648 TRANSACTIONS OF SECTION M. 
pull per unit area which the soil can exert on a layer of water in contact with it. This 
capillary power will obviously depend on the water-content of the soil; when 0/S=1, 
then K—0; the maximum value of K being reached when 0/S—O, 7.¢., when the 
soil is dry. 
The value of K between any given limits of 6/S becomes of practical importance, 
for under field-conditions soils are rarely absolutely dry or completely saturated 
Inches 
50 
Capillary Rise of Water 
Typical Soils 
Calculated from Diagram 
of Experiments by Loughridge 
HEIGHT TO WHICH WATER HAS RISEN 
te) x 12 Naar t 
} Hour |Day IMonth 4Months 
and the water-movements with which we are most concerned are from relatively 
moist to relatively dry sections. 
This capillary power is due to the surface-tension effects produced by the attrac- 
tion between the walls of these capillary pores and the water in the soil, and may 
be most conveniently studied by considering a vertical column of soil with its Jower 
end placed just in contact with a free surface of water. It has previously? been 
2 Loc, cit. 
