INFLUENCE OF ANALOGY. 179 



we have never seen them alive, nor have any testimony 

 to the absolute fact from others. It is obvious, 

 again, that birds or insects having long and very 

 pointed wings, are endowed with great powers of 

 flight ; for we see this structure is universal among 

 the swallows, the humming birds, and the dragon 

 flies. We can be in no danger, therefore, of mistake, 

 in deciding on the slowness or quickness of flight 

 in a bird, although we may never have seen it alive. 

 The form, therefore, — or, as it is sometimes called, 

 the conformation of an animal, — will generally reveal, 

 to the experienced naturalist, the leading points of 

 its natural economy. But these deductions can 

 only be arrived at when the student has made con- 

 siderable proficiency in the science; and has, by 

 a diligent comparison of the structure of species 

 with reference to their natural economy, duly 

 qualified himself for forming opinions which have 

 not yet been confirmed by his own observation. 

 Leaving this subject, therefore, as more suited to 

 another part of this discourse, let us enquire into 

 the second division of our subject ; namely, the pro- 

 perties of animals in regard to their influence or 

 uses in the economy of nature. 



(121.) So far as we have hitherto proceeded, the 

 knowledge to be acquired results from simple ex- 

 perience ; that is, it regards isolated facts, upon 

 which there can be no dispute. The structure of 

 an animal, and its habits or manners, are inde- 

 pendent of all theory ; and, when fully ascertained, 

 are so many truths which may recorded in our 

 chronicles, and appealed to by all parties as matters 

 of indisputable authority. But, when we come to 

 n 2 



