NATUKAL PHILOSOPHY. 243 



enable it to explode in uni-ou cither with the fundamental pulses of the tube, 

 or with the pulses of its harmonic divisions. 



"With a tu!)C six feet nine inches long, by varying the size of the flame, 

 and adjusting the depth to which it readied within, the tube, I have obtained 

 a series of notes in the ratio of the numbers 1, 2, 3, 4, 5. 



These experiments explain the capricious nature of the sounds sometimes 

 obtained by lecturers upon this subject. It is, however, 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 Pog- 

 gendorff's " Annalen," an interesting experiment is described by M. Schaff- 

 gotsch, and made the subject of some remarks by Professor -Poggendorff 

 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. Schaffgotsch does not describe the conditions 

 necessary to the success of his experiment ; and it was while endeavoring to 

 find out these conditions that I alighted upon the facts which form the prin- 

 cipal subject of this brief notice. I may remark that M. Schaffgotsclrs 

 result may be produced, with certainty, if the gas be caused to issue under 

 sufficient pressure through a very small orifice. 



In the first experiments I made use of a tapering brass jet, ten and a half 

 inches long, and having a superior orifice about one-twentieth of an inch in 

 diameter. The shaking of the singing flame, within the glass tube, when the 

 voice was properly pitched, was so manifest as to be seen by several hundred 

 people at once. 



I placed a syrene within a few feet of the singing flame, and gradually 

 heightened the note produced by the instrument. As the sounds of the flame 

 and syrene approached perfect unison, the flame shook, jumping up and 

 down within the tube. The interval between the jumps became greater, 

 until the unison was perfect, when the motion ceased for an instant ; the 

 syrene still increasing in pitch, the motion of the flame again appeared, the 

 jumpings became quicker and quicker, until finally it escaped cognizance by 

 the eye. 



This experiment showed that the jumping of the flame, observed by M. 

 Schaffgotsch, is the optical expression of the beats which occur at each side 

 of the perfect unison; the beats could be heard in exact accordance with the 

 shortening and lengthening of the flame. Beyond the region of these beats, 

 in both directions, the sound of the syrene produced no visible motion of the 

 (lame. What is true of the syrene is true of the A'oicc. 



While repeating and varying these experiments, I once had a silent flame 

 within a tube, and on pitching my voice to the noie of the tube, the flame, iu 



* "With a tube fourteen and a half inches in length and an exceedingly minute jet 

 of gas, I obtained, without altering tLe quantity of gap, a note and its octave ; the 

 flame possessed the power of changing its o\vn dimensions to suit both notes. 



