[jackson] magnetic HORIZONTAL FORCE AT AGINCOURT 



19 



24 hour ordinates is the same as for March. This variation of type 

 is shewn on Plate 2. The portion of the inequahty confined to the 



PLATE K<^£. ^GINCOUrr HOfClZOKTAL FOKCE. 



daylight hours where the amplitudes are large is much the same in 

 all seasons, but the type of the curves vary greatly during the night 

 hours where the departures from the mean are least and the changes 

 are less rapid. The same result was obtained with the D curves. 



The Fourier coefficients for the diurnal inequalities of H as given 

 in Table I were calculated and Table II gives these values for each 

 month of the year for the first four terms of the series Ci sin. («i + t) 

 + C2 sin. (Q!2 + 2t) + . . ..where t represents the time counted from 

 midnight at the rate of 15° to the hour. 



