"32 Mr Molin, An examination of Searle's metJiod 



4000 



9 10 Tl 1Z 13 IV IS IS 17 18 19 20 



jTemptX- 



§ 7. I thought it would be interesting to compare the results 

 given by Searle's method with those obtained by Poiseuille's 

 method. The utility of the latter method for very viscous liquids* 

 is proved by the investigations of Kahlbaum and Eaberf for 

 values of rj in the neighbourhood of 40, and by LadenburgJ for 

 r] = 1-3 X 10^. Fausten§ has found that the length of the dis- 

 charge tube must exceed 45 cm., if the simple Poiseuille formula 



is to represent actual facts. In the formula 



h = Height of liquid corresponding to difierence of pressure 

 between ends of tube. 



R = Internal radius of tube. L = Length of tube. 



p = Density of liquid (= 1-4103 ± 0-0003 grm. cm.-^at 19-8° C). 



m = Mass of liquid discharged. t = time of discharge. 



For shorter tubes, Hagenbach's* correction must be employed; 

 otherwise the value obtained for 77 will be too high. As the liquid 

 flows out into the air in an even jet, it carries kinetic energy with 

 it; in order to allow for this, the value of t] given by Poiseuille's. 



* H. Glaser, Eriangen Diss., 1906. 



t G. W. A. Kahlbaum and S. Raber, Acta Ac. Leap., 84, p. 204, 1905. 



X R. Ladenburg, Ann. d. Phys., 22, p. 298, 1907. 



§ A. Fausten, Bonn. Diss., 1906. 



