344 An Appendix to Mr. Ware’s Paper on Vision. 
those who are most addicted to study become near-sighted 
more rapidly ; and, if no means are nsed to counteract the 
habit, their eyes at length lose irrecoverably the faculry of 
being brought to the adjustment for parallel rays. OF this 
I am myself an example; and as I recollect distinctly the 
progress, it may not be useless to record it here. 
When I first learned to read, at the usual ave of four or 
five years, I could see most distinctly, across a wide church, 
the contents of a table on which the Lord’s Prayer, and the 
Belief, were painted in suitably large letters. In a few 
years, that is, about the ninth or tenth of my age, being 
much addicted*to books, [ could no longer read what was 
painted on this table; but the degree of near-sightedness 
was then so small, that. found a watch-glass, though as a 
meniscus it made the ravs diverge very little, sufficient to 
enable me to read the table as before. Ina year or two 
more, the watch-glass would no longer serve my purpose ; 
but being dissuaded from the use of a common concave 
glass, as likely to injure my sight, I suffered the incon- 
venience of a small degree of myopy, till I was more than 
thirty years of age. That inconvenience, however, gra- 
dually though slowly increasing all the time, at length be- 
came so grievous, that at two or three and thirty I deter- 
mined to try a concave glass; and then found that the num- 
bers 2 and 3 were to me in the relation so well described 
by Mr. Ware; that is, I could see distant objects tolerably 
well with the former number, but still more accurately with 
the latter, Aftercontenting myself a little time with No.2, 
I laid it wholly aside for No. 33 and, in the course of a 
few more years, came to No. 5, at which point my eye has 
now been stationary between fifteen and twenty years. An 
earlier use of concave glasses would probably have made 
me more near-sizhted, or would have brought on my pre- 
sent degree of myopy at an earlier period of life. If my 
friends had persuaded me to read and write with the book 
or paper always as far from my eye as I could see; or if I 
had occasionally intermitted study, and taken to field sports, 
or any employment which would have obliged me to look 
much at distant objects, it is very probabie that [ might 
not bave been near-sighted at all. Possibly the persons 
who become near-sighted by having constantly to adjust 
their eyes to near objects, may not usually change to be 
long-sighted by age. 
On the subject of vision, I may be allowed to take this 
opportunity of relating an experiment made many years ago, 
to decide how far the similarity of the images seen by each 
eye 
