64 THE CREATION OF MATTER 



whilst the red and orange are almost as bright as on the 

 white. If yellow, green, or blue be employed it will be 

 found that each disperses its own hue and absorbs the 

 others. White paper shows all the colours of the 

 spectrum, because it scatters all. Black is black because 

 all the colours are absorbed. No part of the spectrum 

 can be seen on it. A colour is destroyed when it is 

 wanting in the light shining. The yellow flame of 

 sodium does not contain the red rays, and therefore 

 when beams from it are thrown on red paper, all the 

 rays of yellow are absorbed, and there are no red rays to 

 scatter, and therefore the paper is black. Were the sun 

 a glowing globe of sodium yielding only yellow light, no 

 variegated beauty would deck the earth, no lovely flowers 

 would adorn the gardens and fields; its hills would 

 know no rosy light, no purple heath, its fields no mantle 

 of living green. All things would be yellow or black. 

 Those would be yellow which scatter the yellow, and 

 those black which absorb it. Sunlight is made up of 

 all the colours of the spectrum. The substances burning 

 in the great orb of day create every variety of wave. 

 The light of gas and candles also contains all, but not 

 the same proportion of each colour. The yellow is more 

 abundant than in solar light, the blue and violet less 

 abundant. It is for this reason that it is difficult to 

 distinguish blue and green in candle-light, because green 

 materials contain blue rays and blue materials green 

 rays ; and when the blue rays are diminished in numbers, 

 as they are in candle-light, there is not the same clear- 

 ness of distinction. 



Three conditions are therefore necessary to the produc- 

 tion of any colour. First, that its waves should be found 

 in the illuminating light ; second, that the substance on 

 which the light falls should be capable of absorbing the 



