If there was a genuine Celtic belief in an island of the dead, it could have been no more than a local one, else Cæsar would not have spoken as he does of the Celtic Dispater. Such a local belief now exists on the Breton coast, but it is mainly concerned with the souls of the drowned.[1178] A similar local belief may explain the story told by Procopius, who says that Brittia (Britain), an island lying off the mouth of the Rhine, is divided from north to south by a wall beyond which is a noxious region. This is a distorted reminiscence of the Roman wall, which would appear to run in this direction if Ptolemy's map, in which Scotland lies at right angles to England, had been consulted. Thither fishermen from the opposite coast are compelled to ferry over at dead of night the shades of the dead, unseen to them, but marshalled by a mysterious leader.[1179] Procopius may have mingled some local belief with the current tradition that Ulysses' island of the shades lay in the north, or in the west.[1180] In any case his story makes of the gloomy land of the shades a very different region from the blissful Elysium of the Celts and from their joyous _orbis alius_, nor is it certain that he is referring to a Celtic people. Traces of the idea of an underworld of the dead exist in Breton folk-belief. The dead must travel across a subterranean ocean, and though there is scarcely any tradition regarding what happens on landing, M. Sébillot thinks that formerly "there existed in the subterranean world a sort of centralisation of the different states of the dead." If so, this must have been founded on pagan belief. The interior of the earth is also believed to be the abode of fabulous beings, of giants, and of fantastic animals, and there is also a subterranean fairy world. In all this we may see a survival of the older belief, modified by Christian teaching, since the Bretons suppose that purgatory and hell are beneath the earth and accessible from its surface.[1181]