Diurnal Tides of the Coasts of Ireland. 



115 



RathmuUan Tide, Table F. 



Difference of observed and calculated times of vanishing at low 

 water at RathmuUan, expressed in lunar days. 



Age of lunar tide = 4i^ 2Q^. 



Section VII. Diurnal Tide at Portrush. 



From the data calculated from the Diurnal Tables, the solar and 

 lunar diurnal tides at Portrush were obtained separately, as before, 

 and found to give the following results : — 



I. Diurnal tide at high water, 



1. Maximum value of lunar tide for positive heights =0*22 ft. 



2. Maximum value of lunar tide for negative heights = 037 ft. 



3. Maximum value of solar tide =0-25 ft. 



4. Diurnal solitidal interval =\\^ SO"". 



5. Age of lunar tide = 5*^ 9^. 



II. Diurnal tide at low water. 



1. Maximum value of lunar tide for positive heights =0-15 ft. 



2. Maximum value of lunar tide for negative heights =0*19 ft. 



3. Maximum value of solar tide =0-25 ft. 



4. Diurnal solitidal interval =\V^ 30°". 



5. Age of lunar tide =4^ ig*'. 



Adding the first two of each of the preceding, we obtain — 



Range of lunar tide at high water =0-59 ft. 

 Range of lunar tide at low water =0*34 ft. 



Hence by equation (3), 



cot {m-i^ = ^ = cot (29° 57') ; 



