16 CHYMISTRY APPLIED TO AGRICULTURE. 



When all the parts of a plant are decomposed, there is 

 produced an earthy residuum of a brown color, which is 

 called mould. In this, besides the salts and the earths 

 which it contains, are found some oils and extractive 

 principles which escape decomposition. 



The distillation of mould in a retort, produces much 

 carburetted hydrogen, some carbonic acid, a bituminous 

 empyreumatic oil, and some water holding in solution 

 pyroligneous acid and carbonate of ammonia. 



The analyses by fire do not produce any substances, 

 such as exist in vegetables and animals ; they decompose 

 the natural products of the plant, and present their ele- 

 ments under different combinations. The analysis of 

 mould by washing in water, leads us to a better knowledge 

 of its component parts, and of its actions upon vegetation. 

 M. de Saussure found, that pure mould, formed in an open 

 field, leached tv^elve times with boiling water, yielded a 

 dry extract equal to -^ of its weight; rich garden soil, 

 and the light soft earth from a field which bore a good 

 crop, yielded the same extract, but in less quantity. This 

 learned philosopher is convinced, that the excellence of 

 mould does not depend upon the proportion of the ex- 

 tractive matter which it contains. 



Mould furnishes by distillation nearly the same princi- 

 ples after being deprived of its extract by washing, as 

 before ; but its powers of supporting vegetation are less in 

 the first case, than in the second. 



When, after repeated washings, no more extract can be 

 obtained from mould, it is only necessary to moisten it, 

 and leave it exposed to the air for three months, in order to 

 have it yield fresh supplies. These macerations, continued 

 for a long time upon the same mould, have always produced 

 colored infusions, approaching in their qualities to the 

 extract, (Saussure,) which proves that new combinations 

 are formed by the successive changes of vegetable pro- 

 ducts, and that the result of these combinations is soluble 

 in water, after it appears to have exhausted its solvent 

 power upon the bodies. This fact is the more important, 

 as it shows that the nutritive quality of vegetable manures 

 may continue during the whole time of their decomposi- 

 tion, because they form new products soluble in water, 

 which will afterwards serve as nourishment for plants. 

 This fact proves still farther, that some substances, 

 by their nature insoluble in water, may form excellent 



