NICHOLS. — THE VISIBLE RADIATION FROM CARBON. 



105 



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Figure 17. 



•7/*- 



corresponding wave lengths of the comparison source (in this case the 

 acetylene flame), the relative distribution of energy in the visible 

 sprctrum from the carbon rods. The other curves, which I have termed 

 tsochroms, indicate the rise in the energy of any particular wave length of 

 the visible spectrum, with increase of temperature. Each of these curves, 

 taken by itself, is entirely independent of the nature of the light of the 

 comparison source, but the absolute relation of such curves to one another 

 can only be obtained when we know the distribution of energy in the 

 spectrum of that source. By means of the isochroms, it is, however, 

 possible even without this knowledge to compare the rise in intensity 

 of any single wave length of the spectrum with increasing temperature. 

 The set of curves shown in Figure 17 are plotted directly from obser- 



