On Polarization of Light by Refraction: 995 
“Tn all comparisons drawn between the institutions, customs, man- 
ners, &c. of the countries he visited, and those of the United Statés, 
the author of the Tourist sustains the character of a candid unsophisti- 
cated republican gentleman, duly attached to his own country, yet free 
from those narrow prejudices that obscured the vision of Faux, 
Fearon, Captain Basil Hall and others in their tour through the Uni- 
ted States. Every American reader must fell an honorable pride in 
contrasting the candid and ingenuous spirit manifested throughout this 
book, with she: PPR AE censure lavished upon us by those 
authors. 
Ann. Iil.—On the laws of the polarization of light ty parr? ; 
S: by Davin Brewster, LL. D. F.R.S. L.& 
Read before the Royal Society, February 25, 1830. 
In the autumn of 1813 I announced to the Royal Society the dis- 
covery which I had then made of the polarization of light by refrac- 
tion ;* and in the November following I communicated an extensive 
series of experiments which established the general law of the phe- 
nomena. During the sixteen years which have since elapsed, the 
subject does not seem to have made any progress. From experi- 
ments indeed stated to have been performed at all angles of indidente 
with plates of glass, M. Araco announced that the quantity of light 
which the plate polarized by reflexion at any given angle was equal 
to the quantity polarized by transmission; but this result, founded 
upon i incorrect observation, led to false views, and thus contributed to 
stop the progress of this branch of optics. 
Thad shown in 1813, from incontrovertible experiments, that the 
action of each refracting surface in polarizing light, produced a phy- 
sical change on the refracted pencil, and brought it into a State ap- 
proaching more and more to that of complete polarization. But this 
result, which will be presently demonstrated, was opposed as hypo- 
thetical by Dr. Youne and the French philosophers ; and Mr. Hers- 
cuex has more recently given it as his decision, that of the two con- 
tending opinions, that which was first asserted by Maus, and subse- 
quently maintained by Biot, ag ERS and Fresne., is the nee: 
pean, ae 
= _ * In this discovery I was anticipated by Maxvs. 
Vor. XXIiI.—No. 2. 29 
