192 Dr Searle, A Simple Method of determining, etc. ' 
In the case of tube I the tap was opened for 120 seconds, so 
that ¢=120 secs. For tube II the tap was opened for 180 seconds. 
The temperature was 13°8° C. throughout. 
The mean value for the viscosity of air at 13°8° C. is 
= Is) < MO exit, Ci Sees". 
Rh. A. Millikan (Physical Review, No. 1, 1913, p. 79) gives 
n = 1824 x 10-4 {1 + 0027 (¢ — 23)} 
for the viscosity of air at  C. This gives 7 =1:779 x 10~ for the 
viscosity at 13'8° C. 
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