The expression 'astronomical myth' has recently been used, on the title-page of a translation from the French, as synonymous with false systems of astronomy. It is not, however, in that sense that I here use it. The history of astronomy presents the records of some rather perplexing observations, not confirmed by later researches, but yet not easily to be explained away or accounted for. Such observations Humboldt described as belonging to the myths of an uncritical period; and it is in that sense that I employ the term 'astronomical myth' in this essay. I propose briefly to describe and comment on some of the more interesting of these observations, which, in whatever sense they are to be interpreted, will be found to afford a useful lesson. It is hardly necessary, perhaps, to point out that the cases which I include here I regard as really cases in which astronomers have been deceived by illusory observations. Other students of astronomy may differ from me as respects some of these instances. I do not wish to dogmatise, but simply to describe the facts as I see them, and the impressions which I draw from them. Those who view the facts differently will not, I think, have to complain that I have incorrectly described them. At the outset, let me point out that some observations which were for a long time regarded as mythical have proved to be exact. For instance, when as yet very few telescopes existed, and those very feeble, Galileo's discovery of moons travelling round Jupiter was rejected as an illusion for which Satan received the chief share of credit. There is an amusing and yet in one aspect almost pathetic reference to this in his account of his earlier observations of Saturn. He had seen the planet apparently attended on either side by two smaller planets, as if helping old Saturn along. But on December 4, 1612,[54] turning his telescope on the planet, he found to his infinite amazement not a trace of the companion planets could be seen; there in the field of view of his telescope was the golden-tinted disc of the planet as smoothly rounded as the disc of Mars or Jupiter. 'What,' he wrote, 'is to be said concerning so strange a metamorphosis? Are the two lesser stars consumed after the manner of the solar spots? Have they vanished or suddenly fled? Has Saturn, perhaps, devoured his children? Or were the appearances, indeed, illusion or fraud with which the glasses have so long deceived me as well as many others to whom I have shown them? Now, perhaps, is the time come to revive the well-nigh withered hopes of those who, guided by more profound contemplations, have discovered the fallacy of the new observations, and demonstrated the utter impossibility of the existence of those things which the telescope appears to show. I do not know what to say in a case so surprising, so unlooked for, and so novel. The shortness of the time, the unexpected nature of the event, the weakness of my understanding, and the fear of