IV] VARIOUS THEORIES, &c. 6i 



pressure on the column exerted by the water outside 

 is greater than that inside, and the water rises in the 

 tube till equilibrium is established. For tubes of the 

 same material this capillary ascension is inversely pro- 

 portional to the diameter of the tube. If we take a 

 long capillary tube filled with alternate bubbles of air 

 and columns of water (such a system is called ^chapelet 

 de Jamin) it will be found that even huge pressures at 

 one end exhaust their effect before the other end is 

 reached — each of the columns of water shows less and 

 less effect. In each partial column, the anterior end 

 becomes more concave, the hinder end less so ; te. we 

 have two unequally curved films exerting different 

 pressures on the interior of the column in each case, 

 the pressure of the hinder (less concave) surface being 

 larger opposes the external pressure with consider- 

 able effect. Hence the pressure conveyed by the first 

 bubble to those in front, is less than that exerted at 

 the opening of the tube ; the pressure of the second 

 bubble on the third less still, and so on till the visible 

 effect has practically disappeared before the other 

 end of the tube is reached. 



It was concluded from Jamin's researches that 

 a water-column of any height may be held upright 

 if in a fine tube and broken by a sufifiicient number 

 of air bubbles ; and if the tubes are alternately 



