North Sea or German Ocean is the southern arm of the Arctic Ocean, lying between Britain and Norway. It communicates with the Atlantic through the English Channel and Straits of Dover on the south, and by Pentland Firth and the Orkney and Shetland Channels on the north, and with the Baltic through Skager-Rack and Cattegat. It is over 600 miles long and 400 miles wide, and has an area of 180,000 square miles. The sea is in most places quite shallow, averaging 61 fathoms, but on the Norwegian coast is 360 fathoms deep. It is the receptacle of the waters of the Thames, Ouse, Humber, Tyne, Tweed, Forth, Tay, Scheldt, Rhine, Weser and Elbe. The water is probably the least salty of any of the large seas, and, except in the summer, is warmer than the surrounding atmosphere. The tides are irregular, having a large ebb and flow in some places, while it is hardly perceptible in others. The North Sea has long been one of the commercial highways of the world, and affords a valuable fishing-ground.
