492 Prof. A. Schuster on the Scale-Value of 



The air of the room was above that of the bath, the 

 temperature of which was slowly rising without the use of an 

 electric current. The thermometers being replaced in the 

 bath, readings were taken alternately every quarter minute, 

 first with the divisions in front of the thread, and finally with 

 the divisions behind. The numbers obtained were as follows: — 



Tonnelotm 



Joule. 



(Divisions 



in front.) 



(Divisions in front.) 



ll 1)1 8 



4 9 15 



18-509 



li in s 



4 9 30 



458-61 



45 



11 



10 



•63 



10 15 



14 



10 30 



•66 



45 



10 



11 



•69 



11 15..... 



21 



Mean 





Mean 



18-5142 



458-648 



^Divisions 



behind.) 



(Divisions 



behind.) 



li ni s 



4 12 45 



18-551 



h m s 



4 13 



459-03 



13 15 



53 



13 30 



•16 



45 



61 



14 



•39 



14 15 



72 



14 30 



•48 



45 



74 







Mean .... 



.. 18-5622 



459-273 





.. 18-5382 





458-961 



The zeros were now again determined and found :- 

 Tonnelot 0*0075 (mean of 4 observations). 



Joule A 23-192 ( 



6 



?> 



)• 



A small correction is applied to the Joule thermometer for 

 the lagging behind, and we thus got for corresponding tem- 

 peratures : — 



Tonnelot 

 Zero . . 



18*538 

 •008 



Joule 



458*99 

 23-21 



In the first series of comparisons the Joule A was com- 

 pared in this way with the Tonnelot thermometer. The latter 

 had been calibrated and investigated at the Bureau Inter- 

 national des Poids et Mesures, so that its indications could at 

 once be reduced to the normal scale. The results of the 

 comparison are given in Table V. The first column gives 



