162 SELECTIONS FROM ADDRESSES. 



ticular plant be absorbed, the gas will rush in from other parts 

 of the atmosphere, and thus keep a constant supply within 

 reach. In this way a tree can go on without interruption, ex- 

 cept by winter, accumulating carbon for years, and even centu- 

 ries. A single pine tree in Oregon, for instance, is sometimes 

 found to contain 356,000 pounds of carbon ; which required 

 1,305,333 pounds of carbonic acid ; two thirds of which is 870,- 

 222 pounds, all taken from the atmosphere; or 800 pounds 

 yearly ; on the supposition that the tree required 1100 years for 

 its growth. This single example will give some idea of the 

 magnitude of the process that is going on, silently, yet surely, 

 to supply all the forests on the globe. 



And here I cannot but notice a most interesting fact con- 

 nected with this subject, brought to light by modern researches, 

 which, although not bearing directly upon agriculture, is too 

 beautiful a development of Divine wisdom and benevolence, 

 not to be understood by every man. It is well known that in 

 the process of breathing, men and animals consume a vast 

 amount of oxygen, — the essential thing in the atmosphere that 

 sustains life, — and give out into the air an equal amount of 

 carbonic acid ; a gas, which, however essential to the growth of 

 plants, is decidedly hostile, when in large quantities, to the health 

 of animals. Hence it would seem as if the process of breathing 

 from century to century must tend to corrupt the air, by de- 

 priving it of oxygen and loading it with carbonic acid. And- 

 all the fires kindled on the globe produce the same effects. But 

 the agency of vegetation entirely counteracts all these causes of 

 deterioration. Carbonic acid consists of about one third part of 

 carbon, and two thirds of oxygen. Now plants take the very 

 carbonic acid that is given out by animals and fires, and having 

 abstracted the carbon from it, throw back the oxygen into the 

 atmosphere; and thus supply the constant deficiency produced 

 by the respiration of animals and combustion, and remove all 

 superabundance of carbonic acid, and keep the atmosphere 

 always entirely pure. It is estimated that a very large tree 

 will give out enough oxygen to supply the wants of a man; that 

 is, abjut two pounds daily ; for that is his daily consumption. 

 What a wonderful example of that compensation in nature, 



