ON HARMONIC ANALYSIS OF TIDAL OBSERVATIONS. 



337 



table for 13 specially chosen days in 1869 was constructed and compared with the 

 corresponding record. 



To examine the variation of certain constituents with the inclination of the 

 moon's orbit, the record for 1866-7 was analysed. It was decided that the variation 

 was not quite according to the equilibrium principle, but was afterwards always 

 treated as if it were so. 



The new results of analysis were incorporated in the tide-table and then the 

 determination of v^, /u.^ and \^ was suggested and carried out for each of the 

 four years taken. 



The tide-table was again emended and compared with the record : the 

 discrepancies over two typical days are shown in Fig. I. The determination of 

 MS, was suggested and the analysing process applied to each of the four yearly 

 records. The tide-table was emended accordingly and the results again compared 

 with the record. The final discrepancies over the two typical days are shown in 



Figs. I. and II. 



-Difference between Predictions and Kecord for Liverpool, 

 April 26 and 27, 1869. 



Fig. II. It should be stated that the tide-table contained a number of constituents 

 of amplitudes less than O'l ft. 

 Numbers for 



Mf, Mm, Ssa, Sa, Msf 



were also obtained from each of the four yearly records, but were inconsistent from 

 year to year. 



The Ramsgate 1864 record was next further analysed for 



Pp "2. ^2> ^!. MS,. 



A set of quarter-hourly observations taken during several periods within four 

 days in the Fiji Islands, and supplied by Lieut. Hope, R.N., were partially analysed. 

 The difficulties presented by the shortness of the periods led Thomson to apply to 

 the U.S. Coast and Geodetic Survey for a trustworthy record of Pacific tides. He 

 received that of Fort Point, California, for 1858-9, and it was analysed for all the 

 constituents considered at Ramsgate. As a test an hourly tide-table for 14 days 

 was made without ^j, \^, the long-period constituents and MS,, but including several 



1920 z 



