[Sidenote: Corrections of anthropocentric ideas.] As man advances in knowledge he discovers that of his primitive conclusions some are doubtless erroneous, and many require better evidence to establish their truth incontestably. A more prolonged and attentive examination gives him reason, in some of the most important particulars, to change his mind. He finds that the earth on which he lives is not a floor covered over with a starry dome, as he once supposed, but a globe self-balanced in space. The crystalline vault, or sky, is recognized to be an optical deception. It rests upon the earth nowhere, and is no boundary at all; there is no kingdom of happiness above it, but a limitless space, adorned with planets and suns. Instead of a realm of darkness and woe in the depths on the other side of the earth, men like ourselves are found there, pursuing, in Australia and New Zealand, the innocent pleasures and encountering the ordinary labours of life. By the aid of such lights as knowledge gradually supplies, he comes at last to discover that this, our terrestrial habitation, instead of being a chosen, a sacred spot, is only one of similar myriads, more numerous than the sands of the sea, and prodigally scattered through space. [Sidenote: Consequence of discovering the form of the earth.] Never, perhaps, was a more important truth discovered. All the visible evidence was in direct opposition to it. [Sidenote: Detection of its insignificance.] The earth, which had hitherto seemed to be the very emblem of immobility, was demonstrated to be carried with a double motion, with prodigious velocity, through the heavens; the rising and setting of the stars were proved to be an illusion; and, as respects the size of the globe, it was shown to be altogether insignificant when compared with multitudes of other neighbouring ones--insignificant doubly by reason of its actual dimensions, and by the countless numbers of others like it in form, and doubtless, like it, the abodes of many orders of life. And so it turns out that our earth is a globe of about twenty-five thousand miles in circumference. The voyager who circumnavigates it spends no inconsiderable portion of his life in accomplishing his task. It moves round the sun in a year, but at so great a distance from that luminary that, if seen from him, it would look like a little spark traversing the sky. It is thus recognized as one of the members of the solar system. [Sidenote: Other solar bodies.] Other similar bodies, some of which are of larger, some of smaller dimensions, perform similar revolutions round the sun in appropriate periods of time.