102 NATURAL HISTORY. 



being contracted, are more strong than the visual spirits 

 of ordinary eyes are ; as when we see through a level 

 the sight is the stronger ; and so is it when you gathei 

 the eye-lids somewhat close; and it is commonly seen 

 in those that are pore-blind, that they do much gather 

 the eye-lids together. But old men, when they would 

 see to read, put the paper somewhat afar off; the cause 

 is, for that old men s spirits visual, contrary to those of 

 pore-blind men, unite not but when the object is at 

 some good distance from their eyes. 



871. Men see better, when their eyes are over 

 against the sun or a candle, if they put their hand 

 a little before their eyes. The reason is, for that the 

 glaring of the sun or the candle doth weaken the eye; 

 whereas the light circurnfused is enough for the per 

 ception. For we see that an over-light maketh the 

 eyes dazzle ; insomuch as perpetual looking against the 

 sun would cause blindness. Again, if men come out 

 of a great light into a dark room ; and contrariwise, 

 if they come out of a dark room into a light room : 

 they seem to have a mist before their eyes, and see 

 worse than they shall do after they have stayed a little 

 .while either in the light or in the dark. The cause is, 

 for that the spirits visual are, upon a sudden change, 

 disturbed and put out of order ; and till they be recol 

 lected, do not perform their function well. For when 

 they are much dilated by light, they cannot contract 

 suddenly ; and when they are much contracted by 

 darkness, they cannot dilate suddenly. And excess 

 of both these (that is, of the dilatation and contrac 

 tion of the spirits visual), if it be long, destroyeth the 

 eye. For as long looking against the sun or fire 

 hurteth the eye by dilatation ; so curious painting in 



