THE CARBON OF VEGETABLES. 43 



of animals depends on the life and growth of plants. These, therefore, 

 afford both the nutriment for the existence and growth of animals and 

 the essential gaseous element, oxygen, for their respiration. They 

 likewise perform the important office of purifying the air for respira- 

 tion, by separating from it carbon, ammonia, etc. Animals expire car- 

 bon and plants inspire it ; plants expire oxygen and animals inspire it. 

 Thus, by this wonderful economy of nature, both are enabled to exist, 

 and the due composition of the air is uniformly maintained. 



The provisions of the atmosphere are remarkable. It may be thought 

 strange that it furnishes the great quantity of carbon necessary for the 

 support of the whole vegetable world; yet as it is clearly proved that 

 a column of air of about 2,400 Ibs. rests on every square foot of the 

 earth's surface, the 1000th part of this is carbonic acid, 27 per cent 

 of which is carbon. The whole atmosphere, then, contains 3.306 bil- 

 lion Ibs. of carbon, a weight more than equal to all the plants and 

 mineral surface of the earth. The superfices of the leaves and other 

 green parts of plants which absorb carbonic acid gas, are deemed to 

 be more than double the whole surface of the globe, and yet, from de- 

 terminate calculations, they are adequately furnished with all the 

 carbon necessary for the support and growth of the plants. 



The inexhaustible oxygen of the tropics, furnished by the inconceiva- 

 bly luxuriant vegetation under a glowing sun, supplies that required 

 by the deficient heat and vegetation of the temperate and frozen 

 zones; while the superabundant carbon produced by artificial heat, 

 etc., at the north, supplies the plants of the tropics. This equilibrium 

 and mutual interchange of local products is most happily effected by 

 the uniform horizontal current of air moving with the revolution of 

 the earth from the equator to the poles, bringing in its passage from 

 thence its superabundant oxygen, and transporting at the same time, 

 the superabundant carbonic acid generated during our northern win- 

 ters. This acid is greater by night than by day, when it is decom- 

 posed by plants. Thus the health of every country is increased by 

 vegetable cultivation. 



The remains of primeval vegetation are seen in the vast quantities 

 of peat and coal beneath the surface of the earth; showing vegetable 

 nature to have greatly abounded then and the consumption of carbonic 

 acid to have been incomparably greater than now. It is inferred from 

 this that the atmosphere must now be eminently richer in oxygen than 

 at an early period of the world ; as much more so, indeed, as the quan- 

 tity of carbon and hydrogen which those immense deposits contain. 

 The superabundance of carbon at that time readily accounts, then, for 

 the manifestly superior luxuriance of vegetation. The giant plants 

 of those times, the palms., ferns, reeds, etc., by an immense extension 

 of their leaves, dispensed with nutriment from the soil and resembled, 

 from the small development of their roots, many now which do not 



