26 THE TIDES. 



of the earth, near the equator, because the distance 

 of the moon from the poles and the parts near 

 them is not at all, or but very little, changed 

 during the daily revolution of the earth. 



However the greatest rise of the waters, at 

 any place, does not happen at the moment when 

 the moon passes its meridian, but always some- 

 what later. For although the cause of the rise 

 is certainly strongest at that moment, yet the 

 water requires time to run up, and besides the 

 influence of the moon continues to act for some 

 time longer with scarcely diminished power. 

 Meanwhile other points of the earth's surface, 

 lying farther to the west, come in turn to be 

 nearest to and farthest from the moon, and thus 

 the tide-wave always advances from east to west, 

 the water continually mounting up on its forward 

 or westward side, and falling on the hinder or 

 eastward side. 



But you must not suppose from this, that the 

 tide-water actually flows round the whole earth in 

 a little more than a day. The onward rolling of 

 the tide-wave is not a current at all of the water, 

 but a movement only of the wave, on a vast scale 

 indeed, but still of exactly the same kind as that 

 which you can bring about in any vessel of water, 

 by raising up a part of the liquid at any point 

 and then allowing it to fall. Just like such a 

 little wave in a basin does th°, tide-wave rise and 



