STIMULATING MANURES. OH 



the result is a whitish stone, opaque and sonorous, of a 

 sharp and burning taste, absorbing water with noise and 

 heat, and forming with it a paste, which is a perfect hydrate. 

 Good limestone may be deprived of 50 per cent, of its 

 weight by calcination, but it is seldom that the heat of the 

 kilns is sufficient to deprive it of more than from 35 to 40 

 per cent, when the carbonate is dry. 



As soon as lime is exposed to the air, it absorbs moisture 

 from it with great readiness ; gradually cracking and break- 

 ing in pieced. It likewise absorbs the carbonic acid con- 

 tained in the atmosphere, and is thus insensibly reduced to 

 an impalpable powder. 



In this manner, lime resumes the principles of which it 

 had been deprived by calcination, and is reconstituted lime- 

 stone, or calcareous carbonate, without regaining its solidity. 

 In proportion as the recomposition goes on, the lime loses 

 the properties which it had acquired from the action of 

 fire ; it ceases to be caustic, its solubility in water is di- 

 minished, and its affinity for that fluid becomes almost 

 nothing. 



The lime used in agriculture is that which has been 

 slacked by air. Unslacked lime destroys vegetation, at 

 least if it be not combined with manures which moderate 

 its action, or with such bodies as can furnish enough car- 

 bonic acid to saturate it. 



We are indebted to Davy for some experiments which 

 throw a great light upon the action of lime upon vegetation. 

 He has proved that the fibrous portion of plants, deprived 

 of all the particles which can be dissolved by water, presents 

 another series, soluble after having been for some time 

 macerated with lime. Thus lime may be very efficaciously 

 employed, when it is wished to convert dry wood or fibrous 

 roots, and stalks, to the nourishment of plants. Limestone 

 broken, and lime completely restored to the state of a 

 carbonate, do not produce this effect ; it is necessary 

 to employ lime slacked with water, and mixed with a fresh 

 portion of that fluid, and the fibrous substances must remain 

 for some time exposed to th6 action of this solution. In 

 the case of which I have just spoken, the lime renders sol- 

 uble and suited to the nourishment of plants, some sub- 

 stances, which, in their natural state, do not possess this 

 characteristic ; and for this purpose the use of it may be 

 very advantage6us. Thus, when it is desirable to convert 

 ligneous and fibrous plants into manure, it may be done by 

 treating them with lime. 



