62 BULLETIN 835, U. S. DEPARTMENT OF AGRICULTURE. 
at least as great as 15 r . then it would have the condition of the 
flumes above described. If, now. there were a sudden change in the 
slope of the ground toward the horizontal, or if the more loamy soil 
verged into a denser soil, free water might be developed at this point 
as the result of capillary action. 
The capillary siphon might develop, also, in an earthen reservoir 
dam with a puddle or concrete core wall extending only to the flow 
line or slightly above it, and under certain conditions produce satura- 
tion in the lower side of the dam. 
That a capillary siphon as above described is in accord with 
physical laws and was not the result of mechanical defects or error 
in manipulation is readily proven. Briggs (13) and Widtsoe and 
McLaughlin (19) have shown that the quantity of water retained by 
a soil column against gravity depends upon its length. Also that 
a column 1 foot in length will hold at all points a greater percentage 
of water than a column 2 feet in length. Hence, as the length of the 
inclined flume is greater, the percentage of moisture held against 
gravity will be smaller. It would follow, therefore, that beyond a 
certain length of the inclined part of the flume, not all of the water 
furnished by the wick could be retained against gravity by the in- 
clined part of the flume. 
It has been shown in this report that the distribution of moisture 
in vertical soil columns does not decrease uniformly with height 
above water. It has been indicated also that the greatest percentage 
of moisture in the vertical column may not be at the immediate water 
surface. From moisture analyses made of samples, from vertical 
numes, noted in this report, and from a gTeat many other special 
experiments, the writer will -ay that the greatest percentage of mois- 
ture in a vertical soil column with its lower end in water may be 
and frequently is at an appreciable distance above the water. From 
these data and as the result of tests by the writer and others, it can 
be said that a vertical soil column can take up by capillarity from a 
body of free water more water than it can hold against gravity, if 
the free water be removed from the bottom ox the soil colit- 
is, if the vertical tube is filled with soil and the lower end placed in 
a vessel of water and allowed to stand for a month or longer and the 
water is then removed from the tank, a part of the moisture in the 
-oil column will drain out. To repeat — a vertical soil column will 
take up by capillarity from a body of water more moisture than it 
can retain when the source of the water is removed. In \ iew of the 
above statements and the recorded experiments, it appears that capil- 
lary siphon^ may occur in nature, as the result of physical la" 
