58 ' BULLETIN 835, U. S. DEPARTMENT OF AGRICULTURE. 



time in the same flume that gave the natural distribution of moisture 

 and the interchanged distribution. In these cases there was not 

 as great a difference in the relative percentages of moisture at the 

 top and bottom as where all samples showed the interchanged re- 

 lation. 



In the samples given above, it is noticed that this interchanged 

 relation of the distribution of the moisture occurs in both the open 

 and covered flumes. This same fact is true of all of the other work, 

 except that the covered flumes seem to require a little lower tem- 

 perature of the air to cause this result than do the open flumes. It 

 will be noticed in Table 42 that with a relatively low percentage 

 of moisture an interchange of the natural distribution of the mois- 

 ture did not occur. It is probable that if such a distribution should 

 occur, a temperature lower than 26° F. would be required. As shown 

 in this table, for flume 101, with the minimum temperature of 32°, 

 the upper part of the soil still contained a little less moisture than 

 the bottom part of the soil. By comparing results shown for flume 

 101 with other samples taken with higher minimum temperatures, 

 it is evident that a slight difference occurred in the normal distribu- 

 tion of the moisture in the samples. 



Before a definite conclusion can be drawn, additional experiments 

 will have to be made. 



THE CAPILLARY SIPHON. 



The definitions of capillarity and of capillary moisture used in 

 so many of the old textbooks would lead one to conclude that free 

 water would not be developed as a result of capillarity. For in- 

 stance, the old illustration of the towel and the basin of water was 

 used to combat the idea of free water as a result of capillarity. No 

 reference to the probable fallacy of the old doctrine has been stated. 

 In fact, all reference to the relation of gravity and capillary action, 

 except as contained in the old original definition, has been in the 

 most general terms. The prevalent method of disposing of the ques- 

 tion is to say that capillary action is influenced by gravity. (1) 

 There appears to be no statement as to any quantitative relation. 



One of the very first sets of experiments tried at Riverside in the 

 fall of 1915 included flumes inclined at angles of 15° and 80°, and one 

 at 45°. The first of these had an ultimate total length of 20 feet 

 and the last two had lengths of 10 feet each. The moisture in the 

 flume inclined downward at 45° had reached the end of the flume 

 in 18 days, and in the one inclined downward at 30°, the moisture 

 had reached the end of the flume in 21 days. Three or four days 

 after the moisture had reached the end of these flumes, free water 

 was observed dripping from the ends of both. In about a week 



