30 HISTORY OF 



is strongest, are greater than those of the right, 

 which is the most feeble. He has examined 

 several others who were in similar circumstances, 

 and has always found that the best eye saw every 

 object the largest. This he ascribes to habit ; for 

 near-sighted people being accustomed to come 

 close to the object, and view but a small part of 

 it at a time, the habit ensues when the whole of 

 an object is seen, and it appears less to them than 

 to others. 



Infants having their eyes less than those of 

 adults, must see objects also smaller in proportion. 

 For the image formed on the back of the eye will 

 be larger, as the eye is capacious ; and infants, 

 having it not so great, cannot have so large a 

 picture of the object. This may be a reason also 

 why they are unable to see so distinctly, or at 

 such distances as persons arrived at maturity. 



Old men, on the contrary, see bodies close to 

 them very indistinctly, but bodies at a great dis- 

 tance from them with more precision ; and this 

 may happen from an alteration in the coats, or, 

 perhaps, humours of the eye ; and not, as is sup- 

 posed, from their diminution. The cornea, for 

 instance, may become too rigid to adapt itself, 

 and take a proper convexity for seeing minute 

 objects ; and its very flatness will be sufficient to 

 fit it for distant vision. 



When we cast our eyes upon an object ex- 

 tremely brilliant, or when we fix and detain them 

 too long upon the same object, the organ is hurt 

 and fatigued, its vision becomes indistinct, and 

 the image of the body, which has thus too vio- 



