Considering then the whole bearing of the evidence, I refuse to accept the unsupported dicta of those who would have us believe that our admitted position not far from the centre of the stellar universe is a mere temporary coincidence of no significance whatever; or that our sun and hosts of other similar orbs near to us have come together by an accident, and are being dispersed into surrounding space, never to meet again. Until this is proved by indisputable evidence, it seems to me far more probable that we are moving in an orbit of some kind around the centre of gravity of a vast cluster, as determined by the investigations of Kapteyn, Newcomb, and other astronomers; and, consequently, that the nearly central position we now occupy may be a permanent one. For even if our sun's orbit should have a diameter a thousand times that of Neptune, it would be but a small fraction of the diameter of the Milky Way; while so vast is the scale of our universe, that it might be even a hundred thousand times as great and still leave us deeply immersed in the solar cluster, and very much nearer to the dense central portion than to its more diffused outer regions. Here the subject may be left for the present. After having studied the evidence afforded by the essential conditions of life-development on the earth, and the numerous indications that these conditions do not exist on any of the other planets of the solar system, it may be again touched upon in a general review of the conclusions arrived at. FOOTNOTES: [4] _Nature_, October 26, 1899. [5] _The System of the Stars_, p. 385. [6] This account of Professor Kapteyn's research is taken from an article by Miss A.M. Clerke in _Knowledge_, April 1893. [7] _The Stars_, p. 256. The region here referred to is that where the Milky Way has its greatest width (though nearly as wide in the part exactly opposite), and where it may perhaps extend somewhat in our direction. Miss A.M. Clerke informs me that in April 1901 Kapteyn withdrew the conclusions arrived at in 1893, as being founded on illegitimate reasoning as to the relation of parallaxes to proper motions. But as this relation is still accepted, under certain limitations, by Professor Newcomb and other astronomers, who have arrived independently at very similar results, it seems not improbable that, after all, Professor Kapteyn's conclusions may not require very much modification. Professor Newcomb also tells us (_The Stars_, p. 214, footnote) that he has seen the latest of Professor Kapteyn's papers, down to 1901; but he does not therefore express any doubt as to his own conclusions as here referred to. [8] See _Knowledge_ and _The Fortnightly Review_ of April 1903. [9] Sir R. Ball in an article in _Good Words_ (April 1903) says that luminosity is an exceptional phenomenon in nature, and that luminous stars are but the glow-worms and fire-flies of the universe, as compared with the myriads of other animals. CHAPTER IX