CULTIYATION. 213 



rail, or an old brush-heap, be removed iu spring from 

 soil where grass is growing, the grass afterward 

 grows in. those places much larger and better than 

 in other parts of the field. 



This improvement arises from various causes. 



1. The evaporation of water fl-om the soil is pre- 

 vented during drought by the shade afforded by the 

 mulch ; and it is therefore kept in better condition, 

 •IS to moisture and temperature, than when evapora- 

 tion goes on more freely. This coridition is well cal- 

 culated to advance the chemical changes necessary to 

 prepare the matters — both organic and mineral — in 

 the soil for the use of plants. 



2. A heavy mulch breaks the force of rains, and 

 prevents them from compacting the soil, as would be 

 the result were no such precaution taken. 



3. Mulching protects the surface-soil from freez- 

 ing as readily as when exposed, and thus keeps it 

 longer open for the admission of air and moisture. 

 "When unprotected, tlie soil early becomes frozen ; 

 and all water falling, instead of entering, as it should 

 do, passes off over the surface. 



5. The throwing out of winter grain is often pre- 

 vented, because this is due to the frequent freezing 

 and thawing of the surface-soil. 



6. When the wet surface-soil freezes, it is raised up, 

 and the young plants growing in it are raised with 

 it ; when the frost is thawed out, the soil falls back 

 to its original position, while parts of the crowns or 

 roots of the crop remain raised. The next freeze 

 takes hold of them lower down, and lifts them ngain ; 



