D2 On the Norlh-wesl Magnetic Pole. 



most westing. It being reasonable to suppose that the magnetic 

 pole will move as far to the east as it has to the west of the me- 

 ridian of London, the whole period of its movement in a straight 

 line within the earth, from west to east, will be thus 322 years. 

 In the year 1600 the variation at St. Helena was 8° east. In 

 1692 it was 1° west. In 1796 I make it there, from a medium of 

 morning and evening observations on a meridian, 15° 48'34"'5 ; 

 while in London, in 1795, it was 23° 57'. — It is experimentally 

 found, that magnetic action, like that of heat, diminishes in- 

 verselv as the squares of the distances. Again, the south pole, 

 after passing the equator, attracts the south end of the dipping 

 needle (which must, necessarily, possess a north polarity), and 

 the east and west variation in south latitude are generally less 

 than in similar situations in the northern hemisphere. The ac- 

 tion of the south pole, combined with the other cause stated, 

 may go far in accounting for this anomaly. 



It was essentially necessary to take the foregoing view of this 

 most wonderful and interesting subject, previously to recom- 

 mending the conmiencement of a most important series of ex- 

 periments calculated to ascertain decidedly, whether the recently 

 discovered north-west magnetic pole has, or has not, a periodi- 

 cal movement corresponding to east and west variation, increas- 

 ing and decreasing, as has been observed. There can be but 

 one infallible mode of making this grand and conclusive experi- 

 ment, and I take your widely circulating and valuable publica- 

 tion as the channel through which I earnestly call the attention 

 of philosophers and men of science, to a sublime discover)', 

 which British daring and fearless enterprise has, at length, put 

 within the reach of patient and accurate investigation. 



The position of the north-west magnetic pole has been ap- 

 proximated, to a moral certainty. — I take it for granted, that 

 the discovery-ships will proceed again to explore to the utmost 

 the channels in the Polar Basin, to the westward of Baffin's Bay. 

 The principal object must be the ascertaining precisely the posi- 

 tion of the new pole, or I would rather denominate it. the mov~ 

 ing magnetic power, of whose existence no further doubt can 

 remain. — This having been hajjpily achieved by tlie bold com- 

 mander, and by his companions, who have deserved so much of 

 their country, a meridian should be accurately laid off, at some 

 distance from the site of the new magnetic power. The gra- 

 duated circumference and needle applied to this meridian, ought, 

 in principle and construction, to reseiuljle those used by me, and 

 described in the papers I have alluded to. The meridian sustained 

 by a strong post, might lie sheltered !)V a snuiU building devoid 

 of iron. Careful observations made, annually, for a few years, 

 on this mcridiiui, would clearly dctcimiue whether or not the 



north- 



