362 



MR T. C. BAILUK ON THE 



on the weight ascending, the cross-section of the tubing is increased. The nickel bar 

 was protected by a double metal screen from thermal disturbances due to the heater. 

 A constant stream of cold water was kept playing on the unheated end of the bar. 

 The thermometers used were some of the Kew standard thermometers used by Pro- 

 fessor Tait and Dr Mitchell. Temperatures above 200° C. were not used, and as the 

 readings on the majority of the thermometers varied in the course of an experiment 

 through a range of about 1° C, the thermometers were simply read by the naked eye 

 to the nearest quarter of a degree. One could be quite certain of avoiding making any 

 error due to parallax of more than that amount. A little mercury was put in each of 

 the thermometer holes to give good thermal contact between the bulbs of the ther- 

 mometers and the bar. No amalgamation of the nickel has ever been observed. 



A steady state as regards the distribution of temperature along the bar was not 

 reached in five hours from the time the gas at the heater was lighted, and the readings 

 on the thermometers usually increased at the rate of about a quarter of a degree per 

 hour for a few hours more. The following table shows the readings (uncorrected) 

 obtained over an interval of nearly twenty- four hours on 18th July 1894 and the 

 following morning. The gas was lighted at 8.30 a.m. 



Time. 



l 



2 



3 



4 



s 



6 



7 



8 



Temperature J 

 of Air. 



12.30 



175 



130-5 



100 



78 



26 



23 



20-5 



18-2 



190 



1.30 



177 



133 



102-5 



80-5 



28 



25 



22 



191 



19-1 



2.0 



177 



133-3 



103 



81 



28-9 



25-4 



22-5 



19-5 



19-1 



2.15 



176-5 



133 



103 



81-5 



29 



25-8 



22-5 



19-7 



19-1 



2.45 



176-5 



133 



103 



81-5 



29-4 



26" 



23 



20 



19-1 



6.0 



177-8 



134 



104 



82-2 



30 



265 



23-2 



20 



191 



6.30 



178 



134-3 



104-5 



82-5 



30 



26-5 



23 



20 



19-2 



7.0 



178 



134-3 



104 



82-5 



30 



26-5 



231 



20-1 



19-2 



7.30 



177-5 



134 



104 



82-3 



30 



26-5 



23-2 



201 



19-4 



8.0 



178-5 



134-5 



104 



82-5 



30-1 



26-7 



23-4 



20-2 



19-3 



8.30 



178 



134 



104 



82-2 



30 



26-6 



23-1 



20-0 



19-3 



9.0 



178 



134-3 



104 



82-3 



30 



26-5 



23 



20 



19-4 



9.30 



178 



134-3 



104 



82-5 



30 



26-5 



23 



20 



19-4 



10.0 



178 



134 



104 



82-5 



30 



26-5 



23 



20 



193 



11.20 



179 



135 



105 



83 



301 



26-6 



231 



20 



19-4 



1.30 a.m. 



178 



135 



105 



83 



30-1 



26-5 



23-1 



19-9 



19-3 



2.15 



178 



135 



104-7 



83 



30-1 



26-5 



23-1 



19-9 



19-3 



3.30 



179-7 



135-5 



105 



83-4 



30-2 



26-6 



23 



19-9 



19-3 



4.25 



179 



1351 



105 



83-4 



30-2 



26-6 



23 



19-9 



19-2 



5.0 



179 



135 



105 



83-2 



30-2 



26-6 



23 



19-8 



19-2 



6.0 



178-5 



135 



104-8 



83 



30 



26-5 



23 



19-7 



19-0 

 - 



After several sets of readings had been taken, the bar was reversed, and heated at 

 the other end. The thermometers were never shifted from their positions, except when 

 the bar was reversed. They were read on each morning before the burner was lighted, 

 and their readings on those occasions never differed by more than one-third of a degree. 

 The thermometers were corrected for stem exposure by adding to the reading V. tin 



