B. Davis — Small closed Cylinders in Organ-pipes. 185 



Art. XX. — On the Behavior of Small closed Cylinders in 

 Organ-pipes ; by Bergen Davis, Ph.D. 



While experimenting with stationary sound waves in organ- 

 pipes, the following striking effect was obtained. A consider- 

 able number of small gelatine capsules, such as are used for 

 medical purposes, were thrown in a promiscuous pile in the 

 center of the pipe, and when 

 the pipe was blown so as to 

 give its first overtone quite 

 strongly, the small cylinders 

 immediately moved to the 

 middle of the loop of the 

 stationary wave and there 

 arranged themselves in rows 

 across the pipe as shown in 

 the figure. The spacing 

 between the rows was quite 

 regular and the capsules acted 

 as though there was a strong 

 attraction at their ends, in a 

 direction perpendicular to the 

 vibration, and a repulsion at 

 their sides in a direction par- 

 allel to the vibration. 



An investigation was 

 undertaken to determine the 

 effect of the size of the cyl- 

 inders, of the number of 

 rows, and of the amplitude 

 of vibration, upon the dis- 

 tances between the rows. 



The stationary wave was 

 that produced in a stopped 

 organ-pipe speaking its first 

 overtone. Tho side of the 

 pipe was removed and a glass 

 plate substituted for it. At 

 the node nearest the mouth 

 a thin rubber diaphragm was 

 placed across the pipe, which 

 protected the portion badk of the diaphragm from disturbances 

 arising from blowing. This region of the pipe, from the 

 diaphragm to the stopped end, enclosed one-half of the sta- 

 tionary wave. The amplitude of vibration was measured by 

 means of the force acting on a small hollow cylinder closed at 



