270 Mr. Airy on a peculiar Defect in the Eye. 
line inclined to the vertical about 35°, and subtending an angle 
of 2° (by estimation): at the distance of 35inches it appeared a 
very well defined line at right angles to the former, and of the 
same apparent length. It was necessary therefore to make a lens, 
which, when parallel rays were incident, should cause those in 
one plane to diverge from the distance 35 inches, and those in 
another plane from the distance 6 inches. Making the expressions 
above equal to these numbers, and supposing ” = 1,53, we find 
R=3,18, r=4,45. ‘To prevent if possible the eve from becoming 
more short-sighted, I fixed upon the values R= 34, r= 4}. 
After some ineffectual applications to different workmen, I 
at last procured a lens to these dimensions from an artist named 
Fuller, of Ipswich. It satisfies my wishes in every respect. I 
can now read the smallest print at a considerable distance with 
the left eye, as well as with the right. I have found that vision 
is most distinct when the cylindrical surface is turned from the 
eye: and as when the lens is distant from the eye, it alters the 
apparent figure of objects by refracting differently the rays im 
different planes, I judged it proper to have the frame of my 
spectacles made so as to bring the glass pretty close to the eye. 
With these precautions I find that the eye which I once feared 
would become quite useless, can be used in almost every respect 
as well as the other. 
The publication of this case, I imagine, may be not without 
utility. I believe it has generally been found, that where the 
direction of the axis of the eye is distorted, the sight of the eye 
is defective, but not lost: and the distortion is by many ascribed 
to the disuse of the eye, which is occasioned by this defect. If 
it should be found that the defect is at all similar to that which 
I have described, it can be perfectly corrected. The examination 
of the defect in the manner which I have detailed is very easy ; 
and it is merely necessary to write down fully the appearance of 
