266- Notice of a, peculiarity in Vision. 



lines and objects were now seen with about the same degree 

 of definiteness with which vertical ones had been before, 

 whilst vertical objects were seen with the same indistinctness 

 with which horizontal ones had been before ; circles were 

 still, of course, seen as ellipses, but the transverse axis, in- 

 stead of being perpendicular to the horizon as before, now 

 became horizontal. The eyes and mouth of the distant 

 speaker now became much more interesting objects of sight 

 than before. 



Let it be distinctly understood, that my sight has never 

 been so short, or I might say rather so indistinct, as that of 

 many persons. It is also worthy of remark, that whilst in 

 common cases of short sightedness, the individual can see 

 very well, provided the object be placed at his proper seeing 

 distance, / had no seeing distance, but was perpetually mis- 

 taking objects at all distances within the compass of my vis- 

 ion ; that both eyes are affected with the same difficulty, yet 

 that the right one is both stronger and more discriminating 

 than the left ; and that neither the vertical object, seen with 

 the naked eye, nor the horizontal one, seen through the 

 glasses, are seen at more than about half the distance that 

 they are by many good eyes. 



Now on the supposition that, in the economy of vision, 

 the refraction of light is achieved principally by the crys- 

 talline lens of the eye, I think the following conclusions 

 plainly deducible. 



1. That the crystalline lens of my eye, instead of being 

 formed of sections of a sphere, is really formed of sections 

 of a spheroid. 



2. That the transverse axis of this spheroid runs in a hori- 

 zontal direction. 



3. That the horizontal curvature of this lens is just of that 

 degree adapted to produce tolerably correct vision, whilst 

 the vertical curvature is too small, that is, a portion of too 

 small a circle to produce the same effect. 



Things being so, I am readily able to account for the two 

 opposite effects of my concave spectacles. 1st, the interpo- 

 sition of a diffusing glass, (such as they are,) by diminishing 

 the refraction, indisposes the rays of light coming in a hori- 

 zontal plane, for correct vision. 2d, the interposition of the 

 same glass exactly disposes the rays coming in a vertical 

 plane to produce correct vision, because the vertical curvity 

 is so small as to refract these rays in too great a degree. 



In reasoning from facts, thus far, I find no difficulty. The 



