26 



under his view in a complex form ; and he can de- 

 compose them and analyze their component parts 

 only in thought. What a variety of conditions, for 

 example, are necessary to vegetable life f If, in at- 

 tempting to analyze the nature of life, we were to 

 separate from it any of those requisite conditions, its 

 duration must instantly cease, and the object of our 

 researches be frustrated ; so that, in matters like this, 

 the utmost we can ever expect to attain is but an 

 approximation to the truth. 



Mere observation will, however, avail but little 

 without comparison. We must observe attentively 

 the same body in the various positions in which it is 

 placed at different times by Nature ; and we must 

 compare different bodies with each other until we 

 can recognize any invariable relations, which may 

 exist between their structure and the phenomena 

 they exhibit. Thus may such bodies, when diligently 

 observed and carefully compared with each other, 

 be considered as experiments ready prepared by the 

 hand of Nature ; who may be supposed to add to, or 

 subtract from, each, in the manner the Chemist does 

 in his laboratory with the inert materials subject to 

 his control, — and herself to present us with the re- 

 sult of such additions and subtractions. In this way 

 we may arrive at some knowledge of the laws which 

 regulate the phenomena of Natural History, strictly 

 speaking, subject to our observation ; and which are 

 employed by the great Governor of the Universe 

 with the same determinate precision, as those which 

 are opened to our view by the general sciences. 



