VIADUS(Οὐίαο̄ος), a river of Germany, west of the Vistula, mentioned by both Ptolemy (Ptol. 2.11.2) and Marcianus (p. 53) as flowing into the Mare Suevicum or Baltic. Neither of these authors mentions either its source or its course, but it is generally assumed to be the Oder. Ptolemy in another passage (2.11.15) mentions, according to the common reading, a river Ἰαδούα, which some regard as a tributary of the Viadus, and others as a name of the upper Viadus; but Wilberg, the latest editor of Ptolemy, treating Ἰαδούαas a corrupt reading, has altered it to Οὐίαδος.
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