152 OUR HERITAGE THE SEA 



Charybdis to awaken interest in the minds of every 

 public schoolboy, though this race of the Strait of 

 Messina is not much accounted of by the navigator 

 of to-day, and the strait is crossed several times daily 

 by a cumbrous ferry-boat bearing a railway train on 

 its decks. 



Strong winds, of course, have their usual influence 

 upon the tides, setting up quite rapid local currents, 

 and causing an abnormal raising of the water in 

 certain places favourably situated for such manifesta- 

 tions. But as far as the tidal influence of sun or 

 moon is concerned, the great enclosed basins show, 

 as might be expected, but little trace of it. They 

 are aflected undoubtedly, even those great inland 

 seas of America, with their scores of thousands of 

 square miles of fresh water, respond to the call of 

 the moon, and exhibit a tide which, though almost 

 imperceptible, may still be measured by inches. In 

 like manner the Baltic, protected as it is from the 

 inrush of the Atlantic tidal wave, first by the British 

 Isles and then more closely by Denmark, shows little 

 tidal variation. In fact, as far as the tides are con- 

 cerned, it is the easiest navigated sea in the world. 

 The maximum rise and fall scarcely ever exceeds a 

 foot ; but here, as in the Mediterranean, the currents 

 must be watched, especially during and after gales. 



Other almost tideless seas are the Bed Sea and the 

 Persian Gulf, and for the same reason their almost 

 land-locked condition. But the immense evaporation 

 that takes place in these inland seas, owing to their 

 geographical position, necessitates a continual influx 

 of the ocean to supply their need, and so there is a 

 steady movement of current in both of them. But 



