54 



HARBOUR CONSTRUCTION. 



In parts of the North Sea, tidal irregularities are caused by 

 the waters which pass through the Straits of Dover meeting 

 those from the northward, which have been delayed in their 

 passage along the western coasts of Ireland and Scotland, as will 

 be described later on (Chap. IV.). 



Ordinary Spring Tide, Peterhead, N.B. 

 SH_quRB VIII IX X XI o"' I II III IV y V| V || VIII IX X XI 



10 



10 



Ordinary Neap Tide, Peterhead. N.B. 



Noon 



IIHouRsVI VII VIII IX X XI I II III IV V VI VII VIII IX 



Curve 1 of Spring Tide at Southampton^ showing double high water. 



uiHouR9 V VI VII VIII IX X XI XII I II III IV V VI VII VI!! 



FIG. 11. Tidal curves. 



At Batsham, in Tonquin, one portion of the tidal wave, which 

 comes from the Indian Ocean, obliterates another portion from 

 the China Sea, so that scarcely any tide is perceptible. This is 

 due to the interval bet ween -the arrival of these undulations being 

 about equal to the period between high and low water, so that 



1 Enlarged from diagram in Sir Gr. B. Airy's "Tides and Waves" ("Encyclo- 

 paedia Metropolitana "). 



