24° Mr. Brougham’s Experiments and Observations on 
of the hole on the screen, and were always wholly of the co- 
lour in which they were formed, except in the confines of the 
green, where a small quantity of white light fell, and made 
them of all the seven colours ; but this was almost wholly 
prevented by using a prism with a greater refracting angle, 
and holding the pin and screen farther from it. I then re- 
moved the screen, and left the reflector in its place, so as it 
might reach through the rays ; and thus there were formed 
images, having in them, from top to bottom, the seven colours, 
one after another, the lowest division being red, the highest 
violet. They were inclined considerably towards their tops, 
and were much broader at the bottom or red parts than at the 
tops or violet parts. And lastly, the reflector being moved so 
that the images might be disturbed (as in the former experi- 
ment made in the white light), the red was most, the violet 
least dilated. In case these effects might be owing to any pe- 
culiarities in the shape or position of the reflector, I placed at 
three feet from the prism a lens of four inches breadth, to col- 
lect the rays to a focus, six feet beyond which I held a chart, 
and there received the spectrum inverted, the red being up- 
permost, and the violet undermost ; holding the reflector at 
two feet from the focus, and four from the chart, the images 
were formed just as before, only inverted, inclining towards 
the violet, of greater breadth towards the red, and more dis- 
tended towards the same quarter when the reflector was 
moved. 
Obs. 5. Things remaining as in the last part of the last 
experiment, at the focus of the lens I placed a second prism, 
which refracted the rays into a white beam,* and this I 
/ * Optics, Book II. Part II. Prop. 2. 
