'If there were but one nebula, it would be a curious coincidence were this one nebula so placed in the distant regions of space as to agree in direction with a starless spot in our own sidereal system. If there were but two nebulæ, and both were so placed, the coincidence would be excessively strange. What, then, shall we say on finding that there are thousands of nebulæ so placed? Shall we believe that in thousands of cases these far-removed galaxies happen to agree in their visible positions with the thin places in our own galaxy? Such a belief is impossible.' He then applies the same argument to the distribution of the nebulæ as a whole:--'In that zone of celestial space where stars are excessively abundant, nebulæ are rare, while in the two opposite celestial spaces that are farthest removed from this zone, nebulæ are abundant. Scarcely any nebulæ lie near the galactic circle (or plane of the Milky Way); and the great mass of them lie round the galactic poles. Can this also be mere coincidence?' And he concludes, from the whole mass of the evidence, that 'the proofs of a physical connection become overwhelming.' Nothing could be more clear or more forcible; but Spencer not being an astronomer, and writing in a comparatively little read periodical, the astronomical world hardly noticed him; and it was from ten to fifteen years later, when Mr. R.A. Proctor, by his laborious charts and his various papers read before the Royal and Royal Astronomical Societies from 1869 to 1875, compelled the attention of the scientific world, and thus did more perhaps than any other man to establish firmly the grand and far-reaching principle of the essential unity of the stellar universe, which is now accepted by almost every astronomical writer of eminence in the civilised world. THE EVOLUTION OF THE STELLAR UNIVERSE Amid the enormous mass of observations and of suggestive speculation upon this great and most interesting problem, it is difficult to select what is most important and most trustworthy. But the attempt must be made, because, unless my readers have some knowledge of the most important facts bearing upon it (besides those already set forth), and also learn something of the difficulties that meet the inquirer into causes at every step of his way, and of the various ideas and suggestions which have been put forth to account for the facts and to overcome the difficulties, they will not be in a position to estimate, however imperfectly, the grandeur, the marvel, and the mystery of the vast and highly complex universe in which we live and of which we are an important, perhaps the most important, if not the only permanent outcome. THE SUN A TYPICAL STAR It being now a recognised fact that the stars are suns, some knowledge of our own sun is an essential preliminary to an inquiry into their nature, and into the probable changes they have undergone.