CHAPTER XVIII. 



DISCUSSION OF THE DISSOCIATION HYPOTHESIS. 



1. Variation of Intensity. 



SEEING that such an abundance of new facts had now been 

 collected, it really did seem time to discuss the question to which 

 reference has already been made. 



I approached it in the following manner, relying upon the 



FIG. 86. Hypothetical furnaces. The figures between the hypothetical spectra 

 point to the gradual change in the intensities of the lines as the spectrum is 

 observed near the temperature of each of the furnaces. 



spectroscopic behaviour of compound bodies already stated on 

 p. 159, in order to keep as near to facts as possible : 1 



Let us assume a series of furnaces A D, of which A is the 

 hottest (Fig. 86). 



1 Proe. Roy. Soc., No. 191, 1878. 



