TDK FUKK WATlCn OF T;iE SOIL. f20l 



is held in tlie Avick of ;i lamp. The adliesion of the water 

 to the particles of eurLli suspends the flow of the liquid, 

 and it is no longer subject to the laws of hydrostatics. 

 Capillary water is usually designated as moisture, though 

 a soil saturated with capillary water would be, in most 

 cases, wet. The cai)illary power of various soils has al- 

 ready been noticed, and is for coarse sands 25° |„ ; for 

 loams and clays, 40 to 70° |„ ; for garden mould and humus, 

 much higher, 90 to 300 °|„. (See p. 180.) 



I'^or a certain distance above bottom Avater, the soil is 

 saturated with capillary water, and this distance is the 

 greater, the greater the cajiillary power of the soil, i. e., 

 the finer its pores. 



Capillary water is not visible as a distinct liquid layer 

 on or between the particles of soil, but is still recogniza- 

 ble by the eye. Even in the driest weather and in the 

 driest sand (that is, when not shut off" from bottom water 

 by too great distance or an intervening gravelly subsoil) it 

 may b'3 found one or a few inches below the surface where 

 the soil Jool:s moist — has a darker shade of color. 



Hygroscopic Water is that which is not perceptible to 

 the senses, but is appreciated by loss or gain of weight in 

 the boily which acquires or is deprived of it. (11. C. G., 

 p. 54.) The loss experienced by an air-dry soil when kept 

 for some hours at, or slightly above, the boiling point 

 (212° F.,) expresses its content of hygroscopic water. 

 This quantity is variable according to the character of the 

 soil, and is constantly varying with the temperature; in- 

 creasing during the night when it is collected from the at- 

 mosphere, and diminishing during the day when it returns 

 in part to the air. (See p. 104.) The amount of hygros- 

 copic water ranges from 0.5 to 10 or more per cent. 



Value of these Distinctions. — These distinctions be- 

 tween hydrostatic, capillary, and hygroscopic water, are 

 nothing absolute, but rather those of degree. Hygroscopic 

 water is capillary in all respects, save that its quantity is 



