MOON'S DECLINATION CONSIDERED. 



21 



Let us now consider the case of the moon having a 

 declination, which for simplicity I shall suppose less than 

 22 30'. This limitation will not affect our results. We 

 shall, as before, take the two components separately. 



With respect, then, to the component which acts parallel 

 to the equator. Near the equator itself the considera- 

 tions previously applied still hold good. Next consider 

 a place a, whose polar distance is less than the moon's 

 declination, to which therefore the moon is circumpolar, 

 and (with the assumed declination) alternately north and 



Fig. 7. 



south of the zenith. If abed be the circle of rotation of 

 such a place, the distance of the moon from any point in 

 this circle is less than that from the earth's centre. If> 

 then, the direction of the rotation be abed it is obvious 

 that the water will be accelerated through the whole semi- 

 circle, abcj and retarded through cda. The same reasoning 

 as already employed will show that it will be low water 

 at c and high water at a. Now take an intermediate place 

 whose circle of rotation is Imno. Here the water is retarded 

 and rising from I to m and from n to o ; and accelerated 



