Severn, the second river of England, rises on the E. side of Plinlimmon, in Montgomeryshire, and flows in a circuitous southerly direction through Montgomeryshire, Shropshire, Worcestershire, and Gloucestershire, falling into the Bristol Channel after a course of 210 m.; is navigable to Welshpool (180 m.); chief tributaries are the Terne, Wye, and the Stratford Avon; there is a "bore" perceptible 180 m. from the mouth.