Resistance to the Flow of Air through a Pipe. 389' 



(3) is increased by increasing the charcoal absorbing- 



surface ; and 



(4) is dependent on the temperature, following the law 



for ordinary gases, viz., that a lowering of the 

 temperature of the charcoal causes an increase, and 

 a raising of the temperature a decrease in the 

 amount of absorption. 



I desire to express my thanks to Professor Rutherford for 

 suggesting this investigation and for his interest and kindness 

 while it was in progress. 



McGill TJniversit}^ Montreal. 



XXXVI. An Investigation of the Resistance to the Flow of 

 Air through a Pipe, ivith the Deduction and Verification of 

 a Rational Formula. By A. H. GlBSOX, M.Sc, Lecturer 

 in Hydraulics in the Manchester University*. 



(1) Introduction. 



(2) Iiational Formula for Pipe-flo-w. 



(3) Experimental Data. 



(4) Conclusions. 



(5) Effect of Temperature Variations. 



(1) Introduction. 



IN an experimental investigation recently completed by 

 Dr. J. H. Grindley and the author f, the resistance to 

 the flow of air through the pipes used, at velocities below 

 the critical, was used to determine the coefficient of viscosity 

 of the air. In a few of these experiments the velocity was 

 allowed to exceed the critical, and in these cases the results 

 obtained were so widely at" variance with the commonly 

 accepted laws of pipe resistance that the author was led to a 

 further investigation of the phenomenon, and to a comparison 

 of the results obtained by himself and by other experimenters. 

 This investigation showed conclusively that any formula 

 of the usual form 



l(jrn 



(where §p is the difference of pressure at the two ends of a 

 pipe of hydraulic mean depth m(m = dinm. -?-4) and of length 

 /, due to a flow of air through the pipe with mean velocity v) 

 only applies if the coefficient / is varied not only with the 

 physical condition of the interior surface of the pipe, but 



* Communicated bv the Author. 



f Proceedings Royal Soc. ? A. vol. Ixxx. p. 114 (1908). 



