RELATIONS CT SOILS TO WATKR. 293 



grees become filled with water, and it will at length begin to drop out 

 from the under part as it is added above. This property is exhibited in 

 a certain degree by all soils. The rain falls and is drunk in, the dew 

 also descends, and is thus taken possession of by the soil. But after much 

 rain has fallen, the earth becomes saturated, and the rest either runs off 

 from the surface or sinks through to the drains. This happens more 

 speedily in some soils than in others. Thus from 106 lbs. of dry soil, 

 water will begin to drop — if it be a 



Quartz Sand, when it has absorbed 25 lbs. 



Calcareous Sand 29 



Loamy Soil 40 



English Chalk 45— J. 



Clay Loam 50 



Pure Clay 70 



but a dry peaty soil will absorb a very much larger proportion (Schii- 

 bler), before it suffers any to escape. Useful arable soils are found to be 

 capable of thus containing from 40 to 70percent. of their weight of water. 

 If the quantity be less than this, the soils are said to be best adapted for 

 pine plantations, — if greater, for laying down to grass. 



In dry climates this power of holding water must render a soil more 

 valuable, whereas in climates such as ours, where rains rather over- 

 abound, a simple determination of this property will serve to indicate 

 to the practical farmer on which of his fields it is most important to him, 

 in reference to surface water, that the operation of draining should be 

 first and most effectually performed. The more water the soil contains 

 within its pores, the more it has to part with by subsequent evaporation ; 

 and, therefore, the colder it is likely to be. The presence of this water also 

 excludes the air in a great degree, so that for these, as well as for other 

 reasons, it is desirable to afford every facility for the speedy removal of 

 the excess of water from such soils as absorb it, and are capable of con- 

 taining it, in a very large proportion. 



3°. Power of retaining water when exposed to the air. — Unless when 

 rain or dew are falling, or when the air is perfectly saturated with mois- 

 ture, watery vapour is constantly rising from the surface of the earth. 

 The fields, after the heaviest rains and floods, gradually become dry, 

 though this, as every farmer has observed, takes place in some of his 

 fields with much greater rapidity than in others. Generally speaking, 

 those soils which are capable of arresting and containing the largest por- 

 tion of the rain that falls, retain it also with the greatest obstinacy, and take 

 the longest time to dry. Thus a sand will become as dry in one hour as a 

 pure clay in three, or a piece of peat in four hours. This, therefore, not 

 only explains, and shows the correctness of, the well-known distinctions 

 of warm and cold soils, but exhibits another strong argument in favour 

 of a perfect drainage of stiff soils and of such as contain a large proportion 

 of decaying vegetable matter. 



4°. Capillary power of the soil. — When water is poured into the sole 

 of a flower-pot, the soil gradually sucks it in and becomes moist even to 

 the surface. The same takes place in the soil of the open fields. The 

 water from beneath — that contained in the subsoil — is gradually sucked 

 up to the surface. Where water is present in excess, this capillary action, 

 as it is called, keeps the soil always moist and cold. 



