the Inflection , Reflection, and Colours of Light. 257 
shadow, as V'G'R' will be formed, similar to VGR, R' be- 
ing red and V' violet, all which is both theory and expe- 
rience; and the same explanation may be extended to the 
other cases. Now, in all these, the bending power stretching 
to a very small definite distance, and being of different degrees 
of strength at different distances from the body, several pen-' 
cils or small beams, passing through different parts of the 
spheres, will be acted upon by the power in its different states 
of strength ; and each beam will be disposed into an image 
in the way before described ; of these images I have some- 
times observed four, and even, by using great care, the faint 
lineaments of a fifth. In forming them, the power acts 
strongest at the smallest distances, and of consequence bends 
the mean flexible rays, that pass near, farther inwards or out- 
wards than those that pass farther off ; so that the extreme 
rays will in the former case be more separated from the mean 
than in the latter ; and the nearer image will always be the 
largest and most highly coloured, which is consistent with fact. 
This explains fully the celebrated experiment of Sir Isaac 
Newton with the knives, and the explanation is confirmed 
by the experiments which I related above on flexibility, where 
the bending force acted most strongly on those images formed 
out of red light, and least strongly on those formed out of 
violet and blue light. A number of other phenomena are ex- 
plicable on the same principles, being only particular cases as 
it were of the coloured fringes or images ; I shall here mention 
a few of the most remarkable. 
§. When making some of the experiments which I have 
related in the course of this paper, I observed that when the 
sun was surrounded, but not covered, by clear white clouds, 
MDCCXCVI. LI 
