Power of Soils to Absorb Moidure. 69 
THE POWER SOILS HAVE TO ABSORB MOISTURE. 
BY J. H. SALISBURY, 
(Assistant in the Laboratory of Prof. Emmons.) 
All soils, as well as the substances that compose them, have the 
power of absorbing and retaining moisture with a certain force, 
which diminishes as the amount of water absorbed increases; or 
as you approximate a point where the water is no longer taken up, 
and increases as you recede from this point; or approach the dry 
state. The point where the water is no longer taken up, may be 
called the point of saturation. After a soil is saturated, if more 
water be added, it will have a tendency to separate and suspend 
its particles, and render them more moveable among themselves. 
The more water you add, the more fluid will you render the mass. 
It is on this principle that those beds of earth commonly denomi- 
nated quick sand — of which we shall speak farther on — become 
so difficult to control in excavating, or digging into them. 
If you communicate to a mass of soil, saturated with moisture, 
a jolting, jarring motion, or slightly agitate it in any way, the 
foi"ce with which the water is held is disturbed and lessened, so 
that a part of it will be set at liberty, and the mass will tempo- 
rarily become quite fluid. So long as the agitation is continued, 
the point of saturation is lowered. If now to this same mass, ren- 
dered partially fluid by a slight motion, a steady, moderate, equal 
and continued pressure be applied, the free water — previously 
given out — will be taken up, and the mass will be rendered com- 
paratively dry; so much so that it will absorb another portion of 
water, if it be added. Here the point of saturation is elevated, 
and will remain so till the pressure be removed. If to a mass 
saturated, greatly increased, steady and continued pressure be 
applied, it will yield up part of its moisture, lowering the point 
of saturation. 
If what has been said be true, it follows : — 1. That slight and 
continued agitation lessens the retaining power. 2. That steady, 
moderate, equal and continued pressure increases the retaining 
power. 3. That greatly increased, steady and continued pressure 
