220 ANNUAL 11ECOKD OF SCIENCE AND INDUSTKY. 



familiar examples of the hydrogen singing flame and the tube 

 of Kijke are also cases in point. The explanation seems to 

 be that the heat is communicated periodically to the mass 

 of air confined in the sounding-tube at a place where in the 

 course of a vibration the pressure varies. The phenomena, 

 however, are yet quite complex. 



Kayser lias redetermined the velocity of sound in air by 

 a modification of the method of Kundt. The dust figures in 

 the glass cylinder were formed by the transverse vibrations 

 of steel rods excited by a violoncello bow. A small cork 

 piston attached to one end of the rod played in the glass cyl- 

 inder, while a style affixed to the other end of the rod drew 

 its vibrations on a phonautograph cylinder. The vibrations 

 were compared with those of a fork recorded simultaneously. 

 He assigns 332.5 meters as the velocity of sound in free air. 

 The same research enabled him to determine the ratio of 

 the specific heat of air at constant volume to that at con- 

 stant pressure. The true value Kayser finds to be 1.4106. 



Szathmari has ingeniously applied the method of coinci- 

 dences to determine the velocitv of sound in free air. His 



ml 



apparatus consisted of a pendulum whose rate was accurate- 

 ly known, which was made to close an electric circuit at 

 each oscillation, the line beino- 220 meters lono:, and having 

 two bells in its course. When the observer is close to both 

 of the bells, he hears the strokes of both simultaneously; but 

 if one of the bells be removed to a distance, the stroke of 

 this bell is heard after the other, until a point is reached at 

 which the strokes occur again at the same instant. The dis- 

 tance between the bells is that over which the sound moves be- 

 tween two successive strokes of the bells. In the experiments 

 of the author the pendulum had a period of 0.29G1 second. 

 The distance between the bells when the sounds were as^aiii 

 simultaneous was 99.25 meters. From this the value 335.19 is 

 easily obtained as the velocity of sound in free air in meters, 

 lleduced to zero, the value becomes 331.57 meters between 

 Regnault's value and that of Moll and Van Beck. 



M'Leod, according to JYature, has described some experi- 

 ments made with his new apparatus upon the exact number 

 of vibrations made by tuning-forks. lie used two sets of 

 forks belonging to the South Kensington Physical Labora- 

 tory, and a third set just received from Konig. The results 



