Mr. Arry on a peculiar Defect in the Eye. 271 
the brilliant point at different distances, in order to enable the 
theoretical optician to mvent a glass which shall make the vision 
of the eye distinct. If the defects arise from insensibility of the 
nerve, or opacity of the humours, they are beyond his power: 
but any fault in the refracting surfaces it is possible to correct. 
Since I procured this lens, I have been informed that a foreign 
artist has made spectacle-glasses with cylindrical surfaces of 
different radii for general use. What his object can be I am quite 
unable to imagine; certainly no one whose eyes are not defective 
can see with them distinctly. With my right eye which (by the 
method of examination above described) I find to have no other 
defect than short-sightedness, I am unable to read any thing in 
the lens made for my left eye. After many inquiries I have not 
been able to discover that this construction has been used to 
correct any defect in the eye, or even that a defect similar to 
that which I have described, has ever been noticed: In laying 
before this Society the notices of a case which appears at once 
novel and important, I trust that I shall not be thought to have 
trespassed unprofitably upon their time. 
G. B. AIRY. 
Trinity CoLiece, 
Feb. 5, 1825. 
