156 VISION UNDER WATKR. 



Rcplj/. JK N, 



Question whe- After expressing my satisfaction that the present 

 ther W. N. or , . , . "^ . "', -^ , ^ , , , • j. . 



his corrcspon- suDject ot enquiry has been treated by an immediate 



dent have rea- reference to facts, I will take the liberty to make a few 



frora^^^thetr^^^ remarks, chielly with a view to indicate what conclusions 



facts. we ought to deduce from them. 



W. N. because ^ admit that every remark I made upon Dr. Franklin's 



he cannot him- assumption, that men can sec under water, was founded 



water has'con- "po"™y ^wn experience, that the contrary position, with 



eluded that no regard to myself, is true ; and my error appears to have 



one can. The ^q^j^ of the same nature as that of my able oponent. — I, by 

 diver has made j r ^ 



the opposite making a general inference from particular facts, have 

 conclusion concluded that no man can sec or disiinguif^h under wa- 

 li^nil"ed^tosome ^^'' ' — ^^5 on the contrary, making too extended a deduc- 

 menonly. tion from his Qwn observafions, has concluded that I 



have been misled by a false hypothesis, and seems to think 

 that all men can !^ec under zcater, 



I think the present controversy has given us both suf- 

 ficient reason, to enquire whether, among mtn who can 

 see objects in the air at all distances, with considerable 

 distinctness, there be not many who like myself, cannot 

 distinguish at all under water ; and many others, who 

 like my correspondent, can see almost as distinctly in that 

 clement as they do out of it. At all events the former 

 cannot be a question of any doubt to those who find they 

 ' " do not distinguish (or sec) under water. 



Vindication of It fJocs not seem to me necessary to enter upon any dis- 

 the use of the cussiou respecting my cylindrical glass, becausemy expcri- 

 gass\e53e. ment appears to have been misapprehended. There was 

 nothing but water between the eyes and the objects, and 

 yet we could not distinguish them. The vessel being glass, 

 the objects were well enlightened ; in eftbcting which the 

 figure of the glass was of no consequence, as we did not 

 look through it. The experiment of the lens neither 

 confirms nor weakens the truth of the general fact. 

 Whether the Whei; I was ayoung man, I saw objects distinctly at 

 fi2ure"o^ aT to ^^"'^ inches distance. At present I see imperfectly at less 

 see inair at two distances than twelve inches, though I am still near* 



inchesdistance. sighted with regard to objects more remote than four feet 

 Probably not. " , /. . , ' i 



— Butthissecms As the curvature ana refractive density of the human cor- 

 nea 



