on the Affections and Properties of Light. 365 
which appeared so new and uncommon, that I began to doubt 
a little the truth of the premises ; but at any rate was resolved 
to examine more minutely how far these inferences might be 
consistent with fact : and I am happy in being able to announce 
the completeness of that consistency, even beyond my expec- 
tations. The chief consequences were the following. 
1. That a speculum should produce, by flexion and reflexion, 
colours in its reflected light wherever it has the least scratch or 
imperfection on its surface. 
2. That on great inclinations to the incident rays all specula, 
however pure and highly polished, should produce colours by 
flexion. 
3. That they should also in the same case produce colours 
by reflexion. 
4,. That lenses, having the smallest imperfections, should 
produce by flexion colours in their refracted light. 
5. That there should be many more than three, or even four 
fringes by flexion, invisible to the naked eye. And, 
6. That Iceland crystal should have some peculiarities with 
respect to flexion and reflexion ; or if not, that some information 
should be acquired concerning its singular properties respect- 
ing refraction. 
The manner in which the first of these propositions is de- 
monstrated a priori , is evident from the 4th figure, where 
CD is the reflecting surface, v 0 a concavity bearing a small 
ratio to C D, A 0 and A B rays proceeding to C D. The one, 
A B, will be separated into B r red, and B v violet, by deflexion 
from 0, and will be reflected to r'v', forming there the fringes. 
The other, A 0, being reflected, will be separated into B x and 
By, by deflexion from v, forming other fringes, xy, on the 
3 B 2 
