let us imagine ordinary molecules to be developed as vortex-rings out of something much finer and more subtle than themselves, which we have agreed to call the invisible universe. But we may pursue the same train of thought still further back, and imagine the entities which constitute the invisible universe immediately preceding ours to be in themselves ephemeral, although not nearly to the same extent as the atoms of our universe, and to have been formed in their turn as vortex-rings out of some still subtler and more enduring substance. In fine, there is no end to such a process, but we are led on from rank to rank of the order imagined by Dr. Thomas Young, or by Professor Jevons, when he says that ‘the smallest particle of solid substance may consist of a vast number of systems united in regular order, each bounded by the other, communicating with it in some manner yet wholly incomprehensible.’ Our meaning will be made clear by the following diagram. Here (0) denotes the evanescent smoke-ring, (1) the visible universe, (2) the invisible universe immediately anterior to the present, (3) that of the next order, and so on. Again, (0) is developed out of (1); (1) is developed out of (2); (2) out of (3); (3) out of (4), and so on. Further, (1) both precedes and follows (0) in point of duration, while (2) bears a similar relation to (1), (3) to (2), and so on. [Illustration: (Five concentric rings marked 0 to 4)] Again, the material substance of (0) is a phenomenon of that of (1), that of (1) a phenomenon of that of (2), and so on. Go back as far as we choose, we are only led from one phenomenon to another; so that, as far as their essential nature is concerned, all are equally phenomenal, and the mind cannot repose in any order as its ultimate haven of thought, but is driven inexorably forward to look for something different. We see too, that, as far as energy is concerned, that of (1) is greater than that of (0), inasmuch as (1) develops (0), that of (2) greater than that of (1), inasmuch as (2) develops (1), and so on. Therefore, if we go infinitely far back, we shall be led to a universe possessing infinite energy, and of which the intelligent developing agency possesses infinite energy. It will also be seen that, inasmuch as all these various orders exist together at the present moment, the energy of their sum must be infinite, and this energy will never come to an end. In other words, the Great Whole is infinite in energy, and will last from eternity to eternity. [If merely to prevent, in future, the possibility of a mistake which has already been made by some of our critics, including even Professor Clifford, it may be well to sketch here very briefly another and quite different concrete illustration of our idea.