THE TIDES 125 



and Scotland for a distance of over 400 miles between 4.30 

 and 6.30 p. m. G.M.T. on full and change days. 



The tidal wave approaches the Orkneys and Shetlands, 

 owing to retardation of the southern side of the wave in 

 shallow water, almost in a parallel direction to the coast, The 

 undulation has a height of 10 feet at the Orkneys and 5 to 6 

 feet at the Shetlands at springs. 



The North Sea is open to tidal influence at both entrances : 

 on the south through the Straits of Dover, and on the north 

 to the undulation coming round the north of Scotland. This 

 undulation has its south-western portion considerably retarded 

 when it reaches the Orkneys and Shetlands. The tidal wave 

 bends round the northern end of the British Isles, and reaches 

 the coast of Norway at 10 o'clock G.M.T. on full and change 

 days, with a height of under 5 feet, having travelled across the 

 intervening area at a rate of 120 miles per hour. At the time of 

 high-water at Dover (11 o'clock) the same tidal undulation, 

 travelling round north of the British Isles, has reached the 

 south-western corner of Norway. 



The tidal undulation takes seven hours to travel up the 

 English Channel, about 300 miles, while its northern offset 

 only takes two and a half hours to the Faroes, 500 miles, and 

 about five hours to the northern end of the Shetlands, a 

 distance of 600 miles. 



The tidal wave in the Channel is directed towards the 

 Schelde mainly, but part of it is deflected towards the coast 

 of Holland, acquiring a rotatory motion round the Brown 

 Ridges. 



The Norwegian wave appears to be reflected back and 

 to be superimposed on the undulation passing through the 

 Orkney and Shetland Channels, so that it moves towards the 

 east coast of Great Britain in a line almost parallel to the coast, 

 and from Aberdeen to Cromer in a wave from 14 to 16 feet 

 high, except in certain estuaries, such as the Humber and the 

 Wash, where, owing to the formation of the coast, it is forced 

 to a height of from 20 to 23 feet. The southern part of the 



