NICHOLS. 



THE VISIBLE RADIATION FROM CARBON. 



115 



law of radiation of the ideal black body, I have plotted the various iso- 

 chroms obtained in the course of this investigation in logarithmic form ; 

 absolute temperatures being taken as abscissae and the logarithm of the 

 intensity as ordinates. These logarithmic isochroms, as will be seen from 



/Sao' 



Iffoai 



/Soa° 



/to** 



Figure 23. 



Figure 23, in which three curves from Figure 19 are reproduced, are 

 straight lines. The range of temperatures is doubtless much too small 

 to bring out the curvature found by Lummer and Pringsheim, but the 

 curves show clearly the change of direction with the wave length men- 



