220 A SENSE OF POLARITY 



that the impulse was due to an extraneous force, 

 and that the force was in all probability terrestrial 

 magnetism. Afterwards I came upon a passage 

 quoted from the indomitable Arctic explorer, John 

 Rae, who found the icy North a "friendly" realm 

 three-quarters of a century before Stefansson. He 

 says of the musk-ox that their north and south 

 movements were due to a "sense of polarity." The 

 phrase delighted me, as it expressed just what I 

 believed to be the cause of all seasonal migration. 

 Finally, in Professor Newton's article on Migration 

 in the ninth edition of the Encyclopedia Britannica, 

 I came upon the account of the naturalist Midden- 

 dorf's observations on the migration of birds in 

 Russia (1855). He found that the flight of all the 

 migrants was towards the Taimyr Peninsula, the 

 seat of one of the magnetic poles, and concluded 

 that the birds were drawn in that direction or, as 

 he strangely expressed it, were aware of that point 

 and knew how to steer their course. 



Our great ornithologist dismissed the suggestion 

 somewhat contemptuously. In the last (the eleventh) 

 edition of the Encyclopedia, for which Newton's 

 article was re-written, Middendorf's suggestion is 

 omitted. Nevertheless it was to me a pleasing 

 surprise; it was a gratification to learn that this 

 idea, which came to me in the early seventies in 

 southern South America, had occurred independ- 

 ently to two other observers so far apart one 

 in the Arctic regions in 1845, the other in Russia 

 ten years later. 



