SIGHT. 
mmintains, in the dimensions with which 
they are seen by the eye.” Again, it is ob- 
vious, that however large, or however small, 
the field of view, the picture occupies an 
erpial extent on the retina. Similar obser- 
vations may be made with respect to dis- 
tance. The organ of sight can convey only 
tiiat sensation of distance which may be 
produced by a minute picture on the re- 
tina ; that is, nothing but the sensatioij of 
the distances of the different parts of the 
picture, which may bear no proportion to 
the real distances, and can only be ip 
one direction. Similar things may be said 
of motion, that is, change of position. The 
visible sensation of motion is merely that 
produced by the niotion of different parts 
of the picture on the retina. 
The fact is, that not the objects them- 
selves, but the picture formed upon the re- 
tina, is the immediate object pf the sight. 
AVithout the sense of touch it is probable 
that the picture would never have con- 
veyed ideas of real figure, magnitude, mo- 
tion, or position ; still more, that it would 
never have conveyed the idea that external 
objects produced the picture. Of colour it 
does convey sensations, which dp not re- 
ceive correction from the touch, and which 
can be acquired by the sight alone. Per- 
sons completely blind have been known to 
distinguish objects of one colour from those 
of another, but this is by the feel of tlie 
surfaces of tliose Olyects. If they have ne- 
ver at all possessed sight, though tliey may 
speak of colours, and distinguish coloured 
objects, and even have a remote idea of the 
causes of our sensations of colours, yet they 
can have no sensations nor consequently 
ideas of colours. Mr. Locke mentions a blind 
man, who said, that lie imagined tlie colour 
of scarlet resembled the sound of a trumpet. 
The Umits here stated of the direct power 
of the sense of siglit may appear strange to 
those who have not been accustomed to 
distinguish between the sensation, and the ' 
perception of which the sensation forms a 
part. (See Sensation.) We seem to have 
an immediate sensation of the real situation 
and magnitudes, &e. of objects, but what 
lias been before stated is an indisputable fact. 
The case is, the compound idea, formed 
from the sensations of touch, in connection 
with certain visual sensations, are so early 
formed, and so early connected with those 
visual sensations, that we have no recollec- 
tion of the simple idea of sensation, or of 
the formation of the compound idea : in- 
deed, as active agents, we had no concern 
in the formation of our perceptions. Tlmre 
are however numerous circumstances whiqb 
prove the point j the most satisfactory are 
those attending the obtaining of the sight, at 
a period when recollection can register the 
sensations. One such case fell under the 
observation of the able Cheseldeu, and we 
shall state some of the principal circum- 
stances of it, . Mr, C. conched a youth of 
thirteen years of age : when he was allowed 
to use his sight, all objects appeared to him 
alike to touch his eyes, as the things which 
he felt touched his skin. He considered 
solid bodies as planes differently coloured ; 
and when he had learned to distinguish solids 
by their appearances, he was greatly sur- 
prised, when examiniqg the pictures of so- 
lids, to find all the parts plane and smooth 
like the rest ; Im asked which of his senses 
deceived him, his sight or his hearing ? Be- 
ing shown a ininiatnre of his fallier, which 
was painted on a watch-case, be at once 
perceived that it was a representation of 
his father, but expressed great surprise that 
so large a counteuante could be contained 
in so small a space : it appeared to him as 
impossible as for a pint to hold a hogshead. 
Mr. Ware published in the Philosophical 
Transactions of 1800 a case which seemed to 
militate greatly against Mr. C.’s conclusions : 
Mr. W.’s patient from the first had ideas of 
distance and form. But Mr. W. liimself fur- 
nishes a solution of this difficulty ; for wp 
find, from his paper, that his patient had 
always been able to distinguish light and 
vivid colours from shade. 
Sensations of colour are in the early parts of 
life very vivid, and assist considerably in 
the formation of onr mental pleasures ; but 
the other seiisqtions derived from this sense 
are principally important to us, as being by 
association the signs ofthejdeas derived from 
the touch ; and from thgir distinctness, well 
calculated to serve as tlie connecting bond 
of union, and to bring again into the view 
of the mind those ideas. The visual sensa- 
tions, of themselves considered, are seldom 
the objects of reflection ; we seldom evep 
think of them, and while we appear to give 
to the visible appearances of objects our 
minutest attention, we are in part attend- 
ing only to the tangible qualities of which 
the visible appearance is the sign. Were it 
not therefore for association, the sight 
would be of little more use to ns than ^ 
beautiful picture of objects with which wp 
have no concern. But consider its valup 
in connection with association, and it must' 
be regarded as the most perfect and th^ 
