OF QUADRUPEDS AND BIRDS. 133 



My father, though astonished at the result, acknow- 

 ledged that Mr. Craven's reasoning had the greatest 

 air of probability, however incredible it might appear, 

 at the' first view, to those who had never made the 

 comparison between the known speed of quadrupeds 

 and the probable swiftness of birds. " How surpris- 

 ing," said I, " that such a little tender creature as a 

 swallow should be capable of enduring such excessive 

 fatigue, and travelling to such vast distances !" This 

 remark drew from Mr. Craven many observations on 

 the harmony of the structure of birds, with their habits 

 and necessities, and the migration of various kinds of 

 animals ; which show that he has collected knowledge 

 from books as well as from experience, and pleased 

 me so well that I cannot withhold them from you. 

 " The goodness and wisdom of Providence," said he, 

 " have furnished every creature with those things best 

 adapted to its wants. Birds of passage are admirably 

 qualified for such expeditions as their instincts prompt 

 them to undertake. Let us select the swallow as an 

 example. The narrowness of its fronts if the expres- 

 sion be allowable, exposes but a small surface to the 

 resistance of the air. The glossy smoothness of their 

 feathers, which lie so compactly over one another, and, 

 above all, the membraneous cells or cavities distributed 

 in their bones for the reception of air, make them 

 light and buoyant. The length of the outward fea- 



