Scientific view: the earth a globe; its size determined; its position in and relations to the solar system.--The three great voyages.--Columbus, De Gama, Magellan.-- Circumnavigation of the earth.--Determination of its curvature by the measurement of a degree and by the pendulum. The discoveries of Copernicus.--Invention of the telescope.-- Galileo brought before the Inquisition.--His punishment.-- Victory over the Church. Attempts to ascertain the dimensions of the solar system.-- Determination of the sun's parallax by the transits of Venus.--Insignificance, of the earth and man. Ideas respecting the dimensions of the universe.--Parallax of the stars.--The plurality of worlds asserted by Bruno.-- He is seized and murdered by the Inquisition. I HAVE now to present the discussions that arose respecting the third great philosophical problem--the nature of the world. An uncritical observation of the aspect of Nature persuades us that the earth is an extended level surface which sustains the dome of the sky, a firmament dividing the waters above from the waters beneath; that the heavenly bodies--the sun, the moon, the stars--pursue their way, moving from east to west, their insignificant size and motion round the motionless earth proclaiming their inferiority. Of the various organic forms surrounding man none rival him in dignity, and hence he seems justified in concluding that every thing has been created for his use--the sun for the purpose of giving him light by day, the moon and stars by night. Comparative theology shows us that this is the conception of Nature universally adopted in the early phase of intellectual life. It is the belief of all nations in all parts of the world in the beginning of their civilization: geocentric, for it makes the earth the centre of the universe; anthropocentric, for it makes man the central object of the earth. And not only is this the conclusion spontaneously come to from inconsiderate glimpses of the world, it is also the philosophical basis of various religious revelations, vouchsafed to man from time to time. These revelations, moreover, declare to him that above the crystalline dome of the sky is a region of eternal light and happiness--heaven--the abode of God and the angelic hosts, perhaps also his own abode after death; and beneath the earth a region of eternal darkness and misery, the habitation of those that are evil. In the visible world is thus seen a picture of the invisible. On the basis of this view of the structure of the world great religious systems have been founded, and hence powerful material interests have been engaged in its support. These have resisted, sometimes by resorting to bloodshed, attempts that have been made to correct its incontestable errors--a resistance grounded on the suspicion that the localization of heaven and hell and the supreme value of man in the universe might be affected.