166 KAMBLES OF A NATUEALIST. 



depth of the water at a short distance from the 

 shore increases in a similar proportion. Thus the 

 waves, urged by the north-west wind, traverse the 

 whole of the Atlantic as far as the entrance to the 

 Bay of Biscay without having encountered any ob- 

 stacle to their course. But being now compressed 

 between coasts, which gradually approximate more 

 and more closely to one another, they exhibit on a 

 large scale the same phenomenon as the water in the 

 funnel, and flow towards the bottom with a con- 

 stantly increasing velocity. It is only at short dis- 

 tances from the shore that the deep waves striking 

 against the submarine escarpments tend to shoot 

 upwards in an eddying current, like those which we 

 observe to be formed at the water's level along our 

 dykes ; but having been stopped and turned aside by 

 the strata of water which cover them, these ascend- 

 ing currents become changed into a ground swell, 

 which moves with frightful rapidity and strikes 

 against the shore with an irresistible force. During 

 the storm of 1822 the waves which were dashed 

 from the rocks of Arta had a breadth of more than 

 400 yards, and moved at the rate of twenty yards a 

 second. Their progress was therefore nearly twice 

 as rapid as that of a locomotive which is going at the 

 rate of thirty miles an hour. 



According to Colonel Emy, the ground swell plays 

 a very considerable part in the greater number of 

 the remarkable phenomena exhibited by the ocean.* 



* Du mouvement des ondes et des travaux hydrauliques maritimes, 

 by Colonel Emy. M. de Caligny, who is well known in the 

 scientific world for his able experiments on hydraulics, has opposed 



