I2S On Vision. 



remote object Jlppear Indistinct, \vhile,*in the next page, ws 

 are told, that whbn we view a remote object through an 

 aperture of ai)out one-fiftieth of an inch in diameter, if the 

 object be seen in a proper light, it will appear as distinct as 

 to the naked eye. What must be the confusion of that 

 man's ideas, who could foil to discover so glaring a contra- 

 diction ? The true explanation of the paradox, supposing 

 the appearances to have been correctly described, is this : the 

 light admitted was diminished by the contraction of the ori- 

 fice, from two inches to one-fifth of an inch, in the ratio 

 of 100 to one; consequently the pictures of all distant ob- 

 jects must have been rendered extremely faint : but the image 

 of the plumb-line in the window was rendered distinct by 

 the contraction, as it would have been by the contraction 

 of an aperture without any lens, which would have exhi- 

 bited a shadow nearly as distinct, without any trace of i 

 picture of the remoter objects." 



My experiments with the lens might appear a paradox to 

 this reviewer in consequence of his not knowing, that di- 

 stinctness and brightness are diflerent properties. Thus, if 

 we look through a small aperture at the moon, she will ap- 

 pear more distinct than to the naked eye, though less bright : 

 if we look at a remote terrestrial object prop'jrly illuminated 

 for the experiment, it will appear as distinct when viewed 

 through a small aperture, as to the naked eye, but not so 

 bright ; but when the same object is seen in a faint light, 

 through a small aperture, it will appear neither so distinct 

 nor so bright as to the naked eye. 



Now my experiments with the lens were made with ter- 

 restrial objects seen onlv by day-light, but the object seen 

 through the small aperture, was strongly illuminated with 

 the suii's rays, and appeared as distinct as to the naked eye, 

 though not so bright : it might be (and probablv was) this 

 difference between distinctness and brightness that puzzled 

 this gentleman so much. 



It is, however, very singular that this writer should be 

 wrnnEj in all his observations. For in my experiment with 

 a small aperture, ihe plumb-line, which hung down the 

 middle of the window, v.'as so clearly represented upon the 



unpolished 



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