In place of such 'wild and whirling words,' I have endeavoured to state the sober conclusions of the best workers and thinkers as to the nature and origin of the world in which we live, and of the universe which on all sides surrounds us. I leave it to my readers to decide which is the more trustworthy guide. FOOTNOTES: [18] _Transactions of Royal Dublin Society_, vol. vi. (ser. ii.), part xiii. 'Of Atmospheres upon Planets and Satellites.' By G. Johnstone Stoney, F.R.S., etc. etc. [19] _Knowledge_, June 1903. [20] M. Camille Flammarion, in _Knowledge_, June 1903. CHAPTER XV THE STARS--HAVE THEY PLANETARY SYSTEMS? ARE THEY BENEFICIAL TO US? Most of the writers on the Plurality of Worlds, from Fontenelle to Proctor, taking into consideration the enormous number of the stars and their apparent uselessness to our world, have assumed that many of them _must_ have systems of planets circling round them, and that some of these planets, at all events, _must_ possess inhabitants, some, perhaps, lower, but others no doubt higher than ourselves. One of our well-known modern astronomers, writing only ten years ago, adopts the same view. He says: 'The suns which we call stars were clearly not created for our benefit. They are of very little practical use to the earth's inhabitants. They give us very little light; an additional small satellite--one considerably smaller than the moon--would have been much more useful in this respect than the millions of stars revealed by the telescope. They must therefore have been formed for some other purpose.... We may therefore conclude, with a high degree of probability, that the stars--at least those with spectra of the solar type--form centres of planetary systems somewhat similar to our own.'[21] The author then discusses the conditions necessary for life analogous to that of our earth, as regards temperature, rotation, mass, atmosphere, water, etc., and he is the only writer I have met with who has considered these conditions; but he touches on them very briefly, and he arrives at the conclusion that, in the case of the stars of solar type, it is probable that _one_ planet, situated at a proper distance, would be fitted to support life. He estimates roughly that there are about ten million stars of this type, that is, closely resembling our sun, and that if only one in ten of these has a planet at the proper distance and properly constituted in other respects, there will be one million worlds fitted for the support of animal life. He therefore concludes that there are probably many stars having life-bearing planets revolving round them.