reasoning from already accepted properties of matter and energy, to arrive at a true conception of a possible natural order of phenomena. It is obvious, however, that the solar system forms the prototype of the system described above. The motion of the earth and other planets is continuously occurring under the influence of gravitation, thermal, luminous, and other incepting fields which link them to the central mass, the sun. As a result of the action of such fields, energy transformations arise which form the visible phenomena of the system in all its parts, each transformation, whether associated with animate or inanimate matter, being carried out through the medium of some arrangement of matter hereafter referred to as a material machine. The conditions are precisely as laid down above. The system is dominated, in its separate units, and as a whole, by the great principle of the conservation of energy. Each planetary mass, as it revolves in space, is, so far as its energy properties are concerned, an absolutely conservative unit of that system. At the same time, however, each planetary mass remains absolutely dependent on the primary for those great controlling or incepting influences which determine the transformation of its inherent energy.

In the special case of the earth, which will be dealt with in some detail, it is the object of this work to show that its property of complete energy conservation is amply verified by terrestrial phenomena. The extension of the principle from the earth to the whole planetary system has been made on precisely the same grounds as Newton extended the observed phenomena to his famous generalisation with respect to gravitation.