Diurnal Tides on the Coasts of Ireland. 131 



k_ 1 



• 6~386' 



7912 



and, replacing b by its value — ^ — , we find, 



k = depth of sea = 10"25 miles. 



This result differs considerably from that found by Mr. Airy, from other 

 considerations respecting the Semidiurnal Tide, viz., 22 miles ;* but it differs, 

 in the opposite direction, from the depth deducible from the Diurnal Tides, by 

 the aid of the Dynamical Theory. According to this theory, the ratio of the 

 Solar to the Lunar Coefficient, is given by the following equation: — 



n"b , k 



Diurnal Solar Coefficient _ S d' g b /n\ 



Diurnal Lunar Coefficient ~Jl^lT'^n'b k ^ ' 



Substituting, in this equation, the values already given, and assuming the left- 

 hand member from the Diurnal Tide Observations, we obtain, 



0-00323 - 4 ^ 



0-53 = 0-47 j_- 



000345 - 4 ^ 







from which we deduce, 



k_ _!_ 



6~773' 

 and finally, 



k = depth of sea = 5"12 miles. 



It may be interesting to calculate from equation (9), what should be the 

 ratio of the Solar to the Lunar Coefficient in the Diurnal Tide, from the Con- 

 stants of the Semidiurnal Tide, deduced from IVIr. Airy's observations. 



k 

 Substituting, in this equation, for j, its value from the Semidiurnal Obser- 

 vations, ggg, we find, 



* "Philosophical Transactions" for 1845, p. 105. 



s2 



