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The tidal wave
In many cases the tidal wave appears to advance from the centre of an ocean along the surrounding coasts. The advance of the tidal wave around the coasts in Great Britain is illustrated in the following diagram. This tide has a period of oscillation of about 12 hours and moves approximately as follows:
At 0+2 hours it arrives off the coast of Portugal.
At 0+3 hours it arrives off the western coast of France.
At 0+4 hours it arrives off Land's End.
At Land's End part of the tidal wave travels up the Channel and reaches the Straits of Dover at 0+11 hours, while the remainder continues northwards up the West Coast of Ireland until:
at 0+9 hours it arrives West of the Orkney Islands, and then passes into the North Sea
at 0+12 hours it arrives off Peterhead
at 0+24 hours it arrives off Harwich
Off Harwich this tidal wave meets its successor which set out from mid-Atlantic at about 0+12 hours and had travelled up the channel through the Straits of Dover in the intervening period.
Adapted from the Admiralty Manual of Seamanship, Vol II, 1951