22 



BULLETIN 835, IT. g-. DEPARTMENT OF AGRICULTURE, 



found at a height of G inches above the water. In flume 63 there 

 is a greater percentage of moisture in the twelfth inch than in either 

 the sixth or the ninth inches. In both flumes there is a decrease in 

 the percentage of moisture with height above the twelfth inch. In 

 flume 43 there is a much more constant and uniform percentage of 

 inoisture from the twelfth inch to near the top of the wet area 

 than there is in flume 63. In both flumes, the moisture content breaks 

 very abruptly near the upper end of the wet soil and indicates the 

 relatively high percentage of moisture necessary to allow the mois- 

 ture to move from the wet to the dry soil. 



Other and very much more numerous data show the irregularity 

 of moisture distribution in vertical columns even though every pre- 

 caution is taken to have the soil uniform in texture and in density. 

 A superficial study of these data would indicate that a formula that 

 would give the distribution of moisture in vertical soil columns for 

 a period of 30 days would be more complicated than the formula 

 for the movement of moisture. An analysis of the above statement 

 would indicate that the percentage of moisture which, will permit 

 the advance of moisture from the wet to the dry soil is variable, 

 even for uniform temperatures, etc. 



The data for flumes 43 and 63 given above, and numerous other 

 data show a distribution of moisture contrary to general supposition. 



That there is a lack of uniformity in the distribution of moisture 

 in vertical soil columns has been observed by others (6) , (13). 



THE MOVEMENT OF MOISTURE IN HORIZONTAL FLUMES. 



The horizontal capillary movement of moisture within the soil and 

 from a body of free water has not been studied before to any great 

 extent (12). 



Much of what has been said of the vertical flumes is applicable to 

 the horizontal flumes. The chief difference is rather one of degree. 



At the present time there will be discussed only the horizontal 

 flumes open on top to evaporation. 



The number of flumes and the soil contained in each is given in 

 Table 10. 



Table 10. — Soil in "horizontal flumes. 



Number 



offlnme. 



20 

 31 

 50 

 70 

 00 

 200 



Description. 



Decomposed granite soil from Riverside, Calif. 

 Heavy decomposed granite soil from Riverside, Calif. 

 Heavy clay loam from Whittier, Calif. 

 Sand and gravel -wash from Uplands. Calif. 

 Heavy lava ash from Idaho. 

 Light'sand soil from Idaho. 



Figure 3 shows the curves derived from the measurement of 

 the movement of moisture in the horizontal flumes and the time 



