EYES. REFLECTION. 369 



A. The use of two eyes is to increase 

 the light, or take in more rays of light 

 from the object looked at, in order that 

 it may appear more distinct. 



Q. Why do we NOT see things DOUBLE, with 



TWO EYES ? 



A. 1st Because the axis of both 

 eyes is turned to one object; and, therefore, 

 the same impression is made on the ret'ina 

 of each eye. 



2ndly The nerves (which receive the 

 impression) have one point of union, 

 before they reach the brain. 



Q. Why do we SEE OURSELTES in a GLASS ? 



A. The rays of light from our face 

 strike against the surface of the glass, and 

 (instead of being absorbed) are reflected, 

 or sent back again to our eye. 



Q. Why are the rays of light REFLECTED by 

 a MIRROR ? 



A. Because they cannot pass through 

 the impenetrable metal with which the 

 back of the glass is covered; so they 

 rebound back, just as a marble would do 

 if it struck against a wall. 



Q. When a marble is rolled towards a wall, 

 what is that path THROUGH WHICH IT RUNS called ? 



