DEE (Welsh, Dyfrdwy; Lat., and in Milton, Deva), a river of Wales and England. It rises in Bala Lake, Merionethshire, which is fed by a number of small streams. Leaving the lake near the town of Bala it follows a north-easterly course to Corwen, turns thence E. by S. past Llangollen to a point near Overton, and then bends nearly north to Chester, and thereafter north-west through a great estuary opening into the Irish Sea. In the Llangollen district the Dee crosses Denbighshire, and thereafter forms the boundary of that county with Shropshire, a detached part of Flint, and Cheshire. From Bala nearly down to Overton, a distance of 35 m., during which the river falls about 330 ft., its course lies through a narrow and beautiful valley, enclosed on the south by the steep lower slopes of the Berwyn Mountains and on the north by a succession of lesser ranges. The portion known as the Vale of Llangollen is especially famous. Here an aqueduct carrying the Pontcysyllte branch of the Shropshire Union canal bestrides the valley; it is a remarkable engineering work completed by Thomas Telford in 1805. The Dee has a total length of about 70 m. and a fall of 530 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 portion. The estuary, which is 14 m. long, and 514 m. wide at its mouth, between Hilbre Point on the English and Point of Air on the Welsh side, is not a commercial highway like the neighbouring mouth of the Mersey, for though in appearance a fine natural harbour at high tide, it becomes at low tide a vast expanse of sand, through which the river meanders in a narrow channel. The navigation, however, is capable of improvement, and schemes have been set on foot to this end. The tide rushes in with great speed over the sands, and their danger is illustrated in the well-known ballad “The Sands of Dee” by Charles Kingsley. The Dee drains an area of 813 sq. m.