the Inflection , Reflection, and Colours of Light. 259 
was owing entirely to wrinkles formed on the surface of the 
eye by the pressure.* But this could neither form the bows 
with the regularity in which they always appear, nor could 
the colours be in the order above mentioned from the dif- 
ferent refrangibility of the rays ; it will also be obvious to 
any one who tries the thing, that the pressure only increases 
the brightness and breadth of the bows, but does not form 
them. The true solution of the difficulty seems to be this: 
the rays which enter the pupil, are inflected in their passage 
through the fibres, which extend over the cornea, and which 
are very minute, but opaque ; by these they are decompounded 
into fringes, having the red outermost, and the violet inner- 
most ; and the fringes formed by each fibre being joined to- 
gether, form the bow. How then does the pressure enlarge 
and vivify them ? The fibres are naturally extended over the 
surface of a spherical segment ; when this surface is compressed 
into a plane circle, they are condensed into a much less space, 
and consequently brought nearer to one another, the rays are 
therefore more inflected and separated than before. If this 
explanation be true, it will follow, that the like bows may be 
produced by small hairs, like fibres, placed near one another ; 
and this I found perfectly consistent with fact ; the bows are 
in this case brighter than in the other ; and the small hairs on 
a hat, or the hand, made them brighter than any other I have 
tried : a circumstance which I observed in both cases, seems 
to show clearly the identity of the causes ; the white space, 
which reached from the interior bow to the flame, was speckled 
or mottled, in a manner which cannot be easily described, but 
which any one will perceive upon trying the experiment. 
* Led. Optica, Sect. III. adjinem. 
LI 2 
