It will be objected that some of the names herein quoted are not recognized as astronomers. I can only say that in every instance I have found references to the writings and essays of those that might be objected to in the pages of the "Observatory," and other reputable astronomical journals, and in no instances accompanied by adverse comment or criticism. If astronomers--even the distinguished Schiaparelli--quote these names in scientific memoirs, I may venture to do the same in a book written for the general reader. The objection, however, has always presented itself with every controversy; it was conspicuously marked in the passionate discussions over Darwin's "Origin of Species." The intelligent laity recognized the truth of Darwin's proposition long before the zoölogist began to waver. Essays by the unprofessional supporting Darwin's contention were discredited because the writers were not trained naturalists. The history of invention is crowded with instances where devices and processes have been invented by men whose trades or professions were the least likely to enable them to originate such ideas. II IMMEASURABLE DISTANCES OF SPACE _It is therefore perfectly reasonable to suppose that beings not only animated but endowed with reason inhabit countless worlds in space._ SIMON NEWCOMB. Until within recent centuries, man has not only believed that he and his kind were the only intelligent creatures in the universe, but that the little round ball on which he lived was the dominant part thereof. So rooted for ages was this conviction that it became fixed in man's mental structure, and hence the survival of the idea that still lingers in the minds of a few to-day. The conclusion was natural, however, for the behavior of the starry heavens and the Sun and the Moon seemed sufficient evidence that man, and the surface upon which he lived, was the centre of the universe. The stars were bright points of light, the Moon a silver disk, and the Sun a heat and light giving ball of fire, equally diminutive and not far away. Let one realize for a moment the experience of these early people. Everything aerial, with the exception of feathery birds, fluffy bats and flying insects, was composed of the lightest particles--cottony seeds, reluctantly falling snow-flakes, motes in the air, smoke and vaporous cloud, and, in contrast, the rock-foundationed and irregular surface upon which the people dwelt, and flat as far as man had reached. What wonder, then, that man viewed these brilliant points and dazzling disks as objects of no great size and not far away, hauled across the heavens by unseen spirits of some kind. The marvel of it all is, not that they believed as they did, but that any other views of cosmography could have been established. And yet the successive increments of astronomical knowledge, founded apparently on the soundest mathematics, were adopted in their turn.