USE OF CHARCOAL. 373 



singault, one of the most distinguished chemists, every 

 pound of nitrogen which we add to the grass increases 

 the produce one hundred and ten pounds ; and this 

 increased produce of one hundred and ten pounds is 

 effected by the aid of a little more than four pounds of 

 gypsum, or plaster. Another accurate investigator, Sir 

 Humphrey Davy, found, by actual experiment, that the 

 ashes of an acre of red clover contain no less than 

 three bushels of plaster of Paris. This important fact 

 proves that the earth already contains a large amount 

 of this substance, and that it is essential to the growth 

 of clover. This may, perhaps, explain the so-called 

 clover sickness in some land. The requisite supply of 

 plaster has been exhausted. In any case, the addition 

 of plaster to clover lands, and especially to pastures, is 

 of the highest importance. 



The effect of charcoal is somewhat similar to that of 

 plaster. Charcoal will absorb ninety times its own bulk 

 of ammonia, which is held from escaping till it is sep- 

 arated by water, and carried into the earth for the plant. 

 When dry, the operation of fixing the gas is repeated, 

 till the next shower sends the gas into the earth, and 

 the particles of water take its place in the charcoal. In 

 this way, as a top-dressing, charcoal, as well as plaster, 

 performs the most important functions. If we take any 

 decaying animal matter, which has begun to give off its 

 offensive and noxious odor, its ammonia, and cover it 

 with charcoal or plaster of Paris, this escaping gas is 

 immediately stopped. No infectious odor arises from 

 it. The decay of the substance has suddenly ceased. 

 This simple fact will show the intelligent farmer to what 

 purposes these substances may be applied. His choice 

 of these should depend somewhat on the expense of 

 procuring them. The relative expense depends so much 

 upon circumstances, that I need not make the estimate. 

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