33 



number of sea-captains going round Cape Horn. They told me that 

 there was great super:3tition among the sailors about the albatross. 

 They all remembered the story of the Ancient Mariner, and the passage 

 into the " silent sea", where "slimy things with legs did crawl". You 

 remember Coleridge's words about the bird and the prejudices con- 

 nected with it. 



"And the good south wind still blew behind. 

 But no sweet bird did follow. 

 Nor any day for food or play 

 Came to the mariner's hollo ! 



" And I had done a hellish thing. 

 And it would work 'em woe : 

 For all averred I had killed the bird 

 That made the breeze to blow." 



In spite of these difficulties, I obtained my albatross, and made my 

 calculation. I was an hour dissecting the pectoral muscle, another 

 hour making measurements upon it, and another hour transferring 

 those measurements to paper for further measurement. After that was 

 done, it cost me five hours of incessant labour with logarithmic tables 

 to take out the figures and calculate the red line P Q, which represents 

 my first approximation ; and the second approximation, l M, required 

 ten hours of numerical work. I have applied equal labour to every 

 one of these six birds; viz., albatross, giebe, macaw, wood-pigeon, 

 pheasant, and heron. My calculated red line represents what I 

 believed would be the position of the axis of the wing corresponding 

 with the law of least action. It comes, in every case, as you ob- 

 serve, uncommonly close to the black axis, ST; it is sometimes above 

 it, and sometimes below. It presents no suspicious nearness to the 

 black axis, and there is a characteristic about it that I must ask your 

 permission for two minutes to dilate upon. It is a characteristic of 

 every real discovery that, if we make closer and closer approximations, 

 we shall find nearer results to the true, but we shall always find cer- 

 tain residual phenomena left behind which our theory will not explain. 

 Now, in the case of the vulture I have a residual phenomenon. The 

 vulture has not only to soar like the albatross, but he has to possess a 

 power which the albatross does not, of rising in the air in the course 

 of an hour or two, from the level of the Pacific Ocean to the heights 

 of Cotopaxi. He has, therefore, two problems to solve ; he has to 

 soar, and rise to a height rapidly. There is hardly any other bird in 

 which, if we studied their habits, we should not find that there were 

 two or three objects to accomplish with their wings. In this calcula- 

 tion, I have entirely neglected those subsidiary objects ; but in the case 

 of one or two birds like the vulture, where I have made the calcula- 

 tion and brought in the two conditions, I have succeeded in producing 

 the red axis of my ellipse so as to become identical with the black 



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