isa 



ON MANURES. 



tention, although the destruction of living animals, as- 

 worms and insects, is a main benefit of the work. 



Paring and burning, says Mr. Kirwan, reduces the roots 

 of vegetables to coal and ashes, and thus prepares both a 

 stimulant and nutriment for plants, 



Asies. Lord Dundonald observes, that " it is only from the 



ashes of fresh or growing vegetables, that saline substances, 

 or alkaline salts, are to be obtaiued; none can be got from 

 peat or decayed vegetable matter. The saline matter pro- 

 duced in the process consists of vitriolated tartar; the al- 

 kali of the burut vegetables combining with the vitriolic 

 acid, which in different states of combination is contained 

 in. most soils. Vitriolated tartar has very powerful effects 

 in promoting vegetation. " It promotes, as Mr. Senebier 

 remarks, the decomposition of water. I* will hereafter be 

 seen, that hidrogen is a most active food of plants. What- 

 ever, therefore, assists in this decomposition must act a very 

 important part in vegetation. 



Mr. Fourcroy thinks, that the ashes of burnt vegetables, 

 which have been supposed to consist of earth or clay, when 

 the fixed alkali is washed from them, are principally cal- 

 careous phosphorus, like those of animal bones. Lqrd 

 Dundonald is of the same opinion. This observation is a 

 most important one, and ought to be pursued. In regard 

 to the calcination of earths, that of clay and chalk has 

 been already treated. The circumstances are numerous 

 in which this operation may be highly beneficial. 



Loam or sand. Loam is composed of various combinations of sand, clay, 

 and calcareous earths. The effect of fire exerted on sand, 

 whether mixed in the form of loam, or by itself in a sandy 

 loam, has not been sufficiently ascertained ; and to draw 

 conclusions from theory would be dangerous. If I were to 

 reason upon the point, I should imagine that fire would 

 add nothing to the nature of sand which could render it 

 more fertile. The tendency of its operation would be to 

 lessen its small degree of cohesion, from whatever cause 

 arising, and might so far be prejudicial. Iron brought 

 into combination with pure air lessens the aggregation * a 



• Davy. 



It 



