174? STUDY OF NATURAL HISTORY. 



we have just alluded to. Now, this knowledge is 

 to be acquired in two ways; either by actual 

 observation, or by inductive reasoning. The first, 

 of course, is the most simple and the most complete, 

 and lies within the reach, under favourable circum- 

 stances, of every observer. The latter, on the other 

 hand, is more confined, and can only be arrived at 

 by a long course of study. The former is a mere 

 exercise of vision ; but upon the latter we have ge- 

 nerally to reason analogically. We then find that 

 certain modifications of form indicate certain habits ; 

 and that this reciprocity is so universal, that we are 

 enabled to decide whether a bird, whose skin only 

 we have seen, lives in general upon the ground, or 

 among trees; whether it eats insects, or seeds, or 

 both ; or whether a beetle feeds upon green or upon 

 decomposed vegetables. 



(1 18.) To illustrate the importance of that minutely 

 accurate observation which is necessary in ascertain- 

 ing the habits and economy of animals, and at the 

 same time to exemplify the diversity of ways by 

 which nature effects the same object, let us ima- 

 gine a noble forest tree, in whose luxuriant foliage 

 the birds of the air find shelter, and whose leaves 

 supply food to hosts of insects. In this respect, 

 the tree may be considered a world in itself, filled 

 with different tribes of inhabitants, differing not , 

 only in their aspect, but even in the stations or 

 countries they inhabit, and assimilating as little 

 together as the inhabitants of Tartary do with 

 those of England. First, let us look to those insects, 

 which, being destined to live upon vegetable food, 

 are instinctively directed to seek it here : some, as 



