42 



MR. AIRY ON THE LAWS OF THE TIDES 



I have stated in the Encyclopaedia Metropolitana, Tides and Waves, Art. 538, that 



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 I consider the values of j^ deduced from the semimenstrual inequalities in time to be 



real and certain representations of the proportions of the sun's effect to the moon's 

 effect in the seas in the neighbourhood of each station ; those deduced from the 

 heights being liable to the effects of many local disturbing causes which do not affect 

 those deduced from the times. In this view the table above deserves consideration. 

 The littoral stations (including those in the Irish Sea) agree in giving a value of 0'32 

 or 0'33, nearly the same as that found at Brest by Laplace and Sir J. W. Lubbock. 

 But at Port Rush and Ballycastle (the first stations in the North Channel) the lunar 

 tide appears to be diminished in a far greater proportion than the solar tide. And 

 then, after this alteration of relative magnitude has been established in the open sea 

 of the neighbourhood, it appears to be again nearly destroyed by some local cause 



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 affecting the heights, so that in the table of page 35^ the value of ^ is restored to its 



average value. As far as the observations can be trusted for accuracy, the two con- 

 clusions which I have mentioned appear at first sight perfectly certain ; for the great- 



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 est difference of intervals from moon's transit (on which the value of ^ in this page 



depends) is deduced from comparisons of the times of tides of equal vertical range, 

 in which therefore the stream of tide in the neighbouring channels of small depth 

 and width, &c. was the same, and therefore could not disturb the difference of times. 



