The Tides. 231 



depression also becomes greater as the water which should belong 

 to one is in part taken up bj the other. If these intervals were 

 not oscillating as they are ; but continuous in pairs, the result 

 would be the same as in inland lakes. 



The highest spring tides should take place during the equinoxes 

 when the oceans are affected alike for both upper and lower tran- 

 sits by the maximum force for several days in succession,, but 

 from four years careful observations I have found the mean rise 

 and fall greatest during the five months, August to December 

 inclusive ; also the highest and lowest tides and maximum and 

 minimum rise and fall from November to February inclusive. 



The tides are known to rise higher as the moon approaches the 

 earth. As the moon approaches, the common centre comes nearer 

 the earth's centre and the centrifugal force increases as the moon's 

 motion increases from its closer proximity, hence the tides increase. 

 The tides on opposite sides, or corresponding to different transits 

 of the moon, are practically alike when the moon is on the equa- 

 tor, now since the impulse on opposite sides is about as 500 to 900 

 the question will arise why the effect is not in proportion to the 

 cause. As the pendulum will return nearly to the point from 

 which it has fallen so these oscillations would also nearly repeat 

 themselves, but since other waves approach to form the succeed- 

 ing tide it is only necessary that the impulse should be repeated 

 at the regular intervals necessary for equilibrium. There are 

 those who deny the existence of the force at the side remote from 

 the moon, but the inequality of the semidiurnal tides is sufficient 

 to prove the existence of that force. 



It has been stated that the force is nil at the moon's quadra- 

 tures, then why any tides at these phases ? The nil force exists 

 but an instant and as before remarked, these oscillations will 

 nearly repeat themselves even when they are changing with an 

 increasing ratio as they change when approaching quadratures at 

 the equinoxes, in fact Newton said, that when these oscillations 

 were fairly established, the luminaries might be removed, and the 

 tides would continue for an indefinite time. We also find that 

 the effect does not immediately follow the cause, for the inverse 

 order of tides does not take place for several days after change of 



