a 
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On the Refraction of Light. 353 
and a white surface placed at some distance behind it, each puncture 
pet be seen to contain a perfect image of the flame. 
~ The small circular aperture displays some singular appearances, 
when allowed to transmit dispersed light. us, place im-a sun 
beam, admitted through a hole in a dark chamber, a spherical mir- 
ror* of about four lines in diameter, and near it, place in the disper- 
sed rays, a leaden plate containing a few punctures. At a conven- 
ient distance receive on a white surface the shadow of the plate, and 
the following phenomena will be evident: each puncture will contain 
a number of dark circular lines or epicycles, with luminous intervals 
between them. On minute examination these lines ‘will be found 
chromatic, being bordered on.the one side by orange, and on the 
other by bluish light. When the holes in the lead are square or 
thombic, the images received on paper , will be found to comprise 
many smaller squares or rhombs. .‘The development of dark and 
bright lines is not occasioned by a property, exclusively belonging to 
heterogeneous light; for when we admit into the dark chamber a 
beam - through red or blue glass, and adjust in it the spherical mir- 
Yor and punctured plate, the, same dark and bright circles are ob- 
served; but instead of the chromatic fringes that border the circles 
in Wiipcdanid light; we shall at eae dilutions and consis 
tions of the color employed. —- 
ee aha rays emerging front a prism, 1 being transmitted 
through holes in the Jeaden plate, present some. appearances well 
notice. Having admitted a beam of white’ light into a dark 
‘chamber, eideek a hole half an inch wide, Tordered a prism in such 
manner as to decompose the light, and placed in the emerging 
Yays, at some distance from the prism, a plate of lead, having in it a 
hole of one line in diameter. At a distance of four feet from the 
lead, I held a sheet of white paper, expecting to find on the paper 
the base of a luminous cone, such as would be formed. by white light 
under the ‘same circumstances 5 instead of which, there appeared 
from the lead to the white surface a pyramid of light whose. base 
_ on the paper described an oblong figure, bounded on all sides by 
‘Straight lines. On varying the position of the prism, so as to let the 
refracted rays emerge at different angles from ihe incident rays, the 
* Thi i t ought to be pedomed with. a metallic reflector. The bulb of 
but not so well as metal, since the light is Hiable 
crates. answers the purpose 
tobe decomposed by the slightest ine equality ‘of the glass. 
