ABSORPTION OF LIGHT, ETC. 47 



colour, the green of vegetation, as in grass and leaves in 

 general. What is the cause why a green leaf is green, or 

 why a red poppy is red? It is frequently said that the 

 reason why a red poppy is red and that a white lily is 

 white is, that the lily reflects rays of .all kinds, but the poppy 

 reflects only the red ones, and if you place the red poppy in 

 a pure spectrum it is luminous, like a white lily, in the red ; 

 hut if you place it in the green it will be almost black, 

 whereas the white lily will be brilliantly green. JSTow the 

 common explanation, properly understood, is true ; tjut it is 

 not the whole truth, and if understood as it is liable to be 

 understood, it is false. It is true that a red poppy reflects 

 red rays, and a white lily reflects rays of all colours ; but it is 

 not true that the preference for the red to the green in the 

 one case and the equality of action in the other takes place 

 in the act of reflection. It is not a phenomenon of colora- 

 tion by reflection. The coloured light is reflected, or you 

 would not see it ; it is sent out of its course before it 

 enters your eye, and it is true that the light, in its life's 

 history, undergoes reflection ; it is not true that it is in the 

 act of reflection that the one colour gets the preference over 

 the other. Here I have some solution of the colouring 

 matter of green leaves in alcohol, and here is some more 

 alcohol, with which I will dilute the former. I have obtained 

 a beautiful green solution, although the green colour is not 

 seen now by reflected, but by transmitted light. As regards 

 the light which falls upon the surface, there is a little white 

 light reflected, just as there would be from water, but very 

 little is reflected from the surface where the fluid is in contact 

 with the glass ; the chief portion of that reflected being from 

 the outer surface of the glass itself. You would not see any 

 green at all in it unless there were something placed behind 

 so as to reflect the light backwards. You see there that the 

 colour of the green leaf, as ordinarily seen, is due to the 

 combination of reflection with the phenomena of absorption, 

 or the swallowing up of certain kinds of light when light is 

 sent through a perfectly clear medium. I may illustrate this 

 in another manner. Here is a vessel of water, into which I 

 will pour some blue solution. If I send light through it, it 

 will appear of a deep blue, but if I hinder the light from 

 coming behind, which I can do by putting black cloth behind 

 it, it is simply dark ; you do not see the blue colour at all. 



