87 



her 1819 it was found by Sir John Franklin to be 6 East (Journey 

 to the Shores of the Polar Sea, 1819-22, p. 26), and by Lieut.- 

 Colonel Lefroy in 1843, 9 25' East. Thus we perceive that in little 

 more than a century (from 1725 to 1843) the decimation at York 

 Fort had changed progressively, by the operation of secular change, 

 not less than 28, always in the direction of westerly decreasing or 

 easterly increasing ; (which is in effect the same as a movement of 

 translation of the isogonic lines from west to east) . 



In 1841 the Toronto Observatory commenced its observations, 

 and although (from defective instrumental organization) the conclu- 

 sions in regard to the secular change of the declination were not at 

 first as precise as could be desired, they were sufficiently so to justify 

 a strong persuasion that some very notable change had recently 

 taken place in the order of the phenomena, and to lead to the com- 

 mencement, in January 1845, of a special series of monthly determi- 

 nations in a detached building, appropriated chiefly to a close inves- 

 tigation into the direction and amount of the secular change. The 

 result is stated in the 3rd volume of the Toronto Observations, p. cxxvi, 

 and is as follows : "The secular change of the declination from 

 1845 to 1851 inclusive was an annual increase of l'*95 of west decli- 

 nation. From July 1851 to April 1854 (two years and nine months) 

 an annual increase of 2*54 : and assuming the circumstances of a new 

 series commenced in 1855 with the same instrument placed in a new 

 building to be strictly comparable with those of the old series, the 

 increase from April 1854 to October 1855 is at the mean annual rate 

 of 3 f< 54." The progressively increasing amount of the rate of secu- ' 

 lar change is a circumstance which, for obvious reasons, may be ex- 

 pected to follow for a time after the reversal of the direction of the 

 change. 



Attention being thus alive, particular care was taken that the 

 azimuth compass with which Lieut. Blakiston was supplied should 

 be free from instrumental error, and the practice was recommended 

 to him of repeating observations at different hours and on different 

 days. The following is a transcript of the report received from him 

 from York Fort, showing how thoroughly these directions were kept 

 in view : 



