a river of England which rises near Plimlimmon Hill in Montgomeryshire, and before it enters Shropshire receives about 30 streams, and passes down to Ludring, where it receives the Morda, that flows from Osweftry. When it arrives at Monford, it receives the river Mon, passing on to Shrewsbury, which it almost surrounds, then to Bridgeworth; afterwards it runs through the skirts of Staffordshire, enters Worcestershire, and passes by Worcester; then it runs to Tewkebury, where it joins the Avon, and from thence to Gloucester, keeping a north westerly course, till it falls into the Bristol Channel. It begins to be navigable for boats at Welchpool, in Montgomeryshire, and takes in several other rivers in its course, besides those already mentioned, and is the second in England. By means of inland navigation, it has communication with the rivers Mersey, Dee, Ribble, Ouse, Trent, Derwent, Humber, Thames, Avon, &c.; which navigation, including its windings, extends above 500 miles in the counties of Lincoln, Nottingham, York, Lancaster, Westmoreland, Chester, Stafford, Warwick, Leicester, Oxford, Worcester, &c. A canal from Stroud-Water, a branch of the Severn, to join the Thames, was projected and executed for the purpose of conveying a tunnel 16 feet high and 16 feet wide, under Sapperton Hill and Hayley-Wood (very high ground), for two miles and a quarter in length, through a very hard rock, which was lined and arched with brick. This stupendous undertaking was completed, and boats passed through it the 21st of May 1789. By this opening, a communication is made between the river Severn at Framiload and the Thames near Lechlade, and is continued over the Thames near Inglesham, into deep water in the Thames below St John-Bridge, and so to Oxford, &c. and London, for conveyance of coals, goods, &c.