108 



THE ROYAL SOCIETY OF CANADA 



of D at Agincourt (1902-1912). 75th meridian time has been em- 

 ployed and all days were taken in forming the Diurnal inequalities. 



Table II. 



Fourier Coefficients for Diurnal Inequalities of D at Agincourt 1902-1912. 



75th M.T. 



In regard to amplitudes we see that the first three terms have their 

 maximum at midsummer and their minimum in midwinter, whilst 

 the 6 hour term has its maximum at the equinoxes and its minimum 

 at midsummer. An examination of the phase angles shows that in 

 the 24 hour term the occurrence of maximum is earlier in midwinter 

 than midsummer by 33° or 2h. 12m. and that the change is gradual from 

 the one season to the other. The phase angle of the 12 hour term 

 has its maximum earlier in the summer by about 21° or 42 minutes, 

 but the time of earliest occurrence is not so well marked, the September 

 value in this group of years being the larger. In the 8 hour term 

 the phase angle also shows its earliest occurrence of maximum in the 

 summer, being 62° or 1 h. 24m. earlier than in the winter, but the 

 progression from one season to the other is not quite so uniform 

 in the 12 hour and 8 hour terms as in the 24 hour term. The 6 hour 

 term is still less regular in the progression from season to season, 

 but the earliest occurrence is again in the summer, being 112° or lh. 

 52m. earlier than in the winter. 



These results are better seen perhaps by grouping the diurnal 

 inequalities for the various months into the seasons, taking for 

 winter the months January, February, November and December, 

 and for Equinox the months March, April, September and October, 

 and for Summer May, June, July and August. 



