1825.] Velocity of Sound, 277 



The mean result by experimeut on the 28th of June, 1823, is 



^ — — '— = 52,07, in which time sound travelled along 



the basis of 17669,28 metres, or 57988,2264 English feet. 

 Thus, the mean velocity of sound on the 28th of June in V\ is 

 339,34 metres = 1113,669 English feet. 



The mean temperature, when these experiments were made, 

 was at 



Centigrade scale, 



Zevenboompjes 10°,07 , 



Kooltjesberg , 11 36 



Mean temperature 11 215 = t 



Mean height of the barometer, corrected for capillarity, and 

 reduced to 0° of centigrade scale, 



Zevenboompjes 0,7476 metres. 



Kooltjesberg 0,7487 



Mean barometer, or p = 0,74815 



Mean tension of aqueous vapour 



by Mr. Daniell's hygrometer 



F= 0,00840465-=^^'^' 



These quantities being substituted in the formula, we have 

 the velocity of sound, by theory, on the 28th of June, 1823, 

 V = 335%10 metres = 1099,753 English feet ; by experiment, 

 339^34 metres = 1113,669 feet. 



Difference between theory and experiment 4,24 metres = 

 13,916 feet. 



Thus it appears by the experiments both of the 27th and 

 28th of June, that sound travels faster than its theoretical cal- 

 culation. 



The 27th of June, difference of experiment and theory 4™,92 

 28th of June 4^,24 



The difference between the experiments of 27th and 28th of 

 June, is but of 0™,62, or 2,3629 feet; that is about .5^ of the 

 mean result of the experiments of both days. 



The French philosophers found a difference between their 

 experiments of 23d and 24th of June, 1822, of -gV- But the 

 difference of -^-i^, which we obtained, if we reduce the obser- 

 vations of both days to what they would have been in perfectly 

 dry air, and in temperature of 0° cent, is still remarkably 

 lessened. The formula by which the velocity of sound in given 

 hygrometrical circumstances, and a given temperature of the 

 air, is reduced to what it would be in dry air of 0° cent, tempe- 

 rature, calling U' the velocity of sound in dry air of 0° tempe- 

 rature ; U the velocity of sound at a tension of aqueous vapour 

 = F, is as follows : ' 



