A comet is so called from the hair-like stream of light or “tail,” which stretches to a greater or less length from its bright head or “nucleus.” A large comet, when seen to greatest advantage, may have a tail which stretches across one-third of the “vault of heaven,” and may be reckoned by astronomers at as much as one hundred and twenty million miles long. Donati’s comet—which some of my readers will remember, as I do, when it visited us in 1858—was of this imposing size. Halley’s comet, on the other hand, when it was last “here,” namely, in 1835, showed a tail estimated by astronomers to be fifty million miles long. The tail was more than twice as long when Halley’s comet appeared in 1456. There was a big comet “on view” in 1811—the year celebrated for its wine—and in recent times a fine comet appeared in 1861, and another (Coggia’s comet) in 1874. The ancient records of comets are naturally full of exaggeration. Up to Milton’s time—two hundred and fifty years ago—they caused the greatest terror and excitement by their sudden appearance in the sky. This is due to the fact that mankind from the very earliest periods of which we have record has not merely gazed at the “starry host” by night in solemn wonder, but even in early prehistoric times studied and watched the stars so as to know much of their movements and regular comings and goings. The earliest priests, the earliest “wise men,” were those who knew the stars and could fix the seasons by their place; the earliest temples—Stonehenge, and others older still—were star-temples or observatories, and their priests were astronomers. To such a pitch did reverence for star-knowledge attain that our ancestors confused the astral signs of changing season and cycle with the cause itself of change, and attributed all kinds of mundane events and each man’s fate to “the influence of the stars.” Hence the sudden appearance of a flaming comet was held to be a portent, and was always supposed either to foretell or even to produce some very unpleasant event, such as a big war or a pestilence, or the death of some one supposed to be of consequence. The earliest Greek poetry enshrines the superstition, which is handed on by Virgil, and finally by Milton. In Pope’s translation of the _Iliad_ we find the helmet of the terrible Achilles described as shining “Like the red star, that from his flaming hair Shakes down diseases, pestilence, and war.” And Milton, in 1665, in his _Paradise Lost_, wrote— “On th’other side, Incenst with indignation, Satan stood Unterrifi’d; and like a comet burn’d, That fires the length of Ophiuchus huge In th’ Arctic sky, and from his horrid hair Shakes pestilence and war.”