C. GENERAL PHYSICS. 179 



fluid has no perceptible influence on the time of vibration. 

 LubecJc's Inaugural Dissertation, Berlin, 1873. 



THE CAUSE OF WOLF IX THE YIOLINCELLO. 



Mr. Kingsley, in a communication to the Cambridge Phil- 

 osophical Society, states that the wolf, a name given to a 

 well-known defect in the violin, occurs somewhere about 

 low E or E flat, and has been attributed to the finger-board 

 having the same pitch, so that it becomes, as it were, a por- 

 tion of the string stopped down on it, and vibrates with it. 

 Another explanation is given by Savart, viz., that the vio- 

 lincello is constructed of such dimensions that the mass of 

 air included within the instrument resonates to a note mak- 

 ing 85.33 vibrations in a second, a number w 7 hich formerly 

 represented the lowest F on the C string; but w r hich now, 

 owing to the rise of pitch since the beginning of the eight- 

 eenth century, nearly represents the note E immediately 

 below it. Nature, XII., 40. 



THE PYKOPHOXE. 



In 1873 Mr. Kastner brought forward his new invention, 

 the pyrophone, which consists essentially of a flame of hy- 

 drogen gas, burning within a tube in such a way as to pro- 

 duce the well-known singing: sounds on a large scale. If in 

 the tube of glass or any other material, we introduce two or 

 more isolated flames of proper size, and if we place them at 

 a distance from eacli other one third of the length of the 

 tube, these flames will vibrate in unison. This phenomenon 

 is produced as long as the flames remain separated, but ceases 

 as soon as the flames are brought into contact. It is upon 

 this principle that his pyrophone is based ; and the principal 

 objection to the original instrument, which consisted in the 

 necessity of employing hydrogen gas, he has recently over- 

 come, and states that he is now able to employ ordinary 

 illuminating gas; but to do this he is obliged to eliminate 

 the carbon, whereas at first it was impossible to make the 

 tube vibrate with illuminating gas, although the flames were 

 placed in the proper position. According to him, sonorous 

 flames of illuminating gas are in fact enveloped by a photo- 

 sphere which does not exist when the flame is simply lumi- 

 nous. This photosphere contains a detonating mixture of 



