FORMATION OP AX IMAGE. 



251 



MAGK OF THE LILY. 



are completely intermingled, though each one, wonderful 

 as it seems, pursues its way uninterrupted and undisturbed 

 by the rest. A screen held at the place of the lens would 

 receive them blended together, and would reflect their 

 united light oi>!y as a general illumination. But the lens 

 causes each separate pencil, coming from every different 

 point, to converge each toward its own central line. The 

 result is that the colors are all separated; and if the screen 

 is held iu the proper place to receive them, and all light 

 from other sources is excluded, a perfect image of the lily 

 is formed, only it is inverted, since the several pencils cross 

 each other at o in traversing the lens; those from A, for 

 example, coming to a focus at a, and those from B at b. 



This experiment can be easily performed by means of 

 any convex lens, such as a reading-glass, a sun-glass, or 

 even one of the glasses of a pair of spectacles such as are 

 used by elderly persons. Near-sighted glasses, being con- 

 cave instead of convex, and so causing the rays to diverge 

 instead of to converge, of course will not answer. 



The only difficulty in making this experiment perfectly 

 successful is that of keeping all other light except that 

 which 'comes through the. lens away from the screen, or 

 from whatever serves as a screen, to receive the image 



