the Value of the Pitot Constant. 



359 



slope along the length of the pipe was measured for different 

 mean rates of flow by means of the side tubes t u t 2 &c. shown 

 in fig. 2 A. The results are given in Curve III. 



Curve III. 



i-s-o 



Urate" 



I -CO 



o-ro 

















/ 



/ 

















/ 















































y& 































IO 2o 30 40 SO 60 JO CrK ff&C 



It is not easy to say when the curve leaves the straight, 

 that is to say when stream-line motion ceases, but it seems 

 justifiable to state that of the various rates used stream-line 

 motion was certainly present at v = 6*3 cms. per second, 

 possibly present at v = 28*5, and not present at v = 76. It is 

 now possible to compare the experimental \/P curves with 

 the theoretical parabolas for these three mean rates of flow. 

 This is shown in Curves IY, where \/P is plotted with the 

 position of the pitot on a diameter. 



The crosses are the experimental points and the dotted 

 lines are the three corresponding theoretical parabolas obtained 

 by assuming that K = 1'00 and constant. 



It will be seen that in general there is no coincidence o£ 

 an experimental curve with the corresponding parabola ; in 

 fact in the former it is only by neglecting the readings near 

 the side of the pipe that a smooth curve through the origin 

 can be obtained at all, and there seems to be no reason why 

 these readings should be neglected. 



The results at r = 6*3 cms. per second, where the motion 

 was certainly stream-line, show that the pitot pressures across 



