SPECTACLES. 391 



glasses, to enable them to see objects 

 near at hand. 



Q. What sort of glasses are DOUBLE CONVEX 



SPECTACLE-GLASSES ? 



A. Glasses which curve outwards on 

 both' sides. 



The figure A is double convex, or convex 

 on both sides. 



Q. What is the USE of DOUBLE CONVEX 

 spec lade- glasses ? 



A. As the image of near objects is 

 reflected behind the RET'INA, these double 

 convex glasses shorten the focus of the 

 eye, and bring the image into the eye 

 (upon the ret'ina). 



Q. Why do NEAR-SIGHTED persons bring 

 objects CLOSE to the eye, in order to SEE THEM ? 



A. As the distance between the front 

 and back of their eye is too great, distant 

 objects are reflected before they reach the 

 ret'ina; therefore, near-sighted persons 

 bring the objects closer, in order that the 

 reflection may be cast further back, (to 

 reach the ret'ina). 



