IMPROVEMENT OF THE SOIL. 109 



When frosts have bound up the soil^ and it has been 

 again set free by thaws, the roots are left almost without 

 support, as the earth scarcely adheres to them : the roller, 

 applied to lands as soon as they are firm enough to admit 

 of its being passed over them, is very useful, as it reunites 

 the earth to the roots, and repairs the injury done by the 

 frosts and thaws. 



A judgment of the mixture necessary for amending a 

 soil, can be formed only from a perfect knowledge of its 

 defects. 



A soil in the composition of which the best earths are 

 united, does not need to be improved by the addition of 

 new earthy principles : good tillage and the application of 

 manure are sufficient to render it fertile : but that soil in 

 which any one of the earths predominates to such a degree, 

 as to give a character to the whole mass, requires to be 

 corrected by the admixture of substances possessing oppo- 

 site qualities. I shall distinguish soils as argillaceous, 

 calcareous, siliceous, and sandy : these divisions seem to 

 comprise all those requiring to be amended ; and the quali- 

 ty of the earth predominating in each, indicates sufficiently 

 the kind of improvement suitable to it. 



An argillaceous or clayey soil is rendered pasty by 

 rains, and it is hardened and cracked by heat ; it absorbs 

 moisture from the air only on its surface, but it imbibes 

 abundantly the water of rains, and retains it by so strong 

 an affinity, that when the supply is in excess, it remains 

 till it stagnates and causes the roots of plants to decay. 



An argillaceous soil is unfavorable to cultivation ; for 

 when it is acted upon by the frost, the water contained in 

 *ts interstices expands by freezing, and the thaw which 

 sets the earth free, divides it into morsels with which the 

 roots of plants have so little cohesion, that they may be 

 drawn out from it almost without resistance : the roots are 

 at such times in the state of newly planted vegetables ; they 

 have need of being established, of being fixed to, and 

 united with the soil, in order to vegetate. If in this state a 

 root be attacked by a new frost, it dies ; for not being pro- 

 tected by the close adhesion of the soil, the cold acts upon 

 it, as if it were exposed defenceless upon the surface : it is 

 this which renders alternate frosts and thaws more injuri- 

 ous to fields of grain, and to artificial meadows, than the 

 severest cold which continues till spring. It is to obviate 



