210 



CAPILLARITY. 



liquid will stand twice as high in a tube which has half 

 the width of another ; if a tube has one-third the in- 

 ternal diameter of another tube, the liquid will rise in 

 it to a height three times as great as in the wider tube : 

 The height of ascent in capillary tubes is inversely propor- 

 tional to the internal diameter of the tubes. 



If a capillary tube is placed in mercury, the surface 

 of the liquid in the tube is depressed below the surface 

 of the external liquid ; but mercury being not transparent 



ii n i 



FIG. 149 (real size). 



Fio. 150 (real size). 



like water, it is somewhat difficult to observe the de- 

 pression. In order to prove the fact that mercury is 

 depressed in a capillary tube, it is most convenient to use 

 two communicating tubes, like those in fig. 150, one of, 

 which has a very small diameter. 



A liquid placed between two solid walls, which are 

 moistened by it, will rise the higher the narrower the 

 space between the walls. This may be shown by means 

 of two rectangular plates of glass, placed in a liquid, so 

 that their edges on one side may be in contact, and on 



