250 On Refraction. 
Exp. |.—Having placed a piece of money at the bottom of 
a wine-glass on the table, | made the edge intercept my view ; 
on pouring in a small quantity of water the shilling seemed to 
rise; ] now perceived two images of the object, one at the bot- 
tom, and another floating at the top of the water, very apparent 
when the glass was a little inclined to the eye. This floating 
image was agitated by every movement of the water. To ascer- 
tain whether this image was the real cause of vision, I held the 
glass above my eye, and saw the image floating by reflection on 
the surface of the water, as well defined as if reflected from the 
face of a mirror. Further to convince myself that it is this float- 
ing image we see, and not the shilling at the bottom of the 
vessel, | brought my eye ona line with the image, and then gently 
lowering the glass, at the same time keeping my eye intently 
fixed on it, I saw the image by transmitted rays. Thus the 
floating image was seen by the eye, above, ona line with, and be- 
low the water. But it may be objected, If the image were at 
the surface of the water, why see it on looking into the vessel 
much deeper than that surface? This objection is answered by 
analogy with reflecting mirrors; for if we place two candles at 
different distances, although the images are both evidently formed 
and reflected from the same surface, yet they appear to the ob- 
server at very different distances behind the glass. Let us now 
draw a few optical inferences from this interesting experiment. 
Ist. We may infer that when we look through refracting media, 
such as telescopes, microscopes, spectacles, &c. we take our ideas 
not from the rays ‘immediately sent from the object itself to the 
eye, nor from imaginary images at foci, but frem images formed 
in the body of the refracting media. For example: In this ex- 
periment, we take our ideas not immediately from the shilling 
which is covered by the rim of the vessel, but from an image 
formed perpendicularly over it at the surface of the water, which, 
as already mentioned, can be seen by an eye above, below, and 
on a line, or iu the same plane with the surface of the water. 
2dly, That there is here no bending : in this experiment the light 
passes in straight lines from the object at the bottom to the 
image at the surface, and likewise in straight lines from the 
image to the eye of the spectator; there is no bending what- 
ever. 
Exp.2.—Having procured from the glass-house a solid glass 
globe about two inches in diameter, 1 endeavoured to look through 
it at the window, but could only perceive a confused light, with- 
out any appearance of the frames or window; but on withdrawing 
my eye a few inches, I saw not only an inverted image of the 
window, but even the smallest fly became distinct and well de- 
fined. Could any person in this experiment venture to say that 
we 
