48 THE CHEMISTRY OF CREATION'. 



tance off the prism, that the ray of light is 

 broken up into a strip of various colours, which 

 is called the prismatic spectrum. (See cut.) 



PRISMATIC SPECTBUM. 



This shows us that the ray of light is made up 

 of several rays three, as it is commonly now 

 believed, the others being made up by the 

 mingling of these in various ways together. 

 This streak of beautiful colours exhibits to us, 

 then, the Light of the solar ray ; how are we 

 to detect its Heat and Actinic force? If we 

 take a very delicate thermometer, and put it 

 first in the violet part of the streak, then bring 

 it gradually downwards to the red, it would 

 be found that the mercury rose very little in 

 the violet part, and very much in the red part, 

 and, strange to say, even a little beyond it, 

 where we can see no colour at all, it would be 

 highest of all ! This shows us not only the 

 heat of the sunbeam, but also the curious fact, 



