Nipher — On Pressure Measurements in a Fluid Stream. 21 

 The radial acceleration of dm towards the center is 



a = (oh\ 



Then 



Hence 



8' 

 dP = ahdr = (oh- j(b-^F) dr 



i 



F 



dP _ „ 



P' 



or 



(oh"^ 



h±P__^J^ (1) 



b-^P'"^ 

 The mass m of air in the column of length r is 



Jr h' r* r 



8dr = ^ (I 



m =8' /• = I hdr = "^ I {b + P)dr 



Combining this equation with (1) by the elimination of P, 

 we have for any constant angular velocity, 



b + P' r 



J 





^firp (2) 







In this equation the integral in the denominator was de- 

 termined by planimeter measurements between limits ?■ = 

 and r = 100 cm, this outer limit being taken as the value of r 

 in the numerator. The temperature T was assumed 293. 

 The number of rotations per second was assumed ri =: 10, in 



0)2 -6 



which case ^-777^ = 2.339 X 10 



The integration was repeated with values r = 50 cm. and 

 11 = 20. 



