CHARACTERISTIC CURVES OF COMPOSITION. 147 



Mendenhall the analogous conception of word-spectra or characteristic 

 curves. Just as the light-rays of various wave-lengths emitted by a 

 substance combine to form its spectrum, so a combination of words of 

 various lengths in proper definite ratios make up an author's word- 

 spectrum or characteristic curve. The analogy is imperfect, but we 

 admit it. But is it true that each substance has a single spectrum? 

 This was the supposition when the science of spectrum analysis was in 

 its infanc}', and upon this supposition Dr. Mendenhall bases his analogy. 

 The fact is that over forty years ago it was demonstrated that some 

 substances have several spectra, and to-day it is generally believed 

 that all substances have several spectra, corresponding to the several 

 stages of disassociation or molecular composition of their molecules. 

 The analogy to spectrum analysis, therefore, demands the modification 

 of the theory of characteristic curves, which I have tried to point out 

 in the preceding pages. 



