CAUSES OF THE MOTION OF JUICES. 349 
absorbed with force enough to overcome the pressure of 
the atmosphere from three to six times; in other words— 
to sustain a column of water in a wide tube 100 to 200 ft. 
high. (Comptes Rendus, 50, p. 311.) 
Absorbent power is influenced by temperature. Warm 
water is absorbed by wood more quickly and abundantly 
than cold. In cold water starch does not swell to any 
striking or even perceptible degree, although considerable 
liquid is imbibed. In warm water, however, the case is 
remarkably altered. The starch-grains are forcibly burst 
open, and a paste or jelly is formed that holds many times 
its weight of water. (Exp. 27, p. 65.) On freezing, the 
particles of water are mostly withdrawn from their adhe- 
sion to the starch. The ascent of liquids in narrow tubes 
whose walls are unabsorbent, is, on the contrary, dimin- 
ished by a rise of temperature. 
Adhesive or Capillary Attraction.—The absorption of 
a liquid into the cavities of a porous body, as well as its 
rise in a narrow tube, are but expressions of the general 
fact that there is an attraction between the molecules of 
the liquid and the solid. In its simplest manifestation 
this attraction exhibits itself as Adhesion, and this term 
we shall employ to designate the kind of force under con- 
sideration. If a clean plate of glass be dipped in water, 
the liquid touches, and sticks to, the glass. On withdraw- 
ing the glass, a film of water comes away with it. Iftwo 
squares of glass be set up together upon a plate, so that 
they shall be in contact at their vertical edges on one side, 
and one-eighth of an inch apart on the other, it will be 
seen, on pouring a little water upon the plate, that this 
liquid rises in the space between them several inches or 
feet where they are in very near proximity, and curves 
. downwards to their base where the interval is large. 
Capillary attraction—the common designation. of the 
force that causes liquids to rise in fine tubes—is the same 
adhesion which is manifested in all the cases of absorp- 
. 
