342 On the near and distant Sight of different Persons. 
in reading. He tells me, that when he has been employed 
many hours together, for several successive days, in looking 
through a double microscope that magnifies twenty-eight 
times, (in order to enable him to mark the degrees on a 
small brass plate) he has afterwards been able repeatedly 
for a few weeks, to read without his glasses; but then the 
amendment gradually ceases, and he is soon obliged to re- 
turn to the use of the same glasses that he had worn before. 
In the instances that have been mentioned, the distant- 
sightedness affected persons who were considerably adyanced 
in life: but in the three that follow, a similar affection of 
the sight occurred in those that were young; and a like 
good effect was produced by the use of evacuating remedies. 
One of these was a boy eight years old, who suddenly be- 
came presbyopic, and had repeatedly been punished at 
school, on account of his incorrect and defaced wniting ; 
the real cause of it, at that time, being unknown to his 
master. After the presbyopia had continued a fortnight, 
and different local applications had been used, without pro- 
ducing any sensibly good effects, the lad was cured by the 
application of leeches to the temples, and the administration 
of a few purgative medicines. The other instances oc- 
curred in two daughters of the same family. The eldest, 
twenty years of age, had never been able to do fine work, 
and for three years had been greatly assisted by convex 
spectacles. he youngest, a girl of fifteen, had become 
presbyopic about a year ago, and since that time had been 
obliged to use spectacles whenever she read, or worked with 
her needle. The young person, last mentioned, in the course 
of six weeks, (during which time she totally abstained from 
the use of glasses,) was completely relieved from the neces- 
sity of using them, by the application of two leeches to 
each temple twice in a week. The former, in the same 
space of time, experienced much relief from a similar treat- 
ment, but was still unable to do fine work without glasses, 
partly in consequence of the long continuance of the in- 
firmity, and partly on account of her not having abstained 
with equal steadiness from the occasional use of them. 
From the preceding statement, the followiny inferences 
may be deduced. 
First ; near-sightedness is rarely observed in infants, or 
even in children under ten years of age.. It affects the 
higher classes of society more than the lower: and the in- 
stances are few, if any, in which, if the use of concave: 
glasses has been adopted, increasing years have either re- 
moved or lessened this imperfection, 
Secondly 5 
