276 TJie A)ncrican Geologist. November, 1898 
reverse way, upon the size of the tube. The smaller the tubes, 
for a given total area of cross section, the greater the amount 
of water absorbed, and the higher it is elevated. 
Eighth — For a given soil the retention of moisture w'hen 
loss from evaporation is suffered, depends upon the size of the 
capillary tubes; the affinity of the soil particles for water; the 
amount of water supply ; and the length of the capillary tubes, 
or the distance of the "water-table" below the surface. 
Ninth — Its retention of moisture when suffering loss 
through escape below depends, in great measure, upon the 
size of the capillary tube, — the rate of flow through these for 
a given amount of pressure varying as the fourth power of 
the diameter. 
Tenth — Soils, sub-soils, and the water reservoir, may all 
differ in texture. The rate of flow of water to the surface de- 
pends largely upon the nature of their texture and 
the relative positions which they occupy. Further, the pene- 
tration of the ground by meteoric waters depends largely upon 
these same conditions. 
Eleventh — Both the presence and the circulation of water 
in soils depend upon very complex conditions, such as the 
nature, size and shape of particles; their state of aggregation 
or the texture of the mass; and the position and amount of 
water supply. 
Prof. Shaler* has called attention to the protection of beach 
sands from abrasion by the presence of interstitial water held 
between the particles by capillary attraction. 
In another part of the same paper he records observations 
in connection with sand dunes, where the capillary phenomena 
appeared to be of a different sort. The observations were that, 
after a rain-fall of an inch, the dune-sands "would often not 
be wet for more than three-quarters of an inch beneath the sur- 
face," the water escaping to the lower hollows among the 
dunes, without penetrating them ; surface tension, if it be 
the cause here, acting in a negative way to accelerate erosion 
by preserving the sand in a dry state. 
In view of the effects of surface tension under certain con- 
ditions, this phenomenon may possibly be referable to it as 
*In a paper presented at the meeting of the Geological Society, 
December, 1893. 
