the Value of the Pilot Constant. 351 



Curves I, where K (circles) and K x (crosses) are plotted 

 with the velocity o£ the pitot relative to the air, the velocity 

 in the case of the crosses being the mean rate of flow of the 

 air along the pipe. 



Curves I. 



K, 



VOL- 



loo 





--% 



'*--©- 







s>— © — 









X- 



0<?8- 



{ 











































o^v 



X 





















U H^ 























0-86- 

 0-86- 











































041 



























■■ I 



1 





1 



1 



— < — 



"'1 



1 



2oo 



600 006 



1000 1200 IhCO 



1600 IBoo ZOOO C"nv SU 



The results of the centrifugal method show that except for 

 a 1 per cent, variation at low velocities, where the ex- 

 perimental difficulties were considerable, K was 1*002 at all 

 the velocities investigated. 



K l5 on the other hand, although about l'OO at higher 

 velocities, rapidly decreased with decreasing rate of flow. 



Now K : only differs from K when the latter is not constant, 

 so that assuming that the centrifugal value of K is correct 

 the two curves should be identical. There must, therefore, 

 have been some source of error in the pipe method which 

 was not present in the centrifugal method. 



No information could be obtained on this point from the 

 work of others, because the velocities at which the dis- 

 agreement was appreciable were far below those which had 

 been previously investigated. In view of this fact and of 

 the general importance of the question of the flow of air 

 through pipes, a reinvestigation of the pipe method was 

 undertaken. 



