20 Dr. W. S. Day on a Comparison of 



in his experiment, the fact must be considered in making any 

 comparisons between his thermometers and any others. 



Two comparisons were made between Tonnelot 11801 and 

 Tonnelot 11811, and three between Tonnelot 11800 and 

 Tonnelot 11811. In one of the latter comparisons, that of 



21 April, the thermometer 11811 became accidentally heated up 

 to 30° before a reading at 20° was taken, and for this reason, on 

 account of the recovery of the zero being in progress while the 

 comparison was being made, it was thought probable that some 

 irregularity would be shown. This proved to be the case, 

 although it is not certain that the irregularity was due to the 

 overheating. There were also other disturbing influences 

 that made it seem probable at the time that the comparison 

 would not be reliable. The comparison, however, was re- 

 jected. In comparing the Tonnelot thermometers, they were 

 always placed in ice for some hours before a comparison was 

 beoun, in case the first temperatures used were lower than 

 the temperature to which the thermometer had been exposed 

 for some time previously, so that the recovery of the zero 

 mio-ht have a chance to proceed as far as possible before the 

 comparisons were begun. The results of the comparisons of 

 the Tonnelot thermometers with each other are given in 

 Table V. 



Table VI. 



Corrections for reducing the readings of Tonnelot 11800 and 11811, after 

 reduction to the hydrogen scale, to the hydrogen scale as represented 

 by Tonnelot 11801. These corrections are the ordinates of the 

 smooth curves which were deduced from the comparisons given in 

 Table V. 



Temperature. 



T — T 



-"-01 -^OO' 



T — T 



2 



4 



6 





 



-o-ooi 



-0001 

 -0001 



-o-ooi 









 +0-002 

 +0001 

 +0-001 





 +0-001 

 +0-002 

 +0-003 

 +0-005 

 +0-006 

 +0-008 





 



-o-ooi 



-0001 

 -0001 

 -0-002 

 -0-002 

 -0003 

 -0003 

 -0-004 

 -0-005 

 -0005 

 -0004 

 -0003 

 -0-002 

 -0-001 





 +0001 



8 



10 



12 



14 



16 



18 



20 



22 



24 



26 



28 



30 



32 



34 



36 



