DIURNAL INEQUALITIES. FOURIER COEFFICIENTS. 



121 



TABLE XXXI. Vertical Force. Fourier Coefficients. (Unit ly.) 



TABLE XXXII. Inclination. Fourier Coefficients. (Unit 1'.) 



33. Tables XXXIII to XL are devoted to the c and a (amplitude and phase angle; Fourier coefficients 

 in the diurnal inequality as derived from the a and b coefficients in Tables XXIV to XXXII. The tables 

 correspond in pairs, except that there is no c, a, table for Vertical Force corresponding to Table XXX. 

 If the phase angle a varies much throughout the year, the contributions from the individual 12 months to 

 the mean diurnal inequality for the whole year tend to neutralise one another, and so the amplitude of 

 the mean inequality for the year is apt to suggest that the corresponding wave is smaller throughout the 

 year than it actually is. Some writers thus prefer the arithmetic mean of the c's and <z's from the 

 12 monthly data for a particular wave to the corresponding results from the mean diurnal inequality of 

 the whole year. This is the reason why Tables XXXIV, XXXVI, XXXVIII, XXXIX, and XL contain 



R 



