34 



axis, s T. Hence, whether we take into account the other objects which 

 wings may have to accomplish, or the necessary errors of observation, 

 because the black line itself is only an observed line, and a line ob- 

 served after death, I have reason to believe that I have succeeded in 

 showing that we possess a power of prediction with regard to the wings 

 of birds, and to other principles of animal mechanics, that entitles us 

 to say that that science of animal mechanics has entered into the class 

 or group of exact sciences. 



In conclusion, I would say, with regard to prediction, you are all 

 acquainted with the planet Neptune. In fact, the poor planet Neptune 

 is used up ; he has been so hackneyed a subject for lecturers and audi- 

 ences that I will not say anything about him. My friend Professor 

 Tyndall has made most of you acquainted with the extraordinary pre- 

 diction of conical refraction by Sir William Hamilton, whose name 

 will be remembered by those who come after us as that of the greatest 

 mathematician of the nineteenth century. I shall not trouble you with 

 his theory of conical refraction, except to mention a story that possesses 

 an interest as coming from the lips of Sir William Hamilton himself. 

 He told me that he made the calculation late at night. He was not 

 an experimenter, and, as you are aware, the present distinguished Pro- 

 vost of Trinity College, Dr. Lloyd, was the man who actually saw 

 conical refraction first. When Sir VsT^illiam Hamilton took his scribbled 

 paper to Dr. Lloyd, and asked him to make the experiment, any person, 

 not a mathematician (Sir William Hamilton told me), and not accus- 

 tomed to reading his marks, made on little scraps of paper, the backs of 

 letters and the like, would have said, " Oh, he is taking to his friend a 

 piece of paper on which, for fun, he has allowed a spider that he has 

 dipped in ink to run about." 



We find, then, nothing tentative in any branch of Nature. There is 

 nothing tentative in astronomy. No planet ever seeks to move more 

 perfectly in its orbit ; it does so from the beginning. We have no evi- 

 dence that light describes its path by a succession of attempts ; it is 

 singly, doubly, or conically refracted, according to fixed conditions, and 

 has all the appearance of having been always so. The socket and the 

 axis round which birds' wings revolve are placed exactly in the position 

 best suited to produce the best effect ; and here again I find no tentative 

 process. There is no evidence in Nature of birds with imperfect wings; 

 no proof of a succession of blunders before perfection was attained. All 

 is perfect ; and all was always perfect. There have been no ' ' tentative 

 miracles" in nature, no failures, nor trials. The graceful limbs of the 

 beautiful tiger and the expanded pinions of the sweet albatross of 

 Coleridge speak to the ear of reason in language that cannot be mis- 

 understood, 



" The hand that made us is Divine." 



