﻿262 Dr. J. W. Low on the Velocity of Sound in 



The mean of the last six half wave-lengths in the immediate 

 neighbourhood of the surface of the liquid is 109*5 millim. 

 The velocity of sound in air v is calculated by the formula 



,.2 



B 



• Q 



-9 







k 



? 



where B denotes the barometric height, Q the specific gravity 

 of mercury, g the accelerating force of gravity, a the density 

 of air referred to water, and k the ratio of the specific heats. 

 The analogous formula, when vapour is present, is 



.. 2 _ B -Q-.? 



B.Q.g(l + «Q 



k ' Po V Pq 



where u = density of the vapour compared with air, and 

 a= thermal coefficient of expansion of gases. 



S k s> 



\ p h pj 

 =&k(l+at). r w 



_ B . Q . g • k \-\-ut 



1+ U U ""VB = 



1+ U"-\)b 



In further explanation of the above I add 



Air. Ether vapour. 



Density <r=^y^ cr l = u<r = 2-6Q a 



Sp. heat const, pressure , , 



fep. heat const, volume 



Partial pressure p — S S 



