264 AN APPARENT EXCEPTION. 



bunches of hair, hemp, and other textile fibres, 

 when arranged in a similar manner. But it would 

 be unphilosophical to maintain, that an agent 

 which augments capillary attraction, is different 

 from its primary and efficient cause. 



It has been maintained by Laplace, that an 

 increase of temperature diminishes the elevation 

 of liquids in capillary glass tubes first, by aug- 

 menting their capacity, and secondly, by lessen- 

 ing the density of the liquid. He further re- 

 gards it as a general law, that the elevation of 

 any liquid that completely wets the sides of a 

 capillary tube at different temperatures, is in the 

 direct ratio of its density. This view of the sub- 

 ject has been partially corroborated by the ex- 

 periments of Sir David Brewster, who found that 

 cold water rose somewhat higher in a capillary 

 glass tube, than when hot. 



Whatever may be the cause of this singular 

 fact, (which I have also verified by repeated 

 experiments,) it is opposed by a thousand others, 

 which demonstrate that the force and rapidity 

 with which liquids pervade porous solids and 

 capillary tubes, cceteris paribus, are proportional 

 to the temperature of the liquids. 



When I come to treat of the agency of caloric 

 in the phenomena of life, it will be shewn that it 

 is the proximate physical cause of capillary cir- 

 culation throughout the animal and vegetable 

 world, without which there could be no absorp- 

 tion, secretion, nutrition, and growth ; that trees 



