HEIGHT OF TIDE. 11 



of Ik being - r), i.e. by -^-. (This we shall call H. ) The 



greatest tangential force then is 



9 9 1 



40x81ix60 2 11,736,000 365,000' 

 nearly. The tangential force at any given point is 

 = - Hsiu 2o) (<o being the angle from the moon) . Neglect- 

 ing the effect of pressure, the effect of the moon's action 

 through one quadrant : the effect of this maximum con- 

 tinued for the same period : : 1 : JTT (this appears from the 

 construction in fig. 5). 



The number of seconds in the mean lunar day being 

 89432, the velocity generated in one-fourth of this time is 



22358 1 , 



= ^ feet nearly. 



365000 x TT 26 



This is the difference between the greatest eastward 

 and the greatest westward velocity ; therefore the greatest 



eastward velocity is , and the greatest westward velocity 



0/4 



is also 1. 



As the same amount of water passes through a given 

 section in a given time, the increase in height : total 

 depth of the sea : : relative westward velocity of the 

 water : earth's velocity of rotation (relatively to the 

 moon). The last is about 1470 feet per second. Hence 



depth of sea 1 depth of sea 

 the rue of the hde --- x-= -- 



For a sea of three miles in depth this would give for the 



22 



lunar tide 2*4 inches. The solar tide is about -^ of this. 



DO 



OF THE 



IYER8ITY 

 or 



