474 Prof. Tyndall 07i the Sounds produced by 



A tube 25 inches long was placed over an ignited jet of 

 hydrogen : the sound produced was the fundamental note of 

 the tube. 



A tube 12| inches long was bx-ought over the same flame, but 

 no sound was obtained. 



The flame was lowered, so as to make it as small as possible, 

 and the tube last mentioned was again brought over it ; it gave 

 a clear melodious note, which was the octave of that obtained 

 ^ith the 25 -inch tube. 



The 25-inch tube was now brought over the same flame ; it 

 no longer gave its fundamental note, but exactly the same note 

 as that obtained from the tube of half its length. 



Thus we see, that although the speed with which the explo- 

 sions succeed each other depends upon the length of the tube, 

 the flame has also a voice in the matter : that to produce a 

 musical sound, its size must be such as to enable it to explode in 

 unison either with the fundamental pulses of the tube, or with 

 the pulses of its harmonic divisions. 



With a tube 6 feet 9 inches long, by varying the size of the 

 flame, and adjusting the depth to which it reached within the 

 tube, I have obtained a series of notes in the ratio of the num- 

 bers 1, 2, 3, 4, 5. 



These experiments explain the capricious nature of the sounds 

 sometimes obtained by lecturers upon this subject. It is, how- 

 ever, always possible to render the sounds clear and sweet, by 

 suitably adjusting the size of the flame to the length of the 

 tube *. 



Since the experiments of Mr. Faraday, nothing, that I am 

 aware of, has been added to this subject, until quite recently. 

 In a recent number of Poggendorff'^s Annalen, an interesting 

 experiment is described by M. Schafi'gotsch, and made the sub- 

 ject of some remarks by Prof. Poggendorfi" himself. A musical 

 note was obtained with a jet of ordinary coal-gas, and it was 

 found that when the voice was pitched to the same note, the 

 flame assumed a lively motion, which could be augmented until 

 the flame was actually extinguished. M. Schafi^gotsch does not 

 describe the conditions necessary to the success of his experi- 

 ment ; and it was while endeavouring to find out these condi- 

 tions that I alighted upon the facts which form the principal 

 subject of this brief notice. I may remark that M. Schaff"- 

 gotsch's result may be produced, with certainty, if the gas be 

 caused to issue under sufficient pressure through a very small 

 orifice. 



* With a tube 14| inches in length and an exceedingly minute jet of gas, 

 I obtained, without altering the quantity of gas, a note and its octave : the 

 flame possessed the power of changing its own dimensions to suit both notes. 



