1895. ] NEW YORK ACADEMY OF SCIENCES. 155 
On motion, the thanks of the Academy were tendered to Prof. 
Barnard, of Lick Observatory, and Prof. Keeler, of Alleghany, 
for their kindness in sending photographs for exhibition at the 
reception and at this meeting. 
Pres. Rees then showed Barnard’s photographs of the Milky 
Way and of several comets, especially Brooks’. They were dis- 
cussed by Pres. Rees, Mr. C. A. Post and others. Adjourned. 
Wm. HALwock, 
Secretary of Section. 
A STUDY OF THE POLARIZATION OF THE LIGHT 
EMITTED BY INCANDESCENT SOLID 
AND LIQUID SURFACES. 
By R. A. MILLIKAN. 
I: 
INTRODUCTORY. 
In spite of the prodigious activity of physicists during the 
first three quarters of this century in attacking the problems of 
reflection, refraction, and polarization in all their different phases, 
both from the side of experiment and that of mathematical 
theory, the problem of polarization of light by emission seems 
to have received comparatively little attention. Although the 
fact that incandescent solids and liquids emit, at oblique angles 
of emergence, partially polarized light, was discovered more than 
seventy years ago, it does not appear even to-day to be very 
generally known. Few, even of the more complete text-books 
on Physics, make any mention of the fact. Verdet, in his 
“ Optique,” published in 1870, devotes a short paragraph to 
“ Polarization by ,.Emission,” in which he says that ‘‘ there exists 
upon the subject but a small number of experiments due mainly 
to Arago.” Thesummary of these experiments which he subjoins, 
reveals none whatever which are quantitative. Since the time 
of Verdet, no one,:so far as I am able to discover, has made any 
careful or elaborate study of the phenomenon with a view to 
ascertaining its generality, verifying or disproving Arago’s as- 
sumption as to its cause, or classifying different substances with 
reference to their power of producing the phenomenon in greater 
or less degree. 
Since even a hasty examination reveals the fact that different 
