1880.1 on Inv€8ti(jaiions at ll'ujh Temperatures. 2G7 



havo been made by this method at clillbrent times, and with slight 

 modifications in the order of the experiments, leading to the average 

 result that the intensity of the total radiation of the positive pole of 

 the Siemens' arc is ten times that of the same substance at the tempe- 

 rature of the oxyhydrogen flame. If we take an average result of nine 

 to one, then we may infer that the temperature of the limiting positive 

 pole is about 6000^ C, seeing that the mean temperature of the oxy- 

 hydrogen may be taken as 2000' C. The mean value of the total 

 radiation of the Siemens' arc was determined by observing the rate of 

 flow of the water through the annular vessel, represented in Fig. 1, 

 together with the mean increment of temperature. This gave on the 

 average 34,000 gram-units per minute, or a little more than three 

 horse-power. 



[J. D.] 



