What I claim to have done is, to have brought together the various facts and phenomena _they_ have accumulated; to have set forth the hypotheses by which _they_ account for them, or the results to which the evidence clearly points; to have judged between conflicting opinions and theories; and lastly, to have combined the results of the various widely-separated departments of science, and to have shown how they bear upon the great problem which I have here endeavoured, in some slight degree, to elucidate. As such a large body of facts and arguments from distinct sciences have been here brought together, I have given a rather full summary of the whole argument, and have stated my final conclusions in six short sentences. I then briefly discuss the two aspects of the whole problem--those from the materialistic and from the spiritualistic points of view; and I conclude with a few general observations on the almost unthinkable problems raised by ideas of Infinity--problems which some of my critics thought I had attempted in some degree to deal with, but which, I here point out, are altogether above and beyond the questions I have discussed, and equally above and beyond the highest powers of the human intellect. BROADSTONE, DORSET, _September_ 1903. 'The wilder'd mind is tost and lost, O sea, in thy eternal tide; The reeling brain essays in vain, O stars, to grasp the vastness wide! The terrible tremendous scheme That glimmers in each glancing light, O night, O stars, too rudely jars The finite with the infinite!' J.H. DELL. CONTENTS CHAP. PAGE I. EARLY IDEAS, 1 II. MODERN IDEAS, 7 III. THE NEW ASTRONOMY, 24 IV. THE DISTRIBUTION OF THE STARS, 47 V. DISTANCES OF STARS: THE SUN'S MOTION, 73 VI. UNITY AND EVOLUTION OF THE STAR-SYSTEM, 99 VII. ARE THE STARS INFINITE? 135 VIII. OUR RELATION TO THE MILKY WAY, 156 IX. THE UNIFORMITY OF MATTER AND ITS LAWS, 183 X. THE ESSENTIAL CHARACTERS OF ORGANISMS, 191 XI. PHYSICAL CONDITIONS ESSENTIAL FOR LIFE, 206 XII. THE EARTH IN RELATION TO LIFE, 218 XIII. THE ATMOSPHERE IN RELATION TO LIFE, 243 XIV. THE OTHER PLANETS ARE NOT HABITABLE, 262 XV. THE STARS: HAVE THEY PLANETS? ARE THEY USEFUL TO US? 282 XVI. STABILITY OF THE STAR-SYSTEM: IMPORTANCE OF CENTRAL POSITION: SUMMARY AND CONCLUSION, 295