232 FOKMATIOX OF IMAGES. 



upon it in a confused and irregular manner, so that it pro* 

 duces upon the retina of the eye no image regularly re- 

 flected, but only a general impression of light. 



But some surfaces, which have such a constitution in re- 

 spect to the disposition of their particles that they can only 

 reflect the light that falls upon them in a confused and ir- 

 regular manner, seem to have in them some mysterious 

 power of making a selection among the rays thus foiling, 

 and, while a portion are reflected, the others disappear. It 

 is customary to say that they are absorbed that is to say, 

 in the case of green leaves and grass, for instance, the ordi- 

 nary white light from the sun falls upon them, but is not 

 reflected as ichite light. Of the seven primary colors of 

 which the white light is composed, all but the green are 

 in some way apparently suppressed or extinguished. The 

 green is reflected, and, coming to our eyes, produces there 

 the sensation of green. So we say the grass is green. 



It is, of course, an important and curious question what 

 becomes of the rays which disappear. They are said to 

 be absorbed that is, that they enter in some way into the 

 leaves or the grass, and remain there. All light, whether 

 we can correctly picture it to our minds as a vibratory or 

 undulatory motion or not, is undoubtedly the action of 

 some form or some kind of force, and the prevailing idea 

 among scientific men is that that portion of this force 

 which represents green is turned back from the grass- 

 blade, or the leaf of the tree, into the air, while the re- 

 mainder enters the tissues of the plant, and is there con- 

 verted into some other of the numerous forms of hidden 

 force which is always in action among the molecules or 

 atoms of all substances, and on which the properties of the 

 substances and the changes which they undergo depend. 



It is the same with all the other colored substances ex- 

 isting in nature or produced by art. They have the power 



