THE TIDES 143 



there is always a great deal of trouble and worry to 

 the riparian householders when any alteration of it 

 takes place in excess. 



I hope that the very simple theory of the tides 

 may be borne in mind, viz. that the moon moving 

 round the earth once in twenty-four hours draws the 

 whole body of water comprised in the ocean up towards 

 her by reason of her attraction. In the open ocean 

 that swelling upwards is so slight comparatively as to 

 be unnoticed, but when any obstruction of land is met 

 with, it becomes at once exceedingly evident, its 

 effects in velocity and height being the more marked 

 in proportion to the ruggedness and sinuosities of the 

 coast. Sometimes the sun, which exerts less attraction 

 upon the sea than the moon, owing to his vastly 

 greater distance from the earth, pulls with the moon, 

 producing the highest tides (spring tides) ; sometimes 

 he pulls at right angles to the moon, and thus nearly 

 neutralizes her efforts, so that very weak and low tides 

 (neap tides) are the result, and if the attraction of 

 these two celestial bodies were equal, there would be 

 no tide at all. The times of highest tide, or, to use 

 the queer word which astronomers affect, the " syzygy " 

 tides, always occur at new and full moon, and if a gale 

 of wind happens to be blowing in the direction of the 

 flood at the time, an extraordinary elevation of water 

 must take place. 



Whewell, a great authority upon the tides, has 

 carefully calculated the speed of the great tidal waves, 

 and has pointed out how greatly they are affected by 

 the depth of the ocean along which they travel. His 

 conclusions are hard to accept by the seaman, for he 

 says that where the water is five thousand fathoms 



