J3. Davis — Stationary Sound- Waves. 231 



Art. XXII. — On a New Effect produced by Stationary Sound- 

 Waves; by Bergen Davis. 



In the course of an investigation upon the action of sound- 

 waves, under certain conditions, I have found that if a small 

 cylinder, which is closed at one end, is placed in a stationary 

 sound-wave, it will not only arrange itself perpendicularly to 

 the motion of the wave, but will actually move across the wave 

 in a direction perpendicular to the stream-lines. The force 

 producing this motion is of considerable magnitude and it acts 

 normally to the closed end of the cylinder, causing it to move 

 in the direction of the closed end, i. e., the closed end is driven 

 toward the wall of the pipe. 



In investigating this effect I have used an organ pipe for the 

 production of the stationary wave, its length being 70 cra , and 

 the breadth and thickness 6"35 cm by 5 cm , respectively. The 

 pipe when giving its first overtone made 358 vibrations per 

 second. From the dimensions above given, it follows that a 

 node will exist at 22 cm from the mouth-piece, and also at the 

 stopped end. One wall of the pipe was made of glass. A 

 thin rubber diaphragm was placed across the pipe near the 

 node next to the mouth- piece, thus converting the remainder 

 of the pipe into a closed chamber. The air in this chamber 

 was in this way kept free from any currents that might arise 

 from blowing the pipe. A diaphragm of this kind at the node, 

 does not alter the intensity of the sound appreciably. The 

 pipe, when blown very hard furnished a very strong overtone. 



The small cylinders were made from " No. 00 gelatine cap- 

 sules" such as are used for medical purposes. The hemispher- 

 ical ends of these capsules were removed, and flat paper discs 

 substituted for them at one end, the other end being left open. 

 Four of these cylinders were arranged as shown in fig. 1. 

 This system of cylinders was supported by a small glass pivot, 

 which was mounted on the point of a fine needle. The needle 

 was attached to a glass rod which was destined to carry the 

 system into different regions of that part of the pipe located 

 behind the protecting diaphragm. 



The strength of the air blast was measured by a mercurial 

 manometer, which was used to obtain the same force of blast 

 throughout a series of experiments. The pipe was placed 

 vertically with the stopped end downward, and the glass rod 

 bearing the system of cylinders was introduced from below 

 through an airtight opening. It could be moved up and down 

 in the pipe, and the system of cylinders placed in any desired 

 position in the stationary wave. The plane of the system of 



