2S rori'LAk l.ECTl'RRS AND ADDRESSES. 



proves that each must make an acute angle 

 with Oil, the line from the earth's centre to 

 the tidal crest towards which the parts of the 

 earth between it and OM or OS are rotating ; 

 or, in other words, that high water is made 

 something earlier on the average than the time 

 when it would be were there no friction ; that 

 is to say, a little before the rising and setting 

 of the sun and moon. And thus what we have 

 to be proved by observation on the average 

 time of spring tides, is that the time of the lunar 

 tide is more advanced by frictional resistance 

 than is the time of the solar tide : a conclusion 

 quite agreeing with what is to be anticipated 

 by mathematical theory. 1 Considering now for 

 simplicity the lunar tide alone, if we imagine 

 the whole mass of the earth and waters upon 

 it to be bisected by a plane perpendicular to 

 HII', through (), the centre of gravity, it is 

 nbvinus that the attractions of the moon on these 

 two halve:, will not balance round the centre 

 of gravity of the whole, but that, on the con- 



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