106 



THE OCEAN. 



CHAPTER XIII. 



APPARENT IRREGULARITIES OF THE TIDES. — EXTRAORDINARY SIZE OP THE TIDAL 

 WAVE IN CERTAIN BAYS.— INTERFEUENCE OF EBB AND FLOW.— DIURNAL TIDES. 

 — INEQUALITIES OF SUCCESSIVE TIDES. 



Innumerable are the apparent irregularities which occur in the 

 phenomena of the tides, in consequence of the inequalities of the 

 submarine surface, the thousand indentations of the shore, and the 

 alternations of winds and currents. Though the cause of the move- 

 ment be the same everywhere, we can still say that at no point of the 



f^ 



L. 



Figs. 32— 34.— Irr^ularities in the curves of the Tidal waves resulting from the form of the 

 sea-bed, projecting rocks, &c. (after Lubbock). 



sea do the ebb and flow present a perfect agreement in their progress. 

 Each promontory, each islet, each rock is bathed by waters having a 

 distinct rule in the propagation of their tides ; every obstacle which 

 breaks the regular course of the oscillations modifies the whole of 

 the graceful curves which bend around it. The above figures, 

 borrowed from Lubbock, give an idea of these variations in the 

 march of the waves. 



The difference which most strikes the minds of navigators and in- 

 habitants of the coast is that of the height of the tides. In one 

 part of the coast the tide hardly makes itself felt, even during the equi- 

 noctial syzygies ; while elsewhere every tide is a real deluge, spreading 



