On Magnetic Observations transmitted from York Fort, 149 



to au increasing rate. The dip observed by Lieut. Blakiston at 

 York Fort was 83° 53' in 1857, and by Lieut.-Col. Lefroy 83° 47'-2 

 in 1843, showing, as at Toronto, a shght increase to have taken place 

 in that element in the interval. 



I am indebted to Dr. Norton Shaw, Secretary of the Royal Geo- 

 graphical Society, for a copy of dechnations observed by Mr. Palliser 

 in his passage between Fort William and the Red River Settlement. 

 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 48 36 93 30 9 36 9 31 



Lake of the Woods .... 49 27 94 44 1216 1017 



LakeWinipeg 50 28 96 35 15 30 14 25 



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 tlie memory of the profound and sagacious 

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

 the magnetic dechnation 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 tliat 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 

 system in North America, about the meridian of the middle of Cali- 

 fornia, and that of tlie weaker and moving system, about the meri- 

 dian of the British Islands, having a jjrogressive motion towards the 

 cast. Now as the resultant j)henomena in the north of America, 



