PLANTS. 



67 



The Capillary Curve. 



stances dissolved in it, will find their way through a 



medium whose pores are too small to be seen, even with 



the aid of a microscope. 



3. Capillary Attraction The ^attraction of solids and 



liquids for each other, in the case of solids which will 



dissolve, is shown in the fact that 



the two adhere to each other when 



brought in contact. 



If the edge of a piece of glass is 



dipped into water, the water will 



rise a little distance upon the 



glass, and when it is withdrawn 



some moisture will remain upon 



it. If a small glass tube is placed 



in water, the attraction between 



the two will cause the water to rise in the tube. The 



smaller the tube, the higher the water will rise. 



This principle of attraction between 

 solids and liquids, which causes a liquid 

 to pass readily through the minute tubes 

 or pores of a solid, even upward against 

 the force of gravitation, is called capillary 

 attraction, from a Latin word, capillus., 

 which means a hair. The application is 

 to the small, hair-like nature of the tubes 

 through which the principle works. A 



Direct capillarity, familiar example of capillary attraction is 

 the rise of oil in the wick of a lamp. The 



attraction of cotton for oil causes the oil to pass rapidly 



u 1 1 ward through the pores of the wick. 



If one end of a towel is placed in a bowl of water, the 



water will gradually pass along the cotton or linen fibers 



until the whole towel is moistened. 



