( 371 ) 



u^ the volume at the steel point of the volumenometer. 



/?! and j?2 the variation of the volume V^ caused by the pressure 

 of the gas. 



If Ht is the observed pressure, and //„ and u have the same 

 meaning as in Comm. N". 60, the temperature is found from the 

 formula : 



^4 



1 + cd, 



(1) 



^L !+«« '^l + atyi + at^"^ 1-^at, 



The change of volume of the glass stem caused by the change of 

 temperature need not be taken into account, as little as that of u. 

 That of the thermometer reservoir has been calculated by means of a 

 quadratic formula, of which the coefficients ^i and k^ have the fol- 

 lowing values : k, = 23.43 X 10-^ k, = 0.0272 X 10-^ '). 



Put 



+ ^-f V + ^-^^ + r^— = ^ 



I -{- at\ 1 -{- at\ 1 + ««3 1 + ««4 l+«« 



H. 



Vo+^. + ^^^ + n\ + u\ + ii'\ + 



1 + 15« 

 then follows from the above for the temperature: 



= A, 



(2) 



K + ^^ + u,-^-\-:s -^ + V, k, t' 



Ht \-\-at 



t = — , 



-^ ^ u ] 



Ht l-\-at\ " ' 



(3) 



If the term with t^ is omitted, we find an approximate value for 

 the temperature. Now t may be calculated again, while in the term 

 with f this value is substituted. This approximate calculation is quite 

 sufficient. 



^ 6. Survey of a measurement. 



The observations communicated in this ^, yielded the temperature 

 corresponding to the electromotive force of the thermoelement deter- 

 mined in Table IV and V of Comm. 95« and corresponding to the 

 resistance measured in the observation given in Table I of Comm. 

 N°. 95^ (in the last case even almost simultaneous). 



^) These values have been derived from Comm. N". 95^. They refer to the 

 determinations made in 1903 on the expansion of glass. If we calculate the tem- 

 peratures by means of the quadratic and cubic formula derived in the same Comm. 

 from the observations of 1905, we find but slight differences, which amount 

 respectively to — O'^.OU and —0^.016 at —100'', and remain always below 

 0°.01 at - 200^ and lower. 



