oy Stationary Sound- Waves. 



233 



The above table is plotted in a curve shown in fig. 2. The 

 abscissse are distances along the pipe and the ordinates are rates 

 of revolution per second. The full line is the observed curve; 

 the broken line is a sine curve. The agreement of the two 

 curves is sufficiently close to suggest that the rate of revolution 

 at any point in the stationary wave is proportional to the 

 velocity of the vibrating air particles at that point. The 



J0 IS 3.0 ZS 30 35 40 45 SO 



curve rises slightly above the sine curve near the dividing 

 membrane, viz : from 30 to 48. 



So far as I am aware a rotation of this kind has not before 

 been observed. 



The force involved in the above reaction was measured with 

 the aid of a double cylinder supported by a fine wire, which 

 went up through the wall of the organ pipe inside of a glass 

 tube, 20 cm long. This double cylinder was carried at the end 

 of a torsion arm and each cylinder was '757 cm in diameter and 

 3 - l cm in length. The area of cross-section of each cylinder was 

 •45 sq . cm . The pipe was placed in a horizontal position during 

 the torsion experiments. 



The amount of torsion necessary to bring the cylinders back 

 to their original position was read on a graduated circle at the 

 top of the glass tube. 



The mean results of a number of experiments are given 

 below. 



Position of 



cylinders in 



pipe. 



2 



7 

 12 

 17 

 21 

 23 

 27 

 32 

 37 

 41 

 45 



Torsion. 



12° 



72° 



190° 



355° 



480° 



555° 



490° 



315° 



165° 



72° 



14° 



