the Inflection, Reflection, and Colours of Light. 239 
spectrum IK divided into its colours, I being violet, and K 
red. On moving the hole in the desk, and letting through 
other images, the colours were not in all arranged the same 
way, but I moved the pin on its axis, and observed those 
where the order was inverted to move, not only with respect 
to the pin, but also with respect to the contiguous images ; 
and I was surprised to see them assume the order of colours 
first mentioned, namely, the red outermost, and the violet 
innermost. In like manner the images, which before the mo- 
tion were regular, on moving into the places left by the others 
had always the order of their colours inverted, so that the 
thing must be owing to some irregularities in the pin's sur- 
face ; for those which were made by a small glass tube filled 
with quicksilver, and freed from scratches by a blow-pipe, pre- 
served during the motion the proper order of colours. Ano- 
ther irregularity in the arrangement was also observable even 
in the glass tube ; for two contiguous images, by mixing one 
with another for two or three successions, appeared each to 
have outermost a dull colour, between red and violet, and in- 
nermost a green ; but here, unless the succession continued 
through all the images, the outermost of all was red, and the 
innermost image had universally violet in the inside. 
Ohs. 4. I placed at a hole in the window-shut a prism, 
to refract the rays, and received the spectrum at the distance 
of six feet from the window, on a chart ; then, at the distance 
of two feet, I placed a screen with a hole in the middle of it, 
through which I let pass successively the different rays. At 
the distance of one inch from the hole, between it and the 
chart, I placed the reflecting cylindrical body ; the images were 
found on the chart and walls of the room round to the sides 
