36 



THE OPAL SEA 



Undula- 

 tion. 



Drift of 

 water. 



field produces a wave in the stalks correspond- 

 ing to the undulation of the sea, but the stalks 

 do not move forward. Undulation and advance 

 are not the same things. 



There is, however, what is called " drift " 

 which, as applied to sea water, means an ad- 

 vance. With wind and wave continually press- 

 ing against it, water will slowly " drift " from 

 one portion of the ocean to another. Floating 

 substances such as the loose planks of a ship, 

 abandoned at sea, sooner or later find their way 

 to the shore, to be eventually entombed in 

 waves of sand; and the bottle with its fateful 

 message from the lost, is perhaps picked up five 

 thousand miles from where the waves first re- 

 ceived it. But this drift of the sea is a very 

 slow movement. For days the bottle bobs and 

 pitches, the wreckage swings up and down, with 

 wave following wave, and neither seems to 

 change its place. Prevailing winds push them 

 some, and finally a great storm sweeps them 

 into an ocean current. They move slowly even 

 there, but it is largely due to ocean currents 

 that floating objects move at all. 



Now the ocean current that weaves a skein 

 of color through the body of the sea, is quite 

 a different affair from tide or wave or undula- 

 tion. It is a distinct movement forward — a 



Drift of 

 wreckage. 



