DEE, a river of Wales and England. It rises in Bala Lake, Merionethshire. Leaving the lake near Bala, it flows north-east to Corwen and turns east past Llangollen to near Overton, and then bends nearly north to Chester, and thereafter north-west through a great estuary into the Irish Sea. In the Llangollen dis trict the Dee crosses Denbighshire, and thereafter forms the boundary of that county with Shropshire, a detached part of Flint, and Cheshire. From Bala to Overton (35 m.), the river falls about 33o ft., and its course lies through a narrow, beautiful valley, en closed on the south by the steep slopes of the Berwyn Mountains and on the north by a succession of lesser ranges. The Vale of Llangollen is especially famous. Here an aqueduct of the Shrop shire Union canal bestrides the valley ; it is a remarkable engineer ing work completed by Thomas Telford in i8o5. The Dee has a total length of about 7o m. and a fall of 53o ft. Below Overton it debouches upon its plain track. Below Chester it follows a straight artificial channel to the estuary, and this is the only navigable por tion. The estuary, which is 14 m. long, and 51 m. wide at its mouth, between Hilbre Point and Point of Air, is not a commercial highway like the Mersey, for at low tide it becomes a vast expanse of sand, through which the river meanders in a narrow channel. The tide rushes in with great speed over the sands, and their dan ger is illustrated in the well-known ballad "The Sands of Dee" by Charles Kingsley. The Dee drains an area of 813 sq.m.