Humber, the estuary of the rivers Ouse and Trent (and so of the Dove, Derwent, Wharfe, &c), runs 38 miles E. and SE., separating the counties of York and Lincoln, with a breadth varying from 1 to 7 miles. Its drainage basin, with an area of 9770 miles, is the largest in England ; and by means of navigable streams and canals the Humber is connected with the Mersey, the Severn, and the Thames. The navigation is obstructed, especially on the north side, by banks and shoals. By way of the Humber Danes and Northmen made many terrible incursions into England, notably in 867, 1013, 1066, and 1069. The great port on the Humber was anciently Ravenser or Ravenspur, just inside Spurn Head. The process of erosion by the sea was already at work when Henry Bolingbroke landed here in 1399; soon after the place was wholly covered by the encroaching waters, and Hull (q.v.) became the great port on the north shore, as Grimsby (q.v.) now is on the southern side. See The Rivers of England (Cassell, 1889), and Boyle's Lost Towns of the Humber (1889).