19




CofiUarff Attraction



This is shown in the accompa-
nying figure, in which A B C D rep-
resent several tubes of different
bore, open at both ends, and im-
mersed in water, and I III, the
heights to which the water rises in
them severally. It attains the
greatest height in small hair-like
tubes ; and hence the force which
causes the rise is called capillarity, or capillary attraction,
from the Latin word capillus, a hair.
The height to which water will rise in tubes of the
same bore is always the same ; but of other liquids, as oil
of vitriol, alcohol, or solution of common salt, some will
rise higher, and others not so high.
This force is also exerted between two plates, when
brought sufficiently near each other, and immersed in a
fluid.
The experiment is best per-
formed by taking two pieces of
glass, A and B, an inch and a
half wide, and two inches long,
and placing them in a trough of
colored water, D, with two of
the edges in contact, as at C,
while the opposite edges are a
little separated. The two plates
will then make a small angle with each other, and the
water will be observed to rise to a considerable height on
the side C, where the plates touch each other, and grad-
ually to fall toward the other side, forming the well-
known curve called the hyperbola.
If a drop of water be placed in a small conical tube,
by the force of capillarity it immediately begins to move
toward the smallest end of the tube, whatever may be its
position.
