PROPORTION OF RAINFALL 23 



It will be seen that the three different thicknesses of soil 

 yield practically the same results, it being difficult to account for 

 the small but constant differences which occur. On the average, 

 about half the annual rainfall percolates through the gauges, 

 and about one-half is evaporated. It should be borne in mind, 

 however, that the surface of the soil in these gauges is kept 

 free from vegetation of all kinds, so that there is no drying 

 effect due to the crop. Again, as communication between 

 the subsoil and the soil of the gauges is cut off, all capillary 

 movements of water, both downwards during rain and back 

 again during periods of drought, are stopped at a certain point, 

 thus affecting both percolation and evaporation by unknown 

 amounts. 



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