832 Mr. Brougham's Experiments and Observations on 
made by the red was greatest, by the violet, least, and by the 
intermediate rays, of an intermediate size. Also when at the 
back of the hole I held a sharp blade of a knife, so as to pro- 
duce the fringes mentioned by Grimaldo and Newton ; 
those fringes in the red were broadest, and most moved in- 
wards to the shadow, and most dilated when the knife was 
moved over the hole ; and the hole itself on the chart was 
more dilated during the motion when illuminated by the red 
than when illuminated by any other of the rays, and least of 
all when illuminated by the violet. Now in Obs. 1. the angle 
of incidence of the red rays was equal to that of the violet 
and all the rest, and yet the angle of inflection was greatest, 
and least in the violet ; and indeed the difference between the 
two was greater than appears at first from the experiment ; 
for that part of the shadow which was formed by the violet 
fell at a greater distance from the point of incidence, than did 
that part which was formed by the red, from the divergency 
of the different rays upwards by the refraction, as appears in 
fig. 3. where DE is the window, FG the beam propagated 
through the hole F, refracted by the prism KIH, and paint- 
ing on the chart OP qs ; the spectrum vr being separated into 
Lr the red rays incident on the pin CD at C, and Mz> the 
violet incident at D ; the shadow of DC being formed in vr , 
so that v being farther from D than r is from C, therefore (by 
the propositions formerly laid down) the shadow in v should 
be considerably less than that in r, if the rays were equally 
inflected. Lastly, in Obs. 2. the angle of the red’s incidence 
was nearly equal to that of the violet's, by the motion of the 
prism, and the consequent motion of the colours ; only that, 
if there was any difference, it was on the side of the violet ; 
