But Homer says nothing of this comet. If Homer had introduced a comet, we may be sure it would not have shaken sparkles from its blazing tail. Homer said simply that 'Pallas rushed from the peaks of heaven, like the bright star sent by the son of crafty-counselled Kronus (as a sign either to sailors, or the broad array of the nations), from which many sparks proceed.' Strangely enough, Pingré and Lalande, the former noted for his researches into ancient comets, the latter a skilful astronomer, agree in considering that Homer really referred to a comet, and they even regard this comet as an apparition of the comet of 1680. They cite in support of this opinion the portent which followed the prayer of Anchises, 'Æneid,' Book II. 692, etc.: 'Scarce had the old man ceased from praying, when a peal of thunder was heard on the left, and a star, gliding from the heavens amid the darkness, rushed through space followed by a long train of light; we saw the star,' says Æneas, 'suspended for a moment above the roof, brighten our home with its fires, then, tracing out a brilliant course, disappear in the forests of Ida; then a long train of flame illuminated us, and the place around reeked with the smell of sulphur. Overcome by these startling portents, my father arose, invoked the gods, and worshipped the holy star.' It is impossible to recognise here the description of a comet. The noise, the trail of light, the visible motion, the smell of sulphur, all correspond with the fall of a meteorite close by; and doubtless Virgil simply introduced into the narrative the circumstances of some such phenomenon which had been witnessed in his own time. To base on such a point the theory that the comet of 1680 was visible at the time of the fall of Troy, the date of which is unknown, is venturesome in the extreme. True, the period calculated for the comet of 1680, when Pingré and Lalande agreed in this unhappy guess, was 575 years; and if we multiply this period by five we obtain 2875 years, taking 1680 from which leaves 1195 years B.C., near enough to the supposed date of the capture of Troy. Unfortunately, Encke (the eminent astronomer to whom we owe that determination of the sun's distance which for nearly half a century held its place in our books, but has within the last twenty years been replaced by a distance three millions of miles less) went over afresh the calculations of the motions of that famous comet, and found that, instead of 575 years, the most probable period is about 8814 years. The difference amounts only to 8239 years; but even this small difference rather impairs the theory of Lalande and Pingré.[41]