206 Onthe Equilibrium and Motion of Liquids in Porous Bodies. 
immersed, and allowing the column of raised liquid to descend 
to its position of equilibrium, the length of the raised column is 
a+nL, and consequently greater the greater the number n of 
interruptions ; this length may increase indefinitely. 
In the case where the weight of each bead is equal to L, they 
are individually in equilibrium, and a column of indefinite 
height, interrupted only by very small bubbles, and everywhere 
at the atmospheric pressure, may be sustained. 
Secondly. When the tube is depressed in the bath, and the 
liquid allowed to rise to its position of equilibrium, the length of 
the raised column is diminished in proportion to the number of 
bubbles, and becomes a—nL; it is always less than if the column 
were continuous, and it may become negative and decrease inde- 
finitely. 
In accordance with theory, experiment also proves that when 
once a column of liquid, whose length is between the limits a+ nL 
and a—nL, has been placed in the tube it will remain there. 
Some experiments were also made with a view of measuring the 
limit L of the resistance which a single bead can oppose to the 
ressure. It was found that this limit is independent of the 
length of the bead, but that it increases when the bubbles of air 
diminish ; it increases, too, very rapidly when the diameter of 
the tube is diminished, and is equivalent to 54 millims. in a tube 
where the capillary ascension amounts to 200 millims. In such 
a tube, therefore, four interruptions are equivalent to the capillary 
force, and may annul the latter when the liquid rises, or double 
the height of the sustained column when the liquid descends. 
Mercury produces effects much more intense, but alcohol and 
oil oppose no resistance to pressure. 
When a capillary tube, instead of being cylindrical, possesses 
successive contractions and expansions, it exhibits still more 
curious properties. After being once moistened, the thin film 
of liquid which remains adhering to its walls soon collects at the 
contractions, and there forms interrupted beads. Here then a 
chaplet is formed, as it were, spontaneously, and in consequence 
of the nature of the canal, the above-mentioned properties of a 
cylindrical tube become exaggerated in a surprising manner. A 
tube with eight very narrow contractions sufficed to close a baro- 
meter-tube hermetically, and even to overcome a pressure of two 
atmospheres. 
If pressure be applied to one extremity of such a tube, filled 
with water, the latter overflows (/i/tre) without difficulty ; but if 
this pressure is exerted on a compressed gas, the latter replaces 
the water in each successive chamber, and leaves a bead of liquid 
at each contraction ; these beads, by opposing a resistance which 
increases with their number, finally destroy the pressure. 
