APPENDIX B LXI 



Terrestrial Magnetism 



During the fiscal year ending March 31, 1920, the photographic 

 records of the daily changes in the Magnetic elements at Agincourt 

 were obtained without material loss. Magnetic disturbances were 

 of frequent occurrence and often for short periods passed beyond the 

 recording limits of our instruments. The most pronounced dis- 

 turbances took place on the following dates: 1919 — ^April 7, 17; 

 May 2, 3; August 11, 12; September 19, 20; October 1, 2, 3, 5, 6, 

 23; December 14, 15; 1920— March 4, 5, 22, 23. 



Absolute observations were made weekly to keep control of the 

 base line values of the differential instruments. 



Tables showing the Magnetic character of each day have been 

 forwarded as usual to the International Commission on Terrestrial 

 Magnetism. The days selected by the Commission for analysis 

 have been used in the preparation of the Magnetic Reports for both 

 Agincourt and Meanook. The Report for 1919 is now in progress. 



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

 compasses attached to 71 surveyor's theodolites were determined 

 and the results forwarded to him. 



Assistance was given to several members of the staff of the 

 Surveyor-General's Department in determining the constants of 

 their Total Force instruments both before and after their field work, 

 and also to Mr. French of the Dominion Observatory in standard- 

 izing his magnetometer both before and after his field work. 



Special observations were made during the Total Solar Eclipse 

 of May 29 at the request of Dr. Bauer, Director of the Department of 

 Terrestrial Magnetism, Carnegie Institution, Washington, and a report 

 of the results forwarded to him. 



At Meanook only the Declination changes are observed photo- 

 graphically and the instrument for this purpose was maintained in 

 operation throughout the year. During the very cold weather of the 

 winter, dififîculty was again experienced in keeping the clocks running 

 and a considerable number of hours of record were lost. 



Weekly observations were made of Declination and Inclination, 

 and twice monthly of Horizontal Force. 



