Mr Charles Bell on the Motion of the Eye, 3T9 
between the closed eye-lids, has not been accomplished by Almigh- 
ty wisdom. Those who are familiar with this class of experiments, 
will have no difficulty in observing the ridge of accumulated fluid 
remaining after the eye is opened, and gradually falling to its 
level.'” Who would not believe, that Dr Brewster and his philo- 
sophical friends had actually seen the water running down the 
face of the cornea, and in their own eyes, too ; thus stating an 
imperfection of the eye, at the very moment that they were us- 
ing it with such perfection as to discover what we cannot see. 
This, in the proper sense of the word, is a complete hallucina- 
tion. Physiologists did at one time conceive, that, when we see 
spots or lucid circles falling before the eye, it must be from the 
dropping of the water over the face of the cornea^ whereas it 
has been proved by the most satisfactory suite of experiments, 
that these circles and spots proceed from an afiection of the 
retina, and that their apparent motion is owing to the motion of 
the eye-ball. 
Dr Brewster proceeds to illustrate the subject by one of those 
imposing figures, which the common reader takes as demon- 
stration. Let the eye be directed to a small point of light, 
such as the image of a candle diminished by reflection, from a 
convex surface, and let this image be brought near the eye, so 
that the pencils of rays, which diverge from it, may have their 
foci a great way behind the retina when the eye is open ; the 
image of this luminous point will be a circular disc, or a section 
of the cone of rays formed by the refraction of the eye. If, 
when looking at this circular disc and power at A, (PI. XI. 
Fig %,) we shut the eyelids, and then open ;them gradually, 
examining, at the same time, the appearance of the disc, we shall 
at first observe it to have the compressed form shown at B, oc- 
casioned by the ridge of fluid, and then gradually extending it- 
self into its regular scircular form.”” 
The proposition affirmed is, that there is a ridge of fluid 
which gradually falls down upon the face of the cornea. It is not 
seen, but its presence is assumed from a certain change in the 
figure of an object. To have a definite idea of the point under 
consid^ation, let us suppose that there is such a ridge of fluid, 
let us give it a visible magnitude, and let us consider what would 
be its effects. 
