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COMETS AND THE MILKY WAY.

and the generally infantile condition of physical science in the 4th century B.C., it was only natural that the a priori method, or guessing, should greatly predominate in the cosmical theories of that time. But Aristotle’s strength did not lie in his imagination. In this faculty he was inferior to other philosophers whom in analytical power he far surpassed. Thus Alexander von Humboldt says of him (‘Cosmos,’ vol. i. note 48), “the great influence which the writings of Aristotle exercised on the whole of the Middle Ages, renders it a cause of extreme regret that he should have been so opposed to the grander and juster views of the fabric of the universe entertained by the more ancient Pythagorean school.” There was, in fact, a want of sublimity in the fancy of Aristotle, and it so happened that he sometimes contemptuously rejected hypotheses which were not only more beautiful, but more true, than his own. We have seen that this was the case with regard to the earth’s position in the cosmical system. And the same thing occurred as to the nature of comets. The Pythagoreans had declared comets to be “planets of long revolution;” but Aristotle, rejecting this supposition, affirmed them to be transient meteors of our atmosphere, formed out of luminous or incandescent matter which had been thrown off by the stars. And to explain the reason why comets are so rare, he said that the matter out of which they are composed is constantly used up in forming the Milky Way. (‘Meteorol.’ I. viii.) “The nebulous belt, then, which traverses the vault of the heavens, is regarded by the