Page:The story of the comets.djvu/259

. XIV. It is well known that many celebrated Greek philosophers paid much attention to astronomical phenomena, and therefore to comets amongst other things. Anaxagoras explained comets to be produced by the concourse of planets and by their combined splendour. Democritus of Abdera, following Anaxagoras, conceived that comets were the result of a concourse of certain planetary stars. Apollonius and Zeno are reputed to have upheld very similar ideas, but these two are not quoted by Sir G. C. Lewis, the most modern chronicler of ancient scientific ideas.

Lewis's summary of Greek opinion is so conveniently concise that I make no apology for transcribing what he said. "Comets were the object of much speculation among the early Greek astronomers; the opinions of Anaxagoras and Democritus, of the Pythagoreans, and of Hippocrates of Chios, and of his disciple Æschylus, respecting them, are reported and analysed by Aristotle. Differing in other respects they agreed in considering the comets to be planets. Against this general position, Aristotle argues by saying that the planets are always confined within the zodiacal band; whereas many comets have been seen without these limits, and it has often happened that more than one comet has been visible at the same time. He points out further, that some of the fixed stars have been seen with a tail. For this fact, he refers to the general report of the Egyptian observers: he adds, however, that he had himself seen a star in the leg of the constellation Sirius, with a faint tail. He states that it could scarcely be seen if the vision was fixed directly upon it, but it was more visible if the sight was turned slightly on one side. Against the theory that comets were a congeries of planets, he remarks that all those which had been seen in his time disappeared without setting, while they were still above the horizon: they faded away gradually, and left no trace either of one planet or several. He adds that the great comet in the Archonship of Asteius (373 ) appeared in the winter, in a clear sky: on the first day it was not visible,