The Mersey River rises in Derbyshire
and after a course of 70 miles, empties into the Irish Sea
. From Stockport, where it is joined by the Tame, it winds westward through Lancashire
. The Manchester Ship Canal joins the river near Irlam.
Below Runcorn it widens into a large estuary, on the right bank of which lies the great port of Liverpool. A vehicular tunnel two miles long, built in 1934, connects Liverpool with Birkenhead on the left bank.