CRADLE OF THE TIDES. 



4!* 



manner, be drawn through places to which high water 

 comes an hour later, and so on, until we shall have 

 laid down a series of lines for every hour. Such lines, 

 now frequently drawn on physical maps (as in the 

 annexed woodcut), are called cotidal lines. 



The chief " cradle of the tides" appears to be in the 

 Southern Ocean, where we have the greatest unin- 

 terrupted surface of deep water exposed to the in- 

 fluence of the moon. The Pacific, though its area is 

 so great, is so studded with islands and shallows that 

 it presents a much more obstructed basin for the 

 action of the tide-wave than its apparent dimensions 

 and equatorial position would lead us to suppose. 

 The tide-waves formed round the southern polar con- 

 tinent flow on all sides to the northward. That which 

 reaches our coast starts from a point to the south of 

 New Zealand, whence it rapidly advances in the direc- 

 tion of the Cape of Good Hope, arriving at that prc- 

 montory in thirteen hoars after it has left Van Die- 



