In this year of the celebration of the tercentenary of Milton’s birth, it is not a little curious to find that John Milton, himself a scholar of St. Paul’s School, wrote those lines when Edmund Halley, the future Astronomer Royal, had just entered the same great school, then standing in St. Paul’s Churchyard, as it did when I was “one of the fishes,” and used to see men hanging in the Old Bailey—I once saw five[5]—on Monday mornings as I passed on my way to the school. To a Pauline it is not without significance that the return of Halley’s comet is awaited within a year of Milton’s tercentenary, and that the greatest astronomer and the greatest poet of their age were London boys and Paulines. Ancient records tell of comets of gigantic size, of the shape of a sword, the head as big as the moon, and so on. There is no reason to suppose that within historic times there have been any much bigger than that of 1858. Milton, in the lines above quoted, was not referring to an imaginary comet, but to one which actually did appear when he was a boy of ten (1618), in the constellation called Ophiuchus. It was of enormous size, the tail being recorded as longer even than that of 1858. It was held responsible by educated and learned men of the day for disasters. Evelyn says in his diary, “The effects of that comet, 1618, still working in the prodigious revolutions now beginning in Europe, especially in Germany.” The comet of 1665 was, with equal assurance, regarded as the cause of the Great Plague of London. In that year was published the first number of the _Philosophical Transactions_ of the Royal Society of London, then recently founded “for the promotion of natural knowledge.” It contains an account of a paper by a learned French gentleman, M. Auzout, in which an attempt is made to predict the movements among the stars of the comet of 1664. Astronomers had long known and been able to predict the movements of the planets and the swinging of the constellations, but, as the French author observes, “all the world had been hitherto persuaded that the motions of comets were so irregular that they could not be reduced to any laws.” He also hoped, by examining the movements of the comets of 1664 and 1665, to determine “the great question whether the earth moves or not.” At that time the earth was “suspected” to move round the sun, but no proof of that motion had been given. M. Auzout did not succeed in his laudable attempt, simply because Newton’s great discovery of the law of gravitation had not then been made.