172 MIGRATION AND DISTRIBUTION 



the benefit of the species, but it is hard to see how the 

 machinery works. However, I am not going to descant 

 on this now. Clearly your observations have been more 

 interesting than those on the Eddystone, and I hope we 

 shall have from you a paper in the Ibis accordingly ; but 

 more than that they ought to help enormously towards 

 that book on migration generally that I have long been 

 hoping you will one day write ; for you of all men are 

 the man to do it. Still, still the great mystery of how 

 the birds do it remains, and that I begin to fear will 

 never be explained in my time ; but it is no deterrent, 

 or ought not to be, to you. 



The more the facts of migration are ascertained the 

 more likely are we (or our successors) to understand what 

 brings them about ; so I trust you will be setting 

 seriously to work on what ought to be a great book, 

 which will cast into shade everything that has been 

 written before, even the good Barrington's excellent 

 performance. 



Often as I have thought over what appears to be the 

 ' waste " of bird life at sea (a thing which very few people 

 ever take in at all) this last letter of yours fills me with 

 fresh and ever-increasing amazement. The slaughter, if 

 one may so call it, seems so indiscriminate ; there can be 

 scarcely room for Natural Selection to act. Were you 

 able to form any opinion as to the proportion of young 

 to old birds, or were the troops almost wholly one or 

 the other ? * 



Mr. Clarke could not return a satisfactory answer to 

 the last question, owing to the high speed at which the 

 birds were travelling, but he remarked : 



I have a number of notes on the subject of old and 

 young, but in the vast 'majority of cases it was quite 

 impossible to say what the flocks were composed of in 

 this respect. As to the waste of life, I am afraid Nature 

 never contemplated lighthouse and lightship lanterns, 

 and it is difficult to see how she works, if she works at 



* Letter to W. Eagle Clarke, October 22, 1903. 



