74 THE TEXTURE OF THE SOIL [chap. 



dish of distilled water, so that the water stands about 

 i mm. above the lower surface of the soil inside the 

 box ; the dish is then covered over to prevent evapora- 

 tion. The water rises in the soil, displacing the air, 

 and in about an hour's time the soil will have absorbed 

 all the water possible. The box is lifted above the water 

 a little, allowed a few minutes to drain, the excess of 

 water clinging to the under-surface is wiped away with 

 a clean cloth or filter paper, and the whole is then 

 weighed. A previous determination of the moisture 

 present in the " air-dry fine earth " must also be made, 

 to provide all the data necessary for the calculation of 

 the water contained in the saturated soil. This calcu- 

 lation may be made in three ways : either the pro- 

 portion the water in the saturated soil bears to the 

 dry soil, or the proportion of water in the wet soil 

 may be estimated, or again, the proportion by volume 

 that is occupied by water and soil respectively may 

 be calculated. The figures thus obtained will vary very 

 considerably, because the less dense the soils, because of 

 the clay and humus they contain, the more water they 

 will absorb ; thus the proportion which the water 

 absorbed bears to the weight of the dry soil becomes 

 exaggerated in their case. Perhaps the soundest picture 

 of the state of affairs is attained by considering the 

 volume that is occupied by the water in the soil, and 

 expressing it either as a percentage by volume, or as 

 lbs. or inches of water per cubic foot of wet soil. The 

 following figures (p. 75) show the results obtained for 

 four distinctive soils, calculated out in the different ways 

 described above. 



Under natural conditions a soil is rarely saturated 

 to the extent indicated in the table ; as the rain 

 water enters from above, the surface of the soil is 

 wetted first and the air within the soil finds a diffi- 



