236 Mr. Brougham's Experiments and Observations on 
bodies come into perfect contact, P" M", will be infinite ; so 
that the attraction being changed into cohesion, will be infi- 
nite, and the bodies inseparable, contrary to universal expe- 
rience ; so that P can never come nearer to A than a given 
distance. In the case of gravity, PM is inversely as the 
square of AP, so that the curve NMM'" is the cubic hyper- 
bola ; but the demonstration holds, whatever be the proportion 
of the force to the distance. It appears then that flexion, re- 
fraction, and reflectioh, are performed by a force acting at a 
definite distance ; and it is reasonable to think even a priori , 
that as this same force, in other circumstances, is exerted to a 
different degree on the different parts of light, in refracting, 
inflecting, and deflecting them, it should also be exercised 
with the like variations in reflecting them. Let us attend to 
the proof, which enables us to change conjecture into con- 
viction. 
Obs. 1. The sun shining into my darkened chamber through 
a small hole ^th of an inch in diameter, I placed a pin of — th 
of an inch diameter in the conevrf light (one-half inch from 
the hole) inclined to the rays at an angle of about 45 0 , and its 
shadow was received on a chart parallel to it, at the distance 
of two feet. The shadow was surrounded by the three fringes 
on each side, discovered by Grimaldo ; beyond these there 
were two streaks of white light diverging from the shadow, 
and mottled with bright colours, very irregularly scattered up 
and down ; but on using another pin, whose surface was well 
polished, and placing it nearer the hole than before, the co- 
lours in the streaks became much brighter (and the streaks 
themselves narrower), being extended from one side to the 
other, so that, except in a very few points here and there, no 
