Or possibly, astronomers and the earth's inhabitants generally might find out the reverse, though the knowledge would not avail them much, seeing that the messenger who would bring it would be the King of Terrors himself. It was well, perhaps, that Newton's discovery of the law of gravitation, and the application of this law to the comets of 1680 and 1682 (the latter our old friend Halley's comet, then properly so called as studied by him), came in time to aid in removing to some slight degree the old superstitions respecting comets. For in England many remembered the comets of the Great Plague and of the Great Fire of London. These comets came so closely upon the time of the Plague and the Fire respectively, that it was not wonderful if even the wiser sort were struck by the coincidence and could scarcely regard it as accidental. It is not easy for the student of science in our own times, when the movements of comets are as well understood as those of the most orderly planets, to place himself in the position of men in the times when no one knew on what paths comets came, or whither they retreated after they had visited our sun. Taught as men were, on the one hand, that it was wicked to question what seemed to be the teaching of the Scriptures, that changes or new appearances in the heavens were sent to warn mankind of approaching troubles, and perplexed as they were, on the other, by the absence of any real knowledge respecting comets and meteors, it was not so easy as we might imagine from our own way of viewing these matters, to shake off a superstition which had ruled over men's minds for thousands of years.