4 THE CHEMISTRY OF THE SUN. [CHAP. 



that they know all about it, but because it is necessary, in order 

 that their work may go on at all, that they should assume that 

 there is something infinitely finer than matter, and not at all like 

 the attenuated matter which pervades all space. This ether forms 

 the highway along which the vibrations due to the state of unrest 

 of matter travel to our eyes whence they are conveyed by a 

 new channel to our brains, thus begetting in our consciousness 

 the impression of the material world. 



It is thus that modern science explains a truth known in its 

 most general form as early as the time of Plato, who in his 

 Timceus writes that there is no light without fire. 



FIG. 1. Copy of Kepler's diagram. 



In fact, all light is originally produced by the vibration of 

 particles under the influence of heat. Heat somewhere, whether 

 in the sun or a candle or an electric spark, is the producer ; 

 reflecting surfaces anywhere, whether they be clouds in Jupiter 

 or a tree or a ceiling, are the distributors. 



We have now, then, got our light and the cause of it. 



We next come to the question, What special quality of the 

 light is it which we have to utilize in our study of the chemistry 

 either of this or of distant worlds? 



This light is an excessively complex thing, each sunbeam or 



