234 IHE BEASON WHY. 



' The ?yes of the Lord are upon the righteous, and ba ears are open unto their 

 cry." PSALM xxxiv. 



necessary delicacy of an organ formed to receive impressions from 

 so ethereal an element as light, is rendered the more secure to us, 

 since though one eye may become enfeebled, diseased, or wholly 

 lost, the other eye will retain the blessing of sight. 



971. Why, having two eyes, and each eye receiving a 

 reflection upon its retina, does the brain experience only one 

 impression of an object ? 



Because, besides those optical laws which bring upon the two 

 retinas the exactly corresponding images of the same objects, the 

 optic nerves meet before they reach the brain, and blend the 

 impulses which they convey. 



972. Why are the eyes provided with eye-lids ? 



Because the eyes require to be defended from floating particles in 

 in the air, and to be kept moist and clean. The eye-lids form the 

 shutters of the eye, defending it when waking, by closing upon its 

 surface whenever danger is apprehended, moistening its surface when 

 it becomes dry, and covering it securely during the hours of sleep. 



973. Why are the eye-lids fringed with eye-lashes ? 



Because the eye-lashes assist to modify the light, and to protect 

 the eye, without actually closing the eye-lids. When the eye-lids 

 are partially closed, as in very sunny or dusty weather, the 

 eye-lashes cross each other, forming a kind of shady lattice-work, 

 from the interspaces of which the eye looks out with advantage, 

 and sees sufficiently for the guidance of the body. 



974. Why are ice able to see at long or short distances T 



Because the crystalline lens of the eye is a moveable body, and 

 is pushed forward, or drawn back by fine muscular fibres, acccording 

 to the distances of the objects upon which we look. By these means 

 its focus becomes adjusted. 



975. Why do we winTc ? 



Because, by the repeated action of winking, the eye is kept 

 moist and clean, and the watery fluid secreted by little glands in 

 the eye-lids, and at the sides of the eye, is spread equally over the 

 surface, instead of being allowed to accumulate. But the action of 



