C hap. 41.] Cautions for the Prefervation cf Sight. 40 j 



be found among ftudents, and thofe who are con- 

 verfant with fmall and near objects ; every one becom- 

 ing expert in that kind of vifi6n which is moft ufeful 

 to him in his particular profeffion and manner of life. 



Mr. Adams, in his very ufeful efiay on vifion, has 

 given fome rules for the prefervation of the fight> 

 which, for the -benefit of the Itudious reader, I have 

 thought it proper to infert. 



i ft. Never fit for any length of time in abfolute 

 gloom, or expoied to a blaze of light. From this 

 rule may be deduced the impropriety of going haft ily 

 from one extreme to the other, whether of darknefs 

 or of light, and it may be inferred that a fouthern. 

 afpect is improper for thofe whofe fight is weak and 

 tender* adly. Avoid reading a fmall print. 3dly. 

 Do,not read in the dufk, nor, if the eyes are difordered^ 

 by candle light. 4thly. The eye mould not be per- 

 mitted to dwell on glaring objects, more particularly 

 on the firft waking in the morning 5thly. Th'e long 

 fighted mould accuftom themfelves to read with rather 

 lefs light, and fomewhat nearer to the eye than ufual, 

 while thofe who are fhort fighted mould ufe themfelves 

 to read with the book as far off as poliible* 



Dd a 



