the Flow of Air through a Pipe. 397 



since this air was displaced by water under pressure from an 

 air reservoir fitted with a calibrated gauge-glass. 



After leaving the coil it entered a second measuring* 

 reservoir. The pressure in each reservoir was measured by 

 a mercury piezometer, and the mean volume passing the pipe 

 at the mean pressure p m calculated from the volumes leaving 

 the first and entering the second and from their respective 

 pressures. A sketch and description of the complete appa- 

 ratus used may be seen in the Proc. Roy. Soc. A. vol. lxxx. 

 1908, p. 115. 



IV. Conclusions. 



We have then, available for comparison, the results of the 

 whole of the foregoing experiments which, with the exception 

 of these numbered from 18 to 31 of Table V., may be taken 

 as carried out at substantially the same temperature, viz. GG° F. 

 For each of these the values of 



log [V^n^!] an d of log [p m . v m . d] 



have been calculated and plotted, the logarithmic homologaes 

 for the whole series of pipes being shown in fig. 1. 



Fi-. 1. 



If the assumptions made in deducing formula (G) are 

 Phil. Mar/. S. 6. Vol. 17. No. 99. March 1909. 2 E 



