Aug. 20, 1917 



Relation of Soil Water Movement 



415 



RELATION OP the; RAPIDITY WITH WHICH EQUILIBRIUM IS ATTAINED TO 



THE HYGROSCOPICITY 



That at the end of the five days equiUbrium had been practically 

 attained in the case of the finer-textured soils, H to G, may be seen from 

 Table XIV, in which the ratios in the upper layers of the moistened 

 portion of the columns in this experiment are compared with that in 

 similar layers of the same soils in an earlier experiment (2, p. 50) in 

 which, after the addition of water to the surface, the columns had been 

 left undisturbed for much longer periods, 66 to 1 10 days. In the case 

 of the coarser members, as the fine sandy loams K, L, and M, equilibrium 

 was far from having been reached at the end of five days, the ratio being 

 as much as 1.2 to 1.7 higher than when the exposure was for the longer 

 period. With the coarse sands the fall is still greater (2, p. 57). The 

 coarser the soil the greater will be the fall in the ratio after the fifth day. 

 In the earlier experiment the soils were used in only the one degree of 

 moistness. 



Table XIV. — Extent to which equilibrium had been attained by the different soils at the 

 end of five days, as shown by comparing the ratios of water content to hygroscopic coeffi- 

 cient in the first and second j-inch sections in the present experim,ent (/) with those found 

 in an earlier one (II) in which the exposure had been much longer 



Soil. 



A. 

 B. 

 C. 

 D 

 E. 

 G. 

 H 

 I. 



J. 

 K 

 L. 

 M 



Hygro- 

 scopic 

 coeffi- 

 cient. 



^3-3 

 12. 9 

 10.5 

 10. 2 

 10. I 

 8.2 

 7.6 



7-1 

 5-6 



3-4 

 3-4 

 3-3 



Experi- 

 ment 

 No. 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



I 

 II 



Initial 

 ratio. 



I. O 

 I. O 

 I. O 

 I. o 

 I. I 

 I. I 

 I. o 

 1-3 



I. o 

 I. o 

 I. o 

 I. o 

 I. o 

 I. 2 

 I. I 

 I. 2 

 I. O 

 I. O 

 I. I 



1-3 



I. o 



1-3 

 I. I 



1-3 



Amount 

 water 

 added. 



Inches. 



1. 00 



2. II 



1. 00 



2. 12 

 I. 00 

 I. 21 

 I. 00 



.90 

 I. 00 

 I. 42 

 I. 00 

 1.58 

 I. 00 

 1.28 

 I. 00 



.60 

 I. 00 



.89 

 I. 00 



■33 

 I. 00 



.27 

 I. 00 



•35 



Time of 



expo- 

 sure. 



Days. 



5 

 no 



5 

 69 



5 

 100 



5 

 no 



5 

 100 



5 

 106 



5 

 102 



5 

 102 



5 

 70 



5 

 100 



S 

 68 



5 

 100 



Ratio at end of 

 experiment. 



I to 3- 



inch 



section. 



1.9 

 2. O 



1.8 



1.9 



2.4 



2. 2 

 2. I 

 I. O 



4 to 6- 



inch 



section. 



1-7 

 1.8 

 1.6 

 1.8 

 1.9 

 1.9 

 1.9 

 2. o 

 2. o 

 1.8 

 2. o 

 2. o 



2. 2 

 2. I 

 1.9 

 1.9 

 2. 2 

 1.9 



3-0 

 1.9 



2.7 



1.6 



3-0 

 2. o 



Fall in ratio after 

 fifth day. 



