SEEING OBJECTS. 365 



Q. Why can a THOUSAND persons SEE the 

 SAME OBJECT at the same time ? 



A. Because it throws off from its 

 surface an infinite number of rays in all 

 directions; and one person sees one 

 portion of these rays, and another person 

 another. 



Q. Why is the E?E PAINED by a SUDDEN light ? 



A. Because the pupil of the eye is 

 burdened with rays, before it has had 

 time to contract. 



Q. Why does it give us TAIN, if a CANDLE be 

 brought suddenly towards our BED at night time ? 



A. In the dark the pupils of the eyes 

 dilate very much, in order to admit more 

 rays. When a candle is brought before 

 them, the enlarged pupil is overladen 

 with rays, and feels pained. 



Q. Why CAN we BEAR the candle-light after 

 a few moments P 



A. Because the pupil contracts again 

 almost instantly, and adjusts itself to the 

 quantity of light which falls upon it. 



Q,. Why can we SEE NOTHING, when we leave 

 a WELL-LIGHTED room, and go into the DARK ROAD 

 or street ? 



ia 3 



