106 THE OCEAN. [Book IV. 



and the solar counter- tide f g, would then be as shown 

 in Fig. 2. 



Then as regards the lunar tides : the action of the 

 moon on the lunar tides is exactly the reverse of that 

 just described as the action of the sun on the solar 

 tides : for the earth is revolved in its orbit round the 

 sun by the force of solar gravitation, which raises the 

 ■ solar tide ; whereas it is the earth's gravitation which 

 revolves the moon in its orbit round the earth. But 

 we may, for the sake of simplifying the question, just 

 for the present, suppose the earth to be revolved round 

 the moon in the opposite direction to that of the real 

 motion of the moon round the earth. 



Then, as the moon revolves eastwards round the 

 earth, the relative positions of those bodies and the 

 lunar tides are the same as if the earth be supposed 

 to revolve westwards round the moon. Then, as in 

 the case of the solar tide, the lunar tide, i H, in Fig. 3, 

 is drawn to that part of the earth's surface which 

 is in advance in this orbital motion, and the counter- 

 tide, J K, is drawn by astral gravitation to exactly 

 the opposite side of the earth. 



In consequence of the smallness of the moon's orbit, 

 the lunar tides are drawn more towards the moon's 

 meridian than is the case with the solar tides in 

 relation to the sun's meridian. Let us, for the sake 

 of illustration, suppose this difference to be double 

 that in the case of the solar tides. Then, as there is 

 a difference of an hour in the relative distances of the 



