polarisation of light by reflexion from transparent bodies . 1 47 
reflection. The same thing will happen if the direct ray is 
transmitted through a bundle of glass plates in which the 
plane of refraction is perpendicular to the horizon. 
Prop. xix. 
When a polarised ray is incident at any angle upon a transparent 
body , in a plane at right angles to the plane of its primitive pola- 
risation, a portion of the ray zvill lose its property of being re- 
flected, and will entirely penetrate the transparent body. This 
portion of light, which has lost its reflexibility , increases as the 
angle of incidence approaches to the polarising angle, when it 
becomes a maximum . 
A part of this Proposition constitutes one of the beautiful 
discoveries of Malus, who found that at the polarising angle 
the second plate of glass “ would no longer reflect a single 
“ particle of light, either from its first or second surface/' 
The rest of the Proposition I have established by various 
experiments. In realgar, diamond, and oil of cassia, and in 
substances whose refractive power exceeds l.boo, the portion 
of light which suffers reflexion at the polarising angle is very 
considerable, and it will be seen from the Propositions in Sect. 
V., that if strong lights are used, there are no circumstances 
under which every particle of a beam of white light can lose 
its reflexibility. 
