IMPROVED. 119 



dium, that breaks the Rays, in like Manner as a 

 Ball is thrown into a Tube ; or whether, according 

 to the incomparable Sir Ifaac Neivtotty the fame is 

 performed by Attradlion, I fhall not at prefent take 

 upon me to determine : But that the Rays are broke 

 or refrained, few or none will deny, fmee it is de- 

 monllrable by fei^ral Experiments in Opticks. 



Thefe Rays being brought then by Means of the 

 Conn; ex Glafs or Lens to their proper Focus or Point 

 of Convergence upon the Paper, muft (as I have 

 faid) imprint a more perfe£l Image. 



A Coti'vex Glafs of a larger Sphere, which Glafs A Convex 

 may be compared to the Cornea, as the other was ^' g^^^^"^' 

 to the Cryftalline ; I fay, a Glafs of this Sort being {j^g cornca, 

 put a little on the Outfide of the Hole, will make 

 a greater Number of Rays to converge or come to 

 a Point from all Parts of the external Objedl, and 

 to enter in at the Hole upon the Lens or Convex 

 Glafs on the In fide, and confequemtly make the 

 Pidure or Image ftill more perfect. 



The greater the Convexity of the Lensy the larger The great- 

 the Objea will appear ; for the Angle of Vifion ^r the Con- 

 will be greater, but the Axis of Sight or Dillance ^^^ 'cornea 

 from the Objedl will be fhortned ^ fo that Creatures the larger 

 which have their Eyes more Convex than ordinary, the Object 

 or fach as are Purblind, if they have no other De- appears, 

 feft or Weaknefs but what proceeds from fuch Con- 

 vexity, fee Things better, and larger than others ; 

 yet this muil be fuppofed at their own Dillance, 

 which no doubt muft be nearer according as the Eye 

 is more Convex. 



There is no Help for this Defeft in Horfes, I Purblind 

 mean the too great Convexity of the Cornea ; but Horfes fee 

 this I can fay with Truth, fuch Horfes will have a ^^"^^o^v 

 more perfe<fl Sight, or fee Things at more proper old. 

 Diilances when they grow older ; for by tliat Time 

 the Cornea will become flatter and more plain, and 

 the Rays from Objefts at common Diftances will 

 not fall fo divergent upon the Retina as they did 

 before. 



I muft 



