PT. ii. Mr. Darwin and Mr. Buckle. 89 



upon this earth, is dependent upon air, water, and 

 food ; and as the supply of the two first requirements 

 is practically unlimited, the amount of Life cannot 

 exceed the quantity of the third. But Life is repro- 

 duced in much more rapid ratio than food can be 

 augmented. If the countless forms under which it 

 exists were suffered to increase, unrestricted by any 

 check, they would soon overtake the supply of food, 

 which they could not however pass, and the progress 

 of reproduction would thereby be violently and 

 suddenly arrested. But Nature interposes various 

 checks regulating and controlling the operation of 

 this principle, and preserving its system from the 

 rude shock of such a collision. One great means 

 for effecting this is, that so large a number of the 

 animals and insects prey upon each other, and any 

 excess in one portion of the Zoology of the Grlobe is 

 immediately arrested by the action of those others 

 to which it supplies the necessary aliment. Diseases, 

 severities of climate, and other causes, contribute to 

 diminish this redundancy wherever it exists. The 

 necessity for food may be compared to the main- 

 spring of a watch or other complicated machine : it 

 sets the whole in motion, and regulates the move- 

 ment, which would otherwise fall into confusion. 



