z66 Mr. Brougham's Experiments and Observations on 
bility of the violet to that of the red ; and a little attention 
will convince us that we had no reason to expect the analogy 
should be kept up in this respect ; for the refrangibility of the 
rays depends on the species of the refracting medium, and 
follows no general rule ; whereas our calculation has been 
made concerning the action of the bending power at a certain 
distance, greater than that whereat the particles of media act 
on the rays in refracting them. It was observed, in the ma- 
thematical propositions prefixed to this paper, that the angle 
of flexion is less than that of incidence, when, in the case of 
inflection, the angle made by the ray and the body is acute, 
and when, in the case of deflection, that angle is obtuse; and 
when the ray is perpendicular or parallel, the angle of inci- 
dence vanishes in both cases. It is evident, therefore, that in 
both these situations of things the ratio of 1309 to 2036, being 
that of a less to a greater, will not enable us to find the angle 
of flexion, although it serves very well when the ray before 
inflection makes an obtuse, and before the deflection, an acute 
angle. I have therefore' mentioned the angle made by the 
bent ray with the incident, which gives a general formula ; 
for let the angle of incidence be I, and that which the bent 
ray makes with the incident B, then F being the angle of 
flexion, we have F = B I ; so that if I = O ; F = B ; or 
if the incident makes an obtuse angle with the body, in the 
case of deflection, and an acute in that of inflection, then 
F == I — B, and in the remaining case F = I + B. 
These observations enable us to give a very short summary 
of optical science. When the particles of light pass at a cer- 
tain distance from any body, a repulsive power drives them 
off; at a distance a little less, this power becomes attractive ; 
