238 MANtTRES. 



nated by the name of humus^ or mould,* exists by nature, while there 

 are others, and they form the majority, which are either totally des- 

 titute of it, or contain it but in insignificant proportion. To become 

 productive, these soils require the intervention of manure ; for this 

 "here is no substitute, neither the labor which breaks them up, not 

 the climate which so powerfully promotes their fecundity, nor tho 

 salts and alkalies which are such useful auxiliaries of vegetation. 

 Not that land entirely destitute of organic remains is incapable of 

 producing and developing a plant. We have already seen that the 

 atmosphere, light, heat, and moisture, suffice for its existence ; but 

 in such a condition, vegetation is slow and often imperfect ; nor 

 could agricultural industry be advantageously applied to a soil which 

 approached so near to absolute sterility. 



Plants, considered in their entire (?Onstitution, contain carbon, 

 water, (completely formed, or in its elements,) azote, phosphorus, 

 sulphur, metallic oxides united to the sulphuric and phosphoric acids, 

 chloildes, and alkaline bases in combination with vegetable acids ; 

 many of these elements form no part of the atmosphere, and are 

 necessarily derived from the soil. Moreover, the manures most 

 generally made use of are nothing but the detritus of plants, or the 

 remains or excretions of animals, including by the very fact of their 

 origin the whole of the elements which constitute organized beings; 

 and although it is very probable that certain tribes of plants are more 

 adapted than others to appropriate the azote or the ammoniacal va- 

 pors of the atmosphere, experience proves that azotized organic re- 

 mains contribute in the most efficacious manner to the fertility of the 

 soil. Besides, we are far from being able to affirm that the carbon 

 of plants is derived from the carbonic acid of the atmosphere. 

 Doubtless this acid is its principal source ; but it is possible that 

 certain elements of carburetted dungs may be directly assimilated. 



The writers who have treated of manures, have generally formed 

 them into two grand classes : 



1st. Manures of organic origin, in which are again found all the 

 elements of the living matter. 



'2d. Mineral manures, saline or alkaline, which are particularly 

 designated under the name of stimulants, thus ascribing to them the 

 faculty, purely gratuitous, of facilitating the assimilation of the nu- 

 triment which plants find in dung, and of stimulating and exciting 

 their organs. Such a distinction has no real foundation, and nothing 

 shows so much how scanty our knowledge upon this subject has 

 hitherto been as this tendency in the ablest minds to connect vege- 

 table nutrition with the feeding of animals. 



All the agents employed by the agriculturist to restore, preserve, 

 and augment the fecundity of the soil, 1 shall term Manures. In 

 my view gypsum, marl, and ashes are manures, as much as horse- 

 dung, blood, or urine ; all contribute to the end proposed in em])loy- 

 ing them, which is the increase of vegetable production. The hest 



* Mould, or vegetable earth, as the word is generally used, is not exactly humua r 

 but as it derives its principal q'ialities from the presence of the humus of the chemist 

 \ iball eenerally employ the terms as synonymous.— Eng. Ed. 



