452 
Dr. Moll's account of the experiments on 
of June, 1823, the mean velocity of sound in air perfectly 
dry, and at o° temperature, was 332®, 05 = 1089,744 feet in 
a second. 
SECTION VIII. 
Experiments on the 2,5th of June , when the shots were not 
reciprocal. 
The following experiments will I trust prove, that in ex- 
periments on the velocity of sound, such observations can 
only be relied on in which the shots on both stations were 
reciprocal, that is fell within the same second in both places, 
and were equally heard and seen on both stations. The 
25th of June, the cannon fired at Zevenboompjes was not 
heard at Kooltjesberg, but at Zevenboompjes the report of 
the guns fired at the other place was distinctly perceived. 
The following table shows the time preterlapsed between 
the light and report, as observed at Zevenboompjes. 
Number of 
Shots. 
Time between 
light and report. 
1. 
52,31 
2. 
52,59 
4- 
52,47 
7- 
52,20 
8. 
52,47 
1823. J 
IO. 
52,17 
25th June. * 
12. 
52,27 
14. 
52,52 
15- 
52,54 
16. 
52,43 
17. 
51,91 
19- 
52,50 
1 
Observations at the sta- 
tion of Zevenboomp- 
> jes, guns fired at the 
station of Kooltjes- 
berg. 
Sum 628,39, which being divided by 
twelve, the number of observations, gives the passage of 
