The shape given to the representations of stars in old pictures and engravings is a puzzle. Why do they represent a star by the shape of a star-fish? No star ever looks like that, or produces a picture of that shape on the retina. The thing is purely conventional. The shape which we call “star-shaped”—a term we apply to flowers and other things—is not in the least like a real star as seen by an unprejudiced person. What one really sees is an ill-defined point of light. The pretended conventional star of ancient drawings perhaps arose from the simple artifice of picturing tongue-like flames around or upon any representation of a fire or a source of light—“to show what it was meant to be.” Then the notions of perfection and symmetry in regard to the celestial bodies led to the “tongues” being arranged for the purposes of draughtsmanship as perfectly symmetrical-pointed rays of a six- or eight-limbed geometrical design—and latterly it is possible that the mystical figure known as the “pentacle” was utilised by astrologers and others as the emblem of a star. However they arose, neither the weird and astonishing representations of mediæval times nor the geometrical decorative “stars” of later date seem to have any relation to an attempt to represent a star as it really appears to the human eye and the interpreting brain behind it. [Illustration: FIG. 45.—Copied from a portion of the Bayeux Tapestry, showing Harold’s men looking with superstitious wonder at the comet which appeared in the heavens immediately before the departure of William the Conqueror’s expedition to England in A.D. 1066. That comet was none other than Halley’s comet, and has now returned, and is visible from the earth for the twelfth time since the Conquest. (From a lecture on Halley’s comet, delivered in 1908, by Professor H. H. Turner, F.R.S., Halley’s successor in Oxford, published by the Clarendon Press.)]