TRANSACTIONS OF SECTION E. 705 



Tlie Magwitic Poles of the Earth, 



I will now refer to those two areas on the globe where the dipping needle 

 stands vertically, known as the magnetic poles. The determination of the exact 

 position of these areas is of great importance to magnetic science, and I will jnst 

 glance at what is being done to solve the problem. 



Let us consider tlie North Pole first, the approximate position of which we 

 know best from observation. If one were asked to say exactly where that pole has 

 been in observation times, whether it has moved, or where it now is, the answer 

 must be ' I do not know.' It is true that Ross in 1831, by a single observation, 

 considered he liad fixed its position, and I believe hoisted the British flag over the 

 spot, taking possession thereof; but he may or may not have set up his dip circle 

 over a position affected by serious magnetic disturbance, and therefore wa must 

 still be doubtful of his complete success from a magnetic point of view. Although 

 eminent mathematicians have calculated its position, and Neumayer in 1885 gave 

 a place to it on his charts of that year, we have still to wait for observation to 

 settle the question, for one epoch at least. 



Happily, I am able to repeat the good news that the Norwegian, Captain 

 Roald Amundsen, sailed in June last with the express object of making a mag- 

 netic survey of Ross's position and of the surrounding regions, in order to fix the 

 position of the north magnetic pole. Furnished with suitable instruments of the 

 latest pattern, he proposes to continue his investigations until 190.J, when we may 

 look for his return and the fulfilment of our hopes. 



As far as we can now see, the south magnetic pole cannot be approached ver-,- 

 nearly by the traveller, and we can only lay siege to it by observing at stations 

 some distance off but encircling it. We have our own expedition on oue side of 

 it, and now with the return of the ' Gauss ' to South Africa in June last, we have 

 learnt that that vessel wintered in lat. 66° 2' S., long. 89° 48' E., a position on 

 the opposite side of the supposed site of the magnetic pole to that of the 

 ' Discovery.' AVe may now pause to record our warm congratulations to Dr. von 

 Drygiilski and his companions on their safe return, accompanied by the welcome 

 report that their expedition has proved successful. 



In addition to the British and German expeditions, there are the Swedish 

 expedition and the Scottish expedition. Therefore, with so many nationalities 

 working in widely different localities surrounding it, we have every reason to 

 expect that the position of the south magnetic pole will be determined. 



The Secular Change. 



When in the year 1600 Gilbert announod to the world that the earth is a 

 great magnet, he believed it to be a stable magnet ; and it was left to Gellibrand, 

 sonie thirty-four years later, by his discovery of the annual change of the mag- 

 netic declination near Loudon, to show that this could hardly be the case. Ever 

 since then the remarkable and unceasing changes in the magnetism of the earth 

 have been the subject of constant observation by magneticians aud of investi- 

 gation by some of the ablest philosophers in Europe and America. Year after 

 year new data are amassed as to the changes going on in the distribution of the 

 magnetism of the earth, but as yet we have been favoured by hypotheses only as 

 to the causes of the wondrous changes which the magnetic needle records. 



These hypotheses were at one time chiefly based upon a consideration of the 

 secular change in the declination, but it is now certain that we must take into 

 account the whole of the phenomena connected with the movements of the needle, 

 ir we are to arrive at any satisfactory result. Besides, it will not suffice to take 

 our data solely from existing fixed observatories, however relatively well placed 

 and equipped, and valuable as they certainly are, for it now appears that the 

 secular change is partly dependent upon locality, and that even at places not many 

 miles apart differences in results unaccounted for by distance have been obtained. 



The tendency of observation is increasingly to show that the secular change of 

 the magnetic elements is not a world-wide progress of the magnetic needle moving 

 1903. • 2 a 



