"S 



* 





I 

 ■ 



V 



I 





■l 



L. 



L 



... 



* 



1 



w 



b: 











1# 









I 









Ch. IX.] 



AT SUCCESSIVE GEOLOGICAL PERIODS. 



171 



others to multiply ; a power which is circumscribed within 

 certain limits, and which, in all likelihood, is by no means 

 exclusively exerted by our species.* The growth of human 



num. 



many animals 



larger beasts of prey in particular give way before us ; but 



mnumer 



sects, and plants, which are inimical to our interests, increase 

 in spite of us, some attacking our food, others our raiment 

 and persons, and others interfering with our agricultural and 

 horticultural labours. We behold the rich harvest which we 

 have raised by the sweat of our brow, devoured by myriads 

 of insects, and are often as incapable of arresting their de- 

 predations, as of staying the shock of an earthquake, or the 



course of a stream of lava. 



A great philosopher has observed, that we can command 

 nature only by obeying her laws ; and this principle is true 

 even in regard to the astonishing changes which are super- 

 induced in the qualities of certain animals and plants by 

 domestication and garden culture. I shall point out in the 

 next volume that we can only effect such surprising alter- 

 ations by assisting the development of certain instincts, or 



m 



sation, by which individual peculiarities are transmissible 



t 



from 



system 



more 



. by the interference of man deviate far less from the analogy 

 of those effected by other animals than is usually supposed. J 

 We are often misled, when we institute such comparisons, by 

 our knowledge of the wide distinction between the instincts 

 of animals and the reasoning power of man ; and we are apt 

 hastily to infer, that the effects of a rational and irrational 

 species, considered merely as physical agents, will differ almost 

 as much as the faculties by which their actions are directed. 



It is not, however, meant 



foregoing observations 



* See Ch. XLII. 

 t See Ch. XXXVI. 



I See Ch. XXXVIIL, XXXIX., XL., XLII. 





