of the Air contained in a Tube open at both ends. 421 



mined by means of a sonometer, provided with a metallic cord, 

 tuned to a pitch of M. Marloye which gives Ut^, corresponding 

 to 256 entire vibrations. The number of vibrations of the sound 

 produced by the galvanic current, has been found to be 226. 

 The tube I made use of for this experiment was the one de- 

 scribed above. The tube being cool, when a current of air is 

 blown against the edge of one of its openings, a sound is obtained 

 corresponding to 208 vibrations. 



8. If by any means the intensity of the galvanic current be 

 gradually diminished, a period at last comes when the sound 

 ceases. It may then be immediately reproduced by introducing 

 into the upper extremity of the tube another disc. This experi- 

 ment succeeds whatever be the distance between this new disc 

 and that traversed by the galvanic current. This reproduc- 

 tion of the sound is easily explained by what we have seen 

 above (6). 



9. The sound may also be reproduced, but not so as to be 

 permanent, by interrupting the galvanic current, and suffering 

 the tube to cool till it has acquired the temperature of the sur- 

 rounding bodies. If the current be then re-established, the tube 

 immediately emits a sound. This sound commences loud, but at 

 once begins to diminish, and finally dies out. The cooling of 

 the tube is much favoured by exposing it to a current of cold air. 

 This experiment also seems to me not to I'cquire explanation (6). 



10. There is also another very simple way of reproducing the 

 sound, that is, by closing for some time either of the ends of the 

 tube. The current of air being arrested, the temperature of the 

 disc is considerably augmented. In each experiment I remarked 

 that it had become red-hot throughout a considerable part of its 

 extent. On opening the end of the tube, a very loud sound is 

 heard, which, however, only lasts some seconds. 



11. The sounds (8), (9), and (10) were the same as those I had 

 produced before, and corresponded to 226 vibrations. 



12. M. Bosscha, on repeating some of my experiments, has 

 observed that sometimes a sound is produced the instant the 

 flame of the lamp is applied to the disc. That this experiment 

 may succeed, it is necessary that the flame be held at some di- 

 stance from the wire-gauze disc. This sound also only lasts 

 for a short time. It is nearly an octave above the fundamental 

 note of the tube, and from time to time it seems to have a 

 tendency to rise. 



We found in experimenting with the carbonic oxide flame, 

 that when the sound was at the loudest, the flame detached 

 itself from the tube from which the gas issued, and formed a 

 luminous cloud below the disc, the borders of which were 

 animated with a very visible trembling motion ; the distance 



