34 MOLECULAR ATTRACTION. I.ECT. II. 



solid particles, the latter are separated and left on the filter, 

 the substance of which imbibes the liquid. When a drop of 

 chocolate or ink falls upon cloth or filtering paper, it pro- 

 duces a dark central spot, surrounded by a zone of a paler 

 coloured liquid. The same effect takes place when blood 

 is extravasated in the sub-cutaneous cellular tissue ; the 

 serum extends to the margins, and separates from the co- 

 louring matter. 



In the phenomena of imbibition, we have to consider first, 

 the force of adhesion between the liquid, and the surfaces 

 of particular solids placed in contact with them, and after- 

 wards capillary action, properly so called ; for in sugar, in 

 a mass of sand or of ashes, and in organized tissues, there 

 certainly exist very minute cavities, which ramify internally 

 in a more or less tortuous manner. 



Imbibition of different Liquids. The phenomena of im- 

 bibition deserve to be more attentively studied than they 

 have yet been. I shall lay before you the results of some 

 experiments which, in conjunction with Professor Cima, I 

 made on this subject. I wish that it had been in my power 

 to have extended them. 



We filled some tubes of glass of two centimetres [about 

 f of an English inch] with very white sand, which had 

 been sifted through a very fine sieve. The extremity to 

 be immersed in water was closed by a piece of cloth. We 

 had previously taken the precaution of drying the sand in 

 a salt-water bath. It was then introduced by the upper aper- 

 ture of the tube, care being taken not to shake it when the 

 tube was full, lest the sand within should become unequally 

 compressed. Six tubes thus prepared were plunged at the 

 same instant into six different liquids, at a temperature of 

 -f 12 centig. [=53-6 Fahr.]. The action of imbibition, 

 by which the liquids were elevated in the tubes, continued 

 for ten hours, at first being rapid, but gradually becoming 



