m 
Dr. Young’s Lecture 
tance. She used for distant objects a glass of \ inches focus; 
with this she could read as far off as 12 inches, and as near as 
five : for nearer objects she added another of equal focus, and 
could then read at 7 inches, and at 2 
4. Hanson, a carpenter, aged 63, had a cataract extracted 
a few years since from one eye : the pupil was clear and large, 
and he saw well to work with a lens of 2 f inches focus ; and 
could read at 8 and at 15 inches, but most conveniently at 11. 
With the same glass, the lines of the optometer appeared always 
to meet at 1 1 inches ; but he could not perceive that they 
crossed, the line being too strong, and the intersection too dis- 
tant. The experiment was afterwards repeated with the small 
optometer : he read the letters from 2 to 3 inches ; but the 
intersection was always at 2 \ inches. He now fully understood 
the circumstances that were to be noticed, and saw the crossing 
with perfect distinctness : at one time, he said it was a tenth of 
an inch nearer ; but I observed that he had removed his eye 
two or three tenths from the glass, a circumstance which 
accounted for this small difference. 
5. Notwithstanding Hanson’s age, I consider him as a very 
fair subject for the experiment. But a still more unexception- 
able eye was that of Mrs. Maberly. She is about 30, and had 
the crystalline of both eyes extracted a few years since, but 
sees best with her right. She walks without glasses ; and, with 
the assistance of a lens of about four inches focus, can read 
and work with ease. She could distinguish the letters of the 
small optometer from an inch to 2 \ inches; but the intersection 
was invariably at the same point, about 19 tenths of an inch 
distant. A portion of the capsule is stretched across the pupil, 
and causes her to see remote objects double, when without her 
