OF ELLIPTIC POLARIZATION. 
311 
had entertained respecting the action of metals, and I was thus led to revise 
and extend the unpublished experiments which I had made on the subject. 
In order to ascertain the effect of a single metallic surface, I took a crystal- 
lized plate of glass whose central tint was the blueish white of the first order, 
and positive like sulphate of lime. This tint varied from a quarter of a tint in 
value down to zero. The primitive ray was polarized +45°, and the plate of 
steel was horizontal. This ray was received at an incidence near 90°, and the 
principal section of the analysing prism was in the plane +45°, while the 
length of the plate of glass was fixed perpendicular to the plane +45°, or to 
the principal section of the prism, so as to move along with it. 
At an incidence of 88° the metallic action destroyed the action of the equi- 
valent crystallized plate when the section of the analysing prism was turned 
from -{-45° to +38°. 
At an incidence of 83^° the same effect was produced when the same section 
was turned into the plane -j-22|°. 
And at an angle of 75°, viz. the maximum polarizing angle, the compensa- 
tion took place when the axis of the crystal had moved round 45°. 
In like manner, at an angle of 60° the compensation took place when the 
axis of the crystal was turned round 45° -f 22^°, or — 22|° ; and, 
At an angle of incidence of 40° the compensation was effected when the axis 
of the crystal had turned round 45° + 37°, or into the plane — 37°. The same 
results are obtained when the light falls on the metal before it passes through 
the crystal. 
Hence it follows, that at the maximum polarizing angle the effect of the 
equivalent crystal placed in azimuth 45° to the plane of primitive polarization, 
is compensated by the action of the metallic surface, while at greater angles of 
incidence the compensation is effected in azimuths less than 45° ; and, at less 
angles of incidence, in azimuths greater than 45°. 
When the reflexion from the metal is made in a plane perpendicular to the 
meridian, the opposite effect is produced. 
The angles at which the compensation takes place in the preceding experi- 
ments are obviously such, that calling R the angle of rotation of the axis of 
the crystal, it has always to i the angle of incidence the same relation as in the 
formula, tan (45° - R) = —jfzriy 
2 s 
MDCCCXXX. 
