Diurnal Tides of the Coasts of Ireland. 431 



tion. "VVe thus obtain the accelerations given in the following 

 Table. The depths of the sea are thus found. 

 According to the tide theory with friction*, — 



Lunitidal acceleration _n'^—ffkm^ ..„. 



Solitidal acceleration ~n'^—ffkm^' ' ' \ ' 

 In this equation, 



n, n' are the angular velocities of the sun and moon, 



2/4 



\ is the length of tide wave, 

 ff is the force of gravity. 



Substituting the known values of these quantities, excepting k, 

 which is to be given in miles, we find, — 



Lunitidal acceleration _ 13'815— A: ., „> 



Solitidal acceleration — 13-938 — A* ' ' ^ ^ 



The sea depths in the following Table are calculated by means 



of equation (13) : — 



Sea depths derived from Tidal Intervals. 



These depths agree remarkably well together ; and although 

 they difi"er widely from the result obtained from heights, and 

 from the result of Laplace's ' Brest Observations on the Semi- 

 diurnal Tide,' yet we shall find them confirmed in a remarkable 

 manner by the depths of the sea, deducible from the age of the 

 lunar tide. 



3. Affe of the Lunar Diurnal Tide. 



Arranging the ages of the tides given in the several sections of 

 this paper, we find, — 



Airy, ' Tides and Waves,' p. 332. 



