318 
SECOND REPORT- 1832. 
medium thus constituted, will give rise to new vibrations propa¬ 
gated with various velocities corresponding to those of the dif¬ 
ferent rays in the spectrum. 
The complete removal of such a difficulty from the undula- 
tory theory by the analysis of M. Cauchy, must be regarded as 
one of the greatest steps in physical optics ; and philosophers 
will look forward with the most intense anxiety to the develop¬ 
ment of that part of the same theory which renders necessary 
the existence of a triple refraction. 
Such is a very brief notice of some of the most recent disco¬ 
veries and views in physical optics. It would now be a pleasing 
task to point out the desiderata of this branch of science, and 
to indicate the locality of those rich mines which yet remain to 
be explored, did we descry any young and active labourers 
who were likely to gird themselves in earnest for so difficult a 
work. But when we see those who are best fitted for such in¬ 
quiries, either abandoning altogether the study of light, or pur¬ 
suing it in professional harness as a sort of contraband adven¬ 
ture, we almost despair of seeing acquired for our country the 
glory of any fresh achievements. Could we count on the unfet¬ 
tered labours of two of our most eminent natural philosophers, 
who have already evinced such high capacity for optical disco¬ 
very, we might still cope with foreign genius, even though it 
does repose under the sunshine of Royal favour and of Acade¬ 
mic ease. 
There is scarcely any branch of the subjects of double re¬ 
fraction and polarization which does not afford the richest fields 
of discovery. Even the theory of undulations, with all its power 
and all its beauty, is still burthened with difficulties, and cannot 
claim our implicit assent. It has not yet brought under its do¬ 
minion the phenomena of elliptic polarization in all its varieties, 
from the rectilineal polarization of transparent bodies, to the 
almost circular polarization of pure silver. It has not explained 
the singular influence of the force of double refraction over the 
force which polarizes reflected light; and it has great difficul¬ 
ties to struggle with, in accounting for certain phsenomena of 
absorption, to which I shall presently have occasion to refer. 
The determination of the physical data (or the physical con¬ 
stants, as Mr. Babbage calls them,) of these departments of 
science, constitutes a new and almost untrodden field, which 
may be successfully cultivated by almost every variety of talent. 
The refractive indices of the two pencils in all crystallized bo¬ 
dies, measured in reference to fixed points in the spectrum, as 
has been lately done by Rudberg;—the angles at which light 
is polarized by reflexion from crystallized and uncrystallized 
