[ »S ] 



applying a card, with a fmall hole made in it, to the eye, they 

 read at the above-mentioned dirtance with great eafc. 



2. Observing the efted of this experiment to be more ftriking 

 than nfual in a perfon the pupil of whofe eye was very large, 

 I meafured the diftances at which he could read when the pupil 

 was dilated, and when it was contradted, and found the former 

 lefs than the latter by about two inches. 



N. B. These cafes are the more remarkable, as the quantity 

 of light incident from the objedl on the eye is diminifhed in each 

 of thefc experiments *, and confequently the vividnefs of the pic- 

 tures on the retina ; therefore a confiderablc degree of diftindlnefs 

 muft have been procured to overbalance the difadvantage that the 

 lofs of light occafioned. 



3. I HAVE met with cafes, though not frequently, of defedive 

 fighted perfons whofe fight was fuch as to be incapable of being 

 affifted by any double-concave or convex glafiTes. Some of them 

 found vifion a little more diftindt through a pin-hole in Jirong 

 iight, others not. 



These cafes do not appear at all explicable on the vague theory 

 of defedive fight generally received ; and perhaps others of a 

 fimilar defcription may occur, or have already occured to more 

 accurate and extcnfive enquirers. 



* Hence the reafon why thefe experiments are attended with more remarkable 

 efFefts in flrong than in weak light. 



That 



