The Tide-generating Forces 



267 



diurnal and 14 one-third diurnal terms. Table 28a contains a selection of 

 the more important components with their basic values, and it also indicates 

 the symbol by which they are designated. The numerical coefficient of the 

 largest component M 2 is put equal to 100. The amplitude ratios (refer to 

 M. 2 = \00) listed in Table 28a under column coefficient ratio are the most exact 



Table 2Sa. Principal harmonic components 



Name 

 of partial tides 



Speed per 



mean 

 solar hour 



Period 



in 



solar hours 



Coefficient 



ratio 

 M, : 100 



Semi-diurnal components 



Diurnal components 



Long-period components 



Lunar fortnightly 

 Lunar monthly 

 Solar semi-annual 



Mf 

 Mm 

 Ssa 



cos 

 cos 

 cos 



075-55 

 065-45 

 057-55 



1-09803° 

 0-54437 

 0-08214 



327-86 



661-30 



2191-43 



17-2 

 91 

 80 



8-6 

 4-6 

 40 



according to the latest analysis of Doodson and differ slightly from previous 

 computations by other authors. The signs refer to the equilibrium tide r/ 

 (see p. 273). If we select from the complete list those whose relative numerical 

 coefficient is ^ 0-5, we obtain 63 components, of which, however, quite 

 a few are almost insignificant. In practice, one uses mainly the following 

 7 components: 



4 semi-diurnal components: M 2 , S 2 , N 2 ,~P^, and 

 3 diurnal components : K x , O x , P x . 



