1 18 The Aft (j/Fakriery 



read by great Lights, by fo much the more are we 



hazarding our Eye-Sight; and we may thereby 



bring it into fuch a State that we cannot fee at all ; 



when others of the fame Age, who do not hurt 



themfelves by what I am fpeaking of, can read 



diflindliy. Furthermore, People fhould turn their 



Backs upon the Light when they would read, or do 



any Thing that is termM fine Work j but inftead of 



this they turn their Faces direftly towards the 



Light, which is diametrically contradictory to all 



the known Rules in Opticks. 



"Why a There is not any Thing in the Compofition of a 



Horfe fees Horfe's Eye, which fhould caufe him to fee better 



^■h^*'>J-^1> than a Man <:an do, in the Night-time; for it is 



than M^in'' ^"^7 ^^^ being kept more in Darknefs than we are, 



which makes a lefs Light ferve his Turn. So that 



as to Light or Darknefs we talk of them as we do 



of Heat or Cold, to wit, as they afFe<5t our felves, 



not others ; For Example, what's Hot or Cold to 



me may not be fo to another, and when it is dark 



with us, it may not be fo with others, altho' in the 



fame Climate. 



Why Cats, As to a Cat or Owl's feeing better than other 



trc. can fee Creatures in the Night, there cannot be any more 



Merf ^ ^^h" ^^^^ ^'^ ^^^ ^^^^ ^^^" ^^^^' ^° ^^^' ^^^^ ^^°^^ ^''^^" 

 Night'^ ^ ^"^^^ ^'^^^ their Eyes of a finer Contexture or Make, 

 and that therefore the Nerves are fooner affedled. 

 Add to this, the Infide of the Tunica Sclerotica of 

 thefe Creatures is more black than others, and by 

 that Means the Rays of Light are more imbibed, 

 and confequently a ftronger Impreffion made upon 

 the Optick Nerve. And whoever pretends to give 

 any other Account than this, it mult be fuch as is 

 meerly fpeculative and conjectural. But to return. 



The Lens which reprefents the Cryftalhne Hu- 

 mour, is to be placed at its proper Diftance from 

 the Paper behind the Hole in tjie Camera Ohfcura 

 or dark Chamber ; by which Means the Rays of 

 Light are broke or retracted : But whether by a 

 proper Difpofition of the Pores of the Glafs or Me- 



dinm, 



