NATURAL THEOLOGY. 239 



animal feeds is of slow concoction, or yields its 

 chyle with more difficulty, there the passage is 

 circuitous and dilatory, that time and space may 

 be allowed for the change and the absorption 

 which are necessary. Where the food is soon 

 dissolved, or already half assimilated, an unneces- 

 sary or perhaps hurtful detention is avoided, by 

 giving to it a shorter and a readier route. 



V, In comparing the hones of different animals, 

 we are struck, in the bones of birds, with a pro- 

 priety which could only proceed from the wisdom 

 of an intelligent and designing Creator. In the 

 bones of an animal which is to fly, the two quali- 

 ties required are strength and lightness. Where- 

 in, therefore, do the bones of birds (I speak of the 

 cylindrical bones) differ in these respects from the 

 bones of quadrupeds? In three properties: first, 

 their cavities are much larger in proportion to the 

 weight of the bone than in those of quadrupeds ; 

 secondly, these cavities are empty ; thirdly, the 

 shell is of a firmer texture than is the substance 

 of other bones. It is easy to observe these par- 

 ticulars even in picking the wing or leg of a 

 chicken. Now the weight being the same, the 

 diameter, it is evident, will be greater in a hollow 

 bone than in a solid one, and with the diameter, 

 as every mathematician can prove, is increased, 

 c<Bteris paribus, the strength of the cylinder or its 

 resistance to breaking. In a word, a bone of the 

 same weight would not have been so strong in any 



