MIGEATION OF BIRDS 161 



and I suspect the young go off of their own accord. It 

 would take a Hfetime to make this out, and few men 

 have the leisure or opportunity for such continuous 

 observation as would be required. I have been in my 

 younger days especially favoured in that way ; for 

 beginning as a boy, I had nearly twenty years of good 

 opportunities ; but, of course, of those twenty years a 

 great part was spent in learning one's business, I can't 

 say in apprenticeship, for that would imply the teaching 

 or supervision of a master, and master, of course, I had 

 none. Moreover, during that period there were various 

 interruptions, such as schools, college, and going abroad 

 from time to time ; though I had my brother to help me, 

 and he was a far better observer than I. Our joint 

 experience, however, points to what I have stated, and 

 the *' Register " we kept for nearly ten years warrants 

 my having confidence in it ; the more so that since that 

 time the more I read about migration by good observers 

 the more I am confirmed in the opinion.* 



The letters of ill-informed persons to the newspapers 

 about migration, not less than about bird protection, 

 roused Newton's wrath. The " silly season " of 1874 

 was marked by a discussion of this sort, which impelled 

 him to write to Nature a masterly exposition of the facts 

 of migration as far as they were then understood. The 

 discussion began with a theory of migration set forth by 

 a Scandinavian poet, which treated that movement as 

 an attempt on the part of the birds to obtain more light. 

 It is not certain whether the theory was advanced in 

 earnest or merely as a poetic fancy, but it is obvious 

 that it contains its own refutation. The first letter, 

 which professed to give the " latest accepted theory " 

 on the subject and which prompted Newton to reply, 

 is so remarkable that extracts may be quoted from it 

 here. 



* Letter to W. Eagle-Clarke, February 2, 1901. 



M * 



