100 THE ROYAL SOCIETY OF CANADA 



magnetic axis in the summer. Is this due to the northern hemisphere 

 being subjected more directly to the influence of the Sun during the 

 summer ? 



The range of DecHnation throughout the year shows a very 

 great variation from this annual pulsation. The difference between 

 the maximum Easterly and Westerly movements as recorded in the 

 various months are given in table II, columns 2 and 3. There is no 

 periodicity apparent, nor is there any marked parallelism in the 

 ranges at the two places, although generally larger ranges at one 

 place correspond to larger ranges at the other. 



If now we examine diurnal ranges, by which we mean the 

 difference between the greatest East and West movement recorded 

 in the 24 hours, we find that from day to day no periodicity is at once 

 apparent in the amplitude. Days of greater disturbance have as a 

 rule greater amplitudes. If, however, these ranges are meaned for 

 each calendar month we get the result in table II, columns 4 and 5, 

 in which a maximum occurs in summer and a minimum in winter 

 and a certain amount of parallelism is apparent between Agincourt 

 and Meanook, yet the summer values for Meanook are roughly double 

 those of Agincourt, whilst the winter values are only very slightly 

 greater. If the diurnal range is taken from the mean monthly curve 

 obtained by meaning the values at each particular hour of the day, the 

 irregularities due to individual days are greatly diminished and the 

 ranges are then more regular in their progression from season to season 

 at both places, see table II, columns 6 and 7. The winter values at 

 both are of the same order and summer values at Meanook are only 

 about ^ greater than at Agincourt. 



The diurnal variation for each month for each hour of the day 

 for Agincourt and Meanook are given in tables III and IV. + signifies 

 that the Magnet points to the East of its mean position and — to the 

 west. In these tables the standard time at each observatory has been 

 used. In order to show how the diurnal variation appears to be 

 directly dependent on Sun time, the curves have been drawn on chart 

 I for both places according to their Local Mean Times. 



During the winter months, November to February inclusive, the 

 curves agree very well with each other, but during the summer months. 

 May to August inclusive, both the maximum Easterly value and the 

 minimum Westerly value are reached about one hour later at Meanook. 

 The amplitude of the Easterly swing is about one third greater at 

 Meanook, but that of the Westerly is about the same at the two places. 

 This may be partl}^ due to the greater magnetic latitude of Meanook 

 and possibly also to the longer daylight. For the four summer 

 months — May, June, July and August — the sun is above the horizon 



