TIDAL FORCE. 



or THE 

 UNIVERSITY 



OF 



actually exceeaea tne lorce ot gravity. And, as will be 

 seeu by-and-by, it is too minute to produce any indirect 

 effect. 



The tide-producing force then always acts towards EM 

 (in the direction of the arrows in fig. 2) . From this we 

 can deduce theorems relating to the place of high and low 

 water, &c., without requiring to determine the magnitude 

 of the force, which will be hereafter taken into account. 

 At present we need only observe that it is very small 

 compared with gravity. 



First, then, let us consider the case of water limited to 

 an equatorial canal. The moon being supposed in the 

 equator, we shall establish the following theorems : 



i. If there were no friction it would be low water 

 under the moon, and high water in quadratures. 



n. Friction accelerates the times of high and low water. 



in. In addition to the oscillatory motion of the water 

 there is a constant current produced by the action of the 

 moon. 



iv. The eifect of friction on this is to increase the 

 length of the day. 



B2 



