114 CHYMISTRY APPLIED TO AGRICULTURE. 



excellent, and suffers less from drought than elsewhere; 

 being protected from the ill effects of the scorching rays of 

 the sun, by the pebbles lying above its roots. 



Rozier made the experiment of covering a part of the 

 soil of his vineyards with pebbles, and found it attended 

 with good effects, especially as it regarded the quantity of 

 wine obtained. One of my friends owned in Paris, near 

 the barrier d'Enfer, an enclosure, of which the soil was so 

 dry and poor, that notwithstanding all the pains he be- 

 stowed upon it, he could never make any fruit trees thrive 

 there : in order to amend the soil, he covered it with a 

 layer of good earth, which he mixed with the dry sand of 

 the spot ; this gave it some degree of fertility ; but the heat 

 dried his plantations so much, that he could only preserve 

 them by frequent and very expensive waterings : he at 

 length concluded to cover the surface of the ground with a 

 layer of pebbles, and from that time the trees prospered. 



In some countries, recourse is had to fire, as an amender 

 of the soil : this process, called burning, is strongly recom- 

 mended by some practical farmers, and highly disapproved 

 of by others : both sides rely on the test of their own ex- 

 perience ; and both are so sincere in their opinions, 

 that it would be useless to contest the truth of their ob- 

 servations. I can only agree with each of these contra- 

 dictory opinions, and at the same time make known the 

 cases to which burning is applicable, and those to which 

 it is unsuited, in order to enlighten the agriculturist as to 

 the effect of the operation : he can afterwards make for 

 himself just and rational applications of the theory. 



In the process of burning, a layer of from two to four 

 inches in thickness, is removed from the soil in clods : 

 little heaps of combustibles are formed with the broom, 

 thistles, fern, and shrubs that grow upon the spot : these 

 are covered with the clods, and at the end of some days 

 are set on fire ; the combustion of them lasts a longer or 

 shorter time. When the whole has become cool, the heaps 

 of ashes are spread over the surface, and thus mixed with 

 the soil. 



By this operation the constituent parts of a soil are di- 

 vided, and rendered less compact ; the disposition which 

 a clayey ground has to absorb a great quantity of water, is 

 corrected, and this soil rendered less cohesive and pasty ; 

 the inactive vegetable matter contained in it, is converted 

 into manure : the oxidation of its iron is carried to its 



