The Surface Tension of Water. — Ladd. 271 
to the points (a), would still be operative, and water, to re- 
place that evaporated, would be fed from the channels, the 
walls of which are the most easily collapsible, and, with the 
given conditions, these would be the lateral ones; the dowai- 
ward movement being facilitated by gravity and presence of 
the one free surface above. 
It must be borne in mind, that the tension at the points 
(a), and beneath them, throughout the process, is of uniform 
value in each and every tube. 
If, as in the case of our experiment, the attraction be- 
tween the clay ?,nd the water exceeds that between the 
water and the walls of the vessel, a point will be 
reached where the up-pulling at (a), between the clay 
particles, will remove the water from the columns (b) adjacent 
to the sides. The mass is then free to shrink upon itself, in 
horizontal as well as in vertical directions. Water is fed to the 
exposed surfaces so long as the particles can approach each 
other. Shrinkage has been accomplished and a consolidation 
results from the bringing of the fine particles into intimate 
contact. 
When this takes place in nature the lateral tension is un- 
able to contract the mass as a whole. Owing, however, to in- 
equality of conditions, planes of separation are established 
along lines of weakness, and "mud-cracks" result. The smal- 
ler masses thus formed may then shrink further. 
The finer grained the material, the greater the amount of 
surface of the particles, as compared with their mass. Con- 
sequently, there are more contacts; mutual attraction and 
friction more effective; and the mass more completely con- 
solidated. In the case of sand, the mass of the individuals so 
far exceeds the amount of surface at which contacts exist, 
that the bonds are ineffectual, and the material remains inco- 
herent. 
The steps leading to these various results may be illus- 
trated by certain experiments, made by the writer while inves- 
tigating the properties of clays.* 
In order to determine the absorbtive power, amount of 
shrinkage and degree of consolidation of samples of this sub- 
stance the following methods were employed: 
*A more complete description of these is now in press, as a bulletin 
of the Geological Survey of Georgia. 
