L 162 : 



The power of the soil to absorb water by cohe- 

 sive attraction, depends in great measure upon the 

 state of division of its parts ; the more divided they 

 are, the greater is their absorbent power. The differ- 

 ent constituent parts of soils likewise appear to act, 

 even by cohesive attraction, with different degrees of 

 energy. Thus vegetable substances seem to be more 

 absorbent than animal substances ; animal substances 

 more so than compounds of alumina and silica ; and 

 compounds of alumina and silica more absorbent than 

 corbonates of lime and magnesia : these differences 

 may, however, possibly depend upon the differences 

 in their state of division, and upon the surface ex- 

 posed. 



The power of soils to absorb water from air, is 

 much connected with fertility. When this power is 

 great, the plant is supplied with moisture in dry sea- 

 sons j and the effect of evaporation in the day is coun- 

 teracted by the absorption of aqueous vapour from 

 the atmosphere, by the interior parts of the soil during 

 the day, and by both the exterior and interior during 

 night. 



The stiff clays approaching to pipe-clays in their 

 nature, which take up the greatest quantity of water 

 when it is poured upon them in a fluid form, are not 

 the soils which absorb most moisture from the atmos- 

 phere in dry weather. They cake, and present only a 

 small surface to the air ; and the vegetation on them 

 is generally burnt up almost as readily as on sands. 



The soils that are most efficient in supplying the 

 plant with water by atmospheric absorption, are those 



