The study of the stars inevitably leads us to consider the advancing movement in the midst of them of the sun and its attendant train of planets. There can be no reasonable doubt—and the thought is an astounding one—that we are engaged on a voyage through space, without starting-point or goal that we can know of, but which may prove not wholly uneventful. Its progress may possibly bring about, as millenniums go by, changes powerfully influential upon human destinies; nay, an incident in its course may, at any time, by the inscrutable decree of Providence, terminate the terrestrial existence of our race, and consign the records of its civilisation, in dust and cinders, to the arid bosom of a dead planet. A curious sense of helplessness, tempered, however, by a higher trust, is produced as we thus vividly realise, perhaps for the first time, how completely we are at the mercy of unknown forces—how irresistibly our little ‘lodge in the vast wilderness’ of the universe is swept onward over an annual stretch of perhaps five hundred millions of miles, under the mysterious sway of bodies reduced by their almost infinite distances to evanescent dimensions.

But, as things are constituted, the translation of the sun's household is a necessity, albeit one of startling import to ourselves. The stellar system is maintained by the balance of forces, and motion is the correlative of force.