The Tides. 233 



center. This common center is the point attracted by the sun 

 and describes the orbit common to both bodies. The earth's 

 center describes an undulatiog line, bs^ing part of the time within 

 and part of the time without the common orbit. The common 

 center is a variable point, on account of the variable attraction of 

 the sun on the two bodies, and varies or fluctuates between the 

 earth's center and the common center of gravity of the two 

 bodies. The earth revolves about the common center with the 

 same angular velocity that the moon revolves in her orbit. 



The resulting eccentric motion of the earth begets a centrifugal 

 force which coincides with the centrifugal force of the diurnal 

 revolution only under and opposite to the moon in the plane 

 passing through the moon. At other plates it tends only to de- 

 flect the line of gravity. When the common center coincides 

 with the earth's center the force ceases, and is maximum when 

 these points are at their greatest distance. When the moon ap- 

 proaches the earth her velocity increases, also the angular velocity 

 about the common center, hence also the centrifugal force. This 

 force tends also to move matter towards the equator in the plane 

 of its activity. 



From the foregoing argument the following is deduced as the 

 cause of the tides : 



In the first place it is evident that every phase and feature 

 points direct to the moon as the cause of the phenomena, but in 

 the next place the laws of nature show very clearly that the 

 moon is only the implement by which the superior controlling 

 force operates, the moon's efforts as the satellite of the earth being 

 due to the sun's influence. The sun is therefore the prime cause 

 operating in accordance with the grand principle discovered by 

 the great Newton and announced to the world 193 years ago, the 

 principle of univeesal geavitation. 



