^otes to Introductory Lecture. Ixv 



to it. Linnaeus confined submersion to chimney swallows 

 and martins. Kalm his pupil believes the story, and begins 

 the discussion of the subject by saying that " natural history 

 like all other histories depends not always upon the intrinsic 

 degree of probability, but upon facts founded on the testi- 

 mony of people of noted veracity."^ But this testimony must 

 not violate probability, nor be inconsistent with one of the 

 first rules of philosophising, viz. that " like causes produce 

 like effects ;" now, if we find that the lungs of two animals 

 are constructed precisely alike, and that one of them cannot 

 live under water, we must conclude that the other is also defi- 

 cient in that same power. This is the case with man and 

 swallows: both are formed alike, and hence they must be sub- 

 ject to the same laws. Those who wish to see more on this 

 question are referred to a paper I published (anonymously) in 

 the Med. Repository of N. York, vol. 3, p. 2i.l. — 1800. Bar- 

 ton's Fragments, Philad. 1799, Caldwell's Memoirs, 1801, 

 and to " Observations on the brumal retreat of the swallows," 

 hy Thomas Foster, F. Lin. Soc. London, 1813. The argu- 

 ments of this author in favour of the swallow being a bird of 

 passage are indisputable : he has also annexed an index to 

 passages relating to the swallow in the works of the antients, 

 and in modern European authors, which is curious and 

 liighly interesting. 



JS'ote 42. 



Adrian Vandervelde was born in 1639 at Amsterdam, and 

 was a pupil of John Wynants. lie died at the age of 33. 

 See further, Pilkington's dictionary of painters, p. G&'j, 4to. 

 London, 1798, and Camper on the connexion between ana- 

 tomy and drawing, &c. translated from the Dutch by Dr. 

 Cogan, London, 1794. 



JS'ole 43. 



Aristotle long since remarked that tlie motion or steps of 

 animals in general are made in the line of their diagonal : 



* Travels, vol. 2, p. 140. 



