To recapitulate the more general conditions, we find the earth, alike with other planetary masses, pursuing a defined orbital path, and rotating with uniform angular velocity in the lines or under the influence of the gravitation, thermal, luminous, and other incepting fields (§§ 17, 18, 19) which originate in the sun. Its axial rotation, in these circumstances, gives rise to all the secondary transformations (§ 9) of terrestrial axial energy, which in their operation provide the varied panorama of terrestrial phenomena. Terrestrial axial energy is thus diverted into terrestrial secondary processes. Each of these processes is found to be united to or embodied in a definite material machine (§§ 27-30), and is, accordingly, limited in nature and extent by the physical properties and incepting factors associated with the materials of which the machine is composed. By ordinary methods of transmission, energy may pass from one material to another, that is to say from one machine to another, and by this means definite chains of energy processes are constituted, through which, therefore, passes the axial energy originally transformed by the action of the sun. These series or chains of energy processes are also found to be one and all linked at some stage of their progress to the general atmospheric machine (§ 29). The energy operating in them is, in every case, after many or few vicissitudes according to the nature of the intermediate operations, communicated to the gaseous atmospheric material. By the movement of this material in the working of the atmospheric machine (§ 38) the energy is finally returned in its original form of axial energy of rotation. The sun's action is thus in a manner to force the inherent rotatory energy of the planet into the cyclical secondary operations, all of which converge alike towards the general atmospheric mechanism of return. The passage of the energy through the complete secondary operations, and its re-conversion into its original axial form, may be rapid or slow according to circumstances. In equatorial regions, where the influence of the sun's incepting fields is most intense, we find that the inherent planetary axial energy is communicated with great rapidity through the medium of the aqueous vapour to the air masses. By the movement of the latter it may be just as rapidly returned, and the whole operation completed in a comparatively short interval of time. In the same equatorial regions, the transformations of axial energy which are manifested in plant life attain their greatest perfection and vigour. But in this case the complete return of the operating energy may be very slow. The stored energy of tropical vegetation may still in great part remain in the bosom of the earth, awaiting an appropriate stimulus to be communicated to more active material for the concluding stages of that cyclical process which had its commencement in the absorption of axial energy into plant tissue. The duration of the