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SCIENTIFIC AGRICULTURE. 



ra gas must prove destructive to all animal and vegeta- 

 e, if some means were not provided by which it could be 

 removed as fast as it is generated by natural causes : growing- 

 vegetables, although they could not live in this gas alone, 

 require a constant supply of it as an element of food, and 

 this is just sufficient to preserve a wonderful balance in this 

 respect throughout all nature. 



According to Liebig, a healthy man expires from his lungs 

 5 ounces a day, or 100 pounds a year, of carbon: a horse, or 

 cow, expires six times this amount, or 600 pounds a year. 

 ISTow if the crops of an acre of land require 2 tons of carbon in 

 a year, (which is Johnston's estimate,) a farm of 25 acres 

 would require, if all cultivated, 50 tons of carbon. If the 

 family of the farm be reckoned at 5 adults, and the stock at 2 

 horses, 5 cattle, 40 sheep, 5 hogs, including the poultry, the 

 amount of carbon they would all expire would be not far from 

 10 tons in a year. They would then supply from this source 

 alone one-fifth of all the carbon requisite to grow the crops of 

 the farm. 



Coal which is dug from the earth and burned as fuel, adds 

 to the carbon of the atmosphere a new portion, which had 

 been buried in the earth, and consequently lost to vegetation 

 for many centuries. The coal consumed annually in Great 

 Britain, contains 14 millions of tons of carbon, which would 

 supply this element to the crops of twenty-eight millions of 

 acres. [Johnston.] Decay of vegetation, when extensive, as 

 in the peat bogs of Europe, the jungles of India, and the 

 tropical forests of Africa and South America, furnishes im- 

 measurable quantities of carbon. 



The final result of this eremacausis, (slow combustion,) or 

 slow decay, is the same as that of ordinary combustion: the 

 immediate result, however, is different: decay furnishes much 

 less carbon in proportion to the matter consumed than com- 

 bustion; decay produces, also, light carburetted hydrogen, 



