On the Vibration of the Air in a Tube open at both ends. 419 



besides the melting-point come in all probability into play ; but 

 it appears to me that this is the most important. 



I merely make these remarks, so that my views may be cor- 

 rected if they are wrong ; if they are right, I may, by publishing 

 them, save the time of those experimenters who might be tempted 

 to seek from the subject results which it cannot give. 



Royal Institution, May 1859. 



LXXI. Notice of a New Method of causing a Vibration of the Air 



contained in a Tube open at both ends. By P. L. Rijke, 



Professor of Natural Philosophy at the University of Ley den"^. 



1- "ly/TY first experiments were made with a glass tube 0-8 



-'-*-*- metre long, having a diameter of 37 millims. at the 



top and 30 millims. at the bottom. Inside, at the distance of 



0-2 metre from the latter extremity, I had placed a disc of 



wire-gauze, about 50 millims. in diameter, with its edges turned 



back, so that the pressure they exerted on the sides of the tube 



sufficed to keep the disc at the desired height. The gauze was 



made of iron wire of 0-2 millim. diameter, and had about 81 



meshes to the square centimetre. 



The apparatus being thus prepared, it was only necessary to 

 raise the wire-gauze to a red heat by means of a spirit or hydro- 

 gen lamp, and then to extinguish or remove the lamp, in order 

 a few moments afterwards to produce a sound. The sound 

 produced was nearly the fundamental note of the tube. It was 

 loud, but only lasted for a few seconds. 



2. When, instead of a single disc, several were placed in the 

 tube, the sound lasted longer. 



3. The sound ceased immediately the top of the tube was 

 closed, showing that the presence of an ascending current of air 

 is one of the conditions of the phsenomenon. For this reason 

 the mimber of discs must not be excessively multiplied, so as to 

 retard the motion of the air in the tube more than to a certain 

 degree. 



4. The experiment is equally successful, if the disc be heated 

 by means of a carbonic oxide flame. I prepared this gas by 

 acting with Nordhausen sulphuric acid upon oxalic acid. As an 

 excess of precaution, I dried the gas before burning it. 



This experiment proves that the presence of vapour of water 

 is not one of the necessary conditions of the phjenomenon. 



5. Tubes of dimensions different from the one described above 

 might be successfully employed, but they must not be less than 

 0-2 metre long. 



In order that the sound may have its maximum intensity, the 



* CommuuiciiU'd bv tliu Author. 

 2 P2 



