463 



a reading of ii,,, '^^ ^ pressure wliicli was also read on M,„ and 

 therefore accurately known tlirough the direct comparison with the 

 open slandard-gauge. For this calculation the formula is available 

 which represents Schalkwijk's observations within the limits of their 

 accuracy (,Coinm. 70). 



Three nieasnieraeiils were made yielding the following data. The 

 deviations from the mean are not higher than tsVo- The result may 

 certainly be called satisfactory, considering that i/„ gives the pressure 



TABLE 1. 



Date 



30 



13 Febr. 1911 I 1.169C9 c.M3 



21 „ „ ' 1.76633 



22 „ „ I 1. 76017 



Normal vol. 



62.504 aim. 99.568 c.M3 

 62.802 „ i 99.601 „ 

 63.039 „ ; 99.618 „ 



Mean 99.596 „ 



in this case with an accuracy of tAö- -"is was confirmed moreover 

 by a special comparison with the open gauge of Ü — 60, and that 

 the reading of the volume in J/,,» was not more accnrate than 

 to about 1 part in 10000. The mean was therefore taken as the 

 normal volunie. 



4. Results. Only one series of measurements was made. The 

 calculation for il/eo and for the open gauge were exactly as formerly. 

 The only point to be mentioned is, that the corrections for the 

 weight of the air-columns of the open gauge were calculated using 

 the densities as given in the tables which Brinkman deduced from 

 Amagat's observations. (Comp. also Comm. 146c). Table II (p. 468) 

 gives the results of the measurements. 



The deviations from the values which would follow from Schai.k- 

 vvijk's formula are all with the exce[)lion of the first in the same 

 direction. Except in the doubtful observation corresponding to the 

 density 80, the devialion is only about I in 1500, the mean i)ositive 

 deviation (leaving out of account the observation at (/.i ;= 80) 0.0003 

 falls on the limit of what may be considered as established, con- 

 sidering the degree of accuracy of the observations. The fifth column 

 of Table 11 contains for the highest pressures the values according 

 to the formula which was calculated from the series in Comm. 70 

 derived from Amagat's observations and given by Schalkwijk at 



