SWIRLS OF thp: sea 



29 



very high. On the contrary, when the pull of 

 the sun and the moon are at right angles to 

 each other (that is at the first and third quar- 

 ter of the moon) and have a tendency to coun- 

 teract each other's influence, we have the 

 " neap " tides which are always low. 



If the glohe were entirely covered with water 

 of uniform depth the tide would follow the 

 apparent course of the moon from east to west 

 and complete the circle of the globe in ap- 

 proximately twenty-four hours. That is what 

 it endeavors to do now; and in the Antarctic, 

 south of the Continental extremities of Aus- 

 tralia and America, it is supposed to accom- 

 plish it. But farther north, where humanity 

 is able to observe its movements, it is held back 

 and turned from its course by inequalities of 

 ocean depths, by shoals and reefs and coast 

 lines along continents, so that it takes nearly 

 twenty-five hours to accomplish its round, and 

 hence arrives an hour late each day. 



What is known as the " primary tide " is 

 supposed to start from the deep central waters 

 of the Pacific. It travels westward toward the 

 Indian and Atlantic oceans at the rate of a 

 thousand miles an hour. When it meets with 

 the opposition of shallow seas and coast lines 

 portions of it are turned back, reflected toward 



spring and 

 neap tides. 



The west- 

 ern wave. 



