THE WANDERINGS OF THE NORTH POLE. 85 



mauifested by tlie cliaiijies of latitude. We shall now be able to uiider- 

 staiul liow any nioveuieiit of the pole, or rather of the position which it 

 occupies in the earth, would be indicated at Greenwich. Siqipose, for 

 instance, that the pole actually advanced towards Great Britain, and 

 that it moved to a distance of, let us say, 30 feet, the effect of this would 

 be to produce a diminution of the distance between the pole and Green- 

 wich, that is to say, there must be an increase in the distance from 

 Greenwich to the equator. This would corresjiond to a change in the 

 latitude of Greenwich; that latitude would diminish by three-tenths of 

 a second, which is a magnitude quite large enough to be recognizable 

 by the observations I have already indicated as jiroper for the determi- 

 nation of latitude. A shift of the pole to a distance of GO feet would be 

 a conspicuous alteration announced in every observatory in Europe i)ro- 

 vided with instruments of good modern construction. 



Until the last few years there was not much reason to think that the 

 pole exhibited any unequivocal indications of movement. i:^o doubt, 

 displacements resembling those which have now been detinitely ascer- 

 tained have existed for many years, but they were too small to produce 

 any appreciable eflt'ect, except with instruments of a more refined de- 

 scription than those with which the earlier observatories were equipped. 

 It was obvious that the pole did not make movements of anything like 

 a hundred yards in extent; had it done so the resulting variations in 

 latitude would have been conspicuous enough to have obtained notice 

 many years ago. The actual movements which the pole does make are 

 of that sm.all character which require very minute discussion of the 

 observations to establish theni beyond reach of cavil. There is how- 

 ever one striking method of confirming such observations as have been 

 made which leaves no doubt of the accuracy of the results to which 

 they point. Suppose, for instance, that the great observatories in 

 Europe indicate at a certain time that their latitudes have all increased ; 

 this necessarily implies that the equator has receded from them, and 

 that, therefore, the North Pole has approached Europe. If however 

 the North Pole has approached Europe it must liave retreated from 

 those regions on the opposite side of the world — say, for instance, the 

 Sandwich Islands. Observations in the Sandwich Islands should 

 therefore indicate, if our reasoning has been correct, that the pole has 

 retreated from them, and that the equator has therefore advanced in 

 such a way that the latitudes of localities in the Sandwich Islands have 

 diminished. The various observations which have been brought to- 

 gether by the diligence of Mr. Chandler, including those which lie has 

 himself made with an ingenious apparatus of his own design, have been 

 submitted to this test, and they have borne it well. The result has 

 been that it is now possible to follow the movements of the ])ole with a 

 considerable degree of completeness. Prof. Chandler has tracked the 

 pole month after month, year after year, through a period of more than 

 a century of exact observations, and he has succeeded in determining 



