Sometimes the sanctity of the antique stones was secured in the later faith by connecting them with some legend or episode of the orthodox religion. Thus the ancient sacred stone kept at Delphi--no doubt the original oracle of that great shrine, as the rude Delian block was the precursor of the Delian Apollo--was explained with reference to the later Hellenic belief by the myth that it was the stone which Kronos swallowed in mistake for Zeus: an explanation doubtless due to the fact that this boulder was kept, like Monigan’s Irish idol and the Samoan god, wrapped up in flannel; and in the myth, Rhea deceived Kronos by offering him, instead of Zeus, a stone wrapped in swaddling-bands. There is here indeed food for much reflection. The sacred stone of the Trœzenians, in like manner, lay in front of the temple; but it was Hellenised, so to speak, by the story that on it the Trœzenian elders sat when they purified Orestes from the murder of his mother. In modern Europe, as everybody knows, a similar Christianisation of holy wells, holy stones, and holy places has been managed by connecting them with legends of saints, or by the still simpler device of marking a cross upon them. The cross has a threefold value: in the first place, it drives away from their accustomed haunts the ancient gods or spirits, always envisaged in early Christian and mediæval thought as devils or demons; in the second place, it asserts the supremacy of the new faith; and in the third place, by conferring a fresh sanctity upon the old holy place or object, it induces the people to worship the cross by the mere habit of resorting to the shrine at which their ancestors so long worshipped. Gregory’s well-known advice to St. Augustine on this matter is but a single example of what went on over all Christendom. In many cases, crosses in Britain are still found firmly fixed in old sacred stones, usually recognisable by their unwrought condition. The finest {116}example in Europe is probably the gigantic monolith of Plumen in Brittany, topped by an insignificant little cross, and still resorted to by the peasants (especially the childless) as a great place of worship. The prehistoric monuments of Narvia in the Isle of Man have been Christianised by having crosses deeply incised upon them. Other cases, like the Black Stones of Iona, which gave sanctity to that Holy Isle long before the time of Columba, will doubtless occur at once to every reader. With many of the Scotch sculptured stones, it is difficult to decide whether they were originally erected as crosses, or are prehistoric monuments externally Christianised.