Nipher — On Pressure Measurements in a Fluid Stream. 21 

 The radial acceleration of dm towards the center is 



a = Q)h\ 



Then 



Hence 



8' 

 dP = aMr = coV j(b-hP) dr. 



or 



ft)-r- 



b + F YCT (1) 



h+P' 



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



Jr 8' r» r 



8dr = -J' {b + P)dr 

 Jo 



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

 we have for any constant angular velocity, 



6 + P' ^• 





Jr c 

 0^' 



In this equation the integral in the denominator was de- 

 termined by planimeter measurements between limits r = 

 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 n = 10, in 



which case ^pTp = 2.339 X 10 . 



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

 71 = 20. 



