The question of when, how and under what influence the week diffused itself in Northern Europe is one on which we have little knowledge beyond the precarious inferences which may be drawn from the names. Welsh has a complete set of Roman planetary names. It stands in fact alone in this respect among European languages. Saturday is Dydd-sadwrn, Sunday Dydd-sul, Monday Dydd-llun. There has been no tendency to supplant the first two of these, as in Latin Europe by Dominica and Sabbatum, nor again have Sol and Luna been replaced by the Celtic equivalents for Sun and Moon. The natural inference is that the week spread through the Romanized element in Britain, as it did through the rest of the Empire, under planetary rather than Christian influence, and that the names, now become mere names, then found their way into the vernacular. The later isolation of Britain from the sphere of Roman Christianity will, I imagine, give a quite satisfactory explanation why the Church influence which established the 'Lord's day' so firmly in the south was not so effective in this country.
