434 OF CAPILLARY ATTRACTION AND THE COHESION OF FLUID9. 



other, the fluid will rise lo the same height in them both, if they are 

 placed under the same or similar circumstances. 



549. Having given the mean altitude to which the fluid rises, the 

 distance between the plates can easily be ascertained ; for we have 

 only to divide the constant number 0.0214 by the given altitude, 

 and the quotient will give the distance sought ; but if the observed 

 altitude, or the distance between the lowest point of the meniscus 

 and the surface of the fluid in the vessel be given, the operation is 

 more difficult, since it requires the reduction of an adfected quadratic 

 equation. 



By recurring to equation (317), it appears, that 



but we have shown, equations (315 and 319), that the constant 



quantity L ~ , has, from the comparison of experiments, been 



*9 

 assumed zz 0.0214 ; hence it is 



d{ h + \d (1 |TT) = 0.0214 ; 



now, the value of the parenthetical quantity (1 JTT) is also known, 

 being equal to 1 . 7854 . 2146 ; consequently, by substitution, 

 we have 



0.1073d 2 +hd= 0.0214, 



and dividing both sides by 0.1073, it becomes 



d 2 -f- 9. 32hd= 0.1994. 



Let us therefore suppose, that the observed altitude of the fluid, or 

 the value of h is equal to 0.2913 parts of an inch, and on this 

 supposition, the above equation will become 



rf*+ 2.71473^:= 0.1994, 



and this equation being reduced according to the rules for quadratics, 

 we finally obtain 



d = 1.429 1.357 zz 0.072 of an inch. 



550. The preceding theory has reference to the phenomena of capil- 

 lary attraction, as they are displayed in cylindrical tubes and parallel 

 plates of glass ; it would however, be no difficult matter to extend 

 the inquiry to figures of other forms, and placed under various cir- 

 cumstances ; but being aware that an extended inquiry would elicit 

 no new principle, we have thought proper to omit it ; the property 

 disclosed in the following problem, is however, of too curious and 

 interesting a character to be passed over without notice, we shall 

 therefore endeavour to draw up the solution in the most concise and 

 intelligible manner which the nature of the subject will permit. 



