CHAPTER XV. 



OF CAPILLARY ATTRACTION AND THE COHESION OF FLUIDS. 



525. THE subject of Capillary Attraction, and the Cohesion of 

 Fluids, considered merely as a branch of philosophical inquiry, is 

 exceedingly seductive and interesting ; but when viewed in the light 

 of a demonstrative and practical department of physical science, its 

 application is necessarily very circumscribed, and its character is 

 unimportant as an analytical theory. 



It has, however, been very extensively studied, both in this and in 

 foreign countries, and numerous philosophers of the greatest eminence, 

 possessed of the loftiest conceptions and the most profound mathema- 

 tical attainments, have deemed it a topic worthy of their most atten- 

 tive consideration, and have ascribed to its influence, a numerous 

 class of phenomena, in reference to the operations of nature on the 

 various objects of our sublunary world. To this it is owing, that the 

 rains which fall on the higher elevations, do not immediately descend 

 and run to the sea with an increasing velocity, but are retained by 

 the soil, and being slowly filtered down through it, are cleansed from 

 their impurities, and delivered in springs and fountains at the foot of 

 the hills, so as to afford a constant and nearly uniform supply of 

 moisture to the lower levels. 



By capillary attraction, does the oil or melted tallow rise slowly 

 through the wick of a lamp or candle, where it is converted into 

 vapour by the heat of the surrounding flame, and rushing out in every 

 direction, is ignited when it comes in contact with the circumambient 

 air. By capillary attraction, the juices of the earth are absorbed by 

 plants, and carried through their numerous ramifications to the 

 remotest leaf, where they are again partly discharged by evaporation, 

 after a similar manner to that in which the oil is dissipated from the 

 wick of a lamp, or the melted tallow from the wick of a candle. 





