we took the opportunity to test the objectivity of the information received through this sense. Still, one-eyed, colour-blind observation is naturally unable to take account of these sense-messages. To this kind of observation nothing is accessible, we know, except spatial displacements of single point-like entities. Hence we find Bacon and Hooke already attributing the sensation of warmth to minute fast-moving particles of matter impinging on the skin. Some time later we find Locke taking up the same picture. We see from this how little the mechanical theory of heat owes to empirical facts. For even in Locke's time the connexion between heat and mechanical action, as recognized to-day, was completely unknown.

Science treated Mayer in the same way as it treated Howard. It took from him what it wanted for its purpose without concerning itself with the epistemological principle which had led him to his discovery. Thus it was that Mayer's discovery led to most important consequences for the development of modern technical devices, whereas it was the fate of his guiding idea to be first derided, then misunderstood and finally forgotten. The consequence was that the knowledge of the numerical equilibrium between created and expended energy in the economy of nature has widened more and more the abyss separating spirit and matter in human life, instead of leading, as indeed it might have done, to a bridging of the abyss. The thought, therefore, regarding the appearing and disappearing of measurable cosmic substance, to which we are led when following Goethe's method of observing nature, stands in no sort of contradiction to what Mayer himself conceived as the relation of the various forms of energy to one another, and the maintenance of the numerical balance between them.

With this picture of solid matter as being held in spatial extension by its subjection to gravity and levity alike, we proceed to a study of the liquid and gaseous states of matter, while taking into account the role of heat in bringing these states about.

In this respect Tillandsia provides an instance 'worth a thousand, bearing all within itself. For what nature here unmistakably demonstrates serves as an eye-opener to a universal fact of the plant kingdom and of nature in general. The problem of the so-called trace-elements may serve as an illustration of this.

In discussing Howard's discovery of the stages of cloud-formation we found something lacking, for it was clear that the three stages of cloud proper - stratus, cumulus and cirrus - have a symmetry which is disturbed by the addition of a fourth stage, represented by the nimbus. This showed that there was need for a fifth stage, at the top of the series, to establish a balanced polarity. We can now clear up this question of a fifth stage, as follows.

With this idea firmly rooted in his mind, modern man had no difficulty in using it to explain both thermal expansion and the effect of heat on the different states of matter, and so, finally, these states themselves. Thermal expansion was thus attributed to an increase in the average distance between the assumed minute particles, caused by an increase in their rate of movement; the liquid state was held to differ from the solid, and similarly the gaseous from the liquid, by the interspaces between the particles becoming relatively so great that the gravitational pull between them became too weak to hold them together.

Having thus determined our standpoint with regard to the thermodynamic theory of heat and the law of conservation, we may proceed to the study, first of the phenomenon of thermal expansion, and then of the effect of heat on the various states of physical matter, by applying to them, unimpeded by any preconceived mechanistic idea, what we have learnt through our previous studies. We must start by developing a proper picture of the dynamic condition of matter in the solid state.

Following out our method of seeking to gain knowledge of a phenomenon by regarding it as part of a greater whole, let us ask what sort of change a portion of physical substance undergoes in its relation to the earth as a whole when, for instance, through the influence of heat, it passes from a solid to a liquid state. Here we must keep in mind that it is part of the nature of a liquid to have no form of its own. The only natural boundary of a liquid substance is its upper surface. Since this surface always lies parallel with the surface of the earth it forms part of a sphere, the centre point of which is identical with that of the gravitational centre of the earth. The passage of a portion of matter from solid to liquid thus signifies that it ceases to possess a centre of gravity of its own and is now merely obedient to the general gravity-field of the earth. We can thus speak of a transition of matter from the individual to the planetary condition. This is what heat brings about when a solid body melts.

Modern agricultural chemistry has found of a number of chemical elements that their presence in the soil in scarcely traceable amounts is necessary in order to enable the plant to unfold healthily its latent characteristics. All sorts of deficiencies in cultivated plants have led to a recognition that the soil is impoverished of certain elements by intensive modern cultivation, and that it is to the lack of these elements that the deficiencies are due. Much work has meanwhile been done in classifying the various deficiencies and in devising ways of giving the soil chemical substitutes for what is lacking.