1825.] Velocity of Sound. 269 



to the heal evolved by the compression of the particles, of aUr 

 which is effected by the undulations of sound. It was found 

 impossible to determine the quantity of heat thus evolved, by 

 thflsJaiMijapcession which sound occasions in the particles of the 

 aihgfi'fttidiitlMiir^fore it was deemed expedient to multiply Sir, 

 ^ie^^I^U^te formula by a constant factor V i 4- i, th6 

 ^Rf^jyPwIffbil was determined by experiment. Sir Isaac's for-. 



I odi 'io hP<i fi i-^-Um/ ; n- ^po-'l:>vd sdi dim ao-goibyd 

 jb-inommiJ c == a/M . ^/i ^ k, >ijsyi aouboiq oak 



Thus, by the experiments oi the French Academicians or 

 1738, the most accurate on this subject of that time, the value 

 of k was found equal to 0,4254. It is plain that this correction 

 of the original formula is merely empirical, and dependant on, 

 the accuracy of experiments, which in 1738, had certainly not 

 attained the perfection which is required at present. .^ 



In consequence, this formula was thus altered by Laplacg 



ff»aij9i09rii ^di '^'^ ^^n'\/ ~]d~" * \/ c- .oj3 ,j3iaommj8 ^bio/? 



i^^^s^e specific heat of the air^Mter^<?^4&1fl^J3¥^ 

 suVe, and c'is the specific heat orm¥^Si^\im^j^ z.^^Smmt 

 volume.* '^'^" ^-^^^^^ dvtidw no pjojbI 



^''My friend Dr. Van Kees, Professor in the University df 



Liege, gave a demonstration of this correction \ /-, which will 



be subjoined to the present paper,t and which may be compared 



with that of Mr. Poisson.J, The value of- was determined by 



Laplace from experiments of Messrs. Laroche and Berard,§and 

 found equal to 1,4954 ; but later and more accurate experiments 

 of Messrs. Gay Lussac and Welter brought it to- 1,3748. 



Another cause of the difference between actual expeiiments 

 911 the velocity of sound and its theory, exists in the variable 

 force of the wind, which either accelerates or retards the velocity 

 of sound, according to the direction from which it is blowing. 

 It appears that this cause of error may be annihilated in the 

 following manner. Let sounds be excited exactly at the same 

 Ifeft^/^^yl^fch end* .ofa basis, jand let two observers statioy^^dpQ^ 

 ^i$$Qi§nij% measure the velocity with which sounds travels froffj 

 ^j9^^iJ)0fj the basis to the other. ^J^j^j^^uite clear that the actioiiji 

 ftfittel y^y^ must necessarily acGjQl^^^^the velocity ofthespu|[^4 

 ijSCatfe^lM.one end of the basis, as mucn as it will retM^lJ^fkl 



.^loadJ \d 



fl99WJ9d 9.' * VyPl^^^ ^5^ Ann de Phys. et Chim. torn ii^ B!.?|fe9l90 9dT 

 r , f- j.^ T Dissertatio de celentatc soni. 1 rajet. IHla. 



Dsiodniifs t i Annales de Flvys. et de Ohim. Mai 18^,3,-&ifel bfl£ ifI9mna^(J^9 

 § Ibid. Annalesde Cliimie, torn. Ixxxv. p.72. - > - ' , 



