In the south, the Lee and the Blackwater intersect the mountains of Kerry and Cork flowing east, and turn abruptly into estuaries opening south.
Sir John Norris was accordingly ordered to Ireland with a considerable force to subdue him in 1595, but Tyrone succeeded in taking the Blackwater Fort and Sligo Castle before Norris was prepared; and he was thereupon proclaimed a traitor of Dundalk.
But like other O'Neills, he did little out of Ulster, and his great victory over Monro at Benburb on the Blackwater (June 5, 1646) had no lasting results.
The Blackwater in Essex, which rises near Saffron Walden, has a course of about 40 m.
Thus, from north to south there are, on the east coast, the mouths of the Tyne and the Tees, the Humber estuary, the Wash (which receives the waters of the Witham, Welland, Nene and Great Ouse), the Orwell-Stour, Blackwater and ThamesMedway estuaries.
The Blackwater is famous for salmon, and sea-fishing is important.
The main rivers, however, have generally a mountain source, and according as they are fed from bogs or springs may be differentiated as black and bright streams. In this connexion the frequent use of the name Blackwater is noticeable.
The town is a centre for salmon and trout fishing on the Blackwater and its tributary the Funshion.