THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



MARCH 1868. 



XIX. On the Velocity of the Propagation of Waves in Gaseous 

 Media. By V. Regnault*. 



THE formulae which physicists have hitherto employed to re- 

 present the rate of propagation of a wave in a gaseous medium 

 which is either unbounded in all directions, or enclosed in a 

 straight cylindrical tube, assume the gas to be perfectly elastic, 

 and the excess of the elastic force which gives rise to the propa- 

 gation of the wave to be infinitely small in comparison with the 

 elasticity of the medium at rest. 



These hypotheses, being introduced from the first into the cal- 

 culation, necessarily produce their consequences in the resulting 

 formulae; but as not one of the known gases exactly satisfies 

 these conditions, we may expect to find sensible discrepancies 

 between the results of actual experiments and those deduced by 

 calculation from theory. 

 y^ In fact, when we assert that a gas is perfectly elastic, we as- 

 sume : — 



(1) That it exactly obeys Mariotte's law. Experiment, how- 

 ever, shows that all gases deviate more or less from this law. 



* Translated by Frederick Guthrie, F.R.S.E., Professor of Physics and 

 Chemistry, Royal College, Mauritius, from the Comptes Rend us for Febru- 

 ary 3, 1868. [In an introductory paragraph the author states that the ex- 

 periments upon which are based the results now presented to the Academy 

 were completed several years ago. The memoir containing them is already 

 in print, and forms the first part of vol. xxxvii. of the Memoires de 

 V Academie ; but as it will be some time before this volume appears, he has 

 requested and obtained the sanction of the Academy to publish the general 

 conclusions at which he had arrived in the Comptes Rendus, although ex- 

 ceeding the prescribed limits.] 



Phil. Mag. S. 4. Vol. 35. No. 236. March 1868. M 



