This, roughly, constitutes the working of the planetary atmospheric machine, which, while in itself completely reversible and self-contained, forms also at the same time the source and the sink of all the energy working in the secondary transformations. In the ceaseless rounds of these transformations which form planetary phenomena it links together the initial and concluding stages of each series by a reversible process. Energy is thus stored and restored continuously. The planet thus neither gains nor loses energy of axial motion; so far as its energy properties are concerned, it is entirely independent of every external influence. Its uniformity of rotation is absolutely maintained. Each planet of the system will, in the same way, be an independent and conservative unit. 11. _Review of Cosmical System--General Function of Energy_ Reviewing the system as a whole, the important part played by energy in its constitution is readily perceived. The source of the energy which operates in all parts of the system is found in that energy originally applied (§ 3). When the system is finally constituted, this energy is found distributed amongst the planets, each of which has received its share, and each of which is thereby linked to the primary by its influence. It is part of this same energy which undergoes transformation in virtue of the orbital movements of the planets in the field of the gravitative influence. Again, it is found in the form of planetary axial energy, and thence, under the influence of various incepting agencies, it passes in various forms through the whole gamut of planetary phenomena, and finally functions in the atmospheric machine. Every phenomenon of the system, great or small, is, in fact, but the external evidence either of the transformation or of the transmission of this energy--the outward manifestation of its changed or changing forms. Its presence, which always implies its transformation (§ 4), is the simple primary condition attached to every operation. The primal mass originally responded to the application of energy by the presentation of phenomena. Every material portion of the system will similarly respond according to circumstances. Energy is, in fact, the working spirit of the whole cosmical scheme. It is the influence linking every operation of the system to the original transformations at the central axis, so that all may be combined into one complete and consistent whole. It is to be noted, however, that although they have a common origin the orbital energy of each planetary mass is entirely distinct from its energy of axial rotation, and is not interchangeable therewith. The transformation of the one form of energy in no way affects the totality of the other.