CAPILLAR Y A TTRA CTION. (A PP. C.) 67 



done by well-known practical methods, it is prob- 

 able that the process will be very rapid : it would, 

 indeed, be instantaneous, were it not for the cold 

 of evaporation in one vessel and the heat of 

 condensation in the other. Practically, then, the 

 rapidity of the process towards hydrostatic equi- 

 librium through vapour, between detached liquids, 

 depends on the rate of the conduction of heat 

 between the several surfaces through intervening 

 solids and liquids. Without having made either 

 the experiment, or any calculations on the rate of 

 conduction of heat in the circumstances, I feel 

 convinced that in a very short time water would 

 visibly rise in the capillary tube indicated in the 

 diagram (Fig. 32), and that, provided care is taken to 

 maintain equality of temperature all over the surface 

 of the hermetically-sealed vessel, the liquid in the 

 capillary tube would soon take very nearly the 

 same level as it would have were its lower end open ; 

 sinking to this level if the capillary tube were in 

 the beginning filled too full, or rising to it if (as in- 

 dicated in the diagram) there is not enough of liquid 

 in it at first to fulfil the condition of equilibrium. 



The following formulae show precisely the re- 

 lations between curvatures, differences of level, and 

 differences of pressure, with which we are concerned. 



Let p be the density of the liquid, and cr that of 

 the vapour ; and let T be the cohesive tension of 

 the free surface, per unit of breadth, in terms of 

 weight of unit mass, as unit of force. Let h denote 



F 2 



