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MR. AIRY ON THE LAWS OF THE TIDES 



Section XIV. — Semimenstrual inequality in time, proportion of solar and lunar 

 effects from times, and apparent age of tide as shown hy times ; deduced from the 

 time of maximum of the first periodical term in the analysis of individual tides. 



Taking the difference of the means of large intervals and small intervals in the last 



S 

 Table, we deduce from them the value of y^ by the same formula as that employed in 



page 42. The results are as follows : — 



These are the true values of j^*, supposing that the process for finding them has 



been correctly followed. 1 omit here all deductions as to the absolute maximum of 

 semimenstrual inequality in time at each station, for a reason that will be explained 

 in Section XV. 



To obtain the apparent age of tide as shown by times, a process was used analogous 

 to that in page 43 or that in page 106. The times were ascertained (by interpolating 

 between the times in the Tables of formulae in Section X.) at which the actual interval 

 of analysed high water from moon's transit two days previous coincided with the 

 mean interval in the Table of page 107. These times were then compared with the 

 times at which the moon's hour-angle from the sun was 0^, 6^', 12^ IS** ; namely, 

 June 22, 9^ June 30, 20^^ July 7, l9^ July 14, 21^ July 21, 23^ July 30, 16^ August 

 6, 4'', August 13, 5^ August 20, IQ^. The difference was considered to be the appa- 

 rent age of the tide as given by the times. The following are the results : — 



* Tides and Waves, Art. 538. 



