of Cyclically Varying Temperature. 



295 



March 16 th. 



Thermometer No. 4. Wire 0*0025 inch diain. 

 Air temperature 13° C. Circulating water 50° C. 



R before, 0*551 ohm. 

 R after, 0551 ohm. 



B 1 .-B =0-207. 



8 (determined by sulphur vapour) T75. 



Percentage of 

 stroke. 



Observed Resist- 

 ance, ohms. 



pt. 



Temperature on 

 air-scale. 



10 

 20 

 30 

 40 

 60 

 70 



2-434 

 2-354 

 2-364 

 2-236 

 2163 

 2-057 



909 



870 

 875 

 833 



778 

 727 



1100 



1015 



1050 



990 



910 



840 



I was so doubtful of the second and third points that I 

 repeated the first three with the results below : — 



10 

 20 

 30 



2-452 

 2-373 

 2369 



917 



879 

 877 



1115 

 1055 

 1050 



March 20th. 



Same thermometer and wire. 

 Air temperature 13° 0. Circulating water 51° C. 



Percentage of 

 stroke. 



Observed Resist- 

 ance, ohms. 



pt. 



Temperature on 

 air-scale. 



10 



20 

 30 



2-481 

 2-403 

 2-403 



931 

 894 

 894 



1140 



1080 

 1080 



The temperature was variable throughout this experiment 

 and the wire fused during the observation at 40 per cent. 



I consider these experiments to be the most accurate of 

 the whole series. 



Towards the end of February I determined to find 8 by 

 means of an observation in sulphur vapour ; and as some 

 question had arisen as to the action of the high-temperature 

 gases on the platinum wires, more especially as to the variation 

 of the quantity 8, I gold-soldered a platinum wire 0*002 

 diameter on So. 5 thermometer, and determined its fixed 

 points and calculated the 8 before this wire was placed in the 



