IMPROVEMENT OF THE SOIL. 115 



maximum ; and insects and the seeds of injurious plants 

 are destroyed. Hence we perceive that burning belongs 

 to moist, compact soils; it is attended with good effects 

 when the bed of earth is too cohesive, or when it presents 

 veins of blackish oxide of iron : it is suited to nearly all 

 cold and compact lands. 



Burning, especially if it be judiciously conducted, com- 

 pletely changes the nature of a soil, and corrects the great- 

 er part of its imperfections. I have by this means given to 

 agriculture 120 acres of land reputed sterile, formed almost 

 entirely of a ferruginous and very compact clay : the burn- 

 ing extended to the depth of four inches. For twelve years 

 this land, though not very productive, has afforded me good 

 returns. Its former sterility had procured it the name of 

 the Jews^ heath. 



Burning is hurtful to calcareous and light lands; to 

 soils of which the composition is perfect; and to fertile 

 lands, rich in decomposed animal and vegetable sub- 

 stances. 



It is useless to soils purely siliceous, for these can receive 

 no modification from fire. 



In some countries it is customary to burn the stubble 

 upon the field; this method, which is only an imperfect 

 mode of burning, is productive of good in two ways ; in 

 the first place, it purifies the soil from insects, and from the 

 seeds of noxious plants ; and in the second place, it forms a 

 thin layer of carbon, which by its extreme division is capa- 

 ble of being easily absorbed by plants. I believe that even 

 the heat occasioned by the combustion of the stubble and 

 herbs covering the soil, may produce salutary changes in 

 the combinations of the constituent parts. 



The results which I obtained from mixing calcined clay 

 with the sand constituting the soil upon a portion of the 

 plain of Sablons, near Paris, has led me to think, that 

 whenever lands of this nature are cultivated, it may be 

 useful to amend them by the same process : in order to do 

 this, clay may be formed into balls by moistening it with 

 water enough to reduce it to a paste; these balls, after 

 having been calcined in a lime-kiln, or the oven of a pot- 

 tery, may be pounded, and the fragments mixed with the 

 soil. Calcareous, siliceous, and sandy soils may be in this 

 way much improved. 



Of all the agents which may be employed as amend- 

 metits, there is none of v/hich the action is more powerful 



