288 
NEAR AND DISTANT SIGHT. 
Changes in the 
«r£aa of light- 
Blunt the optician, is a double concave glass, ground on a 
/ 
tool of eight inches radius on one side, and eleven inches on 
the other, the mean between which is very nearly nine inches. 
With a glass of this description I can read the smallest print, 
but to distinguish distant objects I am obliged to look through 
that, denominated No. 9, by opticians, which is ground on a 
tool of nine inches radius on both sides. In this respect, my 
eye has varied from what it was a few years ago, when I was 
able to distinguish both near and distant objects correctly, 
through No. 8. This is ground to a radius of eight inches on 
one side, and six inches on the other, and with it I can still 
read a type like that in which the Transactions of the Royal 
Society are printed ; but am unable to distinguish through it 
many distant objects, which I formerly used to see distinctly* 
Hence it appears, that my eyes have a confined range of dis- 
tinct vision, extending only to an inch, or an inch and a 
quarter ; and that they remain nearly in the same state in 
which they were many years ago with regard to near ob- 
jects, but have lost a part of the power which they formerly 
possessed, of adjusting themselves to distant ones. In this 
last respect, they differ from the eyes of those who have natu- 
rally a distant sight ; since, as such persons advance in life, 
they usually retain the power of distinguishing distant objects, 
but lose that of seeing those that are near. 
(To be continuedj 
