It would be an interesting inquiry to follow Copernicus through the train of reasoning which induced him to venture upon these changes; but it is impossible to attempt this, or to explain his system, within the limits to which this sketch is necessarily confined. In one point of view, his peculiar merit appears not to be in general sufficiently insisted upon. If he had merely suggested the principles of his new theory, he would doubtless have acquired, as now, the glory of lighting upon the true order of the solar system, and of founding thereupon a new school of astronomy: but his peculiar and characteristic merit, that by which he really earned his reputation, and which entitles him to take rank by the side of Newton in the history of astronomy, was the result of his conviction, that if his principles were indeed true, they would be verified by the examination of details, and the persevering resolution with which he thereupon set himself to rebuild an astronomical theory from the foundation. This was the reason, at least as much as the fear of incurring censure, why he delayed the publication of his system for thirty-six years. During the greater part of that time he was employed in collecting, by careful observation, the materials of which it is constructed: the opinions on which it is based, comprising the whole of what was afterwards declared to be heretical and impious, were widely known to be entertained by him long before the work itself appeared. He delayed to announce them formally, until he was able at the same time to show that they were not random guesses, taken up from a mere affectation of novelty; but that with their assistance he had compiled tables of the planetary motions, which were immediately acknowledged even by those whose minds revolted most against the means by which they were obtained, to be far more correct than any which till then had appeared.