THE BONES. 39 



diameter it was less than one-eighth of an inch, and 

 the solid tubular part not more than one-hundredth 

 part of an inch in thickness, it could not be broken 

 asunder by the hand. 



It is upon this principle mechanics and engineers 

 act in constructing strong supports, knowing that if 

 any quantity of material is to be fabricated into a 

 rod of a certain length, the rod will be strong in 

 proportion to its thickness; and that if the figure 

 remains the same, that thickness can only be in- 

 creased by making it hollow. Therefore, hollow 

 rods or tubes of the same length and quantity of 

 matter have more strength than solid ones of less 

 diameter. This is but one out of the hundreds of 

 instances, in which the wisdom of man has been 

 perfected by studying the mode by which the great 

 Creator accomplishes His purposes. 



It is evident, that a creature thus furnished with 

 bones so much lighter than those of other animals, 

 must have a prodigious advantage in raising itself 

 in the air. But besides this superior lightness of 

 the skeleton, these bones, from their hollow struc- 

 ture, act as pipes, supplying air in abundance ; and 

 thus not only rendering the bird still lighter, but 

 enabling it to breathe at heights, at which a human 

 being would be gasping for breath. Travellers who 

 have ascended very high mountains, find that when 

 they get near the summits, the air becomes so 

 rarefied and thin, that it is as much as they can do 

 to proceed at a slow pace. Those birds, too, whose 

 habits never lead them into the more elevated 

 regions of the atmosphere, and are, therefore, not 

 so abundantly provided with additional capacities 



