280 



Dr. Moll on the 



[Oct. 



Number 

 of shots. 



Total of 12 shots 560,78 



Time between 

 light and report 



Guns fired at Zevenboomp- 

 jes, heard and seen at 

 Kooltjesberg. 



The mean of which is 50'',98 



which gives a velocity of 346,59 metres = 1137,134 feet in V\ 

 The temperature was at that time 



at Zevenboompjes 11°, 57 

 Kooltjesberg 12 , 54 



Mean temperature 12,055 = t. 



Mean atmospheric pressure at Zevenboompjes 0'",7493. 

 Mean atmospheric pressure at Kooltjesberg 0'",7512. 



Mean pressure of atmosphere 0,75025 = p. 

 Mean tension of aqueous vapour at Zeven-1 ^ 008Q2Q22 



boompjes J ' 



at Kooltjesberg 0,01011376 

 Mean tension of aqueous vapour 0,00952149 = F 



Calculating by this datum we shall have the observed velo- 

 ' city of sound in 1" reduced to dry air and 0° temperature 

 V = 338"»,20 = 1109,927 feet; but the experiments of the 

 25th gave V' = 331'",85 = 1089,087 feet. Difference 6^35 

 = 20,840 feet per 1'' between the experiments of the 25th and 

 26th of June, in which the shots were not reciprocal. This 

 difference is about -^ of the mean of both observations. But 

 the 27th and 28th of June, when the shots were reciprocal, the 

 difference between the results of both days were only 0^,66 = 

 2,166 feet, that is about -5-^ of the mean result of the obser- 

 vations. 



From the comparison of these results we may safely infer, 

 that only such shots will answer the purpose for which these 

 experiments are made, which are exactly fired at the same 

 ^instant on both stations. 



a. It is in this respect, I imagine, that our experiment may 

 claim some attention, as the very great care and ability of our 



