the arm of sea which separates England from France, extending, on the English side, from Dover to the Land's End, and on the French, from Calais to the Island of Ushant. It is 20 miles wide at its narrowest point and 140 miles at its widest point. The Seine is the only important river that flows into it. In this channel are the Isle of Wight and the group of the Channel Islands. The chief ports are Plymouth, Falmouth, Southampton, Porstmouth, Brighton and Dover, in England, and Cherbourg, Havre, Dieppe, Boulogne and Calais, in France.