89 



It happens that four of the stations in this route, at which Mr. 

 Palliser observed the declination in the summer of 1857, had been 

 stations of Lieut. -Col. Lefroy in 1843-44. They are as follows : 



Declination. 

 Lat. Long. 1843-44. 1857. 



Savannah Portage 48 53 N. 90 05 W. 7 46 E. 6 53 E. 



Fort Francis 4836 9330 936 931 



Lake of the Woods 49 27 94 44 1216 1017 



LakeWinipeg 5028 9635 1530 1425 



Means 11 17 E. 10 14 E. 



At all the stations the easterly declination is less in 1857 than in 

 1843-44; and on the average of the four stations it would appear 

 to have decreased about 1 in the fourteen years. 



It would be unjust to the memory of the profound and sagacious 

 philosopher, by whom, more than 150 years ago, the facts both of 

 the magnetic declination in different parts of the globe and of its 

 changes were first collected and framed into an hypothesis (Halley 

 in Phil. Trans. 1692, No. 193), if we were to fail to recognize that 

 this reversal in the direction of the motion of the isogonic lines, in 

 the vicinity of the principal magnetic pole in the northern hemisphere 

 (using the term 'pole' in the physical sense in which Halley employed 

 it), is conformable to the hypothesis which he propounded at that 

 early date, " to explain," according to his own words, "the change 

 in the variation (declination) of the magnetic needle." By the sup- 

 position of a double system of the terrestrial magnetic forces, occa- 

 sioning two poles or principal points of attraction in each hemi- 

 sphere producing resultant phenomena in all parts of the surface of 

 the globe according to their relative strength and proximity, Halley 

 showed that all the apparently complex phenomena of the magnetic 

 direction might be systematically represented ; and by the further 

 supposition that one of the two systems (the stronger one) was fixed, 

 and the other (the weaker one) possessed a gradual and slow motion, 

 that a reasonable explanation could be given of the phenomena of 

 the secular change in different parts of the globe, as far as they were 

 known in his time. At the period when this hypothesis was ori- 

 ginated, viz. in 1692, the two poles in the northern hemisphere were 

 considered to be situated as follows : that of the stronger and fixed 



