Dr. Schroder van der Kolk on the Velocity of Sound. 45 



Zeven- 



Kooltjes- 



<p. 





Zeven- 



Kooltjes- 



<P« 





booraen. 



berg. 





boomen. 



berg. 





52-90 



5117 



o 



32i 



52-02 



52-99 



51-07 



o 



32i 



5201 



•69 



50-89 



43f 



51-77 



•90 



•08 



55 



51-96 



•71 



•68 



26% 



5167 



•64 



•28 



59% 



51-93 



•92 



•80 



m 



51-83 



•90 



•21 



59% 



5202 



•84 



•86 



43| 



51-83 



•87 



•18 



59% 



51-99 



5304 



•89 



32% 



51-93 



•92 



•33 



59% 



52-08 



52-89 



5101 



43$ 



51-93 



•91 



•38 



43f 



5213 



•79 



•00 



49i 



51-87 



•64 



•35 



55 



51-96 



•83 



50-99 



48| 



5189 



■57 



•32 



55 



51-93 



•77 



•96 



32% 



5183 



•90 



•14 



37i 



5201 



•79 



5110 



48^ 



51-92 



•96 



01 



43| 



51-96 



The mean is 51 '94 seconds, whence it follows that the velocity 

 per second is 340*37 metres. 

 For the 28th of June we find — 



Zeven- 

 boomen. 



Kooltjes- 

 berg. 



Mean. 



Zevenboomen. 



Kooltjes- 

 berg. 



Mean. 



51-81 

 •94 

 -77 

 •98 



5217 

 •15 

 •25 



5218 



5212 



•10 



51-28 



52-51 



•46 



•28 



5310 



5017 



51-96 

 52-02 

 51-52 

 52-24 

 52-32 

 52-22 

 52-67 

 5117 



52-40 

 '27 



-27 

 •23 

 •49 

 •56 



5219 

 •62 



51-66 

 •52 

 •99 

 •60 



52-30 



•44 



51-96 



•88 

 52-25 



•08 



Mean 52-18 



51-97 



52-07 



Although the directions of the wind are given for this day 

 also, it was not possible to apply the correction directly to each 

 observation as on the 27th of June, since the force of the wind 

 was not observed but calculated from the time-observations; 

 hence the correction becomes altogether uncertain if the errors 

 of observation are at all considerable. On the 28th of June this 

 was the case, for on that day the observations were not so well 

 made as on the previous one. The Zevenboomen determinations 

 ought always to be greater than those made on the Kooltjesberg, 

 in consequence of the direction of the wind, yet we often find the 

 contrary to be the case, a result which can be due only to errors 

 of observation. I have for this reason applied the correction to 

 the mean, taking the mean direction of the wind. This gives 

 52*08 seconds, whence for the velocity per second we have 339*27 

 metres. 



These two determinations have now to be reduced to what they 

 would be for dry air at 0° C, and under 0*760 metre pressure. 



The mean tension p of aqueous vapour was 



