FOR GREAT BRITAIN AND IRELAND. 



73 



REDUCTION IN THE HEIGHT OF THE WAVES AFTER 

 PASSING INTO CLOSE HARBOURS. 



This is the third paragraph again quoted : 

 " The ultimate object of every harbour is to preserve the 

 tranquillity of the inclosed area by lowering the height of 

 the waves as they enter, and this property is variously 

 possessed by harbours of different forms, and depends on 

 the relative widths of the entrance and the interior, the 

 depth of water, the form of the entrance, and the relation 

 between the direction of the entrance and that of the line 

 of maximum exposure'' 



The writer's observations have led him to fix the centres 

 from which the waves expand as near the middle of the 

 entrance ; these he would term the centres of disturbance, 

 and Mr. Stevenson mentions, at p. 121, that Dr. Thomas 

 Young, in his theory of undulation, in the year 1 807, also 



