LXXII THE ROYAL SOCIETY OF CANADA 



Absolute observations made weekly kept good control of the 

 value of the base line of the differential instruments. 



Tables showing the magnetic character of each day were prepared 

 and copies forwarded to the International Commission on Terrestrial 

 Magnetism. The "selected days" of the Commission are used in 

 the analysis of the Magnetic data for the Annual Magnetic Report. 

 The 1919 Report is now in course of preparation. 



At the request of the Surveyor-General, index corrections for 

 compasses attached to 65 surveyors' theodolites were determined and 

 the results forwarded to him. Assistance was also given to several 

 members of his stafif in determining the constants of their Total Force 

 instruments both before and after their summer field work. 



Mr. French and Major Pearce, of the Dominion Observatory 

 staff, were also assisted in standardizing their magnetometers both 

 before and after their field work. 



At Meanook the photographic records of Declination were 

 obtained with only slight loss. During the very cold weather 

 difficulty was again experienced in maintaining continuous operation 

 of the clocks. This would, to a great extent, be overcome if the 

 differential apparatus were placed underground as at Agincourt. 



The weekly observations of Declination and Inclination were 

 continued throughout the year and twice monthly observations of 

 Horizontal Force. 



The Meanook traces were loaned to the Surveyor-General, and 

 the Agincourt traces to the Dominion Observatory for use in the 

 reduction of their field work. 



The accompanying tables give a summary of the results obtained 

 at Agincourt and Meanook during the fiscal year 1920-21. 



