﻿436 Prof. J. Bayma on the Fundamental 



I confess that I cannot see the conclusiveness of this proof: first 

 because the fact referred to regards incandescent substances 

 only, whilst the molecules to which the author alludes in this 

 conclusion are not supposed to be incandescent ; and therefore 

 he has not the right of applying to the second the law of the 

 first phenomenon : secondly because spectral light is a light 

 elicited from the substance which is being burnt or made self- 

 luminous, whilst the light simply transmitted is a light received 

 from without ; and it is obvious that what is truly said of a self- 

 luminous body with regard to its own light cannot be said truly 

 of a non-luminous body with regard to a light which it receives 

 from without. These two reasons flow from one fundamental 

 fact that heat alters, at least for a time, the molecular constitu- 

 tion of bodies by causing a change in the relation of molecular 

 radii, an increase of vibratory motion, and a modification of mo- 

 lecular distances. Such alterations evidently cannot take place 

 without a proportionate modification of the optical properties of 

 the body. Thus, for instance, hyponitric acid is almost colour- 

 less at the low temperature —20° C, becomes yellow at the 

 temperature 0° C, orange at 15° C, and intensely red when 

 transformed into vapours. It is evident therefore that the 

 period of the luminous vibrations depends on the temperature of 

 the body and changes with it. Accordingly the period of the 

 vibrations of an incandescent body and the quality of the spec- 

 tral light radiated by it while existing in such a violent condi- 

 tion cannot be assumed to indicate the period of vibrations and 

 the quality of the light transmitted or reflected by a body exist- 

 ing in opposite conditions. 



Professor Norton concludes in the following words : 



" This fact .... though so radically at variance with Professor 

 Bayma's theoretical views, is in entire accordance with my own. 

 For, according to these, light originates in certain vibratory move- 

 ments of the atoms of the electric atmospheres of molecules, and 

 when these vibrate naturally in unison with the ray of any colour 

 that falls upon them, they take up its vis viva, and so the ray is 

 transformed into a molecular electric current." 



The reasoning expressed in this passage comes to this. A 

 substance when ignited and incandescent absorbs and stifles 

 such and such rays; therefore such and such rays are always 

 absorbed and stifled by the same substance, even though it be 

 not ignited and incandescent : and the theory which authorizes 

 us to draw such a conclusion is therefore more scientific than 

 any opposite doctrine. The reader will be able to judge for 

 himself of the value of this argument. On the other hand when 

 the atoms of the electric atmospheres of molecules (my molecu- 

 lar envelope) vibrate naturally in unison with the ray of any 



