162 THE OCEAN. [Book VI. 



Besides the foregoing, the theory in Chapter X. 

 accords with and explains the fact of the spring- tides 

 occurring a day or two after new and full moon, and 

 the neap-tides a day or two after the moon's quarters. 

 For it is only some time (approximately stated as 

 two days) after the moon has been in conjunction or 

 opposition that the lunar and solar tides are in con- 

 junction ; and the same time after being in quadra- 

 ture, the lunar and solar tides are in complete oppo- 

 sition. It is because the apparent course of the 

 earth round the moon is in the opposite direction to 

 that of its course round the sun (the real course of 

 the moon round the earth being in the same direction 

 as that of the earth round the sun), that the conjunc- 

 tion of the tide raised by lunar gravitation with that 

 raised by solar gravitation occurs about the time 

 when those bodies are in opposition, and not when 

 those bodies are in conjunction. And it is because 

 the orbit described by the earth in its course round 

 the moon is smaller than that which it describes in its 

 orbit round the sun that the time at which the tides 

 are in conjunction does not coincide exactly with the 

 time at which the sun and moon are in opposition. 



Note.- — Independently of the configuration of the 

 oceans, the meeting of the equatorial tide with those 

 converging towards it from the polar regions, together 

 with the convergence of the meridians, may give the 

 tides a general tendency to a greater rise and fall in 

 the temperate zones than elsewhere. 



