308 NATURAL THEOLOGY. 



XVIII. 



OF THE MEANS BY WHICH THE EYE IS PROTECTED. 



When an astronomer, in the darkness of night, 

 and shaded from the hght of his chamber, moves 

 his telescope from star to star, his eye is accom- 

 modated to faint impressions ; that is, the sensi- 

 biUty of the retina is then accumulated, so that 

 when he directs his instrument to the brighter ob- 

 jects his sensation is painful. And if, at another 

 time, he should be observing the sun, without 

 having guarded the eye by smoking the glasses, 

 or by some other means diminishing their trans- 

 parency — the stroke upon the retina will not 

 only be painful, but may prove destructive to its 

 fine texture, and occasion a defect of vision which 

 will continue through life. If the apparatus in 

 the tympanum of the ear be destroyed, and the 

 defect supplied by an ear-trumpet, the person will 

 be startled by those who speak into this trumpet : 

 for if they are not in the habit of pitching their 

 voices distinctly and softly, the sound will jar 

 painfully upon his ear. By these considerations, 

 we are prepared to contemplate that beautiful 

 provision by which the natural eye is protected 

 against the sudden intrusion of light, or the too in- 



