44j M^f\ Ware's Observations on the near 



that which they use to see those that are near. This circum- 

 stance, in my apprehension, affords a convincing proof that the 

 crystalline humour is indispensably necessary to enable the 

 eye to see at different distances. — It is also worthy of remark, 

 that persons who have had the crystalline humour removed, 

 have less power to ascertain the distance of an object when 

 they look through a convex glass, than when they view it 

 without this assistance ; in consequence of which such persons 

 seldom make use of glasses when they are walking : and the 

 inconvenience of glasses is particularly experienced when they 

 descend a flight of steps, or pass over uneven ground. 



Near sighted persons do not appear to possess the same 

 extent of vision that is enjoyed by those who have a distant 

 sight. Being near sighted, I have repeatedly endeavoured to 

 ascertain my own range of vision : and I find, by examining 

 the focus of my right eye through the abovementioned opto- 

 meter, that I see two converging lines, which appear to meet, 

 with very slight variations, at the distance of three inches from 

 the eye; and no effort I am able to make can keep these 

 lines united further than the distance of four inches and a 

 quarter. They then separate, and continue to diverge. With 

 my left eye, the lines do not appear to meet nearer than four 

 inches, and they continue united as far as five inches and a 

 quarter, after which they also separate and diverge ; so that 

 the range of distinct vision in me does not extend further than 

 an inch and a quarter in either eye ; and within these dis- 

 tances I always hold a book when I read. — I find also the 

 following rule, for determining the concavity of the glass 

 that is best adapted for near sighted persons, to be perfectly 

 correct with respect to myself, and, I believe, it may be safely 



