446 



Miscellaneous. 



would be struck, and the air could not experience any appreciable 

 variation. For even supposing that by some adventitious circum- 

 stances, such as by volcanic agencies, an increased supply of carbonic 

 acid was furnished to the atmosphere, the effect would simply be to 

 induce an increased vegetation, and the excess would be withdrawn. 

 On the other hand, if the amount of carbonic acid became diminished, 

 vegetation would be retarded, and it would attain its normal standard. 

 Such would be the natural effects of vegetation, when the original 

 amount of carbonic acid in the air had become reduced to the point 

 at which it ceased being detrimental to animals, but was still suffi- 

 cient to administer to an ordinary, but not excessive luxuriance of 

 vegetation. 



But here a curious question arises — Does the progress of human 

 society not occasion a greater demand for carbonic acid, and thus serve 

 to destroy the equilibrium between plants and animals ? It can scarce- 

 ly be denied that civilization causes an increase in the aggregate of 

 animal life. The preponderance is great between the animals depend- 

 ing upon man, and those destroyed by him. Nay, even the increase 

 of human beings produced by an augmentation of the comforts of civi- 

 lized life, would demand our serious attention to the enquiry. Once 

 admit, and I do admit it for the sake of argument and probability, 

 that civilization increases the aggregate of animal life, and it is evi- 

 dent we must find some means of compensating to the air for the car- 

 bon and nitrogen abstracted and retained by this increase. For were 

 there no means of compensation, other parts of the earth, existing in 

 a state of nature, would suffer for the supply of those parts subject 

 to the dominion of man. The difficulty of finding an answer to this 

 question has furnished a specious argument to those who refuse to 

 admit that the food of plants is derived from animals ; and yet the 

 explanation is not so difficult. Which would require the most car- 

 bonic acid — America with its forests and extensive prairies, or 

 America peopled by men, and covered by fields of waving corn ? 

 Civilised man enters America, he expels its tenants from their 

 native soil, cuts down their forests, and plants in their stead agri- 

 cultural produce. Strange as it may appear, he has caused neither 

 an increase nor a diminution in the amount required; for it has 

 been proved by Liebeg that the same extent of land produces the 

 same quantity of carbon, whether it be covered with forests or agricul- 

 tural produce. He increases himself to an amazing extent, and thickly 

 peoples that once thinly populated country. True, by his increase, he 

 removes from the air quantities of carbonic acid, but he compensates for 



