450 
Dr. Moll’s account of the experiments on 
English feet. Thus, the mean velocity of sound on the 28th 
of June in T, is 339,34 metres = 1113,669 English feet. 
The mean temperature, when these experiments were 
made, was at 
Mean height of the barometer, corrected for capillarity, 
and reduced to o° of centrigrade 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, m io metres = 1099,753 English feet; by experi- 
ment, 339 m ,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 
calculation. 
The 27th of June, difference of experiment and theory 4 m ,92 
28th of June - 4 ra ,24 
The difference between the experiments of 27th and 28th of 
June, is but of o m ,62, or 2,3629 feet ; that is about T - - of the 
mean result of the experiments of both days. 
Zevenboompjes - 
Kooltjesberg - - 
Mean temperature 
ii°, 07 1 
11 36 
11 215 = t 
