310 
DR. BREWSTER ON THE PHENOMENA AND LAWS 
light concerned were divided into two portions, the one partially reflected in 
the first instance, the other beginning to be refracted, and caused to return by 
the continued operation of the same power. The original interval appears to be 
extremely minute, but is capable of being increased by a repetition of similar 
reflexions as well as obliquity of incidence.” 
1 n a letter which I received from this eminent philosopher, dated March 25th 
I s 1 (j, he thus modifies an objection which he had previously made to my opi- 
nion, that the phenomena were owing to the interference of the light which 
had entered the surface with that which had suffered partial reflexion. 
“ The light which you suppose to have entered a little way into a reflecting 
surface, in the case of total reflexion, is singularly circumstanced with regard 
to the objection I mentioned in my last letter. I did not like the idea of sup- 
posing a surface of any kind to contain a finite space: but, in fact, if your 
theory should be confirmed, this objection might be greatly diminished by the 
consideration, that the thickness of the surface would still be like an infini- 
tesimal of a different order from the interval corresponding to its apparent 
effect, being the versed sine of a curve of which that small interval is the arc, 
and possibly in a circle of curvature not very minute.” 
In continuing my experiments on this subject, I found that the colours of 
total reflexion did not rise in the scale by successive reflexions ; and as they 
modified the tints of crystallized bodies by adding to, or subtracting from, them 
a given portion of a tint, I announced in the end of 1816, in the Journal of the 
Royal Institution, that I had discovered “a new species of moveable polariza- 
tion, in which the complementary tints never rise above the white (the blueish 
white) of the first order, by the successive application of the polarizing influ- 
ence*.” I determined, experimentally, the angles at which this tint was suc- 
cessively produced and destroyed, and thus discovered some of the leading 
properties of total reflexion, before, I believe, M. Fresnel had made any ex- 
periments on the subject. It was he, however, who ascertained that this new 
species of polarization was circular polarization ; and it is impossible to speak 
too highly of the ingenuity and talent which he exhibited in that difficult 
inquiry. 
This view of the phenomena of total reflexion unsettled the opinions which I 
* Journ. Roy. Inst. vol. iii. p. 213. 
