520 Dr. G. Bakker on the 



Practically, we consider the curve LVQWM, where VL 

 and WM are the tangents at the points V and W and 

 calculate the superficies between that curve and LM as 

 parabolic segments. Hence 



C 2 dV 

 Superficies LVQWML = 1 c ~dh=Y 2 -Y 1 = 2a( Pl -p 2 ) 



= f LM x QS - 4LM s/2irf \/ Pl -p. . (13) 



clY 

 QS being the maximum value of -^-, given by equation 11. 



The distance between the centre of gravity and LM is, in 

 virtue of the equations (12) and (9), expressed by 



and equally by 



§QS=f.2V^/Vi^=p. • • • (15) 

 The expressions (14) and (15) give 



yj^ = fy^-T ^-y . . . (16) 

 a \pi Pv 



Eliminating respectively \/p\ —p and a{p x — p 2 ) between the 

 equations (16) and (13), we have for LM : 



LM = A / tS (Pi-p0 3 = 15^ . . (17) 

 077/ H lhp l —p > v J 



where p is denoted by the distance RF in fig. (4). 



Practically, I put also for the thickness of the capillary layer : 



h=-^— (18) 



Pi-P 



Further I have found * for the capillary tension : 



c 2 



H =J i (Pi-P2)dh. 

 This equation and (18) give : 



pJ l ~~ \ p2 c lh—pJ i —ph 



or 



If 2 

 p z= T \ p 2 dh=p = TiF in fig. 4. 



«; i 

 * Phil. Mag. for December 1906, p. 5G3. 



