the Inflection , Reflection, and Colours of Light. 233 
and yet the violet was least inflected, and the red most in- 
flected ; and so of the second inflection, by the knife blade : 
wherefore I conclude that the rays of the sun's light differ in 
degree of inflexibility, and that those which are least re- 
frangible are most inflexible . 
Obs. 3. My room being darkened as before, and a conical 
beam propagated through the small hole in the window-shut ; 
at this hole I placed a hollow prism, made of broken plates 
of mirror, and of such an angle, that when filled with distilled 
water, it cast a spectrum on an horizontal table, and was there 
received on a chart seven feet from the window. I then 
placed on the same table, and in the rays between the chart 
and the prism, at three inches from the chart, two sharp 
knife-blades with even edges, and fixed to a board with wax, 
so as to make an angle with one another; mbving them 
nearer and nearer, till I saw the fringes appear in the red 
light on the chart, and then in the orange and other colours 
successively. I then withdrew one, and the fringes became 
faint and narrow, and not all within the shadow of the re- 
maining knife, but at its edge, and even in the light of the 
spectrum. Lastly, when I slowly approached the other, they 
moved into the shadow, and became broader, and farther se- 
parated one from another, there being the like fringes in both 
shadows ; this I repeated in all the rays, and plainly saw that 
at the approach of the knife, the fringes became broader, and 
farther removed from one another, and from the light, in the 
red than in the violet, or any of the other rays. 
Obs. 4. In repeating the foregoing experiment, I observed 
a very curious phenomenon. When the angle of the knife- 
blades was so held in any of the rays as to make the hyper- 
mdccxcvi. H h 
