There are many burns and waters, but their length seldom exceeds 7 or 8 miles (13 km). Among the longer rivers are the Cree, which rises in Loch Moan and reaches the sea near Creetown after a course of about , during which it forms the boundary, at first of Ayrshire and then of Wigtownshire; the Dee or Black Water of Dee (so named from the peat by which it is coloured), which rises in Loch Dee and after a course mainly S.E. and finally S., enters the sea at St Mary's Isle (actually a peninsula) below Kirkcudbright, its length being nearly 36 miles (58 km); the Urr, rising in Loch Urr on the Dumfriesshire border, falls into the sea a few miles south of Dalbeattie 27 miles (43 km) from its source; the Ken, rising on the confines of Ayrshire, flows mainly in a southerly direction and joins the Dee at the southern end of Loch Ken after a course of 24 miles (39 km) through lovely scenery; and the Deugh which, rising on the northern flank of the Windy Standard, pursues an extraordinarily winding course of 20 miles (32 km) before reaching the Ken. The Nith, during the last few miles of its flow, forms the boundary with Dumfriesshire, to which county it almost wholly belongs.