and the Observed Velocity in Air and Gases. 



19 



merits of MM. Clement and Desormes*, Laplace found ^ = 1*354 ; 

 and MM. Gay-Lussac and Welter, from their experiments, ob- 

 tained £ = l , 3748t. More recently M. Masson has undertaken 

 an elaborate series of experiments, following the method of Gay- 

 Lussac and Welter, from which he deduces for air ^=1'41J. 

 Such experiments demand the utmost delicacy of manipulation, 

 combined with all the refined resources of modern experiment- 

 alists; and perhaps for this reason we are justified in consider- 

 ing Masson' s result as the most worthy of confidence. No men- 

 tion has been made of the results obtained by M. Dulong§, 

 inasmuch as they are deduced from Laplace's formula. 



For purposes of comparison, I subjoin the following Table of 

 the " Theoretical Velocity of Sound " in dry air at 0° Centigrade, 

 as deduced from the various formulae which have been devised to 

 solve this interesting question. The column containing the 

 values of k indicates the factor, the square root of which, multi- 

 plied into the Newtonian velocity, should give the true velocity 

 of sound in air. 



Date. Authority. 



1 687, Newton and 1 

 1759 Lagrange... J 



1816 



1824 

 1847 



1849 

 1851 

 1860 



Laplace and 1 

 Poisson ...J 



Ivory || 



Herapath*[ .. 



Challis** 



Potterff 



EarnshawJ+.. 



Formula for velocity. 



Value of k . 



= slg~h 





1-42511 



>» 



1-354 



i» >» 



1-3748 





1-41 



= */ff h '\/ 3 



1-3333 



= ^gh. V V2 



1-41421 



^V^Y/l-T-^ 



1-40528 



= *Jgh-\/ 2 



1-5000 



'-^/£ 



1-51982 



Experimenter. 



De la Roche and \ 

 Berard. J 

 f Clement and "I 

 1 Desormes. J 

 j Gay-Lussac and 1 

 1 Welter. j 



Masson. 



Velocity at 



0° Cent, in 



metres per 



second. 



279-9602 



334-211 



325-766 



328-2585 

 332-4343 



323-2706 



332-9307 



331-8780 



342-8798 

 345 1375 



* Journal de Physique, Nov. 1819, vol. lxxxix. p. 333 et seq. 

 f Mecanique Celeste, vol. v. book 12. pp. 125 & 127. Paris, 1825. 

 % Peclet's Traite de Physique, 4th ed. vol. i. p. 571. Paris, 1847. 

 Daguin's Traite de Physique, vol. i. p. 884. Paris, 1855. 



§ Memoires de V Academie des Sciences, vol. x. p. 147 et seq. 

 || Phil. Mag. S.l. vol. lxiii. p. 424 (1824) ; vol. lxvi. p. 13 (1825). 

 Ivory seems to have deduced the factor f from Dr. Dalton's law. 

 IF Mathematical Physics, vol. ii. p. 63. London, 1847. 

 ** Phil. Mag. S. 3. vol. xxxiv. p. 98 (Feb. 1849). 



ft Ibid. S. 4, vol. i. p. 104 (Feb. 1851). ++ Ibid.vol.xix. p.455 (June 1860). 



C 2 



Also 



Mr. 



