TIDES AND WAVES 6i 



that bodies of matter, such as the earth and 

 the moon, possess a force called "gravitation" 

 we have come to the conclusion that the force 

 of gravitation of the moon causes our tides. 

 But if we stop to consider the matter we will 

 realise that this very gravitation is itself a 

 mystery and hence the tides, even when ex- 

 plained in this manner, still remain mysteries 

 of the sea. 



The moon of course exerts her attractive 

 force upon all portions of the earth's sur- 

 face, but the water, being free to move, is 

 drawn towards the side of the earth nearest 

 to the moon. The broader the surface of the 

 water the greater will be the amount which 

 follows the moon from east to west. On small 

 bodies of water the tides no doubt occur, 

 though the amount of the water attracted by 

 the moon is so small that it is not noticeable, 

 but on every ocean, and even on the larger 

 lakes, tides are known to occur. No doubt 

 there is a distinct "tidal wave" on every ocean 

 as the moon passes over it, but the largest and 

 principal tide is formed in the Pacific and 

 follows after the moon from east to west, and 



