LXXXVIII THE ROYAL SOCIETY OF CANADA 
Magnetic disturbances were of very frequent occurrence during 
the year, the month of February, 1916, being the only month during 
which no large disturbance was recorded. The greatest storm was 
on June 17th, which was remarkable both for its duration, the magni- 
tude of the disturbing forces, and the rapidity with which the forces 
changed. The extreme values of Declination during this storm were 
5° 6’-2 west and 8° 21’-7 west. The Horizontal Force ranged from 
0-15586 dynes to 0-16418 dynes and the Vertical Force from 0-58040 
dynes to 0-59152 dynes. 
Other disturbances worthy of note were recorded on August 25, 
October 15, and November 5 and 6, of 1915, and on March 17, 1916, 
but neither in amplitude nor duration are any of these comparable 
to that of June 17, 1915. 
The mean diurnal range obtained from the hourly measures 
varied in Declination from a maximum of 14’-4 in August, 1915, 
to a minimum of 6/-5 in December, 1915, in Horizontal Force from a 
maximum of 0-00052 dynes in August to a minimum of 0-00028 
dynes in December, and in Vertical Force from a maximum of 0-00032 
dynes in November, 1915, to a minimum of 0-00006 dynes in Decem- 
ber, 1915, and February, 1916. 
In November at the request of Dr. L. A. Bauer, Director of the 
Department of Terrestrial Magnetism of the Carnegie Institution 
of Washington, Mr. Jackson of the Observatory staff. was sent to 
Washington in order to make a series of comparisons between the 
Agincourt Magnetic instruments and the International Magnetic 
Standard as determined by Dr. Bauer. 
The results of these comparisons are as follows: 
I.M.S.—Agincourt (Standard Declinometer) = —0’-93 
I.M.S.—Agincourt (Elliott Magnetometer 98) = —0-00033H 
I.M.S.—Agincourt (Toepfer Inductor No. 89) = —0’-15 
Commencing January, 1916, all Agincourt data will be reduced 
to International Magnetic Standard. 
During the year 129 compasses attached to Surveyors’ transits, 
were adjusted and compared with the Agincourt Standard Declinom- 
eter, and the index corrections resulting therefrom were supplied 
to the Surveyor General. Assistance was given to Messrs. Purser, 
Wight, and Robinson of the Department of the Interior in standard- 
ising their total force Magnetic Instruments both before and ‘after 
their field work. 
Mr. French of the Dominion Observatory was also given assist- 
ance in comparing his magnetometer with the Agincourt Standards 
both before and after his field work. 
