Excerpt

The Galaxy, or Milky Way, surrounds the borders of our island in space like a stellar garland, and when openings appear in it they are, by contrast, far more impressive than the general darkness of the interstellar expanse seen in other directions. Yet even that expanse is not everywhere equally dark, for it contains gloomy deeps discernible with careful watching. Here, too, contrast plays an important part, though less striking than within the galactic region. Some of Sir William Herschel's observations appear to indicate an association between these tenebrious spots and neighbouring star clouds and nebulae. It is an illuminating bit of astronomical history that when he was sweeping the then virgin heavens with his great telescopes he was accustomed to say to his sister who, note-book in hand, waited at his side to take down his words, fresh with the inspiration of discovery: Prepare to write; the nebulae are coming; here space is vacant.