50 Dr. Jenner on the Migration of Birds. 



« In all the intermediate emotions between these extremes, 

 the varieties of expression in the face are produced by the op- 

 position of the two powers affecting the same muscles ; the 

 one is a voluntary power, by which we restrain the features 

 and conceal emotion ; the other is an involuntary power, which 

 cannot be always controuled, but which will sometimes have 

 sway and mingle its influence." 



[To be continued.] 



I 



VII. Some Observations on the Migration of Birds. By the 



late Edward Jenner, M.D. F.li.S. ; with an Introductory 



Letter to Sir Humphry Davy, Bart. Pres. R.S., by the 



Rev. G. C. Jenner.* 

 Sir, 



T had long been the intention of my late revered uncle, 

 Dr. Jenner, to lay the accompanying Observations on the 

 Migration of Birds before the Royal Society, as well from in- 

 clination, as to redeem a pledge he had given some years ago 

 to that learned body ; but which he svas unable to accomplish, 

 in consequence of his extensive correspondence with almost 

 every part of the globe on the interesting subject of Vaccina- 

 tion, which occupied nearly the whole of the time his more 

 immediate professional avocations would allow him to bestow 

 on other objects. 



It was my peculiar happiness to accompany Dr. Jenner in 

 most of his investigations of the phaenomena of migration ; and 

 the paper I have now the honour of presenting, was left in my 

 hands at the time of his decease. 



Had it pleased Providence to have spared him a little longer, 

 he might probably have corrected some inaccuracies in the 

 style and order of his paper, that may now perhaps appear 

 conspicuous to the reader, but which I did not conceive my- 

 self justified in attempting. 



I have the honour to be, Sir, 

 Your most obedient humble servant, 



Stone, near Berkeley, May 29, 182.'?. G. C. Jenner. 



To Sir Humphry Davy, Bart. 

 President of the Royal Society. 



It is not my intention, in the following pages, to give a ge- 

 neral history of the migration of birds. The order in which 



• From the Philosophical Transactions for 1,824, Part I. 



they 



