MERSY, a river of England, which runs through the counties of Lancaster, York, and Chester, and empties itself into the Irish sea at Liverpool. By means of inland navigation, it has communication with the rivers Dee, Ribble, Ouse, Trent, Derwent, Severn, 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.