INEQUALITIES OF THE TIDES. 



115 



its preponderance on the coasts of the continent as far as the mouths 

 of the Mouse ; the tide coming from the north_, on the other hand, 

 deviates likewise to the right and flows along the coasts of England. 

 The crossing of these two contrary currents gives rise to numerous 



I ow- water Jersrcl o 



^ The. 7una\sS.6.j 8,9.1 o,uareyrat^ned^ 

 ■hcfore/ IheMint/^Tti^Tty water avlim«r. 



Fig. 40.— Crossing of the swellings of the tides in the English Channel and the North Sea, from the 

 Sally Isles to the mouth of the Humber. 



gyratory movements off the coasts of France and Great Britain, the 

 incessantly changing curves of which form a veritable labyrinth * 



In the roadstead of Havre the meeting of the tides results in a remark- 

 able phenomenon, which is at the same time one of the most useful 

 for navigation. Instead of falling immediately after having attained 

 its point of highest tide, the sea remains steady for three hours, and 

 thus permits vessels to sail all over the road, and to penetrate wdth 

 ease into the port, floating constantly over deep water. The seamen 

 saw in this fact a sort of miracle, before its true cause had been re- 

 vealed. When the tide from the Atlantic rolls towards the east to 

 the middle of the Channel, it is arrested in its course by the peninsula 

 of Cotentin, and can only advance freely to the north of the Gulf, to- 

 wards the mouth of the Seine. The marine level is thus more ele- 

 vated at the centre than on its shores, and its waters are spread 

 laterally towards the road of Havre and the other parts of the coast. 

 At the time of low water, when the ebb prevails in the centre of the 

 Channel, the inclination is changed ; but before the waters of Havre 

 can descend towards the central course of the Channel, which carries 

 such an enormous mass of fluid to the ocean, they are kept back 

 by the wave which, after having struck the Cape of Antifer, flows 

 along the shores from north-east to south-west to the Cape of La 

 Heve. Then, when the force of this partial tide fails, another river- 

 tide, which has followed the coast of Normandy from St. Yaast to 

 Trouville, still maintains the level, for a time.f 



In almost all river ports, as we can easily understand, the ebb lasts 

 longer than the flow, for the fluvial current neutralizes the tide during 



t Baude, Revue des Deux Mondes. 



Annales des Fonts 



Chaussees, 1863, first week. 

 I 2 



