92 Prof. J. Dewar. Studies on the Electric Arc. [Jan. 15 ; 



Table L 



Ternperatnre. Deviation. Difference. 



80 32 



• 90 38-5 



100 44-5 



110 52 



120 59-5 



130 66-5 



140 75. -5/ 



150 85 ........ 



160 '. .. 95-5 ........ 



170 106 ........ 



180 117 



190 130-5 ........ 



200 143-5 



210 158 



220 172-5 



230 188 



6 







•o 



Q 



•5 



7 



•5 



7 



•o 



9 



■o 



9 



•5 



10 



•5 



10 



•5 



11 



•o 



13 



•5 



13 



•o 



14 



•5 



14 



•5 



15 



•5 



Table II. 



Temperature. Deviation. 



100 21 



120 29 



150 41 



1G0 46 



180 57 



200 71 



220 86 



355 240 



448 370 



If the differences in the galvanometer readings for every ten 

 degrees in the first table be tabulated, it will be observed the second 

 difference may be regarded as constant, considering the errors of 

 observation, so that a parabolic formula can represent the results 

 with sufficient accuracy. These second differences are far more 

 constant than similar numbers deduced from Rosetti's observations, 

 and his more complete formula in terms of the absolute temperature 

 is too extensive, considering the range of the experiments where tem- 

 perature was accurately known. The results of Table II extend to the 

 boiling points of mercury and sulphur, and the numbers are in near 

 accord with the simple square of the temperature. The alteration in 

 the condition of the radiating surface at high temperatures causes 



