In former times those who cultivated science, or rather those who were called learned, generally based their philosophy on the doctrines of Aristotle; which, as they had been taught to reverence them from their infancy, had become almost interwoven with their constitutions. Hence, though time has unfolded to us their errors, during several centuries, suspicion never hinted their fallibility. The doctrine of the revolutions of the earth, and other planets; of gravitation, magnetism, and other properties now known to belong to matter; have each in their turn met with a strong opposition from the most learned men living at the time of their discovery. But, notwithstanding this opposition, in all ages, a few bold, enquiring minds have had the firmness to dissent from the established doctrines of the schoolmen, and to lay the foundation of new systems, the correctness of which subsequent improvements in science have more or less demonstrated to the world. Although nearly six thousand years have elapsed since man has been placed upon the earth, he yet knows but little of its formation. Notwithstanding all our enterprise, all our boasted acquirements, and discoveries, its true form yet remains uncertain; and although admitted that it is not quite eight thousand miles in diameter, we still have never explored its extent. A space of nearly forty degrees of latitude remains as little known to us, as if it were a part of the surface of Saturn, or an orb revolving round a star of the eighth magnitude. We know nothing of the inhabitants of those regions, or what kind of animate beings exist in them. It was a prevailing opinion among the ancients, the correctness of which they for ages never called in question, that the temperate zones of our globe were alone habitable.――The torrid zone they imagined was composed of nothing but sandy deserts, scorched up by the vertical and insupportable beams of a burning sun. The frigid zones, they believed were begirt with eternal snows, and "thick ribbed ice," which rendered them inaccessible to man, and incapable of supporting animal or vegetable life. Hence none ventured to approach them.