433 On the Solar and Lunar Diurnal Tides of the Coasts of Ireland. 

 Age of Lunar Diurnal Tide. 



A series of values for the depth of the sea may be obtained by 

 comparing the age of the lunar diurn&l tide with the lunidiurnal 

 acceleration of high water already given^ as follows : — 



By the theory of tides, including friction *, it appears that — 



Age of lunidiurnal tide _i^+ghn^ 



i^ —gkm^' 



(14) 



Acceleration of lunidiurnal tide 



i denoting the angular velocity of the moon, and the other letters 

 remaining as before. Introducing the numerical values of the 

 known quantities, we find, expressing k in miles, — 



Age of lunidiurnal tide _ 12"938 + k ,, ^ , 



Acceleration of lunidiurnal tide ~ 12'938 — A'" 



By the aid of this equation, we find the depths of the sea, 

 calculated in the following Table : — 



Mean depth of Sea deduced from Age of Lunar Tide, 



The results just obtained agree very well with each other, and 

 with the results obtained from the diurnal solitidal and lunitidal 

 intervals ; but both results differ widely from the mean depth 

 deduced from heights. How are we to reconcile this difference ? 

 Although this question is difficult to answer fully, yet it should 



» * Airy, ' Tides and Waves/ p. 333. 



