NATURAL THEOLOGY. 241 



duced in one cletch or covey, yet the parent bird 

 have never been encumbered by the load of more 

 than one full-grown egg at one time.^^ 



VIII. A principal topic of comparison between 

 animals is in their instruments of motion. These 

 come before us under three divisions — feet, wings, 

 and fins. I desire any man to say which of the three 

 is best fitted for its use ; or whether the same con- 

 summate art be not conspicuous in them all. The 

 constitution of the elements in which the motion 

 is to be performed is very different. The animal 

 action must necessarily follow that constitution. 

 The Creator, therefore, if w^e might so speak, had 

 to prepare for different situations, for different 

 difficulties; yet the purpose is accomplished not 

 less successfully in one case than in the other. 

 And as between wings and the corresponding 

 limbs of quadrupeds, it is accomplished without 

 deserting the general idea. The idea is modified, 

 not deserted. Strip a wing of its feathers, and it 

 bears no obscure resemblance to the fore-leg of a 

 quadruped. The articulations at the shoulder and 

 the cubitus are much alike ; and, what is a closer 

 circumstance, in both cases the upper part of the 

 limb consists of a single bone, the lower part of 

 two. 



But, fitted up with its furniture of feathers and 



54 It has been elsewhere observed, that when predatory birds 

 gorge themselves, they are sometimes unable to rise on the wing 

 — a sufficient demonstration that the burden of an offspring would 

 have unsuited them for flight. 



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