GLEANINGS 
IN 
SCIENCE. 
JVo. 16. — dtpril, 1830. 
I. — On the Polarization of Light. 
When the particles of light travel through a crystallized body, endowed with the 
property of double refraction, they are supposed to experience certain movements 
of rotation on their centres of gravity, dependent on the nature and direction of the 
forces exerted upon them by the atoms of the crystal. In certain cases the effect 
produced is, to arrange all the atoms of the luminous ray in one direction, with 
their similar faces or poles parallel — This circumstance, which was first observed 
by Malus, is called Polarization, from its analogy to magnetic phenomena. 
Thus, if a ray of light fall upon the surface of a plane glass mirror, at an angle of 
35° 25', the ray which is reflected, is found to be in this condition; all its compo- 
nent atoms are prepared to shew the same submission to any subsequent disturbing 
force, resembling so many minute magnets, suddenly brought within the influence 
of a powerful directive attraction, to which they arrange themselves conformably; 
—those which were right at first, of course remaining steady, while the rest under- 
go oscillations, until they also become polarized. 
Although these functions of the minute invisible atoms of light, may be deem- 
ed purely conjectural, still they serve so well to explain the facts observed, and 
to render intelligible the various modifications of which they are susceptible, 
that, where brevity and perspicuity are desired, it becomes convenient at once 
to assume them as established laws. Indeed, the velocity and the times of oscil- 
lation arc considered, in many cases, capable of calculation, as well as the 
depths to which the action continues in different bodies ! But my object at pre- 
sent is not to enter into any subtle theoretical discussions ; I merely wish to 
give a statement of the principal facts hitherto developed in this curious and little- 
known department of optics, with the aid of such simple diagrams as, I hope, 
will facilitate their comprehension, and very much lessen the task of explanation. 
a y .t «. 
'U ■ v* 
1. Mains observed, that when a ray of light impinged on a glass mirror, at an 
angle of 35° 25', and was reflected thence, if another mirror were presented to the 
reflected ray at the same angle, so as to cause a second reflection in the same plane , 
the whole ray was, as might have been expected, reflected , and became visible to a 
spectator properly situated (figure 1,2); but if the second reflecting plane were 
turned round, so as to form a right angle with the first, (retaining its angle of 
with the ray,) then no light whatever underwent reflection, but on the contrary the 
whole ray passed through the g lass, and was visible in a straight direction, as if no 
glass intervened, (fig. 4.) 
