EXPLANATION OF THE EYE. 



17 



THE INVESTED IMAGE. 



form, by their concentration upon the retina, an image of 

 the luminous point from which they proceed, just as a lens, 

 held in the manner I have described, will gather rays 

 enough coming from the candle on the other side of the 

 room to form an image of the candle on the paper screen. 



"Lawrence," said John, one day, as he had been reading 

 about this in a book, " here's a nice experiment for me to 

 try, if I only had a pair of spectacles." 



" Would my eye-glass answer the purpose ?" asked Law- 

 rence. 



" No," replied John, " I think not. 1 suppose your eye- 

 glass is concave, and what I require is a convex lens. Let 

 me take it a moment, and I can soon tell." 



Lawrence was lying, or, rather, reclining on a sofa in the 

 corner of the room near a window, with his head toward 

 the window, so that the light fell fair upon the page of the 

 book which he was reading. John was sitting at a table 

 near. Lawrence unhooked his glass from the cord to which 



