252 On Refraction. 
within a few years that the organon of Aristotle has given placé 
in our colleges to the nzovum organum of Bacon. 
Having formed the letter T on a sheet of white paper, I held 
the plano-convex lens immediately over it, when it appeared 
considerably enlarged in all its dimensions: on raising the lens 
about two inches from the paper, two inverted images appeared 
nearer to the eye, and floating on the posterior surface, forming 
a kind of circular appearance, in the centre of which the erect 
image appeared very much enlarged; at yet a greater distance 
from the eve, the erect image became so diverging and confused 
as nearly to be invisible, and the two inverted images coalesced 
and formed in one very distinet inverted image, which diminished 
in size with every increase of distance. It immediately occurred 
to me, that this union of these inverted images was the focus of 
the lens, and consequently that the rays never cross to form pic- 
tures. To prove this in the most satisfactory manner, we have only 
to give a circular movement to the lens held over the letter T, 
and we find the image will become inverted at the top and bot- 
tom, erect when at the sides. I next looked through the lens at 
a lighted candle; when close to my eye it appeared magnified; on 
slowly withdrawing my eye to about two inches, I perceived two 
inverted images around the erect one, which formed a brilliant 
and luminous circle, margined on the outside by bright orange 
rays, such exactly as we see in the circle of light before the rays 
are brought to a focus on a sheet of white paper : on now with- 
drawing my eye to yet a greater distance, I found this luminous 
circle, formed by these two inverted images, to diminish or con- 
tract, and when coalesced, they formed at about two inches and a 
half from the eye a beautiful inverted image of the candle: as 
the eye was further removed, this image diminished in size. 
Here we have two sets of images perfectly distinct from one an- 
other and cbeying different laws, the erect image magnified, the 
inverted images diminished by every increase of distanee. [I now 
held the lens opposite the lighted candle, and before a sheet of 
white paper ; at the distance of an inch I perceived a luminous 
circle, margined: with orange rays exactly similar to that I saw 
when looking through the lens at the candle, and formed by the 
lateral images : on repeating this experiment, any person may be 
convinced that there is no crossing of rays to form these images, 
as in fact the inverted image is distinctly seen before the apex of 
a cone is formed. Further to convince, I shall mention the fol- 
lowing conclusive experiment. 
Exp, 5.—Having held the glass globe filled with water op- 
posite a lighted candle, we find a well defined erect image 
formed 5; on placing the plano-convex lens immediately over it, 
the 
