The principal object of this part of the work is to illustrate clearly the general nature, the working, and the limits of secondary processes. For this purpose, the author has found it best to refer to certain more or less mechanical contrivances. The apparatus made use of is merely that utilised in everyday work for experimental or other useful purposes. It is essentially of a very simple nature; no originality is claimed for it, and no apology is offered for the apparent simplicity of the particular energy operations chosen for discussion. In fact, this feature has rather led to their selection. In scientific circles to-day, familiarity with the more common instances of energy operations is apt to engender the belief that these processes are completely understood. There is no greater fallacy. In many cases, no doubt, the superficial phenomena are well known, but in even the simplest instances the mechanism or ultimate nature of the process remains unknown. A free and somewhat loose method of applying scientific terms is frequently the cloak which hides the ignorance of the observer. No attempt will here be made to go beyond the simple phenomena. The object in view is simply to describe such phenomena, to emphasise and explain certain aspects of already well-known facts, which, up to the present, have been neglected.
In some of the operations now to be described, mechanical or "work" energy is the active agent, and material masses are thereby caused to execute various movements in the lines or field of restraining influences. For ordinary experimental convenience, the material thus moved must of necessity be matter in the solid form. The illustrative value of our experimental devices, however, will be very distinctly improved if it be borne in mind that the operations of mechanical energy are not restricted to solids only, but that the various processes of transformation and transmission here illustrated by the motions of solid bodies may, in other circumstances, be carried out in a precisely similar fashion by the movements of liquids or even of gases. The restrictions imposed in the method of illustration are simply those due to the limitations of human experimental contrivance. Natural operations exhibit apparatus of a different type. By the movements of solid materials a convenient means of illustration is provided, but it is to be emphasised that, so far as the operations of mechanical energy are concerned, the precise form or nature of the material moved, whether it be solid, liquid, or gaseous, is of no consequence. To raise one pound of lead through a given distance against the gravitative attraction of the earth requires no greater expenditure of energy than to raise one pound of hydrogen gas through the same distance. The same principle holds in all operations involving mechanical energy.
Another point of some importance which will be revealed by the study of secondary operations is that every energy process has in some manner definite energy limits imposed upon it. In the workings of mechanical or "work" energy it is the mass value of the moving material which, in this respect, is important. The mass, in fact, is the real governing factor of the whole process (§ 20). It determines the maximum amount of energy which can be applied to the material, and thus controls the extent of the energy operation.
But in actions involving the molecular energies, the operation may be limited by other considerations altogether. For example, the application of heat to a solid body gives rise to certain energy processes (§ 27). These processes may proceed to a certain degree with increase of temperature, but a point will finally be attained where change of state of the heated material takes place. This is the limiting point of this particular operation. When change of state occurs, the phenomena will assume an entirely different aspect. The first set of energy processes will now be replaced by a set of operations absolutely different in nature, themselves limited in extent, but by entirely different causes. The first operation must thus terminate when the new order appears. In this manner each process in which the applied energy is worked will be confined within certain limiting boundaries. In any chain of energy operations each link will thus have, as it were, a definite length. In chemical reactions, the limits may be imposed in various ways according to the precise nature of the action. Chemical combination, and chemical disruption, must be looked on as operations which involve not only the transformation of energy but also the transformation of matter. In most cases, chemical reactions result in the appearance of matter in an entirely new form—in the appearance, in fact, of actually different material, with physical and energy properties absolutely distinct from those of the reacting constituents. This appearance of matter in the new form is usually the evidence of the termination, not only of the particular chemical process, but also of the energy process associated with it. Transformation of energy may thus be limited by transformation of matter.
Examples of the limiting features of energy operations could readily be multiplied. Even a cursory examination of most natural operations will reveal the existence of such limits. In no case do we find in Nature any body, or any energy system, to which energy may be applied in unlimited amount, but in every case, rigid energy limits are imposed, and, if these limits are exceeded, the whole energy character of the body or system is completely changed.
14. Incepting Energy Influences
In experimental and in physical work generally, it has been customary, in describing any simple process of energy transformation, to take account only of those energies or those forms of energy which play an active part in the process—the energy in its initial or applied form and the energy in its transformed or final form. This method, however, requires enlarging so as to include another feature of energy transformation, a feature hitherto completely overlooked, namely, that of incepting energy. Now, this conception of incepting energy, or of energy as an incepting influence, is of such vital importance to the author's scheme, that it is necessary here, at the very outset, to deal with it in some detail. To obtain some idea of the general nature of these influences, it will be necessary to describe and review a few simple instances of energy transformation. One of the most illuminating for this purpose is perhaps the familiar process of dynamo-electric transformation.
A spherical mass A (Fig. 1) of copper is caused to rotate about its central axis in the magnetic field in the neighbourhood of a long and powerful electro-magnet. In such circumstances, certain well-known transformations of energy will take place. The energy transformed is that dynamical or "work" energy which is being