M A N 
and even. At firft, he was incapable of fuppoit- 
ing a large quantity of light, and he faw every 
objed much larger than the life; but, in propor- 
tion as he faw objefts that were really large, he 
feemed to think the former were diminifned; and 
though he knev^ the chamber he ufed in the houfe, 
yet, till he faw the latter, he could not be brought 
to conceive how an houfe could be larger than a 
chamber. Before the operation, he had no great 
expeftations from the pieafure he fhould derive 
from a new fenfe: he was only excited by the 
hopes of being able to read and write; and faid, 
that he could receive no greater enjoyment from 
■walking in the garden with his fight, than he had 
without it, fince he ranged there at his eafe, and 
was acquainted with every walk. But when he 
began to make ufe of this new fenfe, he was 
tranfported beyond meafure: every new objed: 
feemed a new fource of delight, and his pieafure 
was great beyond expreffion. 
Chefelden makes mention of many more who 
were reftored to fight in this manner: they all 
feemed to concur in their perceptions with this 
youth; and were particularly embarraffed in learn- 
ing how to dired: their eyes to the objeds they 
wifhed to obfcrve. 
Thus it is, that our feeling correds the fenfe of 
feeing, and that objeds which appear of fo many 
different fizes, at different diftances, are all re- 
duced, by experience, to their natural ftandard. 
But not only the feeling, but alfo the colour, and 
the fplendor of the objed, contribute, in Ibme 
meafure, to afllfl: us in forming fome idea of the 
diilance at which it appears. Thefe objeds which 
we behold moft ftrongly marked with light and 
Ihade, we readily difcover to be nearer than thofe 
in which the colours are more faintly fpread, and 
v/hich, in fome meafure, take a part of their hue 
from the air between them and us. Luminous ob- 
jeds aifo are feen at a greater diftance than fuch as 
areobfcure; and moft probably for this reafon ; be- 
caufe, being iefs correfpondent in colour to the air 
which interpofes, their impreflions are lefs effaced 
by it, and they continue more diftindly vifible: 
thus a black and diftant objed is recognized at a 
Iefs diftance than a bright and glittering one ; and 
a fire by night is vifible miuch farther off" than by 
day. 
The diftance at which any objed can be feen is 
feldom the fame in both eyes: there are few Men 
who have both thefe organs equally ftrong; and 
when this inequality is great, the ftrongeft eye is 
moft generally employed ; and hence proceeds that 
aukward look, which is commonly known by the 
appellation of fquinting or ftrabifm. 
Many reafons confpire to induce us to believe, 
that fuch perfons as are near-fighted fee objeds 
larger than other perfons ; and yet the contrary is 
moft certainly true, for they fee them lefs. Buffon 
informs us, that he himfelf is fhort-fighted; and 
that his left eye is ftronger than his right: he has 
very frequently obferved, on looking at any ob- 
jeds, fuch as the letters of a book, that they ap- 
pear lefs to the weakeft eye; and when he places a 
book, fo that the letters appear double, the images 
of the left eye, which is f];rongeftj are greater than 
chofe of the right, which is the moft feeble. He 
farther tells us, that he has examined feveral other 
perfons who were in fimilar circumft"ances, and has 
always found that the beft eye faw every objed 
the largeft. This he afcribes to habit; for near- 
fighted people being accuftomed to approach the 
objed more clofeiv, and to view but a fmail part 
Vol. IL 
of it at a time, when the entire objed is feen, ic 
appears leis to them than to others. 
As the eyes of infants are lefs than thofe of 
adults, they muft likewife fee objeds in a dimi- 
nifhed light; for the objed formed on the back of 
the eye will be large, in proportion as the eye is 
capacious: and infants having it lefs, cannot enjoy 
fo large a pidure of the objed. This may be a 
reafon alfo why they are unable to fee fo diftindly, 
or at luch diftances, as perfons arrived at maturity. 
Old people, on the contrary, lee bodies v.'hich are 
dole to them very indiftindly, but thofe at a 
greater diftance with more precifion; and this 
probably arifes rather from an alteration in the 
coats, or perhaps humours of the eye, than from 
their diminution, as is generally fuppoied. For 
inftancc; the cornea may become too rigid to 
adapt itfelf, and to aflume a proper convexity 
for perceiving minute objeds; and it's very 
flatnefs will be iufficient to adapt it for diftant 
vifion. 
When we caft our eyes on an objed extremely 
brilliant, or fix and detain them too long on 
the fime objed, the organ is hurt and fatigued ; 
it's vifion becomes indifdnd; and the image of 
the body, which has thus too violently or too per- 
feveringly employed us, is painted on every thing 
we look at, and mixes with every objecl that oc- 
curs: and this is an obvious confcquence of the 
eye taking in too much light, either immediately, 
or by reflexion. Every body expofed to '''^^ light 
for a time, imbibes a quantity of it's ra^ :h 
being brought into darknefs, it cannof cly 
difcharge. Thus, if the hand be expt the 
full glare of day-light for ibme time, ai im- 
mediately fnatched into a dark room, ftill 
appear luminous, and become dark ;rees. 
It is thus with the eye; which, either iftanc 
gaze at the fun, or a fteady continua fome 
lefs brilliant objed, has admitted too light; 
it's humours are, for a while, unfit 1 .n, till 
the fuperabundant light is difcharge ays of 
a rnilder nature have found admiflior 
How inimical to the fight the v, ight 
and luminous objeds is, may be eafil) ich 
people as inhabit countries covered w 
during the greateft part of the year, who 5, 
become blind before tlieir time. TraveTlt. 
crofs thefe regions are obliged to wear crapes 
fore their eyes, in order to preferve them.. Tiiv 
fame precaution is equally necelfary in the fandv 
defarts of Arabia: the reflexion of the light is 
there fo ftrong, that it is impofTible to fupport the 
efted without incurring the moft imminent dan- 
ger of totally lofing the fight. Such perfons, 
therefore, as are obliged to read or write for anv 
length of time, fhould ufe a moderate light; and 
though it may feem infufficient at firft, the eye 
will by degrees accuftom itfelf to the fhade, and 
be lefs injured by the mediocrity of the liglit tlian 
it's excefs. 
The fenfe of hearing, like that of feein.f?, beino- 
intended to give us notice of remote objeds, is 
fubjed to fimilar errors, and equally impoies on 
the underftanding, when we have no opportunity 
of redifying by the touch the ideas it excites. 
The faculty of hearing communicates no diftind 
intelligence of the diftance of ionorous bodies: 
a great noife at a diftance, and a fmall one when 
near, produce the lame ienfation; and uniefs we 
derive information from the other fenfes, we can- 
not diftinguifh the remotenefs of the one from that 
of the other. When we hear an unknown found, 
R we 
