90 Prof. J. Dewar. Studies on the Electric Arc. [Jan. 15, 



bourhood of the poles is greatly diminished by the combustion of the 

 carbons, or that the nitric peroxide formed is subsequently reduced 

 by contact with the red hot carbon, or other reducing products. 



Fig. 3. 



Radiation Experiments. . 



In a report fco the British Association* on the determination of high 

 temperatures in the year 1873, it was experimentally proved that the 

 law of Dulong and Petit could not be used for the estimation of high 

 temperatures, seeing that it " gives a far too rapid increase for the 

 total radiation." It was further observed that the variation of the 

 thermo-electric current strength when the same substance radiates at 

 different temperatures, plotted in terms of the temperature, was a 



* Report of the Committee for Determining High Temperatures by means of the 

 Refrangibility of the Light evolved by Fluid or Solid Substances. Bradford, 1873, 

 Page 461. 



