Ten rotae and tables, contained in Carolingian works for Easter calculation, contain tidal information. The emergence of the terminology associated with these diagrams is explained, notably of the arcane terms malina and Ledon, which would develop into our modern concepts of springs and neaps, and of the term dodrans, first-of-flood. One particular rota, because of its rich illumination, serves most of the offices of an actual tide-table. This article also looks at the difficulty of tracing the transmission of the rotae (...) to the later Middle Ages and the complex scientific knowledge contained in the rota explanations and the commentaries written on them. (shrink)